Text version of the page

GD operation Diesel operation

Power Plants Product programme 2007 - 22655 GAS-DIESEL ENGINES (GD)

Fuel Sharing mode , the ratio between liquid and gas fuel amounts can be controlled and varied during operation. The operating window for the Fuel Sharing mode is 35 to 90% load and the gas/liquid fuel ratio can vary from 80/20 to 15/85. The gas-diesel process can tolerate big variations in the gas quality and is especially suitable for “non-pipeline quality gas”, such as associated gas in oil fi elds. Liquid Fuel mode operation. The liquid fuel can be light fuel oil, heavy fuel oil or crude oil. In this case, the process is the same as the conventional diesel process. In In Gas mode , the gas is injected at high pressure after the pilot fuel and is ignited by the fl ame from the pilot fuel injection. The amount of pilot fuel is equivalent to approximately 5 % of the fuel energy input at full engine load. The gas-diesel engine can be switched over instantly to

DIESEL ENGINES

In the diesel process, liquid fuel is injected into the cylinder at high pressure by camshaft-operated pumps. The fuel is ignited instantly due to the high temperature resulting from the compression. Combustion takes place under constant pressure with fuel injected into the cylinder during combustion. After the working phase, the exhaust gas valves open and the cylinder is emptied of exhaust gases. With the piston in its upper position, the inlet valves open just before the exhaust gas valves close, and the cylinder is fi lled with air. In Wärtsilä engines the inlet valves close just before the piston reaches the bottom dead centre. This method, called “Miller timing”, reduces the work of compression and the combustion temperature, which results in higher engine effi ciency and lower emissions. 35