Research On The Influence Of Impeller Cutting On The Performance Of Hydraulic Turbine

In the process of chemical engineering,A large amount of high pressure liquid energy needs to be recovered.Pump as turbine is one of the main ways to recover these energy.However,when the pump is reversed,it has a narrow working range and can not meet the needs of the selection.Therefore,it is necessary to study the performance of impeller cutting of turbine to enlarge its range of app lication.In this paper,three sets of low and medium specific speed centrifugal pump as turbine chosen from some pump factors' recent designed models has been selected as research target and the impeller of the models are cut for four times.The method of numerical simulation is used to discusse the influence of impeller cutting on external characteristic and internal flow field of low and medium specific speed centrifugal pump as turbine.The calculation results show that :1.With the increase of impeller cutting,the pressure head and shaft power of three low and medium splecific speed hydraulic turbine shows a downward trend.For the pressure head,the amplitude of preesure head decreases more when the turbines is in a small-flow conditions and the pressure head decreases less when the large flow rate is working.For the shaft power,the amplitude of the shaft power decreases less whten the turbine is in the small flow conditions and the shaft power decreases more when the large flow tate is working.2.With the increase of impeller cutting,three low and medium specific speed hydraulic turbines in their small-flow conditions,the hydraulic efficiency showed an upward trend.When turbines are in their optimum operating condition and large flow condition,hydraulic dfficiency shows a downward trend and in the large flow conditions the hydraulic efficiency decreases more pronounced.When the cutting limit reaches the maximum,compared with their original models,the hydraulic efficiency of the six turbines at the optimal operating conditions decreases by 3.2% ?1.57%?0.9%?4.5%?3.56% and 2.12%.3.With the increase of impeller cutting,the static pressure of three low and medium specific speed hydraulic turbines at the inlet is lower than the static pressure at the inlet of non cutting turbine models and the stati c pressure at the outlet become slightly higher.In the small flow condition,with the increase of impeller cutting,the vortex area and dimension of flow field inside the turbine has decreased.In the condition of large flow rate,with the increase of impeller cutting,the velocity distribution at the inlet of turbine impeller is more disorder than that of the original model,and the vortex scale increases obviously.