|Budget Amount *help
¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1999: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1998: ¥900,000 (Direct Cost: ¥900,000)
We previously proposed a new method for premixed combustion of liquid fuel using air bubble blowing. In the present study, this method was applied to heavy oil, which has high boiling temperature and high viscosity. Ceramic foam plate was set in the downstream of the bubble layer not only to hold the flame on it but also to actively feedback the heat released at the flame front toward the upstream side and to promote the evaporation of low volatile liquid fuel. Effects of parameters, such as thickness and porosity of the flame holder (ceramic foam plate), preheat of the fuel, air and fuel supply rate (equivalence ratio) , on the combustion state and the emission characteristics of CO, C0ィイD22ィエD2 and UHC were examined and the following results were obtained.
(1)Thickness and porosity of the flame holder have small effects on the combustion state. Thick flame holder with low porosity is favorable to the flow rectification and the heat feedback, but it promotes fuel pyrolysis and therefor
e deposit formation inside the plate which leads to blocking the mixture flow after a long time use.
(2)When the low volatile fuel is used, fuel supply to the flame holder is done mainly by the small flying fuel particles produced by the collapse of bubbles and secondarily by the fuel vapor, therefore the flame holder functions as the vaporizer of these small particles.
(3)For a high viscous fuel like heavy oil, fuel preheating is necessary to decrease its viscosity and keep the fuel mobility inside the flame holder, which leads to an increase in the flame stability. Fuel preheating is also effective for promoting fuel evaporation.
(4)Uniform red-hot combustion state is obtained over a fairly wide range of air flow rate (I.e., combustion load) , and depending on the air flow rate steady combustion region extends toward the lean side till the equivalence ratio near to 0.5, indicating the promotion of combustion by the heat feedback.
(5)Concerning the emission characteristics, suppression of CO/C0ィイD22ィエD2 to a low level is possible in the lean side and suppression of UHC to the level which clears the indoor concentration regulation is realized over the wide range of combustion load. Less