Influences of the Downwash Flow from a Helicopter Rotor on the Performances of an Infrared Suppressor

Experimental diagnostic study has been performed,and results show that the downwash flow had remark able impacts on the aerodynamic performances, characteristic temperatures,and infrared radiation.With the increase in the downwash flow velocity,the entrainment coefficient decreased,and the exhaust flow temperature increased,resulting in the rapid increases of the exhausting duct temperature and the suppressor surface temperature.And finally,the downwash flow at hovering condition caused an increase of total infrared radiation between 3～5 μm by about 35%.