A method for measurement of spatially resolved radiation intensity and radiative fraction of laminar flames of gaseous and solid fuels

摘要

This work introduces a new method for determination of spatially resolved radiation intensity and radiative fraction for axisymmetric laminar diffusion flames by using a modified DSL-R camera employed to collect monochromatic, 900 nm, images and a Schmidt-Boelter heat flux gauge. A novel instrument, Milligram-scale Flame Calorimeter, is employed to supply the flame with either gaseous fuel or solid fuel pyrolyzate and measure the total heat releas rate associated with the combustion process. The high spatial resolution provided by the images of the camera allows for a multi-emitter treatment of the 20-60 mm tall flames. The flames' shapes and monochromatic radiation intensity profiles are extracted from the images. Using the radiation transport equations formulated for the system's specific geometry, the monochromatic radiation intensities are related to the total heat flux gauge readings collected at several distances from the base of the flame. Subsequently, spatially resolved total radiation intensity data are obtained. Integration of this intensity over the flame surface yields the radiation heat release rate, of which the ratio to the total heat release rate yields the radiative fraction. In this work, methane, propane and acetylene flames have been studied to validate this methodology (covering a wide range of sooting conditions), while polyethylene-fueled flames above and below the smoke point have been analyzed to demonstrate the method's applicability to solid fuels. The results show that the method produces values that are consistent with previous studies, particularly when the assumptions of the previous studies are replicated. Additionally, the data indicate that for flame heights that are all below (or all above) the smoke point, the value of the maximum total radiation intensity does not depend on the total heat release rate. This behavior of the maximum radiation intensity suggests that said parameter is a good candidate to correlate with the radiativ