转子发动机径向密封片的研究综述

径向密封片作为转子发动机最重要的密封部件，安装在转子的三个顶点，径向密封片直接暴露在高温高压燃气中，存在振拍、漏气和磨损三大关键问题，这些问题会导致称为“魔鬼爪痕”的缸体振纹的出现，这些问题直接影响转子发动机的工作性能和使用寿命。NSU、Mazda等公司对径向密封片的发展做出巨大，开发了多种型号径向密封片并采用了多种材料。随着材料技术的发展，一些新型材料与表面处理工艺可以应用于径向密封片，例如:碳纤维、石墨烯等纳米材料，激光表面处理、新型涂层等工艺。本文综述了NSU、Mazda和Curtiss-Wright在径向密封片上取得的成果，最后结合新型结构、新型材料与处理工艺，对径向密封片的未来发展提出建议。 

Research overview of rotary engine apex seals

In 1954, Felix Wankel became the first in the world to successfully develop a rotary engine with the cooperation of the NSU. The invention of the rotary engine is a revolution in the structure of the internal combustion engine. The rotary engine exhibits advantages of simple structure, small and light, stable operation, and better high-speed performance. However, the development of the rotary engine is seriously restricted by its poor sealing problem. The apex seal is provided on each apex of the rotor to keep each working chamber gas-tight. Since it is directly exposed to high-pressure combustion gas and subjected to various kinds of restraint involved in the planetary motion, most efforts have been concentrated on the study of its performance and durability. The apex seal has three key problems: vibration, gas leakage, and wear. These problems will lead to the emergence of chatter marks that are called the nail marks of the devil. These problems directly affect the working performance and service life of the rotary engine. Mazda and NSU have made great contributions to the improvement of apex seals. Many types of apex seals have been developed, such as solid-type, split-type, cross-hollow, and three-piece. Many materials have been used as apex seals, such as alumetizing carbon, special cast iron, and fiber-reinforced ceramics. With the development of material technology, some new materials and treatment processing technology could be applied to the apex seal, e.g., laser surface treatment and new coatings. Carbon fibers, graphene, and nanometer materials could improve the wear resistance and mechanical property. This paper summarized the achievements of Mazda, NSU, and Curtiss-Wright. Finally, according to the new materials and treatment processing technology, the new structures and new materials for the apex seals were given in this paper. The trumpet-shaped notch structure, roller pin structure, cantilever flexure structure and multi apex sealing system can be used to improve the sealing performance of apex seals. Laser surface textured and new materials such as nano-ceramic and graphene are the breakthrough point to solve the sealing and wear problem of apex seals. This paper puts forward some suggestions for the future development of apex seals.