Analysis and Multi-Parametric Optimisation of the Performance and Exhaust Gas Emissions of a Heavy-Duty Diesel Engine Operating on Miller Cycle

A major issue nowadays that concerns the pollution of the environment is the emissions emerging from heavy-duty internal combustion engines. Such concern is dictated by the fact that the electrification of heavy-duty transport still remains quite challenging due to limitations associated with mileage, charging speed and payload. Further improvements in the performance and emission characteristics of conventional heavy-duty diesel engines are required. One of a few feasible approaches to simultaneously improve the performance and emission characteristics of a diesel engine is to convert it to operate on Miller cycle. Therefore, this study was divided into two stages, the first stage was the simulation of a heavy-duty turbocharged diesel engine (4-stroke, 6-cylinder and 390 kW) to generate data that will represent the reference model. The second stage was the application of Miller cycle to the conventional diesel engine by changing the degrees of intake valve closure and compressor pressure ratio. Both stages have been implemented through the specialist software which was able to simulate and represent a diesel engine based on performance and emissions data. An objective of this extensive investigation was to develop several models in order to compare their emissions and performances and design a Miller cycle engine with an ultimate goal to optimize diesel engine for improved performance and reduced emissions. This study demonstrates that Miller cycle diesel engines could overtake conventional diesel engines for the reduced exhaust gas emissions at the same or even better level of performance. This study shows that, due to the dependence of engine performance on complex multi-parametric operation, only one model achieved the objectives of the study, more specifically, engine power and torque were increased by 5.5%, whilst nitrogen oxides and particulate matter were decreased by 30.2% and 5.5%, respectively, with negligible change in specific fuel consumption and CO2, as average values over the whole range of engine operating regimes.