bluuebunny/crossref_metadata_2025_split huggingface dataset:
SOME ASPECTS OF THE NEUROMUSCULAR SYSTEM OF ASCARIS
Authors: del Castillo José , Rivera Amelia , Solórzano Salbador , Serrato Jesus 
Published: December 2014

1. The structure and physiological properties of the somatic neuromuscular system of the nematode Ascaris lumbricoides var. suum are discussed taking into account early work from this laboratory, the results of other workers, and experiments in progress.2. Anatomically, the central feature of the somatic musculature is the presence of a specialized muscular, but not contractile, structure: the syncytium or sarcopile, formed by the terminal processes of the muscle cell arms that contact the nerve cord. In this region, they are electrically coupled to one another and form chemical synapses with the nerve fibres.3. The syncytium serves, primarily, as a nerve‐muscle manifold, or device which allows the neural control of the muscle fields with great economy in the amount of nervous tissue, numbers of chemical junctions and quantities of synaptic transmitters.4. The structure of the syncytium is being studied with the scanning electron microscope. The results reveal the convergence of the arms on discrete sites as they approach the cords, as well as a longitudinal arrangement of the terminal processes as they course over the cords, at least in the posterior region of the animal.5. The characteristics of the electrical coupling between the muscle cells are being investigated. A pattern has been observed that is dependent on the position of the cell pairs with respect to the longitudinal axis of the animal.6. A study of signal propagation in the arms has revealed that the morphology of the muscle cells contributes to the extent and preferential direction of propagation.
A Mechanism of Combustion Instability in Lean Premixed Gas Turbine Combustors
Authors: Lieuwen Tim , Torres Hector , Johnson Clifford , Zinn Ben T. 
Published: December 2014

There has been increased demand in recent years for gas turbines that operate in a lean, premixed (LP) mode of combustion in an effort to meet stringent emissions goals. Unfortunately, detrimental combustion instabilities are often excited within the combustor when it operates under lean conditions, degrading performance and reducing combustor life. To eliminate the onset of these instabilities and develop effective approaches for their control, the mechanisms responsible for their occurrence must be understood.
This paper describes the results of an investigation of the mechanisms responsible for these instabilities and approaches for their control. These studies found that combustors operating in a LP mode of combustion are highly sensitive to variations in the equivalence ratio (ϕ) of the mixture that enters the combustor. Furthermore, it was found that such ϕ variations can be induced by interactions of the pressure and flow oscillations with the reactant supply rates. The ϕ perturbations formed in the inlet duct (near the fuel injector) are convected by the mean flow to the combustor where they produce large amplitude heat release oscillations that drive combustor pressure oscillations. It is shown that the dominant characteristic time associated with this mechanism is the convective time from the point of formation of the reactive mixture at the fuel injector to the point where it is consumed at the flame. Instabilities occur when the ratio of this convective time and the period of the oscillations equals a specific constant, whose magnitude depends upon the combustor design. Significantly, these predictions are in good agreement with available experimental data, strongly suggesting that the proposed mechanism properly accounts for the essential physics of the problem. The predictions of this study also indicate, however, that simple design changes (i.e., passive control approaches) may not, in general, provide a viable means for controlling these instabilities, due to the multiple number of modes that may be excited by the combustion process. This conclusion indicates that active control strategies may be necessary for controlling these instabilities.
Equations of State for Gas Compressor Design and Testing
Authors: Kumar Sumit K. , Kurz Rainer , O’Connell John P. 
Published: December 2014

In the design and testing of gas compressors, the correct determination of the thermodynamic properties of the gas. such as enthalpy, entropy and density from pressure, temperature and composition, plays an important role. Due to the wide range of conditions encountered, pressure, specific volume and temperature (p-v-T) equations of state (EOS) and ideal gas heat capacities, along with measured data, are used to determine the isentropic efficiency of a compressor configuration and to model the actual behavior of real gases and compressors.
There are many possible model choices. The final selection should depend on the applicability of the EOS to the gas and the temperature dependence of the heat capacities, as well as the particular process of interest along with the range of pressures and temperatures encountered. This paper compares the thermodynamic properties from five commonly used equations in the gas compressor industry: the Redlich-Kwong (RK), Redlich-Kwong-Soave (RKS), Peog-Robinson (PR), Benedict-Webb-Rubin-Starling (BWRS), and Lee-Kesler-Plocker (LKP) models. It also compares them with a high accuracy EOS for methane from Wagner and Setzmann in the common range for gas compressors. The validity of a linear temperature dependence for ideal gas heat capacities is also evaluated. The objective was to determine if the models give significant differences in their predicted efficiencies.
It was found that different EOS gave somewhat different enthalpy changes for methane, ethane and nitrogen for real compressions. This appeared to be connected to the different densities given by the models. Interestingly, the isentropic enthalpy changes are quite similar, suggesting that the effect is canceled out when two properties are involved. However, since the efficiency is the ratio of isentropic enthalpy change to actual enthalpy change, the EOS yield different efficiencies. These differences are on the same order as the typical tolerances allowed for prediction and testing of industrial gas compressors (3 to 5%) and comparisons with the highly accurate equation of state for pure methane from Wagner and Setzmann (1991) showed similar differences.
Commonly, the ideal gas heat capacity is assumed linear in temperature from 10 to 150°C (50 to 300°F). Comparison of this form with a quadratic expression from the literature and the highly accurate equation of Wagner and Setzmann for methane, showed insignificant differences among the methods for temperatures up to 600°K (1080°R).
An Experimental Study on the Aerodynamics and the Heat Transfer of a Suction Side Film Cooled Large Scale Turbine Cascade
Authors: Ganzert Wolfgang , Fottner Leonhard 
Published: December 2014

As a part of a more complex research program systematic isothermal investigations on the aerodynamics and heat transfer of a large scale turbine cascade with suction side film cooling were carried out. The film cooling through a row of holes at forty percent chord length on the suction side was supplied by a large plenum chamber. Two injection geometries were hitherto tested and evaluated: cylindrical holes with thirty respectively fifty degrees axial inclination angle and no lateral inclination. Typical engine conditions for the Mach and Reynolds number as well as the inlet turbulence level were maintained.
The aerodynamic studies are based on steady state pressure measurements. The static profile pressure distribution together with oil-and-dye flow visualisation gives information on the surface flow conditions and boundary layer development especially in the near hole region. The measured data also comprise local and integral total pressure loss coefficients obtained by pressure probe traversing at mid span downstream of the cascade. The heat transfer examination set-up is based on the steady state liquid crystal technique using a compound of a thermochromic sheet combined with an electrical surface heating layer attached on an adiabatic blade corpus. Two dimensional pseudo colour plots are used for the documentation of the local surface heat transfer coefficient distribution and hot spot estimation. Laterally averaged and statistically analysed data of the surface heat transfer is applied in overall heat transfer examinations.
All this data is used for a joint aerodynamic flow and surface heat transfer optimisation of a blowing configuration in suction side film cooled turbine cascade.
The most important conclusions can be summarised as follows: Aiming at an optimised design of cylindrical film cooling configurations the axial inclination of the holes should be kept low thus diminishing the suction peak value at the cooling position in the profile pressure distribution and decreasing the mainstream deceleration area upstream of the jets. This also leads to reduced total pressure losses. Through the high influence of the blowing on the aerodynamics the flow in the near hole mixing region is highly three-dimensional. This shows significant effects in the two-dimensional surface distribution and the laterally averaged heat transfer coefficient.
Oil-and-dye pictures confirm the observations qualitatively.
Performance of a Reduced NOx Diffusion Flame Combustor for the MS5002 Gas Turbine
Authors: Feitelberg Alan S. , Starkey Michael D. , Schiefer Richard B. , Pavri Roointon E. , Bender Matt , Booth John L. , Schmidt Gordon R. 
Published: December 2014

This paper describes a reduced NOx diffusion flame combustor that has been developed for the MS5002 gas turbine. Laboratory tests have shown that when firing with natural gas, without water or steam injection, NOx emissions from the new combustor are about 40% lower than NOx emissions from the standard MS5002 combustor. CO emissions are virtually unchanged at base load, but increase at part load conditions. The laboratory results were confirmed in 1997 by a commercial demonstration test at a British Petroleum site in Prudhoe Bay, Alaska.
The standard MS5002 gas turbine is equipped with a conventional, swirl stabilized diffusion flame combustion system. The twelve standard combustors in an MS5002 turbine are cylindrical cans, approximately 27 cm (10.5 inches) in diameter and 112 cm (44 inches) long. A small, annular, vortex generator surrounds the single fuel nozzle that is centered at the inlet to each can. The walls of the cans are louvered for cooling, and contain an array of mixing and dilution holes that provide the air needed to complete combustion and dilute the burned gas to the desired turbine inlet temperature.
The new, reduced NOx emissions combustor (referred to as a “lean head end”, or LHE, combustor) retains all of the key features of the conventional combustor: the only significant difference is the arrangement of the mixing and dilution holes in the cylindrical combustor can. By optimizing the number, diameter, and location of these holes, NOx emissions were substantially reduced. The materials of construction, fuel nozzle, and total combustor air flow were unchanged.
The differences in NOx emissions between the standard and LHE combustors, as well as the variations in NOx emissions with firing temperature, were well correlated using turbulent flame length arguments. Details of this correlation are also presented.
Design and Evaluation of an Auto-Tuning Control System for an Altitude Test Facility
Authors: Luppold R. H. , Meisner R. , Norton J. M. 
Published: December 2014

Simulated altitude testing of large aircraft engines is a very expensive, but essential step in the development and certification of gas turbines used by commercial airlines. A significant contributor to the cost of this process is the time-intensive task of manually tuning the facility control system that regulates the simulated flight condition. Moreover, control system tuning must be performed each time the test conductor changes the flight condition. An adaptive control system that automatically performs this task can significantly reduce the costs associated with this type of engine testing.
This paper examines the features of an auto-tuning controller architecture that contains both disturbance feedforward and PID feedback components in a two-input, two-output multivariable configuration. The paper reviews the underlying concepts of an auto-tuning system and contrasts its advantages/disadvantages with respect to other adaptive control techniques. The algorithm used to automatically tune the controller does not require a facility model. However, a nonlinear facility model was developed and used to substantiate a decoupled-loop design approach, to validate the controller design concept, and to evaluate the resulting adaptive control system design performance. This analysis and other practical design issues that impact the auto-tuning control system performance are addressed in the paper. The paper also presents results that illustrate the automatic tuning sequence and the disturbance rejection performance exhibited by this system during large engine transients at several key points in the flight envelope. The auto-tuning controller described in the paper was implemented at a Pratt & Whitney flight test facility used in the development of large, high bypass ratio gas turbines.
Effect of Blade Curving on the Flow Field Structure in an Annular Turbine Cascade
Authors: Song Yanping , Wang Zhongqi , Lu Wencai , Xu Wenyuan 
Published: December 2014

In the present paper, two annular turbine cascades have been tested in order to investigate the effect of blade curving on the structure of the three-dimensional flow field. The blades in all two cascades have the same section and they are stacked on the trailing edge that is straight in the first and a circular arc in the second. Detailed cascade tests consisted of passage flow parameter traverses, blade and endwall surface pressure distribution, and flow visualization.
The results show that the flow field is three dimensional in an annular cascade with different pressure distributions near two endwalls, whose direct effect is amplified through the creation of passage vortices of different scale and strength at hub and tip. Blade curving changes the pressure field completely, in axial, pitchwise and spanwise directions. The combined effect of 3-D characteristics and blade curving causes significant differences of flow field structure in curved blade.
A Transonic Compressor Design Methodology Including the Influence of 3D Passage Shock Waves
Authors: Gui X. , Zhou S. 
Published: December 2014

Throughflow theory, as a design problem, is extensively used in the design of transonic axial flow compressors and fans. The losses caused by a simplified passage shock named shock loss model were taken into account in the design of transonic stages. However, the influences of shock waves on flow fields are still under development for transonic design. This problem is studied in the present paper.
The basic equations of the throughflow method are re-derived under the concept of discontinuous passage averaging, and then, the distribution shock forces acied on the averaged throughflow fields are obtained. To evaluate these effects on averaged throughflow fields, a passage shock structure model is developed based on the previous models. Finally, the shock influences are assessed and compared in the present paper. It is demonstrated that the distribution shock forces have dramatically effects on the results of design.
Experimental and Numerical Investigation of the Flow in a Centrifugal Compressor Volute
Authors: Hagelstein D. , Hillewaert K. , Van den Braembussche R. A. , Engeda A. , Keiper R. , Rautenberg M. 
Published: December 2014

This paper presents the experimental and numerical investigation of an outward volute of rectangular cross section. The investigation is carried out at the level of
- stage performance,
- volute performance and
- detailed flow field study at selected peripheral positions for various operating points.
The objective of the investigation was to gain further knowledge about the flow structure and loss mechanism in the volute. Simultaneously with the experimental investigation, a numerical simulation of the flow in the volute was carried out.
A 3D Euler-code was used in which a wall friction term and a tuned artificial dissipation term account for viscous effects. A reasonable agreement between the experimental and numerical results is observed. As a result a good and detailed knowledge about the pressure recovery and loss mechanism in the volute is obtained.
Royal Navy Experience of Propulsion Gas Turbines and How and Why This Experience is Being Incorporated Into Future Designs
Authors: Rand James , Wright Nigel 
Published: December 2014

The Royal Navy (RN) has in-service experience of both marinised industrial and aero derivative propulsion gas turbines since the late 1940’s. Operating through a Memorandum of Understanding (MOU) between the British, Dutch, French and Belgian Navies the current in-service propulsion engines are marinised versions of the Rolls Royce Tyne, Olympus and Spey aero engines. Future gas turbine engines, for the Royal Navy, are expected to be the WR21 (24.5 MW), a 5 to 8 MW engine and a 1 to 2 MW engine in support of the All Electric Ship Project.
This paper will detail why the Royal Navy chose gas turbines as prime movers for warships and how Original Equipment Manufacturers (OEM) guidance has been evaluated and developed in order to extend engine life. It will examine how the fleet of engines has historically been provisioned for and how a modular engine concept has allowed less support provisioning.
The paper will detail the planned utilisation of advanced cycle gas turbines with their inherent higher thermal efficiency and environmental compliance and the case for all electric propulsion utilising high speed gas turbine alternators. It will examine the need for greater reliability / availability allowing single generator operation at sea and how by using a family of 3 engines a nearly flat Specific Fuel Consumption (SFC) down to harbour loads can be achieved.
Propagation of Multiple Short Length-Scale Stall Cells in an Axial Compressor Rotor
Authors: Inoue M. , Kuroumaru M. , Tanino T. , Furukawa M. 
Published: December 2014

Evolution and structure of multiple stall cells with short length-scale in an axial compressor rotor have been investigated experimentally. In a low-speed research compressor rotor tested, a short length-scale stall cell appeared at first, but did not grow rapidly in size unlike a so-called “spike-type stall inception” observed in many multi-stage compressors. Alternatively, the number of cells increased to a certain stable state (a mild stall state) under a fixed throttle condition. In the mild stall state the multiple stall cells, size of which was on the same order of the inception cell (a few blade spacings), were rotating at 72% of rotor speed and at intervals of 4.8 blade spacings. With further throttling, a long length-scale wave appeared overlapping the multiple short length-scale waves, then developed to a deep stall state with a big cell.
In order to capture the short length-scale cells in the mild stall state, a so-called ‘double phase-locked averaging technique’ has been developed, by which the flow field can be measured phase locked to both of the rotor and the stall cell rotation. Then, time-dependent ensemble averages of the 3D velocity components upstream and downstream of the rotor have been obtained with a slanted hot-wire, and the pressure distributions on the casing wall with high response pressure transducers.
By a physically plausible explanation for the experimental results, a model for the flow mechanism of the short length-scale stall cell has been presented. The distinctive feature of the stall cell structure is on the separation vortex bubble with a leg traveling ahead of the rotor, with changing the blade in turn on which the vortex leg stands.
Numerical Investigations on the Optimum Design of Return Channels of Multi-Stage Centrifugal Compressors
Authors: Lenke L. J. , Simon H. 
Published: December 2014

Numerical simulations of the flow within return channels for the aerodynamic design are presented. The investigated return channels are typical to join the exit from one stage of a centrifugal machine to the inlet of the next stage and cover the range of high flow coefficients.
Due to the strongly three-dimensional flow structure with high streamline curvature and secondary flows on hub and shroud of the return channel vanes, a modified explicit algebraic Reynolds stress model will be used. Starting with a comparison between measurements and numerical results to demonstrate the performance of the turbulence model in the prediction of losses, exit flow angle and separation behavior, further numerical investigations with different variations of the geometry of the channel will be considered. 3-D turbulent calculations at the design point and part load range show the influence of the design especially of the crossover bend onto the flow structure.
Development Summary of the 300 kW Ceramic Gas Turbine CGT302
Authors: Tatsumi Tetsuo , Takehara Isashi , Ichikawa Yoshihiro 
Published: December 2014

Japanese Ministry of International Trade and Industry has been promoting a 300 kW Ceramic Gas Turbine (CGT) research and development program for 10 years. It was begun in 1988 as a part of the “New Sunshine Project”. The development target is to achieve thermal efficiency of over 42% at a turbine inlet temperature (TIT) of 1350°C. We have been taking a part in this project and developing a regenerative two-shaft CGT302.
This project will be finished at the end of FY1998. In 1998, we confirmed 31.7 ppm NOx emission at 1350°C by engine test. This result cleared the target emission level of 70 ppm. We also achieved 40.5% of thermal efficiency at 1412°C TIT and we are working to achieve the final target and cumulating operating hours to confirm reliability of ceramic components at 1200°C TIT which is considered to be reasonable temperature for commercial use.
This paper describes about ten years development summary of the CGT302.
Detailed Analysis of the Acoustic Mode Shapes of an Annular Combustion Chamber
Authors: Walz Günther , Krebs Werner , Hoffmann Stefan , Judith Hans 
Published: December 2014

To get a better understanding of the formation of thermoacoustic oscillations in an annular gasturbine combustor, an analysis of the acoustic eigenmodes has been conducted using the Finite Element (FE) method. The influence of different boundary conditions and a space dependent velocity of sound has been investigated. The boundary conditions actually define the eigenfrequency spectrum. Hence, it is crucial to know e.g. the burner impedance. In case of the combustion system without significant mixing air addition considered in this paper, the space dependence of the velocity of sound is of minor importance for the eigenfrequency spectrum leading to a maximum deviation of only 5% in the eigenvalues.
It is demonstrated that the efficiency of the numerical eigenvalue analysis can be improved by making use of symmetry, by splitting the problem into several steps with alternate boundaries conditions, and by choosing the shift frequency ωs in the range of frequencies one is interested in.