Development of a Method for Rapid Characterization of Combustion Properties of Biodiesels

Abstract

Knowledge of the combustion and pollutant emission characteristics is an important part in the develop ment and application of biodiesel fuels. A technique for the rapid characterization of flame radiation prop erties and emission characteristics of liquid biodiesels w as developed for this purpose. A 9.525 mm inner dia meter stainless steel tube was used as the burner. The liquid fuel was injected into a heated air stre am at known rates with the use of a syringe pump; the feed line was heated (temperatures of 425 o C) to pre-vaporize the fuel before burning to avoid the effects of evapora tion parameters on combustion. The temperatures of the fuel and air were monitored with K-type thermocouples embedded within the feed lines. Two testing conditions were studied: (Case 1) consisting of a p remixed methane-air flame which functioned as an ignition and stabilizer of the burning liquid fuel vapor and (Case 2) in which a methane-air flame used as an i gnition source and was shut off after the onset of the burn ing of the liquid fuel vapor. For both test conditi ons, the premixed methane-air flame was issued from a stainless steel tubular burner (9.525 mm inner diameter). Commercially available petroleum-based No. 2 diesel fuel and canola methyl ester (CME) biodiesel were tested. Radiation measurements were made with a high-sensitivity pyrheliometer. For Case 1, the baseli ne methane-air flame radiation and background radiation was documented and subtracted from the combined flame radiation to obtain the radiation from the bu rning liquid vapor. The background radiation was subtracted from the measured radiation in Case 2. The radiant fraction of heat release was computed f or both cases. It was found that the radiant heat fra ction for the Case 1 flames was about 5-10% higher than that of the Case 2 flames for the same injection fl ow rates. It was also observed that the radiative heat fraction for the CME biodiesel was less than that f or the No.2 diesel fuel due to the low amount of so ot produced. NO and CO emission measurements were also taken for the Case 2 flames and analyzed. This method provides a quick way of determining the pollutant emission potential of newly-developed liquid biofuels.