Heat transfer optimization of an impinging port-array inverse diffusion flame jet

This paper is an experimental study on the heat transfer optimization of an Innovative Inverse Diffusion Flame (IDF) characterized by a central air jet surrounded by an array of fuel jets for impingement heating. It is found that the diameter ratio between air port and fuel port (da/df) exerts significant influence on the impingement heat transfer performance via changing the hydrodynamics and the thermal structure of the IDF. The effects of the overall equivalence ratio (Φ), the burner-to-plate distance (H), and the air jet Reynolds number (Rea), on the local and average heat fluxes, are investigated and compared between IDFs with different da. Under the same air flow rate (Q˙a) and fuel flow rate (Q˙f), it is found that the IDF jet with smaller da produces higher maximum heat flux (qmax′) and average heat flux in the impingement region (q¯), due to the increased flame temperature (Tf) and turbulence level under larger Rea. Fuel-rich flames produce low fuel utilization efficiency and low heat flux and should be avoided in the practical applications. Fuel-lean condition in the range of Φ = 0.9 to Φ = 1.1 is found to be a desirable operation condition for its high heat flux and fuel efficiency. The current study provides valuable information on the heat transfer optimization of this innovative port-array IDF.