Numercial Analysis On Two-phase Flow Performance Of A Hydraulic-turbine And Study On The Volute Modification

Hydraulic-turbines can be used to recover residual pressure energy in industrial processes.They are the key equipment developed in China's current energy policy.In the recovery of residual pressure energy of some industrial processes,the high-pressure working fluid is a gas-liquid two-phase mixture,and the hydraulic-turbine is required to operate efficiently and stably under the gas-liquid two-phase condition.In order to reveal the gas-liquid phase flow law and energy conversion mechanism of the turbine under two-phase working conditions,the uneven distribution of the gas phase in the turbine is improved,and the energy recovery efficiency of the turbine under the two-phase condition is improved.The Eulerian-Eulerian particle two-phase model and the SST k-?turbulence model are used to study the hydraulic-turbine.The performance of the model under different gas-liquid two-phase conditions is studied.The flow law of the two-phase working fluid in the turbine is analyzed.The mechanism of the two-phase separation in the turbine and the reason that the function of the turbine is decreased with the inlet gas volume fraction are analyzed.A modification scheme for suppressing the gas-liquid separation in the volute is proposed.Numerical calculation and analysis were carried out on the effect of the scheme.The research results show that the hydraulic-turbine has 90%efficiency when working in pure liquid working conditions;with the increase of gas volume fraction in the turbine inlet working fluid,the efficiency and output power of the turbine are significantly reduced.The gas-liquid separation phenomenon in the volute is intensified,and the uneven distribution of the gas phase in the internal flow field of the turbine is intensified,and the gas volume fraction at the outlet side of the impeller increases and gas phase aggregation occurs.At the same time,when the inlet side of the impeller returns,the vortex of the suction surface in the impeller flow passage becomes larger,the energy dissipated increases,and the pressure difference between the pressure surface and the suction surface decreases,resulting in a decrease in turbine output power and efficiency.After adding the partition structure in the volute,the efficiency and output power of the turbine are effectively improved.When the volume fraction of the inlet gas phase is 0.20,the turbine output power can be increased by an average of 30 kW,which can be used in medium flow conditions.The highest efficiency of the turbine is increased by 4.10%.The two-phase working fluid is divided into two parts in the volute,which inhibits the separation of the two-phase working fluid,and the gas content of the two-phase working medium in the rear quarter of the volute increases.The re-adjustment of the gas phase in the volute improves the inlet flow field of the impeller,increasing the pressure on the pressure side of the impeller inlet and increasing the pressure difference between the pressure surface and the suction surface of the vane.At the same time,the turbine suction surface vortex of the turbine after the volute is modified is smaller than the unmodified model,the energy of the vortex dissipation is reduced,and the output power and efficiency of the turbine are effectively improved.