An Application of 3-D Viscous Flow Analysis to the Design of a Low-Aspect-Ratio Turbine

1979 ◽  
Author(s):  
H. C. Liu ◽  
T. C. Booth ◽  
W. A. Tall
Keyword(s):  
Aspect Ratio ◽  
Viscous Flow ◽  
Flow Analysis ◽  
Optimization Procedure ◽  
Tip Clearance ◽  
Specific Work ◽  
Turbine Stage ◽  
Gas Generator ◽  
Low Aspect Ratio

Previously reported cascade test results verified and provided a calibration of the 3-D viscous flow analysis. This paper describes the subsequent AFAPL-sponsored technology program in which the 3-D viscous flow computer program was used to optimize the low-aspect-ratio stator of a high-work turbine stage. The optimization procedure, in conjunction with the radial distribution of energy extraction, led to innovative-but-realistic blading for advanced gas generator turbines. A turbine stage was tested with this stator, in conjunction with an appropriate rotor design. The total-to-total design-point efficiency — 92 percent at 1-percent tip clearance — was achieved at 31.83 Btu/lbm specific work. In addition to stage tests, separate stator tests were conducted including a measurement of total pressure loss and stator reaction torque, which provided baseline data to assess interaction effects during stage testing with stator reaction measurements “in vivo.”

Aerodynamic Effects of an Unshrouded Low Pressure Turbine on a Low Aspect Ratio Exit Guide Vane

2012 ◽  
Author(s):  
Thorsten Selic ◽  
Davide Lengani ◽  
Andreas Marn ◽  
Franz Heitmeir
Keyword(s):  
Aspect Ratio ◽  
Guide Vane ◽  
Low Pressure ◽  
Tip Clearance ◽  
Pressure Probe ◽  
Model Parameters ◽  
Leakage Flow ◽  
Low Pressure Turbine ◽  
Low Aspect Ratio ◽  
The Impact

This paper presents the effects of an unshrouded low pressure turbine (LPT) onto the following exit guide vane row (EGV). The measurement results were obtained in the subsonic test turbine facility at Graz University of Technology by means of a fast response pressure probe in planes downstream of the rotor as well as oil flow visualisation. The test rig was designed in cooperation with MTU Aero Engines and represents the last 1.5 stages of a commercial aero engine. Considerable efforts were put into the adjustment of all relevant model parameters to reproduce the full scale LPT situation. Different tip clearances were evaluated by means of CFD obtained using a commercial Navier-Stokes code and validated with experimental results. The goal is to evaluate the effect of the varying leakage flow on the flow in the low aspect ratio EGV. Special attention is given to the impact on the development of secondary flows as well as the flow structures downstream of the EGV. The effect of the leakage flow causes a change of the flow structure of the EGV, particularly losses. Considering the largest investigated tip-clearance, the losses increased by 71% when compared to a zero-leakage case.

Influence of Blade Sweep on the Energetic Behavior of Axial Flow Turbomachinery Rotors at Design Flow Rate

2004 ◽  
Author(s):  
Ja´nos Vad ◽  
Ali R. A. Kwedikha ◽  
Helmut Jaberg
Keyword(s):  
Aspect Ratio ◽  
Flow Rate ◽  
Axial Flow ◽  
Pressure Rise ◽  
Design Flow ◽  
Tip Clearance ◽  
Total Efficiency ◽  
Low Aspect Ratio ◽  
Axial Velocity Profile ◽  
Bladed Rotor

Experimental and computational studies were carried out in order to survey the energetic aspects of forward and backward sweep in axial flow rotors of low aspect ratio blading for incompressible flow. It has been pointed out that negative sweep tends to increase the lift, the flow rate and the ideal total pressure rise in the vicinity of the endwalls. Just the opposite tendency was experienced for positive sweep. The local losses were found to develop according to combined effects of sweep near the endwalls, endwall and tip clearance losses, and profile drag influenced by re-arrangement of the axial velocity profile. The forward-swept bladed rotor showed reduced total efficiency compared to the unswept and swept-back bladed rotors. This behavior has been explained on the basis of analysis of flow details. It has been found that the swept bladings of low aspect ratio tend to retain the performance of the unswept datum rotor even in absence of sweep correction.

scholarly journals Some Results From Tests on a High Work Axial Gas Generator Turbine

1974 ◽  
Author(s):  
U. Okapuu
Keyword(s):  
Aspect Ratio ◽  
Rotor Blade ◽  
Pressure Ratio ◽  
Tip Clearance ◽  
Design Parameters ◽  
Ratio Test ◽  
Test Results ◽  
Gas Generator ◽  
Degree Of Reaction ◽  
Work Distribution

Aerodynamic test results are presented for a single-stage, axial gas generator turbine of 3.9:1 design pressure ratio. Test results are also shown for a number of variants on this design, indicating the effect on aerodynamic performance of degree of reaction, nozzle and rotor aspect ratio, rotor blade channel design, rotor tip clearance, radial work distribution and effect of nozzle endwall contouring. Detailed aerodynamic observations are compared with analytical predictions. Of the design parameters examined, rotor blade aspect ratio, tip clearance and channel diffusion were found to have the greatest influence on losses. Operation at pressure ratios above the design was found to be improved with “open” rotor stagger, yielding a reduced design point degree of reaction.

Unsteady Aerodynamics of a Low Aspect Ratio Turbine Stage: Modeling Issues and Flow Physics

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
G. Persico ◽  
A. Mora ◽  
P. Gaetani ◽  
M. Savini
Keyword(s):  
Aspect Ratio ◽  
Coming Out ◽  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Fast Response ◽  
Operating Conditions ◽  
Pressure Probe ◽  
Turbine Stage ◽  
Time Resolved ◽  
Low Aspect Ratio

In this paper the three-dimensional unsteady aerodynamics of a low aspect ratio, high pressure turbine stage are studied. In particular, the results of fully unsteady three-dimensional numerical simulations, performed with ANSYS-CFX, are critically evaluated against experimental data. Measurements were carried out with a novel three-dimensional fast-response pressure probe in the closed-loop test rig of the Laboratorio di Fluidodinamica delle Macchine of the Politecnico di Milano. An analysis is first reported about the strategy to limit the CPU and memory requirements while performing three-dimensional simulations of blade row interaction when the rotor and stator blade numbers are prime to each other. What emerges as the best choice is to simulate the unsteady behavior of the rotor alone by applying the stator outlet flow field as a rotating inlet boundary condition (scaled on the rotor blade pitch). Thanks to the reliability of the numerical model, a detailed analysis of the physical mechanisms acting inside the rotor channel is performed. Two operating conditions at different vane incidence are considered, in a configuration where the effects of the vortex-blade interaction are highlighted. Different vane incidence angles lead to different size, position, and strength of secondary vortices coming out from the stator, thus promoting different interaction processes in the subsequent rotor channel. However some general trends can be recognized in the vortex-blade interaction: the sense of rotation and the spanwise position of the incoming vortices play a crucial role on the dynamics of the rotor vortices, determining both the time-mean and the time-resolved characteristics of the secondary field at the exit of the stage.

Unsteady Transonic Flow Analysis for Low Aspect Ratio, Pointed Wings

AIAA Journal ◽  
1974 ◽  
Vol 12 (4) ◽  
pp. 516-522 ◽  
Author(s):  
K. R. KIMBLE ◽  
D. D. LIU ◽  
S. Y. ROU ◽  
J. M. WU
Keyword(s):  
Aspect Ratio ◽  
Transonic Flow ◽  
Flow Analysis ◽  
Low Aspect Ratio

Experimental and Numerical Study of Stall Flutter in a Transonic Low-Aspect Ratio Fan Blisk

2003 ◽  
Author(s):  
A. J. Sanders ◽  
K. K. Hassan ◽  
D. C. Rabe
Keyword(s):  
Aspect Ratio ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Strain Gages ◽  
Pressure Transducers ◽  
Low Aspect Ratio ◽  
Benchmark Data

Experiments are performed on a modern design transonic shroudless low-aspect ratio fan blisk that experienced both subsonic/transonic and supersonic stall-side flutter. High-response flush mounted miniature pressure transducers are utilized to measure the unsteady aerodynamic loading distribution in the tip region of the fan for both flutter regimes, with strain gages utilized to measure the vibratory response at incipient and deep flutter operating conditions. Numerical simulations are performed and compared with the benchmark data using an unsteady three-dimensional nonlinear viscous computational fluid dynamic (CFD) analysis, with the effects of tip clearance, vibration amplitude, and the number of time steps-per-cycle investigated. The benchmark data are used to guide the validation of the code and establish best practices that ensure accurate flutter predictions.

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