🔍 Key Concepts

• Study how the inner wall of control cylinder E is tapered relative to the flat periphery of the valve disk in the close‑up view. • Recall that a smaller flow clearance (smaller gap) causes higher fluid velocity and therefore a larger pressure drop across that gap (Venturi effect/Bernoulli’s principle). • Think about what physically happens to the radial gap between the disk edge and the tapered wall when the entire control cylinder is threaded upward (moved axially) without moving the disk.

💭 Think About

• In the enlarged lower sketch, if you slide the tapered control cylinder E upward while the disk edge stays in the same place, will the point on the taper that lines up with the disk edge have a larger or smaller diameter than before? • Once you decide whether the clearance (annular gap) becomes larger or smaller, how does that change the steam velocity through this passage and therefore the pressure drop across the disk periphery? • Compare each answer choice: first choose which ones match your conclusion about clearance change, then from those, which ones match your conclusion about pressure drop change.

✅ Before You Answer

• Be sure you are looking at the radial gap at the level of the disk edge, not the vertical distance above or below it. • Confirm the direction of the taper on the inside of cylinder E: does the bore get wider or narrower as you move upward? • Before picking an option, double‑check that the pair you choose has a physically consistent relationship between gap size and pressure drop (smaller gap → higher velocity → higher pressure drop; larger gap → lower velocity → lower pressure drop).