Question

An engine has a swept volume of \(300\ cm^3\), clearance volume of \(25\ cm^3\). Its volumetric efficiency is 0.80 and mechanical efficiency is 0.90. The volume of mixture taken in per stroke is

• A. \(325\ cm^3\)
• B. \(275\ cm^3\)
• C. \(240\ cm^3\)
• D. \(270\ cm^3\)

Hint:

Volumetric efficiency links only the actual charge drawn in to the swept volume, not every given number is needed.

Answer 1

The Correct Option is C

Volumetric efficiency tells us what fraction of the swept volume actually fills with fresh charge in one stroke, since a real cylinder never fills up completely due to throttling losses and heating of the incoming charge.

Swept volume here is $300\ cm^3$. An efficiency of 0.80 means 80% of this swept volume gets filled with charge every stroke.

Volume drawn in $= \dfrac{80}{100} \times 300 = 240\ cm^3$.

The clearance volume of $25\ cm^3$ would only matter if compression ratio $\left(\dfrac{V_s+V_c}{V_c}\right)$ were asked, and the mechanical efficiency of 0.90 would only matter if brake power from indicated power were asked. Neither is asked here.

\[\boxed{240\ cm^3}\]