A study of supercritical jet fuel injection

An experimental investigation was conducted to examine the behavior of supercritical fluid (SCF) jets injected into supercritical environments. The behavior of the fluid, JP-10, was studied after it was passed through a pressure-swirl atomizer and entered a nitrogen environment. SCF jet behavior was characterized by the jet cone angle and penetration length. Cone angle and penetration length are reported as functions of density ratio (defined as the ratio of density of the injected fuel to the nitrogen environment), fuel mass flow rate, and pressure-swirl atomizer internal geometry. The density ratio was varied by altering the reduced temperature of the fuel (1.01<T-r<1-10) and nitrogen environment, while keeping the fuel reduced pressure constant at 1.05. Fuel mass flow rate ranged from 1.0 to 3.0 g/s (7.94 to 23.8 lbs/hr). Pressure-swirl atomizer internal geometry was varied by controlling the swirl number, ranging from straight bore to Sn=1.0. It was found that increasing the swirl number for a SCF fluid has the largest effect on jet cone angle, followed by a change in the density ratio; the mass flow rate had the least effect. The penetration length of the SCF jet increased when either the mass flow rate or density ratio increased. The mass concentration field significantly widens when the swirl number of the injector increased, as opposed to changes in the mass flow rate or density ratio which were found to have little effect.