The Series N700’s Environment-Friendly Technology

A. Torii1, I. Naruse1, M. Furuya1, Y. Yamazumi2

1Central Japan Railway Company, Tokyo, Japan, 2West Japan Railway Company, Osaka, Japan

Abstract Harmony with the wayside environment has become more important, especially in the Tokaido Shinkansen. Since the Tokaido Shinkansen is running through one of the most densely populated areas in the world, there are more strict regulations on the emission of external noise than those of any other high-speed railways. While increasing maximum speed, the next-generation Series N700, which started running tests in April of 2005, features more environment-friendly characteristics than the series 700 in terms of reducing external noise, reducing wayside vibration and suppressing compression waves generated upon entry into tunnels. This paper introduces each method of reducing noise emitting from various parts of rolling stock and suppressing compression waves, and its effect, and compares them with those of the series 700 developed in 1997.

1. Introduction The Series N700 is a new improved version of the Series 700, and features the three developmental concepts outlined below. (i) High-tech(cutting edge) rolling stock that run on the Tokaido and Sanyo Shinkansen lines at the highest possible speeds (ii) Further improvements to comfort in passenger cabins (iii) Compatibility with the environment and improvement of energy-saving features In order to make the series N700 the fastest rolling stock for direct operation on the Tokaido and Sanyo Shinkansen, the body inclining system is adopted for the first time in the Shinkansen. This system allows the increase of the operating speed from 250km/h to 270km/h at curves. In addition to the speed increase at curves, the maximum speed is also raised to 300km/h. On the other hand, even though the operating speed increases, it is required to maintain the level of the impact on the wayside environment. Therefore, it is necessary to reduce the external noise and suppress compression waves generated upon entry into tunnels. Suppression of compression waves is a critical issue in Japan where high-speed trains are running through mountainous regions. Although it is obvious that the compression wave becomes weaker as the length of the nose increases, the nose length of the leading car, wh ich is also limited by ground facilities, is restricted in order to maintain passenger capacity. In order to satisfy these conflicting demands, the latest optimizing method, sometimes used for designing aircraft, is applied to develop nose shape. As a result, compression waves are greatly reduced. External noise from dominant sources has been effectively reduced. From the results of the series 700’s running tests, it is found that aeroacoustic and mechanical noise emitting from the gap between cars, bogies, pantographs and the nose of the leading car need to be reduced to further reduce overall noise. Cover-all hoods are installed between all cars to make the gaps smooth. To screen the noise from bogies, all bogies are covered with lightweight skirts. Single-arm pantographs are structured that encase the hinge of its arm in the cover. The aeroacoustic and mechanical noise from the collector head is shielded by the noise-proof walls with which the roof of the body is equipped. With regard to the nose part of the leading car, although a top priority is to suppress the compression wave, the detailed structure of parts, such as the wiper, the handles for maintenance work, the hinged doors for crews, and the plug doors for passengers, is examined carefully during wind tunnel tests at our own research institute, Komaki Research Complex.

2. Suppression of Compression Wave In spite of increasing speed at curves from 250km/h to 270km/h, the level of compression wave needs to be below the current level. The other requirements for the nose shape are shown in the following. (i) Same length of the leading car in order not to remodel ground facilities (ii) Same passenger capacity as the series 700 and the series 300 (iii) Installing doors at the nose section for passenger’s convenience (iv) Securing front visibility for drivers At first, the suppression of compression wave is examined by the conventional method used in developing the series 700. According to the method, in order to make compression wave weaker, it is important to make the changing rate of the cross section area constant. The result shows that it is necessary to make the nose part 3.8 meter longer than that of the series 700. However, since that requires the large-scale remodeling of ground facilities such as stations and rolling stock depot, the extension of the nose part is impractical. Furthermore, the seat capacity is decreased by two rows for ten passengers. Therefore, such a long nose is impossible for the series N700.

Series 700 9.2m

Idea by Conventional Method 13m

Passenger capacity is decreased by two rows

Figure 1: Leading car obtained by conventional method

Hence the latest analysis method, typically used for designing the main wings for aircraft, has been applied for the first time to the development of railway rolling stock. The cross section area, a function of the distance from the nose point, is optimized by genetic algorithm combined with CFD. When designing the nose of the series N700, the optimizing method for designing main wings of aircraft is modified. There are many constraints for designing the nose shape. As mentioned before, the series N700 is required not to extend the nose, to keep the seating capacity and to install doors at the nose section. Although it is obvious that the longer nose is better for suppressing, the seating capacity is decreased. On the other hand, if keeping the same seating capacity as the series 700, the nose would be shorter such that compression wave becomes stronger. The nose part of the series N700 has to cope with these conflicting demands. Accordingly, while the structure of the driver’s cabin, passenger’s cabin and doors at the nose section has been considered carefully, the aerodynamic optimization of the nose shape is conducted. Thousands of calculations combined with the genetic algorithm and the latest CFD have optimized the nose shape of the series N700. Although the nose length is 1.5 meter longer than that of the series 700, all constraints mentioned before are satisfied and the magnitude of compression wave when running at 270 km/h is reduced as much as when the series 700 runs at 250km/h. The result is shown in Figure 2 and 3.

12

10 ) 2 8

6

4 Cross Section Area (m Series N700 2 Series 700 0 0 2 4 6 8 10 12 Distance from the Nose Point (m)

Figure 2: Cross section area of leading cars

Series N700 @270km/h Series 700 @250km/h kPa/sec Magnitude of Compression wave, dp/dt

time sec

Figure 3: Magnitude of compression wave generated upon entry into tunnels

Figure 4: Nose shape of the series N700

3. Reduction of External Noise The external noise level is not allowed to increase due to the strict regulations, although the passing speed at curves is raised by 20km/h, from 250km/h to 270km/h. In case of high-speed railways, since aerodynamic noise is dominant, the noise level is increasing with proportional to the sixth power of speeds. Therefore, the overall noise level needs to be reduced by 1dB less than that of the series 700. The reduction of the noise emitting from more dominant sources becomes more important. Hundreds of running tests, using the series 700 and the experimental train 300X, make it clear that the reduction of noise from the gap between cars is necessary in addition to the noise from pantographs and the leading car. Noise emitting between cars mainly consists of aerodynamic noise from the gap and rolling noise from the bogies. The installation of cover-all hood between all cars makes it possible to reduce noise drastically. This is an integrated extendable hood made of special materials with unique durability and flexibility, which enables both to absorb large displacement when passing at sharp curves, and to restrain flapping when running at high speeds. The configuration of bogie skirt is determined for the purpose of reducing turbulence around bogies and shielding rolling noise, without harming ease of maintenance work for bogies. As a result, external noise emitting between cars can be reduced greatly. In addition, the indoor noise is also reduced such that passengers can use cellular phones without disturbing noise.

Figure 5: Cover-all hood and bogie skirt

As measure for reducing noise emitting from the collector parts, the series N700 is equipped with insulator covers for preventing aerodynamic noise generated from insulators supporting the pantograph and surrounding rooftop equipment, and double side walls to shield current collection and aerodynamic noise. Pantographs are structured to encase the middle hinge and air pipes in the windshield cover, which is streamlined for further noise reduction. Although conventionally supported by four insulators, the pantograph on the series N700 is supported by three insulators to make the cover smaller than that of the series 700. The shielding performance of double side walls is proportional to its weight and size. However, considering the total weight and the height of the center of the gravity, it is impossible to make the side walls heavier and larger. Though the maximum weight of side walls is limited, the adoption of light-weight aluminum honeycomb panel makes it possible to enlarge side walls.

Larger Double Side Walls Series N700 Series 700 Double Side Walls

Four Insulators and Pantograph Pantograph Three Insulators Cable Head

Figure 6: Rooftop equipment of the series N700 and the series 700

Figure 7: Pantograph and insulator cover

The reduction of external noise generated from the nose part of the leading car is also considered, though the top priority is to suppress compression wave. Since the wiper and the handles for maintenance work are mounted at the position where the velocity of flow is faster than that of uniform flow, their detailed structure is determined by wind tunnel tests. Noise separation by two dimensional microphone arrays enables to take measures effectively. The example of the results is shown in Figure 8 and the wiper and the handle for maintenance work are shown in Figure 9.

Figure 8: Contour of noise level generated from the nose part

Figure 9: Wiper and handle for maintenance work

4. Conclusion The next-generation Shinkansen, “Series N700”, is the fastest rolling stock on the Tokaido and the Sanyo Shinkansen, with the aim of perfecting the Shinkansen for the 21st century as the nation’s core means of high-speed mass transportation. One of the development concepts, “Superior Environmental Performance”, is improved much more than that of the series 700, as shown in this paper. The basic performance tests have been finished for one year, using the prototype and then endurance tests are carried out. After finishing all tests, the series N700 will make a debut in 2007.

Reference 1) Naruse and Torii, "Development of the nose shape of the Series N700 Shinkansen," JREA 7. 2004