The tapered runner angle is ____________ at the plenum.

The tapered runner angle is ____________ at the plenum.

• A. Smaller
• B. Larger
• C. Equal
• D. Unknown

Answer: (B)

When air moves from a larger plenum into a narrower runner, the transition has to begin right at the plenum in a way that preserves flow quality. The starting section where the plenum meets the tapered runner is designed with a relatively steep (larger) angle so the contraction begins early. This helps accelerate and straighten the flow as it enters the smaller bore, reducing turbulence and pressure losses at the junction. As the air continues down the runner and the diameter tightens further, the taper can become gentler (smaller angle) to maintain smooth, attached flow and control velocity. So the angle at the plenum is larger because the initial merge from a big chamber into a small duct needs a stronger, early contraction to feed the runner efficiently.

When air moves from a larger plenum into a narrower runner, the transition has to begin right at the plenum in a way that preserves flow quality. The starting section where the plenum meets the tapered runner is designed with a relatively steep (larger) angle so the contraction begins early. This helps accelerate and straighten the flow as it enters the smaller bore, reducing turbulence and pressure losses at the junction. As the air continues down the runner and the diameter tightens further, the taper can become gentler (smaller angle) to maintain smooth, attached flow and control velocity. So the angle at the plenum is larger because the initial merge from a big chamber into a small duct needs a stronger, early contraction to feed the runner efficiently.