Studying the potential efficiency of low heat rejection HCCI engines with a Stochastic Reactor Model 2009-24-0032

The main losses in internal combustion engines are the heat losses to the cylinder walls and to the exhaust gases. Adiabatic, or low heat rejection engines, have received interest and been studied in several periods in history. Typically, however, these attempts have had to be abandoned when problems with lubrication and overheating components could not be solved satisfactorily. The latest years have seen the emerging of low temperature combustion in engines as well as computational powers that provide new options for highly efficient engines with low heat rejection.

Stochastic Reactor Models (SRM) are highly efficient in modeling the kinetics decided low temperature combustion in HCCI and PPC engines. Containing the means to define the variations within the cylinder while employing detailed chemistry, micro mixing and heat transfer modeling, the interaction between heat transfer, exhaust gas energy and the combustion process can be studied with the SRM. A multidimensional study was setup with the SRM to investigate the interaction between heat transfer, exhaust gas energy and the combustion process and its dependency from level of cylinder wall thermal insulation or heat storage, inlet pressure, inlet temperature, mixture strength, mixture and temperature stratification, compression ratio, valve timing, residual gas amount and fuel effects. The investigation reaches into combustion and engine operating regimes that so far have not been investigated experimentally before.

It is found that by using this combined approach a multidimensional span of engine and combustion characteristics can be produced, giving deeper insights in the potential for efficiency increase through combined low temperature combustion and low heat rejection.