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SG operation Dual-fuel operation

Power Plants Product programme 2007 - 22655 ENGINE WORKING PRINCIPLES

SPARK-IGNITED ENGINES (SG)

The SG engines are spark-ignited lean-burn engines. In this process, the gas is mixed with air before the inlet valves. During the intake period, gas is also fed into a small prechamber, where the gas mixture is rich compared to the gas in the cylinder. At the end of the compression phase the gas/air mixture in the prechamber is ignited by a spark plug. The fl ames from the nozzle of the prechamber ignite the gas/air mixture in the whole cylinder. Combustion is fast. After the working phase the cylinder is emptied of exhaust and the process starts again.

DUAL-FUEL ENGINES (DF)

The dual-fuel engine utilizes a “lean-burn” combustion process when operating on gas. Here, the gas is mixed with air before the intake valves during the air intake period. After the compression phase, the gas/air mixture is ignited by a small amount of liquid pilot fuel. After the working phase the exhaust gas valves open and the cylinder is emptied of exhaust gases. The inlet air valves open when the exhaust gas valves close, and the process starts again. The dual-fuel engine is also equipped with a back-up fuel system. This is a normal diesel process with camshaft-operated liquid fuel pumps running in parallel with the process and working as a stand-by. 34