Jet Mixings of Alternating-Lobe Nozzles under Pumping Air Intake and Stamping Air Intake Conditions

Abstract

Jet mixings of a coplanar alternating-lobe nozzle (CoALN), scarfing alternating-lobe nozzle (ScALN), sword alternating-lobe nozzle (SwALN), and sword and chevron alternating-lobe nozzle (SwChALN) were numerically investigated using three different far-field velocities to simulate the conditions of pumping air intake and stamping air intake. It was confirmed that the stamping air intake can be introduced to increase the cool air involved in the mixing for an infrared suppressor of a helicopter. It was found that the stamping air intake increases the amount of cool stream near the mixing tube, which can effectively decrease the temperature of the mixing tube, thus improving the infrared suppression performance. Under the two intake conditions, for a normal infrared suppressor with a short mixing tube, SwALN and SwChALN are recommended; however, for an integrated infrared suppressor with a long mixing tube, CoALN and ScALN should be adopted. The shape of the longitudinal vortices is closely related to the large-scale heat and mass convection. The plumper longitudinal vortices can bring faster mixing to the affected region.