【摘要】 基于一台当量比燃烧的天然气发动机,采用三维燃烧分析与发动机一维热力学计算相结合的方式开展了废气再循环(exhaust gas recirculation,EGR)率及点火时刻对缸内燃烧过程和发动机排温的影响研究。研究结果表明:随着EGR率的增加,燃烧相位后移,燃烧持续期延长,放热率峰值减小,最大压升率、缸内最高燃烧压力和最高平均燃烧温度均降低,再循环废气的稀释作用和热容效应能够抑制混合气的燃烧。随着点火时刻的提前,燃烧重心(CA50)前移,燃烧持续期缩短,最大压升率、缸内压力和放热率峰值均增大。排温随EGR率的增大和点火时刻的提前而降低。保持空气和燃气进气量不变,EGR率增大至23%,点火时刻提前至-18°能够将原机标定功率提升7.4kW,有效燃料消耗率降低4g/(kW·h)。当空气和燃气进气量增加11.6%,EGR率大于19%,点火时刻早于-10.5°时,可将原机标定功率提升36kW并且将排温控制在760℃以内。更多还原

【Abstract】 For a natural gas engine operating in a stoichiometric combustion mode,the effect of exhaust gas recirculation(EGR)and ignition timing on combustion process and exhaust temperature was studied using a combination of three-dimensional combustion analysis and one-dimensional thermodynamic calculation.Results show that increasing the EGR retards combustion phase,prolongs combustion duration,decreases peak heat release rate,and reduces maximum combustion pressure increase rate,resulting in a decrease in maximum combustion pressure and highest average combustion temperature in the cylinder,and finally the dilution and heat capacity effects of EGR inhibit the increase of the combustion rate of the mixture.In contrast to this,advancing the ignition timing leads to advanced angle of 50% mass fraction burned(CA50),shortened combustion duration,and an increase in the maximum pressure increase rate,maximum combustion pressure and peak heat release rate.Moreover,the exhaust temperature decreases with increased EGR and advanced ignition timing.During the engine test,under the condition of keeping the intake of air and gas unchanged,increasing the EGR to 23%,and advancing the ignition timing to-18°in crank angle can increase the rated power of the original engine by 7.4 kW,and reduce the fuel consumption by 4 g/(kW·h).But If the intake of air and gas is increased by 11.6%,when the EGR is greater than 19%,and the ignition timing is earlier than-10.5°in crank angle,the rated power can be increased by 36 kW,while the exhaust temperature is still below 760℃.更多还原