A computational study of two-dimensional serpentine nozzle performance with different annular mixer configurations

Abstract

Serpentine nozzles are widely utilized in many types of military aircraft to maximize survivability due to their ability to suppress infrared radiation emitted from the engine exhaust system. An annular mixer is used in a serpentine nozzle to improve the performance of the nozzle by intensifying the mixing between the ambient air and exhausted gases. Therefore, this study aims to numerically investigate the performance of a two-dimensional single serpentine nozzle with different annular mixer configurations. The performance of the nozzle based on the internal flow behavior and the external jet of different models of an annular mixer is investigated. Herein, different models of annular mixers with different annular diameters of 320 and 340 mm, different annular lengths of 140 and 280 mm, and different mixer shapes are investigated. The simulations are conducted with a 3-dimensional model using commercial STAR CMM+ software. The results demonstrate that a smaller mixer diameter, indicating a higher bypass ratio nozzle, has a lower temperature inside the nozzle and at the external jet compared to a larger mixer diameter, indicating that a lower bypass ratio nozzle can improve the nozzle performance by reducing the infrared radiation. The smaller mixer length can decrease the temperature inside and outside the nozzle but increase the velocity outside the nozzle. Finally, the conical shape of the mixer can reduce the temperature inside the nozzle due to the reduction of the core flow rate but increases the temperature of the exhausted jet due to the lower expansion of flow inside the nozzle compared to the nozzle with a cylindrical shape. This study demonstrates that a mixer with a smaller diameter and shorter length with a cylindrical shape can provide better performance for a nozzle.