Heat transfer of hot flow in a sudden-expansion combustor with vertical mass injection

摘要

This paper aims to investigate experimentally the high-temperature heat transfer of the hot flow stream reattaching in a sudden-expansion combustor with cold air uniformly injected from a porous base which simulates either pyrolysis of fuel vapor or the film cooling effect. The results show that in the range of all inlet temperatures tested the reattachment lengths increased with Reynolds number. A greater inlet temperature extended the recirculation zone, whereas the increase of the injection rate shortened the length. The heat transfer coefficient increased with increasing inlet temperature and Reynolds number, but decreased with increasing injection rate of the cooling air. The maximum heat transfer coefficient was located near the end of the recirculation zone. The nromalized heat transfer coefficient (Nusselt number) was affected by the Reynolds number at the inlet in the whole flow field except near the step (X/H<4). The heat transfer coefficient normalized by the heat capacity (Stanton number), however, was insensitive to the Reynolds number in the recirculation zone. After the recirculation zone, the Stanton numer was still affected by the Reynolds number, although the extent was less that than that of the Nusselt number.