ANALYSIS OF AVERAGING METHODS FOR NON-UNIFORM TOTAL PRESSURE FIELDS

2021 ◽  
pp. 1-23
Author(s):  
Daniel Burdett ◽  
Thomas Povey
Keyword(s):  
Experimental Data ◽  
Mach Number ◽  
Total Pressure ◽  
Rotor Blades ◽  
Performance Parameters ◽  
Guide Vanes ◽  
Component Plane ◽  
Exit Mach Number ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes

Abstract A common objective in the analysis of turbomachinery components (nozzle guide vanes or rotor blades, for example) is to calculate performance parameters, such as total pressure or kinetic energy loss coefficients, from measurements in a non-uniform flow-field. These performance parameters can be represented in a range of ways. For example: line-averages used to compare performance between different radial sections of a 3D component; plane-averages used to assess flow (perhaps loss coefficient) development between different axial planes; and fully mixed-out values used to determine the total loss associated with a component. In this paper, we compare a range of methods for calculating aerodynamic performance parameters including plane-average methods with different weighting schemes and several mixed-out methods. We analyse the sensitivities of the different methods to the axial location of the measurement plane, the radial averaging range, and the exit Mach number. We use high-fidelity experimental data taken in several axial planes downstream of a cascade of engine parts: high pressure (HP) turbine nozzle guide vanes (NGVs) operating at transonic Mach number. The experimental data is complemented by CFD. We discuss the underlying physical mechanisms which give rise to the observed sensitivities. The objective is to provide guidance on the accuracy of each method in a relevant, practical application.

Degradation of Aerodynamic Performance of an Intermediate-Pressure Steam Turbine Due to Erosion of Nozzle Guide Vanes and Rotor Blades

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Koichi Yonezawa ◽  
Tomoki Kagayama ◽  
Masahiro Takayasu ◽  
Genki Nakai ◽  
Kazuyasu Sugiyama ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Steam Turbine ◽  
Rotor Blade ◽  
Rotor Blades ◽  
Flow Angle ◽  
Guide Vanes ◽  
Intermediate Pressure ◽  
Pressure Steam ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes

Deteriorations of nozzle guide vanes (NGVs) and rotor blades of a steam turbine through a long-time operation usually decrease a thermal efficiency and a power output of the turbine. In this study, influences of blade deformations due to erosion are discussed. Experiments were carried out in order to validate numerical simulations using a commercial software ANSYS-cfx. The numerical results showed acceptable agreements with experimental results. Variation of flow characteristics in the first stage of the intermediate pressure steam turbine is examined using numerical simulations. Geometries of the NGVs and the rotor blades are measured using a 3D scanner during an overhaul. The old NGVs and the rotor blades, which were used in operation, were eroded through the operation. The erosion of the NGVs leaded to increase of the throat area of the nozzle. The numerical results showed that rotor inlet velocity through the old NGVs became smaller and the flow angle of attack to the rotor blade leading edge became smaller. Consequently, the rotor power decreased significantly. Influences of the flow angle of at the rotor inlet were examined by parametric calculations and results showed that the angle of attack was an important parameter to determine the rotor performance. In addition, the influence of the deformation of the rotor blade was examined. The results showed that the degradation of the rotor performance decreased in accordance with the decrease of blade surface area.

Prediction of High-Frequency Blade Vibration Amplitudes in a Radial Inflow Turbine With Nozzle Guide Vanes

2013 ◽  
Author(s):  
Martin Schwitzke ◽  
Achmed Schulz ◽  
Hans-Jörg Bauer
Keyword(s):  
Experimental Data ◽  
Forced Response ◽  
Fe Model ◽  
Numerical Work ◽  
Turbine Wheel ◽  
Operating Condition ◽  
Guide Vanes ◽  
Radial Inflow Turbine ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes

Impeller blades in radial inflow turbines are not only exposed to high thermal loads and centrifugal forces. Additional dynamic stresses occur by the aerodynamic excitation of a variety of blade and disc modes and can lead to damages by fatigue. This is a critical consideration for engines with nozzle guide vanes in particular, where excitation is caused by the interaction between guide vanes and rotor blades. This leads to high excitation frequencies, which are within the range of eigenfrequencies of the stiff impeller. Previous experimental analyses provide vibration amplitude data for resonances in a radial inflow turbine equipped with three nozzle rings with varying vane numbers. The experimental data is used for validation of numerical investigations. The numerical work presented involves the simulation of the transient flow field of the entire turbine as a first step. Aerodynamic excitation forces on the blades are derived from the results for various resonance conditions. The influence of the operating condition and the vane number is pointed out. Higher speed and lower vane number increase the amplitudes of the blade force. In a second step, the transient and spatially resolved pressure distribution is used as a boundary condition in an FE model. The damping ratio is an essential parameter in order to calculate the forced response of the structure, and it is determined from the experimental data. The damping behavior is characterized and compared to ratios derived from additional experimental studies using laser vibrometry at the non-rotating turbine wheel under ambient conditions. A disparity in the damping ratios is recovered, depending on the eigenmodes and the boundary conditions. The forced response of the structure is computed using the individual damping ratios for four resonance conditions. Harmonic analyses are conducted, applying the pressure forces from CFD. The calculated amplitudes are validated with data from strain gauge measurements under operating condition. The prediction of the vibration amplitudes shows acceptable agreement to the test data with a tendency towards lower values.

An Impact Assessment of Erosion of Nozzle Guide Vanes and Rotor Blades on Aerodynamic Performance of a Gas Turbine by CFD

2019 ◽  
Author(s):  
Koichi Yonezawa ◽  
Masahiro Takayasu ◽  
Genki Nakai ◽  
Kazuyasu Sugiyama ◽  
Katsuhiko Sugita ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Rotor Blade ◽  
Cfd Simulation ◽  
Rotor Blades ◽  
Total Power ◽  
Guide Vanes ◽  
Turbine Performance ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes

Abstract Nozzle guide vanes (NGVs) and rotor blades deteriorate due to erosion, and this may affect the aerodynamic characteristics of gas turbines. According to previous studies, the erosion of first-stage NGVs significantly affected the blade loading of the first-stage rotor. An increase in the tip gap also may significantly affect the gas turbine performance. In the present study, numerical investigations have been carried out using a real eroded nozzle and blade geometries for two purposes. One purpose was to clarify the influences underlying the deterioration of the nozzle and the rotor blade, such as the effects on the erosion of NGVs in the first stage and the effects of the tip gap on the gas turbine performance. The other was to develop a method to estimate the total gas turbine performance using a CFD simulation and a heat balance analysis. The results show that the erosion of NGV leads to an increased flow rate and affects the operating condition of the gas turbine cycle. This, in turn, can decrease the total thermal efficiency. The experimental results suggest that an increase in the tip gap width decreases rotor output almost linearly, and the numerical results showed the same tendency. The influence of the tip gap in the real gas turbine condition was also examined, revealing that an increase in the tip gap leads to an increase in the pressure loss in the nozzle downstream as well as around the rotor blade itself. Consequently, the total power output and the isentropic efficiency of the turbine decreased.

Numerical Investigation of the Influence of Real World Blade Profile Variations on the Aerodynamic Performance of Transonic Nozzle Guide Vanes

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
R. Edwards ◽  
A. Asghar ◽  
R. Woodason ◽  
M. LaViolette ◽  
K. Goni Boulama ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Flow Pattern ◽  
Pressure Loss ◽  
Total Pressure ◽  
Aerodynamic Performance ◽  
Guide Vanes ◽  
Trailing Edges ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes

This paper addresses the issue of aerodynamic consequences of small variations in airfoil profile. A numerical comparison of flow field and cascade pressure losses for two representative repaired profiles and a reference new vane were made. Coordinates for the three airfoil profiles were obtained from the nozzle guide vanes of refurbished turboshaft engines using 3D optical scanning and digital modeling. The repaired profiles showed differences in geometry in comparison with the new vane, particularly near the leading and trailing edges. A numerical simulation was conducted using a commercial CFD code, which uses the finite volume approach for solving the governing equations. The computational predictions of the aerodynamic performance were compared with experimental results obtained from a cascade consisting of blades with the same airfoil profiles. The CFD analysis was performed for the cascade at subsonic inlet and transonic exit conditions. Boundary layer growth, wake formation, and shock boundary layer interactions were observed in the two-dimensional computations. The flow field showed the presence of shock waves downstream of the passage throat and near the trailing edges of the blades. A conspicuous change in flow pattern due to subtle variation in airfoil profile was observed. The calculated flow field was compared with the flow pattern visualized in the experimental test rig using the schlieren method. The total pressure calculation for the cascade exit showed an increase in pressure loss for one of the off-design profiles. The pressure loss calculations were also compared with the multihole total pressure probe measurement in the transonic cascade rig.

scholarly journals Endwall Heat Transfer and Aerodynamic Measurements in an Annular Cascade of Nozzle Guide Vanes

1995 ◽  
Author(s):  
M. C. Spencer ◽  
G. D. Lock ◽  
T. V. Jones ◽  
N. W. Harvey
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Reynolds Numbers ◽  
Flow Visualisation ◽  
Surface Shear ◽  
Guide Vanes ◽  
Nozzle Guide ◽  
Annular Cascade ◽  
Nozzle Guide Vanes ◽  
Transient Liquid Crystal Technique

Aerodynamic and heat transfer measurements have been made on the hub and casing endwalls of an annular cascade of high pressure nozzle guide vanes. The measurements have been made over a range of engine representative Mach and Reynolds numbers and with large levels of freestream turbulence intensity. The transient liquid crystal technique has been employed, which has the advantage of yielding full surface maps of heat transfer coefficient. Computational predictions and aerodynamic measurements of Mach number distributions on the endwall surfaces are also presented, along with surface-shear flow visualisation using oil and dye techniques. The heat transfer results are discussed and interpreted in terms of the secondary flow and Mach number patterns.

Study over thermal state of gas turbine engine metal-ceramic rotor blades and nozzle guide vanes under thermal shock and thermal-cyclic loading conditions

2004 ◽  
Vol 13 (2) ◽  
pp. 163-166
Author(s):  
A. V. Soudarev ◽  
A. A. Souryaninov ◽  
V. Ya. Podgorets ◽  
V. V. Grishaev ◽  
V.Yu Tikhoplav ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Thermal Shock ◽  
Gas Turbine ◽  
Thermal State ◽  
Rotor Blades ◽  
Guide Vanes ◽  
Turbine Engine ◽  
Metal Ceramic ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes

Investigation of Vortex Shedding and Wake-Wake Interaction in a Transonic Turbine Stage Using Laser-Doppler-Velocimetry and Particle-Image-Velocimetry

2005 ◽  
Vol 128 (1) ◽  
pp. 178-187 ◽  
Author(s):  
E. Göttlich ◽  
J. Woisetschläger ◽  
P. Pieringer ◽  
B. Hampel ◽  
F. Heitmeir
Keyword(s):  
Vortex Shedding ◽  
Particle Image ◽  
Rotor Blades ◽  
Laser Doppler ◽  
Turbine Stage ◽  
Time Resolved ◽  
Guide Vanes ◽  
Wake Interaction ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes

The current paper presents a time-resolved experimental flow investigation in a highly loaded transonic gas turbine stage operating continuously under engine representative conditions. The measurement was performed with a two-component laser-doppler-velocimeter (LDV) and a three-component stereoscopic particle-image-velocimeter (3C-PIV). Unsteady velocity data were obtained in axis perpendicular planes (LDV) and tangential planes (3C-PIV) between stator and rotor as well as downstream of the rotor. The results of the time-resolved investigation at several radii show the vortex shedding process from the trailing edges of nozzle guide vanes and rotor blades. This vortex shedding was found to be phase locked to higher harmonics of the blade passing frequency. Pressure waves evoked by reflection of the trailing edge shocks of the vanes on the passing rotor blades interact with the boundary layers on the rear suction side of the vanes and on the rotor blade surfaces while running upstream and downstream the flow. They are responsible for this phase-locking phenomenon of the shedding vortices. At midspan, the vortices shedding from stator and rotor blades were also observed by PIV. The in-plane vorticity distribution was used to discuss the wake-wake interaction indicating that wake segments from the nozzle guide vanes were chopped by the rotor blades. These chopped segments are still visible in the distributions as a pair of counter rotating vortices. The nozzle wake segments are transported through the rotor passages by the flow, influencing the vortex street of the rotor blades as they pass by with the higher velocity of the main flow. A comparison with a numerical simulation is also given.

Assessment of Transition Modeling and Compressibility Effects in a Linear Cascade of Turbine Nozzle Guide Vanes

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Silvia Ravelli ◽  
Giovanna Barigozzi ◽  
Ernesto Casartelli ◽  
Luca Mangani
Keyword(s):  
Mach Number ◽  
Numerical Procedure ◽  
Local Flow ◽  
Guide Vanes ◽  
Linear Cascade ◽  
Transition Modeling ◽  
Cfd Method ◽  
Extensive Experimental Data ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes

The flow field in a linear cascade of highly loaded turbine nozzle guide vanes (NGVs) has been numerically investigated at low and high-subsonic regime, i.e., exit isentropic Mach number of M2is = 0.2 and 0.6, respectively. Extensive experimental data are available for an accurate assessment of the numerical procedure. Aerodynamic measurements include not only vane loading and pressure drop in the wake but also local flow features such as boundary layer behavior along both pressure and suction sides of the vane, as well as secondary flow structures downstream of the trailing edge (TE). Simulations were performed by using two computational fluid dynamics (CFD) codes, a commercial one and an open-source based in-house code. Besides computations with the well-established shear-stress transport (SST) k–ω turbulence model assuming fully turbulent flow, transition models were taken into account in the present study. The original version of the γ–Reθ model of Menter was employed. Suluksna–Juntasaro correlations for transition length (Flenght) and transition onset (Fonset) were also tested. The main goal was to establish essential ingredients for reasonable computational predictions of the cascade aerodynamic behavior, under both incompressible and compressible regime. This study showed that transition modeling should be coupled with accurate profiles of inlet velocity and turbulence intensity to get a chance to properly quantify aerodynamic losses via CFD method. However, additional weaknesses of the transition modeling have been put forward when increasing the outlet Mach number.

Investigation of Vortex Shedding and Wake-Wake Interaction in a Transonic Turbine Stage Using Laser-Doppler-Velocimetry and Particle-Image-Velocimetry

2005 ◽  
Author(s):  
E. Go¨ttlich ◽  
J. Woisetschla¨ger ◽  
P. Pieringer ◽  
B. Hampel ◽  
F. Heitmeir
Keyword(s):  
Vortex Shedding ◽  
Particle Image ◽  
Rotor Blades ◽  
Laser Doppler ◽  
Turbine Stage ◽  
Time Resolved ◽  
Guide Vanes ◽  
Wake Interaction ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes

The current paper presents a time-resolved experimental flow investigation in a highly loaded transonic gas turbine stage operating continuously under engine representative conditions. The measurement was performed with a two-component Laser-Doppler-Velocimeter (LDV) and a three-component stereoscopic Particle-Image-Velocimeter (3C-PIV). Unsteady velocity data were obtained in axis perpendicular planes (LDV) and tangential planes (3C-PIV) between stator and rotor as well as downstream of the rotor. The results of the time-resolved investigation at several radii show the vortex shedding process from the trailing edges of nozzle guide vanes and rotor blades. This vortex shedding was found to be phase locked to higher harmonics of the blade passing frequency. Pressure waves evoked by reflection of the trailing edge shocks of the vanes on the passing rotor blades interact with the boundary layers on the rear suction side of the vanes and on the rotor blade surfaces while running upstream and downstream the flow. They are responsible for this phase-locking phenomenon of the shedding vortices. At midspan, the vortices shedding from stator and rotor blades were also observed by PIV. The in-plane vorticity distribution was used to discuss the wake-wake interaction indicating that wake segments from the nozzle guide vanes were chopped by the rotor blades. These chopped segments are still visible in the distributions as a pair of counter rotating vortices. The nozzle wake segments are transported through the rotor passages by the flow, influencing the vortex street of the rotor blades as they pass by with the higher velocity of the main flow. A comparison with a numerical simulation is also given.

scholarly journals EXPERIMENTAL AND NUMERICAL ANALYSIS OF LOSS CHARACTERISTICS OF COOLED TRANSONIC NOZZLE GUIDE VANES

2021 ◽  
pp. 1-35
Author(s):  
Daniel Burdett ◽  
Thomas Povey
Keyword(s):  
Aerodynamic Performance ◽  
Loss Coefficient ◽  
Guide Vanes ◽  
Turbine Engine ◽  
University Of Oxford ◽  
Readiness Level ◽  
Exit Mach Number ◽  
Nozzle Guide ◽  
Engine Components ◽  
Nozzle Guide Vanes

Abstract This paper presents high-fidelity experimental traverse measurements downstream of an annular cascade of transonic nozzle guide vanes (NGVs) from a high-pressure (HP) turbine stage. The components are heavily-cooled real engine components from a modern civil gas turbine engine, operated at scaled engine conditions. Tests were conducted in the high technology readiness level (TRL) Engine Component Aerothermal (ECAT) facility at the University of Oxford. High resolution full-area traverse measurements of local kinetic energy (KE) loss coefficient are presented in several axial planes. In particular, we present: circumferential loss coefficient profiles at several radial heights; full-area traverses at three axial planes; and fully mixed-out loss calculations. Analysis of these data gives insight into particular loss structures, overall aerodynamic performance, and wake mixing rates. The effect of exit Mach number on performance is also considered. The data address a gap in the literature for detailed analysis of traverse measurements downstream of HP NGV engine components. Experimental data are compared with steady and unsteady RANS simulations, allowing benchmarking of typical CFD methods for absolute loss prediction of cooled components. There is relatively limited aerodynamic performance data in the literature for heavily cooled NGVs, and this study represents one of the most comprehensive of its type.

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