Spray and combustion characteristics of a liquid-fueled ramjet combustor

Spray characteristics and combustion characteristics of a liquid fueled ramjet combustor were experimentally investigated. A liquid fuel was injected transversely into a subsonic hot vitiation air stream. The penetrations of the liquid jet under hot airflow conditions were larger than those calculated by the empirical equation obtained under room temperature airflow conditions. A V-shaped gutter was attached to the center of the combustor for flame holding. Two different arrangements of the gutter and fuel injector were tested. In one of them, the fuel was injected perpendicular to the gutter axis, and in the other, the fuel was injected parallel to the axis. In the case of perpendicular fuel injection, a region with a temperature higher than 1,500 K was observed at the center of the combustor; this region was long and narrow in the direction of fuel injection. The high temperature region reached the bottom wall due to involvement of the fuel in the wake region of a fuel injector. In the case of parallel injection, the high temperature region covered almost the whole cross section of the combustor except in the vicinity of the bottom wall, and the measured combustion efficiencies were higher than those in the case of the perpendicular fuel injection. Pilot fuel injection from the gutter was very effective for the improvement of combustion characteristics. It was also found that the fuel dispersion in the direction injection of high temperature fuel, which simulates the regenerative cooling of a ramjet combustor, was smaller than that of low temperature fuel due to fuel evaporation.