bluuebunny/crossref_metadata_2025_split huggingface dataset:
NOX as a Function of Fuel Type: C1-to-C16 Hydrocarbons and Methanol
Authors: Lee John C. Y. , Malte Philip C. , Nicol David G. 
Published: December 2014

The response of NOX to fuel type is determined for lean-prevaporized-premixed combustion in on atmospheric pressure jet-stirred reactor (JSR). Pure, straight chain, alkane fuels from C1 (methane) to C16 (hexadecane) and methanol are tested. Testing is conducted under three conditions, each of which is obtained using a particular inlet-jet nozzle for the JSR. For a selected condition, the fuels are burned under nearly identical macroscopic thermal and fluid mechanical fields in the JSR. A constant mixture inlet total temperature is used that provides for complete vaporization of all of the fuels tested without causing pre-flame reactions in the premixer. Two of the nozzles used have single, centered jets and provide a nominal combustion temperature of 1790 K. The third nozzle has eight diverging jets. In this case, the fuel-air equivalence ratio is increased, providing a nominal combustion temperature of 1850 K.
Lowest levels of NOX are measured when methanol is burned. Upon switching to methane, the NOX concentration increases by 62±10%. For the alkane fuels, methane combustion yields the least amount of NOX. Upon switching from methane to ethane, the NOX increases by 22±2%. Further increases in the size of the alkane fuel molecule (from C2 to C16) show small increases (8±5%) in the NOX concentration. Although the JSR-condition selected affects the absolute NOX concentration, the trends in NOX concentration with respect to fuel-type are the same for the three conditions used.
The JSR is modeled as a single perfectly stirred reactor (PSR) operating at the experimental residence time and combustion temperature. This modeling shows that the increase in the NOX measured for the alkane fuels may be explained in terms of the increase in O-atom concentration with increasing C/H ratio. In order to explore the effect of Fenimore prompt NOX, a two-PSRs-in-series model is used. The first PSR is assigned a residence time equal to 5% the total residence time of the reactor. The second PSR accounts for the remaining 95% of the reactor residence time. Because of its short lifetime, the CH radical is effectively restricted to the first PSR, and prompt NOX mainly forms in this zone. Mechanisms directly dependent on the O-atom form NOX throughout the reactor. The modeling suggests that prompt NOX is responsible for the greater concentration of NOX found in the methane combustion compared to the methanol combustion.
Large-Eddy Simulation of Combustion Oscillation in Premixed Combustor
Authors: Murota Tomoya , Ohtsuka Masaya 
Published: December 2014

To analyze combustion oscillation in the premixed combustor, a large-eddy simulation program for premixed combustion flow was developed. The subgrid scale (SGS) model of eddy viscosity type for compressible turbulence (Speziale et al., 1988) was adopted to treat the SGS fluxes. The fractal flamelet model, which utilizes the fractal properties of the turbulent premixed flame to obtain the reaction rate, was developed.
Premixed combustion without oscillation was analyzed to verify the present method. The computational results showed good accordance with experimental data (Rydén et al., 1993).
The combustion oscillation of an “established buzz” type in the premixed combustor (Langhorne, 1988) was also analyzed. The present method succeeded in capturing the oscillation accurately. The detailed mechanism was investigated. The appearance of the non-heat release region, which is generated because the supply of the unburnt gas into the combustion zone stagnates, and its disappearance play an important role.
Fast Response Extraction Probe for Measurement of Air-Fuel Ratio Fluctuations in Lean Premixed Combustors
Authors: Mongia Rajiv , Torres John , Dibble Robert , Lee Darren , Anderson Torger , Sowa William 
Published: December 2014

The extent of air and fuel mixing prior to combustion in lean premixed combustion has been shown to drastically affect combustor performance, both in terms of emissions and stability. Standard extraction probes are often used for measuring the spatial (average over time) distribution of fuel concentration. However, the temporal fluctuations in fuel mole fraction, which are averaged by conventional extraction probes, have been also shown to drastically affect combustor performance. Several methods have been developed to measure the fluctuations in fuel mole fraction both temporally and spatially. These techniques are often difficult or impossible to apply to an operating combustor at high pressures and temperatures.
In this paper, we describe a Fast Response Extraction Probe (FREP) which is capable of measuring temporal mole fraction fluctuations up to frequencies of 1 kHz. A short, capillary tube is inserted into the premixing passage (which is at high pressure) for sampling the flow. The capillary tube is connected to a small gas cell at atmospheric pressure. Light from a 3.39 μm He-Ne laser is passed through the gas cell. By measuring the absorption of laser light, the concentration of hydrocarbons can be determined. The temporal response of the system is dependent on the geometry of the gas cell and sampling tube and the pressure drop through the sampling tube. A model for predicting the time response of the FREP is presented and compared to a laboratory scale experiment. The FREP was also tested in a high-pressure combustion rig at United Technologies Research Center. It is shown that the FREP is capable of measuring fuel-air fluctuations at gas turbine conditions. It is also shown that, at the conditions studied, there is a relationship between pressure oscillations and fuel mole fraction oscillations.
Detailed Experimental Studies of Flow in Large Scale Brush Seal Model and a Comparison With CFD Predictions
Authors: Chen L. H. , Wood P. E. , Jones T. V. , Chew J. W. 
Published: December 2014

A five times scale model of an engine brush seal has been manufactured. The bristle stiffness and pressure were chosen to satisfy close similarity of the relevant non-dimensional parameters, and the choice of parameters is described. The comparison of flow characteristics for the model seal and an engine seal confirmed the non-dimensional similarity.
Detailed pressure measurements were performed within the bristle pack by employing hollow bristles. This novel measurement allowed insight to be obtained into the operation of both clearance and interference seals. In particular, the measured pressure variation in the region of the bristle tips was significant. The deflection of the bristles was determined by comparing the bristle tip pressures with the static pressures along the shaft. Hence the compaction of the pack in this region was found directly.
A numerical modelling of brush seals employing anisotropic flow resistance has been developed. Predictions were compared with the measured pressure distributions within the pack. This enabled sensible selection of the pack resistance distribution to be made. Although uniform anisotropic resistance throughout the pack gave reasonable flow rate characteristics, the pressure distribution was not reproduced. A variation of resistance coefficient consistent with the observed compaction was required to give a solution comparable with the experiments.
The Use of Bio-Fuels as Additives and Extenders for Aviation Turbine Fuels
Authors: Kimble-Thom Melanie A. , Stanley David L. , Cholis John T. , Lopp Denver W. 
Published: December 2014

The use of biologically derived oils and fuels has received increasing visibility in recent years. A combination of fuel availability, refinery capacity and environmental responsibility has resulted in interest in their use in turbine engine fuels.
Such a soy methyl ester (SME) is being evaluated as a possible extender and/or additive for aviation turbine fuel per ASTM D-1655. Laboratory testing indicates additive levels of up to 2% by volume can be used while still meeting ASTM D-1655. Engine testing performed at 20% blending levels have demonstrated potential fuel consumption improvements as well as reduction in NOx emissions. The final blend levels have not yet been determined.
The use of SME even at low levels could provided performance benefits. Because of the oil nature of SME, a small addition could result in significant increases in lubricity. The use of the higher flashpoint SME could result in an upward shift in flashpoint with little or no effect to other physical properties. With increased visibility to work place considerations, the potential for “odor” abatement is also of interest.
U. S. Navy Marine Gas Turbine Qualification Testing for the 21st Century
Authors: Groghan Dan A. , Hartranft John J. 
Published: December 2014

Two primary topics are addressed in this paper:
1. A brief record of the evolution of U. S. Navy (USN) gas turbine qualification and testing requirements that helped produce the successful engines now in service and
2. Examination of these requirements in light of current and projected defense budgets resulting from changes in the world over the past twenty-five years.
The paper proposes changes in the current methods the USN employs in qualifying its gas turbines for surface ship applications. The proposed alternate methods consider commercial testing and service experience as well as testing based on MIL-E-17341 requirements. Finally, the marine gas turbine community is invited to begin a dialogue on the feasibility of these alternate methods.
A Case Study of Mixed Gas-Steam Cycle GT: LM6000 Class Aeroderivative Gas Turbine
Authors: Hanawa Kirk 
Published: December 2014

Many ideas were proposed to aim the generation thermal efficiency up to 60%, such as “Steam-Cooled H-Tech. Combined Cycle”, “Methanol Conversion Regenerative Gas Turbine”, “Kalina Cycle” etc.
The target thermal efficiency of 60% based upon LHV, could be also attained, when applying mixed gas-steam cycle like ISTIG and/or GAS3D for advanced aeroderivative gas turbines, which comprise of multiple shafts with overall pressure ratio more than 50, and TIT more than 2600 F (1700 K).
It might be meaningful to evaluate existing aeroderivative gas turbines like LM6000 etc. by applying such a improving concept, as the more advanced gas turbines to be derived from GE90, PW4000, and Trent800 are not available to date for land applications.
The intercooled ICAD GT of 77 MW was adopted as a base engine, and it was derived that the water /steam-injected WI/GAS3D GT version could produce 106 MW with 56% thermal efficiency, and it must be emphasized that the power curve in variation with ambient temperature is very flat than conventional GT plants.
Heat Transfer Over Non-Porous and Porous Smooth End Wall of a Linear Guide Vane in the Presence of Freestream Turbulence
Authors: Khalatov Artem A. , Shevtsov Sergey V. , Syred Nick 
Published: December 2014

The end wall of a gas turbine guide vane is one of turbine components where cooling is extremely complex due to a three-dimensional fluid flow and heat transfer nature. Most existing end wall heat transfer data were obtained over a non-porous surface with no effect of freestream turbulence. In real situations the typical turbulence level in front of a guide vane varies widely and reaches 25–30 % in some modern gas turbine engines. No doubt, this factor should be taken into account in the design of end wall cooling systems.
New experimental results are presented in this paper describing the effect of freestream turbulence on local heat transfer over non-porous and porous smooth end walls of the same configuration. A linear scaled-up model of a real gas turbine guide vane was employed in the experimental programme. Decay of the axial freestream turbulence in a space between adjacent blades was measured and two simplified versions of the experimental correction functions describing the effect of freestream turbulence on local end wall heat transfer were obtained. The derived correction functions include the axial component of freestream turbulence and should be envisaged as a first attempt to define quantitatively the effect of freestream turbulence over an end wall in different conditions. It was found that both correction functions are virtually identical and agree satisfactorily with the published experimental data, reflecting the effect of freestream turbulence over a flat plate. It confirms the approximately common character of freestream turbulence influence for different boundary conditions. It was concluded that further experimental studies of three-dimensional turbulent structure over an end wall for various boundary conditions are required to develop more exact correlations.
Computational Modeling and Thermal Paint Verification of Film-Cooling Designs for an Unshrouded High-Pressure Turbine Blade
Authors: Gegg Steven G. , Heidegger Nathan J. , Mikkelson Ronald A. 
Published: December 2014

High pressure turbine blades are exposed to an extreme high temperature environment due to increasing turbine inlet temperature. High heat fluxes are likely on the blade pressure surface. Other regions, such as the trailing edge and blade tip may be difficult to cool uniformly. Unshrouded blades present an additional challenge due to the pressure driven transport of hot gas across the blade tip. The blade tip region is therefore prone to severe thermal stress, fatigue and oxidation. In order to develop effective cooling methods, designers require detailed flow and heat transfer information.
This paper reports on computational aerodynamics and heat transfer studies for an unshrouded high pressure turbine blade. The emphasis is placed on the application of appropriate 3-D models for the prediction of airfoil surface temperatures. Details of the film cooling model, boundary conditions and data exchange with heat transfer models are described. The analysis approach has been refined for design use to provide timely and accurate results. Film cooling designs are to be tailored for the best coverage of the blade tip region. Designs include near-tip pressure side films and blade tip cooling holes. Hole placement and angle are investigated to achieve the best coolant coverage on the blade tip. Analytical results are compared to a thermal paint test on engine hardware. In addition to film cooling strategies, other aerodynamic/heat transfer design approaches are discussed to address the cooling requirements for an unshrouded blade.
Study of the Filtration Process Through a Ceramic Candle Filter
Authors: Al-Hajeri M. , Aroussi A. , Pickering S. J. 
Published: December 2014

Ceramic candle filters have been developed for cleaning high-temperature high-pressure (HTHP) gas streams. They meet environmental and economical considerations in Combined cycle power plant, where gas turbine blades can be protected from the erosion that occurs due to using HTHP exhaust from the fluidized bed. Ceramic candle filters are the most promising hot gas filtration technology, which has demonstrated high collection efficiencies at high-temperature high-pressure conditions.
This paper reports a computational fluid dynamics (CFD) investigation of a candle filter. Constant filtration velocity boundary models have been used to investigate the filter in cross flow conditions using the CFD code FLUENT. Different approach (inlet) velocity to filter face velocity ratios and different face velocities (ranging from 2 to 5 cm/s) are used in the CFD calculation. Particles in the diameter range 1 to 100 microns are tracked through the domain. The radius of convergence (or the critical trajectory) is compared and plotted as a function of many parameters. The deposition process and the factors that affect the build up of the filter cake have also been studied.
3D Modelling of NOx Emissions From an Aircraft Afterburner
Authors: Foster T. J. , Wilson C. W. , Pourkashanian M. , Williams A. 
Published: December 2014

Aircraft fitted with afterburner systems for increased thrust have been observed to have NOx emissions with a higher proportion of nitrogen dioxide (NO2) than non-augmented aircraft. These emissions are generally characterised by a brown plume and has implications for aircraft visibility and stealth as well as environmental considerations. This paper describes the CFD modelling of NOx emissions from a modern afterburner system with particular emphasis on the formation of nitric oxide (NO) and the subsequent conversion of NO to NO2.
A commercial CFD code, was used to solve a three dimensional model of a “burn then mix” afterburner system under investigation. A post processor package has been developed and was used to calculate both NO and NO2 concentrations. Four reheat settings were investigated; minimum, 25%, 50% and maximum reheat. For all conditions investigated the bulk of NOx emission was found in the core, stemming from the vitiated combustor air flow. NOx was also formed in the bypass stream, the production zone was found to be close to the fuel sprayers and flame stabiliser at minimum reheat, but moved downstream towards the exit nozzle as reheat power was increased. The model showed that for all the conditions under investigation, over 90% of the NOx produced in the reheat system was formed via the thermal-NO route.
The model has been compared with centre-line traverse data measured at the exit nozzle of the engine on a sea level static test bed. The predicted NOx emissions agreed quantitatively with the experimental measurements to within ± 5%.
A New Durable Gas Turbine Recuperator
Authors: Oswald James I. , Dawson David A. , Clawley Lee A. 
Published: December 2014

A new recuperator has been developed at Rolls-Royce, specifically designed to address the problems recuperators traditionally experience in withstanding thermal cycling and high cost associated with production complexity. Unlike existing recuperators it is made from two continuous sheets of metal wound into a spiral form. It is believed to be the only recuperator in the world manufactured as a continuous process and therefore has inherently lower cost. A significant increase in thermal fatigue resistance relative to state of the art recuperators is achieved due to the compliant structure and careful design of the heat exchanger matrix.
A technology acquisition programme has been carried out which has involved the design, manufacture and rig testing of recuperator cores. The success of the work is now leading to the continuation of the programme to address the application of this technology to specific engine developments from microturbines of 40kW to large industrial and marine turbines of 20MW.
Upgrading of a Small Size Gas Turbine to HAT Cycle Operation: Thermodynamic and Economic Analysis
Authors: Desideri Umberto , Di Maria Francesco 
Published: December 2014

A detailed study is presented in this paper concerning the changes required to transform a GE/Nuovo Pignone PGT2 gas turbine into a humid air turbine (HAT). The PGT2 is a 2 MW single-shaft gas turbine with a two stage centrifugal compressor and single can combustor. These features of the compressor and the combustion chamber are very important, because they reduce to a minimum the modifications necessary to add all the components required for operation in HAT cycle mode.
This paper shows the performance of the PGT2 gas turbine in three different modified configurations: 1) regenerated cycle, 2) intercooled-regenerated cycle and 3) HAT cycle with flue gas condensation. A detailed economic study is presented of the regenerated and the HAT cycles. The intercooled-regenerated cycle was not considered in the economic analysis, because it does not reach the performance of the HAT cycle but it has not the advantage of being a dry cycle.
All the components being added to the PGT2 are sized to determine with a sufficient accuracy their cost. The economic analysis presents a detailed cost analysis of the optimal configurations for maximum efficiency, and allows the calculation of the capital cost of the modified gas turbine. Return of investment is also presented in different economic situations with varying electricity and fuel prices.
The Influence of a Variable Capacity Turbine in the Performance of a Variable Cycle Engine
Authors: Dodds Martin , Pilidis Pericles 
Published: December 2014

An investigation was conducted to examine the effects of a variable flow low pressure turbine on a variable cycle engine’s performance.
One of the greatest challenges, during the design of a variable cycle engine is how to optimise the various cycles and then to match then to the capabilities of the engine components, the use of extensive variable geometry is required to achieve this.
A method of matching variable cycle engines that was developed Cranfield University was adapted to cater for the use of a variable flow low pressure turbine. It was discovered that the implementation of variable geometry within the low pressure turbine could significantly reduce the requirements for variable geometry within the compressor system, at the cost of replacing well proven compressor variable geometry with high risk technology within the LP turbine.
Utilising the variable flow turbine to expand the bypass ratio range of the engine was studied. Increasing the LPM bypass ratio to 1.1 and 1.2 yielded SFC reductions of 3% and 5% respectively, reducing the bypass ratio of the HPM to 0.1 gave a 20% increase in specific thrust. It was found that the performance benefits gained from expanding the bypass ratio are large enough to warrant further investigation into this concept.
Handling of a Semiclosed Cycle Gas Turbine With a Carbon Dioxide-Argon Working Fluid
Authors: Ulizar Inaki , Pilidis Pericles 
Published: December 2014

This paper outlines the handling of a semi closed cycle gas turbine, its working fluid is carbon dioxide and the fuel is low heating value gas from coal. At startup however, air and natural gas are used. The objective of the machine is to produce clean electricity with the smallest efficiency penalty.
Many aspects of the operation of the engine are examined here; these include starting requirements, stator vane and bleed valve scheduling and the working fluid transition from air to carbon dioxide. Other features highlighted are the compressor operating lines and surge margins. The present paper describes the salient features of the three main stages into which the engine operation has been divided. These stages are: startup to synchronous idle, change of working fluid (from air to Carbon Dioxide-Argon) and fuel (from natural gas to coal synthetic gas) at synchronous idle and part load operation.
Preliminary findings show that engine handling can be carried out effectively with variable stators. This is possible because of the two shaft gas generator. Another point of interest is the large increase of corrected speed relative to rotational speed experienced when the working fluid changes from air to carbon dioxide. In general the control of the engine does not seem to present any insurmountable problems despite the complexities arising from the need to change working fluid and fuel.