DISSERTATION

SCOPE

The London Underground, the first underground transport network in the world, built-in 1863,

carries millions of passengers every year, both local citizens and tourists. An engineering breakthrough of its time, other metro and subway infrastructures worldwide built after the 1880s surpassed the London Underground regarding network size, train mechanisms, and HVAC systems.

It is an indoor transport network that can make modern levels of expected energy efficiency much harder to achieve. The HVAC systems require a lot of energy to run. The London Underground has a wide array of ventilation systems installed on the trains and stations to combat pollution and provide fresh air for passengers and staff. The ventilation systems play an important safety role. They become pivotal in the case of fires and other emergencies.

HVAC systems can fail due to overload or lack of current, which would cause passengers discomfort and risk passengers' safety in the case of a fire. Other issues occur, such as failure to detect smoke,

heat, and water. These issues are managed with maintenance, but the disruptions caused by the piston effect are unavoidable.

The project will look at the theoretical calculations that can be used to solve the piston wind velocity and pressure. The simulation will be run on a CFD software called Autodesk CFD, where the results can be analysed. The report will also run several scenarios to study the airflow caused by the piston effect when a train passes through a tunnel.

Project Deliverables

Project timeline

Equation schematics

2D/3D Design

Cost implantation scheme

Cost-saving scheme

Data analysis

Budget list

Prototypes and Prototype testing

COMPUTATIONAL FLUID DYNAMICS

Here are the results of the convergence plot over 100 iterations there are signs that the velocity on xyz will eventually settle and show a uniform plot.

The traces show that there are steady and uniform particles at the front of the tunnel that stays steady in the middle section of the train, however, the particles become non-uniform due to drag. This also shows an increase in pressure suggesting that this is where the blockage effect takes place.

Approval Criteria

The success of the investigation provided enough data to start building an efficient system and produce investigative results for the deadline of 28/04/2023.

Constraints

The need to use several facilities to gather data and analysis will need to be done on and off campus to cover time constraints. There are restrictions to the resources needed to do testing on campus, this can be avoided by project planning.

There are a lot of unknowns, finding accurate updated resources to back my data. Prepare literature to compare results if theoretical calculations are not possible to produce. The study is highly reliant on theoretical assumptions and system configuration. Along with the unknown data needed for comparison, simulations the depth of dynamics is uncharted territory. This can be improved with proactive data collection, assumptions based on theoretical data, and extensive studies around related aerodynamics topics.

Extensive reading on literature background is required due to the time constraint and other limitations that reduce access to data.

Assuming design specification due to the lack of London underground access and schematics.

Assume scaled-down tunnel schematics. Studying the dynamics of underground metro tunnels will help in understanding the characteristics to look for in CFD analysis.

Assumptions

The data will reflect the upper limit of possible mass air flow produced from the piston effect.

Design Parameters:

Measurements have been rounded to the nearest whole number.

The train length is 1180mm, width is 100mm, and height is 125mm

Three tunnels are used for CFD to see the difference in airflow closer to the shafts of the tunnel when the train passes through. The tunnel face parameters are, height 150mm width 160mm, radius corners 30mm, inside height 105mm, inside width 70mm and thickness 15mm.

Tunnel one – the tunnel length is 1650mm
Tunnel two – the tunnel length is 1261mm
Tunnel three – the tunnel length is 1185mm

Flow region one box dimension length 300mm, width 1750mm and height 300mm
Flow region two box dimension length 200mm, width 1350mm and height 250mm
Flow region three box dimensions length 200mm, width 1230mm and height 250mm
Bogie x3
Bogie base dimensions area 35999.42mm^2
base thickness 2mm
bogie wheel attachment pads x16 area171.60mm^2

wheel attachment pad thickness 1m

Trace Particles

The results above of design 3 using Tunnel three – the tunnel length is 1185mm and Flow region three box dimensions length of 200mm, the width of 1230mm and height of 250mm shows the particle traces of airflow as the train passes through the tunnel exit. It shows the airflow at the head of the train being where the fastest airflow is and the air particles that are able to push past the head flow below the train. This can be shown further with the use of a velocity vector plane.

Iso Volume

Here is the iso volume of design 3 based on the range where the velocity magnitude reaches its minimum value coloured with the velocity Vz. This is the volume of air with respect to the velocity magnitude. Data like this is important to visualise where the majority of useful air flow is and is not.

Z-AXIS Plane

With the same design, a plane is plotted along the z-axis. This shows that there is a high velocity at the front of the train and tunnel however there is a lower velocity magnitude at the base and rear of the tunnel. This suggests that pressure increases in these areas. Referring to the convergence plot the pressure is not steady and is gradually increasing.

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