Fill in the table. Pay attention to the types of the boilers and explain the difference between them.
| SIZE | TEMPERATURE | PRESSURE | DIAMETER | |
| Horizontal inclined straight-tube boilers | • | |||
| Longitudinal - drum straight-tube boilers | ||||
| Box-type water legs | ||||
| Sectional - type water legs | ||||
| Straight- tube boilers | ||||
| straight-tube horizontal- inclined boilers | ||||
| Location of the super heater | ||||
| Bent-tube boilers |
7. Answer the questions to the text:
1. What types of water-tube boilers do you know?
2. How many drums do the small boilers have?
3. Are the box -type water legs formed of steel plate?
4. Where are the sectional-type water legs situated?
5. What is the diameter of straight-tube boilers?
6. Do the cross drum straight-tube horizontal-inclined boilers have the same arrangement of straight tubes as the longitudinal?
7. Does the location of the super heater play an important role in the general arrangement of the boiler?
8. Bent-tube boilers all have one or more top steam drums and a single bottom or mud drum, have not they?
Unit 23
Steam Engines
1. Read the text and try to understand the main idea:
Steam Engines.
In a steam engine a closely fitting piston moves in a cylinder that is connected to the steam chest by means of two pipes, which are provided with valves, serve alternately as inlet and exhaust for the steam. As the piston moves forward, steam enters through A and the used steam is forced out through B. When the piston moves in the opposite direction, steam enters the cylinder at B and used steam is forced out at A. that at which it entered it. A considerable quantity of heat would thus be carried to the condenser or the outside air and lost so far as useful work is concerned. In order to prevent this waste as far as possible, an automatic cutoff is provided. When the piston has moved through about one-fourth of its stroke, this slide valve automatically cuts off the supply of steam.
After this cutting off of the steam from the steam chest the steam that has already entered the cylinder expands and pushes the piston forward, through the remainder of the stroke. During this expansion, piston is doing work, the pressure of the steam is being reduced, the temperature of the steam is lowered. The heat contained in steam is thus converted into useful work.
When the piston has reached the end of this stroke, the slide valve opens A and connects B to the steam chest. Live steam is now again admitted to the cylinder behind the piston and pushes the piston toward the left. The dead steam in front of the piston is forced through A. When, as before, the piston has made about one-fourth of its stroke, the slide valve closes B, and the steam behind the piston expands until the piston has reached the cud of its stroke.
2. Answer the following questions:
a) Does a closely fitting piston move in a cylinder that is connected to the steam chest?
b) What are provided with valves, serve alternately as inlet and exhaust for the steam?
c) Would the steam leave the cylinder on exhaust at a temperature nearly as high as that at which it entered it?
d) Would considerable quantity of heat be carried to the condenser or the outside air and lost so far as useful work?
e) In order to prevent this waste as far as possible, an automatic cutoff is provided, is not it?
f) When has the piston moved through about one-fourth of its stroke?
g) Has the cylinder already entered expands and pushes the piston forward?
h) Is the pressure of the steam in the boiler regulated by means of a pop valve?
3. Complete the following sentences:
- As the piston moves forward, steam enters through A and...
-With this simple arrangement, the steam would leave the cylinder on exhaust at a temperature nearly as high as...
- In order to prevent this waste as far as possible...
When the piston has moved through about one-fourth of its stroke...
- After this cutting off of the steam from the steam chest the steam that has already entered the cylinder expands...
- During this expansion, piston is doing work...
- The heat contained in steam is thus converted...
4.Fill in the blanks with the missing words:
· When the piston has reached the end of this, the slide
· valve opens A and connects B to the chest.
· Live steam is now again admitted to the behind the
· piston and pushes the toward the left.
· The dead steam in front of the piston is force.
· The steam behind the expands until the piston has
· reached the cud of its.
· The cycle is then repeated, which allows the steam to escape when the pressure exceeds a certain value.
5.Choose the correct answer:
1. In a steam engine a closely fitting piston moves:
a) in a cylinder
b) in the piston
c) in the valve
9. In order to prevent this waste as far as possible, an automatic cutoff is:
a) repeated
b) provided
c) exceeded
2. When the piston has moved through about one-fourth of its stroke, this slide valve automatically cuts off:
a) the supply of steam
b) the supply of the fan
c) the supply of tubes
3. When the piston has moved through about one-fourth of its stroke, this slide valve automatically cuts off:
a) the supply of steam
b) the supply of the fan
c) the supply of tubes
Unit 24
STEAM TURBINES.
