Influence Of The Maximum Camber Position On The Performance Of Airfoil And Axial Pump Impeller

The water pump is a machine that transfers energy.Since China’s reform and opening up,a large number of pumps have been used in agricultural irrigation,urban construction and flood control and disaster reduction projects.Axial flow pump is an airfoil mainly used in low lift pump station with features of large flow,low head,and high degree of information,widely used in pumping stations for irrigation,drainage,and urban water supply and drainage in the plain area.Now,there are more than 300 large-scale low-head pump stations in China.The flood-fighting,drainage,and inter-basin water transfer engineering system centered on it has been formed,which has promoted China’s modernization and rapid economic development.Axial-flow pump as the main part of the pump station,its performance is very important for the performance of the pump station.The key to determining the performance of the axial-flow pump is the cross-sectional shape(airfoil)of the impeller blade.Therefore,the airfoil has a direct impact on the hydraulic performance and cavitation performance of the axial-flow pump,which also affects the efficiency of the pump system and the safe and reliable operation of the pump station.The optimization of the blade airfoil mostly changes the parameters of the airfoil to change the airfoil performance.The parameterization of the airfoil based on the Bezier curve is widely used in hydraulic turbines,wind turbine,etc.,but is rarely applied to the impeller airfoil of the axial-flow pump.Therefore,it is of significance to use the parameterized airfoil of Bezier curve as the optimization basis.This paper first analyzes the axial-flow pump airfoil in two dimensions,then studies the influence of the maximum camber location on the hydrodynamic characteristics of the airfoil,finally selects three better airfoils as the basis for modeling three-dimensional impellers and compares various performance of the three pumps system.So get the following conclusion:(1)Three kinds of turbulence models including the standard k-ε model,RNG k-ε model and Realizable k-ε model were used to calculate the NACA0012 airfoil.By comparing the experimental results with the performance of the airfoil to be calculated in this paper,it is best to use the RNG k-ε turbulence model for airfoil to calculate and optimize.Through the numerical simulation of a specific airfoil(the original airfoil)to analyze its hydraulic performance.(2)The fourth-order and fifth-order parameterization of the original airfoil by using Bezier curves shows that the fifth-order parameterized airfoil and the original airfoil are the most similar in appearance.Move the position of the maximum camber of the fifth-order parametric airfoil and discover:With the maximum camber position unchanged,the maximum drag coefficient decreases as the maximum camber height decreases.In the case of the same lift coefficient(within 2%error),the height decreases and the minimum pressure increases as the maximum camber position changes.The lift-drag ratio generally increases first and then decreases.The airfoil’s maximum lift ratio is best when the airfoil’s maximun camber is at a relative chord length of 0.4 to 0.6.(3)In the three-dimensional model of the airfoils with the maximum camber at the relative chord lengths of 0.4,0.5,and 0.6,among them,the maximum camber is at the 0.6 position relative to the chord length and the efficiency is 84.53%.Comparing the internal flow lines of different pump sections under different flow rates,it was found that the spiral flow was concentrated on the right side of the outlet elbow and cavitation occurred easily.And the flow state at the inlet end of the outlet elbow get worse as the maximum camber position turn to the right.At a small flow rate,the static pressure distribution of the impeller A is the most uniform,the static pressure distribution of impeller B is more uniform near the optimal flow rate,while the static pressure distribution of impeller C is the most uniform in the large flow area.Therefore,different maximum camber positions can be selected according to the required flow and head value.In span=0.9 position,with the same impeller,its cavitation performance becomes better as the flow rate increases,as the flow rate increases,the minimum pressure value first increases and then decreases.Get the maximum value near the optimal operating conditions,this point is the best cavitation performance.with different impellers,the cavitation performance becomes better with the right shift of the maximum crown position at the same flow.