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Show 300r-----------____________________ ~~--------___ ::s:: 250 N E ~ ~- 200 c: Q,) 'u :e 8 150 U L. .! I/) ; 100 .L-. ~ cu Q,) J: 50 -+-To = 730 K -.-To = 330 K O+---~----_._----~--_+----+_--~----~----~--~--~ 50 60 70 80 90 100 110 120 130 140 150 Nozzle Velocity, m/s Figure 9, Convective heat transfer coefficients at the calorimeter surface The furnace atmosphere was found to be non-luminous, no visible flame eddies were observed, and no combustibles were found in the gas samples extracted from the zones beyond the thin jet flames. The flame jet's cold core looked slightly blue and extended into the impingement regions. No soot deposits were found on the cold surfaces of the calorimeter. Figure 6 illustrates a qualitative comparison between the experimental and the calculated fuel concentrations along the flame jet axis. The mass fuel concentrations decrease with distance from the nozzle exit due to the intense combustion products recirculation. In the impingement zone, the flame jet's cores still contain a considerable amount of unburned fuel. Consequently, the combustion process continues in the impingement region over the calorimeter's surface. The combustion is tenninated essentially through interaction between the combustion products from the different flame jets. Figure 7 shows the measured total heat flux, as well as the calculated radiation heat flux values at the calorimeter surface. It is clearly seen that the convective heat flux is at least two times larger than the radiative heat flux and five to ten times larger than heat flux levels found in conventional furnaces. Despite the high specific frring rate (per unit of the calorimeter's surface ), the radiant heat transfer is relatively moderate due to the thin radiant gas layer. Most of the radiation heat transfer to the calorimeter is from the refractory surface, which is heated primarily by convection from the combustion gases. The average refractory surface temperature (see Figure 8) is 200 to 300 K lower than in conventional furnaces at comparable specific firing rates and heat flux levels. Extremely high fluxes of up to 500 kW/m2 (160,000 12 |