bluuebunny/crossref_metadata_2025 huggingface dataset:
Improving Physical Activity in Hispanics with Diabetes and their Families
Authors: Hu Jie , Wallace Debra C. , Amirehsani Karen A. , McCoy Thomas P. , Coley Sheryl L. , Wiseman Kimberly D. , Silva Zulema A. , Hussami Christina R.
Published: March 2015

Objective

This study examined changes in physical activity among Hispanics with diabetes and their families who received an 8‐week diabetes self‐management intervention.

Design

A quasi‐experimental design was used to conduct a secondary analysis of physical activity data from two intervention studies that used the same protocols and measures.

Sample

A total of 65 patients and 66 family members participated in the studies.

Measures

Physical activity was measured with the International Physical Activity Questionnaire (IPAQ) and pedometers. Self‐report of physical activity was collected pre‐ and postintervention, and pedometer data for the 8 weeks of the intervention period.

Intervention

The interventions consisted of 8 weeks of educational sessions.

Results

IPAQ walking Metabolic Equivalent of Task (MET)‐minutes per week significantly increased for patients (p < .001) and family members (p < .001) from pre‐ to postintervention as did moderate activity MET‐minutes/week for family members (p = .004). Based on pedometer steps, the percentage of sedentary patients declined from 38% to 17% over the intervention record; differences in pedometer steps over time were not significant for patients (p = .803) or family members (p = .144).

Conclusions

Pedometers are a cost effective and user‐friendly method of measuring physical activity. Pedometers can also serve as a motivator to help increase physical activity among Hispanics with diabetes and their family members.
Screening executive function and global cognition with the Nine‐Card Sorting Test: healthy participant studies and ageing implications
Authors: Vigliecca Nora Silvana , Baez Sandra
Published: March 2015

Background

The Nine‐Card Sorting Test provides valid and reliable scores when screening executive function, intelligence, and academic achievement. It is also useful for detecting cognitive impairment and dementia in the elderly and for assessing disease evolution and treatment effectiveness. It deals with three non‐verbal sorting principles, individually and in pairs. The presence of risk in the ability to discover and organize visual logical stimuli is explored.

Objectives

This study aimed to describe performance on the Nine‐Card Sorting Test in a non‐clinical sample, to analyze the effect of demographic variables, and to propose suitable (i.e. the simplest and most homogeneous) cut‐off points for possible deficits. Combinations in pairs (double arrays) were assessed (range: 0–3).

Results

Significant effects of age and education were observed, but no interactions among the demographic variables were seen. Differences between the second and third levels of education and between men and women were not significant. The simplest cut‐off points were as follows: (i) the median for people younger than 45 years old was 2, independent of educational level; (ii) the median for people older than 74 years old was 1, independent of educational level; and (iii) the median for people aged 45–74 years old was 1 for the first level of education and 2 for higher levels of education.

Conclusion

By considering both the statistical nature of the present dependent variable (number of completed categories) and the clear‐cut performance of the different samples studied, this neuropsychological test can be defined as a categorical screening for executive function and global cognition. This is advantageous for reporting risk. Of the whole sample, the 25th percentile (score = 1) represented a valid index for possible deficits. Ageing questions are highlighted. The test is also fruitful for studies on visuospatial organization and its facilitatory and inhibitory mechanisms.
Autopsy‐confirmed hippocampal‐sparing Alzheimer's disease with delusional jealousy as initial manifestation
Authors: Fujishiro Hiroshige , Iritani Shuji , Hattori Miho , Sekiguchi Hirotaka , Matsunaga Shinji , Habuchi Chikako , Torii Youta , Umeda Kentaro , Ozaki Norio , Yoshida Mari , Fujita Kiyoshi
Published: March 2015

Alzheimer's disease (AD) is clinically characterized by gradual onset over years with worsening of cognition. The initial and most prominent cognitive deficit is commonly memory dysfunction. However, a subset of AD cases has less hippocampal atrophy than would be expected relative to the predominance of cortical atrophy. These hippocampal‐sparing cases have distinctive clinical features, including the presence of focal cortical clinical syndromes. Given that previous studies have indicated that severe hippocampal atrophy corresponds to prominent loss of episodic memory, it is likely that memory impairment is initially absent in hippocampal‐sparing AD cases. Here, we report on a patient with an 8‐year history of delusional jealousy with insidious onset who was clinically diagnosed as possible AD and pathologically confirmed to have AD with relatively preserved neurons in the hippocampus. This patient had delusional jealousy with a long pre‐dementia stage, which initially was characterized by lack of memory impairment. Head magnetic resonance imaging findings showed preserved hippocampal volume with bilateral enlarged ventricles and mild‐to‐moderate cortical atrophy. Head single‐photon emission computed tomography revealed severely decreased regional cerebral blood flow in the right temporal lobe. The resolution of the delusion was attributed to pharmacotherapy by an acetylcholinesterase inhibitor, suggesting that the occurrence of delusional jealousy was due to the disease process of AD. Although the neural basis of delusional jealousy remains unclear, this hippocampal‐sparing AD case may be classified as an atypical presentation of AD.
Family support, anticipated support, negative interaction, and psychological well‐being of older parents inThailand
Authors: Thanakwang Kattika
Published: March 2015

Background

A number of studies have consistently indicated that family support has a powerful impact on older parents' well‐being, but little is known about the effects of anticipated support and negative interaction on psychological well‐being. The present study attempted to examine the relationships between family support, negative interaction, and psychological well‐being in older Thai parents.

Methods

The sample included 578 elderly parents aged 60 years and older. Multiple regression models were employed to determine whether received support, anticipated support, and negative interaction influence older parents' well‐being.

Results

Findings revealed that greater emotional and instrumental support received from family members and anticipated support were significantly associated with a greater sense of older parents' psychological well‐being. However, psychological well‐being was lower for those with more negative family interactions.

Conclusion

The results suggest that filial piety and family solidarity should be considered when developing elder care policy and interventions to promote psychological well‐being.
Subjective memory impairment and well‐being in community‐dwelling older adults
Authors: Zuniga Krystle E. , Mackenzie Michael J. , Kramer Arthur , McAuley Edward
Published: March 2015

Background

The relationship between subjective memory impairment (SMI), future cognitive decline, and negative health status provides an opportunity for interventions to reduce memory complaints in high‐risk groups. This study aimed to examine the relationship between SMI and indicators of well‐being in older adults enrolled in an exercise trial. Additionally, the study examined whether two different modes of exercise training, aerobic walking and non‐aerobic flexibility, toning, and balance, differentially influenced subjective memory across the trial.

Methods

Community‐dwelling older adults (n = 179, mean age = 66.4 years) were randomly assigned to a walking or flexibility, toning, and balance group for 12 months. Subjective memory, happiness, perceived stress, and symptom reporting were measured at baseline, 6 months, and 12 months.

Results

A main effect of subjective memory indicated that individuals with the fewest memory complaints had lower perceived stress (P < 0.001), lower physical symptom reporting (P < 0.001), and higher happiness levels (P < 0.001) across all measurement occasions. Both main and interaction effects of time and group on SMI were not significant, suggesting SMI remained stable across the intervention and was not significantly impacted by participation in exercise training.

Conclusions

SMI was not responsive to exercise interventions, and the relationship between SMI and negative well‐being demonstrates a need for interventions to reduce memory complaints in high‐risk groups.
A structural model of age, grey matter volumes, education, and personality traits
Authors: Kitamura Soichiro , Yasuno Fumihiko , Yamamoto Akihide , Kazui Hiroaki , Kudo Takashi , Matsuoka Kiwamu , Kiuchi Kuniaki , Kosaka Jun , Nagatsuka Kazuyuki , Iida Hidehiro , Kishimoto Toshifumi
Published: March 2015

Background

When the relationship between ageing and changes in personality traits is considered, it is important to know how they are influenced by biological and environmental factors. The present study examined the relationships between various factors associated with the effect of ageing on personality traits, including structural changes of the brain and environmental factors such as education.

Methods

We recruited 41 healthy subjects. We administered the NEO Five‐Factor Inventory to assess personality factors. Magnetic resonance imaging was performed, and regional grey matter (GM) volumes were obtained. We identified associations in the correlation analysis of age, cerebral GM volume, years of education, and the personality trait of openness. Path analysis was used to estimate the relationships among these factors.

Results

The path analysis model of age, GM volume, years of education, and the personality trait of openness revealed that age has an indirect negative association with openness through GM volume and years of education. Ageing was related to a decrease in GM volume, which was in turn related to a decrease in the openness score. Older subjects generally had fewer years of education, which was related to a lower openness score.

Conclusions

Maintaining openness against the effects of ageing is desirable, and our results imply that interventions against age‐related cerebral atrophy and the promotion of opportunities for higher education may contribute to the development and stability of a healthy personality during the adult life course.
When is a function a Hilbert modular form?
Authors: Swinnerton‐Dyer Peter
Published: March 2015

This paper gives a simple criterion for a multiple Fourier series to be a Hilbert modular form.
Status of the Automotive Ceramic Gas Turbine Development Program
Authors: Itoh Takane , Kimura Hidetomo
Published: March 2015

The seven-year program, designated “Research and Development of Automotive CGT” commenced in June 1990 with the object of demonstrating the potential advantages of ceramic gas turbine engines for automotive use. This program has been being conducted by the Petroleum Energy Center (PEC) with the support of the Ministry of International Trade and Industry. The engine demonstration project in this program is being handled by a team from the Japan Automobile Research Institute, Inc., (JARi).

This paper describes the activities of the first year of the seven-year program, and includes the project goals and objectives, the program schedule, and the first-stage design of an experimental automotive ceramic gas turbine (CGT) engine and its components. The basic engine is a 100kW, single-shaft gas turbine engine having a turbine inlet temperature of 1350°C and a rotor speed of 110,000 rpm. The primary engine components including the turbine hot flow path components have been designed using monolithic ceramics and are scheduled to be produced during the second year of the program.
Recent Advances in Simulating Unsteady Flow Phenomena Brought About by Passage of Shock Waves in a Linear Turbine Cascade
Authors: Collie J. C. , Moses H. L. , Schetz J. A. , Gregory B. A.
Published: March 2015

High-pressure ratio turbines have flows dominated by shock structures that pass downstream into the next blade row in an unsteady fashion. Recent numerical results have indicated that these unsteady shocks may significantly affect the aerodynamic and mechanical performance of turbine blading. High cost and limited accessibility of turbine rotating equipment severely restrict the quantitative evaluation of the unsteady flowfield in that environment. Recently published results of the Virginia Tech transonic cascade facility indicate high integrity in simulation of the steady state flow phenomena. The facility has recently been modified to study the unsteady effects of passing shock waves. Shock waves are genarated by a shotgun blast upstream of the blade row. Shadowgraph photos and high-response pressure data are compared to previously published experimental and numerically predicted results. Plots are included which indicate large fluctuations in estimated blade lift and cascade loss.
A Study on Stability and Response Analysis of a Nonlinear Rotor System With Mass Unbalance and Side Load
Authors: Shiau Ting Nung , Hwang Jon Li , Chang Yuan Bin
Published: March 2015

The stability of steady state synchronous and nonsynchronous response of a nonlinear rotor system supported by squeeze-film dampers is investigated. The nonlinear differential equations which govern the motion of rotor bearing system are obtained by using the Generalized Polynomial Expansion Method. The steady state response of system is obtained by using the hybrid numerical method which combines the merits of the harmonic balance and collocation methods. The stability of system response is examined using Floquet-Liapunov theory. Using the theory, the performance may be evaluated with the calculation of derivatives of nonlinear hydrodynamic forces of the squeeze-film damper with respect to displacement and velocity of the journal center. In some cases, these derivatives can be expressed in closed form and the prediction of the dynamic characteristic of the nonlinear rotor system will be more effective. The stability results are compared to those using a direct numerical integration method and both are in good agreement.
LQR-Based Least-Squares Output Feedback Control of Rotor Vibrations Using the Complex Mode and Balanced Realization Methods
Authors: Fan G. W. , Nelson H. D. , Crouch P. E. , Mignolet M. P.
Published: March 2015

The complex mode and balanced realization methods are used separately to obtain reduced-order models for general linear asymmetric rotor systems. The methods are outlined and then applied to a typical rotor system which is represented by a 52 degree-of-freedom finite element model. The accuracy of the two methods is compared for this model and the complex mode method is found to be more accurate than the balanced realization method for the desired frequency bandwidth and for models of the same reduced order. However, with some limitations, it is also shown that the balanced realization method can be applied to the reduced-order complex mode model to obtain further order reduction without loss of model accuracy. An “Linear-Quadratic-Regulator-based least-squares output feedback control” procedure is developed for the vibration control of rotor systems. This output feedback procedure eliminates the requirement of an observer for the use of an LQ regulator, and provides the advantage that the rotor vibration can be effectively controlled by monitoring only one single location along the rotor shaft while maintaining an acceptable performance. The procedures presented are quite general and may be applied to a large class of vibration problems including rotor-dynamics.
A Numerical Investigation Into the Nozzle Flow of High By-Pass Turbofans
Authors: Zimmermann H. , Katheder K. , Jula A.
Published: March 2015

Numerical investigations for the interacting flow fields of primary and secondary nozzles confirm, that for high by-pass turbofans there is a strong influence of the fan flow on the discharge and thrust coefficients of the core nozzle and of the fan afterbody shape on the coefficients of the fan nozzle.

After a review of standard methods two new parameters to correlate the thrust of different concepts are proposed and investigations into flight conditions are put forward.

Several nozzle coefficients derived from the integrated velocity profiles and the static pressure field are necessary to assess the quality of nozzle flow.
Numerical Analyses of a Rocket Engine Turbine and Comparison With Air Test Data
Authors: Tran Ken , Chan Daniel C. , Hudson Susan T. , Gaddis Stephen W.
Published: March 2015

Cold air test data on the Space Shuttle Main Engine (SSME) High Pressure Fuel Turbopump (HPFTP) turbine were recently collected at NASA Marshall Space Flight Center (MSFC). The turbine is a two-stage reaction machine, which was designed in the early 1970s (Fig. 1a). Overall performance data, static pressures on the first- and second-stage nozzles, and static pressures along the gas path at the hub and tip were gathered and are compared in this paper with various (1-D, quasi 3-D, and 3-D viscous) analysis procedures. The results of each level of analysis is compared to test data to demonstrate the range of applicability for each step in the design process of a turbine.
Design Features of the ГТД 8000 and ГТД 15000 Marine Gas Turbine Engines
Authors: Romanov Victor I.
Published: March 2015

This paper describes design features and performance data of the ГТД 8000 and ГТД 15000 engines of new generation. The efficiency of these engines is 34–35% (simple cycle, ISO Conditions). The paper presents basic trends of design and technology improvements resulted in a high performance engine. Examples of new gas turbines application are shown.
Solar Centaur Taurus T-6502: The First Installation
Authors: Braun Ardean L.
Published: March 2015

In the summer of 1991, NOVA Corporation of Alberta (NOVA) commissioned the first Solar Centaur Taurus T-6502 turbine unit into service on its natural gas pipeline system. The turbine powered a Solar C304 compressor equipped with dry gas seals and magnetic bearings. This paper describes the turbine/compressor package and the application in which it was installed. Experiences during commissioning, start up and the early months of operation are discussed.
Turbine Rebuild Effects on Gas Turbine Performance
Authors: MacLeod J. D. , Drbanski B.
Published: March 2015

The Engine Laboratory of the National Research Council of Canada (NRCC), with the assistance of Standard Aero Ltd., has established a program for the evaluation of component deterioration on gas turbine engine performance. As part of this project, a study of the effects of turbine rebuild tolerances on overall engine performance was undertaken. This study investigated the range of performance changes that might be expected for simply disassembling and reassembling the turbine module of a gas turbine engine, and how these changes would influence the results of the component fault implantation program.

To evaluate the effects of rebuilding the turbine on the performance of a single spool engine, such as Allison T56 turboprop engine, a series of three rebuilds were carried out. This study was performed in a similar way to a previous NRCC study on the effects of compressor rebuilding. While the compressor rebuild study had found performance changes in the order of 1% on various engine parameters, the effects of rebuilding the turbine have proven to be even more significant. Based on the results of the turbine rebuild study, new methods to improve the assurance of the best possible tolerances during the rebuild process are currently being addressed.

This paper describes the project objectives, the experimental installation, and the results of the performance evaluations. Discussed are performance variations due to turbine rebuilds on engine performance characteristics. As the performance changes were significant, a rigorous measurement uncertainty analysis is included.
Transient Phenomena in Compressor Stations During Surge
Authors: Botros K. K.
Published: March 2015

Transient phenomena are generally inherent in the operation of compressor stations: these are either fast or slow transients. A model describing the governing equation for the gas dynamics, control system, compressor and turbine shafts inertias has been developed. The effect of these inertias is manifested by an example of a compressor station operating near the surge control line. Another example deals with a station that has a cooler placed in the recycle path. This alters the rate at which the compressor shaft decelerates upon shutdown and may cause backward spinning depending on the relative magnitude of the shaft inertia with respect to the cooler volume. Backward spinning of compressor shaft has detrimental effects on dry seals and is undesirable. It was found that by keeping the recycle valve closed upon shutdown, the rate of shaft deceleration will be reduced.
Development of a Regenerator for an Automotive Gas Turbine Engine
Authors: Sayama Junichi , Morishita Teru
Published: March 2015

It is vital to accurately estimate the temperature effectiveness and pressure loss of the regenerator when designing a gas turbine engine because these characteristics basically determine the size, weight, and fuel consumption of the regenerative gas turbine engine. In operation of an actual engine, regenerators often fail to attain the characteristics predicted by conventional methods, because there are many performance-reducing irregularities such as the non-uniform velocity distribution of gases flowing into the core.

In this paper, a prediction method that is based on data from actual engine tests is examined as a way to predict regenerator temperature effectiveness and pressure losses when there are causes for deterioration of these characteristics. This method resulted in a system, taking the deterioration of these characteristics into consideration as they occur in an actual engine, that represents temperature effectiveness and pressure loss as the function of core specifications such as the core size and the core matrix.

This prediction method was then used to predict the regenerator characteristics of actual engines with more than satisfactory results (The accuracy is ±1.25% for temperature effectiveness and ±4% for pressure loss).
Investigation of Compressor Rotor Wake Structure at Peak Pressure Rise Coefficient and Effects of Loading
Authors: Prato J. , Lakshminarayana B.
Published: March 2015

This paper reports an experimental study of the three-dimensional characteristics of the mean velocity in the trailing-edge, near-wake and far-wake regions of a highly loaded low-speed compressor rotor. The wake structure and decay characteristics are compared with the wake data in the same compressor with moderate loading. The experimental investigation was carried out using a rotating five-hole probe. The flow field was surveyed at various radial and axial locations downstream of the compressor rotor. Variations in the axial, tangential and radial components of mean velocity at various axial and radial locations were derived from the data and compared with earlier data at lower loading to discern the effects of loading. It was found that the higher loading had the following effects: Higher total velocity defects were observed in the hub-wall region, increased wake growth rate in the tip region, faster decay of static pressure difference in the trailing-edge region, larger initial wake width in the trailing-edge region, increased rate of growth of the semi-wake width in the trailing-edge region, increased decay rate of radial velocity in the trailing-edge region and decreased decay rate of the radial velocity in the far-wake region. Far wake properties were almost identical in both cases.
Pressure Fluctuation on Casing Wall of Isolated Axial Compressor Rotors at Low Flow Rate
Authors: Inoue Masahiro , Kurdumaru Motoo , Anoo Youichi
Published: March 2015

The pressure fluctuations on the casing wall of two axial flow compressor rotors with various tip clearances have been analyzed by the use of two kinds of correlation functions. Behavior of the pressure fluctuation varies depending on tip clearance and blade solidity. In the case of small tip clearance, the nature of disturbances becomes random as the flow rate is reduced to a stall condition. For moderate tip clearance, coherent-structured disturbances appear intermittently at low flow rate. They appear more frequently as the solidity is increased and the flow rate becomes lower. For large tip clearance, the coherent structured disturbances exist even at considerably higher flow rates. Corresponding to these features there are peculiar patterns in the correlation designated as “phase-locked correlation function”.
Electromechanical Measurement of Turbomachinery Blade Tip-to-Casing Running Clearance
Authors: Sheard A. G. , Turner S. R.
Published: March 2015

It is difficult to make a reliable measurement of running clearance in the hostile environment over the blading of modern gas turbines. When the engine manufacturers require the measurement to be made during tests lasting many hours, or even days, measurement system ruggedness and reliability are of primary importance.

This paper describes how a second generation tip clearance measurement system of much reduced size and weight was developed. The reduction of size and weight facilitates the use of this measurement system for blade tip-to-casing measurements on all engine development tests from rig to flight worthy engines. During the course of commissioning, the measurement system was tested first in the laboratory, then on progressively more demanding test vehicles. The final test was on the high pressure turbine of a modern military full scale development single spool core. During the course of this test, the mean engine Turbine Entry Temperature through the blading over which clearance was measured, exceeded 1800 K and is typical of the applications for this second generation system.
Stability of Fully Developed Rotating Stall
Authors: McCaughan F. E. , Xue Hong Xiao
Published: March 2015

In [McCaughan, 1989b] it was observed that the slopes of both the axisymmetric and rotating stall characteristics play a major role in determining the mode of instability of the engine and the recovery point. That analysis was carried out for the grossly simplified model where the stall cell was considered as a travelling sine wave. That work has been extended to the more reasonable situation where the stall cell is represented by forty Fourier modes. The results from the simple model of three ordinary differential equations are discussed in the light of the more reatistic calculations. In particular we discuss the effects of two parameters; the steepness of the axisymmetric characteristic and the shutoff head.
Three-Dimensional Inviscid Flow Computations in a Spatial Turbopump Inducer Using a Distributed Loss Model
Authors: El Ghazzani E. M. , Bois G. , Geai P. , Leboeuf F.
Published: March 2015

A Clebsch formulation, completely equivalent to the Euler equations is implemented from an Eulerian type variational principle. It leads to the decomposition of the velocity field into a potential and a rotational part and, thus, provides a unified solution scheme for potential and Euler equations.

Although based on an inviscid flow model, this formulation includes a loss scheme.

The numerical method uses a finite element discretization. Particular treatment of convection terms allows a low numerical diffusion. A pseudo time evolution enables a better stability behaviour.

Numerical calculations have been performed on an industrial configuration of spatial turbopump. Different comparisons ere showed between measurements, calculations without and with distributed losses.
Design and Rotor Performance of a 5:1 Mixed-Flow Supersonic Compressor
Authors: Mönig R. , Elmendorf W. , Gallus H. E.
Published: March 2015

In consideration of further jet-engine developments required by applications for supersonic travel aircraft, airbreathing propulsion of space vehicles or only the improvement of conventional high performance turbo engines, highly loaded supersonic compressors seem to meet the future demands. Particularly mixed-flow compressor stages with moderate supersonic rotor- and stator inlet flow reveal the potential of high pressure rise and massflow as well as favorable performance characteristics and efficiency.

The first part of this paper presents analytical considerations for mixed-flow supersonic compressors with strong shock waves. This theoretical approach proves to be of essential importance besides established design tools in order to ensure safe rotor and stage operation in accordance with the design objectives. In this context, the conditions for shock wave stabilization within a diagonal rotor passage are discussed in detail for design and off-design rotational speeds.

The main part of this paper, however, presents the results and flow analysis obtained by extensive experimental investigations of the designed mixed-flow compressor rotor. The investigations were restricted to operation without stator in order to strictly separate rotor performance from rotor-stator interactions.

The results reveal the design goals to be met in general. Massflow, total pressure rise and efficiency in particular show a good agreement with the design properties for near-surge operation at design and off-design conditions.
Fatigue Life Estimation Procedure for a Turbine Blade Under Transient Loads
Authors: Vyas N. S. , Rao J. S.
Published: March 2015

Fatigue analysis and consequent life prediction of turbomachine blading requires the stress load history of the blade. A blade designed for safe operations at particular constant rotor speeds may, however, incur damaging stresses during Start-up and Shut-down operations. During such operations the blade experiences momentary resonant stresses while passing through the criticals which may lie in the speed range through which the rotor is accelerated. Fatigue due to these transient influences may cumulate to lead to failure.

In this paper a technique for fatigue damage assessment during variable speed operations is presented. Transient resonant stresses for a blade with nonlinear damping have been determined using a numerical procedure. A fatigue damage assessment procedure is described. The fatigue failure surface is generated on the S-N-mean stress axes and Miner’s Rule is employed to estimate the cumulation of fatigue.
Investigation of the Part-Load Performance of Two 1.12 MW Regenerative Marine Gas Turbines
Authors: Korakianitis Theodosios , Beier Kurt
Published: March 2015

Regenerative and intercooled-regenerative shaft-power gas turbine engines of low pressure ratio have significant efficiency advantages over traditional aero-derivative engines of higher pressure ratios, and can compete with modern diesel engines for marine propulsion. The design-point performance is extremely sensitive to thermodynamic-cycle parameter choices. The type of components chosen affects power and efficiency significantly. The design-point and off-design-point performance of two 1.12 MW (1500 hp) regenerative gas turbines are predicted with computer simulations. One engine has single-shaft configuration, and the other has a gas-generator / power-turbine combination. The gas-generator / power-turbine engine arrangement is essential for wide off-design operating regime. The performance of each engine driving fixed-pitch and controllable-pitch propellers, or an AC electric bus (for electric-motor-driven propellers) is investigated. For commercial applications the controllable-pitch propeller may have efficiency advantages (depending on engine type and shaft arrangements). For military applications the electric drive provides better operational flexibility.
Active Stabilization of Compressor Instability and Surge in a Working Engine
Authors: Williams J. E. Ffowcs , Harper M. F. L. , Allwright D. J.
Published: March 2015

We have applied feedback control to the compressor of a 45kW auxiliary power unit. Using this, the engine is able to deliver more than 10% extra shaft power before surge occurs.

We achieve control by suppressing a non-axisymmetric flow phenomenon in the diffuser of the centrifugal compressor. Control is effected by modulating a small extra air flow into the impeller.

We present results of modelling and analysis which suggest that linear feedback control will be sufficient to stabilize a compression system, even when both axisymmetric surge and rotating stall are present as possible instabilities.
Experimental Analysis of Transonic Flow Through the Variable Nozzle of a Radial Inflow Turbine
Authors: Gallus H. E. , Lingner U. , Ispas I.
Published: March 2015

The wide range of applications for radial inflow turbines is the reason for an increasing interest in this type of machines in the recent years. An appropriate method to achieve good efficiencies under different operating conditions is the use of variable nozzle vanes. Because of the limited knowledge of the flow phenomena involved, simple models are used for aero-thermodynamical machine design.

A research program was initiated to experimentally study the flow field in a transonic radial nozzle cascade. An air test rig with variable nozzle vanes, derived from an industrial radial inflow turbine, was used for the tests. In this rig no rotor was installed in order to study the flow in the nozzles without any influence of this element. Static pressure distributions have been measured on the vane suction and pressure surfaces and on the shroud endwall within the blading and downstream of the nozzles. Results are presented for different pressure ratios and nozzle setting angles. The experimental results are compared with numerical calculations for inviscid flow based on the two-dimensional Euler equations.
Markov Fatigue in Single Crystal Airfoils
Authors: Annis Charles , De Luca Daniel P.
Published: March 2015

This paper considers the influence of microstructure on macrobehavior in single crystal airfoils by treating the micromechanics of damage accumulation as a Markov process. Single Crystal Fatigue (SCF) is a result of several, simultaneous (competing), damage mechanisms, which are selectively favored by particular combinations of external conditions. As with any real physical process, SCF is also influenced by a stochastic component. This probabilistic influence can be exploited to help explain the macrobehavior.

We begin with a description of single crystal materials and how they differ from more conventional (isotropic) alloys. Relationships are suggested among the more probable of several competing microstructural damage mechanisms and specific rate-controlling parameters. The states of microstructural damage are then described and catalogued, and the various avenues of damage accumulation are investigated. Next, the Markov paradigm is reviewed as it applies to these materials. Finally, a Markov model is presented to describe the rather complex behavior observed in single crystals, and its use in lifing gas turbine engine airfoils is discussed.
Performance Evaluation of Space Solar Brayton Cycle Power Systems
Authors: Diao Zheng-Gang
Published: March 2015

Unlike gas turbine power systems which consume chemical or nuclear energy, the energy consumption and/or cycle efficiency should not be a suitable criterion for evaluating the performance of space solar Brayton cycle power. A new design goal, life cycle cost, can combine all the power system characteristics, such as mass, area, and station-keeping propellant, into a unified criterion. Effects of pressure ratio, recuperator effectiveness, and compressor inlet temperature on life cycle cost were examined. This method would aid in making design choices for a space power system.
Conceptual Study on Radiator Area Reduction of Brayton Cycle Solar Dynamic Power
Authors: Tsujikawa Yoshiharu
Published: March 2015

Higher on-board energy levels will be needed at the turn of the century for the many developing space programs. Among the many solar-powered energy conversion systems, a recuperated closed Brayton cycle (CBC) is the most promising one. This study investigated several aspects of a solar dynamic CBC system; an assessment of a reference 25 kWe system, simulation studies related to various operating conditions, and heat-rejection studies related to the radiating area required to transfer the Brayton cycle waste heat to space. In addition, particular attention is paid to the significance of the reduction of system mass required for radiation of waste heat from a closed Brayton cycle to space. Conceptually the radiator area can be reduced by rejecting the heat from the radiator at a higher temperature level than that of the waste heat of the CBC, operating a kind of heat pump by using a fraction of generated power. Consequently, an optimum radiator area is obtained. Also, for high radiator-to-waste-heat temperature ratios (greater than 5), the total radiator area is remarkably reduced. Further, the required mass resulting from the inclusion of the heat pump is estimated.
Low NOx Combustor for Automotive Ceramic Gas Turbine: II — Reliability Assurance
Authors: Kumakura Hirotaka , Sasaki Masafumi , Suzuki Daishi
Published: March 2015

Two aspects of reliability assurance are discussed. First, This paper deals with the reliability design of the emissions under transient conditions. The optimization was made from the simulation results of the relationship between the response of the variable combustor geometry to follow load changes and the resulting exhaust emission levels. The load variation pattern used in this investigation was that of the Japanese 10-mode regulation. Second, this paper describes the validity of the reliability design prepared for the ceramic liner of the combustor. A service life prediction was made for the liner on the basis of stress analysis results and fatigue parameters.
Particle Diagnostics and Turbulence Measurements in a Confined Isothermal Liquid Spray
Authors: de la Rosa A. Breña , Sankar S. V. , Wang G. , Bachalo W. D.
Published: March 2015

This work reports an experimental study of the behaviour and structure of a liquid spray immersed in a strong swirling field. In order to simulate some of the aerodynamic conditions experienced by a spray in a model combustor, an experimental setup using an acrylic chamber, a vane type swirler, and separate air supplies for both the secondary air and the swirl air were integrated to perform the experiments in the wind tunnel. A vane type swirler exhibiting a high swirl number was used to produce a strong recirculation flow field downstream of a pressure swirl atomizer. Properties of the dispersed phase such as velocity, size distributions, and size-velocity correlations were measured at several locations within the swirling flow field. In addition, mean velocity and turbulence properties were obtained for the gas phase. Flow visualization was performed with a laser sheet to gain further understanding of the formation and influence of the recirculation region on the spray. A 2-component PDPA system with a frequency based Doppler Signal Analyzer was used throughout the measurements, and proved most valuable in the toroidal vortex region where low SNR conditions and non-uniform concentration of seed particles prevail. The results show that flow reversal of the drops is present at this swirl intensity within the recirculation region at distances up to X/D = 2.0. Small variations of drop size distribution within the recirculation region are observed, however large variations outside of it are also present.

Plots of the normal Reynolds stresses and Reynolds shear stresses show double-peak radial distributions which indicate regions in the flow where high mean velocity gradients and large shear forces are present. The decay of turbulence velocities in the axial direction was observed to be very fast, an indication of high diffusion and dissipation rates of the kinetic energy of turbulence.
Engine Testing of a Prototype Low NOx Gas Turbine Combustor
Authors: Smith Kenneth O.
Published: March 2015

The design of a lean-premixed, annular, dry low NOx combustor for Solar’s 5500 hp Centaur Type H gas turbine is discussed. Results from early engine tests of prototype combustion hardware are presented. The emissions results with natural gas fueling meet the development goals of less than 25 ppm NOx (at 15% O2) and 50 ppm CO. Several techniques to extend the low emissions operating range of the lean-premixed system are shown to be effective.
Investigation of Combustion Structure Inside Low NOx Combustors for a 1500°C-Class Gas Turbine
Authors: Matsuzaki H. , Fukue I. , Mandai S. , Tanimura S. , Inada M.
Published: March 2015

This paper describes the cold flow tests and low pressure combustion tests which were conducted for the development of a 1500°C-class low NOx combustion system. In the cold flow tests, the effect of vane angle and the momentum ratio of fuel to air flow on mixing characteristics inside the premixing nozzles was investigated. The stabilization of the flow field inside the combustor was confirmed by measurement of the axial velocity distribution and observations by using a tuft of soft thread.

Combustion characteristics in terms of emissions and stability were investigated initially by low pressure combustion tests, and the gas temperature distribution inside the combustor was measured. NOx emissions for a 1500°C-class gas turbine as low as 50ppm at 15% oxygen at design pressure were demonstrated.
Analysis of Steady and Unsteady Turbine Cascade Flows by a Locally Implicit Hybrid Algorithm
Authors: Hwang C. J. , Liu J. L.
Published: March 2015

For the two-dimensional steady and unsteady turbine cascade flows, the Euler/Navier-Stokes equations with Baldwin-Lomax turbulence model are solved in the Cartesian coordinate system. A locally implicit hybrid algorithm on the mixed type of meshes is employed, where the convective dominated part in the flowfield is studied by TVD scheme to obtain high-resolution results on the triangular elements, and the second- and fourth-order dissipative model is introduced on the O-typed quadrilateral grid in the viscous dominated region to minimize the numerical dissipation. When the steady subsonic and transonic turbulent flows are investigated, the distributions of isentropic Mach number on the blade surface, exit flow angle and loss coefficient are obtained. Comparing the present results with the experimental data, the accuracy and reliability of the current approach is confirmed. By giving a moving wake-type total pressure profile at the inlet plane in the rotor-relative frame of reference, the unsteady transonic inviscid and turbulent flows calculations are performed to understand the interaction of the upstream wake with a moving blade row. The Mach number contours, perturbation component of the unsteady velocity vectors, shear stress and pressure distributions on the blade surface are presented. The physical phenomena, which include periodical flow separation on the suction side, bowing, chopping and distortion of incoming wake, negative jet, convection of the vortices and wake segments, and vortex shedding at the trailing edge, are observed. It is concluded that the unsteady aerodynamic behaviors are strongly dependent on the wake/shock/boundary layer interactions.
An Inviscid-Viscous Interaction Approach to the Calculation of Dynamic Stall Initiation on Airfoils
Authors: Cebeci T. , Platzer M. F. , Jang H. M. , Chen H. H.
Published: March 2015

An interactive boundary-layer method is described for computing unsteady incompressible flows over airfoils, including the initiation of dynamic stall. The inviscid unsteady panel method developed by Platzer and Teng is extended to include viscous effects. The solutions of the boundary-layer equations are obtained with an inverse finite-difference method employing an interaction law based on the Hilbert integral, and the algebraic eddy-viscosity formulation of Cebeci and Smith. The method is applied to airfoils subject to periodic and ramp-type motions and its abilities are examined for a range of angles of attack, reduced frequency and pitch rate.
A Digital Fuel Control System for Marine Propulsion Applications
Authors: Burgess Tim
Published: March 2015

Woodward Governor Company was presented with the challenge of producing a digital gas turbine fuel control for marine applications. The initial application required a fuel control system that would operate in a high shock/vibration and high EMI level environment. The unusual EMI requirements (for an engine room environment) arose from the control being installed in a non-metal hull craft with high intensity radar and communications transmitter RF sources. Existing industrial digital control hardware was adapted to meet the requirements. This paper describes how the industrial hardware was adapted for marine applications.
Modified Combined Cycle With Pressure Fluidized Bed Combustion Boiler
Authors: Dzierzgowski Jacek , Sobkowski Stanislaw
Published: March 2015

The article describes conversion of conventional steam cycle with 200 MW turbine into combined steam-gas cycle with pressure fluidized bed combustion boiler.

In order to raise cycle thermal efficiency an additional combustion chamber before a gas turbine was introduced. Two modifications of the combined cycle were considered. In one of them natural gas in the additional combustion chamber is burnt with the boiler flue gas only. In the other gas is burnt with additional air stream taken from behind the gas turbine compressor.

Optimizing calculations of the cycle thermal efficiency in function of some cycle’s main parameters were carried out.
An Update on the Development of the T407/GLC38 Modern Technology Gas Turbine Engine
Authors: Zoccoli Michael J. , Rusterholz Kenneth P.
Published: March 2015

The T407/GLC38 is a modern technology 6000 SHP class turboshaft/turboprop gas turbine engine which is being developed jointly by Textron Lycoming (Stratford, Connecticut), General Electric Aircraft Engines (Lynn, Massachusetts), Bendix Controls (South Bend, Indiana), and Ruston Gas Turbines (Great Britain).

The gas generator core for the T407/GLC38 engine series is also common to the CFE738, a new generation turbofan which is being developed by General Electric and the Garret Engine Division.

The T407 (military)/GLC38 (commercial) is a derivative of the highly successful U.S. Army/GE27 MTDE engine which has been redesigned to meet commercial engine life standards.

The design philosophy for this engine was directed at achieving high output power per unit airflow, reliability from reduced parts count, ease of maintenance via extensive modularity, and state-of-the-art SFC levels that are up to 25% below those of existing 5000–6000 SHP powerplants. The latter characteristic manifests itself in reduced life cycle and direct operating costs and (where applicable) tradeoff versatility amongst range, time on station, and payload increase.

This paper is a continuation in a documentary series on the T407/GLC38 design and development. It traces the evolution of the T407/GLC38 program from First Engine to Test, wherein all thermodynamic and mechanical objectives were essentially achieved or exceeded, through full system turboprop evaluation, turbofan development testing, and qualification/certification testing completed to date.

A comprehensive review of the test objectives, testing requirements, setup, and basic results are provided; in addition, the relevancy and impact of each phase of engine testing towards the goal of qualification/certification and ultimately production is provided.