点燃式天然气发动机燃烧室结构优化的仿真与试验研究

摘要

利用三维数值仿真的方法,对带有浴盆形燃烧室的天然气发动机缸内流动和燃烧特性进行分析,提出了两种燃烧室结构优化设计方案,试验对比了采用原燃烧室和挤气喷射燃烧室时的发动机性能。结果表明：在不改变压缩比情况下,通过改变活塞头部凸起形状和位置,能够实现浴盆形燃烧室内的挤流与滚流有效耦合；控制点火时刻的火花塞附近气体流速,能提高缸内平均湍动能,加大快速燃烧期内火焰前封面的面积,改善燃烧质量。发动机采用优化的2号挤气喷射燃烧室,能够明显加快发动机燃烧进程,提高发动机的动力性和经济性,发动机功率从75kW 提高到78.7kW,最低比气耗降低4.4%,HC和CO 排放略有降低。%In-cylinder flow and combustion characteristics of natural gas engine with bathtub combustion chamber were analyzed,two optimization schemes were proposed and performance of en-gine was studied when original combustion chamber and squish-inj ection combustion chamber were adopted.The results show that changing shape of piston head can achieve coupling between swirl and squish flow for constant compression ratio,control gas velocity near spark plug,increase mean turbu-lent kinetic energy,extend area of flame front and then improve combustion quality.Test was carried out at conditions of wide-open throttle and different speed to determine the effect of piston geometry on the performance and emissions.It shows that 2 # chamber can accelerate speed of combustion greatly and improve power performance and fuel economy of engine.Power increases from 75kW to 78.7kW,fuel consumption decreases by 4.4%,HC and CO emissions decrease slightly.