bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat Transfer in Rotating Serpentine Passages With Selected Model Orientations for Smooth or Skewed Trip Walls
Authors: Johnson B. V. , Wagner J. H. , Steuber G. D. , Yeh F. C.
Published: February 2015

Experiments were conducted to determine the effects of model orientation as well as buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. Turbine blades have internal coolant passage surfaces at the leading and trailing edges of the airfoil with surfaces at angles which are as large as +/−50 to 60 degrees to the axis of rotation. Most of the previously–presented, multiple–passage, rotating heat transfer experiments have focused on radial passages aligned with the axis of rotation. The present work compares results from serpentine passages with orientations 0 and 45 degrees to the axis of rotation which simulate the coolant passages for the midchord and trailing edge regions of the rotating airfoil. The experiments were conducted with rotation in both directions to simulate serpentine coolant passages with the rearward flow of coolant or with the forward flow of coolant. The experiments were conducted for passages with smooth surfaces and with 45 degree trips adjacent to airfoil surfaces for the radial portion of the serpentine passages. At a typical flow condition, the heat transfer on the leading surfaces for flow outward in the first passage with smooth walls was twice as much for the model at 45 degrees compared to the model at 0 degrees. However, the differences for the other passages and with trips were less. In addition, the effects of buoyancy and Coriolis forces on heat transfer in the rotating passage were decreased with the model at 45 degrees, compared to the results at 0 degrees. The heat transfer in the turn regions and immediately downstream of the turns in the second passage with flow inward and in the third passage with flow outward was also a function of model orientation with differences as large as 40 to 50 percent occurring between the model orientations with forward flow and rearward flow of coolant.
A 9.25 MW Industrial Gas Turbine With Extreme Low Dry NOx and CO Emissions
Authors: Bauermeister Kurt J. , Schetter Bernhard , Mohr Klaus D.
Published: February 2015

In cooperation between Siemens and MAN GHH an industrial gas turbine with an ISO rating of 9.2 5 MW was equipped with a dry low NOx combustion system. Using the hybrid burners of Siemens gas turbines, a new combustion chamber was developed for the gas turbine THM 1304 of MAN GHH. This gas turbine has two V-like arranged combustion chambers, which allow a redesign of the combustion chamber, without changing the remaining parts of the gas turbine and its casing. So it is possible as well, to fit present machines with new combustion chambers. The combustion chambers contain flame tubes of Siemens technology with ceramic tiles and the well proved hybrid burners. After calculation and design the air flow was examined in an isothermal flow model. Finally two prototypes of the combustion chamber mounted on a THM 1304 gas turbine were tested at the MAN GHH gas turbine test bed. Success came very quickly and the test runs are finished now. So for the first time the transfer of the well-known low emission values of the Siemens large scale gas turbines succeeded to an industrial gas turbine of the 10 MW class.
Characterization of Ceramic Composite Materials for Gas Turbine Applications
Authors: Reifsnider Ken , Stinchcomb Wayne , Liao Kin , Oleksuk Lynda , Stinton Dave
Published: February 2015

Ceramic composite materials have the capability to sustain high stress in the presence of high temperatures and aggressive atmospheres. Such materials are being considered for application as cumbustors, burner tubes, heat exchangers, headers, hot-gas filters, and even rotors of stationary gas turbine engines. In the present program, Nicalon preforms of tubular geometry were fabricated with different fiber architectures (filament winding, 3D braiding, or cloth winding) to tailor the mechanical properties for specific applications. However, these applications require that candidate materials be carefully characterized. Mechanical characterization must establish the properties and performance that are essential for structural design of the turbine components. For this purpose, a full complement of properties is needed, i.e., the stiffness and strengths of the composite materials at a range of temperatures, and the fatigue and creep behavior of the materials under the stress states anticipated by the user. This mechanical characterization requires specialized equipment and methodologies, which are now under development by the authors. This paper will present a description of the methodologies required for ceramic composite characterization, and will describe initial results for ceramic composite tubes, a representative geometry for gas turbine components. Future needs and opportunities will also be discussed.
Design and Calculation for Splittered Axial Turbine Cascade
Authors: Zhou D. M. , Zhang Z. G. , Li Y. S.
Published: February 2015

The reliability and improved thermodynamic performance of turbine–generator units have gained increasing importance recently. One way of achieving the optimization of HP performance in impulse steam turbine is to introduce multi–splitter cascade. This paper presents the design criteria about splittered axial turbine cascade as well as the blade airfoil generation, the placement and the number of splitter vanes are also discussed. In the second part of this paper, a new physical model is set up to determine outlet gas angle (or mass flow ratio). In addition, a procedure to calculate 2–D blade to blade flow field using variational FEM is presented in detail. Finally, experimental data are given to demonstrate the availiability of the presented calculation method.
NASA/GE Fan and Compressor Research Accomplishments
Authors: Smith Leroy H.
Published: February 2015

Fan and compressor research projects carried out at GE Aircraft Engines under NASA sponsorship are described in this paper.

Four 1400-fps-tip-speed rotors designed with different airfoil shapes were found to have comparable stall lines but different efficiency trends. A stator placed behind one of these affected its performance somewhat. Adjustments of variable camber inlet guide vanes placed ahead of a 1500 fps stage were found to affect its pumping capability without much affecting its stall line.

For the Quiet Engine Program (QEP), two 1160-fps fans and one 1550-fps fan were tested. Development of the high-speed fan revealed the effects on performance of airfoil shape and part-span shroud blockage. The 950-fps variable-pitch fan for the Quiet Clean Short-Haul Experimental Engine (QCSEE) demonstrated reverse thrust capabilities and a novel method of avoiding large core inlet pressure losses during reverse thrust operation. The 1350-fps Energy Efficient Engine (E3) fan demonstrated excellent performance with a novel quarter-stage arrangement that eliminated the need for inter-spool bleed while giving good dirt removal potential.

The E3 compressor program employed Low Speed Research Compressor tests to identify the most appropriate blading type. High-speed rig tests and engine tests were then used to develop this 23:1-spool-pressure-ratio compressor.

Research on casing boundary layer control through bleeding and blowing led to the discovery that irregular casing geometries usually give stall line enhancements even without auxiliary air circuits. Some of the resulting casing treatment research is reported herein.

Instances in which NASA-sponsored research has affected GE Aircraft Engine products are pointed out.
Digital Control System Development for an Intercooled Recuperated Gas Turbine
Authors: Carlson R. J. , West P. M. , Azouz D. E.
Published: February 2015

The on-going development of a full authority digital engine control (FADEC) system for the US Navy’s Intercooled Recuperated (ICR) gas turbine requires a high level of system coordination to achieve the primary benefits of reduced specific fuel consumption and improved specific output power relative to a simple cycle engine. This paper describes the system requirements analysis and the implementation of control algorithms leading to the preliminary ICR control system design.

The ICR control system is required to coordinate the actions of over 30 actuators using data taken from over 150 sensors. Primary control of the engine output power is provided by regulation of the fuel metering valve. Thermal management of the intercooler, recuperator, and variable area power turbine nozzle results in maximum cycle efficiency within safe operating limits.

The new electronic engine controller (EEC) is based on a new open architecture Futurebus+ backplane and is fully redundant in all operationally critical control functions. The EEC also features an operating panel and video display for local operation and maintenance of the control system. The graphical display and function keys provide access to control functions as well as assist maintenance activities with built-in test diagnostics to trouble shoot failed circuitry.
Computation of Turbulent Evaporating Sprays: Eulerian Versus Lagrangian Approach
Authors: Hallmann M. , Scheurlen M. , Wittig S.
Published: February 2015

A new Eulerian model for turbulent evaporating sprays is presented. It comprises droplet heating and evaporation processes by solving separate transport equations for the droplet’s temperature and diameter. A Lagrangian approach which has been discussed in detail by us at other occasions is used in comparing the results of the new method. A comparison with experimental data shows, that both approaches are successful in predicting the main features of turbulent evaporating sprays.
Surface Heating Effect on Local Heat Transfer in a Rotating Two-Pass Square Channel With 60° Angled Rib Turbulators
Authors: Zhang Y. M. , Han J. C. , Parsons J. A. , Lee C. P.
Published: February 2015

The influence of uneven wall temperature on the local heat transfer coefficient in a rotating, two-pass, square channel with 60° ribs on the leading and trailing walls was investigated for Reynolds numbers from 2,500 to 25,000 and rotation numbers from 0 to 0.352. Each pass, composed of six isolated copper sections, had a length-to-hydraulic diameter ratio of 12. The mean rotating radius-to-hydraulic diameter ratio was 30. Three thermal boundary condition cases were studied: (A) all four walls at the same temperature, (B) all four walls at the same heat flux, and (C) trailing wall hotter than leading with side walls unheated and insulated. Results indicate that rotating ribbed wall heat transfer coefficients increase by a factor of 2 to 3 over the rotating smooth wall data and at reduced coefficient variation from inlet to exit. As rotation number (or buoyancy parameter) increases, the first pass (outflow) trailing heat transfer coefficients increase and the first pass leading heat transfer coefficients decrease, whereas, the reverse is true for the second pass (inflow). The direction of the Coriolis force reverses from the outflow trailing wall to the inflow leading wall. Differences between the first pass leading and trailing heat transfer coefficients increase with rotation number. A similar behavior is seen for the second pass leading and trailing heat transfer coefficients, but the differences are reduced due to buoyancy changing from aiding to opposing the inertia force. The results suggest that uneven wall temperature has a significant impact on the local heat transfer coefficients. The heat transfer coefficients on the first pass leading wall for cases B and C are up to 70–100% higher than that for case A, while the heat transfer coefficients on the second pass trailing wall for cases B and C are up to 20–50% higher.
Advanced Hot Gas Cleaning System for Coal Gasification Processes
Authors: Newby R. A. , Bannister R. L.
Published: February 2015

The United States electric industry is entering a period where growth and the aging of existing plants will mandate a decision on whether to repower, add capacity or do both. The power generation cycle of choice, today, is the combined cycle that utilizes the Brayton and Rankine cycles. The combustion turbine in a combined cycle can be used in a repowering mode or in a greenfield plant installation. Today’s fuel of choice for new combined cycle power generation is natural gas. However, due to a 300-year supply of coal within the United States, the fuel-of-the future will include coal.

Westinghouse has supported the development of coal-fueled gas turbine technology over the past thirty years. Working with the U.S. Department of Energy and other organizations, Westinghouse is actively pursuing the development and commercialization of several coal-fueled processes. To protect the combustion turbine and environment from emissions generated during coal conversion (gasification/combustion) a gas cleanup system must be used. This paper reports on the status of fuel gas cleaning technology and describes the Westinghouse approach to developing an advanced hot gas cleaning system that contains component systems that remove particulate, sulfur, and alkali vapors. The basic process uses ceramic barrier filters for multiple cleaning functions.
Eigenvector Derivatives of Generalized Nondefective Eigenproblems With Repeated Eigenvalues
Authors: Zhang Yong-Qiang , Wang Wen-Liang
Published: February 2015

A new method is presented for computation of eigenvalue and eigenvector derivatives associated with repeated eigenvalues of the generalized nondefective eigenproblem. This approach is an extension of recent work by Dailey and by Juang et al. and is applicable to symmetric or nonsymmetric systems. The extended phases read as follows. The differentiable eigenvectors and their derivatives associated with repeated eigenvalues are determined for generalized eigenproblem, requiring the knowledge of only those eigenvectors to be differentiated. Moreover, formulations for computing eigenvector derivatives have been presented covering the case where multi-groups of repeated first eigenvalue derivatives occur. Numerical Examples are given to demonstrate the effectiveness of the proposed method.
The Effect of Seal Width on Regenerator Effectiveness
Authors: Beck Douglas S.
Published: February 2015

The effect of axial conduction on regenerator effectiveness has been studied in the past under the assumption of zero seal width. The effect of axial conduction coupled with finite seal width is presented. A method for calculating effectiveness assuming axial conduction and finite seal width is presented. Results of example calculations are presented to give the designer a feel for the dependence of seal-width effects on system-parameter values. It is shown that for typical regenerator designs, reductions in effectiveness due to axial conduction coupled with finite seal width can be twice as great as those due to axial conduction under the assumption of zero seal width. Also, it is shown that the required regenerator size to achieve a given effectiveness can increase dramatically when finite seal width is considered in design procedures. It is concluded that consideration of axial conduction should include finite seal width.
Working Group Activities of AGARD Propulsion and Energetics Panel
Authors: Ucer Ahmet S.
Published: February 2015

One of the major activities of AGARD Panels is to form working groups which assemble experts who work on the particular subject for two or three years. As a result of the work an Advisory Report is published which compiles the state of the art knowledge on the chosen specific topic. This paper explains the philosophy and procedures adopted during the formation of working groups of the Propulsion and Energetics Panel.

Working groups concerning gas turbine technologies are presented. The selected working groups aim to improve the computational and experimental knowledge which would lead to the design of advanced aero gas turbine engines. Objective, scope, procedure, and important results of each Working Group will be explained. Working groups which were active during 1980’s and which are presently active are covered.
Experimental Investigation of the Flow in Diffusers Behind an Axial Flow Compressor
Authors: Zierer T.
Published: February 2015

The flow fields of four diffusers situated at the rear of a one-stage axial flow compressor was experimentally investigated. Through modification of the compressor operating point a wide range of variations of the side wall boundary layers and the radial velocity distribution outside of the boundary layers at diffuser inlet could be achieved. The three dimensional flow field at both diffuser inlet and outlet is analysed. Changes of inlet blockage and radial velocity distribution and their resulting effects on pressure recovery are thoroughly presented. Compared with the results of measurements at diffusers, typically with ducted flow inlet conditions, higher values of pressure recovery are observed. Established design rules, based on investigations of diffusers with carefully developed inlet flow, are checked regarding their applicability for diffusers in turbomachine environment.
Laser and Micro-Plasma Welding of Single Crystal Blades: Advantages of Total Process Control
Authors: Pilcher C. , Liburdi J. , Berger C. , Iovene M.
Published: February 2015

The single crystal superalloys, used in the manufacture of advanced gas turbine blades, are known to suffer from poor weldability and have a tendency to form cracks during and after welding. These cracks are largely related to the amount of heat input and metallurgical reactions that occur in the Heat Affected Zone (HAZ) adjacent to the weld. Experience has shown that cracks can be avoided by minimizing the HAZ through the use of proper heat management or process control.

Automation systems can offer the level of process control necessary to significantly reduce weld cracking. The systems have proven to be more repeatable, reliable, and efficient, compared to conventional techniques or earlier attempts at automation. In order to succeed, welding automation requires a complete integration of the process, consisting of tooling, robotic accuracy, vision measurement system, filler material, and welding parameter control. With the proper process control technology, it is possible to weld the tips of single crystal blades with difficult to weld oxidation resistant alloys as well as repair conventional compressor, high pressure and low pressure turbine blades.

This paper describes the welding of LT101 single crystal gas producer (GP) blade tips with highly alloyed filler metals for greater oxidation resistance. Results are presented for blades welded using a Laser beam with powder feed and compared to those welded using Micro-Plasma with the same filler alloys in wire form. The experience emphasizes the need for proper selection and integration of the welding processes, and confirms the importance of total process control to achieve the desired results in difficult and unique welding applications.
A Marine Installation of the Allison 570KF First Phase
Authors: Cheney Peter , Wall Richard
Published: February 2015

With the obsolescence of the original cruise engine of the Canadian Navy DDH 280 Class Destroyers, it became necessary to find and fit a new cruise engine. The Allison 570KF engine was selected and installed during the half life refit and modernisation of the ship class. In addition to the engine replacement there were many changes to the support equipment which have had a large influence on the new installation.

This paper describes the first phase of the set to work and trials of the new installation and the difficulties encountered. Two ships are now at sea and undergoing extensive system trials as they carry out their Naval duties.
Recuperating the LM2500 Gas Turbine
Authors: Thompson Bruce D.
Published: February 2015

The LM2500 Gas Turbine is a reliable simple cycle gas turbine that has been in US Navy service for more than 15 years. For a simple cycle gas turbine its design point fuel efficiency is quite good, approximately 0.400 (lb/hp-hr) at 26,250 BHP under US Navy rating conditions. Off design it is not quite as efficient, although its efficiency does not start to degrade significantly until operation below 10,000 BHP is reached. Operational experience with the LM2500 gas turbine in the US Navy has shown that at least 90% of its operational life will be spent at horsepowers that are less than 10,000. Therefore, in an effort to increase the range and the ability to remain on station of LM2500 powered US Navy ships, methods to improve the LM2500’s low power fuel efficiency were investigated. One area that had been discounted in the past was recuperating the LM2500. On the surface recuperating the LM2500 does not appear to provide much. The primary reason for this is that the design point compressor discharge temperature is within 200 degrees F of the gas turbine exhaust temperature. But off-design the situation changes, particularly if variable area turbine nozzles (VATNs) are introduced to maintain cycle temperatures. This paper will discuss the initial concept design process that was performed by the gas turbine division in the Naval Sea Systems Command (NAVSEA), the activity that is responsible for ship design in the US Navy. This will include the initial assumptions and the gas turbine cycle modeling that was undertaken to determine the potential benefits of recuperating the LM2500. Based on the success of these preliminary efforts, General Electric Company was then tasked to help perform additional cycle analysis. GE, working together with NAVSEA, proceeded to determine the optimum configuration of a Recuperated LM2500 (or LM2500-R). The guiding philosophy behind this effort is “maximum gain with minimal change.” The direction of this effort was to provide a cost effective, retrofitable package, in a reasonable amount of time, to upgrade the LM2500 for improved low power fuel efficiency.
A Knowledge-Based Expert System to Diagnose Turbomachinery Vibration Problems
Authors: Wang Jhy-Horng , Perng Lih-Jong
Published: February 2015

A knowledge–based expert system was developed to diagnose the vibration problems of turbomachinery. A two–step diagnosis was proposed in this work. The huge knowledge base was divided into two sub–bases, called Knowledge Level I and II. Knowledge Level I was first processed to extract a few possible causes, and only these possible causes were re–evaluated by Knowledge Level II. The main purpose of the two–step diagnosis was to speed up the knowledge processing and to make the development of inference procedure easier. The concept of certainty factor was adopted to handle the problem of reasoning under uncertainty. The possible causes of fault were ranked according to the certainty factors.
Study of Two-Phase Flow Downstream of a Gas Turbine Combustor Dome Swirl Cup
Authors: Tolpadi Anil K. , Burrus David L. , Lawson Robert J.
Published: February 2015

The two-phase axisymmetric flowfield downstream of the swirl cup of an advanced gas turbine combustor is studied numerically. The swirl cup analyzed is that of a single annular GE/SNECMA CFM56 turbofan engine that is comprised of a pair of coaxial counter-swirling air streams together with a fuel atomizer. The atomized fuel mixes with the swirling air stream resulting in the establishment of a complex two-phase flowfield within the swirl chamber. The analysis procedure involves the solution of the gas phase equations in a Eulerian frame of reference. The flow is assumed to be nonreacting and isothermal. The liquid phase is simulated by using a droplet spray model and by treating the motion of the fuel droplets in a Lagrangian frame of reference. Extensive Phase Doppler Particle Analyzer (PDPA) data for the CFM56 engine swirl cup has been obtained at atmospheric pressure by using water as the fuel (Wang et al., 1992a). This includes measurements of the gas phase velocity in the absence and presence of the spray together with the droplet size, droplet number count and droplet velocity distribution information at various axial stations downstream of the injector. Numerical calculations were performed under the exact inlet and boundary conditions as the experimental measurements. The computed gas phase velocity field showed good agreement with the test data. The agreement was found to be best at the stations close to the primary venturi of the swirler and to be reasonable at later stations. To compare the droplet data, a numerical PDPA scheme was formulated whereby several sampling volumes were selected within the computational domain. The trajectories of various droplets passing through these volumes were monitored and appropriately integrated. The calculated droplet count and mean droplet velocity distributions were compared with the measurements and showed very good agreement in the case of larger size droplets and fair agreement for smaller size droplets.
Liquidated Damages: An Approach to Addressing Performance Breaches in Contracts
Authors: Schubert R. W. , Fiorelli P. E.
Published: February 2015

This paper will define and explain liquidated damages, a contractually correct method of assuring enforceability and damage recovery in the event of a contract breach. This paper will further point out that failure to use liquidated damage clauses could result in litigation — with litigation’s attendant costs, delays, and sometimes unexpected results.
Deterministic and Stochastic Optimization of a Variable Axial Flow Compressor
Authors: Egorov I. N.
Published: February 2015

A procedure is proposed to determine geometrical parameters and control laws of rows of a variable multistage axial flow compressor (VMAC) which are optimum by a criterion of ensuring turbomachine high efficiency within a wide range of operating modes under the row control. It is demonstrated that in shaping a layout of a variable compressor, it is expedient to determine its row geometry on the basis of control efficiency assessment. The paper illustrates a possibility to increase turbomachine efficiency (up to 8%) through optimum monitoring of its rows when studying a compressor as a separate unit and, also, through a decrease of specific fuel consumption (SFC) by 6% when studying a compressor as included in an engine.

The paper also presents the results of optimum profiling of 7 rows in a 4-stage variable compressor for a stochastic case, which enables to obtain optimum stable (robust) solution, permitting to increase a possibility to ensure design indices in its practical realization by 2 and more times.
Three-Dimensional Elasticity-Based Solutions for Natural Vibrations of Low Aspect Ratio Compressor Blades
Authors: McGee Oliver G.
Published: February 2015

This paper offers three-dimensional (3-D) vibration frequency solutions for low aspect ratio compressor blades. The Ritz method is used to minimize the 3-D elasticity-based dynamical energies with displacements approximated by mathematically complete polynomials satisfying the clamped boundary conditions exactly. The accuracy of the method is established by a convergence study explicitly showing the influence of solution determinant size. Several tables are presented which show the variation of natural frequencies with twist angle in the presence of skewness of low aspect ratio compressor blades. Results obtained using the present Ritz method are used to elucidate those frequency solutions which are inaccessible using beam, plate and shell theories, since kinematic constraints associated with these theories are eliminated in the present 3-D approach.
Research and Development of Turbo Jet Combustor on HST Programme in Japan
Authors: Kuyama T. , Enzaki Y. , Kawano M. , Kobayashi M.
Published: February 2015

The research and development of a turbo jet combustor for a Mach 3 class supersonic transport is underway, as well as the other components of the HST programme in JAPAN. This research and development aims finally at achieving a combustor exit temperature of 1973K while maintaining low NOx levels, high durability, and good exit temperature distribution.

This paper describes the interim status of the combustor research and development, in particular, the liner cooling system and exit temperature distribution control technique.
Environmental Aspects of a 10 MW Heavy Duty Gas Turbine Burning Coke Oven Gas With a Hydrogen Content of 60%
Authors: Becker T. , Perkavec M.
Published: February 2015

In a coking plant in which coal tar is processed coke oven gas occurs as a waste product. Coke oven gas can be used as an alternative fuel for a gas turbine, instead of natural gas, if it meets the local environmental regulations.

As a result of higher flame temperature of coke oven gas caused by the hydrogen content, the NOx emission of a gas turbine burning coke oven gas is higher than in case of natural gas. In Germany a 10 MW gas fired gas turbine has to meet a NOx emission limit of 150 mg/Nm3 @ 15% O2 dry. To reach this goal in case of MS 3002, which is installed in the coking plant as reported in previous ASME paper, steam injection is necessary.

NOx- and CO-emissions of a gas turbine are difficult to be predicted by calculation, therefore measurements had to be done to see how good the predictions were, that were made in face of the local regulations.

This paper deals with the NOx- and CO-emissions of a coke oven gas fired gas turbine with and without steam injection in difference to natural gas fired gas turbine. It shows also significantly lower CO2-emissions, because coke oven gas contains less hydrocarbon which is a great benefit for the greenhouse problem. It illustrates the effect of power augmentation and discusses the different thermal efficiency with steam injection.

This paper gives a short glance to the effects which influence the emissions, so that the specific problems caused by burning coke oven gas can be understood.
A Model-Based Approach to the Control of an Aircraft Gas Turbine Engine
Authors: Qi Oliver F. , Maccallum N. R. L.
Published: February 2015

This paper describes a model-based control approach to synthesizing a nonlinear controller for a single-spool gas turbine engine. Since the main control variable, engine thrust, cannot be directly measured, a model-based observer is constructed using a nonlinear model of the engine in order to provide an on-line estimation of the thrust for feedback control. Both proportional and proportional-integral (PI) observers have been used in the model-based observer design. The latter is intended to provide a robust estimation in the event of modeling errors. The controls are the fuel flow and final nozzle area, and the control structure is the PI controller designed using the KQ (K-matrix compensator, Q-desired response) multivariable design technique. A study has been made of the model-based observer control scheme when the engine is subjected to the disturbance of inlet flow distortion. The results are shown to be acceptable in terms of the thrust response and the transient trajectory on the compressor characteristic.
Unsteady Three-Dimensional Flow Behavior due to Rotor-Stator Interaction in an Axial-Flow Turbine
Authors: Yamamoto A. , Mimura F. , Tominaga J. , Tomihisa S. , Outa E. , Matsuki M.
Published: February 2015

Detailed unsteady flow surveys were conducted before, within and after the second-stage stator passage of a 1.5-stage axial flow turbine by using a single slanted hot-wire anemometry. Among the results reported in the present paper, of particular interest are the behavior of the rotor wakes and the rotor free-streams within the stator passage, and the spacially three-dimensional and time-dependent convection or mixing process between lower- and higher- energy fluids. Effects of the rotor-stator interaction causing unsteady secondary flows and tip-leakage flow are also discussed.
Performance Testing and Strength Prediction of Ceramic-to-Metal Joints
Authors: Selverian J. H. , ONeil Dave A. , Kang Shinhoo
Published: February 2015

Brazed joints were made between silicon nitride and Ni-based and Fe-based super alloys. Room temperature shear (torsion) strengths ranged from 75–242 MPa for Si3N4-to-Incoloy 909 joints and from 30–127 MPa for the Si3N4-to-Inconel 718 joints. At 500 °C the joint strength was 120 MPa while at 650°C and 950°C the joints strengths were less than 20 MPa. These low strengths at 650°C and 950°C were attributed to a reduction in the shrink-fit and to low braze strength at these high temperatures. Finite element analysis (FEA) and a probabilistic failure theory (CARES) were used to predict the joint strengths. The predicted joint strengths agreed well with measured joint strengths in torsional loading at 20°C. Torsion tests were also performed at 650°C. Aspects of the material systems, residual stresses, mechanical behavior, and strength predictions are presented. Two new braze alloys based on the Au-Ni-Cr-Fe system were used to overcome the poor high temperature strength. Joints made with these brazes had good strength (85 MPa and 35 N-m) at 650°C.
Study on the Turbine Vane and Blade for a 1500°C Class Industrial Gas Turbine
Authors: Amagasa S. , Shimomura K. , Kadowaki M. , Takeishi K. , Kawai H. , Aoki S. , Aoyama K.
Published: February 2015

This paper describes the summary of a three year development program for the 1st stage stationary vane and rotating blade for the next generation, 1500°C Class, high efficiency gas turbine. In such a high temperature gas turbine, the 1st turbine vane and blade are the most important hot parts. Full coverage film cooling (FCFC) is adopted for the cooling scheme, and directionally solidified (DS) nickel base super-alloy and thermal barrier coating (TBC) will be used to prolong the creep and thermal fatigue life. The concept of the cooling configuration, fundamental cascade test results and material test results will be presented.
Process Optimization of Hexoloy SX-SiC Towards Improved Mechanical Properties
Authors: Srinivasan G. V. , Lau S. K. , Storm R. S. , Ferber M. K. , Jenkins M. G.
Published: February 2015

Hexoloy SX SiC materials, sintered with the addition of yttrium and aluminum containing compounds, have been demonstrated to possess higher toughness and strength than the boron and carbon doped Hexoloy SA [1]. Under a Department of Energy/Oak Ridge National Laboratory (DOE/ORNL) contract, a complete characterization was conducted on an SX composition selected for high temperature application. The particular composition selected for that study was Generation 1 SX-SiC (SX-G1), which contained about 2 wt% total additives.
Development of a Nonmetallic Abradable Material System for Gas Turbine Applications
Authors: Rose Daniel P. , Price George D. , Bosna Alexander
Published: February 2015

The performance of gas turbine engines is highly dependent upon the clearance between compressor rotating blades or stator vanes, and adjacent shrouds. Auxiliary power units (APU) incorporate abradable coatings on compressor shrouds to allow for very small clearances and rub tolerance. The operating environment of the APU may result in a combination of abrasion between airfoil tips and shrouds, as well as galvanic corrosion of the abradable material. Experience has shown that established thermal spray abradable material systems that offer desirable abradability properties in laboratory testing may perform poorly when subjected to a combination of galvanic corrosion and abradable environment.

This paper discusses development and evaluation of an abradable material that is composed of nonmetallic constituents. This material is not susceptible to galvanic corrosion, and maintains its abradable properties when operating in a combined corrosive and abradable environment. The material development, microstructure, and physical properties are discussed. In addition, the performance of the material in abradability testing, and warm salt fog testing is presented.
The effects of slip condition and multiple stenoses on micropolar fluid flow through a channel of non-uniform cross-section
Authors: Vajravelu K. , Awgichew Gurju , Radhakrishnamacharya G.
Published: February 2015

In this paper, steady incompressible micropolar fluid flow through a non-uniform channel with multiple stenoses is considered. Assuming the stenoses to be mild and using the slip boundary condition, the equations governing the flow of the proposed model are solved, and closed-form expressions for the flow characteristics (resistance to flow and wall shear stress) are derived. The effects of different parameters on these flow characteristics are analyzed. It is observed that both the resistance to the flow and the wall shear stress increase with the heights of the stenoses and the slip parameter; but decrease with the Darcy number. Furthermore, the effects of the wall exponent parameter, the cross-viscosity coefficient and the micropolar parameter on the flow characteristics are discussed.
Numerical solution of Riccati equation using operational matrix method with Chebyshev polynomials
Authors: Öztürk Yalçın , Gülsu Mustafa
Published: February 2015

In this paper, we present numerical technique for solving the Riccati equation by using operational matrix method with Chebyshev polynomials. The method consists of expanding the required approximate solution as truncated Chebyshev series. Using operational matrix method, we reduce the problem to a set of algebraic equations. Some numerical examples are given to demonstrate the validity and applicability of the method. The method is easy to implement and produces very accurate results.
Special properties of a skew triangular matrix ring with constant diagonal
Authors: Habibi Mohammad , Moussavi Ahmad
Published: February 2015

In this paper, we study various annihilator properties in a ring [Formula: see text] with an endomorphism [Formula: see text] and some subrings of the skew triangular matrix rings [Formula: see text]. They allow the construction of rings with a nonzero nilpotent ideal of arbitrary index of nilpotency which have various zero-divisor properties.
Robust chain transitive vector fields
Authors: Lee Manseob , Lee Seunghee
Published: February 2015

Let M be a closed n(≥2)-dimensional smooth Riemannian manifold and let X be a vector field on M. In this paper, we show that the robust chain transitive set is hyperbolic if and only if there are a C1-neighborhood [Formula: see text] of X and a compact neighborhood U of the chain transitive set such that for any [Formula: see text], the index of the continuation on ΛY(U) = ⋂t∈ℝYt(U) of every critical point does not change.
Some theorems and examples around the homogeneous systems and structures of loops and groups
Authors: Dama Moussa
Published: February 2015

Homogeneous systems had their origin in the work of Professor Michihiko Kikkawa. We define a homogeneous system η on a non-empty magma G. Then, η is afterward used to define on G a multiplication μ(a), where a is a fixed element of G. It was shown that (G, μ(a)) is a group if and only if η(y, z) ∘ η(x, y) = η(x, z) for all elements x, y, z of G. Let us note that η(x, y) is an application of G into itself for all elements x, y in G. It is our purpose in this paper to find another equivalent condition for which (G, μ(a)) is a group. And we have obtained η(a, μ(a)(x, y)) = η(a, x) ∘ η(a, y) for all elements x, y in G.
Coefficient Estimates for Two New Subclasses of Biunivalent Functions with respect to Symmetric Points
Authors: Altınkaya Şahsene , Yalçın Sibel
Published: February 2015

We introduce two subclasses of biunivalent functions and find estimates on the coefficientsa2anda3for functions in these new subclasses. Also, consequences of the results are pointed out.
An Incremental High‐Utility Mining Algorithm with Transaction Insertion
Authors: Lin Jerry Chun-Wei , Gan Wensheng , Hong Tzung-Pei , Zhang Binbin
Published: February 2015

Association‐rule mining is commonly used to discover useful and meaningful patterns from a very large database. It only considers the occurrence frequencies of items to reveal the relationships among itemsets. Traditional association‐rule mining is, however, not suitable in real‐world applications since the purchased items from a customer may have various factors, such as profit or quantity. High‐utility mining was designed to solve the limitations of association‐rule mining by considering both the quantity and profit measures. Most algorithms of high‐utility mining are designed to handle the static database. Fewer researches handle the dynamic high‐utility mining with transaction insertion, thus requiring the computations of database rescan and combination explosion of pattern‐growth mechanism. In this paper, an efficient incremental algorithm with transaction insertion is designed to reduce computations without candidate generation based on the utility‐list structures. The enumeration tree and the relationships between 2‐itemsets are also adopted in the proposed algorithm to speed up the computations. Several experiments are conducted to show the performance of the proposed algorithm in terms of runtime, memory consumption, and number of generated patterns.
Pricing Analysis in Geo/Geo/1 Queueing System
Authors: Ma Yan , Liu Zaiming
Published: February 2015

This paper studies the equilibrium behavior of customers and optimal pricing strategies of servers in a Geo/Geo/1 queueing system. Two common pricing mechanisms are considered. The first one is called ex-post payment (EPP) scheme where the server collects tolls proportional to queue times, and the second one is called ex-ante payment (EAP) scheme where the server charges a flat fee for the total service. The server sets the toll price to maximize its own profit. It is found that, under a customer’s choice equilibrium, the two toll mechanisms are equivalent from the economic point of view. Finally, we present several numerical experiments to investigate the effects of system parameters on the equilibrium customer joining rate and servers’ profits.
Application of Sinc-Galerkin Method for Solving Space-Fractional Boundary Value Problems
Authors: Alkan Sertan , Secer Aydin
Published: February 2015

We employ the sinc-Galerkin method to obtain approximate solutions of space-fractional order partial differential equations (FPDEs) with variable coefficients. The fractional derivatives are used in the Caputo sense. The method is applied to three different problems and the obtained solutions are compared with the exact solutions of the problems. These comparisons demonstrate that the sinc-Galerkin method is a very efficient tool in solving space-fractional partial differential equations.
Simultaneous HPLC Determination of Chlordiazepoxide and Mebeverine HCl in the Presence of Their Degradation Products and Impurities
Authors: El-Shaheny Rania N. , Belal Fathalla F.
Published: February 2015

A simple, rapid, and sensitive RP-HPLC method was developed and validated for the simultaneous determination of chlordiazepoxide (CDO) and mebeverine HCl (MBV) in the presence of CDO impurity (2-amino-5-chlorobenzophenone, ACB) and MBV degradation product (veratric acid, VER). Separation was achieved within 9 min on a BDS Hypersil phenyl column (4.5 mm × 250 mm, 5 µm particle size) using a mobile phase consisting of acetonitrile: 0.1 M potassium dihydrogen phosphate: triethylamine (35 : 65 : 0.2, v/v/v) in an isocratic mode at a flow rate of 1 mL/min. The pH of the mobile phase was adjusted to 4.5 with orthophosphoric acid and UV detection was set at 260 nm. A complete validation procedure was conducted. The proposed method exhibited excellent linearity over the concentration ranges of 1.0–100.0, 10.0–200.0, 2.0–40.0, and 2.0–40.0 µg/mL for CDO, MBV, VER, and ACB, respectively. The proposed method was applied for the simultaneous determination of CDO and MBV in their coformulated tablets with mean percentage recoveries of 99.75 ± 0.62 and 98.61 ± 0.38, respectively. The results of the proposed method were favorably compared with those of a comparison HPLC method using Studentt-test and the variance ratioF-test. The chemical structure of MBV degradation product was ascertained by mass spectrometry and IR studies.
Bone Marrow-Derived Mesenchymal Stem Cells Repair Necrotic Pancreatic Tissue and Promote Angiogenesis by Secreting Cellular Growth Factors Involved in the SDF-1α/CXCR4 Axis in Rats
Authors: Qian Daohai , Gong Jian , He Zhigang , Hua Jie , Lin Shengping , Xu Chenglei , Meng Hongbo , Song Zhenshun
Published: February 2015

Acute pancreatitis (AP), a common acute abdominal disease, 10%–20% of which can evolve into severe acute pancreatitis (SAP), is of significant morbidity and mortality. Bone marrow-derived mesenchymal stem cells (BMSCs) have been reported to have a potential therapeutic role on SAP, but the specific mechanism is unclear. Therefore, we conducted this experiment to shed light on the probable mechanism. We validated that SDF-1αsignificantly stimulated the expressions of VEGF, ANG-1, HGF, TGF-β, and CXCR4 in BMSCs, which were inhibited by its receptor agonist, AMD3100. The capacities of proliferation, migration, and repair of human umbilical vein endothelial cells were enhanced by BMSCs supernatant. Meanwhile, BMSCs supernatant could also promote angiogenesis, especially after the stimulation with SDF-1α.In vivo, the migration of BMSCs was regulated by SDF-1α/CXCR4 axis. Moreover, transplanted BMSCs could significantly alleviate SAP, reduce the systematic inflammation (TNF-α↓, IL-1β↓,IL-6↓, IL-4↑, IL-10↑, and TGF-β↑), and promote tissue repair and angiogenesis (VEGF↑, ANG-1↑, HGF↑, TGF-β↑, and CD31↑), compared with the SAP and anti-CXCR4 groups. Taken together, the results showed that BMSCs ameliorated SAP and the SDF-1α/CXCR4 axis was involved in the repair and regeneration process.
Cloud Particles Evolution Algorithm
Authors: Li Wei , Wang Lei , Jiang Qiaoyong , Hei Xinhong , Wang Bin
Published: February 2015

Many evolutionary algorithms have been paid attention to by the researchers and have been applied to solve optimization problems. This paper presents a new optimization method called cloud particles evolution algorithm (CPEA) to solve optimization problems based on cloud formation process and phase transformation of natural substance. The cloud is assumed to have three states in the proposed algorithm. Gaseous state represents the global exploration. Liquid state represents the intermediate process from the global exploration to the local exploitation. Solid state represents the local exploitation. The cloud is composed of descript and independent particles in this algorithm. The cloud particles use phase transformation of three states to realize the global exploration and the local exploitation in the optimization process. Moreover, the cloud particles not only realize the survival of the fittest through competition mechanism but also ensure the diversity of the cloud particles by reciprocity mechanism. The effectiveness of the algorithm is validated upon different benchmark problems. The proposed algorithm is compared with a number of other well-known optimization algorithms, and the experimental results show that cloud particles evolution algorithm has a higher efficiency than some other algorithms.