Increasing public awareness of environmental protection, it has caused a lot of emphasis on the marine industry to create reciprocating diesel environmentally friendly. Conducting research on real objects in the laboratory gives us the solution to the problem. However, such studies generate large financial resources, especially for marine engines also take a lot of time. Creating a simulation on a computer allows for the limited financial resources and also speeding up work on the piston marine engine. Computer simulations allow the creation of more complex physical models, which can describe the process of operating a marine diesel engine. However, the complication models cause a problem of the future understanding of the model and the possibility of subsequent use of it, for example for control of the engine. The more it established the need to simplify complex models of engines for better understand the processes occurring in the engine. The article is a description of the Mean Value Engine Model (MVEM), which were analysed individual blocks of the model together with the modifications related to the environment in which the engine will run. Modular model allows better modifying it and adding new blocks. This model is based mainly designed for application control. Because of the simple structure easy to adjust for different types of engines. This is particularly good for use in motor drivers. It allows better matching engine operating parameters to reduce emissions of harmful substances into the environment and also achieve better efficiency of marine engine.
The work presents a model of the marine diesel engine working process. The research object was the AL25/30 engine. The model consists of partial models of the combustion process in the engine cylinders, the heat exchange process, flows through air and exhaust channels, heat exchange in the intercooler and friction in mechanical components of the engine. The model includes a description of the processes taking place in the turbocharger also. The input data to the model and the verification data were the results of direct measurements on the research facility. The verification showed errors in the calculation of air and exhaust gas parameters not exceeding 11%. The paper also presents an analysis of the results of fast-changing parameters, including combustion pressure in engine cylinders and pressures in individual gas channels. The designed model allows the analysis of the research facility operation and enables its further development towards the assessment of toxic compounds emission to the atmosphere.
The measurement of combustion pressure relies on connecting a pressure sensor to a four-stroke marine engine cylinder by a channel led out from the engine cylinder. The geometry of the channel distorts the results of combustion pressure measurements. The purpose of the work is to create a model of combustion processes in engine cylinders. The model uses a mathematical description of the indicator channel on one of the engine cylinders. The input data to the model and the data necessary for its verification came from the direct measurements on the research facility. The test object was a four-stroke Sulzer 3AL25/30 engine loaded by an electric power generator. During calculations, different diameters and lengths of measurement channel were simulated. The obtained results allowed to formulate the conclusion that the geometry of the measurement channel has a significant impact on the measurement results. The increase of the length of the measuring channel as well as the diameter of the channel causes disturbances in the measurement of the maximum pressure.
The paper presents a method of transforming the time axis to the axis of the crank angle rotation based on the pressure measured in time domain and simplified model of the engine dynamics. Indicating is to register the pressure in synchronism with the engine crank angle rotation. Usually in the ad hoc measurements the crankshaft rotation angle transducer is avoided, and the measurements are performed in time domain. For further analysis time axis is transformed for crank angle axis on the base of linear transform. Pressure waveforms obtained during the research were subject of the described transform. During the research instantaneous angular speed (IAS) of the engine crankshaft has been changed by reducing fuel dosage to selected cylinders. Mean indicated pressure (MIP) was calculated. Values o pressure on the begging and the end of compression, opening and closing angles of valves were also determined.
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