高强化活塞烧蚀失效研究

运用软件AVL FIRE对某型柴油机进行了有近壁燃烧工况时的燃烧特性的数值模拟,同时确定了该型柴油机在有近壁燃烧工况时活塞有限元计算的热边界条件,运用软件ANSYS进行了活塞的烧蚀过程有限元分析,得到了近壁燃烧对活塞烧蚀的影响规律,进行了活塞烧蚀的实机试验,模拟计算结果与试验结果基本吻合.结果表明:所建立的烧蚀计算方法可以很好地模拟活塞的烧蚀过程;柴油机喷油器喷孔磨损变大将导致活塞喉口附近燃气温度和壁面传热系数在较大的曲轴转角内都保持较大的数值,从而使活塞发生烧蚀失效;烧蚀量随着喷油器孔径的增大先增大后减小,在孔径增大15%时达到峰值;烧蚀量随着烧蚀时间的增大而增大,但烧蚀的速度在缓慢减小.

Investigations on ablation failure of high power pistons

Numerical simulation of combustion characteristics at wall burning condition in a diesel engine was conducted using software AVL FIRE, and the thermal boundary conditions of finite element calculation for piston at wall burning condition were obtained. Moreover, the finite element analysis of piston during ablation process was carried out using software ANSYS, and the rules of influence of wall burning on piston ablation were achieved. Meanwhile, a corresponding experiment of piston ablation was made on the diesel engine, and the calculated results accorded with the experimental results. The results show that the resolving method established can be used to simulate the ablation process of piston. The abrasion of injection nozzle, which leads to bigger gas temperature and wall heat transfer coefficient of gas on piston throat in a wide crank angle range, may cause ablation failure of piston. Meanwhile, the ablation amount firstly increases and then decreases with the increase of diameter of injection nozzle, and peaks when the diameter increases by 15%. The ablation amount increases with the ablation time, but the speed of ablation reduces slowly.