Abstract: This disclosure includes engines that are capable of controlling an air-fuel ratio responsive to rapid changes in the calorific value of a fuel gas. Some engines include an A/F valve, a solenoid valve, and a control unit configured to close the A/F valve when an average opening degree of the solenoid valve is lower than a preset target opening degree, and open the A/F valve when the average opening degree is equal to or higher than the target opening degree. In some engines, when the opening degree of the solenoid valve has been an upper limit opening degree or a lower limit opening degree of the solenoid valve over a predetermined number of times, the control unit is configured to compare with the upper or lower limit opening degree, in lieu of the average opening degree, against the target opening degree to open or close the A/F valve.

Abstract: This disclosure includes engines that are capable of controlling an air-fuel ratio responsive to rapid changes in the calorific value of a fuel gas. Some engines include an A/F valve (22), a solenoid valve (21), and a control unit (10) configured to close the A/F valve when an average opening degree of the solenoid valve is lower than a preset target opening degree, and open the A/F valve when the average opening degree is equal to or higher than the target opening degree. In some engines, when the opening degree of the solenoid valve has been an upper limit opening degree or a lower limit opening degree of the solenoid valve over a predetermined number of times, the control unit is configured to compare with the upper or lower limit opening degree, in lieu of the average opening degree, against the target opening degree to open or close the A/F valve.