Statistical models in engineering , Statistical models in engineering , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Statistical Models in Engineering

Improved sooting tendency measurements for aromatic hydrocarbons and their implications for naphthalene formation pathways

A review of physics and correlations of pool fire behaviour in wind and future challenges

Internal combustion engines running on liquid fuels will remain the dominant prime movers for road and air transportation for decades, probably for most of this century. The world’s appetite for liquid transportation fuels derived from petroleum and other fossil resources is already immense, will grow, will at some future time become economically unsustainable, and will become infeasible only in the very long term. The ongoing process of augmenting and eventually replacing petroleum-derived fuels with liquid alternative fuels must necessarily involve approaches that result in comparatively much lower net carbon cycle emissions from the transportation sector, most likely through a combination of carbon sequestration and renewable fuel production. The successful growth and establishment of a sustainable, profitable alternative fuels industry will be best facilitated by approaches that integrate alternative products into petroleum-derived fuel streams (i.e., gasolines, diesel, and jet fuels) and consider synergistic evolution of and integration with prevailing refining and liquid fuel distribution infrastructures. The emergence of low temperature combustion strategies, particularly those implementing dual fuel methods to achieve Reaction Controlled Compression Ignition (RCCI), offers the potential to significantly improve operating efficiency and reduce emissions with minimal aftertreatment. For all advanced combustion engine technologies, but especially for RCCI, a clear understanding of fuel property influences on combustion behaviors will be important to achieving projected engine performance and emissions. To achieve the benefits projected by emerging engine technologies, the properties of petroleum-derived fuels themselves must be modified over time, but the effects of blending candidate alternative fuels with these conventional fuels must also be understood. Predicting the coupled physical and chemical property effects of real fuels on energy conversion system performance and emissions is a daunting problem, even for petroleum-derived real fuels, since each is composed of several hundred to thousands of individual chemical species typically belonging to one of a few organic classes (e.g., n-paraffins, iso-paraffins, cyclo-paraffins, olefins, aromatics). For specific combustion applications, it is often the global combustion response to variations in the composition of fuel mixtures – inclusive of those occurring by blending petroleum-derived fuel with alternative fuel candidates – that is of interest for fuel property optimization. This paper presents an overview of tools used for evaluating and emulating combustion-relevant properties of real fuels and alternative fuel candidates. New analytical and statistical methods can provide important insights as to how the ensembles of distinct molecular structures found in a given fuel mixture contribute to the physical and chemical kinetic properties that govern its combustion in energy conversion processes. Such tools can in turn assist in screening candidate alternative fuels for more detailed study.

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Chemical kinetic and combustion characteristics of transportation fuels

The pyrolysis kinetics of charring materials plays an important role in understanding material combustions especially for construction materials with complex degradation chemistry. Thermogravimetri...

http://spiral.imperial.ac.uk/bitstream/10044/1/25684/2/ef-2014-01380.pdf

Pyrolysis of Medium-Density Fiberboard: Optimized Search for Kinetics Scheme and Parameters via a Genetic Algorithm Driven by Kissinger’s Method

FireFOAM, a new fire modeling code based on the OpenFOAM platform ( www.openfoam.org ), is developed and applied to model a series of purely buoyant fire plumes with heat release rates from 14 to 58 kW. The calculations are compared with McCaffrey’s (1979) experiments. The simulation results demonstrate good quantitative agreement with experimental measurements, and show the scaling relations of mean temperature and velocity in the continuous flame, intermittent and plume regions. The numerical simulations are shown to be strictly conservative in energy. Predicted flame heights and entrainment rates also compare well with experimental correlations. The good agreements in all aspects examined show that the current CFD model performs well for small-scale fire plumes. Turbulent fluctuation intensities and PDF of mixture fraction are presented to gain more insights into the structure of fire plumes.

Large eddy simulation of fire plumes

CFD fire modeling tools are continuously developed and improved to increase their predictive capability of phenomena observed in practical applications. Such models require that “effective” material properties be provided so that the pyrolysis codes used in the models can properly estimate the thermal degradation of solid fuels involved in a fire situation. This paper presents analyses aimed at evaluating the plausibility of obtaining material properties numerically from pyrolysis data collected in a Fire Propagation Apparatus (FPA). A theoretical pyrolysis model is used to simulate the experimental data and the input parameters (i.e. the material properties) are adjusted to provide the best possible agreement between simulations and experiments. This is done via the application of evolutionary optimization methodologies. First, available optimization techniques are evaluated using synthetic data and it is shown that the Shuffled Complex Evolution approach ( [17] ) can recover the input parameters with high accuracy, efficiency, and robustness. Second, the algorithm is applied to experimental FPA pyrolysis data of practical materials: polymethyl methacrylate (PMMA), single-wall corrugated board, and chlorinated polyvinyl chloride (CPVC).

Evaluation of optimization schemes and determination of solid fuel properties for CFD fire models using bench-scale pyrolysis tests

https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=101148

A simplified model for soot formation and oxidation in CFD simulation of non-premixed hydrocarbon flames

Pool fires – An empirical correlation

The medium-scale fire whirl was extensively investigated by experimental means, in order to establish correlations of the burning rate, flame height and flame temperature of fire whirl, and to clarify the difference between fire whirls and general pool fires. Experimental observations and data confirmed that a free burning fire whirl is a highly stable burning phenomenon with large quasi-steady periods. Burning rates of fire whirls depend on pool diameter similarly to those of general pool fires; however the transition turbulent burning occurs sooner as the pool diameter increases. The lip height seems to have little effect on the burning rate of fire whirls. The correlation H ∗ = K · ( Q ˙ ∗ · Γ ∗ 2 ) m was proposed to couple the height of fire whirl to the fire release rate and ambient circulation. It correlates the data from both this work and the literature. Radial temperature profiles in the continuous region of the fire whirl were confirmed to be hump-type, implying the existence of fuel-rich inner core. The pool diameter and heat release rate do not significantly affect the radial temperature profiles in non-dimensional radial coordinates. It was found that the fire plume of fire whirl involves three distinct zones just like that of pool fire, but with different normalized ranges. Fire whirls maintain a higher ratio of continuous flame height to the overall flame height, and also higher maximum centerline excess temperature in continuous flame region, as compared to general pool fires. It was further demonstrated that the fire whirl plume at its origin behaves like a turbulent jet with moderate swirling, and then tends to become buoyancy dominated downstream, with slight swirling. With an increase in dimensionless height adjusted by the plume origin, the plume centerline excess temperature decays rapidly and approaches the theoretical value of −5/3 for free buoyancy plume.

John L. de Ris

Papers

Large eddy simulation of fire plumes

Evaluation of optimization schemes and determination of solid fuel properties for CFD fire models using bench-scale pyrolysis tests

A simplified model for soot formation and oxidation in CFD simulation of non-premixed hydrocarbon flames

Pool fires – An empirical correlation

Experimental research on combustion dynamics of medium-scale fire whirl