ABSTRACT
The uncontrolled combustion phenomenon commonly encountered in spark ignition (SI) gas engines, known as knock, is associated with sudden exceedingly high rates of energy release, excessive heat transfer to the walls, and rapid rates of pressure rise. These must be avoided to ensure acceptable engine operation. Serious operational limits are imposed by engine knock to the increase in power output, efficiency, type of fuel that can be used, and any further reductions in emissions. Much effort is usually expended in the design, operation, and control of spark ignition engines to reduce the likelihood of encountering knock.
