The promoting effect of isopropyl nitrate on the detonation initiation of vapor-liquid two-phase n-heptane/air aerosol

The detonation characteristics of vapor-liquid two-phase fuel/air aerosol are an essential subject in fuel utilization and vapor explosion prevention. In this study, the effects of isopropyl nitrate (iPN) addition on the detonation initiation characteristics of vapor-liquid two-phase n-heptane (HP)/air aerosol were investigated in a detonation tube. The aerosol was generated by injecting liquid HP/iPN mixture into the test section through 12 sets of dispersion systems. Hydrogen-oxygen pre-detonation served as the initiation source. Chemical reaction kinetics simulation was performed to elucidate the underlying reaction mechanism of iPN/HP mixtures. Experimental results demonstrated that the detonation wave velocity of HP/(iPN)/air aerosol ranged from 1480 to 1820 m/s and the detonation pressure varied from 2.6 to 5.2 MPa, whereas iPN/air aerosol exhibited lower velocity (1260 to 1450 m/s) and comparable detonation pressure (3.2 to 5.3 MPa). iPN addition significantly enhanced the detonation initiation sensitivity of HP/air aerosol and reduced the minimum detonable concentration. This promoting effect intensified with increasing iPN content, though excessive iPN content considerably weakened the detonation intensity. Numerical analysis revealed that iPN facilitated detonation initiation by generating reactive radicals (H, CH 3 , OH, and O) during the early stage of the ignition induction period, accelerating the establishment of a radical pool for HP reaction and thereby reducing the reaction induction period of HP. Furthermore, iPN addition introduced new consumption pathways for HP and increased the pathways converting intermediate products into the final product CO 2 . These findings provide valuable insights for fuel formulation optimization and industrial safety management.