Research On The Influence Of The Number Of Guide Vanes And Clocking Effect On Hydraulic Turbine

The energy recovery technology of turbines can recover high-pressure energy from liquid residual pressure during industrial production and achieve efficient use of energy.Pump As Turbine(PAT),which uses a centrifugal pump reversed as a hydraulic turbine,is increasingly being widely used in industries such as petrochemicals and seawater desalination due to its simple structure,ease of operation and maintenance,and economy.Although PAT can recover energy well,it generally suffers from low efficiency,narrow high-efficie nc y zone,and instability during operation.Theoretical analysis shows that adding guide vanes before the impeller inlet of PAT can make the velocity torque distribution at the impeller inlet more uniform.In addition,the timing angle o f the guide vanes(the relative position between the guide vanes and the baffle)also has a certain influence on the hydraulic turbine.This paper carries out research on the aforementioned two problems,and the main research content includes adding guide vanes before the impeller inlet of PAT to achieve uniform distribution of velocity torque and studying the effect of the clocking angle of the guide vanes on the performance of the hydraulic turbine:1.To investigate the influence of guide vane number on the performance of PAT,we referred to the hydraulic model manual of Shenyang Pump Research Institute and selected a M69-25 single-stage centrifugal pump reversed as a hydraulic turbine as the research object,keeping the geometric parameters of the impeller unchanged.We designed special guide vanes for the hydraulic turbine,which are symmetric guide vanes that do not change the velocity torque.After adding the guide vanes,the base circle diameter of the volute increased,so it was necessary to redesign the volute to facilitate the operation of PAT.Numerical simulations showed that when the number of guide vane blades was Z+9,Z+11,and Z+13(Z is the number of impeller blades),the efficiency of PAT increased by 1.48%,1.86%,and 0.58% compared to PAT without guide vanes respectively.Adding guide vanes can make the velocity torque distribution at the impeller inlet more uniform,and the distribution is most uniform with Z+13 guide vanes.After adding guide vanes,the main frequency amplitude and maximum fluctuation amplitude of pressure pulsation in the volute were reduced,and the largest decrease occurred when the number of guide vanes was Z+9.2.When the number of guide vane blades is 14,the overall hydraulic performance of PAT is better.In this chapter,we took the hydraulic turbine with14 guide vanes as the research object to study the influence of clocking effects on PAT performance,and designed five timing angle schemes(5°,10°,15°,20°,25°),with 5° being the initial scheme.Numerical sim ulations showed that as the clocking angle increased,the efficiency of PAT gradually increased.At the optimum operating point,the efficiency of PAT with 25° clocking angle was0.54% higher than that with 5° clocking angle.Under the same operating conditions,the fluctuation amplitude of pressure pulsation at the tongue decreased first and then increased with the increase of clocking angle,with the minimum value occurring at 15° and the maximum value at 25°.The fluctuation amplitude of pressure pulsation inside the guide vane also decreased first and then increased with the increase of clocking angle,and was minimized at 20°,while the maximum amplitude occurred at 5°.