bluuebunny/crossref_metadata_2025 huggingface dataset:
Pressure-Gain Combustion: Part I—Model Development
Authors: Narayanaswami L. , Richards G. A.
Published: February 2008

A model for aerodynamically valved pulse combustion is presented. Particular emphasis is placed on using the model equations to identify characteristic length and time scales relevant to the design of pressure-gain combustors for gas turbine applications. The model is a control volume description of conservation laws for several regions of the pulse combustor. Combustion is modeled as a bimolecular reaction. Mixing between the fresh charge and the combustion products is modeled using a turbulent eddy time estimated from the combustor geometry and flow conditions. The model equations identify two characteristic lengths, which should be held constant during combustor scaleup, as well as certain exceptions to this approach. The effect of ambient operating pressure and inlet air temperature is also discussed.
A Review of the Efficacy of Silicon Carbide Hot-Gas Filters in Coal Gasification and Pressurized Fluidized Bed Combustion Environments
Authors: Judkins R. R. , Stinton D. P. , DeVan J. H.
Published: February 2008

Reviews of relevant literature and interviews with individuals cognizant of the state of the art in ceramic filters for hot-gas cleaning were conducted. Thermodynamic calculations of the stability of various ceramic phases were also made. Based on these calculations, reviews, and interviews, conclusions were reached regarding the use of silicon carbide-based ceramics as hot-gas filter media. Arguments are presented that provide the basis for our conclusion that high-purity silicon carbide is a viable material in the integrated coal gasification combined cycle (IGCC) and pressurized fluidized-bed combustion (PFBC) environments we examined. Clay-bonded materials are, we concluded, suspect for these applications, their extensive use not-withstanding. Operations data we reviewed focused primarily on clay-bonded filters, for which a great deal of experience exists. We used the clay-bonded filter experience as a point of reference for our review and analysis.
Biomass-Gasifier/Aeroderivative Gas Turbine Combined Cycles: Part B—Performance Calculations and Economic Assessment
Authors: Consonni S. , Larson E. D.
Published: February 2008

Gas turbines fueled by integrated biomass gasifiers are a promising option for base-load electricity generation from a renewable resource. Aeroderivative turbines, which are characterized by high efficiencies in small units, are of special interest because transportation costs for biomass constrain conversion facilities to relatively modest scales. Part A of this two-part paper reviewed commercial development activities and major technological issues associated with biomass integrated-gasifier/gas turbine (BIG/GT) combined cycle power generation. Based on the computational model also described in Part A, this paper (Part B) presents results of detailed design-point performance calculations for several BIG/GT combined cycle configurations. Emphasis is given to systems now being proposed for commercial installation in the 25–30 MWe, power output range. Three different gasifier designs are considered: air-blown, pressurized fluidized-bed gasification; air-blown, near-atmospheric pressure fluidized-bed gasification; and near-atmospheric pressure, indirectly heated fluidized-bed gasification. Advanced combined cycle configurations (including with intercooling) with outputs from 22 to 75 MW are also explored. An economic assessment is also presented, based on preliminary capital cost estimates for BIG/GT combined cycles and expected biomass costs in several regions of the world.
The Cascaded Humidified Advanced Turbine (CHAT)
Authors: Nakhamkin M. , Swensen E. C. , Wilson J. M. , Gaul G. , Polsky M.
Published: February 2008

This paper introduces the Cascaded Humidified Advanced Turbine (CHAT) plant, a gas turbine based power generation plant utilizing intercooling, reheat, and humidification. It is based upon the integration of an existing heavy duty gas turbine with an additional shaft comprising industrial compressors and high pressure expander. CHAT capitalizes on the latest proven gas turbine technology, which, combined with a sophisticated thermal cycle configuration, results in substantial improvement in gas turbine efficiency, compared to a simple cycle, while still maintaining typical advantages and merits of a combustion turbine plant. Built with a commercial combustion turbine and available industrial compressors and expanders, the CHAT plant does not require extensive product development and testing. As a result, the CHAT power plant can be offered with specific capital costs up to 20 percent lower than the combined cycle plant, and with competing efficiency. Compared to a combined cycle plant, the CHAT plant offers lower emissions (due to air humidification) and other significant operating advantages with regard to start-up time and costs, better efficiency at part load, lower power degradation at higher ambient temperatures, and simpler operations and maintenance due to elimination of the complexities and costs associated with steam production. The CHAT plant also integrates very effectively with coal gasification and particularly well with the water quench design. This feature has been discussed in previous publications.
Benefits of Compressor Inlet Air Cooling for Gas Turbine Cogeneration Plants
Authors: De Lucia M. , Lanfranchi C. , Boggio V.
Published: February 2008

Compressor inlet air cooling is an effective method for enhancing the performance of gas turbine plants. This paper presents a comparative analysis of different solutions for cooling the compressor inlet air for the LM6000 gas turbine in a cogeneration plant operated in base load. Absorption and evaporative cooling systems are considered and their performance and economic benefits compared for the dry low-NOx LM6000 version. Reference is made to two sites in Northern and Southern Italy, whose climatic data series for modeling the variations in ambient temperature during the single day were used to account for the effects of climate in the simulation. The results confirmed the advantages of inlet air cooling systems. In particular, evaporative cooling proved to be cost effective, though capable of supplying only moderate cooling, while absorption systems have a higher cost but are also more versatile and powerful in base-load operation. An integration of the two systems proved to be able to give both maximum performance enhancement and net economic benefit.
Biomass Externally Fired Gas Turbine Cogeneration
Authors: Eidensten L. , Yan J. , Svedberg G.
Published: February 2008

This paper is a presentation of a systematic study on externally fired gas turbine cogeneration fueled by biomass. The gas turbine is coupled in series with a biomass combustion furnace in which the gas turbine exhaust is used to support combustion. Three cogeneration systems have been simulated. They are systems without a gas turbine, with a non-top-fired gas turbine, and a top-fired gas turbine. For all systems, three types of combustion equipment have been selected: circulating fluidized bed (CFB) boiler, grate fired steam boiler, and grate fired hot water boiler. The sizes of biomass furnaces have been chosen as 20 MW and 100 MW fuel inputs. The total efficiencies based on electricity plus process heat, electrical efficiencies, and the power-to-heat ratios for various alternatives have been calculated. For each of the cogeneration systems, part-load performance with varying biomass fuel input is presented. Systems with CFB boilers have a higher total efficiency and electrical efficiency than other systems when a top-fired gas turbine is added. However, the systems with grate fired steam boilers allow higher combustion temperature in the furnace than CFB boilers do. Therefore, a top combustor may not be needed when high temperature is already available. Only one low-grade fuel system is then needed and the gas turbine can operate with a very clean working medium.
Slot and Vertical Face Grinding of Aerospace Components
Authors: Mindek R. B. , Howes T. D.
Published: February 2008

Workpiece profile accuracy, wheel wear, and thermal damage were investigated for the grinding of slots and vertical faces on MAR-M-247, Inconel 713C, and M-2 tool steel using both alumina and cubic boron nitride (CBN) grinding wheels. It was found when grinding with alumina wheels that the wheel corner and first 2.5 mm of the grinding wheel sidewall account for all the grinding forces in the vertical, horizontal, and transverse directions, and therefore is responsible for all the significant grinding done on the sideface of the workpiece. Since previous work links wheel wear and workpiece thermal damage during grinding to grinding forces, this finding suggests that the area around the wheel corner is the critical region of importance in grinding these types of profiles in terms of wheel wear and the heat input to the workpiece. These, in turn, are linked to workpiece profile accuracy and metallurgical damage. Results also show that striation marks inherent in sidewall grinding can be minimized by controlling the maximum normal infeed rate of the wheel. A method for minimizing the heat input into the workpiece by minimizing grinding force during vertical face grinding is also reported.
Life Cycle Considerations in Propulsion Alternatives for Fast Vessels
Authors: Luck D. L.
Published: February 2008

Fast vessels are being built and operated for a large range of passenger-carrying applications. Fast cargo-carrying vessels are being considered in a variety of sizes as well. A major decision in design and construction of these vessels is the propulsion system; this decision has major impacts on the operation economics as well as the operational capabilities of the vessels. Factors involved in consideration of propulsion alternatives for fast vessels are examined, with emphasis upon the total life cycle operating implications of these factors. A methodology for considering the factors is suggested, and an example is presented with results of the consideration tradeoffs.
Compressor Station Recycle System Dynamics During Emergency Shutdown
Authors: Botros K. K. , Jungowski W. M. , Richards D. J.
Published: February 2008

Transient phenomena associated with gas recycling during compressor emergency shutdown (ESD) have been studied both experimentally and numerically. A scaled-down laboratory test rig has been constructed to study the influence of various underlying parameters on ESD operation. Three different configurations representing different design scenarios were tested. The first configuration has a long recycle system with a volume capacitance representing an air-cooled heat exchanger in the recycle loop, and the recycle valve located close to the discharge side. The second one is the same as the first except the recycle valve is placed close to the suction side. In the third configuration, the cooler capacitance was removed from the recycle loop and the piping capacitance on the discharge side was further reduced. Shutdown tests were carried out from different steady-state initial conditions varying the recycle valve opening time, and the synchronization time between the compressor ESD signal and valve opening signal. Numerical simulations based on the solution of the full one-dimensional conservation equations using the method of characteristics were also conducted for the above configurations. Good agreement was obtained between measurements and simulation results. Numerical simulations were used to analyze other cases, which were not investigated experimentally, to further investigate the interaction between equipment and flow parameters. Results indicate that the valve prestroke time is more crucial than the stroke time and that it should be made short to avoid surging the compressor during ESD. Locating the recycle valve as close as possible to the suction or discharge of the compressor helps reduce unit surge during shutdown.
Optimization of Regenerated Gas Turbines
Authors: Beck D. S.
Published: February 2008

An algorithm for the optimization of regenerated gas turbines is given. For sets of inputs that are typical for automotive applications, the optimum cycle pressure ratio and a set of optimized regenerator parameters that maximize thermal efficiency are given. A second algorithm, an algorithm for sizing regenerators based on outputs of the optimization algorithm, is given. With this sizing algorithm, unique regenerator designs can be determined for many applications based on the presented optimization data. Results of example sizings are given. The data indicate that one core (instead of two cores) should be used to maximize thermal efficiency. The data also indicate that thermal efficiencies of over 50 percent should be achievable for automotive applications if ceramic turbines are used.
Regenerator Effectiveness During Transient Operation
Authors: Beck D. S.
Published: February 2008

Current designs of regenerative gas turbines include high-effectiveness rotary regenerators. The regenerators make the gas turbines highly efficient during steady-state operation. During engine transients, however, engine efficiency can be low because high-effectiveness regenerators tend to have large cores with large thermal masses, and it can take a long time (minutes for example) for these regenerators to reach their steady-state effectivenesses. The following criterion determines the response time of regenerators: τss˜(mc)R/Cx, where τxx (S) is the time period of transient operation; (mc)R (J/K) is the heat capacity of the core; and Cx (W/K) is the heat-capacity rate of the exhaust. This criterion has been verified through analysis and experimentation. The criterion enables the designer to estimate the fraction of an operating cycle during which the regenerator will have reduced effectiveness.
Diesel NOx Catalytic Converter Development: A Review
Authors: Heimrich M. J.
Published: February 2008

This paper summarizes the findings of several technical articles on diesel NOx catalytic converter technology. Simplified theoretical reactions for NOx removal are discussed. Currently, development of catalytic NOx control technology for diesel engines is focused on systems that incorporate fuel hydrocarbons as the chemical reducing agent. Copper-and zeolite-based catalysts have been the predominant systems studied to date, but now catalysts containing precious metals are being investigated. Observed NOx reduction efficiencies typically ranged from 10 to 30 percent on actual engine exhaust systems when exhaust hydrocarbon enrichment strategies were used. Effects of carbon monoxide, sulfur dioxide, and water on NOx reduction efficiencies are reviewed. Recommendations for future research include attempts to broaden the temperature range of efficient NOx reduction, improving hydrocarbon selectivity toward the NOx reduction reaction, and the development of a supplementary reductant delivery system suitable for transient diesel engine operation.
An Automated Diagnostic Expert System for Diesel Engines
Authors: Autar R. K.
Published: February 2008

Fault diagnosis of diesel engines can be a tedious time-consuming process, resulting in extended downtime, thus reducing productivity and increasing operational cost. This problem can be accentuated when experienced expert maintenance personnel are in short supply and also when the rate of development of new-generation engines using leading edge technology does not permit maintenance personnel to keep up with this change. An automated diagnostic system based on artificial intelligence criteria using mechanical signature analyses (MSA) of signals acquired from engine mounted sensors can overcome this problem by providing expert and consistent diagnostic advice. This paper describes the development and implementation of an automated diagnostic expert system for diesel engines. The system uses vibration signals together with oil pressure and temperature, crankcase pressures, exhaust gas temperature and pressure, exhaust emissions, manifold noise levels, inlet manifold pressure, fuel delivery pressure, and instantaneous engine speed to monitor and diagnose engine faults. State-of-the-art techniques used for signal processing to generate data required for effective diagnosis from raw signals acquired form the engine mounted sensors are described. Complexities of signal processing for diesel engines are discussed and solutions of a practical nature suggested. Signal analysis techniques relating to fault condition evaluation are also described.
A Second-Law-Based Optimization: Part 1—Methodology
Authors: El-Sayed Y. M.
Published: February 2008

This paper deals with the optimization of complex energy systems given a cost objective function. The optimization uses a decomposition strategy based on the second law of thermodynamics and a concept for costing the components of a system. A large number of nonlinear decision variables can be optimized with enhanced convergence to an optimum. The paper is in two parts. In this part, the methodology is described. In Part 2, the methodology is applied to a simple energy system of 10 components and 19 manipulated decision parameters. The system is treated once as a single purpose combined cycle and once as a power-heat cogenerating system. The results of the application are summarized and evaluated. Further development is encouraged.
Development of Air-Cooled Ceramic Nozzles for a Power-Generating Gas Turbine
Authors: Tsuchiya T. , Furuse Y. , Yoshino S. , Chikami R. , Tsukuda Y. , Mori M.
Published: February 2008

The development of air-cooled ceramic nozzle vanes for a power-generating gas turbine has been reported. To make up the limited temperature resistance of present ceramic materials, the utilization of a small amount of cooling air has been studied for the first-stage nozzle vanes of a 1500°C class gas turbine. A series of cascade tests were carried out for the designed air-cooled Si3N4 nozzle vanes under 6 atm and 1500°C conditions. It was confirmed that the maximum ceramic temperature can be maintained below 1300°C by a small amount of cooling air. In spite of the increased thermal stresses from local cooling, all Si3N4 nozzle vanes survived the cascade tests, including both steady-state and transients of emergency shutdown. The potential for an air-cooled ceramic nozzle was demonstrated for a 1500°C class gas turbine application.
An Experimental Investigation of the Conversion of NO to NO2 at High Pressure
Authors: Hunderup J. W. , Roby R. J.
Published: February 2008

Unexpectedly high concentrations of NO2 formation have been noted in stack emissions from industrial combustors. NO2 formation has been reported to occur through the so-called “HO2 mechanism” in which NO combines with HO2 to produce NO2 and OH In this study, the formation of NO2 was investigated at superatmospheric pressures through experiments and computer modeling. Computer modeling utilized the CHEMKIN chemical kinetics program and a subset of a previously published C–H–O–N system mechanism. Experimental work was conducted using a high-pressure flow reactor designed and built in the course of the study. The effects of pressure, temperature, and the presence of a NO2-promoting hydrocarbon, methane, were investigated. It was discovered that as pressure increased from 1 atm to 8.5 atm, the rate and amount of NO converted to NO2 also increased. The results also show a temperature “window” between approximately 800 K and 1000 K in which NO to NO2 conversion readily occurred. The presence of methane was seen to enhance NO conversion to NO2, and a ratio of [CH4]/[NO] was found to be a useful parameter in predicting NO2 formation. Significant NO conversion to NO2 was noted for [CH4]/[NO] > 1 at the hydrocarbon injection point. Experimental results validated those trends obtained from modeling with a modified C–H–O–N mechanism.
Theoretical and Experimental Comparisons for Damping Coefficients of a Short-Length Open-End Squeeze Film Damper
Authors: San Andres L. A.
Published: February 2008

Squeeze film dampers (SFD) provide load isolation and attenuate rotor vibrations in high speed turbomachinery. Operating parameters such as whirl frequency, amplitude of journal motion, and value of external pressure supply determine the SFD dynamic force response and its dissipation of mechanical energy. Measurements of pressure fields and fluid film forces in a fully submerged open-end squeeze film damper are presented for tests with rotor speeds to 5000 cpm and low supply pressures. The damper has a clearance of 381 µm (0.015 in.) and the journal describes circular centered orbits of amplitudes ranging from 30 to 50 percent of the bearing clearance. Experimental film pressures depict a vapor cavitation (close to zero absolute pressure) zone increasing in extent as the whirl frequency increases. Estimated fluid film forces from the measured pressure profiles are found to be proportional to whirl speed and lubricant viscosity. Test cross-coupled damping coefficients (Crt) are smaller than predicted values based on the short-length bearing model with a π film cavitation assumption. The direct damping coefficients (Ctt) are larger than theoretical values, especially at low frequencies where the dynamic cavitation region has not grown to half the circumferential flow extent. The experiments demonstrate the viscous character of the fluid film forces in a SFD test apparatus where fluid inertia effects are minimal (squeeze film Reynolds number less than one). On the other hand, the extent of the cavitation zone appears to be dominant on the generation of fluid film forces.
Machine Health Monitoring and Life Management Using Finite-Element-Based Neural Networks
Authors: Roemer M. J. , Hong C. , Hesler S. H.
Published: February 2008

This paper demonstrates a novel approach to condition-based health monitoring for rotating machinery using recent advances in neural network technology and rotordynamic, finite-element modeling. A desktop rotor demonstration rig was used as a proof of concept tool. The approach integrates machinery sensor measurements with detailed, rotordynamic, finite-element models through a neural network that is specifically trained to respond to the machine being monitored. The advantage of this approach over current methods lies in the use of an advanced neural network. The neural network is trained to contain the knowledge of a detailed finite-element model whose results are integrated with system measurements to produce accurate machine fault diagnostics and component stress predictions. This technique takes advantage of recent advances in neural network technology that enable real-time machinery diagnostics and component stress prediction to be performed on a PC with the accuracy of finite-element analysis. The availability of the real-time, finite-element-based knowledge on rotating elements allows for real-time component life prediction as well as accurate and fast fault diagnosis.
Test Results of a New Damper Seal for Vibration Reduction in Turbomachinery
Authors: Vance J. M. , Li J.
Published: February 2008

A new type of labyrinth gas seal for damping vibration and whirl, called the TAMSEAL, has been evaluated in both nonrotating and rotating tests at Texas A&M University. Test results of the prototype, along with comparison tests of a conventional labyrinth seal, show up to 100 times more direct damping than the conventional bladed seal. The new design also has a feature that blocks swirl of the working fluid, which is known to be rotordynamically destabilizing in machines with conventional seals. Coastdown tests of the new seal were conducted at various pressures on a rotordynamic test apparatus with a critical speed at 4000 rpm and compared with identical testing of a conventional labyrinth seal. Rap tests of both seals were also conducted to measure the logarithmic decrement of free vibration, and the leakage of both seals was measured. Test results show large reductions in peak vibration at the critical speed in all cases, with the critical speed being completely eliminated by the TAMSEAL at some pressure drop conditions. The leakage rate of the tested TAMSEAL is higher than the conventional seal at the same clearance, but the large reductions in vibration and whirl amplitudes suggest that the TAMSEAL could be operated with smaller clearances than conventional labyrinth seals.
Strength Prediction of Ceramic Components Under Complex Stress States
Authors: Peralta A. D. , Wu D. C. , Brehm P. J. , Cuccio J. C. , Menon M. N.
Published: February 2008

The capability to perform accurate fast-fracture strength predictions for ceramic components under complex stress states must be available in order to transition the use of advanced, high-strength ceramic materials from the laboratory to the high-strength/high-temperature applications they are intended for. Multiaxial strength prediction theories have provided the prediction capabilities, but only limited testing of these theories under complex states of stress and stress gradient conditions has been performed previously. Presented here are comprehensive test results and strength predictions for ceramic components subjected to complex states of stress and stress gradient conditions. The results show excellent agreement of the predictions from the multiaxial theories with test results for volumetrically distributed flaws. An important finding of this work is the problem that arises in performing component surface strength predictions from database-type specimens. Database-type specimens and component surface properties are not necessary correlated, and in many cases it may be completely inaccurate to use database-type specimen surface properties for component surface strength predictions.
Reliability Analysis of Uniaxially Ground Brittle Materials
Authors: Salem J. A. , Nemeth N. N. , Powers L. M. , Choi S. R.
Published: February 2008

The fast fracture strength distribution of uniaxially ground, alpha silicon carbide was investigated as a function of grinding angle relative to the principal stress direction in flexure. Both as-ground and ground/annealed surfaces were investigated. The resulting flexural strength distributions were used to verify reliability models and predict the strength distribution of larger plate specimens tested in biaxial flexure. Complete fractography was done on the specimens. Failures occurred from agglomerates, machining cracks, or hybrid flaws that consisted of a machining crack located at a processing agglomerate. Annealing eliminated failures due to machining damage. Reliability analyses were performed using two and three-parameter Weibull and Batdorf methodologies. The Weibull size effect was demonstrated for machining flaws. Mixed mode reliability models reasonably predicted the strength distributions of uniaxial flexure and biaxial plate specimens.
Evaluation of a Three-Dimensional Mathematical Model of a Power Station Boiler
Authors: Coelho P. J. , Carvalho M. G.
Published: February 2008

A three-dimensional mathematical model based on the numerical solution of the governing equations of mass, momentum, and energy, and transport equations of scalar quantities is presented. The model is applied to a power station boiler of the Portuguese Electricity Utility for which experimental data are available. Predictions of the gas temperature and chemical species concentrations are compared with the measurements. Three different grids were employed to ensure that conclusions are not affected by the grid refinement. It was found that using a combustion model based on the chemical equilibrium assumption, the predicted gas species concentrations are in good agreement with the data and the temperature profiles display the correct trend, although the temperature was under predicted, especially in the burner region. The influence of the air/fuel ratio and power load were also successfully simulated. The present results reveal the predictive capabilities of the model and its usefulness for design or optimization studies.
A Technique to Achieve Uniform Stress Distribution in Compressive Creep Testing of Advanced Ceramics at High Temperatures
Authors: Liu K. C. , Stevens C. O. , Brinkman C. R. , Holshauser N. E.
Published: February 2008

A technique to achieve stable and uniform uniaxial compression is offered for creep testing of advanced ceramic materials at elevated temperatures, using an innovative self-aligning load-train assembly. Excellent load-train alignment is attributed to the inherent ability of a unique hydraulic universal coupler to maintain self-aligning. Details of key elements, design concept, and principles of operation of the self-aligning coupler are described. A method of alignment verification using a strain-gaged specimen is then discussed. Results of verification tests indicate that bending below 1.5 percent is routinely achievable with the use of the load-train system. A successful compression creep test is demonstrated using a dumb-bell-shaped silicon nitride specimen tested at 1300°C for a period in excess of 4000 h.
Structural Design and High-Pressure Test of a Ceramic Combustor for 1500°C Class Industrial Gas Turbine
Authors: Yuri I. , Hisamatsu T. , Watanabe K. , Etori Y.
Published: February 2008

A ceramic combustor for a 1500°C, 20 MW class industrial gas turbine was developed and tested. This combustor has a hybrid ceramic/metal structure. To improve the durability of the combustor, the ceramic parts were made of silicon carbide (SiC), which has excellent oxidation resistance under high-temperature conditions as compared to silicon nitride (Si3N4), although the fracture toughness of SiC is lower than that of Si3N4. Structural improvements to allow the use of materials with low fracture toughness were made to the fastening structure of the ceramic parts. Also, the combustion design of the combustor was improved. Combustor tests using low-Btu gaseous fuel of a composition that simulated coal gas were carried out under high pressure. The test results demonstrated that the structural improvements were effective because the ceramic parts exhibited no damage even in the fuel cutoff tests from rated load conditions. It also indicated that the combustion efficiency was almost 100 percent even under part-load conditions.
Fuel Nozzle Aerodynamic Design Using CFD Analysis
Authors: Crocker D. S. , Fuller E. J. , Smith C. E.
Published: February 2008

The aerodynamic design of airflow passages in fuel injection systems can be significantly enhanced by the use of CFD analysis. Attempts to improve the efficiency of the fuel nozzle design process by using CFD analyses have generally been unsuccessful in the past due to the difficulties of modeling swirling flow in complex geometries. Some of the issues that have been obstacles to successful and timely analysis of fuel nozzle aerodynamics include grid generation, turbulence models, and definition of boundary conditions. This study attempts to address these obstacles and demonstrate a CFD methodology capable of modeling swirling flow within the internal air passages of fuel nozzles. The CFD code CFD-ACE was used for the analyses. Results of nonreacting analyses and comparison with experimental data are presented for three different fuel nozzles. The three nozzles have distinctly different designs (including axial and radial inflow swirlers) and thus demonstrate the flexibility of the design methodology. Particular emphasis is given to techniques involved in predicting the effective flow area (ACd) of the nozzles. Good agreement between CFD predictions of the ACd (made prior to experiments) and the measured ACd was obtained. Comparisons between predicted and measured velocity profiles also showed good agreement.
Low NOx Premixed Combustion of MBtu Fuels in a Research Burner
Authors: Do¨bbeling K. , Eroglu A. , Winkler D. , Sattelmayer T. , Keppel W.
Published: February 2008

The paper reports on the development and testing of a premix research burner for MBtu fuels. The burner has a quartz glass annular mixing section and a quartz, glass flame tube to allow visualization of the flame. A central lance is used to mount modules for fuel injection, swirl generation, and flame stabilization. This allows a large number of variants with different swirl strength, mixing section length, fuel injection geometry, and flameholder size and shape to be easily tested. Experiments have been performed at atmospheric pressure and under high-pressure conditions (14 bar pressure, 400°C air preheat temperature) for syngas with a H2/CO ratio of up to 5. In a preliminary study, the mixing quality of the tested variants has been assessed with planar laser-induced fluorescence (LIF). High-pressure combustion tests show that low NOx (<10 vppmd @ 15 percent O2) premix combustion of MBtu fuels under industrial GT conditions without dilution is feasible.
NOx Measurements for Combustor With Acoustically Controlled Primary Zone
Authors: Vermeulen P. J. , Ramesh V.
Published: February 2008

Successful NOx measurements at the end of the primary zone of a small tubular combustor of conventional gas turbine design, employing acoustically controlled primary zone air-jet mixing processes, have been made at scaled 1/4 and 1/8 load operating conditions. Testing at 1/8 load significantly increased the effective strength of the acoustic drive, which strongly improved the mixing by the acoustically driven primary zone air-jets. The acoustic drive caused partial blockage of the combustor primary zone airflow. This increased the equivalence ratio and the gas temperature, and made the gas temperature distribution more uniform, except for lean conditions at 1/8 load, in the plane of the NOx measurements. This explained the measured greater NOx “with-drive,” and the distinctly more uniform NOx distribution, which confirmed that mixing was acoustically augmented. The acoustically produced changes were greater at 1/8 load. The acoustic drive significantly changed the combustor operating characteristic so far as mean NOx was concerned, and under lean conditions at 1/8 load mean NOx was reduced, indicating that a value of 10 ppm is possible (a 50 percent reduction).
Application of Rainbow Thermometry to the Study of Fuel Droplet Heat-Up and Evaporation Characteristics
Authors: Sankar S. V. , Buermann D. H. , Bachalo W. D.
Published: February 2008

Advanced, nonintrusive, laser-based diagnostics are being developed for simultaneously measuring the size, velocity, temperature, and instantaneous regression rates of vaporizing/burning fuel droplets in polydisperse flow environments. The size and velocity of the droplets are measured using a conventional phase Doppler particle analyzer (PDPA), and the droplet temperatures are simultaneously measured with a rainbow thermometer. This integrated diagnostic has been applied to the study of fuel droplet heat-up characteristics in a swirl-stabilized kerosene spray flame. It has also been shown that a novel extension of rainbow thermometry can be used additionally to extract the instantaneous droplet vaporization rate. The feasibility of measuring the instantaneous regression rate has also been demonstrated using controlled experiments with a vaporizing/burning stream of ethanol droplets.
Emissions Characteristics of Liquid-Fueled Pilot Stabilized Lean Premixed Flames in a Tubular Premixer-Combustor
Authors: Dutta P. , Gore J. P. , Sojka P. E.
Published: February 2008

Global emissions of NOx in a liquid-fueled lean-premixed tubular combustor with a tubular premixer operating under atmospheric pressure are studied experimentally. The effects of equivalence ratio, premixer length, residence time, fuel type, and fuel atomization and dispersion characteristics on NOx emissions are studied. Measurements of exhaust species concentrations are used as the primary indicator of the effectiveness of premixing-prevaporization upstream of the combustor. Qualitative levels of prevaporization-premixing are determined from Mie-scattering signals measured at the exit of the premixer. Emission measurements show that the equivalence ratio is the dominant operating parameter, with premixing length and residence time being less significant within the present operating range. Ultra low NOx operation (<10 ppmv @ 15 percent 02) is feasible for equivalence ratios less than 0.5. More significantly, small drops persist beyond the premixer even for very long premixers, and Mie-scattering measurements show considerable spatial inhomogeneity, while allowing ultralow NOx operation. One-dimensional evaporation calculations for single drop trajectories confirm that complete evaporation for typical drop size distributions is not possible with reasonable premixer lengths under atmospheric pressure. Fuel dispersion is found to be the most critical parameter for high combustion efficiency, and adverse effects of poor fuel dispersion cannot be overcome by using longer premixers.
Investigation of Wedge Probe Wall Proximity Effects: Part 2—Numerical and Analytical Modeling
Authors: Smout P. D. , Ivey P. C.
Published: February 2008

An experimental study of wedge probe wall proximity effects is described in Part 1 of this paper. Actual size and large-scale model probes were tested to understand the mechanisms responsible for this effect, by which free-stream pressure near the outer wall of a turbomachine may be overindicated by up to 20 percent dynamic head. CFD calculations of the flow over two-dimensional wedge shapes and a three-dimensional wedge probe were made in support of the experiments, and are reported in this paper. Key flow structures in the probe wake were identified that control the pressures indicated by the probe in a given environment. It is shown that probe aerodynamic characteristics will change if the wake flow structures are modified, for example by traversing close to the wall, or by calibrating the probe in an open jet rather than in a closed section wind tunnel. A simple analytical model of the probe local flows was derived from the CFD results. It is shown by comparison with experiment that this model captures the dominant flow features.
Final Report of the Key Technology Development Program for a Next-Generation High-Temperature Gas Turbine
Authors: Sato M. , Kobayashi Y. , Matsuzaki H. , Aoki S. , Tsukuda Y. , Akita E.
Published: February 2008

There is a strong demand for efficient and clean power-generating systems to meet recent energy-saving requirements and environmental regulations. A combined cycle power plant is one of the best solutions to the above [1]. Tohoku Electric Power Co., Inc., and Mitsubishi Heavy Industries, Ltd., have jointly developed three key technologies for a next-generation 1500°C class gas turbine. The three key technologies consist of: (1) high-temperature low-NOx combustion system. (2) row 1 turbine vane and blade with advanced cooling schemes, and (3) advanced heat-resistant materials; (2) and (3) were verified by HTDU (High Temperature Demonstration Unit). This paper describes the results of the above-mentioned six-year joint development.
An Improved Epicyclic Gearbox for Reduced and Controllable Subsynchronous Vibrations in Gas Turbogenerator Applications
Authors: Rakhit A. K.
Published: February 2008

An improvement is made to the design of an epicyclic gearbox that limits the dynamic eccentricities of gearbox components. Gearboxes were manufactured to the new design and tested, showed reduced levels of subsynchronous vibrations at the turbine bearings. The in-situ balancing feature of the gearbox is also found to be very effective in reducing these vibrations further. The improved gearboxes not only assured the service life of the turbine bearings, but also increased the success rate of package testing the first time with substantial cost savings.
A Pump Instability Theory Using an Acoustic Feedback Mechanism
Authors: Corley J. E.
Published: February 2008

A subsynchronous vibration problem with a large water injection pump was solved in 1974 by modifying the discharge piping transition to a long taper configuration. This paper describes a quantitative theory based upon the dynamic modeling of the pump rotor and piping system. The model successfully duplicates the experimental results of the pump instability and reproduces the subsynchronous vibration described in the original paper. The analysis results in a log decrement of the system that is dependent upon the time delay of the acoustic pulsation. It shows that the system can be driven unstable for acoustic path lengths that are much less than the quarter wavelength. The analysis also shows the log decrement is minimized when the time delay is equivalent to exactly that of one eighth wavelength of the resonant frequency of the pump.
Indicators of Fuel Maldistribution in Spark-Ignition Engines
Authors: Alkidas A. C.
Published: February 2008

Several exhaust-emissions-based parameters were experimentally found to be good indicators for fuel maldistribution (both in-cylinder and cylinder-to-cylinder) in spark-ignition engines. The quality of combustion greatly affected these indicators, thus possibly limiting their applicability. Corrections were developed to desensitize these indicators to the quality of combustion.
A Test Device for Premixed Gas Turbine Combustion Oscillations
Authors: Richards G. A. , Gemmen R. S. , Yip M. J.
Published: February 2008

We report the design and operation of a test device suitable for studying combustion oscillations produced by commercial-scale gas turbine fuel nozzles. Unlike conventional test stands, this test combustor uses a Helmholtz acoustic geometry to replicate the acoustic response that would otherwise be observed only during complete engine testing. We suggest that successful simulation of engine oscillations requires that the flame geometry and resonant frequency of the test device should match the complete engine environment. Instrumentation for measuring both pressure and heat release variation is described. Preliminary tests suggest the importance of characterizing the oscillating behavior in terms of a nozzle reference velocity and inlet air temperature. Initial tests also demonstrate that the stabilizing effect of a pilot flame depends on the operating conditions.
The Development of the Junkers Jumo 004B—The World’s First Production Turbojet
Authors: Meher-Homji C. B.
Published: February 2008

This paper describes the pioneering work of Anselm Franz who, while working for the Junkers Engine company in Germany, designed and made operational the world’s first production jet engine, the Junkers Jumo 004, which was the powerplant for the formidable Messerschmitt ME 262 fighter. The paper covers the historical background of jet engine development in Germany during the Second World War and discusses design details of this remarkable axial flow, 1980 lb (900 kg) thrust engine. The development represented a historic achievement for Anselm Franz and his design team at Junkers. Approximately 6000 engines were built at the end of the Second World War in the face of acute shortages and damage to German industry. The Jumo was brought from conceptual design to production in a span of four years. Franz joined Avco Lycoming in 1952 and worked for 16 years. He retired as Vice President in 1968 after making prolific contributions to the development of several Lycoming engines including the T53, the T55, and the AGT-1500. Anselm Franz passed away at the age of 94 in Stratford, Connecticut. This paper is a modest tribute to a jet engine pioneer who, in spite of his extensive contributions to gas turbine technology, will always be remembered as the man who designed the world’s first production turbojet.
Creep Performance of Candidate SiC and Si3N4 Materials for Land-Based, Gas Turbine Engine Components
Authors: Wereszczak A. A. , Kirkland T. P.
Published: February 2008

The tensile creep-rupture performance of a commercially available gas pressure sintered silicon nitride (Si3N4) and a sintered silicon carbide (SiC) is examined at 1038, 1150, and 1350°C. These two ceramic materials are candidates for nozzles and combustor tiles that are to be retrofitted in land-based gas turbine engines, and interest exists to investigate their high-temperature mechanical performance over service times up to, and in excess of, 10,000 hours (≈14 months). To achieve lifetimes approaching 10,000 hours for the candidate Si3N4 ceramic, it was found (or it was estimated based on ongoing test data) that a static tensile stress of 300 MPa at 1038 and 1150°C, and a stress of 125 MPa at 1350°C cannot be exceeded. For the SiC ceramic, it was estimated from ongoing test data that a static tensile stress of 300 MPa at 1038°C, 250 MPa at 1150°C, and 180 MPa at 1350°C cannot be exceeded. The creep-stress exponents for this Si3N4 were determined to be 33, 17, and 8 for 1038, 1150, and 1350°C, respectively. The fatigue-stress exponents for the Si3N4 were found to be equivalent to the creep exponents, suggesting that the fatigue mechanism that ultimately causes fracture is controlled and related to the creep mechanisms. Little success was experienced at generating failures in the SiC after several decades of time through exposure to appropriate tensile stress; it was typically observed that if failure did not occur on loading, then the SiC specimens most often did not creep-rupture. However, creep-stress exponents for the SiC were determined to be 57, 27, and 11 for 1038, 1150, and 1350°C, respectively. For SiC, the fatigue-stress exponents did not correlate as well with creep-stress exponents. Failures that occurred in the SiC were a result of slow crack growth that was initiated from the specimen’s surface.
Experimental Investigation of the Liquid Fuel Evaporation in a Premix Duct for Lean Premixed and Prevaporized Combustion
Authors: Brandt M. , Gugel K. O. , Hassa C.
Published: February 2008

Liquid fuel evaporation was investigated in a premix duct, operating at conditions expected for lean premixed and prevaporized combustion. Results from a flat prefilming airblast atomizer are presented. Kerosine Jet A was used in all experiments. Air pressure, air temperature, and liquid fuel flow rate were varied separately; their relative influences on atomization, evaporation, and fuel dispersion are discussed. The results show that at pressures up to 15 bars and temperatures up to 850 K, nearly complete evaporation of the fuel was achieved, without autoignition of the fuel. For the configuration tested, the fuel distributions of the liquid and evaporated fuel show very little difference in their dispersion characteristics and were not much affected by a variation of the operating conditions.