Experimental and kinetic study on di-tertiary butyl peroxide auto-ignition and its effect on the ignition of n-heptane

Di-tertiary butyl peroxide is commonly used as ignition improver. In this work, auto-ignition properties of di-tertiary butyl peroxide and its promoting effect on n-heptane ignition were investigated systematically using a shock-tube facility. Ignition delay times were determined by measuring the time interval between electronically excited CH* emission and reflected shock pressure signals monitored at shock-tube sidewall. An empirical correlation for ignition delay times of di-tertiary butyl peroxide as a function of temperature, pressure and equivalence ratio was deduced by linear regression analysis. The quantitative effect of di-tertiary butyl peroxide on n-heptane ignition was obtained. The addition of di-tertiary butyl peroxide can dramatically decrease the ignition delay time of n-heptane, especially at high pressures and low temperatures. A two-step dissociation mechanism of di-tertiary butyl peroxide was combined with an n-heptane combustion mechanism to model the ignition characteristics. Sensitivity and reaction pathway analyses were carried out to identify the dominant reactions and fuel consumption paths during the ignition process, and to analysis the effect of di-tertiary butyl peroxide addition. The chain branching reaction CH3 + HO2 = CH3O + OH plays a dominant role in ignition promotion.