前弯叶片液力透平专用叶轮设计与实验

应用蜗壳内速度矩守恒的假设,推导了螺旋形蜗壳常数的计算表达式,得到了叶轮进口处的速度矩。采用无撞击进口、法向出口的液流工况,确定了叶轮的进出口安放角,设计了一前弯型叶片液力透平专用叶轮。设计了叶轮模型,进行了外特性实验。结果表明:对比原型泵作透平的实验结果,新设计的前弯型叶片液力透平专用叶轮显著提高了透平效率,最高效率由原来的59.98%提高到67.91%,最高效率提高了13.22%。采用专用叶轮的效率曲线较原型泵作透平的效率曲线平坦,在0.9~1.2倍最优工况运行区间,效率变化值在1.5%以内,高效区较宽。

Design and Experiment on Pump as Turbine with Forward Curved Blades

A reversed running centrifugal pump can work as a hydraulic turbine. In order to improve the operating performance of pump as turbine (PAT), a special impeller with forward curved blades was designed and experimented. By using the constant velocity moment theory, the calculation expressions of volute constant within spiral volute were developed and the velocity moment before impeller was acquired. Impeller with forward curved blades was designed and manufactured. Its inlet angle at leading edge was determined by using shockless inlet flow while its outlet angle was designed on whirl free outlet flow. Performance test of PAT with designed forward curved blades impeller and conventional back swept blades impeller was performed. The comparison between designed forward curved blades and conventional back curved blades shows that the best efficiency is increased by 13.22%. Compared with original PAT performance curves, the efficiency curve of PAT with forward swept blades is more flat. The efficiecy variation of PAT with forward curved blades is only within 1.5% between 0.9QBEP (flow rate of best efficiency point)and 1.2QBEP operating range. Therefore, the high efficiency operating range of impeller with forward swept blades is wider than conventional back swept impeller.