Ignition delay times of polyoxymethylene dimethyl ether fuels ([formula omitted] and [formula omitted]) and air: Measurements in a rapid compression machine

Abstract

In this work, the auto-ignition of two polyoxymethylene dimethyl ethers, namely OME2 and OME3 (CH3–O–CH2–On–CH3 with n=2 and n=3 respectively), is investigated in a rapid compression machine (RCM). Ignition delay times (IDT) of stoichiometric OME2/air and OME3/air mixtures were measured for pressures ranging from 3 to 10 bar, and temperatures ranging between 570 and 690 K. The RCM data shows that already at these relatively low pressures and temperatures, both OME2 and OME3 auto-ignite within timescales that are well observed within RCM measurements. At the higher investigated pressures, OME2 and OME3 show nearly the same ignition delay time for all the investigated temperatures. In contrast, at lower pressures, the ignition delay time differ more, with OME3 showing longer ignition delay times. The pressure-dependence of ignition delay time exhibits a pronounced nonlinear behavior. We fitted a global Arrhenius equation to our ignition delay data near 10 bar, which well fits our data. Comparing our RCM results for OME2 and OME3 to simulations based on the reaction mechanism of He et al. [1], we found good agreement at a pressure of 10 bar.