可控曲率半径的圆柱形叶片逐点绘型方法

针对中低比转速离心泵,根据叶片进出口边界条件,以逐点绘型方法为基础,提出了一种新的曲率半径可控的叶片绘型方法。该方法的主要特点是曲率半径比值可作为设计常量由设计人员根据需要事先给定,随后分析了曲率半径及比例因子对叶片安放角、叶片包角、相对速度及速度矩等的影响。结果表明,不同曲率半径比值下的叶型参数及流动参数变化范围很大,曲率半径比值较大时,节流损失较大,泵扬程较低,曲率半径比值较小时,脱流损失较大,泵效率较低,存在较优的曲率半径比值区间[1.4,2.4],使叶片安放角平滑变化,泵的综合性能较优,在该优化区间内,取较大的曲率半径比值有利于获得较优的汽蚀性能,比例因子为0时叶片安放角的变化较为平稳,可用于开展离心泵的初步设计。

Point-by-point drawing method for cylindrical blade with adjustable curvature radius

According to the boundary conditions at blade inlet and outlet,a new drawing method for cylindrical blade with adjustable curvature radius is proposed for low-specific-speed centrifugal pump (LSPCP),which is based on the point-by-point construction method.The most notable feature of this new method is that the curvature radius can be specified as a design constant by impeller designer.The influence of curvature radius and scale factor on blade angle,vane wrap angle,relative velocity and velocity moment is analyzed.The results indicate that the parameters of blade profile and flow have a very large change range at different curvature radius ratio:the throttling loss increases and head of pump decreases with the increase of curvature radius ratio,the off-flow loss increases and efficiency of pumps decreases with the decrease of curvature radius ratio.When the ratio of curvature radius is in the interval of 1.4～2.4,the blade angle change is smooth and the performances of the pump are optimal.In the optimal interval,the larger curvature radius ratio is in favour of getting the optimal cavitation performance.In practical applications,the blade angle changes smoothly if the scale factor equals to zero.Therefore,it can be used in the initial pump design.