Abstract: A gas engine is provided to control an air-fuel ratio in response to changes in composition of fuel gas. A gas engine 1 includes: an A/F valve 22; a solenoid valve 21; and a control unit 10 configured to perform perturbation using the solenoid valve 21 and set a relationship between an air-fuel ratio and respective opening degrees of the solenoid valve 21 and the A/F valve 22 under a specific engine operation condition using standard fuel gas. During an actual operation in a period in which the engine operation condition is deemed to be stable, when an opening-degree average value b of the solenoid valve 21 deviates from an opening-degree target value a of the solenoid valve 21 set in the control unit 10 under the above operation condition, the control unit 10 adjusts the opening degree of the A/F valve 22 so that the opening-degree average value b equals the opening-degree target value a.

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: A control unit performs perturbation using the solenoid valve under a specific engine operation condition by a standard fuel gas, by moving the solenoid valve from a predetermined opening degree to a lean side or a rich side while the A/F valve is opened at a predetermined opening degree. During an actual operation in a period in which the operation condition of the gas engine is deemed to be stable, when an output average value b obtained from an upstream oxygen sensor disposed on an exhaust passage of the gas engine deviates from an output target value a of the upstream oxygen sensor set in the control unit under the above operation condition, the control unit adjusts the opening degree of the A/F valve so that the output average value b equals the output target value a.

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.

Abstract: A gas engine 1 which operates in stoichiometric mode under high-load conditions and which operates in lean burn mode under medium- and low-load conditions includes a valve 2 which supplies the gas engine 1 with an air-fuel mixture composed of air and fuel gas. In the valve 2, a valve unit 21 for stoichiometric operation is connected in series to a valve unit 22 for lean burn operation and is also connected to a mixer 24. An opening area of the valve 2 is controlled in such a manner as to ensure a predetermined opening area for effecting stoichiometric operation, to uniformly decrease the opening area over time until a switching operation from stoichiometric operation to lean burn operation ends, to ensure a predetermined opening area for effecting lean burn operation, and to uniformly increase the opening area over time until a switching operation from lean burn operation to stoichiometric operation ends.

Abstract: A gas engine is provided to control an air-fuel ratio in response to changes in composition of fuel gas. A gas engine 1 includes: an A/F valve 22; a solenoid valve 21; and a control unit 10 configured to perform perturbation using the solenoid valve 21 and set a relationship between an air-fuel ratio and respective opening degrees of the solenoid valve 21 and the A/F valve 22 under a specific engine operation condition using standard fuel gas. During an actual operation in a period in which the engine operation condition is deemed to be stable, when an opening-degree average value b of the solenoid valve 21 deviates from an opening-degree target value a of the solenoid valve 21 set in the control unit 10 under the above operation condition, the control unit 10 adjusts the opening degree of the A/F valve 22 so that the opening-degree average value b equals the opening-degree target value a.

Abstract: A control unit performs perturbation using the solenoid valve under a specific engine operation condition by a standard fuel gas, by moving the solenoid valve from a predetermined opening degree to a lean side or a rich side while the A/F valve is opened at a predetermined opening degree. During an actual operation in a period in which the operation condition of the gas engine is deemed to be stable, when an output average value b obtained from an upstream oxygen sensor disposed on an exhaust passage of the gas engine deviates from an output target value a of the upstream oxygen sensor set in the control unit under the above operation condition, the control unit adjusts the opening degree of the A/F valve so that the output average value b equals the output target value a.

Abstract: A gas engine controls an air-fuel ratio in accordance with changes in the composition of fuel gas. The gas engine includes an A/F valve, a solenoid valve, and a control unit to carry out a perturbation process using the solenoid valve. A reference opening degree is specified by adjusting the opening degree of the A/F valve so that the time-average opening degree of the solenoid valve is equal to 50% in a particular engine operating environment created using reference fuel gas. The control unit resets the opening degree of the A/F valve to a value that is lower than the reference opening degree if the valve opening degree is lower than the specified reference opening degree and resets the opening degree of the A/F valve to a value that is higher than the reference opening degree if the valve opening degree is higher than the specified reference opening degree.

Abstract: A gas engine 1 which operates in stoichiometric mode under high-load conditions and which operates in lean burn mode under medium- and low-load conditions includes a valve 2 which supplies the gas engine 1 with an air-fuel mixture composed of air and fuel gas. In the valve 2, a valve unit 21 for stoichiometric operation is connected in series to a valve unit 22 for lean burn operation and is also connected to a mixer 24. An opening area of the valve 2 is controlled in such a manner as to ensure a predetermined opening area for effecting stoichiometric operation, to uniformly decrease the opening area over time until a switching operation from stoichiometric operation to lean burn operation ends, to ensure a predetermined opening area for effecting lean burn operation, and to uniformly increase the opening area over time until a switching operation from lean burn operation to stoichiometric operation ends.