基于数值模拟优化分析的某型汽油机发动机燃烧系统正向开发

Forward Development of the Combustion System for a Practical Gasoline Engine Based on the Numerical Simulation Optimization

文中主要基于喷雾标定的结果进行发动机缸内燃烧系统的正向开发和优化。在喷雾试验数据的基础上建立了喷雾模型,并利用喷雾模型和发动机相关数据进行了缸内燃烧计算,分析了缸内流场和油气混合情况。分析表明:缸内流场方面,在压缩冲程中不同工况下均形成了非常明显的滚流流场,同时滚流比大小的变化存在明显的“双峰”现象,不同工况下均有燃油进入进气道,不同工况下进入进气道的燃油质量占总喷油量的比重各不相同,且转速越低,进入进气道的燃油质量占比越大;油气混合方面,由于喷油器选型与缸内气流匹配较差,缸内喷雾与气流在不同工况下混合不均,导致各工况上止点时刻的油气混合效果均不佳。通过改变喷雾位置、油束方向及喷油比例等方法对油气混合进行了优化,改善了上止点时刻当量比分布,优化了燃烧系统。

The combustion system in the engine cylinder based on the results of spray calibration was mainly analyzed and optimized.A spray model was established on the basis of experimental spray data;the in-cylinder combustion calculation was carried out by using the spray model and engine-related data;and the in-cylinder flow field and the fuel and air mixture were analyzed.The analysis shows that in terms of the flow field in the cylinder,a quite obvious tumble flow field is formed in different working conditions during the compression stroke.At the same time,there is an obvious“double peak”phenomenon with the change of the tumble ratio.Fuel enters the intake port under different working conditions.The quality of fuel entering the intake port under different operating conditions accounts for different proportions of the total fuel injection.The lower the engine speed,the larger the proportion of the fuel entering the intake port.In terms of fuel and air mixing,due to the poor matching of the injector selection and the airflow in the cylinder,the spray and airflow in the cylinder are mixed less uniform under different working conditions,resulting in poor fuel and air mixing at the top dead center of each working condition.In this investigation,by changing the spray position,the direction of the fuel plume,and the fuel injection ratio,the mixture of fuel and air is optimized;the equivalence ratio distribution at the time of top dead center is improved;and the combustion system is optimized.