An experimental comparison of the elliptical and circular nozzles spray and mixing characteristics under different injection pressures

Abstract

This paper presented an experimental comparison of the fuel–air mixing quality and macro spray behaviors for circular and elliptical orifice, through Mie-scattering method based on a laser beam system, at different high injection pressures (120 MPa, 140 MPa, 160 MPa) and backpressures (1 MPa, 3 MPa). It was found that the elliptical orifice exhibited shorter spray tip penetration than the circular one due to the higher air drag force induced by the larger spray surface area. Meanwhile, the difference of penetration between the elliptical and circular sprays was not obvious at the high injection pressure of 160 MPa. Also, the elliptical spray cone angles were always wider than the circular one. The interactions for the elliptical spray cone angle between major and minor planes indicated that the elliptical spray experienced axis-switching even at the high injection pressures. Moreover, the high backpressure can reduce the interaction frequency of the spray cone angle, while the high injection pressure can increase the interaction frequency. Furthermore, the elliptical spray exhibited larger spray areas than the circular spray, which suggested that using an elliptical orifice was helpful to increase the mixture quality of fuel and air. The effect of the elliptical orifice with a small aspect ratio on the spray area was not as significant as the injection pressure and backpressure especially under the high injection conditions. Finally, the elliptical spray had more mass of the entrained air as compared to the circular spray, and the injection pressure and backpressure are all had positive effects on increasing the mass of entrained air. The combination of high injection pressure with the elliptical orifice can increase the mass of entrained air, which can improve the spray and mixing quality greatly.