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This paper presents results of studies investigating the reactivity of primary reference fuel blends in a motored research engine. Reactivity was quantified by measuring exhaust manifold carbon monoxide concentration [CO], cylinder pressure histories, and in-cylinder gas composition. The fuels used were n-heptane (0 PRF), isooctane (100 PRF), and blends of the two with octane values of 0, 25, 55, 63, 75, 87, and 100. A supercharged single-cylinder engine was motored at a constant engine speed and constant inlet pressure as the inlet gas temperature was increased by manifold heating until either the fuel/air mixture autoignited or the maximum temperature of the facility (490 K) was reached. In-cylinder gas samples were obtained and analyzed by gas chromatography for overall fuel reactivity and for the concentrations of light hydrocarbon (

This paper presents experimental results of studies investigating the effect of nitric oxide (NO) on the autoignition chemistry of a primary reference fuel blend with an octane rating of 87 in a motored engine. The experiments were conducted over a range of operating conditions in a single cylinder research engine at compression ratios of 5.2 and 8.2. The inlet manifold was heated and supercharged to pre-stress the fuel-air mixture in order to produce in-cylinder pressure and temperature histories similar to practical engines. The exhaust gas carbon monoxide concentration was monitored and used as a measure of overall reactivity. In-cylinder pressure histories were also recorded and processed to calculate in-cylinder temperature histories. Results showed that at low manifold temperatures, below that necessary to produce negative temperature coefficient behavior, up to 100 ppm of NO promoted reactivity, whereas higher concentrations retarded the reactivity.

The detailed chemical reactions leading to autoignition of n-pentane are investigated in this study. A single-cylinder engine operating in a nonfired mode was used. The engine is supercharged and the temperature of the inlet fuel/air mixture is varied. By increasing the inlet manifold temperature, at a given inlet manifold pressure, the fuel/air mixture can be made to undergo autoignition. In-cylinder pressure and temperature profiles were measured. Gas samples from the combustion chamber were extracted and analyzed using gas chromatography techniques. The detailed chemical reaction mechanisms explaining the products from the different stages of the fuel oxidation process are presented. It is speculated that the generation of OH radicals from the peroxide (QOOH) decomposition is responsible for the autoignition of the n-pentane fuel/air mixture.