bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of a Dual Fuel Catalytic Combustor for a 2.3 MWe Gas Turbine
Authors: Le Gal Jean-Hervé , Martin Gérard , Durand Daniel
Published: December 2014

Biomass derived fuels are an essential alternative for heat and energy production, in order to minimise environmental impact, since they make no net contribution to the increase of CO2 emissions into the atmosphere. In certain countries, biofuels are also interesting since they are available as waste products from the agricultural or forestry industry. Unfortunately, combustion of biofuels often results in high emissions levels of pollutants such as NOx, CO and unburned hydrocarbons.

In gas turbines, catalytic combustion of biofuels has the potential to reduce emissions of these undesired species. The ULECAT project (Ultra Low Emissions CATalytic combustor) described in this paper is the first step of a program aiming at the development of an ultra-low emission gas turbine in the range of 1 to 5 MWe, able to run with both biomass-derived gases and liquid fuels. The objective of the project is to assess the feasibility of a dual fuel catalytic combustor.

Combustor design issues are investigated at full and part load conditions. For the comparison of combustor configuration, modelling provides a useful help for catalytic section design, in particular for the estimation of catalytic activity and wall temperature which strongly influence catalyst life time.

Catalyst development is one of the main topics of this project. It is mainly focused on high temperature catalyst durability and the reduction of NOx formation. This last point is of primary importance in biofuels combustion and certain catalysts have shown an important potential in reducing ammonia conversion into NOx in some operating conditions. Catalyst performances are evaluated at lab scale and also pilot scale in representative gas turbine combustor conditions with both Diesel fuel and biomass derived fuels.
Behavior of Attractors During Surge in Centrifugal Compression System
Authors: Mutou A. , Mizuki S. , Komatsubara Y. , Tsujita H.
Published: December 2014

A dynamical system analysis method is presented, that permits the characterization of unsteady phenomena in a centrifugal compression system. The method maps one experimental time series of data into a state space in which behaviors of the compression system should be represented, and reconstructs an attractor that geometrically characterizes a state of the compression system.

The time series of data were obtained by using a high response pressure transducer and an analog to digital converter at surge condition. For the reconstruction of attractors, a noise free differentiation method in time was employed. The differentiation was made by high order finite difference methods. To remove the influence of noise, the data were passed through a filter using a third order spline interpolation. In this study, the dimension of the state space was restricted to three. The measured data itself and their first and second derivatives in time are used to represent an attractor in the state space.

The modeling of the system behavior from the time series of data by second order ordinary differential equations was attempted. It is assumed that the data and their derivatives satisfy the equations at each time. Then, appropriate coefficients are determined by a least square method.

The reconstructed attractor showed complex cyclic trajectories at a first glance. However, by applying a band pass filter to the original signal, it was found that the attractor consisted of three independent wave forms and formed an attractor with torus-like behavior. In contrast, the solution by the modeled equations showed a type of limit cycle.
Vibroacoustic Early Warning System for Gas Turbines
Authors: Moen Lyder , Jahr Knuth
Published: December 2014

Conventional engine shut-down systems for vibration protection of aero-derivative gas generators and power turbines are usually not appropriate for protecting the machines against component malfunction primary damage.

Consequences often seen are substantial secondary damages to the engine as a result of e.g. ballor roller bearing failure. Effects typically vary from various blade or vane damage, root fretting or blade rubbing, etc.

Conventional engine shut-down systems do not activate until a certain unbalance of energy is released. The nature of the signals related to bearing and bladepass are too small in energy, and lies in too high a frequency range to be monitored by conventional engine protection systems.

This paper highlights the importance of the early detection and trending of vibrations, and taking necessary actions to prevent secondary damage to the engine, and describes the experience from a dedicated vibration and acoustic analysis system designed for early warning of common faults.
Flow Development in an Annular Contraction
Authors: Agrawal A. K. , Tinneti A. , Gollahalli S. R.
Published: December 2014

Power generating gas turbines employ an inlet duct or contraction to accelerate air to the operating inlet velocity of the compressor. Multiple passages of this kind are necessary in gas turbines with cycle modifications such as intercooling. An experimental investigation was carried out to obtain flow characteristics of a curved wall annular contraction. The results are described in terms of the velocity vectors, surface pressure coefficients, static and stagnation pressure distributions, and profiles of mean velocities, turbulence intensity, and Reynolds shear stress. The upstream flow conditions were changed to evaluate how they affected the flow development in the passage. Results show that the static pressure and axial velocity profiles at the contraction exit were uniform. Higher inlet turbulence increased the Reynolds shear stress although the effect on the static and total pressure fields was negligible. The overall stagnation pressure loss was approximately 2 to 3 percent of the dynamic head at the contraction exit.
Experimentally Determined Rotor Power Losses in Homopolar and Heteropolar Magnetic Bearings
Authors: Kasarda M. E. F. , Allaire P. E. , Norris P. M. , Mastrangelo C. , Maslen E. H.
Published: December 2014

The identification of parameters that dictate the magnitude of rotor power losses in radial magnetic bearings is very important for many applications. Low loss performance of magnetic bearings in aerospace equipment such as jet engines and flywheel energy storage systems is especially critical. Two basic magnetic bearing designs are employed in industrial practice today: the homopolar design, where the flux paths are of a mixed radial/axial orientation, and the heteropolar design, where the flux paths are primarily radial in nature.

The stator geometry and flux path of a specific bearing can have a significant effect on the rotor losses. This paper describes the detailed measurement of rotor losses for experimentally comparable homopolar and heteropolar designs. The two test bearing configurations are identical except for geometric features that determine the direction of the flux path. Both test bearing designs have the same air gap length, tip clearance ratio, surface area under the poles, and bias flux levels. An experimental test apparatus was used where run down tests were performed on a test rotor with both bearing designs to measure power losses. Numerous test runs where made for each bearing configuration by running multiple levels of flux density. The components of the overall measured power loss, due to hysteresis, eddy currents, and windage, were determined based on theoretical expressions for power loss. It was found that the homopolar bearing had significantly lower power losses than the heteropolar bearing.
Remediation of Gas Explosion Hazards in Gas Turbine Enclosures
Authors: Sinai Yehuda L. , Barrett Jim
Published: December 2014

Previous calculations exploiting Computational Fluid Dynamics techniques [1], and using the CFX-4 software, have indicated the presence of potential gas dispersion and explosion hazards in the acoustic enclosure and interconnect skid at Keadby power station. On the basis of those calculations, a different ventilation arrangement is proposed as a means of remediating the hazard. The proposed system is promising, indicating simultaneously a reduction in the size of the hazardous cloud and an increase in its detectability.
Status of Westinghouse Hot Gas Filters for Coal and Biomass Power Systems
Authors: Newby R. A. , Lippert T. E. , Alvin M. A. , Bruck G. J. , Sanjana Z. N.
Published: December 2014

Several advanced, coal- and biomass-based combustion turbine power generation technologies using solid fuels (IGCC, PFBC, Topping-PFBC, HIPPS) are currently under development and demonstration. A key developing technology in these power generation systems is the hot gas filter. These power generation technologies must utilize highly reliable and efficient hot gas filter systems if their full thermal efficiency and cost potential is to be realized. This paper reviews the recent test and design progress made by Westinghouse in the development and demonstration of hot gas ceramic barrier filters toward the goal of reliability. The objective of this work is to develop and qualify, through analysis and testing, practical hot gas ceramic barrier filter systems that meet the performance and operational requirements for these applications.
Variations in Upstream Vane Loading With Changes in Back Pressure in a Transonic Compressor
Authors: Probasco Douglas P. , Wolff J. Mitch , Copenhaver William W. , Chriss Randall M.
Published: December 2014

Dynamic loading of an inlet guide vane (IGV) in a transonic compressor is characterized by unsteady IGV surface pressures. This pressure data was acquired for two spanwise locations at a 105% speed operating condition, which produces supersonic relative Mach numbers over the majority of the rotor blade span. The back pressure of the compressor was varied to determine the effects from such changes. Strong bow shock interaction was evident in both experimental and computational results. Variations in the back pressure have significant influence on the magnitude and phase of the upstream pressure fluctuations. The largest unsteady surface pressure magnitude, 40 kPa, was obtained for the near stall mass flow condition at 75% span and 95% chord. Radial variation effects caused by the spanwise variation in relative Mach number were measured. Comparisons to a two-dimensional non-linear unsteady blade/vane Navier-Stokes analysis shows good agreement for the 50% span results in terms of IGV unsteady surface pressure. The results of the study indicate that significant non-linear bow shock influences exist on the IGV trailing edge due to the downstream rotor shock system.
Conceptual Design of the Cooling System for 1700°C-Class Hydrogen-Fueled Combustion Gas Turbines
Authors: Kizuka N. , Sagae K. , Anzai S. , Marushima S. , Ikeguchi T. , Kawaike K.
Published: December 2014

The effects of three types of cooling systems on the calculated operating performances of a hydrogen-fueled thermal power plant with a 1,700°C-class gas turbine were studied with the goal of attaining a thermal efficiency of greater than 60%. The combination of a closed-circuit water cooling system for the nozzle blades and a steam cooling system for the rotor blades was found to be the most efficient, since it eliminated the penalties of a conventional open-circuit cooling system which ejects coolant into the main hot gas stream.

Based on the results, the water cooled first-stage nozzle blade and the steam cooled first-stage rotor blade were designed. The former features array of circular cooling holes close to the surface and uses a copper alloy taking advantage of recent coating technologies such as thermal barrier coatings (TBCs) and metal coatings to decrease the temperature and protect the blade core material. The later has cooling by serpentine cooling passages with V-shaped staggered turbulence promoter ribs which intensify the internal cooling.
A Unique Small Gas Turbine Test Facility for Low-Cost Investigations of Ceramic Rotor Materials and Thermal Barrier Coatings
Authors: Schenk Björn , Eggert Torsten , Pucher Helmut
Published: December 2014

The paper describes a test facility for small-scale gas turbines, which basically has been designed and assembled at the Institute of Combustion Engines of the Technical University Berlin. The facility exposes ceramic rotor components to the most significant loads that occur during real gas turbine operation in a clearly predefined manner (high circumferential velocities and highest turbine inlet temperatures). The test facility allows the investigation of bladed radial inflow turbine rotors, as well as — in a preceding step — geometrically simplified ceramic or coated metallic rotors. A newly designed, ceramically lined, variable geometry combustion chamber allows turbine inlet temperatures up to 1450°C (2640 F). A fast thermal shock unit (switching time of about 1s), which is integrated into the test facility between the combustion chamber and the turbine scroll, can be used to create, for example, severe transient temperature gradients within the rotor components to simulate gas turbine trip conditions. In order to generate steady state temperature gradients, especially during disk testing, the rotor components can be subjected to an impingement cooling of the rotor back face (uncoated in case of TBC-testing). The test facility is additionally equipped with a non-contact transient temperature measurement system (turbine radiation pyrometry) to determine the test rotor surface temperature distribution during operation. Apart from the possibilities of basic rotor material investigations, the test facility can also be used to automatically generate compressor and turbine performance characteristics maps. The latter might be used to assess the aerodynamic performance of bladed ceramic radial inflow or mixed flow turbine rotors with respect to manufacturing tolerances due to near-net-shape forming processes (e.g., gelcasting or injection molding).
Low Ash Fuel and Chemicals From the Convertech Process
Authors: Benter Markus M. , Bywater Ian G. , Scott Ken E.
Published: December 2014

A new, efficient process for reducing the ash content, drying and fractionating raw lignocellulosic materials into chemicals and a dry solid end product, eminently suitable as a fuel for conventional boilers or for milling to a fine powder for gas turbine firing, shows strong potential for renewable power generation. The dry, low ash solids, termed “Cellulig™”, will also be suitable for gasification and to drive gas turbines. Sustainable liquid and gaseous fuels will become increasingly necessary in the 21st century to reduce dependence on imported fuels, to replace dwindling supplies of oil and natural gas and to avoid environmental damage from green house gases. Convertech Group Ltd. has built a demonstration biomass processing plant at Burnham, Canterbury, New Zealand, with investment from the energy industry and the Australian Energy Research and Development Council. The essential chemical and process engineering elements are described and the current and future development opportunities outlined.
Periodic Transition on an Axial Compressor Stator — Incidence and Clocking Effects: Part II — Transition Onset Predictions
Authors: Solomon W. J. , Walker G. J. , Hughes J. D.
Published: December 2014

Transition onset observations from a 1.5-stage axial compressor outlet stator presented in Part 1 of this paper are compared with the predictions of conventional transition correlations applied in a quasi-steady manner.

The viscous/inviscid interaction code MISES is used to predict the blade surface pressure distributions and boundary layer development. The temporal variation in transition onset is then predicted using ensemble-averaged freestream turbulence data from the compressor measurements. This simple procedure captures most significant features of the complex transition process on the compressor, and is clearly superior to fixed transition models based on long-term average freestream turbulence levels.

Parallel computations for both natural and bypass transition modes indicate that the natural transition mode tends to dominate on the compressor. This is at variance with turbine airfoil experience, where bypass transition is clearly more important.

Comparison of prediction and experiment highlights the significance of leading edge potential flow interactions in promoting periodic wake-induced transition. Viscous/inviscid interactions in the neighborhood of transition can also have an important influence on boundary layer stability and separation phenomena.
Aerodynamics of a Fuel Spoke in a Gas Turbine Combustor
Authors: Hu Iris Z. , Correa Sanjay M.
Published: December 2014

The three-dimensional unsteady flow in a gas turbine combustor was studied using CFD means. The flow structure around a fuel spoke is of interest not only because of pollutant issues, but also because of combustor operating issues such as combustion acoustics and potential flame-holding in the premixer. The CFD model was tested extensively in terms of grid density and lime-marching step size before the final calculation was made. It was shown that when a swirling flow crosses over a cylindrical fuel spoke, wake vortices are formed and a strong secondary flow is generated along the spanwise direction. A secondary vortex existed near the tip of the spoke. This complex flow structure affects the quality of fuel and air mixing and can be addressed by CFD-based design methods.
Experiment on Foreign Object Damage of Gas Turbine-Grade Silicon Nitride Ceramic
Authors: Yoshida Hiro , Nakashima Takashi , Yoshida Makoto , Hara Yasushi , Shimamori Toru
Published: December 2014

A new high quality turbine system using monolithic silicon-nitride ceramic is under development. In this study particle impact tests of the silicon-nitride have been tried at room and elevated temperatures with and without tensile load, which simulates centrifugal force of blade rotation. In the experiment 1 mm diameter particle is impacted at velocities up to 900 m s−1. In this paper, critical velocities for bending fracture and Hertzian cracks are examined. Moreover, strength degradation at elevated temperature and spall fracture of the blade are discussed. The main results are: 1) The bending fracture mode critical impact velocity for soft particles is higher than that for hard particles. 2)The impact parameter ϕ for initiation of Hertzian cracks ranges 1.08×10−5 – 1.56×10−5 for the materials tested. 3)Strength degradation at elevated temperature was clearly observed. 4) In the impact tests on blades spall fracture, which was caused by interaction of stress waves, appeared.
Effects of Alloy Composition on the Performance of Diffusion Aluminide Coatings
Authors: Mutasim Zaher , Kimmel Josh , Brentnall William
Published: December 2014

Nickel-based superalloys have been used in the gas turbine hot section components for their outstanding mechanical properties at elevated temperatures. Increasing the alloy strength at high temperature is usually achieved at the expense of the alloy’s environmental stability. Oxidation and high heat flux could be limiting factors in the use of these alloys at temperatures above 1800°F. To help overcome these limitations, protective coatings can be applied to the alloy surfaces to provide oxidation and hot corrosion resistance. These coatings are applied to alloys which can be produced in various forms such as equiaxed, directionally solidified or single crystals with varying chemistries. Elemental additions such as hafnium, rhenium, etc. are added to promote the strengthening of these alloys, and could result in varying effects on the coatability and coating performance. This paper discusses the effects of various substrate elements on the processing and stability of diffusion platinum aluminide coatings.
Entrance Effects on Diffused Film-Cooling Holes
Authors: Kohli A. , Thole K. A.
Published: December 2014

Film-cooling is a widely used method of prolonging blade life in high performance gas turbines and is implemented by injecting cold air through discrete holes on the blade surface. Most experimental research on film-cooling has been performed using round holes supplied by a stagnant plenum. This can be quite different from the actual turbine blade conditions in that a crossflow may be present whereby the internal channel Reynolds number could be as high as 90,000. This computational study uses a film-cooling hole that is inclined at 35° with respect to the mainstream and is diffused at the hole exit by 15°. An engine representative jet-to-mainstream density ratio of two was simulated. The test matrix consisted of fourteen different cases that were simulated for the two different blowing ratios in which the following effects were investigated: a) the effect of the orientation of the coolant supply channel relative to the cooling hole, b) the effect of the channel Reynolds number, and c) the effect of the metering length of the cooling hole. Results showed that the orientation of the coolant supply had a large effect whereby the worst orientation, in terms of a reduced adiabatic effectiveness, was predicted when the channel supplying the cooling hole was perpendicular to the mainstream. For this particular orientation, higher laterally averaged effectiveness occurred at lower channel Reynolds numbers and with the hole having a short metering length.
Analysis of an Accelerating Rotor-Bearing System With Flexible Damped Supports
Authors: Casanova Euro L. , Medina Luis U.
Published: December 2014

This paper deals with the dynamics of an accelerating unbalanced Jeffcott rotor-bearing system mounted on damped, flexible supports. The general equations of motion for such a system are presented and discussed. The rotor response was predicted, via numerical integration, for various cases in runup and rundown conditions and presented in graphical form. The effects of acceleration on the rotor peak amplitude and the speed at which the peak occurs is discussed and compared to steady state predictions.
A Fast Method to Obtain the Nonlinear Response of Multi-Mode Rotors Supported on Squeeze Film Dampers Using Planar Modes: Part II — Parametric Studies
Authors: Yakoub R. Y. , El-Shafei A.
Published: December 2014

This paper is a continuation of Part I, where the advantages of the fast algorithm to obtain the nonlinear response of multi-mode rotors supported on Squeeze Film Dampers (SFDs) are exploited. In Part I, the fast algorithm which relies on planar modal analysis and circular orbits to obtain a polynomial in rotor speed, is described. The advantages of the algorithm showing twenty five orders of magnitude computer time savings are discussed. In this paper, the fast algorithm is used to perform parametric studies on an aircraft gas turbine fan rotor (AGTFR). The parametric studies show the possibility of appropriately locating the SFD, to dampen the rotor modes. In addition, parametric studies are also used to determine the effect of the SFD parameters on the AGTFR unbalance response.
Gas Turbine Distributed Control Systems: Power Supply and Communication Data Bus Design Considerations
Authors: Sobanski Kurt , Martin Ken , Shi Fong , Greenway Brad
Published: December 2014

Over the past several decades, gas turbine control systems have evolved from hydro-mechanical systems to full authority redundant electronic systems. One advanced technology with potential to revolutionize the way engine system designers build new products is high temperature distributed controls. Distributed control systems put electronics close to control functions and reduce the number of interconnects between central processors and sensors or effectors. In distributed systems, power and data buses take the place of multiple discrete analog wire bundles found in centralized control systems. Distributed modules interconnected with power and data buses control effectors such as hydraulic actuators or solenoid valves and read sensors to measure pressures, temperatures and speeds. With distributed controls, many gas turbine applications will require high temperature electronics ruggedized to survive the demanding environment.

For these new systems, manufacturers must determine how to maximize the use of standard interfaces and electronic components and minimize the use of custom parts. Two particular areas would benefit the aerospace industry include distributed system power supplies and communication data buses since these designs play an important role in system cost, weight, size and reliability. Interface standardization will benefit engine manufacturers by lowering system cost and enabling inter-changeability of distributed engine control components from different suppliers. Careful attention to architectural design details for the power supplies and data buses can lead to systems that meet the needs of end users.
Computerized Educational Program in Turbomachinery
Authors: Léotard Philippe , Roy Samuel , Gaulard Frédéric , Fransson Torsten H.
Published: December 2014

The recent astonishing progress in computerized sciences have given birth to multimedia, an electronic revolution sometimes compared to the Industrial Revolution of the 19th century. The application of multimedia to education is one of the pre-eminent challenges of the future for academic and industrial institutions. It will certainly dramatically increase both teaching and learning capabilities.

Turbomachines traditionally belong to a scientific field of high technology. Education in the field of turbomachinery is however today principally performed in a traditional way, via lectures, calculation exercises and laboratory experiments. The use of multimedia technology opens up possibilities, which did not previously exist, to perform systematic parameter studies and calculations in undergraduate education, so that the students are able to get a taste of the physical variables that govern the phenomena lectured.

A “Multimedia Educational Package” within the sector Turbomachinery has been developed. This tool, available on CD-ROM and partially on Internet, mainly focuses at present on Thermodynamic Cycles, Turbomachines and Measuring Techniques in Thermal Engineering.

Interactivity is the key concept of the program. The knowledge assimilated by the user is assessed via multiple choice questions with guided answers. Various aspects of the developed model are also integrated in a Turbomachinery Graduate Curriculum.

Numerous tests have already been carried out during lectures, with a positive response from the students. Both students and teachers profoundly believe that, if combined with traditional education, this multimedia tool will enhance not only the knowledge of students, but also their interest in this field. As far as the authors are aware this is the most comprehensive multimedia educational package for turbomachines which presently exists. Figure 1 shows the introductory interface of this package and Fig. 2 an example of a simulation of velocity triangles in the “Turbomachines City”.
Measurements of Heat Transfer Coefficients in Rib-Roughened Trailing-Edge Cavities With Crossover Jets
Authors: Taslim M. E. , Li T. , Spring S. D.
Published: December 2014

Liquid crystals were used in this experimental investigation to measure the local and average heat transfer coefficients on the walls of six test sections simulating the trailing edge cooling cavity of a modern turbine blade. All test sections had trapezoidal cross sectional areas with two rows of racetrack-shaped slots on two opposite bases. Crossover jets, issued from the slots on one base, impinged on the test section rib-roughened walls and exited from the slots on the opposite wall. The first test section had all smooth walls and served as a baseline. The remaining five test sections were rib-roughened on either one wall or two opposite walls simulating the pressure and suction sides of the blade trailing-edge cooling cavity. In the first four tests, the jets issued into the test section along the test section plane of symmetry. Therefore, the two opposite walls, simulating pressure and suction sides of the blade, saw the same jet effects. This symmetric pattern was altered in test sections 5 and 6 in which the jets were tilted towards one or the other wall at an angle of 6°. The ribs in the roughened test sections, covering only 62% of the wall span, were mounted to the surface with an angle of attack to the jet axis, α, of 30°. The objective of this study was to investigate the effects that crossover jets have on the heat transfer coefficient and pressure recovery in a cooling cavity of a modern gas turbine blade. Major conclusions of this study were that combining the crossover jets with rib-roughened surfaces can be an effective method of cooling the trailing edge cavities and by proper arrangement of the jets and ribs, heat transfer coefficients on the two opposite walls can be tailored.
Stall Inception in the Compressor System of a Turbofan Engine
Authors: Höss B. , Leinhos D. , Fottner L.
Published: December 2014

Compressor flow instabilities have been the subject of a great number of investigations during the past decade. While most of this research work was done on isolated test-rig compressors this paper presents stall inception measurements in the compressor system of a two-spool turbofan engine at various power settings. Several analysing techniques such as temporal low-pass and band-pass filtering, temporal and spatial Fourier transforms including power-spectral-density calculations of the spatial coefficients and a wavelet analysing technique are applied. For the low pressure compressor three different types of stall inception processes were observed depending on the rotor speed. At low-speed stall originates from spike-type precursors, while long wavy pressure fluctuations corresponding to modal waves were observed prior to stall at mid-speed for undistorted inlet flow. At high-speed the rotor shaft unbalancing dominates the stall inception process as an external forcing function. In the case of distorted inlet flow spike-type stall inception behavior dominates throughout the speed range. While filtering and the Fourier spectra give a good insight into the physical background of the stall inception process (but with a very short warning time), the wavelet transform indicates the approach of the stalling process a few hundred rotor revolutions in advance independendy of the type of precursor. Setting up a reliable stall avoidance control based on this analysis scheme seems to be promising.
Elevated-Temperature, ‘Ultra’-Fast Fracture Strength of Advanced Ceramics: An Approach to Elevated-Temperature “Inert” Strength
Authors: Choi Sung R. , Gyekenyesi John P.
Published: December 2014

The determination of ‘ultra’-fast fracture strengths of five silicon nitride ceramics at elevated temperatures has been made by using constant stress-rate (“dynamic fatigue”) testing with a series of ‘ultra’-fast test rates. The test materials included four monolithic and one SiC whisker-reinforced composite silicon nitrides. Of the five test materials, four silicon nitrides exhibited the elevated-temperature strengths that approached their respective room-temperature strengths at an ‘ultra’-fast test rate of 33 × 104 MPa/s. This implies that slow crack growth responsible for elevated-temperature failure can be eliminated or minimized by using the ‘ultra’-fast test rate. These ongoing experimental results have shed light on laying a theoretical and practical foundation on the concept and definition of elevated-temperature “inert” strength behavior of advanced ceramics.
Influence of Vane-Blade Spacing on Transonic Turbine Stage Aerodynamics: Part II — Time-Resolved Data and Analysis
Authors: Busby Judy A. , Davis Roger L. , Dorney Daniel J. , Dunn Michael G. , Haldeman Charles W. , Abhari Reza S. , Venable Brian L. , Delaney Robert A.
Published: December 2014

This paper presents results of a combined experimental/computational investigation into the effects of vane-blade spacing on the unsteady aerodynamics of a transonic turbine stage. Time-resolved data were taken in a shock-tunnel facility in which the flow was generated with a short-duration source of heated and pressurized air. This data is compared with the results obtained from four unsteady Navier-Stokes solvers.

The time-resolved flow for three axial spacings is examined. For each vane-blade spacing, the inlet conditions were nearly identical and the vane exit flow was transonic. Surface-mounted high-response pressure transducers at midspan were used to obtain the pressure measurements.

The computed two-dimensional unsteady airfoil surface pressure predictions are compared with the Kulite pressure transducer measurements. The unsteady and axial spacing effects on loading and performance are examined.

In general the numerical solutions compared very favorably with each other and with the experimental data. The overall predicted stage losses and efficiencies did not vary much with vane/blade axial spacing. The computations indicated that any increases in the blade relative total pressure loss were offset by a decrease in vane loss as the axial spacing was decreased. The decrease in predicted vane total pressure loss with decreased axial spacing was primarily due to a reduction in the wake mixing losses. The increase in predicted blade relative total pressure loss with a decrease in axial spacing was found to be mainly due to increased vane wake/blade interaction.
Viscous and Inviscid Linear/Nonlinear Calculations Versus Quasi 3D Experimental Cascade Data for a New Aeroelastic Turbine Standard Configuration
Authors: Fransson T. H. , Jöcker M. , Bölcs A. , Ott P.
Published: December 2014

This paper presents a new International Standard Configuration to be added to an already existing set of 10 configurations for unsteady flow through vibrating axial-flow turbomachine cascades. This 11th configuration represents a turbine blade geometry with transonic design flow conditions with a normal shock positioned at 75% real chord on the suction side. Out of a set of test cases covering all relevant flow regimes two cases were selected for publication: A subsonic, attached flow case and an off-design transonic case showing a separation bubble at 30% real chord on the suction side are published. The performed tests are shown to be repeatable and suitable for code validations of numerical models predicting flutter in viscous flows.

The validity of the measured data of the two public cases was examined and comparisons with other tests were conducted. Sometimes a large difference in aerodynamic damping was observed on cases with similar flow conditions. This was investigated at three transonic cases with almost identical inlet flow conditions and only small variations in outlet Mach Number. It was found that the differences in the global damping are due to very local changes on the blade surface in the shock region, which obtain a large influence by the integration because of the discrete measuring points. Hence it is recommended not to look at the global damping for code validations but more precisely to the local values. These show a common tendency, which is reproducible with different numerical methods.

This was demonstrated with a potential model, a linear Euler model, a nonlinear Euler model and a Navier-Stokes solver, all applied to predict flutter of each test case with a 2D/Q3D approach. The limitations of inviscid codes to predict flutter in viscous flow regimes is demonstrated, but also their cost advantage in attached flow calculations. The need of viscous code development and validation is pointed out. This should justify and encourage the publication of thoroughly measured test cases with viscous effects.
Characteristics of One Stage Radial Centrifugal Turbine
Authors: Sekavčnik Mihael , Tuma Matija , Florjančič Dušan
Published: December 2014

The paper concerns an investigation of the characteristics of one stage radial centrifugal turbines (RCT). A test turbine with parallel side walls and specific speed nqT ≈ 25 was designed as a special case due to simplicity of the execution. The tests were carried out with air, whrerby the flow, due to small Mach–number, could be considered as incompressible. For that purpose, a special test stand was built, which enables the measurement of required values. The effects of changing some cascade parameters of stator and rotor were investigated. The results of the measurements are presented in shell diagrams in dimensionless form and compared to each other. Paralell to the measurements some calculations of fluid flow in particular parts of RCT were carried out by using TASCflow package. On the basis of experimental and theoretical research an information of optimum RCT design has been obtained from the efficiency and pressure number point of view. The generalised shape of the shell diagrams shows the favourable characteristics particular to RCT, which opens new perspectives on the use of this type of turbine. There are numerous of possibilities of energy recuperation, to use the RCT, especially in a processing industry, which become due to ecological and also economical aspect very interessting.
Effect of the Shear Driven Liquid Wall Film on the Performance of Prefilming Airblast Atomizers
Authors: Rosskamp Heiko , Willmann Michael , Meisl Jürgen , Meier Robert , Maier Georg , Wittig Sigmar
Published: December 2014

Advanced prefilming airblast atomizers are widely used for low emission combustors since they deliver a fine spray almost independently of the fuel flow rate. The droplet spectrum produced by this type of atomizer results from the aerodynamic forces at the atomizer edge and from the fuel properties prior to the film disintegration. Therefore, the wall film temperature is an important parameter affecting the fuel properties and in turn the atomization quality. Even though this atomizer type became well investigated (Lefebvre 1989, Rizk et al. 1987, Sattelmayer et al. 1989), still no general quantitative relationship between atomizer design and spray quality could be established since the fuel state at the atomizer edge cannot be precisely predicted yet.

In extending earlier experimental and theoretical work on airblast atomizers (Sattelmayer et al. 1989, Himmelsbach et al. 1994, Willmann et al. 1997) and recent advances in the numerical modeling of wall film flows (Rosskamp et al. 1997a), this paper presents a numerical approach to judge the effect of fuel mass flow, air flow and the film length (i. e. length of atomizer lip) on the temperature of the liquid at the atomizer edge. The computer code developed provides detailed information on the wall film flow and the nozzle wall temperature. For the prediction of heat transfer to the film a new model has been developed which is based on measurements of the internal film flow (Elsäßer et al 1997).

This new numerical approach can serve as a design tool to evaluate the effects of design modifications during atomizer development with view to their effect on atomization performance. The paper includes the theory for two-phase flow modeling and a generic parameter study that points out that the liquid loading and the length of the atomizer lip are important parameters in atomizer design. The calculations presented in the paper emphasize the necessity of coupled two-phase flow calculations because the film strongly interacts with the gas phase and the predicted atomizer performance is sensitive to changes in the air flow.
Coupled Acoustic-Structure Analysis of an Annular DLE Combustor
Authors: Cronemyr Peter J. M. , Hulme Chris J. , Troger Christian
Published: December 2014

With the advent of today’s dry low emission (DLE) combustors for industrial gas turbines (GT), an additional type of load case other than thermal loading on the combustor structure, has put itself heavily into focus, namely pulsation loading. Although recognised for decades in rocket engines and ram-jets, it was not until the incorporation of diluted flames and completely closed combustors, used to reduce NOx emissions, that thermo-acoustically excited pressure pulsations became an issue in the design of industrial GT combustors.

This paper presents the computational methods that are available for the analysis of this phenomenon, and their application in the development of ABB’s latest annular DLE combustor. Among these are calculations of burner excitation frequency, pressure wave propagation within the combustor, acoustic and structural eigen frequencies, and coupled acoustic structural analysis.

Guidelines for the combustor design to prevent instabilities and coupling of air and structure pulsations are suggested.
Surface Heat Transfer Measurements of a Scaled Rib-Roughened Serpentine Cooling Passage by Use of a Transient Liquid Crystal Technique
Authors: Funazaki Ken-ichi , Ishizawa Kouhei , Yamawaki Shigemichi
Published: December 2014

This study is aimed at providing heat transfer characteristics of the three-pass turbulated serpentine cooling channel inside a 10:1 scaled model of an actual turbine blade. A transient method using Thermochromic Liquid Crystal (TLC) is employed to measure the surface heat transfer distribution inside the model. Great attention is paid to the streamwise decrease in the mainstream temperature due to the heat absorption into the test model. To overcome this problem, the present study employed the linear interpolating method used by Ekkad and Han (1997) to estimate the local air bulk temperature. The soundness of the measuring method is verified through the heat transfer measurements of straight-duct models with and without turbulence promoting ribs. It follows from the heat transfer measurement of the serpentine model, in conjunction with the flow visualization, that the geometries of the cross-section of the cooling passage influence the flow pattern, resulting in substantial change in heat transfer distribution in the serpentine model in comparison with that of the straight-duct model.
Steady and Unsteady Three Dimensional Flow Field Downstream of an Embedded Stator in a Multistage Axial Flow Compressor: Part 3 — Deterministic Stress and Heat-Flux Distribution and Average-Passage Equation System
Authors: Suryavamshi N. , Lakshminarayana B. , Prato J.
Published: December 2014

The results from the area traverse measurements of the unsteady velocity and total temperature downstream of the second stator of a three stage axial flow compressor have been correlated to derive various deterministic stress and heat-flux terms. These terms are consistent with those arising from the average-passage equation system of Adamczyk (1985). The deterministic periodic stress and heat-flux terms were found to be larger than the aperiodic terms for both the normal and shear components. Consequently the terms involving the aperiodic components in the average-passage equations could be neglected for stator exit and rotor inlet flow modeling. The deterministic periodic normal and shear stresses were seen to be most significant in the stator wakes away from the endwall regions. The most significant shear stress correlation was between the axial and tangential velocity components. Since the correlations involving the radial component were small, it is postulated that the dominant mechanism for mixing (in the radial direction) is due to the steady deterministic radial velocity. All three components of deterministic heat-flux were found to be significant in this flow field especially in the wakes. The dominant terms in the average-passage equation system away from the endwalls were due to the tangential gradient compared to the radial gradient terms and both the terms were found to be of equal importance in the hub and casing endwall regions.
Strength Distribution Changes in a Silicon Nitride as a Function of Stressing Rate and Temperature
Authors: Wereszczak Andrew A. , Breder Kristin , Andrews Mark J. , Kirkland Timothy P. , Ferber Mattison K.
Published: December 2014

Machining damage (a surface flaw) and porous-region-flaw (a volume flaw) populations limited the flexure strengths of a commercially available silicon nitride at 25°C, while these same flaws, along with inclusions, limited flexure strengths at 850°C. The machining damage and porous region flaws were the primary interest in the present study because they caused failure at both temperatures. Censoring revealed that the two-parameter Weibull strength distributions representing each flaw population changed as a function of stressing rate (i.e., dynamic fatigue) and temperature. A decrease in the Weibull scaling parameter is recognized as an indication of slow crack growth or time-dependent strength reduction in monolithic ceramics. Available life prediction codes used for reliability predictions of structural ceramic components consider the slow crack growth phenomenon. However, changes in the Weibull modulus are infrequently observed or reported, and typically are not accounted for in these life prediction codes. In the present study, changes in both Weibull parameters for the strength distributions provided motivation to the authors to survey what factors (e.g., residual stress, slow crack growth, and changes in failure mechanisms) could provide partial or full explanation of the observed distribution changes in this silicon nitride. Lastly, exercises were performed to examine the effects of strength distribution changes on the failure probability prediction of a diesel exhaust valve. Because the surface area and volume of this valve were substantially larger than those of the tested bend bars, it was found that the valve’s failure probability analysis amplified some slight or inconclusive distribution changes which were not evident from the interpretation of the censored bend bar strength data.
Refrigeration Process With High Speed Technology
Authors: Kuosa Maunu , Backman Jari , Talonpoika Timo , Sallinen Petri , Larjola Jaakko , Honkatukia Juha
Published: December 2014

The aim of this study was to make a computer program that simulates a standard refrigeration process, and a process provided with a bubble intercooler. A further object of the study was to establish the suitability of a turbocompressor for small refrigeration plants.

Firstly the fundamentals of refrigeration machines and industrial refrigeration systems are discussed. An iteration procedure of steady state refrigeration process calculation is introduced. Fluid properties are calculated with the program units created for the modelling of an ORC power plant. Specific input files were made for 6 process fluids R134a, R123, isopentane, isobutane, toluene and ammonia. The compressor program is linked to the refrigeration process simulation program in order to model single stage and two stage radial compressors. The Turbo Pascal program made for microcomputers is modular, which makes it possible to develop and test the program unit by unit. The maximum deviations of fluid properties from those in tables was found to be less than 1 per cent.

To simulate tailor-made refrigeration plants, a simple model is required. On nominal loads the program estimates an optimum intermediate pressure for the bubble process and optimum rotational speed for the radial compressor(s). The lowering of the rotational speed by an inverter gives high COP-values on partial loads of the plant. Based on the example calculation, a two stage turbocompressor calculated with isopentane as the working fluid, a cooling capacity of 1200 W seems to be feasible.
Experimental Investigation of GTX100 Combustor Liner Cooling System
Authors: Nilsson Ulf E. , Lindqvist Lars O. , Eriksson Ingemar A. G. , Hylén Jonas N.
Published: December 2014

The liner cooling for GTX100’s annular combustor has been successfully tested. Because of high heat load at the flame attachment point, a good design is very important. The design presented here offers robustness and high performance, combined with no dilution. The cooling system is a turbulated convective design, which were experimentally investigated in a plastic (perspex) model of a full scale 60° sector of the combustor. The importance of a high performance liner cooling is obvious. This design generates low pressure drop, better combustion (circumferential even flow from the liner cooling) and it gives lower flame temperature (minimizes the emissions). The influence of disturbances on the cooling and burner performance is presented in this paper.