Combustion control method and combustion control system with variable excess air coefficient for gasoline engine

A combustion control system with variable excess air coefficient for gasoline engine, characterized in that, it comprises a cylinder block structure, a variable valve system, a fuel injection system, a high energy ignition system, an exhaust gas recirculation system, an operating condition monitoring system, and an engine electronic control unit, wherein the cylinder block structure comprises a cylinder, the variable valve system is configured to control an amount of fresh air supplied to the cylinder, the fuel injection system is configured to control an amount of fuel injected into the cylinder, the high energy ignition system comprises a high energy spark plug and is configured for discharge ignition, and the exhaust gas recirculation system is configured to control a quantity and a temperature of re-circulated exhaust gas;

• the engine electronic control unit is electrically connected with the operating condition monitoring system, the variable valve system, the fuel injection system, the high energy ignition system, and the exhaust gas recirculation system, respectively;
• the operating condition monitoring system is configured to monitor an engine operating condition and transmit the monitored result to the engine electronic control unit;
• the engine electronic control unit is configured to determine a current engine load condition based on the engine operating condition, wherein an engine load condition comprises a part load condition, a high load condition, or a full load condition;
• the engine electronic control unit is configured to select an appropriate excess air coefficient combustion mode in accordance with the current engine load condition, wherein:
• when the current engine load condition is the part load condition, the engine is controlled, by means of the engine electronic control unit, to use a lean combustion mode with an excess air coefficient of 1.6˜2.0;
• when the current engine load condition is the high load condition, the engine is controlled, by means of the engine electronic control unit, to use a combustion mode with an excess air coefficient of 1;
• when the current engine load condition is the full load condition, the engine is controlled, by means of the engine electronic control unit, to use a combustion mode with an excess air coefficient of 0.8˜0.9.