Validation of Turbulent Combustion and Knocking Simulation in Spark-Ignition Engines Using Reduced Chemical Kinetics 2015-01-0750

Downsizing or higher compression ratio of SI engines is an appropriate way to achieve considerable improvements of part load fuel efficiency. As the compression ratio directly impacts the engine cycle thermal efficiency, it is important to increase the compression ratio in order to reduce the specific fuel consumption. However, when operating a highly boosted / downsized SI engine at full load, the actual combustion process deviates strongly from the ideal Otto cycle due to the increased effective loads requiring ignition timing delay to suppress abnormal combustion phenomena such as engine knocking. This means that for an optimal design of an SI engine between balances must be found between part load and full load operation. If the knocking characteristic can be accurately predicted beforehand when designing the combustion chamber, a reduction of design time and /or an increase in development efficiency would be possible. A turbulent combustion simulation is required to estimate the pressure and temperature trace in the cylinder for knocking analysis.

In this research, the verification for the turbulent combustion and knocking were done by using the detailed chemistry solver with multi-zone modeling integrated into CONVERGE CFD code. Thereby, it was found that a reduced reaction model can reproduce turbulent combustion and knocking phenomenon under some operation conditions. The verification results show that the pressure trace in the cylinder, Knocking timing and position can be validated with experiment results accurately.