Research on aerodynamic characteristics through airflow clearances in compressor blades of gas turbine engine

Use your smartphone to scan this QR code and download this article ABSTRACT Abstract: Reducing the loss in the airflow clearance among the compressor blades of the rotor disk and stationary blades (guide vanes) is an urgent issue. Furthermore, additional losses of airflow through the clearances among the blades and airfoil losses are the main cause of reducing the efficiency of an axial flow compressor, especially the blade height is small. With a view towards the efficiency improvement of amultistage axial compressorwith ahigh-pressure ratio, it is necessary to manufacture a highly economical compressor with a variety of compression stages. Airflow in the circulation clearances alternating among compressor blades has viscosity, unstable compression, and quite complex flow structure. This needs to be researched into the design with the assistance of modern software (ANSYS CFX, FlowER, etc.). Although this is an important step in the current design orientation, it requires additional practical elements to perform, especially the problem of optimizing the outer rim, the level, and the number of compression stages in the whole compressor. In this paper, authors have used the method of creating three-dimensional (3D) models for blade profiles in a compressor based on analyzing the flow in three-dimensional form and studying their parameters. This paper deals with the geometry problems of the row of rotating blades (cascade) by proposing the structural arrangement of stacking blades in the circular direction and the blade profile formed the S-shape. Investigating and calculating the aerodynamic properties of the airflow through clearances of compressor blades by using ANSYS is one of the new methods. The researched result showed the dependence between the camber angle as the rotating blade formed an S-shape profile rotates regarding the stagger angle of the airfoil and the incident angle of airflow. Some characteristics of aerodynamic properties are distributed according to the blade height in conducting with different curved profiles of the rotating blades on the rotor disk and stationary blades.


INTRODUCTION
With a view towards the efficiency improvement of a 2 multistage axial compressor with a high pressure ra-3 tio, it is necessary to manufacture a highly economical 4 compressor with variety of compression stages. Air

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As well known, reducing the loss in the airflow clear-22 ance among the compressor blades of the rotor disk 23 and stationary blades (guide vanes) is an urgent issue. 24 Furthermore, additional losses of air flow through 25 the clearances among the blades and airfoil losses are 26 the main cause of reducing efficiency of an axial flow 27 compressor, especially the blade height is small. One 28 of the methods to improve the structure of the flow 29 in the area of the tip and hub of blade is to use the 30 blades in a annular form (the slope of the blade profile 31 in the circular direction). The use of a row of annu-32 lar (annular cascade) blade results in a redistribution 33 of the load along the section of the compressor blade 34 profile 2 and structural changes in the unstable influ-35 ence of the rotating blades and stationary blades. The 36 change in pressure and efficiency regarding the blade 37 height depends on the entire load of the compression 38 To find the coefficients (a, b, c, d, f, e), as well as the 88 quantities, we solve the system of equations (2) with 89 some radius value R i . The first five equations rep-90 resent the initial geometry of the camber line in the 91 coordinate system (Figure 1 ( : coordinate of the maximum 101 deflection of the contour average at the radius posi-102 tion R i ; γ 1i and γ 2i -the camber angle of the camber 103 line at the point of intersection with the horizontal 104 axis at the radius position R i ; θ i -the stagger angle 105 of the blade profile at a radius position R i ; P Si -the 106 S-shaped parameter of the camber line of the blade 107 profile; ( β ycti ) gn -the initial air inlet angle of air-108 flow clearance at the radius position R i (when P Si = 0, 109 (β 1ri ) gn -the initial blade inlet angle at position R i ); 110 The parameter P Si change can be made according to 111 a defined rule along the blade height within the range 112 When increasing the parameter P Si corresponds to the 115 larger S-shaped profile at the air oulet angle. Recal-116 culating the coordinates of the blade profile from the 117 coordinate system (Figure 1) to the basic coordinate 118 system, taking into setting of air inlet angle is deter-119 mined by: where: β ycti -air inlet angle; dinates of the contour average line at the basic coor-122 dinate system.

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Here we consider that the contour of the annular 124 blades in the circular direction, by making the axis of 125 the center of the blade form a curve, when the axial 126 position of the center of mass at a radius R i is deter-127 mined by the angle θ 2i (the angle of rotation of the Z-128 axis around the X-axis, the direction from the Z-axis 129 to the Y-axis).  In the first stage, determining the effect of the shape 187 change of the camber line profile according to the 188 blade height to the loss coefficient, air outlet angle 189 from airflow clearances, diffusion coefficient D.

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The study was carried out in the calculation mode ac-191 cording to the flow mass, rotational frequency of the 192 rotor ( _ n np = 1.0; The study follows 12 alternatives for the geometry of 194 the impeller (Table 1, here (P S ) max -the value of the 195 parameter P S when γ 2 > 0).

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The density of the clearance among the rotating blades 197 is made up at the mean radiusis b t = 1.16, the relative 198 bladeheight h b = 1.37, the size of chord b = 36.6 mm, 199 the coefficient According to the CFD results 5 , it is found that, when 201 the camber line of the profile is S-shape, the angle 202 of resistance at the trailing edge will decrease. This 203 change is larger than the effect of the parameter P S on 204 airflow resistance. At the same time, when the con-205 centration − C 1a increases the diffusion coefficient D 206 increases, leading to a change in the distribution of 207 the loss coefficient in the airflow clearance according 208 to the blade height.

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The results obtained according to the distribution of 210 loss coefficients ( Figure 5) are unreliable and need 211 further examination by testing. In the second phase, 212 solve the problem of determining the resistance an-213 gle of the flow in the trailing edge from the airflow 214 clearances with the shape of the camber line of the S-215 shaped blade and when the incident angle of the air-216 flow is nearly optimal.

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In order to get the dependence of the resistance an-218 gle on the geometry of the rotaing blades, use the lay-219 out diagram of the orthogonal centers. In this case, 220 the parameter P S changes within P S = (0.06 ÷ 0.34); 221 average deflection of the cross-sectional profile of 222 , the air inlet angle of the 223 channels(β 1 = 33 ÷ 43 • ), the parameter of rotation 224 speed ω 2 R = (2.29 ÷ 3.29) .10 6 .

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When assessing the camber angle of the air flow, use 226 the formula 6 : Quantitative evaluation of the coefficient m in the cas-237 cade of the S-shape using expression (7), the result is 238 shown in (Figure 6). When the contour of the cam-239 ber line is S-shaped, it will reduce the resistance angle

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Simultaneously with the increase θ 2i , the level of com-266 pression in the middle part of the airflow clearance be-267 tween the two blades decreases, resulting from the re-268 distribution of parameters according to height. When 269 decreasing θ 2 , observing the tendency to reduce the 270 loss coefficient in the centrifugal gap area in the mid-271 dle of the circulation gap found that the reduction in 272 loss coefficient is negligible ( Figure 11):

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The distribution of the average loss coefficient accord-293 ing to the height of the impeller and the direction of 294 the blades when changing the annular structure of the 295 blades is shown in Figure 14. The distribution of the 296 diffusion in the flaps along the height of the blade is 297 shown in Figure 15.

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The paper presents a method of formulating the struc-300 ture of overlap blades in a compressor when applying 301 the S-shaped blades regarding the circular direction. 302 Obtaining a new model for determining the camber 303 angle in the airflow clearances of the rotating blades 304 which camber line is S-shaped, taking into account 305 the thickness, the strugger angle of the cross section 306 and the air inlet angle.

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The article shows that the camber line has been the S-308 shaped blade profile, the camber angle of the air outlet 309 cleareances in a compressor decreases. The larger this 310 change is, the larger the S-shaped profile is and the 311 diffusion coefficient increases.