The Effect of Isentropic Exponent on Transonic Turbine Performance

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
David Baumgärtner ◽  
John J. Otter ◽  
Andrew P. S. Wheeler
Keyword(s):  
Operating Conditions ◽  
Turbine Performance ◽  
Wide Range ◽  
Turbine Vane ◽  
Isentropic Exponent ◽  
Real Gas Effects ◽  
Transonic Turbine ◽  
Exit Mach Number ◽  
Transient Wind ◽  
Annular Cascade

Abstract The isentropic exponent is one of the most important properties affecting gas dynamics. Nonetheless, its effect on turbine performance is not well known. This paper discusses a series of experimental and computational studies to determine the effect of isentropic exponent on the flow field within a turbine vane. Experiments are performed using a newly modified transient wind tunnel that enables annular cascade testing with a wide range of working fluids and operating conditions. For the present study, tests are undertaken using air, CO2, R134a, and argon, giving a range of isentropic exponent from 1.08 to 1.67. Measurements include detailed wall static pressures that are compared with computational simulations. Our results show that over the range of isentropic exponents tested here, the loss can vary between 20% and 35%, depending on vane exit Mach number. The results are important for future turbines operating with real-gas effects and/or those where high gas temperatures can lead to variations in the isentropic exponent.

The Effect of Isentropic Exponent on Transonic Turbine Performance

2019 ◽  
Author(s):  
David Baumgärtner ◽  
John J. Otter ◽  
Andrew P. S. Wheeler
Keyword(s):  
Operating Conditions ◽  
Turbine Performance ◽  
Wide Range ◽  
Turbine Vane ◽  
Isentropic Exponent ◽  
Real Gas Effects ◽  
Transonic Turbine ◽  
Exit Mach Number ◽  
Transient Wind ◽  
Annular Cascade

Abstract The isentropic exponent is one of the most important properties affecting gas dynamics. Nonetheless, its effect on turbine performance is not well known. The paper discusses a series of experimental and computational studies to determine the effect of isentropic exponent on the flow field within a turbine vane. Experiments are performed using a newly modified transient wind tunnel which enables annular cascade testing with a wide range of working fluids and operating conditions. For the present study tests are undertaken using air, CO2, R134a and argon, giving a range of isentropic exponent from 1.08–1.67. Measurements include detailed wall static pressures which are compared with computational simulations. Our results show that over the range of isentropic exponents tested here, the loss can vary by between 20%–35%, depending on vane exit Mach number. The results are important for future turbines operating with real-gas effects and/or those where high gas temperatures can lead to variations in isentropic exponent.

Influence of Pre-History and Leading Edge Contouring on Aero-Performance of a 3D Nozzle Guide Vane

2013 ◽  
Author(s):  
Ranjan Saha ◽  
Boris I. Mamaev ◽  
Jens Fridh ◽  
Björn Laumert ◽  
Torsten H. Fransson
Keyword(s):  
Guide Vane ◽  
Three Dimensional ◽  
Leading Edge ◽  
Stagnation Line ◽  
Wide Range ◽  
Nozzle Guide Vane ◽  
Turbine Vane ◽  
Loss Coefficients ◽  
Exit Mach Number ◽  
Nozzle Guide

Experiments are conducted to investigate the effect of the pre-history in the aerodynamic performance of a three-dimensional nozzle guide vane with a hub leading edge contouring. The performance is determined with two pneumatic probes (5 hole and 3 hole) concentrating mainly on the endwall. The investigated vane is a geometrically similar gas turbine vane for the first stage with a reference exit Mach number of 0.9. Results are compared for the baseline and filleted cases for a wide range of operating exit Mach numbers from 0.5 to 0.9. The presented data includes loading distributions, loss distributions, fields of exit flow angles, velocity vector and vorticity contour, as well as, mass-averaged loss coefficients. The results show an insignificant influence of the leading edge fillet on the performance of the vane. However, the pre-history (inlet condition) affects significantly in the secondary loss. Additionally, an oil visualization technique yields information about the streamlines on the solid vane surface which allows identifying the locations of secondary flow vortices, stagnation line and saddle point.

scholarly journals Flow and Fast Fourier Transform Analyses for Tip Clearance Effect in an Operating Kaplan Turbine

Energies ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 264 ◽  
Author(s):  
Hyoung-Ho Kim ◽  
Md Rakibuzzaman ◽  
Kyungwuk Kim ◽  
Sang-Ho Suh
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Kaplan Turbine ◽  
Turbine Performance ◽  
Wide Range ◽  
Clearance Flow ◽  
Fft Analysis

The Kaplan turbine is an axial propeller-type turbine that can simultaneously control guide vanes and runner blades, thus allowing its application in a wide range of operations. Here, turbine tip clearance plays a crucial role in turbine design and operation as high tip clearance flow can lead to a change in the flow pattern, resulting in a loss of efficiency and finally the breakdown of hydro turbines. This research investigates tip clearance flow characteristics and undertakes a transient fast Fourier transform (FFT) analysis of a Kaplan turbine. In this study, the computational fluid dynamics method was used to investigate the Kaplan turbine performance with tip clearance gaps at different operating conditions. Numerical performance was verified with experimental results. In particular, a parametric study was carried out including the different geometrical parameters such as tip clearance between stationary and rotating chambers. In addition, an FFT analysis was performed by monitoring dynamic pressure fluctuation on the rotor. Here, increases in tip clearance were shown to occur with decreases in efficiency owing to unsteady flow. With this study’s focus on analyzing the flow of the tip clearance and its effect on turbine performance as well as hydraulic efficiency, it aims to improve the understanding on the flow field in a Kaplan turbine.

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.

Upstream Film Cooling on the Contoured Endwall of a Transonic Turbine Vane in an Annular Cascade

2021 ◽  
Author(s):  
Daniel Salinas ◽  
Izhar Ullah ◽  
Lesley Wright ◽  
Je-Chin Han ◽  
John Mcclintic ◽  
...  
Keyword(s):  
Film Cooling ◽  
Turbine Vane ◽  
Transonic Turbine ◽  
Annular Cascade

scholarly journals Evaluating the Use of Leaned Stator Vanes to Produce a Non-Uniform Flow Distribution Across the Inlet Span of a Mixed Flow Turbine Rotor

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Richard Morrison ◽  
Stephen Spence ◽  
Sung In Kim ◽  
Thomas Leonard ◽  
Andre Starke
Keyword(s):  
Leading Edge ◽  
Operating Conditions ◽  
Operating Point ◽  
Mixed Flow ◽  
Design Performance ◽  
Turbine Performance ◽  
Percentage Points ◽  
Wide Range ◽  
Turbine Rotors ◽  
Operating Points

Abstract Current trends in the automotive industry have placed an increased emphasis on downsized turbocharged engines for passenger vehicles. The turbocharger is increasingly relied upon to improve power output across a wide range of engine operating conditions, placing a greater emphasis on turbocharger off-design performance. An off-design condition of significant importance is performance at low turbine velocity ratios, since it is relevant to engine transient response and also to efficient energy extraction from pressure pulses in the unsteady exhaust flow. An increased focus has been placed on equipping turbochargers with mixed flow turbine rotors instead of conventional radial flow turbine rotors to improve off-design performance and to reduce rotor inertia. A recognized feature of a mixed flow turbine is the spanwise variation of flow conditions across the blade leading edge. This is a consequence of the reduction in leading edge radius from shroud to hub, coupled with the increasing tangential velocity of the flow due to conserved angular momentum as the radius decreases. The result is increasingly positive incidence toward the hub side of the leading edge. The resulting region of highly positive incidence at the hub produces separation from the suction surface and generates significant loss within the rotor passage. The aim of this study was to determine if the losses in a mixed flow turbine (MFT) could be reduced by the use of leaned stator vanes, which deliberately created a significant spanwise variation of flow angle between hub and shroud at rotor inlet, to reduce the positive incidence at the hub. The turbine performance with a series of leaned vanes was compared against that of a straight vane using a validated computational fluid dynamics (CFD) model. It was found that increasing vane lean improved turbine performance at all operating points considered. An increase of 3.2 percentage points in stage total-to-static efficiency was achieved at a key off-design operating point. Experimental testing of a set of leaned vanes and the baseline vanes confirmed the advantage of the leaned vanes at all operating points, with an increase in measured efficiency of 2.6 percentage points at the key off-design condition. Unsteady CFD models confirmed the same level of improvement at this operating point. The CFD and experimental results confirmed that the losses in an MFT can be reduced by the use of leaned stator vanes to shape the flow at rotor inlet.

scholarly journals Heat Transfer Effect on Micro Gas Turbine Performance for Solar Power Applications

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6745
Author(s):  
Mahmoud A. Khader ◽  
Mohsen Ghavami ◽  
Jafar Al-Zaili ◽  
Abdulnaser I. Sayma
Keyword(s):  
Heat Transfer ◽  
Power Systems ◽  
Gas Turbine ◽  
Computational Study ◽  
Thermodynamic Cycle ◽  
Operating Conditions ◽  
Micro Gas Turbine ◽  
Turbine Performance ◽  
Wide Range ◽  
The Cost

This paper presents an experimentally validated computational study of heat transfer within a compact recuperated Brayton cycle microturbine. Compact microturbine designs are necessary for certain applications, such as solar dish concentrated power systems, to ensure a robust rotodynamic behaviour over the wide operating envelope. This study aims at studying the heat transfer within a 6 kWe micro gas turbine to provide a better understanding of the effect of heat transfer on its components’ performance. This paper also investigates the effect of thermal losses on the gas turbine performance as a part of a solar dish micro gas turbine system and its implications on increasing the size and the cost of such system. Steady-state conjugate heat transfer analyses were performed at different speeds and expansion ratios to include a wide range of operating conditions. The analyses were extended to examine the effects of insulating the microturbine on its thermodynamic cycle efficiency and rated power output. The results show that insulating the microturbine reduces the thermal losses from the turbine side by approximately 11% without affecting the compressor’s performance. Nonetheless, the heat losses still impose a significant impact on the microturbine performance, where these losses lead to an efficiency drop of 7.1% and a net output power drop of 6.6% at the design point conditions.

Attenuation of Vane Distortion in a Transonic Turbine Using Optimization Strategies: Part I—Methodology

2010 ◽  
Author(s):  
M. Joly ◽  
T. Verstraete ◽  
G. Paniagua
Keyword(s):  
Steady Flow ◽  
High Cycle Fatigue ◽  
Optimization Technique ◽  
Differential Evolution Algorithm ◽  
Operating Conditions ◽  
Cycle Fatigue ◽  
Flow Optimization ◽  
Multi Objective ◽  
Turbine Vane ◽  
Transonic Turbine

Single-stage high-pressure turbines often operate in the transonic regime, resulting in strong shock interactions between the vanes and the rotor blades. With the present study, a Multi-Objective Optimization is applied to the redesign of a transonic vane. The objective of the steady-flow optimization is to attenuate the propagation of shock waves downstream of the vane, while reducing the vane losses. Computation of the resulting unsteady forcing on the rotor is performed to validate the reduction in high-cycle fatigue risk. This first part presents the optimization code developed at the von Karman Institute. An evolutionary optimization strategy is applied with a differential evolution algorithm to address multi-objective problems. Turbine vane design is performed using a parametrization of 2D sections and of the 3D stacking line. Aerodynamic performances are evaluated with the TRAF solver considering robust mesh generations. Metamodels are investigated to provide a fast approximation of the Navier-Stokes computation. A methodology is proposed to assess the accuracy and robustness of the metamodel prediction, i.e. to evaluate the metamodel training effectiveness. The second part of this paper targets at the application of the optimization technique to the transonic turbine vane design. The objective is to reduce the downstream pitchwise static pressure distortion, with no increase of vane losses. The operating conditions are an isentropic exit Mach number of 1.2 and an outlet angle of −74 degree. The methodology includes a 2D section steady-flow optimization design at mid-span. Optimal airfoil passages present a convergent-divergent contraction channel that reduces the trailing edge shock system propagation. Validation of the geometry with the computation of the unsteady force response on the rotor confirms a reduction in high cycle fatigue risk. A multi-point optimization highlights the conflict between reducing the stator/rotor interaction and limiting the losses at off-design. A 3D optimization is finally performed considering simultaneously the lean and 2D section adaptation and enables further improvements of stator/rotor interaction and losses.

scholarly journals Uncertainty in High-Pressure Stator Performance Measurement in an Annular Cascade At Engine-Representative Reynolds and Mach

2021 ◽  
Author(s):  
Lakshya Bhatnagar ◽  
Guillermo Paniagua ◽  
David Gonzalez Cuadrado ◽  
Nyansafo Aye-Addo ◽  
Antonio Castillo Sauca ◽  
...  
Keyword(s):  
High Pressure ◽  
Uncertainty Analysis ◽  
Production Systems ◽  
Single Point ◽  
Measurement Data ◽  
Operating Conditions ◽  
Development Programs ◽  
Wide Range ◽  
Annular Cascade ◽  
Flow Blockage

Abstract The betterment of the turbine performance plays a prime role in all future transportation and energy production systems. Precise uncertainty quantification of experimental measurement of any performance differential is therefore essential for turbine development programs. In this paper, the uncertainty analysis of loss measurements in a high-pressure turbine vane are presented. Tests were performed on a stator geometry at engine representative conditions in a new annular turbine module called BRASTA (Big Rig for Annular Stationary Turbine Analysis) located within the Purdue Experimental Turbine Aerothermal Lab. The aerodynamic probes are described with emphasis on their calibration and uncertainty analysis, first considering single point measurement, followed by the spatial averaging implications. The change of operating conditions and flow blockage due to measurement probes are analyzed using CFD, and corrections are recommended on the measurement data. The test section and its characterization are presented, including calibration of the sonic valve. The sonic valve calibration is necessary to ensure a wide range of operation in Mach and Reynolds. Finally, the vane data are discussed, emphasizing their systematic and stochastic uncertainty.

Axial Turbine Performance Evaluation. Part A—Loss-Geometry Relationships

1968 ◽  
Vol 90 (4) ◽  
pp. 341-348 ◽  
Author(s):  
O. E. Balje´ ◽  
R. L. Binsley
Keyword(s):  
Reynolds Number ◽  
Performance Evaluation ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Published Data ◽  
Blade Height ◽  
Blade Number ◽  
Turbine Performance ◽  
Wide Range ◽  
Partial Admission

Generalized loss correlations for full and partial admission turbines have been derived and critically compared with recently published data. Effects included are Reynolds number, blade angles, blade height, blade number, blade trailing edge thickness, tip clearance, and reaction. These generalized loss relationships are for use in optimization of turbines over a wide range of possible operating conditions.

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