Characteristics of a fuel spray downstream the pressure atomizers under high pressure in the combustion chamber

The paper presents numerical calculations of a fuel spray downstream a swirl-type fuel injector carried out for various pressures in the combustion chamber using the model of liquid film motion. The effect of the chamber pressure, or, to be more exact, the air density in the pressure chamber on the fuel spray characteristics is investigated. The mathematical model was constructed on the assumption of one- dimensional and steady swirling flow. The liquid is considered to be incompressible and have zero pressure gradient in the direction of the film motion and in the tangential direction. The influence of viscous forces on the motion of liquid is neglected, but the viscous interaction at the interface between liquid and gas is taken into account. The change of velocity in the circumferential and normal directions can be neglected, because in practice the film thickness is considerably smaller than the spray radius. It is shown that the pressure increase in the combustion chamber makes spray characteristics significantly different from those observed at atmospheric pressure. An increase of pressure results in increasing the thickness of the fuel film and decreasing the spray-cone angle. It leads to an increase in the average Sauter diameter in the spray of fuel atomized by the pressure atomizer. The air flow downstream the swirl nozzle has the opposite influence on the size of drops in case of increased pressure in the chamber.