One of the limiting factors for improved performance of the spark
ignited internal combustion engine is the phenomenon of knock.
The present investigation makes a survey of the available models for
auto-ignition for introduction into an existing phenomenological
combustion model. A mathematical model of knock, based on a
degenerate branched chain mechanism for the prediction of
autoignition delay time, was considered and introduced into the
combustion model. Experiments were carried out on a single cylinder
variable compression ratio engine to validate the model.
The interaction of acoustic waves with unsteady combustion leading to
unstable combustion and thus triggering knock is considered. This
work examines the relationship between the variation in the power of
the frequency component corresponding to the natural frequency of the
combustion chamber, and the occurrence of knock.
A model based on the relaxation oscillation phenomenon is developed
to calculate the oscillating frequency of the flame front. This
model was developed on the basis that the gas contents of the
combustion chamber in an internal combustion engine can be considered
as a 'lumped parameter' spring mass damper system.
Analysis of the frequency spectrum of flame ionization data show a
favourable comparison with the predictions from the model, thus,
opening the possibility of future work on correlating the acoustic
instability in the combustion chamber to knock in spark ignition
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.