| 摘要 |
PROBLEM TO BE SOLVED: To provide an engine exhaust gas recirculation method capable of realizing a high EGR rate in all operation regions and reducing NOx emissions.SOLUTION: Provided is an exhaust gas recirculation method for an engine 1 that includes a low-pressure-stage turbocharger 5, a high-pressure-stage mechanical supercharger 7, a high-pressure EGR unit 10, a low-pressure EGR unit 11, and a medium-pressure EGR unit 12, an ECU 13 including an EGR switching map 33 for switching an EGR mode over between a high-pressure EGR mode, a medium-pressure EGR mode, and a low-pressure EGR mode on the basis of an engine revolving speed and an indicated fuel injection quantity, determining an operating state of the engine 1 on the basis of the engine revolving speed, the indicated fuel injection quantity, and the EGR switching map 33, selecting one EGR mode, performing EGR in the selected EGR mode, and controlling an EGR rate of the EGR. |
