bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unsteady Flow in Oscillating Turbine Cascade: Part 2 — Computational Study
Authors: He L. 
Published: February 2015

Unsteady flow around a linear oscillating turbine cascade has been experimentally and computationally studied, aimed at understanding the bubble type of flow separation and examining the predictive ability of a computational method. It was also intended to check the validity of the linear assumption under an unsteady viscous flow condition.
Part 2 of the paper presents a computational study of the experimental turbine cascade as discussed in Part 1. Numerical calculations were carried out for this case using an unsteady Navier-Stokes solver. The Baldwin-Lomax mixing length model was adopted for turbulence closure. The boundary layers on blade surfaces were either assumed to be fully turbulent or transitional with the unsteady transition subject to a quasi-steady laminar separation bubble model. The comparison between the computations and the experiment were generally quite satisfactory, except in the regions with the flow separation. It was shown that the behaviour of the short-bubble on the suction surface could be reasonably accounted for by using the quasi-steady bubble transition model. The calculation also showed that there was a more apparent mesh dependence of the results in the regions of flow separation.
Two different kinds of numerical tests were carried out to check the linearity of the unsteady flow and therefore the validity of the Influence Coefficient method. Firstly calculations using the same configurations as in the experiment were performed with different oscillating amplitudes. Secondly calculations were performed with a tuned cascade model and the results were compared with those using the Influence Coefficient method. The present work showed that nonlinear effect was quite small, even though for the most severe case in which the separated flow region covered about 60% of blade pressure surface with a large movement of the reattachment point. It seemed to suggest that the linear assumption about the unsteady flow behaviour should be adequately acceptable for situations with bubble type flow separation similar to the present case.
Inlet Distortion Generated Forced Response of a Low Aspect Ratio Transonic Fan
Authors: Manwaring Steven R. , Rabe Douglas C. , Lorence Christopher B. , Wadia Aspi R. 
Published: February 2015

This paper describes a portion of an experimental and computational program (ADLARF) which incorporates, for the first time, measurements of all aspects of the forced response of an airfoil row, i.e., the flow defect, the unsteady pressure loadings and the vibratory response. The purpose of this portion was to extend the knowledge of the unsteady aerodynamics associated with a low aspect ratio transonic fan where the flow defects were generated by inlet distortions. Measurements of screen distortion patterns were obtained with total pressure rakes and casing static pressures. The unsteady pressure loadings on the blade were determined from high response pressure transducers. The resulting blade vibrations were measured with strain gages. The steady flow was analyzed using a 3D Navier–Stokes solver while the unsteady flow was determined with a quasi–3D linearized Euler solver.
Experimental results showed that the distortions had strong vortical, moderate entropic and weak acoustic parts. The 3D Navier–Stokes analyses showed that the steady flow is predominantly two–dimensional, with radially outward flow existing only in the blade surface boundary layers downstream of shocks and in the aft part of the suction surface. At near resonance conditions, the strain gage data showed blade–to–blade motion variations and thus, linearized unsteady Euler solutions showed poorer agreement with the unsteady loading data than comparisons at off–resonance speeds. Data analysis showed that entropic waves generated unsteady loadings comparable to vortical waves in the blade regions where shocks existed.
Optimum Power Boosting of Gas Turbine Cycles With Refrigerated Inlet Air and Compressor Intercooling
Authors: Ait-Ali Mohand A. 
Published: February 2015

With or without turbine blade cooling, gas turbine cycles have consistently higher turbine inlet temperatures than steam turbine cycles. But this advantage is more than offset by the excessive compressor work induced by warm inlet temperatures, particularly during operation on hot summer days. Instead of seeking still higher turbine inlet temperatures by means of sophisticated blade cooling technology and high temperature-resistant blade materials, it is proposed to greatly increase the cycle net work and also improve thermal efficiency by decreasing the compressor work. This is obtained by using refrigerated inlet air and compressor intercooling to an extent which optimizes the refrigerated air inlet temperature and consequently the gas turbine compression ratio with respect to maximum specific net power.
The cost effectiveness of this conceptual cycle, which also includes regeneration, has not been examined in this paper as it requires unusually high pressure ratio gas turbines and compressors, as well as high volumetric air flow rate and low temperature refrigeration equipment for which reliable cost data is not easily available.
Experimental Investigation and Theoretical Prediction of Flutter Behaviour of a Plane Cascade in Low-Speed Flow
Authors: Hennings H. , Send W. 
Published: February 2015

The Institute of Aeroelasticity operates a test facility which enables aeroelastic investigations of plane cascades in low-speed flow. The test stand serves as a pilot facility to develop tools for analogous investigations in transonic flow. Eleven blades are elastically suspended in a windtunnel with a 1 × 0.2 m2 cross section.
This paper describes the experimental method of determining the flutter boundary by extrapolation of the results measured in subcritical flow. A 2D theoretical model of the 11 blades including the windtunnel walls permits the computation of unsteady pressures, forces and moments in close relation to the experiment. The prediction of flutter is compared with experimental results. In the present investigation, the motion of the blades is constrained to pitch around mid-chord. The vibrating blades are mechanically uncoupled. Any interaction between the blades is effected by the air stream, leading to a sensitive dependence on the aerodynamic forces.
A Distortion Problem in a Single Shaft Military Turbojet
Authors: Kotsiopoulos Petros , Kottarakos Andreas , Pilidis Pericles 
Published: February 2015

Compressor surge is one of the most worrisome in-flight emergencies that users have to face. The phenomenon is influenced by many parameters internal or external to the engine. The purpose of this paper is to describe an investigation into this matter prompted by the operating experience of the Hellenic Air Force. Initially, the most common destabilizing parameters had to be identified and their influence on engine handling was assessed.
The Hellenic Air Force has been facing compressor surge problems, mostly related to the use of the aircraft or the type of mission. The findings of this work give a semi-quantitative explanation of the events observed in practice.
A Framework for Analyzing the Dynamics of Flexibly-Bladed Turbomachines
Authors: Gysling D. L. , Myers M. R. 
Published: February 2015

A framework for analyzing the nonlinear dynamic behavior of flexibly-bladed turbomachines is presented. The analytical description is based on matching a two dimensional, incompressible flow field across a semi-actuator disk representation of a flexible rotor and a rigid stator. The aerodynamic loading on the rotor is derived using control volume formulations applied to discrete blade passages allowing consideration of finite interblade phase angles. Depending on operating parameters, the model exhibits behaviors classified as surge, rotating stall, and stall flutter which are qualitatively consistent with experimentally observed results.
The formulation provides a tractable, nonlinear, state-space description of the dynamics responsible for surge, rotating stall, flutter, and their interaction. An analysis is performed for system parameters representative of a fan in a modern high-bypass ratio aeroengine. The behavior of the operability limiting instability modes is examined using time simulations, eigenvalues plots and two-parameter stability diagrams.
Unsteady Flow Calculation in a Cross-Flow Fan Using a Finite Element Method
Authors: Bert P. F. , Pessiani M. , Combes J. F. , Kueny J. L. 
Published: February 2015

In order to predict rotor-stator interactions in hydraulic turbomachinery, a new multidomain method was implemented in a turbulent flow finite element code. The formulation is based on the mortar element method, extended to sliding meshes. It allows the coupling between several domains using nonconforming discretization on the interface.
This method was used to study the unsteady flow in a cross-flow fan. Such fans are widely used in air-conditioning devices. They consist of a cylindrical rotor with forward curved blades, rotating in a housing. The air passes the blades twice at the inlet and the outlet of the impeller while a large vortex is noticeable inside the impeller which is located in the blading near the stabilizer.
The numerical results are compared to Laser Doppler Velocity measurements and to steady calculations obtained by replacing the blades by a rotating force field. The unsteady calculation shows the formation of the vortex structure at the start-up and the periodic established flow after a few revolutions of the impeller.
Development of Ceramic Gas Turbine Components for the CGT301 Engine
Authors: Hattori Mitsuru , Yamamoto Tsutomu , Watanabe Keiichiro , Masuda Masaaki 
Published: February 2015

NGK Insulators, Ltd. (NGK) has undertaken the research and development on the fabrication processes of high-heat-resistant ceramic components for the CGT301, which is a 300kW recuperative industrial ceramic gas turbine engine. This program is under the New Sunshine Project, funded by the Ministry of International Trade and Industry (MITI), and has been guided by the Agency of Industrial Science & Technology (AIST) since 1988. The New Energy and Industrial Technology Development Organization (NEDO) is the main contractor.
The fabrication techniques for ceramic components, such as turbine blades, turbine nozzles, combustor liners, gas-path parts, and heat exchanger elements, for the 1,200°C engine were developed by 1993. Development for the 1,350°C engine has been underway since 1994. The baseline conditions for fabricating of all ceramic components have been established.
This paper reports on the development of ceramic gas turbine components, and the improved accuracies of their shapes as well as improved reliability from the results of the interim appraisal conducted in 1994.
Effects of Free-Stream Turbulence and Surface Roughness on Film Cooling
Authors: Schmidt Donald L. , Bogard David G. 
Published: February 2015

A flat plate test section was used to study how high free-stream turbulence with large turbulence length scales, representative of the turbine environment, affect the film cooling adiabatic effectiveness and heat transfer coefficient for a round hole film cooling geometry. This study also examined cooling performance with combined high free-stream turbulence and a rough surface which simulated the roughness representative of an in-service turbine. The injection was from a single row of film cooling holes with injection angle of 30°. The density ratio of the injectant to the mainstream was 2.0 for the adiabatic effectiveness tests, and 1.0 for the heat transfer coefficient tests. Streamwise and lateral distributions of adiabatic effectiveness and heat transfer coefficients were obtained at locations from 2 to 90 hole diameters downstream.
At small to moderate momentum flux ratios, which would normally be considered optimum blowing conditions, high free-stream turbulence dramatically decreased adiabatic effectiveness. However, at large momentum flux ratios, conditions for which the film cooling jet would normally be detached, high free-stream turbulence caused an increase in adiabatic effectiveness. The combination of high free-stream turbulence with surface roughness resulted in an increase in adiabatic effectiveness relative to the smooth wall with high free-stream turbulence. Heat transfer rates were relatively unaffected by a film cooling injection. The key result from this study was a substantial increase in the momentum flux ratios for maximum film cooling performance which occurred for high free-stream turbulence and surface roughness conditions which are more representative of actual turbine conditions.
Thermocyclic Behavior of Variously Stabilized EB-PVD Thermal Barrier Coatings
Authors: Schulz U. , Fritscher K. , Peters M. 
Published: February 2015

The demand for increasing gas inlet temperatures in modem gas turbines up to 1500°C and above is the main reason for the need for more reliable thermal barrier coatings. New ceramics should provide higher phase stability and better resistance against chemical attack by pollutants in the combustion gas.
Electron-beam physical vapor deposition (EB-PVD) processed, ZrO2-based TBCs were generated on bond-coated superalloy directionally solidified (DS) samples. Common yttria-stabilized zirconias of two different compositions, as well as novel stabilizers like CeO2 and La2O3 were investigated. A columnar structure was established during high-rate deposition in all cases. Diameter, degree of ordering of the columns and phase composition depended on stabilizer oxide and content. The role of differences of vapor pressures is addressed with regard to chemical homogeneity of the coatings.
The performance of the TBCs having various stabilizers was investigated in a cyclic oxidation furnace test and in a burner rig at Mach 0.3. The results were correlated to the type and content of stabilizer with special emphasis on phase analyses.
Evaporation of new ceramic compositions necessitates special precautions because the vapor pressures of the components may differ too much. A new dual-source evaporation coater allows the production of these innovative TBCs with close control of chemistry. The potential of the equipment will be discussed.
Life-Cycle Engineering Support From the US Navy Gas Turbine Ship Complex
Authors: Socoloski Paul , Maier Michael , Lamberto Michael 
Published: February 2015

The United States Navy has tested propulsion plants since the beginning of the century. There is a long record of successful test programs which have either proven new systems for introduction to the fleet or demonstrated the inability of new systems to meet the requirements of the fleet. Traditionally these test programs concluded with the introduction of the propulsion system into service. With the conception of the Gas Turbine Ship Complex in the mid 1980s, the Navy recognized the need to maintain a facility for conducting life cycle engineering activities to support the more complex gas turbine plants and control systems in the fleet. The Gas Turbine Ship Complex successfully tested the DDG-51 Class propulsion plant before the introduction of the Arleigh Burke and now continues to provide testing of gas turbine plant upgrades, allows training for DDG-51 Class precommissioning crews, enables In-Service Engineers to conduct plant operations to resolve emergent fleet problems and conducts Research and Development on new and upgraded systems.
This paper recounts the premiss for developing the Gas Turbine Ship Complex and shows how the plant has gone beyond traditional propulsion plant test programs to fulfill its mission as a facility for life cycle support of gas turbine ships.
A Comparison of HVOF and LPPS Applied MCrAlY Coating
Authors: van Esch Hans , Greaves Wayne 
Published: February 2015

This study examined the ability of two High Velocity Oxyfuel (HVOF) systems, the Hobart Tafa JP 5000 and the Sulzer Metco DJ 2600 Hybrid, to apply MCrAlY coatings. The results were compared to a Low Pressure Plasma Spray (LPPS) applied material of the same chemistry. Each system is described and the optimum parameters are given. Also, an analysis of the powders is included.
The results were metallurgically evaluated for porosity level, oxygen content and yttrium distribution. Static oxidation tests were also performed on the NiCoCrAlY coating applied by each system. Conclusions were based on the relative performance of the JP 5000 and DJ 2600 Hybrid coatings as compared to the LPPS baseline material.
High Contaminant Air Filtration System for US Navy Hovercraft Gas Turbines
Authors: Ehrhardt Jerome , Piñeiro Iván 
Published: February 2015

The Landing Craft Air Cushion (LCAC) is the U.S. Navy’s high speed hovercraft used for amphibious landings. The LCAC uses four Allied Signal TF40B gas turbines for propulsion and air cushion lift, and two Sundstrand T-62 gas turbines for auxiliary power. Because of the craft’s low height at sea, the air cushion pressure and the propeller thrust the LCAC generates a high volume of sea spray, dust and airborne beach sand during its amphibious mission.
For what can be considered the most severe environment of any U.S. NAVY gas turbine application, a combustion air system was designed to efficiently remove the airborne contaminants of seawater, salt and sand. This paper discusses the design, developmental testing, fleet experience and improvements for the LCAC gas turbine combustion air inlet system.
GTD111 Alloy Material Study
Authors: Daleo Joseph A. , Wilson James R. 
Published: February 2015

Very little property data on this common turbine blade alloy has been published. As longer hours of service are accumulated, maintenance considerations such as developing optimum component life strategies and repair processes become important. The lack of specific material data hampers the effort of users and repair facilities to achieve optimum service from this alloy.
This study measured some of the basic mechanical and metallurgical characteristics of this poly-crystalline nickel base superalloy. Tensile and short term creep rupture properties as well as microstructural and fracture characteristics are presented. Both the as-heat-treated and thermally exposed characteristics at two different temperatures are examined.
Thermal Strains and Their Effect on the Life of Ceramic Matrix Composite Components in Gas Turbine Engines
Authors: Percival Michael J. L. , Beesley Colin P. 
Published: February 2015

Currently available Ceramic Matrix Composites (CMCs) have very low stress carrying capability if they are to achieve the service life required for application in gas turbine engines. As such, they are most likely to find their first applications in non-structural components with low mechanical loads, where the majority of the stress is thermally induced. The thermal cycling experienced in gas turbine engines, coupled with the necessary interfaces with surrounding metal components and other geometric features, means that these thermal stresses are often localised, but in order to produce a valid component design they may significantly exceed the maximum design stress.
The aim of this paper is to discuss the implications for the life of the component of these excess stresses. This will cover the mechanisms for the propagation of localised damage in a strain controlled environment, and the effect of this damage on the thermal conductivity and hence on the induced thermal gradients and thermal strains. Strains corresponding to stresses considerably above the normally accepted design stress can be sustained for a considerable number of cycles, but the influence of extended time periods with damage at elevated temperatures remains unexplored.
Economic Scales for First-Generation Biomass-Gasifier/Gas Turbine Combined Cycles Fueled From Energy Plantations
Authors: Larson Eric D. , Marrison Christopher I. 
Published: February 2015

This paper assesses the scales at which commercial, first-generation biomass integrated-gasifier/gas turbine combined cycle (BIG/GTCC) technology are likely to be most economic when fueled by plantation-derived biomass. First-generation BIG/GTCC systems are likely to be commercially offered by vendors beginning around 2000 and will be based on either pressurized or atmospheric-pressure gasification. Both plant configurations are considered here, with estimates of capital and operating costs drawn from published and other sources. Prospective costs of a farm-grown energy crop (switchgrass) delivered to a power plant are developed with the aid of a geographic information system (GIS) for agricultural regions in the North Central and Southeast US in the year 2000 and 2020. A simplified approach is applied to estimate the cost of delivering chipped eucalyptus from an existing plantation in Northeast Brazil.
The “optimum” capacity (MWopt), defined as that which yields the minimum calculated cost of electricity (COEm), varies by geographic region due to differences in delivered biomass costs. With pressurized BIG/GTCC plants, MWopt is in the range of 230–320 MWs for the sites considered, assuming most of the land around the power plant is farmed for energy crop production. For atmospheric-pressure BIG/GTCC plants, MWopt ranges from 110 to 142 MWe. When a lower fraction of the land around a plant is used for energy farming, values for MWopt are smaller than these. In all cases, the cost of electricity is relatively insensitive to plant capacity over a wide range around MWopt.
The Effect of Periodic Ribs on the Local Aerodynamic and Heat Transfer Performance of a Straight Cooling Channel
Authors: Rau G. , Çakan M. , Moeller D. , Arts T. 
Published: February 2015

The local aerodynamic and heat transfer performance were measured in a rib-roughened square duct as a function of the rib pitch to beight ratio. The blockage ratio of these square obstacles was 10% or 20% depending on whether they were placed on one single (1s) or on two opposite walls (2s). The Reynolds number, based on the channel mean velocity and hydraulic diameter, was fixed at 30000.
The aerodynamic description of the flow field was based on local pressure distributions along the ribbed and adjacent smooth walls as well as on 2D LDV explorations in the channel symmetry plane and in two planes parallel to the ribbed wall(s). Local heat transfer distributions were obtained on the floor, between the ribs, and on the adjacent smooth side wall. Averaged parameters, such as friction factor and averaged heat transfer enhancement factor, were calculated from the local results and compared to correlations given in literature.
This contribution showed that simple correlations derived from the law of the wall similarity and from the Reynolds analogy could not be applied for the present rib height-to-channel hydraulic diameter ratio (e/Dh=0.1). The strong secondary flows resulted in a three-dimensional flow field with high gradients in the local heat transfer distributions on the smooth side walls.