Other affiliations: Michigan State University, Sharif University of Technology, Princeton University ...read more
Bio: Saeed Jahangirian is an academic researcher from Ansys. The author has contributed to research in topics: Combustion & Diffusion flame. The author has an hindex of 9, co-authored 19 publications receiving 502 citations. Previous affiliations of Saeed Jahangirian include Michigan State University & Sharif University of Technology.
TL;DR: In this paper, a surrogate fuel is formulated in an a priori manner through a combustion property matching technique to emulate the gas phase chemical kinetic combustion phenomena of S-8 POSF 4734, an alternative aviation fuel derived from natural gas via the Fischer-Tropsch process.
Abstract: A surrogate fuel is formulated in an a priori manner through a combustion property matching technique to emulate the gas phase chemical kinetic combustion phenomena of S-8 POSF 4734, an alternative aviation fuel derived from natural gas via the Fischer–Tropsch process. A fundamental concept is described which identifies n-dodecane and iso-octane as being appropriate surrogate fuel components for the non-aromatic synthetic fuels. The performance of the formulated 51.9/48.1 mole % n-dodecane/iso-octane mixture as a surrogate for the target real fuel is evaluated by the measurement of a series of combustion phenomena exhibited by both fuels including: (1) The oxidative reactivity of stoichiometric mixtures of each fuel in O2/N2 at 12.5 atm and 500–1050 K, for a residence time of 1.8 s at a fixed carbon content of 0.3% using a variable pressure flow reactor. (2) The autoignition behavior of stoichiometric mixtures of each fuel in air at compressed conditions of 667–1223 K and ∼20 atm by the reflected shock technique. (3) The strained extinction limits of diffusion flames of each fuel at 1 atm. The performance of available kinetic models for n-dodecane/iso-octane mixtures is evaluated by analysis of their computations of this experimental data. Furthermore, the impact of oxidation kinetics unique to the mono methylated alkanes which are the dominant molecular structure in synthetic fuels is examined by an experimental study involving the formulation of an n-decane/iso-octane mixture as a surrogate fuel for 2-methyl heptane, a proposed model molecule for such real fuel components.
TL;DR: In this article, two sets of experiments are described, one involving flame spread in a Narrow Channel Apparatus (NCA) in normal gravity, and the other taking place in actual microgravity.
Abstract: Most previous research on flame spread over solid surfaces has involved flames in open areas. In this study, the flame spreads in a narrow gap, as occurs in fires behind walls or inside electronic equipment. This geometry leads to interesting flame behaviors not typically seen in open flame spread, and also reproduces some of the conditions experienced by microgravity flames. Two sets of experiments are described, one involving flame spread in a Narrow Channel Apparatus (NCA) in normal gravity, and the others taking place in actual microgravity. Three primary variables are considered: flow velocity, oxygen concentration, and gap size (or effect of heat loss). When the oxidizer flow is reduced at either gravity level, the initially uniform flame front becomes corrugated and breaks into separate flamelets. This breakup behavior allows the flame to keep propagating below standard extinction limits by increasing the oxidizer transport to the flame, but has not been observed in other microgravity experiments due to the narrow samples employed. Breakup cannot be studied in typical (i.e., “open”) normal gravity test facilities due to buoyancy-induced opposed flow velocities that are larger than the forced velocities in the flamelet regime. Flammability maps are constructed that delineate the uniform regime, the flamelet regime, and extinction limits for thin cellulose samples. Good agreement is found between flame and flamelet spread rate and flamelet size between the two facilities. Supporting calculations using FLUENT suggest that for small gaps buoyancy is suppressed and exerts a negligible influence on the flow pattern for inlet velocities ⩾5 cm/s. The experiments show that in normal gravity the flamelets are a fire hazard since they can persist in small gaps where they are hard to detect. The results also indicate that the NCA quantitatively captures the essential features of the microgravity tests for thin fuels in opposed flow.
TL;DR: In this article, the authors demonstrate a similar result can be obtained by formulating surrogate hydrocarbon fluid mixtures from distillation cuts of molecular class hydrocarbons or even real gas turbine fuels (for which the specific molecular species classes are no more than qualitatively known).
Abstract: We have demonstrated previously that a (surrogate fuel) mixture of known pure hydrocarbon species that closely matches four combustion property targets (the derived cetane number (DCN), the hydrogen to carbon molar ratio (H/C), the threshold soot index (TSI), and the average molecular weight) of a specific jet fuel, displays fully prevaporized global combustion kinetic behaviors that are closely consistent. Here, we demonstrate a similar result can be obtained by formulating surrogate hydrocarbon fluid mixtures from distillation cuts of molecular class hydrocarbons or even real gas turbine fuels (for which the specific molecular species classes are no more than qualitatively known). Fully prevaporized chemical reactivities of hydrocarbon fluid surrogate mixtures and real jet fuels are compared using a high pressure flow reactor at 12.5 atm pressure, over the temperature range 500–1000 K, at stoichiometric conditions, and for the same fixed molar carbon content. Results are reported for two different real ...
••01 Dec 2016
TL;DR: A home model is analyzed to demonstrate an energy efficient IoT based smart home and the smart system can remotely control the lighting and heating or cooling when an occupant enters or leaves the kitchen.
Abstract: Smart Home technology is the future of residential related technology which is designed to deliver and distribute number of services inside and outside the house via networked devices in which all the different applications & the intelligence behind them are integrated and interconnected. These smart devices have the potential to share information with each other given the permanent availability to access the broadband internet connection. Hence, Smart Home Technology has become part of IoT (Internet of Things). In this work, a home model is analyzed to demonstrate an energy efficient IoT based smart home. Several Multiphysics simulations were carried out focusing on the kitchen of the home model. A motion sensor with a surveillance camera was used as part of the home security system. Coupled with the home light and HVAC control systems, the smart system can remotely control the lighting and heating or cooling when an occupant enters or leaves the kitchen.
TL;DR: In this paper, the Princeton variable pressure flow (PVCF) this paper was used to study the oxidation of n -decane/oxygen/nitrogen in a 1000-ppm fuel in the Princeton Variable Pressure Flow (VPF) reactor at temperatures of 520-830 K and pressures of 8 and 12.5 K.
Abstract: The oxidation of n -decane/oxygen/nitrogen is studied at stoichiometric conditions of 1000 ppm fuel in the Princeton variable pressure flow reactor at temperatures of 520–830 K and pressures of 8 and 12.5 atm. The overall oxidative reactivity of n -decane is observed in detail to show low temperature, negative temperature coefficient (NTC) and hot ignition regimes. Detailed temporal speciation studies are performed at reactor initial temperatures of 533 K and 740 K at 12.5 atm pressure and 830 K at 8 atm pressure. Significant amounts of large olefins are produced at 830 K, at conditions of transition from NTC to hot ignition behavior. The predictions using available chemical kinetic models for n -decane oxidation are compared against each other and the experiments. Only the kinetic models of Westbrook et al., Ranzi et al., and Biet et al. capture the NTC behavior exhibited by n -decane. However, each of these models yields varying disparities in the mechanistic predictions of major intermediate species, including ethylene and formaldehyde. Analyses of the Westbrook et al. model are compared with the new data. The predicted double-peaked species yield of ethylene, a behavior not found for the other models or in the experimental observations results from deficiencies in the C 2 chemistry. Mechanistic validation information about fuel oxidation chemistry is also provided by the measurement of various larger carbon number alkene isomers at 830 K and 8 atm. The modeling analysis suggests that in addition to n -alkyl beta-scission chemistry, alkyl peroxy radical chemistry contributes significantly to the formation of these alkenes. Specific reaction pathways and rate constants which affect the computation of these observations are discussed.
TL;DR: In this paper, a detailed kinetic mechanism for the pyrolysis and combustion of a large variety of fuels at high temperature conditions is presented, and the authors identify aspects of the mechanism that require further revision.
Abstract: The primary objective of the present endeavor is to collect, consolidate, and review the vast amount of experimental data on the laminar flame speeds of hydrocarbon and oxygenated fuels that have been reported in recent years, analyze them by using a detailed kinetic mechanism for the pyrolysis and combustion of a large variety of fuels at high temperature conditions, and thereby identify aspects of the mechanism that require further revision. The review and assessment was hierarchically conducted, in the sequence of the foundational C0–C4 species; the reference fuels of alkanes (n-heptane, iso-octane, n-decane, n-dodecane), cyclo-alkanes (cyclohexane and methyl-cyclo-hexane) and the aromatics (benzene, toluene, xylene and ethylbenzene); and the oxygenated fuels of alcohols, C3H6O isomers, ethers (dimethyl ether and ethyl tertiary butyl ether), and methyl esters up to methyl decanoate. Mixtures of some of these fuels, including those with hydrogen, were also considered. The comprehensive nature of the present mechanism and effort is emphasized.
TL;DR: A detailed overview of recent results on alcohol combustion can be found in this paper, with a particular emphasis on butanols and other linear and branched members of the alcohol family, from methanol to hexanols.
Abstract: Alternative transportation fuels, preferably from renewable sources, include alcohols with up to five or even more carbon atoms. They are considered promising because they can be derived from biological matter via established and new processes. In addition, many of their physical-chemical properties are compatible with the requirements of modern engines, which make them attractive either as replacements for fossil fuels or as fuel additives. Indeed, alcohol fuels have been used since the early years of automobile production, particularly in Brazil, where ethanol has a long history of use as an automobile fuel. Recently, increasing attention has been paid to the use of non-petroleum-based fuels made from biological sources, including alcohols (predominantly ethanol), as important liquid biofuels. Today, the ethanol fuel that is offered in the market is mainly made from sugar cane or corn. Its production as a first-generation biofuel, especially in North America, has been associated with publicly discussed drawbacks, such as reduction in the food supply, need for fertilization, extensive water usage, and other ecological concerns. More environmentally friendly processes are being considered to produce alcohols from inedible plants or plant parts on wasteland. While biofuel production and its use (especially ethanol and biodiesel) in internal combustion engines have been the focus of several recent reviews, a dedicated overview and summary of research on alcohol combustion chemistry is still lacking. Besides ethanol, many linear and branched members of the alcohol family, from methanol to hexanols, have been studied, with a particular emphasis on butanols. These fuels and their combustion properties, including their ignition, flame propagation, and extinction characteristics, their pyrolysis and oxidation reactions, and their potential to produce pollutant emissions have been intensively investigated in dedicated experiments on the laboratory and the engine scale, also emphasizing advanced engine concepts. Research results addressing combustion reaction mechanisms have been reported based on results from pyrolysis and oxidation reactors, shock tubes, rapid compression machines, and research engines. This work is complemented by the development of detailed combustion models with the support of chemical kinetics and quantum chemistry. This paper seeks to provide an introduction to and overview of recent results on alcohol combustion by highlighting pertinent aspects of this rich and rapidly increasing body of information. As such, this paper provides an initial source of references and guidance regarding the present status of combustion experiments on alcohols and models of alcohol combustion.
TL;DR: A methodology for the formulation of surrogate fuels for the emulation of real fuel gas phase combustion kinetic phenomena pertinent to gas turbine combustion is described and tested in this article, where a mixture of n -dodecane/ iso-octane/1,3,5-trimethylbenzene/ n -propylbenzenesene is formulated in a predictive manner to exhibit the same gas phase combustions of a target Jet-A fuel by the sharing of fundamentally significant combustion property targets in addition to a prescribed commonality of chemical kinetically controlling intermediate species.
Abstract: A methodology for the formulation of surrogate fuels for the emulation of real fuel gas phase combustion kinetic phenomena pertinent to gas turbine combustion is described and tested. A mixture of n -dodecane/ iso -octane/1,3,5-trimethylbenzene/ n -propylbenzene is formulated in a predictive manner to exhibit the same gas phase combustion phenomena of a target Jet-A fuel by the sharing of fundamentally significant combustion property targets in addition to a prescribed commonality of chemical kinetically controlling intermediate species. The appropriateness of the surrogate formulation technique is demonstrated by the experimental measurement of various gas phase combustion kinetic phenomena of the proposed surrogate mixture and of the target Jet-A fuel: (1) A variable pressure flow reactor is used to chart the chemical reactivity of a stoichiometric mixture of surrogate fuel/O 2 /N 2 at 12.5 atm and 500–1000 K, for a residence time of 1.8 s at a fixed carbon content of 0.3%. (2) The autoignition behavior of stoichiometric mixtures of surrogate fuel in air is measured with a shock tube at 667–1223 K at ∼20 atm and also with a rapid compression machine at 645–714 K at compressed pressures of 21.7 atm. (3) Detailed measurements of the intermediate species formed in the high temperature oxidation of the target fuel and in the oxidation of the surrogate fuel are performed with a shock tube for reaction times of 1.23–3.53 ms at 18–35 atm and 901–1760 K for 0.0808/0.158/0.1187 mole% mixtures of C/H/O 2 . (4) The laminar burning velocity and strain extinction limits of premixed mixtures of surrogate fuel in O 2 /N 2 are determined by the counter flow twin flame technique. These phenomena are also determined for premixed mixtures of the target fuel and for a previously proposed surrogate fuel composed of n -decane/ iso -octane/toluene in O 2 /N 2 . (5) The high temperature chemical reactivity and chemical kinetic–molecular diffusion coupling of the surrogate fuel is evaluated by measurement of the strained extinction limits of diffusion flames. (6) The propensity of surrogate and real fuel to form soot is tested by laser extinction measurements of the soot volume fractions formed by each fuel in a wick-fed laminar flame diffusion burner as a function of the radial distance of each flame. These experimental data are compared to those previously reported at identical conditions for the target Jet-A fuel and for a similar n -decane/ iso -octane/toluene surrogate fuel. A conceptual theory of real fuel oxidation is proposed and the similarity of the exhibited combustion phenomena of all three fuels is analyzed and interpreted in this context in order to (a) further evaluate the proposed strategy to surrogate fuel formulation and the appropriateness of the proposed theory to real fuel oxidation, (b) evaluate the appropriateness of the proposed n -dodecane/ iso -octane/1,3,5-trimethylbenzene/ n -propylbenzene mixture as a surrogate fuel for the target Jet-A fuel, and (c) to provide direction for the development of a tractable numerical modeling framework to compute real fuel multiphase combustion phenomena.
TL;DR: In this paper, the fundamental combustion and emissions properties of advanced biofuels are reviewed, and their impact on engine performance is discussed, in order to guide the selection of optimal conversion routes for obtaining desired fuel combustion properties.
Abstract: The fundamental combustion and emissions properties of advanced biofuels are reviewed, and their impact on engine performance is discussed, in order to guide the selection of optimal conversion routes for obtaining desired fuel combustion properties. Advanced biofuels from second- and third-generation feedstocks can result in significantly reduced life-cycle greenhouse-gas emissions, compared to traditional fossil fuels or first-generation biofuels from food-based feedstocks. These advanced biofuels include alcohols, biodiesel, or synthetic hydrocarbons obtained either from hydrotreatment of oxygenated biofuels or from Fischer–Tropsch synthesis. The engine performance and exhaust pollutant emissions of advanced biofuels are linked to their fundamental combustion properties, which can be modeled using combustion chemical-kinetic mechanisms and surrogate fuel blends. In general, first-generation or advanced biofuels perform well in existing combustion engines, either as blend additives with petro-fuels or as pure “drop-in” replacements. Generally, oxygenated biofuels produce lower intrinsic nitric-oxide and soot emissions than hydrocarbon fuels in fundamental experiments, but engine-test results can be complicated by multiple factors. In order to reduce engine emissions and improve fuel efficiency, several novel technologies, including engines and fuel cells, are being developed. The future fuel requirements for a selection of such novel power-generation technologies, along with their potential performance improvements over existing technologies, are discussed. The trend in the biofuels and transportation industries appears to be moving towards drop-in fuels that require little changes in vehicle or fueling infrastructure, but this comes at a cost of reduced life-cycle efficiencies for the overall alternative-fuel production and utilization system. In the future, fuel-flexible, high-efficiency, and ultra-low-emissions heat-engine and fuel-cell technologies promise to enable consumers to switch to the lowest-cost and cleanest fuel available in their market at any given time. This would also enable society as a whole to maximize its global level of transportation activity, while maintaining urban air quality, within an energy- and carbon-constrained world.
TL;DR: In this paper, a hybrid chemistry approach to model the high-temperature oxidation of real, distillate fuels is presented, in which the kinetics of thermal and oxidative pyrolysis of the fuel are modeled using lumped kinetic parameters derived from experiments.
Abstract: Real distillate fuels usually contain thousands of hydrocarbon components. Over a wide range of combustion conditions, large hydrocarbon molecules undergo thermal decomposition to form a small set of low molecular weight fragments. In the case of conventional petroleum-derived fuels, the composition variation of the decomposition products is washed out due to the principle of large component number in real, multicomponent fuels. From a joint consideration of elemental conservation, thermodynamics and chemical kinetics, it is shown that the composition of the thermal decomposition products is a weak function of the thermodynamic condition, the fuel-oxidizer ratio and the fuel composition within the range of temperatures of relevance to flames and high temperature ignition. Based on these findings, we explore a hybrid chemistry (HyChem) approach to modeling the high-temperature oxidation of real, distillate fuels. In this approach, the kinetics of thermal and oxidative pyrolysis of the fuel is modeled using lumped kinetic parameters derived from experiments, while the oxidation of the pyrolysis fragments is described by a detailed reaction model. Sample model results are provided to support the HyChem approach.