Effect of natural gas partially premixed coupled EGR on direct injection natural gas engine
Based on a four stroke high pressure direct injection natural gas engine,the coupling effects of five natural gas pre-injection volumes and five EGR rates were simulated and studied to compare and discuss the combustion and emis-sion characteristics of a partially premixed natural gas engine.The results show that compared with the high pressure direct injection mode,partial pre-injection mode has higher peak in-cylinder pressure,peak heat release rate and maximum pres-sure rise rate.Increasing of pre-injection ratio will advance the engine combustion phase and shorten the combustion dura-tion,thereby reducing the engine's indicated fuel consumption rate,but the addition of EGR will weaken this effect.The higher pre-injection rates coupled with moderate EGR can weaken the NOx-soot"trade-off"relationship.The 30％EGR rates coupled with 40％pre-injection can result in engine with lower indicated fuel consumption rates,lower methane,un-burned HC and CO emissions,and better NOx and soot emission characteristics than direct injection solutions.
high pressure direct injection natural gaspartial premixpremixing ratiomethane escapesoot
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