Monitoring of torsional vibration of a crankshaft by instantaneous angular speed observations

Continuous monitoring of diesel engine performance under its operating is critical for prediction of malfunction development and subsequently functional failure detection. Analysis of Instantaneous angular Speed (IAS) of the crankshaft is considered as one of non-intrusive and effective method of detection of combustion quality deterioration. The paper contains presentation of attempt of monitoring of piston engine’s crankshaft torsional vibrations by measurement of Instantaneous Angular Speed at free and power output ends of the engine. It is assumed that calculation of differential value of angular distance run between both ends in the same time shall give the picture of torsion angle magnitudes and phases of the peak values. Fir carrying out such measurements, high frequency of sampling was required. The angular speed measurements is to be done utilising two optical sensors for reading and two perforated discs mounted at shaft’s ends playing the role of speed signal emitters. In the paper is presented description of the measurement system and explanation of its mode of work. It is also shown analysis of measurement accuracy, way errors elimination and method of signals runs filtration. Presented results of experiment derives from test cycle carried out using laboratory stand of Gdynia Maritime University equipped with 3- cylinder self - ignition engine, powering electric generator.