Continuous monitoring of diesel engine performance under its operating is critical for the prediction of malfunction development and subsequently functional failure detection. Analysis of instantaneous angular speed (IAS) of the crankshaft is considered as one of the nonintrusive and effective methods of the detection of combustion quality deterioration. In this paper results of experimental verification of fuel system's malfunction detecting, using optical encoder for IAS recording are presented. The implemented method relies on the comparison of measurement results, recorded under healthy and faulty conditions of the engine. Elaborated dynamic model of angular speed variations enables us to build templates of engine behavior. Recorded during experiment, values of cylinder pressure were taken for the approximation of pressure basic waveform. The main task of data processing is smoothing the raw angular speed signal. The noise is due to sensor mount vibrations, signal emitter machining, engine body vibrations, and crankshaft torsional vibrations. Smoothing of the measurement data was carried out by the implementation of the Savitzky-Golay filter. Measured signal after smoothing was compared with the model of IAS run.

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.

Reliability of the marine propulsion system is closely correlated with the safety of navigation at sea. Typical ship's powertrain has a lot of advantages (mainly efficiency) but is the source of high vibration level. What is more, rough sea conditions can be a source of additional ship vibration, especially for big container ships. Vibrations may have a dangerous influence on ship equipment's strength and consequently on the ship's safety. Torsional vibrations of the marine power transmission system are usually the most dangerous for the shaft line and the crankshaft. The power of propulsion system is quite often measured by commercial measuring device based on instantaneous angular speed (IAS). The angular speed measurements are performed using two optical sensors for reading the IAS, mounted at shaft line. The authors try to use existing apparatus for torsional vibrations' continuous monitoring. Designing monitoring methodology consists several analytical methods. Simplified method of torsional vibration calculation is a first one. Simplified calculation method gives us a determination possibility of torsional vibrations in typical and emergency working conditions. Natural frequency value (resonance location) as well as vibration amplitudes can be estimated on the base of the method. The presented calculation method was verified by comparison with the detailed finite element method calculation and measurements on real ships. The second part of the monitoring system contains methodology of monitoring of piston engine's crankshaft torsional vibrations by measurement of IAS at free and power output ends of the engine's crankshaft. It is assumed that calculation of differential value between both ends shall give the picture of torsion angle magnitudes and phases of the peak values. Analysis method of recorded signals (e.g., recalculation of angular distance sampling into constants time function and frequency base by FFT analysis) is also developed. Description of the measurements of the crankshaft torsional vibration for marine engine with some simulated malfunction (a leak of fuel injection pump, and relayed on mounting of sets of injection valves with different nozzles characteristics-spraying nozzle angle) is presented. Presented results of experiment derive from test cycle carried out using laboratory stand of Gdynia Maritime University equipped with 3-cylinder self-ignition engine, powering electric generator. The planned monitoring system should have detecting possibility of torsional vibration changes (propulsion system malfunction), the ability to assess the degree of danger of failure and eventually determination of the risk of damage and the causes of propulsion system's threat failure.Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

The paper presents results of the calculation, based on simplified engine model, aimed on prediction of IAS (Instantaneous Angular Speed) of the crankshaft fluctuations under faulty engine condition. Gas forces were calculated basing on results of in-cylinder pressure measurements which were used as inputs to the dynamic model. Mass forces were calculated basing on technical particulars of the engine Sulzer 3Al 25/30.Measurements of the incylinder pressure was carried out at laboratory stand in Gdynia Maritime University, equipped with diesel engine Sulzer 3AL 25/30 driving electro-generator. Sulzer 3AL 25/30 is three cylinder, medium speed, four stroke marine diesel engine, with maximum output 408 kW at 750 rpm. In order to evaluate of IAS model utility for diagnostic prediction of the engine behavior, two kinds of malfunctions of engine's fuel system were simulated. First malfunction was fuel leakage from high pressure line; the second was partly plugged injector's nozzle. Construction of high pressure fuel pump enable to fuel leakage simulation. The engine was run out at load 250 kW what is around 65% of nominal. Results of all measurement were smoothed in order to eliminate a noise using SG (Savitzky -Golay) filter. Results of fault condition modeling were compared with healthy engine model and with results of in -cylinder pressure diagrams, in order to create a map of deviations from normal condition.

The paper presents results of the experiment focused on evaluation of records of runs of the engine in good condition as a reference for subsequent detection of faults of fuel system of medium speed diesel engine. The aim of research was determination of limits of instantaneous angular speed's spread spotted between random starts of the engine, without any fault condition simulation. Due to fine variation of the load setup and different ambient condition, every record of angular speed of independent starting, despite of attempts to sustain the same load and rotational speed value, presents some deviations between runs. Having on mind utilization of such measurement as a template for further comparison, is crucial to find out how random changes of ambient conditions and accuracy of revolutionary speed setup affect the IAS magnitude course. The answer was got in way of registration of numerous runs of the test engine after independent starts and hand adjustment of required RPM's. The experiment was carried out at laboratory stand in GdyniaMaritimeUniversity, equipped with diesel engine Sulzer 3AL 25/30 driving electrogenerator. Sulzer 3AL 25/30 is three cylinder, medium speed, four stroke marine diesel engine, with maximum output 400 kW at 750 rpm. Independent records were treated as random variable and were compared each other. Obtained results were compared with differences between healthy engine and with simulated malfunctions of fuel injection.