Modeling of In-cylinder Pressure Oscillations under Knocking Conditions: Introduction to Pressure Envelope Curve

High frequency pressure oscillations are generated under knocking conditions within the combustion chamber of Spark Ignition engines. Although acoustic-oscillation model can give the natural frequencies of these oscillations, very few mathematical models are today available, in scientific literature, to describe the oscillation deadening effect. An analytical formulation of the deadening has been highlighted. Analytical solution has been established for future ECU implementation. Coupling this new concept and an existing high-frequency model, an achieved model of the knocking pressure high frequencies is compared to experimental data. Good behavior is obtained on a natural gas fuelled spark ignition engine.