Lower Flammability Limit of Difluoromethane and Percolation Theory

Kul, Ismail; Gnann, D. L.; Beyerlein, Adolph L.; Desmarteau, D. D.

doi:10.1023/b:ijot.0000038502.85062.eb

Cited by 7 publications

(14 citation statements)

References 4 publications

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“…The methods which we have developed should be ideal for studying isomeric effects because the volume effects and ignition source perturbations which might mask what may be small effects are either eliminated by application of percolation theory or minimized by employing a minimal current-voltage spark. (b) Secondly, we would like to confirm the predictions of percolation theory found in our earlier work [11]. These studies showed that the percentage difference between the LFL of R-32 obtained for the infinite volume limit using percolation theory and that for a 12-L vessel is 3.4%.…”

Section: Introductionsupporting

confidence: 74%

“…Our previous work [11] on trifluoromethane (R-32) showed that the LFL increased with vessel size. This is consistent with Richard [12], who found the LFL of R-134a/R-152a mixtures increased by 0.5 mass% (9.6-10.1 mass%) of the flammable component, R-152a, for measurements in a very large 200-L vessel as compared with the LFL in a 12-L vessel.…”

Section: Introductionmentioning

confidence: 95%

“…Richard also studied R-125/R-152a mixtures in a 200-L vessel and obtained similar results in which the LFL increased by 0.5 mass% (19-19.5 mass%) as compared with the LFL for a 12-L vessel. In our previous work [11], we used percolation theory [13] to explain the effect of vessel size on the LFL, and used the theory to obtain an LFL in the infinite volume limit. In our earlier work, we adhered to all ASTM E681-94 specifications [9], excepting for current and voltage settings.…”

Section: Introductionmentioning

confidence: 99%

“…In this work, the experimental methods and percolation theory developed in our earlier work [11] are used to study the flammability of the isomers 1,1,1-trifluoroethane (R-143a) and 1,1,2-trifluoroethane (R-143). (a) A primary motivation for this study is that we would like to examine isomeric effects because these could give information on how molecular properties may affect flammability of the two isomers, R-143a and R-143, one of which (R-143a) is an important refrigerant whose flammability has been recently studied [14].…”

Section: Introductionmentioning

confidence: 99%

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Flammability Studies of Isomeric Structures of Ethane Derivatives and Percolation Theory

Kul

Blaszkowski

2007

Int J Thermophys

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In order to analyze how isomeric structures will affect the combustion hazard, the lower flammability limits (LFL) of 1,1,1-trifluoromethane (R-143a) and 1,1,2-trifluoroethane (R-143) have been measured using a modified ASTM E681 method. The modification is a spark ignition source in which the current is set at 10 mA and the voltage is adjusted (7-12 kV) so that dielectric breakdown just begins to occur rather than 30 mA at 15 kV specified by the ASTM E681-04 method. An earlier study on the LFL of difluoromethane indicated that flammability limits by the modified ASTM E681 method are affected by vessel size. In order to investigate the vessel volume effect on the measured LFL, experimental measurements of the LFL of R-143 and R-143a are made at 21.5 • C using 5-, 12-, and 20-L vessels. For vessel volumes of 5-L and larger, the LFL systematically shift to higher concentrations of R-143 and R-143a with increasing vessel size which is consistent with a percolation model. Extrapolation of the measured LFL data to infinite vessel size using a percolation model yielded 3.57 and 2.96 mol · m −3 for R-143a and R-143, respectively.

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Section: Introductionsupporting

confidence: 74%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Flammability Studies of Isomeric Structures of Ethane Derivatives and Percolation Theory

Kul

Blaszkowski

2007

Int J Thermophys

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“…The consideration of these correlations could lead to a more precise simulation of certain patterns of cycle-to-cycle fluctuations that standard quasi-dimensional models cannot predict. One of the critical points when developing this kind of simulation model is the flame propagation sub-model, because traditional flame speed correlations fail as the lean flammability limit is approached [42,43]. In these conditions, the assumption of a smooth, spherically progressing flame front should be revised.…”

Section: Discussionmentioning

confidence: 99%

Fluctuations in the Energetic Properties of a Spark-Ignition Engine Model with Variability

Curto-Risso

Medina

Hernández

et al. 2013

Entropy

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We study the energetic functions obtained in a simulated spark-ignited engine that incorporates cyclic variability through a quasi-dimensional combustion model. Our analyses are focused on the effects of the fuel-air equivalence ratio of the mixture simultaneously over the cycle-to-cycle fluctuations of heat release (Q R ) and the performance outputs, such as the power (P ) and the efficiency (η). We explore the fluctuant behavior for Q R , P and η related to random variations of the basic physical parameters in an entrainment or eddy-burning combustion model. P and η show triangle shaped first return maps, while Q R exhibits a structured map, especially at intermediated fuel-air ratios. Structure disappears to a considerable extent in the case of heat release and close-to-stoichiometry fuel-air ratios. By analyzing the fractal dimension to explore the presence of correlations at different scales, we find that whereas Q R displays short-range correlations for intermediate values of the fuel ratio, both P and η are characterized by a single scaling exponent, denoting irregular fluctuations. A novel noisy loop-shaped P vs. η plot for a large number of engine cycles Entropy 2013, 15 3278 is obtained. This plot, which evidences different levels of irreversibilities as the fuel ratio changes, becomes the observed loop P vs. η curve when fluctuations are disregarded, and thus, only the mean values for efficiency and power are considered.

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Application of High Performance Computing for Simulating the Unstable Dynamics of Dilute Spark-Ignited Combustion

Finney

Stoyanov

Pannala

et al. 2013

Understanding Complex Systems

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Lower Flammability Limit of Difluoromethane and Percolation Theory

Cited by 7 publications

References 4 publications

Flammability Studies of Isomeric Structures of Ethane Derivatives and Percolation Theory

Flammability Studies of Isomeric Structures of Ethane Derivatives and Percolation Theory

Fluctuations in the Energetic Properties of a Spark-Ignition Engine Model with Variability

Application of High Performance Computing for Simulating the Unstable Dynamics of Dilute Spark-Ignited Combustion

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