Abstract

The International Maritime Organization (IMO) has developed and enforced the International Convention for the Prevention of Pollution From Ships, in 1973 as modified by the Protocol of 1978 (MARPOL 73/78) Annex VI in 1997. Annex VI includes several emission controls on air pollution. Especially, NOx emission intensity is regulated as the emission of per engine output ? hour [g/kwh] according to speed of marine diesel engines. Therefore, the exact engine output measurement as well as NOx reduction technologies became an important issue.
And the exact estimation of engine output is a fundamental element for engine performance analysis. And in order to obtain the exact output of the engine, the accurate measurement of the pressure within the cylinder is more important than any others. Because the acquisition of the in-cylinder pressure provides many informations about engine performance such as output, P-V, P-θ, rate of heat release and gas temperature etc. Recently the combustion analysis by obtained the pressure in-cylinder with combustion pressure sensor device is recognized as an indispensable equipment for research, development and maintenance of the internal combustion engine.
MIPS (Mean Indication Pressure System), which is electronic indicator, is a typical engine output measurement equipment used on board in vessels but has a significant deviation compared to the mechanical indicator. MIPS collects data by the time based sampling method, so the TDC position has been determined inaccurately due to the influence of the instantaneous velocity fluctuations and load variations. By the result, a considerable amount of errors in calculated indicated horse power has been generated. By the some papers, it has been suggested that 1°CA error of TDC can to 10% evaluation error on IMEP and 25% error in the heat release of the combustion. Therefore the accuracy of TDC position should be within a precision of at least 0.1°CA. And also, TDC is classified into dynamic TDC (peak of compression pressure) and static TDC (geometric TDC, when the piston is located in the most upper point measured using a dial gauge). In generally, the dynamic TDC appears earlier than the static TDC. This difference expressed in degrees of crank angle is called "loss angle" and is derived from the heat loss and the mass loss.
In this study, the cause of errors in existing electronic indicated pressure instrument by time based sampling method was investigated and confirmed. And the loss angle was investigated with analysing the pressure curve in-cylinder of test engine. Simultaneously, the influence of factors for the loss angle was investigated by cycle simulation for low-speed marine diesel engine the timing of fuel injection which is after TDC for satisfaction of NOx regulation since 2000. On these researches, the new method for measuring engine output was proposed and developed.
The new method and its merits could be explained as follows.
The cylinder pressure is measured with time interval sampling method. From the series data of the pressure in-cylinder the position of dynamic TDC is determined. The accurate position of static TDC could be corrected with loss angle. By this new method, it was confirmed that the measurement of accurate engine output was possible. Besides, this method has a very useful merit, as it could be utilized without considering to cylinder position in case of multi-cylinder engine.
And also, by using this method the useful results could be obtained as follows.
- By the comparison between experiment and simulation for loss angle, expected amounts of blow-by gas were carried out which was difficult to measure.
- The deformation of crank shaft by the torsion is estimated approximately during the operation.

Finally using the developed measuring kit, combustion analysis of marine generator engine which was adapted as test engine was carried out. It was verified that the good operation condition of the engine as well as contributing to fuel savings by checking and readjusting accurately the irregular combustion of the test engine were accomplished. From the results all above, it was recognized that the measuring kit by new method for engine output was developed and verified for its utilities.