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.

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.

Hot Streak Clocking Effects in a 1-1/2 Stage Turbine

1995 ◽  
Author(s):  
Daniel J. Dorney ◽  
Karen Gundy-Burlet
Keyword(s):  
Hot Spots ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Navier Stokes ◽  
Pressure Side ◽  
Pressure Surface ◽  
Second Stage ◽  
Numerical Studies ◽  
Temperature Distributions ◽  
Hot Streak

Experimental data has shown that combustor hot streaks can lead to pressure side “hot spots” on first-stage turbine rotor blades. Previous numerical studies have confirmed that unsteady Navier-Stokes procedures can be used to predict the rotor pressure surface temperature increase associated with these combustor hot streaks, and suggest that second-stage turbine stators can also be subjected to increased surface temperatures. In the current investigation, two-dimensional unsteady Navier-Stokes simulations have been performed to study the effects of combustor hot streak position (or clocking) on the temperature distributions along first-stage rotor and second-stage stator airfoils. The predicted results indicate that if the hot streak is positioned such that it impinges upon the first-stage stator, then the suction surfaces of the rotor and second-stage stator attain higher time-averaged temperatures than the pressure surfaces. If the hot streak is positioned such that it does not impinge upon the first-stage stator, then the pressure surfaces of the downstream blades reach higher time-averaged temperatures than the corresponding suction surfaces.

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.

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.

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.

Analysis of Hot Streak Effects on Turbine Rotor Heat Load

1997 ◽  
Vol 119 (3) ◽  
pp. 544-553 ◽  
Author(s):  
T. Shang ◽  
A. H. Epstein
Keyword(s):  
Heat Load ◽  
Three Dimensional ◽  
Axial Flow ◽  
Turbine Rotor ◽  
Inlet Temperature ◽  
Pressure Surface ◽  
Physical Mechanisms ◽  
Design Variables ◽  
Hot Streak ◽  
Turbine Design

The influence of inlet hot streak temperature distortion on turbine blade heat load was explored on a transonic axial flow turbine stage test article using a three-dimensional, multiblade row unsteady Euler code. The turbine geometry was the same as that used for a recently reported testing of hot streak influence. Emphasis was placed on elucidating the physical mechanisms by which hot streaks affect turbine durability. It was found that temperature distortion significantly increases both blade surface heat load nonuniformity and total blade heat load by as much as 10–30 percent (mainly on the pressure surface), and that the severity of this influence is a strong function of turbine geometry and flow conditions. Three physical mechanisms were identified that drive the heat load nonuniformity: buoyancy, wake convection (the Kerrebrock–Mikolajczak effect), and Rotor–Stator interactions. The latter can generate significant nonuniformity of the time-averaged relative frame rotor inlet temperature distribution. Dependence of these effects on turbine design variables was investigated to shed light on the design space, which minimizes the adverse effects of hot streaks.

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]

Analysis of Hot Streak Effects on Turbine Rotor Heat Load

1996 ◽  
Author(s):  
Tonghuo Shang ◽  
Alan H. Epstein
Keyword(s):  
Heat Load ◽  
Three Dimensional ◽  
Axial Flow ◽  
Turbine Rotor ◽  
Inlet Temperature ◽  
Pressure Surface ◽  
Physical Mechanisms ◽  
Design Variables ◽  
Hot Streak ◽  
Turbine Design

The influence of inlet hot streak temperature distortion on turbine blade heat load was explored on a transonic axial flow turbine stage test article using a three-dimensional, multi-blade row unsteady Euler code. The turbine geometry was the same as that used for a recently reported testing of hot streak influence. Emphasis was placed elucidating the physical mechanisms by which hot streaks affect turbine durability. It was found that temperature distortion significantly increases both blade surface heat load nonuniformity and total blade heat load by as much as 10–30% (mainly on the pressure surface), and that the severity of this influence is a strong function of turbine geometry and flow conditions. Three physical mechanisms were identified which drive the heat load nonuniformity — buoyancy, wake convection (the Kerrebrock-Mikolajczak effect), and rotor-stator interactions. The latter can generate significant nonuniformity of the time-averaged relative frame rotor inlet temperature distribution. Dependence of these effects on turbine design variables was investigated to shed light on the design space which minimizes the adverse effects of hot streaks.

Aerothermal Investigation of a Rib-Roughened Trailing Edge Channel With Crossing-Jets—Part I: Flow Field Analysis

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Alessandro Armellini ◽  
Filippo Coletti ◽  
Tony Arts ◽  
Christophe Scholtes
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Side Wall ◽  
Field Analysis ◽  
Navier Stokes ◽  
Trailing Edge ◽  
Present Contribution ◽  
Cross Sectional ◽  
Numerical Predictions ◽  
Rib Roughened

The present contribution addresses the aerothermal, experimental, and computational studies of a trapezoidal cross-sectional model simulating a trailing edge cooling cavity with one rib-roughened wall. The flow is fed through tilted slots on one side wall and exits through straight slots on the opposite side wall. The flow field aerodynamics is investigated in Part I of the paper. The reference Reynolds number is defined at the entrance of the test section and set at 67,500 for all the experiments. A qualitative flow model is deduced from surface-streamline flow visualizations. Two-dimensional particle image velocimetry measurements are performed in several planes around midspan of the channel and recombined to visualize and quantify three-dimensional flow features. The crossing-jets issued from the tilted slots are characterized and the jet-rib interaction is analyzed. Attention is drawn to the motion of the flow deflected by the rib-roughened wall and impinging on the opposite smooth wall. The experimental results are compared with the numerical predictions obtained from the finite volume Reynolds-averaged Navier–Stokes solver, CEDRE.

Three-Dimensional Navier-Stokes Analysis of Turbine Rotor and Tip-Leakage Flowfield

1997 ◽  
Author(s):  
J. Luo ◽  
B. Lakshminarayana
Keyword(s):  
Three Dimensional ◽  
Turbine Rotor ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Mean Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Blade Tip

The 3-D viscous flowfield in the rotor passage of a single-stage turbine, including the tip-leakage flow, is computed using a Navier-Stokes procedure. A grid-generation code has been developed to obtain embedded H grids inside the rotor tip gap. The blade tip geometry is accurately modeled without any “pinching”. Chien’s low-Reynolds-number k-ε model is employed for turbulence closure. Both the mean-flow and turbulence transport equations are integrated in time using a four-stage Runge-Kutta scheme. The computational results for the entire turbine rotor flow, particularly the tip-leakage flow and the secondary flows, are interpreted and compared with available data. The predictions for major features of the flowfield are found to be in good agreement with the data. Complicated interactions between the tip-clearance flows and the secondary flows are examined in detail. The effects of endwall rotation on the development and interaction of secondary and tip-leakage vortices are also analyzed.

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