Utilizing a ground test model

an experimental diagnostic study on the infrared suppressor integrating the exhaust system with the tail part of a helicopter has been performed to investigate the effects of ambient air pumping-mixing and rotor downwash on reducing the exhaust system temperature and diminishing the target infrared signature.The result shows that the gas temperature can be reduced by 50% at least by lobed nozzle which injects ambient air to mix with the hot gas;and rotor downwash flow that cools the tail part of the model will cause a decrease of total infrared radiation between 3-5 μm and 8-14 μm equivalent to about 39% and 33%.In addition

simply enlarging the lobed nozzle is not propitious to the enhancing of the entrained flux

while it will reduce the injection coefficient.