Cutting diesel engine pollutant emissions down to size
The majority of heavy-duty vehicles on Europe's roads are powered by diesel engines that are often associated with noxious air pollution. Engineers have taken up the challenge of reducing these harmful emissions. The GROWTH Programme is supporting their efforts by funding targeted research projects, such as AHEDAT. One of the objectives of AHEDAT was to deliver reliable modelling tools. Scientists with the National Technical University of Athens (NTUA) in Greece were assigned the task of validating a combustion model. They worked with experimental data generated with a test engine run with different air-fuel mixtures at various load levels. With respect to engine parameters, NTUA's analysis indicated that the evolution of cylinder pressure was correctly calculated by the model. A high correlation between model output and measurement data was also observed in the case of Brake Specific Fuel Consumption (BSFC). In addition, NTUA demonstrated that the negative impact of fuel rich combustion on BSFC is minimal, especially at higher loads. However, peak combustion pressure was slightly reduced despite efforts to advance fuel injection. Finally, while exhaust temperature is generally well forecast, some additional model development is needed to ensure thresholds are not exceeded. The model also exhibited the capacity to properly handle pollutant emissions. Estimates of nitric oxide (NO) compared well with field data. Interestingly, the Greeks were able to confirm that NO emissions are, fortunately, not boosted by rich combustion. However, soot production does increase proportionally with the amount of fuel in the air-fuel mixture. Future engine modifications should take these findings into account.
