Numerical Research of Combustible Mixture Inert Components Influence on Compression-Ignition Engines Combustion Process

Abstract

An expression is suggested for determining the coefficient of the oxygen reaction activity K₁ when modeling the process of fuel combustion in the compression-ignition engine. Using coefficient K₁ allows modeling the decrease in the rate of combustible mixture combustion due to the inert components in case of the changes in mixture composition caused by combustion and exhaust gases recirculation (EGR). The numerical research has been performed for the process of combustion of the homogeneous mixture of air and dimethyl ether in the constant volume chamber. The increase in the inert components content in the combustible mixture in case of the EGR (increase of the residual gases coefficient from 0 up to 0.5) results in the slowdown of the dimethyl ether combustion process, decrease in the maximum combustion rate and postponed achieving of this rate. The maximum calculated combustion rate without consideration of the inert components decreases by 23.8%. Taking into account the inert components, it decreases 2.52 times by using coefficient K₁. In the first case, the maximum combustion pressure decreases only by 0.3 MPa and is registered 0.04 ms later. In the second case, the maximum combustion pressure decreases by 0.46 MPa and is registered 0.41 ms later, though the initial amount of oxygen decreases identically—1.86 times. The main causes of the slowdown of the dimethyl ether combustion in conditions under study are the decrease in the initial amount of the oxygen molecules and the 1.53 times decrease in the reaction activity of oxygen.