关键词: 圆转方过渡段;中心线变化规律;膨胀比;总压恢复系数;角涡

Abstract: To study centerline distribution and expansion ratio, which is the ratio of the maximum section area of the runner to the inlet’s area, changing impact on Circular-to-Rectangular transition duct flow field, based on the actual condition of a certain engine, numerical simulations were performed to investigate the transition duct of three different centerline distribution(rapid turning at the exit, modest turning and rapid turning at the entrance) and five expansion ratio(1.00,1.03,1.05,1.07,1.09). The internal flow field of transition duct, the total pressure recovery coefficient of the duct and the non-dimensional average streamwise vorticities were obtained. Results indicate that the static pressure distribution and streamline distribution of the cross section are different in the different structure. There is corner vortex in the cross section of the structure of the rapid turning at the entrance. And the total pressure recovery coefficient decreases along the flow direction of three different structures， while the streamwise vorticities increase and then decrease along the flow direction. In order of the maximum value of the streamwise vorticities of three different structures, it goes: the structure of the rapid turning at the entrance, the structure of the rapid turning at the exit and the structure of modest turning. Compared with the maximum value, the minimum value decreased by 19%. Due to the increase of the expansion ratio, corner vortices will occur in the cross section, and the total pressure recovery coefficient of the duct decreases gradually, and the structure of ε=1.03 has the highest total pressure recovery coefficient at the exit. The streamwise vorticities increase and then decrease along the flow direction. The local non-dimensional average streamwise vorticity at the exit section in the structure of expansion ratio 1.03 is 40.9% smaller than that of 1.07.The modest turning centerline distribution and the expansion ratio of 1.03 are optimal structure parameters.

Key words: Circular-to-Rectangular transition duct;Centerline distribution;Expansion ratio;Total pressure recovery coefficient;Corner vortex