CFD Study for Air Ventilation Optimization in the H-II Transfer Vehicle (HTV) Pressurized Logistic Carrier (PLC)

Abstract

The H-II Transfer Vehicle (HTV), designed and built in Japan, is JAXA's unmanned cargo transfer spacecraft that delivers supplies to the International Space Station (ISS), and its maiden flight (HTV1) was successfully completed in November 2nd, 2009. The HTV delivers up to 6,000 kg of cargo, both pressurized and unpressurized, to the ISS. While the HTV is berthed to the ISS, ISS crew will enter HTV's pressurized logistics carrier (PLC) to transfer onboard supplies to the ISS. After HTV1 design completion, PLC cargo carrying capability enhancement was required, and relocation of air ventilation (AV) system was necessary to obtain additional cargo loading volume. In the present paper, computational fluid dynamics (CFD) was utilized to optimize the diffuser configuration in HTV2 and subsequent for better performance in compatibility rate of wind velocity. Inter module ventilation air is introduced by ducting and injected to PLC through two diffusers, then goes back to ISS through module hatch opening after ventilating inside PLC. AV return grill was eliminated to attain an additional cargo loading volume and lighter air ventilation system. The diffuser was relocated to the place in conjunction with the vestibule area, and a total of seven cases in different configurations were carried out with variations in inlet velocity angle. It was found that the asymmetric angles between the two diffusers would create a large and stable vorticity in the cabin, achieving better performance in compatibility rate of wind velocity. Symmetric angles between the two diffusers would only create impinging jets in the cabin, and the compatibility rate would rather decrease. The CFD analysis was successful in finding a high performance configuration.