Executive Summary
The Japanese bullet train was the first high speed railway system in the world, opening in 1964 right before the Tokyo Olympics. The Shinkansen reduced the journey from Osaka to Tokyo by almost three hours, leading to a huge number of users where this new line had reached surpasses x users within the first x years. Its high economic success has led to it being a crucial part of Japan’s economy, which can be seen by its dominating market share over the airlines in short to middle distances.
The engineers of the Shinkansen line faced many challenges while developing this high-speed railway system and are still busy overcoming these obstacles as they continue to strive for improvement. High speeds in trains can cause interactions involving much greater forces, leading to phenomena such as the hunting motion as well as other large vibrations which can contribute to vibration pollution and structural fatigue.
Long term tests are carried out where data is constantly analysed to ensure the safety of passengers, leading to its perfect record of zero casualties caused by the Shinkansen. This perfect record is also backed up by the advanced technologies which the Shinkansen holds, involving computer systems such as the Central Traffic Control system.
The advancement of technology such as wheel conicity and the electrical multiple power unit system has allowed the Shinkansen to safely reach these high speeds of two to three hundred kilometres per hour while the use of different damping methods involving air springs and yaw dampers guarantee the comfort of the passengers. With the addition of new technology, the currently developing Chuo Shinkansen line along with its use of the SCMaglev system has shown that it is possible to reach much greater speeds of around 500 kilometres per hour.
Contents
1. Introduction ……………………………………………………………………….. 3
2. The reduction of vibrations………………………………………………….. 4
2.1 The importance of vibration reduction…………………………………. 4
2.2 The hunting oscillation………………………………………………………. 4
2.2.1 What is the hunting oscillation?…………………………. 4
2.2.2 Wheel conicity…………………………………………. 5
2.3 Effects of vibration on the environment…………………………… 6
2.4 Effects of damping…………………………………………………….. 6
2.4.1 What is damping?
2.4.2 Air springs
2.4.3 Yaw damping
3. Supplying power………………………………………………………………….. 8
3.1 The electrical multiple power unit system…………………………… 8
3.2 The locomotive system ……………………. 9
4. Safety……………………………………………………………………………………. 10
4.1 Introduction ………………………………………… 10
4.2 The Traffic Control System…………………………………. 10
4.3 Countermeasures for earthquakes…………………………….. 11
5. Economic success……………………………………………………………. 11
6. History
6.1 The development of the Shinkansen…………………………… 8
6.2 The future
7. Conclusion……………………………………………………………………………… 14
2.0 The Reduction of vibrations
2.1 The importance of vibration reduction
The reduction of vibrations in the Shinkansen railway system is one of the main challenges faced by engineers. Vibrations reductions play a key part in the comfort of passengers; how the Shinkansen can reach these high speeds of over 200km/h; the sustainability in the large viaducts which the Shinkansen runs on. Railway induced vibrations may even cause many environmental issues such as causing disturbances to local residents.
As the velocity of the trains increases, engineers face more and more challenges with these vibrations due to the increasing magnitudes of vibrations, leading to newly surfacing problems.
2.2 The Hunting Oscillation
2.2.1 What is the hunting oscillation
The hunting oscillation is the name given to the occurrence of the violent lateral swaying motion of vehicles when their velocity exceeds what is known as the critical hunting velocity. This phenomenon can also occur at speeds below this critical hunting velocity, when certain conditions which may involve factors such as the amount of rail irregularities being exceeded (Cooperrider 1972).
When hunting oscillations occur, the vehicle is in a state of unstable equilibrium. This instability is caused by the magnitude of the adhesion forces gradually increasing, eventually overcoming the opposing inertial forces leading to very strong, violent motions (Moody Joanna Charlotte, 2014). This concept is used to define the critical hunting velocity as the velocity where the adhesion forces of the vehicle are equal to the inertial forces of the vehicle.
The effects of the exceeding the critical hunting velocity can be seen in Figure 2.1 and Figure 2.2. As you can see, there is a dramatic increase in the magnitudes of the lateral oscillations in Figure 2.2, where the vehicle is at the critical hunting velocity, compared to Figure 2.1, where the vehicle is below the critical hunting velocity. These graphs also show that the critical hunting velocity has very little effect on the vertical oscillation of the vehicle.
These powerful hunting oscillations may lead to damages in the wheels and tracks of the railway system and may even lead to derailing accidents. This therefore means that it is very important to account for this phenomenon when designing the Japanese bullet trains, especially as they travel at such high speeds.
2.2.2 Wheel Conicity
The tread shape of the wheels of a railway vehicle plays an important role in the stability of trains running at high speeds. Train wheels are often cone-shaped as its structure allows the motion of the train to be aligned with the track with minimal resistance compared to other wheels such as straight ones, which may face a lot of difficulty when turning. However, it is this conicity of the wheels which can lead to the hunting motion.
If the wheelset of the train becomes displaced on the rail track, the two will have different rolling radii (Fujimoto & Minamoto 1996). This therefore leads to a difference in the velocity of the two wheels, as they are connected to each other so must rotate at the same speed, leading to a continually increasing rotation causing lateral oscillations: the hunting oscillation. A key to reducing the magnitudes of these hunting oscillations is to reduce the conicity of the wheels.
2.3 Effects of vibration on the environment
The main effect of vibrations on the surrounding environment is vibration pollution. Vibration pollution is defined as the vibration in the environment caused by human activities which lead to disturbances in the local area of the source. These disturbances many include physical or psychological disturbances such as effecting the quality of sleep of local residents, which is shown to be reduced by high vibration levels through an experimental study (1).
A major source of vibration pollution is traffic induced vibrations. The vibrations caused from railways is transmitted through the ground and can lead to vibrations in buildings as shown in Figure 2.3.
The reduction of these traffic induced vibrations have now become a key focus in design as of the increase in demands for better living quality throughout the years whereas it was a much smaller area of focus when the Shinkansen was first developed. The main countermeasures to combat these vibrations include the reduction of vibration sources, the cutting of vibration transmission paths in ground soil and the isolation of buildings (1).
2.4 Damping and its effects
2.4.1 Introduction
Damping is an extremely important factor in the reduction of vibration in the Shinkansen. It plays a key role in the comfort and quality of the ride of passengers as well as the durability of the viaducts which the Shinkansens constantly pass on. Shinkansens carry very large kinetic energies due to its high speed. This may potentially lead to significant interactions with the bridges such as causing the bridge to resonate, leading to fatigue problems in these supporting structures.
The development of technology in Shinkansens has led to the number of trains servicing to be five times greater than that of when it was first servicing (2) and also a large increase in speed, causing a much greater burden on the viaducts if the vibrations are not dealt with.
2.4.2 Air springs
One of the key suspension system in the Shinkansen, offering damping, is known as air springs. Air springs make use of the air compressibility and the flow resistance in a pipe leading to very high damping capabilities and softness which ensures the comfort of the passengers. It has been utilized in the Shinkansen since the very first generation (4) although it has been further developed to respond to the greater forces caused by the increase in speeds and demands for higher ride qualities.
The air spring causes damping effects through the fluctuation in pressure due to the compression of air due to movement in the main chamber (4) which is surrounded by the outer cylinder shown in Figure 2.5. This fluctuation in air pressure causes the flow of air through the orifice into the auxiliary air reservoir. It is also stated that it is possible to obtain different characteristics and properties of the air spring by changing the volume of the auxiliary air reservoir and the diameter of the orifice.
2.4.1 Yaw damping
Another key technique used for the reduction of vibrations in the Shinkansen is the use of yaw damping between cars. The primary objective of air springs is to provide a comfortable ride whereas yaw damping focuses more on the reduction of lateral vibrations caused by yaw motion vibrations which is the oscillation or rotation caused about the vertical axis. The car end yaw dampers provide a force proportional to the relative yawing angular velocity between the cars in or to reduce these vibrations.
The research of (3) suggest that the vibrations caused by the yawing motion is the primary vibration of the Shinkansen, which can also be seen in Figure 2.6, and that this yawing motion is greatest at the trail cars. Through the implementations of these yaw motion dampers, it is also shown that it can play a key role in the reduction of the hunting oscillations.
3.0 Supplying power
3.1 The electrical multiple power unit system
The Shinkansen makes use of the electrical multiple power unit system which the motive force is distributed amount each car. This system comes with multiple advantages such as increasing the acceleration ability, decreasing the overall weight of the train cars which also reduces the load on the tracks. This also makes the Shinkansen environmentally friendly as it does not directly run on fuel such as coal and has low energy consumptions.
Unlike locomotives, power must constantly be supplied to the Shinkansen as it comes from external sources. High voltage AC currents are fed through pantographs to the Shinkansen from the overhead power cables. These pantographs play a key role in providing a stable supply of energy to the Shinkansen while moving at high speed.
The pantographs must keep in contact with the overhead wires as much as possible to maintain a continual supply of electrical energy. As shown in Figure 3.1, when contact loss occurs, there is not only a stop in supply but also an electrical discharge given off which arises due to the high potential differences between the wire and the pantograph (6). This discharge can an increase in wear of the contact wire and slider as well as some radio interference so must be kept at a minimal.
Overall, the main challenge faced by the engineers for the pantograph is to find a balance of the contact force where the force is large enough to prevent contact loss however is still kept low in order to minimise the wear and damage of the contacting elements. (7)’s research concludes that there is still room for development to maximise the objectives above after an in-depth study of the pantographs interaction with its surroundings.
3.2 The locomotive system
In the early years of the development of trains, most European countries used the concentrated traction system or the locomotive system. Traditionally, the locomotive system relied on locomotives pulling the train behind it at the front. In contrast to the electric multiple unit systems used in the Shinkansen, this relied on only one car powering the entire train.
In the early stages of development, the European engineers had viewed the use of multiple units on the train as disadvantages due a requirement for high maintenance, a high initial cost and passengers’ discomfort due to noises and activities occurring underneath the passenger cars (5). However, as of the 1990s as technology progressed, these engineers began to accept the advantages of the electric multiple unit system and this design started becoming adopted all around Europe (5).
4.0 Safety
4.1 Introduction
One of the biggest prides of the Shinkansen is the fact that there has not been a single accident since the start of its operation in 1963 which resulted in any injuries or fatalities (Central Japan Rail Company 2017). The Central Japan Rail Company claim that this is only possible due to its staff being ‘highly-skilled in safety awareness’ as well as its ‘train control system with sophisticated technology’.
4.2 Train control system
As a result of the very high speeds of the Shinkansen trains, it is impossible to operate the train while visually checking signals from the train therefore, it required to be carried out automatically by the train control system. There are two parts to the control system of the Shinkansen: the main Control Centre and the local train control system (9). These two components, which are linked through the Central Traffic Control system, are responsible for maximising train safety.
The main functions of the control system include the maintenance of a safe distance between trains, the insurance of a route for the trains, centralisation and automation of control and the signalling of a safe signal even with failure of certain equipment (9). These functions are carried out by two main systems: the audio-frequency track circuit system which transmits signals through the track and the relay interlocking device, which controls the signals and switches in accordance to the instructions received by the Central Traffic Control system.
4.3 2011 Earthquake safety
A major threat to the safety of the Shinkansen train lines in Japan is the constant threat of earthquakes. However, even with all of the major earthquakes which have occurred over the years, the Japanese bullet train is yet to have a single casualty. The installation of the seismometer and strong quakeproof structures are said to play a key role in the safety.
An example of a major earthquake which occurred recently is the 2011 Tōhoku earthquake with a recorded magnitude of 9.0 (11). According to (10), it is said that the seismometer at Kinkazan detected the earthquake just a couple seconds before the earthquake had hit which sent an automatic stop signal, triggering the emergency brakes on 33 trains. Despite all of the major damage done to buildings and structures throughout the country, the Tōhoku line was able to restart its operations in only 49 days after the earthquake although it took much longer in other places including coastal areas, which had sustained much greater damage from this natural disaster. (11).
Track displacements in 2590 places were recorded and 1150 electrification masts were damaged according to (11). The majority of the major structures such as bridges sustained no critical damage. This is believed to be due to the major improvements and developments in the quakeproof engineering technology, especially after experiencing huge damages from the 1995 Great Hanshin-Awaji and 2004 Niigata Chuetsu earthquakes. However, JR East comments that they are not satisfied yet and are working on further developing its quakeproof technology for the Shinkansen train lines to prepare for potential future threats.
5.0 Economic Impacts
The Shinkansen train line has played a huge role in Japan’s thriving economy, with the Tokaido Shinkansen having an annual passenger count of 155 million passengers in 2014 (12). The development of the Shinkansen was one of Japan’s major efforts to aid its recovery from its huge losses due to the war along with the hosting of the Olympics, which also occurred in the same year as the opening of the first every Shinkansen line.
The Tokaido Shinkansen line, opening in 1964, was the first ever Shinkansen line and also the world’s first high speed railway system. It spanned over 550 kilometres between Shin-Osaka station and Tokyo station, connecting the two biggest cities in Japan (13). The journey which had taken just under seven hours had been reduced to around 4 hours.
At that time, the development of high speed railways was pushed heavily in Japan as it was believed to attract money, jobs and tourists (13). Since then, the Shinkansen has become an iconic feature of Japan, becoming one of the major attractions to tourists from overseas as well as leading to an increase in tourism to the Shinkansens destinations due to its convenience benefits.
Currently, the Shinkansen train line dominates the market share against airlines in short to mid-range travelling as shown in Figure 5.1 (12). The Central JR company also boasts its ‘unrivalled’ inter-city transportation capacity with the Tokaidao Shinkansen line averaging around 445 thousand passengers each day (Tokyo to Osaka) compared to Euro stars 28 thousand (London to Paris/Brussels) and Acela Express’s 9 thousand passengers per day average (Boston to Washington D.C.).
6.0 History
6.1 Shinkansen types
The first ever Shinkansen train ran along the Tohoko line from Tokyo to Osaka on the first of October 1964 (14). The Shinkansen 0 Series were the name given to the first class of trains in operation. These Shinkansens had a maximum speed of 220 km/h (15). The production of the 0 Series ended in 1986 and their service ended in 2008. Shinkansens have a relatively short service life of around 15 years, much shorter than that of most rail equipment which has a service life of around 30 years.
The next generation of Shinkansens were called the Shinkansen 100 Series which were produced between 1984 and 1991 (15). The main differences between the 0 Series Shinkansen is the fact that the nose of the train is pointier and that the majority of the driving cars of the 100 Series Shinkansens are not powered. The 100 Series Shinkansens have a maximum speed of 220km/h, which is slightly faster than that of the 0 Series. The 100 Series is also no longer in service, ending in March 2012.
The Shinkansen 300 Series were next introduced in 1992 along with dedicated high-speed railways. These Shinkansen trains were produced between 1990 to 1998 and had a maximum speed of 270km/h. These Shinkansens had curved wedge shaped ends in comparison to the pointy noses of the 100 Series Shinkansens. The 300 Series also ended its service in March 2012, along with the 100 Series.
The 500 Series Shinkansen was developed soon after, making its appearance in 1998. These trains were constructed between 1995 to 1998 and had a maximum speed of 320km/h. Only nine of these trains were built compared to the 3200 vehicles built for the 0 Series. The 500 Series is still currently in service and can be seen between Shin-Osaka and Hakata. The yaw dampers, talked about in the previous sections, began to be implemented at this stage.
The 700 Series Shinkansen began its service straight after the 500 Series in 1999. This series is operated at a speed of 270km/h however is much cheaper to produce, with each train costing around 4 billion yen compared to the 5 billion yen of the 500 Series. The 700 Series Shinkansen trains were constructed between 1997 to 2006 and is still currently in service today.
The N700 Series Shinkansen entered service in 2007 and has a maximum speed of 300km/h. This series began manufacture in 2005 and is still constructed to this day. The N700 Series currently runs between Tokyo and Shin-Osaka in two hours and twenty-two minutes, which is over four hours shorter than the first developed 0 Series.
6.2 The future
Currently under development is the Chuo Shinkansen which uses the SCMaglev system. The SCmaglev system is a super conducting magnetic levitation system which is based on the principle of repulsion between magnets between the train tracks and the cars. The construction started in December 2015 and the Chuo Shinkansen line plans to start its operations of phase 1 in 2027 (15).
The SCMaglev system has been under development since the 1970s. With a planned operating speed of 505km/h, the Chuo Shinkansen aims to reduce the most travel times by over 50% (16). Japan’s Maglev train currently holds the world’s fastest train speed of 603km/h which was recorded in 2015 (16). The operating speed of the Chuo Shinkansen is planned to exceed the current fastest train in operation, the Shanghai Maglev train which has a top speed of 430km/h (source), allowing the Japan to regain the title of having the fastest train in the world.