Boundary Layer Control in a Compressor Cascade Using Distributed Suction

2008 ◽  
Author(s):  
Utpal Chakraborthy ◽  
A. M. Pradeep
Keyword(s):  
Boundary Layer ◽  
Experimental Study ◽  
Mass Flow ◽  
Pressure Loss ◽  
Total Pressure ◽  
Small Diameter ◽  
Total Pressure Loss ◽  
Compressor Cascade ◽  
Detailed Measurement ◽  
Primary Mass

An experimental study in a low speed compressor cascade was carried out to investigate the effect of distributed suction (aspiration) on the cascade performance. Unlike suction used conventionally, distributed suction requires lower mass flow rates and is achieved by suction through holes of very small diameter distributed over the surface. A set of 5 NACA - 65(18)10 blades were used in the experiments that were carried out at a Reynolds number of 1.6 × 105. Detailed measurement of surface static pressure, total pressure loss in the wake of the blades and boundary layer thicknesses were taken at incidence angles in the range −10 to +6 degrees. Significant effect of suction was observed on the total pressure loss distribution at the trailing edge of the blades. The mean total pressure loss coefficient reduced in the range 14 to 36 percent for the various configurations tested. Higher performance improvement was observed at negative incidence angles. Boundary layer measurements revealed that the effect of suction was prominent in the mid-span of the blades. Reduction in boundary layer momentum thickness in the range 8 to 20 percent was observed for the various configurations. The calculated diffusion factor also showed improving trends in line with the observations of total pressure loss and boundary layer thicknesses. The mass flow ratio for the best configuration was only 0.15 percent of the primary mass flow. This experimental study demonstrates the effectiveness of distributed suction (using only a fraction of the primary mass flow) on compressor cascade performance.

Location Effect of Boundary Layer Suction on Compressor Hub-Corner Separation

2014 ◽  
Author(s):  
Ping-Ping Chen ◽  
Wei-Yang Qiao ◽  
Karsten Liesner ◽  
Robert Meyer
Keyword(s):  
Boundary Layer ◽  
Pressure Loss ◽  
Total Pressure ◽  
Three Dimensional ◽  
Base Flow ◽  
Total Pressure Loss ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Corner Separation ◽  
Boundary Layer Suction

The large secondary flow area in the compressor hub-corner region usually leads to three-dimensional separation in the passage with large amounts of total pressure loss. In this paper numerical simulations of a linear high-speed compressor cascade, consisting of five NACA 65-K48 stator profiles, were performed to analyze the flow mechanism of hub-corner separation for the base flow. Experimental validation is used to verify the numerical results. Active control of the hub-corner separation was investigated by using boundary layer suction. The influence of the selected locations of the endwall suction slot was investigated in an effort to quantify the gains of the compressor cascade performance. The results show that the optimal chordwise location should contain the development section of the three-dimensional corner separation downstream of the 3D corner separation onset. The best pitchwise location should be close enough to the vanes’ suction surface. Therefore the optimal endwall suction location is the MTE slot, the one from 50% to 75% chord at the hub, close to the blade suction surface. By use of the MTE slot with 1% suction flow ratio, the total-pressure loss is substantially decreased by about 15.2% in the CFD calculations and 9.7% in the measurement at the design operating condition.

Impact of a Combination of Micro-Vortex Generator and Boundary Layer Suction on Performance in a High-Load Compressor Cascade

2018 ◽  
Author(s):  
Shan Ma ◽  
Wuli Chu ◽  
Haoguang Zhang ◽  
Chuanle Liu
Keyword(s):  
Boundary Layer ◽  
Pressure Loss ◽  
Total Pressure ◽  
Vortex Generator ◽  
Aerodynamic Performance ◽  
Total Pressure Loss ◽  
Control Methods ◽  
Compressor Cascade ◽  
Boundary Layer Suction ◽  
Micro Vortex Generator

The performance of a compressor cascade is considerably influenced by flow control methods. In this paper, the synergistic effects of combination between micro-vortex generators (MVG) and boundary layer suction (BLS) are discussed in a high-load compressor cascade. Seven cases, which are grouped by a kind of micro-vortex generator and boundary layer suction with three locations, are investigated to control secondary flow effects and enhance the aerodynamic performance of the compressor cascade. The MVG is mounted on the end-wall in front of the passage. The rectangle suction slot with three radial positions is installed on the blade suction surface near the trailing edge. The numerical results show that: at the design condition, the total pressure loss is effectively decreased as well as the static pressure coefficient increase when the combined MVG and SBL method (COM) is used, which is superior to MVG in an aerodynamic performance. At the stall condition, the induced vortex coming from MVG could mix the low-energy fluid and mainstream, which result in the reduced separation, and the total pressure loss decreased by 11.54% when the suction flow ratio is 1.5%. The total pressure loss decreases by 14.59% when the COM control methods are applied.

The Effects of Freestream Turbulence on the Profile Boundary Layer and Losses in a Compressor Cascade

1984 ◽  
Author(s):  
R. L. Evans
Keyword(s):  
Boundary Layer ◽  
Pressure Loss ◽  
Total Pressure ◽  
Boundary Layer Separation ◽  
Skin Friction Coefficient ◽  
Total Pressure Loss ◽  
Freestream Turbulence ◽  
Compressor Cascade ◽  
Deviation Angle ◽  
Displacement Thickness

The turbulent profile boundary layer on a one-foot chord compressor cascade blade has been measured with varying levels of freestream turbulence. Increased levels of freestream turbulence were found to increase the fullness of the velocity profiles, with a consequent decrease in displacement thickness and an increase in the skin friction coefficient. A small increase in freestream turbulence causes the cascade total-pressure loss to increase initially, while at the higher turbulence levels boundary layer separation was delayed, resulting in a decrease in the total-pressure loss and deviation angle.

Applications of little blades in a high-load compressor cascade with leaned blade

2021 ◽  
pp. 095440622110164
Author(s):  
Shan Ma ◽  
Xiaolin Sun
Keyword(s):  
Boundary Layer ◽  
Pressure Loss ◽  
Total Pressure ◽  
Active Role ◽  
Low Energy ◽  
Total Pressure Loss ◽  
Stable Operation ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Lean Angle

The development of boundary layer affects the compressor cascade performance to a certain extent. Therefore, the compound lean and little blades are selected to redistribute the boundary layer, and the influences of these two flow control technologies on the axial compressor cascade performance are further studied. The calculated results showed that appropriate high pressure region on the blade suction surface near the end-wall is helpful to reduce the total pressure loss of compressor cascade, which can be achieved by positive lean technique. Meanwhile, the maximum stable operation boundary can be expanded by the application of positive leaned blade. On the other hand, the introduction of negative lean angle not only increases the total pressure loss of cascade, but reduces the stable operation range. As the little blades are introduced in the negative lean compressor cascade, the stable operation range is significantly improved by the introduction of little blades. Especially the cascade with −10° lean angle, the maximum stable operation boundary is increased from 1° to 6°. In the positive lean compressor cascade, although more low-energy fluid is accumulated on the blade suction surface near the mid-span, the little blades still show an active role in reducing the total pressure loss and expending the stable operation range, because the influence range of induced vortex reaches 30%span. The results provide a reference for improving the aerodynamic performance of compressor stator, especially when more low-energy fluid is blocked in the range near the mid-span.

Effects of Riblets on the Loss Behavior of a Highly Loaded Compressor Cascade

2002 ◽  
Author(s):  
Matthias Boese ◽  
Leonhard Fottner
Keyword(s):  
Boundary Layer ◽  
Pressure Loss ◽  
Total Pressure ◽  
Loss Coefficient ◽  
Total Pressure Loss ◽  
Compressor Cascade ◽  
Pressure Loss Coefficient ◽  
Flow Phenomena ◽  
Total Pressure Loss Coefficient ◽  
Highly Loaded

An experimental investigation of the influence of riblet surface structures on the loss behavior of a highly loaded compressor cascade V103-180 featuring a large chord length for high spatial resolution of the flow phenomena was performed. The cascade experiments were carried out at the High Speed Cascade Wind Tunnel of the University of the Armed Forces Munich in order to simulate realistic Mach and Reynolds numbers. The riblets used for the first investigation are of symmetric v-groove type with heights of 0.0762, 0.1143 and 0.1524 mm, respectively [1]. With two total pressure probes simultaneously traversed over one pitch behind the center airfoil, the local total pressure difference between the structured and the smooth blade is determined. From these measurements, the total pressure loss coefficient can be evaluated. For a better understanding of the flow phenomena, the profile pressure distribution is measured for the smooth and the structured blade. Boundary layer calculations were performed in order to optimise the riblet size for the design conditions of the compressor cascade. Resulting from the measurements an optimised riblet configuration (size and shape) has been manufactured and transferred to the cascade. Further flow measurements have been performed in order to evaluate the total pressure loss coefficient. Additional insight into the flow phenomena of the boundary layer has been achieved by laser-two-focus measurements. The experimental results indicate that the riblets mainly influence the suction side boundary layer behaviour. The ideal dimensionless groove height is obtained h+ = 9 leading to a reduction of the loss coefficient of 6–8%. Values of h+ > 20 cause an increase of the loss coefficient due to the development of a turbulent boundary layer separation.

Effects of segmented layer suction and micro-vortex generator on a high-load compressor cascade performance

2021 ◽  
pp. 095440622098050
Author(s):  
Shan Ma ◽  
Wuli Chu ◽  
Xiaolin Sun ◽  
Zhengtao Guo ◽  
Song Yan
Keyword(s):  
Boundary Layer ◽  
Pressure Loss ◽  
Total Pressure ◽  
Vortex Generator ◽  
Total Pressure Loss ◽  
Compressor Cascade ◽  
Boundary Layer Suction ◽  
Axial Location ◽  
Micro Vortex Generator ◽  
Suction Slot

The axial location of full-span boundary layer suction is studied to explore the influences of suction slot on the cascade performance. At the design condition, the slot with 50% axial location shows a superior capability to reduce the total pressure loss. At the near stall condition, the more upstream of the suction slot is moved, the more total pressure loss is reduced, and the suction slot with a location of 0.7 axial chord length cannot effectively reduces the total pressure loss in all conditions. Moreover, a rearranged segmented suction slot according to the distribution characteristics of the flow reversal region is developed and compared with full-span boundary layer suction. The segmented suction slot shows significant advantages in delaying the stall occurrence, and the stall point is delayed from 7.9° to 10.0° compared with the baseline. According to a quantitative analysis method selected to measure the performances of flow control technologies, the wake loss is significantly reduced by the segmented suction slot. Finally, a set of micro-vortex generator is introduced in the cascade with a segmented suction slot, and the conclusion indicates that the portion near the end-wall is very effective to reduce the flow loss.

Endwall Contouring and Fillet Design for Reducing Losses and Homogenizing the Outflow of a Compressor Cascade

2014 ◽  
Author(s):  
Oliver Reutter ◽  
Stefan Hemmert-Pottmann ◽  
Alexander Hergt ◽  
Eberhard Nicke
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Leading Edge ◽  
Total Pressure Loss ◽  
Wall Region ◽  
Optimized Design ◽  
Compressor Cascade ◽  
Outflow Region ◽  
Endwall Contouring ◽  
Operating Points

The following paper deals with the development of an optimized fillet and an endwall contour for reducing the total pressure loss and for homogenizing the outflow of a highly loaded cascade with a low aspect ratio. The NACA-65 K48 cascade profile without a fillet and without endwall contouring is used as a basis. Optimizations are performed using the DLR in-house tool AutoOpti and the RANS-solver TRACE. Three operating points at an inflow Mach number of 0.67 with different inflow angles are used to secure a wide operating range of the optimized design. At first only a fillet is optimized. The optimized fillet is small at the leading edge and rather high, wide and thick towards the trailing edge. It reduces the total pressure loss and homogenizes the outflow up to a blade height of 20 %. Following this a combined optimization of the endwall and the fillet is performed. The optimized contour leads to the development of a vortex, which changes the secondary flow in such a way, that the corner separation is reduced, which in turn significantly reduces the total pressure loss up to 16 % in the design operating point. The contour in the outflow region leads to a significant homogenization of the outflow in the near wall region.

scholarly journals Preliminary Experimental Study on Pressure Loss Coefficients of Exhaust Manifold Junction

2014 ◽  
Vol 2014 ◽  
pp. 1-10
Author(s):  
Xiao-lu Lu ◽  
Kun Zhang ◽  
Wen-hui Wang ◽  
Shao-ming Wang ◽  
Kang-yao Deng
Keyword(s):  
Mass Flow ◽  
Pressure Loss ◽  
Total Pressure ◽  
Loss Coefficient ◽  
Total Pressure Loss ◽  
Flow Ratio ◽  
Pressure Loss Coefficient ◽  
Loss Coefficients ◽  
Total Pressure Loss Coefficient ◽  
Mass Flow Ratio

The flow characteristic of exhaust system has an important impact on inlet boundary of the turbine. In this paper, high speed flow in a diesel exhaust manifold junction was tested and simulated. The pressure loss coefficient of the junction flow was analyzed. The steady experimental results indicated that both of static pressure loss coefficientsL13andL23first increased and then decreased with the increase of mass flow ratio of lateral branch and public manifold. The total pressure loss coefficientK13always increased with the increase of mass flow ratio of junctions 1 and 3. The total pressure loss coefficientK23first increased and then decreased with the increase of mass flow ratio of junctions 2 and 3. These pressure loss coefficients of the exhaust pipe junctions can be used in exhaust flow and turbine inlet boundary conditions analysis. In addition, simulating calculation was conducted to analyze the effect of branch angle on total pressure loss coefficient. According to the calculation results, total pressure loss coefficient was almost the same at low mass flow rate of branch manifold 1 but increased with lateral branch angle at high mass flow rate of branch manifold 1.

Aerodynamic optimisation of a winglet-cavity tip in a high-pressure axial turbine cascade

2016 ◽  
Vol 232 (4) ◽  
pp. 649-663 ◽  
Author(s):  
Zhihua Zhou ◽  
Shaowen Chen ◽  
Songtao Wang
Keyword(s):  
High Pressure ◽  
Mass Flow ◽  
Pressure Loss ◽  
Total Pressure ◽  
Suction Side ◽  
Tip Clearance ◽  
Total Pressure Loss ◽  
Pressure Side ◽  
Tip Clearance Flow ◽  
Clearance Flow

Tip clearance flow between rotating blades and the stationary casing in high-pressure turbines is very complex and is one of the most important factors influencing turbine performance. The rotor with a winglet-cavity tip is often used as an effective method to improve the loss resulting from the tip clearance flow. In this study, an aerodynamic geometric optimisation of a winglet-cavity tip was carried out in a linear unshrouded high-pressure axial turbine cascade. For the purpose of shaping the efficient winglet geometry of the rotor tip, a novel parameterisation method has been introduced in the optimisation procedure based on the computational fluid dynamics simulation and analysis. The reliability of a commercial computational fluid dynamics code with different turbulence models was first validated by contrasting with the experimental results, and the numerical total pressure loss and flow angle using the Baseline k-omega Model (BSL κ-ω model) shows a better agreement with the test data. Geometric parameterisation of blade tips along the pressure side and suction side was adopted to optimise the tip clearance flow, and an optimal winglet-cavity tip was proven to achieve lower tip leakage mass flow rate and total pressure loss than the flat tip and cavity tip. Compared to the numerical results of flat tip and cavity tip, the optimised winglet-cavity design, with the winglet along the pressure side and suction side, had lower tip leakage mass flow rate and total pressure loss. It offered a 35.7% reduction in the change ratio [Formula: see text]. In addition, the optimised winglet along pressure side and suction side, respectively, by using the parameterisation method was studied for investigating the individual effect of the pressure-side winglet and suction-side winglet on the tip clearance flow. It was found that the suction-side extension of the optimal winglet resulted in a greater reduction of aerodynamic loss and leakage mass flow than the pressure-side extension of the optimal winglet. Moreover, with the analysis based on the tip flow pattern, the numerical results show that the pressure-side winglet reduced the contraction coefficient, and the suction-side winglet reduced the aerodynamic loss effectively by decreasing the driving pressure difference near the blade tips, the leakage flow velocity, and the interaction between the leakage flow and the main flow. Overall, a better aerodynamic performance can be obtained by adopting the pressure-side and suction-side winglet-cavity simultaneously.

scholarly journals Gas turbine outlets: test results

2020 ◽  
Vol 4 (394) ◽  
pp. 121-128
Author(s):  
Nikolay N. Ponomarev
Keyword(s):  
Experimental Study ◽  
Gas Turbine ◽  
Pressure Loss ◽  
Total Pressure ◽  
Mutual Influence ◽  
Engineering Calculation ◽  
Total Pressure Loss ◽  
Flow Section ◽  
Pressure Losses ◽  
Flow Parameters

Object and purpose of research. The object of this work is gas turbine outlet consisting of axial-radial diffuser with the struts and the volute. The purpose is to create a methodology for engineering calculations, taking into account the mutual influence of the diffuser and the volute. Materials and methods. Experimental study of the flow in the models of outlets by measuring total and static pressure in characteristic sections. Calculation of integral and averaged flow parameters in measurement sections. Visualization of boundary flows. Based on the experimental results, development of regression models for the correction factors to be applied in the theoretical model, with selection of relevant factors. Main results. An experimental study of 23 variants of models with a total volume of 112 experimental points (modes) was carried out. On the basis of the experiment, methodology and program for engineering calculation of total pressure losses in the outlets were developed. It was found that the installation of guide blades and radial ribs in the diffuser in order to reduce local expansion angles with the ultimate purpose of mitigating total pressure losses actually does not lead to this result due to the because the flow in the diffuser becomes asymmetric due to its interaction with the volute. Visualization of boundary flows in the diffusers and the volutes has been performed, which makes it possible to identify the locations of separations causing increased pressure losses. Conclusion. An engineering method for calculating the total pressure loss in gas turbine outlet has been developed. The technique makes it possible, taking size restrictions into account, to select the geometry of the flow section that ensures minimum total pressure loss.

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