Design Of Variable Speed High-power Hydrodynamic Coupling Based On CFD

With the development of our economy, equipment power and installed capacity increase very quickly in many industries, such as electric power, metallurgy, chemical industry, petroleum, mining and so on, and the demands of the pump and fan increase continuously. So the high-power energy-saving products are required urgently. The effect of saving electricity is conspicuous when variable speed hydrodynamic applies on fans and pumps, the more the power is, the more the saving electricity effect is. Aiming at some key technical problems which the design and manufacture of variable speed high-power hydrodynamic coupling is confronted with, this paper associates with the special subject"Key Technological Research on Hydrodynamic Variable Speed and Saving Energy of Large Pump and Fan"of the National High-tech Research Development Plan (863). Firstly, non-steady numerical calculation is conducted for the gas-liquid two-phase flow of hydrodynamic coupling, based on the calculation results velocity and press distribution of flow is analyzed in detail, and the flow law and behavior are revealed. Then the performance prediction of hydrodynamic coupling is conducted based on flow-field numerical solutions, and the correctness of the theoretical method and calculation is verified by comparing with the test results. Based on this, the modern design method of variable speed high-power hydrodynamic coupling is studied. The parametric design and optimization design is developed by UG and CFD, which can reduce the cost and cycle of design and modify, and make it convenient for the hydrodynamic coupling to popularization and application.Numerical Calculation of Gas-liquid Two-phase Flow in Variable Speed High-power Hydrodynamic CouplingAdjustable-speed function of variable speed hydrodynamic coupling is achieved by changing the liquid filled ratio. The inner has complicated gas-liquid two-phase three-dimension viscous flow. Three multiphase flow models in CFD method, which includes VOF model, Mixture model and Eulerian model, are further studied based on fully understanding the calculation models of gas-liquid two-phase flow and basic control equations of fluid motion as well as certain common used turbulence models and the methods to numerical simulation of turbulence. The calculation of gas-liquid two-phase flow of hydrodynamic coupling is conducted used Mixture model according to its characteristics.The calculation of gas-liquid two-phase flow is conducted through choosing relevant calculation parameters according to the working state of the variable speed high-power hydrodynamic coupling. The concrete calculation parameters are as follows: PISO algorithm is used in velocity-pressure coupling algorithm; the second-order upwind scheme is used in space disperse format; the non-steady model is used in numerical simulation method; sliding mesh theory is used in interface of the pump and turbine; the whole flow passage is used to calculate the flow field; the no-slip wall boundary condition is used in blades and the outer wall. The method and process of three dimensional field calculation is described in detail taking YOCQZ450 variable speed hydrodynamic coupling as example, including the basic assumption, geometric model, mesh model, boundary conditions, calculation steps, convergence criteria, and the internal flow field of hydrodynamic coupling in different conditions are calculated.Flow Field Analysis of Variable Speed Hydrodynamic CouplingIt has important significance of understanding the inner real flow and developing law to reduce the design cycle, low design risk, and improve the property. For fully understanding the distribution characteristic of gas-liquid two-phase flow in hydrodynamic coupling, the numerical calculation of three dimension flow in hydrodynamic coupling is conducted, and take internal flow filed of which the liquid filled ratio is 40% and 80% as example to make flow field analysis on the results of numerical simulation under braking condition( i = 0),traction condition( i =0.5) and rated condition( ). Under braking condition, the turbine holds still, and the impact effect by the high-speed irregular flow of pump is great, so the internal flow field of turbine is complicated, some irregular flow such as vortex and secondary flow appear in turbine. With the increase of the speed ratio, the effect of i =0.97centrifugal force on pressure variation is more and more important, simultaneously more flow take part in the primary cycle under the interaction of the centrifugal force and coriolis forces, which makes the extrusion that the outer loop of pump becomes more serious, so the static pressure on the outer loop of pump is relatively large.Compared with the braking condition, under traction condition, high pressure region on the pressure surface of turbine blade reduces, because with the increases of speed ratio, the incident angle of high-speed liquid impacting turbine from pump is relatively small. Under rated condition, the distribution of the static pressure of pump and turbine is regular, and the pressure value is increased radially in proportion, reaching the maximum at ingress of pump and turbine.Through the numerical calculation and analysis on the flow field of turbine blade and the whole flow field of variable speed hydrodynamic coupling under different condition and liquid filled ratio, the change of velocity and press distribution of the flow field is revealed. Preliminary understanding the flow behavior of the flow field in pump and turbine of hydrodynamic coupling, and the forming reason of the flow behavior is fully analyzed. It is convenient for understanding the working mechanism of the coupling to study the inner real flow and rules, which is helpful to guide the design of hydrodynamic coupling, and improve the property.Characteristics Prediction and Experimental Research on Variable Speed Hydrodynamic CouplingBased on the internal flow calculation, the torques and performance parameters of impeller in hydrodynamic coupling are calculated by using the equation of pump torque, and the original characteristic curve is drawing. The external characteristic experiment on YOCQZ450 variable speed hydrodynamic coupling is done, and the result is contrasted and analyzed with the result of three-dimensional flow field calculation, which indicates that the numerical results have high precision. The result shows that precision of numerical calculate is high, and agrees well with the experimental data. The maximum relative error is less than 15%, which can be accepted to the internal complex two-phase flow in hydrodynamic coupling, so the method of numerical simulation and performance prediction are validated. The numerical simulation results of this paper are very valuable for the analysis of three-dimension two-phase flow field in hydrodynamic coupling. The CFD method could be used to design the hydrodynamic coupling and change the disadvantages of traditional design method which need multiple trial production to setting. It could realize the calculation process on computer, reach the purpose of precise, saving time and money, and many further researches on hydrodynamic coupling can be well continued on the base of that.Research on the Design Method of Variable Speed High-power Hydrodynamic CouplingThe traditional design method of hydrodynamic coupling is based on the preliminary model selection, process variables are determined by resort experiment, finally the basic parameters are determined. But rationality of the design awaits text. While the design based on CFD also needs to know certain prophase basic parameters to establish three-dimensional virtual model, and the result is obtained through calculation which can measure good or bad of the design. The main advantage is to recount to get a better result through modify the parameters of model. However, the traditional design is to conduct test through producing prototype wasting several months and then modifying due to the feedback from the test to the design period. Therefore the modern design method of hydrodynamic coupling is a kind of design method which is the combination of traditional design method, CFD and test mean.The modern design method of variable speed high-power hydrodynamic coupling is studied in this paper, and the software used for parameter design and optimization design of variable speed high-power hydrodynamic coupling is developed based on UG and CFD. The advanced computer technology is combined with CFD to establish three-dimensional virtual model, and the result is obtained through numerical calculation. The main advantage is to recount to get a better result through modify the parameters of model. However, the traditional design is to conduct test through producing prototype wasting several months and then modifying due to the feedback from the test to the design period. In this paper, three kinds of structural optimum design schemes of variable speed high-power hydrodynamic coupling are proposed based on CFD. Numerical simulation and performance prediction are conducted respectively to the three schemes, and the best optimization result is obtained through compare three schemes and base type.