蜗壳型线切割对小型离心泵性能和流场影响的数值研究

Numerical study on effect of cutting volute profile on performance and flow field of small centrifugal pumps

采用小型循环泵可以使燃气热水器实现热水零等待.针对此类型泵所处的特殊运行环境,提出了一种蜗壳型线切割设计方法.以某燃气热水器用离心泵为研究对象,引入切割方位角θ_(s)定义周向切割位置,并采用数值模拟方法,探究不同周向切割位置对泵水力性能和流场的影响.结果表明:蜗壳型线切割使蜗壳过流面积在相应周向范围内呈现先减后增的变化规律,并在蜗壳切割面上形成低压区.而当切割方位角θ_(s)=150°时,该低压区恰好处在叶片出口端,更多介质改经叶片吸力面侧流入蜗壳,对应流道通流量上升,叶片做功能力因叶片两侧压差增大而增强,从而使水泵扬程在大流量工况基本保持不变的基础上,于Q=7 L/min工况点提升约2.7%.但蜗壳型线切割同时破坏了型线的曲率连续性,使蜗壳内的流动损失增加,水泵在各工况的运行效率出现了不同程度的下降.

The use of small circulating pump can make gas water heater realize zero waiting for hot water.In view of the special operating environment of this type of pumps,a volute profile cutting design method was proposed.Taking a centrifugal pump for gas water heater as the research object,the value of volute cutting θ_(s) was changed,and the numerical simulation method was adopted to investigate the impact of different circumferential cutting positions on hydraulic performance and flow field of the pump.The results show that the cutting volute profile makes flow cross-sectional area of the volute to firstly decrease and then increase in the corresponding circumferential range,thus a low pressure area is formed on the cutting surface of the volute.However,when θ_(s)=150°,the low-pressure area happens to be at the outlet end of the blade,and more fluid medium flows into the volute through the suction side of the blade.The side pressure difference increases and strengthens,so that the head of the centrifugal pump increases by about 2.7% under the Q=7 L/min working condition on the basis of maintaining the large flow condition.However,cutting volute destroys the curvature continuity of the volute profile,which results in flow deterioration and low efficiency under various operating conditions.