bluuebunny/crossref_metadata_2025 huggingface dataset:
Montanide ISA 71 VG is Advantageous to Freund's Adjuvant in Immunization Against S. aureus Infection of Mice
Authors: Klimka A. , Michels L. , Glowalla E. , Tosetti B. , Krönke M. , Krut O.
Published: February 2015

The enormous capacity of Staphylococcus aureus to acquire antibiotic resistance makes it a permanent task to search for and to develop new anti‐infectives. One of the possible approaches is the early active immunization of risk patients and animal stocks to prevent S. aureus infections. Based on a S. aureus proteome screen with S. aureus‐specific human antiserum, we have previously identified several anchorless cell wall proteins to be used as novel vaccine candidates. To develop an efficient anti‐S. aureus vaccine, the supplemented adjuvants Montanide™ ISA 71 VG and ISA 206 were compared to Freund's adjuvant in terms of handling, induction of cytokine profile, triggering antigen‐specific immunoglobulin production of different IgG subclasses and provision of increased survival rates in our S. aureus sepsis mouse model. Immunization with ISA 71 VG in comparison with Freund's adjuvant induced slightly delayed but comparably strong increase of antigen‐specific antibody titres and conferred protective effect against S. aureus challenge. In contrast using ISA 206 as adjuvant, significantly lower IgG titres and consequently, no protective effect against S. aureus infection were observed. Handling and tolerability of the Montanide is superior to Freund's adjuvant. Montanide™ ISA 71 VG can serve as an effective adjuvant replacement for Freund's adjuvant in research with a prospective usage in animal and human vaccines against bacterial pathogens.
GALILEO STILL GOES TO JAIL: CONFLICT MODEL PERSISTENCE WITHIN INTRODUCTORY ANTHROPOLOGY MATERIALS
Authors: Aechtner Thomas
Published: February 2015

Historians have long since rejected the dubious assertions of the conflict model, with its narratives of perennial religion versus science combat. Nonetheless, this theory persists in various academic disciplines, and it is still presented to university students as the authoritative historical account of religion–science interactions. Cases of this can be identified within modern anthropology textbooks and reference materials, which often recapitulate claims once made by John W. Draper and Andrew D. White. This article examines 21st‐century introductory anthropology publications, demonstrating how such works perpetuate religion–science myths and the notion that history has been replete with inevitable religion versus science warfare. In particular, this study reveals how such introductory materials propagate discord narratives associated with the Scientific Revolution and the Enlightenment. Affiliated with these anecdotes are oversimplified accounts of religious responses to heliocentrism and evolutionary theory, as well as claims that science has invariably led to the usurpation of religious belief and secularization from Galileo onwards.
Vascular and circulating microRNAs in renal ischaemia–reperfusion injury
Authors: Lorenzen Johan M.
Published: February 2015

Ischaemia–reperfusion (I/R) injury of the kidney is a major cause of acute kidney injury. It may result in worsening or even loss of organ function. Transient occlusion of the renal vessel is followed by a reperfusion period, which induces further tissue damage by release of reactive oxygen and nitrogen species. Ischaemia–reperfusion injury of the kidney may be associated with surgical interventions in native kidneys and is also a common and unavoidable phenomenon in kidney transplantation. MicroRNAs are fascinating modulators of gene expression. They are capable of post‐transcriptional silencing of genetic information by targeting the 3′‐untranslated region of mRNAs, culminating in a suppression of protein synthesis or an increase in mRNA degradation. They might therefore be useful diagnostic and therapeutic entities during renal I/R injury; for instance, miR‐21 has been shown to be enriched in kidney tissue in mice and humans with acute kidney injury. Interestingly, most recent literature suggests that modulation of vascular microRNAs might result in the amelioration of kidney function during renal I/R injury. To that end, miR‐126 and miR‐24, which have been demonstrated to be highly enriched in endothelial cells, were therapeutically modulated and shown to ameliorate renal I/R injury in mice. MicroRNAs in plasma, urine or enriched in microvesicles have been shown to serve as non‐invasive tools for disease monitoring and to have potential impact on downstream mechanisms in recipient cells. This review highlights the latest developments regarding the role of microRNAs in renal I/R injury.
A New Approach to the Challenge of Machinery Prognostics
Authors: Hansen Robert J. , Hall David L. , Kurtz Stewart K.
Published: February 2015

Current generation mechanical diagnostic equipment is designed to identify individual events or trends in the output of sensors mounted on a mechanical component, subsystem, or system. Such equipment can provide a useful indication that a failure condition may be developing, but it cannot provide reliable predictions of the remaining safe or operational life. Typically, these diagnostic systems simply compare the output of individual sensors against a priori thresholds to establish a measure of the system’s health. Two problems result from this approach: (1) there is no advantage taken of possible synergy among the sensors, i.e., the determination of health is one dimensional; and (2) the diagnosis provides only a statement regarding the current equipment health, but docs not provide a prediction of the time remaining to failure. This often leads to an operational environment in which diagnostic equipment outputs arc either ignored because of frequent false alarms or frequent (and costly) time-based preventive maintenance is performed to avoid hazardous failures. This paper describes a new approach to the development of a more robust diagnosis and prognostic capability. It is based on the fusion of sensor-based and model-based information. Sensor-based information is the essence of current diagnostic systems. Model-based information combines dynamic models of individual mechanical components with micromechanical models of relevant failure mechanisms, such as fracture and crack propagation. These micromechanical models must account for initial flaw size distribution and other microstructural parameters describing initial component condition.

A specific application of this approach is addressed, the diagnosis of mechanical failure in meshing gears. Four specific issues are considered: (a) how to couple a validated numerical simulation of gear transmission error (due to tooth spacing irregularity, contour irregularity, or material inhomogeneity) with physically and empirically-based descriptions of fatigue crack growth to predict a failure precursor signature at the component level; (b) how to predict the manifestation of this signature at the subsystem or system level where sensors are located; (c) how to fuse this model-based information with the corresponding sensor-based information to predict remaining safe or operational life of a gear; and (d) issues associated with extending this methodology to bearings and other rotating machinery components.
Retrofitting Turbocompressor Unit and Station Controls
Authors: Leuw Jack P.
Published: February 2015

For TransCanada PipeLines, the need to retrofit station and compressor unit controls has been driven by the requirements to improve reliability, availability and cost and difficulties associated with interfacing new digital control systems with existing analog systems. TransCanada’s massive four year expansion program has exacerbated this need.

TransCanada’s turbo compressor controls are becoming obsolete, they are difficult to troubleshoot and maintain, do not control a unit as effectively as newer digital controls and do not have adequate operator or technician interfaces and diagnostics.

This paper describes TransCanada PipeLines reasons and experiences in retrofitting state-of-the-art digital controls in a cost effective manner while minimizing service interruptions.
A Cogeneration Plant Based on a Steam Injection Gas Turbine With Recovery of the Water Injected: Design Criteria and Initial Operating Experience
Authors: Macchi Ennio , Poggio Aurelio
Published: February 2015

The idea of re-injecting into a gas turbine cycle the steam generated by the heat recovery steam generator (HRSG) is a well-established practice, especially in small-medium size cogeneration plants operating under variable heat demand. Power augmentation, electrical efficiency increase, NOx reduction and operating flexibility are the most obvious advantages brought about by steam injection. On the other hand, the discharge to the ambient of the injected steam has two major drawbacks: (i) a relevant water consumption and (ii) the large thermal loss related to the latent heat of steam. The addition of a recuperator downstream of the HRSG, whereby steam condensation takes place, can solve both problems, by achieving very high first-law efficiencies (over 100%, if reference is made to the lower heating value) and the integral recovery of water. The present paper describes the design philosophy and the operational experience of a cogeneration plant where such a condensation is accomplished. To the Authors’s knowledge, it is the first time in the world that this is achieved with gas turbine exhausts. The plant is located inside the “CARROZZERIA BERTONE”, a car manufacturing factory near Turin, Italy. It was designed to fulfill all the energy needs of the factory: it supplies all the electricity, steam and hot water required by the industrial process and during peaking hours, sells excess electricity to the national grid, at special increased tariffs offered to energy-saving plants in Italy. The plant erection (including the recuperator/condenser) was completed in December 1992; commercial operation began in February 1993.
Dynamic Response of a Cracked Rotor With Some Comments on Crack Detection
Authors: Meng G. , Hahn Eric J.
Published: February 2015

By considering time dependent terms as external excitation forces, the approximate dynamic response of a cracked horizontal rotor is analysed theoretically and numerically. The solution is good for small cracks and small vibrations in the stable operating range. For each steady state harmonic component the forward and backward whirl amplitudes, the shape and orientation of the elliptic orbit and the amplitude and phase of the response signals arc analysed, taking into account the effect of crack size, crack location, rotor speed and unbalance. It is found that the crack causes backward whirl, the amplitude of which increases with the crack. For a cracked rotor, the response orbit for each harmonic component is an ellipse, the shape and orientation of which depends on the crack size. The influence of the crack on the synchronous response of the system can be regarded as an additional unbalance whereupon, depending on the speed and the crack location, the response amplitude differs from that of the uncracked rotor. The nonsynchronous response provides evidence of crack in the sub-critical range, but is too small to be detected in the supercritical range. Possibilities for crack detection over the full speed range include the additional average (the constant) response component, the backward whirl of the response, the ellipticity of the orbit, the angle between the major axis and the vertical axis and the phase angle difference between vertical and horizontal vibration signals.
Experimental and Numerical Investigation of Stator Exit Flow Field of an Automotive Torque Converter
Authors: Marathe B. V. , Lakshminarayana B. , Dong Y.
Published: February 2015

The objective of this investigation is to understand the nature of the complex flow field inside each element of the torque converter through a systematic experimental and numerical investigation of the flow field. A miniature five-hole probe was used to acquire the data at the exit of the stat or at several operating conditions. The flow field is found to be highly three-dimensional with substantial flow deviations, and secondary flow at the exit of the stator. The secondary flow structure, caused by the upstream radial variation of the through flow, induces flow overturning near the core. Flow separation near the shell causes flow underturning in this region. The rate of decay of stator wake is found to be slower than that observed in the wakes of axial flow turbine nozzles. The flow predictions by a Navier-Stokes code are in good agreement with the pressure and the flow field measured at the exit of the stator at the design and the off-design conditions.
The Synchronous Instability of a Compressor Rotor due to Bearing Journal Differential Heating
Authors: de Jongh F. M. , Morton P. G.
Published: February 2015

The paper describes a synchronous vibration instability problem encountered on a centrifugal compressor with oil lubricated bearings. The problem was solved by modification of the compressor rotor, however the root cause was not completely understood at that time. A possible explanation was based on a theory which suggested differential heating of the bearing journals. It was decided to verify ibis theory by experiments. Therefore a test rotor was designed with identical rotor dynamic characteristics to those of the compressor rotor. In order to fill a gap in the published research on bearing thermohydrodynamics an experimental technique was devised to measure the surface temperature variations around one of the journals of this rotor. The dependence of significant temperature differentials across the journal upon its orbit was confirmed.
Velocity Measurements Downstream of the Impellers in a Multistage Centrifugal Blower
Authors: Amulfi G. L. , Micheli D. , Pinamonti P.
Published: February 2015

The paper presents the results of an experimental investigation on a four-stage centrifugal blower, having the aim of obtaining an accurate description of the flow field behind the impellers in several operative conditions and for different geometrical configurations. Actually, the test plant allows to change the turbomachinery characteristics assembling one, two, three or four stages and three different types of diffusers.

In this first research step, the blower has been tested in the four-stage vaneless diffuser configuration.

The unsteady flow field behind the impellers and in the diffusers has been measured by means of a hot-wire anemometer. A Phase Locked Ensemble Averaging Technique has been utilised to obtain the relative flow field from the instantaneous signals of the stationary hot-wire probes.

Several detailed measurements sets have been performed using both single and crossed hot-wire probe, to obtain the velocity vectors and turbulence trends, just behind the blower impellers and in several radial positions of the vaneless diffusers. These measurements have been done at different flow rate conditions, covering unsteady flow rate phenomena (rotating stall) too.

The results obtained allowed to get a detailed flow field analysis in the multistage centrifugal blower, in relation to the geometrical configuration and to the differing operating conditions.
Off Design Flow Measurements in a Centrifugal Compressor Vaneless Diffuser
Authors: Pinarbasi Ali , Johnson Mark W.
Published: February 2015

Detailed measurements have been taken of the 3-d velocity field within the vaneless diffuser af a backswept law speed centrifugal compressor using hat wire anemometry. A 16% below and an 11% above design flowrate were used in the present study. Results at both flowrates show how the blade wake mixes out more rapidly than the passage wake. Strong secondary flows inherited from the impeller at the higher flowrate delay the mixing out of the circumferential velocity variations, but at both flowrates these circumferential variations are negligible at the last measurement station. The measured tangential/radial flaw angle is used to recommend optimum values far the vaneless space and vane angle for design of a vaned diffuser.
Simulation of Cooling Systems in Gas Turbines
Authors: Ebenhoch G. , Speer T. M.
Published: February 2015

The design of cooling systems for gas turbine engine blades and vanes calls for efficient simulation programs. The main purpose of the described program is to determine the complete boundary condition at the coolant side to support a temperature calculation for the solid.

For the simulation of convection and heat pick up of the coolant flow, pressure loss, and further effects to be found in a rotating frame, the cooling systems are represented by networks of nodes and flow elements. Within each flow element the fluid flow is modelled by a system of ordinary differential equations based on the one-dimensional conservation of mass, momentum, and energy. In this respect, the computer program differs from many other network computation programs.

Concerning cooling configurations in rotating systems, the solution for a single flow element or the entire flow system is not guaranteed to be unique. This is due to rotational forces In combination with heat transfer and causes considerable computational difficulties which can be overcome by a special path following method in which the angular velocity is selected as the parameter of homotopy.

Results of the program are compared with measurements for three applications.
The Effect of High Freestream Turbulence on Film Cooling Effectiveness
Authors: Bons Jeffrey P. , MacArthur Charles D. , Rivir Richard B.
Published: February 2015

This study investigated the adiabatic wall cooling effectiveness of a single row of film cooling boles injecting into a turbulent flat plate boundary layer below a turbulent, zero pressure gradient freestream. Levels of freestream turbulence (Tu) up to 17.4% were generated using a method which simulates conditions at a gas turbine combustor exit. Film cooling was injected from a single row of five 35 degree slant-hole injectors (length/diameter = 3.5. pitch/diameter = 3.0) at blowing ratios from 0.55 to 1.85 and at a nearly constant density ratio (coolant density/freestream density) of 0.95. Film cooling effectiveness data is presented for Tu levels ranging from 0.9% to 17% at a constant freestream Reynolds number based on injection hole diameter of 19000. Results show that elevated levels of freestream turbulence reduce film cooling effectiveness by up to 70% in the region directly downstream of the injection hole due to enhanced mixing. At the same time, high freestream turbulence also produces a 50–100% increase in film cooling effectiveness in the region between injection boles. This is due to accelerated spanwise diffusion of the cooling fluid, which also produces an earlier merger of the coolant jets from adjacent holes.
A Neural Network Based Active Rotor Controller With Output Feedback
Authors: Ma Rwei-Ping , Sinha Alok
Published: February 2015

A neural network based output feedback control system has been developed to optimally suppress rotor vibration caused by the rotor unbalance. The unique feature of this new vibration absorber is its ability to optimally control vibration for a wide range of rotor speeds. Numerical examples dealing with a multi-degree-of-freedom rigid rotor supported by radial magnetic bearings are presented to verify the advantages of this novel neural network based output feedback active vibration absorber.
Numerical Investigation of Unsteady Incompressible 3D Turbulent Flow and Torque Transmission in Fluid Couplings
Authors: Bal L. , Kost A. , Fiebig M. , Mitra N. K.
Published: February 2015

The adequate understanding of the flow structure in fluid couplings is necessary for the optimized design of such devices. Up to now, empiricism plays an important role in design. Detailed studies of the unsteady 3D flow and torque transmission in fluid couplings were rarely carried out. In this paper the unsteady Reynolds time-averaged Navier-Stokes equations coupled with the k-ε model have been solved by a finite-volume method. The calculations were done by using boundary-fitted grids with non-staggered variable arrangement for a rotating frame of reference. Flow structures in fluid couplings were obtained. The results give insights into the physical process of torque transmission. A comparsion of the calculated torque transimission with the experimental measurements in the literature shows good agreement for low slip.
Computation of Unsteady 3D Flow and Torque Transmission in Hydrodynamic Couplings
Authors: Kost A. , Mitra N. K. , Fiebig M.
Published: February 2015

For the optimized design of hydrodynamic or fluid couplings an adequate understanding of the flow field in such devices is necessary. In a hydrodynamic coupling, torque is transmitted by fluid circulation due to a speed differential between the rotating pump impeller and a matching turbine runner. Detailed studies of the unsteady 3D flow and torque transmission in fluid couplings are reported here. A finite-volume method with non-staggered variable arrangement is used to solve the unsteady Navier-Stokes equations on boundary-fitted grids and for a rotating frame of reference. The results give further insights into the physical process of torque transmission and allow important conclusions for the design of hydrodynamic couplings.
Design and Development of the WR-21 Intercooled Recuperated (ICR) Marine Gas Turbine
Authors: Shepard Sam B. , Bowen Thomas L. , Chiprich John M.
Published: February 2015

The U.S. Navy is developing an intercooled Recuperated (ICR) marine gas turbine, designated the WR-21, for propulsion of future surface ships. The objectives of this development program and the key technical requirements are summarized. The design of the WR-21 is described in considerable, detail. Meeting all of the design requirements for performance, space, weight, reliability, maintainability and life has been challenging. Numerous design tradeoffs and iterations have been performed to optimize the design within the constraints imposed in the ICR technical specification. Integration of the WR-21 engine into the DDG51 Flight IIA ship, which is the U.S. Navy’s first application, has influenced the WR-21 design. This paper discusses the aspects of the DDG-51 application that were factored into the design of the ICR engine in order to reduce installation costs.
Experimental Identification of Linearized Oil Film Coefficients of Cylindrical and Tilting Pad Bearings
Authors: Arumugam P. , Swarnamani S. , Prabhu B. S.
Published: February 2015

The dynamic behavior of the rotating machinery supported by the hydrodynamic journal bearings is significantly influenced by the dynamic characteristics of the oil-film. In the present work an efficient identification method is used to identify the stiffness and damping coefficients of the tilting pad and cylindrical journal bearings of flexible rotor-bearing system. The method uses FRFs (Frequency Response Functions) obtained by the measurements and the finite element method. The accuracy and feasibility of the method were tested and demonstrated by theoretical simulation. The possible effects of oil-film inertia is also verified by the theoretical simulation. The method can be further extended to identify twelve linearized oil-film coefficients.
Active Control of Dynamic Bearing Loads in Rotating Machinery Using Non-Invasive Measurements
Authors: Clark William W. , Kim Joo-Hyung , Marangoni Roy D.
Published: February 2015

A new technique for measuring and actively controlling dynamic bearing loads in rotating machinery is presented. Bearing loads are estimated using the Deflection-Coefficient Method, a technique which does not rely on a full system model, and which applies commonly-used shaft-deflection measurement equipment to obtain estimates of bearing loads. The estimated bearing load is used as an error signal in an adaptive feedforward disturbance rejection controller. The result is a control system which can selectively minimize dynamic bearing loads in real time in rotating machinery systems. The method is applied to a numerical model of a typical rotating machinery system to suppress dynamic reaction forces at bearing supports.
Application of a Heat Flux/Calorimeter-Based Method to Assess the Effect of Turbulence on Turbine Airfoil Heat Transfer
Authors: Glazer B. , Moon H. K. , Zhang L. , Camci C.
Published: February 2015

The accurate prediction of turbine airfoil metal temperatures remains one of the critical issues in the development of high efficiency engines. Free-stream and wake-generated turbulence plays a major role in the external heat transfer of the cooled airfoils. Turbulence simulation experimental methodology has been employed to provide external heat load similarity between the engine and the elevated temperature cascade rig conditions. The methodology is based on simulation of turbulence intensity to produce equal mainstream heat transfer effects at the stagnation region of the airfoil in both engine and cascade environments. A recently completed fill-scale hot cascade facility provides a realistic simulation of an actual engine in terms of gas-side and coolant-side heat transfer. Significant attention is paid to emulating the free-stream turbulence environment of an actual engine. Indirect measurements of free-stream turbulence are performed with a custom designed calorimetric probe and heat flux probe. Well established stagnation point heat transfer correlations are used to deduce the free-stream turbulence intensity. The cascade rig provides a detailed map of local cooling effectiveness along the airfoil, which can be controlled by varying gas-side and coolant-side convective heat transfer. Results of the experimental study demonstrate the practical benefits of this methodology for more accurate evaluation of the airfoil external heat transfer, particularly when a combustor system is redefined or an engine is uprated and the airfoil cooling system has to be modified.
Thorium Cycle in High Temperature Gas-Cooled Gas Turbine Reactors (HTG-GT) Using Highly Enriched Uranium Obtained From the Dismantling of Nuclear Weapons
Authors: Cerullo Nicola , Guglielmini Giovanni , Di Pietro A.
Published: February 2015

The closed thorium fuel cycle is based on the use of fissile U-233 produced by the thorium fertilization in the original fuel element without any refabrication action, which is very difficult, due to the high activity of Thorium activated products.

The need of a consistent amount of fissile material for beginning the U-Th cycle activity, in order to sustain the Thorium conversion reactions, requires an high initial U-235 enrichment. This condition, due to high investment costs, stopped, in the last years, any initiative in this field.

The end of the cold war and the disarmament agreements pose the problem of the use of military grade fissile materials resulting from the dismantling of nuclear weapons both Russian and American.

In this paper the problem is analyzed and a High Temperature Gas-cooled Gas Turbine (HTG-GT) reactor, using a nuclear U-Th fuel cycle utilizing military grade highly enriched uranium, is proposed.
Flow Field Investigation in the Exit Region of a Radial Inflow Turbine Using LDV
Authors: Murugan D. Muthuvel , Tabakoff Widen , Hamed Awatef
Published: February 2015

Detailed flow investigation in the downstream region of a radial inflow turbine has been performed using a three component Laser Doppler Velocimetry. The flow velocities are measured in the exit region of the turbine at off-design operating conditions. The results are presented as contour and vector plots of mean velocities, flow angles and turbulent stresses. The measured parameters are correlated to the rotor blade rotation to observe any periodic nature of the flow. The measurements reveal a complex flow pattern near the tip region at the rotor exit due to the interaction of the tip clearance flow. The degree of swirl of the flow near the tip region at the rotor exit is observed to be high due to the gross under turning of the flow near the tip region. The effect of the rotor on the exit flow field is observed in the proximity of the rotor exit.
Wall Proximity Effects in Pneumatic Measurement of Turbomachinery Flows
Authors: Smout Peter D. , Ivey Paul C.
Published: February 2015

Conventional 3-hole wedge probes fail to measure the correct static pressure when operating in close proximity to a wall or boundary through which the probe is inserted. The free stream pressure near the outer wall of a turbomachine annulus may be over indicated by upto 20% of the dynamic head.

This paper reports a factorial experiment in which the effects of probe wedge angle, stem length, stem shape, flow yaw and pitch angles on this so-called ‘wall proximity effect’ are quantified at representative flow Mach numbers and turbulence intensities. For a given wedge angle, the probe stem length and Mach number are shown to be statistically the most significant of the tested variables. Wall proximity effect is also shown to be influenced by the probe pitch angle, but is largely independent of yaw angle and free stream turbulence intensity.
Design Considerations for a State of the Art Development Test Cell for Aeroengines
Authors: Stevens Roger C. , Piggott David J.
Published: February 2015

A number of new considerations are beginning to influence the design of development aeroengine test facilities due to technological, environmental and regulatory developments. Whilst the technological developments are of an evolutionary nature, the other developments, for example, the imposition of mandatory environmental noise constraints and the requirement to perform in-cell reverse thrust testing for early Extended Twin Operations certification, may impose step changes in test facility design. This paper examines the influence of these new developments on test cell design and describes how the new requirements were integrated with the traditional considerations in the design of a new “sea level” Test Bed in Derby, UK.
Prediction of Turbine Blade Passage Heat Transfer Using a Zero and a Two-Equation Turbulence Model
Authors: Ameri Ali A. , Arnone Andrea
Published: February 2015

Predictions of the heat transfer rates on the hot surfaces of a turbine cascade blade passage as influenced by the turbulence models was examined. A zero equation turbulence model supplemented by a bypass transition model and a two equation low Reynolds number model were chosen for this study. The experimental data of Graziani et. al. were used for comparison. The comparisons suggest that at least for the experimental data considered in this work the use of a two-equation model does not provide an overall more accurate solution than the zero equation model. This conclusion is strengthened if one takes into account the relative economy of computations with the algebraic model.
A Rotary Heat Exchanger for Automotive and Other Ground Based Gas Turbines
Authors: Day J. Paul
Published: February 2015

This paper discusses the ongoing development of a ceramic regenerator for a high temperature automotive gas turbine engine sponsored by the U.S. Department of Energy.

The ceramic gas turbine has a steady state gas inlet temperature of 774°C and a 982°C peak acceleration temperature which precludes the use of metallic discs. Ceramic materials have successfully operated to 982°C, with a peak acceleration temperature exceeding 1093°C. Ceramic regenerator temperature capability is currently limited by seal tribomaterial properties.

The requirements of the ceramic regenerator, ceramic disc materials being evaluated, and the processing of these materials to obtain the required strength, chemical resistance, cost, including quality control are discussed. The status of the extruded regenerator program to date will also be described.
Rim Sealing of Rotor-Stator Wheelspaces in the Presence of External Flow
Authors: Chew J. W. , Green T. , Turner A. B.
Published: February 2015

Sealing of the cavity formed between a rotating disc and a stator with an asymmetric external flow is considered. In these circumstances circumferential pressure variations in the external flow and the pumping action of the disc may draw fluid into the cavity. Gas concentration measurements, showing this effect, have been obtained from a model experiment with a simple axial clearance seal. In the experiment, guide vanes, fitted upstream of the rim seal, generate an asymmetric external flow. The measurements are shown to be in reasonable agreement with three-dimensional computational fluid dynamics (CFD) calculations and are also compared with more elementary models. The CFD results give further insight into the effects of ingestion within the cavity.
Spa “Mashproekt” Reversible Power Turbines
Authors: Romanov V. I. , Zhiritsky O. G. , Belyaev V. E. , Lupandin V. V.
Published: February 2015

The gas turbine engines incorporating reversible power turbines have been designed and developed by the MASHPROEKT Scientific and Production Association (SPA). They are widely used for powering the former USSR (Russia) Navy ships, as well as the CAPITAN SMIRNOV Ro-Ro type cargo vessels. The GT 3000, GT 8000, GT 15000 and D59 gas turbine engines comprise reversible power turbines. Compared with other marine reversible devices (reversing reduction gear, controllable pitch propeller), the reversible gas turbine has advantages in maneuvrability, reliability and design simplicity. This paper presents specific design features of the SPA MASHPROEKT reversible power turbines.
Design and Test of a Small, High Pressure Ratio Radial Turbine
Authors: Jones Anthony C.
Published: February 2015

This paper describes the aerodynamic design and rig test of a radial inflow turbine having a rotor tip diameter of 4.58 inches. The single stage turbine was designed for use in the Sundstrand Power Systems (SPS) T-100 Multipurpose Small Power Unit (MPSPU). The T-100 is a small, single-shaft, simple-cycle gas turbine engine intended for airborne, vehicular, and ground based auxiliary power application. Nominal power output of the engine is 50 hp, with growth capability to 100 hp with minimal modification.

Aggressive specific fuel consumption goals for the engine led to a demanding turbine efficiency target of 87% total to static, referred to exhaust diffuser exit, at an expansion ratio of 5.7:1 and a flow rate of 0.73 lb/s.

Details of the design approach are given, together with test results from the turbodrive rig. The results include overall stage mapping and rotor exit surveys.
Pressure Measurements in the Blade Passages of a Radial Inflow Turbine
Authors: Srinivasa P. R. Naga , Venkatrayulu N. , Ramachandra R.
Published: February 2015

Pressure measurements were carried out in an unshrouded radial inflow turbine in a closed circuit test facility, at nozzle inlet and exit, vis-a-vis rotor exit. Besides, blade surface pressures on the nozzle and rotor blades, wall static pressures on the back plate of nozzle and rotor blade passages, shroud static pressure variation along the casing from rotor inlet to exit were also measured for four different mass flows through the turbine. The increase of nozzle exit angle resulted in an increase of the stator loss coefficient at any mass flow rate. Rotor pressure measurements showed an adverse pressure gradient on the suction surface close to the hub region. Compared to the total pressure levels near the hub and shroud of the rotor passage, the pressure was higher at the mid height. The swirl at the rotor exit is somewhat stronger near the tip region as compared to the hub and the average loss is more towards the tip.
Stall Inception Behavior in a Centrifugal Compressor
Authors: Chen J. , Hasemann H. , Shi Li , Rautenberg M.
Published: February 2015

In studying the stall inception process, while most results were reported for axial compressors, the present paper investigates the stall inception behavior typified in a centrifugal compressor. The test was conducted with a radially-bladed impeller and in a speed range of 8000–14000 rpm. Extensive pressure transducers were used to study the frequency characteristics of emerging stall waves.

As a result, stall precursors were detected, all with clear mode seen from frequency analysis, but very much different by the behavior of their onset, existence and development. The first type, called the stable-amplitude precursor, exists in a time range of about 20–90 impeller revolutions, with unpredictable and different frequencies from the fully developed stall. Such perturbation, once appeared, may grow to the full stall straightly, or may appear for several times intermittently before finally reaching the full stall, thus acting as a pre-precursor in the whole stall inception process. The second type is the progressive-amplitude precursor when the perturbation emerges as long as 270 impeller revolutions prior to and progressively develops into the full amplitude stall with no change of frequency during this process. The third type, which has been detected for the rotating stall with evident reverse flow symptom, is the precursive pressure increase accompanied with the stable- or progressive-amplitude perturbation, before the full stall establishes. The inception process is also examined for surge during the test of the same compressor, in which the existence of rotating stall in front of every surge cycle and the low frequency precursive wave before surge cycles is demonstrated. Finally, the blade passage frequencies for precursor pressure signals are further analysed to address the monitoring strategy during stall inception process.
Am Experimental Investigation of the Rib Surface-Averaged Heat Transfer Coefficient in a Rib-Roughened Square Passage
Authors: Taslim M. E. , Wadsworth C. M.
Published: February 2015

Turbine blade cooling, a common practice in modern aircraft engines, is accomplished, among other methods, by passing the cooling air through an often serpentine passage in the core of the blade. Furthermore, to enhance the heat transfer coefficient, these passages are roughened with rib-shaped turbulence promoters (turbulators). Considerable data are available on the heat transfer coefficient on the passage surface between the ribs. However, the heat transfer coefficients on the surface of the ribs themselves have not been investigated to the same extent. In small aircraft engines with small cooling passages and relatively large ribs, the rib surfaces comprise a large portion of the passage heat transfer area. Therefore, an accurate account of the heat transfer coefficient on the rib surfaces is critical in the overall design of the blade cooling system.

The objective of this experimental investigation was to conduct a series of thirteen tests to measure the rib surface-averaged heat transfer coefficient, in a square duct roughened with staggered 90° ribs. To investigate the effects that blockage ratio, e/Dh, and pitch-to-height ratio, S/e, have on hrib and passage friction factor, three rib geometries corresponding to blockage ratios of 0.133. 0.167 and 0.25 were tested for pitch-to-height ratios of 5, 7, 8.5 and 10. Comparisons were made between the rib average heat transfer coefficient and that on the wall surface between two ribs, hflor, reported previously. Heat transfer coefficients of the upstream-most rib and that of a typical rib located in the middle of the rib-roughened region of the passage wall were also compared.

It is concluded that:

1) the rib average heat transfer coefficient is much higher than that for the area between the ribs,

2) similar to the heat transfer coefficient on the surface between the ribs, the average rib heat transfer coefficient increases with the blockage ratio,

3) a pitch-to-height ratios of 8.5 consistently produced the highest rib average heat transfer coefficients amongst all tested,

4) under otherwise identical conditions, ribs in upstream-most position produced lower heat transfer coefficients than the mid-channel positions,

5) the upstream-most rib average heat transfer coefficients decreased with the blockage ratio, and

6) thermal performance decreased with increased blockage ratio. While a pitch-to-height ratio of 8.5 and 10 had the highest thermal performance for the smallest rib geometry, thermal performance of high blockage ribs did not change significantly with the pitch-to-height ratio.
Experimental Heat Transfer and Friction in Channels Roughened With Angled, V-Shaped and Discrete Ribs on Two Opposite Walls
Authors: Taslim M. E. , Li T. , Kercher D. M.
Published: February 2015

Experimental investigations have shown that the enhancement in heat transfer coefficients for air flow in a channel roughened with angled ribs is on the average higher than that roughened with 90° ribs of the same geometry. Secondary flows generated by the angled ribs are believed to be responsible for these higher heat transfer coefficients. These secondary flows also create a spanwise variation in heat transfer coefficient on the roughened wall with high levels of heat transfer coefficient at one end of the rib and low levels at the other end. In an effort to basically double the area of high heat transfer coefficients, the angled rib is broken at the center to form a V-shape rib and tests are conducted to investigate the resulting heat transfer coefficients and friction factors. Three different square rib geometries, corresponding to blockage ratios of 0.083, 0.125 and 0.167, with a fixed pitch-to-height ratio of 10, mounted on two opposite walls of a square channel in a staggered configuration are tested in a stationary channel for 5000 < Re < 30000. Heat transfer coefficients, friction factors and thermal performances are compared with those of 90°, 45° and discrete angled ribs. The V-shape ribs are tested for both pointing upstream and downstream of the main flow. Test results show that:

a) 90° ribs represent the lowest thermal performance, based on the same pumping power, and is essentially the same for the 2:1 change in blockage ratio, b) low blockage ratio (e/Dh =0.083) V-shape ribs pointing downstream produced the highest heat transfer enhancement and friction factors. Amongst all other geometries with blockage ratios of 0.125 and 0.167, 45° ribs showed the highest heat transfer enhancements with friction factors less than those of V-shape ribs, c) thermal performance of 45° ribs and the lowest blockage discrete ribs are among the highest of the geometries tested in this investigation, and, d) discrete angled ribs, although inferior to 45° and V-shape ribs, produce much higher heat transfer coefficients and lower friction factors compared to 90° ribs.
Heat Transfer Measurements on Turbine Airfoils Using the Naphthalene Sublimation Technique
Authors: Häring M. , Bölcs A. , Harasgama S. P. , Richter J.
Published: February 2015

Results of heat transfer measurements on a typical turbine blade and a vane in a linear cascade have been obtained using the naphthalene sublimation technique. The tests on the vane were performed at the nominal flow angle, whereas for the turbine blade an off-design angle was chosen to study the influence of a separation bubble on the heat transfer. The exit Mach number was varied from M2=0.2 to 0.4 and the exit Reynolds number ranged from Re2= 300000 to 700000. Comparisons with numerical codes have been conducted.

The measurements were performed in a linear test facility containing five airfoils. Two tailboards and two bypass vanes allowed to achieve a good periodicity of the flow. The aerodynamic flow conditions were measured using pressure taps and Laser-Two-Focus (L2F) anemometry. About forty static pressure taps gave a precise Mach number distribution over the suction and the pressure side of the airfoil. L2F measurements were used to determine the downstream flow angles.

The heat transfer coefficient was measured using the naphthalene sublimation technique. This method is based on the heat and mass transfer analogy for incompressible flow. A 0.5 mm thin naphthalene layer was applied to the middle airfoil and exposed to the flow for about 45 minutes. The sublimation was then measured in over 500 points on the airfoil, which allowed a high resolution of the heat transfer coefficient. Due to its high resolution, the sublimation technique shows the presence of and the precise location of the laminar-to-turbulent transition point and the separation bubble.

The measurements on the vane were compared with two separate two-dimensional boundary layer programs, which were TEXSTAN (Texas University) and TEN (Sussex University). The programs incorporate the k-epsilon turbulence model with several different formulations. The laminar-turbulent transition was predicted quite well with TEN, which slightly damps out the production of turbulent kinetic energy in order to ensure a smooth transition zone. In the case of the blade, the naphthalene sublimation technique was able to predict the size and the location of the separation bubble as well as the reattachment with a very high precision.
An Account of Free-Stream-Turbulence Length Scale on Laminar Heat Transfer
Authors: Dullenkopf K. , Mayle R. E.
Published: February 2015

The effect of length scale in free-stream turbulence is considered for heat transfer in laminar boundary layers. A model is proposed which accounts for an “effective” intensity of turbulence based on a dominant frequency for a laminar boundary layer. Assuming a standard turbulence spectral distribution, a new turbulence parameter which accounts for both turbulence level and length scale is obtained and used to correlate heat transfer data for laminar stagnation flows. The result indicates that the heat transfer for these flows is linearly dependent on the “effective” free-stream turbulence intensity.
The Highly Nonlinear Thermal Behavior of Film Cooling
Authors: Adiutori Eugene F.
Published: February 2015

The current view of film cooling/heating behavior is largely the result of room temperature experiments in which the high temperatures typical of gas turbines were only simulated. The simulation rests on the assumption/deduction that the effect of temperature on film cooling behavior is due solely to the effect of temperature on fluid density.

A few experiments reported in the literature have included wide variation in temperature. In this article, the data from several of these are examined in order to determine the actual, observed effect of temperature on film cooling behavior.

Literature data exhibit a highly linear relationship between Taw and Tfc when the film is injected through a slot, and Tfc/Tms lies in the range 0.8 to 1.27. The data also indicate that this relationship is highly nonlinear when Tfc/Tms is less than approximately 0.8. The nonlinearity is so pronounced that Taw may not decrease even though (Tfc/Tms) is decreased from 0.57 to 0.35.

Nonlinearity in the relationship between Taw and Tfc has a major impact on optimum system design whenever the thermal designer has design control over the film coolant temperature.
Local Heat Transfer Coefficient and Adiabatic Wall Temperature Measurement Beneath Arrays of Staggered and Inline Impinging Jets
Authors: Van Treuren Kenneth W. , Wang Zuolan , Ireland Peter T. , Jones Terry V. , Kohler S. T.
Published: February 2015

Recent work, Van Treuren et al. (1993), has shown the transient method of measuring heat transfer under an array of impinging jets allows the determination of local values of adiabatic wall temperature and heat transfer coefficient over the complete surface of the target plate. Using this technique, an inline array of impinging jets has been tested over a range of average jet Reynolds numbers (10,000–40,000) and for three channel height to jet hole diameter ratios (1, 2, and 4). The array is confined on three sides and spent flow is allowed to exit in one direction. Local values are averaged and compared with previously published data in related geometries. The current data for a staggered array is compared to those from an inline array with the same hole diameter and pitch for an average jet Reynolds number of 10,000 and channel height to diameter ratio of one. A comparison is made between intensity and hue techniques for measuring stagnation point and local distributions of heat transfer. The influence of the temperature of the impingement plate through which the coolant gas flows on the target plate heat transfer has been quantified.