EVALUATION OF OPERATION IN PISTON–CON–ROD SYSTEM OF SHIP PROPULSION ENGINE ON THE BASIS OF HARMONIC TORQUE

Abstract

The following paper has been confined to evaluation of correctness of piston–con–rod system of main engine, on the basis of momentary value changes, measured on the propulsion shaft, caused by decreasing of fuel dose delivered to cylinder until its cut-off. It has been assumed that the engine does not meet requirements if the cost of using it is higher than the outlay or if the engine does not ensure the safety of the ship. At specified external conditions, the load of combustion engine is determined unmistakably by means of two parameters: rotational speed of the engine and the torque. The torque is measured on few ships only and for this reason the position of the injection pump indicator is used as the engine coordinate. This way of qualification of the engine point of work is not precise. The loss of efficiency in one piston – con – rod unit can cause a decrease of the torque developed by the engine. As a result of this, one can establish a new point of engine cooperation with the propeller on the propeller curve at unchanged terms of outside load. It causes a decrease of engine rotational speed which is, however, brought back to the previous one by the governor. Reaction of the engine governor consists in an increase of a fuel dose of injection pumps which, in turn, causes overload of its remaining units. Operation diagnostics of piston – con – rod system of ship propulsion engine, while analysed on the basis of torque momentary values, enables us to control the quality of its operation. It also prevents the engine from getting overloaded in the ship propulsion system, and at the same time increases the safety of its exploitation.