Fuel distribution of sub- and supercritical kerosene jets into swirling air in an annular mixing channel

Abstract

The uniformity of fuel/air mixture in the mixing channel of the lean premixed and prevaporized injector is important for NOx emissions reduction in aircraft engines. In the present study, an optical annular mixing channel is designed to investigate the effects of heated RP-3 fuel on fuel/air mixing at liquid, gas, and supercritical injections. Planar laser-induced fluorescence is employed to obtain multiple cross-sectional fuel distributions along the axial direction of the mixing channel. The results show that for the liquid injections, the droplets tend to move closer to the outer wall due to the effect of the centrifugal force. Increasing air temperature in the range of 450 K to 670 K can promote liquid evaporation and suppress the centrifugal effect, and result in a 70 % increase in the fuel dispersion area. Compared with liquid injections, the gaseous injections are more evenly distributed and closer to the inner wall. And the displacement of the fuel is mainly determined by the fuel–air momentum ratio. Interestingly, the near-critical and supercritical fuel injections in the range of 638–700 K and 2.2–2.5 MPa show bimodal fuel distributions along the radial direction. The fuel distributed close to the outer wall is from the condensed part which moves under centrifugal effect, while the fuel distributed close to the inner wall is from the gaseous part which is mainly affected by injection penetration.