An experimental study on detonation characteristics of binary fuels hydrogen/propane-air mixtures

The paper is aimed to experimentally probe the detonation characteristics of the binary fuel hydrogen/propane-air mixture. The experiments were conducted in an obstructed cylindrical tube with a 92-mm inner diameter and a 12-m length at normal pressure and temperature. Eleven instrument ports and eleven piezoelectric pressure transducers were adopted on the tube wall surface. A Schelkin spiral with a blockage ratio of 0.5 and a pitch with inner diameter as the tube and with the length of 3 m were used to accelerate the flame propagation until the detonation initiated. The studied binary fuel mixtures with equivalence ratio of 1.1 and hydrogen molar fraction varying from 0.5 to 1.0 were prepared by the partial pressure and ignited via a spark plug at about 15-mJ discharge energy. The detonation characteristic parameters such as velocity, pressure and cell size were achieved with pressure transducers and smoking foils, respectively. It can be therefore concluded that the self-sustained detonation is observed as follows: (ⅰ) detonation velocity ratiov/v_CJ varies from 0.99 to 1.0 and pressure ratio p/p_CJ changes from 0.8 to 1.2; (ⅱ) detonation cell size varies from 10 mm to 50 mm. When propane is added to hydrogen/air mixtures, the detonation velocity decreases, but the pressure and cell size inversely increase. The variation trends of the detonation parameters at the beginning change quickly because the detonation characteristics of hydrogen/propane-air mixtures are similar to those of hydrogen/air due to the larger hydrogen molar fraction. Afterwards, the trends gradually slow down because the increasing molar fraction of propane with heavier molecular mass in the mixtures which plays a dominant role in the binary fuels. At last, a relationship between detonation cell size and ZND chemical induction length was obtained. Thus, our conclusion can provide the experimental data in the hydrogen explosion hazard prevention.