Patent ID: 8347861

Claim:
A method of controlling a gas engine system, in which air fed through a turbocharger is mixed with fuel gas flowing through a fuel gas supply line and controlled as to a fuel supply quantity by a fuel flow control valve, and a thus obtained mixture gas is fed into a combustion chamber in order to carry out ignition and combustion of an engine, comprising the steps of, when a case that the fuel gas has a low calorie or an engine output power is high, diverging a portion of the fuel gas in the fuel gas supply line upstream of the fuel flow control valve, a flow rate of the fuel gas diverged into a gas supply diverging pipe being set to a constant value which is less than a flow rate of the fuel gas of a gas supply main pipe, feeding a diverging fuel gas into each of charging air inlet branch arm pipes connected respectively to an intake air port of a cylinder cover from the gas supply diverging pipe through a divergence control valve arranged on the gas supply diverging pipe and subjected to ON/OFF control, and then into the combustion chamber, feeding a remainder of the fuel gas into the fuel flow control valve for controlling a quantity of the fuel gas so as to set the mixture gas to be fed into the combustion to a predetermined air-fuel ratio, the fuel flow control valve being provided to each of gas supply branch pipes which is branched off from the gas supply main pipe for a respective cylinder, feeding the fuel gas into each of the gas supply branch pipes for a quantity controlled at the fuel flow control valve, and then into the combustion chamber, and controlling a sum of the flow rates of the diverging fuel gas having the constant value fed from the divergence control valve and the fuel gas of which the flow rate is controlled by the fuel flow control valve by controlling opening degree of the fuel flow control valve so that the sum of the flow rates is adjusted in accordance with the engine output power, and when the fuel gas has a high calorie or the engine output power is low, closing the divergence control valve, feeding the fuel gas only from the fuel flow control valve into the combustion chamber, and controlling the opening degree of the fuel flow control valve so that the flow rate of the fuel gas is controlled in accordance with the engine output power.