Numerical Investigation of Passive Flow Control Using Wavy Blades in a Highly-Loaded Compressor Cascade

2018 ◽  
Author(s):  
Bo Wang ◽  
Yanhui Wu ◽  
Kai Liu
Keyword(s):  
Numerical Investigation ◽  
Flow Structure ◽  
Cross Flow ◽  
Leading Edge ◽  
Control Flow ◽  
Streamwise Vortices ◽  
Compressor Cascade ◽  
Control Effect ◽  
Suction Surface ◽  
Highly Loaded

Driven by the need to control flow separations in highly loaded compressors, a numerical investigation is carried out to study the control effect of wavy blades in a linear compressor cascade. Two types of wavy blades are studied with wavy blade-A having a sinusoidal leading edge, while wavy blade-B having pitchwise sinusoidal variation in the stacking line. The influence of wavy blades on the cascade performance is evaluated at incidences from −1° to +9°. For the wavy blade-A with suitable waviness parameters, the cascade diffusion capacity is enhanced accompanied by the loss reduction under high incidence conditions where 2D separation is the dominant flow structure on the suction surface of the unmodified blade. For well-designed wavy blade-B, the improvement of cascade performance is achieved under low incidence conditions where 3D corner separation is the dominant flow structure on the suction surface of the baseline blade. The influence of waviness parameters on the control effect is also discussed by comparing the performance of cascades with different wavy blade configurations. Detailed analysis of the predicted flow field shows that both the wavy blade-A and wavy blade-B have capacity to control flow separation in the cascade but their control mechanism are different. For wavy blade-A, the wavy leading edge results in the formation of counter-rotating streamwise vortices downstream of trough. These streamwise vortices can not only enhance momentum exchange between the outer flow and blade boundary layer, but also act as the suction surface fence to hamper the upwash of low momentum fluid driven by cross flow. For wavy blade-B, the wavy surface on the blade leads to a reduction of the cross flow upwash by influencing the spanwise distribution of the suction surface static pressure and guiding the upwash flow.

Experimental investigation on the performance of compressor cascade using blended-blade-end-wall contouring technology

2017 ◽  
Vol 232 (15) ◽  
pp. 2833-2844 ◽  
Author(s):  
Weilin Yi ◽  
Lucheng Ji
Keyword(s):  
Three Dimensional ◽  
Cross Flow ◽  
Control Flow ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Three Dimensional Flow ◽  
Turning Angle ◽  
Corner Region ◽  
Passage Vortex ◽  
End Wall

Three-dimensional flow separations commonly occur in the corner region formed by the blade suction surface and end wall in compressors. How to control or reduce these separations is a vital problem for aerodynamic designers all the time. Blended blade and end wall contouring technology has been proposed to control flow separation for several years and validated in many cases using the numerical method, but experimental data was not obtained so far. So in this paper, the baseline cascade scaling from the NACA65 airfoil with 42° turning angle is designed, tested, and analyzed firstly. Then, based on the experimental results of the baseline cascade, blended blade and end wall contouring is applied to the suction surface and hub corner region of the baseline cascade and the detailed experiment is carried out. The results show that the blended blade and end wall contouring technology can decrease the total pressure loss by 8% and 7% at 0° and +10° incidence angles separately. The improved span range mainly focuses on the 10–25% span height. The rolling change of the passage vortex influenced by the accumulation of low energy fluid driven by cross flow in the hub corner should be the main reason for the performance improvement.

Control of Flow Separations in Compressor Cascade by Boundary Layer Suction Holes in Suction Surface

2013 ◽  
Author(s):  
Jun Ding ◽  
Shaowen Chen ◽  
Hao Xu ◽  
Shijun Sun ◽  
Songtao Wang
Keyword(s):  
Boundary Layer ◽  
Experimental Investigation ◽  
Flow Separation ◽  
Load Capacity ◽  
Leading Edge ◽  
Control Flow ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Boundary Layer Suction ◽  
Aerodynamic Parameters

Boundary layer suction is used in turbomachinery to control flow separation to enhance the loading capacity of a compressor. This paper focuses on both numerical calculation and experimental investigation with boundary layer suction holes made in the suction surface of a compressor cascade with a large camber angle. Experimental and numerical investigations are carried out with suction holes in different positions. In the experimental investigation, exit aerodynamic parameters are measured using a five-hole aerodynamic probe, and ink-trace flow visualization is adopted on cascade surface. Experimental and numerical results indicate that both side and middle suctions on the suction surface can efficiently remove low-energy fluid to increase the cascade load capacity while they effectively restrain the corner flow separation. The cascade aerodynamic performance is obviously improved by middle and side suctions, and it is also significantly altered by the position of suction changes. The middle suction holes have their best positions at about 60–66% chord length from the leading edge, and the side suction holes have their best positions a little downstream the corner separation line.

Performance enhancing for a highly loaded tandem cascade by endwall incoming vortex–corner separation interaction

2021 ◽  
pp. 095440622110187
Author(s):  
Zhiyuan Cao ◽  
Xi Gao ◽  
Cheng Song ◽  
Xiang Zhang ◽  
Fei Zhang ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Control Method ◽  
Leading Edge ◽  
Control Effect ◽  
Suction Surface ◽  
Blade Passage ◽  
Corner Separation ◽  
Pressure Surface ◽  
Passage Vortex ◽  
Highly Loaded

In highly loaded tandem compressor cascades, corner separations can still exist. In order to eliminate corner separations in highly loaded tandem compressor cascades, incoming vortex–corner separation interaction mechanism was investigated. Different schemes of the vortex generators, which located at different pitchwise locations and could generate vortexes with different rotation directions, were designed and investigated numerically. Results show that, severe corner separation occurred at the front blade passage of the tandem cascade; by utilizing flow control method of incoming vortex–corner separation interaction, the corner separation could be reduced significantly. The optimal control effect of incoming vortex on corner separation was achieved with anticlockwise rotation and the vortex generator is located right ahead of the leading edge of tandem cascade, a maximum loss coefficient reduction of 21.8% being achieved. Different from single blade configuration, the boundary layer of tandem cascade was regenerated at rear blade suction surface due to the injection flow from blade gap between the two blades. Though corner separations could be reduced at both conditions, the loss of tandem cascade with clockwise incoming vortex is higher than that with anticlockwise vortex, and a smaller corner separation region at suction surface was achieved by utilizing clockwise vortex. The mechanism was that anticlockwise incoming vortex reduced the corner separation but increased secondary flow, while clockwise vortex enhanced passage vortex and decreased secondary flow. For clockwise incoming vortex near pressure surface, the vortex would be divided into two parts at the leading edge of rear blade, one would go through the blade gap and deteriorate flow fluid near rear blade suction surface, the other flowed downstream along pressure surface. The rotation direction of different incoming vortexes became the same as the passage vortex at rear blade passage of tandem cascade, which was mainly due to the effect of secondary flow.

Flow physics of highly loaded tandem compressor cascade with non-axisymmetric endwall profiling

2020 ◽  
pp. 095765092098310
Author(s):  
Zhiyuan Cao ◽  
Wei Guo ◽  
Cheng Song ◽  
Bo Liu
Keyword(s):  
Static Pressure ◽  
Compressor Cascade ◽  
Control Effect ◽  
Suction Surface ◽  
Blade Loading ◽  
Tandem Configuration ◽  
Blade Passage ◽  
Corner Separation ◽  
Axial Location ◽  
Highly Loaded

Tandem configuration is an effective methodology to reduce flow separation on compressor blade suction surface and to improve blade loading. However, in modern highly loaded cases, corner separation remains as its single blade counterpart. In this study, non-axisymmetric endwall profiling (NAEP) was utilized in a highly loaded tandem cascade (diffusion factor D = 0.69), aiming at reducing its severe corner separation and revealing the unique flow mechanism while NAEP is utilized in tandem cascade. NAEP was designed in both forward (F) blade and rare (R) blade separately, and was investigated numerically in tandem environment. Results show that, NAEP in F blade passage can effectively eliminate the corner separation and reduce loss generation, whereas NAEP in R blade passage has no positive effect on corner separation and even promotes loss production. The optimal NAEP approximately removes the corner separation completely, with loss coefficient reducing by as much as 37.8%. The optimal NAEP for the tandem cascade features optimal axial location at the origin of corner separation. There is an optimal NAEP height (0.02 of blade height), under which NAEP can achieve pretty good control effect while the peak of NAEP varies in a large axial location range. In the tandem configuration, it is found that NAEP transfers blade loading from R blade to F blade; the static pressure increases significantly for the entire cascade, but the static pressure distribution of F blade does not exhibit as the design intent of NAEP. In addition, it is interesting to find that the flow turning near endwall reduces after endwall profiling, which is unique in tandem cascade and is contrast to the view on conventional configuration. On the contrary, NAEP in R blade has no influence on the corner separation of the tandem cascade; due to the decrement of cross-passage pressure gradient for R blade, the flow overturning near endwall reduces.

Influence of endwall slotted injection on performance and flow physics in a compressor cascade

2020 ◽  
pp. 095765092094653
Author(s):  
Zhiyuan Cao ◽  
Cheng Song ◽  
Bo Liu ◽  
Limin Gao
Keyword(s):  
Flow Control ◽  
Leading Edge ◽  
Loss Coefficient ◽  
Control Methods ◽  
Compressor Cascade ◽  
Control Effect ◽  
Suction Surface ◽  
Trailing Edge ◽  
Corner Separation ◽  
Axial Location

Air injection is an effectively methodology to suppress flow separation and to improve blade loading of airfoils and compressors. In order to remove corner separations in a cascade, investigation of endwall slotted injection was carried out numerically in this study. Based on endwall slot schemes of other flow control methods, six different endwall slots were designed, aiming at revealing the axial location effect and pitchwise location effect. For each endwall slot, numerical simulations were performed with six different injection directions to uncover the injection direction effect. Results showed that endwall slotted injection can effectively remove the corner separation. The overall loss coefficient and endwall loss coefficient of the cascade were reduced by 10.3% and 36.8% at most, respectively. Injection from leading edge and mid-chord can reduce endwall loss; however, the optimal axial location of endwall slot is near the trailing edge, where the corner separation is located. Different with other flow control methods, in general, the optimal pitchwise location of endwall slot is not close to suction surface but 0.16 pitch away from it. Injection near the suction surface is more sensitive to injection direction compared with injection at 0.16 pitch away from suction surface. Injection with velocity components both downstream and toward suction surface promises optimal control effect on corner separation. However, at mid-span, trailing edge separation is deteriorated and the flow turning angle is reduced, the flow mechanism being that the low-momentum fluid migrates along spanwise.

Effect of undulating blades on highly loaded compressor cascade performance

2020 ◽  
pp. 095765092090782
Author(s):  
Lirong Su ◽  
Xiaoqing Qiang ◽  
Tan Zheng ◽  
Jinfang Teng
Keyword(s):  
Incidence Angle ◽  
Leading Edge ◽  
Control Technique ◽  
Maximum Magnitude ◽  
Streamwise Vortices ◽  
Compressor Cascade ◽  
Pressure Loss Coefficient ◽  
Positive Effects ◽  
The Impact ◽  
Highly Loaded

Humpback whale’s flipper with leading-edge tubercles has been attracting aerodynamic and hydrodynamic researchers’ attentions by its stall-delayed characteristics. Inspired by this, the undulating configuration is used in a highly loaded compressor cascade as a new type of passive flow control technique. A new model of undulating compressor blade is studied in this paper. To investigate the effect of the undulating configuration on cascade performance without the impact of endwall, steady Reynolds-averaged Navier–Stokes simulations of infinite-span cascades are carried out with and without undulations at an inlet Mach number of 0.5. A parametric study is performed to conclude that, with a suitable wavelength, the undulating blade could achieve a rise in diffusion capacity, accompanied by 12.9% reduction in total pressure loss coefficient at a post-stall incidence angle of 8°, whereas it produces negligible impact in cascade performance at 0° incidence angle. Flow visualization further reveals that wavelength is a crucial parameter, determining the spanwise space for the formation of streamwise vortices. Undulating blades could produce positive effects with maximum magnitude when the counter-rotating streamwise vortices take dominant position along span with an appropriate size.

Corner Separation Control in a Highly Loaded Compressor Cascade Using Plasma Aerodynamic Actuation

2012 ◽  
Author(s):  
Yun Wu ◽  
Xiao-hu Zhao ◽  
Ying-hong Li ◽  
Jun Li
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Total Pressure Loss ◽  
Separation Control ◽  
Compressor Cascade ◽  
Control Effect ◽  
Suction Surface ◽  
Corner Separation ◽  
Pressure Loss Coefficient ◽  
Highly Loaded

Corner separation, which forms over the suction surface and endwall corner of a blade passage, causes significant total pressure loss in highly loaded compressors. Plasma flow control, based on the plasma aerodynamic actuation, is a novel active flow control technique to improve aircrafts’ aerodynamic characteristics and propulsion efficiency. This paper reports computational and experimental results on using three types of plasma aerodynamic actuation (PAA) to control the corner separation in a highly loaded, low speed, linear compressor cascade. Reynolds-Averaged Navier-Stokes simulations were performed to optimize the PAA arrangement. The PAA was generated by a microsecond or nanosecond dielectric barrier discharge in wind tunnel experiments. The total pressure loss coefficient distribution was adopted to evaluate the corner separation control effect. The control effect of pitch-wise PAA on the endwall, in terms of relative reduction of the pitch-wise averaged total pressure loss coefficient in the wake, is much better than that of stream-wise PAA on the suction surface. When both pitch-wise PAA on the endwall and stream-wise PAA on the suction surface are turned on simultaneously, the control effect is the best among all three types of PAA. The main effect of pitch-wise PAA on the endwall is to inhibit the crossflow from neighboring pressure surface to the suction surface, whilest the main effect of stream-wise PAA on the suction surface is to inhibit the boundary layer accumulation and separation. Compared to microsecond discharge PAA, nanosecond discharge PAA is more effective at higher freestream velocity. The mechanisms for nanosecond discharge and microsecond discharge PAA are different for corner separation control.

Numerical Investigation of the Solidity Effect on Linear Compressor Cascades

2014 ◽  
Author(s):  
J. Sans ◽  
M. Resmini ◽  
J.-F. Brouckaert ◽  
S. Hiernaux
Keyword(s):  
Numerical Investigation ◽  
State Of The Art ◽  
Leading Edge ◽  
Operating Conditions ◽  
Compressor Cascade ◽  
Minimum Loss ◽  
Low Speed ◽  
High Mach ◽  
The Stability ◽  
The Impact

Solidity in compressors is defined as the ratio of the aerodynamic chord over the peripheral distance between two adjacent blades, the pitch. This parameter is simply the inverse of the pitch-to-chord ratio generally used in turbines. Solidity must be selected at the earliest design phase, i.e. at the level of the meridional design and represents a crucial step in the whole design process. Most of the existing studies on this topic rely on low-speed compressor cascade correlations from Carter or Lieblein. The aim of this work is to update those correlations for state-of-the-art controlled diffusion blades, and extend their application to high Mach number flow regimes more typical of modern compressors. Another objective is also to improve the physical understanding of the solidity effect on compressor performance and stability. A numerical investigation has been performed using the commercial software FINE/Turbo. Two different blade profiles were selected and investigated in the compressible flow regime as an extension to the low-speed data on which the correlations are based. The first cascade uses a standard double circular arc profile, extensively referenced in the literature, while the second configuration uses a state-of-the-art CDB, representative of low pressure compressor stator mid-span profile. Both profiles have been designed with the same inlet and outlet metal angles and the same maximum thickness but the camber and thickness distributions, the stagger angle and the leading edge geometry of the CDB have been optimized. The determination of minimum loss, optimum incidence and deviation is addressed and compared with existing correlations for both configurations and various Mach numbers that have been selected in order to match typical booster stall and choke operating conditions. The emphasis is set on the minimum loss performance at mid-span. The impact of the solidity on the operating range and the stability of the cascade are also studied.

The Effective Positions to Inject Water Into the Cascade of Compressor

2012 ◽  
Author(s):  
Jie Wang ◽  
Qun Zheng ◽  
Lanxin Sun ◽  
Mingcong Luo
Keyword(s):  
Kinetic Energy ◽  
Total Pressure ◽  
Lower Energy ◽  
Water Injection ◽  
Adverse Pressure Gradient ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Pressure Losses ◽  
Ansys Cfx ◽  
Highly Loaded

Generally, droplets are injected into air at inlet or interstage of a compressor. However, both cases did not consider how to utilize the kinetic energy of these moving droplets. Under the adverse pressure gradient of compressor, the lower energy fluids of blade surfaces and endwalls boundary layers would accumulate and separate. Kinetic droplets could accelerate the lower energy fluids and eliminate the separation. This paper mainly investigate the effective positions where to inject water and how to utilize the droplets’ kinetic energy. Four different injecting positions, which located on the suction surface and endwall, are chosen. The changes of vortexes in the compressor cascade are discussed carefully. In addition, the influences of water injection on temperature, total pressure losses and Mach number are analyzed. Numerical simulations are performed for a highly loaded compressor cascade with ANSYS CFX software.

Investigation Into the Effects of Hub Rotation on the Hub Leakage Flow of Cantilever Stator in a Transonic Axial Compressor

2020 ◽  
Author(s):  
Botao Zhang ◽  
Bo Liu ◽  
Xin Sun ◽  
Hang Zhao
Keyword(s):  
Total Pressure ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Blade Root ◽  
Flow Loss ◽  
Total Pressure Ratio

Abstract In order to explore the similarities and differences between the flow fields of cantilever stator and idealized compressor cascade with tip clearance, and to extend the cascade leakage model to compressors, the influence of stator hub rotation to represent cascade and cantilever stator on hub leakage flow was numerically studied. On this basis, the control strategy and mechanism of blade root suction were discussed. The results show that there is no obvious influence on stall margin of the compressor whether the stator hub is rotating or stationary. For rotating stator hub, the overall efficiency is decreased while the total pressure ratio is increased. At peak efficiency point and near stall point, the efficiency is reduced by about 0.43% and 0.34% individually, while the total pressure ratio is enlarged by about 0.23% and 0.27%, respectively. The gap leakage flow is promoted due to stator hub rotation, and the structure of the leakage vortex is weakened obviously. In addition, the hub leakage flow originating from the blade leading edge of rotating hub may contribute to double leakage near the trailing edge of the adjacent blade. However, the leakage flow directly out of the blade passage with stationary stator hub. The stator root loading and strength of the leakage flow increase with the rotation of the hub, and the leakage vortex is further away from the suction surface of the blade and is stretched to an ellipse closer to the endwall under the shear action. The rotating hub makes the flow loss near the stator gap increase, while the flow loss in the upper part of the blade root is decreased. Meanwhile, the total pressure ratio in the end area is increased. Blade root suction of cantilever stator can effectively control the hub leakage flow, inhibit the development of hub leakage vortex, and improve the flow capacity of the passage, thereby reducing the flow loss and modifying the flow field in the end zone.

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