内燃机环境下液体燃料超临界喷射过程的数值模拟

发布时间：2018-06-07 20:52

本文选题：超临界 + 喷雾　；参考：《大连理工大学》2015年硕士论文

【摘要】：本文以内燃机环境下燃料的超临界喷射为研究对象,着重考察燃料喷雾在超临界工况下的发展过程、实际气体状态方程Soave-Redlich-Kwong (SRK)和 Peng-Robinson(PR)两个方程对超临界工况的适用性、以及气液混合层的可能位置及其演化特性。针对Sandia实验室关于正庚烷喷雾的实验数据(www.sandia.gov/ecn),基于Converge软件采用大涡模拟即LES (Large eddy simulation)和雷诺平均(RANS)方法对以正庚烷为燃料喷入超临界环境中的雾化过程进行了数值模拟。以实际气体状态方程SRK和PR方程为基础,重点研究了LES和RANS下两状态方程对超临界状态下燃料喷雾的正庚烷的质量分数、温度分布的影响；LES下燃料喷雾的质量分数随温度变化,并与实验结果进行对比；以及LES下的射流密度变化、密度梯度变化和蒸汽的质量分数等值线的分布。结果表明,LES下两状态方程计算的正庚烷的质量分数和温度分布有着很大的区别,而RANS方法下两者得到的结果区别很小；同一时间下PR方程模拟的燃料喷雾的贯穿距更大,但是SRK方程模拟的喷雾前端的涡状出现的更早；两状态方程下射流表面都有大的密度梯度；燃料质量分数随温度的变化符合实际的情况。通过本文研究得出了以下的结论：RANS模型不太适用于内燃机喷雾湍流模拟；LES下的正庚烷的质量分数、温度、密度分布相互印证了正庚烷的质量分数在轴向和径向都是随着距离的增大而逐渐减小；PR方程对于超临界工况的计算可能更优于SRK方程；密度值的急剧变化验证了射流表面存在一个介于液体与气体之间的混合层；可以通过大密度梯度的位置来推测混合层的可能位置,混合层随着轴向距离的增大而向外移动；蒸汽的质量分数等值线图也印证之前得出的正庚烷的质量分数的变化情况。
[Abstract]:In this paper, the supercritical injection of fuel in the environment of internal combustion engine is taken as the research object, and the development process of fuel spray under supercritical condition is emphatically investigated. The applicability of the actual gas equation of state Soave-Redlich-Kwong SSRK and Peng-Robinsonian PR) to the supercritical condition is investigated. And the possible location and evolution characteristics of the gas-liquid mixed layer. Based on the experimental data of Sandia laboratory on n-heptane spray (www.sandia.gov-ecng), the atomization process of n-heptane injection into supercritical environment was numerically simulated by means of large eddy simulation (les large eddy simulation) and Reynolds average rags (RANSs) method based on converge software. Based on the actual gas state equations SRK and PR, the effects of the two equations of state under les and rans on the mass fraction of n-heptane in supercritical state and the effect of temperature distribution on the mass fraction of fuel spray under les are studied. The results are compared with the experimental results, and the distribution of jet density, density gradient and the contours of steam mass fraction under les. The results show that the mass fraction and temperature distribution of n-heptane calculated by the two equations of state are very different from those obtained by rans method, and the penetration distance of fuel spray simulated by PR equation at the same time is larger than that obtained by rans method. But the vortex of the spray front end simulated by SRK equation appears earlier; the jet surface has a large density gradient under the two equation of state; the change of fuel mass fraction with temperature is in line with the actual situation. The following conclusions are obtained from the study in this paper: the 1: rans model is not suitable for the mass fraction and temperature of n-heptane in the spray turbulence simulation of internal combustion engine under les. The density distribution verifies that the mass fraction of n-heptane decreases gradually with the increase of distance in axial and radial direction, and the PR equation may be better than SRK equation in supercritical condition. The sharp change of density value verifies the existence of a mixing layer between liquid and gas on the surface of the jet, and the possible position of the mixing layer can be inferred by the position of large density gradient, and the mixing layer moves outward with the increase of axial distance. The isogram of steam mass fraction also confirms the change of n-heptane mass fraction.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TK407.9

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