Estimation of Diesel Engine Combustion Phasing from Crankshaft Torque Data

This work investigates a method for estimating the phasing of combustion events in individual cylinders of a multi-cylinder diesel engine, based on measurements of the crankshaft torque. The investigated method consists of two parts. First, the measured torque signal is separated into its cylinder individual contributions. These contributions are then used in order to estimate cylinder individual combustion phasing using the concept of 50% torque ratio, a measure developed for torque domain combustion phasing analysis. The results show that 50% torque ratio is highly correlated with both 50% pressure ratio and 50% mass fraction burned for the compression ignited combustion in a diesel engine. The investigated method for 50% torque ratio estimation, based on crankshaft torque measurements, is able to produce estimates that have a bias of less than 0.6 CAD for all cylinders. The standard deviation of the estimation errors varies between 3 CAD to 5 CAD for different cylinders.