Kunio Saki

COUNTER-ROTATING PROPELLERS

A double reverse revolution propeller apparatus having a front (6) and a rear (7) propeller is disclosed, in which the rear propeller is rotated at higher speeds than the front propeller. In another aspect, when seizure occurs, an inner shaft (8) is disconnected from an engine at an inner shaft connection unit (10) and connected to an outer shaft at an inner and outer shaft connection unit to be driven in the same direction as the outer shaft. In still another aspect, the ratio in absorption horsepower of the front propeller to the rear propeller is set to be substantially equal to the ratio in rotational speed of the front propeller to the rear propeller. In a further aspect, one or both of the front and rear propellers include a variable pitch propeller. In a still further aspect, the front propeller has more blades than the rear propeller.

Elastohydrodynamic Lubrication of Oil Film Seals Under High Speed Reciprocating Motion (1st Report, Theoretical Analysis of Eleastohydronamic Lubrication for Oil Film Seals)

This study deals with oil film seals (floating bush seals) under high-speed reciprocating motion in hydraulic equipments. Two numerical methods of Elastohydrodynamic lubrication for seal performance are presented. One method is an approximate method on the assumption that profile of seal clearance is straight one. In another method, compliance matrix of floating ring and hydrodynamic analysis based on the finite element method are used. Effects of hydraulic pressure, size of ring, materials of ring and initial clearance on seal performance (minimum oil film thickness and oil leakage rate) are presented. It is shown that the oil leakage rate decrease under high hydraulic pressure owing to contractile displacement of ring. And it is found that seal gap become null in high-speed condition, caused by negative hydrodynamic pressure generated in seal clearance. Also, it is shown that rings with step on inner face are useful to hold clearance under high-speed condition.

Possibility of the Analysis of Two-Dimensional Inverse Problems in Hydrodynamic Lubrication (An Examination Using a Plane Inclined Bearing with Finite Width)

Inverse problems in hydrodynamic lubrication mean that the film pressures are treated as known and Reynolds equation is solved to give the film thickness distribution. In a previous paper, we presented numerical methods for one-dimensional inverse problems. This paper presents the formulation for two-dimensional inverse problems using the finite element method and CIP method. These numerical methods have been applied to a plane inclined bearing with finite width. It is shown that inverse solution for film thickness is correct over almost region, however, on and around inlet corner points, correct solutions are not obtained. Both analysis using the finite element method and CIP method give the same results. The cause of incorrect solutions should further be pursued.

The Inverse Analysis for Hydrodynamic Lubrication Using FEM and CIP Method

This paper presents two numerical methods for an inverse problem in hydrodynamic lubrication. In the inverse problem, the film thickness profile is estimated from a given pressure distribution. In this study, the finite element method and CIP method (Cubic-Interpolated Profile method) are used to solve the inverse problems. Calculated results are presented for unsteady one-dimensional plane inclined bearing and seal in reciprocating motion. In the plane inclined bearing, it is shown that the steady-state film thickness profile is obtained as an asymptotic solution in unsteady-state. And it is shown that the periodic film thickness profiles calculated for seal in reciprocating motion are in good agreement with results given by Hirano and Kaneta. The calculated results show that the numerical methods presented in this study can be used to one-dimensional inverse problems.

二重反転プロペラ用船尾すべり軸受の研究 : 第2報, 内軸給油静圧軸受の性能

This paper shows the results of an analytical calculation of newly designed hydrostatic bearing with pressurized oil supplied through the inner shaft, and that they are in good agreement with the experimental results in terms of oil film thickness, moment support capability and oil flow rate. This paper also presents the results of tests on a full-sized contra-rotating shafting and bearing simulator tester of 60000 GT bulk carrier ship. Asynchronous contra-rotation was proven to assist CR bearing operation in partly fluid film lubrication region and to prevent severe seizure of it.

Boundary Lubrication Properties of Surface Modified Material Produced by Laser and Electron Beam Surface Alloying

The surface-modified material can be produced by laser and electron beam surface alloying of a plasma-sprayed molybdenum layer on Cr-Mo steel. The boundary lubrication properties and the metal structure of the surface alloy have been investigated. The main points of this study are as follows. 1. The surface alloy is thick, about 5 mm, and of uniform composition. 2. The surface alloy shows good wear resistance and good seizure resistance, in the same level as electroplated chromium and plasma-sprayed molybdenum layers. 3. Good wear resistance is attributable to the metal structure which is composed of hard M6C phase and soft α−Fe phase. Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in San Diego, California, October 19–21, 1992

Development of Contra-Rotating Propeller System for Large Ships

To meet the recent strong demands for energy saving, a contrarotating propeller (CRP) system was developed by Mitsubishi Heavy Industries Ltd (MHI) for application to large ships. The idea of a CRP is not new, having originated about 150 years ago. Technical problems that have stood in the way of the practical application of CRP systems for large merchant ships were: (1) the need to develop a reliable bearing and sealing system for contrarotating shafts, (2) a compact reversing gear system, and (3) an optimum design method and a performance evaluation method for a CRP system. Some solutions to these problems were developed by MHI recently, and put into practice by utilizing the oil-lubricated plain bearing system, lip seals, and a star type epicyclic gear system. One of the unique aspects is the introduction of the asynchronous CRP (ACRP) system, where the shaft speed of the forward propeller is lower than that of the aft propeller; by this means a large energy saving was achieved. This system, after one-years full-scale stand tests, was fitted to a car carrier. The carrier has since been put into commercial operation without any troubles and with an energy saving of more than 13 percent. The basic idea of the MHI CRP system, results of stand tests on bearing, seal and shaft alignment, and application of the MHI CRP system to the full-scale ship are reported, together with the results of full-scale measurements and service experience.