The present work investigates the effects of outer stage flare angle on ignition and kernel propagation in a centrally staged optical model combustor based on the kernel dynamics analysis and laser diagnostics of flow...The present work investigates the effects of outer stage flare angle on ignition and kernel propagation in a centrally staged optical model combustor based on the kernel dynamics analysis and laser diagnostics of flow and spray fields.Three outer stage flare angles of 8°,16°,and 25°are researched,respectively.The better ignition performances are found for larger outer stage flare angles.Key properties such as the kernel velocity,kernel trajectory extracted from 6 k Hz high-speed flame images are analyzed in combination with the flow and spray measured via Particle Image Velocimetry(PIV)and Planar Mie Scattering(PMie).Results show that the larger outer stage flare angle imposes a larger opening angle of outer swirl jet(SWJ),shifting the vortex in outer recirculation zone(ORZ)and inner recirculation zone(IRZ)upstream.The spray distribution of a smaller flare angle exhibits a fuel-lean zone near the igniter and this is attributed to the presence of low-angle outer swirl jet that prevents the fuel droplets from arriving at the igniter vicinity.The flame kernel propagates along the path where the strain rate and velocity decrease and the spray droplet density is within the flammable limits.A lower outer stage flare angle increases the strain rate and velocity at the early phase of flame propagation,leading to a longer propagation route and thus increasing the risk of ignition failure.展开更多
基金supported by National Natural Science Foundation of China(Grant No.91641109)National Science and Technology Major Project(2017-III-0004-0028)。
文摘The present work investigates the effects of outer stage flare angle on ignition and kernel propagation in a centrally staged optical model combustor based on the kernel dynamics analysis and laser diagnostics of flow and spray fields.Three outer stage flare angles of 8°,16°,and 25°are researched,respectively.The better ignition performances are found for larger outer stage flare angles.Key properties such as the kernel velocity,kernel trajectory extracted from 6 k Hz high-speed flame images are analyzed in combination with the flow and spray measured via Particle Image Velocimetry(PIV)and Planar Mie Scattering(PMie).Results show that the larger outer stage flare angle imposes a larger opening angle of outer swirl jet(SWJ),shifting the vortex in outer recirculation zone(ORZ)and inner recirculation zone(IRZ)upstream.The spray distribution of a smaller flare angle exhibits a fuel-lean zone near the igniter and this is attributed to the presence of low-angle outer swirl jet that prevents the fuel droplets from arriving at the igniter vicinity.The flame kernel propagates along the path where the strain rate and velocity decrease and the spray droplet density is within the flammable limits.A lower outer stage flare angle increases the strain rate and velocity at the early phase of flame propagation,leading to a longer propagation route and thus increasing the risk of ignition failure.
