To enhance the detection accuracy of cetane number of fuel, in a compression self-igniting internal combustion engine.
When an amount of injected fuel by a pilot injection is very small amount, within a predetermined range of operating condition and environmental condition (S110, S120: YES), pressure (in-cylinder pressure) P and volume V inside the pilot injected combustion chamber are sampled for a predetermined period of time until a main injection of fuel is performed (S130). Then, rate of heat release is calculated from the sampled in-cylinder pressure P and the volume V, to determine amount of heat release Q by integrating the rate of heat release (S140). Furthermore, combustion rate of fuel is calculated (S160) by converting the amount of heat release Q into the amount of fuel, and determining the ratio of the amount of fuel to the amount of injected fuel, and the cetane number of the fuel is identified from the combustion rate (S170).
HARAGUCHI HIROSHI
KOJIMA AKIKAZU
