🔍 Key Concepts

• Two-stroke diesel cycle and why it needs scavenging air every revolution • How a Roots-type blower works (positive displacement, constant volume) • Difference between engine-driven vs exhaust-driven supercharging

💭 Think About

• Ask yourself: In a low‑speed or medium‑speed two‑stroke diesel, when does the blower need to supply air—only at high load, or at all times for every cycle? • Which driving method will guarantee the blower turns in strict proportion to crankshaft speed, even at low RPM when starting? • Which options describe typical turbocharging arrangements rather than a classic Roots scavenging blower?

✅ Before You Answer

• Verify which device is commonly used as a starting/scavenging blower on older or low‑speed two‑stroke diesels. • Check which choice would still supply enough air when exhaust gas energy is too low, such as during starting and low load. • Eliminate any options that depend on valve motion in a way that doesn’t match how a rotary positive‑displacement blower actually operates.