Correct Answer - Option 2 : The ratio of air actually delivered to the amount of piston displacement
Explanation:
Volumetric efficiency:
The volumetric efficiency of an engine
- It is defined as the ratio of the actual air capacity to the ideal air capacity.
- It is also the mass of air that enters in suction stroke to the mass of free air equivalent to the piston displacement at intake temperature and pressure conditions.
\({\eta _{vol}} = \frac{{{V_{actual}}}}{{{V_{swept}}}}\)
which can be further written as
\({\eta _{vol}} = \frac{{\dot m\ \times\ {V_1}}}{{\frac{\pi }{4}{D^2}L \ \times \ \frac{N}{{60}} \ \times \ K}}\)
where \(\frac{\pi }{4}{D^2}\) represents the area of the piston.
From the above formula, we can observe that it depends on
-
The engine speed (N), as it increases, volumetric efficiency decreases.
-
The valve area, as it increases, more air can enter into the cylinder, and the mass flow rate increase.
-
The valve timing, as through the control of valve timing and matching of the intake manifold system volumetric efficiency can be changed.
[Note: The valve area should not be confused with the Piston area ]
