对置活塞二冲程柴油机工作过程耦合仿真与试验研究

发布时间：2018-03-28 02:37

本文选题：对置活塞　切入点：二冲程　出处：《北京理工大学》2015年博士论文

【摘要】：对置活塞二冲程柴油机（Opposed-piston Two-stroke Diesel Engine，简称OP2S）是一种新型往复活塞式内燃机。近年来，OP2S以其高效、高功率密度、平衡性好等优势，成为国内外众多科研机构的研究热点。OP2S的换气过程与缸内过程有着强烈的耦合关系，同时其换气过程、缸内气流运动都与传统柴油机不同，但是对于OP2S工作过程及耦合关系的研究还有待进一步深入开展。本文以折叠曲柄式OP2S为研究对象，针对OP2S与传统柴油机的不同，采用耦合仿真与试验研究相结合的方法，开展OP2S工作过程的研究。分析了OP2S工作过程中多过程、多学科间的耦合关系，建立了动力学、热力学和计算流体力学模型，形成了面向系统仿真研究的仿真平台。围绕OP2S耦合条件下发动机参数变化对工作过程的影响规律、缸内气流运动规律及燃烧特性开展研究。论文的主要研究工作如下： 1、根据OP2S的工作原理，分析了OP2S工作过程中多过程、多学科间的耦合关系，建立了动力学、热力学和计算流体力学模型，形成了面向系统仿真研究的仿真平台。 2、获得了换气过程关键结构参数对换气过程及缸内过程特征参数的影响规律；依据参数影响规律结果，进一步完善了OP2S换气过程评价指标。 3、提出了以IMEP为优化目标的OP2S换气过程关键结构参数优化方法，通过分析各参数与评价指标的相关性系数确定了各参数与评价指标的相关性程度，最终得到一组换气系统结构参数。 4、计算分析了OP2S缸内气流运动的特点。考虑到换气过程与缸内过程的耦合关系，通过冷流计算，对比分析了涡流进气口与滚流进气口对换气过程及缸内气流运动过程的影响。 5、探索了OP2S缸内形成斜轴涡流的方法，提出了采用非对称气腔结合涡流进气口组织缸内斜轴涡流的方法，在此基础上仿真计算了涡流进气口倾角变化对OP2S工作过程的影响，最终得到最优的进气口倾角。 6、计算分析了喷油规律曲线形状、喷油器喷孔直径及喷孔角度对缸内混合气形成及燃烧过程的影响，，在此基础上分析获得最佳喷油规律曲线形状、喷油器喷孔直径及喷孔角度。 7、通过功图计算的方法，分析试验测得发动机示功图，获得了OP2S放热规律特性及燃烧特性，并试验研究了OP2S燃烧循环变动特性。本文在一定程度上丰富了OP2S工作过程的研究手段，并在工作过程机理的探索上取得了一些有益的成果，为OP2S性能的优化提供了支撑，指导了折叠曲柄式OP2S的优化设计工作。
[Abstract]:Opposed-piston Two-stroke Diesel engine (OP2S) is a new type of reciprocating piston internal combustion engine. In recent years, OP2S has the advantages of high efficiency, high power density and good balance. The exchange process of OP2S has a strong coupling relationship with the in-cylinder process. At the same time, the air exchange process and the in-cylinder airflow movement of OP2S are different from those of the traditional diesel engine. However, the research on the working process and coupling relationship of OP2S still needs to be further developed. In this paper, the folded crank type OP2S is taken as the research object. In view of the difference between OP2S and traditional diesel engine, the method of coupling simulation and experimental study is adopted to carry out the research of OP2S working process, and the multi-process in OP2S working process is analyzed. The dynamics, thermodynamics and computational fluid dynamics models are established, and a simulation platform oriented to system simulation is formed. The influence of engine parameters on the working process under OP2S coupling condition is discussed. The main work of this paper is as follows:. 1. According to the working principle of OP2S, the coupling relation of multi-process and multi-discipline in the process of OP2S is analyzed, the dynamics, thermodynamics and computational fluid dynamics model are established, and the simulation platform for system simulation research is formed. 2. The influence of the key structural parameters on the characteristic parameters of the air exchange process and the in-cylinder process is obtained, and the evaluation index of the OP2S ventilation process is further improved according to the results of the influence law of the parameters. 3. The optimization method of key structural parameters in OP2S ventilation process with IMEP as the optimization objective is proposed. The correlation degree between each parameter and the evaluation index is determined by analyzing the correlation coefficient between each parameter and the evaluation index. Finally, a set of air exchange system structure parameters are obtained. 4. The characteristics of air flow movement in OP2S cylinder are calculated and analyzed. Considering the coupling relationship between air exchange process and cylinder process, the effects of swirl inlet and rolling air inlet on the air exchange process and the flow motion in cylinder are compared and analyzed through cold flow calculation. 5. The method of forming oblique shaft swirl in OP2S cylinder is explored, and the method of using asymmetric air cavity combined with swirl inlet to organize inclined shaft eddy current in cylinder is put forward. On this basis, the influence of swirl inlet inclination angle on OP2S working process is simulated and calculated. Finally, the optimal inlet inclination is obtained. 6. The effects of injection curve shape, injection hole diameter and injection hole angle on the formation and combustion process of fuel mixture in cylinder are calculated and analyzed. On the basis of this, the optimum injection law curve shape, injector hole diameter and injection hole angle are obtained. 7. Through the method of power diagram calculation, the engine indicator diagram is analyzed and measured, and the characteristics of OP2S heat release and combustion are obtained, and the variation characteristics of OP2S combustion cycle are experimentally studied. To some extent, this paper enriches the research methods of OP2S working process, and obtains some beneficial results in the exploration of working process mechanism, which provides the support for the optimization of OP2S performance and guides the optimization design of folded crank type OP2S.
【学位授予单位】：北京理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TK421

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