Model based sensor reconstruction

In-cylinder pressure trace using indicator cock pressure information.

Large heavy-duty Diesel engines usually give access to the cylinder via a so-called indicator cock (IC). Due to the construction of the IC, the pressure signal is distorted and cannot be directly interpreted. Simplified models are not precise enough for the pressure correction.

Thus, a model which is parameterized with measurements is applied. Using frequency domain methods, the transfer function of the IC is determined when the engine is at the manufacturer and precise in-cylinder measurements are possible. Using the transfer function, the dynamics of the IC is inverted and the measured pressure is corrected and reliable information on the cylinder pressure can be used for subsequent calculations.

Comparisons with various models are shown and the advantages of the presented method are demon-strated. Measurements of a large Diesel engine are given and the methods are applied. The presented knowledge works as ICCA (Indicator Cock Correction Algorithm) in THE DOCTOR DM 8-32 engine analysis tool of Fuchs International Technology and builds a basis for the second part of the paper.