Study on Optimization Design and Flow Control Mechanism of Little Blades in a Compressor Cascade

2020 ◽  
Author(s):  
Zhengtao Guo ◽  
Wuli Chu ◽  
Xiangyi Chen
Keyword(s):  
Flow Control ◽  
Flow Separation ◽  
Horseshoe Vortex ◽  
Aerodynamic Performance ◽  
Compressor Cascade ◽  
Height Range ◽  
Corner Region ◽  
Pressure Surface ◽  
Passage Vortex ◽  
End Wall

Abstract In view of the characteristics of flow separation in the compressor cascade corner region, a new flow control method for installing little blades in the front of the cascade passage was proposed, which took into account the flow control advantages of end wall fences and vortex generators. Firstly, the little blades could hinder the cross flow on the end wall and the development of the horseshoe vortex pressure surface branch. Secondly, the little blades could generate induced vortices to take away the low-energy fluid near the end wall and the corner region. Based on numerical simulations, the effects of different pitchwise positions, stagger angles and heights of the little blades on the aerodynamic performance of the cascade were studied, and the optimal little blades were obtained by NSGA-II using EBF neural network as the agent model. The results show that the little blades have the optimal pitchwise position, stagger angle and height range for improving the aerodynamic performance of the cascade. When the optimized little blades are introduced in the baseline cascade, the stable working range of the cascade is expanded, and the stall type of the cascade changes from the hub-corner stall to the overload of flow separation near the mid-span. At the near stall attack angle of the baseline, the total pressure loss coefficient is reduced by about 10.38% and the static pressure coefficient is increased by about 4.31%. Meanwhile, the loss of the lower span is decreased and the diffuser capacity of the whole span is improved. The passage secondary loss and wake loss are reduced because of the delay of corner separation. Moreover, the strength of the end wall vortex is weakened and the end wall vortex no longer develops as part of the passage vortex. The induced vortex, horseshoe vortex pressure surface branch and initial passage vortex develop into new passage vortex.

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.

Film Cooling on a Gas Turbine Blade Near the End Wall

1985 ◽  
Vol 107 (1) ◽  
pp. 117-122 ◽  
Author(s):  
R. J. Goldstein ◽  
H. P. Chen
Keyword(s):  
Gas Turbine ◽  
Turbine Blade ◽  
Film Cooling ◽  
Convex Surface ◽  
Horseshoe Vortex ◽  
Gas Turbine Blade ◽  
Film Cooling Effectiveness ◽  
Pressure Surface ◽  
Passage Vortex ◽  
End Wall

The local film cooling effectiveness on a gas turbine blade with a row of discrete cooling jets has been measured using a mass transfer technique. Particular emphasis is placed on phenomena near the end wall of the blade. This region contains a horseshoe vortex system modified by a passage vortex. On the concave (pressure) surface the film cooling performance is not greatly altered by the presence of the end wall. On the convex surface of the blade the film cooling is essentially absent in a triangular region extending from near the region of peak curvature on the blade to its trailing edge. This unprotected region closely corresponds to the location of the passage vortex as indicated by flow visualization. The passage vortex sweeps away the injected coolant flow from the surface. Upstream of the unprotected area the injected flow is skewed toward the middle span of the blade. The influence of the end wall extends about one-half chord length up from the end wall in the present experiments.

A Combined Application of Negative Bowed Blade and Endwall Unsteady Pulsed Holed Suction in a Highly Loaded Compressor Cascade

2018 ◽  
Author(s):  
Shaowen Chen ◽  
Hongxin Zhang ◽  
Qinghe Meng ◽  
Songtao Wang ◽  
Zhongqi Wang
Keyword(s):  
Flow Control ◽  
Flow Separation ◽  
Flow Behavior ◽  
Excitation Frequency ◽  
Aerodynamic Performance ◽  
Flow Ratio ◽  
Compressor Cascade ◽  
Aero Engine ◽  
Suction Flow ◽  
Highly Loaded

With the increasing continually of blade load, a serious three-dimensional (3D) unsteady flow separation is caused in the design of modern advanced aero-engine compressor. The flow separation has a strong influence on the aerodynamic behavior of the flow in the compressor passage such as reducing the pressure rise capability and overall efficiency, and even resulting in stall and surge. Consequently, it is very necessary to apply some effective techniques for suppressing the 3D flow separation in order to improve the aerodynamic performance of aero-engine compressors. The endwall unsteady pulsed holed suction (EUPHS) is first developed. Additionally, the negative bowed blade is a convention passive flow control method. It can make the flow of the midspan move toward the endwall by changing the radial pressure distribution and improve flow behavior of the midspan. Therefore, with the aim of further improving the aerodynamic performance and flow behavior, the EUPHS combined with the negative bowed blade as a new promising compound flow control (CFC) technique is proposed. In this study, only two bleeding holes on the endwalls (one on the upper endwall and another on the lower endwall) are used to achieve suction in a highly loaded compressor cascade. The improvements in aerodynamic performance by endwall steady constant holed suction (ESCHS), EUPHS and CFC are investigated and compared firstly. Some related parameters such as suction-to-inlet time-averaged suction flow ratio and excitation frequency are also discussed and analyzed in detail. The results show that CFC has more potential advantages than ESCHS and EUPHS in reducing the total pressure loss coefficient and is a promising flow control technology to further enhance aerodynamic performance. Based on the optimal suction-to-inlet time-averaged suction flow ratio and excitation frequency, the total pressure loss coefficients for CFC are reduced by 17.7%.

Numerical Simulation of Endwall Fence on the Secondary Flow in Compressor Cascade

2008 ◽  
Author(s):  
Jingjun Zhong ◽  
Ji-Ang Han ◽  
Yanming Liu ◽  
Fu Tian
Keyword(s):  
Numerical Simulation ◽  
Secondary Flow ◽  
Horseshoe Vortex ◽  
Side Branch ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Rotation Direction ◽  
Pressure Surface ◽  
Passage Vortex ◽  
Blockage Effect

In this paper, based on the experimental data, a detailed numerical simulation has been carried out for the compressor cascade composed of CDA blades with fences on the endwall. There are several different configurations of the endwall fences, such as length, height, and pitch-wise location for the endwall fence. The optimum lengths, height, pitch-wise or span-wise location of the fences on the cascade end walls are obtained. The process of endwall fence’s controlling secondary flow in the compressor cascade mainly lies in two ways: hindering crosswise flow from pressure surface to suction surface near the endwall of the cascade; forming and developing of fence vortex, in which the fence blockage effect is more important. Endwall fences has a significant effect on the vortices distribution, in which the formation and development of fence vortex is important. Its formation has a close relationship with the strength of the crossflow at the region between the pressure surface and fence, which is mainly due to the relative airflow movement when the pressure side branch of the horseshoe vortex rolls up and lift along the fence. For the fence vortex and passage vortex have the different rotation direction, it plays an important role in decreasing the secondary flow loss, furthermore, reducing the strength of the passage vortex. In general, stronger crosswise flow induces stronger fence vortex. As height and length of the fence increased, the blockage effect is more obvious, but the additional fence losses increased at the same time. Numerical results show that the fences, with one third of height of the inlet boundary layer thickness and the length of 75 percent axial chord, are most effective when they are located 30 percent of pitch far from the pressure surface of the blade. For all the computational cases, they reduce the cascade loss furthest respectively.

Effect of Boundary Layer Suction on Aerodynamic Performance of High-Turning Compressor Cascade

2013 ◽  
Author(s):  
Longxin Zhang ◽  
Shaowen Chen ◽  
Hao Xu ◽  
Jun Ding ◽  
Songtao Wang
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Experimental Studies ◽  
Aerodynamic Performance ◽  
Parameter Distribution ◽  
Compressor Cascade ◽  
Boundary Layer Suction ◽  
End Wall ◽  
Low Speed Wind Tunnel ◽  
Good Agreement

Compared with suction slots, suction holes are (1) flexible in distribution; (2) alterable in size; (3) easy to fabricate and (4) high in strength. In this paper, the numerical and experimental studies for a high turning compressor cascade with suction air removed by using suction holes in the end-wall at a low Mach numbers are carried out. The main objective of the investigation is to study the influence of different suction distributions on the aerodynamic performance of the compressor cascade and to find a better compound suction scheme. A numerical model was first made and validated by comparing with the experimental results. The computed flow visualization and exit parameter distribution showed a good agreement with experimental data. Second, the model was then used to simulate the influence of different suction distributions on the aerodynamic performance of the compressor cascade. A better compound suction scheme was obtained by summarizing numerical results and tested in a low speed wind tunnel. As a result, the compound suction scheme can be used to significantly improve the performance of the compressor cascade because the corner separation gets further suppressed.

Effect of Blade Aspiration Slot Configuration on the Aerodynamic Performance of a Highly Loaded Aspirated Compressor Cascade

2017 ◽  
Author(s):  
Longxin Zhang ◽  
Le Cai ◽  
Bao Liu ◽  
Jun Ding ◽  
Songtao Wang
Keyword(s):  
Flow Control ◽  
Flow Rate ◽  
Control Method ◽  
Active Flow Control ◽  
Experimental Studies ◽  
Aerodynamic Performance ◽  
Flow Path ◽  
Compressor Cascade ◽  
Flow Loss ◽  
Highly Loaded

As a promising active flow control method, boundary layer suction (BLS) can be used to enhance the aerodynamic performance of the highly-loaded compressor effectively, and due to this reason, extensive studies have been carried out on it. However, contrast to those abundant studies focusing on the flow control effects of BLS, little attention has been paid on the design method of the aspiration flow path. This work presents a 3-D steady numerical simulation on a highly-loaded aspirated compressor cascade. The aspiration slot is implemented at its best location based on the previous experimental studies and the aspiration flow rate is fix to 1.5% of the inlet massflow. The plenum configuration follows the blade shape and remains unchanged. One-side-aspiration manner is adopted to simplify the aspiration devices. Two critical geometry parameters, slot angle and slot width, are varied to study the effects of blade aspiration slot configuration on the cascade loss, radial distribution of the aspiration flow rate and inner flow structures within the aspiration flow path. Results show that the slot configuration does affect the cascade performance. In comparison with the throughflow performance, it is especially true once the flow loss caused by the aspiration flow path is also taken into account, and higher flow loss will be generated within the aspiration flow path if an inappropriate scheme is adopted. In the present investigation, apart from the cases with larger negative slot angle, a wider slot is more preferable to a narrower one, since it could enhance the aspiration capacity near the endwall regions and lower the dissipation loss within the aspiration flow path. In terms of the slot angle, a larger negative value, i.e., the slot direction more aligned with the incoming flow, is not beneficial to improve the throughflow performance, while concerning the flow loss yield by the aspiration flow path, a proper negative slot angle is always optimal.

Experimental Investigations on the Efficiency of Active Flow Control in a Compressor Cascade With Periodic Non-Steady Outflow Conditions

2017 ◽  
Author(s):  
Marcel Staats ◽  
Wolfgang Nitsche
Keyword(s):  
Flow Field ◽  
Flow Control ◽  
Flow Separation ◽  
Active Flow Control ◽  
Experimental Investigations ◽  
Compressor Cascade ◽  
Steady Regime ◽  
Stator Blade ◽  
Active Flow ◽  
The Impact

We present results of experiments on a periodically unsteady compressor stator flow of the type which would be expected in consequence of pulsed combustion. A Reynolds number of Re = 600000 was used for the investigations. The experiments were conducted on the two-dimensional low-speed compressor testing facility in Berlin. A choking device downstream the trailing edges induced a periodic non-steady outflow condition to each stator vane which simulated the impact of a pressure gaining combuster downstream from the last stator. The Strouhal number of the periodic disturbance was Sr = 0.03 w.r.t. the stator chord length. Due to the periodic non-steady outflow condition, the flow-field suffers from periodic flow separation phenomena, which were managed by means of active flow control. In our case, active control of the corner separation was applied using fluidic actuators based on the principle of fluidic amplification. The flow separation on the centre region of the stator blade was suppressed by means of a fluidic blade actuator leading to an overall time-averaged loss reduction of 11.5%, increasing the static pressure recovery by 6.8% while operating in the non-steady regime. Pressure measurements on the stator blade and the wake as well as PIV data proved the beneficial effect of the active flow control application to the flow field and the improvement of the compressor characteristics. The actuation efficiency was evaluated by two figures of merit introduced in this contribution.

A comparison of different unsteady flow control techniques in a highly loaded compressor cascade

2018 ◽  
Vol 233 (6) ◽  
pp. 2051-2065 ◽  
Author(s):  
Hongxin Zhang ◽  
Shaowen Chen ◽  
Yun Gong ◽  
Songtao Wang
Keyword(s):  
Unsteady Flow ◽  
Flow Control ◽  
Flow Separation ◽  
Synthetic Jet ◽  
Control Technique ◽  
Compressor Cascade ◽  
Optimum Result ◽  
Control Techniques ◽  
Constant Suction ◽  
Highly Loaded

A numerical research is applied to investigate the effect of controlling the flow separation in a certain highly loaded compressor cascade using different unsteady flow control techniques. Firstly, unsteady pulsed suction as a new novel unsteady flow control technique was proposed and compared to steady constant suction in the control of flow separation. A more exciting effect of controlling the flow separation and enhancing the aerodynamic performance for unsteady pulsed suction was obtained compared to steady constant suction with the same time-averaged suction flow rate. Simultaneously, with the view to further exploring the potential of unsteady flow control technique, unsteady pulsed suction, unsteady pulsed blowing, and unsteady synthetic jet (three unsteady flow control techniques) are analyzed comparatively in detail by the related unsteady aerodynamic parameters such as excitation location, frequency, and amplitude. The results show that unsteady pulsed suction shows greater advantage than unsteady pulsed blowing and unsteady synthetic jet in controlling the flow separation. Unsteady pulsed suction and unsteady synthetic jet have a wider range of excitation location obtaining positive effects than unsteady pulsed blowing. The ranges of excitation frequency and excitation amplitude for unsteady pulsed suction gaining favorable effects are both much wider than that of unsteady pulsed blowing and unsteady synthetic jet. The optimum frequencies of unsteady pulsed suction, unsteady pulsed blowing, and unsteady synthetic jet are found to be different, but these optimum frequencies are all an integer multiple of the natural frequency of vortex shedding. The total pressure loss coefficient is reduced by 16.98%, 16.55%, and 17.38%, respectively, when excitation location, frequency, and amplitude are all their own optimal values for unsteady pulsed suction, unsteady pulsed blowing, and unsteady synthetic jet. The optimum result of unsteady synthetic jet only slightly outperforms that of unsteady pulsed suction and unsteady pulsed blowing. But unfortunately, there is no advantage from the standpoint of overall efficiency for the optimum result of unsteady synthetic jet because the slight improvement has to require a greater power consumption than the unsteady pulsed suction and unsteady pulsed blowing methods.

Numerical Investigation of a Sweeping Jet Actuator for Active Flow Control in a Compressor Cascade

2018 ◽  
Author(s):  
Qinghe Meng ◽  
Shaowen Chen ◽  
Weihang Li ◽  
Songtao Wang
Keyword(s):  
Flow Control ◽  
Flow Separation ◽  
Control Method ◽  
Fluid Dynamic ◽  
Active Flow Control ◽  
Secondary Flows ◽  
Compressor Cascade ◽  
Skew Angle ◽  
Aerodynamic Loss ◽  
Active Flow

Sweeping Jet Actuator (SJA) was introduced as a potential active flow control method for reducing three-dimension (3D) flow separations in a compressor cascade. Unlike some other actuators, SJA needs no valves or moving parts to convert its steady compressed air source into sweeping jets that oscillates from side to side through the millimeter-sized outlet nozzle. The rather simple and small structure makes it possible to place SJA into the blades. In this study, a 3D numerical simulation using unsteady RANS codes was conducted to investigate the effects of SJA on the flow pattern and the aerodynamic loss mechanism in a compressor cascade. Firstly, the reliability of a commercial Computational Fluid Dynamic (CFD) code was validated and the computed results showed good agreements with experimental data from the literature. Secondly, some possible affecting factors, such as actuating pressure, position of SJA exit and jet skew angle, were analyzed and discussed in detail. Moreover, the effectiveness of active flow control under different locations and stream directions of SJA was studied for obtaining a further understanding of the mechanism of SJA for controlling flow separations. In addition, the generation and interaction of internal secondary flows in the compressor cascade were also investigated, and the oscillating jet process of SJA was presented. The numerical results indicate that using SJA delays effectively the corner flow separation, thus decreases the aerodynamic loss of the compressor cascade. For the optimum scheme within the present research, the reduction of overall time-averaged total pressure loss coefficient achieves about 5.6% compared with the original case without SJA. The streamwise position of SJA has a more remarkable influence in improving performance than the other SJA schemes. The considerable improvements of flow separation in the corner region is considered to be one of the main reasons in overall performance increase.

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