对置活塞柴油机缸内流动对性能影响的研究

发布时间：2018-01-20 13:37

本文关键词： 对置活塞对置气缸发动机缸内流动换气过程燃烧过程　出处：《中北大学》2015年硕士论文　论文类型：学位论文

【摘要】：OPOC（对置活塞对置气缸）发动机是一种新型结构的二冲程发动机，具有结构紧凑、效率高、功率密度大、整机平衡性好、布置方式灵活等优点，拥有广阔的应用前景。OPOC发动机虽然采用了直流扫气、电控喷油、电动增压等技术，但作为二冲程发动机其仍存在着换气质量不高、燃烧不充分等问题。本文在已有研究基础上，详细分析了不同气口结构下的缸内流动状况对OPOC发动机换气及燃烧过程的影响。文章首先计算了OPOC发动机气缸内外两活塞的具体运动规律，进而得到了OPOC发动机的缸内容积以及进排气口流通面积的变化情况，在此基础上设置合理的燃烧参数，建立了OPOC发动机的一维工作过程仿真模型，得到了发动机不同转速下的进排气压力、扫气效率、缸内压力等参数。基于一维仿真结果设定边界条件，建立OPOC发动机换气过程的三维仿真模型，分别对3600r/min、2500r/min以及1600r/min三种转速下的换气过程进行分析，对比不同转速下的缸内瞬态流场以及残余废气分布的变化情况。通过分析发现：在原进排气口结构作用下所形成的缸内流动形式并不合理，高速工况下扫气质量较差。在原进气口模型5°/15°倾角的基础上，分别设计了10°/20°、15°/30°、20°/40°三种不同的改进方案，并对三种扫气方案在不同转速下的缸内流动、废气残留等情况进行了分析。为使发动机在整个工作转速范围内都能具有较高的扫气质量，文章最终选择了15°/30°作为最终的优化方案。为进一步研究所选定的15°/30°优化方案对整机性能的影响，文章对15°/30°方案与原方案在3600r/min下的燃烧过程进行了分析。为保证分析的准确性，建立起了包括换气过程与燃烧过程的发动机整个工作过程的仿真模型。通过与原方案的燃烧过程对比分析发现：所选择的最终优化方案，缸内流动形式更加合理，，在一定程度上加快了燃油的蒸发与雾化，同时可燃混合气分布更加均匀，燃烧过程更加迅速。最终通过对整个工作过程的P-V曲线计算发现，改进方案的发动机功率更大、油耗更低。
[Abstract]:OPOC engine is a new type of two-stroke engine, which has the advantages of compact structure, high efficiency, high power density, good balance and flexible arrangement. The OPOC engine has a broad application prospect. Although the OPOC engine adopts DC scavenging, electronically controlled fuel injection, electric supercharging and other technologies, but as a two-stroke engine, it still has a low air exchange quality. Insufficient combustion, etc. On the basis of the previous studies, the influence of the in-cylinder flow conditions on the air exchange and combustion process of the OPOC engine with different air orifice structures is analyzed in detail in this paper. This paper first calculates the specific motion law of the two pistons inside and outside the cylinder of OPOC engine, and then obtains the change of the cylinder volume and the flow area of the intake and exhaust port of the OPOC engine. On the basis of setting reasonable combustion parameters, the one-dimensional working process simulation model of OPOC engine is established, and the parameters such as inlet and exhaust pressure, scavenging efficiency and in-cylinder pressure are obtained. Based on the one-dimensional simulation results, a three-dimensional simulation model of the OPOC engine ventilation process was established. The air exchange process was analyzed at three rotational speeds: 2500r-min and 1600r-min. By comparing the change of transient flow field and residual exhaust gas distribution in cylinder at different speeds, it is found that the flow form in cylinder formed under the action of the original inlet and exhaust port structure is not reasonable. The scavenging quality is poor at high speed. Based on the 5 掳/ 15 掳inclination of the original inlet model, three different improvement schemes were designed for 10 掳/ 20 掳/ 15 掳/ 30 掳/ 20 掳/ 40 掳respectively. In order to make the engine have a higher scavenging quality in the whole working speed range, the flow in cylinder and the residue of exhaust gas are analyzed under different rotating speed of three kinds of scavenging schemes. Finally, 15 掳/ 30 掳is chosen as the final optimization scheme. In order to further study the effect of the selected 15 掳/ 30 掳optimization scheme on the performance of the whole machine. In this paper, the combustion process of the 15 掳/ 30 掳scheme and the original scheme at 3600r / min is analyzed to ensure the accuracy of the analysis. The simulation model of the whole working process of the engine including the air exchange process and the combustion process is established. Through the comparison and analysis of the combustion process with the original scheme, it is found that the final optimization scheme is selected. The flow pattern in the cylinder is more reasonable, which speeds up the evaporation and atomization of the fuel to a certain extent, and the distribution of the combustible mixture is more uniform at the same time. Finally, the P-V curve of the whole working process is calculated and it is found that the improved scheme has higher engine power and lower fuel consumption.
【学位授予单位】：中北大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TK421

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