Research On The Effect Of Different Blade Tip Shape On The Flow Characteristics Of Centrifugal Pump

In the production and practical application of air-conditioning condensate freshwater pumps,there is often a small difference between the performance parameters of the pump and the requirements for on-site use,the simplest and most effective solution is to cut the working and back surface of the impeller,The resulting shape of the trailing edge of the blades will have a certain effect on the internal flow characteristics of the pump.In this paper,a typical air-conditioning condensate freshwater pump as the research object,on the basis of the existing impeller model put forward three kinds of repair model,that is,cut working surface of the blade's tail,cut back surface of the blade's tail,cut the working and back surface of the blade's tail,create a Computational Fluid Dynamics Model that includes the four models,through the external characteristic parameters,steady flow field changes and unsteady pressure pulsation characteristics,the influence of the shape of the blade tip on the internal flow characteristics of the pump is deeply discussed.The research work of this paper is as follows:(1)A Computational Fluid Dynamics Model for air-conditioning fresh water pumps with four different blade tail shapes,run Pro/E software to build 3D models,use ICEM software for high-quality structured meshing,and import unstructured grid files into Fluent software to do fixed-value simulations of the centrifugal pumps described in this article.(2)The flow-head and flow-efficiency curves of the pump under the four model schemes were analyzed.It was concluded that cutting the back surface of the blade's tail had the most obvious effect on the lift of the pump,cutting the working and back surface of the blade's tail can not only improve the efficiency of the pump but also ensure a wider efficient operating area.It has great significance of engineering.(3)The static pressure cloud diagram,velocity cloud diagram,velocity vector diagram and velocity streamline diagram of the middle section of the pump impeller trailing edge shape under different working conditions were analyzed.It is concluded that when the pump is operated under conditions above 0.8Q,cut the back surface of the blade's tail leads to the fluid kinetic energy can be converted into better pressure energy,and the actual head achieved is also the highest;In the 1.2Q working condition,when cut the working face of the blade's tail,the internal vortex area issmaller,the energy loss is smaller,the efficiency is higher,and the pump operation reaches the optimal operating state.(4)Calculates and analyzes the unsteady pressure pulsation of an air-conditioning condensate fresh water pump,it was found that the pressure pulsation of the centrifugal pump is mainly caused by the dynamic and static interference between the rotation and the guide vanes and the backflow and vortex of the fluid in the volute.Under the three conditions(0.8Q,1.0Q,1.2Q),the three repair programs proposed in this paper can improve the pressure pulsation of the original model pump to a certain extent,under the design conditions(1.0Q),Obviously improve the pressure pulsation of the original model;At the same time,it has been found that the three cutting schemes have different degrees of improvement in the pressure pulsation of the original model pump,and only cutting the back surface of the blade's tail can maximally improve the centrifugal pump pressure pulsation,the pressure pulsation frequency is more concentrated on the blade passing frequency,and the pressure pulsation amplitude is greatly reduced,which is conducive to the stable operation of the centrifugal pump.(5)The steady flow characteristics under different working conditions and the unsteady flow characteristics under design conditions of the blade's trailing edge of the air-conditioning condensate fresh water pump were compared and analyzed.It is concluded that,under steady conditions,the performance of cutting the working surface of the blade's tail is best when operating at a low flow rate(0.8Q).When operating at 1.0Q and 1.2Q,the overall improvement of the performance of the centrifugal pump is the most obvious at cutting the back surface of the blade's tail.Under unsteady conditions,cutting the back surface of the blade's tail ensures maximum pump head and flow efficiency at design flow.The conclusion of this study can provide some theoretical support for the improvement of the performance parameters of air conditioning condensate water pump,and has certain guiding significance.