| Butterfly valve has the characteristics of simple structure and wide application range.It is widely used in pipeline transportation systems such as energy transportation,chemical engineering and water conservancy engineering to control the flow of fluid in the pipeline system.During the regulation of the valve butterfly valve,the torque of valve disc and the flow field behind the valve will change with the opening of the valve.In turn,it will affect the reliability of the butterfly valve during actual use.Therefore,it is necessary to conduct in-depth research on the internal flow characteristics of the valve and the torque characteristics of the valve,and provide reference for the design and use of the butterfly valve.In this paper,DN50 butterfly valve is taken as the research object.Based on the original model,the valve disc of the butterfly valve is simplified,and the valve disc with different shaft diameter ratio(Z=0.1?Z=0.2?Z=0.4)and different dome degree(R=1?R=2.5?R=5)is obtained.The experimental platform of valve characteristics was built to test the flow rate,inlet and outlet pressure and valve disc torque of butterfly valve under different opening.The accuracy of the numerical simulation is verified by comparing the numerical simulation results with the experiments.The main results and conclusions obtained are as follows:1.In terms of flow coefficient,the flow coefficient of butterfly valve increases first and then remains unchanged with the increase of the opening degree,and the resistance coefficient decreases first and then remains unchanged with the increase of the opening degree.With the increase of the shaft diameter ratio of the valve disc,the flow coefficient gradually decreases and the resistance coefficient gradually increases.With the increase of the dome degree of valve disc,the flow coefficient gradually increases and the resistance coefficient gradually decreases.At the same time,as the shaft diameter ratio and the dome of the valve disc increase,the adjustable range of the butterfly valve will be reduced.2.In terms of valve disc torque,during the process of full opening to full closing of the butterfly valve,the hydrodynamic torque received by the valve disc increases first and then decreases.When the valve opening is between 20%and 60%,the torque fluctuates greatly.As the shaft ratio of the valve disc increases,the hydrodynamic torque received by the valve plate gradually decreases,and the torque fluctuation strength decreases.The dome degree of the valve disc has little influence on the torque of the butterfly valve.When the valve opening degree is less than 50%,the butterfly valve torque will increase with the increase of the dome degree When the opening of the valve is more than 50%,the torque of the butterfly valve will decrease with the increase of the dome degree.The maximum value of the valve disc torque and the maximum value of the fluctuation decrease with the increase of the dome degree.3.In terms of downstream flow,the velocity distribution in 4D of the valve is not uniform and is in the recovery flow region.Generally,a peak or trough appears in this region,and then reaches the far-tail region,and the velocity distribution is more uniform.Both the shaft diameter ratio and the dome degree have an effect on the flow after the valve only at a large opening degree,and the larger the above two values,the greater the post-valve speed and the fluctuation strength.4.According to different shaft diameter ratio and different dome butterfly valve characteristics,an improved butterfly valve structure is proposed.Compared with the original structure,the flow coefficient is significantly improved,the valve control interval is significantly increased,and the drag coefficient is reduced.The butterfly valve torque at large opening is significantly reduced,and the pressure distribution on the butterfly valve is more uniform,which provides a reference for the optimization of the butterfly valve. |
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