Structural aspects of coaxial oxy-fuel flames

Oxy-fuel combustion has been proven to increase thermal efficiency and to have a potential for NO_x emission reduction. The study of 25-kW turbulent diffusion flames of natural gas with pure oxygen is undertaken on a coaxial burner with quarl. The structural properties are analysed by imaging the instantaneous reaction zone by OH* chemiluminescence and measuring scalar and velocity profiles. The interaction between the flame front and the shear layers present in the coaxial jets depends on the momentum ratio which dictates the turbulent structure development. Flame length and NO_x emission sensitivity to air leaks in the combustion chamber are also investigated. Received: 5 November 1999/Accepted: 29 April 2000