Comparison of Test Results Obtained on Plane and Annular, Fixed or Rotating Supersonic Blade Cascades

1975 ◽  
Vol 97 (2) ◽  
pp. 245-253 ◽  
Author(s):  
J. Paulon ◽  
J. Reboux ◽  
R. Sovrano
Keyword(s):  
Flow Separation ◽  
Theoretical Calculations ◽  
Suction Side ◽  
Back Pressure ◽  
Test Results ◽  
Flow Configuration ◽  
Pressure Distributions ◽  
Supersonic Regime ◽  
Annular Cascade ◽  
Side Flow

Results of an experimental research on the comparison of flow patterns in linear and annular, fixed and rotating supersonic blade cascades are presented. The fixed plane cascade and the fixed annular cascade give very similar results at low back pressure and the flow configuration (Schlieren pictures) and the pressure distributions are those given by theoretical calculations. In the rotating cascade the fully started supersonic regime was not obtained. At high back pressure, sidewall flow separation perturbates the flow pattern in the plane cascade. In the annular setups, the flow configuration with suction side flow separation is correctly predicted by the theory.

Flow Characteristics of Axial Compressor Tandem Cascades at Large Off-Design Incidence Angles

2013 ◽  
Author(s):  
Tim Schneider ◽  
Dragan Kožulović
Keyword(s):  
Flow Separation ◽  
Flow Characteristics ◽  
Axial Compressor ◽  
Suction Side ◽  
Operating Range ◽  
Current State ◽  
Aerodynamic Interaction ◽  
Mach Numbers ◽  
Side Flow ◽  
Tandem Cascades

In a number of recent and former publications, compressor tandem blade configurations show potential to outperform single blade configurations in terms of turning, loss and operating range at high aerodynamic loading levels. However, very little insight is given into the mechanisms of flow breakdown when comparing tandem blades to single blades at large off-design incidence angles. Single blade cascades tend to fail as a result of either pressure side flow separation for high negative incidence or suction side flow separation for high positive incidence, the latter being mostly accompanied by significant increase of underturning. Tandem blade cascades are expected to show a different behavior due to the aerodynamic interaction in the blade overlapping region. Two different tandem blade configurations are examined together with their respective reference single blades, one being a recently designed and optimized tandem blade for high subsonic inlet Mach numbers, which has also been investigated in cascade wind tunnel testing. The other one is a more generic tandem blade based on NACA65 family, designed for medium inlet Mach numbers using current state-of-the-art understanding of tandem design. The mechanisms of flow breakdown are examined using quasi two-dimensional RANS simulations which are validated with test data for one of the aforementioned tandem configurations. A detailed analysis of the flow structure at heavy off-design conditions gives insight into the characteristics of tandem flow breakdown. In particular, the ability of the tandem configuration to extend the operating range to larger positive incidence is described. The shortcomings of the tandem cascade at large negative incidence are also commented. These and further conclusions can be used to improve tandem blade performance at moderate off-design conditions.

Development of a Fluidic Actuator for Adaptive Flow Control on a Thick Wind Turbine Airfoil

2014 ◽  
Author(s):  
Sebastian Niether ◽  
Bernhard Bobusch ◽  
David Marten ◽  
Georgios Pechlivanoglou ◽  
Christian Navid Nayeri ◽  
...  
Keyword(s):  
Flow Control ◽  
Wind Turbine ◽  
Flow Separation ◽  
Pressure Difference ◽  
Angle Of Attack ◽  
Suction Side ◽  
Turbine Rotor ◽  
Adaptive Flow Control ◽  
Order Of Magnitude ◽  
Side Flow

Wind turbines are exposed to unsteady incident flow conditions such as gusts or tower interference. These cause a change in the blades’ local angle of attack, which often leads to flow separation at the inner rotor sections [1]. Recirculation areas and dynamic stall may occur, which lead to an uneven load distribution along the blade. In this work a fluidic actuator is developed that reduces flow separation. The functional principle is adapted from a fluidic amplifier. High pressure air fed by an external supply flows into the interaction region of the actuator. Two control ports, oriented perpendicular to the inlet, allow for a steering of the actuation flow. One of the control ports is connected to the suction side, the other to the pressure side of the airfoil. Depending on the pressure difference that varies with the angle of attack, the actuation air is directed into one of four outlet channels. These guide the air to different chordwise exit locations on the airfoil’s suction side. The appropriate actuation location adjusts automatically according to the pressure difference between the control ports and therefore incidence. Suction side flow separation is delayed as the boundary layer is enriched with kinetic energy. Experiments were conducted on a DU97-W-300 airfoil [2] at Re = 2.2 · 105. Compared to the baseline, changes in lift with angle of attack were reduced by an order of magnitude. An AeroDyn simulation of a full wind turbine rotor was performed that compares the baseline to a rotor design with adaptive flow control.

Development of a Fluidic Actuator for Adaptive Flow Control on a Thick Wind Turbine Airfoil

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Sebastian Niether ◽  
Bernhard Bobusch ◽  
David Marten ◽  
Georgios Pechlivanoglou ◽  
Christian Navid Nayeri ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Flow Separation ◽  
System Integration ◽  
Pressure Difference ◽  
Angle Of Attack ◽  
Suction Side ◽  
Turbine Rotor ◽  
Adaptive Flow Control ◽  
Order Of Magnitude ◽  
Side Flow

Wind turbines are exposed to unsteady incident flow conditions such as gusts or tower interference. These cause a change in the blades' local angle of attack, which often leads to flow separation at the inner rotor sections. Recirculation areas and dynamic stall may occur, which lead to an uneven load distribution along the blade. In this work, a fluidic actuator is developed that reduces flow separation. The functional principle is adapted from a fluidic amplifier. High pressure air fed by an external supply flows into the interaction region of the actuator. Two control ports, oriented perpendicular to the inlet, allow for a steering of the actuation flow. One of the control ports is connected to the suction side, the other to the pressure side of the airfoil. Depending on the pressure difference that varies with the angle of attack, the actuation air is directed into one of four outlet channels. These guide the air to different chordwise exit locations on the airfoil's suction side. The appropriate actuation location adjusts automatically according to the pressure difference between the control ports and therefore incidence. Suction side flow separation is delayed as the boundary layer is enriched with kinetic energy. Experiments were conducted on a DU97-W-300 airfoil at Re = 2.2 × 105. Compared to the baseline, lift variations due to varying angles of attack were reduced by an order of magnitude. A Fast/Aerodyn simulation of a full wind turbine rotor was performed to show the real world load reduction potential. Additionally, system integration is discussed, which includes suggestions on producibility and operational details.

Upgrading of Tubular Heat Exchangers by the Helical Spacer Method and Evaluation

2002 ◽  
Author(s):  
F. L. Eisinger ◽  
R. E. Sullivan
Keyword(s):  
Theoretical Analysis ◽  
Acoustic Wave ◽  
Heat Exchangers ◽  
Test Results ◽  
Vibration Testing ◽  
Safe Operation ◽  
Shell Side ◽  
Full Load ◽  
Post Modification ◽  
Side Flow

The tubular heat exchangers described exhibited a sensitivity to flow-induced tube vibration at about 50% of their design shell-side flow. Following a detailed theoretical analysis, the heat exchangers were modified by the helical spacer method providing additional tube supports in-between the existing support plates and in the U-bend. This modification aimed at allowing the heat exchangers to operate safely and reliably at full load, including a 25% overload. Post modification sound and vibration testing was performed which confirmed the adequacy of the modification. The test results showed however, that at the overload condition, an unusual acoustic wave inside the shell was developing. It was determined that this wave would not be harmful to the safe operation of the heat exchangers. The paper will discuss the findings in more detail.

Performance Analysis of the Test Results on a Two-Stage Transonic Fan

1983 ◽  
Vol 105 (1) ◽  
pp. 125-129
Author(s):  
Baoshi Chen ◽  
Tianyi Zhang
Keyword(s):  
Mach Number ◽  
Performance Analysis ◽  
Radial Distribution ◽  
Flow Separation ◽  
High Load ◽  
Test Results ◽  
Two Stage ◽  
Stall Margin ◽  
High Incidence ◽  
Transonic Fan

Test results obtained from a two-stage fan are analysed and the reasons that caused the design performance target not to be attained are presented in this paper. Addition of a partspan shroud on rotor 1 caused higher losses and changed radial distribution of parameters. Modification on the flowpath and chord length of stator 1 resulted in excessively high inlet Mach number and flow separation in the hub region. The high load and high incidence at the hub of rotor 2 caused higher losses and reduced stall margin of the fan.

Compressible Flowfield Characteristics of Butterfly Valves

1989 ◽  
Vol 111 (4) ◽  
pp. 400-407 ◽  
Author(s):  
M. J. Morris ◽  
J. C. Dutton
Keyword(s):  
Flow Separation ◽  
Pressure Ratio ◽  
Disk Surface ◽  
Surface Flow ◽  
Operating Conditions ◽  
Local Geometry ◽  
Operating Pressure ◽  
Butterfly Valve ◽  
Pressure Distributions ◽  
Flow Separation And Reattachment

The results of an experimental investigation into the flowfield characteristics of butterfly valves under compressible flow operating conditions are reported. The experimental results include Schlieren and surface flow visualizations and flowfield static pressure distributions. Two valve disk shapes have been studied in a planar, two-dimensional test section: a generic biconvex circular arc profile and the midplane cross-section of a prototype butterfly valve. The valve disk angle and operating pressure ratio have also been varied in these experiments. The results demonstrate that under certain conditions of operation the butterfly valve flowfield can be extremely complex with oblique shock waves, expansion fans, and regions of flow separation and reattachment. In addition, the sensitivity of the valve disk surface pressure distributions to the local geometry near the leading and trailing edges and the relation of the aerodynamic torque to flow separation and reattachment on the disk are shown.

Numerical simulation of fairing separation test for hypersonic air breathing vehicle

2016 ◽  
Vol 231 (2) ◽  
pp. 319-325 ◽  
Author(s):  
Ankit Raj ◽  
K Anandhanarayanan ◽  
R Krishnamurthy ◽  
Debasis Chakraborty
Keyword(s):  
Structural Integrity ◽  
Test Results ◽  
Air Breathing ◽  
Aerodynamic Loads ◽  
Pressure Distributions ◽  
Ground Test ◽  
Computational Fluid Dynamics Simulations ◽  
Euler Solver ◽  
Dynamics Simulations ◽  
Flight Hardware

Fairings are provided to cover hypersonic air breathing vehicle to protect it from adverse aerodynamic loading and kinetic heating. Separation dynamics of fairings is an important event in the launch of vehicle. Extensive computational fluid dynamics simulations are carried out for the design of fairings and vehicle and selection of time sequences of various separation events. A ground test of fairing separation is conducted in the sled facility to check the structural integrity and functionality of various separation mechanisms and flight hardware. Simulations have been carried out to study the separation dynamics of fairings at test conditions using grid-free Euler solver to get the aerodynamic loads and the loads are integrated to get the trajectory of fairings. The aerodynamic loads are provided to verify the structural integrity of various components and the trajectory of panels is used in the test planning. The pressure distributions on the vehicle are compared with the test results.

Surface Roughness Impact on Secondary Flow and Losses in a Turbine Exhaust Casing

2018 ◽  
Author(s):  
Isak Jonsson ◽  
Valery Chernoray ◽  
Borja Rojo
Keyword(s):  
Surface Roughness ◽  
Secondary Flow ◽  
Suction Side ◽  
Pressure Probe ◽  
Time Resolved ◽  
Pressure Distributions ◽  
Turbulence Decay ◽  
Inlet Swirl ◽  
High Level ◽  
The Impact

This paper experimentally addresses the impact of surface roughness on losses and secondary flow in a Turbine Rear Structure (TRS). Experiments were performed in the Chalmers LPT-OGV facility, at an engine representative Reynolds number with a realistic shrouded rotating low-pressure turbine (LPT). Outlet Guide Vanes (OGV) were manufactured to achieve three different surface roughnesses tested at two Reynolds numbers, Re = 235000 and Re = 465000. The experiments were performed at on-design inlet swirl conditions. The inlet and outlet flow of the TRS were measured in 2D planes with a 5-hole probe and 7-hole probe accordingly. The static pressure distributions on the OGVs were measured and boundary layer studies were performed at the OGV midspan on the suction side with a time-resolved total pressure probe. Turbulence decay was measured within the TRS with a single hot-wire. The results showed a surprisingly significant increase in the losses for the high level of surface roughness (25–30 Ra) of the OGVs and Re = 465000. The increased losses were primary revealed as a result of the flow separation on the OGV suction side near the hub. The loss increase was seen but was less substantial for the intermediate roughness case (4–8 Ra). Experimental results presented in this work provide support for the further development of more advanced TRS and data for the validation of new CFD prediction methods for TRS.

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