bluuebunny/crossref_metadata_2025 huggingface dataset:
An Influence of Shroud Design on the Dynamic and Aeroelastic Behavior of Bladed Disc Assemblies
Authors: Jacquet-Richardet G. , Moyroud F. , Fransson T. H.
Published: December 2014

Precise non-linear aeroelastic modeling of shrouded bladed-disc assemblies is generally beyond present capacities and analyses often assume that the behavior of the coupled system remains linear and retains a cyclic symmetrical property. In this paper, several models of shrouded assemblies, in the particular case of fully slipping interfaces, are examined and compared. Considering the cyclic symmetrical property of the structure, only the model where shroud segments can slip and propagation relations are applied in the direction normal to the interface plane, should be used. A reduced model based on a direct discretisation of the whole assembly is presented and validated. The application is based on a first stage shrouded fan. The influence of varying the interface shroud angle is examined in terms of frequency, mode shape and aeroelastic damping.
Effect of Flow Instabilities and Self-Sustained Oscillations on Labyrinth Seal Leakage Resistance
Authors: Rhode David L. , Johnson J. Wayne , Allen Brian F.
Published: December 2014

Two flow instabilities involving a bifurcated flow pattern were discovered for the throughflow jet in a stepped labyrinth seal. A bifurcation stability map was developed showing which combinations of tooth clearance and step height occur in which of the three flow regimes. These instabilities, along with self-sustained flow oscillations, were experimentally explored to obtain a preliminary understanding of their effect on seal leakage. Computer-captured visualization videos were used to measure the throughflow angle oscillation amplitudes, frequencies and mean flow trajectory angles. For small tooth clearances, the intermediate step height case, which exhibited the sharpest flow deflection and largest oscillation amplitude, gave the highest leakage resistance. Further, for larger tooth clearances, the large step height cases, located farthest on the stability map into the Oscillatory Bifurcated regime, gave the highest resistance. Thus, for large clearances the oscillating nature of the Oscillatory Bifurcation flow pattern appears to give enhanced leakage resistance via increased turbulent mixing.
Real Time Thermodynamic Transient Model for Three Spool Turboprop Engine
Authors: Crainic C. , Harvey R. , Thompson A.
Published: December 2014

Previous real time engine models used for control development and test have utilized either linear techniques or simplified aero-thermodynamics. With the increased speed now available from dedicated PC based computer systems it was felt that it should be possible to develop a full aerodynamic and thermodynamic model of the engine that would have the capability to run in a real time bench environment and approach the accuracy of our best unlimited time models.

The paper describes such a model that has successfully been produced for a three spool turboprop engine, and shows that it matches, in a real time environment, the transient performance of a model run with unlimited execution time. This model has the additional capability of starting from zero speed and running back down to zero speed on shut down, all in real time environment.

The model was based on an existing model of a three spool turboprop engine which already included full transient heat transfer and volume dynamics effects. Modifications to this that were necessary to satisfy the requirement to model the starting regime and to decrease the convergence time resulted in a more efficient model methodology. The component map representation was changed as was the iteration logic, by removing internal iterations and by making the solver matrix more strongly diagonal.

For the real time environment the code had to provide a solution within a maximum of 10 ms. The final real-time model only differed from the modified full transient model in the use of the solver logic. The number of overall iterative passes were limited to two, and balances that were shown not to significantly modify the accuracy of the solution were removed. The net result of the work is the elimination of two simplified models.
Thermo-Economics of a Small 50 KW Turbogenerator
Authors: Rodgers C.
Published: December 2014

Recent projections foster the belief that small high temperature heat exchanged gas turbines incorporating ceramic rotors, and ceramic exhaust beat exchangers, may eventually have thermodynamic efficiencies competitive with Diesel cycle engines. Small high speed Brayton cycle gas turbine turbogenerators on the near term verge of production will indeed have improved thermal efficiencies, but ceramic material technology has not yet matured to the engine production stage. Although thermal efficiency is a dominant driver, manufacturing costs and long term engine durability are still a major concern to the engine manufacturer. As a consequence the thermodynamic performances of small gas turbines are still, in this last decade of the 20th century, primarily constrained by the temperature limits of the metallic stator/rotor and metallic heat exchanger.

This paper reviews optimum thermo-economic design considerations for a small 50 KW output turbogenerator, covering the effect of cycle performance parameters on, engine configuration, rotational speeds engine weight, manufacturing and direct operating costs. The effect of design pressure ratio on part load thermal efficiency is also addressed for applications with extended operating time at low output powers.
Effect of Swirl on Combustion Characteristics in Premixed Flames
Authors: Qi S. , Gupta A. K. , Lewis M. J.
Published: December 2014

A double concentric premixed swirl burner is used to examine the structure of two different methane-air premixed flames. Direct flame photography together with local temperature data provides an opportunity to investigate the effects of swirl number distribution in each annulus on the global and local flame structure, flame stability and local distribution of thermal signatures. An R-type thermocouple compensated for high-frequency response is used to measure the local distribution of thermal signatures in two different flames, each of which represents a different combination of swirl number in the swirl burner. In order to improve the accuracy of the temperature data at high-frequency conditions, information on the thermocouple time constant are also obtained under prevailing conditions of local temperature and velocity by compensating the heat loss from the thermocouple sensor bead. These results assist in quantifying the degree of thermal nonuniformities in the flame signatures as affected by the distribution of swirl and to develop strategies for achieving uniform distribution of temperatures in flames.
Effect of Pressure on Emission Characteristics in LBG-Fueled 1500 °C -Class Gas Turbine
Authors: Hasegawa Takeharu , Sato Mikio , Ninomiya Tohru
Published: December 2014

Developing integrated coal gasification combined cycle (IGCC) systems ensures cost-effective and environmentally sound options for supplying future power generation needs. In order to enhance thermal efficiency of IGCC and to reduce NOx emission, a 1500 °C -class gas turbine combustor for IGCC was designed, tested and the performance of the combustor was evaluated under pressurized conditions. The designed combustor had three characteristics: 1) In order to assure the stable combustion burning low-Btu gas (LBG), an auxiliary combustion chamber was installed at the entrance of the combustor. 2) To reduce fuel NOx emission that was produced from the ammonia (NH3) in the fuel, the rich-lean combustion method was introduced. 3) To compensate for the declined cooling-air associated with the higher temperature of the gas turbine, the tested combustor was equipped with a dual-structure transition piece so that the cooling air in the transition piece can be recycled to cool down the combustor liner wall. As a result of combustor tests, it is confirmed that CO emission is less than 20ppm, the conversion rate of NH3 which contains about 1000ppm in the coal gasified fuel to NOx shows 40 percent or below, and the liner wall temperature remained below almost 850 °C under high pressure (1.4MPa), rated load condition.
Performance Deterioration Modeling in Aircraft Gas Turbine Engines
Authors: Zaita Anthony V. , Buley Greg , Karlsons Glen
Published: December 2014

Steady state performance models can be used to evaluate a new engine’s baseline performance. As a gas turbine accumulates operating time in the field, its performance deteriorates due to fouling, erosion and wear. This paper presents the development of a model for predicting the performance deterioration of aircraft gas turbines. The model accounts for rotating component deterioration based on the aircraft mission profiles and environmental conditions, and the engine physical and design characteristics. The methodology uses data correlations combined with a stage stacking technique for the compressor and a tip rub model along with data correlations for the turbine to determine the amount of performance deterioration. The performance deterioration model interfaces with the manufacturer’s baseline engine simulation model in order to create a deteriorated performance model for that engine.
Parametric Performance of Combined-Cogeneration Power Plants With Various Power and Efficiency Enhancements
Authors: Korakianitis T. , Grantstrom J. , Wassingbo P. , Massardo A. F.
Published: December 2014

The design-point performance characteristics of a wide variety of combined-cogeneration power plants, with different amounts of supplementary firing (or no supplementary firing), different amounts of steam injection (or no steam injection), different amounts of exhaust gas condensation etc, without limiting these parameters to present-day limits are investigated. A representative power plant with appropriate components for these plant enhancements is developed. A computer program is used to evaluate the performance of various power plants using standard inputs for component efficiencies; and the design-point performance of these plants is computed. The results are presented as thermal efficiency, specific power, effectiveness, and specific rate of energy in district heating. The performance of the simple-cycle gas turbine dominates the overall plant performance; the plant efficiency and power are mainly determined by turbine inlet temperature and compressor pressure ratio; increasing amounts of steam injection in the gas turbine increases the efficiency and power; increasing amounts of supplementary firing decreases the efficiency but increases the power; with sufficient amounts of supplementary firing and steam injection the exhaust-gas condensate is sufficient to make up for water lost in steam injection; and the steam-turbine power is a fraction (0.1 to 0.5) of the gas-turbine power output. Regions of “optimum” parameters for the power plant based on design-point power, hot-water demand, and efficiency are shown. A method for fuel-cost allocation between electricity and hot water is recommended.
Environmental Influence on the Thermoeconomic Optimization of a Combined Plant With NOx Abatement
Authors: Agazzani A. , Massardo A. F. , Frangopoulos C. A.
Published: December 2014

Methods to analyze, improve and optimize thermal energy systems have to take into account not only energy (exergy) consumption and economic resources but also pollution and degradation of the environment. The term “environomics” implies a method which takes thermodynamic, economic and environmental aspects systematically into consideration for the analysis and optimization of energy systems. For optimization of energy systems, the environmental aspects are quantified and introduced into the objective function.

In this particular work, the environomic approach is followed for the analysis and optimal design of a combined-cycle plant. In addition to the basic configuration, two alternatives for NOx abatement are studied: Selective Catalytic Reduction (SCR) and steam injection. The optimization problem is solved for each configuration and the results are compared with each other. The effect of the unit pollution penalties and of the limits imposed by regulations is studied. Some general conclusions are drawn.
Multiple Evaporation Steam Bottoming Cycle
Authors: Jericha H. , Fesharaki M. , Seyr A.
Published: December 2014

Improvements to the steam bottoming cycles hold the promise of raising the combined cycle thermal efficiency to values near and above 60%. Up to now, steam bottoming cycles with three pressure levels of steam evaporation have been realised. A further advantage seems possible by the use of double fluids, such as mixtures of steam and ammonia.

In the cycle proposed here, the authors limit Themselves to the use of steam and water only, in order to avoid all the difficulties, that may arise from such mixtures. The solution given here, relies on multiple evaporation levels, more than three up to five and even more. They should be to be achieved with the help of newly developed steam turbochargers, which allow the unification of the steam flow from three different neighbouring pressure levels, into one steam flow to be transmitted via the live steam line to the main turbine. This large number of evaporation levels, together with the required economisers for feed water heating and the ensuing superheaters arranged in the proper way, gives a steam water heat acceptance curve, which can be closely matched to the exhaust gas cooling line, so that the heat transfer from the gas turbine exhaust to the steam bottoming cycle can be effected with a minimum of temperature differences.

It should be pointed out that the steam pressures are selected in the undercritical region, and that a total combined cycle efficiency very near to 60% can be achieved. Using most modern gas turbine models together with this novel bottoming cycle will even allow to exceed the value of 60%. Examples given have been calculated for standard gas turbine models.
Inverse Design of Turbomachinery Blading for Arbitrary Blade Thickness in Three-Dimensional Transonic Flow
Authors: Yang Y. L.
Published: December 2014

A three-dimensional inverse design of turbomachinery blading for arbitrary blade thickness was obtained by using two periodic bound vortex sheets representing the pressure side and suction side of a blade row. The mean swirl distribution and blade tangential thickness distribution are specified in the present inverse design method. The prescribed mean swirl distribution is split into two fractions to form the strength of two bound vortex sheets. However, the designed results are uniquely determined by the specification of the mean swirl distribution and blade tangential thickness distribution, while splitting the mean swirl distribution into any two fractions for two bound vortex sheets is irrelevant. The resulting velocity field is composed of three parts: the first is sawtooth integrated from two bound vortex sheets; the second is axisymmetrical to provide an irrotational flow outside the two bound vortex sheets; and the last is potential to ensure mass conservation. The blade shape is determined from either the pressure side or suction side boundary condition, without a difference. Numerical results of a subsonic stator blade row designed by the present inverse design have been compared with three-dimensional Euler solutions and show a good agreement. For transonic calculation, a special form of retarding density was implemented to avoid transformation of the coordinate. However, due to the nonisentropic and rotational nature of shock wave, the present inverse solution does not give a correct answer after shocks. Coupling the entropy change and generation of vorticity after shocks with the present analytical formulation is recommended in the future work.
Development of a Programmable Logic Controller Based Fuel Control System for the G.E. LM-1600 Gas Turbine
Authors: King Dan A. , Patrick Jim
Published: December 2014

Nova Gas Transmission Ltd. (NGTL) has been developing integrated turbine fuel control systems since the late 1980s. This is part of a long term vision to completely integrate the control systems at its compressor stations. These systems are integrated into the “off the shelf” Programmable Logic Controller (PLC) used for unit sequencing and shutdowns.

As part of this effort NGTL began development of a fuel control system for the General Electric LM-1600 gas turbines in 1993. These systems, now successfully in service, proved to be the most challenging to develop. NGTL uses gas turbine packages, eleven of which are LM-1600s, to drive the compressors used in its gas pipeline system. This paper includes some brief background reasons why NGTL has chosen to develop fuel control systems and describes in detail the development of the fuel control system for the LM-1600. Discussion of the control challenges of the LM-1600 includes fuel throttle valve and actuator selection and options, control system hardware and software development (consistent with the General Electric Installation Design Manual (IDM) requirements) and, engine model development. The model application, office testing, site performance testing and the static and dynamic test results are also discussed. The paper also describes NGTL’s future plan for installation of LM-1600 fuel control systems on its fleet.
Ceramic Stationary Gas Turbine Development Program: Fourth Annual Summary
Authors: van Roode Mark , Brentnall William D. , Smith Kenneth O. , Edwards Bryan D. , McClain John , Price Jeffrey R.
Published: December 2014

A team led by Solar Turbines Incorporated is conducting a three phase program under the sponsorship of the United States Department of Energy, Office of Industrial Technologies, to improve the performance of stationary gas turbines in cogeneration through the selective replacement of metallic hot section components with ceramic parts. Preliminary and concept design were completed in Phase I. Detailed design, component fabrication, and rig and engine testing are all being conducted in Phase II. Field engine testing will be performed in Phase III. This review summarizes progress on Phases II and III for the program for 1996.

In 1996 the primary activities involved testing of uncooled first stage silicon nitride blades and SiC/SiC CFCC liners in a Centaur 50S engine modified to accept the ceramic components. Cumulative engine test experience by the end of November, 1996 has reached 52 hrs. The longest operating time on a single engine build at full load is 16 hours. Ceramic parts were also proof tested in rigs prior to engine testing. Preparations are currently underway for a 4,000 hour field test at the enhanced oil recovery site of ARCO Western Energy in Bakersfield, California.
Oxidation Induced Stress-Rupture of Fiber Bundles
Authors: Lara-Curzio Edgar
Published: December 2014

The effect of oxidation on the stress-rupture behavior of fiber bundles was modeled. It is shown that oxidation-induced fiber strength degradation results in the delayed failure of the associated fiber bundle and that the fiber bundle strength decreases with time as t−1/4. It is also shown that the temperature dependence of the bundle loss of strength reflects the thermal dependence of the mechanism controlling the oxidation of the fibers. The effect of gauge length on the fiber bundle strength was also analyzed. Numerical examples are presented for the special case of Nicalon™ fibers.
Variable Polarity GTAW of SMP14 Single Crystal Superalloy: Part One — Effects on Microstructure and Tensile Properties
Authors: Miglietti Warren , Benson Jeff , Blum Fritz , Harms Philip , Pennefather Ros
Published: December 2014

Gas tungsten arc welding (GTAW) using AC or DC current types has been utilised for the manufacture and repair of turbine engine components for many years. The weld repair of single crystal components such as turbine blade tips is also important. However, welding of a single crystal alloy has its associated problems (which will be discussed later). SMP14 is an advanced single crystal, Ni-base superalloy used for turbine blading. This alloy has enhanced mechanical properties at elevated temperatures when compared to equiaxed, directionally solidified and first generation single crystal superalloys. The objective of this task is to investigate the weldability of SMP14 using the new variable polarity GTAW process. Metallurgical investigations were undertaken to evaluate the microstructure of the welded region. Microporosity was found in the weld and there was no evidence of recrystallization, sub-grains beneath the weld or microcracking/microfissuring. Tensile test evaluations revealed that a high strength weld equivalent to equiaxed MAR-M247, Ni-based superalloy could be achieved. This appears to be the highest weld mechanical strength achieved to date when joining any Ni-base single crystal alloy together. Fractography was also utilised to analyse the fracture surfaces of the tensile test samples. Oxidation tests also revealed that the oxidation resistance of the weld was good and will be suitable for weld tip restoration where the weld needs to have good oxidation resistance.
Relationship Between Residual Creep Life and Microstructure of γ′ Strengthened Ni-Base Alloy for Gas Turbine Combustor Parts
Authors: Imano S. , Nakamura S. , Kanaya A. , Kusumoto J. , Watanabe H.
Published: December 2014

To estimate the residual life of heavy duty gas turbine hot section components, we studied the microstructure of aged, stress aged and creep ruptured γ′ strengthened alloy for combustor parts. The coarsening rate of precipitate was evaluated, and the activation energy for coarsening was found to be 327 kJ/mol which is slightly higher than the activation energy of volume diffusion for Al, Ti in a Ni solid solution. According to the experimental results, stress dependency of coarsening is not apparent, and the mean diameter of γ′ for creep ruptured specimens is not sensitive to temperature under the same stress conditions. This phenomenon can be explained with some assumptions. Using these results, methods for estimating metal temperature and creep damage based on microstructural information are performed for stress aged samples. These estimated results were compared with actual values.
Modeling of Industrial Pumping System Dynamics
Authors: Al-Nahwl Ammar A. , Graf Martin B.
Published: December 2014

A method for modeling the dynamics of industrial pumping systems is presented. The approach extends existing models for aero-engine like applications to capture dynamic features of interest in industrial, ground-based, applications. Those include the driver-driven (e.g., turbine-pump or compressor) interaction, the driver speed regulation subsystem, and their impact on stability. The method utilizes a lumped parameter modeling approach that involves developing and analyzing a set of nonlinear ordinary differential equations which describe the system dynamics.

A model of a baseline industrial pumping system comprised of a turbine driving a process compressor is formulated first. Components in the compressor flow path include an inlet duct, a plenum, and a discharge valve. The resulting model captures the system’s instability onset point, the post-stall behavior, and the sensitivity to system parameters. Two non-dimensional groups are found to play a dominant role in characterizing the overall dynamics: the ratio of fluid compliance to fluid inertia on the compressor side (B-parameter), and the ratio of the mechanical inertia of the rotating assembly to the fluid inertia. Low values of the B-parameter have a strong stabilizing effect and are associated with high frequency surge oscillations. In contrast, low values of the mechanical to fluid inertia ratio have a stabilizing effect only in a limited region of the compressor operating range, and have little effect on surge frequency. For the baseline system considered in this study, stabilizing effects of these two ratios were observed at values less than 0.4 and 0.2 respectively.

The baseline system model is then expanded to include a turbine speed controller. This allows examination of large transient events such as station shutdown and the phenomena of turbine hunting. It is found that the parameters of the turbine speed controller can affect the stability during such transients, but have little impact on the post-stall behavior.
Program of Development of Metal-Ceramic Stationary Gas-Turbine 2.5 MW Unit and the Initial Results of Its Implementation
Authors: Soudarev A. V. , Grishaev V. V. , Soudarev B. V. , Podgorets V. J. , Molchanov A. S. , Sourjaninov A. A.
Published: December 2014

The given paper submits some results of implementation of the first two steps of the program (Table 1) of development of a low-toxic high-efficiency metal-ceramic GTE of 2.5MW power intended for stationary power application, this R&D works having been carried out at NITI EM (Research-Technological Institute for Power Engineering) since 1990.
A Study of Fatigue Crack Growth Behavior of HAYNES® 242™ Alloy
Authors: Garimella Laxminarayana , Liaw Peter K. , Lai George Y. , Klarstrom Dwaine L.
Published: December 2014

A study of the variation in fatigue crack propagation behavior with respect to specimen orientation, aging and loading was done for HAYNES® 242™ Alloy. Fatigue crack growth tests were conducted at 650°C in vacuum. Heat treatment of the material resulted in enhanced fatigue crack growth properties. The influence of orientation on the fatigue crack growth properties was found to be minimal, although in some cases, where the notch was oriented perpendicular to the rolling direction, marginal improvement is observed. R-ratio was found to affect the fatigue crack growth behavior significantly. Fatigue crack growth rates increased when the R-ratio was changed from 0 to 0.5 and then decreased when it was further increased to 0.8. Fracture surfaces were characterized by scanning electron microscopy to explain the crack growth behavior. These results have been studied in light of the crack growth characteristics to obtain an understanding of the material behavior when subjected to fatigue loading.
Status of the Automotive Ceramic Gas Turbine Development Program — Seven Years’ Progress
Authors: Nakazawa Norio , Sasaki Masafumi , Nishiyama Tsubura , Iwai Masumi , Katagiri Haruo , Handa Noritoshi
Published: December 2014

The Petroleum Energy Center (PEC) in Japan is overseeing a seven year development program with the purpose of determining the potential of an automotive ceramic gas turbine (CGT), utilizing funding from the Ministry of International Trade and Industry. This program is scheduled to be completed in fiscal year 1996. A Regenerative-Type Single-Shaft Engine was developed, having a target turbine inlet temperature (TIT) of 1350°C and output power of 100kW.

Each component has achieved or nearly met the respective design target level and the output performance tests of the engine have reached their final stage. Durability tests of some components have been completed, and others are ongoing. A 100hr durability test of the engine has also started.

This development project started in FY 1990 after a two year feasibility study and preliminary design effort. After deciding on the engine specifications and completing the structural design, development and testing of individual and multiple components was carried out. Then the developmental progress of each component technology was reviewed and quantified, the results summarized, and corrective measures were applied during the latter half of the CGT development project. Anticipated difficulties, problem areas, and other obstacles which arose during the development were given extra emphasis during the individual component tests and full assembly tests. Many advanced technologies in component performance improvement, application of ceramic materials, engine structures and so forth were accumulated throughout the seven year development period.
Numerical Analysis of Two-Dimensional Compressible Viscous Flow in Turbomachinery Cascades Using an Improved k-ε Turbulence Model
Authors: Biswas Debasish , Iwasaki Hideo , Ishizuka Masaru
Published: December 2014

In the present work two-dimensional viscous flows through compressor and gas turbine blade cascades at low subsonic and transonic speed are analyzed by solving compressible N-S equations in the generalized co-ordinate system, so that sufficient number of grid points could be distributed in the boundary layer and wake regions. An efficient Implicit Approximate Factorization (IAF) finite difference scheme, originally developed by Beam-Warming, is used together with a higher order Total Variation Diminishing (TVD) scheme based on the MUSCL-type approach with the Roe’s approximate Rieman solver for shock capturing. In order to predict the boundary layer turbulence characteristics, shock boundary layer interaction, transition from laminar to turbulent flow, etc. with sufficient accuracy, an improved low Reynolds number k-ε turbulence model developed by the authors is used. In this k-ε model, the low Reynolds number damping factors are defined as a function of turbulence Reynolds number which is only a rather general indicator of the degree of turbulence activity at any location in the flow rather than a specific function of the location itself. Computations are carried out for different flow conditions of compressor and gas turbine blade cascades for which detailed and reliable information about shock location, shock losses, viscous losses, blade surface pressure distribution and overall performance are available. Comparison of computed results with the experimental data showed a very good agreement. The results demonstrated that the Navier-Stokes approach using the present k-ε turbulence model and higher order TVD scheme would lead to improved prediction of viscous flow phenomena in turbomachinery cascades.
A Parallel Unstructured Turbomachinery Code
Authors: Hustad C-W. , Vilmin S.
Published: December 2014

Parallel computing is maturing to become a viable approach for increasing CFD mesh resolution and reducing turnaround times — many of todays commercial programs are already available for parallel architecture machines, and software tools exist to help with automated parallelization of irregular (unstructured) scientific problems. However, despite numerous impressive demonstrations of applications, it is still not exactly clear when and how these will really impact on the way we do turbomachinery CFD. The current paper does not even attempt to answer such a general question, but instead presents the authors experience and views obtained while developing parallel codes for both industry and in conjunction with their own research work.

We give a brief review of events leading up to the present situation, and explain why parallel processing is the accepted route to follow. We then describe our parallel unstructured code; discuss practical issues relating to parallel performance; present some sample test case calculations; and finally consider a possible scenario regarding the role and requirements for similar computations in the future.
Simulation of Transient Load Behaviour of Gas Turbines in High Speed Marine Applications
Authors: White Maurice F.
Published: December 2014

This paper describes a model simulation of the transient behaviour of a twin spool gas turbine which could be used to drive a water jet propulsion system in a high speed vessel. The transient loading is considered to be due to torque variations that can occur due to the effect of air entrainment in the propulsor in a heavy sea. For the simulation, measured shaft torque from a diesel engined vessel operating in waves of height 2.0–2.5 meters were scaled to fit with the design output power of the studied gas turbine. This transient variation of torque was applied to the power turbine shaft in the mathematical model. The objective was to study the behaviour and thermal loading on the turbine under such conditions. Results from simulating the influence of heavy sea conditions show that very large shaft power drops can occur due to wave loading, and that for short periods of time higher gas temperatures can occur than the corresponding steady state values. In conclusion, this type of operation may increase the risk of damage due to cyclic variation of load and temperature, and lead to shorter component lifetimes compared with expected design values.
Ceramic Heat Exchangers-The Key to High Efficiency in Very Small Gas Turbines
Authors: McDonald Colin F.
Published: December 2014

The requirements for the emerging new class of very small gas turbines (ie.25–75kw) to meet the needs of generator sets and hybrid electric vehicles are more demanding, in terms of both capital and power generation costs, than those associated with existing small simple cycle gas turbines. To be successful the reliability, maintenance, and economics of these very small gas turbines must offer advantages over existing prime-movers. With the plateauing of compressor and turbine aerodynamic efficiencies, and turbine inlet temperature increase paced by materials technologies, the use of an exhaust heat recovery exchanger is mandatory to meet performance goals. The first generation of these very small gas turbines, currently in the pre-production phase, are operating with very attractive efficiencies of around 30 percent based on the utilization of existing types of metallic recuperators. Performance advancement and evolution of these engines will be realized as ceramic component technologies mature, and to cost-effectively achieve an efficiency of 35 percent, and to ultimately exploit the full performance potential of over 40 percent efficiency, high temperature ceramic heat exchangers will be needed. In this paper the focus is on the use of the fixed-boundary type of recuperative heat exchanger because of its simplicity, high reliability, and with no moving parts the assurance of maintenance free operation over the life of the engine.
Development of a Dry Low Emission Combustor for the ASE120 Industrial Gas Turbine Engine
Authors: Samuel P. , Lenertz J. E. , Bain D. B. , Mowill R. J.
Published: December 2014

The development of a dry, low-emissions combustor for the AlliedSignal Model ASE120 industrial gas turbine engine is in progress. The combustor is designed to provide 10MW of engine power output and also meet all current exhaust emissions requirements. The combustion system has a single-stage premixer and a novel, yet simple, variable geometry to control the flame temperature over the entire operating range of the ASE120 gas turbine engine. Design concepts of this lean premix-prevaporize combustor operating on air staging technology are presented. Preliminary results from computational fluid dynamics (CFD) analyses of the system are discussed.
A Study of Cycle Performance of Ceramic Gas Turbines
Authors: Sugishita H. , Mori H. , Chikami R. , Tsukuda Y. , Yoshino S. , Tsuchiya T. , Furuse Y.
Published: December 2014

A study has been carried out to assess the performance improvement of a combined cycle used for an industrial power plant when ceramic turbine components are employed. This paper presents the details of this study. Performance improvement is obtained as a result of reduced blade cooling air. In this study four different kinds of combined cycles were investigated and these are listed below:

A. Combined cycle with a simple gas turbine.

B. Combined cycle with an inter-cooled gas turbine.

C. Combined cycle with a reheat gas turbine.

D. Combined cycle with an inter-cooled reheat gas turbine.

Results of this study indicate that the combined cycle with a simple gas turbine is the most practical of the four cycles studied with an efficiency of higher than 60%. The combined cycle with reheat gas turbine has the highest efficiency if a higher compressor exit air temperature and a high gas temperature (over 1000°C) to reheat the combustion system are used. A higher pressure ratio is required to optimize the cycle performance of the combined cycle with the ceramic turbine components than that with the metal turbine components because of reduced blade cooling air. To minimize leakage air for these higher pressure ratios, advanced seal technology should be applied to the gas turbines.
The WISC Gas Turbine Engine
Authors: Shouman A. Radey , Shouman A. R.
Published: December 2014

Combined gas turbine-steam turbine cycles have gained widespread acceptance as the most efficient utilization of the gas turbine for power generation, particularly for large power plants. In order to maximize the achievable thermal efficiency, more than one exhaust heat recovery boiler is used. The current trend is to use three boilers at three different operating pressures, which improves thermal efficiency but significantly increases the initial cost of the plant.

There are advantages in replacing an exhaust heat recovery system using multiple boilers by a single heat exchanger in which the water side pressure is above the critical pressure of water; we shall refer to such a heat exchanger as a supercritical heat exchanger. The supercritical steam leaving the heat exchanger is expanded in a two phase turbine and then fed into the engine combustor. A condenser and a water treatment system are used to recover most of the water in the exhaust stream. A turbine system identical to the basic engine turbine system is added in parallel in order to allow for the operation with increased mass flow due to the steam injection. To achieve maximum efficiency such a turbine should be provided with variable area nozzles. With this arrangement, it becomes possible to inject sufficient steam to produce stoichiometric combustion at the desired turbine inlet temperature. We shall refer to this cycle as the Water Injected Stoichiometric Combustion (WISC) gas turbine cycle. The various components described above can be added to any existing gas turbine engine to change it to the WISC configuration.

The WISC engine offers significant economical advantages. The specific power output per pound of air for the WISC engine is more than five times that of the basic engine, the thermal efficiency is 75% higher than that of the basic engine. This produces a significant reduction in the initial investment in the plant as well as its operating expenses.
Tn
6249
, a New Tn
6162
Transposon Derivative Carrying a Double-Integron Platform and Involved with Acquisition of the
bla
VIM-1
Metallo-β-Lactamase Gene in Pseudomonas aeruginosa
Authors: Di Pilato Vincenzo , Pollini Simona , Rossolini Gian Maria
Published: December 2014

The In70.2 integron platform appears to be a conserved structure involved in the dissemination of the
bla
VIM-1
metallo-β-lactamase gene in
Pseudomonas aeruginosa
. The genetic context of the In70.2 integron platform from
P. aeruginosa
VR-143/97, the VIM-1-producing index strain isolated in Italy in 1997, was fully characterized by a next-generation sequencing approach refined by conventional sequencing. The In70.2 integron platform from VR-143/97 was found to be associated with a defective Tn
402
-like transposon inserted into the
urf2
gene of a Tn
3
family transposon of an original structure, named Tn
6249
, which also carried a partially deleted
mer
operon and an In90 integron platform in a tail-to-tail orientation. Tn
6249
was inserted into a PACS171b-like genomic island, which was in turn inserted into the
endA
gene of the
Pseudomonas
chromosomal backbone. Tn
6249
showed a similar structure and a conserved location with respect to that of Tn
6060
, a Tn
3
family transposon associated with In70.2 and carrying a double-integron platform, which was detected in a VIM-1-producing
P. aeruginosa
strain isolated in Australia in 2008. Both Tn
6249
and Tn
6060
are apparently derived from Tn
6162
, a mercury resistance transposon carrying an integron platform, which was found in
P. aeruginosa
isolates from different geographic locations. The conservation of the genetic context of Tn
6249
and Tn
6060
suggests an
in situ
evolution of these elements after the insertion of a Tn
6162
-like ancestor into the PACS171b-like genomic island (GI) present in the genome of a successful widespread
P. aeruginosa
clonal lineage.
Influenza Viral Load and Peramivir Kinetics after Single Administration and Proposal of Regimens for Peramivir Administration against Resistant Variants
Authors: Sato Masatoki , Ito Masaki , Suzuki Shigeo , Sakuma Hiroko , Takeyama Aya , Oda Shinichi , Watanabe Masahiro , Hashimoto Koichi , Miyazaki Kyohei , Kawasaki Yukihiko , Hosoya Mitsuaki
Published: December 2014

We estimated the efficacy of the current single administration of peramivir on the basis of peramivir pharmacokinetics in the upper respiratory tract (URT) and determined the predictive peramivir concentration-time curve to assess its efficacy against viruses with decreased susceptibility to neuraminidase inhibitors. Serum, nasal swab, or aspiration samples were collected from 28 patients treated with 10 mg/kg body weight peramivir. The sequential influenza viral RNA load and susceptibility after peramivir administration were measured using a quantitative real-time reverse transcription-PCR and neuraminidase inhibition assay. The peramivir concentrations in the serum and URT after a single administration at 10 mg/kg were measured, and the predictive blood and URT peramivir concentration-time curves were determined to assess various administration regimens against resistant variants. The peramivir concentration decreased to <0.1% of the maximum concentration of drug in serum (
C
max
) at 24 h after administration. Rapid elimination of peramivir from the URT by 48 h after administration may contribute to an increase in the influenza A viral load after day 3 but not to a decrease in the influenza B viral load, despite the absence of a decrease in the susceptibility to peramivir. A longer maintenance of a high level of peramivir in the URT is expected by divided administration rather than once-daily administration. When no clinical improvement is observed in patients with normal susceptibility influenza A and B, peramivir readministration should be considered. In severe cases caused by resistant variants, better inhibitory effectiveness and less frequent adverse events are expected by divided administration rather than once-daily administration with an increased dosage.
Tigecycline Treatment Causes a Decrease in Fibrinogen Levels
Authors: Zhang Qian , Zhou Suming , Zhou Jing
Published: December 2014

The objective of this study was to assess the impact of tigecycline treatment on coagulation parameters, specifically fibrinogen, in patients with severe infections. We examined 20 cases of tigecycline-treated patients with severe infections, including hospital-acquired pneumonia, complicated intra-abdominal infections, complicated skin and soft tissue infections, and bloodstream infections. We monitored the relative markers of coagulation and renal and liver function before, during, and after treatment. Fibrinogen (FIB) levels decreased significantly after the use of tigecycline and normalized after the cessation of treatment. FIB levels significantly decreased in the patients treated with the recommended dose or a higher treatment dose. The FIB levels decreased more in the higher-treatment-dose group. There was no difference in the decrease in FIB levels or the FIB level recovery by age. Prothrombin time (PT), activated partial thromboplastin time (APTT), and thrombin time (TT) were prolonged after tigecycline use. The TT decreased after the cessation of treatment, and the PT and APTT also decreased but not to a significant level. There was no change in platelet, alanine aminotransferase (ALT), or creatinine (Cr) levels associated with treatment. The use of tigecycline was associated with decreased FIB levels, which returned to normal after the cessation of treatment. A high-dose treatment group showed greater decreases in FIB levels than did patients treated with the recommended dose. The decline in FIB was not related to patient age. The use of tigecycline was associated with prolonged PT, APTT, and TT.
Malonic Semialdehyde Reductase from the Archaeon Nitrosopumilus maritimus Is Involved in the Autotrophic 3-Hydroxypropionate/4-Hydroxybutyrate Cycle
Authors: Otte Julia , Mall Achim , Schubert Daniel M. , Könneke Martin , Berg Ivan A.
Published: December 2014

The recently described ammonia-oxidizing archaea of the phylum
Thaumarchaeota
are highly abundant in marine, geothermal, and terrestrial environments. All characterized representatives of this phylum are aerobic chemolithoautotrophic ammonia oxidizers assimilating inorganic carbon via a recently described thaumarchaeal version of the 3-hydroxypropionate/4-hydroxybutyrate cycle. Although some genes coding for the enzymes of this cycle have been identified in the genomes of
Thaumarchaeota
, many other genes of the cycle are not homologous to the characterized enzymes from other species and can therefore not be identified bioinformatically. Here we report the identification and characterization of malonic semialdehyde reductase Nmar_1110 in the cultured marine thaumarchaeon
Nitrosopumilus maritimus
. This enzyme, which catalyzes the reduction of malonic semialdehyde with NAD(P)H to 3-hydroxypropionate, belongs to the family of iron-containing alcohol dehydrogenases and is not homologous to malonic semialdehyde reductases from
Chloroflexus aurantiacus
and
Metallosphaera sedula
. It is highly specific to malonic semialdehyde (

K
m

, 0.11 mM;
V
max
, 86.9 μmol min
−1
mg
−1
of protein) and exhibits only low activity with succinic semialdehyde (

K
m

, 4.26 mM;
V
max
, 18.5 μmol min
−1
mg
−1
of protein). Homologues of
N. maritimus
malonic semialdehyde reductase can be found in the genomes of all
Thaumarchaeota
sequenced so far and form a well-defined cluster in the phylogenetic tree of iron-containing alcohol dehydrogenases. We conclude that malonic semialdehyde reductase can be regarded as a characteristic enzyme for the thaumarchaeal version of the 3-hydroxypropionate/4-hydroxybutyrate cycle.
Production of Buttery-Odor Compounds and Transcriptome Response in Leuconostoc gelidum subsp. gasicomitatum LMG18811
T
during Growth on Various Carbon Sources
Authors: Jääskeläinen Elina , Vesterinen Sanna , Parshintsev Jevgeni , Johansson Per , Riekkola Marja-Liisa , Björkroth Johanna
Published: December 2014

Leuconostoc gelidum
subsp.
gasicomitatum
is a common spoilage bacterium in meat products packaged under oxygen-containing modified atmospheres. Buttery off-odors related to diacetyl/acetoin formation are frequently associated with the spoilage of these products. A whole-genome microarray study, together with gas chromatography (GC)-mass spectrometry (MS) analyses of the pathway end products, was performed to investigate the transcriptome response of
L. gelidum
subsp.
gasicomitatum
LMG18811
T
growing on semidefined media containing glucose, ribose, or inosine, which are essential carbon sources in meat. Generally, the gene expression patterns with ribose and inosine were quite similar, indicating that catabolism of ribose and nucleosides is closely linked. Diacetyl/acetoin concentrations as high as 110 or 470 μM were measured when growth was based on inosine or ribose, respectively. The gene expression results for pyruvate metabolism (upregulation of α-acetolactate synthase, downregulation of
l
-lactate dehydrogenase and pyruvate dehydrogenase) were as expected when diacetyl and acetoin were the end products. No diacetyl production (<7.5 μM) was detected with the glucose-containing medium, even though the cell counts of LMG18811
T
was 6 or 10 times higher than that on inosine or ribose, respectively. Although glucose was the most effective carbon source for the growth of
L. gelidum
subsp.
gasicomitatum
, utilization of inosine and ribose resulted in the production of the unwanted buttery-odor compounds. These results increase our understanding of which compounds are likely to enhance the formation of buttery odors during meat spoilage caused by
L. gelidum
subsp.
gasicomitatum
.