bluuebunny/crossref_metadata_2025 huggingface dataset:
Off-Design Analysis of the Semi Closed Gas Turbine Cycle (SCGT) With Low CO2 Emissions
Authors: Fiaschi Daniele , Scatragli Federico
Published: September 2008

The Semi Closed Gas Turbine Cycle (SCGT) was introduced as a short to medium term solution for applying existing CO2 removal techniques to current production gas turbine powerplants. Thus, one of the main goals is the adaptability to existing turmomachinery, with only minor changes to the equipment. In this manuscript, the off–design analysis of two previously proposed and thermodynamically assessed configurations was carried out: the first one is the combined cycle (SCGT/CC), related to an heavy duty gas turbine, whereas the second one is the recuperative–evaporative cycle (SCGT/RE). Both of them may be equipped with intercooled or, either, aftercooled compression, which is done with spray water injection. The analysis was carried out with special reference to the off design conditions of the compressor and to its coupling with turbine when the partial exhausts recirculation is applied to originally open cycle GTs. In the SCGT/CC configurations, the steam pressure levels are increased due to the increased GT exhausts temperature with respect to the open cycle. When no water injection is applied, the working point of the compressor due to the different gas composition and temperature are largely within the operating margins, thus the semi closed configuration may be applied even to compressors with reduced stall bounds and no large decays in compressor efficiency were found compared to the design operation. On the contrary, when water injection is applied, heavy variations of the compressor working point were found, which make the effects of exhausts recirculation comparatively marginal and leads to unavoidable compressor efficiency drop. It suggests that the application of water injection may be suitable only for the short peakload times, whereas current technology allows the shifting to SCGT.
Single-Tube Simulation of a Semi-Intermittent Pressure-Gain Combustor
Authors: Akbari Pezhman , Baronia Dhruv , Nalim Razi
Published: September 2008

This work is aimed to investigate the fundamental combustion and reignition process in semi-intermittent pressure-gain combustors for gas turbine applications. A combustion-torch ignition method is used to simulate reignition in one tube of a pressure-gain combustor by employing burned gas produced in a pre-chamber combustor. Numerical flow and combustion simulations are performed to understand and guide preliminary experimental results. The computational fluid dynamics code StarCD® is used to predict internal flow and combustion upon attempted ignition by a hot gas jet. This study provides improved understanding of the complex, sub-millisecond processes involved: transient supersonic jet mixing, ignition, highly turbulent flame propagation, and shock-flame interaction in near-wall region. The results are useful for successful design of rotary pressure gain combustors or internal combustion wave rotors under various operating conditions.
Fuel Nozzle Performance Analysis Using Laser Techniques and Combustion Chamber With Optical Access
Authors: Pucher G. R. , Underhill P. R. , Allan W. D. , Wang G. , Guy S.
Published: September 2008

Correct functioning of fuel nozzles is paramount to the efficient operation of gas turbine engines. Nozzles exhibiting poor distribution of droplets can be detrimental to combustion and overall engine life due to the creation of hot spots and potential for torching. The traditional technique of assessing nozzle performance involves operation in stagnant air conditions. Fuel spray is collected in the subdivided bins of a mechanical patternation system to determine spray symmetry. Recent improvements in spray analysis involve the use of laser light sheets to illuminate specific ‘slices’ of sprays in either cross sectional or axial planes. Typically, scattered light from the intersection of a laser sheet and a spray is recorded by a digital video camera, and images are averaged and corrected to determine the quality of the spray pattern. Such optical means of assessing spray quality provide great improvement over conventional means in terms of speed, convenience, and information retrieved. Nonetheless, data obtained in stagnant air conditions do not give an indication of spray geometry within combustion chambers under realistic operating conditions of airflow and combustion. This paper describes a project which applied laser-based optical patternation in a T-56 gas turbine combustion chamber rig with optical access under realistic flow conditions. As such, nozzle spray pattern was observed for various air and fuel flows in both cross sectional and plume (chamber axial) orientations. A deliberately damaged nozzle was also assessed for comparison with a good nozzle. Using optical filtration, spray patterns were observed under operationally representative combustion conditions.
Automated Fault Diagnosis of a Micro Turbine With Comparison to a Neural Network Technique
Authors: Davison Craig R. , Birk A. M.
Published: September 2008

In the predicted future of distributed power generation, a large number of users will operate gas turbine powered cogeneration systems. These systems will be small, relatively inexpensive, and installed in locations without ready access to experts in gas turbine maintenance. Consequently, an automated system to monitor the engine and diagnose the health of the system is required. To remain compatible with the low cost of the overall system, the diagnostic system must also be relatively inexpensive to install and operate. Therefore, a minimum number of extra sensors and computing power should be used. A statistical technique is presented that compares the engine operation over time to the expected trends for particular faults. The technique ranks the probability that each fault is occurring on the engine. The technique can be used online, with daily data from the engine forming a trend for comparison, or, with less accuracy, based on a single operating point. The use of transient operating data with this technique is also examined. This technique has the advantage of providing an automated numerical result of the probability of a particular mode of degradation occurring, but can also produce visual plots of the engine operation. This allows maintenance staff to remain involved in the process, if they wish, rather than the system operating purely as a black box, and provides an easy to understand aid for discussions with operators. The technique is compared to an off the shelf neural network to determine its usefulness in comparison to other diagnostic methods. The test bed was a micro turbojet engine. The data to test the system was obtained from both experiment and computer modeling of the test engine.
Development of a Strain Tolerant Ceramic Coating for the Protection of Rotating Blade Tips
Authors: Weatherill Adrian E.
Published: September 2008

Control of the clearance between the tip of rotating blades and the static components is important for the efficient operation of a gas turbine. Decreasing the gap to minimise gas leakage leads to higher efficiency and greater power, but also increases the risk of contact between the two components. Where this occurs, frictional forces cause localised heating which often results in damage to the components. In extreme cases this has resulted in fire and engine damage, particularly where titanium based components were used. The use of sealing systems, where the blade deliberately cuts a path into a softer or porous surrounding material, rely on a good cutting action in order to maintain efficiency and minimise component wear and damage. It is possible to protect blade tips by applying a wear resistant or abrasive coating which can minimise metal to metal contact and provide an enhanced cutting action. Design considerations have lead to the development of a strain tolerant ceramic coating (STCC) which consists of a two layered, thermally sprayed yttria stabilised zirconia coating, applied over a bond coat. The bond coat not only providing good adhesion for the ceramic top layer but by using an HVOF applied MCrAlY, also provides oxidation protection at higher temperatures. This system is suitable for use on both compressor and turbine blades. It is designed to survive between overhauls when it can be easily removed and replaced. The coating was rigorously tested including severe thermal shock loading and long term oxidation. An examination of the microstructure showed that as-sprayed, the ceramic top coat had a dense structure. After testing it was found that the coating had survived by microcracking to relieve the applied stresses. Results from engine operation confirm that this coating system provides the designed protection for rotating blade tips and enables them to operate effectively against a MCrAlY seal.
Nonlinear Flame Transfer Function Characteristics in a Swirl-Stabilized Combustor
Authors: Bellows Benjamin D. , Bobba Mohan K. , Seitzman Jerry M. , Lieuwen Tim
Published: September 2008

An understanding of the amplitude dependence of the flame response to acoustic excitation is required in order to predict and/or correlate combustion instability amplitudes. This paper describes an experimental investigation of the nonlinear response of a lean, premixed flame to imposed acoustic oscillations. Detailed measurements of the amplitude dependence of the flame response were obtained at approximately 100 test points, corresponding to different flow rates and forcing frequencies. It is observed that the nonlinear flame response can exhibit a variety of behaviors, both in the shape of the response curve and the forcing amplitude at which nonlinearity is first observed. The phase between the flow oscillation and heat release is also seen to have substantial amplitude dependence. The nonlinear flame dynamics appear to be governed by different mechanisms in different frequency and flowrate regimes. These mechanisms were investigated using phase-locked, two-dimensional OH PLIF imaging. From these images, two mechanisms, vortex rollup and unsteady flame liftoff, are identified as important in the saturation of the flame’s response to large velocity oscillations. Both mechanisms appear to reduce the flame’s area and thus its response at these high levels of driving.
Effects of Bleed Flow on Heat/Mass Transfer in a Rotating Rib-Roughened Channel
Authors: Jeon Yun Heung , Park Suk Hwan , Kim Kyung Min , Lee Dong Hyun , Cho Hyung Hee
Published: September 2008

The present study investigates the effects of bleed flow on heat/mass transfer and pressure drop in a rotating channel with transverse rib turbulators. The hydraulic diameter (Dh) of the square channel is 40.0 mm. The bleed holes are located between the rib turburators on the leading surface and the hole diameter (d) is 4.5 mm. The square rib turbulators are installed on both leading and trailing surface. The rib-to-rib pitch (p) is 10.0 times of the rib height (e) and the rib height-to-hydraulic diameter ratio (e/Dh) is 0.055. The tests were conducted at various rotation numbers (0, 0.2, 0.4), while the Reynolds number and the rate of bleed flow to main flow were fixed at 10,000 and 10%, respectively. A naphthalene sublimation method was employed to determine the detailed local heat transfer coefficients using the heat/mass transfer analogy. The results suggest that for a rotating ribbed passage with bleed flow of BR = 0.1, the heat/mass transfer on the leading surface is dominantly affected by rib turbulators and the secondary flow induced by rotation rather than bleed flow. The heat/mass transfer on the trailing surface decreases due to the diminution of main flow. The results also show that the friction factor decreases with bleed flow.
Influence of Rib Turbulators on Pin-Fin Heat Transfer in the Trailing Region of Gas Turbine Vane: A Numerical Study
Authors: Kulasekharan N. , Prasad B. V. S. S. S.
Published: September 2008

A numerical investigation is carried out for estimating the influence of rib turbulators on heat transfer and pressure drop of staggered non-uniform pin-fin arrays of different shapes, in a simulated cambered vane trailing region. Pin-fins of square, circular and the diamond shapes, each of two sizes (d) were chosen. The ratio of span-wise pitch to longitudinal pitch is 1.06 and that to the pin size are 4.25 and 3.03, for all pin shapes. A constant heat flux boundary condition is assumed over the coolant channel walls, rib surfaces and circumferential faces of the pin-fins. Reynolds number is varied (20,000<ReD<40,000) by changing the coolant outlet to inlet pressure ratio. Pin end-wall and pin surface averaged heat transfer coefficients and Nusselt numbers are estimated and detailed contours of heat transfer coefficient on both the pressure and suction surfaces are presented. Whilst there is an enhancement in heat transfer and pressure drop with ribs for all the pin shapes, diamond pins have shown the highest enhancement values for both ribbed and non-ribbed configuration.
Buoyancy-Induced Flow in Open Rotating Cavities
Authors: Owen J. Michael , Abrahamsson Hans , Lindblad Klas
Published: September 2008

Buoyancy-induced flow can occur in the cavity between the co-rotating compressor discs in gas-turbine engines, where the Rayleigh numbers can be in excess of 1012. In most cases the cavity is open at the centre, and an axial throughflow of cooling air can interact with the buoyancy-induced flow between the discs. Such flows can be modeled, computationally and experimentally, by a simple rotating cavity with an axial flow of air. This paper describes work conducted as part of ICAS-GT, a major European research project. Experimental measurements of velocity, temperature and heat transfer were obtained on a purpose-built experimental rig, and these results have been reported in an earlier paper. In addition, 3D unsteady CFD computations were carried out using a commercial code (Fluent) and an RNG k-ε turbulence model. The computed velocity vectors and contours of temperature reveal a flow structure in which, as seen by previous experimenters, ‘radial arms’ transport cold air from the centre to the periphery of the cavity, and regions of cyclonic and anti-cyclonic circulation are formed on either side of each arm. The computed radial distribution of the tangential velocity agrees reasonably well with the measurements in two of the three cases considered here. In the third case, the computations significantly over-predict the measurements; the reason for this is not understood. The computed and measured values of Nu for the heated disc show qualitatively similar radial distributions, with high values near the centre and the periphery. In two of the cases, the quantitative agreement is reasonably good; in the third case, the computations significantly under-predict the measured values.
Estimation of Performance Variation of Coal Fired Boilers Cofired With Biomass: Development of a Predicting Tool
Authors: De Sudipta , Kaiadi Mehrzad , Assadi Mohsen
Published: September 2008

Biomass cofiring in existing coal fired boilers has emerged as one of the most prospective technologies in order to address voluntary reduction of green house gases and other emissions, potential portfolio standards, customer service etc. within the context of deregulations. Pilot plant test results have confirmed the potential of biomass cofiring with coal for commercial use. However, being a new and developing technology, there is hardly any tool available for estimation of variation in performance of an existing coal fired boiler due to its retrofitting for biomass cofiring. A predicting tool is developed to estimate this performance variation using available information of pilot plant test results in literature or from data of plant operating with biomass. In order to incorporate future available information, this is developed in a flexible environment of Model Development Kit (MDK) of IPSEpro, a commercially available heat and mass balance program. Development of the models for this predicting tool as well as its limitations and possible future improvement has been discussed in this paper. Some results regarding estimation of change in efficiency, emissions and associated costs using this developed predicting tool has been presented.
Effects of Pressure Ratio and Fin Pitch on Leakage Flow Characteristics in High Rotating Labyrinth Seals
Authors: Li Jun , Yan Xin , Feng Zhenping
Published: September 2008

Labyrinth seals represent an important flow element in the sealing equipment of modern turbomachinery industries. The straight-through and stepped labyrinth seal are widely used in modern steam turbine due to their comparable simple structure and low manufactured costs. The influence of pressure ratio and fin pitch on the leakage flow characteristics of the straight-through and stepped labyrinth seals is numerically determined. The pressure ratio is defined as the outlet static pressure divided by the inlet total pressure. The fin pitch varied in the fixed axial distance of the labyrinth seal. The geometries investigated represent designs of the straight-through and stepped labyrinth seal typical for modern steam turbines. The leakage flow fields in the high rotating straight-through and stepped labyrinth seals are obtained by the Reynolds-Averaged Navier-Stokes solution using the commercial software FLUENT with the fixed seal clearance and fins geometrical structure. The effect of the rotational axis is also taken into account in numerical computations. Numerical simulations covered a range of pressure ratio and fin pitch for the straight-through and stepped labyrinth seals. Dimensionless discharge coefficients, describing the sealing performance, are calculated from the simulation results. The numerical results show that pressure ratio and fin pitch both affects the sealing performance with the fixed seal clearance and fin geometrical structure. The leakage flow rate decreases with the decreasing fin pitch for both the straight-through and stepped labyrinth seal at the fixed pressure ratio. Furthermore, the leakage flow rate decreases with the increasing pressure ratio at the fixed fin pitch for two kinds of labyrinth seals in the present study. This research provides technical support for improved design of labyrinth seals in turbomachinery.
Support for Operation Strategy in CHP Plants With Gas Turbines
Authors: Kosman Gerard , Chmielniak Tadeusz , Kosman Wojciech
Published: September 2008

This paper presents procedure, which supports planning a strategy of operation, repairs and modernizations. Reliability and effectiveness are assumed to form the criteria for appropriate operation with a special attention to working costs. The procedure involves diagnostic analysis. Information derived from diagnostic may be utilized in many ways. It allows to determine losses, which derive from components wear or improper operation, and track the wear rate of machines components. This in turn allows to assess the losses, which appear in case of extended period between routine repairs. The most important application of the diagnostic results is the determination of the working costs for a CHP plant. It establishes a relation between the working costs of a gas turbine and its future time of operation. In addition it analyses the influence of the parameters independent of the gas turbine user (such as ambient conditions) on the operation and costs. The calculations presented in this paper involve a diagnostic module designed for uncooled and cooled gas turbines. The health state is assessed through a set of performance indices. Thermal measurements are the input data for the module, which may utilize even a small number of available measurements. The working costs create the basis for the procedure, which supports planning the strategy of operation and repairs. The procedure consists of several diagnostic rules. It draws conclusions from given premises. A premise includes a set of data, which involve among others working costs calculated according to health state. A conclusion indicates whether a further operation is possible and under what circumstances. The circumstances specify any required adjustments of the operation conditions or suggest an exchange or repair of some turbine components, which might be damaged.
Flame Propagation Following the Autoignition of Axisymmetric Hydrogen, Acetylene and Normal-Heptane Plumes in Turbulent Co-Flows of Hot Air
Authors: Markides Christos N. , Mastorakos Epaminondas
Published: September 2008

Axisymmetric plumes of hydrogen, acetylene or n-heptane were formed by the continuous injection of (pure or nitrogen-diluted) fuel into turbulent co-flows of hot air. Autoignition and subsequent flame propagation was visualized with a high-speed intensified camera. The resulting phenomena include the statistically steady ‘Random Spots’ and the ‘Flashback’ regimes. It was found that with higher velocities and smaller injector diameters, the boundary between Flashback and Random Spots shifted to higher air temperatures. In the Random Spots regime, the autoignition regions moved closer to the injector with increasing air temperature and/or decreasing air velocity. After a localized explosive autoignition event, flames propagated into the unburnt mixture in all directions and eventually extinguished, giving rise to autoignition ‘spots’ of mean radius 2–5mm for hydrogen and 6–10mm for the hydrocarbons. The average flame propagation velocity in both the axial and radial directions varied between 0.5 and 1.2 times the laminar burning speed of the stoichiometric mixture, increasing as the autoigniting regions shifted upstream.
SUSPOWER and ENGAS: Two Major European Research Infrastructures in the Gas Turbine and Energy Conversion Fields
Authors: Martin Andrew , Fransson Torsten , Gro̸nli Morten , Bredesen Arne M.
Published: September 2008

Since the mid-1990’s the European Commission (EC) has provided funding for transnational access schemes that open up existing major research facilities to outside users. In the current 6th Framework Program, two out of 14 funded projects — SUSPOWER and ENGAS — are of prime interest to the gas turbine community. SUSPOWER (KTH, Stockhom, Sweden) encompasses unique large-scale experimental facilities within the area of sustainable thermal power generation. Topics of key interest include high-temperature air combustion, catalytic combustion, gasification, aeroelasticity of turbine/compressor blades, film cooling aerodynamics, and stator/rotor interactions. ENGAS (NTNU, Trondheim, Norway) includes a complex array of specialized laboratories in the topic of environmental gas management. Relevant research topics include combustion of hydrogen and hythane, biomass gasification, CO2 absorption and sequestration, membranes for hydrogen and CO2 separation, gas storage in rock caverns, and hydrogen production and storage. This paper presents information on these projects along with a brief overview of previous EC transnational access activities as related to gas turbine research and development.
Active Hierarchical Fuzzy Control for Gas Turbine Altitude Relighting Using Multi-Objective Optimization
Authors: Kim Sogkyun , Thompson Haydn , Fleming Peter
Published: September 2008

The developments of high bypass turbofan engines and improvements in high temperature materials have resulted in smaller engine cores. These smaller core engines result in correspondingly lower airflows that introduce their own design problems, including failure to reach idle, stagnation, increased time to reach idle and lack of surge margin. Such problem can occur in engine relighting at low altitude and immediately following take-off. Engineers have provided solutions to such problems but they tend to be specific solutions for individual engines. In this paper a systematic approach to improve engine performance in altitude relighting is addressed which does not involve any modification to hardware, including the engine components or the fuel metering unit. The application of active control solutions has been evaluated to improve engine low altitude relighting performance. Initially an active fuzzy controller has been designed to improve the pull-away performance after relight. Further, an active hierarchical fuzzy controller has also been designed to establish if it can offer further benefits. Multi-objective optimization is used, both to optimize the parameters of the fuzzy controllers and also to produce a concise number of fuzzy rules for the fuzzy controller(s). Compared to the conventional controller, with a look-up table approach, the active fuzzy controllers can reduce the time to reach idle speed, by utilising compressor surge margin and increase combustion operability. In this way, a generic and more flexible framework for designing relighting logic emerges, that captures the knowledge incorporated within the design of the original logic. This leads to significant improvements in the design of future relighting control systems.
Materials and Structures Prognosis for Gas Turbine Engines
Authors: Littles Jerrol W. , Morris Robert J. , Pettit Richard , Harmon David M. , Savage Michael F. , Tulpule Sharayu
Published: September 2008

Gas turbine engine diagnostic systems often utilize data trending and anomaly detection to provide a measure of system health. These systems provide significant benefits for trending shifts in engine performance and diagnosing system degradation that requires some maintenance action. However, this approach may be limited in the ability to uniquely identify damage for select components and failure modes. Advanced prognostic systems are being developed to work symbiotically with state of the art diagnostic techniques in use today; these advanced systems use advanced material and component damage evolution modelling linked with system-level structural analyses to intelligently guide the health management system to search for specific signatures that would be expected from key changes in component and system health [1,2,3,4]. Material damage models, advanced component models, and novel system-level structural analyses are being used to generate newly defined “structural transfer functions” (STFs) that provide a link between sensed parameters and the remaining capability of specific components, and the system. The characteristic damage signatures vary by component type and failure mode, and hence the specific STF approach varies among component types. An initial STF approach was developed and demonstrated for a specific component and damage type [5] under an initial feasibility program. This STF-based prognosis approach is fundamentally different from the traditional modal analysis based NDE approach used for crack detection. This presentation will review this novel STF-based prognosis approach, and consider examples of STFs characteristic of specific components and damage types, as well as progress towards the development of tools that are enabling system-level STF development [6].
HAYNES® 282™ Alloy: A New Wrought Superalloy Designed for Improved Creep Strength and Fabricability
Authors: Pike L. M.
Published: September 2008

A new wrought, gamma-prime strengthened superalloy, HAYNES 282 alloy, has been developed for high temperature structural applications, especially those in aero and land-based gas turbine engines. The new alloy possesses a unique combination of creep strength, thermal stability, and fabricability not found in currently available commercial alloys. The new alloy has excellent creep strength in the temperature range of 1200 to 1650°F (650 to 900°C), surpassing that of Waspaloy alloy and approaching that of R-41 alloy. This level of creep strength is realized despite the alloy having a significantly lower volume fraction of the strengthening gamma-prime phase. The lower gamma-prime content of the new alloy provides a considerable improvement in terms of fabricability and resistance to strain-age cracking, a problem often associated with this class of alloys. In this paper, the major characteristics and attributes of the new alloy including mechanical properties, oxidation resistance, thermal stability, and weldability are presented.
Performance and Numerical Flow Investigations of an Industrial Gas Turbine Intake System Under Different Operating Conditions
Authors: Mund Friederike C. , Pilidis Pericles
Published: September 2008

An important loss in an industrial gas turbine is caused by the intake system. Even though these losses have a direct effect on the performance of the engine, the design of the intake system is dominated by local space restriction. Consequently, intake losses are site specific parameters. They correlate with the airflow velocity and therefore operating conditions of the engine affect the intake performance. But due to the high experimental effort necessary to investigate intake losses, only sparse information about this effect is available. For the present study a typical vertical industrial intake duct was investigated numerically for different operating scenarios. The performance simulation of a single shaft heavy duty gas turbine provided boundary conditions for the CFD (Computational Fluid Dynamics) study of the intake duct. For all operating conditions a large scale vortex developed in the intake plenum and entered the compressor. Bearing support struts caused local flow distortion at the compressor inlet. Even for extreme operating scenarios the relative changes of pressure recovery compared to the design point value were small (0.1%). However, the resulting power change was generally in excess of the intake loss deviation. Applied to a heavy duty gas turbine, the maximum deviation of 0.2% of power was equivalent to about 0.4 MW. In most cases lower pressure losses were predicted which benefited the overall engine performance. For the cold scenario the intake performance deteriorated and resulted in a relative reduction of power of nearly 0.5 MW.
CFD Analysis of Fuel Distribution in Concentric Swirling Flows in a Reverse Flow Gas Turbine Combustor
Authors: Reddy K. Sudhakar , Reddy D. N. , Vara Prasad C. M.
Published: September 2008

This paper presents the results of numerical investigations of a turbulent, swirling and recirculating flow without combustion inside a reverse flow gas turbine combustor. In order to establish the characteristics of fuel distribution patterns of the fuel spray injected into swirling flows, flow fields are analyzed inside the swirl combustor for varying amount of swirl strength using a commercial CFD code fluent 6.1.22. Three Dimensional computations are performed to study the influence of the various parameters like injection pressure, flow Reynolds number and Swirl Strength on the fuel distribution patterns. The model predictions are compared against the experimental results, and its applicability over a wide range of flow conditions was investigated. It was observed from the CFD analysis, that the fuel decay along the axis is faster with low injection pressures compared to higher injection pressures. With higher Reynolds numbers the fuel patterns are spreading longer in the axial direction. The higher momentum of the air impedes the radial mixing and increases the constraint on the jet spread. The results reveal that an increase in swirl enhances the mixing rate of the fuel and air and causes recirculation to be more pronounced and to occur away form the fuel injector. The CFD predictions are compared with the experimental data from the phototransistor probe measurements, and good agreement has been achieved.
Characteristics of Combustion Processes in a Stagnation Point Reverse Flow Combustor
Authors: Bobba M. K. , Gopalakrishnan P. , Seitzman J. M. , Zinn B. T.
Published: September 2008

The performance of dry, low NOx gas turbines, which employ lean premixed (or partially premixed) combustors, is often limited by static and dynamic combustor stability, power density limitations and expensive premixing hardware. To overcome these issues, a novel design, referred to as the Stagnation Point Reverse Flow (SPRF) combustor, has recently been developed. Various optical diagnostic techniques are employed here to elucidate the combustion processes in this novel combustor. These include simultaneous planar laser-induced fluorescence (PLIF) imaging of OH radicals and chemiluminescence imaging, and separate experiments with particle image velocimetry and elastic laser sheet scattering from liquid particles seeded into the fuel. The SPRF combustor achieves internal exhaust gas recirculation and efficient mixing, which eliminates local peaks in temperature. This results in low NOx emissions, limited by flame zone (prompt) production, for both premixed and non-premixed modes of operation. The flame is anchored in a region of reduced velocity and high turbulent intensities, which promotes mixing of hot products into the reactants, thus enabling stable operation of the combustor even at very lean equivalence ratios. Also, the flame structure and flow characteristics were found to remain invariant at high loadings, i.e., mass flow rates. Combustion in the non-premixed mode of operation is found to be similar to the premixed case, with the OH PLIF measurements indicating that nonpremixed flame burns at an equivalence ratio that is close to the overall combustor equivalence ratio. Similarities in emission levels between premixed and non-premixed modes are thus attributable to efficient fuel-air mixing in the nonpremixed mode, and entrainment of hot products into the reactant stream before burning occurs.
Engine Deterioration When Exposed to Particulate Flows
Authors: Tabakoff Widen
Published: September 2008

The design and development of high performance turbomachinery operating in a particulate flow environment requires a thorough knowledge of the fundamental phenomena associated with solid particulate flows. Because of the serious consequences of turbomachinery erosion on performance and life, it is important to have reliable methods for predicting their erosion when solid particles are ingested with incoming flow. Many of these studies, which are essential to predicting blade surface erosion intensity and patterns, have been conducted at the University of Cincinnati’s Turbomachinery Erosion Laboratory over the past thirty years. A brief review of the experimental work will be presented for the following materials and coatings: Ti6-4 cemented tungsten carbide (85WC, 6TiC, 9 Co) and MAR-M-246. Coatings include TiC, TiN, Al2O3, and platinum aluminide (RT-22B). While operating aircraft engines or stationary turbines in dust laden or particulate environments the blades and vanes are prone to deterioration by solid particle erosion, which causes decreased engine performance and higher specific fuel consumption. The coatings presented in this paper are shown to prevent such deterioration and thus prolong engine operating life.
Measurements Inside a Bluff-Body Stabilized Gas Turbine Combustor for Application of Pressurized Biomass Derived Low Calorific Value Fuel Gas and Comparison of the Results: Part 2
Authors: van der Wel Marco , de Jong Wiebren , Spliethoff Hartmut
Published: September 2008

In our previous paper [Van der Wel (2005)] the main results about combustion efficiency and emissions have been presented of experiments with a medium size (TUD) combustor of 1.5 MWth operated on low calorific value (LCV) fuel gas with heating values (HHV) ranging from 1.88 to 4.64 MJ/m3n (50 to 120 Btu/scf). In the current paper the experiments are presented where the amount of primary and secondary air are varied in order to examine the effects of stoichiometry on the combustors performance and these results are compared with a previously tested downscaled typhoon combustor from ALSTOM. Also, results are presented with respect to traversing measurements behind the primary zone of the TUD combustor. It was found that the NH3 to NO conversion decreases at increasing pressure and that higher concentrations of methane in the fuel result in higher ammonia to NO conversions. Also it was observed that the swirling typhoon combustor seemed to have less problems achieving lower ammonia conversions than the bluff body stabilized TUD combustor.
A Theoretical Solid Oxide Fuel Cell Model for System Controls and Stability Design
Authors: Kopasakis George , Brinson Thomas , Credle Sydni , Xu Ming
Published: September 2008

As the aviation industry moves towards higher efficiency electrical power generation, all electric aircraft, or zero emissions and more quiet aircraft, fuel cells are sought as the technology that can deliver on these high expectations. The Hybrid Solid Oxide Fuel Cell system combines the fuel cell with a microturbine to obtain up to 70% cycle efficiency, and then distributes the electrical power to the loads via a power distribution system. The challenge is to understand the dynamics of this complex multi-discipline system, and design distributed controls that take the system through its operating conditions in a stable and safe manner while maintaining the system performance. This particular system is a power generation and distribution system and the fuel cell and microturbine model fidelity should be compatible with the dynamics of the power distribution system in order to allow proper stability and distributed controls design. A novel modeling approach is proposed for the fuel cell that will allow the fuel cell and the power system to be integrated and designed for stability, distributed controls, and other interface specifications. This investigation shows that for the fuel cell, the voltage characteristic should be modeled, but in addition, conservation equation dynamics, ion diffusion, charge transfer kinetics, and the electron flow inherent impedance should also be included.
Preliminary Study of a Low Power Plasma Radical Jet Generator for Combustion Systems
Authors: Choi Woong-Sik , Kim Jaecheol , Neumeier Yedidia , Jagoda Jeff
Published: September 2008

A novel radical jet generator (RJG) was developed, whose purpose it is to supply concentrated, relatively low temperature radicals that penetrate into a flammable stream of reactants and trigger or modify a combustion process. The RJG is driven by a plasma whose power is only a fraction of a percent of the total power released in the combustor. In this approach, the plasma induces an incomplete combustion process in a small duct carrying a rich mixture of fuel and air. Results obtained using the developed RJG show that a jet, which consists of partially burnt reactants, some products and is, apparently, rich in radicals produced by the incomplete combustion process triggers extremely steady combustion in a fast moving combustible mixture whose flow rate far exceeds that of the RJG. Importantly, the results show that the jet, rich with radicals, that emerges from the RJG cavity at a temperature well below traditional ignition can ignite a fast moving stream of combustible mixture. Moreover, when injected normal to the main flow, this jet ignites the main stream at a location relatively far from the entrance point of the jet. This makes it possible to keep the combustion process away from solid walls while at the same time eliminating the need for solid flame holders. This in turn, provides an augmenter with reduced I.R signature. Finally, the results show a drastic effect of the RJG upon the flame dynamics in general and combustion instabilities in particular. Flames which displayed large, periodic pressure oscillations became completely stable when the plasma in the RJG was turned on. This suggests a novel use of the RJG to inhibit instabilities in combustors.
Evolution of Surface Deposits on a High Pressure Turbine Blade: Part II — Convective Heat Transfer
Authors: Bons Jeffrey P. , Wammack James E. , Crosby Jared , Fletcher Daniel , Fletcher Thomas H.
Published: September 2008

A TBC-coated turbine blade coupon was exposed to successive deposition in an accelerated deposition facility simulating flow conditions at the inlet to a first stage high pressure turbine (T = 1150°C, M = 0.31). The combustor exit flow was seeded with dust particulate that would typically be ingested by a large utility power plant. The turbine coupon was subjected to four successive 2 hour deposition tests. The particulate loading was scaled to simulate 0.02 ppmw (parts per million weight) of particulate over three months of continuous gas turbine operation for each 2 hour laboratory simulation (for a cumulative one year of operation). Three-dimensional maps of the deposit-roughened surfaces were created between each test, representing a total of four measurements evenly spaced through the lifecycle of a turbine blade surface. From these measurements, scaled models were produced for testing in a low-speed wind tunnel with a turbulent, zero pressure gradient boundary layer at Re = 750,000. The average surface heat transfer coefficient was measured using a transient surface temperature measurement technique. Stanton number increases initially with deposition but then levels off as the surface becomes less peaked. Subsequent deposition exposure then produces a second increase in St. Surface maps of St highlight the local influence of deposit peaks with regard to heat transfer.
Embedded Thin-Film Sensor for Crack Detection and Monitoring in Fracture Critical Turbine Engine Components
Authors: Hudak S. J. , Lanning B. R. , Light G. M. , Chan K. S. , Moryl J. A. , Pruitt J. R.
Published: September 2008

The development and implementation of an integrated health management system has the potential to significantly enhance the reliability and readiness of high-value assets, while concurrently decreasing sustainment costs. A key aspect of this approach is on-board sensing to provide continual feedback on the evolving damage state at the material and component level. This paper summarizes the development and status of an embedded, thin-film, wireless, sensor for detecting and monitoring material damage state (i.e., cracking) in critical turbine engine components at elevated temperature. The potential benefits of on-board detection and monitoring of defects, as compared to periodic depot inspections, were previously assessed using probabilistic simulations. These results provided target sensitivities for the development of the thin-film sensor. The status of the sensor system is summarized including its ability to generate elastic waves and detect/monitor fatigue cracks in engineering materials at temperatures to 500°F (260°C). Crack detection sensitivities with and without load application are compared, as well as those for wired versus wireless signal transmission.
Demonstration of a Hybrid Power and Refrigeration Ammonia-Water Cycle
Authors: Takeshita Keisuke , Amano Yoshiharu , Hashizume Takumi
Published: September 2008

This paper reports on the demonstration of a hybrid power generation and refrigeration cycle in a turbine system which employs ammonia-water mixture as the working fluid. The hybrid cycle is the one in which the ammonia-water mixture turbine cycle and the ammonia absorption refrigerator are combined. To demonstrate the performance enhancement of the hybrid cycle, its steady state characteristics were experimentally investigated. The increase of the coefficient of performance (COP) and the performance improvement of the cycle are mainly due to a reduction of the heat of rectification at the ammonia absorption refrigerator. Therefore, the authors especially focused on the COP, the heat source steam consumption rate, and the heat of rectification when the ammonia mass fraction at the rectifier inlet increased. Results showed the COP and heat source steam consumption rate improved about 20% in hybrid operation, compared with normal operation which drives the ammonia absorption refrigerator and the ammonia-water mixture turbine cycle separately.
Stagnation-Point Reverse-Flow Combustor Performance With Liquid Fuel Injection
Authors: Crane John , Neumeier Yedidia , Jagoda Jeff , Seitzman Jerry , Zinn Ben T.
Published: September 2008

This paper describes an investigation of the performance of the recently developed ultra low emissions, Stagnation-Point Reverse-Flow (SPRF) Combustor when burning liquid fuels (Jet-A and heptane). This study has been undertaken because of the need to burn liquid fuels with low emissions in gas turbines that are used, for example, in aircraft engines, land-based power generation, and marine applications. In contrast with state of the art combustors, in which the reactants and products enter and leave the combustor through opposite ends of the combustor, the reactants and products enter and leave the SPRF combustor through the same plane opposite a closed end. The design of the SPRF combustor allows mixing of reactants with hot combustion products and radicals within the combustor, prior to combustion. Thus, no external premixing of fuel and air is required. Additionally, since the air and fuel enter opposite the closed end of the combustor, they must stagnate near the closed end, thus establishing a region of low velocity just upstream of the closed end that helps stabilize the combustion process. This apparently produces a low temperature, stable, distributed reaction zone. Previous studies with the SPRF combustor investigated its performance while burning natural gas. This paper presents the results of SPRF combustor studies using liquid fuels, both heptane and Jet-A. The performance of the combustor was investigated using an airblast fuel injector, which is suitable for the low fuel flow rates used in laboratory experiments. To reduce pressure losses across the injector, a diffuser was incorporated into the airblast injector. It was found that stable combustor operation was achieved burning Jet-A with emissions of less than 1 ppm NOx and 5 ppm CO, pressure losses less than 5 percent, and a power density on the order of 10 MW/m3 in atmospheric pressure. This power density would linearly scale to 300 MW/m3 in a combustor at a pressure of 30 atmospheres.
The Cummins KTA38GC for Gas Compression: An International Effort
Authors: Kakoczki Richard J. , Brown Jacob A. , Williams Paul , King Tim S.
Published: September 2008

Cummins recognized a sales growth opportunity in the gas compression market place in 2001. Natural Gas Engine Engineering then started developing the smallest displacement engines in the product line first. These are engines in the 37 to 225 kilowatt range and were introduced successfully into the market place over the last four years. Two years ago, the next step up in horsepower, the 19 liter, inline six cylinder KTA 19GC engine at 313 kilowatt was released for production. Marketing then determined that the 450 to 670 kilowatt market was underserved and decided to develop the V12 version of the KTA 19GC, the KTA38GC, to fill this need. It was recognized early in the program that the engine needed to be simple and robust because engine uptime is at a premium in the higher horsepower segments of this market. Thus, simple, robust and proven components were chosen for the engine. The project team started with the KTA38 diesel engine. The team then added the KTA19GC power cylinder components. Next, an ignition system, air/ratio control system and an electronic integrated throttle/governor system were added. These were all “off the shelf” components. When adding these components, an emphasis was placed on simplicity, user friendliness, and self diagnostics with or without a laptop computer. The engine development team was located in Columbus, IN and Clovis, NM, the design team was located in Daventry, England (the final manufacturing location) and Columbus, IN and the analysis team in Pune, India. In addition, our lead customer and distributor, both located in Texas, were closely involved in the project and added considerably to its success. The efforts of these five locations were coordinated in Columbus, IN.