Production and Development of Secondary Flows and Losses in Two Types of Straight Turbine Cascades: Part 2—A Rotor Case

1987 ◽  
Vol 109 (2) ◽  
pp. 194-200 ◽  
Author(s):  
A. Yamamoto
Keyword(s):  
Pressure Gradient ◽  
Production Process ◽  
Experimental Analysis ◽  
Significant Contribution ◽  
Adverse Pressure Gradient ◽  
Secondary Flows ◽  
Suction Surface ◽  
Turning Angle ◽  
Detailed Mechanism ◽  
Turbine Cascades

Part 1 of this paper [1] presents the detailed mechanism of secondary flows and the associated losses occurring within a straight stator cascade with a relatively low turning angle of about 65 deg. The significant contribution of secondary flows on the loss production process was shown only near the blade suction surface downstream from the cascade throat (Z/Cax = 0.74) in which regional flows decelerated due to adverse pressure gradient. In the second part, the same experimental analysis is applied to a straight rotor cascade with a much larger turning angle of 102 deg. Flow surveys were made at 12 traverse planes located throughout the rotor cascade. The larger turning results in a similar but much stronger contribution of the secondary flows to the loss developing mechanism. Evolution of overall loss starts quite early within the cascade, and the rate of the loss growth is much larger in the rotor case than in the stator case.

Production and Development of Secondary Flows and Losses Within Two Types of Straight Turbine Cascades: Part 2 — A Rotor Case

1986 ◽  
Author(s):  
A. Yamamoto
Keyword(s):  
Pressure Gradient ◽  
Production Process ◽  
Experimental Analysis ◽  
Significant Contribution ◽  
Adverse Pressure Gradient ◽  
Secondary Flows ◽  
Suction Surface ◽  
Turning Angle ◽  
Detailed Mechanism ◽  
Turbine Cascades

Part 1 of this paper[1] presented the detailed mechanism of secondary flows and the associated losses occurring within a straight stator cascade with a relatively low turning angle of about 65°. Significant contribution of secondary flows on the loss production process was shown only near the blade suction surface downstream from the cascade throat (Z/Cax=0.74) in which region flows decelerated due to adverse pressure gradient. In the second part, the same experimental analysis was applied to a straight rotor cascade with a much larger turning-angle of 102°. Flow surveys were made at twelve traverse planes located throughout the rotor cascade. The larger turning results in a similar but much stronger contribution of the secondary flows on the loss developing mechanism. Evolution of overall loss starts quite early within the cascade, and the rate of the loss growth is much larger in the rotor case than in the stator case.

The compound bowing design in a highly loaded linear cascade with large turning angle

2020 ◽  
Vol 234 (16) ◽  
pp. 2323-2336
Author(s):  
Xingxu Xue ◽  
Songtao Wang ◽  
Lei Luo ◽  
Xun Zhou
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Pressure Gradient ◽  
Side Effect ◽  
Adverse Pressure Gradient ◽  
Suction Surface ◽  
Turning Angle ◽  
Linear Cascade ◽  
Velocity Triangle ◽  
Highly Loaded

Numerical simulation was carried out to study the influences of blade-bowing designs based on a highly loaded cascade with large turning angle, while the compound bowing design showed much lower endwall loss than the conventional design in this study. Generally, it showed that the increased turning angle would strengthen the adverse pressure gradient on the suction surface, so the side effect of negative blade bowing angle would be enhanced because of the reduced flow filed stability near suction–endwall corner. However, the positive corner bowing angle that applied in the compound bowing design would enhance the flow field stability near the suction–endwall corner by adjusting spanwise pressure gradient and velocity triangle, so the side effect of negative blade bowing angle would be suppressed and lead to weaker secondary flow. In detail, the blade bowing angle (as well as the corner bowing angle in the conventional bowed cascades) was varied from −5° to −30° in this study, while the reductions of the loss coefficient in the compound bowed cascades were about 0.662.16 times higher (the absolute differences were about 0.0067 0.0097) than the corresponding conventional bowed cascades. Moreover, the Reynolds number and Mach number at the outlet plane were kept at 2.4 × 105 and 0.6, respectively, during the bowing design to ensure the comparability.

Production and Development of Secondary Flows and Losses in Two Types of Straight Turbine Cascades: Part 1—A Stator Case

1987 ◽  
Vol 109 (2) ◽  
pp. 186-193 ◽  
Author(s):  
A. Yamamoto
Keyword(s):  
Secondary Flow ◽  
Total Pressure ◽  
Experimental Information ◽  
Secondary Flows ◽  
Accumulation Process ◽  
Flow Angle ◽  
Turning Angle ◽  
Pressure Losses ◽  
Flow Vectors ◽  
Turbine Cascades

The present study intends to give some experimental information on secondary flows and on the associated total pressure losses occurring within turbine cascades. Part 1 of the paper describes the mechanism of production and development of the loss caused by secondary flows in a straight stator cascade with a turning angle of about 65 deg. A full representation of superimposed secondary flow vectors and loss contours is given at fourteen serial traverse planes located throughout the cascade. The presentation shows the mechanism clearly. Distributions of static pressures and of the loss on various planes close to blade surfaces and close to an endwall surface are given to show the loss accumulation process over the surfaces of the cascade passage. Variation of mass-averaged flow angle, velocity and loss through the cascade, and evolution of overall loss from upstream to downstream of the cascade are also given. Part 2 of the paper describes the mechanism in a straight rotor cascade with a turning angle of about 102 deg.

scholarly journals An Experimental Investigation Into the Reasons of Reducing Secondary Flow Losses by Using Leaned Blades in Rectangular Turbine Cascades With Incidence Angle

1988 ◽  
Author(s):  
Wang Zhongqi ◽  
Xu Wenyuan ◽  
Han Wanjin ◽  
Bai Jie
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Secondary Flow ◽  
Incidence Angle ◽  
Main Stream ◽  
Suction Surface ◽  
Flow Losses ◽  
Turbine Stator ◽  
Rear Part ◽  
Turbine Cascades

Up to now the reasons of reducing the secondary flow losses by using leaned blades, especially in the case of great incidence angle, have been little concerned with in published references. The experimental results in this paper have shown that the decisive factor reducing secondary flow losses in turbine stator cascades is the static pressure gradient along the blade height inside the cascade channel near the suction surface, especially in the rear part of it, because the negative pressure gradient in the hub region and the positive one in the tip region are beneficial for the boundary layer in both the regions to be sucked into the main stream region, consequently, the accumulation and the separation of the boundary layer have been weakened in both regions. Moreover, the effectiveness of applying the positively or negatively leaned blades is increased with the increase of a incidence angle, in the hub or the tip regions respectively.

Effect of Solidity on Non-Axisymmetric Endwall Contouring Performance in Compressor Linear Cascades

2018 ◽  
Author(s):  
Liu Xiwu ◽  
Jin Donghai ◽  
Gui Xingmin ◽  
Liu Xiaoheng ◽  
Guo Hanwen
Keyword(s):  
Pressure Gradient ◽  
Flow Separation ◽  
Total Pressure ◽  
Leading Edge ◽  
Adverse Pressure Gradient ◽  
Suction Surface ◽  
Optimum Range ◽  
Geometric Scaling ◽  
Endwall Contouring ◽  
Profile Loss

This paper presents both the computational and experimental results to assess the effectiveness of non-axisymmetric endwall contouring in linear cascades under different solidities. Endwalls were designed by geometric scaling of a prior optimized endwall. The results show that the total pressure loss can be reduced by the contoured endwall (CEW) under different solidities. The mechanism of the improvement of CEW is that the adverse pressure gradient (APG) has been reduced mainly through the groove configuration near the leading edge of the suction surface. Besides, the cross-passage pressure gradient (CPG) has also been reduced, which has the benefits to further suppress the corner separation. Moreover, there is an optimum range of the solidity for the CEW. For a lower solidity, the performance of the CEW at +7 degree incidence presents a rapid deterioration, due to the risk of flow separation near the mid-span, for a higher solidity, the profile loss can be more dominant.

Numerical Investigation of Corner Separation on Compressor Cascade

2013 ◽  
Author(s):  
Jing Ling ◽  
Xin Du ◽  
Songtao Wang ◽  
Zhongqi Wang
Keyword(s):  
Pressure Gradient ◽  
Pressure Distribution ◽  
Separation Zone ◽  
Adverse Pressure Gradient ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Corner Separation ◽  
Pressure Point ◽  
Static Pressure Distribution ◽  
Blade Thickness

This paper studied the effects of suction surface corner separation on the aerodynamic performance and the effects of the blade parameters on suction surface corner separation in rectangular cascade. Corner separation alters the static pressure distribution on the suction surface, establish a C-Shape pressure distribution along spanwise, compared with open separation, closed separation intensifies the C-Shape pressure distribution, increases the streamwise adverse pressure gradient on the suction surface after the lowest pressure point. The diffusion capability in a closed separation was significantly lower than in an open separation on the separation zone, loss was larger than open separation. The changes of blade parameters have great effects on corner separation, not only affect the scale of separation zone, even they will change the separation form. This study show that with the increase of the blade thickness, the maximum thickness position moving afterwards and the increase of the deflection of mean camber line, the streamwise adverse pressure gradient on the suction surface after the lowest pressure point increase, the scale of separation zone increase, even the separation type changes from open separation to closed separation.

Production and Development of Secondary Flows and Losses Within Two Types of Straight Turbine Cascades: Part 1 — A Stator Case

1986 ◽  
Author(s):  
A. Yamamoto
Keyword(s):  
Secondary Flow ◽  
Total Pressure ◽  
Experimental Information ◽  
Secondary Flows ◽  
Accumulation Process ◽  
Flow Angle ◽  
Turning Angle ◽  
Pressure Losses ◽  
Flow Vectors ◽  
Turbine Cascades

The present study intends to give some experimental information on secondary flows and on the associated total pressure losses occurring within turbine cascades. Part 1 of the paper describes the mechanism of production and development of the loss caused by secondary flows in a straight stator cascade with a turning angle of about 65°. A full representation of superimposed secondary flow vectors and loss contours is given at serial fourteen traverse planes located throughout the cascade, which shows the mechanism clearly. Distributions of static pressures and of the loss on various planes close to blade surfaces and close to an endwall surface are given to show the loss accumulation process over the surfaces of the cascade passage. Variation of mass-averaged flow angle, velocity and loss through the cascade, and evolution of overall loss from upstream to downstream of the cascade are also given. Part 2 of the paper describes the mechanism in a straight rotor cascade with a turning angle of about 102°.

The synergistic effect between compound lean and aspiration on aerodynamic performance in compressor cascades

2017 ◽  
Vol 232 (16) ◽  
pp. 3034-3048
Author(s):  
Jun Ding ◽  
Shaowen Chen ◽  
Le Cai ◽  
Songtao Wang ◽  
Zhongqi Wang ◽  
...  
Keyword(s):  
Synergistic Effect ◽  
Pressure Gradient ◽  
Leading Edge ◽  
Adverse Pressure Gradient ◽  
Aerodynamic Performance ◽  
Suction Surface ◽  
Reciprocal Effect ◽  
Blade Passage ◽  
Streamwise Location ◽  
Lean Angle

In this paper, the synergistic effect between compound lean and aspiration on the aerodynamic performance of compressor cascades is discussed. Preliminary experimental data verify the accuracy of the computational fluid dynamics method adopted, and a thorough study on reciprocal effect among lean angle, aspirated flow fraction and aspiration streamwise location is conducted. The calculations show that, due to the shorter streamwise length of the re-grown boundary layer against adverse pressure gradient, the aspiration location located farther downstream from the leading edge can minimize the loss of the blade passage flow. With the application of blade lean, which is similar to the flow control mechanism in the unaspirated cascades, an increase in pressure at the suction surface corner is used to migrate the low momentum fluid from the corners towards the midspan of the suction surface. Meanwhile, the reduced aspirated flow velocity and the improved favorable pressure gradient in the lean anterior plenum can reduce the entropy rise through the plenum. Simultaneously, the suction power required in the blade passage flow is reduced with blade lean, while the suction power for the aspirated flow through the plenum shows the opposite trend.

The Influence of Blade Negative Curving on the Endwall and Blade Surface Flows

1995 ◽  
Author(s):  
Zhongqi Wang ◽  
Wanjin Han
Keyword(s):  
Static Pressure ◽  
Adverse Pressure Gradient ◽  
Vortex Sheet ◽  
Front Part ◽  
Blade Surface ◽  
Suction Surface ◽  
Turning Angle ◽  
Pressure Surface ◽  
Low Aspect Ratio ◽  
Blade Cascade

In order to explore the mechanism reducing the energy losses by use of negative curved blades, an experiment was carried out on turbine rectangular cascades with straight and negative curved blades of high turning angle and low aspect ratio. Ink trace technology was employed to show the flows on the endwalls and blade surfaces. The pressures were measured in detail with static pressure taps on the endwalls and blade surfaces. Experimental results indicate that when negative curved blades are used, a separating saddle of inlet boundary layers goes forward into the passage and approaches the pressure surface, as the streamwise adverse pressure gradient on the cascade inlet endwall becomes lower, compared with that of straight blade cascade. In addition, the static pressure contours are almost parallel lines perpendicular to the endwall on the front part of the suction surface and the curves which internal normals with the positive slopes near the endwall direct to the midspan from high pressure to lower pressure on the middle, this leads to the separation of free vortex sheet pattern on the suction surface. As a result, it is delayed that the separation lines converge towards midspan.

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