Experimental and kinetic modeling studies on oxidation of methanol and di-tert-butyl peroxide in a jet-stirred reactor

Abstract

Methanol is a potential carbon neutral fuel, but it faces the challenge of ignition difficulties in engines. Di-tert-butyl peroxide (DTBP), a cetane number improver, is considered to be added into methanol to improve ignition. However, there is currently no research of experiments and simulations on the kinetic model of methanol and DTBP. Therefore, the oxidation characteristics of methanol and DTBP were experimentally studied in a jet-stirred reactor under temperatures of 400–1000 K and pressures of 1.03 atm, with equivalence ratios of 0.5, 1 and 2 for pure methanol, pure DTBP, blended fuel (97 % CH3OH + 3 % DTBP; 94 % CH3OH + 6 % DTBP). Then, a new reduced CH3OH-DTBP mechanism containing 75 species and 443 reactions was proposed, which was widely validated by experimental data of ignition delay times, laminar flame speeds and species concentration profiles. Next, the simulations were conducted with CHEMKIN PRO to analyze the effect of DTBP on methanol. The major findings are as follows. After adding DTBP, methanol can react at a lower temperature (550 K), which is due to CH3 generated by decomposition of DTBP promotes the enrichment of OH, thereby promoting the oxidation of methanol. The source of OH at 650 K is CH3 → CH3O2 → CH3O2H → CH3O. At 850 K, the early OH comes from R27 (CH3 + HO2=CH3O + OH), while the later OH comes from the decomposition of H2O2. When the temperature is above 850 K, the addition of DTBP has only a slight effect on the oxidation of methanol. As the temperature increases, the effect of DTBP on shortening the ignition delay time weakens. As DTBP concentration increases, the effect also shows a weakening trend. At low temperatures, the contribution of thermal effects caused by DTBP is greater. As DTBP concentration increases, the proportion of thermal effect contribution increases.