TY - JOUR

T1 - Diffusion Combustion of a Hydrogen Microjet at Variations of its Velocity Profile and Orientation of the Nozzle in the Field of Gravitation

AU - Kozlov, Victor V.

AU - Vikhorev, Valentin V.

AU - Grek, Genrich R.

AU - Litvinenko, Yury A.

AU - Shmakov, Andrey G.

PY - 2019/7/3

Y1 - 2019/7/3

N2 - Experimental data on diffusion combustion of round hydrogen microjets with a parabolic and a “top-hat” mean velocity profiles at the nozzle exit at different spatial orientation of the microjets are reported. Most of all, we are interested in the behavior of the so-called «bottleneck flame region» of the jet and its contribution to the diffusion combustion. As is found, in the cases of the jet velocity opposite and orthogonal to the direction of the gravitational force, the main features of combustion are practically the same. Otherwise, at the velocity vector matching the direction of the gravitational force, the combustion characteristics become much different. Combustion in the «bottleneck flame region» is found to be more stable at the parabolic profile while the stability of combustion is reduced at the top-hat velocity distribution at the nozzle exit. Then, the flame detachment occurs in the absence of the «bottleneck flame region» and the microjet combustion is terminated at a much higher velocity. An inversion of the dependence l/d = f(U0) is observed at the transition from the parabolic to the top-hat velocity profile of the jet. The ratio of the «bottleneck flame region» size (l) to the nozzle exit diameter (d) is l/d. The nozzle heating is shown to have a profound effect on the microjet combustion.

AB - Experimental data on diffusion combustion of round hydrogen microjets with a parabolic and a “top-hat” mean velocity profiles at the nozzle exit at different spatial orientation of the microjets are reported. Most of all, we are interested in the behavior of the so-called «bottleneck flame region» of the jet and its contribution to the diffusion combustion. As is found, in the cases of the jet velocity opposite and orthogonal to the direction of the gravitational force, the main features of combustion are practically the same. Otherwise, at the velocity vector matching the direction of the gravitational force, the combustion characteristics become much different. Combustion in the «bottleneck flame region» is found to be more stable at the parabolic profile while the stability of combustion is reduced at the top-hat velocity distribution at the nozzle exit. Then, the flame detachment occurs in the absence of the «bottleneck flame region» and the microjet combustion is terminated at a much higher velocity. An inversion of the dependence l/d = f(U0) is observed at the transition from the parabolic to the top-hat velocity profile of the jet. The ratio of the «bottleneck flame region» size (l) to the nozzle exit diameter (d) is l/d. The nozzle heating is shown to have a profound effect on the microjet combustion.

KW - Diffusion Combustion

KW - Gravitational Force

KW - Round Hydrogen Microjet

KW - Shadowgraph Images

KW - «Bottleneck Flame Region»

KW - “Top-Hat” and Parabolic Velocity Profiles

KW - "Top-Hat" and Parabolic Velocity Profiles

KW - PLANE

KW - JETS

KW - << Bottleneck Flame Region >>

KW - FLAME

UR - http://www.scopus.com/inward/record.url?scp=85053322627&partnerID=8YFLogxK

U2 - 10.1080/00102202.2018.1518323

DO - 10.1080/00102202.2018.1518323

M3 - Article

AN - SCOPUS:85053322627

VL - 191

SP - 1219

EP - 1235

JO - Combustion Science and Technology

JF - Combustion Science and Technology

SN - 0010-2202

IS - 7

ER -