Diagnosing Marine Piston Engines Driving Generators at Different Operational Loads

Abstract

Loads at which diagnostic research should be carried out were selected of operational investigation and preliminary diagnostic tests. It is difficult to keep the load constant during operational tests, so there is a need to apply the theory of the experiment. Operational investigation determined, the average and representative loads of tested engines driving generators. In preliminary diagnostic tests, the effects of loading on values of diagnostic parameters in various domains of signals analysis were checked and used to reduce the range the diagnostic research. Besides, the most useful symptoms were selected based on the correlation with the load. The diagnostic of pressure in the injection subsystem and in-cylinder pressure signals were subjected to time frequency analysis. In the principal studies, attempts were made to investigate the value of diagnostic symptoms while maintaining a constant load. For operating marine combustion engines, it is difficult to obtain repeatable test conditions because it is dependent on the principles of engine control and consumption of electricity by shipboard receivers. In operational tests on sea-going vessels, a wireless load measurement system and a system for processing and analyzing the parameters of working and residual processes were used. The wireless simultaneous load measurement system was effective in cases where load indicators and meters were away from the diagnosed objects. A wireless load and selected signals transmission system was used in tests on the ship. The aim of the article is to develop diagnostic models for bringing different test conditions to the common representative and reliable diagnostic decision. The article presents how to adjust diagnostic parameters of the working process, recorded at slightly different loads, to the value of common and equal load. This was done based on the best-fitted approximation model.