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利用计算机数值计算和图像显示的方法,在时间和空间上对带有浴盆形燃烧室天然气发动机缸内湍流场演变过程、燃烧特性进行了仿真研究。结果表明:浴盆形燃烧室和直进气道的几何结构以及气门的偏置使环形进气射流有强烈的不对称性,进气门关闭后缸内形成大尺度斜轴涡流;在压缩冲程后期,涡流在吸收活塞运动能量同时,受到壁面剪切和挤气射流的耦合作用,提高了缸内湍流水平,在上止点附近形成的自火花塞流向对侧的横向气流,有利于火焰向距离火花塞较远的对侧传播;进入快速燃烧期,活塞顶部凸起限制了火焰前锋面的扩大。因此,适当提高自火花塞指向对侧的横向气流速度、增加火花塞对侧挤气面的面积以及优化活塞头部形状可以改善带有浴盆形燃烧室天然气发动机的燃烧质量。
The evolution and the combustion characteristics of the turbulent flow field in a natural gas engine with a bathtub-shaped combustor were simulated in time and space using computer numerical calculation and image display. The results show that the geometry of the baffled combustor and the rectilinear gas inlet and the biasing of the valve make the annular inlet jets strongly asymmetric, and the large-scale oblique axis vortex forms in the cylinder after the intake valve closes. During the late compression stroke The eddy current absorbs the kinetic energy of the piston and at the same time it is coupled by the shearing of the wall surface and the squeezing jet to increase the level of turbulence in the cylinder and form a transverse airflow from the spark plug to the contralateral side near the top dead center, Far contralateral propagation; into the rapid combustion period, the top of the piston limits the expansion of the flame front. Therefore, it is possible to improve the combustion quality of a natural gas engine with a bathtub-shaped combustion chamber by properly increasing the lateral airflow velocity from the spark plug to the opposite side, increasing the area of the squeeze surface on the opposite side of the spark plug, and optimizing the piston head shape.