Steam locomotive device

Since the steam boiler is the primary source of energy, this makes it the main component of the engine. In this regard, a number of requirements are imposed on the boiler. These requirements primarily include the reliability (safety) of the boiler - due to the fact that the vapor pressure can reach very high values ​​(up to 20 atm. And above), which turns the boiler into a potential bomb, and any design defect can lead to an explosion , thereby at the same time depriving the engine of the energy source. The explosion of the steam boiler was one of the most compelling arguments against the introduction of steam traction in the 19th century. Also, the steam boiler should be convenient to manage, maintain and repair, be able to work on various types and grades of fuel, be as powerful as possible, as well as economical ^[3] .

A steam boiler consists of parts, which for convenience are often divided into five groups ^{[3] [4]} :

1. main parts;
2. headset
3. fittings ;
4. steam line and superheater ;
5. auxiliary equipment.

The main parts of the boiler

A classic steam locomotive boiler consists of the following main parts (from the figure above - from left to right) : a furnace , a cylindrical part and a smoke box ^[4] .

Firebox

The furnace , which is also a combustion chamber , serves to convert chemical energy contained in fuel into heat . Structurally, the firebox is two steel boxes nested into each other: a fire box (the firebox itself) and a casing interconnected by special ties . The firebox works in extremely difficult temperature conditions, since the temperature from the burnt fuel can reach 1600 ° C, and between the fire box and the casing there is a layer of steam under high pressure (tens of atmospheres). Therefore, the furnace is assembled from the smallest possible number of parts, in particular, the fire box consists of five sheets: a ceiling, two side, a back and a tubular grill. The latter is the place of transition from the furnace to the cylindrical part ^[5] .

In the lower part of the furnace there is a grate , which serves to maintain a layer of burning solid fuel. As the name implies, it has a lattice structure that provides an influx of fresh air into the furnace. Large grate grids consist of several separate grates - grates . In the back sheet of the furnace there is a pilot hole through which fuel is dispensed. On powerful steam locomotives in the upper part of the furnace there are circulation pipes and (or) thermosiphons , which serve to increase the circulation of water in the boiler. A special arch made of bricks is attached to these pipes, protecting the ceiling and the tube sheet from exposure to an open flame ^[5] .

Between themselves, the furnaces are distinguished by the shape of the ceiling: with a flat ceiling and radial. A furnace with a flat ceiling, also known as a Belper furnace , has a relatively large volume of fire box, which ensures the completeness of fuel combustion. As a result, such fireboxes were very common among early steam locomotives, and in a number of countries they were produced until the end of steam locomotive construction (for example, Er steam locomotives produced by Czechoslovakia and Poland until 1957 ). However, the Belper furnace is difficult to dock with the cylindrical part of the boiler. In addition, the large width limits the application in terms of size, especially in the upper part, and on powerful steam locomotives it is necessary to establish a large number of connections between the fire box and the casing, since flat sheets are worse able to withstand high boiler pressure. Therefore, with powerful locomotives, they began to use fireboxes with a radial ceiling ( radial firebox ). Radial firebox is lighter than Belper's firebox and better resists high vapor pressure. But the radial furnace has a serious drawback: the relatively small volume of the furnace space, which is why fuel is burned less efficiently, and unburned coal particles can damage the inside of the boiler. Therefore, in the front upper part of such furnaces, an afterburner is often installed, which improves the efficiency of fuel combustion (although this opinion is often exaggerated) ^{[5] [6]} .

The cylindrical part of the boiler

The cylindrical part of the steam boiler is its main part, since it is in it that the main vaporization occurs. In fact, the cylindrical part is a smoke boiler , since water is heated due to a large number (up to several hundred pieces) of smoke pipes passing through it, inside which heat air flows. The shell of the cylindrical part consists of several drums (usually three or more) connected by a telescopic method, that is, one is embedded in the other. For the first time, a multi-tube boiler on steam locomotives was used in 1829, namely, on the famous Stephenson Rocket .

Often in the cylindrical part there is also a superheater , which is placed in pipes, which are basically similar to smoke-filled ones, but larger in diameter. Such pipes are already called heat pipes, and the superheater itself is called fire tube .

Smoke Box

Boiler Headset

Boiler headset - instruments and devices for ensuring the thermal operation of the boiler. They allow you to ensure the burning of the right amount of fuel with the least loss. Depending on the location, the headset of the furnace and the headset of the smoke box are distinguished. It is also worth noting such a device as a soot blower , which can be located both in the furnace and in the firebox of the furnace, or even be portable. A sootblower is used to clean the inner surface of smoke and heat pipes from soot and fouling , thereby increasing heat transfer from hot gases through the pipe walls to water and steam. Cleaning is done by directing the steam jet into the pipes. Subsequently, soot blowers were dismantled on many steam locomotives ^[7] .

Firebox Headset

To the headset of the furnace, it is first worth noting the grate , located in the fire box at the level of the furnace frame. This grate serves to maintain a layer of burning solid fuel, and also, as the name implies, provides for it, due to cracks, the flow of air necessary for burning. Due to the large size (on the steam locomotive of the A series, its dimensions are 3280 × 1830 mm ), the grate is made of individual elements - grate , which are arranged in transverse rows. On the early steam locomotives the grates were motionless, subsequently steam locomotives with movable (swaying) grates began to be built, which made it possible to simplify the cleaning of the furnace from slag and ash . The drive of the swinging grates is mainly pneumatic. Slag and ash from the furnace are poured into a special bunker located under the furnace - an ash pan , the upper part of which covers the entire grate, and the lower one, mainly due to the lack of free space, is located between the sides of the main frame of the engine. To pass air into the furnace, the ash pan is equipped with special valves, which are also used to clean the hopper from toxins. The furnace headset also includes furnace (shurovka) doors , which cover the pilot hole (serves to pour fuel into the firebox), thereby separating the spaces of the firebox and the driver’s booth. Since both the ash pan and the grill provide fresh air to the fire box, clogging (slagging) of their air ducts and cracks can cause a serious drop in boiler power, so when using anthracite and low-calorie coal, a slag humidifier is used , which consists of several tubes with holes located along perimeter of the grate. Periodically, steam is passed through them, which lowers the temperature at the grate itself, and in contact with the slag makes it more porous ^[7] .

If a steam locomotive is heated with oil or fuel oil (common on modern steam locomotives), then oil nozzles and oil pipelines are installed in the furnace. The nozzles provide fine atomization of the fuel, which is necessary for its complete combustion. At the same time, the grate is removed from the furnace, and instead of it, a special brick arch (also known as lining ) is installed in the ash pan and furnace, which serves as additional protection for the furnace from a flame having a higher temperature (over 1600 °) than with coal heating, and also to rationalize the combustion process - if the flame is extinguished briefly, the red-hot arch will help to ignite the fuel entering after the break. However, the total weight of this arch is much higher than that of the grate grate; therefore, the transfer of a steam locomotive from coal to oil heating increases the total weight of the steam locomotive, especially its rear part ^[7] .

Smoke Box Headset

Air is needed for burning fuel, and it needs quite a lot: for 1 kg of coal or fuel oil, respectively, 10-14 kg or 16-18 kg of air are required. Obviously, the supply of such an amount of air to the combustion chamber (furnace) in a natural way is practically impossible, which forces the creation of artificial draft of gases in the boiler. To do this, a special smoke exhaust device is installed in the chimney box, which ensures the flow of air into the furnace by creating a vacuum in the smoke chamber. Steam smoke exhaust devices come in several designs, however, almost all of them work on already exhausted steam coming from a steam steam engine , which allows you to change the air supply depending on the used power of the machine, that is, the more intense the steam engine works, the stronger the combustion and the more steam is being developed ^[7] .

The simplest smoke exhaust device is a cone , which looks like a cone-shaped nozzle mounted under the chimney. The principle of operation of the cone is that the exhausted steam passed through it acquires a high speed (up to 250-350 m / s), after which it is sent to the chimney, where it entrains air and creates a vacuum in the smoke chamber. Cones come in various designs, including single, double, and four-hole, variable and constant cross-section, with a common and separate release. The four-hole cone of variable cross-section with a separate outlet is most widely used, that is, when pairs from the right and left cylinders are released separately. However, despite the simplicity of the design, the cone cannot be used on steam locomotives with condensation of exhaust steam, therefore, the latter uses a fan (gas exhaust) as a smoke exhaust device. The fan is driven by exhaust steam, which, just like with a cone, makes the draft regulation automatic. Due to its advantages, fan traction began to be used even on steam locomotives without condensation of exhaust steam (for example, Soviet SB and C ^mind ), however, due to a number of drawbacks (more complex construction than the cone, and therefore higher repair cost, high backpressure during steam release, the difficulty of working at high cut-offs) in the 1950s. fan draft was replaced by conical ^[7] .

Boiler Features

The boiler is characterized by the following parameters:

• total heating area in m² - this area consists of the heating areas of the furnace, the area of ​​the superheater, as well as the areas of smoke and heat pipes;
• volume of steam space in m³;
• evaporation mirror in m²;
• working pressure in atm;
• The volume of filled water.

The steam engine of a steam locomotive consists of cylinders cast as a whole with spool boxes , a mechanism for transmitting force to the driving wheels ( crank mechanism ) and a steam distribution mechanism. The cylinders of a steam engine (of which there are 2 or more on a steam locomotive) are cast from steel and mounted on the frame with bolts, or the right and left steam engines are cast together, as in later steam locomotives.

The following types of steam engines are used in steam locomotives:

• the machine of single expansion of steam - is simple in design, has high reliability and good profitability;
• a machine for a single expansion of a pair of three or four cylinders - has more power, but is complicated in design;
• Compound machine - also has great power, but it did not justify itself in terms of efficiency. Besides complex construction, it has problems when driving with frequent stops.

Most steam locomotives used simple two-cylinder machines, efficiency was increased by the introduction of a superheater , and power was achieved by the creation of articulated steam locomotives and increased boiler boost.

The steam distribution (usually backstage ) mechanism of a steam locomotive consists of a link 1 swinging on an axis and connected at its lower end to a counter-crank 2 finger, mounted on the drive wheel at an angle to the crank . Movement from the wings is transmitted using radial traction 3 to the upper end of the lever ( pendulum ) 4; the lower end of the pendulum receives movement from the slider 5. The movement of the spool 6 is communicated from the intermediate point of the pendulum. Using the rocker mechanism (valve), all phases of steam distribution are carried out, the power of the steam engine is controlled by changing the degree of filling (cut-off) of the steam in cylinder 7 and the reversal 8 is the return of the steam engine.

In some cases, to temporarily increase the traction force (when starting off and on the ramps), on the steam locomotives, in addition to the main steam engine, an auxiliary booster is installed that transfers the work to the supporting axles of the steam locomotive or on the axis of the tender.

Other elements of a steam locomotive machine:

• oil seals - seals preventing steam leakage;
• bypasses are air bypass devices located on a spool box. Bypass channels connect the cylinder cavities on both sides of the piston and are blocked by a special valve. During normal operation of the steam engine, the bypass valves are closed without affecting the steam distribution system. When the regulator is closed (in the absence of steam supply) and coasting, the bypass valves open, preventing the engine from braking when driving by inertia. Bypass bypasses in Russia were used only on pre-revolutionary steam locomotives, later they were not installed, replacing sliding spools with more efficient operation. The most widespread on domestic steam locomotives was the system of engineer Trofimov.

The crew, or frame-running, part of the engine consists of a frame on which the boiler and cylinders are mounted, wheelsets with axle boxes, springs with balancers and a trolley

• The frame is a metal supporting structure to which the remaining parts of the engine are attached.
• Front trolley - a design that helps the engine fit into turns. For example, in the C series steam locomotives, the Tsar-Krauss cart is used, combining the runner and front driving pairs of wheels. In this case, at the moment of passing the turn, the slider axis rotates, and the moving pair receives the corresponding lateral displacement in the opposite direction.
• Driving wheelset . A steam engine acts on this pair through a piston drawbar .
• Coupling wheelsets . These wheels receive torque from the driving pair via drawbars .

On the centers of all the moving wheelsets, counterweights are molded as a whole to balance the inertia forces of the eccentrically rotating masses (crank, fingers, spokes, and on the drive wheel, in addition, the counter-crank and parts of the connecting rod).

• Runner wheelsets . Runner pairs are usually 1 or 2, in some locomotives are absent altogether (locomotives of formulas 0-X-X).
• Supporting wheelsets are located under the booth or firebox, may be absent (formula X-X-0). Steam locomotives with supporting wheelsets are better suited for reversing.
• Axial axleboxes are boxes in which bearings are placed, usually plain bearings in contact with the journals of the axles. Grease is poured into the axle boxes. In the cutouts of the frame, axle guides are attached: one of these guides is made inclined, and a wedge (axle) is placed between the axle box and the guide, with which the gap can be adjusted.
• Springs - elastic elements located between the axle boxes and the frame. The springs soften the jolts and bumps that the wheelset receives from irregularities in the track and butt clearances. For a better load distribution on individual wheelsets, springs are interconnected by balancers .
• A hitch is a device for connecting cars and a locomotive to a train.
• Buffers - elements located in the hitch and preventing sharp shocks when connecting cars.

In the booth were the drivers ( locomotive crew ) and all the controls of the locomotive were concentrated. The back of the furnace with a drilling hole for loading fuel also entered the booth.

Tender - a special car, attached to the back of a steam locomotive, in which there were supplies of water and fuel for the boiler. Often, tenders had a standard design and were used with several series of steam locomotives. In some steam locomotives, the tender also contained special equipment for condensing the spent steam ( tender capacitors used in arid, poorly provided with water) and an automatic coal feeder (stocker) .

• The brakes . The steam locomotives are mainly equipped with automatic air brakes of Westinghouse , Kazantsev and Matrosov . Compressed air is pumped into a special reservoir by a steam-air pump , and from the reservoir, air is supplied through the main brake line to the brake cylinders of the locomotive and train, using a lever system connected to the brake pads . When the brake valves located in the booth are opened, the pressure in the general air line of the train drops, and the pads are pressed against the wheels by air pressure from the tanks.
• Locomotive speed meter driven by one of the wheels.
• Steam manometer is a device for measuring the pressure of steam in a boiler.
• Sandbox It was usually installed at the top of the boiler. The sandbox contains specially sifted fine dry river sand, which is supplied to the wheels by air pressure when starting off and moving uphill and for emergency braking to improve traction between wheels and rails.
• Whistle The latest series of locomotives used harmonic multi-tone five-tone beeps, which are considered the most beautiful in the world.
• Water gauge glasses - show the water level in the boiler.
• Stocker - a mechanical coal feeder (on late steam locomotives).
• Servomotor - pneumatic translation of rocker stone (on late steam locomotives).

• Nikolsky A. S. Steam locomotives of series S. - “Victoria”, 1997. - 176 p.
• TSB, 2nd ed.

• Locomotive
• Axial formula of a steam locomotive
• Steam engine repair plants

• Steam locomotives of unconventional design (English) .