Natural gas, as a major source of clean energy, has low thermal radiation. Because radiation transfers a considerable portion of heat generated by flame, improving the radiation characteristics of flame is necessary. The aim of this study was to investigate how the injection of small quantities of micro kerosene droplets into a natural-gas flame helps enhance the flame’s thermal radiation and consequently its thermal efficiency. For this purpose, a micronozzle injected kerosene droplets into a natural-gas nonluminous flame. Using an IR filter, a digital camera, an S-type thermocouple, a calibrated thermopile, and image processing software, along with numerical modeling, the radiation properties of a flame were studied. The results show that the injection of kerosene droplets causes an increase of 52% and 11.75% in thermal radiation and efficiency, respectively. Also, mean flame temperature increases by no more than 8% whereas the mean flame emissivity coefficient increases remarkably.

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