Ship power plant with reversible shaft generator unit operating by dual-power machine scheme and variable speed diesel generator

TLDR: In order to eliminate the disadvantages happening in the main engines operation in shared load modes, it is considered to use the shaft generator unit as a propeller shaft unit in the prolonged operation of the vessel at passing with a low speed and maneuvering.

Abstract: The article presents the analysis of the operating modes of small displacement vessels, which states that most of the working time the vessels are in standby mode, or move at low speed. The main ship diesel engines operate at a load of 10-15% (maximum 20%), which impacts the operational performance: the oil and water jacket of the engine do not have time to warm up, fuel and oil consumption increases. There takes place coking of piston rings, intercoolers and other components, which leads to a sharp decrease in the service life of the engine. In order to eliminate the disadvantages happening in the main engines operation in shared load modes, it is considered to use the shaft generator unit as a propeller shaft unit in the prolonged operation of the vessel at passing with a low speed and maneuvering. Such a variant of the shaft generator can be called a reversible shaft generator unit (RSGU) capable of operating in both generator and motor modes. At the same time, it is advisable to power the reversible shaft generator and general ship consumers from a diesel generator, which, in order to save fuel, can be applied as a variable speed diesel generator unit. There is presented a RSGU variant based on an asynchronous machine with a phase rotor and a frequency converter in the rotor (a double power supply machine). The functional and structural schemes of the ship’s electric power system using the variable speed diesel generator and the propulsive system based on the reversible shaft generator are presented. In the Matlab software there are developed the simulation models and presented the results of simulation modeling of the operating modes of the above systems.