Model-based combustion chamber layout for passenger car Diesel engines

The development of the optimal combustion process is a challenge engineers have been struggling with for a long time. The optimization of all the different hardware parameters like combustion chamber geometry, swirl, nozzle flow, number of nozzle holes, tip protrusion and so on, is a big challenge and is currently performed with the use of single-cylinder up to full scale engine testing. More stringent legislation on emission control, growing system complexity and variant diversity make it especially challenging to develop an optimum combustion system. Although tools like CFD are already well accepted and applied in the industry, there is still potential to better support the hardware development phase. Remaining efficiency potential needs to be exploited in an economic way. In this paper we present a new approach to combustion process development. With high speed CFD simulation a large number of different hardware combinations (tens of thousands) are calculated. The results of this huge parameter study are used to set up a multi-dimensional DoE model using AVL’s CAMEO tool. Finally the optimization within the model space for best fuel consumption / Soot emission trade-off can predict which hardware configuration is the most promising, but also which one should not be tested. Finally a validation on the test bed is required. By using this novel approach the most promising hardware for optimal combustion can be found swiftly and efficiently. This reduces the time required at the engine test bench thus significantly reducing the costs while allowing more parameters to be investigated.The piston bowl and fuel injection system defined by 3D CFD was tested by VCC (Volvo Car Cooperation) on a single cylinder test bed and the findings of the CFD based layout could be confirmed.