Investigation of Unsteady Aerodynamic Blade Excitation Mechanisms in Transonic Turbine Stages

2002 ◽  
Author(s):  
Bjo¨rn Laumert ◽  
Hans Ma˚rtensson ◽  
Torsten H. Fransson
Keyword(s):  
Rotor Blade ◽  
Three Dimensional ◽  
Relative Strength ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Pressure Perturbation ◽  
Blade Surface ◽  
Excitation Mechanisms ◽  
Transonic Turbine ◽  
Exit Mach Number

This paper presents a study of the blade pressure perturbation levels and the resulting rotor blade force in three high-pressure transonic turbine stages, based on three-dimensional unsteady viscous computations. The aim is to identify stage characteristics that correlate with the perturbation strength and degree of force realization on the rotor blades. To address the effects of off-design operation, the computations were performed at high subsonic, design and higher vane exit Mach number operating conditions. Furthermore spanwise variations in pressure levels and blade force are addressed. In our investigation the RMS of the pressure perturbations integrated in both time and along the blade surface is utilized as a global measure of the blade pressure perturbation strength on the rotor blade surface. The relative strength of the different pressure perturbation events on the rotor blade surface is also investigated. To obtain information about the relative strength of events related to the blade passing frequency the pressure field is Fourier decomposed in time at different radial positions along the blade arc-length. With the help of the observations and results from the blade pressure study, the radial variations of the unsteady blade force are addressed.

Investigation of Unsteady Aerodynamic Blade Excitation Mechanisms in a Transonic Turbine Stage—Part II: Analytical Description and Quantification

2002 ◽  
Vol 124 (3) ◽  
pp. 419-428 ◽  
Author(s):  
Bjo¨rn Laumert ◽  
Hans Ma˚rtensson ◽  
Torsten H. Fransson
Keyword(s):  
Rotor Blade ◽  
Analytical Description ◽  
Relative Strength ◽  
Pressure Perturbation ◽  
Arc Length ◽  
Blade Surface ◽  
Turbine Stage ◽  
Excitation Mechanisms ◽  
Transonic Turbine ◽  
Pressure Perturbations

This paper presents a study of the blade pressure perturbation levels and the resulting blade forces in a high-pressure transonic turbine stage based on 3-D time dependent viscous computations. Globally, the blade pressure unsteadiness is quantified with the RMS of the pressure perturbations integrated in both time and along the blade surface. Operation point as well as spanwise variations are addressed. Locally, the relative strength of the pressure perturbation events on the vane and rotor blade surface is investigated. To obtain information about the relative strength of events related to the blade passing frequency and higher harmonics, the pressure field is Fourier decomposed in time at different radial positions along the blade arc-length. The amplitude peaks are then related to the pressure events in space-time maps. With the help of the observations and results from the blade pressure study, the radial variations of the unsteady blade force and torque acting on a constant span blade profile section are investigated. The connection between the first and second vane passing frequency pressure amplitudes on the rotor blade surface and the resulting force and the torque amplitudes for three selected blade modes was investigated in detail. In this investigation the pressure was integrated over defined rotor blade regions to quantify local force contributions. Spanwise as well as operation point variations are addressed.

Investigation of Unsteady Aerodynamic Blade Excitation Mechanisms in a Transonic Turbine Stage: Part II — Analytical Description and Quantification

2001 ◽  
Author(s):  
Björn Laumert ◽  
Hans Mårtensson ◽  
Torsten H. Fransson
Keyword(s):  
Rotor Blade ◽  
Analytical Description ◽  
Relative Strength ◽  
Pressure Perturbation ◽  
Arc Length ◽  
Blade Surface ◽  
Turbine Stage ◽  
Excitation Mechanisms ◽  
Transonic Turbine ◽  
Pressure Perturbations

This paper presents a study of the blade pressure perturbation levels and the resulting blade forces in a high-pressure transonic turbine stage based on 3D time dependent viscous computations. Globally, the blade pressure unsteadiness is quantified with the RMS of the pressure perturbations integrated in both time and along the blade surface. Operation point as well as spanwise variations are addressed. Locally, the relative strength of the pressure perturbation events on the vane and rotor blade surface is investigated. To obtain information about the relative strength of events related to the blade passing frequency and higher harmonics, the pressure field is Fourier decomposed in time at different radial positions along the blade arc-length. The amplitude peaks are then related to the pressure events in space-time maps. With the help of the observations and results from the blade pressure study, the radial variations of the unsteady blade force and torque acting on a constant span blade profile section are investigated. The connection between the first and second vane passing frequency pressure amplitudes on the rotor blade surface and the resulting force and the torque amplitudes for three selected blade modes was investigated in detail. In this investigation the pressure was integrated over defined rotor blade regions to quantify local force contributions. Spanwise as well as operation point variations are addressed.

Investigation of Unsteady Aerodynamic Blade Excitation Mechanisms in a Transonic Turbine Stage: Part I — Phenomenological Identification and Classification

2001 ◽  
Author(s):  
Björn Laumert ◽  
Hans Mårtensson ◽  
Torsten H. Fransson
Keyword(s):  
Rotor Blade ◽  
Pressure Fluctuations ◽  
Time Dependent ◽  
Blade Surface ◽  
Turbine Stage ◽  
Unsteady Aerodynamic ◽  
Operation Conditions ◽  
Excitation Mechanisms ◽  
Transonic Turbine ◽  
Exit Mach Number

Based on the results of time dependent 3D viscous computations the aerodynamic mechanisms that cause the unsteady pressure fluctuations on the vane and rotor blade surface of a high-pressure transonic turbine are identified and separately classified in a phenomenological manner. In order to be able to describe separately the influence of wake, potential and shock distortions on the blade surface pressure at design operation conditions, the stator exit Mach number is increased as to enhance the shock distortions and lowered as to enhance potential and wake distortions. In a comprehensive approach the observations from the off-design conditions are utilized to classify every major perturbation observed in the perturbation space-time maps at design operation conditions. The spanwise variations caused by the inherent 3D nature of the flow field and promoted by the 3D shape of the rotor blade are addressed.

Investigation of Unsteady Aerodynamic Blade Excitation Mechanisms in a Transonic Turbine Stage—Part I: Phenomenological Identification and Classification

2002 ◽  
Vol 124 (3) ◽  
pp. 410-418 ◽  
Author(s):  
Bjo¨rn Laumert ◽  
Hans Ma˚rtensson ◽  
Torsten H. Fransson
Keyword(s):  
Rotor Blade ◽  
Pressure Fluctuations ◽  
Time Dependent ◽  
Blade Surface ◽  
Turbine Stage ◽  
Unsteady Aerodynamic ◽  
Operation Conditions ◽  
Excitation Mechanisms ◽  
Transonic Turbine ◽  
Exit Mach Number

Based on the results of time-dependent 3-D viscous computations the aerodynamic mechanisms that cause the unsteady pressure fluctuations on the vane and rotor blade surface of a high-pressure transonic turbine are identified and separately classified in a phenomenological manner. In order to be able to describe separately the influence of wake, potential and shock distortions on the blade surface pressure at design operation conditions, the stator exit Mach number is increased as to enhance the shock distortions and lowered as to enhance potential and wake distortions. In a comprehensive approach the observations from the off-design conditions are utilized to classify every major perturbation observed in the perturbation space-time maps at design operation conditions. The spanwise variations caused by the inherent 3-D nature of the flow field and promoted by the 3-D shape of the rotor blade are addressed.

scholarly journals Investigation of Unsteady Aerodynamic Excitation on Rotor Blade of Variable Geometry Turbine

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Jian Liu ◽  
Wei-Yang Qiao ◽  
Wen-Hua Duan
Keyword(s):  
Pressure Fluctuation ◽  
Rotor Blade ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Variable Geometry ◽  
Blade Surface ◽  
Variable Geometry Turbine ◽  
Mach Numbers ◽  
Fluctuation Energy

To investigate the aerodynamic excitations in variable geometry turbines, the full three-dimensional viscous unsteady numerical simulations were performed by solving N-S equations based on SAS SST method. The aerodynamic excitations at varied expansion ratios with six different vane stagger angles that cause the unsteady pressure fluctuation on the rotor blade surface are phenomenologically identified and quantitatively analyzed. The blade pressure fluctuation levels for turbines with different vane stagger angles in the time and frequency domain are analyzed. As the results suggest, the blade excitation mechanisms are directly dependent on the operating conditions of the stage in terms of vane exit Mach numbers for all test cases. At subsonic vane exit Mach numbers the blade pressure fluctuations are simply related to the potential filed and wake propagation; at transonic conditions, the vane trailing edge shock causes additional disturbance and is the dominating excitation source on the rotor blade, and the pressure fluctuation level is three times of the subsonic conditions. The pressure fluctuation energy at subsonic condition concentrates on the first vane passing period; pressure fluctuation energy at higher harmonics is more prominent at transonic conditions. The variation of the aerodynamic excitations on the rotor blade at different vane stagger angles is caused by the varied expansion with stator and rotor passage. The aerodynamic excitation behaviors on the rotor blade surface for the VGT are significantly different at varied vane stagger angle. Spanwise variation of the pressure fluctuation patterns on is also observed, and the mechanism of the excitations at different spans is not uniform.

scholarly journals The Design and Evaluation of a 14 Stage, 16:1 Pressure Ratio Compressor for an Industrial Gas Turbine

1996 ◽  
Author(s):  
Mohammad R. Saadatmand
Keyword(s):  
Experimental Data ◽  
Gas Turbine ◽  
Rotor Blade ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Suction Surface ◽  
Design Intent ◽  
Flow Through ◽  
Industrial Gas Turbine

The aerodynamic design process leading to the production configuration of a 14 stage, 16:1 pressure ratio compressor for the Taurus 70 gas turbine is described. The performance of the compressor is measured and compared to the design intent. Overall compressor performance at the design condition was found to be close to design intent. Flow profiles measured by vane mounted instrumentation are presented and discussed. The flow through the first rotor blade has been modeled at different operating conditions using the Dawes (1987) three-dimensional viscous code and the results are compared to the experimental data. The CFD prediction agreed well with the experimental data across the blade span, including the pile up of the boundary layer on the corner of the hub and the suction surface. The rotor blade was also analyzed with different grid refinement and the results were compared with the test data.

Cold Blade Profile Generation Methodology for Compressor Rotor Blades Using FSI Approach

2017 ◽  
Author(s):  
Kirubakaran Purushothaman ◽  
Sankar Kumar Jeyaraman ◽  
Ajay Pratap ◽  
Kishore Prasad Deshkulkarni
Keyword(s):  
Aspect Ratio ◽  
Rotor Blade ◽  
Axial Compressor ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Blade Profile ◽  
Interaction Technique ◽  
Compressor Rotor ◽  
Blade Shape ◽  
Blade Geometry

This paper describes a methodology for obtaining correct blade geometry of high aspect ratio axial compressor blades during running condition taking into account of blade untwist and bending. It discusses the detailed approach for generating cold blade geometry for axial compressor rotor blades from the design blade geometry using fluid structure interaction technique. Cold blade geometry represents the rotor blade shape at rest, which under running condition deflects and takes a new operating blade shape under centrifugal and aerodynamic loads. Aerodynamic performance of compressor primarily depends on this operating rotor blade shape. At design point it is expected to have the operating blade shape same as the intended design blade geometry and a slight mismatch will result in severe performance deterioration. Starting from design blade profile, an appropriate cold blade profile is generated by applying proper lean and pre-twist calculated using this methodology. Further improvements were carried out to arrive at the cold blade profile to match the stagger of design profile at design operating conditions with lower deflection and stress for first stage rotor blade. In rear stages, thermal effects will contribute more towards blade deflection values. But due to short blade span, deflection and untwist values will be of lower values. Hence difference between cold blade and design blade profile would be small. This methodology can especially be used for front stage compressor rotor blades for which aspect ratio is higher and deflections are large.

Numerical Three-Dimensional Pressure Patterns in a Recess of a Turbulent and Compressible Hybrid Journal Bearing

2003 ◽  
Vol 125 (2) ◽  
pp. 301-308 ◽  
Author(s):  
Mathieu Helene ◽  
Mihai Arghir ◽  
Jean Frene
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Journal Bearing ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Wire Mesh ◽  
Primary Concern ◽  
Reference Parameters ◽  
Exit Mach Number

The present work investigates the flow in the feeding recess of a hybrid journal bearing. Numerical integration of the complete Navier-Stokes equations was performed with an appropriate turbulence model. Of primary concern is the pressure field on the rotating journal surface that is commonly known as the recess pressure pattern. The goal of the work is to determine the influences of fluid compressibility, operating conditions and recess geometry. Reference parameters selected for this study comprise feeding Reynolds number Rea of 2.105, sliding Reynolds number Rec of 5.103 and recess depth over film thickness ratio e/H of 2.2. Compressibility was considered first. Three values of the axial exit Mach number were selected for computation, namely 0.2, 0.45, and 0.7. As no significant variation was found, the Mach number was fixed at 0.45 in subsequent studies concerning other parameters:     Feeding Reynolds number, Rea       2.104,2.105,4.105     Recess depth, e/H           0, 2.2, 8     Feedhole axis inclination        90°, 135°, 165°     Feedhole location (Figs. 1(a) and 13)   centered, downstream offset. As each parameter is varied, wire mesh plot of pressure and its sectional profiles are examined and effects of varying various parameters are discussed in reference to flow processes as they may affect the support characteristics of the hybrid journal bearing.

scholarly journals Darmstadt Rotor No. 2, II: Design of Leaning Rotor Blades

2003 ◽  
Vol 9 (6) ◽  
pp. 385-391
Author(s):  
Jörg Bergner ◽  
Dietmar K. Hennecke ◽  
Martin Hoeger ◽  
Karl Engel
Keyword(s):  
Mechanical Stability ◽  
Three Dimensional ◽  
Stability Limit ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Navier Stokes ◽  
Structural Constraints ◽  
Transonic Compressor ◽  
Aero Engines ◽  
The Impact

For Darmstadt University of Technology's axial singlestage transonic compressor rig, a new three-dimensional aft-swept rotor was designed and manufactured at MTU Aero Engines in Munich, Germany. The application of carbon fiber–reinforced plastic made it possible to overcome structural constraints and therefore to further increase the amount of lean and sweep of the blade. The aim of the design was to improve the mechanical stability at operation that is close to stall.To avoid the hazard of rubbing at the blade tip, which is found especially at off-design operating conditions close to the stability limit of the compression system, aft-sweep was introduced together with excessive backward lean.This article reports an investigation of the impact of various amounts of lean on the aerodynamic behavior of the compressor stage on the basis of steady-state Navier-Stokes simulations. The results indicate that high backward lean promotes an undesirable redistribution of mass flow and gives rise to a basic change in the shock pattern, whereas a forward-leaning geometry results in the development of a highly back-swept shock front. However, the disadvantage is a decrease in shock strength and efficiency.

Influence of Rotor Blade Aerodynamic Loading on the Performance of a Highly Loaded Turbine Stage

1987 ◽  
Vol 109 (2) ◽  
pp. 155-161 ◽  
Author(s):  
S. H. Moustapha ◽  
U. Okapuu ◽  
R. G. Williamson
Keyword(s):  
Rotor Blade ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Single Stage ◽  
Turbine Stage ◽  
Blade Loading ◽  
Aerodynamic Loading ◽  
Transonic Turbine ◽  
Stage Performance ◽  
Highly Loaded

This paper describes the performance of a highly loaded single-stage transonic turbine with a pressure ratio of 3.76 and a stage loading factor of 2.47. Tests were carried out with three rotors, covering a range of blade Zweifel coefficient of 0.77 to 1.18. Detailed traversing at rotor inlet and exit allowed an assessment of rotor and stage performance as a function of blade loading under realistic operating conditions. The effect of stator endwall contouring on overall stage performance was also investigated using two different contours with the same vane design.

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