A diesel engine on your platform supply vessel has a restricted exhaust silencer/muffler resulting in high exhaust back pressure. With an appreciable load on the engine, what would be the condition of the exhaust gases exiting the stack?
• Diesel engine combustion and how air/fuel ratio affects exhaust color • Effect of high exhaust back pressure on scavenging and air flow through the engine • What different exhaust smoke colors usually indicate on a diesel (black, blue, white, clear)
• With a restricted silencer/muffler, what happens to the flow of exhaust gas and the fresh air getting into the cylinders? • At an appreciable load, is the engine demanding more or less fuel and air, and how would that change if the exhaust can’t get out freely? • Match each smoke color to a typical diesel engine condition: overload/poor combustion, burning lube oil, low temperature/unburned fuel, or good combustion.
• Be clear on what high back pressure does to the air supply and combustion quality in a diesel engine. • For each answer choice, ask: does this smoke color fit overfueling / poor combustion or something else (like burning lube oil or cold cylinders)? • Verify which smoke color is normally associated with insufficient air or restricted gas flow at high load.
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