bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental and Numerical Investigation of Wake-Induced Transition on a Highly Loaded LP Turbine at Low Reynolds Numbers
Authors: Stadtmüller Peter , Fottner Leonhard , Fiala Andreas 
Published: August 2014

Experimental and numerical results of LP turbine cascade tests performed to investigate wake interaction effects on boundary layer transition are presented. The data obtained at different inlet flow angles, turbulence levels and Mach numbers are compared and discussed with special focus on low Reynolds number conditions. For the boundary layer, calculated propagation velocities of disturbances are introduced to explain the transition process on the suction side of the blade over time.
Using a moving bar wake generator and surface-mounted hot films as well as surface pressure tappings, the effects of periodic wake passing were studied in the High-Speed Cascade Wind Tunnel on the aft-loaded LPT profile T106. Blade pitch was increased as compared with design point conditions to achieve a higher blade loading. As a result, a large separation bubble formed on the suction side of the surface and allowed unsteady boundary layer development to be studied in great detail. Starting at a characteristic Reynolds number, massive separation occurred on the suction side under steady state conditions, i.e. the boundary layer was unable to reach the back pressure at the trailing edge. By using the wake generator, it was possible to reduce this separation and thus decrease profile pressure losses by 50%.
The primary objective of the study was to provide unsteady ensemble-averaged hot film data together with information on the wake induced path, sufficient for the validation of numerical simulations. Such a simulation of the experiment was conducted using the Unsteady Boundary Layer Interaction Method, which takes into account the influence of boundary layer displacement on the velocity distribution and the time-dependent turbulence level in the outflow. The computations provide a good description of the wall shear stress in the transitional region and are in good agreement with the experimental data. By plotting propagation directions of boundary layer disturbances in space-time diagrams, it is shown that one characteristic direction is deviated around the so-called becalmed region and the temporarily separated region into the wake-induced transitional region.
The Influence of Multimode Transition Initiated by Periodic Wakes on the Profile Loss of a Linear Compressor Cascade
Authors: Teusch Reinhold , Brunner Stefan , Fottner Leonhard , Swoboda Marius 
Published: August 2014

This paper presents results of boundary layer and loss measurements in a high speed cascade wind tunnel on a linear compressor cascade under the influence of unsteady, periodic wakes. The wakes of an upstream blade row were simulated by cylindrical bars moved by a belt mechanism upstream of the cascade.
Extensive hot-film array, hot-wire and pressure measurements with variation of steady and unsteady inlet flow conditions have been performed for a better understanding of the transition and loss mechanisms on a blade row interacting with wakes.
The incoming wakes are inducing early forced transition in the boundary layer followed in time by calmed regions. Due to its higher shear stress level and its fuller velocity profile, the calmed flow is able to suppress laminar separation bubbles and to delay transition in the region with undisturbed flow between wakes, playing a significant role in the loss generation process.
At the investigated low Reynolds number, where the measurements for the steady flow case showed a well-developed laminar separation bubble, reductions of profile loss up to 20% were observed for the measured configuration. In the case of the high Reynolds number, where in undisturbed flow only a small separation bubble was detected, a profile loss rise up to 30% was measured.
Beside a better understanding of unsteady flow physics the goal of these basic investigations of unsteady transition is to create a wide database for the improvement of transition modeling in unsteady CFD codes.
Systematic Experimental and Numerical Investigations on the Aerothermodynamics of a Film Cooled Turbine Cascade With Variation of the Cooling Hole Shape: Part I — Experimental Approach
Authors: Ganzert Wolfgang , Hildebrandt Thomas , Fottner Leonhard 
Published: August 2014

As a part of a systematic research program isothermal investigations on the aerodynamics and the heat transfer of a large scale turbine cascade with suction side film cooling with shaped holes and compound inclination were carried out. The film cooling through a row of holes at forty percent chord length on the suction side was supplied by a large plenum chamber. The axial component inclination was kept constant at 30°. All holes have a cylindrical inlet combined with a shaped outlet. Three injection geometries were tested. The first two investigated configurations had no lateral inclination. The hole geometries can be briefly described as follows: Fan-shaped holes with lateral expansion, fan-shaped holes with lateral expansion and streamwise laid-back. The last investigation combined the most complex hole shape with a lateral hole inclination of 45°.
Typical engine conditions for the Mach and Reynolds number as well as the inlet turbulence level were maintained. Due to hardware limitations the total temperature was set to 303 Kelvin.
The measured data comprise local and integral total pressure loss coefficients obtained by pressure probe traversing at midspan downstream of the cascade. The static profile pressure distribution together with oil-and-dye flow visualisation gives information on the surface flow conditions and boundary layer development especially in the near hole region. Three dimensional hot wire anemometry is used for detailed flow measurements in the hole region. Based on the steady state liquid crystal heat transfer measurement technique pseudo colour contour plots are used for the documentation of the local surface heat transfer coefficient distribution. Laterally averaged and statistically analysed data of the surface heat transfer is applied in further heat transfer examinations.
The aim of all investigations is an aerodynamical optimisation of film cooling configurations taking into account the thermal aspects.
The most important conclusions can be summarised as follows: Compared to cylindrical holes with the same axial injection angle, shaped holes have a tremendous influence on the flow type in the near hole region. This leads to a more homogeneous pattern of the suction side heat transfer coefficient. The combination of shaped holes and lateral inclination induces definitely higher losses downstream of the cascade compared to the case with no inclination. Due to the lateral injection the former symmetrical vortex branches downstream of the hole are increased asymmetrically. This leads to higher mean heat transfer coefficients in the near hole region downstream of the injection. On the other side laterally blowing increases the homogeneity of the heat transfer coefficient.
A Presentation of Detailed Experimental Data of a Suction Side Film Cooled Turbine Cascade
Authors: Brandt Holger , Ganzert Wolfgang , Fottner Leonhard 
Published: August 2014

This paper presents detailed isothermal investigations on the aerodynamic effects and the heat transfer of suction side film cooling on a highly loaded turbine cascade. The measurements were carried out with inlet flow conditions kept constant at values which are typically found in modern gas turbines. Five configurations with different hole geometries were investigated, a cylindrical hole with two different streamwise inclination angles, a fan shaped hole and a fan shaped hole with laid-back both only inclined in streamwise direction and a fan shaped hole with laid-back and combined streamwise and lateral inclination. The variation of the blowing ratio enabled closer studies of the mixing process and the influence of the various hole configurations on the aerodynamics and the local heat transfer.
To enhance the understanding of the mechanisms and the boundary layer behaviour of these highly three-dimensional flows, much effort has been put on the measurement techniques. The high-resolution data needed was obtained using pressure tappings positioned on the profile, oil-and-dye visualizations on the suction surface, pneumatic probes in the wake and three-dimensional hot wire anemometry in the flow field downstream the holes. Additional heat transfer examinations with a special set-up based on the steady state liquid crystal technique clarified the individual local heat transfer distributions.
All measured data are summarized and documented to be used as a reference for three-dimensional, steady-state numerical calculations.
Thermo-Economic Analysis of an Intercooled, Reheat and Recuperated Gas Turbine for Cogeneration Applications: Part I — Base Load Operation
Authors: Bhargava R. , Bianchi M. , Negri di Montenegro G. , Peretto A. 
Published: August 2014

This paper presents a thermo-economic analysis of an intercooled, reheat (ICRH) gas turbine, with and without recuperation, for cogeneration applications. The optimization analyses of thermodynamic parameters have permitted to calculate variables, such as low-pressure compressor pressure ratio, high-pressure turbine pressure ratio and gas temperature at the waste heat recovery unit inlet while maximizing electric efficiency and “Energy Saving Index”. Subsequently, the economic analyses have allowed to evaluate return on the investment, and the minimum value of gross payout period, for the cycle configurations of highest thermodynamic performance. In the present study three sizes (100 MW, 20 MW and 5 MW) of gas turbines have been examined.
The performed investigation reveals that the maximum value of electric efficiency and “Energy Saving Index” is achieved for a large size (100 MW) recuperated ICRH gas turbine based cogeneration system. However, a non-recuperated ICRH gas turbine (of 100 MW) based cogeneration system provides maximum value of return on the investment and the minimum value of gross payout period compared to the other gas turbine cycles, of the same size and with same power to heat ratio, investigated in the present study. A comprehensive thermo-economic analysis methodology, presented in this paper, should provide useful guidelines for preliminary sizing and selection of gas turbine cycle for cogeneration applications.
Liquid Phase Diffusion Bond Repair of Westinghouse 501F, Row 3 Vanes
Authors: Miglietti Warren M. , Curtis Rich , Hall Brandon , Lazarin Christina M. 
Published: August 2014

During the industrial turbine engine operation of the W501F, Row3 Vanes, cracks develop as a result of thermal fatigue. Other damage found is pitting and dents resulting from corrosion/oxidation and FOD (foreign object damage) respectively. Erosion damage is also commonly found on the airfoils. Finally there is downstream deflection of the inner buttress/seal areas, as a result of axial creep. This paper describes the vacuum LPDB (liquid phase diffusion bond) repair process used to repair all of the above-mentioned damage, including LPDB build up and machining of the hook fit areas.
As a means of qualifying the high temperature diffusion bond process, both metallurgical and mechanical property evaluations were carried out. The metallurgical evaluation consisted of optical and scanning electron microscopy. The wide gap diffusion bonded area consisted of a fine-grained structure with carbide and boride phases dispersed both intergranularly and intragranularly. An EDAX analysis was also conducted and the results are reported.
The chemistry of the repaired area is similar to the base metal which may explain why mechanical tests revealed properties equivalent to that of the base metal. The mechanical evaluations undertaken were tensile tests at room temperature and elevated temperature, as well as stress rupture tests. These results were equivalent to mechanical properties of the X-45 Co-based superalloy, which is the base metal of the vane.
Measurements of Rotordynamic Coefficients of Hybrid Bearings With: (A) A Plugged Orifice, and (B) A Worn Land Surface
Authors: Laurant Franck , Childs Dara W. 
Published: August 2014

Test results are presented for the rotordynamic coefficients of a hybrid bearing that is representative of bearings for liquid-rocket-engine turbopump applications. The bearing is tested in the following two degraded conditions: (a) one of five orifices plugged, and (b) a locally-enlarged clearance to simulate a worn condition. Test data are presented at 24600 rpm, with supply pressures of 4.0, 5.5, and 7.0 MPa, and eccentricity ratios from 0.1 to 0.5 in 0.1 increments.
Overall, the results suggest that neither a single plugged orifice nor significant wear on the bearing land will “disable’ a well designed hybrid bearing. These results do not speak to multiple plugged orifices and are not an endorsement for operations without filters to prevent plugging orifices.
Design and Construction of a Transonic Test-Turbine Facility
Authors: Erhard J. , Gehrer A. 
Published: August 2014

This paper describes the design concept and construction of a continuous operating cold flow transonic test turbine facility, which is a unique combination of a 2 MW axial test turbine and a direct coupled brake compressor. To cover the losses additional air is provided through a separate electrically driven compressor station and fed into the turbine inlet casing via special mixer inserts which are also fed by the hot compressed air from the brake compressor. The main test rig dimensions and its capabilities are outlined.
A brief description of the design process with step by step advanced technology design methods is presented from the first ideas up to the latest plant expansion for special testing conditions where two industrial transonic turbine stages will be tested. The aerodynamic and structural design of our transonic single turbine stage (TTM-Stage) is described in detail and the results of the respective flow simulations are presented.
Endwall Cavity Flow Effects on Gaspath Aerodynamics in an Axial Flow Turbine: Part II — Source Term Model Development
Authors: Hunter Scott D. , Orkwis Paul O. 
Published: August 2014

Axial flow turbine designers are currently using Navier-Stokes flow solvers to reveal the details of the three dimensional flowfield inside individual bladerow passages. This new capability has allowed designers to focus on secondary flow reduction to improve turbine efficiency. These steady bladerow solvers include viscous and film cooling effects and show good agreement with test measurements in the midspan region. However, the difference between computational results and experimental data at the endwalls is significant due to the exclusion of endwall cavity effects. A clear understanding of how the cavity flow interacts with the gaspath aerodynamics, in conjunction with an accurate computational model, is needed to predict accurately the secondary flow patterns and endwall losses.
In Part I, the experimental and computational results from an investigation of the endwall cavity and gaspath flow interaction in a low pressure turbine were presented. Steady and unsteady computational analyses were utilized to model different combinations of the cavity and bladerow geometries. The data and computations confirmed that endwall cavity flows have a significant influence on gaspath aerodynamics and that these flows need to be included in bladerow computations for accurate results. However, the level of effort required to construct the computational grid and obtain a flow solution renders these computational models prohibitive.
In Part II, the development of a source term model for a steady bladerow solver that simulates endwall cavity flows in a low pressure turbine is reviewed. Different levels of model complexity were evaluated to determine the impact of endwall geometry and source term distributions on analysis accuracy. The source term model adequately captured endwall cavity effects and accurately predicted secondary flow in the adjacent bladerow. This source term model gives designers the capability to investigate new ideas of reducing secondary flow in a timely manner, leading to improvements in overall turbine efficiency.
A Test-Based Methodology for A Priori Selection of Gain/Phase Relationships in Proportional, Phase-Shifting Control of Combustion Instabilities
Authors: Vaudrey Michael A. , Saunders William R. , Eisenhower Bryan 
Published: August 2014

Feedback control system design, for general single-in-single-out (SISO) applications, requires accurate knowledge of the loop transfer function. Active combustion control design is usually implemented using such SISO architectures, but is quite challenging because the thermoacoustic response results from a relatively unknown, self-excited system and nonlinear processes that must be understood before learning the gain/phase relationship of the system precisely at the instability frequency. However, recent experiments have shown that it is possible to obtain accurate measurements of the relevant loop transfer (frequency response) functions at frequencies adjacent to the instability frequency. Using a simple tube combustor, operating with a premixed, gaseous, burner-stabilized flame, the loop frequency response measurements have been used to develop a methodology that leads to ‘test-based predictions’ of the absolute phase settings and ‘best’ gain settings for a proportional, phase-shifting controller commanding an acoustic actuator in the combustor.
The contributions of this methodology are twofold. First, it means that a manual search for the required phase setting of the controller is no longer necessary. In fact, this technique allows the absolute value of controller phase to be determined without running the controller. To the authors’ knowledge, this has not been previously reported in the literature. In addition, the ‘best’ gain setting of the controller, based on this new design approach, can be defined as one that eliminates or reduces the limit cycle amplitude as much as possible within the constraint of avoiding generation of any controller-induced instabilities. (This refers to the generation of ‘new’ peaks in the controlled acoustic pressure spectrum.) It is shown that this tradeoff in limit cycle suppression and avoidance of controller-induced instabilities is a manifestation of the well-known tradeoff in the sensitivity/complementary sensitivity function for feedback control solutions. The focus of this article is limited to the presentation of the design method and does not discuss the detailed nonlinear phenomena that must be understood to determine the optimal gain/phase settings at the limit cycle frequency for a real (versus theoretical) combustor system. A companion paper describes how the proposed design method can be used to generate an AI controller that maintains stabilizing control for a range of changing operating conditions.
Demonstration of a Semi-Closed Cycle, Turboshaft Gas Turbine Engine
Authors: Meitner Peter L. , Laganelli Anthony L. , Senick Paul F. , Lear William E. 
Published: August 2014

A semi-closed cycle, turboshaft gas turbine engine was assembled and tested under a cooperative program funded by the NASA Glenn Research Center with support from the U.S. Army. The engine, called HPRTE (High Pressure, Recuperated Turbine Engine), features two distinct cycles operating in parallel; an “inner,” high pressure, recuperated cycle, in which exhaust gas is recirculated, and an “open” through-flow cycle. Recuperation is performed in the “inner,” high pressure loop, which greatly reduces the size of the heat exchanger. An intercooler is used to cool both the recirculated exhaust gas and the fresh inlet air. Because a large portion of the exhaust gas is recirculated, significantly less inlet air is required to produce a desired horsepower level. This reduces the engine inlet and exhaust flows to less than half that required for conventional, open cycle, recuperated gas turbines of equal power. In addition, the reburning of the exhaust gas reduces exhaust pollutants.
A two-shaft engine was assembled from existing components to demonstrate concept feasibility. The engine did not represent an optimized system, since most components were oversized, and the overall pressure ratio was much lower than optimum. New cycle analysis codes were developed that are capable of accounting for recirculating exhaust flow. Code predictions agreed with test results. Analyses for a fully developed engine predict almost constant specific fuel consumption over a broad power range. Test results showed significant emissions reductions.
This document is the first in a series of papers that arc planned to be presented on semi-closed cycle characteristics, issues, and applications, addressing the impact of recirculating exhaust flow on combustion and engine components.
Hybrid Heat Engines: The Power Generation Systems of the Future
Authors: Layne Abbie , Samuelsen Scott , Williams Mark , Hoffman Patricia 
Published: August 2014

A hybrid heat engine results from the fusion of a heat engine with a non-heat-engine based cycle (unlike systems). The term combined cycle, which refers to similar arrangements, is reserved for the combination of two or more heat engines (like systems). The resulting product of the integration of a gas turbine and a fuel cell is referred to here as a hybrid heat engine or “Hybrid” for short.
The intent of this paper is to provide, to the gas turbine community, a review of the present status of hybrid heat engine technologies. Current and projected activities associated with this emerging concept are also presented. The National Energy Technology Laboratory (NETL) is collaborating with other sponsors and the private sector to develop a Hybrid Program. This program will address the issues of technology development, integration, and ultimately the demonstration of what may be the most efficient of power plants in the world — the Hybrid System.
Analyses of several Hybrid concepts have indicated the potential of ultra-high efficiencies (approaching 80%). In the Hybrid, the synergism between the gas turbine and fuel cell provides higher efficiencies and lower costs than either system can alone.
Testing of the first Hybrid concept has been initiated at the National Fuel Cell Research Center (NFCRC).