| Summary: | 碩士 === 崑山科技大學 === 機械工程研究所 === 99 === This study aimed at investigating the combustion characteristics of hydrogen/hydrocarbon (methane or propane) hybrid fuel jet diffusion flames. The effect of hydrogen addition and coaxial air on flame stability, flame appearance, flame height and liftoff heifgt was conducted. First, in the experiment of free jet diffusion flames, it was found that hydrogen addition sustains a progressive improvement in flame stability (including liftoff, blowout and blowoff) and reductions in flame height and lifoff height which may be caused due to an increased gas temperature. As hydrogen concentration was lower than 30%, blowout took place from lifted flame; whereas, as hydrogen concentration was not less than 30%, a stable methane/hydrogen lifted flame was not found and blowoff occurred from attached flame.
Second, the effect of hydrogen addition and coflow air velocity on flame stability of propane/hydrogen hybrid fuel jet diffusion flames with coaxial air was experimentally investigated. The results showed that flame height decreases with an increase of coflow air velocity for fixed hydrogen content and fuel velocity. As hydrogen concentration is lower than 35%, blowout took place from lifted flame; however, as hydrogen concentration was no less than 35%, a stable lifted flame was not observed and blowoff occurred from attached flame. For a fixed fuel velocity, as the hydrogen/propane mixture with a higher hydrogen concentration, liftoff and blowoff occurred at greater coflow velocities. In addition, with increasing coflow air velocity, flame height and liftoff height decreased and increased, respectively, for fixed hydrogen concentration and fuel jet velocity.
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