HIGH SPEED TRAINSHIGH SPEED TRAINS

SANCHIT AGARWAL

Introduction Maglev technologyPropulsion systemHyerloop Kantrowitz limit Components of hyperloopAir bearingsHigh speed rail vs hyperloop

INTRODUCTION

High speed rail or Bullet train is a system of transportation that uses magnetic levitation to suspend, guide and propel vehicles from magnets rather than using mechanical methods, such as friction-reliant wheels, axles.Maglev is short form of  Magnetic Levitation in which trains float on a guideway using the principle of magnetic repulsion. However, instead of using permanent magnets, the principle of electromagnetism is used to create strong and large temporary magnets. When an electric current is passed through a coil of wire, magnetic field is generated around the coil according to Faraday's laws.

The magnetized coil running along the track, called a guideway, allowing the train to levitate between 0.6-6 cm above the guideway. Once the train is levitated, power is supplied to the coils within the guideway walls to create a unique system of magnetic fields that pull and push the train along the guideway. The electric current supplied to the coils in the guideway walls is constantly alternating to change the polarity of the magnetized coils. This change in polarity causes the magnetic field in front of the train to pull the vehicle forward, while the magnetic field behind the train adds more forward thrust

There are two primary types of maglev technology:

1. Electromagnetic suspension (EMS)2. Electrodynamic suspension (EDS)

MAGLEV TECHNOLOGY

EMS EDS

PRINCIPLE Electromagnetic suspension is attractive type magnetic leviation. The system is typically arranged on a series of C-shaped arms, with the upper portion of the arm attached to the vehicle, and the lower inside edge containing the magnets. The rail is situated between the upper and lower edges.

Electrodynamic suspension is a form magnetic leviation in which there superconductors are exposed to time-varying magnetic fields. This induces eddy currents in the conductors that creates a repulsive magnetic field which holds the two objects apart.

PROPULSION

The system consists of aluminum three-phase cable windings in the stator packs that are on the guideway

When a current is supplied to the windings, it creates a traveling alternating current that propels the train forward by pushing and pulling.

When the alternating current is reversed, the train brakes. Different speeds are achieved by varying the intensity of the current.

HYPERLOOP:

Hyperloop is a new way to move people or things anywhere in the world quickly, safely, efficiently, on-demand and with minimal impact to the environment. The system uses electric propulsion to accelerate a passenger or cargo vehicle through a tube in a low pressure environment. The autonomous vehicle levitates slightly above the track and glides at faster-than-airline speeds over long distances. It eliminates direct emissions, noise, delay, weather concerns and pilot error. It’s the next mode of transportation.

KANTROWITZ LIMIT:

Air is compressed with a pressure ratio of 20:1 When we use less pressure instead of vacuum we have to

consider the minimum tube to pod area ratio then we need to increase the diameter of tube or go slow or really , really fast.

Here an electric compressor fan mounted on the nose of the pod that actively transfers high pressure air from the front to the rear of the vessel.

A battery can’t store enough energy to power fan over whole journey so a linear electric motor, a round induction motor rolled flat is provided.

Energy consumed per passenger to travel same distance is very low compared to cars, aero planes , high speed trains.

Components of Hyperloop Transportation System

Low Pressure TubeCapsulePropulsionSuspension

Low Pressure Tube

Main disadvantages of conventional type of transportation system is only the aerodynamic drag and the rolling friction.

The expected pressure inside the tube will be maintained around 100pa (less pressure).

This low pressure minimizes the drag force on the capsule while maintaining the relative ease of pumping out the air from the tube

The tube is made of steel. Pylons are placed at every 100 ft (30 m) to support the tube. Solar arrays will cover the top of the tubes in order to provide power

to the system

.

CAPSULE: The capsules are accelerated via a magnetic linear accelerator affixed at

various stations on the low pressure tube with rotors contained in each capsule.

The capsules are supported via thrust air bearing that operate using compressed air reservoir and aerodynamic lift.

For travel at high speeds, the greatest power requirement is normally to overcome air resistance. Aerodynamic drag increases with the square of speed, and thus the power requirement increases with the cube of speed

Linear accelerators are constructed along the length of the tube at various locations to accelerate the capsules.

Linear induction motors consist of a moving primary (rotor in traditional rotary induction motors) that contains the motor coils, and a stationary secondary (stator in traditional rotary induction motors) that contains a squirrel cage winding. The primary of these motors contains a three-phase winding which carries the current supplied by the AC synchronous or AC vector drive. As current flows in the primary windings, it is induced to flow in the squirrel cage windings of the secondary. The interaction of the electromagnetic fields produced by the currents in the primary and secondary windings generates linear force to propel the primary.

Capsules are accelerated by linear magnetic induction and decelerated by regenerative braking similar to magnetic levitation trains.

Power is needed to make up for propulsion motor efficiency (including elevation changes), aerodynamic drag, charging the batteries to power on-board compressors, and vacuum pumps to keep the tube evacuated.

PROPULSION:

SUSPENSION:Suspending the capsule within the tube presents a substantial

technical challenge due to transonic cruising velocities.Conventional wheel and axle systems become impractical at high

speed due frictional losses and dynamic instability. A viable technical solution is magnetic levitation; however the

cost associated with material and construction is prohibitive. An alternative to these conventional options is an air bearing

suspension. Air bearings offer stability and extremely low drag at a feasible cost by exploiting the ambient atmosphere in the tube.

Air bearings use a thin film of pressurized air to support a load

Air bearings use a thin film of pressurized air to support a load of bearing also called as "fluid film" bearing. Fluid film bearings have no solid-to-solid contact under typical running conditions; instead, a film of lubricating fluid (in our case pressurized air) forms a layer between the solid machine elements and serves to transfer forces from one to the other.

What are air bearings?

Hyperloop advantages over today’s fastest trains

The Hyperloop is much faster driveCheaper to builtEnvironmentally friendly (rail/road via electric cars) Sustainable (uses solar energy) & self-poweringImmune to weatherResistant to Earthquakes

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