Patent ID: 8485158

Claim:
A method of controlling a gas engine that ignites and burns fuel-gas, the gas engine including a turbocharger that pressurizes ambient air and supplies the air to the gas engine to a plurality of cylinders; a gas supply source line, a first gas line having a branch line connected to each cylinder; a first gas valve for each cylinder, the first gas valve being fitted on the branch line to regulate a flow rate of the fuel-gas toward each cylinder; and a gas compressor on the first gas line that compresses-the fuel-gas toward the first gas valve so as to mix the fuel-gas through the first gas line and the air through the turbocharger to form an air fuel-gas mixture, said method comprising: when the fuel-gas is of a low calorific value, or when an output of the engine is high, providing a second gas line toward suction air before the turbocharger, said second gas line being branched from the gas supply source line, providing a second gas valve for the suction air on the second gas line toward the suction air before the turbocharger, and regulating the second gas valve with on-off movements; providing an air gas mixer on the upstream air inflow line of the suction air toward the turbocharger, and mixing the fuel-gas through the second gas line with the ambient air induced toward the turbocharger so as to form an air fuel-gas mixture of a prescribed mixing ratio that is less than a lower limit of flammability of the fuel-gas, and wherein the remaining fuel-gas that is not supplied to the mixer from the gas supply source line is sent to each cylinder through the gas compressor and through the first gas line toward each cylinder, so that a prescribed air fuel ratio is formed in each cylinder by regulating the first gas valve; and when the fuel-gas is of a high calorific value, or when an output of the engine is low, closing the second gas valve for suction air so that the whole fuel-gas from the gas supply source line is directed toward each cylinder through the first gas line.