基于反转双吸泵的液力透平全特性的数值预测

为了研究一种带导叶的双吸泵反转作为液力透平使用时的性能,采用SST k-ω湍流模型,对该双吸泵的性能进行了预测,并对其反转作为液力透平的性能进行研究,对水泵制动工况以及反水泵工况进行预测．通过液力透平全特征曲线分析,该双吸泵额定工况点效率为893％,反转为液力透平时,额定工况点效率可达905％,且当工作水头大于200 m时,该液力透平具有较宽的工作范围;机组双向运行稳定性均较好,双吸泵不存在驼峰现象,液力透平运行特性曲线中存在明显的“S”特性,运行过程中应尽量避免运行在该“S”区域．通过内流场分析,额定工况下双吸泵和液力透平转轮内部流线规则,无回流和脱流现象;但双吸管与叶轮之间流道狭窄,存在强旋流现象;机组运行在反水泵工况时,转轮内的回流将导致产生失速涡;机组运行在水泵制动区时,转轮内将产生失速．液力透平运行时必须考虑运行工况下的空化现象,避免空化的产生．

Numerical prediction on over all performance of double suction pump reverse running as turbine

To study the behavior of a double suction pump with guide vanes when running as a turbine, the performance of the pump was predicted by using the SST k-ω turbulence model; meanwhile, the performance in turbine mode was investigated as well, especially in the braking pump mode and reverse rotation pump mode. It was shown that the pump efficiency at the rated point is 89.3% and the peak efficiency in turbine is as high as 90.5%; moreover, when the head is more than 200 m, the turbine can keep a higher efficiency over a wider flow rate range. The head curve in pump mode doesn′t show a positive slope at all; in turbine mode, however, the curve exhibits a "S" shape zone, suggesting a turbine shouldn′t be operated in that zone. The flow patterns in the runner are smooth and there is no reverse or separation phenomenon in the pump and turbine modes at the duty points. The passage between the runner and the double suction pipe is so narrow that the flow swirls strongly there. When the pump is operated in reverse rotation and braking pump modes, the reverse flow in the runner leads to stall phenomena. It is necessary to consider that cavitation may occur in turbine mode, for o peration safety occurrence of cavitation should be avoided.