Volumetric Efficiency

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

Volumetric efficiency, abbreviated as \( \eta_v \) (Greek symbol eta), a dimensionless number, is the calculation for an internal combustion engine.  This is the calculation for the volumetric efficiency for an internal combustion engine.  For a thermal engine, the combustion process depends on the air-fuel ratio inside the cylinder.  The more air inside the combustion chamber, the more fuel that can be burned and the higher the output engine torque and power.

 

Volumetric Efficiency calculator

 

 

Volumetric Efficiency Formulas

\(\large{ \eta_v = \frac{3456 \; CFM}{CID \; RPM} }\)   
\(\large{ \eta_v = \frac{ s \; 100 }{ TS } }\) (motor)
\(\large{ \eta_v = \frac{ GPM \; 100 }{ TF } }\) (pump)

Where:

 Units English Metric
\(\large{ \eta_v }\)  (Greek symbol eta) = volumetric efficiency \(\large{dimensionless}\)
\(\large{ CFM }\) = air flow in cubic feet per minute \(\large{\frac{ft^3}{min}}\) \(\large{\frac{m^3}{min}}\)
\(\large{ CID }\) = cubic inch displacement \(\large{in^3}\) \(\large{mm^3}\)
\(\large{ CIR }\) = cubic inch per revolution \(\large{\frac{in^3}{rev}}\) \(\large{\frac{mm^3}{rev}}\)
\(\large{ GPM }\) = flow in gallon per minute \(\large{\frac{gal}{min}}\)  \(\large{\frac{L}{min}}\)  
\(\large{ RPM }\) = pump revolution per minute \(\large{\frac{rev}{min}}\) \(\large{\frac{rev}{min}}\)
\(\large{ s }\) = speed \(\large{\frac{ft}{sec}}\)  \(\large{\frac{m}{s}}\)
\(\large{ TF }\) = theoretical flow \(\large{\frac{ft}{sec}}\) \(\large{\frac{m}{s}}\) 
\(\large{ TS }\) = theoretical speed \(\large{\frac{ft}{sec}}\)   \(\large{\frac{m}{s}}\) 

 Solve for:

\(\large{ TS = \frac{ GPM \; 231 }{ CIR } }\) (motor)
\(\large{ TF = \frac{ RPM \; CIR }{ 231 } }\)  (pump) 

 

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Tags: Volume Equations Engine Equations Calculators Efficiency Equations