Noboru Nakai

Shaft Center Variation Caused by Compound Deformation and Rubber Creep on Vibration Damper

Two group of rubber have been renewed after the begining of service of the vibration damper on the main engine. The first renewal was after 5 years and 8 months from the installation and the second after 7 and half years from the first. The rubber used now is the third group over 2 years from the second. It was found out that the estimated values of shaft center with calculating the difference of the rubber-shrinkage correspond with the measured ones. So, the detailed investigation could be carried out for the variation of shaft center by the compound deformation due to heat, elasticity and plasticity and the creep of the rubber on each of group for long time. It happened sometimes that the variation of shaft center became about 1.0 mm with the difference of the environmental temperature, e.g. such as that of before starting and just after stopping engine. The value is the limit to the engine. Then the early large creep reduce like gentle slope after 10-12 months from setting new one

Diagnostic System for 4-Stroke Cycle Diesel Engine by Measurement of Vibration on Cylinder-Jackets

The reliability of the main engine must be extremely high in order to ensure the safe navigation of ships. This paper describes the construction of monitoring system capable of grasping the condition of the engine by using vibration signal of a diesel engine. The vibration was measured by sensors on cylinder jaket walls.The data of vibration were recorded on both normal and abnormal engine conditions. The following two kinds of conditions were used as an abnormal engine condition: running with fuel oil cut and the use of stopped-up fuel injection nozzle. Author executed visual judgment by means of the spectrum of the vibration in three-dimensional mannar and analyzed statistically as one method to estimate the condition of engine by the information from the vibration. It was found that one abnormal cylinder affected on vibration of other normal cylinders. Author succeeded to recognize abnormal engine condition correctly by mean of their information.

Calculation for Roughness Increase of Ship Equipped with CPP by Personal Computer

One of the author had published the paper of“On the Presumption of Bottoms Roughness with Making Use of Propeller Efficiency (Open) on CPP”. When calculating the increase of the bottoms roughness using the personal computer, it is important to give the good approximate performance curves between delivered horse power and ship speed.So, it was found that interpolation method with a cubic periodic spline gives good approximate values.If the spline function gained with the only four measured points can not give the good values, then, by adding two estimated points on the range of low and high ship speed, good performance curves could be gained effectively.Based on the accurate approximation of the performance curves, the increase of the bottoms roughness can easily obtained on the stand-by condition for short time by a personal computer.

Load Test of Differential Drive Shaft Generator and Motor System

This differential driven shaft generator/motor system has been introduced first in 1987, practical system (200V, 200kW) is introduced to FUKAE-MARUIII in 1988. Since the fundamental structure of the machine is the same as conventional synchronous machine, the output frequency of the machine is corrected to constant by compensating motion of the movable stator.Test results of starting characteristics of large capacity induction motors (total 30% rated power of the ACG), and voltage regulating characteristics with variable shaft speed or variable load are good agreement to designed procedure.The machine can be driven as the electronic propulsion motor. Induction starting, synchronization and load characteristics of the machine are also discussed. Since emergency starting of propulsion motor can be established within up to one minute, it presents powerfull function to reliability of the propulsion system.

Differential Drive Shaft Generator and Motor System for “Fukae maru”

Shaft generators driven by main engines have been increaseingly employed by ships to save evergy and labor. For shaft generator system, systems eguipped with thyristor inverters or differential planet gears are often used, however, they are required to be improved in reliability, effeciency and economic performance.A newly our developed shaft generator/motor system meets these requirements. This generator system is unique and first in the world as described below.The rotor (field), connected to the main engine shaft, can change its rotating speed. The armature, which is rotatery, can also be controlled to change speed independently of the rotor (field) .Recently this system is applied to the Fukaemaru of Kobe Univ. of Mercantile Marines.