天然气发动机进气及压缩过程三维仿真分析

赵玥，冷建，王钰琦，林桂宾

中国重汽集团汽车研究总院，山东 济南  250102

摘要：为研究天然气发动机缸内气流运动及天然气混合规律，利用Hypermesh和AVL Fire软件对发动机的进气和压缩过程进行三维仿真，计算进气与压缩过程的流线分布和天然气质量分数分布。结果表明：进气过程中，滚流主要沿气缸纵向变化，随着高速气流流入，在气门下方生成2个滚流区，进气道一侧的滚流较远离进气道一侧的大，在活塞运行到下止点时滚流能量耗散，被涡流吸收；进气过程中，涡流主要沿气缸横向变化，在气缸顶部形成众多无规则的小尺度涡流，气缸下部气流趋于稳定，形成稳定的大尺度涡流；压缩过程中主要产生是滚流、挤流和湍流，活塞上移，涡流运动加强，形成较大尺度的滚流，活塞顶部接近气缸顶部时，产生挤流，挤流运动可以增加上止点附近的湍动能。

关键词：天然气发动机; Hypermesh; AVL Fire;模型网格划分;三维仿真

3D simulation analysis of intake and compression process in a natural gas engine

ZHAO Yue, LENG Jian, WANG Yuqi, LIN Guibin

Sinotruk Automotive Research Institute, Jinan 250102, China

Abstract：In order to study the airflow movement and natural gas mixing in the cylinder of a gas engine, Hypermesh and AVL Fire software are used to conduct three-dimensional simulation of the intake and compression processes of the gas engine. The streamline and natural gas concentration distribution of the intake and compression processes are calculated. The results show that during the intake process, the rolling flow mainly changed along the longitudinal direction of the cylinder, and as the high-speed airflow entered, two rolling flow zones are generated below the valve. The roll flow ratio on one side of the inlet is greater than that on the side away from the inlet, and when the piston reaches bottom dead center, the roll flow energy is dissipated and absorbed by the eddy current. During the intake process, the vortices mainly change laterally along the cylinder, form numerous irregular small-scale vortices at the top of the cylinder. The airflow in the lower part of the cylinder tend to become more stable, form stable large-scale vortices. The main processes generated during compression are rolling, squeezing, and turbulence. As the piston moved up, the vortex motion strengthenes, forming a larger scale rolling flow. When the top of the piston approaches the top of the cylinder, squeezing is generated, which could increase the turbulent kinetic energy near the top dead center.

Keywords:natural gas engine; Hypermesh; AVL Fire; model grid division; 3D simulation