Sanetoshi Saito

Characteristics of heating in a mechanically vibrated superconducting coil

Abstract It is revealed that much heat is generated not only by the eddy current due to the relative displacement between conducting elements in a magnet, but also by the mechanical vibrating deformation of a superconducting coil [Suzuki, E., Cryog. Eng. , 1994, 29 , 495–503]. We measured the characteristics of heating in the mechanically vibrating superconducting coil in resonance using an oil servo actuator. As a result of these experiments, the following facts are made clear: (i) the heat generated in a vibrating superconducting coil is larger in the twisting configuration than in the bending one under the vibrating mode; (ii) the characteristics of the increment in heating in the vibrating coil under the energizing and the de-energizing state are almost the same. We cite as a factor in heating phenomena of the mechanical excitation the frictional heat between the fasteners and a superconducting coil. The size of the displacements in these frictional parts are supposed to be of the order of several micrometres. We intend to make further analyses of the heating phenomena.

Propagation characteristics of tunnel compression waves with multiple peaks in the waveform of the pressure gradient: Part 1: Field measurements and mathematical model

A high-speed train entering a tunnel generates a compression wave. When the compression wave reaches the exit portal of the tunnel, a micro-pressure wave radiates outward. The magnitude of the micro-pressure wave is approximately proportional to the pressure gradient of the compression wave arriving at the exit portal. As the micro-pressure wave can cause environmental problems, tunnel entrance hoods have been installed at many portals of long slab track tunnels on the Japanese high-speed railway, the Shinkansen to reduce the magnitude of the micro-pressure wave. In this study, field measurements were taken in a Shinkansen long slab track tunnel with a hood at its entrance. The compression wave distorts during its propagation through a long slab track tunnel. The dependence of the propagation characteristics on the initial compression waveform was clarified on the basis of field measurements on different trains and hood window configurations. It was shown that compression waves with a waveform of the pressure gradient that has shallow valleys tend to steepen more easily and that the optimum window pattern of the hood depends on the length of the tunnel. Furthermore, a mathematical model corresponding to the results of the field measurements was proposed to describe the distortion of the compression waves.

1117 Micro-pressure wave emitted from slits of a shelter linking neighboring tunnels

Takashi FUKUDA, Railway Technical Research Institute, 2-8-38 Hikari-cho, Kokubunji-shi, Tokyo 185-8540 Sanetoshi SAITO, Railway Technical Research Institute, 2-8-38 Hikari-cho, Kokubunji-shi, Tokyo 185-8540 Masanobu IIDA, Railway Technical Research Institute, 2-8-38 Hikari-cho, Kokubunji-shi, Tokyo 185-8540 Takeshi KURITA, East Japan Railway Company, 2-479 Nisshin-cho, Kita-ku, Saitama-shi, Saitama 331-8513 Satoru OZAWA, Professor emeritus, Tokyo University of Technology

1119 Model Experiment and Analysis of the Micro-pressure Wave Emitted from a Tunnel Hood with Openings

Hirokazu ATSUMI, Railway Technical Research Institute, 2-8-38 Hikari-cho, Kokubunji-shi, Tokyo Tokuzo MIYACHI, Railway Technical Research Institute, 2-8-38 Hikari-cho, Kokubunji-shi, Tokyo Sanetoshi SAITO, Railway Technical Research Institute, 2-8-38 Hikari-cho, Kokubunji-shi, Tokyo Takashi FUKUDA, Railway Technical Research Institute, 2-8-38 Hikari-cho, Kokubunji-shi, Tokyo Shinya NAKAMURA, Railway Technical Research Institute, 2-8-38 Hikari-cho, Kokubunji-shi, Tokyo An impulsive pressure wave emitted from a tunnel portal, called a micro-pressure wave, is one of the important wayside environmental problems in high-speed railways. A tunnel hood with openings on its side wall installed at the portal of the train entrance side is the principal countermeasure for reducing the micro-pressure wave. However, the micro-pressure wave tends to have large peak value around openings of the hood when the micro-pressure wave is emitted from the tunnel exit portal with the hood. In this study, we carried out the model experiment focused on the effects of the tunnel hood with openings installed at the portal of the train exit side. In addition, we developed a simple theoretical model simulated the micro-pressure wave around openings of the hood.