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Text 2. Gas Compressor Units
A gas compressor unit is a mechanical device that increases the pressure of a gas by reducing its volume. Compression of a gas naturally increases its temperature.
Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a gas.
Centrifugal compressors are used throughout industry because they have fewer rubbing parts. Centrifugal fan/blowers are more suited to continuous - duty applications such as ventilation fans, air movers, cooling units, and other uses that require high volume with little or no pressure increase. Centrifugal compressors use a vaned rotating disk or impeller in a shaped housing to force the gas to the rim of the impeller, increasing the velocity of the gas. A diffuser (divergent duct) section converts the velocity energy to pressure energy.
Axial-flow compressors use a series of fan-like rotor blades to progressively compress the gasflow. Stationary stator vanes, located downstream of each rotor, redirect the flow onto the next set of rotor blades. The area of the gas passage diminishes through the compressor to maintain a roughly constant axial Mach number. Axial-flow compressors are normally used in high flow applications, as a medium to large gas turbine engines. They are almost always multi-staged. Beyond about 4:1 design pressure ratio, variable geometry is often used to improve operation.
Reciprocating compressors use pistons driven by a crankshaft. They can be either stationary or portable, can be single or multi-staged, and can be driven by electric motors or internal combustion engines. Small reciprocating compressors from 5 to 30 horsepower (hp) are commonly seen in automotive applications and are typically for intermittent duty. Larger reciprocating compressors up to 1000 hp are still commonly found in large industrial applications, but their numbers are declining as they are replaced by various other types of compressors. Discharge pressures can range from low pressure to very high pressure (>5000 psi or 35 MPa). In certain applications, such as air compression, multi-stage double-acting compressors are said to be the most efficient compressors and are typically larger, noisier and more costly than comparable rotary units.
A diaphragm compressor (also known as a membrane compressor) is a variant of the conventional reciprocating compressor. The compression of gas occurs by the movement of a flexible membrane instead of an intake element. The back and forth movement of the membrane is driven by a rod and a crankshaft mechanism. Only the membrane and the compressor box come in touch with the gas being compressed. Diaphragm compressors are used for hydrogen and compressed natural gas (CNG) as well as in a number of other applications.
Rotary screw compressors use two meshed rotating helical screws to force the gas into a smaller space. These are usually used for continuous operation in commercial and industrial applications and may be either stationary or portable. Their application can be from 3 hp (2,24 kW) to over 500 hp (375 kW) and from low pressure to very high pressure (>1200 psi or 8.3 MPa). They are commonly seen with roadside repair crews powering air-tools. This type is also used for many automobile engine superchargers because it is easily matched to the induction capacity of a piston engine.
Rotary vane compressors consist of a rotor with a number of blades inserted in radial slots in the rotor. The rotor blades slide in and out of slots, keeping contact with the outer wall of the housing. Rotary vane compressors and piston compressors are one of the oldest of compressor technologies. A rotary vane compressor is well suited to electric motor drive and is significantly quieter in operation than the equivalent piston compressor.
Exercise 14. Answer the questions on text 2.
1. What mechanical device is called a gas compressor?
2. What are the main applications of centrifugal compressors?
3. What are the main types of gas compressors?
4. Why are centrifugal compressors more suited to continuous-duty applications?
5. What do axial-flow compressors use to progressively compress the gasflow?
6. How are axial-flow compressors used?
7. What are the main features of reciprocating compressors?
8. What applications may reciprocating compressors be seen?
9. What is the difference between a diaphragm (membrane) and reciprocating compressor?
10. How do diaphragm compressors operate?
11. What is the purpose of rotary screw compressors?
12. Why are rotary vane compressors used rather than equivalent piston compressors?
Exercise 15. Say whether the given statements are true or false. If a statement is wrong, correct. If true, enrich it with details.
1. Compressors are similar to pumps. 2. Centrifugal compressors use a vaned rotating disk or impeller. 3. Axial-flow compressors are almost always multistaged. 4. Rotary screw compressors are multi-stage double-acting compressors. 5. A rotary vane compressor is significantly noisier in operation than the equivalent piston compressor.
Exercise 16. Memorize the following words and word combinations to text 3.
Jet – реактивний
steam – пара (водяна)
alternating current (АС) – змінний струм
petrol – бензин
exhaust – вихлоп; випускати
turbocharger – турбонагнітач
refinery - очисний завод
intermediate product - проміжний продукт
petroleum – нафтопродукт
refrigeration – охолодження
vapour – пара
pneumatic – пневматичний
Exercise 17. Read and entitle text 3.
Text 3.
There are many options for the “prime mover” or motor which powers the compressor. Gas turbines power the axial and centrifugal flow compressors that are part of jet engines. Steam turbines or water turbines are possible for large compressors. Electric motors are cheap and quiet for static compressors. Small motors are suitable for domestic electrical supplies using single phase alternating current. Larger motors can only be used where an industrial electrical three phase alternating current supply is available. Diesel engines or petrol engines are suitable for portable compressors and support compressors used as superchargers from their own crankshaft power.
Gas compressors are used in various applications where either higher pressures or lower volumes of gas are needed. A partial list of gas compressors applications includes:
- pipeline transport of purified natural gas to move the gas from the production site to the consumer;
- petroleum refineries, natural gas processing plants, petrochemical and chemical plants, and similar large industrial plants for compressing intermediate and end product gases;
- refrigeration and air conditioner equipment to move heat from one place to another in refrigerant cycles;
- gas turbine systems to compress the intake combustion air;
- many various industrial, manufacturing and building processes to power all types of pneumatic tools;
- as a medium for transferring energy, such as to power pneumatic equipment, etc;
- some types of jet engines (such as turbojets and turbofans) to provide the air required for combustion of the engine fuel. The power to drive the combustion air compressor comes from the jet’s own turbines;
- turbochargers and superchargers to increase the performance of internal combustion engines by increasing mass flow.
Exercise 18. Translate the following universal words without a dictionary. Mind the difference in their pronunciation and meanings.
Compressor, disk, diffuser, energy, component, mixed, diagonal, diameter, equivalent, industry, fan, ventilation, rotor, stator, turbine, geometry, motor, type, vacuum, spiral, hybrid, diaphragm, membrane, variant, element, commercial, stationary, automobile, stage, electric, phase, diesel, refrigeration, pneumatic, conditioner, mass.
Exercise 19. Find in text 2 the words that can be used both as a noun and a verb. Translate them.
| Model: rub – to rub тертя – тертися |
Exercise 20. Write derivatives of the following verbs. Translate the derivative chains.
Compress, diffuse, reciprocate, suit, charge, direct, place, vary, cost, move, rotate, produce, consume, refine, refrigerate, blow, apply, press, drive, pump, continue, house, transport, connect, equip, increase, relate, ventilate, require, use, convert, progress, maintain, combust, act.
Exercise 21. Give the initial form of these words and translate the pairs.
Relatively, extremely, similarly, progressively, roughly, normally, commonly, typically, larger, noisier, fewer, greater, most, more, higher, costly, smoothly, quietly, reliably, eccentrically, smaller, usually, significantly, quieter, lower, easily, oldest.
Exercise 22. Determine the parts of speech of the following words. Translate them.
Housepower, multi-stage, airflow, drawback, gasflow, downstream, crankshaft, roadside, turbojet, turbofan, turbocharger, output, axial-flow.
Exercise 23. Translate and comment upon the following grammar forms.
Increases, reduces, can be, can achieve, is used, to turn, has, are used, cannot achieve, are suited, uses, can be driven, are seen, are found, are replaced, can range, to be, may be, is fixed, is matched, is mounted, can be used, use, to move, to provide, to increase, to drive, comes.
Exercise 24. Match English and Ukrainian equivalents.
| 1) centrifugal compressor 2) impeller 3) horse power 4) reciprocating compressor 5) ratio 6) axial-flow compressor 7) mixed-flow compressor 8) crankshaft 9) piston 10) vane 11) screw 12) pump 13) charge 14) refrigeration | a) осьовий відцентровий компресор b) відцентровий компресор c) коефіцієнт d) колінчатий вал e) поршень f) лопатка g) осьовий компресор h) крильчатка i) поршневий компресор j) потужність у кінських силах k) охолодження l) заряд m) гвинт n) насос |
Exercise 25. Translate the following word combinations into English (a) and into Ukrainian (b).
а) Механічний прилад; швидкість газу; енергія тиску; осьова швидкість; енергетично-ефективний; коефіцієнт тиску; вентилятор вентиляційної системи; охолоджувальний прилад; лопатка ротора; лопатка статора; газотурбінний двигун; двигун внутрішнього згорання; автоматичне застосування; ефективний компресор; механізм колінчатого валу; вакуумний насос; парова турбіна; пневматичне обладнання; реактивний двигун; обід крильчатки;
b) vaned rotating disk; thousands of horse power; output pressure; mixed-flow compressor; radial velocity; rubbing part; multiple stages; multi-staged compressors; continuous-duty application; air mover; fan-like rotor blade; stationary stator vanes; constant axial Mach number; intermittent duty; discharge pressure; diaphragm compressor; flexible membrane; intake element; back and forth movement; compressor box; turbocharger; rotary screw compressor; rotary vane compressor; single phase alternating current; petrol engine; vapour-compression refrigeration; combustion air compressor.
Exercise 26. Combine the words listed in columns A and B to make all possible “noun+noun” word combinations.
| A | B |
| Velocity pressure compression combustion gas multi-stage scroll diaphragm membrane crankshaft pump screw piston vane steam diesel | mechanism energy component ratio increase engine compressor turbine unit operation |
Exercise 27. Give the terms to the following definitions.
1. A mechanical device that increases the pressure of a gas by reducing its volume.
2. A compressor which uses a vaned rotating disk or impeller, increasing the velocity of the gas.
3. Single or multi-staged compressors, using pistons driven by a crankshaft.
4. A compressor with a series of fan-like rotating rotor blades to progressively compress the gas flow.
5. A variant of the conventional reciprocating compressor, which uses membrane instead of an intake element to compress gases.
6. A compressor with two meshed rotating helical screws to force the gas into a smaller space.
7. Compressors, consisting of a rotor with a number of blades inserted in radial slots in the rotor.
Exercise 28. Explain the meanings of the following terms.
Match, engine, device, steam, fan, capacity, liquid, mixed-flow compressor, blade, scroll pump, membrane, piston compressor, cooling, vaned disk, divergent duct, compress, diesel engine, impeller.
Exercise 29. Complete the sentences using information contained in text 2.
1. Centrifugal compressors use a vaned rotating disk or … in a shaped housing. 2. A … section converts the velocity energy to pressure energy. 3. Axial-flow compressors use a series of fan-like rotating … … to progressively compress the gas flow. 4. Stationary … … redirect the flow onto the next set of rotor blades. 5. Reciprocating compressors use … driven by a … . 6. In a diaphragm compressor the compression of gas occurs by the movement of a flexible …, instead of an intake element. 7. … … … use two meshed rotating helical screws to force the gas into a smaller space. 8. Rotary vane compressors consist of a rotor with a number of … inserted in radial … in the rotor. 9. A … … compressor is significantly quieter in operation than the equivalent piston compressor. 10. … … power the axial and centrifugal flow compressors that are part of jet engines. 11. … … or … … are possible for large compressors. 12. Small … … are suitable for domestic electrical suppliers using single phase alternating current. 13. Diesel engines or petrol engines are suitable for portable compressors and support compressors used as … from their own … power.
Exercise 30. Translate and answer the following questions in English.
1. Яке призначення газового компресора? 2. Які основні типи газових компресорів? 3. Як працює відцентровий компресор? 4. З чого складається осьовий компресор? 5. Чому осьовий компресор використовується у потужних газотурбінних двигунах? 6. На чому базується робота поршневого двигуна? 7. Які існують типи поршневих двигунів? 8. Де застосовуються поршневі двигуни? 9. Який тип компресора вважають різновидом поршневого компресора? 10. Як відбувається стиснення газу у мембранному компресорі? 11. Чому один з типів компресорів називається роторним гвинтовим компресором? 12. Де застосовується цей тип компресорів? 13. З чого складається роторний лопатний компресор? 14. Які особливості роботи має такий тип компресорів? 15. За якими ознаками підрозділяють усі типи компресорів? 16. У яких галузях газотранспортної промисловості використовують газові компресори?
Exercise 31. Choose the correct answer to the questions on texts 1 and 2.
1. Where is compression of gas accomplished?
a) in gas pipelines;
b) in compressor stations;
c) in refinery stations.
2. What type of compression requires a reliable source of electricity nearby?
a) using a turbine;
b) using an electric motor;
c) using a reciprocating engine.
3. What type of an engine may be powered with natural gas from the pipeline?
a) turbine driven;
b) electrically driven;
c) reciprocating engine.
4. What do compressor stations usually contain to filter the gas prior to compressor?
a) combustion chambers;
b) liquid separators;
c) valves.
5. What is used to allow or stop gas flow along a certain section of a pipeline?
a) separators;
b) valves;
c) filters.
6. What mechanical device serves to compress gas reducing its vo-lume?
a) a combustion chamber;
b) a turbine;
c) a gas compressor.
7. What type of compressors uses a vaned rotating disk?
a) axial-flow compressor;
b) centrifugal compressor;
c) rotary vane compressor.
8. What types of compressors are almost always multi-staged and used as a medium to large gas turbine engines?
a) reciprocating compressors;
b) rotary screw compressors;
c) axial-flow compressors.
9. What types of compressors operate more smoothly, quietly and reliably than other types of compressors?
a) diaphragm compressors;
b) scroll compressors;
c) rotary vane compressors.
10. Which of compressors operate with pistons being used as in automotive applications as still in large industrial applications?
a) rotary screw compressors;
b) rotary vane compressors;
c) reciprocating compressors.
11. What compressors are usually used for continuous operation in commercial and industrial applications to force the gas into a smaller space?
a) rotary screw compressors;
b) rotary vane compressors;
c) centrifugal compressors.
12. Which of compressor types are one of the oldest of compressor technologies?
a) reciprocating compressors and diaphragm compressors;
b) rotary vane compressors and piston compressors;
c) centrifugal compressors and mixed-flow compressors.
13. What powers the axial and centrifugal compressor?
a) petrol engines;
b) steam turbines;
c) gas turbines.
Exercise 32. Speak on:
5. Compressor Stations.
6. Gas compressors.
7. Gas compressors applications.
Unit VII. Turbines
Exercise 1. Memorize the following words and word combinations to text 1.
Rotary – ротаційний
extract – видаляти
vortex – вихор
coin – вигадувати (слова, вирази)
assembly – вузол, агрегат
impart – передавати
rotate – обертати(ся)
windmill – вітряк
casing – кожух, корпус
pressure head – висота гідростатичного натиску
velocity head – швидкісний натиск
collect – збирати
impulse turbine – активна турбіна
jet – струмінь
spin – крутити, вертіти
accelerate – прискорювати
nozzle – сопло, форсунка, патрубок
casement – покриття
runner – ротор
reaction turbine – реактивна турбіна
torque – обертаючий момент
immerse – занурювати(ся)
suction – всмоктування
draft – тяга, тягова сила / зусилля
draft tube – відсмоктувальна труба
Francis turbine - турбіна Френсіса
harness – використовувати (у якості рушійної сили)
expand – розширяти
airfoil – аеродинамічна поверхня
deflect – відхиляти(ся) від напрямку
utilize – використовувати
tip – закінцівка
reduction gear – редуктор, знижуюча передача
intermediate – проміжний
inlet – вхідний отвір
combustor - камера згорання
subsonic - дозвуковий (про швидкість)
supersonic - надзвуковий
transonic - колозвуковий
Exercise 2. Read, translate and give the gist of text 1.