中心喉嘴距对复合射流泵性能影响的数值模拟

基于射流传能分析理论,提出将中心射流和环形射流相结合的复合射流泵技术。为了确定较为合理的中心喉嘴距范围,通过紊流数值模拟方法研究了复合射流泵合适的中心喉嘴距范围及水力结构特征。对比分析了不同中心喉嘴距对复合射流泵流场及性能的影响。结果表明:(1)当中心喉嘴距较小时,喉管进口前存在限制流道的节流现象,易影响射流传能效果;(2)当中心喉嘴距较大时,在吸入室前端由于中心工作液与被吸液流速差较大,会产生较大的剪切损失,且喉管后端中心工作液对被吸液的提携能力低于环形工作液,导致整体传能效率偏低;(3)当中心喷嘴出口在吸入室中部附近时,整体传能效果较佳。研究确定较佳的中心喉嘴距范围为0.2～0.8倍的环形喉嘴距,其高效率区较宽广。研究成果可为复合射流泵的实际应用提供科学依据。

Numerical simulation on influence of central nozzle-to-throat clearance on perform- ance of compound jet pump

Based on the analysis of jet flow energy transfer，a compound jet pump combining central jet flow with annular jet flow is proposed herein． In order to determine a reasonable range of the central nozzle-to-throat clearance ( CNC) ，the appropriate CNC and the hydraulic structure characteristics of the compound jet pump are studied through the method of numerical simulation of turbulence，while the influences from different CNCs on the flow field and performance of the compound jet pump are comparatively analyzed． The result shows that ( 1) when CNC is smaller，a throttling phenomenon to restrict the flow passage occurs in front of the inlet of throat-tube，which is prone to impact the effect of jet flow energy transfer; ( 2) when CNC is larger，larger shearing loss is to occur at the front-end of the suction chamber due to the difference between the flow velocities of both the cen- tral working fluid and the suction fluid，while the lifting capacity of the central working fluid at the rear-end of the throat-tube for the suction fluid is lower than the flow velocity of the annular working fluid，thus leads the total energy transfer efficiency is a little bit too lower; ( 3) when the central nozzle outlet is located near the mid-part of the suction chamber，the overall energy transfer effect is more perfect． It is determined from the study that the better range of the central nozzle-to-throat clearance ( CNC) is 0. 2～ 0. 8 times of the annular nozzle-to-throat clearance; from which the efficient zone is more wider． The study result can provide a scientific basis for the actual application of compound jet pump．