Translated articles
Design system for optimum contra-rotating propellers*
NORIYUKI SASAKI1, MITSUNORI MURAKAMI2, KAZUO NOZAWA3, SHUNJI SOEJIMA4, AKIRA SHIRAKI5, TAKESHI AONO1, TOMEO FUJIMOTO2, ISAO FUNENO3, N0RIO ISHII4, and HIROSHI ONOGI5
1 Sumitomo Heavy Industries Ltd., 19 Natsushima-cho, Yokosuka 237-8555, Japan
2 Hitachi Zosen Corporation, 2-2-11 Funamachi, Taisyo-ku, Osaka 551-0022, Japan
3 Kawasaki Heavy Industries Ltd., 1-1 Kawasaki-cho, Akashi 673-0014, Japan
4Mitsui Engineering and Shipbuilding Co. Ltd., 1 Yawatakaigan-dori, Ichihara 290-8601, Japan
5NKK Corporation, 1 Kumozukoukan-cho, Tsu 514-0301, Japan
Abstract： A new type of contrarotating propeller (CRP) system has been developed through the cooperative research work of five shipbuilding companies in Japan (Hitachi Zosen Corporation; Kawasaki Heavy Industries, Ltd.; Mitsui Engineering and Shipbuilding Co., Ltd.; NKK Corporation; and Sumitomo Heavy Industries, Ltd.). This paper describes a design system for an optimum CRP, which is one of the numerous outcomes of this work. The optimum design system is composed of three theoretical programs： (1) the design program of the optimum CRP; (2) the steady lifting surface program of the CRP; (3) the unsteady lifting surface program of the CRP. These theoretical programs will be discussed in the first part of the paper, and the design system supported by these theoretical programs will then be verified by comparing calculated and experimental results.
Key words： contrarotating propellers (CRP), optimum design, theoretical calculation, energy-saving
Address correspondence to： N. Sasaki
Received for publication on Oct. 15, 1997; accepted on Dec. 10, 1997
* Translation of an article that appeared in the Journal of The Society of Naval ☆Architects of Japan, vol. 180 (1996)： The original article won the SNAJ prize, which is awarded annually to the best papers selected from the SNAJ Journal, JMST, or other quality journals in the field of naval architecture and ocean engineering.
Introduction
In response to the need for energy saving because of the problem of environmental pollution, a new contrarotating propeller (CRP) system was developed in a cooperative effort by five shipbuilding companies, i.e., Hitachi Zosen Corporation; Kawasaki Heavy Industries, Ltd.; Mitsui Engineering and Shipbuilding Co., Ltd.; NKK Corporation; and Sumitomo Heavy Industries, Ltd. This development considered every aspect of the problem, with the aim of producing a practical system which could be adopted by full-scale vessels. The main objectives of the project can be summarized as follows：
1. the development of a design system for the CRP (propellers and shafting);
2. the development of a new contrarotating bearing;
3. the design of full-scale propellers and shafting;
4. a confirmation test of the performance of both propeller and shafting using large-scale models.
This paper describes the design system for the resulting optimum CRP.
Basically, a CRP is a highly efficient propulsion system, initially proposed more than 100 years ago, which is able to approach the ideal propeller efficiency by
recovering the rotating energy loss originating from a fore propeller by a contrarotating aft propeller. However it is very difficult to design or develop an efficient, sophisticated CRP without accurate design tools based on reliable theoretical programs because of the strong interaction between the fore and aft propellers.
The design system for an optimum CRP consists of the following three types of theoretical program, as shown in Fig.1：
1. a design program for an optimum CRP;
2. a steady lifting surface program for the CRP;
3. an unsteady lifting surface program for the CRP.
The design program for an optimum CRP is based on simplified propeller theory, and can be used to calculate the optimum principal dimensions, such as pitch and thickness distributions, etc., for fore and aft propellers suit able for a range of design conditions. These functions have been reported in a previous paper.1 However, the program was further improved by adding as optimum routine based on information obtained from the cooperative development work. This is a method of
