bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of the Cold Spray Particle Deposition Process
Authors: Xie Jing , Nélias Daniel , Walter-Le Berre Hélène , Ogawa Kazuhiro , Ichikawa Yuji
Published: April 2015

Cold spray is a rapidly developing coating technology for depositing materials in the solid state. In this work, the cold spray particle deposition process was simulated by modeling high-velocity impacts of spherical particles onto a flat substrate under various conditions. For the first time, we proposed the coupled Eulerian–Lagrangian (CEL) numerical approach as a means of solving the high-strain rate deformation problem. Using this approach, we observed a compressive stress region at the interface between the particles and the substrate induced by large plastic strains in the materials. Due to the high contact pressure (about 1 GPa) and the short contact time (about 40 ns), the high-strain rate (106 s-1) plastic deformation region was only a few micrometers deep and was localized mainly at the bottom of the particle and substrate surface. The ability of the CEL method to model the cold spray deposition process was assessed through a systematic parametric study including impact velocity, initial particle temperature, friction coefficient, and materials combination. The higher the impact velocity, the higher the initial kinetic energy, leading to more substantial plastic deformations and significant temperature increases in the substrate. The initial particle temperature has a greater influence on the equivalent plastic strain than on the temperature increase in the substrate. Friction has a limited effect on the temperature distribution and increase in the substrate, and the equivalent plastic strain increases only slightly as the friction coefficient rises. Four combinations of particle/substrate materials (Cu/Cu, Al/Al, Cu/Al, and Al/Cu) were considered in our study. Obviously, the particle's material had a greater influence on the deposition process and on the deformation than the substrate material. Concerning the particle's material, a higher-density material, such as Cu, has a higher initial kinetic energy, which has the advantage of increasing the contact area and contact time, resulting in better bonding between particles and substrate. Compared to other numerical methods (Lagrangian, arbitrary Lagrangian–Eulerian (ALE), and smooth particle hydrodynamics (SPH)), the CEL approach is globally more accurate and more robust in high-strain rate deformation regimes.
Scalability Planning for Cloud-Based Manufacturing Systems
Authors: Wu Dazhong , Rosen David W. , Schaefer Dirk
Published: April 2015

Cloud-based manufacturing (CBM) has recently been proposed as an emerging manufacturing paradigm that may potentially change the way manufacturing services are provided and accessed. In the context of CBM, companies may opt to crowdsource part of their manufacturing tasks that are beyond their existing in-house manufacturing capacity to third-party CBM service providers by renting their manufacturing equipment instead of purchasing additional machines. To plan manufacturing scalability for CBM systems, it is crucial to identify potential manufacturing bottlenecks where the entire manufacturing system capacity is limited. Because of the complexity of manufacturing resource sharing behaviors, it is challenging to model and analyze the material flow of CBM systems in which sequential, concurrent, conflicting, cyclic, and mutually exclusive manufacturing processes typically occur. To address and further study this issue, we develop a stochastic Petri nets (SPNs) model to formally represent a CBM system, model and analyze the uncertainties in the complex material flow of the CBM system, evaluate manufacturing performance, and plan manufacturing scalability. We validate this approach by means of a delivery drone example that is used to demonstrate how manufacturers can indeed achieve rapid and cost-effective manufacturing scalability in practice by combining in-house manufacturing and crowdsourcing in a CBM setting.
Generation of a Fine Grain Layer in the Vicinity of Frictional Interfaces in Direct Extrusion of AZ31 Alloy
Authors: Alexandrov Sergei , Jeng Yeau-Ren , Hwang Yeong-Maw
Published: April 2015

The present paper deals with the generation of hard layers in the vicinity of frictional interfaces in metal forming processes. The primary objective of the paper is to introduce a general approach to relate the strain rate intensity factor and parameters that characterize the microstructure and thickness of such layers. This approach is used in conjunction with axisymmetric direct extrusion of an AZ31 alloy. The thickness of the hard layer is determined experimentally. Also determined is the distribution of average grain size and hardness near the friction surface. The strain rate intensity factor is found using an available semi-analytical solution.
Flow-Excited Acoustic Resonance of Isolated Cylinders in Cross-Flow
Authors: Arafa Nadim , Mohany Atef
Published: April 2015

The flow-excited acoustic resonance of isolated cylinders in cross-flow is investigated experimentally where the effect of the cylinder(s) proximity to the acoustic particle velocity nodes of the cross-modes is presented in this paper. For the case of a single cylinder, the cylinder's location does not significantly affect the vortex shedding process; however, it affects the excitation level of each acoustic cross-mode. When the cylinder is moved away from the acoustic particle velocity antinode of a specific acoustic cross-mode, a combination of the cross-modes is excited with intensities that seem to be proportional to the ratio of the acoustic particle velocities of these modes at the cylinder's location. For the cases of two and three hydrodynamically uncoupled cylinders positioned simultaneously side-by-side in the duct, it is observed that the first three acoustic cross-modes are excited. When one cylinder is positioned at the acoustic particle velocity antinode of a specific cross-mode and another cylinder is positioned at its acoustic particle velocity node, i.e., a cylinder that should excite the resonance and another one that should not excite it, respectively; the excitation always takes over and the resonance occurs at a further elevated levels. It is also observed that the acoustic pressure levels in the cases of multiple cylinders are not resulting from a linear superposition of the excited level obtained from each individual cylinder which indicates that the removal of cylinders at certain locations may not be a viable technique to eliminate the acoustic resonance in the case of tube bundles.
Minimizing Human Tracking Error for Robotic Rehabilitation Device
Authors: Homich Andrew J. , Doerzbacher Megan A. , Tschantz Eric L. , Piazza Stephen J. , Hills Everett C. , Moore Jason Z.
Published: April 2015

This paper explores the design of a novel robotic device for gait training and rehabilitation, a method to estimate a human's orientation within the rehabilitation device, as well as an optimal state space controller to actuate the rehabilitation device. The robotic parallel bars (RPBs) were designed to address the shortcomings of currently available assistive devices. The RPB device moves in response to a human occupant to maintain a constant distance and orientation to the human. To minimize the error in tracking the human, a complementary filter was optimized to estimate the human's orientation within the device using a magnetometer and gyroscope. Experimental measurements of complementary filter performance on a test platform show that the filter estimates orientation with an average error of 0.62 deg over a range of angular velocities from 22.5 deg/s to 180 deg/s. The RPB device response was simulated, and an optimal state space controller was implemented using a linear quadratic regulator (LQR). The controller has an average position error of 14.1 cm and an average orientation error of 14.3 deg when tracking a human, while the simulation predicted an average error of 10.5 cm and 5.6 deg. The achieved level of accuracy in following a human user is sufficiently sensitive for the RPB device to conduct more advanced, realistic gait training and rehabilitation techniques for mobility impaired patients able to safely support their body weight with their legs and arms.
Transient Amplitude Amplification of Mistuned Blisks
Authors: Bonhage Marius , Pohle Linus , Panning-von Scheidt Lars , Wallaschek Jörg
Published: April 2015

This article discusses the problem of exceeding amplitudes of mistuned structures caused by accelerated traveling waves type excitation, i.e., traveling waves with time variant frequencies. These waves cause resonance passages of, e.g., rotating structures. To calculate the resonance passage a semi-analytical solution is proposed. Thus, high accuracy is guaranteed. The topic of exceeding amplitudes is initially approached by studying a discrete lumped mass model with detuned parameters. It can be shown that under certain circumstances the maximum amplitude of the transient resonance passage is even higher than the maximum amplitude of the steady-state solution. To investigate this phenomenon on a real bladed disk, the number of degrees of freedom of the blisk is reduced using component mode synthesis (CMS). By applying the semi-analytical solution to the reduced model, the envelopes of the vibration during resonance passage can be calculated. Processing extensive parametric studies it can be pointed out under which circumstances the probability rises that higher maximum amplitudes occur during resonance passage compared to steady-state conditions.
Mistuning Effects on Aero-elastic Stability of Axial Compressor Rotor Blades
Authors: Wang Yanrong , Fu Zhizhong , Jiang Xianghua , Tian Aimei
Published: April 2015

The mistuning effects on the aero-elastic stability of axial compressor rotor blades have been investigated by employing aero-elastic eigenvalue method. An axial compressor rotor suffered from flutter failure has been analyzed with four intentional mistuning patterns and their sensitivities to random mistuning. Through a comparison of four intentional mistuning patterns, the mistuning mechanism of improving aero-elastic stability may be understood from the combining effects of frequency offset and the destruction of periodicity by the introduction of mistuning. Increasing the amount of alternate mistuning cannot provide any additional improving effects on the aero-elastic stability when the mistuning amount reaches a critical value. However, the further mistuning effects can be obtained by placing several groups (isolation zone) with additional frequency offset relative to the alternately mistuned system. The random mistuning can always improve the aero-elastic stability of the tuned system. However, for the intentionally mistuned system, the inclusion of random mistuning with a small level may weaken the improving effects of intentional mistuning and even makes the system unstable.
Vibration Baseline, a Useful Concept for Condition Monitoring of Rotating Equipment
Authors: Gorter J. , Klijn A. J.
Published: April 2015

The condition of rotating equipment can be assessed using vibration measuring techniques. A number of these techniques including signal processing and analysis methods will be discussed briefly.

Finally experiences on gas turbines and centrifugal compressors, operating in the Dutch gas transmission system, will be used to define a useful vibration baseline for condition monitoring, maintenance purposes and availability.
Axial Flow Automotive Turbocharger
Authors: Rahnke C. J.
Published: April 2015

Turbocharger “lag” or poor response to engine load changes can be improved by reducing the rotating inertia of the turbocharger turbine, compressor and shaft system. Recently designed, second generation turbochargers all have small diameter, light weight rotating assemblies in an effort to minimize inertia and improve response. An automotive turbocharger with an axial flow turbine rather than a conventional radial inflow turbine is presented here as an alternative method of reducing inertia. The rotating inertia of the axial flow turbine and a centrifugal compressor is about one half that of the same compressor combined with a radial inflow turbine. In steady-state engine dynamometer tests, the same wide-open throttle performance was obtained with both turbochargers. Engine dynamometer transient tests showed that the turbocharger with the axial flow turbine attained full boost 25–40% faster than did the turbocharger with the radial inflow turbine.
Application of a Vehicular Designed, Heavy Duty Gas Turbine Engine to a Military Generator Set
Authors: Laux Samuel C. , Ware Robert N.
Published: April 2015

The Patriot Air Defense Missile System (formerly SAM-D) is being deployed in Europe. The powerplant supplying electricity to the radar set and to the engagement control station is DOD Model D-424A, powered by the Allison Model GT-404 industrial gas turbine (IGT) engine. Designed as a vehicular engine, the application in a generator set is an interesting one, utilizing many of the following features originally intended to enhance the performance of trucks and buses:

• Dual, rotating disk regenerators dramatically improve fuel consumption by transferring heat energy from the exhaust gas stream to compressor discharge.

• Power transfer, intended to provide part load fuel economy in vehicles, is modified to furnish free-shaft start-fixed shaft run in generator sets.

• Free-shaft starts allow successful operation down to −50°F without auxiliary heaters.

The resultant gas turbine engine driven generator set — 150 kW, transportable, skid mounted, alternating current 400 Hz, tactical — has met the military requirements for performance and reliability.
An Improved Simple Method for Designing Optimum Annular Diffusers
Authors: Cai R. , Jiang H. , Zhu Y.
Published: April 2015

In ASME paper 83-GT-42, a simple method for designing optimum annular diffusers was proposed and good results were obtained. But it is essentially a 1-D approximate method adapted for axial annular diffusers only. Actually, within the same assumption and limitation, it can be modified and improved effectively by the Mean-Stream-Line Method developed by the Chinese scientists led by Prof. C.H. Wu. The calculation can be done rapidly for axial, radial and mixed type diffusers, and the 2-D flow field in the diffusers can also be determined easily. A set of simple BASIC codes has been programed on the pocket computer Sharp PC-1500 and some calculation examples are given.
Operating Experience of the Jeff (A) in the Arctic
Authors: Edwards Jack J.
Published: April 2015

During the winter of 1983–84, the JEFF (A), a self-propelled air cushion vehicle owned by the U.S. Navy and leased to RMI, operated under a time charter to Sohio Alaska Petroleum Company in the arctic region contiguous to the Beaufort Sea. The purpose of the JEFF (A) operation was to gather engineering data to expand the data base for arctic-use air cushion vehicle design and to provide additional insight into the relationship between air cushion vehicles and the indigenous logistic network. In the process of the data gathering, the JEFF (A) operated for more than three hundred hours from two distinct operational sites, hauled in excess of 1.8 million pounds of oil field support cargo, and participated in the conduct of three discrete engineering test programs. This paper will cover the operational experience of the JEFF (A) during the period, the modification made to the craft to perform in the arctic environment and the lessons learned from the experience.
Reliability, Availability and Maintainability of the General Electric LM2500 System: A Discussion of Factors Especially Relevant to Cogeneration and Similar Continuous-Duty Applications
Authors: Jackson J. A.
Published: April 2015

The capability of continuous operation with interruptions as infrequent and brief as possible is important in cogeneration applications. Reliability and availability constitute key parts of the economic equation that determines whether cogeneration is a financially viable activity. Long-term operational experience of the gas turbine and off-engine system components in various applications combined with the provisions for rapid and efficient maintenance contribute significantly to the attractiveness of the LM2500 in cogeneration service. Actual cogeneration experience demonstrates good and improving performance in support of continuous processes and the generation of revenue-producing power.
The 18MW Rolls-Royce Spey Marine Gas Turbine
Authors: Thomas W. J. R.
Published: April 2015

This paper aims to discuss the factors which led to the selection of the Spey as a marine gas turbine, and the market forces which have made an uprating of the simple cycle unit necessary, and which are now leading to the conception of an advanced cycle version of the gas turbine at even higher power and efficiency. The operational characteristics of warships using these Spey units are compared with those of ships using other propulsion systems. While this paper stands on its own, it can also be regarded as the first part of a series of two; the second part, to be published in Beijing during the September 1985 ASME Gas Turbine Exposition, will deal with that further possible uprating of the Spey to about 22 MW using intercooling and heat exchange to improve its thermal efficiency to about 43%.
A Stream Function Relaxation Method for Solving Transonic S1 Stream Surface With Pre-Determination of the Density
Authors: Manchu Ge
Published: April 2015

On the basis of Prof. Wu’s 3-D flow theory (ref.1, 2, 3, 4, 5), a general streamfunction equation in non-orthogonal curvilinear coordinates is developed. The equation can be used to calculate subsonic or transonic flows on S1 or S2 stream surfaces of turbomachinery. In this paper streamlines coordinates and a mixed difference scheme are adopted in solving the stream function equation. A procedure for pre-determination of the density is developed and used to determine the unique-value of density from the known value of the stream function. Numerical examples are given.
Removal of Alkali Vapors by a Fixed Granular-Bed Sorber Using Activated Bauxite as a Sorbent
Authors: Lee Sheldon H. D. , Henry Richard F. , Myles Kevin M.
Published: April 2015

Studies have been conducted to develop a fixed granular-bed sorber for the removal of alkali vapors in a pressurized fluidized-bed combustion (PFBC) combined-cycle system. A laboratory-scale pressurized alkali-vapor sorption test unit was used to characterize activated bauxite, the most effective sorbent identified earlier, for its alkali vapor sorption capability in a gas stream with temperature (≤900°C), pressure (10 atm absolute), and composition closely simulating the actual PFBC flue gas. A scale-up of laboratory tests is being conducted in a 15.2-cm-dia (6-in.-dia) PFBC system to demonstrate the granular-bed sorber concept. The NaCl-vapor sorption chemistry of activated bauxite is described. The extent of alkali-vapor evolution from the activated bauxite bed itself is discussed, along with an evaluation of the significance of its alkali vapor contribution to a downstream gas turbine. Details of the design of a high-temperature/high-pressure alkali sorber system for the demonstration of the sorber are presented.
T56 Derivative Engine in the Improved E-2C
Authors: Laughlin T. P. , Toth Joseph
Published: April 2015

Airborne Early Warning for the Navy fleets has been provided for the past 20 years by the Grumman/Allison E-2 Airframe/T56 engine combination. Although avionic capability has been continually updated to meet the increased threat, the airframe and powerplant have seen only minor changes. Projected mission requirements and future avionic system enhancements require payload increases being limited by the power capability of the present T56 powerplant. Of paramount importance in the E-2 carrier deck operation is the single engine rate of climb capability of the aircraft. This paper discusses the logical evolution of a replacement engine for the E-2C — a derivative T56 engine contracted and designated by the Navy as the T56-A-427 — to meet the projected single engine takeoff and other mission requirements. The T56-A-427 provides 24% power and 13% fuel consumption improvements with identical installation interfaces, and substantially improves E-2C performance characteristics across the flight envelope. Furthermore, the paper shows that meeting these stringent performance requirements with a derivative engine results in a low risk development program and an engine with improved maintainability and reliability, which can capitalize on the in-place logistics support base of the T56 — the world’s longest production run gas turbine engine.
Combustion Characteristics of the GE LM2500 Combustor With Hydrogen-Carbon Monoxide-Based Low Btu Fuels
Authors: Sabla P. E. , Kutzko G. G.
Published: April 2015

An experimental test program was conducted with the objective of evaluating the combustion performance of fuel gases comprised of mixtures of carbon monoxide, hydrogen, and nitrogen. These gases were intended to be representative of alternate fuels that might be produced by air blown coal or biomass gasifiers. The purpose of this test program was to identify if the LM2500 combustion system would burn fuels at heating values (150 Btu/SCF – 250 Btu/SCF) typical of those produced by gasifier processes. Two combustor configurations were tested and two representative gas compositions were evaluated. The objectives of this test were to determine the flammability or burning limits for the two combustor designs and the impact of the low heating value gas on combustor exit temperature performance. Both designs exhibited burning limits substantially below the target caloric level. The exit temperature measurement showed the exit temperature distribution quality was adversely affected due to the high volumetric gas flows. However, this exit temperature distribution degradation is not severe enough to make the burning of a low heating value fuel prohibitive in the LM2500 engine.
An Experimental Study on Gas Turbine/Battery Hybrid Powered Vehicle
Authors: Watanabe A. , Fukuda D.
Published: April 2015

A gas turbine/battery hybrid system adopted as the power plant to propell a passenger car has been in development to seek a better fuel economy to drive. The gas turbine engine is a single-shaft type having 86000 rpm which is coupled directly with a generator to yield electricity. The power is used either to propell wheels and/or to charge battery depending upon the operating conditions of the system. The aim of this study is to attain a better fuel economy by operating the engine only around its rating point regardless to the driving conditions of the vehicle. The experimental vehicle has been studied to evaluate the potential of this unique system. Based on the detailed study of the components of the system and the road-load testings of the vehicle, the potential is seen for the system to be superior than a conventional vehicle. This paper will descrive the experimental results of the vehicle performances by this stage suggesting a good potential of the system when developed fully.
The Prediction of Surge Margins During Gas Turbine Transients
Authors: Maccallum N. R. L. , Pilidis P.
Published: April 2015

This paper describes how allowance for the thermal effects of non-adiabatic flow, altered boundary layer development, changes in tip clearances and changes in seal clearances have been incorporated into a general gas turbine transient program. This program has been applied to a two-spool bypass engine. Revised predictions of surge margins in three common transients have been obtained. When the engine undergoes a “cold” acceleration, the thermal effects on the trajectory and on the surge line give a much increased proportion of unused surge margin in the H.P. Compressor, as compared to adiabatic predictions. In a “hot” acceleration this improvement is considerably reduced.
A Simple Procedure to Compute Losses in Transonic Turbines Cascades
Authors: Martelli Francesco , Boretti Alberto
Published: April 2015

The prediction of losses in transonic flow in turbines is an important step in the design of turbine stages, but at the same time requirements of simplicity and speed are needed to allow the work of designers. The paper presents a procedure developed to match this goal. It uses classical codes, experimental correlations and simple geometrical models of the shock system. The result of a time marching method with standard mesh is used to run an Integral Boundary layer calculation in which shock wave interaction effects have been included. The shock system is made up of this information plus empirical correlation and a suitable procedure. A mixing calculation is then performed to get the downstream total pressure. The method has been tested with various kinds of turbine blades of which losses and data for calculations have been published. The results are quite good and the procedure appears simple and fast.
Coal-Fueled Turbines: Deposition Research
Authors: Carpenter L. K. , Crouse F. W. , Halow J. S.
Published: April 2015

The U.S. Department of Energy, Office of Fossil Energy, through its Morgantown Energy Technology Center, has initiated a program for the application of less expensive fuels for use in gas turbines; the overall objective is to develop an environmentally sound integrated direct-fired, coal fueled gas turbine system which will produce cost-competitive energy. The fuel is coal and may be in several forms which include a micronized powder, a slurry (with water, methanol, etc.), or a minimally cleaned, coal-derived gas.

The application of coal fuels to gas turbines raises a number of technical questions, a principal one being the development of deposits within the turbine. Several programs have been initiated, that are aimed at development of an understanding of turbine deposition from coal fuels. Some of DOE’s research activities which are discussed within this paper include efforts in: (a) nozzle cascade tests utilizing advanced and conventional blade cooling to minimize deposition, (b) bench-scale combustion/deposition tests, (c) laboratory research aimed at defining particle stickiness, and (d) theoretical efforts to model gas stream nucleation of particles and the resulting deposition on blades cooled to various temperatures.
Development of the Centaur Type H Gas Turbine Engine
Authors: Padgett G. L. , Davis W. W.
Published: April 2015

In response to the needs of the market place for turbines in the 5000 to 6000 hp class, Solar Turbines Incorporated has responded with an uprate of their Centaur engine. Discussed in this paper are the features of the uprated engine, the Development Plan and the methodology for incorporating into the design the advanced aerodynamic and mechanical technology of the Mars engine. The Mars engine is a high efficiency 12,500 hp engine which operates at a turbine inlet temperature of 1935°F. State-of-the-art computer aided methods have been applied to produce the design, and the results from this approach are displayed.
An Eleven Parameter Axial Turbine Airfoil Geometry Model
Authors: Pritchard L. J.
Published: April 2015

The mathematical derivation, and FORTRAN code, of a comprehensive but easy to use geometry model for axial flow turbine nozzles and rotors is presented. To uniquely define an airfoil on a cylinder the aerodynamicist need only specify the number of blades, and at each radius of interest: the axial and tangential chord, throat, uncovered turning, leading and trailing edge radii, inlet and exit blade angles, and inlet wedge angle. Default values exist for six of these geometric variables, which proves useful when starting a design. Both the suction and the pressure surfaces are described entirely by analytical functions. Sample airfoils are included that demonstrate the effect of each parameter upon blade shape.
An Investigation of the Response of Temperature Sensing Probes to an Unsteady Flow Field
Authors: Agnew B. , Elder R. L. , Terrel M.
Published: April 2015

The response of temperature measuring devices to pulsating flow fields has been a source of concern to compressor designers. A conventional temperature sensing device is known to respond to the highly energetic wake flow leaving a rotor and due to the long thermal time constant of the probe a temperature lying between the hot wake temperature and the relatively cooler main stream temperature tends to be indicated. This indicated temperature can be in serious error if included in a calculation to define the energy flux.

This work is concerned with a theoretical and experimental examination of temperature sensor response to an unsteady pulsating flow typical of that occuring in a compressor.
Dual-Orifice Atomizer Performance Under Varying Air Density Conditions
Authors: Jasuja A. K.
Published: April 2015

The spray quality and spatial distribution characteristics of a pressure atomizer of the dual-orifice type have been experimentally investigated using the well-established, non-intrusive techniques of laser droplet sizing and photography. Tests were conducted on kerosine and gas oil at air pressures up to about 8 atmospheres. The characteristics of spray quality and spatial distribution have been shown to undergo a noticeable change over a wide range of main fuel flows. An increase in the air density results in an improvement in the spray quality, but, is accompanied with a reduction in spray penetration. The dropsize correlation evolved earlier for the simplex pressure atomizer has been applied with success to the dual-orifice atomizer featured in this investigation.
Flow Measurements in Two Cambered Vane Diffusers With Different Passage Widths
Authors: Stein W. , Rautenberg M.
Published: April 2015

To investigate the influence of the vaneless space between impeller exit and the diffuser vanes, datailed flow measurements in two diffusers with the same vane geometry but different passage width are compared.

The three-dimensional character of the flow changes between impeller exit and the entry to the two dimensional vanes depending on the shape of the shroud. After initial measurements with a constant area vaneless space, the width of the vaned diffuser was later on reduced by 10%. The compressor maps show an increase in overall pressure rise and efficiency with the width reduction.

To get further details of the flow field, measurements of the static pressure distribution at hub and shroud have been performed at several operation points for both diffusers. At the same points the flow angle and total pressure distribution between hub and shroud upstream and downstream of the vanes have been measured with probes. The maximum efficiency of the narrow diffuser is nearly 2% higher than for the wide diffuser. The measurements give further details to explain this improvements.
Full Coverage Discrete Hole Film Cooling: The Influence of Hole Size
Authors: Andrews G. E. , Asere A. A. , Gupta M. L. , Mkpadi M. C.
Published: April 2015

The influence of hole size and hence blowing rate on full coverage discrete hole wall cooling for gas turbine combustion chamber applications was investigated. Two temperature conditions were used firstly a 750K gas temperature and 300K coolant, and secondly a realistic combustor primary zone conditions of 2100K flame temperature and 700K coolant. It was shown that a large hole size resulted in a significant improvement in the overall cooling effectiveness due to a reduced film heat transfer coefficient. At high temperature the cooling effectiveness was reduced due to radiative heat transfer from the flame gases. At low coolant flow large temperature increases of the coolant occurred within the wall and approached the transpiration situation.
Effect of Alternate Fuels on the Performance of the Garrett T76 Turboprop
Authors: Davis F. G. , Ball I. C. , Graham M. L. , White C. D.
Published: April 2015

A Garrett T76 turboprop was used as the test vehicle to evaluate the effects of varying fuel properties on engine hot-section performance and durability. This program was funded by the Naval Air Propulsion Center (NAPC) as part of their program to determine fuel effects on Navy fleet engines. The test fuels were supplied by NAPC and the fuel properties covered a range of values that are being considered for possible future fuel specification modification.

Testing was performed on a full-scale combustion rig at conditions duplicating actual engine operation and on a T76 engine. Rig tests were used to determine turbine inlet temperature quality, lean stability, and ground ignition and altitude relight limits. Engine tests evaluated combustor liner temperatures, gaseous emissions, smoke, carbon deposition and fuel thermal stability. Following testing, regression analyses were performed to quantify the effects of specific fuel property values on combustor performance and durability.
Discharge Coefficients of Impingement and Film Cooling Holes
Authors: Chu Tay , Brown A. , Garrett S.
Published: April 2015

In this article measurements of fluid flow through impingement and film cooling holes for typical turbine blade cooling systems are presented. The purpose of the measurements was to determine hole discharge coefficients over a range of Reynolds numbers from 5,000 to 30,000 and to observe in this range the dependence of discharge coefficient on Reynolds number. The effect of hole geometry, that is, sharp edged inlet or corner radius inlet, on discharge coefficients is also measured. Correlations relating discharge coefficients to Reynolds number, corner radius to hole diameter ratio, and blowing parameter are suggested.
Atomization of Coal Water Mixtures: Evaluation of Fuel Nozzles and a Cellulose Gum Simulant
Authors: Rosfjord T. J.
Published: April 2015

An experimental evaluation of four air-assist fuel nozzles has been conducted to determine atomization levels of coal-water mixture (CWM) fuels at operating conditions simulating a high pressure combustor. Two of the nozzles were commercial units marketed for use in atmospheric burners, while two nozzles were specially designed for CWM operation in a high pressure combustor. Sprays from all four injectors were characterized in tests performed over a range of liquid and air flowrates. Most of the tests were performed using a cellulose-gum water solution prepared to match the viscosity and drip characteristics of an available CWM. Atomization data acquired from a limited test series using the CWM were found to be properly represented by the gum solution data. High levels of atomization (SMD ∼ 10 micron) were achieved by two of the nozzles — one commercial unit and one special unit — at an assist airflow level corresponding to a nozzle air-fuel ratio between 0.6–0.8.
TiN coated aluminum electrodes for DC high voltage electron guns
Authors: Mamun Md Abdullah A. , Elmustafa Abdelmageed A. , Taus Rhys , Forman Eric , Poelker Matthew
Published: April 2015

Preparing electrodes made of metals like stainless steel, for use inside DC high voltage electron guns, is a labor-intensive and time-consuming process. In this paper, the authors report the exceptional high voltage performance of aluminum electrodes coated with hard titanium nitride (TiN). The aluminum electrodes were comparatively easy to manufacture and required only hours of mechanical polishing using silicon carbide paper, prior to coating with TiN by a commercial vendor. The high voltage performance of three TiN-coated aluminum electrodes, before and after gas conditioning with helium, was compared to that of bare aluminum electrodes, and electrodes manufactured from titanium alloy (Ti-6Al-4V). Following gas conditioning, each TiN-coated aluminum electrode reached −225 kV bias voltage while generating less than 100 pA of field emission (<10 pA) using a 40 mm cathode/anode gap, corresponding to field strength of 13.7 MV/m. Smaller gaps were studied to evaluate electrode performance at higher field strength with the best performing TiN-coated aluminum electrode reaching ∼22.5 MV/m with field emission less than 100 pA. These results were comparable to those obtained from our best-performing electrodes manufactured from stainless steel, titanium alloy and niobium, as reported in references cited below. The TiN coating provided a very smooth surface and with mechanical properties of the coating (hardness and modulus) superior to those of stainless steel, titanium-alloy, and niobium electrodes. These features likely contributed to the improved high voltage performance of the TiN-coated aluminum electrodes.
Increased bismuth concentration in MBE GaAs1−xBix films by oscillating III/V flux ratio during growth
Authors: Wood Adam W. , Babcock Susan E. , Li Jincheng , Brown April S.
Published: April 2015

The authors have examined bismuth concentration profiles in GaAs1−xBix films grown by molecular beam epitaxy using high angle annular dark field imaging (Z-contrast imaging) in an aberration-corrected scanning transmission electron microscope in conjunction with x-ray diffraction. Samples were grown with a gradient in each of the component fluxes, and therefore, the III/V ratio across the substrate. Rotating the sample during growth exposed the growth surface to an oscillating III/V flux ratio. Sinusoidal [Bi] profiles resulted in the growth direction, the wavelength and number of which were consistent with the growth rate and the rate of substrate rotation. However, the magnitude of [Bi] in the observed fluctuations was greater than the maximum [Bi] achieved using the same Bi flux and Ga/As flux ratios in steady-state conditions on a stationary substrate, suggesting that varying the III/V flux ratio during growth promotes the incorporation of Bi in GaAs1−xBix films. A proposed qualitative model for how this enhancement might occur hypothesizes a critical role for alternating growth and shrinkage of Ga-Bi predroplet clusters on the surface as the growing material is rotated through Ga-rich and As-rich flux compositions.
Alkaline and ultrasonic dissolution of biological materials for trace silicon determination
Authors: Viveros Robert D. , Liberman Alexander , Trogler William C. , Kummel Andrew C.
Published: April 2015

A simple method for trace elemental determination in biological tissue has been developed. Novel nanomaterials with biomedical applications necessitate the determination of the in vivo fate of the materials to understand their toxicological profile. Hollow iron-doped calcined silica nanoshells have been used as a model to demonstrate that potassium hydroxide and bath sonication at 50 °C can extract elements from alkaline-soluble nanomaterials. After alkali digestion, nitric acid is used to adjust the pH into a suitable range for analysis using techniques such as inductively coupled plasma optical emission spectrometry which require neutral or acidic analytes. In chicken liver phantoms injected with the nanoshells, 96% of the expected silicon concentration was detected. This value was in good agreement with the 94% detection efficiency of nanoshells dissolved in aqueous solution as a control for potential sample matrix interference. Nanoshell detection was further confirmed in a mouse 24 h after intravenous administration; the measured silica above baseline was 35 times greater or more than the standard deviations of the measurements. This method provides a simple and accurate means to quantify alkaline-soluble nanomaterials in biological tissue.
Leisure-Time Physical Activity Does not Attenuate the Association Between Occupational Sedentary Behavior and Obesity: Results From Alberta’s Tomorrow Project
Authors: Nicholas Joshua A. , Siou Geraldine Lo , Lynch Brigid M. , Robson Paula J. , Friedenreich Christine M. , Csizmadi Ilona
Published: April 2015

Background:

Sedentary behavior has been proposed as a risk factor for obesity that is distinct from physical inactivity. This study aimed to examine the association between occupational sedentary behavior and obesity, and to determine if this association is independent of leisure-time physical activity (LTPA).

Methods:

Fully employed participants enrolled between 2001 and 2008 to Alberta’s Tomorrow Project, a prospective cohort study in Alberta, Canada, were studied (n = 12,409). Associations between occupational sedentary behavior and waist circumference (WC), waist-to-hip ratio (WHR), and body mass index (BMI) were examined using multiple binary and multinomial logistic regressions.

Results:

In men, a positive association was observed between daily occupational sedentary hours and WC, WHR, BMI, and with high risk profiles that incorporated both BMI and WC (P < .01). Controlling for vigorous-intensity LTPA in all models strengthened associations between sedentary behavior and measures of obesity. In contrast, inverse associations were observed for occupational sedentary hours and WHR for women (P < .05).

Conclusions:

In fully employed men, occupational sedentary behavior was positively associated with obesity risk that was not attenuated by physical activity. In women, an increase in obesity risk was not observed with sedentary behavior. Gender differences in the health effects of sedentary behavior require further study.
Cytomegalovirus infection enhances the immune response to influenza
Authors: Furman David , Jojic Vladimir , Sharma Shalini , Shen-Orr Shai S. , L. Angel Cesar J. , Onengut-Gumuscu Suna , Kidd Brian A. , Maecker Holden T. , Concannon Patrick , Dekker Cornelia L. , Thomas Paul G. , Davis Mark M.
Published: April 2015

Cytomegalovirus infection of young adult humans and mice enhances immune responses to influenza.
Candida albicans Cek1 Mitogen-Activated Protein Kinase Signaling Enhances Fungicidal Activity of Salivary Histatin 5
Authors: Li Rui , Puri Sumant , Tati Swetha , Cullen Paul J. , Edgerton Mira
Published: April 2015

Candida albicans
is a major etiological organism for oropharyngeal candidiasis (OPC), while salivary histatin 5 (Hst 5) is a human fungicidal protein that protects the oral cavity from OPC.
C. albicans
senses its environment by mitogen-activated protein kinase (MAPK) activation that can also modulate the activity of some antifungal drugs, including Hst 5. We found that phosphorylation of the MAPK Cek1, induced either by
N
-acetylglucosamine (GlcNAc) or serum, or its constitutive activation by deletion of its phosphatase Cpp1 elevated the susceptibility of
C. albicans
cells to Hst 5. Cek1 phosphorylation but not hyphal formation was needed for increased Hst 5 sensitivity. Interference with the Cek1 pathway by deletion of its head sensor proteins, Msb2 and Sho1, or by addition of secreted aspartyl protease (SAP) cleavage inhibitors, such as pepstatin A, reduced Hst 5 susceptibility under Cek1-inducing conditions. Changes in fungal cell surface glycostructures also modulated Hst 5 sensitivity, and Cek1-inducing conditions resulted in a higher uptake rate of Hst 5. These results show that there is a consistent relationship between activation of Cek1 MAPK and increased Hst 5 susceptibility in
C. albicans
.
Berberine Blocks the Relapse of Clostridium difficile Infection in C57BL/6 Mice after Standard Vancomycin Treatment
Authors: Lv Zhi , Peng Guoli , Liu Weihua , Xu Hufeng , Su JianRong
Published: April 2015

Vancomycin is a preferred antibiotic for treating
Clostridium difficile
infection (CDI) and has been associated with a rate of recurrence of CDI of as high as 20% in treated patients. Recent studies have suggested that berberine, an alternative medical therapy for gastroenteritis and diarrhea, exhibits several beneficial effects, including induction of anti-inflammatory responses and restoration of the intestinal barrier function. This study investigated the therapeutic effects of berberine on preventing CDI relapse and restoring the gut microbiota in a mouse model. Berberine was administered through gavage to C57BL/6 mice with established CDI-induced intestinal injury and colitis. The disease activity index (DAI), mean relative weight, histopathology scores, and levels of toxins A and B in fecal samples were measured. An Illumina sequencing-based analysis of 16S rRNA genes was used to determine the overall structural change in the microbiota in the mouse ileocecum. Berberine administration significantly promoted the restoration of the intestinal microbiota by inhibiting the expansion of members of the family
Enterobacteriaceae
and counteracting the side effects of vancomycin treatment. Therapy consisting of vancomycin and berberine combined prevented weight loss, improved the DAI and the histopathology scores, and effectively decreased the mortality rate. Berberine prevented CDIs from relapsing and significantly improved survival in the mouse model of CDI. Our data indicate that a combination of berberine and vancomycin is more effective than vancomycin alone for treating CDI. One of the possible mechanisms by which berberine prevents a CDI relapse is through modulation of the gut microbiota. Although this conclusion was generated in the case of the mouse model, use of the combination of vancomycin and berberine and represent a novel therapeutic approach targeting CDI.
Bistable Expression of CsgD in Salmonella enterica Serovar Typhimurium Connects Virulence to Persistence
Authors: MacKenzie Keith D. , Wang Yejun , Shivak Dylan J. , Wong Cynthia S. , Hoffman Leia J. L. , Lam Shirley , Kröger Carsten , Cameron Andrew D. S. , Townsend Hugh G. G. , Köster Wolfgang , White Aaron P.
Published: April 2015

Pathogenic bacteria often need to survive in the host and the environment, and it is not well understood how cells transition between these equally challenging situations. For the human and animal pathogen
Salmonella enterica
serovar Typhimurium, biofilm formation is correlated with persistence outside a host, but the connection to virulence is unknown. In this study, we analyzed multicellular-aggregate and planktonic-cell subpopulations that coexist when
S
. Typhimurium is grown under biofilm-inducing conditions. These cell types arise due to bistable expression of CsgD, the central biofilm regulator. Despite being exposed to the same stresses, the two cell subpopulations had 1,856 genes that were differentially expressed, as determined by transcriptome sequencing (RNA-seq). Aggregated cells displayed the characteristic gene expression of biofilms, whereas planktonic cells had enhanced expression of numerous virulence genes. Increased type three secretion synthesis in planktonic cells correlated with enhanced invasion of a human intestinal cell line and significantly increased virulence in mice compared to the aggregates. However, when the same groups of cells were exposed to desiccation, the aggregates survived better, and the competitive advantage of planktonic cells was lost. We hypothesize that CsgD-based differentiation is a form of bet hedging, with single cells primed for host cell invasion and aggregated cells adapted for persistence in the environment. This allows
S
. Typhimurium to spread the risks of transmission and ensures a smooth transition between the host and the environment.