Abstract: Aiming at the problem of fuel economy, an off-road single-cylinder air-cooled 170F gasoline engine is taken as the research object, and high thermal efficiency is the core goal. Simulation software is used to optimize the combustion chamber shape and compression ratio.Simulation software was used to optimize the shape and compression ratio of the combustion chamber. Under the premise of ensuring that no abnormal combustion occurs, CONVERGE is used to establish a simulation model, and the impact of four high compression ratio combustion chambers on engine performance is designed and simulated. Determine the ideal combustion chamber model through specific analysis of the simulation data. The research results show that under the premise of further improvement of its own small strengthening technology, the compression ratio of slight knock can be considered. At this time, the compression ratio is 10.5, the indicated thermal efficiency of the whole machine is increased by 46.61% compared with the original machine, and the theoretical fuel consumption rate is reduced to 252.69 g/(kW·h), which is 31.79% lower than that of the original machine. This kind of combustion chamber improvement method has a good prospect of energy saving and emission reduction. It has a certain application universality on different models of similar machines and has the ability to be practically promoted.

Key words: Efficiency of heat engine;Gasoline engine; Off-road; CFD simulation calculation

摘要： 针对燃油经济性问题，论文以非道路单缸风冷 170F 汽油机为研究对象，高热效率为核心目 标，运用仿真软件对燃烧室形状和压缩比进行优化。在保证不发生异常燃烧的前提下，使用 CONVERGE 建立仿真模型，并设计仿真了四款高压缩比燃烧室对发动机性能的影响。通过对仿真 数据的具体分析来确定较为理想的燃烧室模型。研究结果表明，在自身小型强化技术进一步完善 的前提下，可考虑轻微爆震的压缩比情况，此时压缩比为 10.5，整机指示热效率较原机提升 46.61%， 理论燃油消耗率下降至 252.69 g/(kW·h)，较原机下降 31.79%。该种燃烧室改良方法有较好的节能 减排前景，在同类机械不同机型上有一定的应用普适性，具有实用推广的能力。

关键词: 热效率；汽油机；非道路；CFD 仿真