Numerical Study On Flow Control And Infrared Radiation Characteristics Of Fixed Geometrical Two-Dimensional Nozzle

Compared to mechanical control nozzle with complex actuators, fluidic control nozzle has simple structures, light weight, reliable operation and many other advantages. In this paper, numerical simulation was carried out to study the aerodynamic performance and infrared radiation characteristics of fixed geometrical nozzle. Special concerns were focused on the throat-area-control and thrust-vector-control modes. The factors such as jet injection mode, throat aspect ratio(AR), nozzle pressure ratio(NPR), jet total pressure and temperature were taken into consideration. The main contents and conclusions are summarized as the follows:1. Influences of different parameters under throat-area-control modeWith regards to the aerodynamic performance of nozzle, aerodynamic throat area control by the secondary flow injection is obvious under low nozzle pressure ratio(extended expansion), while the thrust loss and total pressure loss are large. Under high nozzle pressure ratio(fully expansion and under expansion), the secondary flow injection lead to relatively larger thrust coefficient and total pressure recovery coefficient, but the effect on the aerodynamic throat area control is weak. As the throat aspect ratio increases, the geometric height of the throat is decreased, resulting in a weakerness of throat area control effect and slao an increasement of nozzle loss. The increase of the secondary flow pressure can significantly enhance the area control effect, but it will bring more losses. Total temperature of secondary flow has little effect on the aerodynamic performance of nozzle. As for the infrared radiation performance of exhaust system, infrared radiation of hot wall and plume is behaved a "pear-shaped" distribution feature in both the horizontal and the vertical planes. The total pressure ratio and temperature of the secondary flow has little effect on the infrared radiation emitted from the hot wall in 3-5μm band. However, infrared radiations emitted from the hot wall in 8-14μm band and from the hot plume in 3-5μm band are positively related to the secondary flow total temperature and inversely related to the secondary flow total pressure ratio.2. Influences of different parameters under thrust-vector-control modeWith regards to the aerodynamic performance of nozzle, due to strong shock waves, a larger thrust vector angle can be relized by the secondary flow injection under low nozzle pressure ratio condition(extended expansion). However, the secondary flow injection under high nozzle pressure ratio condition(fully expansion and under expansion) has weaker action on the thrust vectoring. Both the throat aspect ratio and the total pressure of secondary flow have effects on three secondary flow injection schemes, including the secondary flow injection on the diffusion section, secondary flow injection at the throat location, and combined injection. The differences are mainly behaved on the oblique shock wave strength and recirculation zone. As the shock wave is enhanced, the primary flow deflects more obviously, however, more pressure loss is occurred. As for the infrared radiation performance, the secondary flow total pressure has different effects on the infrared radiation characteristics of exhaust system for the different secondary flow injection schemes. The infrared radiation is inversely related to the secondary flow total pressure ratio in genernal. Infrared radiation distributions of the hot wall and the plume in the horizontal plane are symmetrical. While in the vertical plane, the peak or valley location of the infrared radiation is tightly associated with the primary flow deflection.