High-speed rail at 400 mph in five years… the challenge is to control noise and vibration

Recently, as the government has begun to build a high-speed railroad that allows trains to run at more than 400 kilometers per hour, attention has turned to Hyundai Rotrotem, which has a monopoly on the domestic high-speed rail market. Hyundai Rotrotem succeeded in developing a high-speed train capable of reaching speeds of more than 400 kilometers per hour in 2012, but was unable to commercialize it due to problems such as the domestic railway environment. It has been pointed out that Hyundai Rototem needs to solve problems such as vibration control and noise in vehicles in order to stably operate high-speed trains at 400 kilometers per hour.

On the 7th, the government held a ceremony to commemorate the start of the Pyeongtaek-Osong high-speed rail double track at the central plaza of Cheongju Culture and Manufacturing Complex. The ‘Pyeongtaek-Osong High-Speed Rail Double Track’ is a project to build an additional 46.9-kilometer-long high-speed rail line at a depth of 40 to 50 meters underground in the saturated Pyeongtaek-Osong section where the Gyeongbu, Honam, and Suseo high-speed rail lines meet, and is expected to be built to allow the country’s first 400-kilometer-per-hour high-speed train to be operated by 2028. “We will accelerate the construction of the next generation of world-class high-speed railways so that high-speed trains developed with our technology can run at 400 kilometers per hour,” said President Yoon Seok-yeol at the ceremony.

Graphic=Jung Seo-hee

There is no stop at Pyeongtaek Branch on the Osong-Pyeongtaek Branch section of the project, but the nearby Pyeongtaek Jise Station (SRT stop) takes 24 minutes from Osong Station. If a 400-kilometer-per-hour high-speed rail line is installed in the future, the travel time between Osong and Pyeongtaek Jije Station is expected to decrease to the mid-to-late 10s.

The government’s 400km/h high-speed rail project is likely to be won by Hyundai Rotrotem. Hyundai Rototem has been developing the HEMU-430X, a power-distributed (power is distributed among multiple vehicles) high-speed vehicle, with the Korea Institute of Railroad Technology as a national project for about eight years since 2007. When HEMU reached a top speed of 421.4 km/h in a test run in March 2013, Korea became the fourth country in the world to develop a high-speed train in the 400 km/h range after Japan (1996 – 443 km/h), France (2007 – 574.8 km/h), and China (2010 – 487.3 km/h).

Haemu is the English acronym for High-speed Electric Multiple Unit 430km/h eXperiment, which also means “auspicious sea mist”.

HEMU-430X, a 400-kilometer-per-hour bullet train developed by Hyundai Rotem. /Courtesy of Hyundai Rotem

However, high-speed rail is currently limited to 300 kilometers per hour (km/h), and even the most recently commercialized high-speed trains have a maximum speed of 320 km/h. This is because the coefficient of friction (a value that shows the relationship between weight and friction force) decreases when the train runs at more than 300 km/h, causing the train wheels to wander off the track. When the train wheels spin, the tracks and wheels are chipped away, and when this accumulates, the wheels become bumpy and the tracks are deformed, increasing the risk of안전놀이터 accidents such as derailment.

Currently, the tracks for high-speed rail in Korea are not suitable for high-speed travel over 400 kilometers per hour. In order for trains to travel at high speeds reliably, tracks must have low curvature (the degree of bending of a curve or curved surface) and slope, as well as stricter axle weight (the weight of the wheels of a pair of railcars on the rail surface) limits, track limits, and roadbed (the foundation for laying railroad tracks) limits. In order for trains to reach high speeds, the distance between stations must also be long enough.

In response, Hyundai Rotrotem first commercialized the KTX Eum (EMU-260), a 260km/h power-distributed high-speed train with a lower top speed, and in September last year, the EMU-320, a high-speed train with a higher top speed of 320km/h, was released.

The high-speed vehicle Hamu (HEMU-430X) exceeded 421 kilometers per hour in the first phase of test operation in March 2013./Provided by Hyundai Rotem

When traveling at high speeds, it is necessary to have the technology to control not only the condition of the track, but also the swaying of the vehicle itself and the noise it generates. Immediately after its opening, passengers complained of excessive noise and vibration in some sections of Hyundai’s KTX-I, and Hyundai had to replace parts that reduce vibration and shock and reshape the wheels of the train. The EMU-320 also had its delivery date pushed back by more than a year to address noise and vibration issues.

Hyundai Rotem is expected to improve the sea moorings to give it a run for its money in the upcoming 400-kilometer-per-hour high-speed rail project. “Simply improving the route environment does not mean that high-speed trains can run immediately,” said an official from the rolling stock industry. “It is expected that additional technological supplements will be made to ensure stable operation with minimal shaking even at high speeds of more than 400 kilometers per hour.”