VII PTNSS Congress - 27th-29th June 2017
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The ambiguity of marine piston engines indication parameters obtained during engine operation.

Among, medium and slow-speed marine engines, electronically controlled fuel injection have been appearing, where the exploiter interference in the regulation is unnecessary and even harmful. However, a lot engines with mechanically controlled injection pumps is still in service. Moreover many new models of them is actually design for future use. In this type of engines indication and measurements of the temperature of exhaust manifolds are the basis for their regulation. Well known rules determine when and how the injection angle and fuel quantity had to be changed to achieve equality of pressures and temperatures. Usually it is assumed that, if the exhaust gases temperatures and maximum pressures on all cylinders are equal and proportional to the engine load, all engine components meet the objective function properly. Upon this it might be sentenced that engine is technically proficient and will remain in this state for a long time. During the engine operation, some symptoms of degradation might appeared, which was masked by systematically carried out engine regulations. In practice it was founded many cases where the recorded temperature of exhaust gases were inadequate to the inside cylinder pressure. Such situation raised doubts about the correctness of measurements results both temperature and pressure. In such situations the regulation of engine fuel injection system can be harmful. The paper presents cases, where the measurement results were ambiguous. These examples show that equality of exhaust gas temperatures and pressures maximum is not sufficient to confirm the good technical condition of the engine or the actual state of its regulation. It was demonstrated that the existing Polish Navy rules for the assessment of the technical condition and operation rules engines should be changed.
Topic: Engine testing, durability, reliability and diagnostics
Author: Marek Łutowicz