bluuebunny/crossref_metadata_2025 huggingface dataset:
Second-Law Analysis of a Compressed Air Energy Storage (CAES) System
Authors: Weiner D. , Shnaid I.
Published: March 2015

Compressed Air Energy Storage (CAES) system consumes excess energy from base load steam power plant, converts it into stored pneumatic energy and then releases it during peak load period through a gas turbine.

A comprehensive analysis of exergy flows, inputs, outputs and losses in the entire (CAES and steam plant) system is carried out. The irreversible losses and the system efficiency are more realistically presented, than according to the conventional first-law analysis.

Various CAES system schemes and cycle characteristics are studied. It is shown that in some cases the overall thermal efficiency is higher in the combined CAES-Steam Plant System, than in an industrial gas turbine.
Vibration of a Rigid Shaft Supported by Radial Ball Bearings With Several Defects
Authors: Franco J. M. , Akturk N. , Gohar R.
Published: March 2015

In this paper a vibration analysis of a rigid shaft-ball bearing system has been carried out, in order to approximate the nonlinear load-deformation characteristics of the ball/race contacts, an approximation by means of the Taylor series is studied. The response of an imperfect model system in both time and frequency domains is analyzed. Factors affecting the vibration characteristics of the system such as rotating unbalance, the varying diameter of the balls and the surface waviness are investigated. The vibration analysis of the system, including various external excitations, is carried out for each set of conditions and for more than one defect simultaneously.

It is shown that the mathematical model of the total ball load-deflection relationship has a linear part that depends on the initial deflection, a small time dependent component, the load-deflection coefficient; and a number of terms contributing to nonlinearity of the contact stifness.
Numerical Solutions for Unsteady Subsonic Vortical Flows Around Loaded Cascades
Authors: Fang J. , Atassi H. M.
Published: March 2015

A frequency domain linearized unsteady aerodynamic analysis is presented for three-dimensional unsteady vortical flows around a cascade of loaded airfoils. The analysis fully accounts for the distortion of the impinging vortical disturbances by the mean flow. The entire unsteady flow field is calculated in response to upstream three-dimensional harmonic disturbances. Numerical results are presented for two standard cascade configurations representing turbine and compressor bladings for a reduced frequency range from 0.1 to 5. Results show that the upstream gust conditions and blade sweep strongly affect the unsteady blade response.
Influence of Surface Heating Condition on Local Heat Transfer in a Rotating Square Channel With Smooth Walls and Radial Outward Flow
Authors: Han J. C. , Zhang Y. M. , Lee C. P.
Published: March 2015

The effect of surface heating condition on the local heat transfer coefficient in a rotating square channel with smooth walls and radial outward flow was investigated for Reynolds numbers from 2,500 to 25,000 and rotation numbers from 0 to 0.352. The square channel, composed of six isolated copper sections, has a length-to-hydraulic diameter ratio of 12. The mean rotating radius to the channel hydraulic diameter ratio is kept at a constant value of 30. Four surface heating conditions were tested: (1) four walls uniform temperature, (2) temperature ratio of leading surface to side wall and trailing surface to side wall is 1.05 and 1.10, respectively, (3) trailing surface hot and remaining three walls cold, and (4) leading surface hot and remaining three walls cold. The results show that the heat transfer coefficients on the leading surface are much lower than that of the trailing surface due to rotation. For case (1) of four walls uniform temperature, the leading surface heat transfer coefficient decreases and then increases with increasing rotation numbers, and the trailing surface heat transfer coefficient increases monotonically with rotation numbers. However, the trailing surface heat transfer coefficients for cases (2) and (3) are slightly lower than case (1), and the leading surface heat transfer coefficients for cases (2) and (4) are significantly higher than for case (1). The results suggest that the local wall heating condition creates the local buoyancy forces which reduce the effects of the bulk buoyancy and Coriolis forces. Therefore, the local heat transfer coefficients on the leading and trailing surfaces are altered by the surface local heating condition.
Numerical Simulation of the Flow Field Around Supersonic Air-Intakes
Authors: Freskos G. , Penanhoat O.
Published: March 2015

The demand for efficiency in today’s and in future civil aircraft is such that experimental studies alone do not suffice to optimize aircraft aerodynamics. In this context, much effort has been spent in the past decade to develop numerical methods capable of reproducing the phenomena that occur in the engine flow field.

This paper presents some studies in Computational Fluid Dynamics related to supersonic inlets.

Two approaches are considered. First, there is a need for code capable of calculating in a cost-efficient way the entire flow field around a 2D or 3D inlet, e.g. to perform parametric studies. To this effect, a computing method based on grid construction by mesh generator dedicated to inlet shapes and on the discretization of the unsteady Euler equations with an explicit upwind scheme was developed. The treatment of complex geometries led us to adopt a multiblock grid approach. Therefore particular attention was paid to the treatment of the boundary conditions between the different domains.

Secondly, there is a need for code that can capture local phenomena in order to get a better understanding of inlet behaviour (shock/shock, shock/boundary layer interactions, etc.). To this effect a 2D turbulent Navier-Stokes code is used. The 2 equations k-ε turbulence model included in the program seems to be one of the most successful models for calculating flow realistically. Correction of the near-wall influence extends its capability to complex flow configurations, e.g. those with separated zones.
A Fully Three-Dimensional Inverse Method for Turbomachinery Blading in Transonic Flows
Authors: Dang T. Q.
Published: March 2015

This paper presents a procedure to extend a recently developed fully three-dimensional inverse method for highly-loaded turbomachine blades into the transonic-flow regime. In this inverse method, the required three-dimensional blade profile to produce a prescribed swirl schedule is determined iteratively using the blade boundary conditions. In the present implementation, the flow is assumed to be inviscid and the blades are assumed to be infinitely thin. The relevant equations are solved in the conservative forms and are discretized in all three directions using a finite-volume technique. Calculations are carried out for the design of high-pressure axial- and centrifugal-compressor rotors. These examples include prescribed swirl schedules that correspond to blade design that are shock-free and blade design that have rapid compression regions in the blade passage.
Calculation of Three-Dimensional Boundary Layers on Rotor Blades Using Integral Methods
Authors: Karimipanah M. T. , Olsson E.
Published: March 2015

The important effects of rotation and compressibility on rotor blade boundary layers are theoretically investigated. The calculations are based on the momentum integral method and results from calculations of a transonic compressor rotor are presented. Influence of rotation is shown by comparing the incompressible rotating flow with the stationary one. Influence of compressibility is shown by comparing the compressible rotating flow with the incompressible rotating one.

Two computer codes for three-dimensional laminar respectively turbulent boundary layers, originally developed by SSPA Maritime Consulting AB, have been further developed by introducing rotation and compressibility terms in the boundary layer equations. The effect of rotation and compressibility on the transition have been studied. The Coriolis and Centrifugal forces which contribute to the development of the boundary layers and influence its behaviour, generate crosswise flow inside the blade boundary layers, the magnitude of which depends upon the angular velocity of the rotor and the rotor geometry.

The calculations show the influence of rotation and compressibility on the boundary layer parameters. Momentum thickness and shape factor increase with increasing rotation and decrease when compressible flow is taken into account. For skin friction such effects has inverse influences. The different boundary layer parameters behave similarly on suction and pressure side with the exception of the cross-flow angle, the cross-wise momentun thickness and the skin friction factor.

The codes use a nearly orthogonal streamline coordinate system, which is fixed to the blade surface and rotates with the blade.
An Investigation of Factors Influencing the Calibration of 5-Hole Probes for 3-D Flow Measurements
Authors: Dominy R. G. , Hodson H. P.
Published: March 2015

The effects of Reynolds number, Mach number and turbulence on the calibrations of commonly used types of 5-hole probe are discussed. The majority of the probes were calibrated at the exit from a transonic nozzle over a range of Reynolds numbers (7×103 < 80×103 based an probe tip diameter) at subsonic and transonic Mach numbers. Additional information relating to the flow structure were obtained from a large scale, low speed wind tunnel. The results confirmed the existence of two distinct Reynolds number effects. Flow separation around the probe head affects the calibrations at relatively low Reynolds numbers while changes in the detailed structure of the flow around the sensing holes affects the calibrations even when the probe is nulled. Compressibility is shown to have little influence upon the general behaviour of these probes in terms of Reynolds number sensitivity but turbulence can effect the reliability of probe calibrations at typical test Reynolds numbers.
On Modeling Centrifugal Compressors for Robust Control Design
Authors: Murphy K. M. , Marchio D. , Kalata P. , Fischl R.
Published: March 2015

This paper considers the development of a Linear, Time Invariant (LTI) model for centrifugal compressor systems for robust control design. The objective is to obtain a LTI model of the compressor system so that robust controllers can be designed to control the outlet pressure and mass flow. The control variables are the motor armature voltage and the inlet valve position. The approach taken in this paper is to (1) obtain the non-linear, input-output dynamic reactions of the various components (inlet valve, ducts, compressor, nozzle and DC-motor), (2) identify the model parameters and variables (pressure, mass flow, etc.), (3) obtain a linear model of the system, (4) design a controller based on the LTI model and (5) test the designed controller on the non-linear model of the compressor system.
Operating Experience and Site Performance Testing of the CW251B12 Gas Turbine Engine
Authors: Diakunchak Ihor S.
Published: March 2015

The first CW251B12 engine has been operating for about a year at a paper mill in a cogeneration application. The engine generates electricity, and the exhaust heat is used in a supplementary fired Heat Recovery Steam Generator (HRSG) to produce steam. The steam generated in the HRSG plus additional process steam is used to produce electrical power in a condensing steam turbine. Steam extracted from the steam turbine is in turn used in the paper mill. This paper describes the operating experience of the gas turbine and provides some details of the site performance test.
Turbulent Flow and Heat Transfer in Gas Turbine Blade Cooling Passages
Authors: Cunha F. J.
Published: March 2015

A numerical analysis methodology has been created to predict the heat transfer within the air cooling passages of gas turbine blades. In this paper, the turbulent flow heat convection with developed velocity and temperature fields is studied for cavities with turbulators. The influence of Coriolis forces and rotational buoyancy effects were also included. The k-equation turbulence model was employed over most of the cross section while a modified Van Driest’s version of the mixing length hypothesis is used in the near-wall sublayer. This methodology was successfully benchmarked against experimental results for air cooling passages of turbine blades. Analytical results are presented in terms of the Reynolds, Rossby and rotational Rayleigh numbers for realistic operating conditions.
New Advanced Cooling Technology and Material of the 1500°C Class Gas Turbine
Authors: Matsuzaki H. , Shimomura K. , Fukuyama Y. , Araki T. , Ishii J. , Yamamoto M. , Shibuya S. , Okuhara I.
Published: March 2015

This paper describes the advanced cooling technology and materials (directionally solidified and single-crystal superalloys) which are considered key technological factors when developing the 1500°C class high temperature gas turbine.

Adopting a 1500°C class gas turbine developed on the basis of the new technology, a combined cycle plant is likely to achieve a plant thermal efficiency of more than 55% (LHV).
Laminar Boundary Layer Flow and Heat Transfer With Favorable Pressure Gradient at Constant K Values
Authors: Zhou Dadong , Wang Ting
Published: March 2015

Approximate algebraic correlations for the two-dimensional laminar boundary layer flow and heat transfer with favorable pressure gradient at constant K (≡vUe2dUedx) values were found by using Pohlhausen’s integral method. Two thermal boundary conditions were considered: constant wall heat flux and constant wall temperature. These correlations were tabulated and compared in the limits KRex → 0 and KRex → ∞ with the similarity solutions of the Blasius flow and the convergent-channel flow. The comparisons between these correlations and those obtained numerically from the STAN5 code were excellent. The results showed that the momentum boundary layer grows at the leading edge with an initial rate like the Blasius flow to a maximum value, then decreases and asymptotically approaches the behavior of a convergent-channel flow. As KRex increases, the skin friction coefficient decreases and approaches a constant; the Pohlhausen’s pressure gradient parameter (Λ≡δ2vdUedx) increases from zero at the leading edge and approaches a constant. While hydrodynamically asymptotical solutions were obtained, no asymptotical thermal similarity was found. Skin friction coefficient and various integral parameters could be collapsed into a corresponding single curve when suitable normalization factors were chosen. The effects of Prandtl number and unheated starting length were also analyzed.
Ramjet NOx Emission: Use of a 3D CFD Method for the Combustor Design of a Super/Hyper-Sonic Transport Propulsion System
Authors: David E. , Bauddin C. , Schultz J. L. , Ansart D. , Meunier S.
Published: March 2015

As part of SNECMA participation in developing the ramjet of Large-scale Japanese Project for “SUPER/HYPER-SONIC TRANSPORT PROPULSION SYSTEM”, an injection system of lean premix type has been studied.

This concept based on a low fuel/air ratio combustion allows a high reduction of NOx emission. Fuel and air mixing must be rapid and homogeneous in order to obtain the full potential of this principle.

For that purpose, a numerical study has been carried out to find the optimal mechanism on carburation homogeneity. Results of a parametric study are presented and show influences of various injection and flame holder systems on air/fuel flow distributions.

Numerical simulations have been performed with the 3D CFD ECRIN code. It is commonly used at SNECMA for combustion analysis. The main features of this code are presented and more particularly the combustion and NOx emission modeling. A comparison of calculated NOx emission indexes with experimental results obtained in a tubular combustor conducts to a good agreement between experiments and computations.
Some Topics of Research on Hypersonic Airbreathing Engines at National Aerospace Laboratory
Authors: Sakata Kimio , Nouse Hiroyuki , Minoda Mitsuhiro
Published: March 2015

Some research tupics on hypersonic airbreathing engines conducted at National Aerospace Laboratory in Japan (NAL) are introduced. Variable Cycle engine (VCE) for the next generation supersonic transports (SST), Combined turbo-ramjet engine for hypersonic transports (HST) and turbo-engines, such as Airturbo-ramjet engine (ATR), and Scramjet engine for Space Plane propulsion systems are being studied. Engine system design to make evaluate capability for Space Plane and system optimization are described. Component studies; supersonic air-intake with mixed and internal compression configuration, hydrogen fueled ram-combustor, supersonic combustion chamber, high temperature and highly loaded turbo-component, regenerative heat exchanger and noise reduction nozzle are being conducted and some results are presented. In the material study, carbon/carbon composites, metal compound metal matrix composites and functionally gradient material (FGM) are also investigated and evaluated for application to high temperature and/or light weight structures.
Experimental Evaluation of a Two-Stage Slagging Combustor Design for a Coal-Fueled Industrial Gas Turbine
Authors: Cowell L. H. , LeCren R. T.
Published: March 2015

A full-size combustor for a coal-fueled industrial gas turbine engine has been tested to evaluate combustion performance prior to integration with an industrial gas turbine. The design is based on extensive work completed through one-tenth scale combustion tests. Testing of the combustion hardware is completed with a high pressure air supply in a combustion test facility at the Caterpillar Technical Center. The combustor is a two-staged, rich-lean design. Fuel and air are introduced in the primary combustion zone where the combustion process is initiated. The primary zone operates in a slagging mode inertially removing coal ash from the gas stream. Four injectors designed for coal-water mixture (CWM) atomization are used to introduce the fuel and primary air. In the secondary combustion zone additional air is injected to complete the combustion process at fuel-lean conditions. The secondary zone also serves to reduce the gas temperatures exiting the combustor. The combustor has operated at test pressures of 7 bars with 600K inlet temperature. Tests have been completed to set the air flow split and to map the performance of the combustor as characterized by pollutant emissions, coal ash separation, and temperature profile. Test results with a comparison to subscale test results are discussed. The test results have indicated that the combustor operates at combustion efficiencies above 98% and with pollutant emissions below design goals.
Coal-Water Slurry Testing of an Industrial Gas Turbine
Authors: Wenglarz R. A. , Wilkes C. , Bourke R. C. , Mongia H. C.
Published: March 2015

This paper describes the first test of an industrial gas turbine and low emissions combustion system on coal-water-slurry fuel. The engine and combustion system have been developed over the past five years as part of the Heat Engines program sponsored by the Morgantown Energy Technology Center of the U.S. Department of Energy (DOE). The engine is a modified Allison 501-K industrial gas turbine designed to produce 3.5 MW of electrical power when burning natural gas or distillate fuel. Full load power output increases to approximately 4.9 MW when burning coal-water slurry as a result of additional turbine mass flow rate.

The engine has been modified to accept an external staged combustion system developed specifically for burning coal and low quality ash-bearing fuels. Combustion staging permits the control of NOx from fuel-bound nitrogen while simultaneously controlling CO emissions. Water injection freezes molten ash in the quench zone located between the rich and lean zones. The dry ash is removed from the hot gas stream by two parallel cyclone separators.

This paper describes the engine and combustor system modifications required for running on coal and presents the emissions and turbine performance data from the coal-water slurry testing. Included is a discussion of hot gas path ash deposition and planned future work that will support the commercialization of coal-fired gas turbines.
Development and Industrial Application of the “All-Over-Controlled Vortex Distribution Method” for Designing Radial and Mixed Flow Impellers
Authors: Wang S. J. , Yuan M. J. , Xi G. , Liu S. X. , Qi D. T. , Chai X. J.
Published: March 2015

Sixteen years ago an inverse method of designing radial, mixed flow impellers was proposed by the first author of this paper, which was based on a quasi-three-dimensional stream surface theory. The contradictions between the full controlling of the flow field in the whole impeller and the designed bables’ smooth machinability can be perfectly resolved with the above method (So it is called “all-over-controlled vortex distribution method”). This paper presents the developments and industrial applications of the above method in the last decade. Two single centrifugal compressor model stages with the 3-D impellers designed by this method are studied in detail, and several performance curves of the multistage centrifugal compressors designed by this method are also presented.
Performance Monitoring of Gas Turbines for Failure Prevention
Authors: Dundas Robert E. , Sullivan Daniel A. , Abegg Frank
Published: March 2015

The concept of performance monitoring for prevention of certain serious failures in gas turbines is described. The use of compressor mapping as the key to avoiding surge is developed, and an example is presented showing how the compressor in a steam-injected gas turbine can be much closer to surge in one of two nearly-identical operating points on a steam-injection control envelope than the compressor in the other. The technique of monitoring blade-path temperature spread in the exhaust of a gas turbine is then described, and examples of its value in preventing combustor burnout and turbine blade failures in high-frequency fatigue are given. Next, a concept of diagnosing internal deterioration by recognizing patterns of deviation of operating parameters from baseline data is described, and illustrated for a single-shaft generator-drive gas turbine. Finally, the use of a modern computer-controlled data acquisition system to perform the above monitoring functions in real time is demonstrated.
On-Line Detergent Washing: Reducing the Environmental Effects on the LCAC Gas Turbine Engines
Authors: Patterson Jeffrey S. , Spring Soren K.
Published: March 2015

The Landing Craft Air Cushion (LCAC) gas turbine engines operate in an extremely harsh environment and are exposed to excessive amounts of foreign contaminants. The present method of crank washing is effective when properly performed, but is labor intensive and increases craft downtime. Naval Ship Systems Engineering Station (NAVSSES) designed and installed a prototype on-line detergent wash system which reduced maintenance and craft downtime. Initial test results indicated that the system reduced engine performance degradation and corrosion.
On Application of Statistics to Verification of Turbomachinery Calculation Methods
Authors: Krzyżanowski Jerzy , Krzyślak Piotr , Gluch Jerzy
Published: March 2015

Turbomachinery thermodynamic and fluid-flow calculations are based on more or less sophisticated theoretical models. Correction factors are used to match the calculation results to the measured characteristics of the machine. Evaluation of these coefficients is based as a rule on experiments carried out in simplified geometrical configurations: profile cascades, separate models of machinery stages, air instead of gas or steam etc. This leads inevitably to differences between the calculated and measured characteristics of a real machine. Application of real machine characteristics obtained from field, routine measurements to verification of the coefficients may allow to minimize those differences. Proper application of statistical procedures to experimental and calculated data may contribute to compensation of low accuracy of the routine measurements. In the paper such an approach will be demonstrated for a steam turbine calculation procedure. Threefold reduction of the systematic displacement and three-and-a-half reduction of the scatter between the calculated and measured specific heat consumption of the 200 MW steam turbine cycle was indicated to proove the effectivness of the method. The procedure presented may also be used for other types of power equipment.
Rotor Design for Large Industrial Gas Turbines
Authors: Endres W.
Published: March 2015

The overall designs of rotors for modern large industrial gas turbines are all very similar; however, the manufacturers have widely different internal designs. Building up the discs and drums to form the rotor is achieved either by a number of different mechanical joining techniques or by welding. In addition the rotor materials, the mechanical integrity, proof testing and critical rotor areas are also discussed. The conflicting design requirements, i.e. for supporting the centrifugal loads, protecting the rotor against the hot gases and warming the rotor during a start-up without excessive thermal stress, lead to very different design solutions. Thus in this paper the stresses, low cycle fatigue and the operational behavior of some typical designs are compared.

The investigation was limited to turbines with moderate pressure ratio (<16) and low cooling air temperatures allowing the rotors to be made of high strength ferritic steels.

The result shows a preference for welded designs with discs of constant stress which are free of holes in the center. Strength, low cycle fatigue and safety aspects, as well as operational advantages like avoidance of vibrations and ease of inspection speak for this solution.

However, all three considered designs are presently being used by different manufacturers and meet all requirements for successful operation.
Design of an Incompressible High-Pressure Vaneaxial Fan Using CFD
Authors: Lee Y. T. , Feng J. , Slipper M. E. , Merkle C. L.
Published: March 2015

An advanced computational fluid dynamics (CFD) modelling design method using a numerical viscous/inviscid coupling procedure has been developed. The method is employed to analytically evaluate the performance of various combinations of high pressure vaneaxial fan rotor, stator and diffuser geometries. The procedures used in the CFD design method ensure a free-vortex blading, a separation-free profile, and a configuration with optimum rotor-stator interaction. Two test fans which have aerodynamic performance and geometrical characteristics close to the desired fan operating range are used to provide code verification and empirical information for the total design effort. A design example is presented. Aerodynamic and aeroacoustic test data will be presented in a later paper.
An Approach for Multi-Stage Calculations Incorporating Unsteadiness
Authors: Giles Michael
Published: March 2015

This paper describes a mathematical approach to the calculation of unsteady flow in multi-stage turbomachinery. An asymptotic formulation is used, with the small asymptotic parameter being the level of unsteadiness in each blade row. The baseline flow is the nonlinear steady flow that is computed by many existing multi-stage calculation methods. The first order linear perturbation is the unsteady flow field arising from stator/rotor interactions between neighboring blade rows. The second order correction contains the information about the time-averaged effect of unsteadiness on the mean flow. The advantage of this asymptotic approach is that it leads to a set of equations which can be solved numerically very much more cheaply than the full nonlinear unsteady flow equations, while still retaining the key features of the flow.
Investigation of Rotor Blade Roughness Effects on Turbine Performance
Authors: Boynton J. L. , Tabibzadeh R. , Hudson S. T.
Published: March 2015

The cold air test program was completed on the SSME (Space Shuttle Main Engine) HPFTP (High Pressure Fuel Turbopump) turbine with production nozzle vane rings and polished coated rotor blades with a smooth surface finish of 30 microinch (0.76 micrometer) RMS (Root Mean Square). The smooth blades were polished by an abrasive flow machining process. The test results were compared with the air test results from production rough coated rotor blades with a surface finish of up to 400 microinch (10.16 micrometer) RMS. Turbine efficiency was higher for the smooth blades over the entire range tested. Efficiency increased 2.1 percentage points at the SSME 104 percent RPL (Rated Power Level) condition. This efficiency improvement could reduce the SSME HPFTP turbine inlet temperature by 57 degrees Rankine (32 degrees Kelvin) increasing turbine durability. The turbine flow parameter increased and the mid-span outlet swirl angle became more axial with the smooth rotor blades.
Meridional Flow Calculation Using Advanced CFD Techniques
Authors: Kiousis P. , Chaviaropoulos P. , Papailiuou K. D.
Published: March 2015

Working experience on traditional Meridional Flow Solvers has revealed difficulties concerning both convergence and accuracy of the solution. These difficulties have been observed for instance in certain industrial applications where steep gradients of flow and/or geometrical quantities are present. Transonic flow conditions can cause extra difficulties. All these difficulties may be circumvented when advanced CFD techniques are utilized.

A computational tool, suitable for the solution of the Meridional Through Flow equations for Turbomachinery applications is presented. Assuming that the flow is compressible and inviscid the governing equations are obtained using a streamfunction formulation for the pitch-averaged flow equations. Viscous corrections have been incorporated in the inviscid model in terms of flow angle deviation and total pressure losses.

Governing equations, are discretized using body fitted finite difference schemes. An artificial density upwinding scheme assures convergence in the transonic region. Particular attention has been paid to the numerical integration procedure which is based on a preconditioned gradient method (GMRES).

Calculation results for low and high-speed turbomachines are presented and discussed.
Study of Pressurized Fluidized Bed Combustion Combined Cycles With Gas Turbine Topping Cycle
Authors: Bohn D. , Dibelius G. H. , Pitt R. U. , Faatz R. , Cerri G. , Salvini C.
Published: March 2015

Coal based combined cycles for efficient generation of electricity or cogeneration of thermal and mechanical (electrical) power can be realized making use of Pressurized Fluidized Bed Combustion (PFBC). A draw-back with respect to the efficiency, however, is imposed from the combustion system limiting the temperature to some 850°C. This threshold may be overcome by integrating a high pressure, high temperature gas turbine topping cycle into the process. In a first step, the high pressure, high temperature gas turbine is fired by natural gas, and the exhaust gas of the turbine is fed to the PFB combustor as an oxygen carrier. In a future advanced system, the fuel gas may be provided by an integrated coal gasification process.

A basic reference case has been established based on commercially available gas turbine equipment, hot gas filtration systems as actually tested in various pilot installations, and on a conservative steam cycle component technology. With an ISO gas turbine inlet temperature of 1165°C and an overall compression ratio of 16 up to 30, the entire process yields a net efficiency of some 46% (LHV) and an overall power output of some 750 MW with the gaseous fuel making up for some 50% of the overall energy input. Both the efficiency and the power output have been found rather insensitive with respect to a variation of the overall compression ratio. However, for a non-intercooled compression, an increase of the maximum process pressure would allow for the energy input to be shifted towards coal (and to reduce the natural gas input), and in particular for an elevated PFB combustor pressure considered mandatory for compactness as well as for combustion efficiency including emissions.

The numerous calculations for the design, the optimization and the prediction of part-load operation of complex systems are efficiently performed with a semi-implicit method, the results of which have been checked carefully against those of a more conventional sequential approach and found in good agreement.
Past and Future of Industrial Cogeneration in The Netherlands
Authors: Blok Kornelis , Turkenburg Wim C.
Published: March 2015

Gas turbine based combined heat and power generation (cogeneration) has developed strongly in the Netherlands in the past twenty years and has the potential to do so also in the future. In this paper the effect of government incentives, both in the past and in the future, is explored.

In the years 1968 through 1988 1200 MW of industrial cogeneration capacity was installed, based primarily on gas turbines technology. This brought total cogeneration capacity to 1800 MW. The amount of electricity generated by private companies tripled in the period 1968 through 1988. In 1988 industrial power generation supplied 37 MJe, which is equal to nearly 15% of the total amount of electricity consumed in the Netherlands.

In the period up to 1978 there was hardly any governmental policy directed towards stimulation of industrial cogeneration. From 1978 onwards a number of stimulating measures have been brought into operation. From an analysis of implementation and effects of government incentives we conclude that the investment grants provided by the government had a considerable effect on the profitability of cogeneration investments. To a lesser extent this was also valid for relatively cheap standby power contracts that were provided by the utilities. However, stimulation of cogeneration only occurred as far as it concerned electricity production for owner consumption. The production of electricity which had to be sold to the utility grid has never been profitable enough from the industrial viewpoint, notwithstanding the provided incentives, like improved buy-back tariffs.

The future potential of industrial cogeneration has been calculated using a computer model in which a simulation and economic optimization is carried out individually for each of the 300 largest industrial plants in the Netherlands. Using this computer model it can be calculated that in principle the cogeneration capacity in the Netherlands can still be doubled. The cogeneration capacity that can be expected to be realized without any government incentive is estimated to be less than 400 MW. The application of investment grants up to 40% can at best double this figure. Carbon taxes of up to $150 per tonne C are somewhat more effective. In order to realize a large part of the ultimate potential stronger policy measures are necessary, which could be regulation which forbids the use of large-scale steam raising in conventional boilers. Without the application of such physical regulation not much may be expected of private industrial investments in cogeneration. However, utility initiatives presented recently hold the promise of realizing a large part of the potential of industrial cogeneration in the Netherlands.
A Combined Experimental and Theoretical Study of Flow and Pressure Distributions in a Brush Seal
Authors: Bayley F. J. , Long C. A.
Published: March 2015

A relatively simple theory is presented which can be used to model the flow and pressure distributions in a brush seal matrix. The model assumes laminar, compressible, isothermal flow and requires knowledge of an empirical constant: the seal porosity value.

Measurements of the mass flowrate together with radial and axial distributions of pressure were taken on a non-rotating experimental rig. These were obtained using a 122 mm bore brush seal with 0.25 mm radial interference.

The experimental data are used to estimate the seal porosity. Measurements of the pressure distributions along the backing ring and under the bristle tips are discussed. Predicted mass flows are compared with those actually measured and there is reasonable agreement considering the limitations of the model.
A High Speed Capacitance Based System for Gauging Turbomachinery Blading Radius During the Tip Grind Process
Authors: Sheard A. G. , Westerman G. C. , Killeen B. , Fitzpatrick M.
Published: March 2015

During the manufacture and overhaul of gas turbines it is necessary to ensure that all blades in a stage are of an equal and known length to minimise the loss in performance that arises as a consequence of the clearance between rotor tip and engine casing. Modern compressor and turbine blades are generally loose fitting in their root fixings and only adopt their true working position when running.

In this paper, a new technique for measuring the rotor radius over individual blades is described. The measurement technique utilises a capacitance based clearance measurement system which enables rotor radius to be measured over each blade while spinning fast enough to ensure that the blades are centrifugally loaded into their true working position. The measurement technique is described, as is the system utilised to calibrate and reduce output into engineering units. The mechanical design of the “measurement head” is presented and the CNC lathe to which it interfaces described. Finally, the results of an experimental programme, utilising a fully bladed compressor disc undertaken to ascertain system performance, are presented.
An Automated Flow Line for Gas Turbine Blade Repair
Authors: Doll David B.
Published: March 2015

The expansion of United Airlines into a global airline has brought with it a substantial increase in the requirements for maintenance support. Existing operations for the repair of shrouded turbine blades were not structured to efficiently repair the increasing volume of unserviceable blades generated by the airline.

The methodology of re-engineering the repair process for shrouded turbine blades in order to generate economies of scale is discussed. The design concepts for an integrated flow line with automated material handling and real time decision making are presented. Operation of the line including manual and automated inspection, automated grinding and welding and manual blending is described. Performance of the line is compared to the prior shop environment, and lessons learned in the accomplishment of the project are discussed.
Direct Numerical Simulation of Nitric Oxyde Evolution in Underexpanded Jets
Authors: Gathmann Ralf Jens , Baudoin Christophe , Chollet Jean-Pierre
Published: March 2015

The evolution of nitric oxydes in exhaust jets of aircraft engines is studied by direct numerical simulations. An extended Zeldovich mechanism models the chemical reactions far from equilibrium. For O and O2 molecules equilibrium is assumed. The NO formation can be studied as a function of different parameters e.g. expansion ratio, jet temperature or jet Mach number. The chemical reactions are highly temperature-dependant leading to high reaction rates in the hot regions behind strong shocks. In particular nearly all NO is formed behind the central shock in the first shock cell. It turns out that for jet exit temperatures of T < 2000K only negligeable NO-formation in the jet is observed. The NO formation is significant only in hot jets with high expansion ratios.
On the Concept of Durability in Evaluation of Equipment Life-Cycle Cost
Authors: Ondryas Igor S.
Published: March 2015

In the increasingly competitive global marketplace the users of industrial products face the challenge of predicting accurate life-cycle costs of their equipment and machinery. The deregulation of many industries resulted in inability of operating companies to pass over to the customer the increased costs of their products, which may have been caused by inaccurate predictions of the equipment operating costs. This evolution in the 1980’s have emphasized the need for accurate predictions of the equipment operating costs and have meant the difference between profit and loss. This paper presents the concept of equipment Durability to be used in the process of evaluation the equipment life cycle cost and subsequent equipment selection. It is also the first part or primer to the paper which describes the Durability Surveillance Program on the Advanced Gas Turbines sponsored by EPRI titled “Durability Surveillance Program on the Advanced Gas Turbine GE Frame 7 F” (1).
Rotor Cavity Flow and Heat Transfer With Inlet Swirl and Radial Outflow of Cooling Air
Authors: Staub F. W.
Published: March 2015

To improve the reliability of turbine disc life prediction, experimental verification is required of analytical tools that calculate the flow field and heat transfer coefficients in turbine-stator cavities. As a first step, a full-scale model of the forward cavity of a typical aircraft gas turbine was employed using a high-molecular-weight gas (Refrigerant-12) at ambient pressure and temperature conditions to match the dimensionless parameters at engine conditions. The cavity temperature and selected cavity velocity profiles were measured using electrical heat addition with liquid crystal surface temperature measurement to obtain local disc heat transfer coefficients. A part of the cooling gas flow was added through a rotating inner seal with the remainder added at high angular swirl in the direction of rotation at a larger radius. Rotational Reynolds numbers were varied up to 9×106 with the radial Reynolds number variation up to 9000. A first-order comparison is given of the velocity distribution and disc heat transfer coefficients calculated by a CFD code and the measured values. The disc heat transfer coefficients can be dominated by the inlet swirl flow or by the rotor speed, depending on whether the coolant flow is greater or smaller than that generated by the rotor alone acting as a free disc.
Analysis of Three-Dimensional Viscous Flow in a Supersonic Axial Flow Compressor Rotor With Emphasis on Tip Leakage Flow
Authors: Perrin G. , Leboeuf F. , Dawes W. N.
Published: March 2015

A three-dimensional computation has been performed for a supersonic axial flow compressor rotor by solving the Navier-Stokes equations. The results of the computation are used to analyse the tip leakage flow in more detail. As well as the global behaviour of the tip leakage vortex, the analysis focuses on the origins of this vortex. It is shown that the main source of its vorticity is the shear layer at the tip of the blade associated with the shedding of the blade loading. A separation occurs, with respect to the axial velocity component, as the jet leakage flow, crossing the clearance gap, encounters the upstream incoming flow. Although the entropy increase of this separation is low, it has a strong effect on the mixing around the leakage vortex. Overall, for this compressor and the choosen operating point, the tip leakage effects are localised near the tip wall and suction side of the blade.
Second-Order Effects of Unsteadiness on the Performance of Turbomachines
Authors: Fritsch Gerd , Giles Michael
Published: March 2015

A 2D, linearized approach is used to investigate second-order effects of unsteadiness on the time-mean efficiency of turbomachinery. The objective is to quantify unsteady losses with a nonzero time-mean and to examine numerical simulations with respect to the modeling of unsteady flow fields and loss mechanisms. Results of simulations constitute the input to the analytical models employed.

Two unsteady loss mechanisms, one of inviscid and the other of viscous nature, are considered. The unsteady circulation losses, i.e., the transfer of kinetic energy into the unsteady part of the flow field through vorticity shed at the trailing edge of a blade, was first considered by Keller (1935) and later by Kemp and Sears (1956). The vorticity is shed in response to an unsteady blade circulation and determined from Kelvin’s circulation theorem which is valid in compressible homentropic flow. Use of a numerical simulation to obtain circulation amplitudes avoids the limitations of thin-airfoil theory and yields results more realistic for modern turbomachinery. For the unsteady viscous loss mechanism, i.e., the dissipation in an unsteady boundary layer on the blade surface, Lighthill’s high-reduced-frequency limit (1955) is used to obtain the local velocity distribution in the laminar sublayer and the corresponding time-mean unsteady dissipation. The input to the model is the time-harmonics of the pressure gradient along a blade surface obtained from a simulation. A numerical study of the errors introduced by a departure from the high-reduced-frequency limit is presented. Losses from both sources are found to be small.
A Compact, Intercooled and Regenerated Gas Turbine for HALE Applications
Authors: Kolden Jennifer J. , Bigbee-Hansen William J. , Iverson Donald G.
Published: March 2015

A mechanically coupled, two spool, intercooled and regenerated gas turbine engine designed for a high altitude, long endurance (HALE) mission is described. The design philosophy was based on minimization of total energy expended using a two stage optimization process utilizing a multivariate regression and optimization technique. This optimization process addressed the impact of the propulsion system as installed on an air vehicle, including all installation effects. Weight and drag of the complete nacelle as they were affected by the characteristics of the engine was included. A brake specific fuel consumption (BSFC) of 0.262 lb/hr/hp (0.159 kg/hr/kw) and mission average specific fuel consumption (MSFC) of 0.266 lb/hp-hr (0.160 kg/kW-hr) was estimated for the bare engine and an MSFC of 0.327 lb/hp-hr (0.199 kg/kW-hr) was estimated for the fully installed engine, including the nacelle drag penalty, where MSFC is defined as the total fuel required to complete the mission divided by the total energy expended during the mission.

A comparison with other gas turbine and reciprocating engines currently considered as candidates for HALE applications is also presented.
Mechanical Properties Evaluation of Generation-I SX-SiC
Authors: Srinivasan G. V. , Chia K. Y. , Lau S. K. , Storm R. S. , Ferber M. K. , Jenkins M. G.
Published: March 2015

Mechanical properties of a developmental high strength and high toughness SiC, Generation I SX, have been evaluated under a Department of Energy (DOE)/Oak Ridge National Laboratory (ORNL) subcontract. The mechanical properties determined included flexural strength, tensile strength, and fracture toughness at room and elevated temperatures. Stress rupture, dynamic fatigue and creep at elevated temperatures also have been evaluated. The strength limiting factors have been identified at room and elevated temperatures. The strength controlling mechanisms are discussed. The microstructure-mechanical property relationship has been established.
Optimization of a Multistage Axial Compressor in a Gas Turbine Engine System
Authors: Egorov I. N.
Published: March 2015

The work presents a procedure to determine the design parameters of multistage axial compressor (MAC) rows, the parameters optimum from the point of view to assure the best integrated indices of gas turbine engine (GTE) both at the design and off-design operation mode.

Effectiveness of the proposed approach has been demonstrated with regards to solving the problems of optimum contouring by the radius of 7 rows of 4-stage fan included in a two-shaft turbofan. For the examples under consideration respective problems of non-linear programming have been set whose dimensionality reached up to 63 of the design parameters of fan blade rows.

It is shown, that the requirement to provide the best engine characteristics, integrated matching both GTE component parts (in our case these are compressor blade rows) and integrated characteristics of components included in an engine is of more importance than assuring the highest efficiency of separate components under consideration.