Effects of branch structure of alkylbenzenes on spray auto-ignition of n-decane and alkylbenzenes blends

Spray auto-ignition characteristics of the blends of n-decane and several alkylbenzenes were carried out on a heated constant-volume spray combustion chamber. The derived cetane numbers of the fuel blends were determined, and the temperature-dependent ignition delay times and combustion durations were measured across a range of temperatures from 808 to 911 K. The results reveal that blending alkylbenzene to n-decane inhibits fuel spray auto-ignition propensity. For mono-alkylbenzenes, the fuel blend containing toluene has a higher derived cetane number than those with ethylbenzene and n-propylbenzene, but has a lower derived cetane number than the fuel blend containing n-butylbenzene. For those binary fuels containing ethylbenzene, n-propylbenzene and n-butylbenzene, their derived cetane numbers increase with the side alkyl chain length. The derived cetane numbers of the fuel blends with C8H10 isomers follow the trend of n-decane/ o-xylene > n-decane/ethylbenzene > n-decane/ m-xylene ∼ n-decane/ p-xylene, given the alkylbenzene blending fraction. For the blends with C9H12 isomers, those containing 1,2,3-trimethylbenzene and 1,3,5-trimethylbenzene have the highest and lowest derived cetane numbers, respectively, while the fuel blends containing 1,2,4-trimethylbenzene, n-propylbenzene and i-propylbenzene have comparatively intermediate derived cetane numbers. The blending effects of alkylbenzenes on ignition delay time are consistent with the observation on fuel derived cetane numbers. Both the number and proximity of substituted methyl groups significantly affect fuel auto-ignition propensity, and the adjacent methyl groups could increase the auto-ignition propensity. The combustion duration for the test fuels, except for n-decane and the n-decane/ n-butylbenzene blend, monotonically decreases with increased temperature. The non-monotonic dependence of combustion duration on temperature, for neat n-decane and the n-decane/ n-butylbenzene blend, may result from the increased diffusive burnt fraction. Finally, the comparison between gas-phase and spray auto-ignition reactivity of the test fuels highlights the contribution of both fuel physics and chemistry in spray auto-ignition.

Theoretical and Experimental Analysis of the Metal-Based Ignition Propensity Test Thermodynamics

SummaryThis research analysed in detail the performance of the new alternative ignition propensity test prescribed in the standard ASTM E2187-16, which is based on the utilization of a substrate comprising a thin steel plate along with one filter paper. The analysis was performed both experimentally, by means of infrared temperature measurements, and theoretically by using a comprehensive finite element model that was able to predict the temperature of the substrate with errors of only 7.3% and 15.7% in space and time, respectively. While the new alternative test was able to reduce the variability of the heat absorbance from 33% to only 4% with respect to the conventional tests, it showed several downsides that critically reduce its reliability. The heat absorbance of the alternative test did not correctly emulate the conventional procedure as it absorbed as much heat as twice. The gravity effect on the plate increased the air gap thickness more than twice, thereby decreasing potentially the heat absorbance by 13%. In addition, a mechanical analysis showed that compressive stresses due to high temperature gradients could cause irreversible buckling, creep and yielding of the plate. Experiments showed that in fact the concavity of the plate was prone to increase after testing. Assuming the maximum concavity allowed by the standards, the heat absorbance was halved in respect to a perfectly flat plate. In view of these results, the utilization of the conventional test method still appears clearly more appropriate than the alternative one.

The effects of the lower ignition propensity cigarettes standard in Estonia: time-series analysis

BackgroundIn 2011, the lower ignition propensity (LIP) standard for cigarettes was implemented in the European Union. Evidence about the impact of that safety measure is scarce.ObjectiveThe aim of this paper is to examine the effects of the LIP standard on fire safety in Estonia.MethodsThe absolute level of smoking-related fire incidents and related deaths was modelled using dynamic time-series regression analysis. The data about house fire incidents for the 2007–2013 period were obtained from the Estonian Rescue Board.ResultsImplementation of the LIP standard has reduced the monthly level of smoking-related fires by 6.2 (p<0.01, SE=1.95) incidents and by 26% (p<0.01, SE=9%) when estimated on the log scale. Slightly weaker evidence was found about the fatality reduction effects of the LIP regulation. All results were confirmed through counterfactual models for non-smoking-related fire incidents and deaths.ConclusionsThis paper indicates that implementation of the LIP cigarettes standard has improved fire safety in Estonia.