Numerical Investigation On Aerodynamics And Infrared Radiation Characteristics For Single Expansion Ramp Nozzle With An Curved Exhaust Passage

Single expansion ramp nozzle (SERN) is a new style integrate exhaust nozzle, which has a lot ofadvantages, for instance, suppressing the infrared radiation and the radar radiation, low resistance ofthe nozzle’s after body, and also, the whole weight is light, especially the non-symmetry of the nozzlecan improve the agility and maneuverability of the airplanes.Based on computational fluid dynamics/infrared radiation (CFD/IR) numerical calculations,using standard k turbulent model and standard wall functions, the effects of different structuresand nozzle pressure ratio (NPR) on the aerodynamic and infrared radiation characteristics wererevealed for SERN, including sidewall length, ramp angle, convergent nozzle area ratio, ramp length,slots area ratio, angle of slots and second flow.The results show that: As the length of sidewall increases, the thrust-vector angle is enlarged,axial thrust coefficient is decreased at small NPR, axial thrust coefficient improves at large NPR, andthere is a little influence of sidewall to the infrared radiation of plume and total nozzle. With increaseof ramp angle, the axial thrust coefficient is decreased rapidly and thrust-vector angle is enlarged, theinfrared radiation of total nozzle increases. When ramp angle is10°and NPR is four, five and six,with increase of contraction ratios, the axial thrust coefficient improves, and the largest is0.966,thrust-vector angle is enlarged from3.64°to10.2°, the infrared radiation of plume is decreased43.5%. With increase of ramp length, the big axial thrust coefficient needs high NPR. With increase ofNPR, the axial thrust coefficient increases firstly and then decreases, meantime, the thrust-vectorangle reduces, the infrared radiation is decreased.On the condition of low NPR，the slots form the “aerodynamic boundary” to improve theaerodynamic performances of the nozzle, and the axial thrust coefficient increases3%. On thecondition of high NPR，the hot gases enter the slots to decrease the thrust coefficient. With the slots,the infrared radiation intensity of SERN is largely decreased. The infrared radiation intensity isdecreased90%at0°on XOY plane. With increase of slots area ratio, the infrared radiation intensity isdecreased. When there is no hot gas to enter the slots, the angle of slots has little influence to theinfrared radiation of the plume and total nozzle. When there is hot gas to enter the slots, with increaseof slot angle, the infrared radiation is increased. With increase of second flow, the total infraredradiation is mostly decreased10%at XOY plane. The infrared radiation of total nozzle is decreasedabout20%from-10°to5°at XOZ plane.