Influence of 3D Hot Streaks on Turbine Heat Transfer

1997 ◽  
Author(s):  
Karen L. Gundy-Burlet ◽  
Daniel J. Dorney
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Navier Stokes ◽  
Adiabatic Flow ◽  
Turbine Cooling ◽  
Aerodynamic Pressure ◽  
Hot Streak

Experimental data have shown that combustor temperature non-uniformities can lead to pressure side burning on first-stage turbine rotor blades. Although most modern turbines operate in an environment with significant heat transfer, the majority of hot streak experiments and simulations during the last decade have assumed adiabatic flow. This assumption can cause errors in the prediction of turbine cooling requirements. In the present investigation, three-dimensional unsteady Navier-Stokes simulations have been performed for a 1-1/2 stage high-pressure turbine geometry operating in subsonic flow. Combustor hot streaks and heat transfer effects at the airfoil surfaces were included in the simulations. The predicted aerodynamic (pressure) data shows close agreement with the available experimental data. The predicted heat flux results agree with experimental observations.

Effects of Tip Clearance on Hot Streak Migration in a High-Subsonic Single-Stage Turbine

2000 ◽  
Author(s):  
Daniel J. Dorney ◽  
Douglas L. Sondak
Keyword(s):  
Experimental Data ◽  
Three Dimensional ◽  
Single Stage ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Radial Spreading ◽  
Rotor Surface ◽  
Hot Streak ◽  
Turbine Airfoils

Experimental data have shown that combustor temperature non-uniformities can lead to the excessive heating of first-stage rotor blades in turbines. This heating of the rotor blades can lead to thermal fatigue and degrade turbine performance. The results of recent studies have shown that variations in the circumferential location, or clocking, of the first-stage vane airfoils can be used to minimize the adverse effects of the hot streaks due to the hot fluid mixing with the cooler fluid contained in the vane wake. In addition, the effects of the hot streak/airfoil count ratio on the heating patterns of turbine airfoils have been quantified. In the present investigation, three-dimensional unsteady Navier-Stokes simulations have been performed for a single-stage high-pressure turbine geometry operating in high subsonic flow to study the effects of tip clearance on hot streak migration. Baseline simulations were initially performed without hot streaks to compare with the experimental data. Two simulations were then performed with a superimposed combustor hot streak; in the first the tip clearance was set at the experimental value, while in the second the rotor was allowed to scrape along the outer case (i.e., the limit as the tip clearance goes to zero). The predicted results for the baseline simulations show good agreement with the available experimental data. The simulations with the hot streak indicate that the tip clearance increases the radial spreading of the hot fluid, and increases the integrated rotor surface temperature compared to the case without tip clearance.

scholarly journals Effects of Hot Streak Shape on Rotor Heating in a High-Subsonic Single-Stage Turbine

2000 ◽  
Author(s):  
Daniel J. Dorney ◽  
Karen L. Gundy-Burlet
Keyword(s):  
Experimental Data ◽  
Surface Area ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Single Stage ◽  
Rotor Blades ◽  
Navier Stokes ◽  
Strong Function ◽  
Hot Streak ◽  
Turbine Airfoils

Experimental data have shown that combustor temperature non-uniformities can lead to the excessive heating of first-stage rotor blades in turbines. This heating of the rotor blades can lead to thermal fatigue and degrade turbine performance. The results of recent studies have shown that variations in the circumferential location (clocking) of the hot streak relative to the first-stage vane airfoils can be used to minimize the adverse effects of the hot streak. The effects of the hot streak/airfoil count ratio on the heating patterns of turbine airfoils have also been evaluated. In the present investigation, three-dimensional unsteady Navier-Stokes simulations have been performed for a single-stage high-pressure turbine operating in high subsonic flow. In addition to a simulation of the baseline turbine, simulations have been performed for circular and elliptical hot streaks of varying sizes in an effort to represent different combustor designs. The predicted results for the baseline simulation show good agreement with the available experimental data. The results of the hot streak simulations indicate: that a) elliptical hot streaks mix more rapidly than circular hot streaks, b) for small hot streak surface area the average rotor temperature is not a strong function of hot streak temperature ratio or shape, and c) hot streaks with larger surface area interact with the secondary flows at the rotor hub endwall, generating an additional high temperature region.

Effects of Tip Clearance on Hot Streak Migration in a High-Subsonic Single-Stage Turbine

2000 ◽  
Vol 122 (4) ◽  
pp. 613-620 ◽  
Author(s):  
Daniel J. Dorney ◽  
Douglas L. Sondak
Keyword(s):  
Experimental Data ◽  
Three Dimensional ◽  
Single Stage ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Radial Spreading ◽  
Rotor Surface ◽  
Hot Streak ◽  
Turbine Airfoils

Experimental data have shown that combustor temperature nonuniformities can lead to the excessive heating of first-stage rotor blades in turbines. This heating of the rotor blades can lead to thermal fatigue and degrade turbine performance. The results of recent studies have shown that variations in the circumferential location, or clocking, of the first-stage vane airfoils can be used to minimize the adverse effects of the hot streaks due to the hot fluid mixing with the cooler fluid contained in the vane wake. In addition, the effects of the hot streak/airfoil count ratio on the heating patterns of turbine airfoils have been quantified. In the present investigation, three-dimensional unsteady Navier–Stokes simulations have been performed for a single-stage high-pressure turbine geometry operating in high subsonic flow to study the effects of tip clearance on hot streak migration. Baseline simulations were initially performed without hot streaks to compare with the experimental data. Two simulations were then performed with a superimposed combustor hot streak; in the first the tip clearance was set at the experimental value, while in the second the rotor was allowed to scrape along the outer case (i.e., the limit as the tip clearance goes to zero). The predicted results for the baseline simulations show good agreement with the available experimental data. The simulations with the hot streak indicate that the tip clearance increases the radial spreading of the hot fluid, and increases the integrated rotor surface temperature compared to the case without tip clearance. [S0889-504X(00)02204-2]

Study of Hot Streak Phenomena in Subsonic and Transonic Flows

1996 ◽  
Author(s):  
Daniel J. Dorney ◽  
Douglas L. Sondak
Keyword(s):  
Shock Waves ◽  
Hot Spots ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Navier Stokes ◽  
Trailing Edge ◽  
Flow Speeds ◽  
Hot Streak ◽  
Turbine Design

Experimental data have shown that combustor hot streaks can lead to pressure side “hot spots” on first-stage turbine rotor blades. Although many modern turbines operate at high subsonic or transonic flow speeds, the majority of bot streak experiments and numerical simulations performed during the last decade have been for low-speed flows. The presence of shock waves in a turbine stage can significantly affect the surface temperature distributions, and a knowledge of the interaction between shock waves and combustor hot streaks may help in the turbine design process. In the present investigation, quasi-three-dimensional unsteady Navier-Stokes simulations have been performed for a high-pressure turbine operating at two vane settings. At the open-vane setting, the flow is predominantly high subsonic with no trailing-edge shock waves, and at the closed-vane setting there are trailing-edge shocks.

Measurements and Predictions of Heat Transfer on Rotor Blades in a Transonic Turbine Cascade

2004 ◽  
Vol 126 (1) ◽  
pp. 110-121 ◽  
Author(s):  
Paul W. Giel ◽  
Robert J. Boyle ◽  
Ronald S. Bunker
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Thin Foil ◽  
Reynolds Numbers ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Maximum Point ◽  
Stagnation Region ◽  
Design Point ◽  
Laminar To Turbulent Transition

Detailed heat transfer measurements and predictions are given for a power generation turbine rotor with 127 deg of nominal turning and an axial chord of 130 mm. Data were obtained for a set of four exit Reynolds numbers comprised of the facility maximum point of 2.50×106, as well as conditions which represent 50%, 25%, and 15% of this maximum condition. Three ideal exit pressure ratios were examined including the design point of 1.443, as well as conditions which represent −25% and +20% of the design value. Three inlet flow angles were examined including the design point and ±5deg off-design angles. Measurements were made in a linear cascade with highly three-dimensional blade passage flows that resulted from the high flow turning and thick inlet boundary layers. Inlet turbulence was generated with a blown square bar grid. The purpose of the work is the extension of three-dimensional predictive modeling capability for airfoil external heat transfer to engine specific conditions including blade shape, Reynolds numbers, and Mach numbers. Data were obtained by a steady-state technique using a thin-foil heater wrapped around a low thermal conductivity blade. Surface temperatures were measured using calibrated liquid crystals. The results show the effects of strong secondary vortical flows, laminar-to-turbulent transition, and also show good detail in the stagnation region.

scholarly journals Compressible, Turbulent, Viscous Flow Computations for Blade Aerodynamic and Heat Transfer

1996 ◽  
Author(s):  
A. A. Boretti
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Reynolds Number ◽  
Partial Differential Equations ◽  
Differential Equations ◽  
Viscous Flow ◽  
Three Dimensional ◽  
Time Dependent ◽  
Navier Stokes ◽  
Partial Differential

The paper presents a computer code for steady and unsteady, three-dimensional, compressible, turbulent, viscous flow simulations. The mathematical model is based on the Favre-averaged Navier-Stokes conservation equations, closed by a statistical model of turbulence. Turbulence effects are represented by using a low Reynolds number K-ω model. The numerical model makes use of a finite difference approximation in generalized coordinates for space discretization. The solution of time-dependent, three-dimensional, non-homogeneous, partial differential equations is obtained by solving, in a prescribed, symmetric pattern, three time-dependent, one-dimensional, homogeneous partial differential equations, representing convection and diffusion along each generalized coordinate direction, and one ordinary differential equation, representing generation and destruction. An explicit, multi-step, dissipative, Runge-Kutta scheme is finally adopted for time discretization. The code is applied to simulate the flow through a linear cascade of turbine rotor blades, where detailed experimental data are available. Blade aerodynamic and heat transfer are computed, at variable Reynolds and Mach numbers and turbulence levels, and compared with experimental data. While the aerodynamic prediction is relatively unaffected by the properties of both mathematical and numerical models, the heat transfer prediction proves to be extremely sensitive to models details. Low Reynolds number K-ω turbulence models theoretically reproduce laminar, turbulent and transitional boundary layers. However, their practical use in a Navier-Stokes code does not allow to entirely capture the effects of turbulence intensity and Mach and Reynolds numbers on blade heat transfer.

Heat Transfer in Film-Cooled Turbine Blades

1993 ◽  
Author(s):  
Vijay K. Garg ◽  
Raymond E. Gaugler
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Film Cooling ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Explicit Finite Difference ◽  
Control Volumes

In order to study the effect of film cooling on the flow and heat transfer characteristics of actual turbine blades, a three-dimensional Navier-Stokes code has been developed. An existing code (Chima and Yokota, 1990) has been modified for the purpose. The code is an explicit finite difference code with an algebraic turbulence model. The thin-layer Navier-Stokes equations are solved using a general body-fitted coordinate system. The effects of film cooling have been incorporated into the code in the form of appropriate boundary conditions at the hole locations on the blade surface. Each hole exit is represented by several control volumes, thus providing an ability to study the effect of hole shape on the film-cooling characteristics. Comparison with experimental data is fair. Further validation of the code is required, however, and in this respect, there is an urgent need for detailed experimental data on actual turbine blades.

Influence of Hot Streak/Airfoil Count Ratios on High Pressure Stage of a Vaneless Counter-Rotating Turbine

2008 ◽  
Author(s):  
Qingjun Zhao ◽  
Huishe Wang ◽  
Fei Tang ◽  
Xiaolu Zhao ◽  
Jianzhong Xu
Keyword(s):  
High Pressure ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Peak Temperature ◽  
Combined Effects ◽  
High Pressure Turbine ◽  
Flow Angle ◽  
Count Ratio ◽  
Hot Streak

In order to reveal the effects of the hot streak/airfoil count ratio on the heating patterns of high pressure turbine rotor blades in a Vaneless Counter-Rotating Turbine, three-dimensional unsteady Navier-Stokes simulations have been performed. In these simulations, the ratio of the number of hot streaks to the number of the high pressure turbine vanes and rotors is 1:3:3, 1:2:2, 2:3:3 and 1:1:1, respectively. The numerical results show that the migration characteristics of the hot streak in the high pressure turbine rotor are predominated by the combined effects of secondary flow and buoyancy. The combined effects induce the high temperature fluid migrate towards the hub in the high pressure turbine rotor. And the combined effects become more intensified when the hot streak/airfoil count ratio increases. The results also indicate that the peak temperature of the hot streak is dissipated as the hot streak goes through the high pressure turbine vane or the rotor. The dissipated extent of the peak temperature in the high pressure turbine stator and the rotor is increased as the hot streak-to-airfoil ratio increases. And the increase of the hot streak/airfoil count ratio trends to increase the relative Mach number at the high pressure turbine outlet. The relative flow angle from 23% to 73% span at the high pressure turbine outlet decreases as the hot streak-to-airfoil ratio increases. The results also indicate that the isentropic efficiency of the Vaneless Counter-Rotating Turbine is decreased as the hot streak/airfoil count ratio increases.

Transition Modeling Effects on Turbine Rotor Blade Heat Transfer Predictions

1996 ◽  
Vol 118 (2) ◽  
pp. 307-313 ◽  
Author(s):  
A. A. Ameri ◽  
A. Arnone
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Turbine Rotor ◽  
Algebraic Model ◽  
Navier Stokes ◽  
Turbine Rotor Blade ◽  
Transition Length ◽  
Transition Modeling

The effect of transition modeling on the heat transfer predictions from rotating turbine blades was investigated. Three-dimensional computations using a Reynolds-averaged Navier–Stokes code were performed. The code utilized the Baldwin–Lomax algebraic turbulence model, which was supplemented with a simple algebraic model for transition. The heat transfer results obtained on the blade surface and the hub endwall were compared with experimental data for two Reynolds numbers and their corresponding rotational speeds. The prediction of heat transfer on the blade surfaces was found to improve with the inclusion of the transition length model and wake-induced transition effects over the simple abrupt transition model.

Effects of 3-D Local Unsteadiness on Heat Transfer Prediction in Turbulated Passages

2003 ◽  
Author(s):  
Pamela A. McDowell ◽  
William D. York ◽  
D. Keith Walters ◽  
James H. Leylek
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Turbulence Model ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Successful Outcome ◽  
Small Scale ◽  
Cross Sectional ◽  
Fully Implicit

A newly developed unsteady turbulence model was used to predict heat transfer in a turbulated passage typical of turbine airfoil cooling applications. Comparison of fullyconverged computational solutions to experimental measurements reveal that accurate prediction of heat transfer coefficient requires the effects of local small-scale unsteadiness to be captured. Validation was accomplished through comparison of the time- and area-averaged Nusselt number on the passage wall between adjacent ribs with experimental data from the open literature. The straight channel had a square cross-sectional area with multiple rows of staggered and rounded-edge ribs on opposite walls that were orthogonal to the flow. Simulations were run for Reynolds numbers of 5500, 16500, and 25000. Computational solutions were obtained on a multi-block, multi-topology, unstructured, and adaptive grid, using a pressure-correction based, fully-implicit Navier-Stokes solver. The computational results include two-dimensional (2-D) and three-dimensional (3-D) steady and unsteady simulations with viscous sublayers resolved (y+ ≤ 1) on all the walls in every case. Turbulence closure was obtained using a new turbulence model developed in-house for the unsteady simulations, and a realizable k-ε turbulence model was used for the steady simulations. The results obtained from the unsteady simulations show greatly improved agreement with the experimental data, especially at realistically high Reynolds numbers. The key 3-D physics mechanisms responsible for the successful outcome include: (1) shear layer roll-up over the turbulators; (2) recirculation zones both upstream and downstream of the rib faces; and (3) reattachment regions between each rib pair. Results from the unsteady case are superior to those of the steady because they capture the aforementioned mechanisms, and therefore more accurately predict the heat transfer.

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