The Influence of Compressor Aerodynamics on Pressure Probes: Part I — In Rig Calibrations

2004 ◽  
Author(s):  
S. Coldrick ◽  
P. C. Ivey ◽  
R. G. Wells
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
High Speed ◽  
Good Accuracy ◽  
Steady State Flow ◽  
Flow Measurements ◽  
Low Speed ◽  
Current Design ◽  
Compressor Aerodynamics ◽  
Unsteady Effects

Steady state flow measurements as obtained by multi hole pneumatic pressure probes are relevant to the current design process. These probes are calibrated in a uniform flow in a wind tunnel prior to their application in the test compressor. It is known that the probes do not behave in the same way in the test compressor as in the wind tunnel, one of the factors is that the flow in the compressor is fluctuating and this is thought to influence the probe’s operation. This two part paper investigates the influence of unsteady effects on probe operation. Part one covers an experimental investigation in which two pneumatic probes were calibrated firstly in a wind tunnel, then in low and high speed compressors. The probe that was used for the low speed compressor was scaled up from its high speed counterpart due to the increased size of the machine. The calibration graphs obtained by yawing the probe in the wind tunnel were reproduced with good accuracy when the same process was performed in the compressors. Whereas for the low speed compressor, the probe Reynolds number was the same as in the wind tunnel, the high speed compressor operated at a much larger Reynolds number.

The Influence of Compressor Aerodynamics on Pressure Probes: Part 2 — Numerical Models

2004 ◽  
Author(s):  
S. Coldrick ◽  
P. C. Ivey ◽  
R. G. Wells
Keyword(s):  
Reynolds Number ◽  
Steady State ◽  
Wind Tunnel ◽  
Measurement Errors ◽  
High Speed ◽  
Good Accuracy ◽  
Numerical Models ◽  
Compressor Blade ◽  
Cfd Simulations ◽  
Compressor Aerodynamics

This paper presents the second part of an investigation into the influences of the aerodynamics of compressor blade rows on measurements made using steady state pneumatic pressure probes. In part one, the in rig calibrations of the probes in the low and high speed compressors showed that the wind tunnel derived calibration in yaw could be reproduced with good accuracy in the compressor, despite the flow in the compressor being unsteady, and in the case of the high speed compressor, of a different Reynolds number. In this part, CFD simulations of the flow about a probe, both within a low speed compressor and a steady, uniform flowfield are presented. The influence of the pressure gradient existing within the stators in which the probe is positioned was found to be small, as was the effects of unsteady flow. The major contribution to measurement errors appears to lie within the probe blockage effect.

Comparison of Two Highly Loaded Low Pressure Turbine Cascades Under the Influence of Wake-Induced Transition

2000 ◽  
Author(s):  
Stefan Brunner ◽  
Leonhard Fottner ◽  
Heinz-Peter Schiffer
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
High Speed ◽  
Wind Tunnels ◽  
Turbine Cascade ◽  
Flow Conditions ◽  
Inlet Flow ◽  
Low Speed ◽  
Positive Effects ◽  
Turbine Cascades

Recent research has revealed positive effects of unsteady flow on the development of profile boundary layers in turbine cascades at conditions with a laminar suction side separation bubble. Compared to steady flow, a reduction of total pressure loss over a broad range of Reynolds-numbers has been shown. A new design of turbine blades with an increased blade loading (high lift) is possible if the effects of rotor-stator interaction are taken into account. With previous investigations at low speed cascade wind tunnels just one of the parameters Mach- or Reynolds-number could be adjusted during the tests. In order to verify the promising results gained at low speed cascade wind tunnels also at realistic Mach- and Reynolds-number combinations the present investigation has been carried out at the High Speed Cascade Wind Tunnel of the University of the Federal Armed Forces Munich. Being built inside a large pressure tank this high speed cascade wind tunnel offers the possibility to vary the Mach- and the Reynolds-number in the test section independently of each other in order to correctly simulate the flow conditions inside turbomachines. Thereby the experimental gap between investigations at low speed cascade wind tunnels and investigations at turbine-rig setups can be closed. In turbomachines, periodically unsteady flow is caused by the relative motion of rotor and stator rows. A wake generator has been designed and built in order to simulate a moving blade row upstream of a linear turbine cascade in the High Speed Cascade Wind Tunnel of the Universität der Bundeswehr München. The wakes are generated with cylindrical bars moving with a velocity of up to 40 m/s in the test section upstream of the cascade inlet plane. Measurements have been performed on two highly loaded low pressure turbine cascades (turbine cascade A and B) at varying Reynolds-numbers with steady and unsteady inlet flow conditions. For the unsteady inlet flow conditions, the frequency (Strouhal-number) of the wake passing has been altered by varying the speed of the bars. The turbulence intensity and the velocity deficit of the bar wakes have been measured with a 1D hot-wire probe. Wake-induced transition is qualitatively mapped out by employing a simultaneous surface hot-film anemometry system. Measurements of the surface pressure distribution and wake traverses have been performed. Due to an enlarged pitch to chord length ratio, turbine cascade B has a 15% larger lift than turbine cascade A, despite both having the same inlet and outlet conditions. Thereby the turbine cascades A and B have different airfoil shapes in order to take maximum advantage of the positive effects of rotor-stator interaction. Both cascades show a positive influence of unsteady inlet flow conditions to the boundary layer of the suction side, compared to steady inlet flow conditions, with respect of measured losses. With cascade A a maximum reduction of total pressure loss of 34% and with cascade B of 28% has been achieved, both compared to the appropriate steady inlet flow case. At design conditions of the turbine cascades (β1 = 135°, Ma2th = 0.7, Re2th = 100000) with unsteady inlet flow, both cascades have very similar low losses. Consequently, by taking into account the positive effects of wake-induced transition during the design process, new high lift blading with nearly the same low losses at unsteady inlet flow conditions could be achieved. This leads to a reduction of weight and cost of the whole turbine module for a constant stage loading.

The Influence of Reynolds Number at High Mach Numbers

1944 ◽  
Vol 48 (398) ◽  
pp. 45-48 ◽  
Author(s):  
A. Ferri
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Pressure Distribution ◽  
Stagnation Point ◽  
Pressure Difference ◽  
High Speed ◽  
Total Drag ◽  
Air Jet ◽  
Variable Point ◽  
High Mach

The experiments were carried out in the high speed wind tunnel at Guidonia on three brass spheres of 40, 60 and 80 mm. diameter, supported on rear spindles and on two steel cylinders of 15 and 30 mm. diameter respectively, which passed through the air jet.Both the total drag and pressure difference between the front stagnation point and a variable point at the rear were measured.The pressure distribution on similar models which could be rotated and which were provided with pressure holes was also determined.

scholarly journals Experimental Evaluation of the High-to-Low Speed Transformation Process for a Highly Loaded Core Compressor Stage

1998 ◽  
Author(s):  
P. A. Lyes ◽  
R. B. Ginder
Keyword(s):  
High Speed ◽  
Transformation Process ◽  
Geometric Constraints ◽  
Flow Visualisation ◽  
Flow Measurements ◽  
Flow Angle ◽  
Low Speed ◽  
Oil Flow ◽  
Clearance Flow ◽  
Inlet Conditions

A set of low speed blading has been designed to represent an embedded stage from the DERA C147 high speed research compressor. The aim of the design was to undertake a careful high-to-low speed transformation of the geometry of a high speed stage and evaluate the transformation process through comparing detailed flow measurements taken in both the high and low speed environments. The high-to-low speed transformation process involves compromises due to both geometric and aerodynamic constraints. Geometric constraints include the parallel annulus of the low speed compressor and also its size and power which restrict the Reynolds number that can be achieved. Aerodynamically the high speed blades have to be subsonic and the effects of Mach number on loss buckets and boundary layer development limit the extent to which a full high-to-low speed match is possible. The low speed blading has been tested at Cranfield University’s 4-stage research compressor facility. Detailed traverse measurements were taken at rotor and stator exit along with blade surface static pressure measurements and oil flow visualisation. These, along with previous traverse measurements from the C147 compressor, have been used to show that a good comparison of pressure, flow angle, and endwall loss distributions can be achieved despite the compromises inherent in the transformation process. However some interesting differences were apparent and these are discussed. In addition, 3D flow calculations have been performed on both the rotor and stator using measured inlet conditions. These predictions model the endwall corner flow well. However, further work is needed to obtain better modelling of the clearance flow of both blade rows.

Axial Loss Development in Low Pressure Turbine Cascades

2012 ◽  
Author(s):  
Bastian Muth ◽  
Reinhard Niehuis
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
High Speed ◽  
Density Ratio ◽  
Low Pressure ◽  
Numerical Results ◽  
Validation Data ◽  
Engine Operation ◽  
Flow Angle ◽  
Operation Conditions

The objective of this work presented in this paper is to study the performance of low pressure turbines in detail by extensive numerical simulations. The numerical flow simulations were conducted using the general purpose code ANSYS CFX. Particular attention is focused on the loss development in axial direction within the flow passage of the cascade. It is shown that modern CFD tools are able to break down the integral loss of the turbine profile into its components depending on attached and separated flow areas. In addition the numerical results allow to show the composition of the loss depending on the Reynolds number. The method of the analysis of axial loss development presented here allows for a much more comprehensive investigation and evaluation of the quality of the numerical results. For this reason the paper also demonstrates the capability of this method to quantify the influence of the axial velocity density ratio, the inflow turbulence level, the inflow angle and the Reynolds number on the loss configuration and the flow angle of the cascade as well as a comparison of steady state and transient results. The validation data of this LPT-Cascade have been obtained at the High Speed Cascade Wind Tunnel of the Institute of Jet Propulsion. For this purpose experiments were conducted within the range of Re2th = 40’000 to 400’000. To gather data at realistic engine operation conditions, the wind tunnel allows for an independent variation of Reynolds and Mach number. The experimental results presented herein contain detailed pressure measurements as well as measurements with 3-D-hot-wire anemometry. However, this paper shows only integral values of the experimental as well as the numerical results to protect the proprietary nature of the LPT-design.

scholarly journals On active control of laminar–turbulent transition on two-dimensional wings

2011 ◽  
Vol 369 (1940) ◽  
pp. 1382-1395 ◽  
Author(s):  
Ralf Erdmann ◽  
Andreas Pätzold ◽  
Marcus Engert ◽  
Inken Peltzer ◽  
Wolfgang Nitsche
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Active Control ◽  
High Speed ◽  
Control Algorithm ◽  
Frequency Range ◽  
Wind Tunnel Experiments ◽  
Low Speed ◽  
Turbulent Transition ◽  
Mach Numbers

This paper gives an overview of drag reduction on aerofoils by means of active control of Tollmien–Schlichting (TS) waves. Wind-tunnel experiments at Mach numbers of up to M x =0.42 and model Reynolds numbers of up to Re c =2×10 6 , as well as in-flight experiments on a wing glove at Mach numbers of M <0.1 and at a Reynolds number of Re c =2.4×10 6 , are presented. Surface hot wires were used to detect the linearly growing TS waves in the transitional boundary layer. Different types of voice-coil- and piezo-driven membrane actuators, as well as active-wall actuators, located between the reference and error sensors, were demonstrated to be effective in introducing counter-waves into the boundary layer to cancel the travelling TS waves. A control algorithm based on the filtered- x least mean square (FxLMS) approach was employed for in-flight and high-speed wind-tunnel experiments. A model-predictive control algorithm was tested in low-speed experiments on an active-wall actuator system. For the in-flight experiments, a reduction of up to 12 dB (75% TS amplitude) was accomplished in the TS frequency range between 200 and 600 Hz. A significant reduction of up to 20 dB (90% TS amplitude) in the flow disturbance amplitude was achieved in high-speed wind-tunnel experiments in the fundamental TS frequency range between 3 and 8 kHz. A downstream shift of the laminar–turbulent transition of up to seven TS wavelengths is presented. The cascaded sensor–actuator arrangement given by Sturzebecher & Nitsche in 2003 for low-speed wind-tunnel experiments was able to shift the transition Δ x =240 mm (18%  x / c ) downstream by a TS amplitude reduction of 96 per cent (30 dB). By using an active-wall actuator, which is much shorter than the cascaded system, a transition delay of seven TS wavelengths (16 dB TS amplitude reduction) was reached.

Active control of high-speed and high-Reynolds-number jets using plasma actuators

2007 ◽  
Vol 578 ◽  
pp. 305-330 ◽  
Author(s):  
M. SAMIMY ◽  
J.-H. KIM ◽  
J. KASTNER ◽  
I. ADAMOVICH ◽  
Y. UTKIN
Keyword(s):  
Reynolds Number ◽  
Nozzle Exit ◽  
High Speed ◽  
Low Reynolds Number ◽  
Plasma Actuators ◽  
Mixing Enhancement ◽  
Azimuthal Mode ◽  
Potential Core ◽  
Low Speed ◽  
Low Reynolds

Localized arc filament plasma actuators are used to control an axisymmetric Mach 1.3 ideally expanded jet of 2.54 cm exit diameter and a Reynolds number based on the nozzle exit diameter of about 1.1×106. Measurements of growth and decay of perturbations seeded in the flow by the actuators, laser-based planar flow visualizations, and particle imaging velocimetry measurements are used to evaluate the effects of control. Eight actuators distributed azimuthally inside the nozzle, approximately 1 mm upstream of the nozzle exit, are used to force various azimuthal modes over a large frequency range (StDF of 0.13 to 1.3). The jet responded to the forcing over the entire range of frequencies, but the response was optimum (in terms of the development of large coherent structures and mixing enhancement) around the jet preferred Strouhal number of 0.33 (f = 5 kHz), in good agreement with the results in the literature for low-speed and low-Reynolds-number jets. The jet (with a thin boundary layer, D/θ ∼ 250) also responded to forcing with various azimuthal modes (m = 0 to 3 and m = ±1, ±2, ±4), again in agreement with instability analysis and experimental results in the literature for low-speed and low-Reynolds-number jets. Forcing the jet with the azimuthal mode m = ±1 at the jet preferred-mode frequency provided the maximum mixing enhancement, with a significant reduction in the jet potential core length and a significant increase in the jet centreline velocity decay rate beyond the end of the potential core.

scholarly journals Control of Reynolds number in a high speed wind tunnel

2009 ◽  
Vol 1 (1) ◽  
pp. 69-77 ◽  
Author(s):  
Maurício G. Silva ◽  
Victor O. R. Gamarra ◽  
Vitor Koldaev
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
High Speed

Effect of Gurney Flaps on an Elliptical Airfoil

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Lance W. Traub
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Separated Flow ◽  
Pitching Moment ◽  
Airfoil Surface ◽  
Low Speed ◽  
Gurney Flaps ◽  
Lift Curve ◽  
The Impact ◽  
Low Speed Wind Tunnel

A low-speed wind tunnel investigation is presented characterizing the impact of Gurney flaps on an elliptical airfoil. The chordwise attachment location and height of the flaps were varied, as was the Reynolds number. The results showed strong nonlinearities in the lift curve which were present for all tested geometries. Flap effectiveness was seen to diminish as the flap was moved closer to the trailing edge stemming from flap submersion in separated flow. For the tested cases, the measured lift coefficients showed a weak Re dependency. The upper airfoil surface was shown to carry approximately 80% of the total lift load. The top surface caused a pitching moment reversal associated with nonlinearity in the lift curve.

Cellular Vortex Shedding From Linearly Tapered Finite Cylinders

2020 ◽  
Author(s):  
David M. Rooney ◽  
John C. Vaccaro ◽  
Rafael Smijtink
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Aspect Ratio ◽  
Finite Length ◽  
Vortex Shedding ◽  
Circular Cylinders ◽  
Hot Wire ◽  
Low Speed ◽  
Low Speed Wind Tunnel ◽  
Number Of Cells

Abstract Hot-wire measurements were taken in the wake of ten finite length circular cylinders, six of which were also tapered, in a uniform flow in a low speed wind tunnel. The Reynolds number based on mean cylinder diameter ranged from 2100 ≤ Re ≤ 5500, the aspect ratio (AR) of the cylinders varied from 16 ≤ AR ≤ 64, and the taper ratio (RT) varied from 21.3 ≤ RT ≤ 96. The vortex shedding along the spans of the cylinders coalesced into discrete cells, the range of Strouhal numbers and the number of cells being a function of the cylinder aspect ratio and taper ratio. It was found that the number of discrete cells is linearly related to a cylinder geometry ratio (CGR) defined as CGR = AR(1 + AR/RT).

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