bluuebunny/crossref_metadata_2025 huggingface dataset:
Design Improvements Suggested by Computational Flow and Thermal Analyses for the Cooling of Marine Gas Turbine Enclosures
Authors: Graf Edward , Luce Timothy , Willett Fred
Published: November 2008

Land based and marine gas turbine generators as well as mechanical drive units are often surrounded by an enclosure. A housing insures that the environmental noise regulations are met. In a marine environment, it also protects the crew from potential physical harm associated with the drive train: burns from high surface temperatures and bodily trauma from high speed rotating elements. The large amount of heat given off by the gas turbine is removed from the enclosure by a continuous stream of injected cooling air. Cooling air flow may be provided by using a motor-driven cooling fan or by the use of an eductor utilizing the aerodynamic effect of the gas turbine exhaust flow. Past design of enclosure cooling was based on well utilized rules of thumb, such as the number of compartment air changes per minute. The dearth of detailed enclosure design technical data combined with the large number of gas turbine design and packaging contracts for which our company is presently the prime contractor, has led us to pursue a multi-level systematic investigation of these flows. This paper reports the first phase of the detailed numerical simulations of various typical enclosure geometries and cooling schemes. The RANS computational fluid dynamic work included ‘cold flow’ screening analyses to optimize the flow patterns inside the enclosure. Then the optimized enclosure was studied as a complex thermal problem that included compressibility, convective and radiative heat transfer inside the enclosure and conduction through the enclosure walls to the outside. The results of this study allow us to insure that outside wall temperatures are maintained at a safe level and that local circumferential temperature variations about the gas turbine drive shaft will not cause rotor distortion.
Identification of Frequency Dependent Parameters in a Flexible Rotor System
Authors: Wang Qingyu , Maslen Eric H.
Published: November 2008

In a rotor-bearing system, there are usually some under- or un-modelled dynamic components which are considered frequency dependent, such as foundations, bearings, and seals. This paper presents a method to identify the dynamic behavior of these components using an otherwise accurate engineering model of the system in combination with available measurements of system frequency response functions. The approach permits treatment of flexible rotors and allows that the system test excitations and measurement sensors are not collocated. Because all engineering models contain some residual error and all measurements incorporate an element of noise or uncertainty, the quality of the identified parameters must be estimated. This paper introduces application of μ-analysis to solve this problem, resulting in acceptable solution time and hard guarantees of solution reliability. Two illustrative examples are provided, showing that the presented approach is an efficient method to identify and bound these parameters.
Characteristics of a Magnetically Levitated Flexible Rotor When in Contact With One or More Auxiliary Bearings
Authors: Keogh Patrick S. , Seow Yuan Hui , Cole Matthew O. T.
Published: November 2008

The case for installing auxiliary bearings in parallel with magnetic bearings is often made with regard to touchdown, when a complete system failure occurs. The work reported in this paper focuses on the case when rotor/auxiliary bearing contact occurs, but the magnetic bearings retain their functionality. One may envisage future transportation applications in which this situation would occur, for example, during high acceleration levels induced by turbulence. An understanding of the rotor dynamic response during contact conditions could enable auxiliary bearing life expectancy to be extended using appropriate control action from the still functional magnetic bearings. To achieve this, a system model is required for control strategy design purposes. This paper considers the development of a non-linear system model for predicting the contact dynamics in a flexible rotor/magnetic/auxiliary bearing system. Previous experimental work produced similar contact dynamic response characteristics; whether due to unbalance or circular forcing through a magnetic bearing. Initial model-based predictions of these tests did not provide sufficiently accurate reproduction of the measured orbits, particularly in the presence of auxiliary bearing misalignment and multi-plane rotor contact. Parameter variations are thus undertaken to investigate the reasons for these differences. Contrary to expectations, uncertainty in the magnetic bearing characteristics during contact conditions appears to offer an explanation.
Lean Premixed Combustion of Carbon-Monoxide-Hydrogen-Methane Fuel Mixtures Using Porous Inert Media
Authors: Alavandi S. K. , Agrawal A. K.
Published: November 2008

Lean premixed combustion of carbon monoxide (CO), hydrogen (H2), and methane (CH4) fuel mixtures with air was investigated experimentally. Combustion at atmospheric pressure was stabilized within porous inert medium made of silicon-carbide coated carbon foam with 4 pores per centimeter. CH4 in the fuel was varied from 100% to 0% (by volume), with the remaining fuel containing equal amounts of CO and H2. Experiments at a fixed air flow rate were conducted by varying the adiabatic flame temperature and fuel composition. Profile of CO and NOx emissions in the axial and transverse directions were taken to identify the post-combustion zone and uniformity of combustion. At a given flame temperature, fuels with CO/H2 produced lower CO and NOx emissions compared to those for CH4. The temperature at the lean blow off limit was significantly lower (compared to CH4) if the fuel contained CO and H2, each greater than 35% by volume.
Liquid Fuel Combustion Using Heat Re-Circulation Through Annular Porous Media
Authors: Newburn E. Ryan , Agrawal Ajay K.
Published: November 2008

A counter-flow annular heat recirculating burner was designed for lean pre-vaporized, premixed combustion. Prior to entering the combustor reactants are passed through a porous media-filled preheating annulus surrounding the combustor. Kerosene is dripped by gravity onto the porous media and vaporized by the heat conducted through the combustor wall. Experiments were conducted to evaluate heat transfer and combustion performance at various equivalence ratios, heat release rates, and inlet air temperatures. Results show low CO emissions over a range of equivalence ratios. NOx emissions were high at high heat release rates, indicating inadequate pre-vaporization and premixing of fuel with air. Heat recirculation and heat loss characteristics are presented at various operating conditions.
An Experimental Investigation of the Effect of an Active Magnetic Damper on Reducing Subsynchronous Vibrations in Rotating Machinery
Authors: Kasarda M. , Mendoza H. , Kirk R. G. , Wicks A.
Published: November 2008

Presented here are results from an experimental study investigating the reduction of subsynchronous vibrations in rotating machinery by adding a single active magnetic bearing actuator to a flexible rotor-bearing system. In this scenario, the Active Magnetic Bearing (AMB) actuator is used as an Active Magnetic Damper (AMD) and is not utilized for rotor support. The AMD can be used to increase stability margins by adding more damping in strategic locations on a rotor allowing for increased tolerance to instability mechanisms and enabling increased performance and efficiency in turbomachinery. Results from an experimental 3-mass test rig supported in fluid-film bushings are presented here. The study shows that subsynchronous vibrations are reducible with an AMD located near the mid-span of the rotor and up to a 98% reduction in the amplitude of subsynchronous vibrations is demonstrated. The overall results from this work demonstrate that reduction in subsynchronous response is feasible and that full rotor dynamic analysis and design is critical for the successful application of this approach as critical speed locations can be altered.
Experimental and CFD Study of Exhaust Ejectors With Bent Mixing Tubes
Authors: Maqsood Asim , Birk A. M.
Published: November 2008

This paper presents preliminary results of a study performed on bent ejectors having applications in the aerospace industry. The ejectors consisted of a simple round primary nozzle and a bent mixing tube. The effects of bend angles on pumping characteristics were studied. A cold flow wind tunnel was used to provide the primary flow of air at ambient temperature at a maximum mass flow rate of 1.6 kg/sec. Velocity and pressure measurements were taken upstream of the nozzle and at the exit of mixing tube. The study was done with and without swirl in the primary flow. It was observed that swirl in primary flow improved the pumping performance of the bent. CFD analysis was performed using a commercial CFD code and the results were compared with the experiments. It was observed that the bend in the ejector had a significant effect on the pumping performance. The entrainment ratio decreased and then increased with the degree of bend. An ejector with a 45° bend in the geometry had 28% less entrainment ratio than a same size straight ejector. It was found that swirl in the primary flow improves the performance of the bent ejector. A maximum 17% increase in the entrainment ratio was observed with swirl in the case of a 67.5° bent ejector. In both 22.5° and 67.5° bent ejectors the pressure rise was slightly improved by 20° swirl in the primary flow. CFD was generally successful in predicting the trends as observed in the experiment results. CFD predictions of pumping were within ± 7% of the experiments.
Passive Control of Dynamic Pressures in a Dry, Low NOx Combustion System Using Fuel Gas Circuit Impedance Optimization
Authors: Goldmeer Jeffrey , Sanderson Simon , Myers Geoff , Stewart Jesse , D’Ercole Michele
Published: November 2008

Dry, Low NOx (DLN) gas turbine combustion systems that use the lean, premixed combustion technique for emissions control are susceptible to dynamic pressure oscillations. During the initial full-load prototype testing of the MS5002E, excessive dynamic pressures were encountered when attempting fully premixed combustor operation, preventing the gas turbine from meeting a 15 ppm NOx emissions target. A series of experiments were performed to examine potential acoustic differences between the original laboratory fuel injection system and the prototype hardware used in the field test. The experimental results were used to validate an analytical model that was used to optimize the fuel circuit geometry for dynamics reduction. The resulting revised design demonstrated a ten-fold reduction in dynamic pressure amplitudes. As a result, the system was able to operate over the premixed mode operating range and provides the desired NOx levels with acceptable dynamic pressures and operability.
Generation of Physically Based Analysis Factors to Improve Synthesis Models of Jet Engines
Authors: Canalias Xavier , Ko¨pf Frank , Sahm Peter
Published: November 2008

The ANalysis by SYNthesis (ANSYN) technique is a standard performance analysis method widely used in industry. It is currently used to evaluate engine performance from tests and to derive correcting factors (i.e. ANSYN factors) that modify certain parameters of the components’ characteristics in order to allow the reproduction of real engine behaviour by means of a synthesis calculation. Once they have been determined, these ANSYN factors can be implemented into the common synthesis tools to accurately predict the behaviour of the engine in non-tested conditions. The definition of how the engine synthesis will be modified to reproduce the measured cycle is called the “matching scheme”. It is the choice of the parameters that will not be modified, the ones that will be scaled and the ones that will be used as a reference. A good choice of the ANSYN factors and of the magnitudes used to tabulate them will make possible their physical interpretation and analysis, which can lead to the identification of inaccurate assumptions and phenomena that had not been accurately taken into account in the previous performance models. This understanding of their origin is a prerequisite for any improvement of the models and could lead to an enhanced process for the development of non-dimensional jet engine characteristics. In this study, a matching scheme for the RR-BR710 engine has been set up, implemented and applied. This method is an alternative to some of the currently used in the Rolls-Royce Deutschland ANSYN tools. The main goal of the present work has been the definition of a matching scheme that leads to the obtention of physically meaningful ANSYN factors. This allows their subsequent analysis and interpretation and can provide useful information on engine component operation and on the phenomena responsible for the observed deviations from predicted engine behaviour.
Recent Advancements in Aircraft Engine Health Management (EHM) Technologies and Recommendations for the Next Step
Authors: Jaw Link C.
Published: November 2008

This paper summarizes the findings of a survey of recent advancements in aircraft Engine Health Management (EHM) technologies. The survey has been motivated by the desire to understand new technologies and application trends in EHM, especially in the last few years, when EHM related research and development (R&D) has increased significantly. Although the R&D primarily covers four areas: system partition, system architecture, EHM functionalities, and algorithmic approaches, the latter two have represented the majority of the published work; hence they are the focus of this paper. While recent advancements are providing building blocks for continued maturation of EHM technologies in the future, the survey has revealed a fundamental inconsistency in defining and representing EHM problems. This inconsistency creates barriers in exchanging EHM-related ideas and results; it also undermines the effectiveness of multi-organizational cooperation. Hence another purpose of this paper is to recommend a consistent approach to treating the problems that EHM is trying to address. Finally, the survey recognizes the need for a unified framework for comparing the performance of various algorithms for solving various types of EHM problems. The author hence suggests that an industry review, modeled after the industry review for multi-variable engine controls in late 1970s, be held. This EHM Industry Review is aimed at defining a series of theme problems for EHM and invite experts in the industry and academia to apply their expertise to solving these problems. The Industry Review will be concluded with a conference to present the results and sharing experience. Traditionally, engine condition monitoring has led the way for condition-based maintenance and health management technologies because of the safety and dispatch requirements of aircraft engines. Hence, the author believes that the results, conclusions, and recommendations presented in this paper can be generalized to all types of equipment, systems, and vehicles, i.e., to EHM (Equipment Health Management), IVHM (Integrated Vehicle Health Management) and ISHM (Integrated System Health Management).
Performance Demonstration of the Full Size Multi Cluster Combustor for DME Under Real Engine Conditions
Authors: Saitou Takeo , Miura Keisuke , Inoue Hiroshi , Kobayashi Nariyoshi , Suzuki Shin-Ichi
Published: November 2008

DME (dimethyl ether: CH3OCH3) is currently attracting worldwide attention because it is a clean fuel which can be synthesized from various materials such as natural gas, coal, biomass, etc. But DME has the possibility of spontaneous ignition in gas turbine use because of its low auto-ignition temperature. To avoid spontaneous ignition or flash-back, a coaxial jet cluster nozzle burner configuration was proposed previously which can mix air and fuel effectively within a short time. In this work, demonstration tests were carried out for the developed full size combustor, called the multi cluster combustor for 25MW class gas turbine. The combustor, which is composed of cluster nozzle burners, was tested under practical gas turbine operating conditions from start up to base load using a full pressure combustion test rig. In the tests, LNG was also used as the test fuel because it is expected to be used as a back up fuel when DME is first introduced for wide commercial use. Test results showed good combustion performances for the developed multi cluster combustor. NOx emission level was below 24ppmv (15%O2) and combustion efficiency was over 99.9% for the base load condition of the 25MW class gas turbine when fueled with DME or LNG. Dynamic pressure level and liner metal temperature were low. No flash-back phenomena occurred throughout the demonstration tests.
Experimental and Numerical Research on Application of MGC Material for High Temperature Turbine Nozzles
Authors: Fujimoto Shu , Okita Yoji
Published: November 2008

In recent years, a material called MGC (Melt-Growth Composite) has been developed. This material has innovative characteristics such that it can maintain its high strength for up to 1700°C, with an excellent oxidization resistance performance. These characteristics are quite ideal for the gas turbine application. This paper deals with numerical and experimental study on the performance of MGC turbine nozzles conducted in 2003. Firstly the bow stacked solid nozzle has been designed by using numerical analyses under the gas flow condition at 1700°C that is the final target inlet gas temperature of the MGC turbine project (2001–2005). Secondly three MGC nozzles have been manufactured on trial and one of them has been tested in steady hot gas flow at 1500°C that is the target inlet gas temperature in 2003, temperature and stress fields have been evaluated numerically and the design of this MGC turbine nozzle has been validated for the steady gas flow at 1500°C. Furthermore another has been tested under a TRIP condition (TRIP: Emergency engine stop by fuel cutoff) from 1500°C level, transient temperature fields on the nozzle surface have been obtained and temperature and stress fields have been evaluated numerically. This stress analysis shows that quite large stress was generated in the nozzle in the TRIP test and therefore in future newly re-designed shape of MGC turbine nozzles is required.
The Entropy and Exergy Analyses of Wet Compression Gas Turbine
Authors: Shao Yan , Zheng Qun
Published: November 2008

Wet compression is an effective way of gas turbine power augmentation, but at the same time it causes some new thermodynamic problems. How to evaluate the thermodynamic parameters and how to improve the wet compression process and wet compression gas turbine cycle are key to the actual applications of the technique in industries. From the entropy and exergy views, wet compression processes are analyzed in this paper. By calculating the entropy and exergy variations with the established thermodynamic models of wet compression process, we presented some interesting results that could used to reduce the increase of entropy and the loss of exergy in the wet compression process. On the basis of thermodynamic analysis of wet compression, the entropy and exergy effects at different evaporative rates, different pressure ratios etc. are further investigated in this paper.
Experimental Study of an Exhaust Ejector With Entraining Diffuser
Authors: Chen Qi , Birk A. M.
Published: November 2008

Air-air ejectors are used in a wide range of industrial applications. In gas turbine installations, ejectors are typically used for entraining ventilation air or cooling of exhaust ducting. In some gas turbine applications, the exhaust system must be cooled to limit temperatures inside the structure or to manage heat signatures. The ducts are usually cooled by ejectors with film or effusion cooled diffusers. Entraining diffusers typically have poor pressure recovery and as a result, the ejector performance is affected. This paper presents experimental results on the performance of an air-air ejector with an entraining diffuser. The effects of inlet swirl, and primary nozzle area ratio on the diffuser pressure recovery and ejector pumping were studied. The ejector experiments were carried out on a cold flow wind tunnel that can provide primary air flow rates up to 2.2 kg/s at ambient temperature. Velocity, pressure and temperature measurements were taken in the annulus upstream of the primary nozzle, at the nozzle exit, at the diffuser inlet, on the diffuser walls, and at the diffuser exit. The results show that swirl strongly improves flow non-uniformity at the diffuser exit. The peak pumping performance and the strongest diffuser gap flows was observed with 20° of swirl in the primary nozzle flow. At the no swirl condition, the nozzle area ratio slightly affected the overall entrainment ratio. However, the large nozzle area ratio resulted in the best pumping when swirl was applied.
Computational Comparison of an Air-Air Ejector System Utilizing a Primary S-Bend Transition Duct Employing the Realizable k-ε Turbulence Model
Authors: Mateer J. C. , Birk A. M. , Poirier D.
Published: November 2008

A computational study of an air-air ejector system, utilizing a primary S-bend transition duct, was compared with experimental results. Two primary ducts, differing in offset, consisted of an annular-to-circular-to-oblong transition which incorporated a total area increase of 62.4% with the duct performing 16% diffusion. The ducts were analyzed both alone and in ejector configuration under varying degrees of inlet swirl. The ejector geometry consisted of the duct with a downstream mixing tube. Several mixing tubes, of oblong cross sectional shape, differing in both length and area, were tested in various parametric configurations. Ejector performance was established on the basis of pumping capability, duct back pressure, and outlet effective area. Experimental work commenced on a cold flow test rig, with duct inlet conditions being measured with four 3-hole pitot probes. The duct outlet profiles were measured using a 7-hole probe which traversed the entire exit area. Three conditions of inlet swirl were analyzed: 0°, 20° and 40°. Experimental results showed an increase in pumping performance with increased inlet swirl, mixing tube length, area ratio and standoff. An optimum standoff value of 0.25Dh2 was observed. CFD simulations were based on experimental mass flow inlet conditions utilizing the realizable k-ε turbulence model. CFD results showed that the realizable k-ε turbulence model was quite capable of modeling the complex flow for the associated geometry, and correctly predicted flow features as well as performance trends for all geometrical configurations tested. However, the CFD was unable to properly predict the duct inlet static pressure leading to erroneous back pressure results.
Unsteady Aerodynamic Characteristics of Oscillating Cascade With Separation Bubble in High Subsonic Flow
Authors: Watanabe Toshinori , Aotsuka Mizuho
Published: November 2008

Unsteady aerodynamic characteristics of an oscillating cascade composed of DCA (Double Circular Arc airfoil) blades were studied both experimentally and numerically. The test cascade was operated in high subsonic flow fields with incidence angles up to 5 degrees. Above 3 degrees of the incidence, a separation bubble was produced at the leading edge. The principal concern of the present study was placed on the influence of the separated region on the vibration instability of the cascade blades. The experiment was conducted in a linear cascade wind tunnel in which seven DCA blades were equipped. The central one could be oscillated in a pitching mode. The influence coefficient method was adopted for the measurement, where the unsteady aerodynamic moments were measured on the central blade and neighboring ones. For the numerical analysis, a quasi 3-D N-S code with k–ε turbulence model was developed. The experimental and numerical results complemented each other to obtain detailed understanding of the unsteady aerodynamic behavior of the cascade. It was found that the separation bubble at the leading edge governed the vibration characteristics of blades through the oscillation of the separation bubble itself on the blade surfaces. From the results of parametric studies, the phase shift of the oscillation of the separation bubble was found to be a key factor for determining the unsteady aerodynamic characteristics of the oscillating blades.
Evaluation of Interstage Water Injection Effect on Compressor and Engine Performance
Authors: Roumeliotis I. , Mathioudakis K.
Published: November 2008

The present paper examines the effect of water injection at the compressor inlet or between stages, on its operation. A wet compression model coupled with an engine performance model is used. The wet compression model produces the compressor performance map when water is present and consists of a one dimensional stage stacking model, coupled with a droplet evaporation model. The effect of water injection on overall performance and individual stage operation is examined. The map generation procedure is embedded in an engine performance model and a study of water injection effect on overall engine performance is undertaken. The possibility to evaluate the effect on various parameters such as power, thermal efficiency, surge margin, as well as the progression of droplets through the stages is demonstrated. The results indicate that water injection causes significant stage rematching, leading the compressor towards stall and that the performance enhancement is greater as the injection point moves towards compressor inlet.
A New Gas Turbine Enclosure Ventilation Design Criterion
Authors: Santon Roger C. , Ivings Matthew J. , Pritchard David K.
Published: November 2008

Dilution ventilation is a widely used means of protection against the risk of explosion within gas turbine acoustic enclosures arising from the leakage and accumulation of flammable gas and its ignition from the turbine. In ASME 98GT-215 a safety criterion was proposed for the design of ventilation by defining the allowable size of flammable gas cloud as a proportion of the enclosure volume. This criterion was theoretically based, with a significant safety factor. Whilst generally viable, it was found to be difficult to achieve in some cases. A research project, described in ASME GT-2002-30469, was launched to define a criterion more accurately and with known conservatism based on a detailed programme of experimental explosions and Computational Fluid Dynamics (CFD) modelling. The $600k project was largely financed by the gas turbine industry, including suppliers and users, and by CFD contractors. The paper describes the project aims, its scope of work, and includes the main results, the new criterion and conclusions.
Results of the First Application of the SwirlFlash™ Wet Compression System on a 150MW Heavy-Duty Gas Turbine
Authors: Deneve Michae¨l , De Tandt Bernard , Cornelis Niko , Bultereys Christiaan , Gijbels Sigrid
Published: November 2008

In general, the compressor takes approximately 2/3 of the expansion work delivered by the turbine. Any reduction of compressor work would improve the power output of the gas turbine. One way of doing this is to inject an amount of water in the inlet air. The amount of water that can be absorbed by the air is limited due to the relative humidity. The SwirlFlash™ system of Alpha Power Systems is an over-spray injection system, which delivers an over-saturated mixture to the compressor. Adiabatic compression will heat up the mixture and the water will evaporate inside the compressor. The heat required for evaporation will cool down the air, which results in a lower compressor discharge temperature. This lower discharge temperature leads to a reduction of compressor work. The lower compressor work and the increased fuel flow will raise the gas turbine power output. This paper is the result of the evaluation of the SwirlFlash™ system installed at the Herdersbrug power plant of Electrabel Belgium. The wet compression system was commissioned in 2003. In this paper, the principle of the wet compression system and the Herdersbrug installation are described as well as the influence of this system on several parameters such as the compressor discharge temperature, the gas flow, the steam production, the power gain and the heat rate. The influence on the emissions, humming and the interference with anti-icing are also discussed. Finally, the material related aspects and the vibration behavior are treated.
Rotordynamic Coefficients of Labseals for Turbines: Comparing CFD Results With Experimental Data on a Comb-Grooved Labyrinth
Authors: Schettel Joachim , Deckner Martin , Kwanka Klaus , Lu¨neburg Bernd , Nordmann Rainer
Published: November 2008

The main goal of this paper is to improve identification methods for rotordynamic coefficients of labseals for turbines. This aim was achieved in joint effort of the Technische Universita¨t Mu¨nchen, working on experimental identification methods for rotordynamic coefficients, the University of Technology, Darmstadt, working on prediction methods, and Siemens AG, realizing the results. The paper focuses on a short comb-grooved labyrinth seal. Short labseals, amongst others the above mentioned comb-grooved labyrinth, were examined. by means of a very accurately measuring test rig. The rotor was brought into statically eccentric positions relative to the stator, in order to measure the circumferential pressure distribution as a function of pressure, rotating speed and entrance swirl. The data collected were used to validate results obtained with a numerical method. The theoretical approach is based on a commercial CFD tool, which solves the Navier Stokes equations using numerical methods. As a result, a detailed model of the flow within the test rig is produced. The efforts of computation here are greater than when compared with the likewise wide-spread Bulk flow models, however improved accuracy and flexibility is expected. As the validation of the model is successful, it could then be used to gain further insight in the flow within the seal, and to understand the results better. This showed that rotordynamic coefficients of labseals gained from different test rigs are not necessarily comparable.
Experimental Characterization of a Remoting System for Dynamic Pressure Sensors
Authors: Ferrara Giovanni , Ferrari Lorenzo , Sonni Gabriele
Published: November 2008

Concerning measurements with dynamic pressure sensors, one of the most interesting aspects is the influence of a remoting system interposed between the sensor and the measurement point. This mounting system, once correctly characterized, allows one to use the same sensor for different measurement points, reducing the total number of sensors used. In addition, in all the applications involving high temperatures (e.g. combustion chamber), a remoting system allows the use of cheaper dynamic pressure sensors with lower operating temperature capability. A remoting system for dynamic pressure sensors made up by a remoting duct, between the sensor and the measurement point, followed by a damping duct has been characterized for different tube lengths. Tests were carried out with two kinds of sources: a diaphragm-less shock tube for the first set of tests and an acoustic speaker for the second. Results are here reported and commented.
Development of Controls for Dynamic Operation of Carbonate Fuel Cell-Gas Turbine Hybrid Systems
Authors: Roberts Rory A. , Brouwer Jack , Liese Eric , Gemmen Randall S.
Published: November 2008

Hybrid fuel cell/gas turbine (FC/GT) systems have been shown through experiment and simulation to be highly efficient technologies with low emissions. Maintaining efficient, low emission, and safe operation, whether during disturbances or regular operational transients, is a challenge to both understand and address. Some likely disturbances can arise from changes in ambient temperature, fuel flow variations induced by supply pressure disturbances, fuel composition variability, and power demand fluctuations. To gain insight into the dynamic operation of such cycles and address operating challenges, dynamic modeling tools have been developed at two different laboratories. In this paper these models are used to simulate the dynamic operation of an integrated MCFC/GT hybrid system and to subsequently develop and test control strategies for the hybrid power plant. Two control strategies are developed and tested for their ability to control the system during various perturbations. Predicted fuel cell operating temperature, fuel utilization, fuel cell and GT power, shaft speed, compressor mass flow and temperatures throughout the FC/GT system are presented for the controlled response to a fuel cell voltage increase in order to show the effect of a load decrease.
Impact of Ethane, Propane, and Diluent Content in Natural Gas on the Performance of a Commercial Microturbine Generator
Authors: Hack Richard L. , McDonell Vincent G.
Published: November 2008

The impact of fuel composition on performance of power generation devices is gaining interest as a desire to diversify fuel supplies increases. In the present study measurements of combustion performance were conducted on a commercial natural gas fired 60-kW gas turbine as a function of fuel composition. A statistically designed experiment was carried out and exhaust emissions were obtained for significant amounts of ethane and propane. In addition, a limited study of the effect of inerts was examined. The results show that emissions of NOx, CO, and NOx/NO are not well correlated with common descriptions of the fuel such as higher heating value or methane number. The results and trends indicate that the presence of higher hydrocarbons in the fuel leads to appreciably higher NOx emissions for both test devices operating under similar lean conditions, while having less impact on CO emissions.
Evaluation of Hybrid Fuel Cell Turbine System Startup With Compressor Bleed
Authors: Tucker David , Lawson Larry , Gemmen Randy , Dennis Richard
Published: November 2008

Current design concepts for hybrid systems call for the use of presently available turbine systems. Simply stated, the combustor of a turbine system is replaced with a high temperature fuel cell whose excess heat is used to drive the turbine. However, the startup of a turbine in such a direct fired fuel cell turbine hybrid system is made problematic through the increased pressure losses introduced by heat recuperation, and the relatively large cathode volume now present between the compressor discharge and the turbine inlet. This work evaluates the use of compressor bleed air to avoid stall and surge during the startup of a fuel cell turbine hybrid power system using the Hybrid Performance (Hyper) project hardware simulation facility at the National Energy Technology Laboratory (NETL), U.S. Department of Energy. Because integration of a fuel cell and often multiple recuperators into the compressed air stream results in a higher required pressure ratio for any given compressor inlet mass flow, a strategy must be developed to avoid compressor stall during startup. Turbine starts were attempted using the NETL Hyper project facility over a range of compressor bleed mass flows. The experimental facility at NETL makes use of a natural gas burner controlled by a real time fuel cell model to simulate the thermal output of a solid oxide fuel cell. Pressure vessels, used for simulating the cathode and post combustion volumes, and exhaust gas recuperators are integrated into the system with a modified turbine and compressor on a single shaft. The startup profiles are compared to the stall line of the compressor map to quantitatively evaluate the efficacy of the applied method in avoiding stall and surge during startup events.
Thermoacoustic Stability Analysis of an Annular Combustion Chamber With Acoustic Low Order Modeling and Validation Against Experiment
Authors: Kopitz Jan , Huber Andreas , Sattelmayer Thomas , Polifke Wolfgang
Published: November 2008

A low order acoustic network model is used to examine the stability of an annular combustor for different operating points. The results obtained by this approach are compared against experimental data from a full annular combustor. This annular combustor, in contrast to commonly used single burners or sector rigs, was used to include also 2-dimensional effects like the influence of circumferential modes, which can occur in practical gas turbine applications. The influence of the flame enters the network model simulation through an experimentally measured flame transfer function in terms of the response of heat release to acoustic velocity fluctuations. This flame transfer function, which has been measured at a stable operating point, is then used as a basis for the determination of flame transfer functions at other operating points by means of scaling methods. The transition to instability is thereby simulated by determination of the complex eigen modes, applying methods from control theory. The analytically determined stability behavior is compared to the experimentally measured one, with the aim to enhance and validate the network model approach as a means of predicting combustion instabilities in early design stages.
Gas Turbine Fault Detection and Diagnosis Using Nonlinear Feature Extraction Methods
Authors: Mukherjee Joydeb , Kini Venkataramana B. , Menon Sunil , Eswara Lalitha
Published: November 2008

Accurate gas turbine fault detection and diagnosis (FDD) is essential to improving airline safety as well as in reducing airline costs associated with delays and cancellations. In this paper, we present FDD methods based on feature extraction methods using nonlinear principal component analysis (NLPCA) and curvilinear component analysis (CCA). The underlying principle of both methods is to find the most representative feature space corresponding to gas turbine normal and faulty operations. During operation, new sensor data is located in this feature space and then it is determined whether a particular fault is indicated. NLPCA is an extension of linear PCA methods to the nonlinear domain; therefore, it is intrinsically better suited to nonlinear domains such as the gas turbine engine. The CCA method is another approach to clustering having superior properties for determining cluster manifolds automatically compared to the popular selforganizing map (SOM) method of clustering. The developed methods are tested with snapshot data collected at takeoff, both normal and faulty, from a turbofan gas turbine propulsion engine and the results are presented.
Technology Options for Gas Turbine Power Generation With Reduced CO2 Emission
Authors: Griffin Timothy , Bu¨cker Dominikus , Pfeffer Allen
Published: November 2008

ALSTOM Power R&D laboratories run various programs aimed at finding options that reduce or avoid CO2 emissions through: • High efficiency power generation equipment to utilize fossil fuels with the lowest possible emissions, and • Technologies to remove and sequester CO2 created in power plants in an environmentally and economically favorable manner. In this paper, an overview of on-going CO2 mitigation activities for gas turbine power generation is addressed. Energy efficiency improvements for both new and existing fossil fuel power plants are briefly reviewed. Customer requirements for future power plants with reduced CO2 emissions are discussed. Novel power generation cycles with exhaust gas recirculation for enhanced CO2 removal are introduced and evaluated. Conclusions are drawn regarding their efficiency, energy consumption and technical feasibility.
On-Board Characterization of Engine Dynamics for Health Monitoring and Control
Authors: Uluyol Onder , Kim Kyusung , Ball Charles
Published: November 2008

This paper introduces a feature extraction method for characterization of gas turbine engine dynamics for the purpose of engine health monitoring as well as optimum control. For a vehicle health monitoring system that is comprehensive in its scope, and timely and accurate in its diagnosis, high fidelity engine models and a large amount of high-speed data both in steady-state as well as in transients are needed. However, limited computational resources available on-board, and the limited bandwidth capacity and the high cost of real-time data transmission place serious barriers in fulfilling that need. The approach presented in the paper seeks to overcome these barriers by separating the initial feature extraction stage of diagnostics algorithms from the modeling and trending stages. The first part which includes the detection of time instances that are critical to diagnosis and control is performed on board, while the latter is performed on a ground station. The approach is applied to the startup transient in a propulsion engine. A 50-fold reduction in data size is realized while achieving a highly accurate prognosis of hydro-mechanical assembly (HMA) failures.
Application of Unsteady Aerodynamics and Aeroelasticity in Heavy-Duty Gas Turbines
Authors: Montgomery Matthew , Tartibi Mehrzad , Eulitz Frank , Schmitt Stefan
Published: November 2008

Modern computer simulations can predict some aspects of the unsteady aerodynamic phenomena associated with turbomachinery blade rows. This allows analysts to investigate aeroelastic phenomena, such as flutter, and blade-row interactions, such as forced response and unsteady effects on performance. This paper describes tools and design processes used to numerically investigate unsteady aerodynamic phenomena in heavy-duty gas turbines. A linearized Navier-Stokes method from the DLR has been used to predict the aerodynamic damping of both compressor and turbine airfoils under a variety of operating conditions. Some of these predictions were validated with engine experience. Other CFD codes, including TRACE from the DLR and ITSM3D from the University of Stuttgart, have been used to predict blade-row interaction. This includes the prediction of forced response due to rotor-vane interaction and unsteady effects on performance. The effects of airfoil clocking, including the effects of cooling flow injection, have also been investigated.
Detailed Chemical Kinetic Modeling of JP-8/Jet-A Ignition and Combustion
Authors: Mawid M. A. , Park T. W. , Sekar B. , Arana C.
Published: November 2008

Significant progress towards development and validation of a detailed chemical kinetic mechanism for the US Air Force JP-8 fuel is presented in this article. Three detailed chemical kinetic mechanisms for three JP-8 surrogate fuels, as given in Table I, were developed and reported in this study. The main objective is to investigate the performance of the developed three mechanisms for three different surrogate fuel blends and determine the suitability of each mechanism to chemically model the US Air Force petroleum-derived JP-fuel. The detailed JP-8 chemical kinetic reaction mechanism, we have been developing [1–3] for a 12-component surrogate fuel blend, has been used as a basis for the development of two additional detailed reaction mechanisms for the other two surrogate fuel mixtures. Submechanisms for the monosubstituted aromatics such as toluene, m-xylene, butylbenzene, and for the bicyclic aromatics such as 1-methylnaphthalene were all assembled and integrated with the detailed JP-8 reaction mechanism [1–3]. Pressure-dependent rate parameters up to 10 atmospheres for 41 reactions were also included. The three mechanisms were evaluated by predicting the ignition and combustion characteristics of a JP-8 fuel-air mixture in Plug Flow Reactor (PFR) and a Perfectly-Stirred Reactor (PSR) over a temperature range of 933–1020 K and pressure of 1 atm. The results indicated that overall the mechanism for the 6-component JP-8 surrogate 3 (Table I) can predict similar ignition-delay periods as those predicted by the 12-component JP-8 surrogate fuel 1 for atmospheric pressure condition. However, the PSR calculations pointed out to the existence of differences in lighter hydrocarbon species concentration profiles such as CH4, C2H4, C3H6, and C4H8 and important emission species such as CO and CO2 as predicted by the mechanisms that exhibited comparable ignition delay times. The study suggests that, for the conditions considered here, that the developed mechanisms still require further evaluation under various combustion environments, including transport phenomena, to determine the suitability of the chemical kinetic mechanism for either surrogate fuel 1 or 3 to chemically simulate the actual US Air Force JP-8 fuel.
Field Test Validation of the DLN2.5H Combustion System on the 9H Gas Turbine at Baglan Bay Power Station
Authors: Feigl Markus , Setzer Fred , Feigl-Varela Rebecca , Myers Geoff , Sweet Bryan
Published: November 2008

The lean, premixed H combustion system was targeted to deliver low NOx and CO emissions from 50% to 100% combined cycle load in both the Frame 7H (60 Hz) and Frame 9H (50 Hz) heavy-duty industrial gas turbines. The H System™ is the first gas turbine combined-cycle technology capable of achieving 60% thermal efficiency. The present paper describes field test performance of the combustion system during the launch and operation of the initial MS9001H installation at Baglan Bay power station near Port Talbot, Wales. The 480 MW 9H combined cycle, fired using the 14-chamber DLN2.5H combustion system, was comprehensively evaluated during the gas turbine Characterization Test program over a period of several months in late 2002 and 2003. Results are reported for exhaust emissions, combustor component durability, operability, and other key combustion system performance parameters over the full gas turbine operating range. The present paper also describes the operability of the H combustion system throughout a rigorous validation of the power plant system, including National Grid Council testing, load rejections, and other key system transients.
Effect of Projectile Materials on Foreign Object Damage of a Gas-Turbine Grade Silicon Nitride
Authors: Choi Sung R. , Racz Zsolt , Bhatt Ramakrishna T. , Brewer David N. , Gyekenyesi John P.
Published: November 2008

Foreign object damage (FOD) behavior of AS800 silicon nitride was determined using four different projectile materials at ambient temperature. The target test specimens rigidly supported were impacted at their centers by spherical projectiles with a diameter of 1.59 mm. Four different types of projectiles were used including hardened steel balls, annealed steel balls, silicon nitride balls, and brass balls. Post-impact strength of each target specimen impacted was determined as a function of impact velocity to better understand the severity of local impact damage. The critical impact velocity where target specimens fail upon impact was highest with brass balls, lowest with ceramic ball, and intermediate with annealed and hardened steel balls. Degree of strength degradation upon impact followed the same order as in the critical impact velocity with respect to projectile materials. For steel balls, hardened projectiles yielded more significant impact damage than annealed counterparts. The most important material parameter affecting FOD was identified as hardness of projectiles and was correlated in terms of critical impact velocity, impact deformation, and impact load.