Marine diesels working cycle monitoring on the base of IMES GmbH pressure sensors data

Abstract

The paper presents algorithms for marine diesel engines' working process monitoring designed by analyzing data obtained with IMES pressure sensors. Main features and properties of IMES sensors, used for 2-and 4-stroke modern marine diesel engines, are presented here. The pressure-time diagrams were taken as a basis for creating algorithms for marine diesel engines' working process monitoring. The task of preliminary calculation of top dead center position (TDC) of a cylinder was solved using polytropic compression equation. TDC position was calculated using the equation P' = 0. Then algorithm for calculating the average indicator pressure and the indicator power of the cylinder has been determined. The CFD methods show how indicator valve channel influences the results of marine diesel engines' working process monitoring. With the example of compression curves in a cylinder, it's shown amplitude and phase distortions introduced into pressure measurements by the indicator valve channel. Such research work is important and actual in time due to the use of marine diesel portable performance analysis systems.

Determination of top dead centre location based on the marine diesel engine indicator diagram analysis

“…Further, the system manual says that such a method is based on "... the fundamental thermodynamic laws of the working process in the ICE cylinder". This implies the fact that in the ab- This statement is not entirely correct, because there is a thermodynamic displacement of the pressure diagram due to the transfer of heat to cylinder walls [3,11]. Due to thermodynamic displacement, the entire pressure diagram shifts slightly to the left, the compression maximum is up to the TDC and, accordingly, the curve  d dP / also crosses "0" slightly to the left of the actual TDC value.…”

“…The TDC sensor is installed on an idle engine. Then, when the engine rotates under load, several events occur that shift the position of the TDC relative to its static position: -change of micro gaps in the bearings of the crank mechanism and the piston; -torsional vibrations of the crankshaft; -thermodynamic displacement of TDC [11]; -displacement of the TDC when measuring pressure through the indicator valve channel [3]. These indicator valves are equipped with all the low-and medium-speed diesels from the time of receipt of a well-known Rudolf Diesel's patent No.…”

“…During pressure measurement, the channel introduces errors such as signal delay, throttling, and wave errors, the first one can be very significant -up to several degreesand it increases with increasing engine speed. As a result, due to only the last factor, the TDC position can shift by several degrees relative to its static position [3,4].…”

“…Such a wonderful property of the P'm point could quickly solve all the problems of analytic determination of TDC and the task of analytical data synchronization when diagnosing engines. However, it must be recognized that the presence of noise in the discrete pressure data P(t), even if correctly excluded [3], can significantly reduce the accuracy of this elegant method. However, this method can be effectively used in a preliminary assessment of TDC.…”

“…Diagnostics of marine engines and the selection of optimal operating modes are based on the analysis of indicator pressure diagrams in the working cylinder depending on the angle of crankshaft rotation (°CA) ( , ) [1][2][3]. In parallel with indicator diagrams obtained during operation, fuel supply and gas distribution diagrams can be considered, which increase the reliability of diagnostics [4 -6].…”