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.

Axial Loss Development in Low Pressure Turbine Cascades

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Bastian Muth ◽  
Reinhard Niehuis
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Density Ratio ◽  
Low Pressure ◽  
Numerical Results ◽  
Validation Data ◽  
Engine Operation ◽  
Flow Angle ◽  
Low Pressure Turbine ◽  
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 the axial direction within the flow passage of the cascade. It is shown that modern computational fluid dynamics (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 one 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 low pressure turbine (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 3D 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.

Effect of Roughness and Unsteadiness on the Performance of a New Low Pressure Turbine Blade at Low Reynolds Numbers

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Francesco Montomoli ◽  
Howard Hodson ◽  
Frank Haselbach
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Beneficial Effect ◽  
High Speed ◽  
Leading Edge ◽  
Suction Side ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
High Lift ◽  
Wake Passing

This paper presents a study of the performance of a high-lift profile for low pressure turbines at Reynolds numbers lower than in previous investigations. By following the results of Coull et al. (2008, “Velocity Distributions for Low Pressure Turbines,” ASME Paper No. GT2008-50589) on the design of high-lift airfoils, the profile is forward loaded. The separate and combined effects of roughness and wake passing are compared. On a front loaded blade, the effect of incidence becomes more important and the consequences in terms of cascade losses, is evaluated. The experimental investigation was carried out in the high speed wind tunnel of Whittle Laboratory, University of Cambridge. This is a closed-circuit continuous wind tunnel where the Reynolds number and Mach number can be fixed independently. The unsteadiness caused by wake passing in front of the blades is reproduced using a wake generator with rotating bars. The results confirm that the beneficial effect of unsteadiness on losses is present even at the lowest Reynolds number examined (Re3=20,000). This beneficial effect is reduced at positive incidence. With a front loaded airfoil and positive incidence, the transition occurs on the suction side close to the leading edge and this results in higher losses. This has been found valid for the entire Reynolds range investigated (20,000≤Re3≤140,000). Roughening the surface also had a beneficial effect on the losses but this effect vanishes at the lower Reynolds numbers, i.e., (Re3≤30,000), where the surface becomes hydraulically smooth. The present study suggests that a blade with as-cast surface roughness has a lower loss than a polished one.

Investigation of CFD Prediction Capabilities for Low Reynolds Turbine Aerodynamics

2009 ◽  
Author(s):  
Bastian Muth ◽  
Marco Schwarze ◽  
Reinhard Niehuis ◽  
Matthias Franke
Keyword(s):  
Mach Number ◽  
Wind Tunnel ◽  
Flow Separation ◽  
High Speed ◽  
Operating Conditions ◽  
Engine Operation ◽  
Number Range ◽  
Operation Conditions ◽  
Transition Models ◽  
Low Reynolds

The objective of this work is to study the performance of low pressure turbines operating at low Reynolds numbers by extensive experiments and to validate numerical simulation results with the experimental data. Particular attention is payed to the prediction capabilities of current numerical turbulence and transition models in order to be able to benchmark the performance of future turbine airfoil profiles and to optimise their aero design. The LPT-Cascade under consideration has been investigated at the High Speed Cascade Wind Tunnel of the Institute of Jet Propulsion to gather information about the performance of turbine airfoils under low Reynolds operating conditions. The experiments were executed in the range of Re = 40′000 to 400′000 with steady state inflow conditions at different Mach number levels. The main focus of the investigation thereby was on the range of Re = 40′000 to 70′000. The high speed cascade wind tunnel of the University of Federal Armed Forces Munich allows for an independent Reynolds and Mach number variation such that an extensive database can be generated for realistic engine operation conditions. One major test objective was related to flow separation phenomena on the suction surface and its influence on the performance of the turbine profile. For this purpose both the loss behaviour and the pressure distribution on suction and pressure surface of the blade were measured and analysed. In addition to the experiments numerical flow simulations were conducted for the same turbine profile. In order to achieve more information on the influence of different turbulence and transition models on the flow separation, transition, and reattachment behaviour, two different CFD codes were used for comparison purposes. On the one hand the CFD code TRACE, which is developed by the German Aerospace Center (DLR) and MTU Aero Engines and on the other hand the general purpose code ANSYS CFX were applied. The aim is to assess the prediction capabilities of the different codes especially in the low Reynolds number range.

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 Characterization of Periodic Incoming Wakes in a Low-Pressure Turbine Cascade Test Section by Means of a Fast-Response Single Sensor Virtual Three-Hole Probe

2019 ◽  
Vol 4 (3) ◽  
pp. 26
Author(s):  
Julien Clinckemaillie ◽  
Tony Arts
Keyword(s):  
Total Pressure ◽  
High Speed ◽  
Control Volume ◽  
Low Pressure ◽  
Fast Response ◽  
Pressure Probe ◽  
Flow Angle ◽  
Low Pressure Turbine ◽  
Wide Range ◽  
Good Agreement

This paper aims at evaluating the characteristics of the wakes periodically shed by the rotating bars of a spoked-wheel type wake generator installed upstream of a high-speed low Reynolds linear low-pressure turbine blade cascade. Due to the very high bar passing frequency obtained with the rotating wake generator (fbar = 2.4−5.6 kHz), a fast-response pressure probe equipped with a single 350 mbar absolute Kulite sensor has been used. In order to measure the inlet flow angle fluctuations, an angular aerodynamic calibration of the probe allowed the use of the virtual three-hole mode; additionally, yielding yaw corrected periodic total pressure, static pressure and Mach number fluctuations. The results are presented for four bar passing frequencies (fbar = 2.4/3.2/4.6/5.6 kHz), each tested at three isentropic inlet Mach numbers M1,is = 0.26/0.34/0.41 and for Reynolds numbers varying between Re1,is = 40,000 and 58,000, thus covering a wide range of engine representative flow coefficients (ϕ = 0.44−1.60). The measured wake characteristics show fairly good agreement with the theory of fixed cylinders in a cross-flow and the evaluated total pressure losses and flow angle variations generated by the rotating bars show fairly good agreement with theoretical results obtained from a control volume analysis.

Analysis of Laminar-Turbulent Transition of a Low-Loss Generic Low Pressure Turbine Distribution

2015 ◽  
Author(s):  
Christian Brück ◽  
Christoph Lyko ◽  
Dieter Peitsch ◽  
Christoph Bode ◽  
Jens Friedrichs ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Pressure Distribution ◽  
Turbulence Intensity ◽  
Suction Side ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
Test Case ◽  
Low Loss ◽  
Low Pressure Turbine

The efficiency of modern Turbofan engines can be significantly increased by using a gearbox between compressor and turbine of the low pressure section. Rotational speed of the low pressure turbine (LPT) in a Geared Turbofan is much higher than in normal LPT’s which lead to necessary adjustments in blade design. This work has investigated the transition behavior of a modified profile geometry for low-loss at engine cruise conditions. Typical LPT conditions have thus been chosen as baseline for the experimental work. A pressure distribution has been created on a flat plate by means of contoured walls in a low speed wind tunnel. The paper will analyze the experimental results and show additionally the numerical predictions of the test case. The experimental part of this paper describe how the blade was Mach number scaled to obtain the geometry of the wind tunnel wall contour. The pressure distribution for the incompressible test case show a very good agreement to the compressible case. Boundary layer (BL) measurements with hot-wire-anemometry have been performed at high spatial resolution under a freestream turbulence of almost 8%. Different Reynolds numbers have been investigated and will be compared with special attention being paid to the transition on the suction side by contour plots (turbulence levels, turbulent intermittency) and integral BL parameters. It was found that the transition on the suction side is not completed for small Reynolds numbers but takes place at higher velocities. In the numerical part studies by means of steady RANS simulations with k-ω – SST turbulence model and γ-Reθ transition model have been conducted. The aim is to validate the RANS solver for the low-loss LPT application. Hence, comparison is made to the measured data and the transitional behavior of the BL. Furthermore, additional parameter variations have been conducted (turbulence intensity and Reynolds number). The numerical investigations show partially a good comparison for the BL development indicating the different transition modi with increasing Reynolds number and turbulence intensity.

scholarly journals Particle–wall collisions in a viscous fluid

2001 ◽  
Vol 433 ◽  
pp. 329-346 ◽  
Author(s):  
G. G. JOSEPH ◽  
R. ZENIT ◽  
M. L. HUNT ◽  
A. M. ROSENWINKEL
Keyword(s):  
Reynolds Number ◽  
Viscous Fluid ◽  
High Speed ◽  
Particle Density ◽  
Particle Surface ◽  
Density Ratio ◽  
Experimental Studies ◽  
Stokes Number ◽  
Coefficient Of Restitution ◽  
The Impact

This paper presents experimental measurements of the approach and rebound of a particle colliding with a wall in a viscous fluid. The particle's trajectory was controlled by setting the initial inclination angle of a pendulum immersed in a fluid. The resulting collisions were monitored using a high-speed video camera. The diameters of the particles ranged from 3 to 12 mm, and the ratio of the particle density to fluid density varied from 1.2 to 7.8. The experiments were performed using a thick glass or Lucite wall with different mixtures of glycerol and water. With these parameters, the Reynolds number defined using the velocity just prior to impact ranged from 10 to approximately 3000. A coefficient of restitution was defined from the ratio of the velocity just prior to and after impact.The experiments clearly demonstrate that the rebound velocity depends on the impact Stokes number (defined from the Reynolds number and the density ratio) and weakly on the elastic properties of the material. Below a Stokes number of approximately 10, no rebound of the particle occurred. For impact Stokes number above 500 the coefficient of restitution appears to asymptote to the values for dry collisions. The coefficients of restitution were also compared with previous experimental studies. In addition, the approach of the particle to the wall indicated that the particle slowed prior to impacting the surface. The distance at which the particle's trajectory varied due to the presence of the wall was dependent on the impact Stokes number. The particle surface roughness was found to affect the repeatability of some measurements, especially for low impact velocities.

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.

Analysis of the Combustion Process in a EURO III Heavy-Duty Direct Injection Diesel Engine

2002 ◽  
Vol 124 (3) ◽  
pp. 636-644 ◽  
Author(s):  
J. M. Desantes ◽  
J. V. Pastor ◽  
J. Arre`gle ◽  
S. A. Molina
Keyword(s):  
High Speed ◽  
Direct Injection ◽  
Combustion Process ◽  
Engine Performance ◽  
Injection Pressure ◽  
Pollutant Emissions ◽  
Injection Timing ◽  
Engine Operation ◽  
Operation Conditions ◽  
Representative Points

To fulfill the commitments of future pollutant regulations, current development of direct injection (DI) Diesel engines requires to improve knowledge on the injection/combustion process and the effect of the injection parameters and engine operation conditions upon the spray and flame characteristics and how they affect engine performance and pollutant emissions. In order to improve comprehension of the phenomena inherent to Diesel combustion, a deep experimental study has been performed in a single-cylinder engine with the main characteristics of a six-cylinder engine passing the EURO III legislation. Some representative points of the 13-mode engine test cycle have been considered modifying the nominal values of injection pressure, injection load, intake pressure, engine speed, and injection timing. The study combines performance and emissions experimental measurements together with heat release law (HRL) analysis and high-speed visualization. Controlling parameters for BSFC, NOx, and soot emissions are identified in the last part of the paper.

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
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