废气再循环率及点火时刻对天然气发动机燃烧和排温的影响

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EG R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...

Effects of EGR and Ignition Timing on Combustion and Exhaust Temperature of Natural Gas Engine

Based on a natural gas engine using stoichiometric combustion mode, the effects of exhaust gas recirculation (EGR) rate and ignition timing on in-cylinder combustion process and engine exhaust temperature were studied by three dimension combustion analysis coupling engine one dimension thermodynamic calculation. Results show that with the increase of EGR rate, the combustion phases move backward, the combustion duration increases and the peak heat release rate decreases, consequently resulting in lower maximum rate of pressure rise, maximum in-cylinder combustion pressure and peak mean combustion temperature. Both the dilution effect and heat capacity effect of EGR gas can inhibit the mixture combustion rate. With the advance of ignition timing, 50% burned crank angle (CA50) move forward, the combustion duration becomes shorter, while the maximum rate of pressure rise, the peak in-cylinder pressure and heat release rate increase. In addition, the exhaust temperature decreases with the increase of EGR rate and the advance of ignition timing. In the case of keeping both the air and natural gas intake quantity, the engine rated power increases by 10 PS and the break specific fuel consumption (BSFC) decreases by 4 g/kW×h when the EGR rate is increased to 23% and the ignition timing is advanced to -18°. The engine rated power can be increased by 50 PS and the exhaust temperature can be controlled within 760 °C when both the air and natural gas intake quantity increase by 11.6 %, the EGR rate is larger than 19% and the ignition timing is earlier than -10.5°.