Final Report Summary - HELIOS (High Pressure Electronically controlled gas injection for marine two-stroke diesel engines)
Executive Summary:
The project has been successful as it enabled the creation of a new two-stroke ship engine generation based on gas. During the project the research platform was constructed, many components needed for a gas fuelled engine were developed and tests were carried out at the research platform. It has been verified that the gas fuelled engine offers significant environmental benefits and a much better operation efficiency than traditional engines.
The general objective of Helios was to develop a research platform for an electronically controlled, two-stroke, low-speed, marine diesel engine that operates on direct injection of Compressed Natural Gas (CNG) ready for the LNG market. This objective is met, and a prime result of Helios is a new, gas-fuelled engine, a dual-fuel unit that MAN Diesel & Turbo offers to the market. Helios has in general generated many positive results and increased the knowledge base in several technical fields:
• Development of gas engine components
• New gas injection valve and other main components
• New gas control block
• New gas composition sensor
• New handheld calibration device
• Dedicated control and safety system
• Laser optical temperature measurements
• Tribology and corrosion problems checked
• Development of new high-temperature materials
First orders of gas-fuelled ship engines
Helios has stimulated the introduction of a gas fuelled ship engine to the market. Many ship owners have already placed orders for the gas engine. In the beginning of 2014 ship owners had ordered in total 49 gas fuelled engines (incl. options) to be delivered to the yards from 2014-2018. The engines are considered the most environmentally friendly, two-stroke, low-speed vessels. The potential for more orders in this new emerging market segment is great.
Cooperation
The Helios results were obtained through an innovative collaboration of different universities and companies. Four of the nine partners were universities, that provided valuable inputs and used the research platform for testing of new ideas and methods. The research platform was established at MAN Diesel & Turbo in Copenhagen for testing and verifying of new concepts.
Environmental benefits
The gas engine complies with the IMO’s Tier II requirements and, in combination with EGR (Exhaust Gas Recirculation), its emissions fall also below the Tier III limits. A particularly significant, environmental benefit is the very low methane slip. The major benefits stemming from the Helios project are better than estimated in the DOW. Compared with a traditional HFO engine the reductions sum up to 23% for CO2 emissions, 24% for NOx, and PM is reduced by 85%.
Project Context and Objectives:
Background
Marine low-speed two-stroke Diesel engines are the de-facto standard for propulsion of commercial vessels. Since fuel costs usually represent more than 50% of the operating costs of ship transportation, the development of the present main engine technology has been pushed towards the highest thermal efficiency possible and towards the usability of the least expensive of fuels, which has until now been residual or heavy fuel oil (HFO).
Objective
The general objective of the Helios project was to develop a generation of electronically controlled two-stroke low speed marine diesel engine that operates on high-pressure Compressed Natural Gas (CNG) and/ or Liquefied Natural Gas (LNG) as an alternative hydrocarbon fuel to HFO. A new ship engine generation is needed in order to intensify the greening of waterborne transport. The gas engine provides a higher efficiency as well as significant reductions of pollutants and greenhouse gasses. Combined with EGR it complies with IMO´s environmental restrictions. The IMO’s Marine Environmental Protection Committee (MEPC) has introduced emission targets which will affect the maritime industry in the coming years. Within this context Liquefied Natural Gas (LNG) is increasingly seen as a cleaner and viable alternative to heavy fuel oil. LNG as fuel has the potential to reduce the CO2 emissions by around 23% and SOx to almost zero depending on the gas composition. Other environmental benefits are:
NOx 24% reduction
PM 85% reduction
Methane “slip” 0.2-0.3 g/kWh
CO Very low
Smoke Almost eliminated
Thermal
efficiency Very high
Shale gas
Simultaneously with the new environmental requirements shale gas is becoming available offering an alternative fuel at very low prices especially in USA. Shale gas can also become a big new energy source in e.g. China and Europe. This develops a part of the background for future market demand for gas fuelled engines.
Benefits in the maritime sector
Helios has provided a step forward for the maritime sector in a new emerging technical area. Helios safeguards Europe’s leading position in the field of two-stroke ship engines.This is to the benefit of the market sector, including the sub suppliers, but also to the ship owners, as it balances the Asian dominance of the supply side. At present, core technology in marine main propulsion engines is held by European companies. However large two-stroke engine manufacture is almost entirely done on license and has predominantly moved to East Asia. The large two-stroke engine manufacturing companies are increasing in size and the financial strength now comparable or even larger than the European licensors. The European licensors' success is depending on keeping a lead in technology which can be licensed for local manufacture otherwise the engine manufactures will be motivated to built up own capabilities in engineering and R&D. Helios strengthens the knowledge base in Europe and enables sub suppliers to take part in the manufacture of gas fuelled engines.
Challenges
Helios included a number of rather great challenges. First of all, the thermodynamic efficiency of the gas engine must be very good, requiring the engine to run with at least similar if not higher compression ratios than HFO engines. Hence the usual premixed combustion concept used on conventional gas engines cannot be used - instead the gas fuel must be burned under Diesel-like conditions, despite the poor ignition properties of gas. As gas, by nature, will reduce particulate emissions and accordingly nearly eliminate abrasive wear, this mode of operation fundamentally opens the possibility of using new high temperature materials, allowing higher exhaust gas temperatures and hereby improving significantly the efficiency of waste heat recovery (WHR) systems, with improved total energy efficiency as a consequence.
Activities and tests
The main objective of the project was to establish a suitable R&D platform to reflect a new generation of technology in engine optimization, control, monitoring and in emissions control. A large part of the work within Helios was related to tests of various types, from functional tests of the gas engine platform, tests for compliance with current emission legislation and tests for optimization of engine concept with regard to fuel economy. Throughout the project, advanced measurements and diagnostics methods were applied in order to gain insight in the physical processes of gas injection, pilot fuel injection, ignition, combustion and emission formation.
Further, the marine engine research and optimization frame opened the regime of higher exhaust gas temperatures, contributing significantly towards advanced utilization of the waste heat recovery systems. A distinct part of the project aims towards the gas engine monitoring in automatic tuning for best engine performance, complemented by building specific tools and algorithms for assessing and recording of the engine on line optimized energy efficiency.
The Helios activities can be categorised as applied science and development with a clear market focus.
Safety
Safety of a gas fuelled engine is a central issue and directed the technical development during the project. The MSC.285(86) “Interim Guidelines on Safety for Natural Gas-Fuelled Engine Installations in Ships” is the valid Guideline until the International Code of Safety for Ships using Gases or other Low flashpoint fuels (IGF-Code) will come into force. The IGF-Code is currently under development and the Code will probably come into force in 2016. In contrast to the Interim Guideline the IGF-Code will also cover internal combustion engines with a high pressure gas injection system.
Innovation potential
The development of a new engine generation involves challenges, but its innovation potential is great. A ship engine is a very advanced and complex mechanism consisting of a number of technologies and components. The technology and components can be changed and developed in the search of a perfect engine.
Helios generated a number of technologies that have great spin-off value by their own e.g. a gas composition sensor system and the components for gas supply. The application of high-temperature materials onto existing components will enhance significantly the efficient energy utilisation potential on a wider market. The developed diagnostics methods, sensors and online calibration procedures will contribute to the overall technological progress of European industry. The developed concepts for high-pressure natural gas storage and distribution will form the basis for new standards on high-pressure gas handling in the energy industry.
Helios resulted in a gas injection system together with an additional injection system for small amounts of Diesel fuel (the so-called pilot injection) to ensure a safe ignition at all operating points. This required an entirely new system for engine control and monitoring that was designed and also optimized for different operating conditions. Due to the poor ignition properties of natural gas, the cylinder processes is monitored continuously with a system of sensors and electronics that will require calibration with the engine in operation. Furthermore, the control system is able to deal effectively with the uncertainty of the actual gas properties for continuous optimization of the fuel efficiency. The lack of sulphur in the natural gas, although beneficial from an environmental point of view, leads to tribological challenges, because sulphur components have, generally, very good lubrication properties. That was investigated during the project. The change of fuel to natural gas will not only involve changes to the engine, but will require the development of guidelines and rules on how to install tank and distribution systems for natural gas on board of ships. The increased exhaust gas temperatures, aiming at better utilization of waste heat recovery systems, lead to excessive thermal stress on certain critical engine components.
The innovation potential of a ship engine was fully exploited in Helios and transformed into new products. A new ship engine generation was created including a range of new products, components, methods and tools.
Project Results:
WP1 Zero-emission marine gas engine
Objective
The main objective was to develop and verify a research platform being able to operate on natural gas based on the existing MDT research engine in Copenhagen.
Results
Conversion of the research engine to gas operation required installation of new components, development and testing of components as well as development of a new safety and engine management system. Furthermore, the data acquisition system, to be used for testing in the other WPs, was designed and installed. The list below is showing further parts of WP1:
• Development, design, purchase and installation of equipment
• FMEA , Failure Mode Effect Analysis
• Authority approval off gas supply system
• Education of personel according to ATEX rules
• Running-in of systems
• Design of special ME-GI component tools
The tasks were successfully carried out and according to the time schedule. The running-in of the new engine as well as basic performance tests included a large efforts. The engine operation on gas amounted to 420 hours and 301 tonnes of gas were used.
The WP was a research platform and enabled a number of tests carried out for the other WPs.
The tests for other WPs pushed the development of gas engine components and methods. Carrying out the tests with external partners was appreciated as it generated new ideas and approaches. In total 14 longer tests were carried out. In addition to that a large number of smaller tests were made simultaneously with other major tests.
Conclusions
WP1 included the very basic efforts of the construction of a gas fuelled engine. The system was developed and the wide range of components have been installed. On that new technical basis it has been possible for MDT to offer two stroke gas engines to the market.
WP2, Testing and optimisation towards compliance with current standard
Objectives
The overall main objectives of WP2 were to demonstrate that the ME-GI two-stroke engine can meet the current Tier II NOx emission legislation, and that it has an efficiency which is competitive with that of the same type of engine operating on conventional diesel oil/HFO. Those two objectives were to be met while ensuring that the engine stability in terms of combustion quality as well as variations in engine torque and speed should be as good as for the conventional ME engine.
Research and results
In WP2 systematic parametric tests were carried out in order to reduce engine out emissions while maximizing the thermal efficiency, over a range of engine loads. The performance when operating on gas was benchmarked against conventional operation on diesel. After the construction of the research platform in WP1 three longer measurement campaigns were executed within WP2. The first campaign in May/June 2011 included performance and emission measurements. In this campaign a reduction in NOx was demonstrated, but gas consumption could not yet be measured. In a second measurement campaign in August 2011 a first first gas consumption evaluation was performed, albeit at limited precision. The NOx reduction potential of co-combustion of pilot oil and natural gas was confirmed with NOx reductions from a Tier II level to approximately 30% below that level. The third and most extensive measurement campaign was conducted during March/April 2012. The results of this campaign are presented below. In total 81 full engine tests, including specific fuel oil /gas consumption (SFOC), emission, performance, and materials temperatures measurements, were performed in this campaign as part of a design of experiments (DOE) optimization study.
Direct benchmarking of gas mode operation against diesel oil mode operation was made. A significant reduction in NOx emission of approximately 24% (cycle average) as well as a slightly improved SFOC was documented. This could be achieved without any deterioration in cycle-to-cycle combustion stability. As the engine fulfils Tier II emission limits for NOx already in diesel mode, the gas engine thus fulfils Tier II NOx limits with a wide margin.
Unburnt hydrocarbon (UHC) emission are, howeer, more than doubled when switching from diesel oil to gas. This is not explained by an increased methane slip, as the measured methane slip (potent green house gas) is actually very low compared to duel fuel and lean burn Otto engines (<10 times) with low pressure gas fuelling. The main reason for this is the fact that the gas is combusted while it is being injected directly into the combustion chamber, just like a conventional diesel spray combustion process. CO2 emissions are decreased by about 23% compared to diesel operation. This combined with the effects of the methane emissions results in a total decrease in green-house gas (GHG) emissions of around 20% compared to diesel operation.
The NOx reduction provided by the switch to gas offers further efficiency improvements, otherwise not accessible due to emission legislation. By increasing the compression and maximum cylinder pressures the SFOC could be reduced on the account of increased NOx emission (while still keeping below that of diesel oil mode operation). It was demonstrated that it is possible to reduce SFOC by more than 4 g/kWh from diesel oil to gas at 75% load (and even more at 50% load) in this way.
Conclusion
The gas engine performance and emissions mapped out in WP2 have formed the basis for the engine specifications offered by MAN for the ME-GI engine family, and has demonstrated that operation below TierII NOx emissions limits is possible. It has thus directly contributed to the successful market reception of the ME-GI concept, which has eventually resulted in several orders being placed.
WP3 Zero-emission marine gas engine
Partners: MDT and ULUND
Objectives
WP3, which covers three different research themes: 1) operation with exhaust gas recirculation (EGR) in order to reduce NOx, 2) tests of early injection of gas to achieve partially premixed combustion aiming for NOx reduction and to investigate safety aspects, 3) laser optical investigations of gaseous fuel injection, ignition and flame propagation, as well as surface temperature measurements on critical components, to further understanding of in-cylinder processes.
Research and results
A full comparison was performed between engine operation on diesel and on gas, with and without EGR. The use of EGR was demonstrated to drastically reduce the levels of NOx emissions, at the cost of slightly increased specific fuel oil consumption (SFOC). From operation at 25%, 50%, 75% and 100% load the cycle weighted specific NOx emissions could be calculated. For gas with EGR they were found to be about 20% below the future Tier III emission limits.
Early injection of gas was investigated in tests performed on a single cylinder, with a single gas injector in operation. For the early timed gas injections unstable operating conditions with occasional gas misfires could be reached, with large cycle-to-cycle variations.
A number of optical measurement campaigns were undertaken on the ME-GI engine, in collaboration with WP8. The spectral content of flame emission both in diesel and gas operation was mapped out, high-speed photography both in the visible and in the UV was performed, surface temperature measurements using laser excited thermographic phosphors were demonstrated, and laser-sheet fluorescence imaging of the gas jet was attempted.
A high-speed movie of the flame ignition and propagation is shown below. In this view, the gas atomizer is located to the left of the pilot atomizer. At the beginning two quite distinct flames are seen, with the rightmost pilot appearing brighter, as the gaseous combustion will form less luminous soot at a lower temperature. The brighter pilot flame is then seen to penetrate into the larger gas flame. At around 15 ms the pilot fuel is being switched off, and in the later parts of the sequence the gas flame is seen to continue burn.
The engine cover for gas operation was fitted with extra diesel injector holes. Those, as well as the starting air valve, could be used to obtain optical access to the combustion chamber. For this purpose two different types of insert were manufactured. The first type could be inserted into a fuel injector port and featured a borescope connected to a camera. The second type could be inserted into the starting air valve and featured laser sheet forming optics and a prism for laser sheet steering. Both types were fitted with sapphire windows at the end, protruding into the engine cylinder. Through careful engine operation windows could be kept reasonably clean for several hours during gas operation.
Conclusion
Compliance with Tier III emission limits will be crucial for ME-GI engines sold in 2016 and afterwards. The demonstration of ME-GI operation well under those limits, through the use of EGR within Helios WP3 was thus a very important milestone for ensuring future success of the ME-GI concept. The experiences gained through optical studies of the gas ignition and combustion process will assist future efforts aimed at optimizing the ME-GI process further.
WP4 High temperature components marine gas engine
Objectives:
• Development of heavy duty Dual Fuel P/M HIP compound exhaust valve spindle
• Ability to withstand heavy fuel related high temperature corrosion
• Ability to withstand high temperature seat wear during service on gas with reduced deposits
Research and results:
• Selection and development of qualified materials
• In depth characterisation of metalurgical, physical and mechanical properties of material candidates.
• Characterisation of material interaction at bonding zones and influence on the mechanical properties
• Development of a design, based on FEM modelling and calculations
• Development of a production concept including production parameters
• Production of first prototype spindles
• Prototype service test and first inspections on commercial vessel
WP5 Gas engine tuning for best energy efficiency
Objectives of WP5:
• Development of a gas control and performance strategy that enables the engine to run optimized for energy efficiency.
• To tune the engine to achieve optimum efficiency requires a robust method for extracting the key performance parameters for input to the gas control strategy. Development of algorithms for robust extraction of these parameters becomes central point hereof.
• Development of algorithms and methods for evaluating energy efficiency improvements, hereby validating tuning of the engine for best performance.
Results:
A gas engine control strategy has been developed to operate the dual fuel engine auto-intermittently in two fixed gas modes: Minimum pilot fuel oil (maximum gas) and minimum gas mode (maximum fuel oil). This solution avoids operating the gas engine with varying gas/fuel oil ratios. This strategy is, among others, driven by requirements set by IMO regulations, which requires test and verification of engine emissions at any operating load and fuel oil /gas mixture. At the same time, the gas control strategy reduces the task of identifying the set of parameters, which provides the best engine performance tuning, to just two modes; thus being equivalent to the control strategy of pure HFO operated engines. up, requiring an increased gas flow and at the same time an increased gas pressure. A solution was developed allowing to ramp up to full gas operation while using smaller components designed to deliver maximum capacity at steady state, was to increase the HFO pilot amount during ramping up the gas until a point at which the gas supply system is able to deliver the required gas amount.
For robust extraction of Pmax, various filtering techniques havebeen applied and tested with the aim of implementing these on the data acquisition hardware (PMI DAU) itself utilising up to 200kHz sample rate, rather than transferring the more sparse information included in the 360 pulse triggered values available at the PC application.
The activities in scope of the Helios project have included tests at a number of engines in order to validate and potentially adjust the algorithm for detection of TDC and measuring the indicated load of the engine. Initial tests using the research platform engine indicates that TDC can be identified within a standard deviation of less than 0.1 degrees, which is regarded to be within adequate precision.
Further, is was found that the geometry of the indicator pipe and the indicator valve dramatically influence the measured results, thus leading to a modified indicator design. Hereby reducing the observed heat flash effects as well as increasing the life time of the sensor.
Conclusion
The combustion process in a dual fuel engine operated on gas must be continuously monitored and close-loop controlled in order to operate the engine at its optimum performance level within the required safety and operational limits of the gas running mode control strategy. The current processes for a pure diesel operated engine are not sufficient in this respect.
A gas control strategy has been developed and implemented that allows for the standard auto-tuning functions already developed for pure HFO-operated engines to be implemented for the gas engine as well, including strategies for operating the engine in dual fuel gas/oil mixed mode and effectively controlling the engine while ramping up the gas amount without the need for excessive demands on the gas supply system.
Filtering techniques were successfully tested for extraction of a robust cylinder maximum pressure Pmax. Measures to ensure a more accurate measured mean indicated pressure was identified and implemented, including validating method for robust determination of top dead center.
WP6, Cylinder pressure measuring and calibration
Introduction
On-line pressure sensors for cylinder pressure measurement are an integrated part of the gas engine control and safety system. In order to maintain reliable operation of these sensors a traceable calibration concept is required, allowing the calibration of the on-line sensors without sending it ashore for calibration at an accredited calibration institute.
The calibration process must be able to be executed while the engine is running. The calibration process must allow to be executed by low skilled operators / crew on board.
Objectives of WP6:
• Identification of requirement for traceable calibrated online cylinder pressure measurements for control and tuning.
• Development of a concept meeting these requirements, including the procedures and the equipment that have to be applied.
• Implementation, testing and verification of the system for traceable calibration on a full scale test.
Results:
The description of the main features and characteristics of the intended solution as part of WP 6 was divided into three main sections, the hardware development, the software development and the execution of the calibration process.
The hardware concept and the software for communication between the calibration equipment and the DAU from the engine have been developed in close cooperation between the two partners MDT and Kistler.
The calibration equipment consists of the HCD (Handheld calibration device) and portable reference sensors with TEDS (Transducer electronic data sheet) called PiezoSmart®.This sensor stores the configuration data for determination of the gain and range and exchanges these parameters with the HCD thus errors due to manual data handling are prevented(human factor).The HCD is powered from the PMI-DAU from MDT, the bidirectional communication between the HCD and the DAU is realised by two AC-coupled LVDS lanes.
The HCD is controlled via an asynchronous full duplex serial interface the concept allows for full duplex
operation with the DAU as master and the HCD as slave.
Conclusion
The concept, procedure and equipment to execute a traceable calibration have been described and successfully tested in the laboratories of Kistler and MDT as well as at the MDT research engine in Copenhagen. The concept for traceable calibration has been commercialised, by including it as a standard for all MDT ME engines, both Gas operated and HFO operated. The step 2 prototypes was completely CE-tested and certified by Kistler. In addition to that the robustness of the device was tested at MDT and Kistler through Highly Accelerated Lifetime Tests (HALT).
WP7 System criteria for high pressure onboard gas supply
Objective
The objective of the work package 7 is to establish design and safety specifications for a high pressure fuel gas supply system of a two stroke engine. In this regard the development of equipment for a safe fuel supply onboard as well as collision damage scenarios of the gas supply system of merchant vessels have been evaluated.
Investigations and results
The Interim Guidelines MSC.285(86) includes a collision resistance of gas fuelled vessels due to a minimum distance requirement of the LNG storage tanks from the ship outer shell depending on the ship type. Within the work package 7 the collision resistance of a gas fuelled 6500 TEU Container Vessel and a container feeder (1200 TEU) is investigated based on the GL-Rules I-1-1 Section 33 “Strengthening against Collisions”. Derived from the collision analysis safe and applicable distance requirements of the fuel containment for a two stroke engine have been developed and submitted to IMO within the IGF-Code development. The distance requirements of LNG storage tanks from the ship outer shell are still under discussion at IMO.
Another focus was given to the design of a gas conditioning and pressurizing system for the fuel gas supply to an ME-GI 2-stroke dual fuel engine onboard merchant vessel. Main aspects for development are the demand of the fuel gas supply and the interfaces to the ship / engine. This development includes an overview of possible variants of fuel gas supply systems. One criterion for the type of fuel gas supply system (FGSS) is the type of consumers. Also a process simulation of the main parts of the fuel gas supply was developed by TGE.
- Hazard identification (HAZID)
For the developed fuel gas supply system of a 1800 TEU container vessel a hazard identification (HAZID) was performed. The aim of the Hazid is to identify possible system weaknesses and to improve the system. The analysis was orientated on the Failure Mode and Effects Analysis method and the requirements given in IEC 60812. The analysis focussed on the identification of hazards caused by LNG or NG leakages.
A number of recommendations for technical and procedural measures have been identified to prevent failures, to reduce the failure frequency and the effects. The HAZID was limited to normal operation conditions (gas mode of the engine). The analysis showed that no single point failure can lead to a critical situation on board the vessel (high Risk area). If the actions mentioned in the Hazid will be successfully implemented, there are no objections for a safe operation of the system from this part of the risk analysis.
For safety reasons double walled pipes are mandatory for fuel gas supply systems onboard merchant vessels according to the Interim Guideline (MSC.285(86)) and the draft of the IGF-Code. For gas-fuelled two-stroke engines normally a ventilated double walled pipe from the fuel preparation to the engine is used. The required internal pressure can amount to 350 bar. There is no experience with high pressure double wall pipe systems on board so far.
- CFD
In order to determine the influence of the leak of the inner pipe on the integrity of the outer pipe for a jacketed pipe, a CFD and a finite element analysis was carried out by using finite volume / element software. The results from the CFD analysis were applied to the FE-model. In the CFD analysis the pressure and temperature acting on the inner surface of the outer pipe were determined.
Resulting from the internal pressure, the equivalent stress (von Mises) and displacement of the pipe were determined and compared with allowable values. It was shown, that the stress of the outer pipe of a jacketed piping is quite low in the case of a leakage compared to the high internal pressure of the inner pipe. The deformation and the corresponding stress are uncritical compared to the yield strength of typical pipe materials.
Conclusion
Within Work Package 7 design and safety specifications for the distribution systems for the high-pressure gas supply on board merchant vessels have been developed. The conceptual design principles ensure the safe interface between the gas supply system and the control and safety system of the engine. In addition the results of Work Package 7 have been presented at relevant committees to identify the legislative needs and to develop safe and applicable rules.
LNG as fuel is an environmental friendly and commercially attractive way of propulsion. It has been shown that technical and safe solutions for high pressure gas supply to ME-GI are available and approved by detailed research. The presented work package supports the application of this new propulsion concept onboard merchant vessel.
WP8 Optical cylinder diagnostics
Objective
The overall objective of Work Package 8 was to develop and apply advanced optical and laser based measurement techniques to assist in the development of the gas engine concept. Particular objectives were:
• Development and application of a surface temperature measurement technique for critical in-cylinder components based on a laser based phosphorescence technique.
• Application of laser based measurement techniques for visualization of fuel jets and flame propagation in order to study the fundamental processes regarding gas jet injection and ignition using the Diesel pilot.
Results
The work on detectors for phosphor thermometry resulted in improved knowledge about saturation effects and how these can be avoided, minimized or compensated for. Furthermore, one group of photo multiplier tubes (Gateable PMT’s) proved to be superior for this type of single-shot lifetime-based temperature measurements.
The in-cylinder phosphor measurements in the large bore gas engine were successful. For the first time, crank angle resolved surface temperatures could be probed in such a large engine during operation. Although not initially planned for, an additional measurement campaign on fiber based thermometry was performed at the end of the project. The final evaluation of this data has not been performed at present, but everything indicates that the fiber based approach is robust and capable of generating solid data also with minimal optical access. There is a mutual interest to proceed with this work also after Helios has ended. The surface thermometry research performed within Helios has generated several peer-reviewed papers, (see below).
The in-cylinder visualization of injection and ignition was overall less successful. The pre-studies performed at ULUND were all positive. Prof of principle measurements were successfully performed showing the feasibility of laser induced fluorescence imaging of both fuel tracer and formaldehyde under relevant engine conditions. The optical challenges of introducing a high power, ultra-violet, divergent laser sheet into the combustion chamber was solved and the performance was proven both in the laboratories at ULUND and in the research engine at MAN. Laser pulse energies according to the design goal could be delivered in the form of a narrow sheet, as desired, and sent into the engine without damaging the critical components in the boroscope.
However, as indicated earlier, there were severe problems with one of the steel inserts during the full scale tests at MAN. Hence, the PLIF imaging could not be performed as expected. The good news is that everything, including the mentioned pre-studies, still speaks in favor of the general approach used. The problems that prevented the PLIF imaging from being performed were of mechanical nature and as for the phosphor thermometry there is a mutual desire to continue this work.
Conclusion
The knowledge-building connected to phosphor thermometry has greatly benefitted from the Helios project. The fundamental study on detector non-linearity/saturation and signal evaluation routines would be very hard to perform in a similarly thorough manner without the Helios. The results generated here will improve measurement precision and accuracy, not only for the specific studies performed on the gas engine in the Helios project, but in general for all other applications where phosphor thermometry is employed. Surface temperatures could be measured, in this extremely harsh environment, with high temporal resolution (sub crank angle degree). Also from a knowledge-building perspective, Helios provided a unique opportunity for researchers in the academia to work on and get experiences from large scale marine engines running on new fuels.
Feasibility studies showed that it is possible to perform both fuel tracer and formaldehyde LIF imaging under relevant conditions. Furthermore the optical challenges imposed by such large engines with limited optical access could be solved, i.e. an optical device for delivering a high power laser sheet into the combustion chamber was developed and built.
WP9 Gas engine piston rings
Objectives
The objectives focused on providing solutions overcoming the bad tribological conditions expected to appear in gas engine without sulphur in the fuel.
Results
The suitability of the selected material candidates was investigated using the laboratory test, which indicated that they have a higher scuffing resistance than the materials used today. The test results also showed that even a minimum amount of oil present in the contact is enough to avoid scuffing.
The main findings of WP9 are very positive with regards to the design and materials selection for the gas engine piston rings:
No indication of abnormal wear was observed on the piston rings from the gas engine test in Korea.
The presence of high amounts of sulphur in HFO engines may provide some extra protection in cases of temporary lubrication failure. However, the rig test indicates that a minimal supply of oil to the ring/cylinder contact surface guarantees that scuffing will not occur.
a. Additional sulphur coming from the fuel oil shown not critical for avoiding scuffing.
b. No need to neutralize sulphuric acid by adding alkaline agents in the cylinder lubricant (as in HFO engine) => reduced risk to form deposits
=> this threat to the oil film eliminated
This indicates:
c. the risk for scuffing could be kept very low by just securing that the system for internal lubrication in the cylinder is absolutely reliable.
d. the system should guarantee that the whole cylinder circumference is lubricated, without interruptions.
If these points are fulfilled, no other special material-based solutions for the ring or cylinder liner should be needed. Nevertheless, if the reliability of the tribosystem is to be further strengthened, a proper coating with possibilities for oil retention and/or self-lubricating properties might be the solution. The test results indicate that the candidate materials have good properties for this.
Conclusion
In general positive results have been obtained indicating that wear and corrosion due to a sulphur free fuel can be avoided if an efficient lubrication system is used. Further investigations will be needed to understand the scuffing phenomena in engines and to ensure that the laboratory scale scuffing tests can be reliably transferred to engine conditions.
WP10 On line gas composition sensor
Objectives
The general objectives of WP 10 is to design and build an ex-proofed sensor system based on linear Raman spectroscopy for the on line analysis of mixture composition and calorific value of natural gas for a pressure up to 350 bar. In WP10, a sensor system based on Raman spectroscopy for the online analysis of mixture composition and its calorific content was designed and built. The main requirements of the system are a high accuracy, a high time resolution, a high mobility and a sensitivity to a multiplicity of different species. The system has to be able to measure at high pressures (up to 350 bar) and must not be affected by pressure and temperature fluctuations. Moreover, the sensor has to be ex-proofed. Main tasks of WP 10 are the design of the sensor and the sampling cell, the mounting and the high pressure testing of the gas cell, laboratory tests with suitable test gases at low pressure and high pressure conditions, the installation of the sensor at the test engine at MAN Diesel & Turbo in Copenhagen and the demonstration of the online-gas analysis.
Research and main results
The Raman set-up including a high pressure cell was integrated in the upper part of a compact, ex-proofed housing (600x800x500 mm). In the lower part, electrical devices like power supplies, signal converter and switch relays are located. The high pressure cell was made of stainless steel and is designed for a maximum pressure of 350 bar. The data evaluation is based on the contour fit principle, which compares theoretical spectra with experimental once. The theoretical spectrum is calculated by the superposition of the weighed spectra of the natural gas components, whereas the weight factors are determined by the spectrum of a gas mixture of known composition. From the gas composition, the upper heating value and the Wobbe index are determined.
Conclusion
Summarizing, all deliverables and the milestone were fulfilled. A comparison with the gas chromatograph was performed under laboratory and under technical conditions and showed good results. The high pressure cell was tested successfully at a pressure of 400 bar. After this successful pressure test, test measurements under high pressure conditions were performed with a special interest on the influence on pressure fluctuations on the accuracy of the measurement. Finally, the sensor was successfully applied to different runs of the gas engine.
Potential Impact:
Socio economic and societal implications
Helios was a joint European initiative to strengthen the two-stroke ship engine technology as a stronghold in Europe. It is of importance that this technology is of European origin, because it pulls a large sub supplier sector and counterbalance the Asian dominance within ship building. It is to the benefits of the large European shipping sector that the technology is concentrated in Europe. The two-stroke ship engines are manufactured in Asia, but many sub supplies from Europe are used. Helios has provided opportunities for European companies to become sub suppliers for the construction of many future gas fuelled engines. The partner companies of Helios have this opportunity and use it, but also companies outside the consortium have developed a technical basis for becoming sub suppliers, as they had tasks during the development of the gas fuelled engine. In this way Helios was a technical push, that resulted in innovations, new products on the market. It cannot be assessed how many jobs are being created due to Helios, nor can it be estimated what is the export value of the technology.
Helios is a technical response to the new environmental requirements in the field of shipping. The gas fuelled engine complies with IMO Tier II and III regulations when it is combined with EGR (Exhaust Gas Recirculation).The new gas technology shows the authorities that the environmental restrictions have a technical answer. The ship owners ordered 49 gas fuelled engines, which shows that the market is ready to implement new technologies in order to address the new international requirements. Among the orders are engines for LNG tankers, container vessels as well as a few engines for retrofitting.
Main dissemination
Helios has caused much dissemination. Among the major achievements were
- An open conference with 100 participants to explain about the Helios results as well as the gas engines in general
- Mentioning at the most important international conference for ship engines – ISME and CIMAC
- 21 scientific papers
- Features and opening articles in the leading shipping magazines
- More than 30 articles in branch media, incl. online presentations
Gas as a maritime fuel is a central issue that attracts much attention in the sector, so dissemination was successful. For example the press release of the final open conference resulted in at least 20 articles, though most of them online. The target groups of the dissemination included primarily the maritime sector, but also the specific scientific fields of tribology, thermal diagnostics and sensor systems. The coverage in branch magasines as "Marin Propulsion" and "Container, Shipping and Trad" was indeed satisfactory.
The webpage had 890 visits from many countries, among which most from Denmark (18%).
Exploitation of results
The largest exploitation result is that 49 orders for the delivery of gas fuelled ship engines have been signed. In each case these orders pull sub suppliers from the consortium or from outside.
Much new technology has been generated by Helios, when solutions had to be found. The major part of the technology can be commercialised, another part includes new scientific understanding that leads to further research.
The positive results have been generated in an innovation process, where the efforts were concentrated on:
- Research
- Development of components
- Development of methods
- Development of systems
- Establishment of standards
- Manufacture of prototypes
- Testing
The outcome of the cooperation and interaction within these efforts was innovation.
Developing the research platform generated a number of innovations, as new products, systems and tools were necessary to solve technical problems. After the reserach engine at MDT was ready, the interaction of development efforts and testing proved very effective. In this process the universities and the companies had a fruitful cooperation. MDT will continue the cooperation with ULUND and UPPU. It is also possible that the cooperation of ERL and MDT will continue as the gas composition sensor system would be highly valuable in the gas engine – but it stills needs development. The R&D efforts were focussed and well defined from the beginning – the goal was to construct a gas fuelled engine. In this way Helios was very market oriented and the market requirements were clear, defined by the IMO regulations. The successful introduction of the new gas fuelled engine in the market is to the benefit of the companies in the consortium. The companies were involved with:
MDT: Licensing of design and technolgy
GL: Clasification for new ships
TGE: Design of gas systems
Kistler: Delivery of handheld calibration device
The gas composition sensor system of Erlangen University is not yet fully ready for the market, but it has the possibility of a succesful commercialisation, as the demand exists in the maritime sector, but it would also be valuable in other sectors, e.g. within biogas utilization.
Sandvik is at the moment not a sub supplier to the engine manufacturers, but its patented production process of high temperature materials certainly has bright perspectives and a generic character.
The gas engine is a locomotive for innovations and exports.
List of Websites:
www.helios-fp7.eu
Niels Freese
MAN Diesel & Turbo
Niels.Freese@man.eu
The project has been successful as it enabled the creation of a new two-stroke ship engine generation based on gas. During the project the research platform was constructed, many components needed for a gas fuelled engine were developed and tests were carried out at the research platform. It has been verified that the gas fuelled engine offers significant environmental benefits and a much better operation efficiency than traditional engines.
The general objective of Helios was to develop a research platform for an electronically controlled, two-stroke, low-speed, marine diesel engine that operates on direct injection of Compressed Natural Gas (CNG) ready for the LNG market. This objective is met, and a prime result of Helios is a new, gas-fuelled engine, a dual-fuel unit that MAN Diesel & Turbo offers to the market. Helios has in general generated many positive results and increased the knowledge base in several technical fields:
• Development of gas engine components
• New gas injection valve and other main components
• New gas control block
• New gas composition sensor
• New handheld calibration device
• Dedicated control and safety system
• Laser optical temperature measurements
• Tribology and corrosion problems checked
• Development of new high-temperature materials
First orders of gas-fuelled ship engines
Helios has stimulated the introduction of a gas fuelled ship engine to the market. Many ship owners have already placed orders for the gas engine. In the beginning of 2014 ship owners had ordered in total 49 gas fuelled engines (incl. options) to be delivered to the yards from 2014-2018. The engines are considered the most environmentally friendly, two-stroke, low-speed vessels. The potential for more orders in this new emerging market segment is great.
Cooperation
The Helios results were obtained through an innovative collaboration of different universities and companies. Four of the nine partners were universities, that provided valuable inputs and used the research platform for testing of new ideas and methods. The research platform was established at MAN Diesel & Turbo in Copenhagen for testing and verifying of new concepts.
Environmental benefits
The gas engine complies with the IMO’s Tier II requirements and, in combination with EGR (Exhaust Gas Recirculation), its emissions fall also below the Tier III limits. A particularly significant, environmental benefit is the very low methane slip. The major benefits stemming from the Helios project are better than estimated in the DOW. Compared with a traditional HFO engine the reductions sum up to 23% for CO2 emissions, 24% for NOx, and PM is reduced by 85%.
Project Context and Objectives:
Background
Marine low-speed two-stroke Diesel engines are the de-facto standard for propulsion of commercial vessels. Since fuel costs usually represent more than 50% of the operating costs of ship transportation, the development of the present main engine technology has been pushed towards the highest thermal efficiency possible and towards the usability of the least expensive of fuels, which has until now been residual or heavy fuel oil (HFO).
Objective
The general objective of the Helios project was to develop a generation of electronically controlled two-stroke low speed marine diesel engine that operates on high-pressure Compressed Natural Gas (CNG) and/ or Liquefied Natural Gas (LNG) as an alternative hydrocarbon fuel to HFO. A new ship engine generation is needed in order to intensify the greening of waterborne transport. The gas engine provides a higher efficiency as well as significant reductions of pollutants and greenhouse gasses. Combined with EGR it complies with IMO´s environmental restrictions. The IMO’s Marine Environmental Protection Committee (MEPC) has introduced emission targets which will affect the maritime industry in the coming years. Within this context Liquefied Natural Gas (LNG) is increasingly seen as a cleaner and viable alternative to heavy fuel oil. LNG as fuel has the potential to reduce the CO2 emissions by around 23% and SOx to almost zero depending on the gas composition. Other environmental benefits are:
NOx 24% reduction
PM 85% reduction
Methane “slip” 0.2-0.3 g/kWh
CO Very low
Smoke Almost eliminated
Thermal
efficiency Very high
Shale gas
Simultaneously with the new environmental requirements shale gas is becoming available offering an alternative fuel at very low prices especially in USA. Shale gas can also become a big new energy source in e.g. China and Europe. This develops a part of the background for future market demand for gas fuelled engines.
Benefits in the maritime sector
Helios has provided a step forward for the maritime sector in a new emerging technical area. Helios safeguards Europe’s leading position in the field of two-stroke ship engines.This is to the benefit of the market sector, including the sub suppliers, but also to the ship owners, as it balances the Asian dominance of the supply side. At present, core technology in marine main propulsion engines is held by European companies. However large two-stroke engine manufacture is almost entirely done on license and has predominantly moved to East Asia. The large two-stroke engine manufacturing companies are increasing in size and the financial strength now comparable or even larger than the European licensors. The European licensors' success is depending on keeping a lead in technology which can be licensed for local manufacture otherwise the engine manufactures will be motivated to built up own capabilities in engineering and R&D. Helios strengthens the knowledge base in Europe and enables sub suppliers to take part in the manufacture of gas fuelled engines.
Challenges
Helios included a number of rather great challenges. First of all, the thermodynamic efficiency of the gas engine must be very good, requiring the engine to run with at least similar if not higher compression ratios than HFO engines. Hence the usual premixed combustion concept used on conventional gas engines cannot be used - instead the gas fuel must be burned under Diesel-like conditions, despite the poor ignition properties of gas. As gas, by nature, will reduce particulate emissions and accordingly nearly eliminate abrasive wear, this mode of operation fundamentally opens the possibility of using new high temperature materials, allowing higher exhaust gas temperatures and hereby improving significantly the efficiency of waste heat recovery (WHR) systems, with improved total energy efficiency as a consequence.
Activities and tests
The main objective of the project was to establish a suitable R&D platform to reflect a new generation of technology in engine optimization, control, monitoring and in emissions control. A large part of the work within Helios was related to tests of various types, from functional tests of the gas engine platform, tests for compliance with current emission legislation and tests for optimization of engine concept with regard to fuel economy. Throughout the project, advanced measurements and diagnostics methods were applied in order to gain insight in the physical processes of gas injection, pilot fuel injection, ignition, combustion and emission formation.
Further, the marine engine research and optimization frame opened the regime of higher exhaust gas temperatures, contributing significantly towards advanced utilization of the waste heat recovery systems. A distinct part of the project aims towards the gas engine monitoring in automatic tuning for best engine performance, complemented by building specific tools and algorithms for assessing and recording of the engine on line optimized energy efficiency.
The Helios activities can be categorised as applied science and development with a clear market focus.
Safety
Safety of a gas fuelled engine is a central issue and directed the technical development during the project. The MSC.285(86) “Interim Guidelines on Safety for Natural Gas-Fuelled Engine Installations in Ships” is the valid Guideline until the International Code of Safety for Ships using Gases or other Low flashpoint fuels (IGF-Code) will come into force. The IGF-Code is currently under development and the Code will probably come into force in 2016. In contrast to the Interim Guideline the IGF-Code will also cover internal combustion engines with a high pressure gas injection system.
Innovation potential
The development of a new engine generation involves challenges, but its innovation potential is great. A ship engine is a very advanced and complex mechanism consisting of a number of technologies and components. The technology and components can be changed and developed in the search of a perfect engine.
Helios generated a number of technologies that have great spin-off value by their own e.g. a gas composition sensor system and the components for gas supply. The application of high-temperature materials onto existing components will enhance significantly the efficient energy utilisation potential on a wider market. The developed diagnostics methods, sensors and online calibration procedures will contribute to the overall technological progress of European industry. The developed concepts for high-pressure natural gas storage and distribution will form the basis for new standards on high-pressure gas handling in the energy industry.
Helios resulted in a gas injection system together with an additional injection system for small amounts of Diesel fuel (the so-called pilot injection) to ensure a safe ignition at all operating points. This required an entirely new system for engine control and monitoring that was designed and also optimized for different operating conditions. Due to the poor ignition properties of natural gas, the cylinder processes is monitored continuously with a system of sensors and electronics that will require calibration with the engine in operation. Furthermore, the control system is able to deal effectively with the uncertainty of the actual gas properties for continuous optimization of the fuel efficiency. The lack of sulphur in the natural gas, although beneficial from an environmental point of view, leads to tribological challenges, because sulphur components have, generally, very good lubrication properties. That was investigated during the project. The change of fuel to natural gas will not only involve changes to the engine, but will require the development of guidelines and rules on how to install tank and distribution systems for natural gas on board of ships. The increased exhaust gas temperatures, aiming at better utilization of waste heat recovery systems, lead to excessive thermal stress on certain critical engine components.
The innovation potential of a ship engine was fully exploited in Helios and transformed into new products. A new ship engine generation was created including a range of new products, components, methods and tools.
Project Results:
WP1 Zero-emission marine gas engine
Objective
The main objective was to develop and verify a research platform being able to operate on natural gas based on the existing MDT research engine in Copenhagen.
Results
Conversion of the research engine to gas operation required installation of new components, development and testing of components as well as development of a new safety and engine management system. Furthermore, the data acquisition system, to be used for testing in the other WPs, was designed and installed. The list below is showing further parts of WP1:
• Development, design, purchase and installation of equipment
• FMEA , Failure Mode Effect Analysis
• Authority approval off gas supply system
• Education of personel according to ATEX rules
• Running-in of systems
• Design of special ME-GI component tools
The tasks were successfully carried out and according to the time schedule. The running-in of the new engine as well as basic performance tests included a large efforts. The engine operation on gas amounted to 420 hours and 301 tonnes of gas were used.
The WP was a research platform and enabled a number of tests carried out for the other WPs.
The tests for other WPs pushed the development of gas engine components and methods. Carrying out the tests with external partners was appreciated as it generated new ideas and approaches. In total 14 longer tests were carried out. In addition to that a large number of smaller tests were made simultaneously with other major tests.
Conclusions
WP1 included the very basic efforts of the construction of a gas fuelled engine. The system was developed and the wide range of components have been installed. On that new technical basis it has been possible for MDT to offer two stroke gas engines to the market.
WP2, Testing and optimisation towards compliance with current standard
Objectives
The overall main objectives of WP2 were to demonstrate that the ME-GI two-stroke engine can meet the current Tier II NOx emission legislation, and that it has an efficiency which is competitive with that of the same type of engine operating on conventional diesel oil/HFO. Those two objectives were to be met while ensuring that the engine stability in terms of combustion quality as well as variations in engine torque and speed should be as good as for the conventional ME engine.
Research and results
In WP2 systematic parametric tests were carried out in order to reduce engine out emissions while maximizing the thermal efficiency, over a range of engine loads. The performance when operating on gas was benchmarked against conventional operation on diesel. After the construction of the research platform in WP1 three longer measurement campaigns were executed within WP2. The first campaign in May/June 2011 included performance and emission measurements. In this campaign a reduction in NOx was demonstrated, but gas consumption could not yet be measured. In a second measurement campaign in August 2011 a first first gas consumption evaluation was performed, albeit at limited precision. The NOx reduction potential of co-combustion of pilot oil and natural gas was confirmed with NOx reductions from a Tier II level to approximately 30% below that level. The third and most extensive measurement campaign was conducted during March/April 2012. The results of this campaign are presented below. In total 81 full engine tests, including specific fuel oil /gas consumption (SFOC), emission, performance, and materials temperatures measurements, were performed in this campaign as part of a design of experiments (DOE) optimization study.
Direct benchmarking of gas mode operation against diesel oil mode operation was made. A significant reduction in NOx emission of approximately 24% (cycle average) as well as a slightly improved SFOC was documented. This could be achieved without any deterioration in cycle-to-cycle combustion stability. As the engine fulfils Tier II emission limits for NOx already in diesel mode, the gas engine thus fulfils Tier II NOx limits with a wide margin.
Unburnt hydrocarbon (UHC) emission are, howeer, more than doubled when switching from diesel oil to gas. This is not explained by an increased methane slip, as the measured methane slip (potent green house gas) is actually very low compared to duel fuel and lean burn Otto engines (<10 times) with low pressure gas fuelling. The main reason for this is the fact that the gas is combusted while it is being injected directly into the combustion chamber, just like a conventional diesel spray combustion process. CO2 emissions are decreased by about 23% compared to diesel operation. This combined with the effects of the methane emissions results in a total decrease in green-house gas (GHG) emissions of around 20% compared to diesel operation.
The NOx reduction provided by the switch to gas offers further efficiency improvements, otherwise not accessible due to emission legislation. By increasing the compression and maximum cylinder pressures the SFOC could be reduced on the account of increased NOx emission (while still keeping below that of diesel oil mode operation). It was demonstrated that it is possible to reduce SFOC by more than 4 g/kWh from diesel oil to gas at 75% load (and even more at 50% load) in this way.
Conclusion
The gas engine performance and emissions mapped out in WP2 have formed the basis for the engine specifications offered by MAN for the ME-GI engine family, and has demonstrated that operation below TierII NOx emissions limits is possible. It has thus directly contributed to the successful market reception of the ME-GI concept, which has eventually resulted in several orders being placed.
WP3 Zero-emission marine gas engine
Partners: MDT and ULUND
Objectives
WP3, which covers three different research themes: 1) operation with exhaust gas recirculation (EGR) in order to reduce NOx, 2) tests of early injection of gas to achieve partially premixed combustion aiming for NOx reduction and to investigate safety aspects, 3) laser optical investigations of gaseous fuel injection, ignition and flame propagation, as well as surface temperature measurements on critical components, to further understanding of in-cylinder processes.
Research and results
A full comparison was performed between engine operation on diesel and on gas, with and without EGR. The use of EGR was demonstrated to drastically reduce the levels of NOx emissions, at the cost of slightly increased specific fuel oil consumption (SFOC). From operation at 25%, 50%, 75% and 100% load the cycle weighted specific NOx emissions could be calculated. For gas with EGR they were found to be about 20% below the future Tier III emission limits.
Early injection of gas was investigated in tests performed on a single cylinder, with a single gas injector in operation. For the early timed gas injections unstable operating conditions with occasional gas misfires could be reached, with large cycle-to-cycle variations.
A number of optical measurement campaigns were undertaken on the ME-GI engine, in collaboration with WP8. The spectral content of flame emission both in diesel and gas operation was mapped out, high-speed photography both in the visible and in the UV was performed, surface temperature measurements using laser excited thermographic phosphors were demonstrated, and laser-sheet fluorescence imaging of the gas jet was attempted.
A high-speed movie of the flame ignition and propagation is shown below. In this view, the gas atomizer is located to the left of the pilot atomizer. At the beginning two quite distinct flames are seen, with the rightmost pilot appearing brighter, as the gaseous combustion will form less luminous soot at a lower temperature. The brighter pilot flame is then seen to penetrate into the larger gas flame. At around 15 ms the pilot fuel is being switched off, and in the later parts of the sequence the gas flame is seen to continue burn.
The engine cover for gas operation was fitted with extra diesel injector holes. Those, as well as the starting air valve, could be used to obtain optical access to the combustion chamber. For this purpose two different types of insert were manufactured. The first type could be inserted into a fuel injector port and featured a borescope connected to a camera. The second type could be inserted into the starting air valve and featured laser sheet forming optics and a prism for laser sheet steering. Both types were fitted with sapphire windows at the end, protruding into the engine cylinder. Through careful engine operation windows could be kept reasonably clean for several hours during gas operation.
Conclusion
Compliance with Tier III emission limits will be crucial for ME-GI engines sold in 2016 and afterwards. The demonstration of ME-GI operation well under those limits, through the use of EGR within Helios WP3 was thus a very important milestone for ensuring future success of the ME-GI concept. The experiences gained through optical studies of the gas ignition and combustion process will assist future efforts aimed at optimizing the ME-GI process further.
WP4 High temperature components marine gas engine
Objectives:
• Development of heavy duty Dual Fuel P/M HIP compound exhaust valve spindle
• Ability to withstand heavy fuel related high temperature corrosion
• Ability to withstand high temperature seat wear during service on gas with reduced deposits
Research and results:
• Selection and development of qualified materials
• In depth characterisation of metalurgical, physical and mechanical properties of material candidates.
• Characterisation of material interaction at bonding zones and influence on the mechanical properties
• Development of a design, based on FEM modelling and calculations
• Development of a production concept including production parameters
• Production of first prototype spindles
• Prototype service test and first inspections on commercial vessel
WP5 Gas engine tuning for best energy efficiency
Objectives of WP5:
• Development of a gas control and performance strategy that enables the engine to run optimized for energy efficiency.
• To tune the engine to achieve optimum efficiency requires a robust method for extracting the key performance parameters for input to the gas control strategy. Development of algorithms for robust extraction of these parameters becomes central point hereof.
• Development of algorithms and methods for evaluating energy efficiency improvements, hereby validating tuning of the engine for best performance.
Results:
A gas engine control strategy has been developed to operate the dual fuel engine auto-intermittently in two fixed gas modes: Minimum pilot fuel oil (maximum gas) and minimum gas mode (maximum fuel oil). This solution avoids operating the gas engine with varying gas/fuel oil ratios. This strategy is, among others, driven by requirements set by IMO regulations, which requires test and verification of engine emissions at any operating load and fuel oil /gas mixture. At the same time, the gas control strategy reduces the task of identifying the set of parameters, which provides the best engine performance tuning, to just two modes; thus being equivalent to the control strategy of pure HFO operated engines. up, requiring an increased gas flow and at the same time an increased gas pressure. A solution was developed allowing to ramp up to full gas operation while using smaller components designed to deliver maximum capacity at steady state, was to increase the HFO pilot amount during ramping up the gas until a point at which the gas supply system is able to deliver the required gas amount.
For robust extraction of Pmax, various filtering techniques havebeen applied and tested with the aim of implementing these on the data acquisition hardware (PMI DAU) itself utilising up to 200kHz sample rate, rather than transferring the more sparse information included in the 360 pulse triggered values available at the PC application.
The activities in scope of the Helios project have included tests at a number of engines in order to validate and potentially adjust the algorithm for detection of TDC and measuring the indicated load of the engine. Initial tests using the research platform engine indicates that TDC can be identified within a standard deviation of less than 0.1 degrees, which is regarded to be within adequate precision.
Further, is was found that the geometry of the indicator pipe and the indicator valve dramatically influence the measured results, thus leading to a modified indicator design. Hereby reducing the observed heat flash effects as well as increasing the life time of the sensor.
Conclusion
The combustion process in a dual fuel engine operated on gas must be continuously monitored and close-loop controlled in order to operate the engine at its optimum performance level within the required safety and operational limits of the gas running mode control strategy. The current processes for a pure diesel operated engine are not sufficient in this respect.
A gas control strategy has been developed and implemented that allows for the standard auto-tuning functions already developed for pure HFO-operated engines to be implemented for the gas engine as well, including strategies for operating the engine in dual fuel gas/oil mixed mode and effectively controlling the engine while ramping up the gas amount without the need for excessive demands on the gas supply system.
Filtering techniques were successfully tested for extraction of a robust cylinder maximum pressure Pmax. Measures to ensure a more accurate measured mean indicated pressure was identified and implemented, including validating method for robust determination of top dead center.
WP6, Cylinder pressure measuring and calibration
Introduction
On-line pressure sensors for cylinder pressure measurement are an integrated part of the gas engine control and safety system. In order to maintain reliable operation of these sensors a traceable calibration concept is required, allowing the calibration of the on-line sensors without sending it ashore for calibration at an accredited calibration institute.
The calibration process must be able to be executed while the engine is running. The calibration process must allow to be executed by low skilled operators / crew on board.
Objectives of WP6:
• Identification of requirement for traceable calibrated online cylinder pressure measurements for control and tuning.
• Development of a concept meeting these requirements, including the procedures and the equipment that have to be applied.
• Implementation, testing and verification of the system for traceable calibration on a full scale test.
Results:
The description of the main features and characteristics of the intended solution as part of WP 6 was divided into three main sections, the hardware development, the software development and the execution of the calibration process.
The hardware concept and the software for communication between the calibration equipment and the DAU from the engine have been developed in close cooperation between the two partners MDT and Kistler.
The calibration equipment consists of the HCD (Handheld calibration device) and portable reference sensors with TEDS (Transducer electronic data sheet) called PiezoSmart®.This sensor stores the configuration data for determination of the gain and range and exchanges these parameters with the HCD thus errors due to manual data handling are prevented(human factor).The HCD is powered from the PMI-DAU from MDT, the bidirectional communication between the HCD and the DAU is realised by two AC-coupled LVDS lanes.
The HCD is controlled via an asynchronous full duplex serial interface the concept allows for full duplex
operation with the DAU as master and the HCD as slave.
Conclusion
The concept, procedure and equipment to execute a traceable calibration have been described and successfully tested in the laboratories of Kistler and MDT as well as at the MDT research engine in Copenhagen. The concept for traceable calibration has been commercialised, by including it as a standard for all MDT ME engines, both Gas operated and HFO operated. The step 2 prototypes was completely CE-tested and certified by Kistler. In addition to that the robustness of the device was tested at MDT and Kistler through Highly Accelerated Lifetime Tests (HALT).
WP7 System criteria for high pressure onboard gas supply
Objective
The objective of the work package 7 is to establish design and safety specifications for a high pressure fuel gas supply system of a two stroke engine. In this regard the development of equipment for a safe fuel supply onboard as well as collision damage scenarios of the gas supply system of merchant vessels have been evaluated.
Investigations and results
The Interim Guidelines MSC.285(86) includes a collision resistance of gas fuelled vessels due to a minimum distance requirement of the LNG storage tanks from the ship outer shell depending on the ship type. Within the work package 7 the collision resistance of a gas fuelled 6500 TEU Container Vessel and a container feeder (1200 TEU) is investigated based on the GL-Rules I-1-1 Section 33 “Strengthening against Collisions”. Derived from the collision analysis safe and applicable distance requirements of the fuel containment for a two stroke engine have been developed and submitted to IMO within the IGF-Code development. The distance requirements of LNG storage tanks from the ship outer shell are still under discussion at IMO.
Another focus was given to the design of a gas conditioning and pressurizing system for the fuel gas supply to an ME-GI 2-stroke dual fuel engine onboard merchant vessel. Main aspects for development are the demand of the fuel gas supply and the interfaces to the ship / engine. This development includes an overview of possible variants of fuel gas supply systems. One criterion for the type of fuel gas supply system (FGSS) is the type of consumers. Also a process simulation of the main parts of the fuel gas supply was developed by TGE.
- Hazard identification (HAZID)
For the developed fuel gas supply system of a 1800 TEU container vessel a hazard identification (HAZID) was performed. The aim of the Hazid is to identify possible system weaknesses and to improve the system. The analysis was orientated on the Failure Mode and Effects Analysis method and the requirements given in IEC 60812. The analysis focussed on the identification of hazards caused by LNG or NG leakages.
A number of recommendations for technical and procedural measures have been identified to prevent failures, to reduce the failure frequency and the effects. The HAZID was limited to normal operation conditions (gas mode of the engine). The analysis showed that no single point failure can lead to a critical situation on board the vessel (high Risk area). If the actions mentioned in the Hazid will be successfully implemented, there are no objections for a safe operation of the system from this part of the risk analysis.
For safety reasons double walled pipes are mandatory for fuel gas supply systems onboard merchant vessels according to the Interim Guideline (MSC.285(86)) and the draft of the IGF-Code. For gas-fuelled two-stroke engines normally a ventilated double walled pipe from the fuel preparation to the engine is used. The required internal pressure can amount to 350 bar. There is no experience with high pressure double wall pipe systems on board so far.
- CFD
In order to determine the influence of the leak of the inner pipe on the integrity of the outer pipe for a jacketed pipe, a CFD and a finite element analysis was carried out by using finite volume / element software. The results from the CFD analysis were applied to the FE-model. In the CFD analysis the pressure and temperature acting on the inner surface of the outer pipe were determined.
Resulting from the internal pressure, the equivalent stress (von Mises) and displacement of the pipe were determined and compared with allowable values. It was shown, that the stress of the outer pipe of a jacketed piping is quite low in the case of a leakage compared to the high internal pressure of the inner pipe. The deformation and the corresponding stress are uncritical compared to the yield strength of typical pipe materials.
Conclusion
Within Work Package 7 design and safety specifications for the distribution systems for the high-pressure gas supply on board merchant vessels have been developed. The conceptual design principles ensure the safe interface between the gas supply system and the control and safety system of the engine. In addition the results of Work Package 7 have been presented at relevant committees to identify the legislative needs and to develop safe and applicable rules.
LNG as fuel is an environmental friendly and commercially attractive way of propulsion. It has been shown that technical and safe solutions for high pressure gas supply to ME-GI are available and approved by detailed research. The presented work package supports the application of this new propulsion concept onboard merchant vessel.
WP8 Optical cylinder diagnostics
Objective
The overall objective of Work Package 8 was to develop and apply advanced optical and laser based measurement techniques to assist in the development of the gas engine concept. Particular objectives were:
• Development and application of a surface temperature measurement technique for critical in-cylinder components based on a laser based phosphorescence technique.
• Application of laser based measurement techniques for visualization of fuel jets and flame propagation in order to study the fundamental processes regarding gas jet injection and ignition using the Diesel pilot.
Results
The work on detectors for phosphor thermometry resulted in improved knowledge about saturation effects and how these can be avoided, minimized or compensated for. Furthermore, one group of photo multiplier tubes (Gateable PMT’s) proved to be superior for this type of single-shot lifetime-based temperature measurements.
The in-cylinder phosphor measurements in the large bore gas engine were successful. For the first time, crank angle resolved surface temperatures could be probed in such a large engine during operation. Although not initially planned for, an additional measurement campaign on fiber based thermometry was performed at the end of the project. The final evaluation of this data has not been performed at present, but everything indicates that the fiber based approach is robust and capable of generating solid data also with minimal optical access. There is a mutual interest to proceed with this work also after Helios has ended. The surface thermometry research performed within Helios has generated several peer-reviewed papers, (see below).
The in-cylinder visualization of injection and ignition was overall less successful. The pre-studies performed at ULUND were all positive. Prof of principle measurements were successfully performed showing the feasibility of laser induced fluorescence imaging of both fuel tracer and formaldehyde under relevant engine conditions. The optical challenges of introducing a high power, ultra-violet, divergent laser sheet into the combustion chamber was solved and the performance was proven both in the laboratories at ULUND and in the research engine at MAN. Laser pulse energies according to the design goal could be delivered in the form of a narrow sheet, as desired, and sent into the engine without damaging the critical components in the boroscope.
However, as indicated earlier, there were severe problems with one of the steel inserts during the full scale tests at MAN. Hence, the PLIF imaging could not be performed as expected. The good news is that everything, including the mentioned pre-studies, still speaks in favor of the general approach used. The problems that prevented the PLIF imaging from being performed were of mechanical nature and as for the phosphor thermometry there is a mutual desire to continue this work.
Conclusion
The knowledge-building connected to phosphor thermometry has greatly benefitted from the Helios project. The fundamental study on detector non-linearity/saturation and signal evaluation routines would be very hard to perform in a similarly thorough manner without the Helios. The results generated here will improve measurement precision and accuracy, not only for the specific studies performed on the gas engine in the Helios project, but in general for all other applications where phosphor thermometry is employed. Surface temperatures could be measured, in this extremely harsh environment, with high temporal resolution (sub crank angle degree). Also from a knowledge-building perspective, Helios provided a unique opportunity for researchers in the academia to work on and get experiences from large scale marine engines running on new fuels.
Feasibility studies showed that it is possible to perform both fuel tracer and formaldehyde LIF imaging under relevant conditions. Furthermore the optical challenges imposed by such large engines with limited optical access could be solved, i.e. an optical device for delivering a high power laser sheet into the combustion chamber was developed and built.
WP9 Gas engine piston rings
Objectives
The objectives focused on providing solutions overcoming the bad tribological conditions expected to appear in gas engine without sulphur in the fuel.
Results
The suitability of the selected material candidates was investigated using the laboratory test, which indicated that they have a higher scuffing resistance than the materials used today. The test results also showed that even a minimum amount of oil present in the contact is enough to avoid scuffing.
The main findings of WP9 are very positive with regards to the design and materials selection for the gas engine piston rings:
No indication of abnormal wear was observed on the piston rings from the gas engine test in Korea.
The presence of high amounts of sulphur in HFO engines may provide some extra protection in cases of temporary lubrication failure. However, the rig test indicates that a minimal supply of oil to the ring/cylinder contact surface guarantees that scuffing will not occur.
a. Additional sulphur coming from the fuel oil shown not critical for avoiding scuffing.
b. No need to neutralize sulphuric acid by adding alkaline agents in the cylinder lubricant (as in HFO engine) => reduced risk to form deposits
=> this threat to the oil film eliminated
This indicates:
c. the risk for scuffing could be kept very low by just securing that the system for internal lubrication in the cylinder is absolutely reliable.
d. the system should guarantee that the whole cylinder circumference is lubricated, without interruptions.
If these points are fulfilled, no other special material-based solutions for the ring or cylinder liner should be needed. Nevertheless, if the reliability of the tribosystem is to be further strengthened, a proper coating with possibilities for oil retention and/or self-lubricating properties might be the solution. The test results indicate that the candidate materials have good properties for this.
Conclusion
In general positive results have been obtained indicating that wear and corrosion due to a sulphur free fuel can be avoided if an efficient lubrication system is used. Further investigations will be needed to understand the scuffing phenomena in engines and to ensure that the laboratory scale scuffing tests can be reliably transferred to engine conditions.
WP10 On line gas composition sensor
Objectives
The general objectives of WP 10 is to design and build an ex-proofed sensor system based on linear Raman spectroscopy for the on line analysis of mixture composition and calorific value of natural gas for a pressure up to 350 bar. In WP10, a sensor system based on Raman spectroscopy for the online analysis of mixture composition and its calorific content was designed and built. The main requirements of the system are a high accuracy, a high time resolution, a high mobility and a sensitivity to a multiplicity of different species. The system has to be able to measure at high pressures (up to 350 bar) and must not be affected by pressure and temperature fluctuations. Moreover, the sensor has to be ex-proofed. Main tasks of WP 10 are the design of the sensor and the sampling cell, the mounting and the high pressure testing of the gas cell, laboratory tests with suitable test gases at low pressure and high pressure conditions, the installation of the sensor at the test engine at MAN Diesel & Turbo in Copenhagen and the demonstration of the online-gas analysis.
Research and main results
The Raman set-up including a high pressure cell was integrated in the upper part of a compact, ex-proofed housing (600x800x500 mm). In the lower part, electrical devices like power supplies, signal converter and switch relays are located. The high pressure cell was made of stainless steel and is designed for a maximum pressure of 350 bar. The data evaluation is based on the contour fit principle, which compares theoretical spectra with experimental once. The theoretical spectrum is calculated by the superposition of the weighed spectra of the natural gas components, whereas the weight factors are determined by the spectrum of a gas mixture of known composition. From the gas composition, the upper heating value and the Wobbe index are determined.
Conclusion
Summarizing, all deliverables and the milestone were fulfilled. A comparison with the gas chromatograph was performed under laboratory and under technical conditions and showed good results. The high pressure cell was tested successfully at a pressure of 400 bar. After this successful pressure test, test measurements under high pressure conditions were performed with a special interest on the influence on pressure fluctuations on the accuracy of the measurement. Finally, the sensor was successfully applied to different runs of the gas engine.
Potential Impact:
Socio economic and societal implications
Helios was a joint European initiative to strengthen the two-stroke ship engine technology as a stronghold in Europe. It is of importance that this technology is of European origin, because it pulls a large sub supplier sector and counterbalance the Asian dominance within ship building. It is to the benefits of the large European shipping sector that the technology is concentrated in Europe. The two-stroke ship engines are manufactured in Asia, but many sub supplies from Europe are used. Helios has provided opportunities for European companies to become sub suppliers for the construction of many future gas fuelled engines. The partner companies of Helios have this opportunity and use it, but also companies outside the consortium have developed a technical basis for becoming sub suppliers, as they had tasks during the development of the gas fuelled engine. In this way Helios was a technical push, that resulted in innovations, new products on the market. It cannot be assessed how many jobs are being created due to Helios, nor can it be estimated what is the export value of the technology.
Helios is a technical response to the new environmental requirements in the field of shipping. The gas fuelled engine complies with IMO Tier II and III regulations when it is combined with EGR (Exhaust Gas Recirculation).The new gas technology shows the authorities that the environmental restrictions have a technical answer. The ship owners ordered 49 gas fuelled engines, which shows that the market is ready to implement new technologies in order to address the new international requirements. Among the orders are engines for LNG tankers, container vessels as well as a few engines for retrofitting.
Main dissemination
Helios has caused much dissemination. Among the major achievements were
- An open conference with 100 participants to explain about the Helios results as well as the gas engines in general
- Mentioning at the most important international conference for ship engines – ISME and CIMAC
- 21 scientific papers
- Features and opening articles in the leading shipping magazines
- More than 30 articles in branch media, incl. online presentations
Gas as a maritime fuel is a central issue that attracts much attention in the sector, so dissemination was successful. For example the press release of the final open conference resulted in at least 20 articles, though most of them online. The target groups of the dissemination included primarily the maritime sector, but also the specific scientific fields of tribology, thermal diagnostics and sensor systems. The coverage in branch magasines as "Marin Propulsion" and "Container, Shipping and Trad" was indeed satisfactory.
The webpage had 890 visits from many countries, among which most from Denmark (18%).
Exploitation of results
The largest exploitation result is that 49 orders for the delivery of gas fuelled ship engines have been signed. In each case these orders pull sub suppliers from the consortium or from outside.
Much new technology has been generated by Helios, when solutions had to be found. The major part of the technology can be commercialised, another part includes new scientific understanding that leads to further research.
The positive results have been generated in an innovation process, where the efforts were concentrated on:
- Research
- Development of components
- Development of methods
- Development of systems
- Establishment of standards
- Manufacture of prototypes
- Testing
The outcome of the cooperation and interaction within these efforts was innovation.
Developing the research platform generated a number of innovations, as new products, systems and tools were necessary to solve technical problems. After the reserach engine at MDT was ready, the interaction of development efforts and testing proved very effective. In this process the universities and the companies had a fruitful cooperation. MDT will continue the cooperation with ULUND and UPPU. It is also possible that the cooperation of ERL and MDT will continue as the gas composition sensor system would be highly valuable in the gas engine – but it stills needs development. The R&D efforts were focussed and well defined from the beginning – the goal was to construct a gas fuelled engine. In this way Helios was very market oriented and the market requirements were clear, defined by the IMO regulations. The successful introduction of the new gas fuelled engine in the market is to the benefit of the companies in the consortium. The companies were involved with:
MDT: Licensing of design and technolgy
GL: Clasification for new ships
TGE: Design of gas systems
Kistler: Delivery of handheld calibration device
The gas composition sensor system of Erlangen University is not yet fully ready for the market, but it has the possibility of a succesful commercialisation, as the demand exists in the maritime sector, but it would also be valuable in other sectors, e.g. within biogas utilization.
Sandvik is at the moment not a sub supplier to the engine manufacturers, but its patented production process of high temperature materials certainly has bright perspectives and a generic character.
The gas engine is a locomotive for innovations and exports.
List of Websites:
www.helios-fp7.eu
Niels Freese
MAN Diesel & Turbo
Niels.Freese@man.eu
