Influence of flow channel geometry on aerodynamic performance of low-pressure guides An Baitao, Wang Songtao, Han Wanjin, Wang Zhongqi 21. Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 1 1 College of Energy Science and Engineering, Harbin Institute of Technology. Harbin J50001 of Heilongjiang has a numerical simulation guide. The meridional flow channel has a longer machine and the transition section has a larger outer and divergent angle. A flow to the separation guide vane leaves here, the inlet flows. Numerical study The optimized design of the outer wall and the airfoil of the Mingji improved the aerodynamic performance of the guide. Under the same initial conditions of the calculation domain, the energy loss of the guide is significantly reduced. Optimization Design 1 Introduction To improve the efficiency of the wheel. More and more 4D design sisters want to be applied to the actual impeller mechanical design. The cascade flow passage is a dimensional space composed of upper and lower end walls and blades. For the guide cascade, the energy loss is caused by the interaction between the fluid and the end wall and the blade, so how to optimize the upper and lower end wall profiles and the blade shape is The key to controlling the flow loss of the turbine dimension space. The main method of controlling the secondary flow by blade forming is to design the new leaf type and the media matching of the leaf-shaped twisting and shaping. In this regard, the results have made a full and gradual progress in reducing the loss of cascades. For the study of the shape of the end wall. Also playing a very famous school must have done a meaningful workbook experiment on the upper end of the bullying using various forms of non-axisymmetric shape end walls. These experimental results show that the optimization of the geometric parameters of the flow path may reduce the turbine damage angle and the flow efficiency of the original design prototype is low. In order to improve the prototype of the dynamic cell, it is recommended to modify the expansion angle of the outer wall profile, and to improve the shape of the blade. Using the 5 equation solver, the performance of the two guides was compared and the influence of the flow path on the performance of the guide was analyzed.
Fund project. 1 973, gold-funded project; 99902230 2 singularity and method calculation model is divided into two types: prototype and modified. The geometric parameters of the prototype blade are the same as in the literature. The main difference between the geometric parameters of the modified blade and the prototype is that the upper end wall profiles of the two guides are different. The top-end bullying line of the retrofit scheme uses the most accompanying line recommended in Document 6.
2 leaf types are different. The prototype is a uniformly loaded leaf type modified into a rear loading leaf type. 3 stacking methods are different. The prototype is a straight blade, which is modified to bend the root of the positive curved blade. 20. The top is curved. 8. The middle is transitioned from the top to the bottom with a straight line segment of the line segment. The two guide blades are small, and the four axial strings are along the leaf. The high direction has a sweeping design. It is difficult to make the axial chords equal in the direction of the leaf height. 5, the inlet angle of the prototype, the geometrical intake angle of the prototype along the blade height direction is 90, the geometrical intake angle of the modified height along the blade height is different and has a fixed negative angle design. Is 75.170.879.5, 3.
The number 1 calculation method uses a step precision of 1 property of 1 and 1 formulas. The specific sub-division format and the derivation of the square scale 7 Because the method considers the physical characteristics of the real flow better, the solution accuracy and numerical stability are better. The arrangement of the check grid points is 1 point at 1 point along the flow direction 91. The direction of the leaves is 38 points. The entry conditions are a total temperature of 8 and a total pressure of 4.7 engineering atmospheres. 4 is the dimension calculation grid of the low pressure guide. The initial conditions of the computational domains of the two turbines are the same.
3 Calculation results analysis 3.1 Comparison of aerodynamic performance The size of the energy loss of the cascade is the best to show the advantages and disadvantages of the turbine. 5 gives the 85th exit of the guide. 5=7 pitch average total pressure recovery coefficient of the height of the blade. In the mid-coordinate generation, except for the 7080 small-segment leaf exhibition, the total loss of the modified scheme along the whole blade is smaller than the prototype. This point can be more clearly explained from the contour loss of the 6-flow surface, and the modification is in the high-loss area with high The range of high loss areas caused is significantly smaller than the prototype. At the same time, except for the upper end wall, there is no high loss zone, which eliminates the peak of the vortex intensity of the low energy fluid near the upper end wall, and the total loss of the two guides is calculated. The prototype was changed to 5.96 for the prototype 6.62, and the relative prototype loss was reduced by 10.1.
3.2 Influence of the end wall profile The upper end wall of the meridional channel has a larger divergence angle, and there is a strong reverse gradient near the leading edge of the flow. The flow has been separated at the upper end. However, the separation zones of the two guides are different. Observed 7 found that the separation zone of the prototype has obvious vortex structure and the separation zone is larger, the modified separation zone is smaller in scale, and there is no obvious human scale rotation in the separation zone. Run. This shows that the iso-velocity gradient line on the upper wall of the retrofit scheme has a better control effect on the separation of the airflow. 8 It can also be seen in the process from the beginning to the end of the expansion. The change of pressure distribution along the flow direction near the end wall is relatively stable. However, the prototype card force distribution has a wide range of ups and downs, and the flow is unstable.
Although the separation zones caused by the two expansion flows are different in form, the effects on the loss of the guides have in common. First, both separation zones produce large separation losses. Secondly, a sharply thickened boundary layer is formed at the inlet of the guide, and interacts with the cylindrical leading edge of the cascade to form a large-scale strong-rotating inlet horseshoe vortex. The vortex system is not in the range of the cascade, and the lower channel is closely attached to the inlet channel of the suction channel. The degree of progress is improved, and the strong total pressure recovery coefficient of the channel vortex will be affected along the leaf height distribution and scale. Obviously this effect is strong in the prototype. There is a large-scale low-pressure zone in the front part of the upper end wall of the middle prototype. The low-pressure zone not only enlarges the upper channel vortex but also the low-energy fluid in the low-pressure zone is not completely sucked by the upper channel vortex at the upper end wall of the outlet. Low energy fluid.
3.3 Effect of the airfoil The optimization of the endwall profile improves the inlet flow of the guide cascade, but the flow loss in the cascade flow path is still less likely to decrease, and the modified leaf type is a more effective implementation. The modification has redesigned the leaf type. The specific measures are as follows.
3.3.1 The rear loading of the leaf type can be seen from the 9th. After the modified root, the loading characteristics are obvious. The lowest pressure point of the mountain prototype is 73. The length of the diffuser section is the same as the original fire. The airflow is expanding. The first section is not separated 103. In addition, the lateral pressure difference of the section is smaller than that of the other part, and the other parts are transverse; the force gradient is smaller than the prototype, especially the reduction of the inlet lateral 1 force gradient. Pingshuo weakens the strength of the forced squat. The most important source of loss in the middle of the prototype is the diffuse flow after the throat. 9 The prototype has a large gradient of the back pressure gradient in the diffuser section. The corresponding prototype has a large range of high pressure zones at the trailing edge, and its flow will become very unstable and cause an increase in flow loss in the middle of the cascade. After the modified type adopts the rear loading blade, the expansion process of the diffusing section is relatively stable. The flow loss is small.
3.3.2 Increasing the axial chord length of the blade root As seen from the meridional flow path profile, the lower end wall is convergent immediately before the inlet of the cascade. At the near leading edge, the flow path is dilated and expanded. 93 can observe the existence of the axial chord length range of the small-scale diffused flow area of ​​the prototype, and also reflects the phenomenon that the more touching the 1 touch, the lower end wall of the ship fierce 1 (4) is the end wall section and the pressure is bounded into the cascade flow. In the middle. Thereby changing the flow of the root inlet 3.3.3 the blade is being bent due to the positive bending of the blade. A so-called type pressure distribution will be formed which is directed from the end regions to the middle. Due to the large angle of the root. The reduction in root loss is very advantageous. It is generally believed that positively curved blades can reduce secondary flow losses at both ends. But the central loss will increase accordingly. However, the loss in the central part of the reform has not increased. The use of this and the rear loading of the leaf type is justified because the fluid in the post-loading leaf type is along the suction side. The order is attached flow, and most of the fluid that migrates from the two ends to the middle is absorbed by the blue stream, so the central loss is still smaller than the prototype. At the same time, you should see 1.
Due to the top positive bend, the upper channel vortex loss peak is slightly increased because the radial pressure gradient causes the upper end wall low energy fluid to migrate downward and get caught in the upper channel vortex.
3.3.4 Reduce the angle of the top of the blade How to twist the large separation of the top flow. It is always the main question for retrofit design considerations. Reducing the angle of attack of the airflow at the top of the blade is an effective measure to weaken the top separation. Near the tip of the blade, the prototype geometry intake angle is 90, corresponding to the intake angle of attack, and the modified geometry intake angle is 75. The corresponding intake angle is 14.9, so the expansion of the airflow in the separation zone near the tip of the blade is modified. Intensified, so that the separation zone develops downstream, and the flow of the suction surface is improved. By, yes, the loss of the vine boundary layer in the low-speed zone near the modified suction surface is lower than that of the prototype.
In addition, 10, the lateral pressure difference in the front part of the modified flow channel is much smaller than that of the prototype, which reduces the concentration of the fluid in the separation zone to the suction angle zone while matching the top positive bend, and the top loss is also reduced.
4 Conclusion First, the modified outlet energy loss is significantly lower than the prototype, and the aerodynamic performance is significantly improved. Secondly, the flow-through part of the 7-inch low-pressure guide is refined, including the selection of the end wall profile to improve the bending and torsion shaping of the blade, which optimizes the flow geometry and makes the pressure distribution in the cascade flow space more attractive. Reasonable and progressive to reduce flow losses. In this paper, the geometric parameters such as the posterior loading of the isothermal gradient curve and the positively curved blade are better matched.
Song Yanping. The main research results and application of curved and twisted blades. Thermal power fM, 1999, 14859 An Botao, Han Wanjin, Lu Wencai, and so on. The influence of meridional diffuser on the occurrence and development of vortices in the annular cascade flow channel. Journal of Aerodynamics, 20 muscles 436365.
An Botao, Han Wanjin, Wang Songtao, and so on. Wang Songtao, Yuan Ning, Wang Zhongqi, etc. of the large expansion angle meridional channel type line pair loss. The order precision 0010 with 0 property, the application of the format in the calculation of viscous flow field. Journal of Engineering Thermophysics, 1999, 203299303.
Wang Songtao, Wu Meng, Wang Zhongqi, and so on. Influence of channel vortex structure stability on loss 4. Journal of Engineering Thermophysics, 2000214425429.
Hui edited on page 567, publishing house, 1987.
Wang Wei, Zhou Yin Jiang Jianguo. Thermal balance analysis and optimization scheme for municipal waste incineration power generation system. Urban environment and urban ecology, 200 15313.
Xiao Hancai, Li Ke. Research on the selection of thermal system solutions in waste heat power generation projects. Journal of Changsha University of Electric Power, Natural Science Edition, 20063.
peace. The National Energy Conservation Plan and Infrastructure Work Conference was held in Beijing. 19944 Ye Jianming, Chen Yu stack. Economic analysis of waste heat power generation. Power Engineering. 195144.
Iq He Qinwei, Li Zhencheng Wu Xiegong. 15 to save energy. Polyester Industry, 2002 Tan Tianen, Mai Benxi, Ding Huihua. The principle of chemical engineering is elbow. Version 2. Beijing Chemical Industry Press, 199, 1 13 Chen Yihua. Mathematical model can. Chongqing Chongqing University Press, 1994.
é˜Tan Haoqiang. Programming design. Beijing Tsinghua University Press, 1997.
15 Chen Mingyu Ling Yongxiang. Calculation method 1. Xi'an Xi'an Jiaotong University Press, 1996.
Iq Feng Wei, Li Qinling. Principles and technical examples of chemical energy conservation. Beijing Chemical Industry Press, 1998.
Qiao Li touch, the heart of the heart and pressure of the residual limbs near-infrared spectroscopy analysis technology to predict the coal content of volatile matter research = elbow 018 to do 0, shirts also 6.86 摹 试 试 ! !!
Plus, it’s a slap in the face of the smashing of the ice, and the smashing of the ice.
Plastic Grilles,Plastic Return Air Grille,Plastic Air Vent Grilles,Plastic Ventilation Grilles
Guangzhou Jointair Co., Ltd. , https://www.jointairaccessories.com