scholarly journals Unsteady Simulation of a Transonic Turbine Stage with Focus on Turbulence Prediction

2021 ◽  
Vol 6 (3) ◽  
pp. 36
Author(s):  
Wolfgang Sanz ◽  
David Scheier
Keyword(s):  
Boundary Conditions ◽  
Secondary Flows ◽  
Correct Prediction ◽  
Turbine Stage ◽  
Free Stream Turbulence ◽  
Eddy Viscosity Model ◽  
Unsteady Simulation ◽  
Unsteady Rans ◽  
Transonic Turbine ◽  
Inlet Conditions

The flow in a transonic turbine stage still poses a high challenge for the correct prediction of turbulence using an eddy viscosity model. Therefore, an unsteady RANS simulation with the k-ω SST model, based on a preceding study of turbulence inlet conditions, was performed to see if this can improve the quality of the flow and turbulence prediction of an experimentally investigated turbine flow. Unsteady Q3D results showed that none of the different turbulence boundary conditions could predict the free-stream turbulence level and the maximum values correctly. Luckily, the influence of the boundary conditions on the velocity field proved to be small. The qualitative prediction of the complex secondary flows is good, but there is lacking agreement in the prediction of turbulence generation and destruction.

scholarly journals Endwall Heat Transfer Measurements in a Transonic Turbine Cascade

1998 ◽  
Vol 120 (2) ◽  
pp. 305-313 ◽  
Author(s):  
P. W. Giel ◽  
D. R. Thurman ◽  
G. J. Van Fossen ◽  
S. A. Hippensteele ◽  
R. J. Boyle
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Turbine Blade ◽  
Large Scale ◽  
Model Verification ◽  
Quality Data ◽  
Free Stream Turbulence ◽  
Transonic Turbine ◽  
Mach Numbers ◽  
Inlet Conditions

Turbine blade endwall heat transfer measurements are presented for a range of Reynolds and Mach numbers. Data were obtained for Reynolds numbers based on inlet conditions of 0.5 and 1.0 × 106, for isentropic exit Mach numbers of 1.0 and 1.3, and for free-stream turbulence intensities of 0.25 and 7.0 percent. Tests were conducted in a linear cascade at the NASA Lewis Transonic Turbine Blade Cascade Facility. The test article was a turbine rotor with 136 deg of turning and an axial chord of 12.7 cm. The large scale allowed for very detailed measurements of both flow field and surface phenomena. The intent of the work is to provide benchmark quality data for CFD code and model verification. The flow field in the cascade is highly three dimensional as a result of thick boundary layers at the test section inlet. Endwall heat transfer data were obtained using a steady-state liquid crystal technique.

Impact of Swirling Entropy Waves on a High Pressure Turbine

2021 ◽  
pp. 1-14
Author(s):  
Andrea Notaristefano ◽  
Paolo Gaetani
Keyword(s):  
Secondary Flows ◽  
Temperature Perturbation ◽  
Turbine Stage ◽  
High Pressure Turbine ◽  
Blade Cooling ◽  
Unsteady Aerodynamic ◽  
Experimental Campaign ◽  
Severe Reduction ◽  
Inlet Conditions ◽  
Noise Production

Abstract The harsh environment exiting modern gas turbine combustion chamber is characterized by vorticity and temperature perturbations, the latter commonly referred as entropy waves. The interaction of these unsteadiness with the first turbine stage causes non-negligible effects on the aerodynamic performance, blade cooling and noise production. The first of these drawbacks is addressed in this paper by means of an experimental campaign: entropy waves and swirl profile are injected upstream of an axial turbine stage through a novel combustor simulator. Two injection positions and different inlet conditions are considered. Steady and unsteady experimental measurements are carried out through the stage to address the combustor-turbine interaction characterizing the injected disturbance, the nozzle and rotor outlet aerothermal field. The experimental outcomes show a severe reduction of the temperature perturbation already at stator outlet. The generated swirl profile influences significantly the aerodynamic, as it interacts with the stator and rotor secondary flows and wakes. Furthermore, the clocking position changes the region most affected by the disturbance, showing a potential modifying the injection position to minimize the entropy wave and swirl profile impact on the stage. Finally, this work shows that in order to proficiently study entropy waves, the unsteady aerodynamic flow field stator downstream has to be addressed.

Impact of Swirling Entropy Waves on a High Pressure Turbine

2021 ◽  
Author(s):  
Andrea Notaristefano ◽  
Paolo Gaetani
Keyword(s):  
Secondary Flows ◽  
Temperature Perturbation ◽  
Turbine Stage ◽  
High Pressure Turbine ◽  
Blade Cooling ◽  
Unsteady Aerodynamic ◽  
Experimental Campaign ◽  
Severe Reduction ◽  
Inlet Conditions ◽  
Noise Production

Abstract The harsh environment exiting modern gas turbine combustion chamber is characterized by vorticity and temperature perturbations, the latter commonly referred as entropy waves. The interaction of these unsteadiness with the first turbine stage causes non-negligible effects on the aerodynamic performance, blade cooling and noise production. The first of these drawbacks is addressed in this paper by means of an experimental campaign: entropy waves and swirl profile are injected upstream of an axial turbine stage through a novel combustor simulator. Two injection positions and different inlet conditions are considered. Steady and unsteady experimental measurements are carried out through the stage to address the combustor-turbine interaction characterizing the injected disturbance, the nozzle and rotor outlet aerothermal field. The experimental outcomes show a severe reduction of the temperature perturbation already at stator outlet. The generated swirl profile influences significantly the aerodynamic, as it interacts with the stator and rotor secondary flows and wakes. Furthermore, the clocking position changes the region most affected by the disturbance, showing a potential modifying the injection position to minimize the entropy wave and swirl profile impact on the stage. Finally, this work shows that in order to proficiently study entropy waves, the unsteady aerodynamic flow field stator downstream has to be addressed.

Secondary Flows and Loss Caused by Blade Row Interaction in a Turbine Stage

2004 ◽  
Vol 128 (3) ◽  
pp. 484-491 ◽  
Author(s):  
Graham Pullan
Keyword(s):  
Three Dimensional ◽  
Passive Scalar ◽  
Secondary Flows ◽  
Turbine Stage ◽  
Vortical Structures ◽  
Unsteady Simulation ◽  
Steady Simulation ◽  
Absolute Frame ◽  
Blade Row Interaction ◽  
Inlet Boundary Condition

A study of the three-dimensional stator-rotor interaction in a turbine stage is presented. Experimental data reveal vortices downstream of the rotor which are stationary in the absolute frame—indicating that they are caused by the stator exit flowfield. Evidence of the rotor hub passage vortices is seen, but additional vortical structures away from the endwalls, which would not be present if the rotor were tested in isolation, are also identified. An unsteady computation of the rotor row is performed using the measured stator exit flowfield as the inlet boundary condition. The strength and location of the vortices at rotor exit are predicted. A formation mechanism is proposed whereby stator wake fluid with steep spanwise gradients of absolute total pressure is responsible for all but one of the rotor exit vortices. This mechanism is then verified computationally using a passive-scalar tracking technique. The predicted loss generation through the rotor row is then presented and a comparison made with a steady calculation where the inlet flow has been mixed out to pitchwise uniformity. The loss produced in the steady simulation, even allowing for the mixing loss at inlet, is 10% less than that produced in the unsteady simulation. This difference highlights the importance of the time-accurate calculation as a tool of the turbomachine designer.

scholarly journals Influence of Vane-Blade Spacing on Transonic Turbine Stage Aerodynamics: Part II — Time-Resolved Data and Analysis

1998 ◽  
Author(s):  
Judy A. Busby ◽  
Roger L. Davis ◽  
Daniel J. Dorney ◽  
Michael G. Dunn ◽  
Charles W. Haldeman ◽  
...  
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Numerical Solutions ◽  
Unsteady Aerodynamics ◽  
Total Pressure Loss ◽  
Turbine Stage ◽  
Airfoil Surface ◽  
Time Resolved ◽  
Transonic Turbine ◽  
Inlet Conditions

This paper presents results of a combined experimental/computational investigation into the effects of vane-blade spacing on the unsteady aerodynamics of a transonic turbine stage. Time-resolved data were taken in a shock-tunnel facility in which the flow was generated with a short-duration source of heated and pressurized air. This data is compared with the results obtained from four unsteady Navier-Stokes solvers. The time-resolved flow for three axial spacings is examined. For each vane-blade spacing, the inlet conditions were nearly identical and the vane exit flow was transonic. Surface-mounted high-response pressure transducers at midspan were used to obtain the pressure measurements. The computed two-dimensional unsteady airfoil surface pressure predictions are compared with the Kulite pressure transducer measurements. The unsteady and axial spacing effects on loading and performance are examined. In general the numerical solutions compared very favorably with each other and with the experimental data. The overall predicted stage losses and efficiencies did not vary much with vane/blade axial spacing. The computations indicated that any increases in the blade relative total pressure loss were offset by a decrease in vane loss as the axial spacing was decreased. The decrease in predicted vane total pressure loss with decreased axial spacing was primarily due to a reduction in the wake mixing losses. The increase in predicted blade relative total pressure loss with a decrease in axial spacing was found to be mainly due to increased vane wake/blade interaction.

Influence of Vane-Blade Spacing on Transonic Turbine Stage Aerodynamics: Part II—Time-Resolved Data and Analysis

1999 ◽  
Vol 121 (4) ◽  
pp. 673-682 ◽  
Author(s):  
J. A. Busby ◽  
R. L. Davis ◽  
D. J. Dorney ◽  
M. G. Dunn ◽  
C. W. Haldeman ◽  
...  
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Numerical Solutions ◽  
Unsteady Aerodynamics ◽  
Total Pressure Loss ◽  
Turbine Stage ◽  
Airfoil Surface ◽  
Time Resolved ◽  
Transonic Turbine ◽  
Inlet Conditions

This paper presents results of a combined experimental/computational investigation into the effects of vane–blade spacing on the unsteady aerodynamics of a transonic turbine stage. Time-resolved data were taken in a shock-tunnel facility in which the flow was generated with a short-duration source of heated and pressurized air. This data is compared with the results obtained from four unsteady Navier–Stokes solvers. The time-resolved flow for three axial spacings is examined. For each vane–blade spacing, the inlet conditions were nearly identical and the vane exit flow was transonic. Surface-mounted high-response pressure transducers at midspan were used to obtain the pressure measurements. The computed two-dimensional unsteady airfoil surface pressure predictions are compared with the Kulite pressure transducer measurements. The unsteady and axial spacing effects on loading and performance are examined. In general the numerical solutions compared very favorably with each other and with the experimental data. The overall predicted stage losses and efficiencies did not vary much with vane/blade axial spacing. The computations indicated that any increases in the blade relative total pressure loss were offset by a decrease in vane loss as the axial spacing was decreased. The decrease in predicted vane total pressure loss with decreased axial spacing was primarily due to a reduction in the wake mixing losses. The increase in predicted blade relative total pressure loss with a decrease in axial spacing was found to be mainly due to increased vane wake/blade interaction.

Numerical and Experimental Analysis of the Effects of Non-Axisymmetric Contoured Stator Endwalls in an Axial Turbine

2010 ◽  
Author(s):  
Thorsten Poehler ◽  
Jochen Gier ◽  
Peter Jeschke
Keyword(s):  
Horseshoe Vortex ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Experimental Investigations ◽  
Time Interval ◽  
Axial Turbine ◽  
Passage Vortex ◽  
Unsteady Rans ◽  
Endwall Contouring ◽  
Inlet Conditions

Numerical and experimental investigations have been performed to determine the effects of non-axisymmetric stator endwall contouring on the efficiency of an axial turbine stage. The influences of the contoured endwalls on the secondary flows in the stator and the rotor have been analyzed by conducting steady and unsteady RANS simulations as well as measurements in the 1.5-stage axial cold air turbine test rig of the Institute of Jet Propulsion and Turbomachinery. Both numerical and experimental results show an aerodynamic improvement of efficiency and secondary kinetic energy through non-axisymmetric endwall contouring. The non-axisymmetric endwall contour induces a vortex, which separates the pressure side leg of the horseshoe vortex from the passage vortex resulting in redistributed and reduced secondary flows. The modified secondary flow pattern increases the torque of the rotor blade in the hub region as a consequence of improved inlet conditions for the rotor as well as a reduction of the time interval the secondary flows are convected through the rotor passage within. Concerning the shroud region the endwall contour had no significant impact on the efficiency as a consequence of a dominating tip clearance vortex system.

Secondary Flows and Loss Caused by Blade Row Interaction in a Turbine Stage

2004 ◽  
Author(s):  
Graham Pullan
Keyword(s):  
Three Dimensional ◽  
Passive Scalar ◽  
Secondary Flows ◽  
Turbine Stage ◽  
Vortical Structures ◽  
Unsteady Simulation ◽  
Steady Simulation ◽  
Absolute Frame ◽  
Blade Row Interaction ◽  
Inlet Boundary Condition

A study of the three-dimensional stator-rotor interaction in a turbine stage is presented. Experimental data reveal vortices downstream of the rotor which are stationary in the absolute frame — indicating that they are caused by the stator exit flowfield. Evidence of the rotor hub passage vortices is seen, but additional vortical structures away from the endwalls, which would not be present if the rotor were tested in isolation, are also identified. An unsteady computation of the rotor row is performed using the measured stator exit flowfield as the inlet boundary condition. The strength and location of the vortices at rotor exit are predicted. A formation mechanism is proposed whereby stator wake fluid with steep spanwise gradients of absolute total pressure is responsible for all but one of the rotor exit vortices. This mechanism is then verified computationally using a passive-scalar tracking technique. The predicted loss generation through the rotor row is then presented and a comparison made with a steady calculation where the inlet flow has been mixed out to pitchwise uniformity. The loss produced in the steady simulation, even allowing for the mixing loss at inlet, is 10% less than that produced in the unsteady simulation. This difference highlights the importance of the time-accurate calculation as a tool of the turbomachine designer.

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