Patent ID: 6026778
Filing Date: 2000-02-22
Classification: G01N

Abstract:
Method for decoking a combustion chamber of a diesel engine used for measuring the cetane number of a reference fuel, by injecting the fuels sequentially into the combustion chamber previously filled with air in order to create a flammable mixture, the said decoking method comprising:decreasing the compression ratio in the diesel engine in order to obtain a spontaneous-ignition lag of between 1.05 and 1.2 times the initial self-ignition lag after a length of time of between 20 and 40 seconds,adjusting the compression ratio in order to keep the spontaneous-ignition lag at the value reached in the previous step, for 1 to 10 seconds, andincreasing the compression ratio in order to obtain a spontaneous-ignition lag of between 0.8 and 0.6 times the initial spontaneous-ignition lag after a length of time of between 40 and 80 seconds,adjusting the compression ratio in order to keep the spontaneous-ignition lag at the value reached in the previous step, for 1 to 10 seconds,decreasing the compression ratio in order to return the spontaneous-ignition lag to its initial value in a length of time between 20 and 40 seconds, whereby, between two measurement cycles, strong turbulence in the flammable mixture and the gases resulting from the combustion of the flammable mixture are created so as to at least partially detach the solid residues of combustion that have been deposited on the walls of the combustion chamber.