bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental and Theoretical Investigations of Heat Transfer in Closed Gas-Filled Rotating Annuli II
Authors: Bohn D. , Emunds R. , Gorzelitz V. , Krüger U.
Published: February 2015

Increasing the thermal efficiency by higher turbine inlet temperatures is one of the most important aims in the area of gas turbine development. Because of the high temperatures not only the turbine vanes and blades have to be cooled, but also the knowledge of the mechanically and thermally stressed parts in the hottest zones of the rotor are of great interest. The prediction of the temperature distribution in a gas turbine rotor containing closed, gas-filled cavities, for example in between two discs, has to account for the heat transfer conditions encountered in these cavities. In an entirely closed annulus forced convection is not present, but a strong natural convection flow exists, induced by a non uniform density distribution in the centrifugal force field.

In /3/ experimental and numerical investigations on rotating cavities with pure centripetal heat flux had been carried out. The present paper deals with investigations on a pure axially directed heat flux. An experimental set-up was designed to realize a wide range of Ra-numbers (2·108<Ra<5·1010) usually encountered in cavities of gas turbine rotors.

Parallel to the experiments numerical calculations have been conducted. The numerical results are compared with the experimental data. The numerical scheme is also used to account for the influence of Re-numbers on heat transfer without changing the Ra-number. This influence could not be pointed out by experiments, because a variation of the Re-Ra characteristic of the employed annuli was not possible.

It was found that the numerical and experimental data are in quite good agreement, with exception of high Ra-numbers, where the numerical scheme predicts higher heat transfer than the experiments show. One reason may be that in the experiments the inner and outer cylindrical walls were not really adiabatic, an assumption used in the numerical procedure. Moreover the assumption of a 2-D flow pattern may become invalid for high Ra-numbers. The influence of 3-D effects was studied with the 3-D-version of the numerical code.

In opposite to the radial directed heat transfer it was found that the Nu-number is much smaller and depends strongly on the Re-number — whereas the radial heat transfer is only weakly influenced by the Re-number.
Modelling Alkali Salt Vapour Deposition in the British Coal Topping Cycle System
Authors: Fackrell John E. , Tabberer Richard J. , Young John B. , Fantom Ian R.
Published: February 2015

The British Coal Topping Cycle is a proposed advanced coal-fired power generation system in which gases derived from the coal and containing low levels of alkali vapours are passed to a gas turbine. The deposition of these vapours onto the turbine blades needs to be assessed because deposited alkali salts may accelerate corrosion and hence reduce blade lifetimes.

A model for the thermochemical behaviour was derived by assuming frozen chemistry in the external and boundary layer flows, but equilibrium at the surface and within the deposit, including an allowance for non-ideal behaviour in the deposit. The model is currently formulated for sodium and potassium chlorides and sulphates in the deposit and can deal with deposition to either a solid or liquid deposit. The boundary layer mass transfer has been calculated by both a simple heat transfer analogy model and a numerical solution of the two-dimensional diffusion equation within the boundary layer.

Some examples of general results obtained with the model are described, including a comparison of the effects of different deposit phase, non-ideal behaviour and film cooling. Some predictions are compared with measurements of alkali salt deposition obtained in experiments simulating the conditions expected in a Topping Cycle system.
Film Cooling Effectiveness and Heat Transfer Coefficients for Slot Injection at High Blowing Ratios
Authors: Bittlinger G. , Schulz A. , Wittig S.
Published: February 2015

In continuation of earlier studies comparing heat transfer results for flow over a backward facing step and a jet in crossflow, a comprehensive data base for slot film cooling is presented. Specifically, heat transfer measurements adjacent to the injection slot for high blowing ratios were of interest. The heat transfer distributions for these conditions are of increasing significance in modern combustor liners. The new data base includes velocity and temperature profile measurements, adiabatic wall temperature and heat transfer measurements and will serve as a data base for testing newly developed numerical models.
A Model for Calculating Turbulent Friction and Heat Transfer Coefficients of a Rectangular Duct With Angled Ribs on Two Opposite Walls
Authors: Tran Le T.
Published: February 2015

A new model is presented in this paper to calculate the pressure drop and the heat transfer coefficient for a rectangular duct with two smooth walls and two rough walls. Ribs on the rough walls may be at an angle with the main flow and are distributed in a repeated pattern. The model is based on the law-of-the-wall theory, which is known to give satisfactory results for turbulent flows in a circular duct or a channel, and for two-dimensional boundary layer flows. When the theory is applied to a rectangular duct, it gives simplified relationships between the friction, heat transfer coefficients, the flow Reynolds number, and geometry parameters, which include the rib angle, rib height, the rib pitch, and the duct aspect ratio. Comparisons with experimental data show that the present model gives satisfactory results for a wide range of Reynolds numbers and geometry parameters. A Prandtl number dependence is retained for applications involving fluids other than air.
Using Team and Fault Tree Analysis to Determine Areas of Responsibility for Machinery Failure
Authors: Forbes William H.
Published: February 2015

This paper illustrates how NOVA, its vendors and subvendors have successfully applied the “Team Concept” and “Fault Tree Analysis” to resolve problems encountered with seven (7) warranted turbo-compressor packages. It describes the “TEAM/FAULT TREE” process used, as well as the benefits of such an exercise (ie. the quick identification of a technical solution and the facilitation of commercial negotiations to a satisfactory conclusion for all parties concerned).
Gas Turbine Temperature Spread Monitoring Detection of Combustion System Deterioration
Authors: Knowles Martin
Published: February 2015

Deterioration in the burners or combustion chamber of a gas turbine can result in uneven and unstable air flow and excessive temperature profiles, any of which will produce unnecessary and potentially damaging stress cycles.

Detection relies on comparisons of thermocouples located circumferentially at a convenient point in the hot gas path. The techniques usually recommended by engine manufacturers compare absolute values taking no account of any initial asymmetry due to manufacturing tolerances, thermocouple positioning or turbulence of the gas flow at the measurement point.

The initial profile of measured temperatures can be established empirically over the operating range and it is deviation from this profile which provides a sensitive measure of deterioration in the combustion system. This more sensitive technique provides earlier detection of impending failure.

This paper reviews the normally recommended approach, presents the case for detecting departure from the footprint and looks at a case study.
Analysis, Design, and Testing of a Low Profile Deflection Pad™ Thrust Bearing in an Industrial Gas Turbine
Authors: Jain Dilip , Zeidan Fouad , Wittmeyer Michael
Published: February 2015

This paper describes the analysis, design, and testing of a low profile thrust bearing in a DR 990 industrial gas turbine. High unit loads and speeds, and the need to maintain low frictional power loss presented many challenges. The thrust pad design utilizes a flexure pivot, which allow near optimum performance for a wide range of speeds and loads in comparison to a fixed geometry taper land design. The use of high conductivity material for the thrust pads and directed lubrication allowed operation at lower temperatures. Finite element analysis was used to model the pad structure and pivot support. This analysis was confirmed by measuring the pad tilt using an eddy current probe. The test was conducted in a controlled thrust rig allowing accurate application and measurement of the thrust load. Precision manufacturing of the spherical seat and the application of a proprietary coating allowed better aligning capability under load. The bearing was tested in an engine at a range of speeds and loading conditions. The results are presented and compared with the existing fixed geometry bearing design. The bearing is currently running in an engine in the field and has accumulated 2,400 hours of operation with no forced outages.
An Overview of International Electrical and Safety Codes and Standards Governing the Application of Turbomachinery in Hazardous Areas
Authors: Kidd H. Allan , Talabisco George
Published: February 2015

A plethora of codes, standards, and guidelines exist throughout the world offering a significant amount of input for the design engineer as he attempts to safely apply hydrocarbon processing equipment to hazardous areas. Fire suppression standards generated in and applicable to use in North America are also used throughout Europe. Off shore techniques are more stringent and must be carefully followed to protect the owner’s investment and for the safety of the equipment operators.

This paper is a digest of all internationally recognized codes issued through commonly employed authorities extracting the peculiarities from each and building upon some basic premises to form a design specification that can be modified to suit the specific application or individual company policies.

The discussion will be limited to enclosed and unenclosed gas turbine drivers and hydrocarbon gas processing compressors. Indoor and out door installations of this type equipment will also be considered.
Heat Transfer Predictions in Rotating Radial Smooth Channel: Comparative Study of k-ε Models With Wall Function and Low-Re Model
Authors: Tekriwal Prabhat
Published: February 2015

The two-equation models (k-ε) have been employed to predict turbulent flow and heat transfer for radially outward flow in a cooling duct rotating in orthogonal mode. The low-Reynolds-number model, which permits integration of the Navier-Stokes equations to the wall, has been used. The results from the low-Re model and the high-Re model with “Wall Function” are compared with the experimental data available in literature. Computations have been made for a range of Reynolds numbers (2500 to 25000) and a range of rotation numbers (0.088 to 0.24). Different conditions such as uniform wall temperature, uniform wall heat flux and uneven wall temperatures have been used as boundary conditions for heat transfer. The low-Re model does not perform as well as the Wall Function model in predicting heat transfer for flows at high Reynolds number. However, the low-Re model predictions are better than those from the high-Re Wall Function model for flows at low Reynolds number. In fact, for the geometry considered (1.27 cm × 1.27 cm duct) it becomes necessary to use the low-Re model for flows at low Reynolds number because of the limitation of the Wall Function. Heat transfer predictions from the low-Re model are within 10–40% for flows at low Reynolds number. The disadvantage of the low-Re model, in addition to the large number of cells requirement, is the slow convergence rate.
Spa “Mashproekt” Combined Cycle Plants
Authors: Kovalenko A. V. , Belyayev F. F. , Lazarev V. V. , Lupandin V. V.
Published: February 2015

The paper describes the history of design, development and 15 years’ sea-going experience of the MASHPROEKT combined cycle plants.

Four R060 type ships powered by eight combined cycle plants each rated at. 25.000 h.p. and three naval ships with six cruise combined cycle plants each rated at. 10, 000 h.p. are in service now. Using of combined cycle permitted to increase their thermal efficiency by 20–30 per cent.

To increase efficiency at a speed of 15…18 knots, a special mode of operation is used: the gas turbine and waste heat boiler operate at one board and steam generated by this waste heat boiler is used for a steam turbine of other board. Total operation life of all marine gas turbine units exceeds 330,000 hours.
A Catalytic Combustor for High-Temperature Gas Turbines
Authors: Vortmeyer Nicolas , Valk Martin , Kappler Günter
Published: February 2015

Catalytic combustion has been the subject of thorough research work for over two decades, mainly in the U.S. and Japan. However, severe material problems in the ceramic or metallic monolith prevented regular operation in most cases. Still, during these two decades, turbine inlet temperatures were raised remarkably, and lean premix combustors have become standard in stationary gas turbines.

In view of these facts, a simple “monolith-in-tube” concept of a catalytic combustor was adapted for the use in high-temperature gas turbines. Its essential feature is the fact that a considerable portion of the homogeneous gas phase reaction is shifted to the thermal reactor, thus lowering the catalyst temperature. This is achieved by the employment of very short catalyst segments. The viability of this concept has been demonstrated for a variety of pure hydrocarbons, alcohols as well as common liquid fuels.

Extensive experimental investigations of the atmospheric combustor lead to the assessment of parameters such as reference velocity, fuel-to-air ratio and fuel properties. The maximum combustor exit temperature was 1,673 K with a corresponding catalyst temperature of less than 1,300 K for Diesel fuel. Boundary conditions were in all cases combustion efficiency (over 99.9%) and pressure loss (less than 6%).

Additionally, a model has been developped to predict the characteristic values of the catalytic combustor such as necessary catalyst length, combustor volume and emission characteristics. The homogeneous reaction in the thermal reactor can be calculated by a one-dimensional reacting flow model.
Unsteady 3D Flow in a Single-Stage Transonic Fan: Part I — Unsteady Rotor Exit Flow Field
Authors: Cherrett M. A. , Bryce J. D. , Ginder R. B.
Published: February 2015

Detailed unsteady aerodynamic measurements have been taken in a single-stage transonic fan with a very high stator-hub loading. 2D dynamic yawmeter probes, capable of measuring mean and fluctuating levels of stagnation pressure, static pressure and yaw angle have been traversed at rotor exit, and downstream of the stator along with several types of pneumatic 3D probe. Part I of this paper describes the dynamic yawmeters and their performance, and presents ensemble-averaged stagnation pressure and random stagnation pressure unsteadiness measurements taken at rotor exit. These are used to illustrate the salient features of the rotor flow field, and the effects of compressor aerodynamic loading. Part II presents measurements taken at stator exit.
Assessment of Damage in Ceramics and Ceramic Matrix Composites Using Ultrasonic Techniques
Authors: Rokhlin S. K. , Chu Y. C. , Baaklini G. Y.
Published: February 2015

This paper addresses the application of ultrasonic methods to damage assessment in ceramics and ceramic matrix composites. It focuses on damage caused by thermal shock and oxidation at elevated temperatures. The damage-induced changes in elastic constants and elastic anisotropy are determined by measuring the velocities of ultrasonic waves in different propagation directions within the sample. Thermal shock damage measurement is performed in ceramic samples of reaction bonded silicon nitride (RBSN) and aluminum oxide. Thermal shock treatment from different temperatures up to 1000°C is applied to produce the microcracks. Both surface and bulk ultrasonic wave methods are used to correlate the change of elastic constants to microstructural degradation and to determine the change in elastic anisotropy induced by microcrack damage. Oxidation damage is studied in silicon carbide fiber/reaction bonded silicon nitride matrix (SCS-6/RBSN) composites. The oxidation is done by exposing the samples in a flowing oxygen environment at elevated temperatures, up to 1400°C, for 100 hours. Significant changes of ultrasonic velocities were observed for composites before and after oxidation. The elastic constants of the composites were determined from the measured velocity data. The Young’s modulus in the fiber direction as obtained from ultrasonic measurements decreases significantly at 600°C but retains its original value at temperatures above 1200°C. This agrees well with the results of destructive tests by other authors. The transverse longitudinal and shear moduli obtained from ultrasonic measurements decrease continually until 1200°C. The results of this work show that the damage-induced anisotropy in both ceramics and ceramic matrix composites can be determined successfully by ultrasonic methods. This suggests the possibility of assessing damage severity using ultrasonic techniques.
Flow Behavior With an Oscillating Motion of the Impinging Jet in a Dump Diffuser Combustor
Authors: Honami Shinji , Shizawa Takaaki , Sato Atsushi , Ogata Hideki
Published: February 2015

The paper presents the flow behavior with an oscillating motion of an impinging jet upon a flame dome head and its reattachment to the casing wall, when a distorted flow is provided at the inlet of the dump diffuser combustor. Laser Doppler Velocimeter was used for the measurements of the time-averaged flow within a sudden expansion region. Surface pressure fluctuation survey on the flame dome head and flow visualization by a smoke wire technique with a high-speed video camera were conducted from the view point of the unsteady flow feature of the impinging jet. There exists the high vorticity region at the jet boundary resulting in the production of the turbulence kinetic energy. In particular, higher vorticity is observed in the higher velocity side of the jet. The jet near the dome head has the favorable characteristics about the flow rate distribution into the branched channel. Reynolds shear stress and turbulence energy are remarkably produced near the reattachment region. The jet has an oscillating motion near the dome head with asymmetric vortex formation at the jet boundary.
Dynamic Constraints on HRSG Drum Design
Authors: Galopin J.-F.
Published: February 2015

Heat Recovery Steam Generator start-ups are most often thought of as being a delicate step in the pressurization of the boiler, as are trips and shutdowns. One reason for this is the so-called swell effect and the problems which can arise when this event occurs while another might be the different controls that have to be monitored at the same time. A dynamic software is actually used by Cockerill Mechanical Industries (C.M.I.) to simulate the behaviour of all significant thermodynamic variables of the system as well as the temperatures of the materials, and typical control variables versus time.

During the development of this software, special care has been given to the study of the influence of the vaporizer pressure drop on the temperature and pressure gradient at the inlet of the drum, where critical thermal and mechanical stresses might appear. The circulation pump specifications have been taken into account. A discussion is presented in order to measure the influence of this pressure drop on the highest observed stresses during the swell effect as well as the pressure gradient used during the pressurization on the fatigue analysis of the drum and its nozzles. Their design is then briefly overviewed using two methods of calculations.
System Optimization of Humid Air Turbine Cycle
Authors: Xiao Yunhan , Lin Rumou , Cai Ruixian
Published: February 2015

The humid air turbine (HAT) cycle, proposed by Mori et al. and recently developed by Rao et al. at Flour Daniel, has been identified as a promising way to generate electric power at high efficiency, low cost and simple system relative to combined cycle and steam injection gas turbine cycle. It has aroused considerable interest.

Thermodynamic means, such as intercooling, regeneration, heat recovery at low temperature and especially non-isothermal vaporisation by multi-phase and multi-component, are adopted in HAT cycle to reduce the external and internal exergy losses relative to the energy conversion system. In addition to the parameter analysis and the technical aspect of HAT cycle, there is also a strong need for “systems” research to identify the best ways, of configuring HAT cycle to integrate all the thermodynamic advantages more efficiently to achieve high performance.

The key units in HAT cycle are analyzed thermodynamically and modelled in this paper. The superstructure containing all potentially highly efficient flowsheeting alternatives is also proposed. The system optimization of the HAT cycle is thus represented by a nonlinear programming problem. The problem is solved automatically by a successive quadratic algorithm to select the optimal configuration and optimal design parameters for the HAT cycle.

The results have shown that the configuration of the HAT cycle currently adopted is not optimal for efficiency and/or specific power, and the current pressure ratio are too high to be favorable for highest performance. Based on the current technical practice, the optimal flowsheeting for thermal efficiency can reach 60.33% when TIT=1533K, while the optimal flowsheeting for specific power can achieve 1300kW/kg/s air for TIT at 1533K. The optimal flowsheeting configuration is compared favorably with the other existing ones.
Experimental Investigation of Rotor/Rotor Interaction in a Hydrodynamic Torque Converter Using Hot-Film Anemometry
Authors: Browarzik Volker
Published: February 2015

Unsteady flow measurements were performed to investigate the internal flow field of a torque converter, especially unsteady rotor/rotor-interaction in the region between pump exit and turbine inlet.

Instantaneous flow data were measured with hot-film probes and a computer based data acquisition system. The commonly used ensemble averaging method was adapted to this special case with two independently rotating impellers.

Velocity profiles of the flow in the relative frame of reference of the pump impeller were evaluated and they were used to generate a computer animation.

The paper gives an overview over the test facilities and the background of the present investigations. It follows a discussion of some essential aspects concerning the use of hot-film anemometry. The methods used to evaluate the data are described in detail and measuring results of the region between pump exit and turbine inlet are presented.
An Inviscid-Viscous Method to Model Leading Edge Separation Bubbles
Authors: Calvert W. John
Published: February 2015

Separation bubbles are likely to occur near the leading edges of sharp-edged blade sections in axial compressors and turbines, particularly when the sections are operated at positive incidence. Typically the flow reattaches a short distance from the leading edge as a turbulent boundary layer, the thickness of which depends on the details of the separation bubble. The overall performance of the blade section can be significantly affected by the thickness of this initial boundary layer — in some cases blade stall is mainly associated with the change in thickness of the layer as blade incidence is increased. A recent experimental study at the Whittle Laboratory, Cambridge demonstrated the importance of the blade leading edge shape on the separation bubble. In the present work, an inviscid-viscous method has been set up to model the experimental data and to provide a way of predicting the performance of this critical region for different leading edge shapes.
New Catalytic Combustion Technology for Very Low Emissions Gas Turbines
Authors: Betta R. A. Dalla , Schlatter J. C. , Nickolas S. G. , Yee D. K. , Shoji T.
Published: February 2015

A catalytic combustion system has been developed which feeds full fuel and air to the catalyst but avoids exposure of the catalyst to the high temperatures responsible for deactivation and thermal shock fracture of the supporting substrate. The combustion process is initiated by the catalyst and is completed by homogeneous combustion in the post catalyst region where the highest temperatures are obtained. This has been demonstrated in subscale test rigs at pressures up to 14 atmospheres and temperatures above 1300°C (2370°F). At pressures and gas linear velocities typical of gas turbine combustors, the measured emissions from the catalytic combustion system are NOx < 1 ppm, CO < 2 ppm and UHC < 2 ppm, demonstrating the capability to achieve ultra low NOx and at the same time low CO and UHC.
Optimum Control of Variable Components in Aircraft Gas Turbine Engines Under Non-Stationary Flow Disturbances at the Inlet
Authors: Egorov I. N. , Kreitinin G. V.
Published: February 2015

A numerical method has been preposed to determine optimum laws to control gas turbine engine (CTE) variable components, including an independent control of blade rows in a multistage axial flow compressor under strong non-stationary flow disturbances at the inlet, optimum laws to control a turbofan under non-stationary thermal effects at the inlet have been obtained using mathematical models with various degree of filling in detail the flow in an engine flow path. There is shown a possibility to considerably increase a range of the CTE stable operation through the use of dynamic control of stator blades in a multistage axial flow compressor, also possibilities of practical use of optimum laws to control engine variable components in the system of preventing an unstable operation are being discussed.
Use of Computer Simulation Techniques to Assess Thrust Rating as a Means of Reducing Turbo-Jet Life Cycle Costs
Authors: Devereux B. , Singh R.
Published: February 2015

This paper investigates the concept of thrust rating as a means towards reducing the life cycle costs of turbo-jet engine ownership. Towards this end, the concepts of life usage and thrust rating will be discussed to provide a clear understanding of the goals and methods involved in this investigation. In general, all “serviceable” engines will experience varying levels of performance above baseline values. Thrust rating ideally seeks to limit engine performance to baseline values, thereby converting performance into life.

In particular, this paper will present a general computer simulation technique that may be applied to any turbo-jet engine to quantify the life cycle savings resulting from the adoption of thrust rating techniques. The inter-relationships that exist between thrust rating and many practical in-service aspects of turbo-jet usage including performance degradation, operational roles and maintenance practices and policies will be investigated. Some strengths and limitations of the simulation technique will also be identified. This paper will discuss general guidelines for investigating the feasibility of performing thrust rating on various turbo-jet engines. While this technique is likely to be of greatest interest to users of high performance military turbo-jet engines, its principles can be adapted for other gas turbine uses.
The Generalized Untwist Problem of Rotating Blades: A Coupled Aeroelastic Formulation
Authors: Liu Gao-Lian
Published: February 2015

The untwist of rotating blades in turbomachines treated so far in the literatare simply as a pure elasticity problem is generalized and formulated rigorously as a problem of aeroelasticity by variational principles (VPs) and generalized VP (GVP). It takes into account not only the centrifugal force, but also the aeroelastic interaction between blades and the flow as well as the elastic distortion of the cross section shape of blades, assuming the material to be linearly elastic but nonisotropic. Thus, a new rigorous theoretical basis for the finite element analysis of blade untwist in turbomachine design is provided.
Influence of Inlet Conditions on Flow and Combustion Characteristics of a Model Annular Combustor
Authors: Baron F. , Kanniche M. , Mechitoua N.
Published: February 2015

k-ε model coupled with chemical equilibrium hypothesis is applied to a sector of an annular gas turbine combustion chamber similar to the one used in small gas turbine engines. The β-function is used as probability-density-function (pdf) of the distribution of a mixing rate scalar. The computation results are compared with velocity, temperature and species concentration measurements with air-to-fuel ratio of 29 and two inlet air temperatures of 315 K and 515 K. The measurements are reported in the PhD thesis of Tse [2] and in Bicen et al. [1].

Computed velocity and temperature are in good agreement with measurements, except close to primary injection holes where the normal impacts of air jets with the bulk flow involve strong streamline curvature which cannot be well predicted by standard k-ε model.

Computed species concentrations are in good agreement with measurements, except (as expected) for CO concentration which is overestimated. Since the kinetic of CO burn-up is limited, the overestimation of CO concentration is a consequence of the simplified chemical reaction step.
An Investigation of the Effect of Cascade Area Ratios on Transonic Compressor Performance
Authors: Wadia A. R. , Copenhaver W. W.
Published: February 2015

Transonic compressor rotor performance is highly sensitive to variations in cascade area ratios. This paper reports on the design, experimental evaluation and three-dimensional viscous analysis of four low aspect ratio transonic rotors that demonstrate the effects of cascade throat area, internal contraction and trailing edge effective camber on compressor performance. The cascade throat area study revealed that tight throat margins result in increased high speed efficiency with lower part speed performance. Stall line was also improved slightly over a wide range of speeds with a lower throat-to-upstream capture area ratio. Higher internal contraction, expressed as throat-to-mouth area ratio, also results in increased design point peak efficiency, but again costs performance at the lower speeds. Reducing the trailing edge effective camber expressed as throat-to-exit area ratio, results in an improvement in peak efficiency level without significantly lowering the stall line. Among all four rotors, the best high speed efficiency was obtained by the rotor with tight throat margin and highest internal contraction, but its efficiency was the lowest at part speed. The best compromise between high speed and part speed efficiency was achieved by the rotor with a large throat and a lower trailing edge effective camber. The differences in the shock structure and the shock boundary layer interaction of the four blades was analyzed using a three-dimensional viscous code. The analytical results are used to supplement the data and provide further insight into the detailed physics of the flow field.
Aerodynamic Performance of a Transonic Turbine Guide Vane With Trailing Edge Coolant Ejection: Part I — Experimental Approach
Authors: Kapteijn Cornelis , Amecke Jochen , Michelassi Vittorio
Published: February 2015

Inlet guide vanes (IGV) of high temperature gas turbines require an effective trailing edge cooling. But this cooling influences significantly the aerodynamic performance caused by the unavoidable thickening of the trailing edge and the interference of the cooling flow with the main flow.

As part of a comprehensive research programme an inlet guide vane was designed and manufactured with two different trailing edge shapes. As a general result turns out from the cascade tests, that the flow behaviour upstream of the trailing edge remains unchanged. The homogeneous values downstream show higher turning and higher losses for the cut-back blade, especially in the supersonic range. Additional test were conducted with carbon dioxide ejection, in order to analyse the mixing process downstream of the cascade.
A Reduced Order Model of Unsteady Flows in Turbomachinery
Authors: Hall Kenneth C. , Florea Răzvan , Lanzkron Paul J.
Published: February 2015

A novel technique for computing unsteady flows about turbomachinery cascades is presented. Starting with a frequency domain CFD description of unsteady aerodynamic flows, we form a large, sparse, generalized, non-Hermitian eigenvalue problem which describes the natural modes and frequencies of fluid motion about the cascade. We compute the dominant left and right eigenmodes and corresponding eigenfrequencies using a Lanczos algorithm. Then, using just a few of the resulting eigenmodes, we construct a reduced order model of the unsteady flow field. With this model, one can rapidly and accurately predict the unsteady aerodynamic loads acting on the cascade over a wide range of reduced frequencies and arbitrary modes of vibration. Moreover, the eigenmode information provides insights into the physics of unsteady flows. Finally we note that the form of the reduced order model is well suited for use in active control of aeroelastic and aeroacoustic phenomena.
Multiobjective Optimization of a Flexible Rotor in Magnetic Bearings With Critical Speeds and Control Current Constraints
Authors: Shiau Ting Nung , Kuo Chun Pao , Hwang Jiunn Rong
Published: February 2015

This paper presents the single objective optimization and the multi-objective optimization for a flexible rotor system with magnetic bearings. The weight of rotor shaft and the transmitted forces at the magnetic bearings are minimized either individually or simultaneously under the constraints on the critical speeds and the control currents of magnetic bearings. The design variables are the cross-sectional area of the shaft, the bias currents of magnetic bearings, and the positions of the disk and the magnetic bearings. The dynamic characteristics are analyzed using the generalized polynomial expansion method and the sensitivity analysis is also studied. For single objective optimization, the method of feasible directions (MFD) is applied. For multi-objective optimization, the methods including the weighting method (WM), goal programming method (GPM), and the fuzzy method (FM) are employed. It is found that the system design can be significantly affected by the choices of the bias currents of magnetic bearings, the position of the disk with unbalance and the magnetic bearings. The results also show that a better compromized design can always be obtained for multi-objective optimization.
Regional and Business Aircraft Mission Emissions
Authors: Rizk Nader K. , Smith Duane A.
Published: February 2015

To meet the design requirements of next generation aircraft engines and the expected trends of more stringent emissions regulations, better calculation methods for aircraft mission emissions need to be established. In the present investigation, a number of steps were taken to define an appropriate calculation technique. The data obtained for a full-scale annular combustor rig were compared with engine emissions to illustrate that the level of rig-to-engine agreement was good enough to use the rig data to formulate a proposed mission NOx calculation technique. Conventional methods were then used to correlate the rig data in terms of various operating parameters. It was demonstrated that the level of agreement with data was improved by including both combustion and geometrical aspects in the correlations of NOx, CO, UHC, and smoke. A semianalytical approach, which was based on detailed chemical kinetic scheme and simulated the combustor by a number of reactors representing various combustion zones, was used to correlate the data of the annular combustor. The results illustrated that better estimates of emissions were obtained over conventional methods. Two mission profiles that represented the operation of turbofan-powered regional and business aircrafts were selected to evaluate their mission emissions using the semianalytical method. An approach that utilized only the four ICAO test points in the semianalytical method was formulated to provide the total aircraft mission emissions. Results obtained by this approach were comparable to those calculated using correlations based on extensive testing of the combustor; thus, by using such a method considerable savings in cost and effort could be achieved during combustor development. The results also demonstrated the possibility of correlating the emissions in terms of ambient pressure and temperature and fuel flow rate; thus, accurate estimates of altitude emissions could be obtained.
High-Performance Power Systems for the Near-Term and Beyond
Authors: Klara Julianne M.
Published: February 2015

Demand for electricity in the United States is expected to grow in the foreseeable future, requiring approximately 200 gigawatts of new generating capacity by 2010. Coal-based power plants built to supply this additional baseload capacity will be required to perform at high thermal efficiency and meet tough environmental regulations, all at competitive electric generating costs. The Department of Energy (DOE) / Pittsburgh Energy Technology Center (PETC) is managing a program called Combustion 2000 that is aimed at developing technologies that will assure the continued use of coal to meet the Nation’s power generating needs well into the 21st century. The High-Performance Power System (HIPPS) element of Combustion 2000 is based on an indirectly fired combined cycle. By using an indirectly fired gas turbine and a conventional steam cycle, HIPPS cleanly produces electricity from coal at a thermal efficiency that is about one-third higher than that of today’s conventional coal-based power plants.

DOE/PETC’s HIPPS program, which is described in this paper, aims to demonstrate a commercial-scale prototype plant by 2004. An engineering analysis was performed to assess the feasibility of accelerating the demonstration of HIPPS by using only those materials available today. Results predict attractive efficiencies and competitive electric generating costs for a near-term design. The feasibility of HIPPS as a repowering option has also been examined. Preliminary projections reveal that added generating capacity and reduced emissions can be accomplished at an increased overall plant efficiency and with the potential to minimize capital expenditure.
Diagnosis of Turbine Engine Transient Performance With Model-Based Parameter Estimation Techniques
Authors: Bird Jeff W. , Schwartz Howard M.
Published: February 2015

This review surveys knowledge needed to develop an improved method of modelling the dynamics of gas turbine performance for fault diagnosis applications. Aerothermodynamic and control models of gas turbine processes are examined as complementary to models derived directly from test data. Extensive, often proprietary data are required for physical models of components, while system identification (SI) methods need data from specially-designed tests. Current methods are limited in: tuning models to test data, non-linear effects, component descriptions in SI models, robustness to noise, and inclusion of control systems and actuators. Conclusions are drawn that SI models could be formulated, with parameters which describe explicitly the functions of key engine components, to offer improved diagnostic capabilities.
Gas Turbine Education in the Netherlands
Authors: van Buijtenen J. P. , Splinter J.
Published: February 2015

This paper describes the Dutch educational system for gas turbine engineering. The history of the gas turbine industry and education is given briefly. Recently the industry took the initiative of creating a foundation ‘to stimulate gas turbine education’. Courses are implemented in the general educational structure. The cooperation of academia and industry has proved to be very fruitful.
Turbine Engine Icing Spray Bar Design Issues
Authors: Bartlett C. Scott
Published: February 2015

Techniques have been developed at the Engine Test Facility (ETF) of the Arnold Engineering Development Center (AEOC) to simulate flight through atmospheric icing conditions of supercooled liquid water droplets. Ice formed on aircraft and propulsion system surfaces during flight through icing conditions can, even in small amounts, be extremely hazardous. The effects of ice are dependent on many variables and are still unpredictable. Often, experiments are conducted to determine the characteristics of the aircraft and its propulsion system in an icing environment. Facilities at the ETF provide the capability to conduct icing testing in either the direct-connect (connected pipe) or the free-jet mode.

The requirements of a spray system for turbine engine icing testing are described, as are the techniques used at the AEDC ETF to simulate flight in icing conditions. Some of the key issues facing the designer of a spray system for use in an altitude facility are identified and discussed, and validation testing of the design of a new spray system for the AEDC ETF is detailed. This spray system enables testing of the newest generation of high-thrust turbofan engines in simulated icing conditions.
Rotational Noise Analysis and Prediction for an Axial Fan With Unequal Blade Pitches
Authors: Akaike S. , Kikuyama K. , Kitada M. , Kuwayama K.
Published: February 2015

The rotational noise is one of the main sources of the noise emitted from a fan. This type of noise has discrete frequency components, which is so harsh that many methods have been developed to reduce the noise. Studies on the rotational noise, however, have hardly been made to clarify the generation mechanism and find concrete methods to reduce the noise.

In order to suppress the discrete frequency components of the rotational noise, the spacing of the blades were changed and the comparison was made with a fan having equally spaced blades. The discrete frequency components were found to be suppressed in the unequally spaced fan and the noise tended to have a nature of whitenoise if the blade spacing and blade setting angles were properly chosen.

The instantaneous pressure change on the shroud was measured in order that the pressure change was related to the discrete frequency noise was closely related to the pressure changes on the blade surfaces. By expressing the pressure change due to the blade passing in terms of the blade spacing and decomposing it into Fourier series, the noise characteristics was analyzed. The prediction result for the rotational noise emitted by an equally spaced fan was presented and found to agree well with the experiment.
The Effect of Tip Clearance on a Swept Transonic Compressor Rotor
Authors: Copenhaver William W. , Mayhew Ellen R. , Hah Chunill
Published: February 2015

An experimental and numerical investigation of detailed tip clearance flow structures and their effects on the aerodynamic performance of a modern low-aspect-ratio, high-through-flow, axial transonic fan is presented. Rotor flow fields were investigated at two clearance levels experimentally, at tip clearance to tip blade chord ratios of 0.27 and 1.87 percent, and at four clearance levels numerically, at ratios of zero, 0.27, 1.0, and 1.87 percent. The numerical method seems to calculate the rotor aerodynamics well, with some disagreement in loss calculation which might be improved with improved turbulence modeling and a further refined grid. Both the experimental and the numerical results indicate that the performance of this class of rotors is dominated by the tip clearance flows. Rotor efficiency drops six points when the tip clearance is increased from 0.27 to 1.87 percent, and flow range decreases about 30 percent. No optimum clearance size for the present rotor was indicated. Most of the efficiency change occurs near the tip section, with the interaction between the tip clearance flow and the passage shock becoming much stronger when the tip clearance is increased. In all cases, the shock structure was three-dimensional and swept, with the shock becoming normal to the endwall near the shroud.
Experimental and Computational Investigation of the Tip Clearance Flow in a Transonic Axial Compressor Rotor
Authors: Suder Kenneth L. , Celestina Mark L.
Published: February 2015

Experimental and computational techniques are used to investigate tip clearance flows in a transonic axial compressor rotor at design and part speed conditions. Laser anemometer data acquired in the endwall region are presented for operating conditions near peak efficiency and near stall at 100% design speed and at near peak efficiency at 60% design speed. The role of the passage shock / leakage vortex interaction in generating endwall blockage is discussed. As a result of the shock / vortex interaction at design speed, the radial influence of the tip clearance flow extends to 20 times the physical tip clearance height. At part speed, in the absence of the shock, the radial extent is only 5 times the tip clearance height. Both measurements and analysis indicate that under part-speed operating conditions a second vortex, which does not originate from the tip leakage flow, forms in the endwall region within the blade passage and exits the passage near midpitch. Mixing of the leakage vortex with the primary flow downstream of the rotor at both design and part speed conditions is also discussed.
Development of Two-Dimensional Wakes Within Curved Channels, Theoretical Framework and Experimental Investigation
Authors: Schobeiri M. T. , John J. , Pappu K.
Published: February 2015

The development of a wake flow downstream of a cylindrical rod within a curved channel under zero streamwise pressure gradient is theoretically and experimentally investigated. The measured asymmetric wake quantities such as the mean velocity and turbulent fluctuations in longitudinal and lateral directions as well as the turbulent shear stress are transformed from the probe coordinate system into the curvilinear wake eigen-coordinate system. For the transformed non-dimensionalized velocity defect and the turbulent quantities, affine profiles are observed throughout the flow regime. Based on these observations and using the transformed equations of motion and continuity, a theoretical frame work is established that generally describes the two-dimensional curvilinear wake flow. The theory also describes the straight wake as a special case, for which the curvature radius approaches infinity. The comparison of the theory with the experimental data pertaining to the curvilinear and straight wakes demonstrate the general validity of the theory.
Derivation of Compressor Stage Characteristics, for Accurate Overall Performance Map Prediction
Authors: Tsalavoutas A. , Stamatis A. , Mathioudakis K.
Published: February 2015

In the present paper a method for deriving stage characteristics, which can provide accurate prediction of a multistage compressor map is presented. The method combines optimization techniques with the principles of stage stacking. The stage characteristics are produced by modifying some initial generic ones, until the desired accuracy in the prediction at selected points on the overall map is achieved. There are several reasons why prediction based on the initial stage characteristics can be inaccurate, the following three being the main ones. The first is due to inaccuracy in the representation of the stage characteristics themselves. The second is due to lack of exact knowledge of the geometric data of the various stages. Finally the third reason consists of the “weak” modelling representation of complex physical phenomena with one dimensional approaches. Therefore, even when the exact stage characteristics are known, this does not guarantee the accurate prediction of the compressor performance. On account of the above, it is preferable to acquire realistic “effective” stage characteristics which can be used for synthesizing overall compressor characteristics and assessing the effects of stage faults. In this paper, both of these aspects are successfully tackled as demonstrated by applying the method to different test cases.