不同出入口条件下气液喷射器喷射性能的数值模拟

Numerical Simulation of Ejection Performance of Gas-Liquid Ejector under Different Inlet and Outlet Conditions

针对气液喷射器传统二维几何模型和模拟中未考虑温度导致气液相变的不足,建立三维几何模型,导入考虑时间、温度影响的气液相变UDF程序,用CFD软件模拟气液喷射器喷射性能.40000 s条件下有相变的模拟结果与实际情况符合较好.改变气液喷射器出入口气液相的速度和压力条件,得到气液喷射器轴线速度、压力、温度、引射比及气液相体积分数等参数.结果表明,随液化天然气(LNG)入口速度增加,气液喷射器引射比增大,合理的LNG入口速度能使喷射器内各相体积分数及引射比趋于稳定,有利于喷射器正常喷射;随混合出口压力增加,引射比减小,LNG体积分数增大,过大的出口压力会导致气液喷射器内喷射偏斜、扩散室出口气相闪蒸汽(BOG)液化现象,不利于喷射器正常喷射.液相入口速度11~12 m/s、混合出口压力0.101~0.304 MPa时,气液喷射器喷射性能最优.

According to the shortage of both traditional two-dimensional design and no considering of gas-liquid phase change in numerical simulation, the ejection performance of gas-liquid ejector was simulated by CFD software. Three-dimension model was established and phase change UDF procedure influenced by time and temperature was used. The simulation results are in good agreement with experiments when phase change caused by temperature is taken into account after 40000 s. The axis velocity, pressure, temperature, entrainment ratio, volume fraction of gas and liquid were obtained by changing the inlet and outlet conditions of gas-liquid ejector. The results showed that entrainment ratio increases with inlet liquid velocity, and reasonable inlet velocity can stabilize volume fraction of gas and liquid and entrainment ratio and benefit to ejection. As outlet pressure increases, entrainment ratio decreases, while volume fraction of LNG increases. Higher outlet pressure can result in inclined flow and BOG liquefaction at the outlet of diffuser which are harmful to ejection. For the specific ejector described in this paper, it is the best ejection performance that liquid inlet velocity is from 11 m/s to 12 m/s and mixture outlet pressue is from 0.101 MPa to 0.304 MPa.