考虑温度相变气液喷射器喷射性能瞬态模拟

Transient simulation of gas-liquid ejector performance with considering temperature-affected phase change

针对以往稳态法和未考虑温度相变研究气液喷射器性能的缺陷,利用CFD软件,导入受温度影响的UDF相变程序,进行欧拉法瞬态气液喷射器性能影响的数值模拟,得到随时间变化的混合管入口中心固定点湍动能、湍流耗散率和喷射器的引射比、加热系数及含气率,数值模拟与实验结果吻合较好。结果表明:气液喷射器两相流体气化、液化效果及喷射性能,不仅取决于冷热流体的冷热量,还与喷射器运行时间密切相关。对于文中所述气液喷射器,当t<10 000 s时,喷射性能参数不稳定,不能进行正常喷射;当10 000 s<t<40 000 s时,湍动能及湍流耗散率趋于稳定,瞬态且有气液相变参与的引射比及加热系数符合实际周期相变化规律;当t=40 000 s时,湍流耗散率达到最低值,液化效果最强,喷射器喷射效果最好;当t>40 000 s时,湍流耗散率增加,喷射性能有所降低。

According to the shortages of traditional steady state and numerical simulation without considering temperature-affected gas-liquid phase change,the ejection performance of gas-liquid ejector was simulated by CFD with the phase-change UDF procedure influenced by time and temperature. The turbulent kinetic energy,dissipation rate of fixed point at the inlet of mixing chamber,and entrainment ratio,heat coefficient and gas rate of ejection were obtained,which were in good agreement with experiments. The results show that gasification,liquefaction and ejection performance are associated with the quantity of cold and heat liquid,especially with the time（ t） of ejector operating. For the specific ejector described in this paper,the normal ejection could not occur for t 〈10 000 s because of unsteady performance parameters. The entrainment ratio and heat coefficient presented a periodic variation and agreed well with experiments because of steady turbulent kinetic energy for 10 000 s 〈t 〈40 000 s. The highest ejection performance was found because of the smallest turbulent kinetic energy and gas rate,the biggest entrainment ratio and the best liquefaction for t = 40 000 s. The ejection performance decreased with the increase of turbulent dissipation for t 〉40 000 s.