Gas-phase autoignition of diesel/gasoline blends over wide temperature and pressure in heated shock tube and rapid compression machine

Abstract

Diesel/gasoline blended fuel, also named as dieseline, has attracted worldwide interests in varied advanced engine combustion modes dominated by mixing time scale and chemical reaction time scale. However, the research on ignition properties and chemical reaction mechanism of diesel/gasoline blends over wide operating conditions is still lacking. In current study, ignition delay time measurement of diesel/gasoline blends with different diesel proportion (30%, 50%, and 70% by volume) were conducted in a heated shock tube and a heated rapid compression machine (RCM) covering a broad range of temperatures between 636 and 1317 K at pressures between 6 and 20 bar for gas-phase dieseline/O2/N2 mixture at varying equivalence ratios from 0.5 to 1.5. The experimental results revealed different dependence of ignition delay time on pressure, equivalence ratio and composition at different temperatures and varying negative-coefficient (NTC) behaviors were also observed at intermediate-temperature regime. The increase in proportion of diesel led to shorter ignition delay times under all conditions, though the ignition data at high temperature only showed marginal discrepancies. Besides, a crossover of ignition data occurred at the highest temperature for varying equivalence ratios. A tertiary surrogate for diesel and a tertiary surrogate for gasoline were chosen to calculate conditions after reflected shock in shock tube and compression in RCM. Then, simulations of ignition delay time for diesel/gasoline blends were conducted using a detailed model. Finally, kinetic analyses were performed to gain insight into the ignition characteristic of diesel/gasoline blends.