海上能源供给技术与装备是实现国家海洋战略目标的关键支撑要素。近年来国内外中高流速洋流能发电技术取得显著成效，然而我国大部海域属中低流速区，如南海大部、东海大部，年平均流速均小于1m/s，一方面国内外现有技术尚难以实现低速流动海水动能的高效提取和转换，另一方面海域科学仪器、海防设施和岛礁建设对可再生能源供电的迫切需求却与日俱增。本申请项目以中低流速洋流为资源利用背景，针对洋流机组低速高效命题和现有装备存在问题，另辟蹊径提出“大长径比约束”条件下直驱结构优化设计的技术新思路，研究水平轴大长径比外转子对称型直驱新方案，揭示其低速高效的机理和量化规律，同时研究离心式外转子全密封工艺，从根本上去除传统机械动密封阻尼和渗水忧患，有望突破低速高效原型机设计和水平轴装备主轴动密封两大技术屏障，达到“一高三低”的研究目标（即高效原型机和低速、低耗、低噪技术指标跃升），为催生洋流能利用新型装备奠定基础。

Power supply technologies of ocean energy are key supports to the national ocean strategy. The power generation technologies of high and middle speed current have made rapid progress worldwidely in recent years. However most of domestic ocean is low speed current area，for example, the average flow speed in South China sea and East China sea is under 1m/s. It is difficult for the existing technology to capture and convert the low-speed flow kinetic energy efficiently. On the other hand, the ocean exploitation devices, coastal facilities and the island construction have urgent demands on the renewable energy power supply. In order to capture the low speed marine current, aiming at the high efficiency at low velocity and problems of existing devices, this project put forward to the new idea of the optimal design of “big length-diameter ratio” direct-driven marine current turbine. The research on the new structure of horizontal-axis big length-diameter ratio, external rotor and symmetric direct-driven will be carried out to reveal the principles and rules of low-speed high-efficiency turbine. Besides, the manufacture technology of centrifugal sealing of the external rotor will also be researched to eliminate the problems of friction and leakage of the traditional mechanical sealing, thus the two technology barriers that are low-speed high-efficient prototype design and moving sealing design of the main shaft will be broken through, and the research goal of “one high and three low” (high efficient prototype, low speed, low consumption and low noise) will be reached, so the foundation will be laid for the utility of the new devices of the ocean current energy.