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VENTILATION SYSTEMS OF TRANSPORT TUNNELS: CLASSIFICATION,
STRUCTURE AND PRINCIPLES OF OPERATION
Abdazimov Shavkat Khakimovich
Associate Professor, Department of Technosphere Security,
Tashkent State Transport university
Doctor of Science (DSc), Associate Professor,
Email: shavkathakimovich1961@gmail.com
Abduvakhitov Sherzod Ravshan ugli
Specialist for engineering structures of the “Qamchiq” tunnel
at the Department of safety control and labor
protection of JSC “Uzbekistan Railways”
Applicant of Tashkent State Transport university
Email: abduvaxitovs@gmail.com
Annotation.
The article discusses the types of tunnels, the features of their ventilation and the
equipment used. The main focus is on transport tunnels, where ventilation is necessary to ensure
safe driving conditions and protection from harmful emissions. Two types of ventilation are
described: natural, based on thermal pressure, and mechanical, which provides air supply and
removal using fans. Axial and jet fans, their design, principles of operation and advantages are
presented in detail. Ventilation schemes are considered: longitudinal, transverse and combined,
each of which has its advantages and disadvantages. Special attention is paid to fire protection and
smoke removal in case of fires. It is indicated that the choice of ventilation system affects the size
and design of the tunnel, therefore it is determined at an early stage of design. The material may
be useful for specialists in the field of construction and operation of underground transport
facilities.
Keywords:
Tunnel, ventilation, transport facilities, axial fans, jet fans, natural ventilation,
mechanical ventilation, longitudinal ventilation, transverse ventilation
СИСТЕМЫ ВЕНТИЛЯЦИИ ТРАНСПОРТНЫХ ТОННЕЛЕЙ: КЛАССИФИКАЦИЯ,
УСТРОЙСТВО И ПРИНЦИПЫ РАБОТЫ
Аннотация.
В статье рассматриваются виды тоннелей, особенности их вентиляции и
применяемое оборудование. Основное внимание уделяется транспортным тоннелям, где
вентиляция необходима для обеспечения безопасных условий движения и защиты от
вредных выбросов. Описаны два типа вентиляции: естественная, основанная на тепловом
напоре, и механическая, обеспечивающая подачу и удаление воздуха с помощью
вентиляторов. Подробно представлены осевые и струйные вентиляторы, их конструкция,
принципы работы и преимущества. Рассматриваются схемы вентиляции: продольная,
поперечная и комбинированная, каждая из которых имеет свои плюсы и недостатки.
Особое внимание уделено противопожарной защите и удалению дыма при возникновении
пожаров. Указано, что выбор системы вентиляции влияет на размеры и конструкцию
тоннеля, поэтому определяется на раннем этапе проектирования. Материал может быть
полезен для специалистов в области строительства и эксплуатации подземных
транспортных сооружений.
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Ключевые слова:
Тоннель, вентиляция, транспортные сооружения, осевые вентиляторы,
струйные вентиляторы, естественная вентиляция, механическая вентиляция, продольная
вентиляция, поперечная вентиляция
Tunnel- this is an underground or mountain-like enclosed structure, usually built to provide for
the movement of vehicles (cars, trains) or pedestrians.
All tunnels have several safety systems, one of which is the ventilation system.
The main tasks of ventilation in tunnels are:
ensuring the necessary cleanliness and temperature, pressure, humidity, and air velocity in the
tunnel;
significant reduction of the content of harmful substances in the transport zone and in the air
discharged from the tunnel at the locations of air outlets (ventilation corners);
ensuring the rapid removal of combustion products, smoke removal, and assistance in
evacuating people in the event of a fire;
Preventing freezing of roads, tunnel equipment, and operational equipment in areas with cold
climates.
Ventilation systems and equipment in large tunnels can account for up to 30% of their costs.
Ventilation in transport tunnels is provided by natural or mechanical methods.
1. Natural ventilation of tunnels occurs under the influence of thermal pressure, which is created
by the temperature difference between the tunnel and the outside air. Its effectiveness largely
depends on the geographical and altitude conditions of the tunnel location, the length of the tunnel,
as well as the number and volume of moving traffic, as well as other factors.
2. Mechanical ventilation of tunnels (artificial ventilation) is carried out by supplying fresh air
through air exchange, removing polluted air, or simultaneously supplying clean and waste-free air.
In tunnels up to 300 m long, natural ventilation is allowed, in tunnels longer than 300 m, the issue
of ventilation is resolved before the design of tunnel structures, since the choice of ventilation
system in most cases determines the dimensions of the tunnel section. Therefore, first the
ventilation system is installed, the amount of air required for ventilation of the tunnel is calculated,
the required cross-sectional area of the ventilation ducts is determined, and the cross-
sectional dimensions of the tunnel are calculated. In addition, when designing the tunnel, it is
necessary to provide for mechanical devices that will remove toxic smoke from the tunnel in the
event of a fire. The parameters of the smoke exhaust system are also determined by calculation.
Free ventilation is ventilation in which air flow occurs without fans or mechanical means, due to
the following physical phenomena:
1.
Temperature difference - the difference in air temperature between the indoor and outdoor
environment (especially noticeable in the winter season).
2.
Wind pressure - the force of wind blowing through open openings.
3.
Thermal convection - hot air rises and cold air sinks, creating a natural current.
The design air pressure in the tunnel is determined as the algebraic sum of all aerodynamic
resistances created in the transport zone, longitudinal and transverse channels during air exchange
and air distribution, as well as due to natural air draft. Additional data that must be taken into
account in aerodynamic design: meteorological parameters, barometric pressure difference and
wind. Artificial ventilation of tunnels involves the removal of all harmful gases and dust particles
from the tunnel by artificially creating an air flow using mechanical fans.
Advantages:
Low construction and operating costs.
No electricity required.
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Maintenance is easy due to the simplicity of the system.
Disadvantages:
Only effective under certain conditions (e.g., if there is a temperature difference).
Long and action-packedNot enough for tunnels.
Cannot quickly vent smoke in case of fire.
There are various types of ventilation systems in tunnel construction, designed to remove dust and
toxic gases during its construction and operation. The main functions of ventilation systems in
tunnels are:
Providing a working environment with clean air.
Ensuring fire safety.
Elimination of exhaust gases.
To prevent the accumulation of fuel and toxic gases and to eliminate the risk of explosion of
these types of gases.
A fan is a mechanical device designed to supply air directly into an object or extract air from an
object, as well as to circulate and move air through the air ducts of ventilation systems, creating
the necessary pressure difference.
According to their design features and operating principle, fans are divided into axial (axial) and
centrifugal fans. Also, according to the direction of rotation of the blades of the device
(unidirectional or bidirectional) - the right and left sides rotate at the same speed.
Axial flow fans
Axial fans are the preferred technology for large volumes of air and are ideal for cross or semi-
cross tunnel systems. They are also suitable for smoke collection. The advantages of axial fans
can include:
Low noise level during operation;
High efficiency;
Easy to operate;
Low cost and simplicity of design;
Low power consumption;
Long service life;
Protect the engine from overload, sparks, moisture;
The ability to change the speed of rotation of the blades by changing the speed of the motor;
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Axial fan structure
Centrifugal fan - This is a type of fan that draws air in from the center and exhausts it in a
perpendicular direction (from the sides). Centrifugal fans are a cost-effective solution for forced
ventilation and smoke extraction from enclosed, underground areas. The main purpose of
centrifugal fans is to remove dust and toxic gases from a contaminated parking lot or smoke
trapped in a fire zone by creating a high-velocity air flow. In other words, they help move air from
the point of entry to the point of exhaust. Centrifugal fans are multifunctional: they serve both as
conventional ventilation and as smoke extraction during a fire. This type of fan is very useful in
tunnels with traffic in both directions or where the wind can significantly affect the air flow in the
tunnel.
Advantages:
Creates high pressure;
It carries air over long distances;
Resistant to dust and gaseous air;
Reliable and durable.
Disadvantages:
Takes up a lot of space;
The noise level may be relatively high;
High energy consumption (sometimes).
Centrifugal fans
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In road and railway tunnels, which are an integral part of modern transport infrastructure, there is
a great need for effective ventilation systems to ensure safety and a healthy environment.
Especially when there is a need to quickly remove smoke, gas particles and heat, a mechanical
ventilation system is recognized as the most optimal solution. Mechanical ventilation systems
include longitudinal, transverse and mixed methods. According to their names and operating
principles, they operate on the principles listed below and have a number of advantages and
disadvantages, including:
Cross ventilation
- This is a system that organizes air movement through the tunnel in a
transverse direction (i.e., through inlets and outlets, in a cross-sectional manner). In this method,
air is introduced from one side and expelled from the opposite side.
In this system, fresh air is supplied to the tunnel through inlet fans, and exhaust fans expel
polluted air. In this way, the air flow is constantly renewed.
Advantages:
Simple in structure: cheaper and easier to operate than other complex systems.
Takes up little space: no large ducts or pipes required.
Flexibility: Suitable for small to medium-length tunnels.
Disadvantages
Ineffective for long tunnels: the air flow may not reach the end of the tunnel.
The smoke may not be completely removed: especially if there is heavy traffic.
Energy consumption may be high: in continuous operation.
The transverse ventilation system is characterized by its simplicity and low cost. It is an ideal
solution, especially for short and medium-length tunnels. However, in long tunnels or in areas
with high levels of gas and smoke, it should be used in conjunction with other systems (e.g.
longitudinal or mixed ventilation).
Cross ventilation system
Longitudinal ventilation is a ventilation system that ensures the movement of air along the
longitudinal direction of the tunnel (i.e. from the entrance to the exit). In this method, the air flow
moves in the same direction as the road itself. Ventilation is carried out using jet fans.
Jet fans are installed in the ceiling (upper part) of the tunnel and they move the air flow in the
direction of traffic.
Working principle:
1.
Sensors detect the amount of gas or smoke in the air.
2.
Jet fans start automatically.
3.
The air moves from the inlet to the outlet in a strong current.
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4.
Smoke and gases mix with the air and are released from the end of the tunnel.
5.
Airspeed is appropriate for traffic safety.
The longitudinal ventilation system is a ventilation solution for modern tunnels, characterized by
simplicity, efficiency and automated control. Especially in areas with high traffic flow and rapid
accumulation of hazardous gases, this system plays an important role in ensuring fire safety and
human health. In the future, these systems are expected to be integrated with artificial
intelligence-based control systems.
Longitudinal ventilation system
Mixed ventilation system
Mixed method (combination ventilation) is a combination of two or more ventilation systems used
to provide ventilation in transport tunnels. In this system, longitudinal and transverse ventilation
methods usually work together.
Mixed ventilation system— is a combination of longitudinal and transverse ventilation systems
for air renewal and exhaust of polluted air in transport tunnels. Such systems in many cases
provide high efficiency, depending on the length and characteristics of the tunnel.
The mixed ventilation system is characterized by its high efficiency and flexibility. By using this
system, it is possible to renew the air in transport tunnels, effectively remove smoke and harmful
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gases. Although the installation and maintenance costs of the system are high, its effectiveness
and role in ensuring safety are important.
The mixed ventilation system is based on the following principles:
First stage: The air moves in a longitudinal direction. This is useful, for example, when
traffic is light or when there are high levels of smoke and gas.
Second stage: Air is exhausted in a transverse direction, especially if there is a large
amount of smoke or harmful gases in the air. In this case, a transverse ventilation system helps to
quickly exhaust the air flow.
Automatic control system: Sensors and detectors are used to monitor air quality and
control ventilation in real time.
Mixed ventilation system
is characterized by its high efficiency and flexibility. By using this
system, it is possible to renew the air in transport tunnels, effectively remove smoke and harmful
gases. Although the installation and maintenance costs of the system are high, its effectiveness
and role in ensuring safety are important.
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