Numerical and experimental investigation of infrared radiation characteristics of a turbofan engine exhaust system with film cooling central body

A new concept of film cooling central body for the exhaust system of turbofan engine was brought out to suppress the infrared radiation of engine in this paper. The ability of infrared suppression was estimated by experiments and numerical calculations. The numerical method, which use forward–backward ray tracing and narrow band model, had been validated by the experimental results. The aerodynamic characteristics and infrared radiation distribution of exhaust system with/without film cooling central body were investigated for several different configurations. The experimental results reveal that the bypass flow can be used to cooling the central body and suppress the infrared radiation at the rear aspect of the engine. The inlet area of lugs in the bypass passage determined the mass flow rate into the central body. To obtain the effects of the film cooling holes configuration on the surface temperature and infrared radiation intensity of the exhaust system, a series of computations on full scale exhaust system have been performed. The numerical simulation results indicate that the film cooling central body can suppress the infrared radiation of the inside enclosure by 40–70% comparing to the central body without the film cooling at zero degree aspect (normal to nozzle outlet). The film cooling central body for exhaust system of turbofan engine has remarkable ability to suppress the infrared radiation from the inside enclosure of nozzle.