| With its remarkable and reliable speed regulation and energy saving characteristics,high-power hydraulic coupling has become the first choice of speed regulation and energy-saving equipment for large nuclear power plants and thermal power stations.With the rapid development of the national economy,in order to meet the demand of the constantly developing capacity of generating sets,the high-power hydraulic coupling continues to develop towards the direction of high power and high speed.In contrast,the Reynolds number of the gas-liquid two-phase flow field inside the coupling device increases sharply,which leads to the increase of flow loss,the decrease of energy capacity and the instability of output characteristics.At the same time,the influence of flow channel structural parameters on the performance of the gas-liquid two-phase flow field is more sensitive under the condition of high Reynolds number.Compared with the conventional operating conditions,the internal and external characteristics of the flow field have changed significantly,and the existing design theory of the fluid coupling channel structure based on similar conditions needs to be verified.In this paper,yotc510 type hydraulic coupling is selected as the analysis model,and computational fluid dynamics(CFD)numerical calculation method is used to study the influence of the flow channel cavity structure parameters on the characteristics of the fluid coupling under high speed and high power.Based on the analysis results,the optimized structure parameters of the flow channel are proposed,the optimized flow channel structure parameters were proposed,the flow field characteristics of the structure under transient conditions were analyzed,and the accuracy of the numerical calculation results was verified through experiments.The work in this paper provides a method and theoretical basis for the design and optimization of the flow channel structure of high-power hydraulic couplings.The main research contents and conclusions of this article are as follows:(1)The effect of impeller number on the performance of high-power hydraulic couplings.The effect of impeller number on the performance of high-power hydraulic couplings.Three-dimensional modeling software was used to build a three-dimensional geometric model of different blade number schemes for pump wheels and turbines,and the flow channel model was extracted for hexahedral mesh division.Based on the numerical simulation method,the internal gas-liquid two-phase flow law of high-power hydraulic coupling is analyzed,the internal flow field pressure,velocity,fluid trace information and external characteristic torque value are extracted,and the flow field motion rule of different blade number schemes is compared and analyzed.The results show that the optimal number of blades for the pump wheel and turbine should be 47 and 48.Too many blades will affect the effective cavity volume of the coupling,which will increase the friction loss between the fluid and the blades and reduce the efficiency.If the conversion is insufficient,the impact loss and volume loss increase.If there are too few blades,the fluid circulation flow will not be converted sufficiently,and the impact loss and volume loss will increase.(2)The influence of curvature radius of pump wheel inlet and outlet on hydraulic coupling performance.Under the premise of keeping other parameters unchanged,adjust the value of the inlet and outlet curvature radius of the pump wheel,form different schemes and carry out simulation work to obtain the characteristic information of the flow field inside and outside,and compare and analyze the influence of the inlet and outlet curvature radius of the pump wheel on the performance of the coupling.It is concluded that increasing the inlet curvature radius of the pump wheel in a reasonable range can effectively increase the energy capacity,improve the torque coefficient of the pump wheel,so that the coupling device has a better ability to transfer torque;reducing the outlet radius of the pump wheel can effectively avoid secondary flow and vortex in the flow field and reduce the energy loss caused by eddy diffusion.The better combination of pump wheel inlet and outlet radius should be 53.4 and 80.(3)Proposing reasonable cavity structure parameters and carry out characteristics for prediction and experimental verification.According to the influence trend of impeller blade number and cavity channel structure parameters on high-power hydraulic coupling,a set of reasonable channel structure parameters is proposed for modeling and numerical simulation,based on the analysis of the typical transient flow conditions of the channel scheme,the main reasons for the decrease of circulating flow rate and efficiency of the high-power hydraulic coupling were explored.The external characteristic torque curve calculated by simulation is compared with the experimental curve to verify the effectiveness of the numerical simulation method. |
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