Combustion control using a Model-based MFB50 estimation methodology

Combustion control has always been a key factor in modern Internal Combustion Engines management systems, being even more crucial nowadays to improve drivability and reduce pollutant emissions. The position where 50% of fuel mass burned over an engine cycle is reached (MFB50) provides very important information about the effectiveness of combustion, such as the kind of combustion that is taking place. MFB50 can be evaluated using in-cylinder pressure sensors, even though at present, they are not widely used for on-board applications, as a result of problems due to measurement reliability and cost. Even if it might be possible to solve some of the problems related to measurement reliability in the future, pressure sensors will constitute a relevant part of the whole engine control system cost. This work presents a model based MFB50 estimation algorithm that requires no additional cost, because it's based on the instantaneous engine speed measurement, which is already performed in modern engine control systems. This procedure, whose computational cost is compatible with a common engine control unit, has been applied successfully to a turbocharged Diesel engine mounted on-board a vehicle.