Numerical Simulation Study On The Effect Of Adjustable Guide Vanes On The Performance Of Axial Flow Pump Equipment

Axial flow pumps,which have the characteristics of large flow and low head,play an important role in urban flood control and drainage,agricultural irrigation,and water level regulation of ship locks in China.As important flow passage devices,impeller and guide vane assembly and installation form have a significant impact on the performance of axial flow pump devices.However,at present,the conventional guide vane design is fixed,and only the impeller blade placement angle can be adjusted under non design conditions,resulting in lower pump performance.Therefore,studying the effects of integral and partial adjustment of adjustable guide vanes on the performance of axial flow pumps with fixed impeller blade placement angles has certain engineering practical value and theoretical research significance.In this paper,under different flow rates,the optimal combination is found by changing the placement angle of the integral impeller blade and the guide blade.Based on this,the impact of adjusting the placement angle of the inlet blade on the performance of an axial flow pump is studied.In this paper,UG software is used to model the inlet and outlet channels and guide vane segments of an axial flow pump,and ANSYS Mesh is used to mesh them;TurboGrid is used for three-dimensional modeling and mesh generation of impeller segments.After grid independence analysis and calculation,the total number of grids selected for calculation is about 3.97 million.Finally,numerical simulation analysis is performed by using CFX software.In this paper,the research on the impact of impeller and guide vane placement angle on the hydraulic performance of axial flow pump devices mainly includes the following contents:(1)Analyze the impact of impeller blade placement angles of 0 °,±2°,and ±4° on the external and internal flow characteristics of axial flow pumps under different operating conditions.Taking the highest efficiency of the axial flow pump device as an indicator,select the impeller blade placement angle of-2° for subsequent research and analysis.At this time,the efficiency is 73.09%,which is 1.04%higher than the initial scheme efficiency of 72.05%.(2)Analyze the impact of adjusting the overall placement angle of the guide vane on the external and internal flow characteristics of the axial flow pump under different operating conditions when the impeller blade placement angle of the axial flow pump is taken as-2°.The study found that with the increase of flow rate,the overall adjustment angle of the guide vane corresponding to the optimal efficiency of the axial flow pump under various operating conditions shows a corresponding increase trend.That is,with the increase of flow rate,in order to improve the efficiency,the guide vane should be adjusted clockwise.By changing the overall placement angle of the guide vane,the efficiency of the axial flow pump device can be further improved.Under low flow conditions,adjusting the overall placement angle of the guide vanes can effectively improve the efficiency of the axial flow pump device:when the flow rate is 297L/s,the efficiency after adjustment is increased by 4.41%compared to the efficiency before adjustment;When the flow rate is 330L/s,the efficiency is 2.93%higher than that before adjustment.Under high flow conditions,adjusting the overall placement angle of the guide vanes can also improve the efficiency of the axial flow pump device to a certain extent:when the flow rate is 363L/s,the efficiency is 1.13%higher than that before adjustment.(3)The method of sectional adjustment of guide vanes is proposed.After selecting the overall adjustment of the guide vane placement angle,the three operating conditions of Q=297L/s,Q=330L/s,and Q=363L/s,which have relatively good hydraulic performance and relatively excellent flow patterns in the internal flow of the axial flow pump,are selected as the basis for the calculation and analysis of sectional adjustment of guide vanes of axial flow pumps.Changing the inlet angle of the guide vane can further improve the hydraulic performance of the axial flow pump device,but the effect is limited.Under low flow conditions,adjusting the overall placement angle of the guide vane can further improve the efficiency of the axial flow pump device:when the flow rate is 297L/s,adjusting the placement angle of the guide vane increases the efficiency by 0.85%compared to before adjustment;When the flow rate is 330L/s,after adjusting the guide vane placement angle,the efficiency increases by 1.87%compared to before adjustment.Under high flow conditions,continuing to adjust the inlet placement angle of the guide vane inlet section is not conducive to further improving the hydraulic performance,but will result in a reduction in the efficiency of the axial flow pump device.When the flow rate is 363L/s,the adjustment effect is poor.(4)After selecting the guide vane inlet placement angle,the influence of adjusting the guide vane inlet placement angle on the pressure pulsation of an axial flow pump is analyzed.It is found that when the inlet angle of the guide vane is constant,the pulsation intensity value at the monitoring point at the impeller inlet decreases with the increase of the flow rate;The fluctuation intensity value at the monitoring point at the impeller outlet has little change;The pulsation intensity values at the monitoring points at the middle section and outlet of the guide vane have a decreasing trend;When the flow rate is constant,generally speaking,the influence of adjusting the inlet angle of the guide vane on the pressure fluctuation in each region is not significant,but there is a certain angle that makes the pressure fluctuation at the impeller outlet section relatively stable.