液力透平几何参数对压头-流量曲线的影响

Influence of Geometric Parameters on Head-Flow Curve of Pump as Turbine

摘要:

为了适应化工过程工业中生产调节对透平性能的影响，要求液力透平的压头随流量的变化较小，即压头-流量曲线比较平坦。在液力透平蜗壳内速度矩守恒的前提下，推导得出了透平理论压头和流量及透平几何参数的关系式，通过分析得到影响其曲线平坦度的几何参数为：蜗壳包角、叶轮出口安放角、叶轮出口边参数和叶片数。选取一台低比转数泵反转作透平为研究对象，改变蜗壳包角、叶轮出口安放角、叶轮出口边参数和叶片数等几何参数，确定了13种研究方案，利用ANSYS-Fluent软件对13种方案进行数值模拟和试验。结果表明：在一定范围内减小蜗壳包角，增大叶轮出口安放角，压头-流量曲线变得平坦；存在最佳叶轮出口边位置和最佳叶片数，可使透平压头-流量曲线更加平坦；蜗壳包角对压头-流量曲线斜率的影响显著。

关键词:液力透平; 压头-流量曲线; 数值模拟

Abstract:

In order to adapt to the influence of production regulation on turbine performance in chemical process industry, it is required that the head of pump as turbine changes little with the flow rate, which makes the head-flow curve relatively flat. On the premise of conservation of velocity moment in volute of pump as turbine, the relationship between the theoretical head, the flow rate and the geometric parameters of the turbine was derived. The four main geometric parameters affecting the slope of the headflow curve were obtained by studying the relationship: wrap angle of volute, blade outlet angle, blade outlet edge and blade number. A low specific speed pump was selected as the research object for pump as turbine. Thirteen research schemes were determined by changing the geometric parameters of pump as turbine. The wrap angle of volute, blade outlet angle, blade outlet edge and blade number were changed in thirteen research schemes and simulated and tested by ANSYS-Fluent software. The results showed that the head-flow curve became flat with the decrease of wrap angle of volute and the increase of blade outlet angle within a certain range, and the optimal blade outlet position and blade number made the head-flow curve more flat. The influence of wrap angle of volute on the slope of head flow curve was remarkable.

Key words:hydraulic turbine; head-flow curve; numerical simulation