Experimental Investigation of Mode Shape Sensitivity of an Oscillating LPT Cascade at Design and Off-Design Conditions

2006 ◽  
Author(s):  
Damian M. Vogt ◽  
Torsten H. Fransson
Keyword(s):  
Mode Shape ◽  
Three Dimensional ◽  
High Sensitivity ◽  
Turbine Rotor ◽  
Shape Sensitivity ◽  
Aeroelastic Stability ◽  
Turbine Rotor Blade ◽  
Reduced Frequency ◽  
Lp Turbine ◽  
Bending Modes

The effect of negative incidence operation on mode shape sensitivity of an oscillating low pressure (LP) turbine rotor blade row has been studied experimentally. An annular sector cascade has been employed in which the middle blade has been made oscillating in controlled three-dimensional rigid-body modes. Unsteady blade surface pressure data were acquired at midspan on the oscillating blade and two pairs of non-oscillating neighbor blades and reduced to aeroelastic stability data. The test program covered variations in reduced frequency, flow velocity and inflow incidence; at each operating point a set of three orthogonal modes was tested such as to allow for generation of stability plots by mode recombination. At nominal incidence it has been found that increasing reduced frequency has a stabilizing effect on all modes. The analysis of mode shape sensitivity yielded that the most stable modes are of bending type with axial to chordwise character whereas high sensitivity has been found for torsion-dominated modes. Negative incidence operation caused the flow to separate on the fore pressure side. This separation was found to have a destabilizing effect on bending modes of chordwise character whereas an increase in stability could be noticed for bending modes of edgewise character. Variations of stability parameter with inflow incidence have hereby found being largely linear within the range of conditions tested. For torsion-dominated modes the influence on aeroelastic stability was close to neutral.

Experimental Investigation of Mode Shape Sensitivity of an Oscillating Low-Pressure Turbine Cascade at Design and Off-Design Conditions

2006 ◽  
Vol 129 (2) ◽  
pp. 530-541 ◽  
Author(s):  
Damian M. Vogt ◽  
Torsten H. Fransson
Keyword(s):  
Mode Shape ◽  
Three Dimensional ◽  
High Sensitivity ◽  
Low Pressure ◽  
Turbine Rotor ◽  
Shape Sensitivity ◽  
Aeroelastic Stability ◽  
Low Pressure Turbine ◽  
Reduced Frequency ◽  
Bending Modes

The effect of negative incidence operation on mode shape sensitivity of an oscillating low-pressure turbine rotor blade row has been studied experimentally. An annular sector cascade has been employed in which the middle blade has been made oscillating in controlled three-dimensional rigid-body modes. Unsteady blade surface pressure data were acquired at midspan on the oscillating blade and two pairs of nonoscillating neighbor blades and reduced to aeroelastic stability data. The test program covered variations in reduced frequency, flow velocity, and inflow incidence; at each operating point, a set of three orthogonal modes was tested such as to allow for generation of stability plots by mode recombination. At nominal incidence, it has been found that increasing reduced frequency has a stabilizing effect on all modes. The analysis of mode shape sensitivity yielded that the most stable modes are of bending type with axial to chordwise character, whereas high sensitivity has been found for torsion-dominated modes. Negative incidence operation caused the flow to separate on the fore pressure side. This separation was found to have a destabilizing effect on bending modes of chordwise character, whereas an increase in stability could be noted for bending modes of edgewise character. Variations of stability parameter with inflow incidence have hereby found being largely linear within the range of conditions tested. For torsion-dominated modes, the influence on aeroelastic stability was close to neutral.

Mode Shape Sensitivity of the High Pressure Turbine Rotor Excitation Due to Upstream Stators

2002 ◽  
Author(s):  
Markus Jo¨cker ◽  
Torsten H. Fransson
Keyword(s):  
High Pressure ◽  
Mode Shape ◽  
Rotor Blade ◽  
High Sensitivity ◽  
Turbine Rotor ◽  
Mode Shapes ◽  
Navier Stokes ◽  
Shape Sensitivity ◽  
High Pressure Turbine ◽  
Unsteady Aerodynamic

The excitability of single rotor blade mode shapes due to the excitations by upstream stators in high-pressure turbine stages is subject of the present work. An evaluation of unsteady aerodynamic analyses of the stator-rotor interaction towards their sensitivity to the rotor blade mode shape is presented and applied. The unsteady aerodynamic analyses were performed at midspan sections with a well validated 2D/Q3D hybrid Euler/Navier Stokes non-linear flow solver (UNSFLO). The mode shape is parametrized by a torsion axis location in the plane of the blade section, which allows the construction of excitability maps as a function of 2D rigid body mode shapes. Excitability itself is derived from a generalized force analysis. The evaluation demonstrates the high sensitivity of excitability to the mode shape, which suggests that only small modifications in mode shape can significantly change the risk of blade mode excitation. It also highlights the central importance of the relative phase of unsteady blade pressure harmonic. Changes in axial gap can significantly modify the excitability and transform highly excited modes to less excited modes and vice versa. The variation of rotational speed (−5% to +10%) did not show remarkable changes in the mode excitability of the investigated rotor.

Physics-Based Part Orientation and Sentencing: A Solution to Manufacturing Variability

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Wen Yao Lee ◽  
William N. Dawes ◽  
John D. Coull
Keyword(s):  
Three Dimensional ◽  
Turbine Rotor ◽  
Navier Stokes ◽  
Performance Control ◽  
Turbine Rotor Blade ◽  
Geometric Tolerancing ◽  
Performance Variability ◽  
Geometric Tolerances ◽  
Aero Engine ◽  
Part Orientation

Abstract Casting deviations introduce geometric variability that impacts the aerodynamic performance of turbomachinery. These effects are studied for a high-pressure turbine rotor blade from a modern aero-engine. A sample of 197 blades were measured using structured-light three-dimensional scanning, and the performance of each blade is quantified using Reynolds-averaged Navier–Stokes (RANS) simulations. Casting variation is typically managed by applying geometric tolerances to determine the suitability of a component for service. The analysis demonstrates that this approach may not be optimal since it does not necessarily align with performance, in particular the capacity and efficiency. Alternatively, functional acceptance based on the predicted performance of each blade removes the uncertainty associated with geometric tolerancing and gives better performance control. Building on these findings, the paper proposes a method to set the orientation of the fir-tree, which is machined after casting. By customizing the alignment of each blade, performance variability and scrap rates can be significantly reduced. The method uses predictions of performance to reorient the castings to compensate for manufacturing-induced errors, without changing the design-intent blade geometry and with minimal changes to the manufacturing facility.

Unsteady and Calming Effects Investigation on a Very High Lift LP Turbine Blade: Part I — Experimental Analysis

2002 ◽  
Author(s):  
Thomas Coton ◽  
Tony Arts ◽  
Michae¨l Lefebvre ◽  
Nicolas Liamis
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Numerical Study ◽  
Turbine Rotor ◽  
High Lift ◽  
Turbine Rotor Blade ◽  
Pressure Loss Coefficient ◽  
Lp Turbine ◽  
Exit Mach Number ◽  
Very High

An experimental and numerical study was performed about the influence of incoming wakes and the calming effect on a very high lift low pressure turbine rotor blade. The first part of the paper describes the experimental determination of the pressure loss coefficient and the heat transfer around the blade mounted in a high speed linear cascade. The cascade is exposed to incoming wakes generated by high speed rotating bars. Their aim is to act upon the transition/separation phenomena. The measurements were conducted at a constant exit Mach number equal to 0.8 and at three Reynolds number values, namely 190000, 350000 and 650000. The inlet turbulence level was fixed at 0.8%. An additional feature of this work is to identify the boundary layer status through heat transfer measurements. Compared to the traditionally used hot films, thin film heat flux gages provide fully quantitative data required for code validation. Numerical computations are presented in the second part of the paper.

Assessment of a 3D Linear Euler Flutter Prediction Tool Using Sector Cascade Test Data

2005 ◽  
Author(s):  
Hans Ma˚rtensson ◽  
Damian M. Vogt ◽  
Torsten H. Fransson
Keyword(s):  
Turbine Blades ◽  
Tip Clearance ◽  
Mode Shapes ◽  
Test Case ◽  
Prediction Tool ◽  
Reduced Frequency ◽  
3D Geometry ◽  
Annular Sector ◽  
Lp Turbine ◽  
Bending Modes

An assessment and validation of a numerical prediction tool for flutter are made using new experimental data from experiments on turbine blades in a sector cascade. The 3D geometry is that of a low-pressure (LP) turbine blade with twist and a profile that changes along span in an annular sector cascade. The numerical model is a linear harmonic Euler equation solver. Rig results are obtained for the blade by oscillating 1 blade out of 7 in the annular sector cascade. The blade is oscillated in the rig using a mechanical type of actuator to control the mode. The mode shapes in the rig consist of torsion and bending modes around a pivot mechanism fixed inside the hub end wall. The frequencies obtained in the rig are in the range up to 219 Hz, or reduced frequency based on full chord k = 0.5, which covers the range of useful reduced frequencies typically found in turbine designs. Under reference running conditions the unsteady pressure responses are found qualitatively in line with the experiment. The test case is shown to be challenging to the numerical tool in terms of effects of tip clearance as well as off-design effects. In order to improve results tip clearance modeling and inclusion of viscous terms are identified as key factors.

Three-Dimensional Analysis of Turbine Rotor Flow Including Tip Clearance

1993 ◽  
Author(s):  
R. Heider ◽  
J. M. Duboue ◽  
B. Petot ◽  
G. Billonnet ◽  
V. Couaillier ◽  
...  
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Turbine Rotor Blade ◽  
Calculation Results ◽  
Rotor Flow

A 3D Navier-Stokes investigation of a high pressure turbine rotor blade including tip clearance effects is presented. The 3D Navier-Stokes code developed at ONERA solves the three-dimensional unsteady set of mass-averaged Navier-Stokes equations by the finite volume technique. A one step Lax-Wendroff type scheme is used in a rotating frame of reference. An implicit residual smoothing technique has been implemented, which accelerates the convergence towards the steady state. A mixing length model adapted to 3D configurations is used. The turbine rotor flow is calculated at transonic operating conditions. The tip clearance effect is taken into account. The gap region is discretized using more than 55,000 points within a multi-domain approach. The solution accounts for the relative motion of the blade and casing surfaces. The total mesh is composed of five sub-domains and counts 710,000 discretization points. The effect of the tip clearance on the main flow is demonstrated. The calculation results are compared to a 3D inviscid calculation, without tip clearance.

Nonaxisymmetric Turbine End Wall Design: Part I— Three-Dimensional Linear Design System

1999 ◽  
Vol 122 (2) ◽  
pp. 278-285 ◽  
Author(s):  
Neil W. Harvey ◽  
Martin G. Rose ◽  
Mark D. Taylor ◽  
Shahrokh Shahpar ◽  
Jonathan Hartland ◽  
...  
Keyword(s):  
Flow Field ◽  
Design Method ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Secondary Flows ◽  
Navier Stokes ◽  
Design System ◽  
Linear Superposition ◽  
Turbine Rotor Blade ◽  
End Wall

A linear design system, already in use for the forward and inverse design of three-dimensional turbine aerofoils, has been extended for the design of their end walls. This paper shows how this method has been applied to the design of a nonaxisymmetric end wall for a turbine rotor blade in linear cascade. The calculations show that nonaxisymmetric end wall profiling is a powerful tool for reducing secondary flows, in particular the secondary kinetic energy and exit angle deviations. Simple end wall profiling is shown to be at least as beneficial aerodynamically as the now standard techniques of differentially skewing aerofoil sections up the span, and (compound) leaning of the aerofoil. A design is presented that combines a number of end wall features aimed at reducing secondary loss and flow deviation. The experimental study of this geometry, aimed at validating the design method, is the subject of the second part of this paper. The effects of end wall perturbations on the flow field are calculated using a three-dimensional pressure correction based Reynolds-averaged Navier–Stokes CFD code. These calculations are normally performed overnight on a cluster of work stations. The design system then calculates the relationships between perturbations in the end wall and resulting changes in the flow field. With these available, linear superposition theory is used to enable the designer to investigate quickly the effect on the flow field of many combinations of end wall shapes (a matter of minutes for each shape). [S0889-504X(00)00902-8]

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.

An Experimental and Computational Study of Transonic Three-Dimensional Flow in a Turbine Cascade

1984 ◽  
Vol 106 (2) ◽  
pp. 414-420 ◽  
Author(s):  
J.-J. Camus ◽  
J. D. Denton ◽  
J. V. Soulis ◽  
C. T. J. Scrivener
Keyword(s):  
Computational Study ◽  
Three Dimensional ◽  
Inviscid Flow ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Turbine Rotor Blade ◽  
Dimensional Effects ◽  
Blade Section ◽  
Exit Mach Number ◽  
End Wall

Detailed experimental measurements of the flow in a cascade of turbine rotor blades with a nonplanar end wall are reported. The cascade geometry was chosen to model as closely as possible that of a H.P. gas turbine rotor blade. The blade section is designed for supersonic flow with an exit Mach number of 1.15 and the experiments covered a range of exit Mach numbers from 0.7–1.2. Significant three-dimensional effects were observed and the origin of these is discussed. The measurements are compared with data for the same blade section in a two-dimensional cascade and also with the predictions of two different fully three-dimensional inviscid flow calculation methods. It is found that both these calculations predict the major three-dimensional effects on the flow correctly.

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