bluuebunny/crossref_metadata_2025 huggingface dataset:
Augmented reflex cutaneous vasodilatation following short‐term dietary nitrate supplementation in humans
Authors: Levitt Erica L. , Keen Jeremy T. , Wong Brett J.
Published: April 2015

New Findings

What is the central question of this study?

Nitrate supplementation via beetroot juice has been shown to have several benefits in healthy humans, including reduced blood pressure and increased blood flow to exercising muscle. Whether nitrate supplementation can improve blood flow to the skin in heat‐stressed humans has not been investigated.

What is the main finding and its importance?

Similar to previous studies, we found that nitrate supplementation reduces blood pressure. Nitrate supplementation increased vasodilatation in the skin of heat‐stressed humans but did not directly increase skin blood flow.

Nitrate supplementation has been shown to increase NO‐dependent vasodilatation through both NO synthase (NOS)‐dependent and NOS‐independent pathways. We hypothesized that nitrate supplementation would augment reflex cutaneous active vasodilatation. Subjects were equipped with two microdialysis fibres on the forearm randomly assigned as control (Ringer solution) or NOS inhibition (20 mm l‐NAME). Whole‐body heating was performed to raise core temperature by 0.8°C above baseline core temperature. Maximal cutaneous vasodilatation was achieved via 54 mm sodium nitroprusside and local heating to 43°C. Skin blood flow (measured by laser‐Doppler flowmetry) and blood pressure were measured. Cutaneous vascular conductance (CVC) was calculated as skin blood flow divided by mean arterial pressure (MAP) and expressed as a percentage of maximal CVC (%CVCmax). Subjects underwent heat stress before and after nitrate supplementation (3 days of beetroot juice; 5 mm, 0.45 g nitrates per day). During heat stress, MAP was reduced following nitrate supplementation compared with the control conditions (before 88 ± 3 mmHg versus after 78 ± 2 mmHg; P < 0.05); however, resting MAP was not different between conditions (before 88 ± 3 mmHg versus after 83 ± 2 mmHg; P = 0.117). Nitrate supplementation increased plateau CVC at control sites (before 67 ± 2%CVCmax versus after 80 ± 5%CVCmax; P = 0.01) but not at l‐NAME‐treated sites (before 45 ± 4%CVCmax versus after 40 ± 5%CVCmax; P = 0.617). There was no change in the calculated percentage of NOS‐dependent vasodilatation before and after supplementation (before 59 ± 4% versus after 64 ± 6%; P = 0.577). These data suggest that nitrate supplementation augments CVC and reduces MAP during heat stress.
On-Line Temperature Measurement Inside a Thermal Barrier Sensor Coating During Engine Operation
Authors: Yañez Gonzalez A. , Pilgrim C. C. , Feist J. P. , Sollazzo P. Y. , Beyrau F. , Heyes A. L.
Published: April 2015

Existing thermal barrier coatings (TBCs) can be adapted enhancing their functionalities such that they not only protect critical components from hot gases but also can sense their own material temperature or other physical properties. The self-sensing capability is introduced by embedding optically active rare earth ions into the thermal barrier ceramic. When illuminated by light, the material starts to phosphoresce and the phosphorescence can provide in situ information on temperature, phase changes, corrosion, or erosion of the coating subject to the coating design. The integration of an on-line temperature detection system enables the full potential of TBCs to be realized due to improved accuracy in temperature measurement and early warning of degradation. This in turn will increase fuel efficiency and will reduce CO2 emissions. This paper reviews the previous implementation of such a measurement system into a Rolls-Royce jet engine using dysprosium doped yttrium-stabilized-zirconia (YSZ) as a single layer and a dual layer sensor coating material. The temperature measurements were carried out on cooled and uncooled components on a combustion chamber liner and on nozzle guide vanes (NGVs), respectively. The paper investigates the interpretation of those results looking at coating thickness effects and temperature gradients across the TBC. For the study, a specialized cyclic thermal gradient burner test rig was operated and instrumented using equivalent instrumentation to that used for the engine test. This unique rig enables the controlled heating of the coatings at different temperature regimes. A long-wavelength pyrometer was employed detecting the surface temperature of the coating in combination with the phosphorescence detector. A correction was applied to compensate for changes in emissivity using two methods. A thermocouple was used continuously measuring the substrate temperature of the sample. Typical gradients across the coating are less than 1 K/μm. As the excitation laser penetrates the coating, it generates phosphorescence from several locations throughout the coating and hence provides an integrated signal. The study successfully proved that the temperature indication from the phosphorescence coating remains between the surface and substrate temperature for all operating conditions. This demonstrates the possibility to measure inside the coating closer to the bond coat. The knowledge of the bond coat temperature is relevant to the growth of the thermally grown oxide (TGO) which is linked to the delamination of the coating and hence determines its life. Further, the data are related to a one-dimensional phosphorescence model determining the penetration depth of the laser and the emission.
Experimental Thermal Field Measurements of Film Cooling Above the Suction Surface of a Turbine Vane
Authors: Stewart Willam R. , Bogard David G.
Published: April 2015

Two-dimensional thermal profiles were experimentally measured downstream of a single row of film cooling holes on both an adiabatic and a matched Biot number model turbine vane. The measurements were taken as a comparison to computational simulations of the same model and flow conditions. Previously, adiabatic and overall effectiveness comparisons have been made between experimental and computational data. To improve computational models of the evolution of a film cooling jet as it propagates downstream, the thermal field above the vane, not just the footprint on the vane surface, must be analyzed. This study expands these data to include 2D thermal fields above the vane at 0, 5, and 10 hole diameters downstream of the film cooling holes. Four blowing ratios were tested, M = 0.28, 0.65, 1.11, and 2.41. In each case, the computational jets remained colder than the experimental jets because they did not diffuse into the mainstream as quickly. In addition, the computational results for the higher two blowing ratios exhibited the effects of the kidney vortex commonly studied in film cooling, but the experimental thermal fields were not dominated by this vortex. Finally, in comparing results above adiabatic and matched Biot number models, these thermal fields allow for an accurate analysis of whether or not the adiabatic wall temperature was a reasonable estimate of the driving temperature for heat transfer.
Mesoscale Robotic Assembly With Orthogonal Optical Alignment for UV-LIGA Parts
Authors: Ye Xin , Zhang Xiaofeng , Wan Bile , Zhang Zhijing , Liu Pan
Published: April 2015

This paper proposes an assembly system for ultraviolet-lithographie galvanik abformung (UV-LIGA) parts with a robotic manipulator. Both images of base part and object part could be obtained simultaneously from an in-house orthogonal optical alignment vision system. Two microgrippers were introduced to realize the reliable clamping. An initial calibration method was presented to ensure assembly accuracy. Assembly experiments were conducted with success rates of 80% and the time consumption of 20 min for all four parts assembly. Suspected causes of failure are motion mechanisms' uncertainty, part dislocation resulted from inertia force when microgripper is moving, and the error which is produced in the detection process because of random factors.
The Impact of Sustainability on Consumer Preference Judgments of Product Attributes
Authors: Goucher-Lambert Kosa , Cagan Jonathan
Published: April 2015

Despite significant interest from consumers, sustainable products often struggle to find success in the marketplace. This failure is frequently attributed to the perception that consumers remain unwilling to sacrifice product attributes such as form, function, or price in order to adopt a product whose environmental impact is less than that of a competing product. This work aims to better understand how knowing a product's environmental impact affects preference for that product's disparate attributes. Three products of various monetary investments and numbers of relevant features were explored through a conjoint analysis experiment that uncovers consumer preference for discrete form, function, and price attributes. In this work, single use spoons, reusable water bottles, and home washing machines were used for analysis. These three products were decomposed into form, function, and price attributes that were varied in discrete levels. After a form-only ratings-based conjoint analysis study was conducted to find high, medium, and low preference form designs for each participant, two separate form–function–price discrete choice studies were conducted for each of the three products. These two discrete choice trials were identical in all aspects except in the second trial participants were provided with calculated environmental impact values for all design configurations; the presented environmental impact information was a dependent variable based on a life cycle analysis calculation using the current product configuration being shown to the participant. Further, adding this information raises the decision to one of a social or moral choice. Results show that when participants are provided with this additional piece of information, their preference for form, function, and price attributes of a product is greatly impacted. In particular, we find that for the products chosen here, the importance of functional attributes increases in the context of environmental impact metrics, while the importance of form decreases and the importance of price decreases modestly. In other words, placing the preference judgment within a social or moral choice context changes decisions about product preferences.
Optimal Design of Safe Planar Manipulators Using Passive Torque Limiters
Authors: Zhang Meiying , Gosselin Clément
Published: April 2015

This paper presents a synthesis approach to build safe planar serial robotic mechanisms for applications in human–robot cooperation. The basic concept consists in using torque limiting devices that slip when a prescribed torque is exceeded so that the maximum force and the maximum power that the robot can apply to its environment are limited. In order to alleviate the effect of the change of pose of the robot on the joint to Cartesian force mapping, it is proposed to include more torque limiters than actuated joints. The design of isotropic force modules is addressed in order to produce proper force capabilities while ensuring safety. The proposed isotropic module of torque limiting devices leads to such characteristics. In addition to modeling the contact forces at the end-effector, the forces that can be applied by the robot to its environment when contact is taking place elsewhere along its links are also analyzed as well as the power of potential collisions. Examples of manipulator architectures and their static analysis are given. Finally, the design of a spatial serial manipulator using the isotropic planar force modules developed in the paper is illustrated.
Modification of the ICARE System for Pediatric Therapy
Authors: Nelson Carl A. , Stolle Cale J. , Burnfield Judith M. , Buster Thad W.
Published: April 2015

Effective gait therapy is critical to children who have difficulty walking due to developmental, neurologic, or orthopedic conditions. Current gait training technologies can be cost prohibitive and often do not address the needs of children of varying sizes. In addition, clinicians often need to provide significant physical assistance to children with profound weakness. Based on the success of an elliptical-based adult-sized intelligently controlled assistive rehabilitation elliptical (ICARE) system for gait training, a modified technology was proposed to address the needs of younger/smaller children. The new design relied on a screw-and-slider joint to adjust the effective length of the crank link in the elliptical mechanism, reducing the step length and stride height simultaneously. The new trajectories of the foot pedal were normalized against stride length and showed nearly identical trajectories between pediatric strides and adult strides. Simulation results and human usability studies verified that the design was feasible.
A New Gas Path Fault Diagnostic Method of Gas Turbine Based on Support Vector Machine
Authors: Zhou Dengji , Zhang Huisheng , Weng Shilie
Published: April 2015

As a crucial section of gas turbine maintenance decision-making process, to date, gas path fault diagnostic has gained a lot of attention. However, model-based diagnostic methods, like nonlinear gas path analysis (GPA) and genetic algorithms, need an accurate gas turbine model, and diagnostic methods without gas turbine model, like expert system, need a knowledge database. Both are difficult to gain. Thus, data-driven approach for gas path diagnosis, like artificial neural network, is increasingly attractive. Support vector machine (SVM), a novel computational learning method, seems to be a good choice for data-driven gas path fault diagnosis of gas turbine. In this paper, SVM is employed to diagnose a deteriorated gas turbine. The effect of sample number, kernel function, and monitoring parameters on diagnostic accuracy are studied, respectively. Additionally, the diagnostic result of SVM is compared to the result of artificial neural networks. The comparing result confirms that SVM has an obvious advantage over artificial neural networks method based on a small sample of data and can be employed to gas path fault diagnosis of gas turbine. In addition, SVM with radial basis kernel function is the best choice for gas turbine gas path fault diagnosis based on small sample.
Fault Analysis and Optimal Balancing of Bowing of Steam Turbine Rotor Under Long-Term Service
Authors: Chen Jingming , Jiang Dongxiang , Liu Chao
Published: April 2015

In recent years, bowing of steam turbine rotor under long time service occurs in several high-parameter units. Collected data show that the bending of the haywire rotor is increasing continuously, which results in excessive vibration in operation and even causes over-limit vibration during start-up. In order to suppress the vibration, balancing is utilized in field with the traditional approach that the balancing mass is placed in the section of the rotor close to the bearing. However, the balancing with the traditional approach could only reduce the vibration temporarily. In the long time scale, the bowing is still propagating or even gets worse after the balancing. To determine the cause of bowing and form optimal balancing approach, analysis is carried out in this work including: (i) fault cause and its treatment of bowing of steam turbine rotor under long time service is studied with elastic–plastic mechanics and creep mechanism taken in account; (ii) a case study was carried out, where the bowing process was simulated and validated with the field monitoring data; (iii) the phenomenon of the traditional balancing method was illustrated with rotordynamics analysis, where the influence of whirling is included. Based on the analysis, the cause of bowing is determined as uneven creep effect. And the balancing method would influence the whirling mode, which would worsen bowing in the traditional balancing method. Based on this conclusion, an optimized balancing method was developed to reduce the vibration and prevent bowing propagation simultaneously.
Effect of Premixed Fuel Preparation for Partially Premixed Combustion With a Low Octane Gasoline on a Light-Duty Multicylinder Compression Ignition Engine
Authors: Dempsey Adam B. , Curran Scott , Wagner Robert , Cannella William
Published: April 2015

Gasoline compression ignition (GCI) concepts with the majority of the fuel being introduced early in the cycle are known as partially premixed combustion (PPC). Previous research on single- and multicylinder engines has shown that PPC has the potential for high thermal efficiency with low NOx and soot emissions. A variety of fuel injection strategies have been proposed in the literature. These injection strategies aim to create a partially stratified charge to simultaneously reduce NOx and soot emissions while maintaining some level of control over the combustion process through the fuel delivery system. The impact of the direct injection (DI) strategy to create a premixed charge of fuel and air has not previously been explored, and its impact on engine efficiency and emissions is not well understood. This paper explores the effect of sweeping the direct injected pilot timing from −91 deg to −324 deg ATDC, which is just after the exhaust valve closes (EVCs) for the engine used in this study. During the sweep, the pilot injection consistently contained 65% of the total fuel (based on command duration ratio), and the main injection timing was adjusted slightly to maintain combustion phasing near top dead center. A modern four cylinder, 1.9 l diesel engine with a variable geometry turbocharger (VGT), high pressure common rail injection system, wide included angle injectors, and variable swirl actuations was used in this study. The pistons were modified to an open bowl configuration suitable for highly premixed combustion modes. The stock diesel injection system was unmodified, and the gasoline fuel was doped with a lubricity additive to protect the high pressure fuel pump and the injectors. The study was conducted at a fixed speed/load condition of 2000 rpm and 4.0 bar brake mean effective pressure (BMEP). The pilot injection timing sweep was conducted at different intake manifold pressures, swirl levels, and fuel injection pressures. The gasoline used in this study has relatively high fuel reactivity with a research octane number of 68. The results of this experimental campaign indicate that the highest brake thermal efficiency (BTE) and lowest emissions are achieved simultaneously with the earliest pilot injection timings (i.e., during the intake stroke).
Effects of Tip Endwall Contouring on the Three Dimensional Flow Field in an Annular Turbine Nozzle Guide Vane: Part 2 — Numerical Investigation
Authors: Arts Tony
Published: April 2015

This paper describes the numerical investigation of the three dimensional flow through a low speed, low aspect ratio, high turning annular turbine nozzle guide vane with meridional tip endwall contouring. This rotational flow field has been simulated using a finite volume discretization and a time marching technique to solve the three dimensional, time dependent Euler equations expressed in a cylindrical coordinates system. The results are presented under the form of contour plots, spanwise pitch-averaged distributions and blade static pressure distributions. Detailed comparisons with the measurements described in part I of the paper are also provided.
Inverse Design of Coolant Flow Passage Shapes With Partially Fixed Internal Geometries
Authors: Kennon Stephen R. , Dulikravich George S.
Published: April 2015

A method is described for the inverse design of complex coolant flow passage shapes in internally cooled turbine blades. This method is a refinement and extension of a method developed by the authors for designing a single coolant hole in turbine blades. The new method allows the turbine designer to specify the number of holes the turbine blade is to have. In addition, the turbine designer may specify that certain portions of the interior coolant flow passage geometry are to remain fixed (eg. struts, surface coolant ejection channels, etc.). Like the original design method, the designer must specify the outer blade surface temperature and heat flux distribution and the desired interior coolant flow passage surface temperature distributions. This solution procedure involves satisfying the dual Dirichlet and Neumann specified boundary conditions of temperature and heat flux on the outer boundary of the airfoil while iteratively modifying the shapes of the coolant flow passages using a least squares optimization procedure that minimizes the error in satisfying the specified Dirichlet temperature boundary condition on the surface of each of the evolving interior holes. Portions of the inner geometry that are specified to be fixed are not modified. A first order panel method is used to solve Laplace’s equation for the steady heat conduction within the solid portions of the hollow blade, making the inverse design procedure very efficient and applicable to realistic geometries. Results are presented for a realistic turbine blade design problem.
Fluid Flow and Heat Transfer Characteristics in the Entrance Regions of Circular Pipes
Authors: Lloyd S. , Brown A.
Published: April 2015

This paper describes the results of an experimental investigation into the velocity and turbulence fields and to a lesser extent the heat transfer in the entrance regions of short, circular cross-section pipes with length to diameter ratios up to 20 over the Reynolds number range from 35,000 to 170,000. The velocity and turbulence fields were measured by hot-wire anemometers backed up with pressure measurements and flow visualisation and the heat transfer by heat flux meters.
Design of a Supplementary-Fired Heat Recovery Module for Cogeneration Applications
Authors: Smith Kenneth O. , Dobos Charles J.
Published: April 2015

The conceptual design of a Heat Recovery Module (HRM) for cogeneration applications is described. The HRM is a prepackaged, pretested and skid-mounted system sized for the 500 to 1000 kW class of industrial gas turbine. Key features of the module include:

• a highly compact, once-through boiler fabricated using finned Incoloy 800 tubing

• a dual-fuel supplementary burner for greater system operating flexibility

• a prepackaged water treatment system incorporating feedwater softening rather than deionization

• a fully integrated microprocessor-based control system

Design criteria and operating characteristics are presented.
Extension of Gas Turbine Disc Life by Retrofitting a Supplemental Cooling System
Authors: Little D. , Wilson J. , Liburdi J.
Published: April 2015

The turbine disc lives in some industrial gas turbines are limited to much less than 100,000 hours by the formation of high temperature creep cracks when the engine is operated continuously at full load. Turbine users have experienced many costly repairs and even a wreck due to this recurring problem. The problem can be eliminated and the existing uncracked disc lives extended well beyond the 100,000 hour milestone by the retrofit of a supplemental disc cooling system.

The engineering work involved in properly identifying the cause and designing the cooling modification, including performance, aerodynamic, cooling network, finite element heat transfer, and stress analysis is explained. The build and test of the prototype cooling air system on a mechanical drive unit is discussed and test results demonstrating the success of the method given.

The concept of adding a supplemental disc cooling system to extend the expiring turbine disc lives of many mature frames has been demonstrated to be both practical and economical.
Tepco Futsu 2000 MW Combined Cycle Power Plant Design Features
Authors: Tomlinson Leroy O. , Kojima T.
Published: April 2015

The Tokyo Electric Power Company, Inc. Futsu Combined Cycle Power Generation plant is the World’s largest combined cycle power plant and when it enters commercial service in 1986 will be one of the most efficient. This plant will burn liquefied natural gas. Low heat rejection to cooling water, low sound level, low emissions and high stacks minimize the environmental impact of this large power generation plant. Features contributing to the ability of this plant to generate power economically and reliably while burning high cost fuel and producing minimum environmental impact are presented in this paper.
Laser Measurements of Fly Ash Rebound Parameters for Use in Trajectory Calculations
Authors: Tabakoff W. , Malak M. F.
Published: April 2015

This paper describes an experimental method used to find the particles restitution coefficients. The equations that govern the motion of solid particles suspended by a compressible gas flow through a turbomachine depend on the restitution coefficients. Analysis of the data obtained by Laser Doppler Velocimeter (LDV) System of the collision phenomenon gives the restitution ratios as a function of the incidence angle. From these ratios, the particle velocity components after collision are computed and used as the initial conditions to the solution of the governing equations of motion for the particles trajectory. The erosion of metals impacted by small dust particles can be calculated by knowing the restitution coefficients. The alloy used in this investigation was 410 stainless steel.
Re-Engining the Harrier
Authors: Cyrus John D. , Vowles W. M.
Published: April 2015

During the last twenty-eight years the capabilities of the Harrier have improved markedly, due in large measure to advances in the Pegasus propulsion system. New engine models and component improvements with their increased performance and/or weight reductions have produced increased range and payload capability for the aircraft. Because the Harrier is likely to continue in use well into the next century, an engine-aircraft-mission study has been conducted to identify the potential benefits arising from replacing the existing Pegasus engine with an advanced technology engine. These studies have shown that thrust increases associated with increased technology can improve mission capability substantially; radius can be increased by as much as 50% on a mission with a vertical takeoff requirement. However, as takeoff constraints are relaxed, aircraft restraints limit the benefits of the advanced technology engines.
AGT 101: Advanced Gas Turbine Technology Update
Authors: Kidwell J. R. , Kreiner D. M.
Published: April 2015

The Garrett/Ford AGT101 program has made significant progress during 1984 in ceramic component and engine test bed development, including initial ceramic engine testing. All ceramic components for the AGT101 [1644K (2500F)] engine are now undergoing development. Ceramic structures have been undergoing extensive analysis, design modification, and rig testing. AGT101 [1644K (2500F)] start capability has been demonstrated in rig tests. Also, 1644K (2500F) steady-state testing has been initiated in the test rigs to obtain a better understanding of ceramics in that environment.

The ceramic turbine rotor has progressed through cold spin test 12,040 rad/sec (115,000 rpm) and hot turbine rig test, and is currently in initial phases of engine test. Over 400 hours of engine testing is expected by March, 1985, including approximately 150 hours of operation and 50 starts on the 1422K (2100F) engine. All activities are progressing toward 1644K (2500F) engine testing in mid 1985.
Fuel Flexibility in Compressed Air Energy Storage Plants
Authors: Basler B. , Zaugg P.
Published: April 2015

The pneumatic storage of energy is one of the few economical storage processes which can be considered at present for large quantities of energy. Present Compressed Air Energy Storage (CAES) plants are designed on the basis of construction and operating experience at Huntorf, the world’s first air-storage plant [1]. That means, that the turbine of the plant is equipped with combustors to increase the power output during turbine operation, and to reduce the volume and cost of the air storage facility as well as the quantity and cost of the required charging energy [2]. In this paper it is explained that the Brown Boveri CAES turbomachinery is able to burn a variety of different fuels. This opens in many cases the possibility to choose a cheaper or better available fuel to reduce furthermore the operating cost of this kind of power plant.
Improvement of Pump Performance at Off-Design Conditions
Authors: Paulon J. , Fradin C. , Poulain J.
Published: April 2015

Industrial pumps are generally used in a wide range of operating conditions from almost zero mass flow to mass flows larger than the design value.

It has been often noted that the head-mass flow characteristic, at constant speed, presents a negative bump as the mass flow is somewhat smaller than the design mass flows.

Flow and mechanical instabilities appear, which are unsafe for the facility.

An experimental study has been undertaken in order to analyze and if possible to palliate these difficulties. A detailed flow analyzis has shown strong three dimensional effects and flow separations.

From this better knowledge of the flow field, a particular device was designed and a strong attenuation of the negative bump was obtained.
Status of the AGT 100 Advanced Gas Turbine Program
Authors: Groseclose Lance E. , Johnson Richard A.
Published: April 2015

Recent activities on the AGT 100 Advanced Gas Turbine Program have included engine testing, aerodynamic component development, and ceramic material and component development. Engine testing has progressed in total hours and hours per build, without a major failure. A special mechanical loss test was conducted. Aerodynamic component activity has included the compressor, combustor and regenerator. Ceramic development was continued in areas of basic materials, processing, component fabrication and evaluation, and engine testing.
The KC-135/CFM56 Re-Engine Program
Authors: Packer Paul H. , Goodman Mark P.
Published: April 2015

This paper reviews the preliminary studies that led to the KC-135/CFM56 Re-Engine Program and discusses the motivation for re-engining an aircraft, designed in the mid 1950s, with a modern high bypass turbofan. The selected engine, the CFM56-2B-1, and other major aircraft modifications are described. The KC-135R test program methods and results are addressed with particular attention given to engine and aircraft performance. The overall benefits of the program relating to mission capability, environmental impact, and cost are also presented.
Axial Flow Contra-Rotating Turbines
Authors: Louis J. F.
Published: April 2015

Two types of contra-rotating stages are considered; the first uses guide vanes and the second is vaneless. The wheels of the first type use bladings which are mirror images of each other and they operate with inlet and outlet swirl. The second type uses dissimilar bladings in each of the two wheels with axial inlet velocity to the first wheel and axial outlet velocity for the second wheel. An analysis of their performance indicates that both types can reach stage loading coefficients comparable or larger than conventional turbines with the same number of wheels. A comparison of the contra-rotating stages with conventional ones indicate a significant stage efficiency advantage of the contra-rotating over the conventional single rotation stages due mainly to the elimination of stationary vanes. The off-design performance indicates that relative wheel speed must be controlled. The attributes of contra-rotating turbines suggest their potential use in high performance aircraft engines, in dynamic space power systems and in low speed industrial gas turbines.
Alternative Fuels for Gas Turbines
Authors: Ball R. W.
Published: April 2015

The gas turbines owned and operated by utilities throughout the world burn expensive fuels and are under-utilised. Much research work has been done into burning cheaper, alternative fuels. The range of alternative fuels that are available is extensive and the gas turbine can be adapted to burn most of them. The adaptation process will cost the utility money, the pay back period for which depends on the utilisation of the modified plant. Modification of gas turbine plant to burn acceptable fuels can delay purchase of new plant. No major problems are envisaged in the modification of gas turbine plant operated in New Zealand.
The F-16 Common Engine Bay
Authors: Porcher C. E.
Published: April 2015

In 1979 the United States Air Force elected under the Engine Model Derivative Program (EMDP) to explore derivative engine concepts by the General Electric Company and the Pratt and Whitney Aircraft Division of United Technology Corporation with the objective of improving engine durability and reducing engine ownership cost for future procurements of their first line fighter engines. Concurrently, General Dynamics was invited to develop the necessary airframe/engine interface definition to assure engine compatibility with the airplane requirements. This EMDP development culminated in 1981 with the Alternate Fighter Engine (AFE) competition with General Electric proposing the F110-GE-100 engine and Pratt and Whitney Aircraft proposing the F100-PW-220. Both engines were placed in Full Scale Development and both met the USAF objectives of 4000 TAC cycle life and improved engine cost and warranty for application to the F-15 and F-16 fighters. General Dynamics evolved the concept of the Common Engine Bay which has all aircraft interfaces compatible with either AFE engine and the current Pratt and Whitney Aircraft F100-PW-200 engine. The original F-16 nacelle design, with minor modification of the interfaces and engine mount structure, was adapted to permit full interchangeability for the F100-PW-200, F100-PW-220, or the F110-GE-100 engines. Design requirements were set to permit a common airplane with no break in the production line or aircraft model change and with appropriate simple kits to permit interchangeability of any of the three engines in the field at the organizational level. This manufacturing capability allows the USAF the flexibility to conduct subsequent competitive procurement of the engine.
The Effect of Fuel Composition Upon Combustion Performance in a Rolls Royce Tyne Combustor
Authors: Bowden T. T. , Pearson J. H.
Published: April 2015

The combustion performance of a wide range of fuel types has been examined utilizing a single combustor from a Rolls-Royce Tyne gas-turbine engine. The results provide further evidence to suggest that fuel total hydrogen content provides a better indication of fuel combustion perfomance than does aromatic content. However, an even better prediction of fuel combustion performance is given by smoke point, although the acknowledged imprecision of the smoke point test does militate against its use as a primary specification requirement.

Analysis of certain fuels by 13C NMR and low resolution mass spectroscopy demonstrates that it is those fuels with high concentrations of polycyclic aromatics whose combustion performance in terms of flame radiation and exhaust emissions, is underpredicted by fuel total hydrogen content. There are indications that low concentrations of high molecular weight polycyclic aromatics may substantially impair combustion performance.
Gas Turbine Combustor Development Tools for Production Designs
Authors: Finger Stephen N. , Dubell Thomas L.
Published: April 2015

Gas turbine engine combustor design and development has long held a somewhat undeserved reputation as a “Black Art”. This reputation was earned because those unfamiliar with the technology perceived the large amount of development testing required indicated a lack of fundamental knowledge of combustion. Fundamental knowledge exists and provides the foundation for design and to guide decisions on development. However, considerable trial and error work is required to satisfy many and sometimes conflicting performance goals because complete quantification of separated flow aerodynamics, three dimensional flowfields, anisotropic two phase flow, chemical reaction and heat addition is a challenge not yet met. Therefore, there is considerable reliance on use of rigs during the preliminary design phase and on the use of rigs and engines during development. Well founded use of experimental tools is necessary and must be adequately planned for in any program for a combustor intended for production. This paper describes these tools and how they should be used in such a program.
A New Approach to the Calculation of Transonic Flow Through Two Dimensional Turbomachine Blade Rows
Authors: Denton J. D. , Xu L.
Published: April 2015

All methods of solving the Euler equations face the problem of errors in entropy. These errors are especially important at the leading edge of blade rows where any numerical errors will cause entropy to be produced and to convect downstream to influence the downstream flow, especially that on the blade surfaces.

A new numerical method is described which overcomes this problem by solving a conservation equation for entropy. This equation effectively replaces the usual momentum equation along streamlines. Sources of entropy are introduced to allow for shock loss with the magnitude of the source being determined from the Rankine-Hugoniot relations. A semi-implicit scheme is used to solve the continuity equation whilst the entropy and flow direction are updated by conventional explicit methods.

The flow through a selection of test cascades has been calculated with this new method and its predictions compared with exact solutions as well as with experimental data and with a conventional Euler solver. The results show that the new method is more accurate than the conventional one, it converges in fewer iterations but requires slightly longer computer times.
Design and Experimentation of a Combustor for High Combustion Intensity
Authors: Mestre André , Cadiou Anne
Published: April 2015

The length and volume requirements of small gas turbines for missiles or propelled targets lead to combustor designs with high combustion intensity and large value of the air loading parameter Ω.

The conventional combustors have used conditions corresponding to Ω values in the 1 to 10 kg m−3s−1 range. The increase of Ω required for combustors in missiles conduces for existing liners to a decrease of combustion efficiency and to an increase of pressure losses.

Technical solutions have been worked out to make a combustor operating with a large air loading parameter: 25kgm-3s-1⩽Ω⩽50kgm-3s-1 and a correct combustion efficiency (η = 0.955). Test performed at atmospheric pressure with direct visualization of the combustion zone has shown a uniform primary flame and a moderately heated liner that can withstand short duration flights.
Pulsating Combustion Applied to a Small Gas Turbine
Authors: Kentfield J. A. C. , Yerneni P.
Published: April 2015

A description is given of, what is believed to be the first test ever made of a gas turbine in which a valveless pulsed combustor replaced the conventional steady flow combustor. It is explained that the main incentive for using a pulsed combustor in a gas turbine is to achieve a net stagnation pressure gain between the compressor outlet and the turbine inlet. Brief descriptions are given of the pulsed combustor and the adaptation of the small gas turbine, which was of the gas generator type, to receive the pulsating combustion system. Results are presented which show that the gas turbine operated successfully using the pulsed combustor and that a very small net stagnation-pressure gain was achieved. An indication is given of possible future developments which should result in improved performance.
Conical Grid Plate Flame Stabilizers for Combustor Primary Zones
Authors: Ali A. F. , Andrews G. E.
Published: April 2015

Emission results are presented for a jet shear layer flame stabiliser design consisting of a 90° conical flame stabiliser with an array of holes and a central annular vaporiser fuel injection system. This design was tested with premixed propane and air and with direct propane injection into the vaporiser at two blockages and approach velocities. The results showed that an array of jet shear layers could be fuelled by a single fuel injector without incurring excessive NOx emissions. An increase in the primary zone residence time was found to result in an improved combustion efficiency, with no increase in NOx, provided that the stabiliser blockage was increased to maintain the pressure loss.
Computation of the Detached Shock and the Entrance Flow Field in a Supersonic or Transonic Cascade
Authors: Yaonan Hua
Published: April 2015

A method is presented in this paper for determining the shape of the detached shock and flow field quantities in the supersonic entrance region on an arbitrary stream surface of revolution. The equation of characteristics and the corresponding equation of compatibility are derived. The shape of the detached shock obtained is taken as the initial-value curve to calculate the supersonic entrance region by means of the method of characteristics. Consequently, the unique inlet flow angle is also calculated. Typical computations show that this method is both effective and rapid.
Energy Efficient Operation of Gas Turbine Compressor Sets
Authors: Boyce M. P. , Bowman J. C. , Meher-Homji C. B. , Focke A. B.
Published: April 2015

This paper presents techniques in which greater productivity and fuel savings can be achieved by the use of online monitoring and diagnostic systems and compressor management systems applied to turbo-compressors. With maintenance life cycle costs for gas turbines being about one-fifth of fuel life cycle costs, the incentives for maintaining good operating efficiency is high. An online monitoring and diagnostic system can go a long way in pin-pointing areas in which performance decrements occur. There is also large monetary savings by operating load compressors with minimum recirculation. Secondary benefits of such systems include automated vibration analysis and automated diagnostic of common faults.

This paper also covers some case histories that illustrate benefits and generic system diagrams that illustrate such systems.
Evaluation of Alternative Power System Designs for Offshore Applications
Authors: Young Ralph , Johnson William
Published: April 2015

A variety of gas turbine-generator sets are available for offshore power generation systems. The design of the power system can have significant impact on the weight and space requirements, as well as cost, reliability, and thermal efficiency characteristics. This paper describes an economic analysis methodology that includes capital costs, weight and space costs, fuel costs, and lost production costs. Production losses are calculated by means of reliability, availability, and maintainability (RAM) analyses.
Evaluation of Combustion Turbine Systems for the Direct Combustion of Coal
Authors: Berman Paul A. , Horazak Dennis A. , Pillsbury Paul W.
Published: April 2015

A combustion turbine combined cycle that uses coal-derived dirty fuels can be economical if the fuel is processed at the plant site and cost of electricity (COE) is used as the criterion for configuring the power system and selecting its components. In a DOE/METC-sponsored study, 12 combinations of power components and conditioning components were evaluated for each of two fuels: a gas made from coal and a coal/water slurry. One baseline system was selected from each group of 12 systems, based on its potential to achieve a low COE. Each baseline system was then parametrically evaluated to show the effects of specific components on the COE of the power plant. In one of these studies, on-site coal conversion was shown as the key to reducing the COE and the operating cost of the plant, thus improving the chances of the plant being used for baseload operation.
Heat Transfer Results and Operational Characteristics of the NASA Lewis Research Center Hot Section Cascade Test Facility
Authors: Gladden Herbert J. , Yeh Frederick C. , Fronek Dennis L.
Published: April 2015

The NASA Lewis Research Center gas turbine hot section test facility has been developed to provide a “real-engine” environment with well known boundary conditions for the aerothermal performance evaluation/verification of computer design codes. The initial aerothermal research data obtained at this facility are presented and the operational characteristics of the facility are discussed. This facility is capable of testing at temperatures and pressures up to 1600 K and 18 atm which corresponds to a vane exit Reynolds number range of 0.5×106 to 2.5×106 based on vane chord. The component cooling air temperature can be independently modulated between 330 and 700 K providing gas-to-coolant temperature ratios similar to current engine application. Research instrumentation of the test components provide conventional pressure and temperature measurements as well as metal temperatures measured by IR-photography. The primary data acquisition mode is steady state through a 704 channel multiplexer/digitizer. The test facility was configured as an annular cascade of full coverage film cooled vanes for the initial series of research tests. These vanes were tested over a wide range of gas Reynolds number, exit gas Mach number and heat flux levels. The range of test conditions was used to represent both actual operating conditions and similarity state conditions of a gas turbine engine. The results are presented for the aerothermal performance of the facility and the full coverage film cooled vanes.
A Review and Analysis of Boundary Layer Transition Data for Turbine Application
Authors: Gaugler Raymond E.
Published: April 2015

A Symposium on Transition in Turbines was held recently at the NASA Lewis Research Center. One recommendation of the working groups was the collection of existing transition data to provide standard cases against which models could be tested. This paper represents a preliminary response to that recommendation.

A number of data sets from the open literature that include heat transfer data in apparently transitional boundary layers, with particular application to the turbine environment, were reviewed and analyzed to extract transition information from the heat transfer data. The data were analyzed using a version of the STAN5 two-dimensional boundary layer code. The transition starting and ending points were determined by adjusting parameters in STAN5 until the calculations matched the data. The results are presented as tables of the deduced transition location and length as functions of the test parameters. The data sets reviewed cover a wide range of flow conditions, from low speed, flat plate tests to full scale turbine airfoils operating at simulated turbine engine conditions. The results indicate that free stream turbulence and pressure gradient have strong, and opposite, effects on the location of the start of transition and on the length of the transition zone.
Interdependence of Centrifugal Compressor Blade Geometry and Relative Flow Field
Authors: Krain H.
Published: April 2015

The influence of the impeller blade geometry on the calculated relative flow field has been studied by means of an impeller design program available at DFVLR [9]. Several geometrical parameters were varied, however, the meridional channel geometry was always kept constant. By this approach the blade wrap angle has been found to react significantly on the relative flow which is illustrated by comparing two designs with different wrap angles. Primarily in the hub/leading edge area a better boundary layer flow connected with a reduction of blade loading was obtained by increasing the wrap angle. But also in the shroud/pressure side area the increased blade looping attributed to an additional flow stabilization.