液氧涡轮泵多级液封轮密封空化流动特性分析

Analysis on Sealing Cavitation Flow Characteristics of Liquid Oygen Turbopump Multistage Liquid-Sealing Impellers

关键词:  多级液封轮  液氧涡轮泵  密封性能  低温空化  熵产率

Key words:  Multistage liquid-sealing impellers  Liquid oxygen turbopump  Sealing performance  Cryogenic cavitation  Entropy generation rate

摘要:

在考虑低温空化特性的基础上，提出了适用于液氧涡轮泵多级液封轮低温空化流动的数值计算方法，并采用液氮下的试验数据验证了可行性，最后对多级液封轮内低温空化流动及密封特性进行了数值研究。结果表明：与液氮试验值相比，后腔温度及压力的最大计算偏差分别为8.2%和6.7%，数值计算方法可行；多级液封轮内汽相体积约为液相体积的2~3倍，一级液封轮起主要密封作用，二级液封轮处于低压汽相环境中，部分工况后腔有局部憋压，可适当增加泄出口数量或直径以避免憋压；流场有-4~9K的温度变化，最高和最低温度分别位于一级、二级液封轮处，体现了低温空化的热力学效应；流场中高熵产率区主要分布于一级液封轮中，是能量损失的主要区域，脉动速度熵产率ΔS_D'是熵产率的主要来源；多级液封轮在一级液封轮处形成了稳定的汽液交界面，相变半径由工况Ⅰ至Ⅳ递增，经泄出口排出的均为汽相介质，总流量在0.1~0.44kg/s，流量较小，有效地阻止了液氧的泄漏。

Abstract:

Considering the cryogenic cavitation characteristics， a numerical calculation method applicable to the cryogenic cavitation flow of multistage liquid-sealing impellers of liquid oxygen turbine pump was proposed， and the feasibility by using the experimental data under liquid nitrogen was verified. And the cryogenic cavitation flow and sealing characteristics inside the multistage liquid-sealing impellers were studied numerically. The results show that compared to the liquid nitrogen test values， the maximum calculated deviation for the rear chamber temperature and pressure is 8.2% and 6.7% respectively， and the numerical calculation method is feasible. The volume of vapor phase in multistage liquid-sealing impellers is about 2~3 times of the volume of liquid phase， the primary liquid-sealing impeller plays the main sealing performance， the secondary liquid-sealing impeller is in the low pressure vapor phase environment，some working conditions have local pressure holding in the back cavity， the number or diameter of drainage outlet can be increased appropriately to avoid pressure holding. The flow field has a temperature variation from -4K to 9K. The highest and lowest temperatures are located at the primary and secondary liquid-sealing impellers， reflecting the thermodynamic effect of cryogenic cavitation. The high entropy production area in the flow field is mainly distributed in the primary liquid-sealing impeller， which is the main region of energy loss， and the pulsating velocity entropy production ΔS_D' is the main source of entropy production. The multistage liquid-sealing impeller forms a stable vapor-liquid intersection at the primary liquid-sealing impeller， and the radius of phase change increases from working condition Ⅰ to Ⅳ. The discharge through the drainage outlet is all vapor-phase medium， and the total flow rate is between 0.1kg/s and 0.44kg/s， which is small and effectively prevents the leakage of liquid oxygen.