Knocking Characteristics of Hydrocarbons

Lovell, Wheeler G.

doi:10.1021/ie50468a033

Cited by 133 publications

(53 citation statements)

References 7 publications

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“…Early reports by Lovell attempted to correlate the octane ratings of 325 hydrocarbons with their structure. 23 The ON values of pure hydrocarbons were used by Pera and Knop 6 to determine the ON of TPRF mixtures using a linear-by-mole blending rule. Ramadan et al 24 proposed a polynomial fit for ethanol blended in PRFs and TPRFs, in an attempt to provide an empirical relationship for the nonlinearity observed in ethanol−gasoline blends.…”

Section: Introductionmentioning

confidence: 99%

Chemical Kinetic Insights into the Octane Number and Octane Sensitivity of Gasoline Surrogate Mixtures

2017

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Gasoline octane number is a significant empirical parameter for the optimization and development of internal combustion engines capable of resisting knock. Although extensive databases and blending rules to estimate the octane numbers of mixtures have been developed and the effects of molecular structure on autoignition properties are somewhat understood, a comprehensive theoretical chemistry-based foundation for blending effects of fuels on engine operations is still to be developed. In this study, we present models that correlate the research octane number (RON) and motor octane number (MON) with simulated homogeneous gas-phase ignition delay times of stoichiometric fuel/air mixtures. These correlations attempt to bridge the gap between the fundamental autoignition behavior of the fuel (e.g., its chemistry and how reactivity changes with temperature and pressure) and engine properties such as its knocking behavior in a cooperative fuels research (CFR) engine. The study encompasses a total of 79 hydrocarbon gasoline surrogate mixtures including 11 primary reference fuels (PRF), 43 toluene primary reference fuels (TPRF), and 19 multicomponent (MC) surrogate mixtures. In addition to TPRF mixture components of iso-octane/n-heptane/toluene, MC mixtures, including n-heptane, iso-octane, toluene, 1-hexene, and 1,2,4-trimethylbenzene, were blended and tested to mimic real gasoline sensitivity. ASTM testing protocols D-2699 and D-2700 were used to measure the RON and MON of the MC mixtures in a CFR engine, while the PRF and TPRF mixtures' octane ratings were obtained from the literature. The mixtures cover a RON range of 0−100, with the majority being in the 70−100 range. A parametric simulation study across a temperature range of 650−950 K and pressure range of 15−50 bar was carried out in a constant-volume homogeneous batch reactor to calculate chemical kinetic ignition delay times. Regression tools were utilized to find the conditions at which RON and MON best correlate with simulated ignition delay times. Furthermore, temperature and pressure dependences were investigated for fuels with varying octane sensitivity. This analysis led to the formulation of correlations useful to the definition of surrogates for modeling purposes and allowed one to identify conditions for a more in-depth understanding of the chemical phenomena controlling the antiknock behavior of the fuels.

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Section: Introductionmentioning

confidence: 99%

Chemical Kinetic Insights into the Octane Number and Octane Sensitivity of Gasoline Surrogate Mixtures

2017

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“…Many years of experiments have shown [14] that these variables influence the knock tendencies and octane ratings of different hydrocarbons, and our modeling work has shown, in fundamental chemical kinetic terms, how they control engine knock in spark-ignition engines [8,9,11], ignition in the rapid compression machine [7,15], and ignition in shock tubes [16][17][18]. In the present work, we further extend the range of structures and sizes of alkane fuels suitable for detailed kinetic studies by developing detailed kinetic mechanisms for the eight isomers of heptane (i.e., excluding n-heptane).…”

Section: Introductionmentioning

confidence: 99%

Chemical kinetic modeling study of shock tube ignition of heptane isomers

Westbrook

Pitz

Curran

et al. 2001

Int J of Chemical Kinetics

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High-temperature detailed chemical kinetic reaction mechanisms are developed for all nine chemical isomers of heptane (C 7 H 16 ), following techniques and models developed previously for other smaller alkane hydrocarbon species. These reaction mechanisms are tested by computing shock tube ignition delay times for stoichiometric heptane/oxygen mixtures diluted by argon. Although no corresponding experiments have been reported in the literature for most of these isomers of heptane, intercomparisons between the computed results for these isomers and comparisons with available experimental results for other alkane fuels are used to validate the reaction mechanisms as much as possible. Differences in the overall reaction rates of these heptane isomers are discussed in terms of differences in their molecular structure and the resulting variations in rates of important chain branching and termination reactions. The implications of these results regarding ignition of other alkane fuels are discussed.

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“…The conditions were a flow rate of 0.5 cc/cc-hr (LHSV), 700ºF, and hydrogen pressure of 1200 psig. The product made had a smoke point of 23.0, tetralin content of 0.6 wt%, aromatic content 4.8%, decalin content of 14.3 wt %.…”

Section: Hydrogenation Of Light Fractionmentioning

confidence: 99%

Refinery Integration of By-Products from Coal-Derived Jet Fuels

Clifford¹,

Boehman²,

Chen³

et al. 2008

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The final report summarizes the accomplishments toward project goals during length of the project. The goal of this project was to integrate coal into a refinery in order to produce coalbased jet fuel, with the major goal to examine the products other than jet fuel. These products are in the gasoline, diesel and fuel oil range and result from coal-based jet fuel production from an Air Force funded program.The main goal of Task 1 was the production of coal-based jet fuel and other products that would need to be utilized in other fuels or for non-fuel sources, using known refining technology. The gasoline, diesel fuel, and fuel oil were tested in other aspects of the project.Light cycle oil (LCO) and refined chemical oil (RCO) were blended, hydrotreated to removed sulfur, and hydrogenated, then fractionated in the original production of jet fuel. Two main approaches, taken during the project period, varied where the fractionation took place, in order to preserve the life of catalysts used, which includes 1) fractionation of the hydrotreated blend to remove sulfur and nitrogen, followed by a hydrogenation step of the lighter fraction, and 2) fractionation of the LCO and RCO before any hydrotreatment. Another aspect was to hydrotreat decant oil for testing of the delayed coker. The yield and quality of jet fuel and the quality of all fuels were better when hydrotreating the whole blend to remove sulfur and nitrogen and fractionating gasoline and jet fuel for further hydrogenation. When fractionating the RCO and LCO before any hydrotreatment, the yield of jet fuel and diesel fuel decreased, and the yield of the fuel oil increased and was a low quality.Task 2 involved assessment of the impact of refinery integration of JP-900 production on gasoline and diesel fuel. Fuel properties, ignition characteristics and engine combustion of model fuels and fuel samples from pilot-scale production runs were characterized. The model fuels used to represent the coal-based fuel streams were blended into full-boiling range fuels to simulate the mixing of fuel streams within the refinery to create potential "finished" fuels. The representative compounds of the coal-based gasoline were cyclohexane and methyl cyclohexane, and for the coal-base diesel fuel they were fluorine and phenanthrene. Both the octane number (ON) of the coal-based gasoline and the cetane number (CN) of the coal-based diesel were low, relative to commercial fuels (~60 ON for coal-based gasoline and ~ 20 CN for coal-based diesel fuel). Therefore, the allowable range of blending levels was studied where the blend would iv achieve acceptable performance. However, in both cases of the coal-based fuels, their ignition characteristics may make them ideal fuels for advanced combustion strategies where lower ON and CN are desirable. The ignition characteristics and reaction pathways were examined for these fuels in a modified octane rating engine used as a form of rapid compression machine and in an ignition quality tester (IQT). Methyl cyclohexane was observed to...

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Knocking Characteristics of Hydrocarbons

Cited by 133 publications

References 7 publications

Chemical Kinetic Insights into the Octane Number and Octane Sensitivity of Gasoline Surrogate Mixtures

Chemical Kinetic Insights into the Octane Number and Octane Sensitivity of Gasoline Surrogate Mixtures

Chemical kinetic modeling study of shock tube ignition of heptane isomers

Refinery Integration of By-Products from Coal-Derived Jet Fuels

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