| The study is based on a kind of turbofan exhaust system with axisymmetric convergent-divergentnozzle. Firstly, this paper studied the characteristics of flow field and infrared radiation of sixtwo-dimensional nozzles with different aspect ratios numerically. And the effects of the turbofanexhaust system with two-dimensional nozzle on the infrared radiation suppression are analyzedquantitatively. Then, this paper studied the effect of two-dimensional nozzle with the shielding walland the tabs on the end of the nozzle like as the F-22on the infrared radiation suppression. This paperalso studied the characteristics of aerodynamic and infrared radiation of three full-sizetwo-dimensional convergent–divergent nozzles with different cooling structures(cooling holes arelocated on the tabs, two narrow walls of the divergent part and two wide walls of the divergent part).The results show that:(1) The total pressure recovery coefficient and the thrust coefficient of the two-dimensionalnozzles become lower than that of the axisymmetric nozzle. Compared to axisymmetric nozzle, thethrust coefficient and the total pressure recovery coefficient of two-dimensional nozzle with aspectratio of3.33decrease by2.14%and6.08%respectively, the thrust coefficient and the total pressurerecovery coefficient of two-dimensional nozzle with aspect ratio of8decrease by3.17%and8.48%respectively. Two-dimensional nozzle can suppress infrared radiation very well. The higher of theaspect ratio, the better of the infrared radiation suppression. For the two-dimensional nozzle withaspect ratio of8, in the detect direction of0,the infrared radiation of exhaust plume has decreased by50.1%relative to axisymmetric nozzle, the total infrared radiation has decreased by45.23%relativeto axisymmetric nozzle.(2) After adding shielding wall to the two-dimensional (AR=3.33) nozzle, the thrust coefficientof the two-dimensional nozzle increased by0.67%and the total pressure recovery coefficient of thetwo-dimensional nozzle increased by1.88%.The cold air in the interlayer can promote the mixing ofthe exhaust plume and decrease the infrared radiation of exhaust plume by33.12%relative totwo-dimensional nozzle without shielding wall in the detect direction of90, it can also cool thetemperature of the inner wall and decrease the infrared radiation of inner wall by43.16%relative totwo-dimensional nozzle without shielding wall in the detect direction of0, the total infrared radiationhas decreased by4.36%relative to two-dimensional nozzle without shielding wall in the detectdirection of0. (3) The tabs on end of the nozzle like as F-22did not have a obvious effect of improving the totalpressure recovery coefficient and the thrust coefficient. But it can suppress the infrared radiation ofinner wall well by40.27%relative to two-dimensional nozzle without shielding wall in the detectdirection of0，the total infrared radiation has decreased by5.25%relative to two-dimensional nozzlewithout shielding wall in the detect direction of0.(4) In certain circumstances, increasing the cooling holes of the wall can make surfacetemperature more uniform. However, if insufficient cooling air flow will lead to the gas getting intothe cooling holes, resulting in local temperature is too high, thereby increasing the infrared radiation.Increasing the cooling air can significantly reduce the surface temperature of wall, thereby reducingthe infrared radiation intensity. |
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