液氮非定常空化流动时空演化特征试验  

Experimental investigation of temporal and spatial behaviors in liquid nitrogen cavitating flows

作　　者：陈家成 梁文栋 李子亮 耿昊 陈泰然[1,3] 王国玉 CHEN Jiacheng;LIANG Wendong;LI Ziliang;GENG Hao;CHEN Tairan;WANG Guoyu(School of Mechanical Engineering,Beijing Institute of Technology,Beijing 100081,China;Beijing Aerospace Propulsion Institute,Beijing 100076,China;Chongqing Innovation Center,Beijing Institute of Technology,Chongqing 401120,China)

机构地区：[1]北京理工大学机械与车辆学院,北京100081 [2]北京航天动力研究所,北京100076 [3]北京理工大学重庆创新中心,重庆401120

出　　处：《火箭推进》2024年第6期116-126,共11页Journal of Rocket Propulsion

基　　金：国家自然科学基金(52009001);北京理工大学科技创新计划(2024CX06078);重庆市自然科学基金(cstc2021jcyj-msxmX1046)。

摘　　要：基于低温介质空化流动实验装置和高速纹影测量系统,研究了液氮非定常空化流动密度分布的时空演化特征。试验中应用高速摄影技术与纹影测量技术对温度为77 K的液氮在不同空化数下的空穴结构与密度分布进行了综合测量。基于试验结果,分析了初生空化、片状空化以及大尺度的云状空化这3种典型低温空化流型的非定常特性与空穴结构演化。研究结果表明:①通过纹影测量系统捕捉到了在背光试验中观察不到的空化引起的密度梯度结构。②在无空化流动时,液氮经过喉口未发生明显的密度变化,在空化条件下,经过喉口的液氮空化流动中观察到了空化流动的密度梯度,且这一区域出现在附着型空穴上方,起始于喉口,离开空穴时消失;③空化区域汽液混合物声速远小于液相,局部马赫数增大,介质受到压缩后密度发生改变,产生条纹状密度梯度结构;④条纹结构区域密度梯度的变化对应于当地空化流动时空演化特征。The objective of this paper is to build a schlieren optical system based on the experimental device for cavitation flow in cryogenic fluids,and to study the spatial and temporal characteristics of the density distribution in liquid nitrogen cavitating flows.In the experiment,the structure and density distribution of liquid nitrogen cavities at different cavitation numbers for 77 K were measured by applying high-speed photography and chlieren technology.The unsteady behaviors of incipient cavitation,sheet cavitation,and large-scale cloud cavitation in liquid nitrogen were investigated.The results show that:①The schlieren optical system can capture the cavitation-induced density gradient that is not observed in backlighting experiments.②The significant change of density in liquid nitrogen is not observed under the non-cavitation condition.The rectangular structures are observed in the cavitating flows.This demonstrates that the density of the liquid phase changes.The rectangular structure appears above the attached cavity,begins at the throat,and disappears when leaving the cavity.③The sound velocity of the vapor-liquid mixture in the cavitation region is much smaller than that of the liquid phase,and the local Mach number increases.The density of the fluid changes as it is compressed,producing a striated density gradient structure.④The unsteady characteristics of the rectangular structures are consistent with the cavitating flows.

关 键 词：液氮 空化流动 纹影测量 密度梯度 非定常特性 

分 类 号：V431[航空宇航科学与技术—航空宇航推进理论与工程] TV131.32[水利工程—水力学及河流动力学]