In this study, the combustion characteristics of low calorific gas (LCG) fuels are investigated by numerical simulation. PREMIXED code is used to predict the flame structure and NO emission with two mechanisms, which are GRI 3.0 and USC II chemical reaction mechanisms for CH4 and LCG 8000 and LCG 6000, respectively. Also, elementary reactions related with production and destruction for OH radical are studied because OH radical is dominant for burning velocity and NO emission. As results, the production and the destruction of OH radical for CH4 and LCG 8000 using GRI 3.0 are dominated by reactions of No. 4, No. 2 and No. 3 and by No. 5, No. 3 and No. 7, respectively. For LCG 6000 using USC II, reactions of No. 3, No. 4 and No. 11 and of No. 7, No. 8 and No. 12 dominates to the production and the destruction, respectively. In addition, NO emissions for LCG gas fuel are generated by thermal NO because the flame temperatures are over 1800 K.

In this study, the laminar burning velocity of low calorific gas fuels are verified through the comparison and examination of experimental and predicted results. The bunsen burner which has contraction nozzle is used to measure the laminar burning velocity with the cone angle method. In addition, PREMIXED code combined with two mechanism, i.e., the GRI 3.0, and USC II reaction mechanisms is used to predict the laminar burning velocity. As heating value decrease, the laminar burning velocity correspondingly decreases due to inert gases in the fuels. Through the comparison and analysis of the experimental results and the predicted results, it is confirmed that LCF 9000 and LCF 8000 with the GRI 3.0 reaction mechanism and LCF 7000 and 6000 with the USC II reaction mechanism have a similar distribution of laminar burning velocity between the experimental result and the predicted result. This similarity is due to a large amount of propane, which is not suitable for the GRI 3.0 reaction mechanism in LCF 7000 and 6000.

The coal gasification fuel is important to replace petroleum fuel. Also they have many benefits for reducing the air pollution. Measurements on the combustion characteristics of synthetic gas from coal gasification have been conducted as compared with LPG in constant volume combustion chamber. The fuel is low caloric synthetic gas containing carbon monoxide 30%, hydrogen 20%, carbon dioxide 5%, and nitrogen 45%. To elucidate the combustion characteristics of the coal gasification fuel, the combustion pressures, combustion durations, and pollutants(NOx, CO2, CO) are measured with equivalence ratios(ø), and initial pressures of fuel-air mixture in constant volume chamber. In the case of the coal gasification fuel, maximum combustion pressure and NOx concentration are lower rather than LPG fuel. However CO and CO2 emission concentration are similar to that of LPG fuel.