AIR-RATIO MEASURING METHOD, AIR-RATIO MEASURING DEVICE AND COMBUSTION CONTROL DEVICE

PROBLEM TO BE SOLVED: To measure the air ratio of a fuel-air mixture even in the case when the air ratio is under 1.0. SOLUTION: In an air-ratio measuring method measuring the air ratio of the fuel-air mixture of fuel gas and combustion air, the fuel-air mixture for measurement having dilution air mixed with the fuel-air mixture is fed to a burner for measurement, and the fuel-air mixture for measurement is burned by the burner for measurement. The quantity of the dilution air fed to the burner for measurement is detected, and the quantity of the fuel-air mixture fed to the burner for measurement is detected. The concentration of the remaining oxygen gas in the exhaust gas burned by the burner for measurement is detected, and the air ratio of the fuel-air mixture is found on the basis of the quantity of dilution air fed, the quantity of the fuel-air mixture fed and the concentration of the remaining oxygen gas in the exhaust gas burned by the burner for measurement.