bluuebunny/crossref_metadata_2025 huggingface dataset:
Advances in the competitiveness of pan‐European rail freight services: findings from a case study
Authors: Islam Dewan Md Zahurul , Eidhammer Olav
Published: March 2015

The European rail freight market is ostensibly a free market where, from 1 January 2007, both incumbent and new‐entrant operators are able to compete on every line and in every European Union country. The main objective of this research paper is to assess the advances in the competitiveness of the pan‐European rail freight services operated by a new‐entrant (private) operator. Its main focus is to assess and contribute to the understanding of the advances towards competitiveness and the future prospects in the open European rail freight market, including dealing with challenges (e.g. dormant and departure of partners, suspension of the project, indistinct roles and responsibilities of operating partners) at different phases of the research, development and service offerings, that will be an important contribution to the Research and Development (R&D) policy and management arena in the Europe rail freight transport sector. The current research applies a case study research approach. The assessment of the rail freight service is performed by conducting two phases: first, a comparison of the progress between first and second year of the REorganisation of Transport networks by advanced RAil freight Concepts (RETRACK) rail freight service, operated by a new entrant and conducted on the corridor between two hubs – Cologne, Germany, and Györ, Hungary, and secondly a comparison of the opinions of customers on the RETRACK service and its competitors. From the comparative study between the first and second years, the study finds that the new‐entrant operator was able to offer an increased number of services by consolidating cargo from satellite connections at both ends of the operational corridor by adopting a pragmatic and flexible approach. The customer satisfaction survey suggests that the new‐entrant operator offered better service in terms of price, transit time, reliability and information flow/management compared to its competitors' services (offered by incumbent rail operators) on the corridor. However, their service was inferior to that of its competitors, in terms of frequency and availability of service. These less‐well performed service factors have improved gradually over time. The study suggests that intra‐rail competition has improved, but that inter‐modal completion is yet to be achieved. The ups and downs of the project provide important lessons for R&D management, academia and policy makers. The study suggests that a pan‐European rail freight service can be efficiently and effectively run by new‐entrant operators, and this will lead to more intra‐modal competition. However, they have yet to achieve competitiveness that will result in a shift of cargo from road to rail by offering an improved service that at least matches the major attributes of road freight service, e.g. price, transit time, door‐to‐door service and working in a collaborative way with other actors.
Relative contributions of emphysema and airway remodelling to airflow limitation in COPD: Consistent results from two cohorts
Authors: Tho Nguyen Van , Ryujin Yasushi , Ogawa Emiko , Trang Le Thi Huyen , Kanda Rie , Goto Kenichi , Yamaguchi Masafumi , Nagao Taishi , Lan Le Thi Tuyet , Nakano Yasutaka
Published: March 2015

Background and objective

The relative contributions of emphysema and airway remodelling to airflow limitation remain unclear in chronic obstructive pulmonary disease (COPD). We aimed to evaluate the relative contributions of emphysema and airway wall thickness measured by quantitative computed tomography (CT) to the prediction of airflow limitation in two separate COPD cohorts.

Methods

Pulmonary function tests and whole‐lung CT were performed in 250 male smokers with COPD, including 167 from University Medical Center at Ho Chi Minh City, Vietnam, and 83 from Shiga University of Medical Science Hospital, Japan. The same CT analysis software was used to measure the percentage of low attenuation volume (%LAV) at the threshold of −950 Hounsfield units and the square root of wall area of a hypothetical airway with an internal perimeter of 10 mm (Pi10). The standardized coefficients in multiple linear regressions were used to evaluate the relative contributions of %LAV and Pi10 to predictions of FEV1/FVC and FEV1% predicted.

Results

Both %LAV and Pi10 independently predicted either forced expiratory volume in 1 s/forced vital capacity (FEV1/FVC) or FEV1% predicted (P ≤ 0.001 for all standardized coefficients). However, the absolute values of the standardized coefficients were 2−3 times higher for %LAV than for Pi10 in all prediction models. The results were consistent in the two COPD cohorts.

Conclusions

%LAV predicts both FEV1/FVC and FEV1 better than Pi10 in patients with COPD. Thus, emphysema may make a greater contribution to airflow limitation than airway remodelling in COPD.
Mechanical cues in orofacial tissue engineering and regenerative medicine
Authors: Brouwer Katrien M. , Lundvig Ditte M. S. , Middelkoop Esther , Wagener Frank A. D. T. G. , Von den Hoff Johannes W.
Published: March 2015

Cleft lip and palate patients suffer from functional, aesthetical, and psychosocial problems due to suboptimal regeneration of skin, mucosa, and skeletal muscle after restorative cleft surgery. The field of tissue engineering and regenerative medicine (TE/RM) aims to restore the normal physiology of tissues and organs in conditions such as birth defects or after injury. A crucial factor in cell differentiation, tissue formation, and tissue function is mechanical strain. Regardless of this, mechanical cues are not yet widely used in TE/RM. The effects of mechanical stimulation on cells are not straight‐forward in vitro as cellular responses may differ with cell type and loading regime, complicating the translation to a therapeutic protocol. We here give an overview of the different types of mechanical strain that act on cells and tissues and discuss the effects on muscle, and skin and mucosa. We conclude that presently, sufficient knowledge is lacking to reproducibly implement external mechanical loading in TE/RM approaches. Mechanical cues can be applied in TE/RM by fine‐tuning the stiffness and architecture of the constructs to guide the differentiation of the seeded cells or the invading surrounding cells. This may already improve the treatment of orofacial clefts and other disorders affecting soft tissues.
Sealing Leakages of Public Funds Abuse: The Malawi “Cashgate” Case
Authors: Majanga Byson B.
Published: March 2015

The accountancy profession subscribes to the values of accountability, integrity, honesty, accuracy among others and that is the reason accountants are required in any field of work to provide an independent report of how the resources are deployed to bring the outcome and assess if indeed the outcome from the use of such resources is as it had been expected by all the stakeholders. This requirement is common to all sectors of the economy, whether in the public or private sector. The paper discusses the changing role of the accountant in the public sector in response to the growing concerns of public resource abuse. Africa, Malawi in particular, has been a victim of gross resource abuse by public officers through among others fraud, corruption, theft and gross mismanagement. Malawi has recently been rated highly in terms of corrupt practices with the public sector taking a leading position leading to gross mismanagement of public resources since the dawn of democracy in 1994. The study takes a look at the changing roles of an accountant in the public sector where the control environment in the financial management system, and the political will of those in charge of the public sector, are not the same as those in the private sector. The accounting weaknesses or challenges as revealed by the reviewed audit reports are scrutinised and the role of the accountant with respect to each challenge is reviewed and recommendations suggested which if implemented, may block the future recurrence of such weaknesses in the financial management systems in the public sector.
Requirements Development: Approaches and Behaviors of Novice Designers
Authors: Mohedas Ibrahim , Daly Shanna R. , Sienko Kathleen H.
Published: March 2015

Elicitation and development of product requirements are crucial aspects of front-end design and have significant impacts on future product success. This study sought to better understand how novice designers approach the development of product requirements during a front-end design task. Results showed that the stakeholder validity of participants' requirements and the level of tailoring of the requirements to the design context and stakeholders were highly correlated to the number of distinct information sources used and moderately correlated to participants' dependency on particular information sources. Furthermore, an in-depth exploration of participants' information gathering behavior during the design task elucidated specific strategies and processes that may explain why some participants were more successful than others.
Flank Wear Characterization in Aluminum Alloy (6061 T6) With Nanofluid Minimum Quantity Lubrication Environment Using an Uncoated Carbide Tool
Authors: Najiha M. S. , Rahman M. M. , Yusoff A. R.
Published: March 2015

This study is focused on the categorical analysis of flank wear mechanisms in end milling of aluminum alloy AA6061 with minimum quantity lubrication (MQL) conditions using nanofluid. Wear mechanisms for the water-based TiO2 nanofluid with a nanoparticle volume fraction of 1.5% are compared with conventional oil-based MQL (0.48 ml/min and 0.83 ml/min) using an uncoated cemented carbide insert. Micro-abrasion, micro-attrition, and adhesion wear leading to edge chipping are identified as the main wear mechanisms. Aluminum deposits on the tool flank surface are observed. Results show that the water-based nanofluid shows potential as a capable MQL cutting media, in terms of tool wear, replacing the conventional oil-based MQL.
Numerical Solution of High-Order Fractional Volterra Integro-Differential Equations by Variational Homotopy Perturbation Iteration Method
Authors: Neamaty A. , Agheli B. , Darzi R.
Published: March 2015

In this paper, variational homotopy perturbation iteration method (VHPIM) has been applied along with Caputo derivative to solve high-order fractional Volterra integro-differential equations (FVIDEs). The “VHPIM” is present in all two steps. In order to indicate the efficiency and simplicity of the proposed method, we have presented some examples. All of the numerical computations in this study have been done on a personal computer applying some programs written in Maple18.
On the Energetics of a Mechatronic Elevator System
Authors: Chen Kun-Yung , Fung Rong-Fong
Published: March 2015

The energy balance equation consisting of mechanical and electrical parts of a mechatronic elevator system is studied in this paper. The total input energy is equal to the mechanical and electrical energies, where a weighting factor should be added for the mechatronic system. The calculus of variation is implemented to find the minimum input electrical energy control (MIEEC) and minimum dissipation energy control (MDEC), which are compared and found to have the same results. From numerical simulations, it is confirmed to demonstrate that the energy balance equation must contain a weighting factor in a mechatronic system.
Mixed Array of Compliant Interconnects to Balance Mechanical and Electrical Characteristics
Authors: Okereke R. I. , Sitaraman S. K.
Published: March 2015

Various designs of compliant interconnects are being pursued in universities and industry to accommodate the coefficient of thermal expansion (CTE) mismatch between die and substrate or substrate and board. Although such interconnects are able to mechanically decouple the components, electrical parasitics of compliant interconnects are often high compared to the electrical parasitics of solder bump or solder ball interconnects. This increase in electrical parasitics is due to the fact that compliant interconnects typically having longer path lengths and smaller cross-sectional areas to provide compliance, which in turn, increases their electrical parasitics. In this paper, we present a mixed array of compliant interconnects as a tradeoff between mechanical compliance and electrical parasitics. In the proposed implementation, the die area is subdivided into three regions where high compliance, medium-compliance, and low-compliance interconnect variants are situated in the outer, middle, and inner regions of the die, respectively. By introducing the low-compliance variants into the assembly, interconnects with greatly reduced electrical parasitics can be used as power/ground interconnects, while the high-compliance interconnects, situated near the die edges, can be used as signal interconnects. This paper demonstrates the implementation of this configuration and also presents the experimental characterization of such heterogeneous array of interconnects.
Finite Element Modeling of Shot Peening Residual Stress Relaxation in Turbine Disk Assemblies
Authors: Meguid S. A. , Maricic Luke A.
Published: March 2015

Surface enhancement techniques such as shot peening are extensively used to increase the fatigue life of components in gas turbine engines. Due to the combined thermomechanical nature of the loading encountered within an engine, aeroengine designers have avoided incorporating the beneficial effects in their analysis. This can lead to overdesign and early retirement of critical engine components. A finite element modeling procedure is introduced that incorporates the shot peening residual stresses on a fir-tree turbine disk assembly. Unlike traditional equivalent loading approaches, the method models the actual impact of shots on the assembly and is the first time this approach is used to introduce peening residual stresses in turbine disks. In addition, the stability of these residual stresses in response to cyclic thermomechanical loadings at the contact interface is also studied. The results reveal that thermomechanical overload can nearly fully relax the shot peening residual stresses within the first cycle due to the combined effects of decreased material yield strength and plastic deformation. This work will enable aeroengine designers to assess critical surface treated components for structural integrity, optimal design, and residual life.
The Development of Direct Absorption and Storage Media for Falling Particle Solar Central Receivers
Authors: Siegel Nathan P. , Gross Michael D. , Coury Robert
Published: March 2015

Spherical sintered bauxite particles between 200 μm and 700 μm in diameter have been shown to be effective in the direct absorption and storage of concentrated solar energy. These particles are commercially available in large quantities and exhibit as-received solar weighted absorptance (αs) greater than 0.90, which gradually degrades with extended heating in air at 700 °C and above. The degradation mechanism is an oxidation reaction that can be reversed via thermal or chemical reduction, resulting in αs > 0.95 along with enhanced resistance to further degradation for some formulations. Certain metal oxide pigments, added to Al2O3:SiO2, have proven to achieve solar weighted absorptance levels similar to those of the commercially available particles and may be promising alternatives to currently available materials.
The Increasing Role of Heat Exchangers in Gas Turbine Plants
Authors: McDonald Colin F.
Published: March 2015

In the introductory phase of gas turbine deployment for industrial service there was a natural reluctance to incorporate heat exchangers, although some variants included recuperators and intercoolers to enhance performance, since only modest values of compressor and turbine efficiency could be realized. Today, following half a century of intensive development, the situation is quite different, since high turbomachinery efficiencies contribute to attractive levels of performance for contemporary simple cycle plants. Because further aerodynamic advancements are likely to be incremental in nature, significant increase in plant performance can only be realized by either going to higher turbine inlet temperature, or utilizing more complex thermodynamic cycles, or both. It is in the latter two cases that heat exchangers will play an increasing role in the evolutionary advancement of gas turbine plant efficiency. This paper highlights the potential use of heat exchangers for a wide range of gas turbine applications, including industrial prime-movers, electrical power generation, marine service, and perhaps their ultimate use in aircraft propulsion systems. In the last decade, significant heat exchanger technology advancements have been made, to the point where previous impediments (to their widespread acceptance) associated with reliability, have been overcome. It is encouraging that today many proven heat exchanger hardware options are available to gas turbine users, and this will enhance their utilization across the full spectrum of applications, and indeed in the long-term may well make the simple cycle gas turbine obsolete.
Revamp Experiences With Centrifugal Pipeline Compressors
Authors: Hoppock William G.
Published: March 2015

Centrifugal pipeline compressors are often restaged to meet new operating requirements. Several examples of compressor revamps are presented to illustrate various factors which can influence these restaging efforts. Examples involving both single-stage and multi-stage compressors are included. Various types of modern impeller designs used in pipeline revamps are discussed. An explanation is given of the boundaries which define a typical pipeline compressor range chart.
Aerodynamic Research on Highload Axial Compressor With a Chordwise Split
Authors: Zhang Zhi-Gang , Shen Ping-Cheng , Zhu Hong , Lu Jia-Hua , Li Yan-Sheng
Published: March 2015

This paper deals with a novel configuration of axial compressor cascade with chordwise split. Contrast to tandem cascade and cascade with a slot from pressure surface to suction surface, the cascade with a chordwise split not only controls the separation of boundary layer, increases flow turning angle and stage load, thus the compressor length can be shortened or pressure ratio increased, but also the flow pattern in the split is different.

The research work done shows that the cascade with chordwise split avoids or delays the separation of boundary layer on blade surface effectively thus may lead to a larger camber angle. The theoretical model and program for locating the split position and predicting flow field in cascade passage by using Finite Element Method are given.

Experiments have verified the mathematical model and the preferable effects of the chordwise split. The results of calculation correspond to the test data satisfactorily.
Development Test Status T-100 Multipurpose Small Power Unit
Authors: Napier James C. , Thompson Robert G. , Rodgers Colin
Published: March 2015

An advanced technology small gas turbine program is being sponsored by the U.S. Army to complete the design, fabrication, and test of the T-100 Multipurpose Small Power Unit (MPSPU).

This paper describes the basic design features and current development status of the T-100. This small gas turbine power unit is designed for airborne, vehicular, and ground auxiliary power applications at low cost.

The T-100 design incorporates the most current aerothermodynamic and structural component technologies with extensive small turbomachinery and combustor experience gained from a similar class gas turbine two decades ago.

The T-100 design, fabrication, and component rig testing of the Inlet Protection System (IPS) compressor, combustor and turbine have been successfully completed. Engine testing is now in progress on the 50 HP (37.4 kw) rated unit.
On Decoupling the Equations of Motion of Nonclassically Damped Systems
Authors: Ma F. , Hwang J. H.
Published: March 2015

One common procedure in the solution of a damped linear systems with small off-diagonal damping elements is to neglect the off-diagonal elements of the normalized damping matrix. The extent of approximation introduced by this method of decoupling the system is evaluated, and tight error bounds are derived by alternative techniques. An effective procedure to improve the accuracy of the approximate solution is outlined.
Noninteractive Macroscopic Reliability Model for Ceramic Matrix Composites With Orthotropic Material Symmetry
Authors: Duffy Stephen F. , Manderscheid Jane M.
Published: March 2015

A macroscopic noninteractive reliability model for ceramic matrix composites is presented. The model is multiaxial and applicable to composites that can be characterized as orthotropic. Tensorial invariant theory is used to create an integrity basis with invariants that correspond to physical mechanisms related to fracture. This integrity basis is then used to construct a failure function per unit volume (or area) of material. It is assumed that the overall strength of the composite is governed by weakest link theory. This leads to a Weibull type model similar in nature to the principle of independent action (PIA) model for isotropic monolithic ceramics. An experimental program to obtain model parameters is briefly discussed. In addition, qualitative features of the model are illustrated by presenting reliability surfaces for various model parameters.
Phase and Time-Resolved Measurements of Unsteady Heat Transfer and Pressure in a Full-Stage Rotating Turbine
Authors: Dunn M. G.
Published: March 2015

This paper presents detailed phase-resolved heat-flux data obtained on rotor blades and a comparison of simultaneously obtained time-resolved heat-flux and static pressure data obtained on the stationary shroud of a Garrett TFE 731-2 HP full-stage rotating turbine. A shock tube is used to generate a short-duration source of heated and pressurized air and platinum thin-film gages are used to obtain heat-flux measurements. Blade results are presented at several selected blade locations. Shroud surface pressure and heat-flux time histories are presented for comparable locations relative to the blade position. For these measurements, the turbine was operating at the design flow function, the design stage pressure ratio, and at 100% corrected speed.
A Three Dimensional Inverse Method in Turbomachinery: Part I — Theory
Authors: Borges João Eduardo
Published: March 2015

There are surprisingly few inverse methods described in the literature that are truly three-dimensional. Here, one such method is presented. This technique uses as input a prescribed distribution of the mean swirl, i.e., radius times mean tangential velocity, given throughout the meridional section of the machine. In the present implementation the flow is considered inviscid and incompressible and is assumed irrotational at inlet to the blade row. In order to evaluate the velocity field inside the turbomachine, the blades (supposed infinitely thin) are replaced by sheets of vorticity whose strength is related to the specified mean swirl. Some advice on the choice of a suitable mean swirl distribution is given. In order to assess the usefulness of the present procedure, it was decided to apply it to the design of an impeller of a low-speed radial-inflow turbine. The results of the tests are described in the second part of this paper.
Local-Global Analysis of Crack Growth in Continuously Reinforced Ceramic Matrix Composites
Authors: Ballarini Roberto , Ahmed Shamim
Published: March 2015

This paper describes the development of a mathematical model for predicting the strength and micro-mechanical failure characteristics of continuously reinforced ceramic matrix composites. The local-global analysis models the vicinity of a propagating crack tip as a local heterogeneous region (LHR) consisting of spring-like representation of the matrix, fibers and interfaces. This region is embedded in an anisotropic continuum (representing the bulk composite) which is modeled by conventional finite elements.

Parametric studies are conducted to investigate the effects of LHR size, component properties, interface conditions, etc. on the strength and sequence of the failure processes in the unidirectional composite system. The results are compared with those predicted by the models developed by Marshall et al. (1985) and by Budiansky et al. (1986).
Prediction of Heat Transfer Characteristics for Discrete Hole Film Cooling for Turbine Blade Applications
Authors: Tafti Daneshmund K. , Yavuzkurt Savash
Published: March 2015

A two-dimensional (2-D) injection model is used with a 2-D low Reynold’s number k-ε model boundary layer code. The three-dimensional effects of the discrete hole injection process is introduced in the 2-D prediction scheme through an “entrainment fraction” (T). An established correlation between T and the injection parameters obtained in a previous paper is used to predict the film cooling effectiveness (η̄) and heat transfer coefficients for multirow injection, injection into a laminar boundary layer and finally injection on convex curved surfaces. Predictions of η̄ are in good agreement with experimental data for most of the cases tested. Predictions of Stanton numbers defined by St(0) and St(1) are good for low injection ratios (M) but as M increases the values are underpredicted. In spite of some shortcomings, in the authors’ opinion the present 2-D prediction scheme is one of the most comprehensive developed so far. It is seen that the entrainment fraction T is quite universal in its application to 2-D predictions of the discrete hole film cooling process.
CAES Plant Performance and Economics as a Function of Underground Salt Dome Storage Transient Processes
Authors: Nakhamkin M. , Swensen E. , Schainker R. B. , Mehta B.
Published: March 2015

This paper presents a discussion of the computer model developed to quantify the effects of transient processes occurring during injection, storage and withdrawal of compressed air from underground storage in a salt dome.

The following mechanisms are considered when modelling the thermodynamic behavior of the compressed air within the cavern:

1) Temperature variations due to the compression and expansion of the air.

2) Heat transfer by convection at the cavern wall.

3) Heat transfer by conduction inside the salt formation.

4) Enthalpy changes as air is injected into and withdrawn from the cavern.

The paper presents a description of the physical processes in the storage cavern, the calculation methodology, and results of the model as applied to the conditions of the storage cavern designed for the Alabama Electric Cooperative 100 MW CAES plant.
A Mini-Packaged Gas Turbine Cogeneration Unit
Authors: Babus’Haq Ramiz , O’Callaghan Paul , Probert Douglas
Published: March 2015

The cogeneration process is the simultaneous production of electrical (or mechanical) power and heat, where the latter is a by-product of the power release process. In this investigation a mini-packaged gas turbine cogeneration unit is proposed for commercial and small industrial sectors. Its advantages are compared with those of a similar unit, but with a reciprocating engine as its prime mover.

While the basic concept of co-generation is quite simple and attractive, the analysis of its financial viability is complex. Thus a simple procedure has been devised to assess the economic viability of the proposed mini package. It has revealed that a pay-back period shorter than four years can be achieved by employing such a unit.
Exergy Analysis of Viable Options for Steam/Water Injection in Gas Turbines
Authors: Manfrida G. , Bidini G. , Alessandrello P. P.
Published: March 2015

Steam or water injection in gas turbines has become a proven technique for improving output, emissions control, and, in some cases, even efficiency in powerplants. A parametric analysis based on the second-law approach is conducted for some of the most promising injection schemes, e.g., STIG and regenerative-evaporative cycles with and without compressor intercooling. After an examination of the potentials and limits of each solution, a new scheme, PSTIG, is proposed, which combines the major advantages of steam injection and combined gas/steam cycles and, in addition, offers superior peakload capability.
Application of Gas Turbines for Large Reciprocating Compressor Drive
Authors: Giacomelli E. , Bernardini F. , Pini A. , Andree H.
Published: March 2015

The use of variable-speed drive systems such as gas turbines enhances the functional flexibility of reciprocating compressors.

This paper covers the main design aspects with correlation to direct experience of design, production, testing and operation on such units.

Thorough consideration has been given to a recent application onshore, where MS 1002 R (regenerative cycle) gas turbines, with 34% efficiency and 4620 kW ISO, drive a four-cylinder machine for natural gas storage in artificial caverns.

The selection criteria from the user’s point of view are analysed.

The theoretical and experimental results of torsional analysis, which represents one of the most important aspects for the complexity of the coupling of train components, are discussed.

The experience gained till now makes it possible to forecast an increasing application of gas turbine-compressor arrangements thanks to the energy-saving, advantages and the high reliability obtained with special design procedures design and modern full-load test facilities.
A Method of Predicting the Energy Losses in Vaneless Diffusers of Centrifugal Compressors
Authors: Dou Huashu
Published: March 2015

The flow losses in the veneless diffusers of centrifugal compressors is investigated. It is found that the total energy loss in vaneless diffusers is a function of Bsin2 α0 when inlet flow conditions and radius ratio between inlet and outlet are given. A wall friction coefficient equation is derived and a method of predicting the total energy loss excepting mixing loss is presented. A comparison is made between results obtained from this method and experimental data generated by the author as well as data from the literature. Good agreement is obtained.
A Numerical Three-Dimensional Thermal Stress Analysis for Cooled Blades
Authors: Srinivasan J. , Gowda R. M. S. , Padmanabhan R.
Published: March 2015

A modern gas turbine engine subjects the turbine rotor blade to severe thermal stress conditions. Thermal stresses constitute a major part of the state of stress in the blade. Improved blade design with optimum weight, long creep life and structural integrity necessitates more refined thermal stress analysis. In this work a plane blade profile is assumed to take the form of a second degree surface with constant curvatures. The general second degree polynomial allows all the six static equilibrium equations to be considered in evaluating the strained surface. The three dimensional state of stress is determined considering the lateral deformations of the blade profile. A numerical procedure is adopted to solve the non-linear simultaneous equations arising due to the self equilibrating thermal stress system. The results are close to that of original analysis. However, this procedure employs all the necessary equilibrium conditions and relaxes the constraints imposed due to the plane surface assumption to a lower level. The method of analysis is discussed in this paper.
Garrett Multipurpose Small Power Unit (MPSPU) Program Status
Authors: Kidwell J.
Published: March 2015

The Garrett Auxiliary Power Division’s Multipurpose Small Power unit (MPSPU), Contract DAAJ02-86-C-0006, sponsored by the Aviation Applied Technology Directorate, Ft. Eustis, Virginia, has progressed through detail design and analysis to component and power unit development testing. The MPSPU Advanced Development program is structured to provide advanced technology for current and future United States Army and other Department of Defense auxiliary power unit/secondary power system applications for aircraft, combat vehicles, and mobile tactical shelters. The MPSPU has been designed for low specific fuel consumption, low weight and volume, low acquisition and life cycle costs and high reliability and durability. This paper discusses the design and current developmental status of the Garrett GTP50 MPSPU as reported by Kidwell (1988).
Effects of Density Ratio on the Hydrodynamics of Film Cooling
Authors: Pietrzyk J. R. , Bogard D. G. , Crawford M. E.
Published: March 2015

This paper presents the results of a detailed hydrodynamic study of a row of inclined jets issuing into a crossflow with a density ratio of injectant to freestream of two. Laser Doppler anemometry was used to measure the vertical and streamwise components of velocity for a jet-to-freestream mass flux ratio of 0.5. Mean velocity components and turbulent Reynolds normal and shear stress components were measured at locations in a vertical plane along the centerline of the jet from 1 diameter upstream to 30 diameters downstream of the jet. The results, which have application to film cooling, give a quantitative picture of the entire flow field, from the approaching flow upstream of the jet, through the interaction region of the jet and freestream, to the relaxation region downstream where the flow field approaches that of a standard turbulent boundary layer.
Aerodynamic and Torque Characteristics of Enclosed Co/Counter Rotating Disks
Authors: Daniels W. A. , Johnson B. V. , Graber D. J.
Published: March 2015

Experiments were conducted to determine the aerodynamic and torque characteristics of adjacent rotating disks enclosed in a shroud. These experiments were performed to obtain an extended data base for advanced turbine designs such as the counter-rotating turbine. Torque measurements were obtained on both disks in the rotating frame of reference for co-rotating, counter-rotating and one-rotating/one-static disk conditions. The disk models used in the experiments included disks with typical smooth turbine geometry, disks with bolts, disks with bolts and partial bolt covers and flat disks. A windage diaphragm was installed at mid-cavity for some experiments. The experiments were conducted with various amounts of coolant throughflow injected into the disk cavity from the disk hub or from the disk OD with swirl. The experiments were conducted at disk tangential Reynolds number up to 1.6×107 with air as the working fluid. The results of this investigation indicated that the static shroud contributes a significant amount to the total friction within the disk system, the torque on counter-rotating disks is essentially independent of coolant flow total rate, flow direction and tangential Reynolds number over the range of conditions tested and a static windage diaphragm reduces disk friction in counter-rotating disk systems.
Secondary Flows and Vortex Motion in a High-Efficiency Backswept Impeller at Design and Off-Design Conditions
Authors: Hah C. , Krain H.
Published: March 2015

The 3-D viscous flowfield of a 4.7:1 pressure ratio backswept impeller was studied experimentally and numerically by using laser velocimetry and an advanced 3-D viscous code. The impeller was designed by a CAD method, and a maximum rotor efficiency of 94% was achieved. Both the experimental and the theoretical approach revealed comparatively smooth impeller discharge velocity profiles at all three operating conditions (design, choke, and near surge) differing widely from the well-known jet/wake type flow pattern. The 3-D viscous code was used for detailed flowfield studies, i.e., secondary flows; vortex motion and tip-clearance effects were analyzed at design and off-design conditions. The comparison of experimental and numerical results indicates that the tip-clearance effect should be properly modeled to predict the impeller flow pattern properly and that optimum shape of rotor exit flow pattern can be obtained by controlling the swirling vortex motion.
Simulation of Compressor Performance Deterioration due to Erosion
Authors: Tabakoff W. , Lakshminarasimha A. N. , Pasin M.
Published: March 2015

Experimental results obtained from cascades and one stage compressor performance tests before and after erosion were used to test a fault model to represent erosion. This model was implemented on a stage stacking program developed to demonstrate the effect of erosion in a multistage compressor. The effect of the individual stage erosion on the overall compressor performance is also demonstrated.
The Use of De-Swirl Nozzles to Reduce the Pressure Drop in a Rotating Cavity With a Radial Inflow
Authors: Farthing P. R. , Chew J. W. , Owen J. M.
Published: March 2015

A combined theoretical and experimental study is described in which de-swirl nozzles were used to reduce the radial pressure drop in a rotating cavity with a radial inflow of air. The nozzles, which were attached to the outer part of the cavity, were angled such that the angular speed of the air at inlet could be in the opposite direction to that of the cavity. Solutions of the momentum-integral equations were used to predict the resulting radial distributions of pressure throughout the cavity.

Flow visualization was used to confirm the flow structure, and transducers attached to one of the rotating discs in the cavity were used to measure the radial pressure distributions. Results are presented for ‘swirl fractions’ (that is, the ratio of the angular speed of the air leaving the nozzles to that of the cavity) in the range −0.4 to + 0.9, and for 0.01 < | CW | Reϕ−0.8 < 0.5, where CW and Reϕ, are the nondimensional flow rate and rotational Reynolds number, respectively. The measured pressures are in good agreement with the predicted values, and the pressure drop across the cavity can be significantly less than that associated with solid-body rotation. The flow rate produced by the pressure drop across the cavity is not unique: there are up to three possible values of flow rate for any given value of pressure drop.
An Analysis Methodology for Internal Swirling Flow Systems With a Rotating Wall
Authors: Williams M. , Chen W. C. , Bache G. , Eastland A.
Published: March 2015

This paper presents an analysis methodology for the calculation of the flow through internal flow components with a rotating wall such as annular seals, impeller cavities and enclosed rotating disks. These flow systems are standard components in gas turbines and cryogenic engines and are characterized by subsonic viscous flow and elliptic pressure effects. The Reynolds averaged Navier-Stokes equations for turbulent flow are used to model swirling axisymmetric flow. Bulk-flow or velocity profile assumptions aren’t required. Turbulence transport is assumed to be governed by the standard two-equation high Reynolds number turbulence model. A low Reynolds number turbulence model is also used for comparison purposes. The high Reynolds number turbulence model is found to be more practical. A novel treatment of the radial/swirl equation source terms is developed and used to provide enhanced convergence. Homogeneous wall roughness effects are accounted for. To verify the analysis methodology, the flow through Yamada seals, an enclosed rotating disk, and a rotating disk in a housing with throughflow are calculated. The calculation results are compared to experimental data. The calculated results show good agreement with the experimental results.
Behaviour of a Two Rows of Holes Coolant Film Along the Pressure Side of a High Pressure Nozzle Guide Vane
Authors: Arts T. , Bourguignon A. E.
Published: March 2015

The purpose of this paper is to quantify the influence on external convective heat transfer of a coolant film whose position varies along the pressure side of a high pressure turbine nozzle guide vane. The measurements were performed in the short duration Isentropic Light Piston Compression Tube facility of the von Karman Institute. The effects of external and internal flow are considered in terms of Mach number, Reynolds number, freestream turbulence intensity, blowing rate and coolant to freestream temperature ratio. The way to evaluate these results in terms of film cooling efficiency and heat transfer coefficient is finally discussed.
Regional Heat Transfer and Pressure Drop in Two-Pass and Three-Pass Flow Passages With 180-Degree Sharp Turns
Authors: Chyu M. K.
Published: March 2015

The heat transfer distributions for flow passing through a two-pass (one-turn) and a three-pass (two-turn) passages with 180-degree sharp turns are studied by using the analogous naphthalene mass transfer technique. Both passages have square cross-section and length-to-height ratio of 8. The passage surface, including top wall, side walls and partition walls, is divided into 26 segments for the two-pass passage and 40 segments for the three-pass passage. Mass transfer results are presented for each segment along with regional and overall averages. The very non-uniform mass transfer coefficients measured around a sharp 180-degree turn exhibit the effects of flow separation, reattachment and impingement, in addition to secondary flows. Results of the three-pass passage indicate that heat transfer characteristics around the second turn is virtually the same as that around the first turn. This may imply that, in a multiple-pass passage, heat transfer at the first turn has already reached the thermally developed (periodic) condition. Over the entire two-pass passage, the heat transfer enhancement induced by the single-turn is about 45% to 65% of the fully developed values in a straight channel. Such a heat transfer enhancement decreases with an increase in Reynolds number. In addition, overall heat transfer of the three-pass passage is approximately 15% higher than that of the two-pass one. This 15% increase appears to be Reynolds number independent. The pressure loss induced by the sharp turns is found to be very significant. Within the present testing range, the pressure loss coefficient for both passages varies significantly with the Reynolds number.
Operating Experience With a 42.5 MW Gas Turbine Used in a Cogeneration Plant at a Paper Mill in the U.S.
Authors: O’Neill S. T.
Published: March 2015

The CW251B10 Gas Turbine has been in service at the Procter & Gamble Paper Mill located at Mehoopany, Pennsylvania since July 1985, and has exhibited outstanding reliability and availability since that time. It operates continuously at base load supplying both electricity and process air for the plant. This paper reviews the operating history of the gas turbine, and describes some of the problems experienced, together with their solutions.
Reynolds Number Effects on the Performance of a Turbofan Engine
Authors: Kozu Masao , Yashima Satoshi
Published: March 2015

Reynolds Number effects on the matching performance of a small twin-spool turbofan engine were investigated through the altitude tests of the F3-30 engine which was developed to power the Japan Air Self Defence Force’s T-4 intermediate trainer.

Analyzing the test results made it clear that the change of the aerodynamic characteristics of the low pressure turbine due to Reynolds Number effects is as significant as these of fan and compressor, and it caused the difference between the predicted and measured engine performance at high altitudes.

Correlation factors on the Reynolds Number for each of the component characteristics (pressure ratio, airflow and efficiency of fan and compressor, and gas flow and efficiency of low pressure turbine) were obtained, and simulation of the engine performance using these factors coincided well with the test data which were obtained from the altitude tests of the F3-30 at Arnold Engineering Development Center of U. S. Air Force.
Effect of Inlet Flow Angle on the Erosion of Radial Turbine Guide Vanes
Authors: Eroglu Hasan , Tabakoff Widen
Published: March 2015

The results of an investigation of the particle dynamics and the blade erosion at the impact locations in radial turbine guide vanes are presented. The attention is focused in particular on the effect of inlet flow angle on the erosion of the blades, since the flow entering the guide vanes usually has an incidence angle due to the upstream scroll geometry. The total erosion per blade is calculated as a function of inlet flow angle for three different particle diameters which are 5, 15 and 60 microns respectively. According to the results of this investigation, for each particle size there is an inlet flow angle for minimum erosion of the guide vanes. This fact has to be accounted for in the design of the radial turbines operating in particulate flow environments.
Combustion Engineering at Laval University
Authors: Odgers J. , Kretschmer D.
Published: March 2015

In 1966 Professor Dr. A. F. Schlader conceived the idea of introducing some form of research project on combustion engineering as an addition to the existing thermodynamics and heat transfer opportunities offered to graduate students. With help from the university and the National Research Council, he was able to establish a laboratory capable of testing a single combustion chamber (atmospheric inlet conditions) and another laboratory containing a small test rig for water flow visualisation. In 1968 the mechanical engineering department was augmented by the addition of a full-time professor to do research and teach combustion. For five years the teaching was limited to graduate courses, and at the same time, the laboratories were gradually being extended and improvements made, particularly with respect to instrumentation.

A major step was taken by the introduction of a course at the undergraduate level, and some five years after this, an additional undergraduate course was added as well as a complementary course on instrumentation. Laval University is one of few Canadian universities which offer a selection of undergraduate courses pertinent to combustion. All the undergraduate courses are ‘choice’, and the enrollment is generally from 10 to 35 students per course. On the retirement of Prof. Schlader a new professor was engaged. The expansion of the laboratories and their facilities continued to evolve such that they have become accepted as being of international stature. Initially almost all the work was concerned with gas turbine combustion, but of recent years several fundamental studies using laboratory flames have been carried out, and work has been done on automobile engine combustion and even some furnace work and the combustion of oil spills.
A Magnetic Damper for First Mode Vibration Reduction in Multimass Flexible Rotors
Authors: Kasarda M. E. F. , Allaire P. E. , Humphris R. R. , Barrett L. E.
Published: March 2015

Many rotating machines such as compressors, turbines and pumps have long thin shafts with resulting vibration problems. They would benefit from additional damping near the center of the shaft. Magnetic dampers have the potential to be employed in these machines because they can operate in the working fluid environment unlike conventional bearings. This paper describes an experimental test rig which was set up with a long thin shaft and several masses to represent a flexible shaft machine. An active magnetic damper was placed in three locations: near the midspan, near one end disk, and close to the bearing. With typical control parameter settings, the midspan location reduced the first mode vibration 82%, the disk location reduced it 75% and the bearing location attained a 74% reduction. Magnetic damper stiffness and damping values used to obtain these reductions were only a few percent of the bearing stiffness and damping values. A theoretical model of both the rotor and the damper was developed and compared to the measured results. The agreement was good.