Multi-objective optimization on flow characteristics of pressure swirl nozzle: A LES-VOF simulation

Abstract

Due to simple structure and good atomization performance, pressure swirl nozzles are favored in aero-engine, agriculture, and numerous industrial combustion applications. Spray characteristics are crucial to evaluating nozzle performances, and are affected by factors such as the discharge orifice diameter (dori), inlet pressure (p), and liquid viscosity (μl). In this paper, a multi-objective optimization on flow characteristics of pressure swirl nozzle is numerically studied by coupling of large-eddy simulation (LES) with volume-of-fluid (VOF) method. It is found that, although the discharge orifice diameter is the key factor for a spray angle, the air core formation is mainly affected by μl and p, with obvious air core formed when μl < 0.02 Pa‧s and p > 0.02 Mpa. The mass flow rate of the liquid is increased with higher liquid viscosity, even though the axial velocity is decreased. In addition, the air core formation is discussed by analyzing the flow field in the nozzle. It is found that the formation of the air core is mainly due to the centrifugal force overcoming the viscous force; thus, the viscosity, rather than pressure difference, is more likely to play the key role.