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10. Combustion and Reacting Flows

A low NOx porous radiant burner using lean methane/hydrogen/air mixtures and its application to a novel hot water boiler

We measure surface temperatures and emissions of a low NOx porous radiant burner using lean methane/air mixtures blending with various percentages of hydrogen (XH2 = 10%, 30%, 50% in vol.%) at an equivalence ratio phi=0.65. The Ni-Al porous burner was manufactured by applying the high-temperature self-propagating synthesis method having a hollow top-dome cylindrical geometry of 150 mm-height, 66 mm-outer diameter, and 9 mm-porous shell thickness with a total surface of S=0.03106 m2. The burner with a porosity of about 0.6 is operated at an internal combustion mode using three different volume flow rates (Q=250, 303, 379 SLPM) corresponding to three different power levels (P=10, 12, 15 kW), where the firing rates FR=P/S are varied from 322 kW/m2 and 386 kW/m2 to 483 kW/m2. The porous surface temperature distributions are recorded by an infrared (IR) camera with 640 x 480 IR pixels at 25 frames/s. Their corresponding radiant heat powers (Pm) are measured by a power meter positioned at a distance of d=500 mm from the middle of the cylindrical porous burner for the estimation of radiant heat efficiency (E=PR/FR), where PR=(d/r)^2*Pm/S and r is the inner radius of the cylindrical burner. Results show that the surface temperatures increase with XH2 and P; E increases with increasing XH2 at the same FR, but it decreases with increasing P. The highest measured NOx and CO emissions occur at P=15 kW and at XH2=50%: [NOx]=31 ppm and [CO]=13.5 ppm corrected at 3% oxygen concentration. Both [NOx] and [CO] emissions can be simultaneously low, showing a clean combustion when using the present porous radiant burner. Finally, for application, a novel hot water boiler using three equilaterally-positioned porous radiant burners inside fin-tube heat exchangers is proposed and discussed.

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Author Information

Hao-Yu Hsieh
Mr.
Presenting author
Shenqyang (Steven) Shy
Prof.
Corresponding author
Wei-Wun Wang
Mr.