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<p>In recently ships are being equipped with shaft generators to comply with stricter marine environmental regulations and reduce fuel consumption. Shaft generators utilize the rotational power of the propulsion diesel engine to generate electricity, potentially reducing fuel consumption by up to 20% compared to traditional methods of using auxiliary generators installed on the ship. Moreover, shaft generators provide a stable power supply to the main machinery during navigation. When the capacity of the shaft generator is designed to match that of one auxiliary generator, it allows for the removal of one auxiliary generator, leading to reduced maintenance costs. However, shaft generators are installed in the limited space of the engine room and are integrated with the intermediate shaft connected to the propulsion diesel engine, resulting in excessive loads on the bearings supporting the intermediate shaft and the adjacent main bearings. Additionally, the heavy rotor of the shaft generator increases the diameter of the intermediate shaft, which decreases the shafting flexibility and amplifies the load reaction influence coefficient. Consequently, the load distribution on the bearings becomes more susceptible to displacement variations. This study examines the Energy Efficiency Design Index and shaft alignment and whirling vibration characteristics of a large crude oil tanker equipped with a shaft generator. Based on those results, an optimal shafting arrangement is proposed to improve shafting flexibility and enhance design safety. The results indicate that while the application of a shaft generator improves the EEDI by 5.5% compared to conventional vessels due to increased fuel efficiency, it reduces shafting flexibility, causing significant changes in the load reaction on the main bearings at the aft of the main engine. To mitigate the increased load reaction influence number the removal of the stern tube bearing at the fore of the vessel and the adjustment of the intermediate shaft bearing position and height were implemented. These adjustments improved shafting flexibility, minimized the variation in bearing reaction forces under all operating conditions, and produced a more gradual shaft deformation curve. In contrast, the change in the natural frequency of the propeller blade was minimal, with a variation of only 3.3%.</p>

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Optimum arrangement of the propulsion shafting system for a ship equipped with a shaft generator

  • 期刊论文

  • 发表日期：

    2025年8月7日

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  • You-Hee Cho,
  • Yang-Gon Kim

摘要

In recently ships are being equipped with shaft generators to comply with stricter marine environmental regulations and reduce fuel consumption. Shaft generators utilize the rotational power of the propulsion diesel engine to generate electricity, potentially reducing fuel consumption by up to 20% compared to traditional methods of using auxiliary generators installed on the ship. Moreover, shaft generators provide a stable power supply to the main machinery during navigation. When the capacity of the shaft generator is designed to match that of one auxiliary generator, it allows for the removal of one auxiliary generator, leading to reduced maintenance costs. However, shaft generators are installed in the limited space of the engine room and are integrated with the intermediate shaft connected to the propulsion diesel engine, resulting in excessive loads on the bearings supporting the intermediate shaft and the adjacent main bearings. Additionally, the heavy rotor of the shaft generator increases the diameter of the intermediate shaft, which decreases the shafting flexibility and amplifies the load reaction influence coefficient. Consequently, the load distribution on the bearings becomes more susceptible to displacement variations. This study examines the Energy Efficiency Design Index and shaft alignment and whirling vibration characteristics of a large crude oil tanker equipped with a shaft generator. Based on those results, an optimal shafting arrangement is proposed to improve shafting flexibility and enhance design safety. The results indicate that while the application of a shaft generator improves the EEDI by 5.5% compared to conventional vessels due to increased fuel efficiency, it reduces shafting flexibility, causing significant changes in the load reaction on the main bearings at the aft of the main engine. To mitigate the increased load reaction influence number the removal of the stern tube bearing at the fore of the vessel and the adjustment of the intermediate shaft bearing position and height were implemented. These adjustments improved shafting flexibility, minimized the variation in bearing reaction forces under all operating conditions, and produced a more gradual shaft deformation curve. In contrast, the change in the natural frequency of the propeller blade was minimal, with a variation of only 3.3%.