T. Аs you know the compressor is one of the major components of any gas-turbine engine. Do you remember the other two components of a gas-turbine engine?
S. They are: the combustion chamber and the turbine wheel.
T. Yes, quite right. Three major components of any gas-turbine engine are: the compressor, the combustion chamber and the turbine wheel. And what is the function of the compressor? Answering this question use the model - The function of ... is to ... .
S. The function of the compressor is to compress the passing air and to provide the required pressure ratio.
T. What does the air pass through?
S. It passes through the engine inlet.
T. That's correct. Write down the word "to require" and its derivatives - "required” (потрібний, необхідний/нужный, необходимый) “requirement" (вимога, потреба /требование, необходимость). Along with the primary functions a compressor has a secondary ones: to supply air to the engine, to cool the internal hot section, to provide cabin pressurization (герметизація / герметизация), air conditioning (кондиціювання повітря / кондиционирование воздуха) and other functions that require compressed air delivery. And now you know more about the compressor and can give extended answer to the question: What's the function of the compressor?
S. The primary function of the compressor is to compress the air passing through the engine, to provide required pressure ratio and to perform other secondary functions.
T. Good job. Thank you. Now we shall consider types of compressors. They are: the centrifugal type, axial single-rotor type and axial-split compressor types. Who can translate these terms?
S. Відцентровий, осьовий та двовальний/центробежный, осевой и двухвальный.
T. Right you are. The centrifugal type of compressor produces a high pressure rise in a single stage (ступінь / ступень). One row (ряд / ряд) of blades is called a stage. The centrifugal compressor type is easy to manufacture, durable (довговічний / долговечный) and low in cost and weight. Тhe word "low" is not new for you. We have come across this word in previous units. In what word combinations did you happen to use it?
S. Lowered position – опущене положення / опущенное положение, lower half – нижня половина / нижняя половина.
Т. That’s correct. And the word combination "low in cost" is translated as "низька (собі)вартісь; дешевий/низкая (себе)стоимость; дешовый". Could you give the antonym to it?
S. High in cost, expensive, in everyday English - dear.
T. Right you are. The axial-flow compressor is higher in cost in comparison with the centrifugal compressor because it is more complicated in construction.
Exercise 3. Read, translate and give the gist of text 1.
Text 1. Compressor Types
One of the major components of any gas-turbine engine is a compressor. The compressor provides compression of mass of air entering the engine inlet to obtain a required pressure ratio, that is it increases air pressure and decreases its volume. Pressure of the ambient air entering the engine inlet duct must be increased and the compressor causes a pressure rise in the air delivered.
Compression of the air before its expansion through the turbine is effected by one of two basic types of compressor, one giving centrifugal flow and the other axial flow.
The axial-flow compressors are subdivided into the axial single rotor type and the axial split compressor type. The centrifugal compressor works very well in smaller turboprop and turbojet engines. It cannot provide the necessary pressure ratio for modern gas-turbine engines. But this type is easy to manufacture, durable, low in cost and low in weight. Typical pressure ratio obtainable with a centrifugal compressor is 5 to 1.
The axial-flow compressor is more efficient than the centrifugal compressor. It can provide pressure ratio of 12 to 1. But it is more complicated in construction and therefore higher in cost.
The most efficient is an axial-split compressor. It can provide the pressure ratio of 20 to 1. But it is of a very complicated design. It is not easy to manufacture and, of course, rather high in cost. The axial split compressor provides the highest pressure ratio and is widely used in modern gas turbine engines.
Exercise 4. Find in text 1 ten words that can be used both as а noun and a verb. Give their translation.
перевірка / проверка
перевіряти / проверять
Exercise 5. Answer the questions on text 1.
1. What is a compressor? 2. What is the function of the compressor? 3. What air does the compressor compress? 4. What are the three basic types of air compressors? 5. What types are axial-flow compressors subdivided into? 6. What compression ratio does the centrifugal compressor produce? 7. Is the centrifugal compressor easy to manufacture? 8. Which compressor is more efficient – the centrifugal or the axial flow compressor? 9. What pressure ratios are obtainable with axial-flow compressors? 10. What compressor can provide the pressure ratio of 12 to 1? 11. What compressor is the most efficient and what compression ratio can be obtained with it?
Exercise 6. Translate the following universal words without a dictionary.
Exercise 10. Translate the following words paying attention to the meaning of the prefixes: sub- (під-, нижче/под-, ниже); super- over- (пере-, понад, вище/пере-, сверх, выше); semi- (напів-/полу-); pre- (перед/пред); co- (разом, спів-, ко- /вместе; со-, кo-).
co-: coauthor, cooperation, co-existence, coaxial, collaborate, coordination.
Exercise 11. Fill in the blanks with the following terms: gas-turbine, compression ratio, axial-split, 20, major components, centrifugal, axial-flow, compress.
1. There are three ... common to most turbine engines. 2. The axial-flow compressor is more efficient than the ... compressor. 3. The… … compressor produces the highest pressure ratio. 4. The function of the compressor is to ... the air and to provide the required … …..
5. Typical … obtainable with the axial-split compressor is 12:1.
6. The centrifugal compressor cannot provide the necessary pressure ratio for modern ... engines. 7. The … … compressor can provide pressure ratio of 12:1.
Exercise 12. Put questions to the italicized words.
1. This engine works on a four-stroke cycle, consisting of induction, compression, combustion and exhaust. 2. Airplanes use thrust to propel them through air. 3. A gas turbine engine consists of two main rotating parts, a compressor and a turbine. 4. The compressor supplies air to cool its internal hot section. 5. The rocket engine does not use atmospheric air as the propulsive fluid stream. 6. The compressor discharges the air into the diffuser at correct velocity, pressure and temperature.
Exercise13. Paraphrase the sentences according to the model.
Model: The compressor compresses the air.
a) The compressor serves for compressing the air.
b) The compressor is used to compress the air.
c) The function of the compressor is to compress the air.
1. The compressor produces a high pressure ratio. 2. The diffuser directs air from the compressor to the combustion chamber. 3. The split compressor provides the highest pressure ratio. 4. The combustion chamber expands the air by burning fuel. 5. The compressor also supplies air to cool its internal hot sections.
Exercise 14. Translate text 2 in a written form.
Text 2. Types of Air Compressors
Three basic types of air compressors are used in gas-turbine engines: centrifugal flow, axial flow single rotor and axial-split compressor type. Centrifugal flow compressor receives air at its centre and makes it move outward at high velocity into a diffuser to increase pressure. Compressor with airflow parallel to the axis of the engine is called axial flow. It raises pressure of air but doesn’t change its direction. Each of these compressors has its advantages and disadvantages.
A centrifugal compressor produces a high-pressure ratio in a single stage. It is easy to manufacture, durable and low in cost.
An axial-flow compressor is more efficient than the centrifugal-flow compressor and it will handle a larger volume of air for a given diameter. It also provides higher pressure ratios than are possible with the centrifugal compressor.
An axial-split compressor provides very high pressure ratio - 20:1. But it is of a very complicated design. It is not easy to manufacture and, of course, rather high in cost.
Exercise 15. Memorize the active vocabulary.
1. що розходиться, дивергентний 2. що відхиляється
2. расходящийся, дивергентный 2. отклоняющийся
1. колектор 2. патрубок
1. коллектор 2. патрубок
build up (pressure)
створювати / нарощувати (тиск)
создавать / наращивать (давление)
Exercise 16. Practise out the dialogue.
T. And now let's consider the structure of the centrifugal compressor. The centrifugal compressor consists of the rotor and stator. The centrifugal compressor rotor, in its turn consists of the impeller, the guide vanes and two stub shafts. “Impeller” means "крильчатка, нагнітач / крыльчатка, нагнетатель", “shaft” is “вал / вал” and “the stub shaft" means "кореневий вал/корневой вал".
Look at this picture (Fig. II.2.1). This is the impeller. It is a single-sided or the single-entry impeller. ”Entry” is ”вхід / вход”. So, ”the single-entry” or ”the single-sided impeller” means ”одновхідна / одновходная” or ”односто- роння крильчатка / односторонняя крыльчатка”. So, what impeller does Fig.II.2.1 illustrate?
S. It illustrates the single-sided or single-entry impeller.
T. Look at figure II.2.2. This is a double-sided or double-entry impeller. Most gas turbine engines of the centrifugal type utilize the double-sided impeller. The verb "utilize" is the synonym to the verb "use".