| Compared with axisymmetric nozzle, the non-axisymmetric circular to rectangular nozzle can suppress the infrared radiation signature of hot jet obviously with less performance loss. On the other hand, the nozzle fixed tabs can enhance the hot and high-speed jets mixing. It can rapidly reduce the jet's speed and the length of core area.First, the numerical simulation of aerodynamics characteristics of 2-dimensional circular to rectangular nozzle fixed tabs, the exit of which is like the shape of sawtooth, is studied. The standard k ?εturbulence model is chosen among several turbulence models after the work of comparing. 3-dimension flow fields of the sawtooth-shape nozzles are numerically investigated. The temperature and velocity fields of nozzles with different aspect ratio, tab's amount and angle are obtained. The aerodynamics characteristics are analyzed, such as streamwise vorticity structures, the mixing coefficient, the total pressure recovery coefficient and the thrust coefficient.The results reveal that the streamwise vorticity created near the sawtooth-shape exit can reduce the length of core area. It can get a higher mixing coefficient (31.3%) with less total pressure loss in a shorter mixing distance. If tab is deflected to make the jet impact it vertically, the mixing coefficient can reach a higher level (33.68%).The high temperature components and exhaust flume are the significant infrared radiation sources of the aeroengine. Aiming at this fact, the second work of this thesis is to research the effect on the infrared radiation suppression of the wall and exhaust flume with the sheltering baffle structure by CFD/IR numerical simulation.The investigating shows: The suppression effect of only one sheltering baffle is not good enough because it is heating by the high temperature exhaust flume. The infrared radiation suppression of the two sheltering baffles and one sheltering baffle surrounded with the cold air can to be 48.5% and 51%.
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