Contact-Surface Tailoring for Oxy-Fuel Ignition in a High-Pressure Shock Tube

Depending on the shock-tube design and geometry, the window for performing precise chemical kinetics experiments in undiluted oxy-fuel mixtures may be particularly narrow due to disturbance waves propagating in the test section after the reflected-shock/contact-interface interaction. The present study investigated the nature of these waves in nonreacting [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] mixtures in a high-pressure shock tube. The [Formula: see text] content corresponding to a stoichiometric balance was replaced with [Formula: see text] to avoid the strong-ignition exothermicity while preserving the gas-dynamic characteristics of the reacting mixture. A contact-surface tailoring model for diverging shock tubes was developed and used to maintain uniformity in the test conditions such that experimental observation times may be extended. For the shock tube used herein ([Formula: see text]), our calculations show that tailoring with He-based driver mixtures is limited to reflected-shock temperatures below 900 K in [Formula: see text] and below 1000 K in [Formula: see text]. Tailoring with He-based drivers is not possible for reflected-shock temperatures above 800 K in [Formula: see text] or [Formula: see text], but it is attainable for greater temperatures when [Formula: see text]. Moreover, [Formula: see text]-based driver mixtures permit tailoring for temperatures up to 1800 K in all test gases, except for [Formula: see text], where tailoring is limited to 1200 and 1600 K for [Formula: see text] of 0.25 and 1.00, respectively. Good agreement was observed between the predicted and experimental compositions for tailored [Formula: see text], [Formula: see text], and [Formula: see text] driver mixtures.