Evaluation of Tunnel Ventilation System at

Delhi Underground Metro Station

Vaibhav Joshi, Dr. Dilbag Singh

Department of Instrumentation and Control Engineering,

Dr. B R Ambedkar National Institute of Technology,

Jalandhar, Punjab, India vaibhav.joshi00@gmail.com, singhd@nitj.ac.in

Abstract: This paper inspects underground

stations and evaluates the tunnel safety norms and

practices followed at the Delhi Metro Rail

Corporation Ltd. (DMRC) by taking into

consideration the Subway Simulation System

(SES) and the Tunnel Ventilation System (TVS)

being employed for tunnel operations of the metro

train. The various modes of tunnel operation have

been analyzed on the basis of various National Fire

Protection Association (NFPA) standards. A

comparison with other successful mass rapid

transit systems across the world has also been

undertaken. Shortcomings along with

corresponding improvements of the existing

system have been stated and a Mass Rapid Transit

System (MRTS) has been designed for the city of

Jalandhar which takes into account various

factors and commuting trends of the city dwellers.

Keywords: Tunnel Ventilation System (TVS),

Subway Simulation System (SES), Mass Rapid

Transit System (MRTS), National Fire Protection

Association (NFPA)

I. INTRODUCTION

There have been some numerous fire incidents in

underground train stations internationally in the past.

The October 25, 1995 city subway fire in the capital

city of Baku, Azerbaijan rendered 300 dead and 270

wounded. Another fire incident on November 18,

1987 at the Kings Cross subway station, London caused by the dropping of a matchstick by a

passenger. The matchstick dropped into the gears of

the escalators and ignited the oils and some

inflammable toxic material. The incident left 31 dead

and 27 wounded. The February 18, 2003 arson fire

[1] at the subway in the Daegu city of South Korea

caused nearly 200 deaths. The heavy casualties of

these incidents were mainly due to the smoke and the

failure of the smoke management systems.

The above data shows that effective smoke

management is of utmost importance. The smoke in a

fire generally lowers the visibility and causes slower

evacuation. Moreover, the toxic gases released due to

incomplete combustion cause fatality in a short

duration of time [2], [3]. In general, fires are very

complex in nature, such as turbulence, combustion

radiation, combustible materials, fire locations, fire

location, space geometry etc., which affect the fire

and smoke propagation. The experiments in a scaled

underground station provide useful information.

However, the practical conditions differ from the

experimental conditions and thus these experiments

are not sufficient to provide completely robust

management systems.

Park et al. [4] conducted a numerical study to

evaluate fire outbreak in an underground station.

They took measurements from an actual underground

station platform for numerical analysis to investigate

the ventilation of the station and smoke in case of a

fire. The velocity measured at various points was

compared with the results obtained by numerical

analysis.

For the smoke management system to work more

effectively, a sound foundation design of the subway

has to be laid down. An important factor in advancing

the design methodology for tunnel ventilation is the

tremendous progress in the computer technology

applicable to tunnel safety. Faster and more

affordable computers encourage a wider use of design

simulation programs, such as Subway Environment

Simulation (SES) and Computational Fluid Dynamics

(CFD) to provide quick and inexpensive answers to

complicated network models of airflows and smoke

control.

This paper explicates the basics of the architecture

of an underground metro station, states the

rudimentary principle and purpose of the Subway

Simulation System (SES) and ascertains the basic

procedure involved in the process. Shortcomings and

suggestions regarding the tunnel safety system at the

Delhi metro rail Corporation Ltd. have been put

forward in comparison with other underground metro

rail systems around the world. An elementary mass

rapid transit system (MRTS) has also been proposed

for the city of Jalandhar, India.

II. BASIC ARCHITECTURE

The basic architecture of an underground DMRC

station has three levels, the ground level, the

concourse and the platform or subway level as shown

in figure 1.

Figure 1: Basic architecture

The ground level consists of the entry/exit arena

connected to the surface roads. The concourse

comprises of the main public hub, ticket counter,

plant rooms and the Station Control Room (SCR).

The platform is the location for boarding on or off the

train.

The concourse is air conditioned using the

Environmental Control System (ECS) but the

platform and the tunnel region experience the most

extreme conditions of heat and humidity and are most

vulnerable to fire outbreaks.

III. SUBWAY ENVIRONMENT SIMULATION

The Subway Environment Simulation (SES) system is

a computer designer- oriented tool which provides

estimates of airflows, temperatures and humidity

levels as well as air conditioning requirements for

both operating and multiple track subway systems.

This simulation tool was developed by Parsons

Brinckerhoff [5] in 1975 and has been employed ay

DMRC for various applications. It approximates the

ventilation system capacity to control the spread of

smoke, thus enabling the designer to design the TVS

system accordingly.

It provides the most effective size, configuration,

spacing and location for ventilation and fan shafts. A

forecast of the impact vehicle air conditioning on

overall heat rejection, temperature and humidity in

the system is furnished. It takes into account

operating schedules headways, vehicle speeds and

train sizes and provides inputs on power demand, air

velocities and pressure transients crucial to a subway

designer. Other factors are also taken into

consideration for e.g. effect of track vertical

alignment and variations due to heat sink.

The procedure for carrying out SES may be divided

into several steps:

1) Collection and Study of Data: It includes architectural plans, alignment sections, weather data,

geo technical data, passenger forecast data for the

station and the rolling stock data and train operation

plan. This data is procured from different surveys and

forecasts using statistical measures.

2) Inputting the Data: SES is based on the FPS system all the available data has to be converted in

FPS system for e.g. aerodynamic model of the

corridor, node diagrams and node sections. After this

the derived parameters from the data collected are

determined. These include train route modeling,

ventilation plan arrangements.

3) SES Inputs: The various data required for designing are procured form surveys and forecasts

using statistical measures. These include weather

data, track-way ventilation system, fan data, route

data. Besides this train schedule and train data is

obtained from the O&M department.

4) SES Outputs: The output parameters of the SES act as the governing principles for the design of the

underground station. These parameters include

airflow rate, temperature, humidity, pressure,

cooling/heating requirements, air velocity and energy

consumption. An updated train status informing about

the location and speed is also paramount to subway

designing.

IV. TUNNEL VENTILATION SYSTEM

At DMRC, the Tunnel Ventilation System (TVS) is

designed according to the output of the Subway

Environment Simulation (SES). The design weather

data from the ASHRAE handbooks [6] has been used

to arrive at the design criteria. The TVS is used for

maintaining a workable environment in the tunnels

during the expected range of operating conditions. It

provides ventilation and air movement control over

the tunnel area and track-way adjacent to each station

meant for train locomotion.

TVS has been designed to fulfill two prime

purposes:

1. An effective means of controlling smoke flows

during emergency conditions (such that both patrons

and employees can evacuate safely and also, the fire

fighting personnel can reach an incident location

without traversing a smoke filled path).

2. An acceptable environment in the tunnel and

station track-way conducive to the operation of Delhi

Metro trains.

3. A safe environment for the passengers as well as

the employees to operate at the platform and track-

way.

A. System Architecture

The TVS consists of two reversible Tunnel

Ventilation Fans (TVF) located at each of the north

and south end tunnel ventilation plant rooms. These

fans operate to provide forced ventilation in the

tunnels during the congestion and emergency modes.

For each of the tunnel ventilation fans, corresponding

Tunnel Ventilation Dampers (TVD) are installed for

controlling the air flow as required. Fixed eversible

Tunnel booster Fans (TBF) and supply nozzles

maintain the required thrust in the tunnel. All the

Reversible fans are capable of accepting a direction

reversal command without any time delay.

B. Modes of Operation

There are four modes of operation that were

manually created to suite different conditions [7].

Each mode has a corresponding manner in which the

components operate.

The four modes of operation are:

1) Normal: the operation of station and tunnel is

going as expected and the TVS is not engaged.

2) Congestion: Meant for situations like natural

disaster in which people tend to seek shelter in the

station and there is an uncertain situation.

3) Emergency: Meant for the extreme situations

like fire and flooding etc.

4) Maintenance: This mode is activated mostly at

night but may be used if maintenance is required

even during the day time in some urgent

circumstances.

In the congestion mode, the train has stopped in the

tunnel beyond a predetermined time period and this

causes the tunnel temperature to rise [8].

Consequently, it prevents the train air conditioning

from working properly. To assist the operator, the

tunnel temperatures in each section are monitored by

a temperature sensor (one located on each track in a

tunnel) and sent to the relevant Station Control Room

(SCR) and the operational Control Center (OCC). The

TVS system then follows the command from the

control center.

Figure 2: Track-way Exhaust Fan system

In the event of Congestion, to prevent the

accumulation of warm tunnel air around idling train

leads to activation of TVF push pull mode as shown in figure 2. The nearest station acts in supply mode

and farthest station acts in extract mode. The TVS can operate in various modes as listed below:

1) Open mode: The track-way exhaust fans can

operate in both the directions i.e. to supply or to

extract air. The supply or extraction process can be

executed both up-line and down-line. The tunnel

ventilation fans in extract direction can operate only

in open mode i.e. discharge to atmosphere.

2) Close mode: The track-way exhaust fans can

operate in operate only in supply mode up-line and

down-line.

In the emergency mode, an area of the tunnel is

under fire or contains smoke. Emergency conditions

are the TVS operational modes for any variety of

occurrences including transit vehicle malfunctions,

derailment or fire that may result in smoke conditions

in the tunnel. The TVS of one of the station acts in a

supply mode and that of the other station acts in an

extract mode depending upon the location of the fire

and the direction of safe passage for the passengers as

shown in figure 3.

Figure 3: Tunnel ventilation Fans (TVF) in emergency mode

V. DESIGN PRACTISES AND EXAMPLES

ABROAD

A. London Underground Rail System

Colloquially referred to as The Tube, it is the worlds oldest underground rail system consisting of 270 stations and around 400 kilometers of track,

making it the second longest metro system in the

world by route length after the Shanghai Metro. Lines

on the Underground can be classified into two types:

subsurface lines and deep-level lines [9]. The

subsurface lines, which were dug by the cut-and-

cover method while the deep-level or tube lines, which were bored using a tunneling shield.

The Tube has no provision of air conditioning;

however the new S-stock trains however will have air

conditioning system for providing a comfortable

environment for commuting. In summer,

temperatures on parts of the Underground can

become very uncomfortable due to its deep and

poorly ventilated tube tunnels. Posters may be

observed on the Underground network advising

passengers to carry a bottle of water to help keep cool

without the air conditioning. Each line is being

upgraded to improve capacity and reliability, with

new computerized signaling, automatic train

operation (ATO), track replacement and station

refurbishment, and, wherever needed, new rolling

stock.

B. Taipei Railway Underground Project

The Taipei Railway underground project

undertaken in the capital city of Taiwan consists of a

tunnel with length of 22.5 kilometers, including five

underground stations and three emergency stops. The

emergency procedure design concept, in adapting the

NFPA 130 [10] as a design guide, is to provide a

smoke-free escape route should a fire occur in the

tunnel or on the underground platform. The ceiling

plenum has been adopted as smoke reservoir to

alleviate the smoke descending rate, and thus

facilitate more time for evacuation [11]. The

evacuation system lacks a stairwell pressurization

system for handicapped patrons. The tunnel

ventilation fans, when operated on an emergency

mode, introduce an upwind along the stairwell so that

evacuees can run upstairs under tenable conditions.

The emergency operation mode has been developed

innovatively to improve ventilation system

performances. The design concept is to operate the

system on an Exhaust Only mode for the first six minutes to comply with the NFPA 130 [10], for a safe

evacuation of the passengers. It is then followed by an

unbalanced push-pull mode to provide a smoke- free

entry point for the firefighters through the primary

and tertiary staircases. For the evacuation process, the

system considers factors like bottlenecks, pushing and

taking over while calculating the total evacuation

time needed for reaching from the farthest exit point

or for passing through the exit points [12]. The smoke

diction, humane confirmation and announcement of

fire, each step takes time to complete, which add up

to around four minutes for all the passengers to leave

the platform and six minutes to leave the station, thus

complying with the NFPA 130 criteria [10]. The

Taipei Railway under ground project has been in

operation since 1999 and has a satisfactory safety

record.

C. Sydney Metro Project

The project had been undertaken to design a new

underground line through Sydneys central business district consisting of seven underground stations via

seven kilometers of tunnels. The stations have been

designed following the guidelines of NFPA 130, 2010

[10] and Building Control of Australia (BCA) so that

evacuation off the platform would be possible in four

minutes. The evacuation modeling has been carried

out using SIMULEX modeling software which takes

into account the variations in human size, mobility

and movement speeds apart from other factors.

According to the concept design for the smoke

control systems throughout tunnels to separate the

two areas with platform edge doors and provide

separate smoke control systems in both areas. The

tunnels have a longitudinal ventilation system

controlled from fans located at either end of the

station which also provides an Over Track-way

Exhaust (OTE) system above the tracks. In case of a

fire the OTE would clear the smoke from the tunnel

space, although smoke would inevitably enter the

platform areas through the open train and the platform

edge doors. To ensure tenable conditions, the

mechanical smoke exhaust system located on the

platform would start operating. For designing of the

smoke control system, Computational Fluid

Dynamics (CFD) [13] smoke modeling has been

carried out using Fire Dynamics Simulator software.

The station design includes twin-bore tunnels

throughout the line with crossovers between the two

bores at three locations along the tunnel. At these

locations the TVS is designed to reduce smoke spread

between the two bores for all fire scenarios near the

crossover. The CFD analysis demonstrated that in all

fire scenarios near the crossover sections, smoke

spread would be reduced in the non-incident tunnel.

VI. SUGGESTIONS AND IMPROVEMENTS

The practice of halting trains in the tunnel during

congestion at DMRC places a lot of burden on the

TVF system and also causes passenger

inconvenience. Trains halted in the tunnel run the risk

of having their air-conditioning units unload as

dwelling trains cause the temperatures in the tunnel to

rise. Also, for the purpose of conceptual design, the

fan sizing is based on the logical course of only one

train being permitted in the ventilation zone. If more

than one train is to be allowed, added heat and

increased ventilation equipment are to be considered.

During an incident of vehicular congestion, the Train

Service Regulator should halt as many subsequent

DMR trains as possible at the station itself. This

would place lesser burden on the TVF and allow the

passengers to alight to subsequent trains into the

station.

Currently the DMR Tunnel Ventilation System is

using the closed system concept and the open system

concept. The open system requires the sir-

conditioning to use 100% outside whereas in the

closed system the station air is re-circulated to the

station air-conditioning system. The Platform Screen

Doors (PSD) concept which is not being employed

may also be incorporated in the designing of future

underground metro systems. Platform screen doors

are actually solid, transparent barriers that are aligned

with the vehicle doors such that the passenger

entry/exit to the DMR trains is automated. The PSD

system has the inherent ability to isolate the air-

conditioning from the hot & humid air in the tunnels

and also partially prevent the smoke and toxic gases

from entering the platform in emergency and

congested conditions. They also provide the least

operating cost for the environment control systems.

On the site, another improvement may be to set up

the tunnel at the top of exhaust pipe while the

ventilation system and smoke extraction system be set

up separately using vertical exhaust to replace the

horizontal direction of the smoke method.

VI. PROPOSED MASS TRANSIT SYSTEM FOR

JALANDHAR

Owing to the success of the Delhi mass rapid transit

system, a system similar in structure is proposed for

the city of Jalandhar with the exception of the whole

system being underground. The Jalandhar metro

system would provide an efficient and effective land

transport network that is integrated, efficient, cost-

effective and sustainable to meet the needs of the

growing urban population. This paper proposes only

two initial routes and a single central station which

may be extended during further stages of planning.

The basic design has been inspired by the Delhi metro

system while the inspiration for the fire safety

systems and parameters comes from the Beijing Mass

Rapid Transport System (MRTS).

A. Basic Route Planning

Since the layout of the city is longitudinal, two

main corridors, North-South and East-West would be

the institutional routes. Jyoti Chowk near the central town would be the atrium of the corridors. The north-

south corridor would be collateral to the railway line,

running beneath the Grand Trunk (G.T.) road, thus

connecting the northern outskirts to the centre of the

city and up to the Inter State Bus Stand (I.S.B.T)

providing service along with the existing bus and auto

service. The east-west corridor would connect the

western regions of Model town with the railway station and terminating at the IOCL colony as shown

in figure 4. The Jalandhar metro would provide

service in neighborhoods where only the auto service

exists as well as complementing the bus service on

other, more popular routes. Feeder auto service may

also be provided for connecting the nearby areas to a

metro station.

Fig 4: Proposed Jalandhar metro route map. Blue line indicates the

route of the train. Red dot is the central atrium.

B. Basic Station Layout

The NFPA 130 [10] is to be adopted as the base

design guide. A typical underground station would

consist of concourse level at the first basement and a

platform at the second basement. The central portion

of the concourse would serve as the ticketing hall

where ticket machines, automatic machine gates,

station control room are located. Equipment rooms

serving the operations of the station would be located

on both ends of the station. Where possible, small

shops, Automatic Teller Machines (ATM), public

telephones etc. would be provided. The platform

would approximately be the length of the rolling

stock used in the system and separated from the

tracks by the platform screen doors (PSD) thus

adopting the PSD concept. The platform beneath the

concourse would basically be an open area for the

waiting/boarding passengers. The platform and

concourse levels are linked by open staircases and

escalators at the public areas. Enclosed staircases at

both ends would be provided to cater quick egress

from the station in the event of an emergency.

C. Fire Safety and Egress

Conforming to the requirements of the NFPA 130

[10], the underground station would be of non-

combustible construction built to a fire resistance

period of four hours. In addition to the open staircases

and escalators, enclosed staircases would be provided

at each end of the station as a secondary means of

egress. The fair gates installed would be fully open in

the event of an emergency. Escalators would be

stopped in an emergency. The passengers would be

able to leave the station within 4 minutes, a time

frame set by the NFPA 130 [10]. Exit signs and exit

direction lights would also be provided to identify the

exit routes.

D. Fire Detection and Protection

The Jalandhar MRT system would comply with the

standards set by the NFPA 130 [10]. Each station

would be provided with automatic fire sprinkler,

automatic fire alarm system, total flooding gas fire

suppression system, fire hose reel system and portable

fire extinguisher. Voice communication systems

would also be provided for necessary communication

during an emergency.

D. Smoke Control System

The smoke control system designed for the track-

way (outside the platform screen doors) would consist

of tunnel ventilation fans (TVF) at both ends of the

station and under platform exhausts (UPE) and over

track-way exhausts (OTE) as shown in figure 5. The

combined exhaust capacities would exceed the smoke

generation rate to provide effective smoke extraction

while make-up air is being induced through the

staircase. The tunnel would be set up at the top of

exhaust pipe while the ventilation system and smoke

extraction system would be set up separately using

vertical exhaust to replace the horizontal direction of

the smoke method. This would provide improved

smoke control. Operation of the emergency tunnel

ventilation system would be initiated from the

Operational Control Centre (OCC). Local controls

would be permitted to override the OCC in all modes

if the OCC becomes inoperative at any point of time.

Fig 5: The system would consist of four ducts above the tracks and a false ceiling above the platform.

CONCLUSION

This paper started with a critique about the

overwhelming research efforts put into establishing a

tunnel ventilation system at the Delhi Metro Rail

Corporation Ltd., discussing the subway environment

simulation system which acts as an analysis system,

briefly addressing the shortcomings of the existing

arrangement and suggesting some improvements

therein. The existing tunnel safety system currently

being employed at the Delhi Metro Rail underground

stations was found to be efficient, effective and robust

enough to be able to adapt to extreme conditions thus

maintaining a clean satisfactory record so far without

any accidents so far.

Some designs and approaches adopted by

successful underground rail systems across the globe

have been analyzed on the basis of which an

elementary mass rapid transit system was designed

for the city of Jalandhar, India. This underground

metro system would cover parts of the city currently

untouched by the bus service while assisting the bus

service in other heavily populated areas thus helping

to cope up with the growing population of the city.

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B. Beijing Mass Rapid Transit System

Beijing has eight operational subway lines. Smoke

exhaust and emergency ventilation systems are

provided for underground stations and tunnel. Due to

the space limitations, the normal ventilation and air-

conditioning systems are integrated with the smoke

control system. However, normal ventilation mode

can be shifted to emergency mode immediately once

a fire is detected.

Figure 2: Procedure for carrying out SES

COLLECTION AND STUDY OF

DATA

INPUTTING THE DATA

SES INPUTSSES OUTPUTS