scholarly journals Effect of purge air on rotor endwall heat transfer of an axial turbine

2017 ◽  
Vol 1 ◽  
pp. F29ZWY ◽  
Author(s):  
Sebastiano Lazzi Gazzini ◽  
Rainer Schädler ◽  
Anestis I. Kalfas ◽  
Reza S. Abhari ◽  
Sebastian Hohenstein ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Gas Turbines ◽  
Suction Side ◽  
Local Heat ◽  
Heat Fluxes ◽  
Secondary Flows ◽  
Adiabatic Wall ◽  
Axial Turbine ◽  
Purge Flow

AbstractIn order to gain in cycle efficiency, turbine inlet temperatures tend to rise, posing the challenge for designers to cool components more effectively. Purge flow injection through the rim seal is regularly used in gas turbines to limit the ingestion of hot air in the cavities and prevent overheating of the disks and shaft bearings. The interaction of the purge air with the main flow and the static pressure field of the blade rows results in a non-homogenous distribution of coolant on the passage endwall which poses questions on its effect on endwall heat transfer. A novel measurement technique based on infrared thermography has been applied in the rotating axial turbine research facility LISA of the Laboratory for Energy Conversion (LEC) of ETH Zürich. A 1.5 stage configuration with fully three-dimensional airfoils and endwall contouring is integrated in the facility. The effect of different purge air mass flow rates on the distribution of the heat transfer quantities has been observed for the rated operating condition of the turbine. Two-dimensional distributions of Nusselt number and adiabatic wall temperature show that the purge flow affects local heat loads. It does so by acting on the adiabatic wall temperature on the suction side of the passage until 30% of the axial extent of the rotor endwall. This suggests the possibility of effectively employing purge air also as rotor platform coolant in this specific region. The strengthening of the secondary flows due to purge air injection is observed, but plays a negligible role in varying local heat fluxes. For one test case, experimental data is compared to high-fidelity, unsteady Reynolds-Averaged Navier–Stokes simulations performed on a model of the full 1.5 stage configuration.

High Resolution Heat Transfer Measurements on the Stator Endwall of an Axial Turbine

2014 ◽  
Vol 137 (4) ◽  
Author(s):  
Benoit Laveau ◽  
Reza S. Abhari ◽  
Michael E. Crawford ◽  
Ewald Lutum
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
High Resolution ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
Mass Flow ◽  
Wall Temperature ◽  
Adiabatic Wall ◽  
Axial Turbine ◽  
The Heat Transfer Coefficient

In order to continue increasing the efficiency of gas turbines, an important effort is made on the thermal management of the turbine stage. In particular, understanding and accurately estimating the thermal loads in a vane passage is of primary interest to engine designers looking to optimize the cooling requirements and ensure the integrity of the components. This paper focuses on the measurement of endwall heat transfer in a vane passage with a three-dimensional (3D) airfoil shape and cylindrical endwalls. It also presents a comparison with predictions performed using an in-house developed Reynolds-Averaged Navier–Stokes (RANS) solver featuring a specific treatment of the numerical smoothing using a flow adaptive scheme. The measurements have been performed in a steady state axial turbine facility on a novel platform developed for heat transfer measurements and integrated to the nozzle guide vane (NGV) row of the turbine. A quasi-isothermal boundary condition is used to obtain both the heat transfer coefficient and the adiabatic wall temperature within a single measurement day. The surface temperature is measured using infrared thermography through small view ports. The infrared camera is mounted on a robot arm with six degrees of freedom to provide high resolution surface temperature and a full coverage of the vane passage. The paper presents results from experiments with two different flow conditions obtained by varying the mass flow through the turbine: measurements at the design point (ReCax=7.2×105) and at a reduced mass flow rate (ReCax=5.2×105). The heat transfer quantities, namely the heat transfer coefficient and the adiabatic wall temperature, are derived from measurements at 14 different isothermal temperatures. The experimental data are supplemented with numerical predictions that are deduced from a set of adiabatic and diabatic simulations. In addition, the predicted flow field in the passage is used to highlight the link between the heat transfer patterns measured and the vortical structures present in the passage.

Volumetric Velocimetry Measurements of Purge–Mainstream Interaction in a One-Stage Turbine

2021 ◽  
Vol 143 (4) ◽  
Author(s):  
A. J. Carvalho Figueiredo ◽  
B. D. J. Schreiner ◽  
A. W. Mesny ◽  
O. J. Pountney ◽  
J. A. Scobie ◽  
...  
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Suction Side ◽  
Secondary Flows ◽  
Blade Passage ◽  
One Stage ◽  
Passage Vortex ◽  
Purge Flow ◽  
Secondary Flow Field

Abstract Air-cooled gas turbines employ bleed air from the compressor to cool vulnerable components in the turbine. The cooling flow, commonly known as purge air, is introduced at low radius, before exiting through the rim-seal at the periphery of the turbine discs. The purge flow interacts with the mainstream gas path, creating an unsteady and complex flowfield. Of particular interest to the designer is the effect of purge on the secondary-flow structures within the blade passage, the extent of which directly affects the aerodynamic loss in the stage. This paper presents a combined experimental and computational fluid dynamics (CFD) investigation into the effect of purge flow on the secondary flows in the blade passage of an optically accessible one-stage turbine rig. The experimental campaign was conducted using volumetric velocimetry (VV) measurements to assess the three-dimensional inter-blade velocity field; the complementary CFD campaign was carried out using unsteady Reynolds-averaged Navier–Stokes (URANS) computations. The implementation of VV within a rotating environment is a world first and offers an unparalleled level of experimental detail. The baseline flow-field, in the absence of purge flow, demonstrated a classical secondary flow-field: the rollup of a horseshoe vortex, with subsequent downstream convection of a pressure-side and suction-side leg, the former transitioning in to the passage vortex. The introduction of purge, at 1.7% of the mainstream flowrate, was shown to modify the secondary flow-field by enhancing the passage vortex, in both strength and span-wise migration. The computational predictions were in agreement with the enhancement revealed by the experiments.

Mist/Steam Cooling in a Heated Horizontal Tube—Part 2: Results and Modeling

1999 ◽  
Vol 122 (2) ◽  
pp. 366-374 ◽  
Author(s):  
Tao Guo ◽  
Ting Wang ◽  
J. Leo Gaddis
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Experimental Studies ◽  
Local Heat Transfer ◽  
Horizontal Tube ◽  
Local Heat ◽  
Heat Fluxes ◽  
Steam Flow ◽  
Transfer Model ◽  
Steam Cooling

Experimental studies on mist/steam cooling in a heated horizontal tube have been performed. Wall temperature distributions have been measured under various main steam flow rates, droplet mass ratios, and wall heat fluxes. Generally, the heat transfer performance of steam can be significantly improved by adding mist into the main flow. An average enhancement of 100 percent with the highest local heat transfer enhancement of 200 percent is achieved with 5 percent mist. When the test section is mildly heated, an interesting wall temperature distribution is observed: The wall temperature increases first, then decreases, and finally increases again. A three-stage heat transfer model with transition boiling, unstable liquid fragment evaporation, and dry-wall mist cooling has been proposed and has shown some success in predicting the wall temperature of the mist/steam flow. The PDPA measurements have facilitated better understanding and interpreting of the droplet dynamics and heat transfer mechanisms. Furthermore, this study has shed light on how to generate appropriate droplet sizes to achieve effective droplet transportation, and has shown that it is promising to extend present results to a higher temperature and higher pressure environment. [S0889-504X(00)02502-2]

A new experimental approach for heat transfer coefficient and adiabatic wall temperature measurements on a Nozzle Guide Vane with inlet temperature distortions

2021 ◽  
pp. 1-33
Author(s):  
Tommaso Bacci ◽  
Alessio Picchi ◽  
Bruno Facchini ◽  
Simone Cubeda
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Wall Temperature ◽  
Gas Turbines ◽  
Experimental Approach ◽  
Guide Vane ◽  
Adiabatic Wall ◽  
Nozzle Guide Vane ◽  
Nozzle Guide

Abstract Modern gas turbines lean combustors are used to limit NOx pollutant emissions; on the other hand, their adoption presents other challenges, especially concerning the combustor-turbine interaction. Turbine inlet conditions are generally characterized by severe temperature distortions and swirl degree, which is responsible for very high turbulence intensities. Past studies have focused on the description of the effects of these phenomena on the behavior of the high pressure turbine. Nevertheless, very limited experimental results are available when it comes to evaluate the heat transfer coefficient (HTC) on the nozzle guide vane surface, since relevant temperature distortions present a severe challenge for the commonly adopted measurement techniques. The work presented in this paper was carried out on a non-reactive, annular, three-sector rig, made by a combustor simulator and a NGV cascade. It can reproduce a swirling flow, with temperature distortions at the combustor-turbine interface plane. This test apparatus was exploited to develop an experimental approach to retrieve heat transfer coefficient and adiabatic wall temperature distributions simultaneously, to overcome the known limitations imposed by temperature gradients on state-of-the-art methods for HTC calculation from transient tests. A non-cooled mockup of a NGV doublet, manufactured using low thermal diffusivity plastic material, was used for the tests, carried out using IR thermography with a transient approach. In the authors' knowledge, this presents the first experimental attempt of measuring a nozzle guide vane heat transfer coefficient in the presence of relevant temperature distortions and swirl.

High Resolution Heat Transfer Measurements on the Stator Endwall of an Axial Turbine

2014 ◽  
Author(s):  
Benoit Laveau ◽  
Reza S. Abhari ◽  
Michael E. Crawford ◽  
Ewald Lutum
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
High Resolution ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
Mass Flow ◽  
Wall Temperature ◽  
Adiabatic Wall ◽  
Axial Turbine ◽  
The Heat Transfer Coefficient

In order to continue increasing the efficiency of gas turbines, an important effort is made on the thermal management of the turbine stage. In particular understanding and accurately estimating the thermal loads in a vane passage is of primary interest to engine designers looking to optimize the cooling requirements and ensure the integrity of the components. This paper focuses on the measurement of endwall heat transfer in a vane passage with a 3D airfoil shape and cylindrical endwalls. It also presents a comparison with predictions performed using an in-house developed RANS solver featuring a specific treatment of the numerical smoothing using a flow adaptive scheme. The measurements have been performed in a steady state axial turbine facility on a novel platform developed for heat transfer measurements and integrated to the nozzle guide vane row of the turbine. A quasi-isothermal boundary condition is used to obtain both the heat transfer coefficient and the adiabatic wall temperature within a single measurement day. The surface temperature is measured using infrared thermography through small view ports. The infrared camera is mounted on a robot-arm with six degrees of freedom to provide high resolution surface temperature and a full coverage of the vane passage. The paper presents results from experiments with two different flow conditions obtained by varying the mass flow through the turbine: measurements at the design point (ReCax = 7,2.105) and at a reduced mass flow rate (ReCax = 5,2.105). The heat transfer quantities, namely the heat transfer coefficient and the adiabatic wall temperature, are derived from measurements at 14 different isothermal temperatures. The experimental data are supplemented with numerical predictions that are deduced from a set of adiabatic and diabatic simulations. In addition, the predicted flow field in the passage is used to highlight the link between the heat transfer patterns measured and the vortical structures present in the passage.

Volumetric Velocimetry Measurements of Purge-Mainstream Interaction in a 1-Stage Turbine

2020 ◽  
Author(s):  
A. J. Carvalho Figueiredo ◽  
B. D. J. Schreiner ◽  
A. W. Mesny ◽  
O. J. Pountney ◽  
J. A. Scobie ◽  
...  
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Suction Side ◽  
Secondary Flows ◽  
Complex Flow ◽  
Blade Passage ◽  
Passage Vortex ◽  
Purge Flow ◽  
Secondary Flow Field

Abstract Air-cooled gas turbines employ bleed air from the compressor to cool vulnerable components in the turbine. The cooling flow, commonly known as purge air, is introduced at low radius, before exiting through the rim-seal at the periphery of the turbine discs. The purge flow interacts with the mainstream gas path, creating an unsteady and complex flow-field. Of particular interest to the designer is the effect of purge on the secondary flow structures within the blade passage, the extent of which directly affects the aerodynamic loss in the stage. This paper presents a combined experimental and Computational Fluid Dynamics (CFD) investigation into the effect of purge flow on the secondary flows in the blade passage of an optically-accessible 1-stage turbine rig. The experimental campaign was conducted using Volumetric Velocimetry (VV) measurements to assess the three-dimensional inter-blade velocity field; the complementary CFD campaign was carried out using URANS computations. The implementation of VV within a rotating environment is a world first and offers an unparalleled level of experimental detail. The baseline flow-field, in the absence of purge flow, demonstrated a classical secondary flow-field: the roll-up of a horseshoe-vortex, with subsequent downstream convection of a pressure-side and suction-side leg, the former transitioning in to the passage vortex. The introduction of purge, at 1.7% of the mainstream flow-rate, was shown to modify the secondary flow field by enhancing the passage vortex, both in strength and span-wise migration. The computational predictions were in agreement with the enhancement revealed by the experiments.

High Resolution Heat Transfer Measurement Technique on Contoured Endwall With Non-Uniform Thermal Resistance

2015 ◽  
Author(s):  
Benoit Laveau ◽  
Reza S. Abhari ◽  
Michael E. Crawford ◽  
Ewald Lutum
Keyword(s):  
Heat Transfer ◽  
Gas Turbines ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Axial Turbine ◽  
Surface Response ◽  
Correction Technique ◽  
Transfer Measurement ◽  
The Impact ◽  
Heat Transfer Measurement

The introduction of endwall contouring in the design of modern gas turbines has helped to improve the aerodynamic performance. In fact, the management of secondary flows and the control of purge air flow are limiting the generation of losses and enhancing the use of coolant air. The impact of such geometrical features on the endwall thermal loads is then of primary interest for designers in charge of optimizing the cooling of the components and ensuring their mechanical integrity. This paper focuses on heat transfer measurement on a contoured vane endwall installed in an axial turbine. The measurements were performed on a dedicated platform installed in the axial turbine rig of ETH Zurich, using a quasi-isothermal boundary condition and an infrared camera traversed by a multi-axis robot-arm. Due to the complex geometry, a mis-attachment of the insulating Kapton layer was observed in several regions of the passage and corrupted the measurements of about 20% of the endwall. An experimental correction method based on the surface response to laser step heating was developed. A specific setup was constructed and used to map the surface response of a calibration plate with flat bottom holes and the heat transfer platform. A model linking the response to the bubble thickness was obtained and used to successfully correct the results. The heat transfer data were obtained for two turbine operating conditions at ReCax = 720000 and 520000. The correction technique, commonly used for defects detection, has been applied in a quantitative manner to provide successful correction of the measurements for different operating conditions.

scholarly journals Detailed Measurements of Local Heat Transfer Coefficient and Adiabatic Wall Temperature Beneath an Array of Impinging Jets

1993 ◽  
Author(s):  
Kenneth W. Van Treuren ◽  
Zuolan Wang ◽  
Peter T. Ireland ◽  
Terry V. Jones
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Wall Temperature ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Impinging Jets ◽  
Local Heat Transfer Coefficient ◽  
Target Plate ◽  
Adiabatic Wall

A transient method of measuring the local heat transfer under an array of impinging jets has been developed. The use of a temperature sensitive coating consisting of three encapsulated thermochromic liquid crystal materials has allowed the calculation of both the local adiabatic wall temperature and the local heat transfer coefficient over the complete surface of the target plate. The influence of the temperature of the plate through which the impingement gas flows on the target plate heat transfer has been quantified. Results are presented for a single inline array configuration over a range of jet Reynolds numbers.

Detailed Measurements of Local Heat Transfer Coefficient and Adiabatic Wall Temperature Beneath an Array of Impinging Jets

1994 ◽  
Vol 116 (3) ◽  
pp. 369-374 ◽  
Author(s):  
K. W. Van Treuren ◽  
Z. Wang ◽  
P. T. Ireland ◽  
T. V. Jones
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Wall Temperature ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Impinging Jets ◽  
Local Heat Transfer Coefficient ◽  
Target Plate ◽  
Adiabatic Wall

A transient method of measuring the local heat transfer under an array of impinging jets has been developed. The use of a temperature-sensitive coating consisting of three encapsulated thermochromic liquid crystal materials has allowed the calculation of both the local adiabatic wall temperature and the local heat transfer coefficient over the complete surface of the target plate. The influence of the temperature of the plate through which the impingement gas flows on the target plate heat transfer has been quantified. Results are presented for a single in-line array configuration over a range of jet Reynolds numbers.

A Presentation of Detailed Experimental Data of a Suction Side Film Cooled Turbine Cascade

2000 ◽  
Author(s):  
Holger Brandt ◽  
Wolfgang Ganzert ◽  
Leonhard Fottner
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Gas Turbines ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Local Heat Transfer ◽  
Suction Side ◽  
Local Heat ◽  
Turbine Cascade ◽  
Shaped Hole

This paper presents detailed isothermal investigations on the aerodynamic effects and the heat transfer of suction side film cooling on a highly loaded turbine cascade. The measurements were carried out with inlet flow conditions kept constant at values which are typically found in modern gas turbines. Five configurations with different hole geometries were investigated, a cylindrical hole with two different streamwise inclination angles, a fan shaped hole and a fan shaped hole with laid-back both only inclined in streamwise direction and a fan shaped hole with laid-back and combined streamwise and lateral inclination. The variation of the blowing ratio enabled closer studies of the mixing process and the influence of the various hole configurations on the aerodynamics and the local heat transfer. To enhance the understanding of the mechanisms and the boundary layer behaviour of these highly three-dimensional flows, much effort has been put on the measurement techniques. The high-resolution data needed was obtained using pressure tappings positioned on the profile, oil-and-dye visualizations on the suction surface, pneumatic probes in the wake and three-dimensional hot wire anemometry in the flow field downstream the holes. Additional heat transfer examinations with a special set-up based on the steady state liquid crystal technique clarified the individual local heat transfer distributions. All measured data are summarized and documented to be used as a reference for three-dimensional, steady-state numerical calculations.

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