Influence of the Blade Count Ratio on Aerodynamic Forcing: Part II—High Pressure Transonic Turbine

2011 ◽  
Author(s):  
Florian Fruth ◽  
Damian M. Vogt ◽  
Torsten H. Fransson
Keyword(s):  
High Pressure ◽  
Rotor Blade ◽  
Linear Time ◽  
Unsteady Aerodynamics ◽  
Rotor Blades ◽  
Mode Shapes ◽  
Monotonic Trend ◽  
Count Ratio ◽  
Mode Excitation ◽  
Transonic Turbine

The influence of the Blade Count Ratio (BCR) on the aerodynamic forcing of a transonic high pressure turbine has been investigated numerically. Main focus here was put on the change in unsteady aerodynamics, modal properties and the mode excitation. Using a scaling technique, six different transonic turbine stages with different numbers of scaled blades but maintained steady aerodynamics were generated and further analyzed. In the analysis a non-linear, time marching CFD solver was used and the unsteady, harmonic forces projected onto the mode shapes. For this transonic turbine the unsteady pressure at the rotor blade decreases in amplitude and spanwise distribution from low to high blade count ratios. In chordwise direction a local minimum for intermediate blade count ratios was found for the rotor and stator blades. Mode frequencies decreased monotonically with an increasing BCR. Significant mode changes for modes 5 and 6 of the different BCRs were captured using the Modal Assurance Criteria. It was found that for these transonic turbines the blade count ratio and reduced frequency are amongst others key parameters for a reduction in aerodynamic forcing. Even though an almost monotonic trend was found for the stator blade excitation, the rotor blade excitation behaves highly non-monotonic. A maximum value in excitation potential was found close to reported blade count ratio values. Optimization of certain modes is possible but case dependent, due to the non-monotonic nature. Moreover it was found that for a minor increase in upstream blade count the mean unsteady forces on the rotor blades is reduced, but the mode excitation not necessarily has to decrease.

Unsteady Aerodynamics and Interactions Between a High Pressure Turbine Vane and Rotor

2004 ◽  
Author(s):  
Ryan M. Urbassik ◽  
J. Mitch Wolff ◽  
Marc D. Polanka
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Potential Field ◽  
Rotor Blade ◽  
Second Harmonic ◽  
Unsteady Aerodynamics ◽  
Pressure Measurements ◽  
High Pressure Turbine ◽  
Turbine Vane ◽  
Unsteady Pressure Measurements

A set of experimental data is presented investigating the unsteady aerodynamics associated with a high pressure turbine vane (HPV) and rotor blade (HPB). The data was acquired at the Turbine Research Facility (TRF) of the Air Force Research Laboratory. The TRF is a transient, blowdown facility generating several seconds of experimental data on full scale engine hardware at scaled turbine operating conditions simulating an actual engine environment. The pressure ratio and freestream Reynolds number were varied for this investigation. Surface unsteady pressure measurements on the HPV, total pressure traverse measurements downstream of the vane, and surface unsteady pressure measurements for the rotor blade were obtained. The unsteady content of the HPV surface was generated by the rotor potential field. The first harmonic decayed more rapidly than the second harmonic with a movement upstream causing the second harmonic to be most influential at the vane throat. The blade unsteadiness appears to be caused by a combination of shock, potential field, and vane wake interactions between the vane and rotor blade. The revolution averaged data resulted in higher unsteadiness than a passing ensemble average for both vane and rotor indicating a need to understand each passage for high cycle fatigue (HCF) effects.

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.

Rotor Blade Unsteady Aerodynamic Gust Response to Inlet Guide Vane Wakes

1993 ◽  
Vol 115 (1) ◽  
pp. 197-206 ◽  
Author(s):  
S. R. Manwaring ◽  
S. Fleeter
Keyword(s):  
Rotor Blade ◽  
Guide Vane ◽  
Axial Flow ◽  
Unsteady Aerodynamics ◽  
Rotor Blades ◽  
Inlet Guide Vane ◽  
Unsteady Aerodynamic ◽  
Forcing Function ◽  
Reduced Frequency ◽  
Flow Compressor

A series of experiments is performed in an extensively instrumented axial flow research compressor to investigate the fundamental flow physics of wake-generated periodic rotor blade row unsteady aerodynamics at realistic values of the reduced frequency. Unique unsteady data are obtained that describe the fundamental unsteady aerodynamic gust interaction phenomena on the first-stage rotor blades of a research axial flow compressor generated by the wakes from the inlet guide vanes. In these experiments, the effects of steady blade aerodynamic loading and the aerodynamic forcing function, including both the transverse and chordwise gust components, and the amplitude of the gusts, are investigated and quantified.

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.

A CFD Approach to Fluid Dynamic Optimum Design of Steam Turbine Stages With Stator and Rotor Blades

2010 ◽  
Author(s):  
Xin Yuan ◽  
Tadashi Tanuma ◽  
Xiaofeng Zhu ◽  
Zhirong Lin ◽  
Daisuke Nomura
Keyword(s):  
High Pressure ◽  
Steam Turbine ◽  
Optimum Design ◽  
Rotor Blade ◽  
Fluid Dynamic ◽  
Rotor Blades ◽  
Turbine Stage ◽  
Tip Leakage ◽  
Pressure Steam ◽  
End Wall

An advanced aerodynamic design optimization system for steam turbine stages considering rotor blade tip leakage and blade end-wall non-axis-symmetric contouring has been developed. Using this system, fluid dynamic optimizations were carried out for a steam turbine stage with stator and rotor blades. The system includes parametric modeling of blade and end-wall contouring, evaluation system with in-house or package CFD software and optimization strategy module. The designs of rotor blade and hub end-wall surface in a typical large-scale high-pressure steam turbine stage were optimized in order to know this design optimization impact on enhancing the stage efficiency. Results show that: from the current well designed high pressure steam turbine stage, the demonstrated efficiency enhancement with the present optimum design is around 0.2% under consideration of rotor tip leakage. Design cycle could be greatly shortened by parallel optimization algorithm and cluster PC, and especially four days could be sufficient for an optimization with one thousand iterations on 20 CPUs of 2.0G cluster PC.

Blade Count and Clocking Effects on Three-Bladerow Interaction in a Transonic Turbine

2003 ◽  
Vol 125 (4) ◽  
pp. 632-640 ◽  
Author(s):  
H. D. Li ◽  
L. He
Keyword(s):  
Design Parameter ◽  
Rotor Blade ◽  
Computational Study ◽  
Rotor Blades ◽  
The Other ◽  
Variation Pattern ◽  
Interaction Mechanisms ◽  
Parametric Studies ◽  
Stator Blade ◽  
Transonic Turbine

A computational study of the multirow interaction mechanisms has been carried out for a one-and-a-half stage (NGV-rotor-stator) transonic turbine. In addition to measurable subharmonic unsteadiness on the rotor blades induced by two fundamental stator passing frequencies, a significant aperiodic (“mistuned”) circumferential variation of unsteady forcing magnitude by about three times has been observed in the downstream stator blades. Further parametric studies with various stator blade counts illustrate that the circumferential variation pattern of the unsteady forcing is dictated by the NGV-stator blade count difference, while the local stator forcing magnitude is affected by its circumferential clocking position relative to the upstream NGV blades. The present work suggests that the circumferential clocking together with the choice of blade count should be considered as an aeromechanical design parameter. For cases with stator-stator (or rotor-rotor) blade counts resulting in a tuned (or nearly tuned) unsteady forcing pattern, the clocking position should be chosen to minimize the unsteady forcing. On the other hand, if the choice of blade counts leads to a significant aerodynamic aperiodicity (mistuning), the clocking-forcing analysis can be used to identify the most vulnerable blade that is subject to the maximum forcing.

Lagrangian formulation for the rapid estimation of helicopter rotor blade vibration characteristics

2014 ◽  
Vol 118 (1206) ◽  
pp. 861-901 ◽  
Author(s):  
I. Goulos ◽  
V. Pachidis ◽  
P. Pilidis
Keyword(s):  
Rotor Blade ◽  
Computational Cost ◽  
Vibration Characteristics ◽  
Rotor Blades ◽  
Helicopter Rotor ◽  
Mode Shapes ◽  
Small Scale ◽  
Transverse Displacement ◽  
Euler Beam ◽  
Rapid Estimation

Abstract This paper presents a numerical formulation targeting the rapid estimation of natural vibration characteristics of helicopter rotor blades. The proposed method is based on application of Lagrange’s equation of motion to the kinematics of blade flap/lag bending and torsion. Modal properties obtained from Bernoulli-Euler beam and classical torsional vibration theory, are utilised as assumed deformation functions in order to estimate the time variations of strain and kinetic energy for each degree of freedom. Integral expressions are derived, describing the generalised centrifugal force and torsional moment acting on the blade in terms of normal coordinates, for flap/lag transverse displacement and torsional deformation. Closed form expressions are provided for the direct analysis of hingeless, freely-hinged and spring-hinged articulated rotor blades. Results are presented in terms of natural frequencies and mode shapes for two small-scale rotor blade models. Extensive comparisons are carried out with experimental measurements and nonlinear finite element analysis. Predictions of resonant frequencies are also presented for two full-scale rotor blade models and the results are compared with established multi-body dynamics analysis methods. It is shown that, the proposed approach exhibits excellent numerical behaviour with low computational cost and definitive convergence characteristics. The comparisons suggest very good and in some cases excellent accuracy levels, especially considering the method’s simplicity, computational efficiency, and ease of implementation.

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.

Rotor Blade Unsteady Aerodynamic Gust Response to Inlet Guide Vane Wakes

1991 ◽  
Author(s):  
Steven R. Manwaring ◽  
Sanford Fleeter
Keyword(s):  
Rotor Blade ◽  
Guide Vane ◽  
Axial Flow ◽  
Unsteady Aerodynamics ◽  
Rotor Blades ◽  
Inlet Guide Vane ◽  
Unsteady Aerodynamic ◽  
Forcing Function ◽  
Reduced Frequency ◽  
Flow Compressor

A series of experiments are performed in an extensively instrumented axial flow research compressor to investigate the fundamental flow physics of wake generated periodic rotor blade row unsteady aerodynamics at realistic values of the reduced frequency. Unique unsteady data are obtained which describe the fundamental unsteady aerodynamic gust interaction phenomena on the first stage rotor blades of a research axial flow compressor generated by the wakes from the Inlet Guide Vanes. In these experiments, the effects of steady blade aerodynamic loading and the aerodynamic forcing function, including both the transverse and chordwise gust components, and the amplitude of the gusts, are investigated and quantified.

Influence of the Hub Endwall Cavity Flow on the Time-Averaged and Time-Resolved Aero-Thermodynamics of an Axial HP Turbine Stage

2002 ◽  
Author(s):  
R. De´nos ◽  
G. Paniagua
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Significant Influence ◽  
Total Pressure ◽  
Rotor Blade ◽  
Static Pressure ◽  
Cavity Flow ◽  
Turbine Stage ◽  
Time Resolved ◽  
Transonic Turbine

This experimental research investigates the influence of the hub endwall cavity flow on the aerodynamics and heat transfer of a high-pressure transonic turbine stage tested under engine representative conditions. The measurements include the hub and tip endwall static pressure downstream of the vane, the static pressure and heat transfer on the rotor blade at 15% span and on the hub platform as well as the stage downstream total pressure and temperature. Both steady and unsteady aspects are addressed. The hub endwall cavity flow has a significant influence on both the time-averaged and time-resolved components of the measured quantities. The effects are shown to be mainly due to an increase of the pitchwise averaged static pressure at hub downstream of the vane when cavity flow ejection is activated.

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