Study On Blocking Effect And Flow Field Uniformity Optimization Of Spin Body In Closed Space

Under extreme environmental conditions,the electromechanical performance of large-scale equipment such as power grid equipment,airplanes,and high-speed railways will be significantly reduced,which will seriously affect their safety and stability.At present,there is no low-cost instrument and equipment system for testing and testing electrical and electronic products,aircraft,high-speed rail,wind turbines and other equipment materials,devices and scaled models under comprehensive conditions that combine extremely low temperature and complex environments with high-speed motion.In order to simulate various harsh environments such as extreme cold,extremely low air pressure,haze,sand and dust in the laboratory,and conduct mechanical and electrical characteristics research,the detection device must be placed in a confined space.If the traditional wind tunnel is still used for design and construction Will consume extremely high cost and price.Therefore,this article considers adopting the"reverse wind tunnel"thinking to establish a high-speed rotating motion platform in a closed limited space.Driven by the main shaft and connecting rod,the guide rail and the sliding table are supported,so that the detected object is fixed in a position that can accelerate and uniform the airflow.In the device structure of the flow effect,it is expected to form an equivalent wind tunnel test effect.Compared with the high-speed linear motion simulated by the traditional wind tunnel,the high-speed rotating motion has a linear velocity difference in the radial direction,so the airflow field distribution on both sides of the mainstream direction will inevitably be uneven.To achieve the wind tunnel test effect,it must be adopted Measures to modulate the flow field around the sample.Therefore,this paper studies the effect of adding a flow-sharing structure to the high-speed rotating platform and optimizes its parameters by carrying out numerical simulation calculations of fluid mechanics to improve the uniformity of the internal test flow field.At the same time,the gauge pressure distribution characteristics of the sample model placed in an accelerated flow-sharing structure with a better flow field,the rotational movement of the non-accelerated flow-sharing structure,and the gauge pressure distribution characteristics in the three cases of the conventional straight-air tunnel test are compared.Analysis,and also explored the blocking effect of the scaled-down sample model under the conditions of different speeds and different blocking ratios,and the main conclusions are as follows:(1)Simulation calculations show that the uniformity of the velocity and direction of the flow field around the sample in the accelerated flow-sharing structure during rotation is closely related to the size parameters of the accelerating current sharing structure.The optimized design of the accelerated flow-sharing structure can significantly improve the quality of the test flow field.The three dimensional parameters(the height of the opening on both sides of the inner and outer sides and the length of the contraction section)in the central rotation plane of the contraction section and the diffusion section have an influence on the average dynamic pressure coefficient and the airflow deflection angle in the test section.For the contraction segment,the average dynamic pressure coefficient changes approximately in a"V"-shaped curve with the height of the openings on both sides,and both parameters have a greater influence on it,and the dynamic pressure coefficient gradually increases with the length of the contraction segment However,the influence is relatively small;the average airflow deflection angle changes in a"V"-shaped curve with the three dimensional parameters of the contraction section.For the diffuser,the average dynamic pressure coefficient first increases and then decreases with the height of the outer opening of the diffuser and the length of the diffuser first,and then decreases with the height of the inner opening of the diffuser.The change trend of the average airflow deflection angle affected by the diffuser section is more complicated,in which the height and length of the outer opening have a greater influence,while the height of the inner opening has a smaller influence.(2)Through orthogonal experiments,the primary and secondary effects of various factors on the uniformity of the airflow in the test section were further explored and verified,including the rotation speed and radius of rotation that were not explored in the previous single-parameter effects.The primary and secondary order of the factors affecting the average dynamic pressure coefficient in the test section is:radius of rotation r>outer opening height of the contraction section h₂>inner opening height of the contraction section h₄>three parameters of the diffusion section>contraction section length L and rotation speed n.The primary and secondary order of the factors that affect the average airflow deflection angle in the test section is:contraction length L>contraction section inner opening height h₄>diffusion section outer opening height D₂>diffusion section length L₀>other factors.All the calculation examples in this paper can obtain the minimum average dynamic pressure coefficient of 0.00738 in the test section.Although it does not meet the requirement of less than 0.005 in the national military standard,it is sufficient for the airflow characteristic test of external insulation equipment.The minimum airflow deflection angle obtainable by all the calculation examples is0.0698°,and most of the calculation examples can meet the national military standard that?is less than 0.2°.In summary,the use of the rotating acceleration flow sharing structure designed in this paper has played a significant role in improving the uniformity of the airflow size and direction,and can provide a certain reference basis for the design of the final rotating test platform under complex environmental conditions.(3)Without accelerating the rotating motion of the current sharing structure,the gauge pressure and flow velocity distribution on both sides of the square column model are obviously asymmetric,and the windward surface gauge pressure gradually increases along the radial direction;but there is a rotation test of the rotating acceleration current sharing structure,the square column gauge pressure The symmetry of the distribution and the uniformity of the flow field have been significantly improved,and are similar to the distribution law in the case of a direct-blowing wind tunnel,which proves that the rotating acceleration flow sharing structure has a good effect on the optimization of the flow field quality.In the rotating acceleration current sharing structure,the rotation speed of the rotating platform and the blockage ratio have an influence on the wind pressure coefficient of each surface of the square pole;taking the 2%blockage ratio as the reference standard,as the blockage ratio increases from 2%to 8%,the average The change range of the wind pressure coefficient increases with the increase of the rotation speed.The change range of the average wind pressure coefficient at 8%blocking ratio at30 rpm is 23.06%compared to 2%,while the change at 150 rpm reaches 44.91%.The roof insulator model with a scale of 0.3 times is placed in the accelerating current sharing structure.The results show that the pressure on the upper and lower surfaces at the junction of the umbrella skirt and the umbrella diameter on the leeward surface is almost the same as the distribution law when the train is running in a normal straight line.The value is small,but the overall negative pressure is small in the middle,and the negative pressure at the upper and lower ends is larger.