Numerical investigation on the effects of re-organized shock waves on the flow separation for a highly-loaded transonic compressor cascade

2012 ◽  
Vol 21 (1) ◽  
pp. 13-20 ◽  
Author(s):  
Yan gang Wang ◽  
Rui Guo ◽  
Longbo Zhao ◽  
Siyuan Ren
Keyword(s):  
Shock Waves ◽  
Numerical Investigation ◽  
Flow Separation ◽  
Compressor Cascade ◽  
Transonic Compressor ◽  
Highly Loaded

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.

The Present Challenge of Transonic Compressor Blade Design

2018 ◽  
Author(s):  
A. Hergt ◽  
J. Klinner ◽  
J. Wellner ◽  
C. Willert ◽  
S. Grund ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Shock Waves ◽  
Unsteady Flow ◽  
Flow Behavior ◽  
Flow Behaviour ◽  
Compressor Cascade ◽  
Transonic Compressor ◽  
Flow Phenomena ◽  
Transonic Cascade

The flow through a transonic compressor cascade shows a very complex structure due to the occuring shock waves. In addition, the interaction of these shock waves with the blade boundary layer inherently leads to a very unsteady flow behaviour. The aim of the current investigation is to quantify this behaviour and its influence on the cascade performance as well as to describe the occuring transonic flow phenomena in detail. Therefore, an extensive experimental investigation of the flow in a transonic compressor cascade has been conducted within the transonic cascade wind tunnel of DLR at Cologne. In this process, the flow phenomena were thoroughly examined for an inflow Mach number of 1.21. The experiments investigate both, the laminar as well as the turbulent shock wave boundary layer interaction within the blade passage and the resulting unsteady behaviour. The experiments show a fluctuation range of the passage shock wave of about 10 percent chord for both cases, which is directly linked with a change of the inflow angle and of the operating point of the cascade. Thereafter, RANS simulations have been performed aiming at the verification of the reproducibility of the experimentally examined flow behavior. Here it is observed that the dominant flow effects are not reproduced by a steady numerical simulation. Therefore, a further unsteady simulation has been carried out in order to capture the unsteady flow behaviour. The results from this simulation show that the fluctuation of the passage shock wave can be reproduced but not in the correct magnitude. This leads to a remaining weak point within the design process of transonic compressor blades, because the working range will be overpredicted. The resulting conclusion of the study is that the use of scale resolving methods such as LES or the application of DNS is necessary to correctly predict unsteadiness of the transonic cascade flow and its impact on the cascade performance.

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.

The Present Challenge of Transonic Compressor Blade Design

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Alexander Hergt ◽  
J. Klinner ◽  
J. Wellner ◽  
C. Willert ◽  
S. Grund ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Shock Waves ◽  
Unsteady Flow ◽  
Flow Behavior ◽  
Complex Structure ◽  
Compressor Cascade ◽  
Transonic Compressor ◽  
Flow Phenomena ◽  
Transonic Cascade

The flow through a transonic compressor cascade shows a very complex structure due to the occurring shock waves. In addition, the interaction of these shock waves with the blade boundary layer inherently leads to a very unsteady flow behavior. The aim of the current investigation is to quantify this behavior and its influence on the cascade performance as well as to describe the occurring transonic flow phenomena in detail. Therefore, an extensive experimental investigation of the flow in a transonic compressor cascade has been conducted within the transonic cascade wind tunnel of DLR Institute of Propulsion Technology at Cologne. In this process, the flow phenomena were thoroughly examined for an inflow Mach number of 1.21. The experiments investigate both the laminar and the turbulent shock wave boundary layer interaction within the blade passage and the resulting unsteady behavior. The experiments show a fluctuation range of the passage shock wave of about 10% chord for both cases, which is directly linked with a change of the inflow angle and of the operating point of the cascade. Thereafter, Reynolds-averaged Navier–Stokes (RANS) simulations have been performed aiming at the verification of the reproducibility of the experimentally examined flow behavior. Here, it is observed that the dominant flow effects are not reproduced by a steady numerical simulation. Therefore, a further unsteady simulation has been carried out to capture the unsteady flow behavior. The results from this simulation show that the fluctuation of the passage shock wave can be reproduced but not in the correct magnitude. This leads to a remaining weak point within the design process of transonic compressor blades because the working range will be overpredicted. The resulting conclusion of this study is that the use of scale-resolving methods such as LES or the application of DNS is necessary to correctly predict unsteadiness of the transonic cascade flow and its impact on the cascade performance.

Boundary layer investigations on a highly loaded transonic compressor cascade with shock/laminar boundary layer interactions

2003 ◽  
Vol 217 (4) ◽  
pp. 349-356 ◽  
Author(s):  
L Hilgenfeld ◽  
P Cardamone ◽  
L Fottner
Keyword(s):  
Boundary Layer ◽  
Laminar Boundary Layer ◽  
Suction Side ◽  
Navier Stokes ◽  
Compressor Cascade ◽  
Flow Solver ◽  
Transonic Compressor ◽  
Shock System ◽  
The One ◽  
Highly Loaded

Detailed experimental and numerical investigations of the flowfield and boundary layer on a highly loaded transonic compressor cascade were performed at various Mach and Reynolds numbers representative of real turbomachinery conditions. The emerging shock system interacts with the laminar boundary layer, causing shock-induced separation with turbulent reattachment. Steady two-dimensional calculations have been performed using the Navier—Stokes solver TRACE-U. The flow solver employs a modified version of the one-equation Spalart—Allmaras turbulence model coupled with a transition correlation by Abu-Ghannam/Shaw in the formulation by Drela. The computations reproduce well the experimental results with respect to the profile pressure distribution and the location of the shock system. The transitional behaviour of the boundary layer and the profile losses in the wake are properly predicted as well, except for the highest Mach number tested, where large separated regions appear on the suction side.

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%.

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