In the present study, the weight loss by pyrolysis with increasing temperature was measured by TGA under atmospheric (0.1 MPa) and reduced (10-30 Pa) pressures of nitrogen for Japanese Miike, Akabbira, Taiheiyo coals. The reducedpressure condition was employed to minimize the effects of intra-particle secandary reactions, in addition to the conventional atmospheric pressure condition. The activation energy and frequency factor obtained by analysis of the data with various heating rates assuming the first order reaction kinetics for each coal were almost kept constant respectively at the temperature range where the rate of weight loss was large, while the values were quite different among coals and between pressure condi-tions. The effects of mass transfer were suggested to be remarkable under the atmos-pheric pressure.
The lean combustion limit of methane-air mixture around gasoil sprays in the direct injection diesel engine has been measured experimentally. The experimental results show if the equivalence ratio of the mixture which is formed in the intake pipe is greater than 0.034, the mixture burns and the output power which is 15 % of calorific value of supplied methane is produced. It is confirmed that the intensity of combustion luminance which measured by using of optical fiber thermometer decreases with increasing of supplying methane. The time histories of pressure and temperature in the cylinder have been calculated by the modified two zone model which is developed to apply for diesel fumigation system. The lean combustion limit of the mixture around gasoil sprays is estimated by thismodel.