“全空穴”模型中的非冷凝气质量分数研究  

A Study on Non-Condensable Gas Mass Factor in Full Cavitation Model

作　　者：李强[1] 魏建勤[2] 

机构地区：[1]桂林航天工业学院汽车工程系,桂林541004 [2]浙江大学能源系,杭州310027

出　　处：《内燃机工程》2016年第2期127-136,共10页Chinese Internal Combustion Engine Engineering

摘　　要：采用Fluent的"全空穴"模型模拟了不同非冷凝气质量分数下的柴油喷孔内超空穴流,非冷凝气质量分数的变化范围为1.5×10^(-8)~7.5×10^(-5),并与试验结果进行了对比。"全空穴"模型假设空穴是由于非冷凝气和/或液体蒸发形成的。模拟结果显示:非冷凝气质量分数对喷孔内超空穴流场的影响占主导地位,非冷凝气质量分数不仅影响空穴数量,还影响孔内压力分布,进而影响空穴分布。在试验条件下,当非冷凝气质量分数较大时,如取10^(-5)数量级,计算的喷孔内超空穴场形态与试验定性不吻合,喷孔中下游区域的空穴主要集中在喷孔中心区,而不是在壁面附近,但连续方程残差比其他小的非冷凝气质量分数小2~3个数量级,且达到收敛所需要的迭代次数也少得多;当非冷凝气质量分数减小时,如小于1.5×10^(-6)时,计算的孔内空穴场与试验结果定性一致,但达到收敛所需要的迭代次数增多,且收敛时的残差值较大。总之,采用较大的非冷凝气质量分数,计算收敛快,残差值小,但计算的喷孔内空穴场与试验空穴场定性不吻合;使用与试验空穴场定性吻合的非冷凝气质量分数,收敛所需要的迭代次数较多,计算残差较大。Based on a full cavitation model which assumed that cavitation was formed by non- condensable gas and/or liquid evaporation. The super cavitation flow in diesel nozzle was simulated using different non-condensable gas mass factor, from 1. 5 × 10^（-8） to 7. 5 × 10^（-8）, and the simulation data were compared with the experiment data. The simulation results show that the super cavitation flow field in noggle orifice is dominated by the non-condensing gas mass fraction which not only affects the number of cavitation and pressure distribution, but also affects the cavitation distribution. By using a large non- condensing gas mass fraction, the simulation can be calculated with fast convergence and small residuals, and the calculated cavitation field can be in agreement with the measured cavitation field. While using a small non-condensing gas mass fraction, the simulation can be carried out with more iterations and large residuals, but the calculated cavitation field can not be in agreement with the measured cavitation field. The feature of non-condensing gas mass fraction is more obvious for the calculation of two phase flow in a full siged high pressure injection noggle. For more complex noggle orifice flow, this feature will lead to calculation distortion, because the cavitation distribution in injection noggle can not be predicted.

关 键 词：内燃机 柴油 喷孔 双相流 模型 非冷凝气质量分数 

分 类 号：O511[理学—低温物理]