FUEL GAS SUPPLY METHOD AND DEVICE FOR GAS ENGINE

In an gas engine provided with a gas supply pipe 35 branching into a supercharger-side gas supply pipe 33 and a cylinder-side gas supply pipe 37, a supercharger-side gas adjusting valve 43 and a cylinder-side gas adjusting valve 45 for controlling flow rates of passages, when gas concentration of the fuel gas changes, the cylinder-side gas adjusting valve 45 is controlled first to keep the output of the gas engine constant and then the supercharger-side gas adjusting valve 43 is controlled to achieve the fuel gas flow rate Q1 based on the constant flow ratio by means of a gas supply controller 63, while maintaining the flow rate ratio Q1/Q2 at a constant value where Q1 is a fuel gas flow rate in the supercharger-side gas supply pipe 33 and Q2 is a fuel gas flow rate in the cylinder-side gas supply pipe 37