In this article, we discuss the importance of the analysis of indicator diagrams and indicated parameters in operational diagnostics of marine engines. An innovative method was devised to improve the effectiveness of diagnostics based on this information. It consisted of the elimination of harmful measurement spaces during cylinder pressure measurements as well as an in-depth analysis of the resultant indicator diagrams based on the functions of heat release. This research demonstrated a negative impact on the quality of indicator diagrams and the values of the parameters indicated by cylinder pressure measurements with sensors mounted on indicator cocks. The elimination of the indicator cock and measuring channel in the cylinder pressure measurements affected the quality of the indicator diagrams and, based on the calculated heat-release functions, allowed the emergence of new (additional) diagnostic symptoms. This could significantly improve the effectiveness of diagnostics performed in operating conditions and, as a result, the effective, trouble-free, and ecological operation of marine engines, thus meeting the growing environmental and operational safety requirements.

The article presents selected problems regarding the correct analysis of cylinder pressures in ship piston engines. Correctly prepared and the analyzed indicator diagram helps in formulating appropriate diagnostic conclusions, with the help of which it is possible to achieve the optimal, in economic and environmental terms, regulation of the ship's engine. Cylinder pressure measurements are classified as difficult and also burdened with many errors. Therefore, the main topic of the article is to present a new concept for cylinder pressure measurements. Artykuł przedstawia wybrane problemy analizy przebiegów ciśnień cylindrowych w okrętowych silnikach tłokowych. Prawidłowo sporządzony i przeanalizowany wykres indykatorowy pomaga w formułowaniu wniosków diagnostycznych, za pomocą których można doprowadzić do optymalnej, pod kątem ekonomicznym i ekologicznym, regulacji silnika okrętowego. Pomiary ciśnień cylindrowych zaliczane są do trudnych, a także obarczonych wieloma błędami, dlatego też głównym tematem artykułu jest przedstawienie nowej koncepcji pomiarów przebiegów ciśnień cylindrowych.

The article discusses one of the most popular methods of diagnosing selected damages of marine piston engines, which is the indication or measurement of pressure changes in the engine’s combustion chamber. Improving the quality of indicator diagrams may contribute to the increase in the efficiency of using the parameters indicated in the diagnostics of marine piston engines. Measurement errors during engine indication are primarily caused by measuring channels that connect the combustion chamber to the pressure sensor. One way to avoid these errors is to install the pressure sensor directly in the combustion chamber. It seems that it is possible to eliminate these errors. However, there is a risk that the pressure sensor will be damaged by the effect of high temperature on it during combustion of the fuel-air mixture in the engine’s combustion chamber. The article presents the results of tests that indicate that the measured temperatures in the place where the sensor was installed (in the combustion chamber) did not exceed the critical value specified by the pressure sensor manufacturer. The article also presents the results of cylinder pressure measurement not only in the combustion chamber but also in two other points - on the thread of the indicator cock and in the measuring channel between the indicator cock and the cylinder head. The tests were carried out in a wide range of engine load technically efficient and with simulated damage in the fuel injection system. The article presents a comparative analysis of the parameters read out of the indicator diagram for the three above-mentioned pressure measurement locations. It was shown that the pressure measurements carried out directly in the combustion chamber are free from errors resulting from the influence of measuring channels and indicator cock.