基于流体体积模型的叶轮宽径比对水车性能的影响

Effect of width-to-diameter ratio of impellers on waterwheel performance based on volume of fluid model

为了研究一种环保、简易的微水头发电水车装置,建立了水车在河流中的三维模型,采用流体体积(VOF)模型,压力-速度耦合选择PISO格式进行求解,对不同叶轮宽径比的水车进行非定常流动分析.结果表明:叶轮宽径比为3.93的胸射式水车效率区最为宽广,最优效率最高.叶轮宽径比增大使得流道的阻塞效应增强,上、下游水位差增大,出现明显涡流现象.不同宽径比的水车叶轮叶片转矩呈现同一周期性变化规律,当水车处在枯水期运行时,叶片运动过程中浸入水中的两叶片间会出现回流现象,使得转矩有小范围的极值出现.未浸入水中的两叶片间压力随叶轮宽径比增大而增大.5种叶轮宽径比的水车叶片均在叶尖处正面压力达到最大,且叶轮宽径比为3.93的水车浸水叶片正、背面压力差最大,提高了叶片的做功能力.该结果对胸射式水车的叶轮结构设计与性能分析能够起到指导作用.

In order to study an eco-friendly and simple waterwheel device with a micro water head,a three-dimensional model of the waterwheel in the river was established.The volume of fluid(VOF)model was used,and the pressure-velocity coupling was solved in the PISO format.The width-to-dia-meter ratio of different impellers was calculated.Unsteady flow analysis was performed on the waterwheels.The results show that the chest shot waterwheel with an impeller width-to-diameter ratio of 3.93 has the widest efficiency zone and the highest optimal efficiency.The increase of the width-to-diameter ratio of the impeller increases the blocking effect of the flow channel,and the water level difference between the upstream and downstream increases,and the obvious vortex phenomenon appears.Torques of waterwheel blades with different width-to-diameter ratios show the same periodic change,when the waterwheel is running in the dry season,there will be a backflow phenomenon between the two blades immersed in the water during the movement of the blades,so that the torque has a small range of extreme values.The pressure between the two blades that are not immersed in water increases as the width-to-diameter ratio of the impeller increases.The front pressure of the waterwheel blades of five width-to-diameter ratios reaches the maximum at the tip of the blade,and the waterwheel with an impeller width-to-diameter ratio of 3.93 has the largest pressure difference between the front and back sides of the waterwheel blades,which improves the blade′s performance.The results play a guiding role in the design of the impeller structure of the chest shot waterwheel.