Knock Intensity Distribution and a Stochastic Control Framework for Knock Control

Abstract

One of the main factors limiting the efficiency of spark-ignited engines is the occurrence of engine knock. In high temperature and high pressure in-cylinder conditions, the fuelair mixture auto-ignites creating pressure shock waves in the cylinder. Knock can significantly damage the engine and hinder its performance; as such, conservative knock control strategies are generally implemented that avoid such operating conditions at the cost of lower thermal efficiencies. Significant improvements in the performance of conventional knock controllers are possible if the properties of the knock process are better characterized and exploited in knock controller designs. One of the methods undertaken to better characterize knocking instances is to employ a probabilistic approach, in which the likelihood of knock is derived from the statistical distribution of knock intensity.

Impact of fuel surrogate formulation on the prediction of knock statistics in a single cylinder GDI engine

“…Regardless the specific combination of countermeasures, effects on combustion duration must be carefully addressed. In fact, strategies causing a combustion phasing delay simultaneously reduce engine efficiency, since lower work can be extracted 14 ; furthermore, they are often limited by the need to prevent excessive turbine inlet temperatures. It is well established in literature that a competition exists in SI engines between flame propagation and autoignition (AI) in the unburnt mixture.…”