轴向间距对贯流式水轮机水力性能的影响

为了寻找贯流式水轮机中导叶与转轮轴向间距的合理取值,在保证其结构紧凑性的同时,获得良好的水力性能,在其他主要参数不变的情况下,通过试验与数值计算相结合的方法,分别对导叶与转轮之间轴向间距s值为30, 40, 50, 60和70 mm 的微贯流式水轮机模型进行全流场数值计算,研究轴向间距对贯流式水轮机水力性能的影响.结果表明:水轮机的水头随着轴向间距的增大而增加,水轮机的轴功率随着轴向间距的增大呈现先上升后稳定的趋势;综合各流量条件,水轮机通常在适中的轴向间距下取得较高的效率,该模型在s=40 mm时效率达到最高.选择适中的轴向间距可以改善转轮叶片表面压力分布和流态;过大的轴向间距会导致转轮进口发生负撞击,出现脱流现象;转轮出口的湍动能随着轴向间距的扩大而减小.在最优工况下,轴向间距从30 mm扩大至70 mm的过程中,转轮内部的水力损失逐渐增加,增加幅度达到15.6%,而出水管中的水力损失则减小了19.7%,总水力损失呈增加趋势.综合考虑,选用s=40 mm 作为最终方案.

Influence of axial spacing on hydraulic performance of tubular turbine

In order to find a reasonable value for the axial distance between the guide vane and the runner in the tubular turbine, as well as obtaining good hydraulic performance while ensuring its compact structure, the numerical calculation of the full flow field was carried out for the micro tubular turbine models with axial distance s of 30, 40, 50, 60 and 70 mm between the guide vane and the runner to study the influence of axial spacing on the hydraulic performance of a tubular turbine by combining numerical calculation and experiments. The results show that: the water head of the turbine increases with the expansion of the axial distance, and the axial (shaft) power of the hydraulic turbine increases first and then stabilizes with the expansion of the axial distance. Considering various flow conditions, higher efficiency was obtained, and the efficiency of the model reaches the maximum when s=40 mm. Choosing appropriate axial spacing can improve the pressure distribution and flow pattern on the surface of runner blades. Excessive axial spacing will cause negative impact at the inlet of the runner and result in flow separation. The turbulent kinetic energy at the outlet of the runner decreases with the increase of axial spacing. under optimal working conditions, when the axial distance is spacing is expanded from 30 mm to 70 mm, the hydraulic loss inside the runner gradually increases by 15.6%, while the hydraulic loss in the outlet pipe decreases by 19.7%, and the total hydraulic loss shows an increasing trend. Considering comprehensively, s=40 mm was selected as the final scheme.