Heat Transfer From a Shrouded Rotating Disk to a Single Fluid Stream

1965 ◽  
Vol 87 (4) ◽  
pp. 485-492 ◽  
Author(s):  
J. W. Mitchell ◽  
D. E. Metzger
Keyword(s):  
Heat Transfer ◽  
Gas Turbines ◽  
Radial Flow ◽  
Rotating Disk ◽  
Test Facility ◽  
Algebraic Expression ◽  
Fluid Stream ◽  
Model Study ◽  
Transfer Behavior ◽  
Initial Results

This paper presents the initial results of a model study to determine the heat-transfer characteristics of radial-flow gas turbines. A test facility was constructed and several unconventional experimental techniques were developed for use in the facility. An idealized model consisting of a shrouded rotating disk with a single radially inward airflow was studied. The flow pattern and heat-transfer behavior were analytically and experimentally determined. The experimentally determined heat transfer is correlated by an algebraic expression over the range of nondimensional parameters characteristic of radial-flow gas-turbine operation.

Heat Transfer From a Shrouded Rotating Disk With Film Cooling

1966 ◽  
Vol 88 (1) ◽  
pp. 140-146 ◽  
Author(s):  
D. E. Metzger ◽  
J. W. Mitchell
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Gas Turbines ◽  
Radial Flow ◽  
Rotating Disk ◽  
Operating Conditions ◽  
Main Stream ◽  
Cooling Method ◽  
Model Study ◽  
Transfer Behavior

A study of the cooling effect of secondary fluid injection on the heat transfer between a shrouded rotating disk and a radially inward main flow stream is presented. The investigation is intended as a model study of film-cooled, radial-flow gas turbines. The film-cooling method is reviewed, and the nondimensional parameters governing the heat transfer are obtained. Experimental results, covering the range of radial-flow, gas-turbine operating conditions, were obtained from a film-heated, rotating-disk facility. The heat-transfer behavior of the main stream only was determined separately, and the film-cooling results are presented as ratios of the heat transfer obtained with film cooling to the heat transfer obtained with only the single radial inflow.

Physical Interpretation of Flow and Heat Transfer in Preswirl Systems

2006 ◽  
Vol 129 (3) ◽  
pp. 769-777 ◽  
Author(s):  
Paul Lewis ◽  
Mike Wilson ◽  
Gary Lock ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Turbulent Flow ◽  
Gas Turbines ◽  
Flow Parameter ◽  
Rotating Disk ◽  
Turbine Rotor ◽  
Scaled Model ◽  
Flow Rates

This paper compares heat transfer measurements from a preswirl rotor–stator experiment with three-dimensional (3D) steady-state results from a commercial computational fluid dynamics (CFD) code. The measured distribution of Nusselt number on the rotor surface was obtained from a scaled model of a gas turbine rotor–stator system, where the flow structure is representative of that found in an engine. Computations were carried out using a coupled multigrid Reynolds-averaged Navier-Stokes (RANS) solver with a high Reynolds number k-ε∕k-ω turbulence model. Previous work has identified three parameters governing heat transfer: rotational Reynolds number (Reϕ), preswirl ratio (βp), and the turbulent flow parameter (λT). For this study rotational Reynolds numbers are in the range 0.8×106<Reϕ<1.2×106. The turbulent flow parameter and preswirl ratios varied between 0.12<λT<0.38 and 0.5<βp<1.5, which are comparable to values that occur in industrial gas turbines. Two performance parameters have been calculated: the adiabatic effectiveness for the system, Θb,ad, and the discharge coefficient for the receiver holes, CD. The computations show that, although Θb,ad increases monotonically as βp increases, there is a critical value of βp at which CD is a maximum. At high coolant flow rates, computations have predicted peaks in heat transfer at the radius of the preswirl nozzles. These were discovered during earlier experiments and are associated with the impingement of the preswirl flow on the rotor disk. At lower flow rates, the heat transfer is controlled by boundary-layer effects. The Nusselt number on the rotating disk increases as either Reϕ or λT increases, and is axisymmetric except in the region of the receiver holes, where significant two-dimensional variations are observed. The computed velocity field is used to explain the heat transfer distributions observed in the experiments. The regions of peak heat transfer around the receiver holes are a consequence of the route taken by the flow. Two routes have been identified: “direct,” whereby flow forms a stream tube between the inlet and outlet; and “indirect,” whereby flow mixes with the rotating core of fluid.

A New Test Facility to Investigate Film Cooling on a Non-Axisymmetric Contoured Turbine Endwall: Part I — Introduction and Aerodynamic Measurements

2015 ◽  
Author(s):  
Franz Puetz ◽  
Johannes Kneer ◽  
Achmed Schulz ◽  
Hans-Joerg Bauer
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Pressure Distribution ◽  
Film Cooling ◽  
Gas Turbines ◽  
Guide Vane ◽  
Leading Edge ◽  
Suction Side ◽  
Test Facility ◽  
Endwall Contouring

An increased demand for lower emission of stationary gas turbines as well as civil aircraft engines has led to new, low emission combustor designs with less liner cooling and a flattened temperature profile at the outlet. As a consequence, the heat load on the endwall of the first nozzle guide vane is increased. The secondary flow field dominates the endwall heat transfer, which also contributes to aerodynamic losses. A promising approach to reduce these losses is non-axisymmetric endwall contouring. The effects of non-axisymmetric endwall contouring on heat transfer and film cooling are yet to be investigated. Therefore, a new cascade test rig has been set up in order to investigate endwall heat transfer and film cooling on both a flat and a non-axisymmetric contoured endwall. Aerodynamic measurements that have been made prior to the upcoming heat transfer investigation are shown. Periodicity and detailed vane Mach number distributions ranging from 0 to 50% span together with the static pressure distribution on the endwall give detailed information about the aerodynamic behavior and influence of the endwall contouring. The aerodynamic study is backed by an oil paint study, which reveals qualitative information on the effect of the contouring on the endwall flow field. Results show that the contouring has a pronounced effect on vane and endwall pressure distribution and on the endwall flow field. The local increase and decrease of velocity and the reduced blade loading towards the endwall is the expected behavior of the 3d contouring. So are the results of the oil paint visualization, which show a strong change of flow field in the leading edge region as well as that the contouring delays the horse shoe vortex hitting the suction side.

Heat and Mass Transfer on the Unsteady Magnetohydrodynamic Flow Due to a Porous Rotating Disk Subject to a Uniform Outer Radial Flow

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
Mustafa Turkyilmazoglu
Keyword(s):  
Heat Transfer ◽  
Radial Flow ◽  
Magnetic Interaction ◽  
Rotating Disk ◽  
Transient Behavior ◽  
Temperature Fields ◽  
Shear Stresses ◽  
Surface Shear ◽  
Entire Family ◽  
Integration Algorithm

An unsteady flow and heat transfer of an incompressible electrically conducting fluid over a porous rotating infinite disk impulsively set into motion are studied in the present paper. The disk finds itself subjected to a uniform normal magnetic field. The particular interest lies in searching for the effects of an imposed uniform outer radial flow far above the disk on the behavior of the physical flow. The governing Navier–Stokes and Maxwell equations of the hydromagnetic fluid, together with the energy equation, are converted into self-similar forms using suitable similarity transformations. A compact, unconditionally stable, and highly accurate implicit spectral numerical integration algorithm is then employed in order to resolve the transient behavior of the velocity and temperature fields. The time evolution and steady state case of some parameters of fundamental physical significance such as the surface shear stresses in the radial and tangential directions and the heat transfer rate are also fully examined for the entire family of magnetic interaction, radial flow, and suction/blowing parameters.

Influence of Fluid Dynamics on Heat Transfer in a Preswirl Rotating-Disk System

2004 ◽  
Vol 127 (4) ◽  
pp. 791-797 ◽  
Author(s):  
Gary D. Lock ◽  
Michael Wilson ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Gas Turbines ◽  
Fluid Dynamic ◽  
Rotating Disk ◽  
Impinging Jets ◽  
Coolant Flow ◽  
Viscous Effects ◽  
Scaled Model ◽  
Flow Rates

Modern gas turbines are cooled using air diverted from the compressor. In a “direct-transfer” preswirl system, this cooling air flows axially across the wheel space from stationary preswirl nozzles to receiver holes located in the rotating turbine disk. The distribution of the local Nusselt number Nu on the rotating disk is governed by three nondimensional fluid-dynamic parameters: preswirl ratio βp, rotational Reynolds number Reϕ, and turbulent flow parameter λT. This paper describes heat transfer measurements obtained from a scaled model of a gas turbine rotor-stator cavity, where the flow structure is representative of that found in the engine. The experiments reveal that Nu on the rotating disk is axisymmetric except in the region of the receiver holes, where significant two-dimensional variations have been measured. At the higher coolant flow rates studied, there is a peak in heat transfer at the radius of the preswirl nozzles associated with the impinging jets from the preswirl nozzles. At lower coolant flow rates, the heat transfer is dominated by viscous effects. The Nusselt number is observed to increase as either Reϕ or λT increases.

An Experimental Study of Mist/Air Film Cooling on a Flat Plate With Application to Gas Turbine Airfoils: Part 1 — Heat Transfer

2013 ◽  
Author(s):  
Lei Zhao ◽  
Ting Wang
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Gas Turbines ◽  
Thermal Stresses ◽  
Test Facility ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Blowing Ratio ◽  
Turbine Airfoils ◽  
Air Film

Film cooling is a cooling technique widely used in high-performance gas turbines to protect the turbine airfoils from being damaged by hot flue gases. Motivated by the need to further improve film cooling in terms of both cooling effectiveness and coolant coverage area, the mist/air film cooling scheme is investigated through experiments in this study. A small amount of tiny water droplets (7% wt.) with an average diameter about 5 μm (mist) is injected into the cooling air to enhance the cooling performance. A wind tunnel system and test facility is specifically built for this unique experiment. A Phase Doppler Particle Analyzer (PDPA) system is employed to measure droplet size, velocity, and turbulence information. An infrared camera and thermocouples are both used for temperature measurements. Part 1 is focused on the heat transfer result on the wall and Part 2 is focused on the two-phase droplet multiphase flow behavior. Mist film cooling performance is evaluated and compared against air-only film cooling in terms of adiabatic film cooling effectiveness and film coverage. A row of five circular cylinder holes is used, injecting at an inclination angle of 30° into the main flow. For the 0.6 blowing ratio cases, it is found that adding mist performs as wonderfully as we mindfully sought: the net enhancement reaches a maximum 190% locally and 128% overall at the centerline, the cooling coverage increases by 83%, and more uniform surface temperature is achieved. The latter is critical for reducing wall thermal stresses. When the blowing ratio increases from 0.6 to 1.4, both the cooling coverage and net enhancement are reduced to below 60%. Therefore, it is more beneficial to choose a relatively low blowing ratio to keep the coolant film attached to the surface when applying the mist cooling. The concept of Film Decay Length (FDL) is introduced and proven to be a useful guideline to quantitatively evaluate the effective cooling coverage and cooling decay rate.

Numerical Characterization of Flow and Heat Transfer in Preswirl Systems

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Riccardo Da Soghe ◽  
Cosimo Bianchini ◽  
Jacopo D'Errico
Keyword(s):  
Heat Transfer ◽  
Gas Turbines ◽  
Turbulence Modeling ◽  
Numerical Study ◽  
Physical Phenomenon ◽  
Rotating Disk ◽  
Computational Procedure ◽  
Eddy Simulation ◽  
Static Pressure Distribution

This paper deals with a numerical study aimed at the validation of a computational procedure for the aerothermal characterization of preswirl systems employed in axial gas turbines. The numerical campaign focused on an experimental facility which models the flow field inside a direct-flow preswirl system. Steady and unsteady simulation techniques were adopted in conjunction with both a standard two-equation Reynolds-averaged Navier–Stokes (RANS)/unsteady RANS (URANS) modeling and more advanced approaches such as the scale-adaptive-simulation (SAS) principle, the stress-blended eddy simulation (SBES), and large eddy simulation (LES). Overall, the steady-state computational fluid dynamics (CFD) predictions are in reasonable good agreement with the experimental evidences even though they are not able to confidently mimic the experimental swirl and pressure behavior in some regions. Scale-resolved approaches improve the computations accuracy significantly especially in terms of static pressure distribution and heat transfer on the rotating disk. Although the use of direct turbulence modeling would in principle increase the insight in the physical phenomenon, from a design perspective, the trade-off between accuracy and computational costs is not always favorable.

Development of an Experimental Test Facility for Investigating Mist/Air Film Cooling Application in Gas Turbine Airfoils

2013 ◽  
Author(s):  
Ting Wang ◽  
Lei Zhao
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Gas Turbines ◽  
High Performance ◽  
Average Diameter ◽  
Test Facility ◽  
Two Phase ◽  
Cooling Performance ◽  
Turbine Airfoils ◽  
Air Film

Film cooling is a cooling technique widely used in high-performance gas turbines to protect the turbine airfoils from being damaged by hot flue gases. Motivated by the need to further improve the turbine hot section cooling performance, a new cooling scheme, mist/air film cooling is investigated. A small amount of tiny water droplets with an average diameter about 7 μm (mist) is injected into the cooling air to enhance the cooling performance. One key feature in understanding mist cooling is the ability to capture droplet information. This paper presents the experimental facility and instrumentation of a mist/air film cooling study with both heat transfer and droplet measurements. A wind tunnel system and test facilities are built. A Phase Doppler Particle Analyzer (PDPA) system is employed to measure the two-phase flow characteristics, including droplet size, droplet dynamics, velocity, and turbulence. Infrared camera and thermocouples are both used for temperature measurements. An extensive uncertainty analysis is performed to assist in identifying large uncertainty sources and planning for experimental procedure. It was found during the experiment design process that resolving the mist agglomeration problem is the key in successfully generating a well-controlled mist/air mixture and reducing experimental uncertainties. The test apparatus has proven to serve the purpose well to investigate mist/air film cooling with both heat transfer and droplet measurements. Selected experimental data is presented.

Heat Transfer Measurements Using Liquid Crystals in a Preswirl Rotating-Disk System

2005 ◽  
Vol 127 (2) ◽  
pp. 375-382 ◽  
Author(s):  
Gary D. Lock ◽  
Youyou Yan ◽  
Paul J. Newton ◽  
Michael Wilson ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Gas Turbines ◽  
Fluid Dynamic ◽  
Turbine Blades ◽  
Rotating Disk ◽  
Impinging Jets ◽  
Viscous Effects ◽  
Scaled Model ◽  
Flow Rates

Preswirl nozzles are often used in gas turbines to deliver the cooling air to the turbine blades through receiver holes in a rotating disk. The distribution of the local Nusselt number, Nu, on the rotating disk is governed by three nondimensional fluid-dynamic parameters: preswirl ratio, βp, rotational Reynolds number, Reϕ, and turbulent flow parameter, λT. A scaled model of a gas turbine rotor–stator cavity, based on the geometry of current engine designs, has been used to create appropriate flow conditions. This paper describes how a thermochromic liquid crystal, in conjunction with a stroboscopic light and digital camera, is used in a transient experiment to obtain contour maps of Nu on the rotating disk. The thermal boundary conditions for the transient technique are such that an exponential-series solution to Fourier’s one-dimensional conduction equation is necessary. A method to assess the uncertainty in the measurements is discussed and these uncertainties are quantified. The experiments reveal that Nu on the rotating disk is axisymmetric except in the region of the receiver holes, where significant two-dimensional variations have been measured. At the higher coolant flow rates studied, there is a peak in heat transfer at the radius of the preswirl nozzles. The heat transfer is governed by two flow regimes: one dominated by inertial effects associated with the impinging jets from the preswirl nozzles, and another dominated by viscous effects at lower flow rates. The Nusselt number is observed to increase as either Reϕ or λT increases.

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