bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Vane/Blade Spacing on the Heat Flux for a Transonic Turbine
Authors: Dunn M. G. , Haldeman C. W. , Abhari R. S. , McMillan M. L.
Published: August 2014

An experimental and analytical research program determining the influence of vane/blade spacing on the vane and blade time-averaged and unsteady heat-flux for a full-scale rotating turbine stage was performed. The turbine stage was operated at a transonic vane exit condition, with pressure and heat-flux measurements obtained throughout the stage. This paper focuses on the midspan heat-flux measurements for both the vane and blade at three vane/blade axial spacings: 20%, 40%, and 60% of vane axial chord. The time-averaged heat-flux results for the vane and the blade are compared with predictions obtained using a 2-D, Reynolds-averaged multi-blade row code, UNSFLO, developed by Giles (1984). The measured and predicted unsteady heat-flux envelopes (as a function of vane/blade spacing) are also compared with predictions. For selected locations on the blade, a direct comparison between the measured phase-averaged surface pressure and the measured phase-averaged Nusselt number history is presented. At some locations along the surface the pressure and the heat flux are shown to be in phase, but at other locations they are not. The influence of vane/blade spacing on the blade heat load was found to be small, and much less than the differences caused by changes in the Reynolds number during the experimental matrix.
Aerodynamics and Heat Transfer in a Turbine Blade at Design and Off-Design Angles of Incidence
Authors: Xu C. , Amano R. S.
Published: August 2014

A novel numerical method was developed to deal with the studies of the aerodynamic and heat transfer of flow passing through blade cascades at both design and off-design conditions. The Navier-Stokes equations are discretized and integrated in a coupled manner in this study. The time-marching was achieved by using time integration approach in the present method. The flux terms are discretized based on a cell finite volume formulation as well as a flux-difference splitting. The flux-difference splitting can ensure the scheme with rapid convergence and the finite volume technique can ensure the equation for the conservation of mass, momentum and energy. A hybrid difference scheme for quasi-three-dimensional procedure based on the discretized and integrated Navier-Stokes equations as developed to study flow and heat transfer in turbine blade passages. The numerical method possesses the positive features of the explicit and implicit algorithms, providing a relatively rapid convergence process and having a less restricted stability constraint. The computed results were compared with other numerical study results and experiments and showed fairly good agreement.
Experimental Analysis of the Effect of Swirl on the Pressure Field in Whirling 50% Eccentric Annular Seal
Authors: Robic Bernard , Morrison Gerald
Published: August 2014

This work presents measurements of the dynamic and mean pressure distributions on the stator wall of a 50% eccentric whirling annular seal for three different pre-swirl conditions: −45, 0 and +45 degrees and two flow cases, Taylor number of 6,600/Reynolds number of 12,000 and Taylor number of 3,300/Reynolds number of 24,000. A data reduction calculation of the forces and moments generated by the pressure field has been performed, and a description of the effect of swirl on the pressure field has been presented.
Selection of Cycle Configurations for Combined Cycle Cogeneration Power Plants
Authors: Tawney Rattan , Ehman John , Brown Mona
Published: August 2014

Power industry growth and deregulation are causing fundamental changes in the economics of power production and distribution. In order to remain competitive, power producers now seek to improve plant economics through cogeneration, the simultaneous generation of power and production of steam for process use. The majority of manufacturing processes are of a continuous type that require high flexibility for power and steam systems (i.e., require various flows and conditions of steam at various power production levels).

This paper focuses on several ranges of process steam flows and conditions in order to provide a basis for comparison of the most common cycle configurations in combined cycle applications. A non-reheat, advanced technology gas turbine combined cycle facility will be used as the reference plant. Plant design, cycle performance, and economics of each configuration will be evaluated based on requirements of flexibility and process steam flows. This paper will provide guidelines for selection of cycle configurations for cogeneration power plants that will maximize Return on Equity for the owner.
PEACES: A Program for the Economic Analysis of Combined Energy Systems
Authors: Roy-Aikins Joseph
Published: August 2014

Industrial concerns, the world over, are embracing gas/steam turbine combined cycles and combined heat and power as means of meeting energy needs. The main reason is that the potential for energy savings is huge, due to the utilisation of waste heat as useful energy — the key to the excellent thermodynamic performance exhibited by combined energy systems. Excellent thermodynamic performance may not be matched by excellent economic performance, and in certain cases it may not be economical to choose a combined energy system over a mix of supply from conventional plants. The factors governing the economics of combined energy are numerous, though a few are decisive. In choosing a plant for a given duty, an economic assessment of life-cycle costs should be carried out for candidate plants, to arrive at the most economically viable investment proposal, among alternatives.

With this in mind, a computer program PEACES was developed to aid the appraisal of energy investment proposals based on combined energy systems. The economic model on which the program was structured is described in this paper. A case study is carried out, where the software was used at arriving at the most economically viable solution for meeting the energy needs at an industrial site.
Set-Up of an Adaptive Method for the Diagnosis of Gas Turbine Operating State by Using Test-Bench Measurements
Authors: Bettocchi R. , Spina P. R. , Benvenuti E.
Published: August 2014

The paper presents an application in the field of a method for the analysis of the gas turbine operating state, which uses the Cycle-Deck developed by the gas turbine manufacturer and the measurements taken by means of the standard machine instrumentation.

The method is applied for diagnosing the operating state of a number of gas turbines in operation at the test-bench in order to check in the field the validity and applicability of the methodology.
Influence of Ambient Conditions on an Aeroderivative Gas Turbine Based Cogeneration Plant — A Comparison of Numerical Simulation With Field Performance Data
Authors: Carcasci Carlo , Facchini Bruno , Grillo Francesco
Published: August 2014

Gas turbine performances are directly related to outside conditions. The use of gas turbines in combined gas-steam power plants, also applied to cogeneration, increases performance dependence by outside conditions, because plants boundary conditions become more complex.

In recent years, inlet air cooling systems have been introduced to control air temperature and humidity at compressor inlet resulting in an increase in plant power and efficiency.

In this paper, the dependence of outside conditions for an existing cogenerative plant, located in Tuscany (Italy), is studied. The plant is equipped with two GE-LM6000 aeroderivative gas-turbines coupled with a three pressure level heat recovery steam generator, cogenerative application being related to the industrial district. The ambient temperature has been found to be the most important factor affecting the plant performance, but relative air humidity variation also has considerable effects.

The field performance data are compared with a numerical simulation. The simulation results show a good agreement with the field performance data. The simulation allows evaluation of design and off-design plant performance and can become a useful tool to study the outside condition influence on power plant performance.
Design Implementation of the Intercooler System of the WR-21
Authors: Cabanos Phil A.
Published: August 2014

This paper describes the design implementation of the Intercooler System of the WR-21 Intercooled Recuperated Gas Turbine Engine (ICR). The Intercooler System extracts heat from the gas exiting the Intermediate Pressure Compressor (IPC) by means of on-engine, air-to-liquid heat exchangers. The heat transfer liquid is 50/50 ethylene glycol/water (EG). The heat is carried out of the engine by the EG to an off-engine EG-to-seawater heat exchanger. The seawater ultimately dumps the heat into the sea. The ICR is designed primarily for ship application where space is at a premium. Three design innovations that provide solutions to operational and emergency problems, resulting in a compact off-engine skid assembly will be introduced.

1. A system design that will handle pump shut downs and allow engine operation while the intercooler is isolated (bypass mode) — without putting the liquid system outside the enclosure under pressure.

2. A reservoir that is vented to atmosphere, that is only about 130 gallons in volume, that provides make-up and allows flow of 800–1000 US gpm (3000–3785 l/min) without causing turbulence in the reservoir.

3. A device that removes slugs of air trapped in the system during initial fill-up and continually deaerates the system.
A Low Temperature CVD Process for Aluminum and Aluminide Coatings
Authors: Liburdi J. , Lowden P. , Moravek V.
Published: August 2014

A novel, low temperature Organometallic Chemical Vapour process (LOM), developed by Liburdi Engineering is presented in this paper. The process, which is widely used in the electronics industry to apply thin layers of pure aluminum, has been successfully scaled from a 3″ (75 mm) diameter quartz reactor to a production hot wall metal retort with an internal diameter of 18″ (0.45m) and a height of 60″ (1.5m). The capability for simultaneously coating external and internal surfaces is discussed. The aluminum layer can be used directly for low temperature atmospheric corrosion protection in place of IVADIZING or diffusion heat treated to produce an oxidation resistant aluminide coating for superalloys. Results of cyclic oxidation and salt fog corrosion testing are presented. The potential for alloying with modifying elements such as platinum to further enhance its high temperature oxidation resistance and to use the process in conjunction with thermal barrier coatings are presented. Potential applications ranging from coating of heat exchangers and automotive catalytic converters to the coating of industrial and aero turbine blades with complex cooling passages are presented.
New Cost Effective Milling Technologies for Manufacturing Blisks
Authors: Bacon Richard M.
Published: August 2014

Many of the new designs for both military and civil aircraft engines are replacing single bladed rotor assemblies with blisk assembled rotors because of the efficiency and performance benefits. Blisks are usually manufactured from hard exotic materials which means that they can be difficult to manufacture and their cycles times can be long and subsequently the components become very expensive. In order to make them more affordable to engine designers and manufacturers alternative, more efficient methods of manufacturing have been developed to help reduce their cost. This paper outlines some of the developments that have been achieved in the milling of blisks so as to make them more commercially available.
Investigation Concerning the Aerothermodynamic Performance Perturbation of a 19MW Intercooled Air Compressor
Authors: Haq Inam U. , Al-Jameel Ali H. , Al-Khalidi Khalid N.
Published: August 2014

This paper investigates the performance problem of a large capacity multistage centrifugal air compressor when operated continuously for an extended period of time without overhauling. The compressor flow constitutes fifty percent of the plant production and plays a critical role in meeting the annual contract capacity and can not tolerate performance instability due to high intercooler temperatures, ambient conditions and, fouling of the internal components. During a recent harsh summer operation, the compressor was undergone to surge many times and prompted to initiate a performance evaluation study to identify the cause(s) of surge and the extent of performance deterioration. High cooling water supply temperature and ambient conditions crippled the performance of the compressor. Engineering analysis identified the excessive accumulation of condensed water in the water chamber of the second intercooler as the most logical reason of the compressor surge during the instances of high ambient conditions i.e. relative humidity and temperature greater than 80% and 35°C, respectively. During heavy load of condensed water, the blockage and insufficient size of the condensate drain caused build up of water level in the water collecting chamber which offered instantaneous hindrance to airflow to the next section and, hence, led to the compressor surge. During normal ambient conditions, the overall performance of the compressor was found satisfactory when compared with the commissioning after a long term of continuous operation without maintenance.
Development of High Tech and Increased Efficiency Retrofit Options for the GE MS3002 Gas Turbine
Authors: Coppola A. , Francini S. , Noera F.
Published: August 2014

This paper deals with a new complete uprate for the after-market of the General Electric MS3002H/J/AT two-shaft gas turbine. The new version, called MS3002KHE, is being developed to increase cycle efficiency by a minimum of 8% over the existing JAT units.

After a brief introduction, marketing evaluations behind the selected target chosen are pointed out.

A description of the GT components which were focused to be uprated follows, with an explanation of all implemented development activities.
Energy Optimisation and Reduction of CO2-Emission on the North Sea Sleipner Gas Production Platform
Authors: Underbakke Harald , Jakobsen Jon
Published: August 2014

There is increasing focus in the industry towards energy efficiency and reduction of CO2 emission. In Norway this has also been strengthened by the introduction of the CO2-tax which in most cases more than doubles the fuel cost. In the North Sea production platforms operated by Statoil there has been a continuing optimisation program to reduce amount of fuel and flare gas for many years.

Optimisation has been done in maintaining high efficiency in gas turbine power production, reducing especially gas compression power demand by simple modifications and process optimisation, and reduce flaring by operating procedures and simple modifications. This has on the Sleipner platforms led to reduction of fuel gas consumption by more than 15 % and flaring has been reduced by 90 %. The total reduction of CO2 to atmosphere from Sleipner field is some 250 000 tons CO2 per year. Many of these improvements would also have been justifiable without the CO2-tax. This paper describes the various fuel and flare reduction activities done on the Sleipner field and outlines some of the possible further improvements currently being considered.
Experimental Investigation of Mode Localization and Forced Response Amplitude Magnification for a Mistuned Bladed Disk
Authors: Judge John , Pierre Christophe , Mehmed Oral
Published: August 2014

The results of an experimental investigation on the effects of random blade mistuning on the forced dynamic response of bladed disks are reported. The primary aim of the experiment is to gain understanding of the phenomena of mode localization and forced response blade amplitude magnification in bladed disks. A stationary, nominally periodic, twelve-bladed disk with simple geometry is subjected to a traveling-wave, out-of-plane, “engine order” excitation delivered via phase-shifted control signals sent to piezo-electric actuators mounted on the blades. The bladed disk is then mistuned by the addition of small, unequal weights to the blade tips, and it is again subjected to a traveling wave excitation. The experimental data is used to verify analytical predictions about the occurrence of localized mode shapes, increases in forced response amplitude, and changes in resonant frequency due to the presence of mistuning. Very good agreement between experimental measurements and finite element analysis is obtained. The out-of-plane response is compared and contrasted with the previously reported in-plane mode localization behavior of the same test specimen. This work also represents an important extension of previous experimental study by investigating a frequency regime in which modal density is lower but disk-blade interaction is significantly greater.
Synchronous Response Estimation in Rotating Machinery
Authors: Maslen Eric H. , Sortore Christopher K. , Vázquez José A. , Knospe Carl R.
Published: August 2014

Synchronous response estimation attempts to determine the forced response (displacement) of a rotor at critical points which cannot be measured directly. This type of prediction, if accurate and reliable, has broad potential use in the rotating machinery industry. Many machines have close clearance points on their shafts, such as seals, which can easily be damaged by excess vibration. Accurate estimates of the actual level of vibration at these points could usefully assist machine operators in troubleshooting and in protecting the equipment from expensive damage. This type of response information can be used both to generate less conservative alarm limits and, if magnetic bearings are available, to directly guide the bearing controllers in restricting the rotor motion at these critical points.

It is assumed that the disturbance forces acting upon the rotor are predominantly synchronous. The response estimate is constructed using the measurable response in conjunction with an estimator gain matrix derived from a model of the transmissibilites of the rotor system. A fundamental performance bound is established based on the single-speed set of measurements by bounding the response to the unmeasurable component of the disturbance force. Acknowledging that some model uncertainty will always exist, a robust performance analysis is developed using structured singular value (μ) analysis techniques. Assuming some reasonable levels of uncertainty for the model parameters (natural frequencies, modal dampings, mode shapes, bearing stiffnesses and dampings) the results of the estimator construction and analysis establish feasibility of the proposed estimation.

Two reference rotor models that are representative of industrially sized machines are used to demonstrate and evaluate the estimation. The unmeasurable response estimation errors consistently lie below 25 μm for the examples examined.
Robust Performance Analysis of Uncertain Magnetic Bearings
Authors: Namerikawa Toru , Fujita Masayuki
Published: August 2014

This paper deals with uncertain model structures, model validation and robust performance analysis of active magnetic bearing systems.

The dynamics of active magnetic bearing systems are characterized by their instability and complex dynamics of rotor and electromagnets. One of the most critical problems of AMBs is a description of a complex behavior of the dynamics of electromagnets and their forces. The exact description of them is almost hopeless, some approximations and assumptions must be employed, and consequently a discrepancy between the real physical system and the nominal design model cannot be avoided. This discrepancy of the magnetic bearing systems is a serious problem of stability and performance. Hence feedback control is indispensable to stabilize the system, further the closed-loop systems of AMBs should have robustness for stability and performance against model uncertainties.

First we derive a nominal mathematical model of AMBs as a linear state-space model under some assumption and idealization, then we consider the discrepancy between the real physical systems and the obtained nominal design model. This discrepancy can be expressed as the structured uncertainties by Linear Fractional Transformation. These uncertainties include linearization error, parametric uncertainties, unmodeled dynamics, and gyroscopic effect. Then we set the interconnection structure which contains the above structurally represented uncertainties. Next we design a robust controller which achieves robust performance condition. Finally, we validate the interconnection structure with the nominal model and uncertainties, and analyze the robustness of stability and performance of the closed-loop system via the mixed structured singular value.
The μ Approach to Control of Active Magnetic Bearings
Authors: Fittro Roger L. , Knospe Carl R.
Published: August 2014

Many important industrial problems in the control of rotating machinery with active magnetic bearings concern the minimization of the rotor vibration response to poorly characterized disturbances at a single or several shaft locations, these typically not corresponding to those of a sensor or actuator. Herein, we examine experimental results of a multivariable controller obtained via μ synthesis with a laboratory test rig. These indicate that a significant improvement in performance can be obtained with a multivariable μ controller over that achieved with an optimal decentralized PD controller.
A Magnetic Bearing System for More-Electric Engines
Authors: Field R. Jett , Sortore Christopher K. , Iannello Victor
Published: August 2014

Magnetic bearing systems for more-electric engines (MEEs) are under development for aircraft and industrial applications to improve performance and reduce maintenance requirements. Key features of the magnetic bearing system are high performance, high temperature actuators with integrated sensors; a high speed digital controller; a high reliability, fault-tolerant system architecture; modular amplifiers; active control of tip clearance; and adaptive control algorithms. Critical components of the magnetic bearing system have been demonstrated in an engine manufacturer’s rotordynamic test stand and other components are in various stages of development.
A Numerical Investigation of the Unsteady Flow in Centrifugal Stages
Authors: Peeters Martin , Sleiman Mohamad
Published: August 2014

Computational Fluid Dynamics (CFD) has matured to the point where it can now be used effectively in impeller and diffuser design. The effective use of CFD for a complete centrifugal stage, however, still remains a challenge. The interaction between an impeller and its diffuser is not well understood and the level of modelling required to explain it is not really known. The goal of this paper is to present some results that can aid in this understanding. A numerical scheme is outlined that is capable of both steady and unsteady stage analysis. Results are presented for a stage consisting of an impeller and pipe diffuser using steady mixing plane analysis. Furthermore, unsteady results for a centrifugal stage consisting of an impeller and a vane diffuser are presented and compared to isolated steady analyses of each component.

The results indicate that centrifugal stage performance is not well predicted using steady analysis. Differences in both the diffuser static pressure rise and the impeller pressure ratio are significant and it may be concluded that steady analysis is too unreliable for centrifugal stage predictions. Unsteady results also captured an important interaction phenomenon observed experimentally.
Trailing Edge 3D Free Shear Layers
Authors: Schröder N. , Hofmann G. , Hourmouziadis J.
Published: August 2014

This paper reports on an investigation of coherent structures and the characteristic flow field of trailing edge shed vorticity, which can be found downstream of blade rows as well as behind lobed exhaust mixers. The corresponding, fundamental flow case of a free, skewed mixing layer was studied both experimentally in a low-speed test facility and numerically using Standard k,ε-Model and Large Eddy Simulation (LES).

The investigation gave a new insight into the flow structure. Along the complete development length there is a coexistence of the streamwise vortices generated by cross-shear with the spanwise vorticity of Von-Karman vortex street or two-dimensional Kelvin-Helmholtz instability. This was confirmed by extensive flow-field measurements using five-hole probes and X-wire anemometry as well as by CFD. The measurement of the mixing layer spreading resulted in a growth rate of the skewed mixing layer very similar to that of the two-dimensional flow. The development of energy thickness downstream of the trailing edge, representing the mixing losses, was found to be practically independent of skewing angle. The spacing and the fluctuation of the streamwise vortex cores were not accessible to probe measurement, but were determined by visualization and large eddy simulation. The separation of vorticity-components gave stable distributions in streamwise and spanwise direction until vortex breakdown, which appears to be independent of the initial state of the boundary layer. A criterion for streamwise vortex breakdown was identified by correcting the development length with the equivalent shear layer parameter. The content of turbulent kinetic energy as a measure for turbulence production and mixing efficiency is discussed.
The Influence of Low Solidity Vaned Diffusers on the Static Pressure Non-Uniformity Caused by a Centrifugal Compressor Discharge Volute
Authors: Sorokes James M. , Koch Jay M.
Published: August 2014

The paper is a sequel to an earlier work by Sorokes et al. 1998, “Investigation of the Circumferential Static Pressure Non-Uniformity Caused by a Centrifugal Compressor Discharge Volute.” The earlier work described experimental and computational fluid dynamics analyses of the non-uniform static pressure distortion caused by the discharge volute in a high pressure, centrifugal compressor with vaneless diffusers. This paper describes additional testing and analytical work done using low solidity vaned diffusers (LSD’s) in place of select vaneless diffusers to determine the alternate diffuser’s effectiveness in eliminating or reducing the magnitude of the non-uniform pressure field. As in the earlier studies, the experiments described in this paper were done using a heavily instrumented gas re-injection compressor operating at over 6000 psia discharge pressure. Instrumentation was installed to measure static, total, and dynamic pressure as well as impeller strain and mechanical vibrations. A brief description of the compressor and instrumentation are provided.

Concurrent with the experimental work, CFD runs were completed to study the effect of the alternate vaned diffusers. The CFD pressure profile trends agreed well with the experimental results and provided analytical corroboration for the conclusions drawn from the test data.

Conclusions are drawn regarding: a) the effectiveness of the LSD’s on the pressure non-uniformity; b) the associated effects on the measured dynamic strains in the impellers; and c) the usefulness of computational fluid dynamics (CFD) in assessing the aerodynamic forces associated with the non-uniformity.
Improvement of the Flow Range of Transonic Centrifugal Compressors With a Low-Solidity Cascade Diffuser
Authors: Hayami Hiroshi
Published: August 2014

If the pressure ratio of a typical single-stage centrifugal compressor is larger than four, the velocity relative to the impeller and to the diffuser exceeds the velocity of sound. The flow range of transonic centrifugal compressors with a vaned diffuser is usually very narrow. Low-solidity cascade diffusers with solidity 0.69 have been successfully applied as a part of the diffuser system of a transonic centrifugal compressor. On the basis of this type of diffuser, a series of experiments to broaden the operating range are discussed focusing on the control of the geometry of impeller and/or diffuser; one was to reduce the inducer blade turning upstream of the throat, and the other was to reduce the inlet passage width of diffuser. The milder inducer blade camber realized the improvement in flow range by 1.5 times to the original one. Regarding the diffuser inlet passage width contraction, the flow range was not broadened so much owing to the change in impeller characteristics, but the input power was reduced and then the high speed efficiency was much improved.
Flow Interaction From the Exit Cavity of an Axial Turbine Blade Row Labyrinth Seal
Authors: Pfau A. , Treiber M. , Sell M. , Gyarmathy G.
Published: August 2014

The structure of labyrinth cavity flow has been experimentally investigated in a three fin axial turbine labyrinth seal (four cavities). The geometry corresponds to a generic steam turbine rotor shroud. The relative wall motion has not been modeled. The measurements were made with specially developed low-blockage pneumatic probes and extensive wall pressure mapping.

Instead of the classical picture of a circumferentially uniform leakage sheet exiting from the last labyrinth clearance, entering the channel, and uniformly spreading over the downstream channel wall, the results reveal uneven flow and the existence of high circumferential velocity within the entire exit cavity. The circumferential momentum is brought into the cavity by swirling fluid from the main channel. This fluid penetrates the cavity and breaks up the leakage sheet into individual jets spaced according to the blade passages. This gives rise to strong local cross flows that may also considerably disturb the performance of a downstream blade row.
Investigation of the Spanwise Transport of the Rotor – Stator Slot Flow in a Test Turbine
Authors: Lindqvist Lars O. , Wickholm Joakim E. , Fransson Torsten H. , Torisson Tord
Published: August 2014

Modern gas turbines are working in a high temperature environment. The needs for cooling the first stage discs and airfoils are inevitable. In order to avoid overcooling it is necessary to have as much information of the temperature redistribution along the flow path as possible. This paper presents results from both a numerical and an experimental investigation of the temperature redistribution.

The numerical part of this investigation is based on 3D Navier-Stokes calculations, where a single stage test turbine is modeled. Combined with an experimental testing of the calculated geometry the influences of the slot flow, which enters the main gas from a slot at the hub section between the stator and the rotor, are evaluated.

The test turbine is working with air at low temperature, typically in the order of atmospheric conditions. In order to simulate the temperature distribution caused by the slot flow trace gas technique is used.

The influence of three parameters, the slot mass flow, the velocity ratio and the pressure ratio, was studied.

The main result of changing the slot mass flow is a change in the absolute value of the temperature minimum. In addition a slight dependence of the penetration depth was observed.

The spanwise transport of the slot flow within the rotor is highly dependent on the velocity ratio. However, some distance downstream of the trailing edge, the core of the slot flow merges together for different velocity ratios.

Varying the turbine stage pressure ratio, from 1.14 to 1.34, did not affect the spanwise transport. Since the pressure ratio is a representative of the main gas mass flow, a decreased pressure ratio results in a higher degree of cooling, as less main gas is present.
Design Optimization of Axial Flow Compressor Blades With Three-Dimensional Navier-Stokes Solver
Authors: Lee Sang-Yun , Kim Kwang-Yong
Published: August 2014

Numerical optimization techniques combined with a three-dimensional thin-layer Navier-Stokes solver are presented. The techniques are used to find an optimum shape of a stator blade in an axial compressor through calculations of single stage rotor-stator flow. The Baldwin-Lomax model is chosen to describe turbulence. For the numerical optimization, search direction is calculated using the steepest decent method and the conjugate direction method. The golden section method is used to determine optimum moving distance along the search direction. The object of the present optimization is to maximize the efficiency. An optimum stacking line is found which produces a custom-tailored three-dimensional blade design.
Three-Dimensional Turbulent Flow of the Tip Leakage Vortex in an Axial Compressor Rotor Passage
Authors: Ma Hongwei , Jiang Haokang
Published: August 2014

Three-dimensional turbulent flow of the tip leakage vortex in a single-stage axial compressor rotor passage is studied using a 3-Component Laser Doppler Velocimetry. The measurement results indicate that the tip leakage vortex originates at about 10% axial chord, 8% pitch away from the suction surface, and becomes strongest at about 30% chord.

With the flow downstream, the vortex core moves toward the pressure surface and to a lower radial location, leading to substantial flow mixing, blockage and turbulence in the tip region. The radial component of turbulence intensities is found to be the highest while the axial-radial component of Reynolds stresses is the largest.

Breakdown of the leakage vortex occurs inside the rear rotor passage, which makes the flow more turbulent in a wider region downstream. This viewpoint is confirmed by the measurements of unsteady static pressure on the casing wall.

Breakdown of a leakage vortex is observed clearly in a compressor cascade with a small clearance. Unsteady interactions of the broken vorticities and the suction surface’s boundary layer are shown obviously inside the downstream passage.
The Influence of Transient Inlet Distortions on the Instability Inception of a Low Pressure Compressor in a Turbofan Engine
Authors: Leinhos Dirk C. , Schmid Norbert R. , Fottner Leonhard
Published: August 2014

While studies on compressor flow instabilities under the presence of inlet distortions have been carried out with steady distortions in the past, the investigation presented here focuses on the influence of transient inlet distortions as generated by variable geometry engine intakes of super- and hypersonic aircrafts on the characteristic and the nature of the instability inception of a LPC. The flow patterns (total pressure distortion with a superimposed co- or counter-rotating swirl) of the distortions are adopted from a hypersonic concept aircraft. A LARZAC 04 twin-spool turbofan was operated with transient inlet distortions, generated by a moving delta-wing, and steady total pressure distortions starting close to the LPC’s stability limit until it stalled. High frequency pressure signals are recorded at different engine power settings. Instabilities are investigated with regard to the inception process and the early detection of stall precursors for providing data for a future stability control device. It turned out that the transient distortion does not have an influence on the surge margin of the LPC compared to the steady distortion, but that it changes the nature of stall inception. The pressure traces are analysed in the time and frequency domain and also with tools like Spatial FFT, Power Spectral Density and Travelling Wave Energy. A Wavelet Transformation algorithm is applied as well. While in the case of clean inlet flow the compressor exhibits different types of stall inception depending on the engine speed, stall is always initiated by spike-type disturbances under the presence of steady or transient distortions though modal disturbances are present in the mid speed range that do not grow into stall, but rather interact with the inlet flow and produce short lengthscale disturbances. The obtained early warning times prior to stall are adversely affected by transient distortions in some cases. The problem of appropriate threshholding becomes evident. The best warning times have been acquired using a statistical evaluation of the Wavelet coefficients which might be promising to apply in a staged active control system which could include different phases of detection and actuation depending on the current precursor.
Rotating Instabilities in an Axial Compressor Originating From the Fluctuating Blade Tip Vortex
Authors: Mailach R. , Lehmann I. , Vogeler K.
Published: August 2014

Rotating instabilities (RI) have been observed in axial flow fans, centrifugal compressors as well as in low-speed and high-speed axial compressors. They are responsible for the excitation of high amplitude rotor blade vibrations and noise generation. This flow phenomenon moves relative to the rotor blades and causes periodic vortex separations at the blade tips and an axial reversed flow through the tip clearance of the rotor blades.

The paper describes experimental investigations of RI in the Dresden Low-Speed Research Compressor (LSRC). The objective is to show that the fluctuation of the blade tip vortex is responsible for the origination of this flow phenomenon.

RI have been found at operating points near the stability limit of the compressor with relatively large tip clearance of the rotor blades. The application of time-resolving sensors in both fixed and rotating frame of reference enables a detailed description of the circumferential structure and the spatial development of this unsteady flow phenomenon, which is limited to the blade tip region.

Laser-Doppler-Anemometry (LDA) within the rotor blade passages and within the tip clearance as well as unsteady pressure measurements on the rotor blades show the structure of the blade tip vortex.

It will be shown that the periodical interaction of the blade tip vortex of one blade with the flow at the adjacent blade is responsible for the generation of a rotating structure with high mode orders, termed as rotating instability (RI).
One-Sided Control of Surge in a Centrifugal Compressor System
Authors: Willems Frank , de Jager Bram
Published: August 2014

Active surge control is studied in a centrifugal compressor system. To stabilize surge, a bleed valve is applied which is nominally closed and only opens to stabilize the system around the desired operating point. This bleed valve is controlled using a linear output feedback controller based on plenum pressure measurements. In this study, the practical limitations of this one-sided surge controller are examined. Experiments show that the performance of the controller is affected by measurement noise and the desired equilibrium point in the controller, which is not accurately known in the unstable operating region. Fully-developed surge is stabilized with relatively small stationary bleed valve mass flow using the proposed controller in combination with a small band-pass filter. Measurements are compared with the results of the Greitzer model. This model shows qualitative agreement with experiments. For the examined compressor system, a 3.5% extension of the stable operating region is obtained using the one-sided surge controller.
A Test Rig for Frictionally Damped Bladed Segments
Authors: Berruti T. , Goglio L. , Filippi S. , Gola M. M. , Salvano S.
Published: August 2014

The paper describes the development of an instrumented test rig suitable to carry out vibration testing of the bladed segments of a turbine (belonging to a stator low pressure stage) in which the friction occurring at the contact of neighboring segments is used in service to damp the vibrations.

The system is able to assign the desired preload to the segment and to measure the forces exerted in the contact and the relative displacements due to slipping.

The main results that can be obtained concern the type of motion that takes place (stick/slip) and the effect of the interlocking on it, the friction coefficients, the contact tangential stiffness, and, more generally, the frequency response.
The Use of Kalman Filter and Neural Network Methodologies in Gas Turbine Performance Diagnostics: A Comparative Study
Authors: Volponi Allan J. , DePold Hans , Ganguli Ranjan , Daguang Chen
Published: August 2014

The goal of Gas Turbine Performance Diagnostics is to accurately detect, isolate and assess the changes in engine module performance, engine system malfunctions and instrumentation problems from knowledge of measured parameters taken along the engine’s gas path. Discernable shifts in engine speeds, temperatures, pressures, fuel flow, etc., provide the requisite information for determining the underlying shift in engine operation from a presumed nominal state. Historically, this type of analysis was performed through the use of a Kalman Filter or one of its derivatives to simultaneously estimate a plurality of engine faults. In the past decade, Artificial Neural Networks (ANN) have been employed as a pattern recognition device to accomplish the same task. Both methods have enjoyed a reasonable success.
Model Development and Simulation of Transient Behavior of Heavy Duty Gas Turbines
Authors: Kim J. H. , Song T. W. , Kim T. S. , Ro S. T.
Published: August 2014

This paper describes models for a transient analysis of heavy duty gas turbines, and presents dynamic simulation results of a modern electricity generation engine. Basic governing equations are derived from integral forms of unsteady conservation equations. Mathematical models of each component are described with the aid of unsteady one-dimensional governing equations and steady state component characteristics. Special efforts have been made to predict the compressor characteristics including the effect of movable vanes, which govern the running behavior of the whole engine. The derived equation sets are solved numerically by a fully implicit method. A controller model that maintains constant rotational speed and target temperature (turbine inlet or exhaust temperature) is used to simulate real engine operations. Component models, especially those of the compressor, are validated through a comparison with test data. Simulated is the dynamic behavior of a 150MW class engine. The simulated time-dependent variations of engine parameters such as power, rotational speed, fuel, temperatures and guide vane angles are compared with field data. Simulated results are fairly close to the operation data.
Extending the Service Life of Gas Turbine Hardware: (II) Engine Testing
Authors: Hampson Leonard M. , Warnes Bruce M.
Published: August 2014

An engine test program was undertaken to evaluate a novel component repair process. First stage, high pressure turbine airfoils with either a simple aluminide (Codep on Rene’80) or a high activity Pt aluminide (RT-22 on Rene’142) were studied. Components refurbished with a partial strip, repair and CVD recoat process were installed in rainbow rotors which included new airfoils and/or components with full repairs (complete strip, weld repair and recoat). Following engine service on commercial aircraft, airfoils from the rainbow rotors were examined. The results of the evaluation suggest the desirable qualities of the CVD low activity Pt aluminide coat/overcoat process observed in the laboratory study could be achieved on engine hardware. Hence, a novel repair process is now available to turbine users, which may extend the service life of expensive turbine hardware.
Active Control Algorithms for the Control of Rotor Vibrations Using HSFDs
Authors: El-Shafei A.
Published: August 2014

The Hybrid Squeeze Film Damper (HSFD) has proven itself to be an effective controlling device of vibration in rotating machinery. The critical stage in the development of the HSFD as an active vibration suppressant, is the development of the control algorithms for active control of rotor vibrations. This paper summarizes, evaluates and compares the control algorithms for HSFD supported rotors. Quantitative as well as qualitative measures of the effectiveness of the control algorithms are presented. The study includes the PID-type controllers, LQR, gain scheduling, adaptive and bang-bang controllers. The adaptive, gain scheduling and nonlinear proportional controllers, have proved to be quite effective in the active control of HSFD supported rotors, with impressive results.
On Flowfield Periodicity in the NASA Transonic Flutter Cascade: Part II — Numerical Study
Authors: Chima R. V. , McFarland E. R. , Wood J. R. , Lepicovsky J.
Published: August 2014

The transonic flutter cascade facility at NASA Glenn Research Center was redesigned based on a combined program of experimental measurements and numerical analyses. The objectives of the redesign were to improve the periodicity of the cascade in steady operation, and to better quantify the inlet and exit flow conditions needed for CFD predictions. Part I of this paper describes the experimental measurements, which included static pressure measurements on the blade and endwalls made using both static taps and pressure sensitive paints, cobra probe measurements of the endwall boundary layers and blade wakes, and shadowgraphs of the wave structure. Part II of this paper describes three CFD codes used to analyze the facility, including a multibody panel code, a quasi-three-dimensional viscous code, and a fully three-dimensional viscous code. The measurements and analyses both showed that the operation of the cascade was heavily dependent on the configuration of the sidewalls. Four configurations of the sidewalls were studied and the results are described. For the final configuration, the quasi-three-dimensional viscous code was used to predict the location of mid-passage streamlines for a perfectly periodic cascade. By arranging the tunnel sidewalls to approximate these streamlines, side-wall interference was minimized and excellent periodicity was obtained.
An Update of the Virtual Energy Laboratory
Authors: Perez-Blanco H. , Albright Paul
Published: August 2014

The Virtual Energy Lab (VEL) is a PC based didactic tool for use in conjunction with courses on technical thermodynamics and thermal system design. The tool can also be used for conceptual design of large-scale systems incorporating cogeneration schemes of varied types. The user can learn how to combine conventional thermal systems in creative ways to enhance exergetic efficiency.

In the present work, we describe upgrades to this tool, and we present several examples to show the possibilities of energy cascading. The features of ease of learning, user ability to specify important parameters and ready targeting of conceptual designs were preserved in the updated version.
What is the Electric Output of a Cogeneration Project Worth?
Authors: de Kok Alexandra C. , Hill Jane P.
Published: August 2014

The economics of cogeneration depend on whose perspective is being considered. A retail electric customer is concerned with the degree to which electric purchases at regulated tariffs can be reduced. A public utility’s perspective includes where the unit would fit in the generation “stack,” how much the unit would operate, and the opportunity costs of operating the cogeneration unit as opposed to other available units. An independent power producer (IPP) has many of the same objectives as an electric utility. However, an IPP has no franchised service territory guaranteeing markets for electricity it produces, although an IPP escapes many issues associated with regulation.

Because of these different perspectives, a cogeneration project which is economic for one entity might not be for another. In addition, even if cogeneration is thought to be economic for all three, the optimal equipment selection and operating scenario can vary substantially among potential investors.

This paper discusses the factors which influence economic viability of cogeneration from the perspectives of different potential investors.