Alternative fuel for heavy duty (AFFORHD)

A tribology test method for high vapour pressure liquids has been completed. This method uses a pin on rotating ring method to determine friction coefficients and wear between surfaces lubricated by high vapour pressure liquids. Friction and wear with pure DME have been studied, and the high wear nature of pure DME with basic fuel injection pump materials confirmed. DME results were compared to unlubricated surfaces, and were better than no lubrication, but far from results with acceptable diesel fuel. Material tests have been performed with diamond like carbon coating on both parts. With DME, the friction was halved, but the wear was unacceptably high. Tests with additional coating materials are planned and sample preparation underway. The test method will provide a test method with which to correlate test results from future DME injection systems, and the intention is to eventually provide a test bench procedure for the development for materials in DME injection pumps prior to production. This method, when combined with results from lubricity testing, should be applicable to development of high-pressure pumps for a wide variety of fluids for transport (petrol, lpg, diesel fuel) as well as many other process technologies.

BP, being a major oil company, has the ability to estimate the fundamental parameters dictating the "Delivered Cost of DME to Europe". The total delivered cost of DME to a European filling station will be the result of economic interactions between: -·feedstock gas price, -·DME plant location, size, and infrastructure development required, -·shipping cargo size, -·distance / shipping costs from the DME plant to a terminal, -·distance / shipping costs from the terminal to fleet depot, -·necessary new infrastructure needed, -·and any modifications necessary to existing infrastructure used. The economic optimum of these interactions as well as final DME market price would factor into where to site the plant and the terminal. To reduce unit costs, large DME plant and LPG ship sizes were assumed (7,200 tonne/day of DME and 75,000m3). The AFFORHD LCA report average round trip distances for transporting DME were 1,500km one way (1,600 nautical miles round trip) by ship to a terminal and 160km by truck from a terminal to a filling station, respectively; this is the minimum distance for supplying DME to Europe based on manufacture in Algeria and delivery to a Naples, Italy terminal. To be consistent with the LCA report, this study's base case sited the DME plant in Algeria and the receiving terminal in Naples, Italy. DME's physical properties are such that it can be handled, stored, and transported like LPGs. This study uses LPG shipping, trucking, and depot costs - adjusted for physical properties - for DME. The main conclusions are: - DME can be delivered to a European fleet depot for a cost of between 0.20 and 0.22 euro / litre as energy equivalent of diesel based on a natural gas feedstock price of $ 0.75 / MM Btu. - For Brent crude oil prices of between 20 and 30 $ / barrel, 10ppm sulphur diesel can be delivered to a European fleet depot for a cost of between 0.19 and 0.25 euro / litre. - These delivered costs are before government taxes and duties. -·DME and diesel delivered costs are directly competitive on a $ / tonne basis at $0.75 / MM BTU gas and 26 to 30$ / barrel Brent, depending on DME shipping distance. -·Economies of scale (larger plant and ship sizes) reduce the unit costs of delivering DME to market.

Combustion system investigations with DiMethyl Ether (DME) have been carried out on a single cylinder test engine within the AFFORHD project. The purpose of these tests was to identify the combustion system requirements for a compression ignition engine using DME as the fuel. Investigations into injection pressure (up to 750 bar), injector spray configurations, and intake swirl level and combustion bowl shape were carried out. From this a preferred combustion system has been demonstrated and these results were transferred to the multi-cylinder engine being used for the project. Tests have been made on a six-cylinder heavy-duty engine fitted with a prototype fuel injection system developed within this project. The results of the combustion development investigations were applied to this engine.

As part of the AFFORHD project a FMEA (Failure mode and Effect Analysis) type safety assessment of the DME fuel system has been carried out. A FMEA is a well-known technique, which provides a quick insight into the hazards of an installation. The conclusion of this assessment was that the main risks are presented by DME leakages and by failure modes located in the tank system. Due to the specifications of all the mechanical parts (LPG guidelines like R67), leakages are supposed to present a risk comparable to that of a gasoline type motor, the higher severity balanced by a lower likelihood.

Following the development work of the individual parts of the project the integration of all parts into the vehicle was performed at Volvo. This was done to integrate into the vehicle the complete engine with new fuel system, fuel supply system and electronics and solve integration related issues as they appeared. This work was successfully carried out and resulted in the final AFFORHD truck. In particular the following subsystems were put together in the vehicle: - The fuel tank and fuel supply lines with integration of the tubes for low-pressure transport of the fuel and the cooler. - The injection system on the engine. - The electrical harness according to new-implemented functions. The work also included final de-bugging for tuning. Following the integration part was tuning the overall system on the vehicle to reach drivability target while maintaining the same emissions and fuel consumption. The vehicle development work was mainly concentrated on emissions and start up strategies. Calibration activities were limited to that needed to reach emission and consumption objectives, and such that the field test could be conducted without problems. The experimental part was dedicated to the precise evaluation of the behaviour of the vehicle developed for running on DME. In combination with the fine-tuning of the transient driving behaviour and the speed governing of the engine resulted in a representative vehicle for validating the DME technology. The main part of the vehicle control hardware is standard Volvo equipment, which has been put through an Electro Magnetic Compatibility [EMC] test. As the complete vehicle has been finally tuned for field tests it will be put through an EMC test to avoid any problems during driving with the interference of electro-magnetic radiation.

The Life-Cycle Assessment (LCA) has focused the environmental impact linked to the use of Dimethyl ether (DME) as an alternative fuel for heavy-duty vehicles. The method, which is used in this project, is Life Cycle Assessment according to ISO 14040, which is used to investigate and calculate the environmental impact of a product or system over its whole lifetime. The LCA includes "Well to Wheel" data for DME and Fisher Tropsch Diesel (FTD). Methanol is included on "Well to Tank" basis. The main conclusions are the following: - DME from natural gas has the highest energy efficiency. - DME from biomass gives the best potentials for CO2 reductions. - FTD from natural gas has slightly higher energy efficiency than DME from biomass. - FTD plants have a multiple output of products. This leads to even lower energy efficiency since a large portion of the output cannot be used in the energy efficient diesel driveline. - According to EPS the environmental impact of both fossil and bio fuels are strongly linked to use of resources. The main recommendations are: - In order to use limited energy resources in the best way DME are to be preferred compared to MeOH and FTD. - In order to decrease CO2 emissions from heavy duty vehicles in the most efficient way, DME should be chosen as fuel when produced via energy source gasification.

Within the AFFORHD programme, a fuel injection system for the direct injection of Dimethylether (DME) into a heavy-duty diesel cycle engine has been developed. The system is a 'low pressure' common rail type system and comprises a high-pressure pump, rail and injectors with associated components and devices. Emphasis has been laid on the particular characteristics of DME, namely its low lubricity, low viscosity and special requirements in terms of elastomers and sealing. Suitable solutions have been found for the system and prototype systems have been produced for use in the project. The system has been extensively tested on the test rig before fitting to the engine. Durability tests have also been carried out, indicating that the system has reached a sufficient degree of maturity for the requirements of this project. The system injects the required quantities of fuel at the required pressures and timings into the cylinder at the desired pressures. Engine tests indicate that the system meets the targets and the engine performance targets have been met. In addition to good engine performance, low emissions levels (NOx <2.0g/kW.hr) with spotless combustion have been achieved.

From existing DME fuel systems is known that tank systems with electronics inside the DME tank have a high failure rate. DME has no lubricity properties and it harms most gasket- and o-ring materials. With that in mind a solution was sought for a DME feed pump that needs no electronics inside the tank and has no sliding parts that are in contact with DME. The result is a DME feed pump with an active inlet valve, capable of pumping 2.2 litres of DME per minute at a pressure of 15 bars. The pump is mounted inside the fuel tanks and operated by hydraulics. Only one hydraulic connection going into the tank is necessary. This pump can also be used for other gaseous fuels that are stored in a liquefied form like LPG. A prototype of this low pressure DME feed system has been built into a Volvo truck. The system comprises 5 tanks of 116 litre each as well as hydraulics and electronics for autonomous operation. Independent of flow the system delivers DME at 15 bars towards the high-pressure fuel injection system at the engine. At the end of the project the truck with this fuel feed system installed operated properly, a field test is foreseen.

A new generation Volvo fuel injection control system (FIE ECM) was modified for use with the DME fuel injection system developed by AVL PTI. New software was developed to control the common rail type DME fuel injection system. The control system was developed so that project partners could develop and implement new DME specific algorithms. After implementation of the functionality a period of optimisation work followed with new software and datasets being installed and run on the engine at AVL NA with the purpose of running it in a vehicle. The engine control system was run in a large engine speed/load area with the pedal and at the same time the engine speed was changed with the dyno. All the controllers were active and worked well enough to have the engine installed in a vehicle. Also the starting functionality was tested and found to work in the test bench. During the last months of the project the engine was installed in the vehicle and the ECU was found to perform well also in this environment and the operation of the vehicle was successfully demonstrated at the final project meeting. The new software gives a short software development loop, necessary for the optimisation work in this project. The hardware has reached a very production like appearance and the software optimisation work has met the target of Euro5 exhaust emission level.

A combination of experimental and theoretical (Molecular Dynamics Calculations) calculations has improved our understanding of the processes involved in the region of boundary lubrication. For simple molecules, the influence of molecular structure has been shown, and a new lubrication region called "Quasi-Boundary lubrication has been proposed. In this region, continuum properties, such as viscosity are not meaningful. This study represents the first time that the fundamental processes leading to wear and friction have been studied in detail with molecular dynamics, and results correlated with experimental lubricity testing. It has been shown that a primary property influencing the lubricity is the number of atoms per unit surface area present in the final molecular layers of lubricant squeezed out from between the lubricated surfaces. It has also been shown that long chain type molecules have better lubricity properties than their branched isomers. Though viscosity is not the property that best describes lubricity considerations (boundary lubrication), this is not to say that viscosity is insignificant, as it is important in many other situations. Since few studies of lubrication have been performed with high vapour pressure liquids, additional viscosity measurements have been made with these fluids to supplement previous DME results. These results are significant in future studies of lubrication with low viscosity substances in particular, but also with other lubricants where boundary lubrication is encountered. Through an understanding of the basic processes involved, future developments in lubricity improving additives and surface materials and treatments can be based on fundamental principles instead of conjecture. This may make it possible to develop more effective solutions to boundary type lubrication, not only with DME but also with a large number of other lubricants in other physical situations. Work in progress is underway for more complicated molecular structures, such as branched chain molecules and molecules with dipole moments. The results of the work are routinely and promptly presented in relevant scientific journals and technical conferences.

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