Ignition delay times of decalin over low-to-intermediate temperature ranges: Rapid compression machine measurement and modeling study

Abstract

Autoignition characteristics of decalin, a bicyclic alkane, were investigated in a heated rapid compression machine (RCM) over a wide range of conditions. Ignition delay time (IDT) was measured at compressed pressures of 10, 15 and 20 bar, for equivalence ratios of 0.5, 1.0, 1.5 and 2.0, and at temperatures in the range 631−930 K. Negative temperature coefficient (NTC) behavior of decalin ignition delay time was observed within the temperatures of 750−860 K, in which the ignition delay time increases with rising temperature. The dependence of ignition delay time on compressed pressure, equivalence ratio, and oxygen concentration was systemically studied. A reasonable modification was made to a literature mechanism. The simulation results using the tuned mechanism are found to well capture the dependence of the measured ignition delay time on temperautre, pressure, equivalence ratio, and oxygen concentration over the entire temperature range. Correlation formulas of the simulated and measured ignition delay times were proposed to quantitatively reveal the ignition delay time dependence and to evaluate the mechanism performance. A reaction pathway analysis was carried out at low temperature (700 K), NTC temperature (850 K), and high temperature (1000 K), respectively, to identify the dominant reaction pathways consuming decalin and intermediate species. A sensitivity analysis was also performed at different temperatures and equivalence ratios to find out the important reactions that promote and inhibit decalin autoignition.