bluuebunny/crossref_metadata_2025_split huggingface dataset:
Local and Mean Heat Transfer Coefficients Along the Internal Housing Walls of Aero Engine Bearing Chambers
Authors: Glahn A. , Busam S. , Wittig S. 
Published: December 2014

A proper matching of the heat transfer to the lubrication oil in bearing chambers and subsequent vent and scavenge pipes is one of the major tasks in the design process of secondary air/lubrication oil systems of modern jet engines. For a calculation of lubrication oil flow rates, which should be kept as small as possible in order to reduce parasitic losses due to larger pumps, filters and coolers, a sufficient knowledge of all heat transfer phenomena involved in bearing chamber flows is required. Beside heat sources such as the bearing friction, the heated sealing air flow and the churning and ventilation of two-phase mixtures, the heat transfer at the housing walls has to be considered. The present paper deals with an experimental investigation of the latter effect based on engine relevant pressure and temperature levels bearing chamber operating conditions. Air/oil flow heat transfer measurements at the internal bearing chamber walls are described utilizing the temperature gradient method. It is a stationary technique based on a two-dimensional finite element calculation procedure.
Influences of sealing air flow rate, lubrication oil flow rate and rotational speed on local heat transfer coefficients are discussed. Mean heat transfer coefficients that have been calculated from local data are presented in terms of operational parameters.
Effects of Ambient Conditions and Fuel Composition on Combustion Stability
Authors: Janus Michael C. , Richards George A. , Yip M. Joseph , Robey Edward H. 
Published: December 2014

Recent regulations on NOx emissions are promoting the use of lean premix (LPM) combustion for industrial gas turbines. LPM combustors avoid locally stoichiometric combustion by premixing fuel and air upstream of the reaction region, thereby eliminating the high temperatures that produce thermal NOx. Unfortunately, this style of combustor is prone to combustion oscillation. Significant pressure fluctuations can occur when variations in heat release periodically couple to acoustic modes in the combustion chamber. These oscillations must be controlled because resulting vibration can shorten the life of engine hardware.
Laboratory and engine field testing have shown that instability regimes can vary with environmental conditions. These observations prompted this study of the effects of ambient conditions and fuel composition on combustion stability. Tests are conducted on a subscale combustor burning natural gas, propane, and some hydrogen/hydrocarbon mixtures. A premix, swirl-stabilized fuel nozzle typical of industrial gas turbines is used. Experimental and numerical results describe how stability regions may shift as inlet air temperature, humidity, and fuel composition are altered. Results appear to indicate that shifting instability regimes are primarily caused by changes in reaction rate.
The Turbulence That Matters
Authors: Mayle R. E. , Dullenkopf K. , Schulz A. 
Published: December 2014

A unified expression for the spectrum of turbulence is developed by asymptotically matching known expressions for small and large wave numbers, and a formula for the one-dimensional spectral function which depends on the turbulence Reynolds number Reλ is provided. In addition, formulas relating all the length scales of turbulence are provided. These relations also depend on Reynolds number.
The effects of free-stream turbulence on laminar heat transfer and pre-transitional flow in gas turbines are re-examined in light of these new expressions using our recent thoughts on an ‘effective’ frequency of turbulence and an ‘effective’ turbulence level. The results of this are that the frequency most effective for laminar heat transfer is about 1.3U/Le, where U is the free-stream velocity and Le is the length scale of the eddies containing the most turbulent energy, and the most effective frequency for producing pre-transitional boundary layer fluctuations is about 0.3U/η where η is Kolmogorov’s length scale. In addition, the role of turbulence Reynolds number on stagnation heat transfer and transition is discussed, and new expressions to account for its effect are provided.
Active Stabilization of Axial Compressors With Circumferential Inlet Distortion
Authors: van Schalkwyk C. M. , Paduano J. D. , Greitzer E. M. , Epstein A. H. 
Published: December 2014

This paper describes the first experimental validation of transfer function modeling and active stabilization for axial compressors with circumferential inlet distortion. The inlet distortion experiments were carried out in a three stage low-speed compressor. Theory-experiment comparisons of steady performance, unsteady stall precursor, and forced response (transfer function) data were all used to assess a control-theoretic version of the Hynes-Greitzer distorted flow model. The tests showed good agreement between theory and data and demonstrated that a priori predictions, based on geometry and steady-state performance data, can be used to design control laws which stabilize rotating stall with inlet distortion.
Based on these results, active feedback control has been used to stabilize the inlet distortion induced instability associated with rotating stall onset. The stabilization allowed stall free operation to be extended below the natural (distorted flow) stall point by up to 3.7% for a 0.8 dynamic head distortion. For a 1.9 dynamic head distortion, 40% of the mass flow range lost due to inlet distortion was regained through active control. The paper elucidates the difficulties associated with active control with distortion, and introduces a new control law that addresses many of these challenges.
Experiments in Active Control of Stall on an Aeroengine Gas Turbine
Authors: Freeman Christopher , Wilson Alexander G. , Day Ivor J. , Swinbanks Malcolm A. 
Published: December 2014

This paper describes work carried out between 1989 and 1994 to investigate the application of ‘Active Stall Control’ to a Rolls-Royce Viper turbojet. The results demonstrate that stall control is feasible and can increase the stable operating range by up to 25% of pressure rise. Stall disturbances were detected using rings of high response pressure transducers positioned at different axial planes along the compressor, and processed using a PC-based data acquisition and control system. Actuation was provided by six hydraulically operated sleeve valves positioned to recirculate air over all or part of the compressor.
Stall was artificially induced using combinations of inbleed into the combustor outer casing, fuel spiking, hot gas ingestion and inlet pressure spoiling, thus replicating many of the transient conditions commonly observed to make a compressor prone to stall. Results are compared from a number of stall control strategies including those demonstrated at low speed by Paduano et al [1993] and Day [1993]. Best results were obtained with detection of non-axisymmetric disturbances coupled with axisymmetric control action. A control system of this type is demonstrated to be capable of extending the stable engine operating range at all speeds and with each method of inducing stall.
Experimental Investigation and Mathematical Modelling of Clearance Brush Seals
Authors: Turner Mike T. , Chew John W. , Long Chris A. 
Published: December 2014

In this paper an experimental programme and a CFD based mathematical model using a brush seal at two bristle to rotor clearances (0,27 mm. and 0,75 mm.), are presented. The experimental programme examined the radial pressure distributions along the backing ring, the axial pressure distribution along the rotor, and the mass flow through the seal, through a range of pressure ratios while exhausting to atmosphere.
The results from this experimental programme have been used to further calibrate a CFD based model. This model treats the bristle pack as an axisymmetric, anisotropic porous region, and is calibrated by the definition of non-linear resistance coefficients in three orthogonal directions. The CFD analysis calculates the aerodynamic forces on the bristles, which are subsequently used in a separate program to estimate the bristle movements, stresses and bristle and rotor loads.
The analysis shows that a brush seal with a build clearance produces a very different flow field within the bristle pack to one with an interference, and the need to understand the bulk movements of the bristles. These are shown to be affected by the level of friction between the bristles and the backing ring, which has an important effect on the bristles wear and seal leakage characteristics.
Biomass-Fired Atmospheric Gas Turbine Plant-I
Authors: Fesharaki M. , Halozan H. , Jericha H. , Kulhanek G. 
Published: December 2014

Considering the expected climate change, biomass is one of the promising energy sources for the future. However, burning and only producing low temperature heat means wasting exergy. To utilise this renewable fuel, highly efficient cogeneration plants are requierd. Existing, small and medium sized power generation systems using gas turbines, have, either complicated flow schemes, or problems with fuel charging of pressurised combustion chambers, which are yet to be solved.
Here is a solution is presented requiring no preparation of the biomass fuel. In several publications (Jericha 1991, Fesharaki 1995, Fesharaki 1996) the inverted gas turbine cycle has been presented. This project deals with the investigation and the development of an atmospheric biomass combustion chamber, combined with an inverted gas turbine cycle. The system consists of a combustor with wood grate firing, working at atmospheric pressure. The exhaust gas from the combustor, with a temperature of 1050 °C, is cooled by water or steam injection, to a temperature of 730 °C. The exhaust gas is purified in a cyclone and expanded in a gas turbine to a pressure of 0.3 to 0.4 bar. The exhaust gas of the turbine can be used for operating a single-pressure steam generator, and for district heating. The exhaust gas is purified again by condensing the moisture in the exhaust gas, which stems from the biomass and the steam, or water injection after the combustion chamber. The purified gas is recompressed to atmospheric pressure, which is used for combustion-air preheating. With such a system a high electrical efficiency can be achieved, dependent upon the turbo machines, and the use of an additional bottoming steam cycle.
Considering the Austrian situation a feasibility study is being carried out. Special attention has been paid to:
Turbine design,
Exhaust gas purification,
and the cycle control. The feasibility study shows, that this concept is practicable, and that several biomass existing heating systems in Austria could be converted for production of electricity.
A Comparison of the Influence of Fuel/Air Unmixedness on NOx Emissions in Lean Premixed, Non-Catalytic and Catalytically Stabilized Combustion
Authors: Schlegel A. , Streichsbier M. , Mongia R. , Dibble R. 
Published: December 2014

Experimental results on the influence of temporal unmixedness on NOx emissions are presented for both non-catalytic and catalytically stabilized, lean premixed combustion. The test rig used for the experiments consists of a fuel/air mixing section which allows variation of the degree of temporal unmixedness while maintaining a uniform “average over time” concentration profile over the cross section at the inlet to the combustion chamber. The unmixedness is measured as “rms fluctuations in fuel concentration” by an optical probe using laser absorption at 3.39μm over a 9mm gap. “Average over time” measurements are taken with “conventional” suction probe analyzers. The combustion chamber is an insulated, tubular reactor (i.d. 26.4mm). At the inlet to the combustion chamber a honeycomb monolith section is inserted. This monolith is either catalytically active or inactive for catalytically stabilized or non-catalytic combustion respectively. For both modes, the exact same inlet conditions are applied. In catalytically stabilized combustion a fraction of the fuel is consumed within the catalyst and the remaining fuel is burnt in the subsequent homogeneous combustion zone.
It is shown that catalytically stabilized combustion yields lower NOx emissions and, more important, that the effect of temporal fuel/air unmixedness on NOx emissions is much smaller than with non-catalytic combustion under identical inlet conditions. Experimental evidence leads to the conclusion, that the catalyst is capable of reducing temporal fluctuations in fuel concentration and/or temperature in the combustion process, thereby preventing excess NOx formation. As a result, the requirements on mixing quality are less stringent when using catalytically stabilized combustion instead of conventional, non-catalytic combustion.
Computational and Experimental Evaluation of Integral Catalytic Ignitor/Injector for Gas Turbine Applications
Authors: Jackson Greg S. , Etemad Shahrokh , Karim Hasan , Pfefferle William C. 
Published: December 2014

The provision of an ignition source in the central region of a liquid-fired combustor reduces the requirement for wide spray angles, rich primary zones, and their associated performance drawbacks such as high levels of soot and NOx formation and high liner wall temperatures. Various ignition devices have been considered for providing centrally located ignition sources. The current paper presents a study of one alternative concept — the integral catalytic torch ignitor/injector — as a means for providing both combustor light-off and enhanced flame stability in the combustor primary zone.
An integral catalytic torch in a fuel injector offers the potential to significantly improve ignition arid flame stability and thus the opportunity to operate combustor primary zones at leaner conditions, which may improve emissions, pattern factor, and combustor liner durability. This paper presents computational and experimental results for a conventional liquid-fired combustor with the addition of a catalytic torch (replacing the pilot pressure atomizer) down the centerline of an air-blast fuel injector. The benefits of a lean primary zone with an integral catalytic torch/injector were investigated both computationally and experimentally by comparing combustor performance with standard and successively leaner primary zones. Pattern factor and emissions are compared with different primary zone jet configurations to observe if the central torch can enhance the operability of leaner primary zones in conventional combustor geometries. The experimental and computational results suggest that the integral catalytic torch can provide more than adequate ignition capabilities with improved combustor emissions when it is combined with a relatively lean operating primary zone.
Low Emissions Combustion System for the Allison ATS Engine
Authors: Smith Duane A. , Frey Steve F. , Stansel David M. , Razdan Mohan K. 
Published: December 2014

This paper describes the development of an ultra-low emissions combustion system for Allison’s Advanced Turbine System (ATS) engine, which is being developed in cooperation with the U.S. Department of Energy. The simple cycle engine is designed to have a thermal efficiency that is 15% better than today’s best in class engine, and exhaust emissions of 9 ppm NOx, 20 ppm CO, and 20 ppm UHC. The approach taken to meet the low emissions goals is based on ultra-lean premixed fuel-air combustion supported by a catalyst. The progress toward development and integration of lean premix (LPM), catalytic and post-catalytic stages, and the combustor-to-turbine transition duct into an overall ATS combustion system is presented.
A parametric computational fluid dynamics (CFD) study was conducted on the performance of lean premix modules at ATS conditions. Various lean premix modules were tested extensively under atmospheric conditions to determine airflow capacity, flashback propensity, lean blowout (LBO) fuel-air ratios, and fuel concentration profiles at the module exit. Kinetic modeling using the GRI mechanism has been used to estimate ignition delay times in the post-catalytic zone. Comparison between the modeling results and experimental data at high pressure shows good agreement. A detailed computational analysis was performed to design the combustion-to-turbine transition duct. The results indicate that the scroll duct configuration produces an acceptable mass flow uniformity and swirl angle exiting the duct into the turbine section. High pressure sector rig tests have been performed to evaluate staging interaction issues. The results indicate that the series staged approach can facilitate incorporation of the catalytic combustion system by expanding the operability range. NOx emissions levels of 9 ppm or less can be sustained over a wide range of equivalence ratios.
Once-Through Heat Recovery Steam Generators Working With Sub- and Supercritical Steam Conditions for Combined Cycles
Authors: Dechamps P. J. , Galopin J.-F. 
Published: December 2014

This paper characterizes the performances of once-through heat recovery steam generators in combined cycle applications. Although the concept of once-through boilers has been extensively used for fired boilers, this circulation mode is rather new in combined cycles.
Once-through circulation is required at very high pressures, including supercritical conditions, for which there is a possible advantage in terms of the plant efficiency. The concept is also certainly the best solution for high subcritical pressures, such as those required by repowering applications.
In addition to cycle performance, this paper describes the advantages and disadvantages of the once-through in heat recovery applications. The operational behaviour of such heat recovery steam generators is discussed, together with the main design implications.
A prototype plant running in supercritical steam conditions is also described, as well as some of its possible applications.
First V84.3A Gas Turbine Installation at Hawthorn Station
Authors: Johnson T. , Becker B. , Seume J. , Termuehlen H. 
Published: December 2014

The first V84.3A gas turbine as tested at the full-load test facility of the Siemens gas turbine factory in Berlin, Germany has now been installed at the Kansas City Power & Light (KCP&L) Company’s Hawthorn Power Station. The unit will be started in spring of this year and is scheduled to be available in June for the 1997 summer peak.
In times when active power is not in demand, the generator can be operated as a synchronous condenser. For this mode of operation, a synchronous clutch has been installed between the gas turbine and the generator.
The advanced V84.3A gas turbine has been chosen because of its high simple cycle efficiency based on the measured 38% in the test facility, providing peaking capacity with a minimum on fuel costs. In addition, later conversion to highly efficient combined cycle operation can easily be performed without the need for external air or even steam cooling systems.
High Efficiency-Coal and Gas (HE-C&G): An Advanced Hybrid Power Plant Concept With Sequential Combustion Gas Turbines GT24/GT26
Authors: Fetescu Mircea 
Published: December 2014

The High Efficiency-Coal and Gas (HE-C&G) is a hybrid power plant concept integrating Conventional Steam Power Plants (CSPP) and gas turbine / combined cycle plants. The gas turbine exhaust gas energy is recovered in the HRSG providing partial condensate and feedwater preheating and generating steam corresponding to the main boiler live steam conditions (second steam source for the ST).
The concept, exhibiting very high design flexibility, integrates the high performance Sequential Combustion gas turbines GT24/GT26 technology into a wide range of existing or new CSPP.
Although HE-C&G refers to coal as the most abundant fossil fuel resource, oil or natural gas fired steam plants could be also designed or converted following the same principle.
The HE-C&G provides very high marginal efficiencies on natural gas, up to and above 60%, very high operating and dispatching flexibility and on-line optimization of fuel and O&M costs at low capital investment.
This paper emphasizes the operating flexibility and resulting benefits, recommending the HE-C&G as one of the most profitable options for generating power especially for conversion of existing CSPP with gas turbines.
Effects of Engine Aging on Aircraft NOx Emissions
Authors: Lukachko Stephen P. , Waitz Ian A. 
Published: December 2014

The impact of representative paths of engine degradation on aircraft cruise NOx emissions was investigated. Engine cycles corresponding to older, current, and future subsonic and supersonic technologies were developed and used to determine the sensitivities of combustor conditions to various changes in component efficiencies and flow capacities due to aging. Estimates of relative changes in NOx emissions levels were made using established empirical correlations that relate emissions to combustor flow parameters. The analysis methodology was validated through comparisons to test data where available.
It was found that the sensitivity of specific fuel consumption (SFC) and combustor flow parameters to component aging is enhanced by increases in cycle temperatures and pressures. This ultimately results in a higher sensitivity of NOx emissions to engine degradation for cycles representative of more advanced technology. At constant thrust, turbine degradation typically acts to decrease NOx emissions while compressor aging results in an increase in NOx emissions; both occurring at the expense of SFC. Sample degradation scenarios were used to highlight the balance between turbine and compressor aging effects. Changes in NOx emissions in the −1% to +4% range were predicted for typical aging scenarios. The applicability of these results to the formulation of aircraft emissions inventories is considered.
Automatic Genetic Optimization Approach to 2D Blade Profile Design for Steam Turbines
Authors: Trigg M. A. , Tubby G. R. , Sheard A. G. 
Published: December 2014

In this paper a systematic approach to the optimization of 2D blade profiles is presented. A genetic optimizer has been developed which modifies the blade profile and calculates its profile loss. This process is automatic, producing profile designs significantly faster and with significantly lower loss than has previously been possible.
The optimizer developed uses a genetic algorithm to optimize a 2D profile, defined using 17 parameters, for minimum loss with a given flow condition. The optimizer works with a “population” of 2D profiles with varied parameters. A CFD mesh is generated for each profile, and the result is analyzed using a 2D blade to blade solver, written for steady viscous compressible flow, to determine profile loss. The loss is used as the measure of a profile’s “fitness”. The optimizer uses this information to select the members of the next population, applying crossovers, mutations, and elitism in the process. Using this method the optimizer tends towards the best values for the parameters defining the profile with minimum loss.