The Analysis Of Axial Flow Pump Blade Inner Stress

Axial flow pump is used widely in most departments of the civil economy, which makes it significant to ensure that the pump works well. Blade is the key component of an axial flow pump, the reliability of which is critical to the safety of the pump. Cracks are the main factors in many cases of impeller accident. Therefore, it is very important to check the strength of blade by scientific and appropriate methods. The water pressure is difficult to analyze because of the complex shape the blade takes. So many designers of pump simplify the blade as cantilever girder. But only the mean stress can be obtained by this method, and a very high safety-coefficient is used for the stress concentration. To add the thickness of blade will not only affect the hydraulic capability of the pump, but also do wasting. In all, it is difficult to ensure the principle of safety, high efficiency and economy.The paper uses the pressure field computed by CFD, and calculates the inner stress with the elasticity theory by finite element method. Because it is difficult to load the boundary condition in software named MSC.marc, programmes are compiled in Fortran to modify the files that MSC.marc can read. In the analysis of the model in MSC.marc, the concentrated stress and the stress distribution is got correctly, and the blade strength is checked . And then, it is necessary to calculate the blade inner stress by altering the thickness of blade root and the diameter of handle. A trend line is drawn by which the concentrated stress for some root thickness or handle diameter is known.In the analysis of the blade, three typical cases of pump are concerned( the original of the blade is the hydraulic model named Zm60), and different root thickness and handle diameter is considered. After comparing the results, it is obvious that traditional method does ensure the safe performance of pump, but the result doesn't reflect the concentrated stress, which exists in the blade, and that the data of concentrated stress on intake is bigger than that of exit, and that not only the thickness of root and tine but also the diameter of handle have a non-linear influence on the concentrated stress, and that the maximum displacement takes place on the tine of blade intake.