Numerial Simulation Study Of Nitrogen-richened Air Combustion Process And Emission In Diesel Engine

Energy source and environment protection are main problems that confronted to the humankind.As the development of society,the amount of automobile increase and automobile not only become the main energy consumption source but also the largest emission pollution resource.As a developing country,the conflict between energy source and environmental protection should be resolved to keep the country harmonious and sustainable development.The researchers in the internal combustion engine business should find new combustion form with higher thermal efficiency and corresponding alternative fuels.Nitrogen -enriched combustion——one of the clean combustion method,with the potential of high efficiency and low emission has been one of the hottest topics in the world. Along the experimental works,Nitrogen-enriched simulation on the combustion model,combustion mechanism and variable parameters had been paid much attention.The important pocession production density of H2O2&CH2O of Nitrogen-enriched combustion was investigated with gas reaction chemical kinetics software-CHEMKIN combined with n-heptanes detail reaction mechanism.The effects of intake charge temperature,rotate speed and the nitrogen concentration in the air were studied,which to n-heptane combustion;Second ,the CAE software GT-POWER that is one module of GT-SUITE was used to simulate Nitrogen-enriched combustion in diesel engine.The effect of the nitrogen concentration in the air and rotate speed were studied and the results show:1. When the intake charge temperature is certain,along with in nitrogen increases contently,the production district of CH2O becomes wide,the peak rises.As nitrogen concentration in the air raises to 82%,after 30/°TDC,the total amount of the CH2O varies little.That says the CH2O doesnot oxidation consume any longer in the high temperature reaction,which is counteract by the nitrogen.As the nitrogen enriches,the timing of the peak of pocession production H2O2 delays.When the nitrogen concentration in the air reacher one certain point,the reaction H2O2+M→OH·+OH·+M can't carry through successfully,which is one of counteraction by the nitrogen.The more N2 in the charge,the more obvious of the behave of fire retarding agent.2. In the n-heptane combustion process,as the nitrogen concentration in the air enriches, the effect of important pocession production of CH2O is very obvious,which behaves fire retarding agent character of N2.At the same time, the effect of intake charge temperature is also obvious.When the nitrogen concentration is kept constant,as the intake charge temperature rises, the timing of the peak of pocession production H2O2 advances,the peak of pocession production H2O2 reduces,the production district of H2O2 becomes narrow. As the procession production,H2O2 oxidation consumes quickly,which is beneficial to the n-heptane combustion.3. The peak of pocession production CH2O varies little when the rotate speed rises,but the production district of CH2O becomes wide when the rotate speed rises,which is obviously especial the high nitrogen concentration.when the rotate speed rises,the peak of pocession production H2O2 increases,the production district of H2O2 becomes wide,the timing of pocession production H2O2 delays , which is also obviously especial the high nitrogen concentration.4. When the intake charge temperature is kept constant , as the nitrogen concentration increases,the peak in-cylinder pressure reduces,the pressure rise ratio reduces,the timing of the peak in-cylinder pressure delays,that the combustion can be delayed.When rotate speed is kept constant,as the nitrogen concentration increases,the peak in-cylinder pressure reduces;When nitrogen concentration is kept constant,as the rotate speed increases,the peak in-cylinder pressure rises.5. When the intake charge temperature and rotate speed are kept constant,as the nitrogen concentration increases,NOX emission reduce obviously.It is explained the characteristic that Nitrogen-enriched combustion could reduce NOX emission in diesel engine.When the intake charge temperature and the nitrogen concentration are kept constant,as rotate speed increases,NOX emission rises and the peak of NOX emission varies little.As the rotate speed increases,the peak of NOX emission rises obviously especially the high nitrogen concentration.The conclusion can be made that the emission can be improved by enriching the nitrogen volume fraction in the air.