Abstract
In the present report, the experiments of two different kinds were performed by use of the solid fuel samples, whose ash contents were varied extremely. The one is the experiment in the thermo-balance (in this case, burning boundary surface area does not change during the period of combustion), and the other is the experiment on the spherical sample (in this case, burning boundary surface area is reduced during the period of combustion).
As the result, from the experiment in the thermo-balance, it is supposed that the reactions have three steps, that is: the dehydration of moisture, the dehydration of crystal water and the reaction of combustion respectively.
And in the application of the Yagi Model to the spherical samples, we can not reached to a comfortable result.
