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.

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%.

Unsteady RANS Simulations of a Highly Loaded Low Aspect Ratio Compressor Stator Cascade With Active Flow Control

2010 ◽  
Author(s):  
Christoph Gmelin ◽  
Mathias Steger ◽  
Frank Thiele ◽  
Andre´ Huppertz ◽  
Marius Swoboda
Keyword(s):  
Aspect Ratio ◽  
Flow Control ◽  
Active Flow Control ◽  
Pressure Rise ◽  
Suction Side ◽  
Synthetic Jet ◽  
Compressor Cascade ◽  
Low Aspect Ratio ◽  
Rans Simulations ◽  
Highly Loaded

A highly loaded compressor cascade is analyzed by means of time-resolved 3D RANS simulations. Due to the low aspect ratio of the cascade, strong three-dimensional effects emerge, such as large corner vortices and trailing edge separation at the midspan. The feasibility of the simulation using a commercial software and the applicability of controlling the separated regions using zero net mass flux synthetic jets is analyzed. The work includes two control concepts that are investigated separately. One aims to affect the secondary flow emerging from the sidewalls via actuation at the cascade casing walls. The other aims to reattach the separated flow to the blade suction side using an actuator on the blade. Beneficial flow control parameters characterizing a synthetic jet are determined for both locations by a systematic variation. Special attention is drawn to the global efficiency of the stator cascade by means of total pressure loss and pressure rise.

Flow control using unsteady pulsed holed suction with different excitation models in a highly loaded compressor cascade

2017 ◽  
Vol 232 (6) ◽  
pp. 593-607 ◽  
Author(s):  
Hongxin Zhang ◽  
Shaowen Chen ◽  
Yun Gong ◽  
Songtao Wang
Keyword(s):  
Flow Control ◽  
Pressure Loss ◽  
Total Pressure ◽  
Control Flow ◽  
Total Pressure Loss ◽  
Control Technique ◽  
Compressor Cascade ◽  
Pressure Losses ◽  
Optimal Excitation ◽  
Highly Loaded

Unsteady pulsed holed suction as a new unsteady flow control technique is first proposed. Unsteady excitation models of four different waveforms (Waveforms 1, 2, 3, and 4) based on unsteady pulsed holed suction are investigated to analysis comparatively the control effects of flow separations in a certain highly loaded compressor. Some related unsteady aerodynamic parameters such as excitation frequency and excitation location are studies. The unsteady pulsed holed suctions of the four different modes (Waveforms 1, 2, 3, and 4) all effectively control flow separations. Their optimum frequencies are all an integer multiple of the natural frequency of vortex shedding. And their excitation locations gaining positive effect and optimal excitation locations are both same. The optimal excitation location is near the separation point of upper endwall in unexcited case. But, they show markedly different performances in reducing the total pressure losses. The unsteady pulsed holed suction of Waveform 3 shows greater advantage at different excitation frequencies and excitation locations. The optimum result is obtained by the unsteady pulsed holed suction of Waveform 3. The total pressure loss is reduced by 16.8%. Simultaneously, the unsteady pulsed holed suctions of the four different modes all can provide better effects than the steady constant holed suction in reducing the total pressure loss with the same suction-to-inlet time-averaged suction flow ratio ms. Especially at ms = 0.29%, for the steady constant holed suction, it is too small to effectively control flow separation, and consequently the total pressure loss are increased by 8.3%. However, for the unsteady pulsed holed suctions of Waveforms 2 and 3, the total pressure losses are reduced by 9.1% and 4.3%, respectively.

scholarly journals Active flow control by means of synthetic jets on a highly loaded compressor cascade

2011 ◽  
Vol 225 (7) ◽  
pp. 897-908 ◽  
Author(s):  
V Zander ◽  
M Hecklau ◽  
W Nitsche ◽  
A Huppertz ◽  
M Swoboda
Keyword(s):  
Flow Control ◽  
Large Scale ◽  
Active Flow Control ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Experimental Investigations ◽  
Compressor Cascade ◽  
Actuation Frequency ◽  
Active Flow ◽  
Highly Loaded

This article presents the potential of active flow control to increase the aerodynamic performance of highly loaded turbomachinery compressor blades. Experimental investigations on a large-scale compressor cascade equipped with 30 synthetic jet actuators mounted to the sidewalls and the blades themselves have been carried out. Results for a variation of the inflow angle, the jet amplitude, and the actuation frequency are presented. The wake measurements show total pressure loss reductions of nearly 10 per cent for the synthetic jet actuation. An efficiency calculation reveals that the energy saved by actuation is nearly twice the energy consumption of the synthetic jets.

Active Flow Control Techniques on a Stator Compressor Cascade: A Comparison Between Synthetic Jet and Plasma Actuators

2012 ◽  
Author(s):  
Maria Grazia De Giorgi ◽  
Stefania Traficante ◽  
Carla De Luca ◽  
Daniela Bello ◽  
Antonio Ficarella
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Active Flow Control ◽  
Pressure Ratio ◽  
Boundary Layer Separation ◽  
Synthetic Jet ◽  
Plasma Actuators ◽  
Compressor Cascade ◽  
Control Techniques ◽  
Active Flow

In this work a CFD analysis is applied to study the suppression of the boundary layer separation into a highly-loaded subsonic compressor stator cascade, by different active flow control techniques. Active flow control techniques have the potential to delay separation and to increase the pressure ratio. In particular three different techniques have been applied: the actuation by steady jet, by zero net mass flux Synthetic Jet (SJA) and by plasma actuator. Several works have investigated the use of synthetic jet and plasma actuators on the airfoil, but only few studies have compared the effect of these devices. Concerning the synthetic jet actuator, a suction/blowing type boundary condition is used, imposing a prescribed sinusoidal velocity depending on velocity amplitude, jet frequency and jet angle of ejection with respect to the wall. Concerning the plasma actuation, the effect is modeled into numerical flow solvers by adding the paraelectric force that represents the plasma force into the momentum equation. The plasma, generated by Dielectric Barrier Discharge, acts as a momentum source to the boundary layer allowing it to remain attached throughout a larger portion of the airfoil. The time-averaged body force component, acting on the fluid, depends on the frequency and on the applied voltage, the charge density, the electrical field and the dimensional properties of the actuator, like width of the electrodes and gap between the electrodes. Using this numerical model, the effect of plasma actuators to suppress the flow separation over the blade has been investigated, increasing the turbo-machinery performance too. Finally, the comparison between the different actuation devices shows that, reducing the secondary flow structures, each actuation technique beneficially affects the performance of the stator compressor cascade, even if in the steady jet the costs are relevant.

scholarly journals Model-Based Analysis of Flow Separation Control in a Curved Diffuser by a Vibration Wall

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1781
Author(s):  
Weiyu Lu ◽  
Xin Fu ◽  
Jinchun Wang ◽  
Yuanchi Zou
Keyword(s):  
Flow Field ◽  
Flow Control ◽  
Flow Separation ◽  
Vibration Frequency ◽  
Flow Instability ◽  
Control Technique ◽  
Simplified Model ◽  
Main Stream ◽  
Control Performance ◽  
Flow Separation Control

Vibration wall control is an important active flow control technique studied by many researchers. Although current researches have shown that the control performance is greatly affected by the frequency and amplitude of the vibration wall, the mechanism hiding behind the phenomena is still not clear, due to the complex interaction between the vibration wall and flow separation. To reveal the control mechanism of vibration walls, we propose a simplified model to help us understand the interaction between the forced excitation (from the vibration wall) and self-excitation (from flow instability). The simplified model can explain vibration wall flow control behaviors obtained by numerical simulation, which show that the control performance will be optimized at a certain reduced vibration frequency or amplitude. Also, it is shown by the analysis of maximal Lyapunov exponents that the vibration wall is able to change the flow field from a disordered one into an ordered one. Consistent with these phenomena and bringing more physical insight, the simplified model implies that the tuned vibration frequency and amplitude will lock in the unsteady flow separation, promote momentum transfer from the main stream to the separation zone, and make the flow field more orderly and less chaotic, resulting in a reduction of flow loss.

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.

scholarly journals Control of flow separation over a circular cylinder using synthetic jet

2021 ◽  
Vol 2119 (1) ◽  
pp. 012025
Author(s):  
A. S. Lebedev ◽  
M. I. Sorokin ◽  
D. M. Markovich
Keyword(s):  
Circular Cylinder ◽  
Flow Control ◽  
Flow Separation ◽  
Gas Turbines ◽  
Acoustic Noise ◽  
Reverse Flow ◽  
Flow Region ◽  
Synthetic Jet ◽  
Separation Flow ◽  
Longitudinal Length

Abstract The development of methods of active separation flow control is of great applied importance for many technical and engineering applications. Understanding the conditions for the flow separation from the surface of a bluff body is essential for the design of aircrafts, cars, hydro and gas turbines, bridges and buildings. Drag, acoustic noise, vibrations and active flow mixing depend drastically on the parameters of the vortex separation process. We investigated the possibility of reducing the longitudinal length of a reverse-flow region using the method of «synthetic jet» active separation flow control. The experiment was carried out on a compact straight-through wind channel with a 1-m long test section of a cross-section of 125x125 mm. The jet was placed at the rear stagnation point of a circular cylinder. The Reynolds number, based on the cylinder diameter and the free-stream velocity, was 5000 and the von Kármán street shedding frequency without the synthetic jet was equal to 64.8 Hz. For the first time, for such a set of parameters, we applied high speed PIV to demonstrate that the injection of the synthetic jet into the cylinder wake region leads to a significant reduction in the longitudinal length of the reverse-flow region.

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