A graph of the changes in an engine’s operating speed can be used to assess the quality of the combustion in its cylinders. In this paper, the authors carried out tests on a Buckau-Wolf R8VD-136 ship engine, which was directly driving the propeller. This engine is owned by the Laboratory of Marine Engine Rooms at the Maritime University of Szczecin. For standard rotational speeds ranging from 200 to 280 rpm, with increments of 20 rpm, the authors measured the changes in the instantaneous speed for the engine’s normal operating conditions (reference graphs) as well as with one of the cylinders being out of operation. A no-combustion situation was successively introduced into each cylinder for each preset rotational speed. The obtained graphs of the instantaneous speed were then used to determine certain quantitative indicators, which the authors believe can provide information about the technical condition of the engine. The analysis concerned the averaged graphs of the speed under the conditions set for five consecutive engine operating cycles. The indicators that were calculated included the maximum difference in the speed over the engine’s full operating cycle, the uniformity of the engine speed and the differential speed area factor, the latter a term that has been proposed by the authors. The values of the individual indicators that were obtained from the reference graphs and the graphs with no combustion in one of the cylinders were compared. All indicators are sensitive to cylinder misfire. Conclusions were then drawn on the usefulness of these indicators in assessing the condition of an engine.
In this paper, the authors have discussed the subject of fire and explosion hazards during the operation of a modern ship's high-power internal combustion engines. The causes of the occurrence of and the methods of preventing explosions in the starting manifolds of modern piston combustion engines equipped with a pneumatic starting system, with starting valves on the cylinder heads, have been specified. The concept of an active system for monitoring the technical condition of the starting valves has been presented in order to quickly diagnose leakages and reduce the risk of explosion. A conceptual design of a prototype of a non-invasive, new generation leak detector for starting valves and its technical design have been presented. Exemplary implementations of the prototype detector have been shown and its selected functionalities have been discussed. This paper has ended with an assessment of the possibility of further development and the applications of this device.