🔍 Key Concepts

• Roots-type blower construction and how it moves air • Behavior of a direct reversible engine when changing rotation (ahead to astern) • Relationship between blower rotation, engine rotation, and direction of airflow

💭 Think About

• Think about whether a Roots blower depends on direction of shaft rotation to move air, or whether it is arranged so that air always flows the same way. • When a direct reversible engine goes from ahead to astern, what happens to the camshaft and other driven equipment—do they change rotation or valve timing only? • Which answer choices would guarantee that the cylinders always get air the same way, regardless of engine direction?

✅ Before You Answer

• Confirm how a Roots blower’s rotors move air from inlet to outlet and what happens if you reverse rotation. • Decide whether the blower must change rotation with the engine, or stay the same, for proper scavenging and charging when going astern. • Check which option best maintains a consistent airflow path through the engine’s intake system in both ahead and astern directions.