книги / English for Aerospace Engineering

turbine, which drives the compressor. If the turbine and compressor are efficient, the pressure at the turbine discharge will be nearly twice the atmospheric pressure, and this excess pressure is sent to the nozzle to produce a high velocity stream of gas which produces a thrust. Substantial increases in thrust can be obtained by employing an afterburner. It is a second combustion chamber positioned after the turbine and before the nozzle. The afterburner increases the temperature of the gas ahead of the nozzle. The result of this increase in temperature is an increase of about 40 percent in thrust at takeoff and a much larger percentage at high speeds once the plane is in the air.

The turbojet engine is a reaction engine. In a reaction engine, expanding gases push hard against the front of the

engine. The turbojet sucks in air and compresses or squeezes it. The gases flow through the turbine and make it spin. These gases bounce back and shoot out of the rear of the exhaust, pushing the plane forward.

A turboprop engine is a jet engine attached to a propeller. The turbine at the back is turned by the hot gases, and this turns a shaft that drives the propeller. Some small airliners and transport aircraft are powered by turboprops.

Like the turbojet, the turboprop engine consists of a compressor, combustion chamber, and turbine, the air and gas pressure is used to run the turbine, which then creates power to drive the compressor. Compared with a turbojet engine, the turboprop has better propulsion efficiency at flight speeds below about 500 miles per hour. Modern turboprop engines are equipped with propellers that have a smaller diameter

but a larger number of blades for efficient operation at much higher flight speeds. To accommodate the higher flight speeds, the blades are scimitar shaped with swept back leading edges at the blade tips. Engines featuring such propellers are called propfans.

A turbofan engine has a large fan at the front, which sucks in air. Most of the air flows around the outside of the engine, making it quieter and giving more thrust at low speeds. Most of today's airliners are powered by turbofans. In a turbojet all the air entering the intake passes through the gas generator, which is

31

composed of the compressor, combustion chamber, and turbine. In a turbofan engine only a portion of the incoming air goes into the combustion chamber. The remainder passes through a fan, or low pressure

compressor, and is ejected directly as a "cold" jet or mixed with the gas generator exhaust to produce a "hot" jet. The objective of this sort of bypass system is to increase thrust without increasing fuel consumption. It achieves this by increasing the total air mass flow and reducing the velocity within the same total energy supply.

This is another form of gas turbine engine that operates much like a turboprop system. It does not drive a propellor. Instead, it provides power for a helicopter rotor. The turboshaft engine is designed so that the speed of the helicopter rotor is independent of the rotating speed of the gas generator.

This permits the rotor speed to be kept constant even when the speed of the generator is varied to modulate the amount of power produced.

The ramjet is the most simple jet engine and has no moving parts. The speed of the jet "rams" or forces air into the engine. It is essentially a turbojet in which rotating machinery has been omitted. Its application is restricted by the fact that its compression ratio depends wholly on forward speed. The ramjet develops no static thrust and very little thrust in general below the speed of sound. As a consequence, a ramjet vehicle requires some form of assisted takeoff,

such as another aircraft. It has been used primarily in guided missile systems. Space vehicles use this type of jet.

https://www.grc.nasa.gov/www/k 12/UEET/StudentSite/engines.html

32

Unit 7. Propulsion

The word propulsion is derived from two Latin words: pro meaning before or forwards and pellere meaning to drive.

Propulsion means to push forward or drive an object forward.

A propulsion system is a machine that produces thrust to push an object forward.

On airplanes, thrust is usually generated through some application of Newton's third law of action and reaction. A gas, or working fluid, is accelerated by the engine, and the reaction to this acceleration produces a force on the engine.

I. Read the following words paying attention to the pronunciation:

Propulsion [prəˈpʌlʃ(ə)n], exceed [ɪkˈsiːd], velocity [vɪˈlɒsɪtɪ], afterburners [ˈɑː əˌbɜːnə], bypass [ˈbæɪpɑːs], hypersonic [haɪpəˈsɒnɪk].

II. Read the text carefully to get accurate information.

Why are there different types of engines? If we think about Newton's first law of motion, we realize that an airplane propulsion system must serve two purposes. First, the thrust from the propulsion system must balance the drag of the airplane when the airplane is cruising. And second, the thrust from the propulsion system must exceed the drag of the airplane for the airplane to accelerate. In fact, the greater the difference between the thrust and the drag, called the excess thrust, the faster the airplane will accelerate.

Some aircraft, like airliners and cargo planes, spend most of their life in a cruise condition. For these airplanes, excess thrust is not as important as high engine efficiency and low fuel usage. Since thrust depends on both the amount of gas moved and the velocity, we can generate high thrust by accelerating a large mass of gas by a small amount, or by accelerating a small mass of gas by a large amount. Because of the aerodynamic efficiency of propellers and fans, it is more fuel efficient to accelerate a large mass by a small amount. That is why we find high bypass fans and turboprops on cargo planes and airliners.

Some aircraft, like fighter planes or experimental high speed aircraft, require very high excess thrust to accelerate quickly and to overcome the high drag associated with high speeds. For these airplanes, engine efficiency is not as

33

important as very high thrust. Modern military aircraft typically employ afterburners on a low bypass turbofan core. Future hypersonic aircraft will employ some type of ramjet or rocket propulsion.

https://www.grc.nasa.gov/www/k 12/airplane/bgp.html

ACTIVE WORDS

propulsion [prəˈpʌlʃ(ə)n] ‒ двигательная установка exceed [ɪkˈsiːd] ‒ превышать

excess thrust ‒ избыточная тяга velocity [vɪˈlɒsɪtɪ] ‒ скорость

afterburners [ˈɑːftəˌbɜːnə] ‒ авиафорсажная камера bypass [ˈbæɪpɑːs] ‒ байпас, перепуск

hypersonic [haɪpəˈsɒnɪk] ‒ сверхзвуковой, ультразвуковой

engine efficiency ‒ относительный эффективный КПД; КПД двигателя

III. Find English equivalents in the text.

Двигатель, закон, двигательная установка, уравновешивать, лобовое сопротивление, тяга, превышать, авиалайнеры, грузовые самолеты, крейсер ский режим, избыточная тяга, эффективность, низкий расход топлива, количество, масса, величина, пропеллеры, вентиляторы, турбовинтовые двигатели, истребители, экспериментальные высокоскоростные самолеты, КПД двигателя, военные самолеты, гиперзвуковые самолеты.

IV. Scan the text to determine whether these statements are true (T) or false (F).

1)Propulsion means to push forward or drive an object backward.

2)A propulsion system is a machine that produces drag to push an object

forward.

3)First, the thrust from the propulsion system must balance the drag of the airplane when the airplane is blasting off.

4)Second, the thrust from the propulsion system must exceed the drag of the airplane for the airplane to slowdown.

5)It's probably the greater the difference between the thrust and the drag, called the excess thrust, the faster the airplane will accelerate.

6)Some aircraft, like airliners and fighter planes, spend most of their life in a cruise condition.

7)For these airplanes, excess thrust is as important as high engine efficiency and low fuel usage.

34

8)Because of the aerodynamic efficiency of propellers and fans, it is more fuel efficient to accelerate a small mass by a large amount.

9)Some aircraft require very high excess thrust to accelerate quickly and to overcome the high drag.

10)For these airplanes, engine efficiency is not as important as very high

speed.

V. Complete the following sentences. Choose the ending according to the text.

1)The thrust from the propulsion system must balance the drag of the

airplane

2)The thrust from the propulsion system must exceed the drag of the

airplane

3)In fact, the greater the difference between the thrust and the drag, called

4)Some aircraft, like airliners and cargo planes, spend most of their life in

5)For these airplanes, excess thrust is

6)Because of the aerodynamic efficiency of propellers and fans, it is more fuel efficient to

7)That is why we find high bypass fans and turboprops on

8)Some aircraft, like fighter planes or experimental high speed aircraft, require very high excess thrust to

9)For these airplanes, engine efficiency is

10)Modern military aircraft typically employ

11)Future hypersonic aircraft will employ

a)a cruise condition.

b)accelerate a large mass by a small amount.

c)accelerate quickly and to overcome the high drag.

d)afterburners on a low bypass turbofan core.

e)cargo planes and airliners.

f)for the airplane to accelerate.

g)not as important as high engine efficiency and low fuel usage.

h)not as important as very high thrust.

i)some type of ramjet or rocket propulsion.

j)the excess thrust.

k)when the airplane is cruising.

35

VI. Complete the sentences.

An airplane (силовая установка) must serve two purposes. First, the (тяга) from the (силовая установка) must (уравновешивать) the (сопротивление) of the airplane when the airplane (находится в полете). And second, the (тяга) from the (силовая установка) must (превышать) the (сопротивление) of the airplane. Some aircraft, like (авиалайнеры) and (грузовые самолеты), spend most of their life in a (крейсерском режиме). For these airplanes, (избыточная тяга) is not as important as (высокая эффективность двигателя) and (низкий расход топлива). Some aircraft, like (истребители) or (экспериментальные высокоскоростные самолеты), require very high (избыточная тяга) to (ускорения) quickly and to (преодоления) the high (сопротивления) associated with (высокими скоростями). For these airplanes, (КПД двигателя) is not as important as very high (тяга). Modern (военные самолеты) typically employ (форсажные камеры) on a low bypass turbofan core. Future (гиперзвуковые самолеты) will employ some type of (прямоточного воздушно реактивного двигателя) or (ракетного двигателя).

Unit 8. Materials for Aircraft Engines

I. Read the following words paying attention to the pronunciation:

Alloy [ˈælɔɪ], microstructure [ˈmaɪkrə(ʊ)ˌstrʌktʃə], analogous [əˈnæləɡəs], rectangular [rekˈtæŋɡjʊlə], array [əˈreɪ], cement [sɪˈment], composition [kɒmpəˈzɪʃ(ə)n], chromium [ˈkrəʊmɪəm], tungsten [ˈtʌŋst(ə)n], rhenium [ˈriːnɪəm], titanium [tɪˈteɪnɪəm], tantalum [ˈtæntələm], oxidation [ɒksɪˈdeɪʃ(ə)n], aluminum [əˈluːmɪnəm], strengthening [ˈstreŋθənɪŋ], wrought [rɔːt], magnesium [mæɡˈniːzɪəm], ceramic [sɪˈræmɪk], ultimate [ˈʌltɪmət], fibre [ˈfaɪbə], silicon [ˈsɪlɪk(ə)n].

II. Read the text carefully to get accurate information.

Primary author: Stewart Miller

Modern Alloys

A modern turbine blade alloy is complex in that it contains up to ten significant alloying elements, but its microstructure is very simple. The structure is analogous to an `Inca wall', which consisted of rectangular blocks of stone stacked in a regular array with narrow bands of cement to hold them together.

36

In the alloy case the `blocks' are an intermetallic compound with the approximate composition Ni3 (Al,Ta), whereas the `cement' is a nickel solid solution containing chromium, tungsten and rhenium.

Superalloys have always contained phases of this type, but in recent years the titanium in the original intermetallic has been replaced by tantalum. This change gave improved high temperature strength, and also improved oxidation resistance. However, the biggest change has occurred in the nickel, where high levels of tungsten and rhenium are present. These elements are very effective in solution strengthening.

Since the 1950’s, the evolution from wrought to conventionally cast to directionally solidified to single crystal turbine blades has yielded a 250 °C increase in allowable metal temperatures, and cooling developments have nearly doubled this in terms of turbine entry gas temperature. An important recent contribution has come from the alignment of the alloy grain in the single crystal blade, which has allowed the elastic properties of the material to be controlled more closely. These properties in turn control the natural vibration frequencies of the blade.

Thermal barrier coatings have been used for some years on static parts, initially using magnesium zirconate but more recently yttria stabilised zirconia. On rotating parts, the possibility of ceramic spalling is particularly dangerous, and strain tolerant coatings are employed with an effective bond coat system to ensure mechanical reliability.

Further increases in temperature are likely to require the development of ceramic matrix composites. A number of simply shaped static components for military and civil applications are in the engine development phase and guide vanes have been manufactured to demonstrate process capability, such techniques involve advanced textile handling and chemical vapour infiltration.

However, it is the composite ceramic rotor blade that provides the ultimate challenge. It will eventually appear because the rewards are so high, but it will take much longer to bring it to a satisfactory standard than was anticipated in the 1980’s. Research work has concentrated for some years on fibre reinforced ceramics for this application, as opposed to monolithic materials which possess adequate strength at high temperatures but the handicap of poor impact resistance.

Today's commercially available ceramic composites employ silicon carbide fibres in a ceramic matrix such as silicon carbide or alumina. These materials are capable of uncooled operation at temperatures up to 1200 °C, barely beyond the

37

capability of the current best coated nickel alloy systems. Uncooled turbine applications will require an all oxide ceramic material system, to ensure the long term stability at the very highest temperatures in an oxidising atmosphere. An early example of such a system is alumina fibres in an alumina matrix. To realise the ultimate load carrying capabilities at high temperatures, single crystal oxide fibres may be used. Operating temperatures of 1400 °C are thought possible with these systems.

https://www.azom.com/article.aspx?ArticleID=90

ACTIVE WORDS alloy [ˈælɔɪ] — сплав (металлов), сплавить, легировать rectangular [rekˈtæŋɡjʊlə] — прямоугольный

stack [stæk] — складывать array [əˈreɪ] — матрица

band [bænd] — полоса, полоска

composition [kɒmpəˈzɪʃ(ə)n] — состав (хим.), спец. смесь, сплав chromium [ˈkrəʊmɪəm] — хром

tungsten [ˈtʌŋst(ə)n] — вольфрам rhenium [ˈriːnɪəm] — рений

superalloy [ˌsuːpərˈalɔɪ] — специальный сплав (жаропрочный и т.п.) суперсплав

titanium [tɪˈteɪnɪəm] — титан tantalum [ˈtæntələm] — тантал oxidation [ɒksɪˈdeɪʃ(ə)n] — окисление aluminum [əˈluːmɪnəm] — алюминий nickel [ˈnɪk(ə)l] — никель

solid [ˈsɒlɪd] — твердый solution [səˈluːʃ(ə)n] — раствор

strengthening [ˈstreŋθənɪŋ] — техн. упрочнение

wrought [rɔːt] — кованый, катаный, обработанный давлением conventionally [kənˈvenʃ(ə)nəlɪ] — условно, традиционно alignment [əˈlaɪnm(ə)nt] — техн. выравнивание

thermal barrier coating] — покрытие, создающее термический барьер; теплозащитное покрытие

magnesium [mæɡˈniːzɪəm] — магний

yttria stabilized zirconia — диоксид циркония, стабилизированный оксидом иттрия

38

spalling — отслаивание, растрескивание vane [veɪn] — лопасть, лопатка

vapour [ˈveɪpə] — infiltration инфильтрация паров ultimate [ˈʌltɪmət] — конечный, окончательный fibre [ˈfaɪbə] — волокно

reinforce [riːɪnˈfɔːs] — укреплять, усиливать handicap [ˈhændɪkæp] — препятствие, помеха silicon [ˈsɪlɪk(ə)n] — кремний

alumina [əˈluːmɪnə] — окись алюминия

III.Find English equivalents in the text.

a)сплав; монокристаллический; монолитный; керамическая матрица; волокно; раствор;

b)никель; хром; вольфрам; рений; титан; тантал; кремний; магний; алюминий;

c)жаропрочность; стойкость к окислению; устойчивые к деформациям; механическая надежность; ударопрочность; долгосрочная стабильность.

IV. Read the text and complete it with the necessary words.

1)A modern turbine blade __ contains up to ten significant alloying

elements.

2)In the alloy case the `blocks' are an intermetallic compound, the `cement' is a nickel solid __.

3)The solution contains __, tungsten and rhenium.

4)In recent years the titanium in Superalloys has been replaced by __.

5)This change improved high temperature strength and oxidation __.

6)The biggest change has occurred in the __, where high levels of tungsten and rhenium are present.

7)These elements are very effective in solution __.

8)Thermal barrier __ have been used for some years on static parts.

9)On rotating parts strain tolerant coatings are employed to ensure mechanical __.

10)Further increases in temperature are likely to require the development of ceramic __ composites.

39

How to Read Chemical Formulas & Equations

HCl — [eiʧ si: el] HBr — [eiʧ bi: a:]

H2SO4 — [eiʧ tu: es ou fɔ:] CF4 — [si: ef fɔ:]

Cu2O — [si: ju: tu: ou]

V. Read the text and complete it with the necessary words.

A modern (лопатки турбины) (сплав) contains up to ten significant alloying elements. In the alloy case the `blocks' are an intermetallic (компонент), the `cement' is a (твердый раствор никеля). The (раствор) contains (хром), (вольфрам) and (рений). In recent years the (титан) in superalloys has been replaced by (тантал). This change improved (жаропрочность) and oxidation (стойкость). The biggest change has occurred in the (никель), where high levels of (вольфрам) and (рений) are present. These elements are very effective in solution (укрепления). (Термические барьерные покрытия) have been used for some years on (статических) parts. On (вращающихся) parts strain tolerant coatings are employed to ensure (механическую надежность). Further increases in temperature are likely to require the development of (композиты с керамической матрицей).

Unit 9. Systems: what are the challenges?

I. Read the following words paying attention to the pronunciation:

Optimization [ˌɒptɪmaɪˈzeɪʃən], safety [ˈseɪftɪ], guarantee [ɡær(ə)nˈ ː], crew [kruː], sustainable [səˈsteɪnəb(ə)l], architecture [ˈɑːkɪtektʃə], trajectory [trəˈdʒekt(ə)rɪ], hydraulic [haɪˈdrɔːlɪk], hybridization [ˌhaɪbrɪdaɪˈzeɪʃ(ə)n].

II. Read the text carefully to get accurate information.

Systems: what are the challenges?

Systems play a central role in aircraft operation, flight optimisation and air transport safety. They guarantee optimal aircraft operability on the ground and in flight, allowing the crew to perform efficient mission management using the most advanced flight management, communication and control systems, as well as a

40