bluuebunny/crossref_metadata_2025 huggingface dataset:
SiC Fiber Reinforced SiC-Si Matrix Composites Prepared by Melt Infiltration (MI) for Gas Turbine Engine Applications
Authors: Corman Gregory S. , Brun Milivoj K. , Luthra Krishan L.
Published: December 2014

General Electric (GE) has developed silicon carbide fiber reinforced SiC-Si matrix composites by silicon melt infiltration (MI) for use in gas turbine engine applications. This paper focuses on a process based on tow prepreging and lamination of unidirectional tapes. Silicon melt infiltration yields a fully dense, near net shape composite with a relatively high thermal conductivity, actually higher than many superalloys at temperatures up to 800°C, and a high proportional limit, or matrix cracking stress. Room and elevated temperature mechanical properties of the composite are presented. Following exposure to various simulated turbine environments this material shows relatively good retention of strength and toughness. The fabrication of turbine shroud and combustor liner components for high pressure combustion rig testing is also described.
Gas Turbine Combustor Design Parameter Analysis for Soot Reduction Using CFD
Authors: Crocker D. Scott , Puri Rahul
Published: December 2014

AlliedSignal’s F124 combustor is analyzed using CFD as part of an effort to improve the design of the combustor. A reduction of soot emissions, without negative impact on other performance features such as liner life and lean stability, was the primary objective. The existing F124 combustor (TFE1042) was modeled using the commercial CFD-ACE+ software package to validate the CFD results and provide a basis for comparison for the modified design. Two design of experiment (DOE) matrices of the redesigned combustor were analyzed using CFD modeling. The results of the CFD solutions led to the selection of two configurations for combustor rig experimental testing. The test configurations were selected based on CFD predicted trends for smoke, ignition, lean stability and pattern factor. Engine tests demonstrated a smoke number reduction from more than 40 to less than 10. Lean stability was degraded as a result of a leaner primary zone, but adequate lean stability margin was maintained.
Development History and Field Experiences of the First FT8 Gas Turbine With Dry Low NOx Combustion System
Authors: Schlein Barry C. , Anderson David A. , Beukenberg Markus , Mohr Klaus D. , Leiner Hans L. , Träptau Wolfgang
Published: December 2014

This paper describes the FT8-2 Dry Low NOx (DLN) combustor development process and reviews the development history and initial field experience at a natural gas pipeline station in Germany. The development process is primarily focused on defining a fuel nozzle or injector, investigating emissions, fuel-air mixing, flame stability, acoustics, flashback resistance, and flame disgorgement. Empirical development tools including single nozzle and sector combustion rigs, as well as flame imaging techniques, are discussed. A summary of in-house engine development testing is provided. The control methodology used to meet emissions, while maintaining combustor pressure pulsations at an acceptable level, is provided. The natural gas compressor station design and operational experience with a GHH BORSIG compressor driven by the FT8 engine in Werne, Germany is summarized. Also presented are details of the very short conversion period from Standard to DLN combustor with the first successful ignition of the engine 26 days after work had begun.
Total Operating Activities of Gas Turbine Components — Total Equivalent Operating Hours (TEOH)
Authors: Lee Jung-Ho
Published: December 2014

Timely inspection and maintenance are essential requirements in maintaining the high Reliability, Availability and Maintainability (RAM) of gas turbine units. The timing of inspections is determined by using the concept of the amount of accumulated operating activities of units between the inspection intervals. In tradition, operating hours and number of startups are used to measure these activities. Indeed, they are two major factors of the activities.

Gas turbines in general run in various duties, environments and operation modes. Under these conditions, it is important to have a well-defined tool and correctly quantified total operating activities of components to plan for timely inspection and refurbishment.

In this paper, the single parameter of Total Equivalent Operating Hours (TEOH) is proposed to be used as a tool to serve the purpose. In developing the TEOH, the linear fraction rule of damage, a theory of interaction fraction rule of damage, a theory of interaction between the creep and fatigue damages is applied to find the equivalent operating hours from the number of startups.
The Measurement of Local Wall Heat Transfer in Stationary U-Ducts of Strong Curvature, With Smooth and Rib Roughened Walls
Authors: Iacovides Hector , Jackson David C. , Kelemenis George , Launder Brian E.
Published: December 2014

The paper presents some of our recent experimental investigations of convective heat transfer in flow through stationary passages relevant to gas-turbine blade-cooling applications. The main objective of this effort is to produce local heat transfer data for CFD validation. Local Nusselt number measurements in flows through round-ended U-bends of square cross-section, with and without artificial wall roughness are presented. Our earlier LDA measurements of flows through these passages are first briefly reviewed and then the liquid-crystal technique for the measurement of local wall heat transfer inside passages of complex geometries is then presented. Tightly curved U-bends generate strong secondary motion and cause flow separation at the bend exit, which substantially raise turbulence levels. Wall heat transfer is significantly increased, especially immediately downstream of the U-bend, where it is over two times higher than in a straight duct. The local heat-transfer coefficient around the perimeter of the passage is also found to vary considerably because of the curvature-induced secondary motion. The introduction of surface ribs, results in a further increase in turbulence levels, a reduction in the size of the curvature induced separation bubble and a complex flow development after the bend exit with additional separation regions along the outer wall. Heat-transfer levels in the straight sections are more than doubled by the introduction of ribs. The effects of the bend on the overall levels of Nusselt number are not as strong as in the smooth U-bend, but are still significant. The effects of the bend on the perimetral variation of local heat-transfer coefficients within the ribbed downstream section are also substantial.
Heat Transfer and Fluid Flow in a Square Duct With 12 Different Shaped Vortex Generators
Authors: Liou Tong-Miin , Chen Chung-Chu , Tsai Tzi-Wei
Published: December 2014

Detailed local Nusselt number distributions, streamwise mean flow patterns and cross-sectional secondary flow patterns, and friction factors in the first pass of a sharp turn two-pass square channel with various configurations of longitudinal vortex generator arranged on one wall were measured using transient liquid crystal thermography, laser-Doppler velocimetry, and pressure transducer probing, respectively. The Reynolds number, based on channel hydraulic diameter and bulk mean velocity, was fixed at 1.2 × 104. The vortex generator height-to-hydraulic diameter ratio and pitch-to-height ratio were 0.12 and 10, respectively. Comparisons in terms of heat transfer augmentation and uniformity and friction loss are first performed on 12 configurations of longitudinal vortex generator. The fluid dynamic mechanisms and wall confinement relevant to heat transfer enhancement are then documented for three-selected vortex generator models. In addition, the differences in fluid flow and heat transfer characteristics between a single vortex generator and a vortex generator array are addressed for the delta wing 1 U and 45° V U models which provide better thermal performance. The direction and strength of the secondary flow with respect to the heat transfer wall are found to be the most important fluid dynamic factors affecting the heat transfer promotion through the channel wall, followed by the convective mean velocity, and then the turbulent kinetic energy. Furthermore, the effects of the two-dimensional heat conduction near the vortex generator edge and unseen heat transfer areas on the Nusselt number estimation are documented in detail.
Steady and Unsteady Heat Transfer in a Transonic Film Cooled Turbine Cascade
Authors: Popp O. , Smith D. E. , Bubb J. V. , Grabowski H. C. , Diller T. E. , Schetz J. A. , Ng Wing-Fai
Published: December 2014

This paper reports on an investigation of the heat transfer on the suction side of a transonic film cooled turbine rotor blade in a linear cascade. Heat transfer coefficient and film effectiveness are first determined for steady conditions. The unsteady effects of a passing shock on the heat transfer are then investigated. The film cooling pattern used is a showerhead design with three rows on the suction side, one row at the stagnation point and two rows on the pressure side. The experiments were performed at engine representative temperature and pressure ratios using air as coolant. Heat transfer measurements are obtained using a Heat Flux Microsensor, and surface temperature is monitored with a surface thermocouple. Static pressure is monitored with a Kulite pressure transducer. The shock emerging from the trailing edge of the NGV and impinging on the rotor blades is modeled by passing a shock wave along the leading edges of the cascade blades. The steady-state heat transfer coefficient is 8% higher with film cooling than without film cooling. Shock heating of the freestream flow is determined to be the major contribution to the unsteady variation of heat flux, leading to an increase of about 30°C to 35°C in recovery temperature and adiabatic wall temperature.
Degradation of Silicon Nitrides in High Pressure, Moisture Rich Environments
Authors: Ferber M. K. , Lin H. T. , Parthasarathy V. , Brentnall W.
Published: December 2014

This paper provides a review of a recent study undertaken to examine the long-term reliability of silicon nitride and silicon carbide ceramics exposed to a representative gas turbine environment. A typical test exposure consisted of 500 hours at 1204°C and 1.5 atm of water vapor carried in an air environment at 10 atm of total pressure. Following each exposure specimens were weighed, measured, and then sectioned for optical and scanning electron microscopy. The total exposure duration was 1500 h for the silicon nitride and 2500 h for the silicon carbide.
Hot Gas Filters for Coal and Biomass Power Systems
Authors: Newby R. A. , Lippert T. E. , Alvin M. A. , Bruck G. J. , Sanjana Z. N. , Smeltzer E. E.
Published: December 2014

Several advanced, coal- and biomass-based combustion turbine power generation technologies are currently under development and demonstration. A key technology component in these power generation systems is the hot gas filter. These power generation technologies must utilize highly reliable and efficient hot gas filter systems to protect the turbine and to meet environmental constraints if their full thermal efficiency and cost potential is to be realized. Siemens Westinghouse Power Corporation (SWPC) has developed a hot gas filter system to near-commercial status for large-scale power generation applications. This paper reviews recent progress made by SWPC in hot gas filter test development programs and in major demonstration programs. Two advanced hot gas filter concepts, the “Inverted Candle” and the “Sheet Filter”, having the potential for superior reliability are also described.
A Reduced Order Model of Mistuning Using a Subset of Nominal System Modes
Authors: Yang M.-T. , Griffin J. H.
Published: December 2014

Reduced order models have been reported in the literature that can be used to predict the harmonic response of mistuned bladed disks. It has been shown that in many cases they exhibit structural fidelity comparable to a finite element analysis of the full bladed disk system while offering a significant improvement in computational efficiency. In these models the blades and disk are treated as distinct substructures.

This paper presents a new, simpler approach for developing reduced order models in which the modes of the mistuned system are represented in terms of a sub-set of nominal system modes. It has the following attributes: the input requirements are relatively easy to generate; it accurately predicts mistuning effects in regions where frequency veering occurs; as the number of degrees of freedom increases it converges to the exact solution; it accurately predicts stresses as well as displacements; and it accurately models the deformation and stresses at the blades’ bases.
Combustion Oscillations in Burners With Fuel Spray Atomisers
Authors: Zhu M. , Dowling A. P. , Bray K. N. C.
Published: December 2014

Most types of combustion-driven devices experience combustion instabilities. For aero-engine combustors, the frequency of this oscillation is typically in the range 60–120Hz and is commonly called ‘rumble’. The rumble oscillations involve coupling between the air and fuel supplies and unsteady flow in the combustor. Essentially pressure fluctuations alter the inlet fuel and air, thereby changing the rate of combustion, which at certain frequencies further enhances the pressure perturbation and so leads to self-excited oscillations. The large residence time of the liquid fuel droplets, at idle and sub-idle conditions, means that liquid and gaseous phases must both be considered. In the present work, we use a numerical model to investigate forced unsteady combustion due to specified time-dependent variations in the fuel and air supplies. Harmonic variations in inlet air and fuel flows have been considered and the resulting unsteady combustion calculated. The influence of droplet size distribution has also been investigated. The calculations provide insight into understanding the interaction between atomization, unsteady combustion and flow oscillations.
A New Method of Data Reduction for Single-Sensor Pressure Probes
Authors: Dambach R. , Hodson H. P.
Published: December 2014

The use of multi-sensor fast-response pressure probes is now relatively common place. Unfortunately, these probes are often larger than ideal. It is for this reason that single sensor probes are sometimes used in investigations of unsteady flow. In use, the single sensor probe must be placed at a number of different orientations to the flow, often achieved by simply rotating the stem of the probe mount. The run time of a given experiment increases in proportion to the number of orientations employed. Furthermore, the number of orientations is usually more than is strictly required due to poor conditioning of the experiment. This results in a significant amount of redundant information being available and run-time costs being increased. This paper describes a data reduction technique that reduces the run time cost of using single sensor fast response probes to the minimum. This is achieved by using all of the data obtained in the experiment so that there is no redundancy no matter how many orientations are employed. The method relies on comparing the measured data with the calibration data in order to obtain a best fit between the two datasets.
Surface Micromachined Silicon Carbide Accelerometers for Gas Turbine Applications
Authors: DeAnna Russell G.
Published: December 2014

A finite-element analysis of possible silicon carbide (SiC), folded-beam, lateral-resonating accelerometers is presented. Results include stiffness coefficients, acceleration sensitivities, resonant frequency versus temperature, and proof-mass displacements due to centripetal acceleration of a blade-mounted sensor. The surface micromachined devices, which are similar to the Analog Devices® Inc., (Norwood, MA) air-bag crash detector, are etched from 2-μm thick, 3C-SiC films grown at 1600 K using atmospheric pressure chemical vapor deposition (APCVD). The substrate is a 500 μm-thick, (100) silicon wafer. Polysilicon or silicon dioxide is used as a sacrificial layer. The finite-element analysis includes temperature-dependent properties, shape change due to volume expansion, and thermal stress caused by differential thermal expansion of the materials. The finite-element results are compared to experimental results for a SiC device of similar, but not identical, geometry. Along with changes in mechanical design, blade-mounted sensors would require on-chip circuitry to cancel displacements due to centripetal acceleration and improve sensitivity and bandwidth. These findings may result in better accelerometer designs for this application.
Gas Turbine Applications for Large Air Separation Units
Authors: Smith A. R. , Dillon J. L.
Published: December 2014

Oxygen production rates of 10,000 to 20,000 tons per day from large, cryogenic air separation units are being studied by many alternative fuel project developers. These projects utilize oxygen to partially oxidize hydrocarbon materials, producing a clean synthesis gas that can be used as a fuel or for conversion into valuable chemical products. Specific market applications include natural gas or waste material conversion processes and multi-train integrated gasification combined cycle facilities. In an effort to reduce specific facility cost project developers increase facility output to obtain economies of scale, resulting in large oxygen requirements for the partial oxidation step. One of the challenges to provide cost effective oxygen is the economic supply of large quantities of compressed air for use in the cryogenic air separation process. To date, gas turbines have found limited application for use in air separation facilities due to their relatively high capital cost compared to traditional electric motor drives. The need for large, single train air separation units to support alternative fuel projects creates opportunities for the use of gas turbines. This paper explores the use of commercially available equipment, configured to integrate with air separation processes, to improve the economics of oxygen production. Long term developmental equipment configurations are presented to further improve the economics of these facilities.
Progress of an Externally Fired Evaporative Gas Turbine Cycle for Small Scale Biomass Gasification
Authors: Marroyen Daniel , Bram Svend , De Ruyck Jacques
Published: December 2014

The present paper reports on a demonstration project supported by the THERMIE program of the European Commission and by the VLIET program of the Flemish Government. A CHP gas turbine plant fueled by product gas from a biomass fluidized bed gasifier has been constructed. The demonstration scale is 500 kWe for production of power and heat for the university campus district heating. At the present stage 150 kW power has been delivered to the grid. Problems encountered and results achieved during the first startups of the power plant will be discussed. In the future some natural gas topping combustion will be included to overcome the temperature limitation of materials used in the metallic high temperature air heater. Water injection in this air heater will be included to enhance power output and to allow flexible power to heat ratios. The target commercial scale is 2 to 5 Mwe using atmospheric gasification and external firing through a high temperature metallic heater.
Computational Simulation of Gas Turbines: Part I — Foundations of Component-Based Models
Authors: Reed John A. , Afjeh Abdollah A.
Published: December 2014

Designing and developing new aerospace propulsion systems is time-consuming and expensive. Computational simulation is a promising means for alleviating this cost, but requires a flexible software simulation system capable of integrating advanced multidisciplinary and multifidelity analysis methods, dynamically constructing arbitrary simulation models, and distributing computationally complex tasks. To address these issues, we have developed Onyx, a Java-based object-oriented domain framework for aerospace propulsion system simulation. This paper presents the design of a common engineering model formalism for use in Onyx. This approach, which is based on hierarchical decomposition and standardized interfaces, provides a flexible component-based representation for gas turbine systems, subsystems and components. It allows new models to be composed programmatically or visually to form more complex models. Onyx’s common engineering model also supports integration of a hierarchy of models which represent the system at differing levels of abstraction. Selection of a particular model is based on a number of criteria, including the level of detail needed, the objective of the simulation, the available knowledge, and given resources. The common engineering model approach is demonstrated by developing gas turbine component models which will be used to compose a gas turbine engine model in Part II of this paper.
The Effect of Discrete Pilot Hydrogen Dopant Injection on the Lean Blowout Performance of a Model Gas Turbine Combustor
Authors: Nguyen Oanh , Samuelsen Scott
Published: December 2014

In view of increasingly stringent NOx emissions regulations on stationary gas turbines, lean combustion offers an attractive option to reduce reaction temperatures and thereby decrease NOx production. Under lean operation, however, the reaction is vulnerable to blowout. It is herein postulated that pilot hydrogen dopant injection, discretely located, can enhance the lean blowout performance without sacrificing overall performance. The present study addresses this hypothesis in a research combustor assembly, operated at atmospheric pressure, and fired on natural gas using rapid mixing injection, typical of commercial units. Five hydrogen injector scenarios are investigated. The results show that (1) pilot hydrogen dopant injection, discretely located, leads to improved lean blowout performance and (2) the location of discrete injection has a significant impact on the effectiveness of the doping strategy.
Steady-State and Transient Performance Simulation of a Turboshaft Engine With Free Power Turbine
Authors: Kong Changduk , Ki Jayoung , Koh Kwangwoong
Published: December 2014

Steady-state and transient performance analysis programs for 200kw-class small turboshaft engine with free power turbine were developed. An existing turbojet engine was used for the gas generator of the developed turboshaft engine, and it was modified to satisfy performance requirements of this turboshaft engine. To verify the availability of steady-state performance program for this engine: the program was applied to the same type gas turbine test unit, and the analysis results were compared to experimental results.

The developed transient performance analysis program using the CMF (Constant Mass flow) method was utilized to analysis in the cases of fuel step increase and the ramp increase.
Measurement and Visualization of Leakage Effects of Rounded Teeth Tips and Rub-Grooves on Stepped Labyrinths
Authors: Rhode David L. , Allen Brian F.
Published: December 2014

The effect of rounded labyrinth teeth tips and worn abradable lands has been found to give substantially increased leakage, which is well known to give reduced machine efficiency. Very little information concerning this exists, and some of the first measurements and visualization movies for stepped labyrinths are provided here to give an enhanced understanding of this phenomenon. A unique, very large-scale seal test facility was used. Glitter, and alternatively fluorescein dye, was employed as the flow tracer material. The flow visualization movies were digitally stored on the hard drive of a computer.

Large decreases of leakage resistance due to the presence of worn teeth as well as rub-grooves were found. For the cases considered, the leakage resistance decrease for the large step height configurations were 85 percent, 55 percent and 70 percent for the small, medium and large pre-rub clearances, respectively. It was also found that the resistance varied with wear geometry, in order from highest to lowest resistance, as: (a) ungrooved-unrounded-teeth, (b) ungrooved-rounded-teeth, (c) grooved-unrounded-teeth and (d) grooved-rounded-teeth. Further, a substantial tooth tip recirculation zone was visually observed only for the grooved-unrounded-teeth cases, and it was shown to be the mechanism by which the unrounded teeth give this configuration a higher resistance than do the rounded teeth.
Conceptual Recovery of Exhaust Heat From a Conventional Gas Turbine by an Inter-Cooled Inverted Brayton Cycle
Authors: Tsujikawa Y. , Ohtani K. , Kaneko K. , Watanabe T. , Fujii S.
Published: December 2014

Improvements in industrial gas turbine performance have been made in last decade. Advances in the gas turbine technologies such as higher turbine inlet temperature, materials, and manufacturing techniques justify the development of new combined or cogeneration cycle schemes, with more advance heat recovery capabilities. This paper describes the performance analysis of an Inverted Brayton Heat Recovery (IBHR) cycle, which is combined with conventional gas turbine and worked as a bottoming cycle. The optimum characteristics have been calculated and it is shown that this cycle is superior to the conventional combined cycle and cogeneration systems in terms of thermal efficiency and specific output. The main feature of this new concept is that the inverted Brayton cycle with inter-cooling is introduced. Further, a new estimating function, “the emission coefficient of carbon-dioxide” has been successfully introduced to assess the environmental compatibility.
Contact Stresses in Dovetail Attachments: Finite Element Modeling
Authors: Sinclair G. B. , Comier N. G. , Griffin J. H. , Meda G.
Published: December 2014

The stress analysis of dovetail attachments presents some challenges. These challenges stem from the high stress gradients near the edges of contact and from the nonlinearities attending conforming contact with friction. To meet these challenges with a finite element analysis, refined grids are needed with mesh sizes near the edges of contact of the order of one percent of the local radii of curvature there. A submodeling procedure is described which can provide grids of sufficient resolution in return for moderate computational effort. This procedure furnishes peak stresses near contact edges which are converging on a sequence of three submodel grids, and which typically do converge to within about five percent.
Improved Operating Efficiency Through the Use of Stabilized Thermocouples
Authors: Jablin Jeff , Storar Michael R. , Gray Phillip L.
Published: December 2014

The development of a “stabilized” temperature sensor has led to significant increases in turbine operating efficiency by maximizing output when compared with present sensor technology. These stabilized type K and E thermocouples are superior to existing standard non-stabilized thermocouples because they are not prone to the typical aging effects in the 400 to 600°C (752 to 1112°F) temperature range that can result in measurement errors.

A complete set of 18 stabilized type K thermocouples were installed on the exhaust of several gas turbines used for power generation. These thermocouples were subjected to normal operating conditions for a period of one year. During that year, the increase in turbine output has ranged from 0.5% to almost 2.0%. This increase in output also translates into significant cost savings. In addition, the stabilized thermocouples have given the turbine maintenance technicians more confidence in the accuracy of their temperature measurements and resulted in improved troubleshooting and decision making.
Experimental Investigation of the Aerodynamic Stability of an Annular Compressor Cascade Performing Tuned Pitching Oscillations in Transonic Flow
Authors: Hennings H. , Belz J.
Published: December 2014

A prerequisite for aeroelastic stability investigations on vibrating compressor cascades is the detailed knowledge of the unsteady aerodynamic loads acting on the blades. In order to obtain precise insight into the aerodynamic damping of a vibrating blade assembly, a basic experiment was performed where unsteady pressure distributions were measured for subsonic and transonic flow conditions.

The experiments were performed on a non-rotating, two-dimensional section of a compressor cascade in an annular test facility. The cascade consists of 20 blades (NACA3506 profile) mounted on elastic spring suspensions. In order to measure the unsteady pressure distribution, the cascade was set to tuned pitching oscillations (traveling wave modes). Each blade was driven to controlled harmonic torsional motions around midchord by a magnetic excitation system and by inductive displacement probes which measure the feedback signal of the motion. Steady and unsteady pressures were measured by steady pressure taps and piezo-electric pressure transducers, respectively. The measurement of the unsteady aerodynamic response to a shock vibrating on the suction side of the blades was enabled by a dense spacing of transducers in this region.

The global aerodynamic stability is assessed by a damping coefficient evaluated from the out-of-phase parts of the unsteady moment coefficients and by the contributions from the local work coefficient, using the measured pressure data.
Combined-Simultaneous Gust and Oscillating Compressor Blade Unsteady Aerodynamics
Authors: Frey Kuk Kim , Fleeter Sanford
Published: December 2014

Experiments are performed in a 3-stage axial flow research compressor to investigate and quantify the simultaneous-combined gust and motion induced unsteady aerodynamic response of compressor 1st stage rotor blades. The gust response unsteady aerodynamics are experimentally modeled with a 2/rev forcing function. The torsion mode unsteady aerodynamics are investigated utilizing an experimental influence coefficient technique in conjunction with a unique drive system. Combined gust and oscillating unsteady aerodynamics are obtained by superposition of the separate oscillating blade row and the gust response unsteady aerodynamics. Simultaneous gust and motion induced unsteady aerodynamic response are obtained by driving the torsion mode oscillation in the presence of the 2/Rev forcing function. The effects of steady loading are quantified, with airfoil oscillation amplitude effects also studied. The combined unsteady aerodynamics establish the applicability limitations of the superposition principle at high oscillation amplitudes and high loading. In addition, the gust-blade motion phase angle is identified as a key parameter, with the accuracy of forced response prediction and the alteration of blade row stability due to gust interaction dependent on the gust-blade motion phase.
Hybrid Gas Turbine and Fuel Cell Systems in Perspective Review
Authors: White David J.
Published: December 2014

The concept of hybrids combining fuel cell and gas turbine systems is without question neoteric, and probably is less than eight years old. However, this concept is in a sense a logical development derived from the many early systems that embodied the key features of rotating machinery to compress air. It was the introduction of high temperature fuel cells such as the solid oxide fuel cell (SOFC) that allowed the concept of hybrid gas turbine fuel cell systems to take root. The SOFC with an operating temperature circa 1000° C matched well with small industrial gas turbines that had firing temperatures on the same order.

The recognition that the SOFC could be substituted for the gas turbine combustor was the first step into the realm of fuel cell topping systems. Fuel cells in general were recognized as having higher efficiencies at elevated pressures. Thus the hybrid topping system where the gas turbine pressurized the fuel cell and the fuel cell supplied the hot gases for expansion over the turbine promised to provide a high level of synergy between the two systems.

Bottoming systems using the exhaust of a gas turbine as the working fluid of a fuel cell such as the molten carbonate fuel cell (MCFC) have been identified and are potential future power generation hybrid systems. The MCFC is especially well suited to the bottoming role because of the need to have carbon dioxide present in the inlet air stream. The carbon dioxide in the gas turbine exhaust allows the high temperature blower, normally used to recirculate and inject exhaust products into the inlet air, to be eliminated.

Hybrid systems have the potential of achieving fossil fuel to electricity conversion efficiencies on the order of 70% and higher. The costs of hybrid systems in dollars per kilowatt are generally higher than say an advanced gas turbine that is available today but not by much. The net energy output over the life of a hybrid topping system is similar to that of a recuperated gas turbine but possibly lower than a high-efficiency simple-cycle machine, depending on the efficiency of the hybrid.

Methodologies to aid in the selection of the hybrid system for future development have to be developed and used consistently. Life cycle analyses (LFA) provide a framework for such selection processes. In particular the concept of net energy output provides a mechanism to assign relative worth to competing concepts.
Analysis of Transonic Flow Fields Inside a High Pressure Ratio Centrifugal Compressor at Design and Off Design Conditions
Authors: Hah Chunill , Krain Hartmut
Published: December 2014

This paper reports on an experimental and numerical study of detailed flow structures in a transonic centrifugal compressor impeller at various operating conditions. Experimental data were obtained from conventional and laser-two-focus measurements inside the impeller. Numerical results were obtained from steady, three-dimensional Reynolds-averaged Navier-Stokes calculations. Both the experimental data and the numerical solutions at the design condition indicate that the flow incidence is high near the hub and flow separation exists near the leading edge. Due to the flow separation, low momentum fluid migrates rapidly to the tip area resulting in further loss generation through increased shock/boundary layer interaction. At a higher flow rate, a second passage shock develops near the leading edge of the splitter blade, further increasing shock/boundary layer interaction.

Numerical studies were performed to explore possible design modifications for better efficiency and higher pressure rise. First, the blade camber near the leading edge was modified to improve the incidence. Second, the blade thickness was reduced by 50 percent. The incidence modification eliminates the flow separation near the leading edge and makes a more uniform flow split between the two channels, resulting in better flow distribution at the impeller exit. The simulated blade thickness reduction, along with the modified incidence, improves the efficiency by about 5 percent and increases the impeller pressure rise from 6.1:1 to 7.1:1.
HSP70 mediates degradation of the p65 subunit of nuclear factor κB to inhibit inflammatory signaling
Authors: Tanaka Takashi , Shibazaki Azusa , Ono Rumiko , Kaisho Tsuneyasu
Published: December 2014

The heat shock protein HSP70 prevents excessive inflammation in mice by mediating the degradation of an NF-κB subunit.
Science Signaling
Podcast: 16 December 2014
Authors: Tu Benjamin P. , VanHook Annalisa M.
Published: December 2014

Npr2 and TORC1 regulate the ability of yeast to synthesize and utilize glutamine when the cells are grown on a nonfermentable carbon source.
Bioprinting Cartilage Scaffolds
Authors: Gough Nancy R.
Published: December 2014

Sheep knee meniscus was regenerated by spatiotemporal delivery of two growth factors embedded in a 3D-printed anatomically correct scaffold.
Prostaglandin Promotes Myelination
Authors: Ferrarelli Leslie K.
Published: December 2014

A feedback loop between axons and Schwann cells may help develop new treatments for patients with peripheral neuropathy.
Potent Plasmodium falciparum Gametocytocidal Activity of Diaminonaphthoquinones, Lead Antimalarial Chemotypes Identified in an Antimalarial Compound Screen
Authors: Tanaka Takeshi Q , Guiguemde W. Armand , Barnett David S. , Maron Maxim I. , Min Jaeki , Connelly Michele C. , Suryadevara Praveen Kumar , Guy R. Kiplin , Williamson Kim C.
Published: December 2014

Forty percent of the world's population is threatened by malaria, which is caused by
Plasmodium
parasites and results in an estimated 200 million clinical cases and 650,000 deaths each year. Drug resistance has been reported for all commonly used antimalarials and has prompted screens to identify new drug candidates. However, many of these new candidates have not been evaluated against the parasite stage responsible for transmission, gametocytes. If
Plasmodium falciparum
gametocytes are not eliminated, patients continue to spread malaria for weeks after asexual parasite clearance. Asymptomatic individuals can also harbor gametocyte burdens sufficient for transmission, and a safe, effective gametocytocidal agent could also be used in community-wide malaria control programs. Here, we identify 15 small molecules with nanomolar activity against late-stage gametocytes. Fourteen are diaminonaphthoquinones (DANQs), and one is a 2-imino-benzo[d]imidazole (IBI). One of the DANQs identified, SJ000030570, is a lead antimalarial candidate. In contrast, 94% of the 650 compounds tested are inactive against late-stage gametocytes. Consistent with the ineffectiveness of most approved antimalarials against gametocytes, of the 19 novel compounds with activity against known anti-asexual-stage targets, only 3 had any strong effect on gametocyte viability. These data demonstrate the distinct biology of the transmission stages and emphasize the importance of screening for gametocytocidal activity. The potent gametocytocidal activity of DANQ and IBI coupled with their efficacy against asexual parasites provides leads for the development of antimalarials with the potential to prevent both the symptoms and the spread of malaria.
Efficacy and Safety of Faldaprevir, Deleobuvir, and Ribavirin in Treatment-Naive Patients with Chronic Hepatitis C Virus Infection and Advanced Liver Fibrosis or Cirrhosis
Authors: Zeuzem Stefan , Soriano Vicente , Asselah Tarik , Gane Edward J. , Bronowicki Jean-Pierre , Angus Peter , Lohse Ansgar W. , Stickel Felix , Müllhaupt Beat , Roberts Stuart , Schuchmann Marcus , Manns Michael , Bourlière Marc , Buti Maria , Stern Jerry O. , Gallivan John-Paul , Voss Florian , Sabo John P. , Böcher Wulf , Mensa Federico J.
Published: December 2014

Patients with advanced hepatic fibrosis or cirrhosis with chronic hepatitis C virus (HCV) infection represent an unmet need. The HCV NS3/4A inhibitor, faldaprevir, was evaluated in combination with the nonnucleoside NS5B inhibitor, deleobuvir, with or without ribavirin in treatment-naive patients with HCV genotype 1 infection in the SOUND-C2 study. Here, the efficacy and safety of this interferon-free regimen in a subset of patients with advanced liver fibrosis, including those with compensated cirrhosis, were assessed. Patients (n= 362) were randomized to once-daily faldaprevir with either twice-daily (BID) or three-times-daily (TID) deleobuvir for 16 (TID16W), 28 (TID28W and BID28W), or 40 (TID40W) weeks with or without ribavirin (TID28W-NR). Patients were classified according to fibrosis stage (F0 to F2 versus F3 to F4) and the presence of cirrhosis (yes/no). In total, 85 (24%) patients had advanced fibrosis/cirrhosis (F3 to F4) and 33 (9%) had cirrhosis. Within each treatment arm, differences in rates of sustained virologic response 12 weeks after completion of treatment (SVR12) between patients with mild to moderate fibrosis (F0 to F2) versus F3 to F4 did not show a consistent pattern and were not statistically significant (63% versus 47% for TID16W, 53% versus 76% for TID28W, 48% versus 67% for TID40W, 70% versus 67% for BID28W, and 40% versus 36% for TID28W-NR, respectively;P> 0.05 for each arm). The most frequent adverse events in patients with/without cirrhosis were gastrointestinal and skin events, which were mostly mild or moderate in intensity. The degree of liver fibrosis did not appear to affect the probability of achieving SVR12 following treatment with the interferon-free regimen of faldaprevir, deleobuvir, and ribavirin. (This study has been registered at ClinicalTrials.gov under registration no. NCT01132313.)
In Vivo
Pharmacokinetics and Pharmacodynamics of the Lantibiotic NAI-107 in a Neutropenic Murine Thigh Infection Model
Authors: Lepak Alexander J. , Marchillo Karen , Craig William A. , Andes David R.
Published: December 2014

NAI-107 is a novel lantibiotic compound with potent
in vitro
activity against Gram-positive bacteria, including methicillin-resistant
Staphylococcus aureus
(MRSA). The purpose of this study was to examine the activity of NAI-107 against
S. aureus
strains, including MRSA, in the neutropenic murine thigh infection model. Serum pharmacokinetics were determined and time-kill studies were performed following administration of single subcutaneous doses of 5, 20, and 80 mg/kg body weight. The dose fractionation included total doses ranging from 1.56 to 400 mg/kg/72 h, divided into 1, 2, 3, or 6 doses. Studies of treatment effects against 9
S. aureus
strains (4 methicillin-susceptible
Staphylococcus aureus
[MSSA] and 5 MRSA) using a 12-h dosing interval and total dose range of 1.56 to 400 mg/kg/72 h were also performed. A maximum effect (
E
max
) model was used to determine the pharmacokinetic/pharmacodynamic (PK/PD) index that best described the dose-response data and to estimate the doses required to achieve a net bacteriostatic dose (SD) and a 1-log reduction in CFU/thigh. The pharmacokinetic studies demonstrated an area under the concentration-time curve (AUC) range of 26.8 to 276 mg · h/liter and half-lives of 4.2 to 8.2 h. MICs ranged from 0.125 to 0.5 μg/ml. The 2 highest single doses produced more than a 2-log kill and prolonged postantibiotic effects (PAEs) ranging from 36 to >72 h. The dose fractionation-response curves were similar, and the AUC/MIC ratio was the most predictive PD index (AUC/MIC, coefficient of determination [
R
2
] = 0.89; maximum concentration of drug in serum [
C
max
]/MIC,
R
2
= 0.79; time [
T
] > MIC,
R
2
= 0.63). A ≥2-log kill was observed against all 9
S. aureus
strains. The total drug 24-h AUC/MIC values associated with stasis and a 1-log kill for the 9
S. aureus
strains were 371 ± 130 and 510 ± 227, respectively. NAI-107 demonstrated concentration-dependent killing and prolonged PAEs. The AUC/MIC ratio was the predictive PD index. Extensive killing was observed for
S. aureus
organisms, independent of the MRSA status. The AUC/MIC target should be useful for the design of clinical dosing regimens.
Postexposure Prophylactic Effect of Hepatitis B Virus (HBV)-Active Antiretroviral Therapy against HBV Infection
Authors: Watanabe Tsunamasa , Hamada-Tsutsumi Susumu , Yokomaku Yoshiyuki , Imamura Junji , Sugiura Wataru , Tanaka Yasuhito
Published: December 2014

Retrospective study indicates that hepatitis B virus (HBV)-active nucleoside (nucleotide) analogues (NAs) used for antiretroviral therapy reduce the incidence of acute HBV infections in human immunodeficiency virus (HIV)-infected patients. Learning from HIV postexposure prophylaxis (PEP), we explored the possibility of using NAs in PEP following HBV exposure, if preexposure prophylaxis is feasible clinically. Using freshly isolated primary human hepatocytes cultured
in vitro
, we analyzed the effect of HBV-active tenofovir and lamivudine in primary HBV infection and also the effect of treatment with these NAs after HBV infection. HBV-active NAs applied from 24 h before inoculation could not prevent the secretion of hepatitis B surface antigen into the culture medium, and cessation of the NAs after inoculation allowed the cells to establish an apparent HBV infection. In contrast, hepatitis B immune globulin was able to prevent HBV infection completely. NA treatment before infection, however, can control the spread of HBV infection, as detected by immunohistochemistry. Practically, starting NA treatment within 2 days of primary HBV infection inhibited viral spread effectively, as well as preexposure treatment. We demonstrated that preexposure NA treatment was not able to prevent the acquisition of HBV infection but prevented viral spread by suppressing the production of mature progeny HBV virions. The effect of postexposure treatment within 2 days was similar to the effect of preexposure treatment, suggesting the possibility of HBV PEP using HBV-active NAs in HIV- and HBV-susceptible high-risk groups.
Overexpression of Penicillin V Acylase from Streptomyces lavendulae and Elucidation of Its Catalytic Residues
Authors: Torres-Bacete Jesús , Hormigo Daniel , Torres-Gúzman Raquel , Arroyo Miguel , Castillón María Pilar , García José Luis , Acebal Carmen , de la Mata Isabel
Published: December 2014

Thepvagene fromStreptomyces lavendulaeATCC 13664, encoding a novel penicillin V acylase (SlPVA), has been isolated and characterized. The gene encodes an inactive precursor protein containing a secretion signal peptide that is activated by two internal autoproteolytic cleavages that release a 25-amino-acid linker peptide and two large domains of 18.79 kDa (α-subunit) and 60.09 kDa (β-subunit). Based on sequence alignments and the three-dimensional model ofSlPVA, the enzyme contains a hydrophobic pocket involved in catalytic activity, including Serβ1, Hisβ23, Valβ70, and Asnβ272, which were confirmed by site-directed mutagenesis studies. The heterologous expression ofpvainS. lividansled to the production of an extracellularly homogeneous heterodimeric enzyme at a 5-fold higher concentration (959 IU/liter) than in the original host and in a considerably shorter time. According to the catalytic properties ofSlPVA, the enzyme must be classified as a new member of the Ntn-hydrolase superfamily, which belongs to a novel subfamily of acylases that recognize substrates with long hydrophobic acyl chains and have biotechnological applications in semisynthetic antifungal production.
Role of Plasmids in Lactobacillus brevis BSO 464 Hop Tolerance and Beer Spoilage
Authors: Bergsveinson Jordyn , Baecker Nina , Pittet Vanessa , Ziola Barry
Published: December 2014

Specific isolates of lactic acid bacteria (LAB) can grow in the harsh beer environment, thus posing a threat to brew quality and the economic success of breweries worldwide. Plasmid-localized genes, such as
horA
,
horC
, and
hitA
, have been suggested to confer hop tolerance, a trait required for LAB survival in beer. The presence and expression of these genes among LAB, however, do not universally correlate with the ability to grow in beer. Genome sequencing of the virulent beer spoilage organism
Lactobacillus brevis
BSO 464 revealed the presence of eight plasmids, with plasmids 1, 2, and 3 containing
horA
,
horC
, and
hitA
, respectively. To investigate the roles that these and the other five plasmids play in
L. brevis
BSO 464 growth in beer, plasmid curing with novobiocin was used to derive 10 plasmid variants. Multiplex PCRs were utilized to determine the presence or absence of each plasmid, and how plasmid loss affected hop tolerance and growth in degassed (noncarbonated) beer was assessed. Loss of three of the eight plasmids was found to affect hop tolerance and growth in beer. Loss of plasmid 2 (
horC
and 28 other genes) had the most dramatic effect, with loss of plasmid 4 (120 genes) and plasmid 8 (47 genes) having significant, but smaller, impacts. These results support the contention that genes on mobile genetic elements are essential for bacterial growth in beer and that beer spoilage ability is not dependent solely on the three previously described hop tolerance genes or on the chromosome of a beer spoilage LAB isolate.