关键词: 贫油直喷；收敛出口；旋流角度；旋流数；回流区

Abstract: In order to investigate the flow characteristic of lean direct injection (LDI) combustor， the swirlers with convergent outlet were proposed for single element LDI combustor， the flow characteristic of four models ， which the swirl angles are 35°， 38°， 40° and 45°， respectively， was investigated by numerical simulation under non-reaction and reaction conditions. The effects of swirl angle and combustion heat release on the velocity distribution at the cross section of convergent outlet， swirl number and recirculation zone were obtained. The results indicated that under the non-reaction condition， the velocity profiles at the cross section of convergent outlet change from ‘inner high outer low’ to ‘inner low outer high’ as the swirl angle increases， and the recirculation zone is more likely to be formed if the axial velocity is low near the inner wall and high near the outer wall， each model could form a stationary central recirculation zone expect the 35° model. Under the reaction condition， the effects of combustion heat release on weak swirling flow are significant. The convergent outlet velocity profile of 35° model changes from ‘inner high outer low’ to ‘inner low outer high’， and the recirculation zone is formed at the downstream of the swirler， which indicates that the combustion heat release could promote the swirling flow towards vortex breakdown mode. For the swirling flow which the recirculation zone could be formed under non-reaction conditions， the effects of heat release on it are small， however， the reverse pressure gradient would be disappeared more quickly due to the gas expansion， resulting in the size and length of the recirculation zone under reaction condition being slightly smaller than those under non-reaction condition.

Key words: Lean direct injection；Convergent outlet；Swirl angle；Swirl number；Recirculation zone