Predicting Start of Combustion Using a Modified Knock Integral Method for an HCCI Engine 2006-01-1086

Homogeneous Charge Compression Ignition (HCCI) is a promising combustion concept for internal combustion engines to reduce emissions and fuel consumption. Unlike spark ignition and diesel engines in which ignition is controlled by spark and spray injection timing respectively, HCCI combustion auto-ignites given the correct mixture conditions which makes HCCI ignition difficult to control. It is thus critical to understand the characteristics of HCCI ignition timing in order to find suitable strategies for ignition control.

This paper presents a modified model of ignition timing which is based on the Knock-Integral Method. Since this model doesn't require instantaneous in-cylinder parameters, it is suitable for control application on HCCI combustion. The model is tested using both simulation results of a Thermo-Kinetic Model and experimental data. With seven model parameters, the ignition timing of over 250 HCCI points at different conditions for four different Primary Reference Fuels (PRF) is predicted to within an average error of less than 1.5 degrees of crank angle.

This model is computationally efficient and could be implemented in the engine control unit of an HCCI engine to calculate the required inputs that are needed to get the desired ignition timing.