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Author: Anandkumar Makwana
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Stricter environmental requirements, worldwide air traffic growth, and unsteady fuel prices all has led to an increased interest in alternative jet fuels. Additionally, several nations are investing resources identifying local fuel sources to make the fuel supply more resilient against disruptions and flexible to use of multiple, reliable fuel stocks. The alternative jet fuels that are being defined have unusual molecular distributions relative to current fuels. These differences in molecular structure affect the gas-phase kinetics during combustion, and hence the use of alternative fuels can impact emissions differently than conventional fuels. The differences in the emission characteristics between a newly developed alternative fuel and conventional fuel highlight the need to focus the research efforts on understanding how the fundamental properties of the fuel can affect emissions. The current work focuses on investigating the chemical effects of fuel molecular structure on the emission behavior of the fuels. In particular, the study explores how the fuel composition and premixing affect the production of polycyclic aromatic hydrocarbons (PAH), hazardous air pollutants (HAPs), and soot in a combustion environment. The study uses two experimental configurations: a jet flame and a model gas turbine combustor. Laser induced incandescence (LII) and laser extinction (LE) are used to obtain two-dimensional soot volume fraction in the flames. Laser induced fluorescence (LIF) is used to obtain the two-dimensional aromatic species distribution in the flames. Additionally, numerical analysis is used to investigate the effects of premixing on the soot formation processes in the jet flames for a high molecular weight fuel.
Author: Anandkumar Makwana
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Stricter environmental requirements, worldwide air traffic growth, and unsteady fuel prices all has led to an increased interest in alternative jet fuels. Additionally, several nations are investing resources identifying local fuel sources to make the fuel supply more resilient against disruptions and flexible to use of multiple, reliable fuel stocks. The alternative jet fuels that are being defined have unusual molecular distributions relative to current fuels. These differences in molecular structure affect the gas-phase kinetics during combustion, and hence the use of alternative fuels can impact emissions differently than conventional fuels. The differences in the emission characteristics between a newly developed alternative fuel and conventional fuel highlight the need to focus the research efforts on understanding how the fundamental properties of the fuel can affect emissions. The current work focuses on investigating the chemical effects of fuel molecular structure on the emission behavior of the fuels. In particular, the study explores how the fuel composition and premixing affect the production of polycyclic aromatic hydrocarbons (PAH), hazardous air pollutants (HAPs), and soot in a combustion environment. The study uses two experimental configurations: a jet flame and a model gas turbine combustor. Laser induced incandescence (LII) and laser extinction (LE) are used to obtain two-dimensional soot volume fraction in the flames. Laser induced fluorescence (LIF) is used to obtain the two-dimensional aromatic species distribution in the flames. Additionally, numerical analysis is used to investigate the effects of premixing on the soot formation processes in the jet flames for a high molecular weight fuel.
Author: Meredith Colket
Publisher:
ISBN: 9781624106033
Category : Fuel switching
Languages : en
Pages : 0
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Book Description
In summarizing the results obtained in the first five years of the National Jet Fuel Combustion Program (NJFCP), this book demonstrates that there is still much to be learned about the combustion of alternative jet fuels.
Author: Yefu Wang
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
This study is part of a larger effort to establish a science-based model to predict the emissions from gas turbine engine combustors using alternative fuels. In order to validate and improve the chemical mechanisms in the model, four binary fuel mixtures comprised of the hydrocarbon compounds representative of the classes compounds that are expected in alternative aviation fuels. In each fuel mixture, n-dodecane was the base component. The second component was m-xylene, methylcyclohexane, iso-octane, or n-heptane that were selected to represent the molecular structures of aromatic, cyclo-paraffin, iso-paraffin, and n-paraffin. The binary fuel mixture (25% m-xylene and 75% n-dodecane in liquid volume fraction) was also evaluated as a surrogate for JP-8. A burner system was developed and built to produce co-flow laminar jet flames with liquid fuel mixtures. The experimental conditions for flames were set at three equivalence ratios ([phi]) of the fuel jet--[phi]=[infinity symbol], [phi]=6, and [phi]=2--to simulate the soot-rich zones in gas turbine engine combustors. The combination of laser extinction and laser-induced incandescence (LII) was applied to obtain the spatial distributions of soot volume fraction quantitatively. "Small aromatics" and "large aromatics," containing 1-2 aromatic rings and 3-4 aromatic rings respectively, were detected by laser-induced fluorescence (LIF). A special configuration of thermocouple probe was developed to obtain the temperature distributions in the soot-free regions of the flames. Experimental results indicated that the PAH and soot from all paraffin fuels are similar, but PAH and soot of the aromatic fuel were much larger than for the paraffin fuels. The amount of soot was found to be higher in aromatic flames than in paraffin flames by a factor of between 2-4. The maximum LIF signals from both small and large aromatics along centerline were found to be approximately ten times higher in the aromatic fuel than in paraffin fuels. Similar results, especially soot volume fraction distributions, was found between JP-8 and the m-xylene/n-dodecane fuel. The experimental results were compared in detail to simulation results provided by Dr. Katta of Innovative Scientific Solutions, Inc. Basic consistent distribution trends for each fuel mixture were established with the simulation results. Similar qualitative distributions of soot volume fraction and semi-quantitative LIF signals from aromatic species as well as temperature were found for flames burnt with all fuel mixtures, even though the simulation always displayed large areas of soot and aromatics existing regions. The maximum soot volume fraction along centerline in flames was estimated with values similar to experimental data for paraffin fuels. Several potential explanations were produced for the significant discrepancy of soot distributions in aromatic flames between the simulation and experimental data. Other simulation results, including the distributions of OH and rates of soot nucleation, soot surface growth, and soot oxidation were presented to gain insight into the reasons for the discrepancies between the simulations and the experiment.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 10
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Author: Francesco Montomoli
Publisher: Springer
ISBN: 3319929437
Category : Technology & Engineering
Languages : en
Pages : 204
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Book Description
This book introduces design techniques developed to increase the safety of aircraft engines, and demonstrates how the application of stochastic methods can overcome problems in the accurate prediction of engine lift caused by manufacturing error. This in turn addresses the issue of achieving required safety margins when hampered by limits in current design and manufacturing methods. The authors show that avoiding the potential catastrophe generated by the failure of an aircraft engine relies on the prediction of the correct behaviour of microscopic imperfections. This book shows how to quantify the possibility of such failure, and that it is possible to design components that are inherently less risky and more reliable. This new, updated and significantly expanded edition gives an introduction to engine reliability and safety to contextualise this important issue, evaluates newly-proposed methods for uncertainty quantification as applied to jet engines. Uncertainty Quantification in Computational Fluid Dynamics and Aircraft Engines will be of use to gas turbine manufacturers and designers as well as CFD practitioners, specialists and researchers. Graduate and final year undergraduate students in aerospace or mathematical engineering may also find it of interest.
Author: Exxon Research and Engineering Company. Government Research Laboratories
Publisher:
ISBN:
Category : Combustion
Languages : en
Pages : 148
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Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 704
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Book Description
Author: Timothy C. Lieuwen
Publisher: Cambridge University Press
ISBN: 052176405X
Category : Science
Languages : en
Pages : 385
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Book Description
The development of clean, sustainable energy systems is a preeminent issue in our time. Gas turbines will continue to be important combustion-based energy conversion devices for many decades to come, used for aircraft propulsion, ground-based power generation, and mechanical-drive applications. This book compiles the key scientific and technological knowledge associated with gas turbine emissions into a single authoritative source.
Author:
Publisher:
ISBN:
Category : Mechanics, Applied
Languages : en
Pages : 400
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Book Description
Author: Shazib Z. Vijlee
Publisher:
ISBN:
Category : Flame stability
Languages : en
Pages : 206
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Book Description
Synthetic jet fuels are studied to help understand their viability as alternatives to traditionally derived jet fuel. Two combustion parameters - flame stability and NOX emissions - are used to compare these fuels through experiments and models. At its core, this is a fuels study comparing how chemical makeup and behavior relate. Six 'real', complex fuels are studied in this work - four are synthetic from alternative sources and two are traditional from petroleum sources. Two of the synthetic fuels are derived from natural gas and coal via the Fischer Tropsch catalytic process. The other two are derived from Camelina oil and tallow via hydroprocessing. The traditional military jet fuel, JP8, is used as a baseline as it is derived from petroleum. The sixth fuel is derived from petroleum and is used to study the effects of aromatic content on the synthetic fuels. The synthetic fuels lack aromatic compounds, which are an important class of hydrocarbons necessary for fuel handling systems to function properly. Several single-component fuels are studied (through models and/or experiments) to facilitate interpretation and understanding. Methane is used for detailed modeling as it has a relatively small and well-understood chemical kinetic mechanism. Toluene, iso-octane, n-octane, propylcyclohexane, and 1,3,5-trimethylbenzene are included as they are all potential surrogates for jet fuel components. The flame stability study first compares all the `real', complex fuels for blowout. A toroidal stirred reactor is used to try and isolate temperature and chemical effects. The reactor has a volume of 250 mL and a residence time of approximately 8.0 ms. The air flow rate is held constant such that the inlet jets are sonic and turbulent mixing is present throughout the reactor. The fuel flow rate (hence equivalence ratio) is slowly lowered until the flame cannot sustain itself and it extinguishes. The results show that there is very little variation in blowout temperature and equivalence ratio for the synthetic fuels when compared to JP8 with low levels (0, 10, and 20%) of the aromatic additive. However, the 100% aromatic fuel behaved significantly differently and showed a lower resistance to blowout (i.e., it blew out at a higher temperature and equivalence ratio). The modeling study of blowout in the toroidal reactor is the key to understanding any fuel-based differences in blowout behavior. A detailed, reacting CFD model of methane is used to understand how the reactor stabilizes the flame and how that changes as the reactor approaches blowout. A 22 species reduced form of GRI 3.0 is used to model methane chemistry. The model shows that the reactor is quite homogenous at high temperatures, far away from blowout, and the transport of chain-initiating and chain-branching radical species is responsible for stabilizing the flame. Particularly, OH radical is recirculated around the reactor with enough concentration and at a high enough rate such that the radicals interact with the incoming fuel/air and initiate fuel decomposition. However, as equivalence ratio decreases, the reactor begins to behave in a more zonal nature and the radical concentration/location is no longer sufficient to initiate or sustain combustion. The knowledge of the radical species role is utilized to investigate the differences between a highly aliphatic fuel (surrogated by iso-octane) and a highly aromatic fuel (surrogated by toluene). A perfectly stirred reactor model is used to study the chemical kinetic pathways for these fuels near blowout. The differences in flame stabilization can be attributed to the rate at which these fuels are attacked and destroyed by radical species. The slow disintegration of the aromatic rings reduces the radical pool available for chain-initiating and chain-branching, which ultimately leads to an earlier blowout. The NOX study compares JP8, the aromatic additive, the synthetic fuels with and without an aromatic additive, and an aromatic surrogate (1,3,5-trimethylbenzene). A jet stirred reactor is used to try and isolate temperature and chemical effects. The reactor has a volume of 15.8 mL and a residence time of approximately 2.5 ms. The fuel flow rate (hence equivalence ratio) is adjusted to achieve nominally consistent temperatures of 1800, 1850, and 1900K. Small oscillations in fuel flow rate cause the data to appear in bands, which facilitated Arrhenius-type NOX-temperature correlations for direct comparison between fuels. The fuel comparisons are somewhat inconsistent, especially when the aromatic fuel is blended into the synthetic fuels. In general, the aromatic surrogate (1,3,5-trimethylbenzene) produces the most NOX, followed by JP8. The synthetic fuels (without aromatic additive) are always in the same ranking order for NOX production (HP Camelina > FT Coal > FT Natural Gas > HP Tallow). The aromatic additive ranks differently based on the temperature, which appears to indicate that some of the differences in NOX formation are due to the Zeldovich NOX formation pathway. The aromatic additive increases NOX for the HP Tallow and decreases NOX for the FT Coal. The aromatic additive causes increased NOX at low temperatures but decreases NOX at high temperatures for the HP Camelina and FT Natural Gas. A single perfectly stirred reactor model is used with several chemical kinetic mechanisms to study the effects of fuel (and fuel class) on NOX formation. The 27 unique NOX formation reactions from GRI 3.0 are added to published mechanisms for jet fuel surrogates. The investigation first looked at iso-octane and toluene and found that toluene produces more NOX because of a larger pool of O radical. The O radical concentration was lower for iso-octane because of an increased concentration of methyl (CH3) radical that consumes O radical readily. Several surrogate fuels (iso-octane, toluene, propylcyclohexane, n-octane, and 1,3,5-trimethylbenzene) are modeled to look for differences in NOX production. The trend (increased CH3→ decreased O → decreased NOX) is consistently true for all surrogate fuels with multiple kinetic mechanisms. It appears that the manner in which the fuel disintegrates and creates methyl radical is an extremely important aspect of how much NOX a fuel will produce.
