Study on ammonia/n-heptane dual-fuel spray ignition and pollutants formation
The Large-eddy simulation was conducted to investigate the effects of ambient temperature(Ta)on the ignition and pollutant formation in NH3/n-C7H16 dual-fuel spray.The results indicate that increasing Ta promotes the ignition of n-C7H16 spray and NH3/n-C7H16 dual-fuel spray.At the same Ta,the ignition delay time of dual-fuel spray is about 30%longer than that of n-C7H16 spray.In the dual-fuel spray,NO2 is distributed in the middle region of the spray with equivalence ratio greater than 1 and temperature between 900～1 150 K.Subsequently,N2O is concentrated in the internal region of the spray with equivalence ratio greater than 1 and temperature between 1 150～1 500 K,while NO mainly distributes in the head region of the spray with equivalence ratio of 1 and temperature greater than 2 000 K.Moreover,increasing Ta promotes the production of NO in the dual-fuel spray while inhibiting the generation of NO2 and N2O.Chemical kinetic analysis reveals that NO in the dual-fuel spray is mainly generated by high-temperature reactions related to HNO,while approximately 85%of NO2 and N2O are produced through reactions R285 and R251.
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