v The propeller has a higher runaway speed;
v The hydraulic thrust is higher;
v With increasing head the suitable specific speed becomes lower;
v In selecting a turbine an effort is made to use a runner the required power at the greatest practicable speed.
Specific Speed.
The specific speed provides a means of comparing the speed of all types of hydraulic turbines on the same basis of head and horsepower capacity.
4.Complete the sentences.
1. Power may be developed from water...
2. Hydraulic turbines may be grouped...
3. With the impulse wheel the potential energy of the water...
4. Impulse wheels are used...
5. With the Francis types the water...
6. The higher speed of propeller runner results...
7. The fixed-blade propeller type unit has...
8. Propeller-type runners are constructed...
9. The adjustable-blade propeller type is...
10. The hydraulic thrust is higher...
5. Agree or disagree with the statements:
- The propeller has a lower runaway speed.
- The hydraulic thrust is higher than Francis type.
- With increasing head the suitable specific speed becomes higher.
- The specific speed provides a means of comparing the speed of all types.
- Hydraulic turbines may be grouped in two general types.
- The kinetic energy of the circumference at any instant.
6.Answer the following questions:
1. How can the power be developed in hydraulic turbines?
2. May the hydraulic turbines be grouped in two general classes?
3. Is the potential energy of the water transformed into kinetic energy?
4. Are the impulse wheels used at lower heads?
5. Does the Francis Runner enter from a casing or flume?
6. Has the propeller-type affected marked economies?
7. Has the flxed-blade propeller-type unit a high efficiency?
8. What is the material used for making propeller-type runner?
9. What is the best-known unit of adjustable-blade runners?
10. What factors of affecting selection do you know?
Choose the words from the box to complete sentences.
| Runaway speed | Specific speed | Guide |
| Thrust | Types | Classes |
1. The propeller has a higherthus involving a correspondingly more expensive design of generator.
2. The hydraulic ______ is higher, requiring a more costly _____ bearings.
3. With increasing head the suitable ________ becomes lower.
4. The specific speed provides a means of comparing the speed of all _______ hydraulic turbines.
5. The long passageway from the end of ______ vanes to runner vanes of a propeller.
6. Hydraulic turbines may be grouped in two general...
Unit 26
Basic Elements of Hydraulic Systems
l. Remember and study the elements of hydraulic systems.
The basic elements of hydraulic systems are:
1. The fluid.
2. The generator element (pump).
3. The transmission element (pipes and connections).
4. The control element (valve or restrictor).
5. The motor element (jack or continuous motor).
6. Tank and filter.
Read and translate the abstract.
The elementary form of pump can only work as a pump while the piston is moving into the cylinder and acts as a motor while the piston moves back. If non-return valves are added, the inlet valve is connected to a tank and the piston is given a to-and-to motion, the device becomes a source of continuous supply of liquid, except for interruptions during the suction stroke, which can be avoided by having two or more cylinders and pistons. Thus we obtain a continuous pump.
3. Find the Ukrainian equivalents of the word-combinations:
o Valve
o Tank
o Transmission
o Connections
o Pipes
o Fluid
o Cylinder
o Continuous motor
o Pistons
o Filter
Use the words from Ex. 3 and make up sentences with them.
Translate into English.
§ Елементарна форма насосу
§ Рухатись в циліндрі
§ Діяти як мотор
§ Зворотній клапан
§ Рухатись назад
§ Приєднуватись до баку
§ Зворотно - поступові рухи
§ Засіб стає джерелом
§ Продовжене постачання рідини
§ Два або більше циліндра
6. Answer the following questions:
1. What are the basic elements of hydraulic systems?
2. How can the elementary form of pump work?
3. Does the motor act while the piston moves back?
4. When are the non-return valves added?
5. Is the inlet valve connected to a tank?
6. Does the device become a source of continuous supply of liquid?
Unit 27
