Experimental and kinetic modelling studies on di-n‑butyl ether (DBE) low temperature auto-ignition

Abstract

Di-n‑butyl ether (DBE), mainly derived from lignocellulosic biomass, is a long-chain linear ether that is regarded as a promising alternative for diesel in compression-ignition engines. Therefore, understanding of the auto-ignition characteristics of DBE is of great importance. In this work, ignition delay times (IDTs) of DBE/O2/N2 mixtures were experimentally measured on a rapid compression machine (RCM). The experiments were conducted at the compressed temperatures ranging from 525 to 707 K, the compressed pressures at 7 and 10 bar, and the equivalence ratios of 0.7, 1.0 and 1.4. A negative temperature coefficient (NTC) behavior was observed for the total IDTs in the tested temperature range. The effects of compressed temperature, compressed pressure, fuel fraction and oxygen fraction, on both the first-stage and total IDTs, were also discussed. Validated against the experimental measurements, two existing DBE chemical kinetic models were found to have less satisfactory performances for the IDT prediction. Therefore, a tuned model based on the Thion model was presented, and it was found to well capture the fuel NTC behaviors and improve the IDTs prediction at the test conditions. Moreover, the tuned model was tested against the measurements on IDTs and species mole fraction profiles in the literature. The tuned model reasonably predicts the measured IDTs on a shock tube at high temperatures and on a flow reactor at low temperatures. The double-NTC behavior of DBE oxidation observed in jet-stirred reactor (JSR) and plug flow reactor (PFR) experiments can be also reasonably predicted.