实际气体、阻塞和湍流效应对超临界CO_(2)干气密封性能的影响

Influence of Real Gas,Choked Flow,and Turbulence Effect on Performance of Supercritical CO_(2) Dry Gas Seals

超临界CO_(2)(supercritical CO_(2),SCO_(2))干气密封是SCO_(2)布雷顿循环系统中的关键零部件之一,但高压差、高转速和临界点附近CO_(2)的非常规物性仍使其设计极具挑战。综合考虑实际气体效应、阻塞效应和湍流效应,该文建立SCO_(2)干气密封稳态性能求解模型,研究不同压力、温度、转速和膜厚下各实际效应对SCO_(2)干气密封开启力和泄漏率的影响规律,探讨各实际影响对密封性能的影响机制,获得了不同运行参数下的关键影响因素。结果显示:湍流效应和实际气体效应对SCO_(2)干气密封的稳态性能影响显著,阻塞效应影响较弱。湍流下密封开启力随转速的变化与层流下完全不同,这是由湍流效应对静压和动压开启力共同作用的结果。表明实际气体效应和湍流效应是SCO_(2)干气密封设计中需要重点关注的因素。

Supercritical carbon dioxide(SCO_(2))Brayton cycle is a highly promising energy conversion process.Dry gas seals with low leakage rate employed as SCO_(2)compressor and turbine shaft-end seal can significantly improve system efficiency.However,the high pressure,high speed and unconventional properties of CO_(2)near the critical point still make it a challenging task for performance prediction of a dry gas seal.A numerical model for steady-state performance considering the effects of real gas,choked flow and turbulence in a SCO_(2)dry gas seal was established.The influences of various effects on opening force and leakage rate of a SCO_(2)dry gas seal were investigated under different working conditions.The results show that both turbulence and real gas effects have a significant influence on the steady-state performance of a SCO_(2)dry gas seal,and the influence of choked flow effect is the lowest.The turbulence effect makes the tendency of opening force varied with rotating speed completely different from that predicted by laminar model,which is the result of combined action of turbulence effect on static pressure force and dynamic pressure force.