进气道结构对增压汽油机燃烧过程影响的数值模拟

Numerical Simulation on the Effect of Intake Port Structure on the Combustion Process of a Turbocharged Gasoline Engine

为提高某三缸增压进气道喷射汽油机的燃烧效率,利用三维CFD软件AVL-FIRE对原汽油机进气道在各气门升程下的进气过程进行了稳态数值模拟计算,并对其原汽油机在1,000,r/min、3,000,r/min和5,000,r/min全负荷下的燃烧过程进行了瞬态数值模拟计算;基于计算结果提出了两种进气道优化设计方案.对优化前后的缸内速度场、湍动能场、温度场、瞬时放热率及燃烧持续期进行了对比研究.研究结果表明:与原气道方案相比,优化气道方案的滚流比更大,在缸内组织了更强的气流运动,点火时刻缸内的湍动能更大且分布更为合理,火焰发展期和快速燃烧期更短.通过优化进气道结构适当提高增压汽油机的滚流比,可以改善压缩行程后期缸内的气流运动,提高点火时刻缸内的湍流强度,对提高混合气的燃烧速度、促进缸内燃烧十分有利,从而可有效提升汽油机的燃烧效率.

In order to improve the combustion efficiency of a three cylinder turbocharged port fuel injection gasoline engine,a three-dimensional CFD software AVL-FIRE wasused to conduct the steady numerical simulation on the original intake port of the original engine under all valve lifts and transient numerical simulation on the combustion process at 1,000,r/min,3,000,r/min and 5,000,r/min under full load,and two intake port optimization proposals were presented. The influence of the intake port structure on the combustion characteristic parameters such as velocity field,turbulent kinetic energy field,temperature field,heat release rate and combustion duration were compara-tively studied. Results show that compared with the original intake port,the optimized intake port shows the greater tumble ratio and has organized stronger airflow in cylinder,the turbulent kinetic energy at ignition timing is greater and its distribution is more reasonable,and the flame development period and rapid combustion period are shorter. It is indicated that improving the tumble ratio through the optimization of the intake port structure can enhance the air motion in cylinder near TDC,and improve the turbulence intensity at ignition timing,which is helpful to speed up the combustion and promote the combustion efficiency effectively.