方柱-强旋组合旋涡脱落机制研究

Study on Vortex Shedding Mechanism of Square Cylinder Coupling with Strong Swirl Flow

关键词:  旋流  钝体绕流  涡脱落

Key words:  Swirl flow  Bluff body  Vortex shedding

摘要:

强旋流和钝体绕流均可构造低速回流区以利于高速气体稳定燃烧,本文通过在钝体中心开孔通入旋流气体模拟研究了旋流流动对钝体绕流旋涡脱落的影响规律。计算结果表明,在旋流作用下,钝体绕流涡脱规律更加复杂,涡脱由上下边界层失稳主导变为由旋流管中的旋流涡主导,并且形成的涡尺度增大,在脱落过程中会由于旋涡的破碎产生“点潭”以增强周围涡强度。同时,柱体涡和旋流涡的相互作用可以减小流动阻力,增加回流区长度和回流质量流量,从而强化传热传质,起到强化燃烧增加燃烧稳定性的效果。

Abstract:

In order to stabilize combustion of highspeed gas,both the strong swirl and the flow around blunt bodies can form low velocity recirculation zone. The vortex shedding mechanism of the flow around bluff body with swirling flow through the central opening is predicted. Compared with the vortex shedding mechanism of the square cylinder blunt,the computational results show that the vortex shedding mechanism of the coupling combustion stabilizer is controlled by the vortex of the swirling flow instead of the cylindrical vortex. During one shedding period,the heat and mass can be enhanced by the vortex source which is brought by the vortex breaking. Also,the flow around bluff body with swirling flow through the central opening can reduce drag,increase the length of the recirculation zone and reflux mass,and increase the number of vortexes so as to enhance the heat and mass transfer. Thus,coupling combustion stabilizer can enhance the stability of flame.