基于简化机理的四冲程点燃式活塞发动机爆震燃烧数值模型

Detonation Combustion Numerical Model of Four-Stroke Ignition Piston Engine Based on Simplified Mechanism

关键词:  四冲程点燃式活塞发动机  航空煤油  化学反应机理  爆震燃烧  宏观参数与现象

Key words:  Four-stroke ignition piston engine  Aviation kerosene  Chemical reaction mechanism  Detonation combustion  Macroscopic parameters and phenomena

摘要:

爆震问题是限制发动机性能发挥的关键问题之一，因此针对性地构建四冲程点燃式活塞发动机爆震燃烧模型，探究爆震燃烧的机理具有十分重要的意义。基于四川大学提出的73.0%（质量分数） 正十二烷， 14.7%1，3，5-三甲基环己烷和12.3%正丙基苯组成的RP-3航空煤油的三组分替代模型，采用先简化后合并的思路，应用直接关系图法（DRG）、基于误差传递的直接关系图法（DRGEP）、奇异摄动法（CSP）等简化方法构建了包含127种物质、360步反应的RP-3航空煤油简化机理，通过与详细机理的滞燃期预测结果对比，发现初始温度在900~1200K时，简化机理与详细机理的滞燃期预测结果误差在30%以内，验证了简化机理的有效性。在此基础上基于CONVERGE平台，采用G方程耦合化学反应动力学机理的方法构建了基于简化机理的四冲程点燃式活塞发动机的爆震燃烧数值计算模型并校核，最后基于模型模拟了发动机的爆震燃烧过程。结果表明：采用RP-3航空煤油简化机理耦合三维数值计算构建的爆震燃烧数值计算模型能够有效地模拟四冲程点燃式活塞发动机爆震燃烧过程末端混合气自燃现象，体现爆震燃烧过程中缸内平均参数的变化特征，描述缸内压力、温度及中间物质空间分布的演化情况。

Abstract:

Detonating combustion has become one of the key issues limiting engine performance. Therefore， it is of great significance to construct detonation combustion numerical model of four-stroke ignition piston engine to explore detonation combustion mechanism. Based on the three-component substitution model of RP-3 aviation kerosene consisting of 73.0% （mass fraction） n-dodecane， 14.7% 1，3，5-trimethyl-cyclohexane and 12.3% n-propylbenzene proposed by Sichuan University， presented the idea of simplifying first and then merging， and applying the direct relation graph method （DRG）， direct relation graph method considering error passing （DRGEP） and computational singular perturbation （CSP） mechanism simplification methods to finally construct a simplified mechanism of RP-3 aviation kerosene containing 127 substances and 360 steps. By comparing results of the ignition delay period prediction with those of the detailed mechanism， it is found that when the initial temperature is between 900K and 1200K， the error of the ignition delay period prediction results of the simplified mechanism and the detailed mechanism is within 30%， which verified the effectiveness of the simplified mechanism. On this basis， based on the CONVERGE platform， the detonation combustion numerical calculation model of the four-stroke ignition piston engine was constructed and checked by using the G equation coupled chemical reaction dynamics mechanism. Finally， the detonation combustion process of the four-stroke ignition piston engine was simulated. The results show that the detonation combustion numerical calculation model constructed by the RP-3 aviation kerosene simplification mechanism coupled with three-dimensional numerical calculation can effectively simulate the self-ignition phenomenon of the mixture gas in the detonation combustion process of the four-stroke ignition piston engine， and reflect the variation characteristics of average parameters in cylinder during detonation combustion， and describe the evolution of pressure and temperature and spatial distribution of intermediate materials in cylinder.