bluuebunny/crossref_metadata_2025 huggingface dataset:
Carabid beetles (Coleoptera:Carabidae) in coniferous plantations inHokkaido,Japan: effects of tree species and environmental factors
Authors: Kaizuka Jun , Iwasa Mitsuhiro
Published: August 2014

The distribution, species composition and abundance of carabid beetles in monospecific plantations of three different coniferous tree species (Japanese spruce,Sakhalin fir and larch) were investigated by baited pitfall traps inHokkaido,Japan. In total, 16 150 carabid beetles consisting of 31 species in 13 genera were collected in 2011 and 2012. The most predominant species wasPterostichus thunbergii Morawitz, followed bySynuchus melantho(Bates) andCarabus opaculus(Putzeys). Average numbers of beetles per trap were significantly reduced in larch. Large‐sizedCarabusspecies (C. arboreus arboreus Lewis andC. opaculus) were collected in large numbers inJapanese spruce. There was no significant difference in diversity and equitability among the three kinds of plantation. The ordination of redundancy analysis showed that medium‐sized forest generalists,Pterosticus subovatus(Motschulsky) andP. thunbergii, were highly associated withJapanese spruce andSakhalin fir, and the forest specialistSynuchus nitidus(Motschulsky) was withSakhalin fir. In contrast, in larch there was no such associated forest species, and some species ofCarabus,PterostichusandSynuchuswere considerably reduced in number, suggesting that larch has unfavorable effects on some forest species. The most important environmental variables influencing carabid assemblages were soil moisture and foliage layer cover. Practices in forest management to minimize the effects of plantations on carabid assemblages are discussed.
Exocrine glands of the ant Myrmoteras iriodum
Authors: Billen Johan , Mandonx Tine , Hashim Rosli , Ito Fuminori
Published: August 2014

This paper describes the morphological characteristics of nine major exocrine glands in workers of the formicine ant Myrmoteras iriodum. The elongate mandibles reveal along their entire length a conspicuous intramandibular gland, which contains both class‐1 and class‐3 secretory cells. The secretory cells of the mandibular glands show a peculiar appearance, with a branched end apparatus, which is unusual for ants. The other major glands (pro‐ and postpharyngeal gland, infrabuccal cavity gland, labial gland, metapleural gland, venom gland and Dufour gland) show common features for formicine ants. The precise function of the glands could not yet be experimentally demonstrated, and to clarify this will depend on the availability of live material of these enigmatic ants in future.
Retrograde flexible ureteroscopic approach of upper urinary tract pathology: What is the status in 2014?
Authors: Geavlete Petrisor , Multescu Razvan , Geavlete Bogdan
Published: August 2014

Flexible uretero‐renoscopy witnessed dramatic technological improvements, ultimately translating in more diverse indications, better instrument durability, procedural efficacy and safety. Diagnostic exploration of the upper urinary tract, treatment of selected cases of ureteral and especially pyelocaliceal stones, caliceal diverticulum and infundibular stenosis, treatment, and follow‐up of upper urinary tract tumors are the main indications for this approach. We review the technique, results and complications of retrograde flexible ureteroscopy, with an emphasis on the latest developments of the method.
Probing Site Symmetry Around Eu3+ in Nanocrystalline ThO2 Using Time Resolved Emission Spectroscopy
Authors: Gupta Santosh K. , Bhide Madhusudan Krishnadas , Godbole Shrikant Vasant , Natarajan Venkataraman
Published: August 2014

ThO2:Eu3+ nanoparticles were synthesized at 300°C by combustion route using urea as a fuel and characterized by thermogravimetric/differential thermal analysis, X‐ray diffraction, transmission electron microscopy, and photoluminescence techniques. To investigate the effect of annealing temperature, as synthesized powder were heated further at 500°C, 700°C, and 900°C. It was observed that extent of asymmetry around Eu3+ at 700°C/900°C is very high as compared to as‐prepared or 500°C annealed sample. Based on the time resolved emission spectroscopic investigations, it was inferred that two different types of Eu3+ ions were present in the ThO2 nanoparticles. In ThO2 structure, Eu3+ ions occupy two sites; cubic (Oh) and noncubic (<C2v) as can be confirmed from our emission studies. Short‐lived species T1 (~1.3–3.4 ms) predominates at higher annealing temperature arises because of Eu3+ ions occupying noncubic (<C2v) sites without inversion symmetry, whereas long‐lived species T2 (~4.6–6.6 ms) can be ascribed to Eu3+ ions occupying cubic sites (Oh) with inversion symmetry.
Association between gastroesophageal reflux and pathologic apneas in infants: a systematic review
Authors: Smits Marije J. , van Wijk Michiel P. , Langendam Miranda W. , Benninga Marc A. , Tabbers Merit M.
Published: August 2014

Background

In infants, apneas can be centrally mediated, obstructive or both and have been proposed to be gastroesophageal reflux (GER) induced. Evidence for this possible association has never been systematically reviewed.

Purpose

To perform a systematic review using PubMed, EMBASE and Cochrane databases to determine whether an association between GER and apnea in infants exists. Studies with n ≥ 10 infants, aged <12 months, were included. GER had to be studied by pH‐metry or pH‐impedancemetry. GER episodes were defined as pH <4 for ≥5 s and/or a drop of >50% of baseline in impedance signal in distal channels. An apneic event was defined as a cessation of breathing for >20 s, or ≥10 s with hypoxemia or bradycardia. An epoch of ≤2 min was used to define temporal relation between GER and apnea. Methodological quality of studies was assessed with Newcastle Ottawa Scale (NOS). Of 1959 abstracts found, 6 articles met the inclusion criteria. All studies had poor methodological quality. A total of 289 infants were included. The temporal association of GER followed by apnea was assessed in all studies, with epochs varying from 10 s to 2 min. One study found an increase of apneic events after GER, the remaining 5 studies did not find an association. Two studies assessed apnea followed by GER as well, but did not find sufficient evidence for association. This systematic review showed insufficient evidence for an association between GER and apneas in infants. High quality studies using uniform inclusion criteria, definitions according to accepted guidelines, and patient relevant outcome measures are needed.
Productivity Versus Employment: Quantifying the Economic Effects of an EU–Japan Free Trade Agreement
Authors: Benz Sebastian , Yalcin Erdal
Published: August 2014

The European Union and Japan recently entered into negotiations over a bilateral free trade agreement intended to stimulate growth and create wealth. Since customs duties are already low, the success of the liberalisation process hinges on the elimination of non‐tariff barriers. The purpose of this paper is to shed light on two possible liberalisation scenarios: a less ambitious liberalisation and a comprehensive liberalisation. In contrast to classic studies, our paper builds on the modern trade literature, accounting for the dominance of intra‐industry trade in both economies and the existence of heterogeneous firms. Furthermore, we model a search‐and‐matching labour market, allowing us to quantify employment effects of trade liberalisation. We find that a comprehensive liberalisation increases Japanese GDP by 0.86 per cent, whereas the EU experiences only an additional 0.21 per cent of real GDP growth. Most of the growth in real GDP is due to firms' efficiency gains, whereas unemployment is reduced by only a small amount. Other world regions experience small reductions of GDP due to trade diversion effects.
NASA’s HSCT — Past and Future Prospects
Authors: Mercure Robert A.
Published: August 2014

With the termination of the government/industry partnership on the High Speed Civil Transport (HSCT) program in late 1998, the prospects for a U.S. SuperSonic Transport (SST) appears uncertain. However, NASA’s goal of “Reducing travel time to the Far East and Europe by 50% within 25 years” remains intact. The decision by industry to build an HSCT has been postponed and there is now more time to explore advanced technologies and revolutionary concepts that could make a supersonic aircraft an environmentally compatible and economically viable success.

Studies will likely continue to examine future constraints regarding flight speed, range, size, market impacts and economics. The technology challenges may appear formidable, but the potential revenue generated and the benefits realized in reduced travel time by an HSCT will provide the incentive to continue the research.
Characterization of Melt Infiltrated SiC/SiC Composite Combustor Liners Using Meso- and Micro-NDE Techniques
Authors: Ellingson W. A. , Sun J. G. , More K. L. , Hines R.
Published: August 2014

Melt-infiltrated ceramic matrix composite SiC/SiC material systems are under development for use in combustor liners for low-emission advanced gas turbines. Uncertainty in repeatability of processing methods for these large components (33–76 cm diameter), and hence possible reduced reliability for the end user, requires that appropriate test methods, at both meso- and micro-scale, be used to ensure that the liners are acceptable for use. Nondestructive evaluation (NDE) methods, if demonstrated to reliably detect changes caused by processing, would be of significant benefit to both manufacturer and end user. This paper describes the NDE methods and their applications in detecting a process upset in a melt-infiltrated 33 cm combustor liner and how high-resolution scanning electron microscopy was used to verify the NDE data.
Response of a Model Gas Turbine Combustor to Variation in Gaseous Fuel Composition
Authors: Flores R. M. , Miyasato M. M. , McDonell V. G. , Samuelsen G. S.
Published: August 2014

The effect of fuel composition on performance is evaluated on a model gas turbine combustor designed to mimic key features of practical devices. A flexible fuel injection system is utilized to control the placement of the fuel in the device to allow exploration and evaluation of fuel distribution effects in addition to chemistry effects. Gas blends reflecting the extremes in compositions found in the U.S. are considered. The results illustrate that, for the conditions and configuration studied, both fuel chemistry and fuel air mixing play a role in the performance of the device. While chemistry appears to be the predominant factor in stability, a role is noted in emissions performance as well. It is also found that changes in fuel distribution associated with changes in fuel momentum for fixed firing rate also have an impact on emissions. For the system considered, a strategy for sustaining optimal performance while fuel composition changes is illustrated.
Implementation and Validation of a New Soot Model and Application to Aeroengine Combustors
Authors: Balthasar M. , Mauss F. , Pfitzner M. , Mack A.
Published: August 2014

The modelling of soot formation and oxidation under industrially relevant conditions has made significant progress in recent years. Simplified models introducing a small number of transport equations into a CFD code have been used with some success in research configurations simulating a reciprocating diesel engine.

Soot formation and oxidation in the turbulent flow is calculated on the basis of a laminar flamelet library model. The gas phase reactions are modelled with a detailed mechanism for the combustion of heptane containing 89 species and 855 reactions developed by Frenklach and Warnatz and revised by Mauss. The soot model is divided into gas phase reactions, the growth of polycyclic aromatic hydrocarbons (PAH) and the processes of particle inception, heterogeneous surface growth, oxidation and condensation. The first two are modelled within the laminar flamelet chemistry, while the soot model deals with the soot particle processes.

The time scales of soot formation are assumed to be much larger than the turbulent time scales. Therefore rates of soot formation are tabulated in the flamelet libraries rather than the soot volume fraction itself. The different rates of soot formation, e.g. particle inception, surface growth, fragmentation and oxidation, computed on the basis of a detailed soot model, are calculated in the mixture fraction / scalar dissipation rate space and further simplified by fitting them to simple analytical functions. A transport equation for the mean soot mass fraction is solved in the CFD-code. The mean rate in this transport equation is closed with the help of presumed probability density functions for the mixture fraction and the scalar dissipation rate. Heat loss due to radiation can be taken into account by including a heat loss parameter in the flamelet calculations describing the change of enthalpy due to radiation, but was not used for the results reported here.

The soot model was integrated into an existing commercial CFD code as a post-processing module to existing combustion CFD flow fields and is very robust with high convergence rates. The model is validated with laboratory flame data and using a realistic 3-D BMW Rolls-Royce combustor configuration, where test data at high pressure are available. Good agreement between experiment and simulation is achieved for laboratory flames, whereas soot is overpredicted for the aeroengine combustor configuration by 1–2 orders of magnitude.
Introduction of Intercooling in a High Bypass Jet Engine
Authors: Papadopoulos Tilemachos , Pilidis Pericles
Published: August 2014

In this paper an exercise to introduce intercooling in a high bypass civil turbofan is outlined. The engine selected as the basic propulsion system is a three spool high bypass turbofan with a bypass ratio 6.4. The air leaving the IP compressor is cooled in the bypass duct prior to entering the HP compressor.

This preliminary investigation appears to indicate that the main benefit to be gained is an increase in the net thrust from the engine without increasing the turbine inlet temperature. To keep engine diameter constant, the bypass ratio has not been changed. This results in a requirement to significantly increase the pressure ratio to reduce the SFC levels to an acceptable value.

A sizing exercise has been carried out to understand the weight and volume penalties imposed by heat pipe intercooling hardware. The preliminary sizing exercise indicates that the weight penalty is very large. The performance of the aircraft using the intercooled engines is also investigated and some improvements in performance are predicted.

Overall this investigation is considered to be positive so that further investigations should be considered. It appears that an intercooled engine can produce a somewhat higher thrust at a given turbine entry temperature at similar SFC levels of current engines, or, if a small increase in SFC is acceptable, the increase in thrust is quite important.
Integration of a Gas Turbine (GT) With a Compressed Air Storage (CAES) Plant Provides the Best Alternative for Mid-Range and Daily Cyclic Generation Needs
Authors: Nakhamkin Michael , van der Linden Septimus
Published: August 2014

There is a significant emphasis on peaking power, particularly recognized in the US power generation market. Orders for gas turbines are at their peaks, with OEMs taking orders for delivery in the year 2002, or later. Though a simple cycle GT is the recognized power plant of choice for daily cycle and peak power supply, it still has the highest fuel consumption rate per kWh produced (heat rate, Btu/kWh or Btu/kWh) with associated high emissions.

The massive additions of GT power plants for primarily peak/cycling applications should generate needs for better utilization of installed capacities. The Compressed Air Energy Storage (CAES) plant is demonstrated as the best and cost-effective plant for storing significant amounts of the off-peak energy and releasing the peak energy as needed.

This paper presents an innovative power plant concept, which is based on the integration of a conventional GT with the unfired CAES, air-bottoming cycle — denoted as GT-CAES. This concept is analyzed and compared to a conventional CAES cycle.

Also, the paper presents characteristics of this concept based on ABB’s GT24/26 combustion turbine, the characteristics produced for a number of GT-CAES projects which are in various stages of development.
Development of a Maintenance Program for Major Gas Turbine Hot Gas Path Parts
Authors: Moritsuka Hideto , Fujii Tomoharu , Takahashi Takeshi
Published: August 2014

The thermal efficiency of gas turbine combined cycle power generation plants increase significantly in accordance with turbine inlet temperature. Gas turbine combined cycle power plants operating at high turbine inlet temperature are popular as a main thermal power station among our electric power companies in Japan. Thus, gas turbine hot gas parts are working under extreme conditions which will strongly affect their lifetime as well as maintenance costs for repaired and replaced parts. To reduce the latter is of major importance to enhance cost effectiveness of the plant.

This report describes a gas turbine maintenance management program of main hot gas parts (combustor chambers, transition peices, turbine 1st. stage nozzles and 1st. stage buckets) for management persons of gas turbine combined cycle power stations in order to obtain an optimal gas turbine maintenance schedule considering rotation, repair and replacement or exchange of those parts.
Combustion Turbine Inlet Conditioning: A State-of-the-Art Method of Increasing Generating Capacity Without the Addition of New Basic Generation Hardware
Authors: Tisdale Lloyd B. , Hauck Robert L.
Published: August 2014

While the market for electrical energy has increased at unprecedented rates, (both in the U.S. and other parts of the world), and the simultaneous advent of deregulation adds speculation to the mix, the ability of manufacturers to keep pace with new generating equipment orders has pushed deliveries from months to years. Additionally, as demand increases for new generating equipment, the inevitable market forces elevate prices to new levels. One obvious solution is to find a cost and time effective method to achieve more stable and predictable performance from both new generation equipment and existing generation equipment.

The objective of this paper is to provide a simple guide for engineers, owners, manufacturers, and operators to select the design and concept for producing the maximum, stable and predictable additional capacity on new and existing generating equipment through the use of single lift modular packaged mechanical inlet chilling, or packaged chilling modules (PCM’s).
An Investigation of Heat Transfer in a Film Cooled Transonic Turbine Cascade: Part I — Steady Heat Transfer
Authors: Smith D. E. , Bubb J. V. , Popp O. , Grabowski H. , Diller T. E. , Schetz J. A. , Ng W. F.
Published: August 2014

Experiments were performed in a transonic cascade wind tunnel to investigate the film effectiveness and heat transfer coefficient on the suction side of a high-turning turbine rotor blade. The coolant scheme consisted of six rows of staggered, discrete cooling holes on and near the leading edge of the blade in a showerhead configuration. Air was cooled in order to match the density ratios found under engine conditions. Six high-frequency heat flux gauges were installed downstream of the cooling holes on the suction side of the blade. Experiments were performed with and without film and the coolant to freestream total pressure ratio was varied from 1.02 to 1.19. In order to simulate real engine flow conditions, the exit Mach number was set to 1.2 and the exit Reynolds number was set to 5×106. The freestream turbulence was approximately 1%. The heat transfer coefficient was found to increase with the addition of film cooling an average of 14% overall and to a maximum of 26% at the first gauge location. The average film cooling effectiveness over the gauge locations was 25%. Both the heat transfer coefficient and the film cooling effectiveness were found to have only a weak dependence upon the coolant to freestream total pressure ratio at the gauge locations used in this study.
Infrared Low Temperature Turbine Vane Rough Surface Heat Transfer Measurements
Authors: Boyle R. J. , Spuckler C. M. , Lucci B. L. , Camperchioli W. P.
Published: August 2014

Turbine vane heat transfer distributions obtained using an infrared camera technique are described. Infrared thermography was used because non-contact surface temperature measurements were desired. Surface temperatures were 80°C or less. Tests were conducted in a three vane linear cascade, with inlet pressures between 0.14 and 1.02atm., and exit Mach numbers of 0.3, 0.7, and 0.9, for turbulence intensities of approximately 1 and 10%. Measurements were taken on the vane suction side, and on the pressure side leading edge region. The designs for both the vane and test facility are discussed. The approach used to account for conduction within the vane is described. Midspan heat transfer distributions are given for the range of test conditions.
Heat Transfer and Flow Characteristics of an Engine Representative Impingement Cooling System
Authors: Son Changmin , Gillespie David , Ireland Peter , Dailey Geoffrey M.
Published: August 2014

A study of a large-scale model of an engine representative impingement cooling system has been performed. A series of tests have been carried out to fully characterise the behaviour of the system. These include cold flow diagnostic tests to determine the pressure loss and the static pressure distribution, and flow visualisation to assess surface shear. The surface shear stress pattern provided by multiple stripes of coloured paint applied to the target surface yielded important information on the near wall flow features far from the jet axis. The row solved flow and pressure distributions are compared to industry standard predictions.

Heat transfer tests using the transient liquid crystal technique were also conducted using coatings comprised of a mixture of three thermochromic liquid crystals. Analysis of the thermochromic liquid crystal data was enhanced by recent developments in image processing. In addition, an energy balance approach to analysing signals from fast response thermocouples for air temperature measurement was applied to verify the levels of heat transfer coefficients on surfaces not coated with the temperature sensitive liquid crystal.
Flow and Heat Transfer of Confined Impingement Jets Cooling
Authors: Wang Ting , Lin Mingjie , Bunker Ronald S.
Published: August 2014

Experimental studies on heat transfer and flow structure in confined impingement jets were performed. The objective of this study was to investigate the detailed heat transfer coefficient distribution on the jet impingement target surface and flow structure in the confined cavity.

The distribution of heat transfer coefficients on the target surface was obtained by employing the transient liquid crystal method coupled with a 3-D inverse transient conduction scheme under Reynolds number ranging from 1039 to 5175. The results show that the average heat transfer coefficients increased linearly with the Reynolds number as Nu = 0.00304 Pr0.42Re. The effects of cross flow on heat transfer were investigated. The flow structure were analyzed to gain insight into convective heat transfer behavior.
Heat Transfer Enhancements in Rotating Two-Pass Coolant Channels With Profiled Ribs: Part 1 — Average Results
Authors: Acharya S. , Eliades V. , Nikitopoulos D. E.
Published: August 2014

The effect of ribs with different cross-stream profiles are investigated through detailed, surface mass (heat) transfer distributions along four active walls of a square duct containing a sharp 180° bend. The duct simulates two passes of an internal coolant channel in a gas turbine engine with ribs mounted on two opposite walls. Mass (heat) transfer measurements, taken using the naphthalene sublimation technique, are presented for Reynolds numbers of 30,000, and rotation number of 0.3. Comparisons are made with conventional ribs having a rectangular cross-section. It is shown that the use of certain profiled ribs provides considerable heat transfer enhancements over conventional ribs with the same blockage ratio in the duct. These enhancements are attributed to the generation of longitudinal vorticity (or secondary flows) by the profiled ribs in the channel.
Rotating Effect on Fluid Flow in a Smooth Duct With a 180-Deg Sharp Turn
Authors: Chen Chung-Chu , Liou Tong-Miin
Published: August 2014

Laser-Doppler velocimetry (LDV) measurements are presented of turbulent flow in a two-pass square-sectioned duct simulating the coolant passages employed in gas turbine blades under rotating and non-rotating conditions. For all cases studied, the Reynolds number characterized by duct hydraulic diameter (Dh) and bulk mean velocity (Ub) was fixed at 1 × 104. The rotating case had a range of rotation number (Ro = ΩDh/Ub) from 0 to 0.2. It is found that both the skewness of streamwise mean velocity and magnitude of secondary-flow velocity increase linearly, and the magnitude of turbulence intensity level increases non-linearly with increasing Ro. As Ro is increased, the curvature induced symmetric Dean vortices in the turn for Ro = 0 is gradually dominated by a single vortex most of which impinges directly on the outer part of leading wall. The high turbulent kinetic energy is closely related to the dominant vortex prevailing inside the 180-deg sharp turn. For the first time, the measured flow characteristics account for the reported spanwise heat transfer distributions in the rotating channels, especially the high heat transfer enhancement on the leading wall in the turn. For both rotating and non-rotating cases, the direction and strength of the secondary flow with respect to the wall are the most important fluid dynamic factors affecting local heat transfer distributions inside a 180-deg sharp turn. The role of the turbulent kinetic energy in affecting the overall enhancement of heat transfer is well addressed.
The Effects of Injection Angle and Hole Exit Shape on Turbine Nozzle Pressure Side Film Cooling
Authors: Zhang Luzeng J. , Pudupatty Ram
Published: August 2014

Using the pressure sensitive paint (PSP) technique, film cooling effectiveness was measured on a turbine vane pressure surface, with a four-row showerhead cooling hole configuration and a single row of holes on the pressure side. Nitrogen gas was used to simulate film cooling flow providing an oxygen concentration map corresponding to an effectiveness map by the mass transfer analogy. Three showerhead coolant injection angles (45°, 90°, and 135°) were studied and two pressure side injection angles (20° and 40°) for cylindrical holes and a 40° angle for shaped hole were studied. In addition, studies were performed on three combinations of shower head and pressure side injections. Film effectiveness was measured for each of the cases at three blowing ratios. The pressure sensitive paint (PSP) was used to indicate oxygen concentration and was calibrated at various temperatures and pressures to obtain better accuracy before being applied to the airfoil surface. The results indicate that 45° spanwise angle injection provides best film coverage for the shower head injections. For pressure side injections, the 20° cylindrical hole injection results in the highest effectiveness values and the shaped hole improves film effectiveness immediately downstream from the injection point. The film effectiveness for three combined injections and the interaction between showerhead injection and the pressure side injection are also presented and discussed.
Film Cooling Downstream of a Row of Discrete Holes With Compound Angle
Authors: Goldstein R. J. , Jin P.
Published: August 2014

A special naphthalene sublimation technique is used to study the film cooling performance downstream of one row of holes of 35° inclination angle and 45° compound angle with 3 diameter hole spacing and relatively small hole length to diameter ratio (6.3). Both film cooling effectiveness and mass/heat transfer coefficients are determined for blowing rates from 0.5 to 2.0 with density ratio of unity. The mass transfer coefficient is measured using pure air film injection, while the film cooling effectiveness is derived from comparison of mass transfer coefficients obtained following injection of naphthalene-vapor-saturated air with that of pure air injection. This technique enables one to obtain detailed local information on film cooling performance. General agreement is found in local film cooling effectiveness when compared with previous experiments. The laterally-averaged effectiveness with compound angle injection is higher than that with inclined holes immediately downstream of injection at a blowing rate of 0.5 and is higher at all locations downstream of injection at larger blowing rates. A large variation of mass transfer coefficients in the lateral direction is observed in the present study. At low blowing rates of 0.5 and 1.0, the laterally-averaged mass transfer coefficient is close to that of injection without compound angle. At the highest blowing rate used (2.0), the asymmetrical vortex motion under the jets increases the mass transfer coefficient drastically ten diameters downstream of injection.
Experimental and Numerical Investigation of Wake-Induced Transition on a Highly Loaded LP Turbine at Low Reynolds Numbers
Authors: Stadtmüller Peter , Fottner Leonhard , Fiala Andreas
Published: August 2014

Experimental and numerical results of LP turbine cascade tests performed to investigate wake interaction effects on boundary layer transition are presented. The data obtained at different inlet flow angles, turbulence levels and Mach numbers are compared and discussed with special focus on low Reynolds number conditions. For the boundary layer, calculated propagation velocities of disturbances are introduced to explain the transition process on the suction side of the blade over time.

Using a moving bar wake generator and surface-mounted hot films as well as surface pressure tappings, the effects of periodic wake passing were studied in the High-Speed Cascade Wind Tunnel on the aft-loaded LPT profile T106. Blade pitch was increased as compared with design point conditions to achieve a higher blade loading. As a result, a large separation bubble formed on the suction side of the surface and allowed unsteady boundary layer development to be studied in great detail. Starting at a characteristic Reynolds number, massive separation occurred on the suction side under steady state conditions, i.e. the boundary layer was unable to reach the back pressure at the trailing edge. By using the wake generator, it was possible to reduce this separation and thus decrease profile pressure losses by 50%.

The primary objective of the study was to provide unsteady ensemble-averaged hot film data together with information on the wake induced path, sufficient for the validation of numerical simulations. Such a simulation of the experiment was conducted using the Unsteady Boundary Layer Interaction Method, which takes into account the influence of boundary layer displacement on the velocity distribution and the time-dependent turbulence level in the outflow. The computations provide a good description of the wall shear stress in the transitional region and are in good agreement with the experimental data. By plotting propagation directions of boundary layer disturbances in space-time diagrams, it is shown that one characteristic direction is deviated around the so-called becalmed region and the temporarily separated region into the wake-induced transitional region.
The Influence of Multimode Transition Initiated by Periodic Wakes on the Profile Loss of a Linear Compressor Cascade
Authors: Teusch Reinhold , Brunner Stefan , Fottner Leonhard , Swoboda Marius
Published: August 2014

This paper presents results of boundary layer and loss measurements in a high speed cascade wind tunnel on a linear compressor cascade under the influence of unsteady, periodic wakes. The wakes of an upstream blade row were simulated by cylindrical bars moved by a belt mechanism upstream of the cascade.

Extensive hot-film array, hot-wire and pressure measurements with variation of steady and unsteady inlet flow conditions have been performed for a better understanding of the transition and loss mechanisms on a blade row interacting with wakes.

The incoming wakes are inducing early forced transition in the boundary layer followed in time by calmed regions. Due to its higher shear stress level and its fuller velocity profile, the calmed flow is able to suppress laminar separation bubbles and to delay transition in the region with undisturbed flow between wakes, playing a significant role in the loss generation process.

At the investigated low Reynolds number, where the measurements for the steady flow case showed a well-developed laminar separation bubble, reductions of profile loss up to 20% were observed for the measured configuration. In the case of the high Reynolds number, where in undisturbed flow only a small separation bubble was detected, a profile loss rise up to 30% was measured.

Beside a better understanding of unsteady flow physics the goal of these basic investigations of unsteady transition is to create a wide database for the improvement of transition modeling in unsteady CFD codes.
Systematic Experimental and Numerical Investigations on the Aerothermodynamics of a Film Cooled Turbine Cascade With Variation of the Cooling Hole Shape: Part I — Experimental Approach
Authors: Ganzert Wolfgang , Hildebrandt Thomas , Fottner Leonhard
Published: August 2014

As a part of a systematic research program isothermal investigations on the aerodynamics and the heat transfer of a large scale turbine cascade with suction side film cooling with shaped holes and compound inclination were carried out. The film cooling through a row of holes at forty percent chord length on the suction side was supplied by a large plenum chamber. The axial component inclination was kept constant at 30°. All holes have a cylindrical inlet combined with a shaped outlet. Three injection geometries were tested. The first two investigated configurations had no lateral inclination. The hole geometries can be briefly described as follows: Fan-shaped holes with lateral expansion, fan-shaped holes with lateral expansion and streamwise laid-back. The last investigation combined the most complex hole shape with a lateral hole inclination of 45°.

Typical engine conditions for the Mach and Reynolds number as well as the inlet turbulence level were maintained. Due to hardware limitations the total temperature was set to 303 Kelvin.

The measured data comprise local and integral total pressure loss coefficients obtained by pressure probe traversing at midspan downstream of the cascade. The static profile pressure distribution together with oil-and-dye flow visualisation gives information on the surface flow conditions and boundary layer development especially in the near hole region. Three dimensional hot wire anemometry is used for detailed flow measurements in the hole region. Based on the steady state liquid crystal heat transfer measurement technique pseudo colour contour plots are used for the documentation of the local surface heat transfer coefficient distribution. Laterally averaged and statistically analysed data of the surface heat transfer is applied in further heat transfer examinations.

The aim of all investigations is an aerodynamical optimisation of film cooling configurations taking into account the thermal aspects.

The most important conclusions can be summarised as follows: Compared to cylindrical holes with the same axial injection angle, shaped holes have a tremendous influence on the flow type in the near hole region. This leads to a more homogeneous pattern of the suction side heat transfer coefficient. The combination of shaped holes and lateral inclination induces definitely higher losses downstream of the cascade compared to the case with no inclination. Due to the lateral injection the former symmetrical vortex branches downstream of the hole are increased asymmetrically. This leads to higher mean heat transfer coefficients in the near hole region downstream of the injection. On the other side laterally blowing increases the homogeneity of the heat transfer coefficient.
A Presentation of Detailed Experimental Data of a Suction Side Film Cooled Turbine Cascade
Authors: Brandt Holger , Ganzert Wolfgang , Fottner Leonhard
Published: August 2014

This paper presents detailed isothermal investigations on the aerodynamic effects and the heat transfer of suction side film cooling on a highly loaded turbine cascade. The measurements were carried out with inlet flow conditions kept constant at values which are typically found in modern gas turbines. Five configurations with different hole geometries were investigated, a cylindrical hole with two different streamwise inclination angles, a fan shaped hole and a fan shaped hole with laid-back both only inclined in streamwise direction and a fan shaped hole with laid-back and combined streamwise and lateral inclination. The variation of the blowing ratio enabled closer studies of the mixing process and the influence of the various hole configurations on the aerodynamics and the local heat transfer.

To enhance the understanding of the mechanisms and the boundary layer behaviour of these highly three-dimensional flows, much effort has been put on the measurement techniques. The high-resolution data needed was obtained using pressure tappings positioned on the profile, oil-and-dye visualizations on the suction surface, pneumatic probes in the wake and three-dimensional hot wire anemometry in the flow field downstream the holes. Additional heat transfer examinations with a special set-up based on the steady state liquid crystal technique clarified the individual local heat transfer distributions.

All measured data are summarized and documented to be used as a reference for three-dimensional, steady-state numerical calculations.
Strategy for a Cost Optimized Operation of a Flexible Cogeneration Gas Turbine Plant
Authors: Hein D. , Kwanka K. , Nixdorf M.
Published: August 2014

A new gas turbine cogeneration plant based on the Cheng cycle was installed to supply electricity and heat for the Technische Universität München’s campus site at Garching. To utilize fully the Cheng cycle flexibility, an optimizing system was developed which controls the mode of operation continuously and adapts the point of operation without manual interface. Only with such a system it is possible to exploit the full economic potential of the system. The paper presents the technical framework and some aspects of the control strategy used to minimize the costs based on three years of operating experience.
Modular Uprating and Upgrading Solutions in ABB ALSTOM POWER Gas Turbines
Authors: De Backer Wilfried , Bopp Carsten
Published: August 2014

As a reference for future papers on uprating and upgrading experience, this paper presents ABB ALSTOM POWER’s latest generation of modular uprating and upgrading solutions that provide the theoretical background and the technical solution for the gas turbines types GT11D, GT13D and GT11N/N1.
Thermo-Economic Analysis of an Intercooled, Reheat and Recuperated Gas Turbine for Cogeneration Applications: Part I — Base Load Operation
Authors: Bhargava R. , Bianchi M. , Negri di Montenegro G. , Peretto A.
Published: August 2014

This paper presents a thermo-economic analysis of an intercooled, reheat (ICRH) gas turbine, with and without recuperation, for cogeneration applications. The optimization analyses of thermodynamic parameters have permitted to calculate variables, such as low-pressure compressor pressure ratio, high-pressure turbine pressure ratio and gas temperature at the waste heat recovery unit inlet while maximizing electric efficiency and “Energy Saving Index”. Subsequently, the economic analyses have allowed to evaluate return on the investment, and the minimum value of gross payout period, for the cycle configurations of highest thermodynamic performance. In the present study three sizes (100 MW, 20 MW and 5 MW) of gas turbines have been examined.

The performed investigation reveals that the maximum value of electric efficiency and “Energy Saving Index” is achieved for a large size (100 MW) recuperated ICRH gas turbine based cogeneration system. However, a non-recuperated ICRH gas turbine (of 100 MW) based cogeneration system provides maximum value of return on the investment and the minimum value of gross payout period compared to the other gas turbine cycles, of the same size and with same power to heat ratio, investigated in the present study. A comprehensive thermo-economic analysis methodology, presented in this paper, should provide useful guidelines for preliminary sizing and selection of gas turbine cycle for cogeneration applications.
Utilization of Cryogenic Exergy of LNG by MGT (Mirror Gas Turbine)
Authors: Tsujikawa Y. , Kaneko K. , Fujii S.
Published: August 2014

In the course of the worldwide efforts to suppress the global warming, the saving energy becomes more important. Recently, the LNG (liquefied natural gas) terminals in our country have received more than 50 million tons of LNG per year. Therefore, the utilization of the cryogenic exergy in connection with the regasification of LNG gains more and more importance. The aim of this paper is the recovery of the energy consumed in liquefaction using the MGT (Mirror Gas Turbine), which is a kind of new combined cycle of a conventional gas turbine worked as a topping cycle and TG (inverted Brayton cycle) as a bottoming cycle. The optimum characteristics have been calculated and it is shown that this cycle is superior to the current-use gasification systems in employing seawater heats in terms of thermal efficiency and specific output. In the present cycle, the cold of LNG is used to cool the exhaust gas from a turbine of TG, and then the exergy of the liquefied natural gas is transformed to electric energy with a very high efficiency. The main feature of this new concept is the removal of an evaporation system using seawater.
Liquid Phase Diffusion Bond Repair of Westinghouse 501F, Row 3 Vanes
Authors: Miglietti Warren M. , Curtis Rich , Hall Brandon , Lazarin Christina M.
Published: August 2014

During the industrial turbine engine operation of the W501F, Row3 Vanes, cracks develop as a result of thermal fatigue. Other damage found is pitting and dents resulting from corrosion/oxidation and FOD (foreign object damage) respectively. Erosion damage is also commonly found on the airfoils. Finally there is downstream deflection of the inner buttress/seal areas, as a result of axial creep. This paper describes the vacuum LPDB (liquid phase diffusion bond) repair process used to repair all of the above-mentioned damage, including LPDB build up and machining of the hook fit areas.

As a means of qualifying the high temperature diffusion bond process, both metallurgical and mechanical property evaluations were carried out. The metallurgical evaluation consisted of optical and scanning electron microscopy. The wide gap diffusion bonded area consisted of a fine-grained structure with carbide and boride phases dispersed both intergranularly and intragranularly. An EDAX analysis was also conducted and the results are reported.

The chemistry of the repaired area is similar to the base metal which may explain why mechanical tests revealed properties equivalent to that of the base metal. The mechanical evaluations undertaken were tensile tests at room temperature and elevated temperature, as well as stress rupture tests. These results were equivalent to mechanical properties of the X-45 Co-based superalloy, which is the base metal of the vane.
A Study on Five-Axis Flank Machining of Centrifugal Compressor Impellers
Authors: Tsay Der Min , Chen Huo Chu , Her Ming Jane
Published: August 2014

Referring to machining technologies used for turbomachinery components, generally there are two cutting strategies: point cutting and flank cutting. Based on considerations of the cost, efficiency, and surface roughness, flank cutting by using a five-axis machining tool is a promising way to machine blade surfaces of turbomachinery components constructed by ruled surfaces. In this article, a flank cutting technology for centrifugal compressor impellers is developed by using the B-spline curve interpolation, ruled surface construction, and coordinate transformations. Also, an impeller with twelve blades is actually machined to verify the proposed approach by using a five-axis machining center.
Simulation of the Rotational Vibration Response of a Spur Gear Pair With One Cracked Tooth
Authors: Berri Sidi M. , Klosner J. M.
Published: August 2014

The present study introduces a developed simulator on rotational vibrations of a power transmission spur gear set with one cracked pinion tooth. The simulator computes the expected vibration response of the meshing gears by solving the differential equations of motion. In additions to accounting for the time-varying stiffness of the meshing tooth pair, the simulator also includes gear errors and damping. Dynamic tooth loads as a function of crack size are also computed. The simulated outputs depict precisely the experimental behaviors. Results for rotational vibrations of the power transmission system are presented as a function of crack size.
Measurements of Rotordynamic Coefficients of Hybrid Bearings With: (A) A Plugged Orifice, and (B) A Worn Land Surface
Authors: Laurant Franck , Childs Dara W.
Published: August 2014

Test results are presented for the rotordynamic coefficients of a hybrid bearing that is representative of bearings for liquid-rocket-engine turbopump applications. The bearing is tested in the following two degraded conditions: (a) one of five orifices plugged, and (b) a locally-enlarged clearance to simulate a worn condition. Test data are presented at 24600 rpm, with supply pressures of 4.0, 5.5, and 7.0 MPa, and eccentricity ratios from 0.1 to 0.5 in 0.1 increments.

Overall, the results suggest that neither a single plugged orifice nor significant wear on the bearing land will “disable’ a well designed hybrid bearing. These results do not speak to multiple plugged orifices and are not an endorsement for operations without filters to prevent plugging orifices.
Analysis and Testing of a Magnetic Bearing Energy Storage Flywheel With Gain-Scheduled, MIMO Control
Authors: Hawkins Lawrence A. , Murphy Brian T. , Kajs John
Published: August 2014

The design and initial testing of a five axis magnetic bearing system in an energy storage flywheel is presented. The flywheel is under development at the University of Texas Center for Electromechanics (UT-CEM) for application in a transit bus. The bearing system for the prototype features homopolar permanent magnet bias magnetic bearings. The system has been successfully tested to the maximum design speed of 42,000 rpm. A gain-scheduled, MIMO control algorithm was required to control the system modes affected by rotor gyroscopics. The implementation and basis for this control scheme is discussed. The cross-axis forces produced by this approach are described in terms of circumferential cross-coupled stiffness and damping to explain the effect on system stability. Dynamic test results are discussed relative to the rotordynamic and control system design.