Comparative study of experimental and modeling autoignition of cyclohexane, ethylcyclohexane, and n-propylcyclohexane

Ignition delay times were measured for cyclohexane, ethylcyclohexane, and n-propylcyclohexane at atmospheric pressure, equivalence ratios of 0.5, 1.0, and 2.0, and temperatures of 1110-1650 K behind reflected shock waves with a fixed fuel concentration of 0.5%. Computational simulations were made using three generally accepted mechanisms, yielding acceptable agreements with the current measurements at the tested equivalence ratios. Nonetheless, there is a slight overprediction at φ = 2.0 for n-propylcychexane. Ethylcyclohexane and n-propylcyclohexane have shorter ignition delay times than cyclohexane at high temperatures. However, this difference decreases with the decrease in the temperature. Simulation and comparison to previous data indicate that the oxidation rates of ethylcyclohexane, n-propylcyclohexane, and n-butylcyclohexane are in the order of n-propylcyclohexane > ethylcyclohexane ≈ n-butylcyclohexane. Kinetic analysis is performed to obtain insight into the observation.