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The coupling problems between shafting torsional vibration and speed control system of diesel engine are very common. Neglecting the coupling problems sometimes lead to serious oscillation and vibration during the operation of engines. For example, during the propulsion shafting operation of a diesel engine, the oscillation of engine speed and the severe vibration of gear box occur which cause the engine is unable to operate. To find the cause of the malfunctions, a simulation model coupling the speed control system with the torsional vibration of deformable shafting is proposed and investigated. In the coupling model, the shafting is simplified to be a deformable one which consists of several inertias and shaft sections and with characteristics of torsional vibration. The results of instantaneous rotation speed from this proposed model agree with the test results very well and are successful in reflecting the real oscillation state of the engine operation. Furthermore, using the proposed model, the speed control parameters can be tuned up to predict the diesel engine a stable and safe running. The results from the tests on the diesel engine with a set of tuned control parameters are consistent with the simulation results very well. [ABSTRACT FROM AUTHOR]

• The control of premixed and late combustion is crucial for marine diesel engine. • An effective procedure is proposed for detecting SOC, SODC and SOLC. • Instantaneous energy concept and peak detection are utilized in this procedure. • This procedure is validated by two different types of marine diesel engines. In order to improve the energy efficiency and suppress the environmental pollutants of marine diesel engines, analysis and control of combustion phases including late combustion phase and premixed combustion phase are considered as an attractive potential strategy. Consequently, it is necessary to accurately identify the combustion parameters that are representative to these combustion phases, such as start of combustion (SOC), start of diffusive combustion (SODC) and start of late combustion (SOLC). The real-time analysis of the combustion phases can be further applied for closed-loop combustion control (CLCC). However, the existing methods can't guarantee the accurate detection of combustion parameters simultaneously even though high computational resources are invested. In this study, the resonance excitation of in-cylinder pressure was found to be capable for identifying all of the three combustion phases parameters. Hence, several effective signal processing techniques were proposed to detect these combustion phases parameters from resonant pressure signal. Without complex mathematic algorithms, the proposed method shows high potential for CLCC since it is relatively easier and faster to achieve than other existing techniques. The accuracy of this method was validated by experimental heat release rate and in-cylinder temperature. Furthermore, based on combustion phase parameters obtained, the estimations of combustion state and energy efficiency were discussed. Finally, this method was also applied for combustion phase detection in another type of marine diesel engine, which verified the robustness of this method. [ABSTRACT FROM AUTHOR]