离心泵作液力透平叶轮出口滑移系数的解析计算方法及验证  

Analytical methods and verification for determining slip factor at impeller outlet of centrifugal pumps as turbines

作　　者：史广泰[1] 杨军虎[2] 苗森春 

机构地区：[1]西华大学能源与动力工程学院,成都610039 [2]兰州理工大学能源与动力工程学院,兰州730050

出　　处：《农业工程学报》2015年第11期66-73,共8页Transactions of the Chinese Society of Agricultural Engineering

基　　金：国家自然科学基金资助项目(51169010);"十二五"国家科技支撑计划资助项目(2012BAA08B05)

摘　　要：为了通过理论的方法准确预测液力透平的性能,该文分析了叶轮内部相对环流流动的特征,提出了3种计算离心泵反转作液力透平叶轮出口滑移系数的方法,得到了相应的叶轮出口滑移系数解析计算公式,然后采用10组离心泵反转作液力透平的试验数据对所提出的滑移系数计算公式进行验证,最后得出与试验结果较为吻合的解析公式。结果表明:当假设叶片工作面上的相对涡诱导速度与叶轮出口边上的相对涡诱导速度的比值等于叶片和涡心所张曲边三角形的面积与叶轮出口边和涡心所张曲边三角形的面积之比时,得到的液力透平叶轮出口滑移系数的计算公式最准确,可用于较准确地预测液力透平的性能。在计算液力透平叶轮内的滑移时只需计算叶轮出口的滑移。该研究结果为更加精确地通过理论方法预测液力透平的性能提供了参考。A centrifugal pump can be operated in its reverse rotational direction as a turbine-a prime motor, and its impeller is a kind of centripetal impeller. It can convert the high pressure energy of a fluid into the rotational mechanical energy of the rotor to drive a generator to generate electricity or drive a working machine, realizing an energy recycling of the high pressure fluid. It is well-known that the slip phenomenon exists in turbomachinery, such as hydraulic turbine, steam turbine, roto-dynamic pumps and compressors. This is also true for a centrifugal pump as turbine. The slip velocity may be smaller in a hydraulic turbine than a centrifugal pump. However, this is not the case for a centrifugal pump as turbine because its number of blades is much less compared with the hydraulic turbine. The constraint ability of blade is less for fluid giving rise a smaller slip factor. In addition, a slip factor is the key parameter to estimate the turbine output power based on its existing geometry and designed flow condition to check if its output power has met the requirement by end-users. Unfortunately, this topic is not well documented currently. In this paper, we put forward an analytical method to accurately determine the slip factor at the impeller outlet in a centrifugal pump as turbine in order to predict the turbine performance correctly. Firstly, the relative eddy flow in an impeller passage with closed inlet and outlet was analyzed for a centrifugal pump in its turbine mode. Secondly, three assumptions were made for the induced velocity by the eddy on the blade pressure side, then the slip velocities and the corresponding slip factors at the impeller outlet under these assumptions were derived analytically. Finally, the slip factor formulas were validated by means of the theoretical heads of ten centrifugal pumps as turbines based on their experimental data. Two cases, namely, the slip factors at both impeller inlet and outlet, and the slip factor at the impeller outlet alone, were studied, respectively. It

关 键 词：泵 叶轮 速度 滑移系数 泵作透平 理论水头 相对涡 

分 类 号：TH311[机械工程—机械制造及自动化]