Improved Methodologies for Time Resolved Heat Transfer Measurements, Demonstrated on an Unshrouded Transonic Turbine Casing

2015 ◽  
Author(s):  
Matthew Collins ◽  
Kam Chana ◽  
Thomas Povey
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
High Frequency ◽  
Processing Technique ◽  
Temperature Cycling ◽  
Test Facility ◽  
Inlet Temperature ◽  
Data Set ◽  
Time Resolved ◽  
Transonic Turbine

The HP rotor tip and over-tip casing are often life-limiting features in the turbine stages of current gas turbine engines. This is due to the high thermal load, and high temperature cycling both at low and high frequency. In the last few years there have been numerous studies of turbine tip heat transfer. Comparatively fewer studies have considered the over-tip casing heat transfer. This is in part, no doubt, due to the more onerous test facility requirements to validate computational simulations. Because the casing potential field is dominated by the passing rotor, to perform representative over-tip measurements a rotating experiment is an essential requirement. In this paper we describe improved methodologies for time resolved heat transfer measurements. Specifically we show that: 1. Changes in driving temperature (within limits) can be accounted for in both time-resolved and steady heat transfer measurement processing. This allows useful data to be extracted even under varying inlet temperature. 2. Superposition of several runs with different starting wall temperatures can be used to improve the accuracy of time resolved regressions by extending the wall temperature range over which the unsteady regressions are conducted. 3. A new time-resolved data processing technique that can be applied to data sets involving changes in wall temperature has been developed and is applied to experimental measurements to compute time resolved TAW and Nu. These improvements are demonstrated using unsteady heat transfer measurements conducted on the stationary casing above an unshrouded transonic turbine. The measurements were taken in the Oxford Turbine Research Facility (OTRF), an engine-scale rotating turbine facility which replicates engine-representative conditions of Mach number, Reynolds number, and gas-to-wall temperature ratio. High density arrays of miniature thin-film heat-flux gauges were used with a spatial resolution of 0.8 mm and temporal resolution of ∼120 kHz. The small size of the gauges, the high frequency response, and the improved processing methods allowed very detailed measurements of the heat transfer in this region. Time-resolved measurements of TAW and Nu are presented for the casing region (−30 % to +125% CAX) and compared to other results in the literature. The results provide an almost unique data set for calibrating CFD tools for heat transfer prediction in this highly unsteady environment dominated by the rotor over-tip flow.

Improved Methodologies for Time-Resolved Heat Transfer Measurements, Demonstrated on an Unshrouded Transonic Turbine Casing

2016 ◽  
Vol 138 (11) ◽  
Author(s):  
Matthew Collins ◽  
Kam Chana ◽  
Thomas Povey
Keyword(s):  
Heat Transfer ◽  
Temperature Cycling ◽  
Test Facility ◽  
Turbine Engines ◽  
Data Set ◽  
Time Resolved ◽  
High Frequency Response ◽  
High Thermal Load ◽  
Turbine Casing ◽  
Computational Fluid Dynamics Cfd

The high pressure (HP) rotor tip and over-tip casing are often life-limiting features in the turbine stages of current gas turbine engines. This is due to the high thermal load and high temperature cycling at both low and high frequencies. In the last few years, there have been numerous studies of turbine tip heat transfer. Comparatively fewer studies have considered the over-tip casing heat transfer. This is in part, no doubt, due to the more onerous test facility requirements to validate computational simulations. Because the casing potential field is dominated by the passing rotor, to perform representative over-tip measurements a rotating experiment is an essential requirement. This paper details the measurements taken on the Oxford turbine research facility (OTRF), an engine-scale rotating turbine facility which replicates engine-representative conditions of Mach number, Reynolds number, and gas-to-wall temperature ratio. High density arrays of miniature thin-film heat-flux gauges were used with a spatial resolution of 0.8 mm and temporal resolution of ∼120 kHz. The small size of the gauges, the high frequency response, and the improved processing methods allowed very detailed measurements of the heat transfer in this region. Time-resolved measurements of TAW and Nu are presented for the casing region (−30% to +125% CAX) and compared to other results in the literature. The results provide an almost unique data set for calibrating computational fluid dynamics (CFD) tools for heat transfer prediction in this highly unsteady environment dominated by the rotor over-tip flow.

Uncertainty Analysis of Heat Transfer Predictions Using Statistically Modeled Data From a Cooled 1-1/2 Stage High-Pressure Transonic Turbine

2013 ◽  
Vol 136 (6) ◽  
Author(s):  
Harika S. Kahveci ◽  
Kevin R. Kirtley
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
High Pressure ◽  
Wall Temperature ◽  
Temperature Measurements ◽  
Navier Stokes ◽  
Inlet Temperature ◽  
Statistical Representation ◽  
Computational Fluid Dynamics Analysis ◽  
Transonic Turbine

This paper compares predictions from a 3D Reynolds-averaged Navier–Stokes code and a statistical representation of measurements from a cooled 1-1/2 stage high-pressure transonic turbine to quantify predictive process sensitivity. A multivariable regression technique was applied to both the inlet temperature measurements obtained at the inlet rake, the wall temperature, and heat transfer measurements obtained via heat-flux gauges on the blade airfoil surfaces. By using the statistically modeled temperature profiles to generate the inlet boundary conditions for the computational fluid dynamics analysis, the sensitivity of blade heat transfer predictions due to the variation in the inlet temperature profile and uncertainty in wall temperature measurements and surface roughness is calculated. All predictions are performed with and without cooling. Heat transfer predictions match reasonably well with the statistical representation of the data, both with and without cooling. Predictive precision for this study is driven primarily by inlet profile uncertainty followed by surface roughness and gauge position uncertainty.

An Experimental Study of Film Cooling in a Rotating Transonic Turbine

1994 ◽  
Vol 116 (1) ◽  
pp. 63-70 ◽  
Author(s):  
R. S. Abhari ◽  
A. H. Epstein
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Test Facility ◽  
Turbine Stage ◽  
Suction Surface ◽  
Time Resolved ◽  
Pressure Surface ◽  
Transonic Turbine ◽  
Percent Decrease ◽  
Time Resolved Measurements

Time-resolved measurements of heat transfer on a fully cooled transonic turbine stage have been taken in a short duration turbine test facility, which simulates full engine nondimensional conditions. The time average of this data is compared to uncooled rotor data and cooled linear cascade measurements made on the same profile. The film cooling reduces the time-averaged heat transfer compared to the uncooled rotor on the blade suction surface by as much as 60 percent, but has relatively little effect on the pressure surface. The suction surface rotor heat transfer is lower than that measured in the cascade. The results are similar over the central 3/4 of the span, implying that the flow here is mainly two dimensional. The film cooling is shown to be much less effective at high blowing ratios than at low ones. Time-resolved measurements reveal that the cooling, when effective, both reduced the dc level of heat transfer and changed the shape of the unsteady waveform. Unsteady blowing is shown to be a principal driver of film cooling fluctuations, and a linear model is shown to do a good job in predicting the unsteady heat transfer. The unsteadiness results in a 12 percent decrease in heat transfer on the suction surface and a 5 percent increase on the pressure surface.

Comparison of Temperature Profile and Heat Transfer Predictions With Statistically-Modeled Data From a Cooled 1-1/2 Stage High-Pressure Transonic Turbine

2013 ◽  
Author(s):  
Harika S. Kahveci ◽  
Kevin R. Kirtley
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
High Pressure ◽  
Temperature Profile ◽  
Wall Temperature ◽  
Temperature Measurements ◽  
Navier Stokes ◽  
Inlet Temperature ◽  
Statistical Representation ◽  
Transonic Turbine

This paper compares predictions from a 3-D Reynolds-Averaged Navier-Stokes code and a statistical representation of measurements from a cooled 1-1/2 stage high-pressure transonic turbine to quantify predictive process sensitivity. A multivariable regression technique was applied to both the inlet temperature measurements obtained at the inlet rake, and the wall temperature and heat transfer measurements obtained via heat-flux gauges on the blade airfoil surfaces. By using the statistically-modeled temperature profiles to generate the inlet boundary conditions for the Computational Fluid Dynamics (CFD) analysis, the sensitivity of blade heat transfer predictions due to the variation in the inlet temperature profile and uncertainty in wall temperature measurements and surface roughness is calculated. All predictions are performed with and without cooling. Heat transfer predictions match reasonably well with the statistical representation of the data, both with and without cooling. Predictive precision for this study is driven primarily by inlet profile uncertainty followed by surface roughness and gauge position uncertainty.

scholarly journals An Experimental Study of Film Cooling in a Rotating Transonic Turbine

1992 ◽  
Author(s):  
Reza S. Abhari ◽  
A. H. Epstein
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Test Facility ◽  
Turbine Stage ◽  
Unsteady Heat Transfer ◽  
Suction Surface ◽  
Time Resolved ◽  
Pressure Surface ◽  
Transonic Turbine ◽  
Time Resolved Measurements

Time-resolved measurements of heat transfer on a fully cooled transonic turbine stage have been taken in a short duration turbine test facility which simulates full engine non-dimensional conditions. The time average of this data is compared to uncooled rotor data and cooled linear cascade measurements made on the same profile. The film cooling reduces the time-averaged heat transfer compared to the uncooled rotor on the blade suction surface by as much as 60%, but has relatively little effect on the pressure surface. The suction surface rotor heat transfer is lower than that measured in the cascade. The results are similar over the central 3/4 of the span implying that the flow here is mainly two-dimensional. The film cooling is shown to be much less effective at high blowing ratios than at low ones. Time-resolved measurements reveal that the cooling, when effective, both reduced the d.c. level of heat transfer and changed the shape of the unsteady waveform. Unsteady blowing is shown to be a principal driver of film cooling fluctuations, and a linear model is shown to do a good job in predicting the unsteady heat transfer. The unsteadiness results in a 12% decrease in heat transfer on the suction surface and a 5% increase on the pressure surface.

A Method of Solving Three Temperature Problem of Turbine With Adiabatic Wall Temperature

2021 ◽  
Author(s):  
Zeyu Wu ◽  
Xiang Luo ◽  
Jianqin Zhu ◽  
Zhe Zhang ◽  
Jiahua Liu
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Reynolds Number ◽  
Wall Temperature ◽  
Reference Temperature ◽  
Inlet Temperature ◽  
Adiabatic Wall ◽  
Rotating Cavity ◽  
Temperature Problem ◽  
Turbulence Parameters

Abstract The aeroengine turbine cavity with pre-swirl structure makes the turbine component obtain better cooling effect, but the complex design of inlet and outlet makes it difficult to determine the heat transfer reference temperature of turbine disk. For the pre-swirl structure with two air intakes, the driving temperature difference of heat transfer between disk and cooling air cannot be determined either in theory or in test, which is usually called three-temperature problem. In this paper, the three-temperature problem of a rotating cavity with two cross inlets are studied by means of experiment and numerical simulation. By substituting the adiabatic wall temperature for the inlet temperature and summarizing its variation law, the problem of selecting the reference temperature of the multi-inlet cavity can be solved. The results show that the distribution of the adiabatic wall temperature is divided into the high jet area and the low inflow area, which are mainly affected by the turbulence parameters λT, the rotating Reynolds number Reω, the high inlet temperature Tf,H* and the low radius inlet temperature Tf,L* of the inflow, while the partition position rd can be considered only related to the turbulence parameters λT and the rotating Reynolds number Reω of the inflow. In this paper, based on the analysis of the numerical simulation results, the calculation formulas of the partition position rd and the adiabatic wall temperature distribution are obtained. The results show that the method of experiment combined with adiabatic wall temperature zone simulation can effectively solve the three-temperature problem of rotating cavity.

Effect of Temperature Nonuniformity on Heat Transfer in an Unshrouded Transonic HP Turbine: An Experimental and Computational Investigation

2010 ◽  
Author(s):  
Imran Qureshi ◽  
Andy D. Smith ◽  
Kam S. Chana ◽  
Thomas Povey
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Aerodynamic Characteristics ◽  
Test Facility ◽  
Effect Of Temperature ◽  
Inlet Temperature ◽  
Experimental Measurements ◽  
Turbine Stage ◽  
Cfd Simulations ◽  
Turbine Inlet

Detailed experimental measurements have been performed to understand the effects of turbine inlet temperature distortion (hot-streaks) on the heat transfer and aerodynamic characteristics of a full-scale unshrouded high pressure turbine stage at flow conditions that are representative of those found in a modern gas turbine engine. To investigate hot-streak migration, the experimental measurements are complemented by three-dimensional steady and unsteady CFD simulations of the turbine stage. This paper presents the time-averaged measurements and computational predictions of rotor blade surface and rotor casing heat transfer. Experimental measurements obtained with and without inlet temperature distortion are compared. Time-mean experimental measurements of rotor casing static pressure are also presented. CFD simulations have been conducted using the Rolls-Royce code Hydra, and are compared to the experimental results. The test turbine was the unshrouded MT1 turbine, installed in the Turbine Test Facility (previously called Isentropic Light Piston Facility) at QinetiQ, Farnborough UK. This is a short duration transonic facility, which simulates engine representative M, Re, Tu, N/T and Tg /Tw at the turbine inlet. The facility has recently been upgraded to incorporate an advanced second-generation temperature distortion generator, capable of simulating well-defined, aggressive temperature distortion both in the radial and circumferential directions, at the turbine inlet.

Unsteady Rotor Heat Transfer in a Transonic Turbine Stage

2002 ◽  
Author(s):  
F. Didier ◽  
R. De´nos ◽  
T. Arts
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Strong Dependence ◽  
Convective Heat Transfer Coefficient ◽  
Operating Conditions ◽  
Turbine Stage ◽  
Trailing Edge ◽  
Time Resolved ◽  
Number Distribution ◽  
Transonic Turbine

This experimental investigation reports the convective heat transfer coefficient around the rotor of a transonic turbine stage. Both time-resolved and time-averaged aspects are addressed. The measurements are performed around the rotor blade at 15%, 50% and 85% span as well as on the rotor tip and the hub platform. Four operating conditions are tested covering two Reynolds numbers and three pressure ratios. The tests are performed in the compression tube turbine test rig CT3 of the von Karman Institute, allowing a correct simulation of the operating conditions encountered in modern aero-engines. The time-averaged Nusselt number distribution shows the strong dependence on both blade Mach number distribution and Reynolds number. The time-resolved heat transfer rate is mostly dictated by the vane trailing edge shock impingement on the rotor boundary layer. The shock passage corresponds to a sudden heat transfer increase. The effects are more pronounced in the leading edge region. The increase of the stage pressure ratio causes a stronger vane trailing edge shock and thus larger heat transfer fluctuations. The influence of the Reynolds number is hardly visible.

Experimental Investigation of Vane Clocking in a One and 1/2 Stage High Pressure Turbine

2004 ◽  
Author(s):  
Charles W. Haldeman ◽  
Michael G. Dunn ◽  
John W. Barter ◽  
Brian R. Green ◽  
Robert F. Bergholz
Keyword(s):  
High Pressure ◽  
Low Pressure ◽  
Test Facility ◽  
Maximum Efficiency ◽  
High Pressure Turbine ◽  
Data Set ◽  
Time Resolved ◽  
Low Pressure Turbine ◽  
Turbine Vane ◽  
Vane Clocking

Aerodynamic measurements were acquired on a modern single-stage, transonic, high-pressure turbine with the adjacent low-pressure turbine vane row (a typical civilian one and one-half stage turbine rig) to observe the effects of low-pressure turbine vane clocking on overall turbine performance. The turbine rig (loosely referred to in this paper as the stage) was operated at design corrected conditions using the Ohio State University Gas Turbine Laboratory Turbine Test Facility (TTF). The research program utilized uncooled hardware in which all three airfoils were heavily instrumented at multiple spans to develop a full clocking dataset. The low-pressure turbine vane row (LPTV) was clocked relative to the high-pressure turbine vane row (HPTV). Various methods were used to evaluate the influence of clocking on the aeroperformance (efficiency) and the aerodynamics (pressure loading) of the LPTV, including time-resolved and time-averaged measurements. A change in overall efficiency of approximately 2–3% due to clocking effects is demonstrated and could be observed using a variety of independent methods. Maximum efficiency is obtained when the time-average surface pressures are highest on the LPTV and the time-resolved surface pressure (both in the time domain and frequency domain) show the least amount of variation. The overall effect is obtained by integrating over the entire airfoil, as the three-dimensional effects on the LPTV surface are significant. This experimental data set validates several computational research efforts that suggested wake migration is the primary reason for the perceived effectiveness of vane clocking. The suggestion that wake migration is the dominate mechanism in generating the clocking effect is also consistent with anecdotal evidence that fully cooled engine rigs do not see a great deal of clocking effect. This is consistent since the additional disturbances induced by the cooling flows and/or the combustor make it extremely difficult to find an alignment for the LPTV given the strong 3D nature of modern high-pressure turbine flows.

Comparison of Time-Resolved Turbine Rotor Blade Heat Transfer Measurements and Numerical Calculations

1991 ◽  
Author(s):  
R. S. Abhari ◽  
G. R. Guenette ◽  
A. H. Epstein ◽  
M. B. Giles
Keyword(s):  
Heat Transfer ◽  
Rotor Blade ◽  
Pressure Ratio ◽  
Time History ◽  
Turbine Rotor ◽  
Numerical Calculations ◽  
Test Facility ◽  
Time Resolved ◽  
Turbine Rotor Blade ◽  
History Of

Time-resolved turbine rotor blade heat transfer data are compared with ab initio numerical calculations. The data was taken on a transonic, 4-to-1 pressure ratio, uncooled, single-stage turbine in a short duration turbine test facility. The data consists of the time history of the heat transfer distribution about the rotor chord at midspan. The numerical calculation is a time accurate, 2-D, thin shear layer, multiblade row code known as UNSFLO. UNSFLO uses Ni’s Lax-Wendroff algorithm, conservative boundary conditions, and a time tilting algorithm to facilitate the calculation of the flow in multiple blade rows of arbitrary pitch ratio with relatively little computer time. The version used for this work had a simple algebraic Baldwin-Lomax turbulence model. The code is shown to do a good job of predicting the quantitative time history of the heat flux distribution. The wake/boundary layer and transonic interaction regions for suction and pressure surfaces are identified and the shortcomings of the current algebraic turbulence modelling in the code are discussed. The influence of hardware manufacturing tolerance on rotor heat transfer variation is discussed. A physical reasoning explaining the discrepancies between the unsteady measurement and the calculations for both the suction and pressure surfaces are given, which may be of use in improving future calculations and design procedures.

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