Performance Test And Simulation Study Based On RCCI Combustion Mode Of Diesel Engine

With the development of modern industry,energy and environmental issues become increasingly prominent,the standard of diesel engine emission is becoming more and more strict,and power performance requirements of diesel engine are increasing,it need us to improve diesel engine combustion efficiency and reduce emission pollutants. In order to achieve this goal,this paper took simulation and test as two parts and used reactivity controlled compression ignition to study impact on combustion characteristics of pre-mixed gasoline proportional and rate of EGR.In the simulation,this paper used three-dimensional CFD software coupled with a chemical kinetics which contain chemical reaction kinetics mechanism to establish the numerical model,numerically calculate and study RCCI combustion characteristics and emission pollutants. The paper used iso-octane to represent gasoline and n-heptane to represent diesel,changed proportion of gasoline,concentration of intake oxygen and injection pressure. The result showed that under working condition of 1400 rpm and 16 mg equivalent cycle diesel,with increase of proportion of gasoline,maximum of cylinder pressure and combustion temperature decreased,n-heptane could be better mixed with air,emissions of xNO and Soot decreased,iso-octane mixed with air could be influenced by quenching effect and gap effect at the edge of combustion chamber to produce more THC. With decrease of of oxygen concentration,combustion temperature decreased,reaction activity weakened,ignition delay increased,emissions of xNO decreased,but Soot not to be oxidized timely,Soot emission was higher. Increase of injection pressure could made increase of fuel kinetic energy and combustion temperature.In the test,based on a single cylinder diesel engine,port injection of gasoline mixed with air was ignited by direct injection of diesel,made use of gasoline characteristics of higher octane number and lower cetane number to improve fuel reaction activity. In low load condition,with increase of proportion of gasoline,peak cylinder pressure and heat release rate decreased,ignition delay increased,combustion duration shortened,xNO and Soot emissions decreased,however,THC and CO emissions increased. Engine thermal efficiency could be maintained at level of diesel engine. In high load condition,with increase of proportion of gasoline,xNO and Soot emissions decreased,because of high pressure and high temperature,the ratio of complete combustion fuel increased,led decrease of CO emissions,however,peak cylinder pressure and pressure rising rate rose,that could make engine work rude. Using some proportion of EGR could reduce engine temperature,peak cylinder pressure and pressure rising rate. In experiments and simulation,emission could be reduced through RCCI combustion.