可调式蒸汽喷射器的三维数值模拟及分析

Numerical Simulation and Theoretical Analysis of Adjustable Steam Ejector

在实际工业中,工作蒸汽压力经常波动,传统喷射器由于其结构固定,在操作工况偏离设计值时,性能往往会严重恶化。本文借助数值模拟工具STAR-CCM+,采用有限体积法、壁面函数修正法和标准k-ε湍流模型,对可调式蒸汽喷射器的超音速混合过程进行了三维数值模拟。分析了操作参数(背压pC、工作蒸汽压力pP和引射蒸汽压力pH)和结构参数(面积比Ar)对喷射器工作性能的影响。结果表明:1在变工况条件下,可调式喷射器能够削弱进出口参数对喷射器性能的影响,拓宽喷射器的可操作范围;2在给定工况条件下,存在一个最佳面积比A*r,使喷射系数达到最大值;3临界背压pc*随面积比的增大而降低。

The 3-dimensional flow-fieldin supersonic missing of the adjustable steam ejector was empirically approximated with the standard k-ε turbulence model, analytically calculated in wall function method, numerically simulated in finite element method （FEM） with software STAR-CCM ＋ , and experimentally tested, to stabilize its routine operation at fluctuated motive steam pressures. The influence of the operation conditions, including but not limited to the backing pressure （Pc）,motive steam pressure （pp）, suction steam （Prl） and cross-sectional area ratio of the mixer-inlet and nozzle throat （Ar＊ ）, on the characteristics of the ejector was investigated. The results show that the adjustable steam ejector is capable of operating stably in a fairly wide range of a fluctuated motive pressure,and that the area ratio （At） has a major impact on the entrainment ratio （u） and critical back pressure （pc）-To be specific, as the ratio （Ar＊） increases, the critical back pressure （Pc） decreases;but under a given working condition the entrainment ratio （u） changes in an increase-decrease mode, peaking at an optimized ratio （Ar＊）.