Coupled analysis of the film-cooling and infrared characteristics of an axisymmetric vectoring exhaust nozzle

The film-cooling and infrared radiation analysis of a high-performance aero-engine nozzle wall is the key problem in developing a vector propulsion technology. This study adopts a narrow band model to investigate the cooling and radiation of a vectoring nozzle and, in particular, to compute the gas spectral characteristic in infrared band. The radiative heat transfer between the hot gas and the wall is considered with an enclosure model. The calculation of film cooling is performed through a cooling effectiveness method. A coupled heat balance equation of heat flux and wall temperature is established on the multi-layer structure of the nozzle, including the wall, heat shield, and outer shield. The temperature distribution of the nozzle wall is determined by solving the equation through the Newton-Raphson method. A simulation program is developed, and the expansion part of an experimental nozzle in NASA TN D-1988 is investigated for verification. Another vectoring nozzle with a multi-row of film cooling is also investigated. Results of temperature distribution under deflection and non-deflection conditions are presented, as well as the infrared radiation observed from the rear hemisphere of the nozzle outlet. This study shows that the film in the heat shield remarkably cools the convergent part of the nozzle, thereby increase the temperature on the expansion part of the nozzle. The deflection of the nozzle can change the distribution of the wall temperature and the radiation on the expansion part, which is lower on the deflection side than on the opposite side. The radiation from the nozzle outlet is high, particularly along the deflection direction in the rear hemisphere.