Study on flow heat transfer and strength characteristics of a double-layer thin-wall active cooling nozzle

Abstract

With the increase in auxiliary power units (APU) operating temperature and the demand for infrared radiation suppression, the traditional single-layer nozzle can not meet its performance requirements. This paper proposes a new type of double-layer thin-wall active cooling nozzle. The flow heat transfer and strength characteristics of the double-layer cooling nozzle are studied by numerical study with exhaust temperature, the velocity of entrained fluid and rib configuration as variables. The results show that when the maximum exhaust temperature is 1003 K, and the velocity of entrained fluid is increased to 1.94 m·s−1, the cooling factor can reach 0.94, and the radiation heat dissipation effect of the nozzle is significantly reduced. When the velocity of entrained fluid is 3 m·s−1, the maximum temperature of the nozzle outer wall with different rib configurations is 447 K, and the radiation heat dissipation effect on the compartment and the external environment is significantly diminished. Compared with long straight ribs, the cooling effect of multiple ribs configuration is more effective; however, the stress concentration phenomenon is more significant. Meanwhile, the change of rib configuration leads to the inconsistency of plastic strain distribution of the nozzle and the risk of local structural failure. Therefore, the design of double-layer thin-wall cooling nozzles should consider the active cooling effect and structural characteristics comprehensively to ensure the reliability of operation and stealth requirements.