Abstracts
Among many nominated papers, three technical papers and an annual review have been published in this volume.
However, there are excellent papers in the unselected ones, some of them, are summarized hereafter for readers' reference.
Contra-Rotating Propeller
By Yoshitarou Sakamoto, Hiroshi Kushiyama, Keiichi Nitta
The contra-rotating propeller (CRP) is an energy saving system in which two propellers are installed in tandem on a shaft center line and driven in reverse of each other. The energy of the rotational flow, which is generated by the forward propeller and not used effectively, is recovered by the aft propeller and transformed to an effective propelling force. Today, seven Japanese shipyards have possessed the design and manufacturing technology of the CRP after conquered the several technical difficulties of many years and four large merchant ships equipped with the CRP are continuing business voyages successfully. Three types of CRP systems were developed individually by the two shipyards and the group of 5 shipyards under the different conceptions in Japan. For example, three different type contra-rotating radial bearings were developed and adopted in the each system. They are composed of spherical roller bearings, hydrostatic bearings and AHT (Advanced Hydrostatic Taperland) bearings respectively. At present, CRP ships of a 37,000 DWT bulk carrier, a 4, 176 gross tonnage car carrier and two 258,000 DWT crude oil tankers are continuing business voyages. Their results of official sea trails and business voyages have proved some remarkable advantages of the CRP comparing with a conventional propeller. It is reported that not only the 14 - 15 percent energy savings were achieved but also the low vibration especially at astern conditions and good maneuverability which means necessary of no check rudder, more symmetrical turning trace of the ship in right and left direction and shorter maneuvering distance of the ship at crash stop conditions were confirmed.
─Reprinted from Journal of the M.E.S.J., vol.33, No.9─
Ferrograph Analysis on Bearing Metal Lubricating Condition of Low Speed Diesel
By Takaaki Hashimoto, Nobuhiro Baba, Hideo Aoki
The bearing metal of a marine diesel engine is basically disassembled every five years as a part of a special survey. However, this disassembling and assembling works require a large amount of manpower and time. Moreover, it is also dangerous. The classification society to which the authors belong has dedicated considerable time and efforts to examining whether used oil analysis can be applied as an alternative to the aforementioned periodic survey.
This paper reports on the correlation between the used oil analysis results by ferrography and the inspection results of 2 stroke diesel bearing metal obtained at special surveys.
As a result, the authors believe that the continuos engine system oil ferrograph analysis can be effective as one form of a condition monitoring based survey.
─Reprinted from Journal of the M.E.S.J., vol.33, No. 11─
