zoomContra Rotating Propeller System

With the climate in the shipping industry as competitive as ever, the shipowners look favorably on any breakthrough that could lead to cutting shipping costs.

That is why Japan Marine United Corporation’s (JMU) innovative fuel-saving Contra Rotating Propeller System (CRP) has made waves within the shipping community.

This technology, which was developed independently by JMU, is a propulsion system in which two propellers are arranged on the same shaft and can generate propulsive force in the same axial direction while rotating in opposite directions.

In an exclusive interview given to World Maritime News, Takuro Yoshikawa, General Manager at Japan Marine United Europe Limited, shed some additional light on JMU’s CRP System, and its effects on the shipping industry. Yoshigava presented the benefits of the CRP during this year’s Posidonia event in Athens, Greece.

WMN: What are the main differences between the standard system that is being used on most of the vessels and the CRP, and how long did the system development and testing process take?

Yoshikawa: “Contra rotating propellers (CRP) are well established as one of the most efficient technologies.

However, the application of the CRPs to large merchant vessels has been limited, because of the difficulty in producing a reliable CR shafting which can support the large horsepower.

JMU started its development and studies on the CRP system for large merchant ships in 1984.

In 1989, JMU completed a prototype on the 37,000DWT bulk carrier, fully utilizing its long established gear technology, studies and design know-how on propeller and shafting, as well as various tank testing technologies.

Since then, JMU has installed the system to over 20 vessels. At present, JMU is the only company building the large merchant vessel s equipped with CRP system.”

WMN: In your presentation you mention that the 97,000 dwt bulk carrier Shoyoh is the world’s first large size bulker equipped with the CRP System. Could you further elaborate on the project and the system installation process?

Yoshikawa: “Shoyoh is the first vessel of three eco-designed sister vessels built by Japan Marine United Corporation (JMU) Kure shipyard.

The vessel has been designed and optimized for carrying thermal coal to coal-fired power station in Japan.

With energy saving and GHG reduction in mind, these advanced technologies and new designs have been incorporated into the vessel.”

WMN: How is the CRP system affecting overall fuel consumption and emissions?

Yoshikawa: “CRP, which consists of two contra-rotating propellers positioned in tandem, is a thrust system in which the aft propeller recovers lost energy due to rotating flow occurring behind the fore propeller and changes it to thrust.

To get the further energy saving effect, JMU has developed additional energy saving devices, which can be applied with CRP. Semi-circular Duct and Rudder Bulb are applied to the vessel.

The advanced CRP & ESD system has achieved a greater energy saving of around 16% compared to vessels without these devices.”

WMN: Do you have any projects ongoing at the moment?

Yoshikawa: “In a project under discussion, we expect high possibility to adopt the CRP system. As the project is a “private deal”, we cannot reveal any further information. But what we are hoping and planning to do is to expand CRP’s scope of operation, making it applicable to any type of vessel.”

World Maritime News Staff, July 9th, 2014