Abstract: When flying at high speeds in the atmosphere，the tremendous aerodynamic heat flux and resistance pose significant challenges to both the structural materials and thrust of an aircraft. Active flow control technology，which employs CO₂ as the working fluid，holds great potential for cooling and drag reduction. The present study investigates the cooling and drag reduction characteristics of a CO₂ reverse jet at the nose cone of an aircraft using numerical simulations. Under different jet parameters，condensation may occur at the front end of the CO₂jet. When condensation does not occur，the cooling and drag reduction abilities of CO₂ are comparable to those of commonly fluids. However，when condensation takes place，the cooling effectiveness improves significantly while the drag reduction ability weakens. As the total temperature of CO₂ in the jet increases，the proportion of solid CO₂ in the condensation zone decreases，and the detachment shock distance increases. Due to the impact of the condensation phenomenon，the drag reduction effect significantly decreases with decreasing total temperature of the CO₂ jet. As the total pressure of the jet increases from low to high，the flow field undergoes a transition between long and short jets. The pressure in front of the blunt body initially decreases，then increases，and finally decreases again. The wall stanton number monotonically decreases，leading to an improved cooling effect. In contrast，increasing jet angle results in a weakened cooling and drag reduction effect. When the jet angle exceeds 60°，the cooling effect is lost entirely. Additionally，as the angle of attack of the incoming flow increases，the difference in thermal and resistance environments between the upwind and leeward regions of the blunt body becomes increasingly asymmetric，and the cooling and drag reduction effect of the jet on the upwind region is weakened.

Key words: active flow control, CO₂ opposing jet, cooling and drag reduction, jet condensation, aircraft thermal management