Performance characteristics of subway theoretical knowledge

Subway vehicles are the means of transportation used by subways to transport passengers, belonging to the category of modern urban rapid rail transit. So what do you know about the subway? The following is my theoretical knowledge about subway, I hope you like it!

1. subway theory knowledge? Brief introduction of the vehicle from the structure: the train adopts decentralized power arrangement. All kinds of non-power cars and power cars (or semi-power cars) are combined into a relatively fixed grouping according to needs, and consoles are arranged at both ends. Due to the limitations of tunnel clearance, vehicle clearance and equipment clearance, the design requirements of vehicles and their various on-board equipment are quite compact. At the same time of convenient maintenance, try to use modularity.

Structurally, the car body is developing in the direction of light weight, mainly adopting the modular car body structure design of large-section hollow extruded aluminum profiles and adopting the overall load-bearing structure; The suspension system has a good damping system; Adopt electric (regenerative braking and resistance braking) and air mixed braking; Vehicle connection adopts compact coupler to realize automatic mechanical, electrical and pneumatic connection; The closed all-through passage is adopted between vehicles, with large throughput.

In terms of operational performance, the subway is required to be safe, punctual and fast, because it serves people with high density and large passenger capacity in cities and is competitive with public transport systems and cars. At the same time, passengers should be provided with proper space, quiet environment and air conditioning to make them feel comfortable and convenient.

In the operation mode, ATO, that is, automatic train driving system, is applied. The main traction drive adopts the world advanced frequency modulation and voltage regulation AC drive. The auxiliary system adopts advanced IG-BT technology.

Vehicles are the most critical and complicated equipment in the subway system. It is a multi-disciplinary comprehensive product, involving machinery, electricity, control, materials and other fields. In a word, vehicles are organically combined through various relatively independent subsystems to realize the safe, reliable and high-quality operation of trains.

Second, the theoretical knowledge of the subway? Mechanical part 1, body

The general body adopts modular design. It includes a self-supporting frame, a cab connected by bolts and an intermediate end. The car body frame and middle end are made of aluminum alloy profiles and plates, and the cab is made of section steel. The welding profile is connected with the middle end and the cab end through a mechanical fastening device. The cab and middle end are covered by a large FRP cover. Energy is absorbed through the extrusion tube in the connector system. When an accident happens, the anti-climbing device at the front end of the car can disperse the collision force.

Trains are connected together through a through passage, which is designed with a folding shed and a cross board on the coupler. The surface painting of the train is carried out according to the characteristics of the city.

Step 2: doors

Choose different doors according to different vehicle operating environments. Take Guangzhou Metro Line 2 as an example. It is driven by two-way motor, and adopts belt drive and screw device as transmission mechanism. EDCU (Electronic Door Control Unit) controls the opening, closing and locking of doors. Operate the control button in the driver's cab, control the motor rotation through EDCU to open and close the door, and set up obstacle detection to reopen the door. The status signal of the door is given by the travel switch, and the fault signal is transmitted by EDCU to VTCU (Vehicle and Train Control Unit) through hard coded wires.

In terms of safety and reliability, movable doors are generally suitable for trains with the speed below 100km/h/h, especially for the outer doors, which belong to the external hanging structure and the lower part is suspended without support. When the train runs in the tunnel, with the increase of the speed, its air resistance ratio increases greatly, which produces great pressure on the hanging door. If the structure and strength of the door do not improve with the increase of speed, the door will produce unstable factors such as shaking, which will affect the safety and reliability of the door.

Because the structure of the movable door determines that a certain gap must be ensured between the door and the car body, the sealing performance of the movable door is poor. When the train reaches a certain speed (above 100km/h), there will be air channeling in the train, which will bring discomfort to passengers; When the vehicle enters and exits the tunnel, the external pressure changes, the internal pressure changes, and the comfort decreases. Due to the poor sealing of the movable door, the noise generated by the moving parts of the vehicle is easy to be transmitted into the car; At the same time, because the movable door is concave or convex on the car body, when the train runs, it will cause vortex in the nearby air, and the air resistance is large, which limits the use speed of the movable door.

Because the plug door and the car body keep the train streamlined in the same plane, it has the characteristics of good sealing and low air resistance, but the structure of the plug door is more complicated than that of the movable door and the cost is higher.

Although the forms and types of doors are different, their functions and performance parameters are similar.

For safety reasons, the escape device is located in the middle of the front wall, including a large window hinged at the top and a ladder between two driver platforms. In general, the ladder is folded and hidden. When the train can't reach the next stop, use the escape device to evacuate passengers.

3. Coupler and buffer device

The coupler buffer device is composed of coupler and buffer, which is installed on the traction beam of the underframe and is a safety component of the vehicle. Its functions are:

(1) connect vehicles to form a group of trains;

(2) transmitting longitudinal traction and impact;

(3) reducing the dynamic interaction between vehicles;

(4) Realize the connection between the circuit and the gas circuit.

There are three kinds of coupler buffer devices: automatic coupler, semi-automatic coupler and semi-permanent coupler. All three couplers have recoverable energy absorption function and adopt rubber buffers. There are also overload protection devices on the automatic coupler and semi-permanent drawbar, and irrecoverable foldable deformation tubes. Its structure adopts advanced close-fitting couplers, and the convex cones and concave cones on the hook heads of adjacent vehicles are mutually inserted, which plays a close connection role. Its advantages are saving manpower and ensuring safety and convenience. Disadvantages are: complex structure and low strength. Therefore, it is suitable for light rail vehicles such as subway and light rail.

4. monsters

Bogie is a supporting operation device that supports the car body and undertakes the vehicle running along the track. In order to pass through the curve conveniently, a center plate or a rotating shaft is arranged between the car body and the bogie, and the bogie can rotate relative to the car body around the center shaft. In order to improve the running quality of the vehicle and meet the running requirements, a spring device and a braking device are installed on the bogie. For the motor train, the bogie is also equipped with a traction motor and a deceleration mechanism to drive the vehicle to run. The bogie is mainly composed of the following parts: wheelset axle box device, elastic suspension device, frame, braking device, traction motor and gear transmission device, and bogie supporting car body device. In addition, the communication antenna of ATC is installed on the trailer bogie.

When the vehicle runs on the track, it is often accompanied by complex vibration and impact due to track irregularity, rail joint, turnout, rail surface defect and wear, wheel tread inclination, wear and axle eccentricity and other reasons. In order to improve the stability of operation, it is necessary to install a spring damping device. Air spring has obvious advantages in improving the dynamic performance and running quality of vehicles, and is widely used in subway and light rail. In order to improve the vibration performance of vehicles, hydraulic shock absorbers are mostly used in subways.

Because the subway undertakes the task of transporting passengers and runs in underground tunnels or overhead lines, bogies are required to have low noise and good vibration reduction performance, and can adapt to the changes of heavy load and no load. Generally, air springs and rubber springs are widely used as elastic suspension elements, and spring vibration reduction devices include a series of suspensions. Herringbone multi-layer rubber spring or conical spring, secondary suspension? Air spring, vertical hydraulic shock absorber, transverse hydraulic shock absorber, anti-roll torsion bar, transverse rubber buffer.

Traction drive device plays a very important role in electric bus and is the core device to drive the train. Comprise a traction motor, a gear coupling and a gear. Its function is to transfer the power output by the traction motor to the wheelset. The driving mechanism of the vehicle is a deceleration device, which is used to make the traction motor with high speed and small torque drive the moving shaft with large resistance torque. The requirements for the driving mechanism are: the power of the traction motor can be exerted; Motor-electromechanical pivot should be concentric with coupling to reduce the force of uneven line on gear. Brief description of transmission line with block diagram;

The traction motor adopts three-phase AC induction motor. Because of this electric drive mode, the traction performance is good and the operation is reliable, which makes the vehicle have good traction and braking performance.

5. Braking device

According to mature subway experience, brake shoes are used for friction braking. In order to improve friction and wear resistance, most subway vehicles use synthetic brake shoes. However, the thermal conductivity of synthetic brake shoes is poor, so choose products with good thermal conductivity? Powder metallurgy brake shoe. It not only has good friction performance, but also has good wear resistance. In the brake shoe braking mode, kinetic energy can be converted into heat energy, but the ability of heat energy to diffuse into the atmosphere is relatively small. When the required braking power is large, the possible heat energy can not be dissipated into the atmosphere, but gathered in the brake shoe and wheel tread area, which will increase its temperature, and even lead to the brake shoe melting or wheel tread cracking in severe cases. Therefore, when braking with brake shoes, the braking power should be limited, that is, a certain acceleration slip adjustment should be installed on the vehicle.

When braking, dynamic braking turns the traction motor into a generator, and the kinetic energy of the train is converted into electrical energy. Different ways to deal with these electric energy have formed different dynamic braking methods, mainly resistance braking and regenerative braking. Among them, regenerative braking is to convert the kinetic energy of the EMU into electric energy through the motor, and then feed the electric energy back to the power grid for use by other trains. Obviously, this method can not only save energy, but also reduce the environmental pollution when braking, and it is basically wear-free, so it is the first choice for the subway industry at present. In terms of braking control system, the current braking systems mainly include air braking system and electric braking control system. After comparing the two systems, it is found that electric braking has more advantages. The main advantages of electric braking are good consistency of vehicle braking and release, small longitudinal impact and short braking distance, which is convenient for the cooperation between dynamic braking and air braking.

6, vehicle internal equipment

Fixed equipment in the vehicle, such as vehicle power, ventilation, heating, air conditioning, seats, handles, etc. Services for passengers and vehicles are mostly hung on the underframe, such as battery box, relay box, main control box, electric air compressor unit, master air cylinder, power transformer, various electrical switches and contactor boxes. Air conditioners with high failure rate need to be cleaned frequently, and most of them adopt top repair and disassembly repair. In this equipment, the controller has a high failure rate, which mainly affects the passenger room environment, does not affect driving, and needs to replace a large number of spare parts.

Third, the performance characteristics and advantages of the subway

Land saving: Because of the high value of urban land in general metropolises, building railways underground can save ground space and make the ground land available for other purposes.

Noise reduction: the railway is built underground, which can reduce the noise on the ground.

Reduce interference: Because the running route of the subway does not overlap or cross other traffic systems (such as ground roads), there is less traffic interference, which can save a lot of commuting time.

Energy saving: Under the problem of global warming, subway is the best public transport. Because the subway runs smoothly, it saves a lot of commuting time, makes people happy, and also replaces a lot of energy consumed by driving.

Reduce pollution: ordinary cars use gasoline or petroleum as energy, and subways use electric energy, so there is no tail gas emission and no pollution to the environment.

Other advantages

Compared with other urban means of transportation, subway has many advantages besides avoiding urban ground congestion and making full use of space.

1, with a large volume. The transportation capacity of subway is 7~ 10 times that of ground bus, which is incomparable by any urban means of transportation.

2, punctuality, punctuality rate is generally higher than the bus.

The speed is very fast, and the subway train is flying fast in the underground tunnel. The maximum running speed is generally 80 kilometers per hour, which can exceed 100 kilometers, and some even reach 120 kilometers.

disadvantaged

High construction cost: The subway project has a long line and a wide range of influence, which usually requires measures such as demolition, reconstruction and protection of buildings, pipelines and roads along the line, and the expenses outside the project are also relatively large. Most subway projects are underground, and the cost of underground construction is higher than that of above-ground construction.

Long preparation time: It takes a long preparation time to build a subway, even a test, because it requires planning and government approval. It takes a very long time from the beginning of brewing to putting it into action and breaking ground. It may be as short as a few years and as long as more than ten years.

Some disasters have weak resilience: although the subway has strong resilience to snowstorms and hail. But the ability to resist earthquakes, floods, fires and terrorism is very weak. Due to the structure of the subway, it is very easy to have a tragedy because of these factors. Because of this, since the appearance of subway, engineers have been studying how to improve the safety of subway.

The specific disadvantages are as follows:

1 earthquake

It will lead to the derailment of moving vehicles, so the subway is designed to stop immediately when an earthquake occurs. In order to prevent the subway tunnel from collapsing, the subway structure in the earthquake zone must be particularly strong.

2. Flood

Because the system in the subway is below the horizon, the rainwater on the ground can easily be poured into the facilities in the subway. Therefore, adequate waterproof and drainage facilities must be planned in subway design. Even so, the subway station may be flooded. Therefore, in case of heavy rain, the damp-proof board at the entrance of the subway station and the waterproof gate on the route should be closed. A well-known example is that when Typhoon Li Na hit, the Taipei MRT was flooded. In addition, Beijing Metro 1 Line was closed for several hours due to heavy rain.

3. Fire

In the past, people paid little attention to the fire prevention facilities in subway stations. Once a fire breaks out at the station, it will be filled with smoke instantly, causing serious disasters. 19871154381On 8 October, a fire broke out at King's Cross Station in London, England, killing 3 1 person. One of the causes of the fire was the extensive use of wooden buildings in the London Underground. Therefore, the Japanese subway department stipulates that smoking is prohibited in subway stations to avoid fire.

On February 28th, 2003, a fire broke out in the subway station in Daegu, South Korea. 13 cars were burned, 192 people were killed and 148 people were injured. In addition to the combustible materials used in the interior decoration of trucks, the imperfect smoke exhaust facilities in the station area is also an important factor. A large number of harmful substances such as carbon monoxide are produced when the vehicle materials are burned, resulting in many people being poisoned and killed.