Abstract
Porous burner has a potential of lower-emission in a combustion of liquid fuels. However, it would be less attractive owing to its complexity and inefficiency in operations of the fuel vaporizing, in view of a practical application. To solve the problem described above, an ignition promoted system is proposed with taking advantages of characteristics of the porous burner. In this research, a fuel-vaporizing combustor equipped with porous burner made of Al 2O 3 and 1.7 MHz-ultrasonic oscillator was manufactured based on the calculating of a rate of fuel-penetration through the porous media. It was supposed that the fuel-penetration was derived from a capillary effects and the local pressurization of ultrasonic influenced by pore size and ultrasonic propagation. Combustion characteristics of ethanol fuel with manufactured combustor were investigated experimentally. At a term of startup, it is confirmed that vaporization of ethanol was promoted by ultrasonic and instantaneous ignition was achieved. Vaporizing combustion was sustained with recovering a part of its thermal radiation heat through the porous burner because Al 2O 3 had transparency for light which had near IR wavelength. Complete combustion was achieved within Al 2O 3 burner under the equivalence ratio ranged from 0.63 to 0.80, which showed that the combustion mode was similar to a premixing combustion. However, NO x concentration was comparatively high value, 59–97 ppm (O 2 0% base) in the stable combustion region because a heat value per surface area of the flame was increased due to a local high temperature zone caused by a shortened flame.
Published Version
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