Use of Multiple Pressure Transducers to Find In-Cylinder Knock Location

Four pressure transducers were installed into a split-head CFR engine to determine the spatial and temporal location of engine knock. The CFR engine was operated for these experiments using a primary reference fuel of 80% iso-octane and 20% n-heptane (octane number of 80). The compression ratio was varied to obtain different intensities of knock in the acquired data sets. Pressure transducer signals were recorded using a high speed data acquisition system and the resulting traces were analyzed to find where knock was occurring within the combustion chamber. A two dimensional triangulation scheme was developed to locate the knock origin based on the time difference between the acoustic signals detected by the pressure transducers. Limitations in spatial resolution due to digital sampling rate and variations in the speed of sound are discussed.