Question

40. If piston displacement is deducted from the total volume of cylinder, the remaining volume is known as

• A. Swept volume
• B. Clearance volume
• C. Displacement volume
• D. Compression ratio

Hint:

Total Volume (\(V_t\)) = Swept Volume (\(V_s\)) + Clearance Volume (\(V_c\)).
Compression ratio (\(r\)) is the ratio of these volumes: \(r = \frac{V_t}{V_c} = \frac{V_s + V_c}{V_c} = 1 + \frac{V_s}{V_c}\).
The clearance volume prevents the piston from striking the cylinder head and provides space for combustion.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
In internal combustion engines, the reciprocating movement of the piston within the cylinder liner defines specific critical reference volumes.
These volumes are determined by the physical limits of piston travel, known as Top Dead Center (TDC) and Bottom Dead Center (BDC).
Key Formula or Approach:
The physical relationship between the cylinder volumes is represented by the formula:
\[ V_t = V_s + V_c \]
where:
\(V_t\) is the total cylinder volume,
\(V_s\) is the swept volume (piston displacement),
\(V_c\) is the clearance volume.

Step 2: Detailed Explanation:
Let us define each of these volume components to clarify their relationship:
1. Total Cylinder Volume (\(V_t\)): The maximum possible volume enclosed within the cylinder when the piston is at its lowest point of travel, which is Bottom Dead Center (BDC).
2. Swept Volume Piston Displacement (\(V_s\)): The volume swept through by the piston as it moves from BDC to Top Dead Center (TDC).
It is calculated based on the cylinder bore diameter (\(d\)) and the piston stroke length (\(L\)):
\[ V_s = \frac{\pi}{4} \cdot d^2 \cdot L \]
3. Clearance Volume (\(V_c\)): The small, residual volume of the combustion chamber remaining above the piston head when the piston reaches its highest point of travel, Top Dead Center (TDC).
Rearranging the basic volumetric equation shows that if we deduct the piston displacement (swept volume, \(V_s\)) from the total volume of the cylinder (\(V_t\)), we obtain the clearance volume:
\[ V_c = V_t - V_s \]
Therefore, this remaining space is the clearance volume.

Step 3: Final Answer:
The remaining volume is known as the clearance volume.