Experimental Measurement of Ignition Delay Times of Thermally Cracked n‑Decane in a Shock Tube

• Published in: Energy & fuels Vol. 31; no. 3; pp. 3262 - 3269
• Main Authors: Pei, Shanshan, Wang, Hongyan, Zhang, Xiangwen, Xu, Shengli, Liu, Guozhu
• Format: Journal Article
• Language: English
• Published: American Chemical Society 16.03.2017
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/acs.energyfuels.6b03242

The ignition characteristics of endothermic hydrocarbon fuels (with different pyrolysis degrees) were investigated in a shock tube using n-decane as model compound. Six component surrogates (CH4/C2H4/C2H6/C3H6/C3H8/n-C10H22, marked as cracked n-decane) for thermally cracked n-decane were proposed based on the chemical compositions from the thermal stressing of n-decane on electrically heated tube under 5 MPa. Ignition delay times were measured behind reflected shock waves over a temperature range of 1296–1915 K, a pressure of 0.1–0.2 MPa, and equivalence ratios of 0.5–2.0. n-Decane showed a shorter ignition delay time than cracking gas at 0.1 MPa, demonstrating higher reactivity. For cracked n-decane, it was found that thermal cracking could improve the ignitability under certain conditions to a limited degree, i.e., at T > 1480 K for x = 37.97% and x = 17.61% and at T < 1480 K for x = 62.15% (x represents the conversion of thermal cracking of n-decane) in this work. Unimolecular decomposition reactions of n-decane producing active radicals and H atom would help chain initiation via H-abstraction reaction for unreacted fuels. This initial stage might accelerate ignition by activating cracking gas at these conditions. The empirical correlations for the ignition delay time of cracking gas and n-decane were also analyzed and compared with previous works. Two models were also used to simulate the experimental data of n-decane and cracking gas and showed good agreement with experimental results, and a combined model was utilized to predict results of cracked n-decane.