Study on the Variable Speed Diesel Generator and Effects on Structure Vibration Behavior in the DC Grid

Abstract

Global warming and air pollutants are in general major worldwide concerns including for the marine shipping industry. Equipped with new technologies, the onboard DC grid has proven several advantages, including up to 27% reduction in specific fuel consumption with reduced emissions. That can be achieved by installing an optimized variable speed diesel generator. The engine speed is adjusted according to the required power, which allows to always keep the best efficiency of the combustion process. However, it also exposes some changes in the behavior of the structure vibrations. Measurements on an experimental variable speed diesel generator show that vibration increases when trying to slow down the engine for the same load. This behavior is closely related to the resonance in low rev range that usually occurs with general gensets. In other words, we can conclude that the DC grid’s variable speed generator may be beneficial for fuel efficiency, but not for mechanical life and safety. Several measures had been given, of which the alternation of the natural frequency is presented as an economical and efficient solution. The ultimate goal is to maintain operational safety while respecting reduced fuel consumption.

Keywords

• structure vibration
• variable speed diesel generator
• DC grid
• fuel consumption
• emissions