Researchers at Chalmers University of Technology (Sweden) have developed a method for analyzing combustion events in an internal combustion engine based on crankshaft torque measurements. They present their method in a paper published in the journal Control Engineering Practice.
Called the “torque ratio concept”, the method could also be extended to angular speed measurements, they said.
The torque ratio concept provides a parametrized model for the combustion progress from which, e.g. combustion phasing can be extracted. The torque ratio concept is derived mathematically and related theoretically to other combustion analysis methods, such as pressure ratio and net heat release. Finally, analysis on recorded data from a five cylinder spark ignited engine verifies the relationships between the three methods. For combustion phasing, the 50% torque ratio is an equivalent measure to 50% pressure ratio and can be transformed into the 50% net heat release position by using a derived volume ratio function.
—Andersson et al.