Experimental Investigation of Endwall and Suction Side Blowing in a Highly Loaded Compressor Stator Cascade

2010 ◽  
Author(s):  
Daniel Nerger ◽  
Horst Saathoff ◽  
Rolf Radespiel ◽  
Volker Gu¨mmer ◽  
Carsten Clemen
Keyword(s):  
Experimental Investigation ◽  
Flow Control ◽  
Control Method ◽  
Active Flow Control ◽  
Pressure Rise ◽  
Suction Side ◽  
Spanwise Direction ◽  
Flow Power ◽  
Active Flow ◽  
Highly Loaded

The following paper describes an experimental investigation of a highly loaded stator cascade with a pitch to chord ratio of t/l = 0.6. Experiments without as well as with active flow control by means of endwall and suction side blowing were conducted. Five-hole-probe measurements in pitchwise and spanwise direction as well as endwall oil flow visualizations were carried out in order to determine the performance of the cascade and to analyze the flow phenomena occuring. To quantify the effectivity of the active flow control method, taking the additional energy input into account, corrected losses and an efficiency, which relates the difference of flow power deficit with and without active flow control to the flow power of the blowing jet itself, were evaluated. Even though an increase of static pressure rise could be achieved, a decrease of the total pressure losses was possible for a few operating points only.

Experimental Investigation of Endwall and Suction Side Blowing in a Highly Loaded Compressor Stator Cascade

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Daniel Nerger ◽  
Horst Saathoff ◽  
Rolf Radespiel ◽  
Volker Gümmer ◽  
Carsten Clemen
Keyword(s):  
Experimental Investigation ◽  
Flow Control ◽  
Control Method ◽  
Active Flow Control ◽  
Pressure Rise ◽  
Suction Side ◽  
Additional Energy ◽  
Flow Power ◽  
Active Flow ◽  
Highly Loaded

The following paper describes an experimental investigation of a highly loaded stator cascade with a pitch to chord ratio of t/l=0.6. Experiments without as well as with active flow control by means of endwall and suction side blowing were conducted. Five-hole-probe measurements in pitchwise and spanwise directions as well as endwall oil flow visualizations were carried out in order to determine the performance of the cascade and to analyze the flow phenomena occurring. To quantify the effectivity of the active flow control method, taking the additional energy input into account, corrected losses and an efficiency, which relates the difference of flow power deficit with and without active flow control to the flow power of the blowing jet itself, were evaluated. Even though an increase of static pressure rise could be achieved, a decrease of the total pressure losses was possible for a few operating points only.

Experimental Investigations on Highly Loaded Compressor Airfoils With Active Flow Control Under Non-Steady Flow Conditions in a 3D-Annular Low-Speed Cascade

2016 ◽  
Author(s):  
Christian Brück ◽  
Christine Tiedemann ◽  
Dieter Peitsch
Keyword(s):  
Flow Control ◽  
Active Flow Control ◽  
Pressure Rise ◽  
Side Wall ◽  
Suction Side ◽  
Pressure Measurements ◽  
Flow Conditions ◽  
Active Flow ◽  
The Impact ◽  
Highly Loaded

This investigation discusses the impact of a non-steady outflow condition on the compressor stator flow in an annular cascade which is periodically chocked through a rotating disc in the wake, to simulate the expected conditions for a pulsed detonation engine (PDE). A 2D controlled diffusion airfoil of the highly loaded linear stator cascade by [1] has been transferred to the annular compressor test rig to compare results under non-steady conditions via multi-colored oil flow visualization on the suction side and pressure measurements in the wake of the blades. Three different Strouhal numbers of the choking device are investigated and analyzed by phase averaged pressure measurements downstream of the stator to visualize the unsteady flow characteristics. Triggered by the changed incidence angle due to the choking, separation on the suction side and in the hub region form a periodic event depending on the position of the blockage device. Active flow control (AFC) is implemented by means of side wall actuation at the hub to improve flow conditions. Pressure measurements show that the turning of the blades can be raised and a static pressure rise is gained by the AFC while periodic choking is active.

Binary Repetitive Model Predictive Active Flow Control Applied to an Annular Compressor Stator Cascade With Periodic Disturbances

2021 ◽  
Author(s):  
Benjamin Fietzke ◽  
Rudibert King ◽  
Jan Mihalyovics ◽  
Dieter Peitsch
Keyword(s):  
Flow Control ◽  
Mass Flow ◽  
Active Flow Control ◽  
Pressure Rise ◽  
Suction Side ◽  
Pressure Loss Coefficient ◽  
Periodic Disturbances ◽  
Pressure Gain Combustion ◽  
Active Flow ◽  
Side Flow

Abstract Novel pressure gain combustion concepts invoke periodic flow disturbances in a gas turbine’s last compressor stator row. This contribution presents studies of mitigation efforts on the effects of these periodic disturbances on an annular compressor stator rig. The passages were equipped with pneumatic Active Flow Control (AFC) influencing the stator blade’s suction side, and a rotating throttling disc downstream of the passages inducing periodic disturbances. For steady blowing, it is shown that with increasing actuation amplitudes Cμ, the extension of a hub corner vortex deteriorating the suction side flow can be reduced, resulting in an increased static pressure rise coefficient Cp of a passage. The effects of the induced periodic disturbances could not be addressed intrinsically, by using steady blowing actuation, Considering a corrected total pressure loss coefficient ζ*, which includes the actuation effort, the stator row’s efficiency decreases with higher cμ due to the increasing costs of the actuation mass flow. Therefore, a closed-loop approach is presented to address the effects of the disturbances more specifically, thus lowering the actuation cost, i.e., mass flow. For this, a Repetitive Model Predictive Control (RMPC) was applied, taking advantage of the periodic nature of the induced disturbances. The presented RMPC formulation is restricted to a binary control domain to account for the used solenoid valves’ switching character. An efficient implementation of the optimization within the RMPC is presented, which ensures real-time capability. As a result, Cp increases in a similar magnitude but with a lower actuation mass flow of up to 66%, resulting in a much lower ζ* for similar values of cμ.

Detailed Analysis of Boundary Layer Control by Fluidic Oscillators on a Highly Loaded Profile

2018 ◽  
Author(s):  
Julia Kurz ◽  
Reinhard Niehuis
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Flow Separation ◽  
High Speed ◽  
Active Flow Control ◽  
Suction Side ◽  
Transition Process ◽  
Frequency Spectra ◽  
Active Flow ◽  
Highly Loaded

One application method of active flow control is the exploitation of the interaction between transition and flow separation on a profile. As turbulent flows are able to withstand higher adverse pressure gradients the enforcement of the transition process can be utilized to prevent or to reduce flow separation. This paper focuses on gaining a better understanding of high frequency active flow control (AFC) by fluidic oscillators and its influence on the transition process for a separated boundary layer. Flow control is applied on a highly loaded turbine exit case (TEC) profile which was in particular designed for this application. The profile is investigated in the high-speed cascade wind tunnel at the Bundeswehr University Munich. Significant loss reduction by AFC could be observed by total pressure loss determination in the low Reynolds number regime. In order to gain a better understanding of development of the suction side boundary layer, several boundary layer profiles are determined by hot-wire measurements at six axial positions on the suction side of the profile. Differences between the boundary layer development and the extent of the separation can be detected. Furthermore, a stability analysis of the boundary layer upstream of separation is conducted and compared to the measured frequency spectra.

Active Flow Control Concepts on a Highly Loaded Subsonic Compressor Cascade: Résumé of Experimental and Numerical Results

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Christoph Gmelin ◽  
Vincent Zander ◽  
Martin Hecklau ◽  
Frank Thiele ◽  
Wolfgang Nitsche ◽  
...  
Keyword(s):  
Flow Control ◽  
Active Flow Control ◽  
Suction Side ◽  
Numerical Results ◽  
Pressure Probe ◽  
Control Parameters ◽  
Compressor Cascade ◽  
Wide Range ◽  
Active Flow ◽  
Highly Loaded

This paper presents experimental and numerical results for a highly loaded, low speed, linear compressor cascade with active flow control. Three active flow control concepts employing steady jets, pulsed jets, and zero mass flow jets (synthetic jets) are investigated at two different forcing locations: at the end walls and the blade suction side. Investigations are performed at the design incidence for jet-to-inlet velocity ratios of approximately 0.7 to 3.0 and two different Reynolds numbers. Detailed flow field data are collected using a five-hole pressure probe, pressure tabs on the blade surfaces, and time-resolved particle image velocimetry. Unsteady Reynolds-Averaged Navier-Stokes simulations are performed for a wide range of flow control parameters. The experimental and numerical results are used to understand the interaction between the jet and the passage flow. Variation of jet amplitude, forcing frequency and blowing angle of the different control concepts at both locations allows determination of beneficial control parameters and offers a comparison between similar control approaches. This paper combines the advantages of an expensive yet reliable experiment and a fast but limited numerical simulation. Excellent agreement in control effectiveness is found between experiment and simulation.

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.

scholarly journals Binary Repetitive Model Predictive Active Flow Control Applied to an Annular Compressor Stator Cascade with Periodic Disturbances

2021 ◽  
Author(s):  
Benjamin Fietzke ◽  
Jan Mihalyovics ◽  
Rudibert King ◽  
Dieter Peitsch
Keyword(s):  
Flow Control ◽  
Active Flow Control ◽  
Pressure Rise ◽  
Suction Side ◽  
Pressure Loss Coefficient ◽  
Periodic Disturbances ◽  
Flow Disturbances ◽  
Pressure Gain Combustion ◽  
Active Flow ◽  
Side Flow

Abstract Novel pressure gain combustion concepts invoke periodic flow disturbances in a gas turbine's last compressor stator row. This contribution presents studies of mitigation efforts on the effects of periodic disturbances on an annular compressor stator rig. The passages were equipped with pneumatic active flow control influencing the stator blade's suction side, and a rotating throttling disc downstream of the passages inducing periodic disturbances. For steady blowing, it is shown that with increasing actuation amplitudes $c_\mu$, a hub corner vortex's extension deteriorating the suction side flow can be reduced, resulting in an increased static pressure rise coefficient~$C_p$ of a passage. The effects of the induced periodic disturbances could not be addressed, by using steady blowing actuation. Considering a corrected total pressure loss coefficient $\zeta^*$, which includes the actuation effort, the stator row's efficiency decreases with higher $c_\mu$. Therefore, a closed-loop approach is presented to address the effects of the disturbances more specifically, thus lowering the actuation effort. For this, a Repetitive Model Predictive Control (RMPC) was applied, taking advantage of the disturbance's periodic nature. The presented RMPC formulation is restricted to a binary control domain to account for the used solenoid valves' switching character. An efficient implementation of the optimization within the RMPC is presented, which ensures real-time capability. As a result, $C_p$ increases in a similar magnitude but with a lower actuation mass flow of up to 66\,\%, resulting in a much lower~$\zeta^*$ for similar values of $c_\mu$.

Active Flow Control Concepts on a Highly Loaded Subsonic Compressor Cascade: Re´sume´ of Experimental and Numerical Results

2011 ◽  
Author(s):  
Christoph Gmelin ◽  
Vincent Zander ◽  
Martin Hecklau ◽  
Frank Thiele ◽  
Wolfgang Nitsche ◽  
...  
Keyword(s):  
Flow Control ◽  
Active Flow Control ◽  
Suction Side ◽  
Numerical Results ◽  
Pressure Probe ◽  
Control Parameters ◽  
Compressor Cascade ◽  
Wide Range ◽  
Active Flow ◽  
Highly Loaded

The paper presents experimental and numerical results for a highly loaded, low speed, linear compressor cascade with active flow control. Three active flow control concepts by means of steady jets, pulsed jets, and zero mass flow jets (synthetic jets) are investigated at two different forcing locations, i.e. at the end walls and the blade suction side. Investigations are performed at the design incidence for jet-to-inlet velocity ratios from approximately 0.7 to 3.0 and two different Reynolds numbers. Detailed flow field data are collected using a five-hole pressure probe, pressure tabs on the blade surfaces, and time-resolved particle image velocimetry. Unsteady Reynolds-Averaged Navier-Stokes simulations are performed for a wide range of flow control parameters. The experimental and numerical results are used to understand the interaction between the jet and the passage flow. Variation of jet amplitude, forcing frequency, and blowing angle of the different control concepts at both locations allows determination of beneficial control parameters and offers a comparison between similar control approaches. The paper combines the advantages of an expensive but accurate experiment and a fast but limited numerical simulation.

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.

Interaction Phenomena of High Frequency Pulsed Blowing in LP Turbine-Like Boundary Layers at High Speed Test Conditions

2018 ◽  
Author(s):  
Valentin Bettrich ◽  
Martin Bitter ◽  
Reinhard Niehuis
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Boundary Layer Flow ◽  
High Frequency ◽  
Active Flow Control ◽  
Suction Side ◽  
Operating Point ◽  
Layer Flow ◽  
Lp Turbine ◽  
Active Flow

The use of fluidic oscillators for active flow control applications is a proven and efficient concept. For the well-known highly loaded LP turbine profile T161, the total pressure losses could already reduced by 40% at low Reynolds numbers, were usually flow separation occurs. For further improvements of the active flow control concept, it is essential to understand the driving flow phenomena responsible for the loss reduction mechanism, which are discussed in this paper. The results presented are based on experimental investigations on a flat plate with pressure gradient, imposed with an aerodynamically highly loaded low pressure turbine suction side flow and equipped with active flow control. The analogy to the suction side of the T161 is shown and validated against former cascade measurements. Based on the T161 equivalent operating point of Re = 70,000 and a theoretical out flow Mach number of Ma2,th = 0.6, the focus is set on the interaction of the boundary layer flow with high frequency actuation. The chosen actuator, a high frequency coupled fluidic oscillator, is designed to independently adjust mass flow and frequency. The flat plate is equipped with an array of high frequency actuators to control the flow separation. For this study one oscillator operating point at 6.7kHz is presented and the influence on transition and loss reduction compared to the non-actuated case is discussed. This oscillator operating point was found to be most efficient and the steady and unsteady mixing behavior of the high frequency actuator impact and the low pressure turbine like suction side boundary layer flow is investigated in much detail. Depending on the measurement technique, the isentropic Mach number distribution, frequency spectra, standard deviation, skewness and kurtosis are evaluated. The most important results are on the one hand, that the chosen concept is more efficient compared to former studies in means of mass flow investment, which is mainly based on the chosen oscillator outlet position and frequency. On the other hand, in a transonic flow the mixing and interaction of the high frequency pulses and the boundary layer flow require about 10% of the surface length to even establish and about to 30% to be completed. These results of the mixing behavior between actuator and boundary layer for compressible flow conditions help to attain a fundamental understanding for future designs of active flow control concepts.

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