🔍 Key Concepts

• Location and purpose of the auxiliary blower in a turbocharged two-stroke diesel engine air system • Difference between scavenge air system and crankcase space • How scavenge air pressure changes between low load and full load when using a turbocharger

💭 Think About

• Look closely at where the blower in the illustration takes suction from and where it discharges. Is it connected to the crankcase or to the scavenge air receiver/ports? • Think about turbocharger operation: at which load condition does the turbocharger naturally produce enough scavenge air pressure without help? At which condition does it need assistance? • Would you ever want to maintain either a strong positive pressure or a vacuum inside the crankcase of a large diesel? What are the safety and lubrication implications?

✅ Before You Answer

• Verify which part of the engine the auxiliary blower is physically connected to in the drawing – crankcase vs. scavenge air space. • Check your basic principle: turbocharger air supply at low load compared to full load. • Remember standard practice for crankcase conditions on trunk and crosshead diesels: crankcase is normally vented near atmospheric pressure, not pressurized or pulled into vacuum by a blower.