Pre-ignition Cylinder Pressure of an Engine

on . Posted in Fluid Dynamics

Tags: Pressure Engine

Pre-ignition in an engine refers to the combustion of the air-fuel mixture in the combustion chamber before the spark plug ignites it.  This can lead to engine knock, which can damage the engine and reduce performance.  Pre-ignition can be caused by a variety of factors, including high cylinder pressure, hot spots in the combustion chamber, and carbon deposits.

Pre-ignition cylinder pressure, abbreviated as p, is the pressure in the cylinder before ignition occurs.  This pressure can be measured using a pressure transducer or pressure gauge.  The pre-ignition cylinder pressure is affected by a variety of factors, including engine speed, load, air-fuel ratio, and ignition timing.  In general, high pre-ignition cylinder pressures can increase the likelihood of pre-ignition and engine knock.  This can be mitigated by reducing the engine load, adjusting the air-fuel ratio, and retarding the ignition timing.

The pre-ignition cylinder pressure can also be used to calculate the engine compression ratio, which is the ratio of the volume of the combustion chamber with the piston at bottom dead center (BDC) to the volume of the combustion chamber with the piston at top dead center (TDC).  The compression ratio affects engine performance and can be optimized for specific applications.  It is important to note that the pre-ignition cylinder pressure is just one of many factors that can affect engine performance and should be considered in conjunction with other factors such as air-fuel ratio, ignition timing, and engine speed and load.


Pre-ignition Cylinder Pressure of an Engine formula

\( p  =  p_o \; CR^{\gamma}  \)     (Pre-ignition Cylinder Pressure of an Engine)

\( p_o  =   p \;/\; CR^{\gamma} \)

\( CR^{\gamma}  =   p \;/\; p_o \)

Symbol English Metric
\( p \) = pre-ignition cylinder pressure  \(lbf\;/\;in^2\)  \(Pa\)
\( p_o \) = cylinder pressure at bottom dead center \(lbf\;/\;in^2\) \(Pa\)
\( CR \) = compression ratio \(dimensionless\)
\( \gamma \)   (Greek symbol gamma) = specific heat ratio \(dimensionless\)


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Tags: Pressure Engine