Midline Heat Transfer and Pressure Measurements on an Incident Tolerant Blade Section for a Variable Speed Power Turbine at Low to Moderate Reynolds Numbers in a Transonic Turbine Cascade

2014 ◽  
Author(s):  
Leolein P. Moualeu ◽  
Forrest E. Ames ◽  
Yildirim B. Suzen
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Pressure Measurements ◽  
Turbine Cascade ◽  
Variable Speed ◽  
Power Turbine ◽  
Blade Section ◽  
Transonic Turbine

scholarly journals Use of Transition Modeling to Enable the Computation of Losses for Variable-Speed Power Turbine

2012 ◽  
Author(s):  
Ali A. Ameri
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Variable Speed ◽  
Accurate Analysis ◽  
Pressure Losses ◽  
Analysis Tools ◽  
Power Turbine ◽  
Wide Range ◽  
Transition Modeling

To investigate the penalties associated with using a variable speed power turbine (VSPT) in a rotorcraft capable of vertical takeoff and landing, various analysis tools are required. Such analysis tools must be able to model the flow accurately within the operating envelope of VSPT. For power turbines low Reynolds numbers and a wide range of the incidence angles, positive and negative, due to the variation in the shaft speed at relatively fixed corrected flows, characterize this envelope. The flow in the turbine passage is expected to be transitional and separated at high incidence. The turbulence model of Walters and Leylek was implemented in the NASA Glenn-HT code to enable a more accurate analysis of such flows. Two-dimensional heat transfer predictions of flat plate flow and two and three dimensional heat transfer predictions on a turbine blade were performed and reported herein. Heat transfer computations were performed because it is a good marker for transition. The final goal is to be able to compute the aerodynamic losses. Armed with the new transition model, total pressure losses for three-dimensional flow of an Energy Efficient Engine (E3) tip section cascade for a range of incidence angles were computed in anticipation of the experimental data. The results obtained form a loss bucket for the chosen blade.

Implicit-LES Simulation of Variable-Speed Power Turbine Cascade for Low Free-Stream Turbulence Conditions

2018 ◽  
Author(s):  
Ali Ameri
Keyword(s):  
Free Stream ◽  
Reynolds Numbers ◽  
Scale Model ◽  
Variable Speed ◽  
Low Reynolds Numbers ◽  
Free Stream Turbulence ◽  
Pressure Loss Coefficient ◽  
Power Turbine ◽  
Actual Design ◽  
Low Reynolds

It is a challenge to simulate the flow in a Variable Speed Power Turbine (VSPT), or, for that matter, rear stages of low pressure turbines at low Reynolds numbers due to laminar flow separation or laminar/turbulent flow transition on the blades. At low Reynolds numbers, separation induced-transition is more prevalent which can result in efficiency lapse. LES has been used in recent years to simulate these types of flows with a good degree of success. In the present work, very low free stream turbulence flows at exit Reynolds number of 220k were simulated. The geometry was a cascade which was constructed with the midspan section of a VSPT design. Most LES simulations to date, have focused on the midspan region. As the endwall effect was significant in these simulations due to thick incoming boundary layer, full blade span computation was necessitated. Inlet flow angles representative of take-off and cruise conditions, dictated by the rotor speed in an actual design, were analyzed. This was done using a second order finite volume code and a high resolution grid. As is the case with Implicit-LES methods, no sub-grid scale model was used. Blade static pressure data, at various span locations, and downstream probe survey measurements of total pressure loss coefficient were used to verify the results. The comparisons showed good agreement between the simulations and the experimental data.

Transonic Turbine Cascade Measurements for a Variable Speed Power Turbine Blade at Low to Moderate Reynolds Numbers: Aerodynamic Loss Surveys

2015 ◽  
Author(s):  
J. A. Long ◽  
L. P. G. Moualeu ◽  
N. J. Hemming ◽  
F. E. Ames ◽  
Y. B. Suzen
Keyword(s):  
Reynolds Number ◽  
Turbine Blade ◽  
Total Pressure ◽  
Reynolds Numbers ◽  
Turbulence Level ◽  
Variable Speed ◽  
Aerodynamic Loss ◽  
Power Turbine ◽  
The Impact ◽  
Aerodynamic Losses

The influence of low to moderate Reynolds number and low to moderate turbulence level on aerodynamic losses is investigated in an incidence tolerant turbine blade cascade for a variable speed power turbine. This work complements midspan heat transfer and blade loading measurements which are acquired in the same cascade at the same conditions. The aerodynamic loss measurements are acquired to quantify the influence of Reynolds number and turbulence level on blade loss buckets over the wide range of incidence angles for the variable speed turbine. Eight discrete incidence angles are investigated ranging from +5.8° to −51.2°. Noting that the design inlet angle of the blade is 34.2° these incidence angles correspond to inlet angles ranging from +40° to −17°. Exit loss surveys, presented in terms of local total pressure loss and secondary velocities have been acquired at four exit chord Reynolds numbers ranging from 50,000 to 568,000. These measurements were acquired at both low (∼0.4%) and moderate (∼4.0%) inlet turbulence intensities. The total pressure losses are also presented in terms of cross passage averaged loss and turning angle. The resulting loss buckets for passage averaged losses are plotted at varied Reynolds numbers and turbulence condition. The exit loss data quantify the impact of Reynolds number and incidence angle on aerodynamic losses. Generally, these data document the substantial deterioration of performance with decreasing Reynolds number.

Parametric Effects on Heat Transfer of Impingement on Dimpled Surface

2004 ◽  
Author(s):  
Koonlaya Kanokjaruvijit ◽  
Ricardo F. Martinez-Botas
Keyword(s):  
Heat Transfer ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
Pressure Measurements ◽  
Spatially Resolved ◽  
Nusselt Numbers ◽  
Plate Spacing ◽  
Parametric Effects ◽  
Dimple Surface ◽  
Flat Portion

Jet impingement on a dimpled surface is investigated experimentally for Reynolds numbers in the range 5000–11500, and jet-to-plate spacing from 2 to 12 jet-diameters. These include spatially resolved local Nusselt numbers with impingement both on the dimpled itself and on the flat portion between dimples. Two dimple geometries are considered: hemispherical dimples and double or cusp elliptical dimples. All experiments were carried under maximum crossflow, that is the spent air exits along one way. At the narrow jet-to-plate spacing, such as H/Dj = 2, a vigorous recirculation occurred, which prevented the dimpled plate to enhance heat transfer. The effect of impinging jet positions meant that impinging onto dimples generated more and higher energetic vortices, and this led to better heat transfer performance. Cusped elliptical dimples increase the heat transfer compared to a flat plate less than the hemispherical geometry. The influence of dimple depth was also considered, the shallower dimple, d/Dd = 0.15, improves significantly the heat transfer by 64% compared to that of the flat surface impingement at H/Dj = 4, this result was 38% higher than that for a deeper dimple of d/Dd = 0.25. The very significant increase in average heat transfer makes dimple surface impingement a candidate for cooling applications. Detailed pressure measurements will form a second part of this paper, however, plenum pressure measurements are illustrated here as well as a surface pressure measurement on both streamwise and spanwise directions.

scholarly journals Aerodynamic Measurements of a Variable-Speed Power-Turbine Blade Section in a Transonic Turbine Cascade at Low Inlet Turbulence

2013 ◽  
Author(s):  
Ashlie B. McVetta ◽  
Paul W. Giel ◽  
Gerard E. Welch
Keyword(s):  
Reynolds Number ◽  
Total Pressure ◽  
Secondary Flows ◽  
Variable Speed ◽  
Flow Conditions ◽  
Flow Angle ◽  
Power Turbine ◽  
Angle Data ◽  
Transonic Turbine ◽  
Exit Mach Number

Aerodynamic measurements obtained in a transonic linear cascade were used to assess the impact of large incidence angle and Reynolds number variations on the 3-D flow field and midspan loss and turning of a 2-D section of a variable-speed power-turbine (VSPT) rotor blade. Steady-state data were obtained for ten incidence angles ranging from +15.8° to −51.0°. At each angle, data were acquired at five flow conditions with the exit Reynolds number (based on axial chord) varying over an order-of-magnitude from 2.12 × 105 to 2.12 × 106. Data were obtained at the design exit Mach number of 0.72 and at a reduced exit Mach number of 0.35 as required to achieve the lowest Reynolds number. Midspan total-pressure and exit flow angle data were acquired using a five-hole pitch/yaw probe surveyed on a plane located 7.0 percent axial-chord downstream of the blade trailing edge plane. The survey spanned three blade passages. Additionally, three-dimensional half-span flow fields were examined with additional probe survey data acquired at 26 span locations for two key incidence angles of +5.8° and −36.7°. Survey data near the endwall were acquired with a three-hole boundary-layer probe. The data were integrated to determine average exit total-pressure and flow angle as functions of incidence and flow conditions. The data set also includes blade static pressures measured on four spanwise planes and endwall static pressures. Tests were conducted in the NASA Glenn Transonic Turbine Blade Cascade Facility. The measurements reflect strong secondary flows associated with the high aerodynamic loading levels at large positive incidence angles and an increase in loss levels with decreasing Reynolds number. The secondary flows decrease with negative incidence as the blade becomes unloaded. Transitional flow is admitted in this low inlet turbulence dataset, making it a challenging CFD test case. The dataset will be used to advance understanding of the aerodynamic challenges associated with maintaining efficient power turbine operation over a wide shaft-speed range.

scholarly journals Aerodynamic and Heat Transfer Measurements on Blading for a High Rim-Speed Transonic Turbine

1989 ◽  
Author(s):  
R. C. Kingcombe ◽  
S. P. Harasgama ◽  
N. P. Leversuch ◽  
E. T. Wedlake
Keyword(s):  
Heat Transfer ◽  
Rotor Blade ◽  
Static Pressure ◽  
Surface Heat ◽  
Pressure Measurements ◽  
Performance Measurements ◽  
Cold Flow ◽  
Overall Performance ◽  
Transonic Turbine ◽  
Annular Cascade

A high rim speed turbine, incorporating some 3-D features has been designed and tested at RAE Pyestock. There has been cold flow turbine testing, with overall performance measurements, rotor exit traversing as well as surface static pressure measurements on the vane and rotor. The vane has also been tested in annular cascade on the Isentropic Light Piston Cascade giving surface heat transfer measurements on the vanes and endwalls as well as aerodynamic information. The data have been used to compare with design predictions and the reasons for the differences observed, particularly on the rotor blade, are explored.

Aerodynamic Performance of a Transonic Turbine Cascade at Off-Design Conditions

2000 ◽  
Vol 123 (3) ◽  
pp. 510-518 ◽  
Author(s):  
D. B. M. Jouini ◽  
S. A. Sjolander ◽  
S. H. Moustapha
Keyword(s):  
Axial Velocity ◽  
Density Ratio ◽  
Reynolds Numbers ◽  
Aerodynamic Performance ◽  
Base Pressure ◽  
Turbine Cascade ◽  
Blade Loading ◽  
Profile Losses ◽  
Transonic Turbine ◽  
Mach Numbers

The paper presents detailed measurements of the midspan aerodynamic performance of a transonic turbine cascade at off-design conditions. The measurements were conducted for exit Mach numbers ranging from 0.5 to 1.2, and for Reynolds numbers from 4×105 to 106. The profile losses were measured for incidence values of +14.5 deg, +10 deg, +4.5 deg, 0 deg, and −10 deg relative to design. To aid in understanding the loss behavior and to provide other insights into the flow physics, measurements of blade loading, exit flow angles, trailing-edge base pressures, and the axial velocity density ratio (AVDR) were also made. It was found that the profile losses at transonic Mach numbers can be closely related to the base pressure behavior. The losses were also affected by the AVDR.

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