Unit II

1. Guide to Propulsion

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For aircraft, the principal of action and reaction is very important. It helps to explain the generation of lift from an airfoil. In this problem, the air is deflected downward by the action of the airfoil, and in reaction the wing is pushed upward. Similarly, for a spinning ball, the air is deflected to one side, and the ball reacts by moving in the opposite direction. A jet engine also produces thrust through action and reaction. The engine produces hot exhaust gases which flow out the back of the engine. In reaction, a thrusting force is produced in the opposite direction.

Exercise 1. Guess the meaning of the international words.

Nouns

machine, group, problem, maximum, factor, period, mass, variation, vibration, minute, gas, turbine, rocket, form, system, electricity, contact, cylinder, compress, temperature, date, propeller, pulse, idea, pressure, reaction, oxygen, atmo­sphere, vacuum, impulse, mission, product, limitation.

Adjectives

mechanical, interesting, specific, nuclear, atomic, electric, atmo­spheric, principal, aerial, modern, basic, chemical, planetary, thermal, dynamic

Verbs

to occupy, to combine, to utilize, to accelerate

Essential Vocabulary to propel propulsion source to produce device to require reliable reliability payload to permit = to allow to deal with to receive thrust specific fuel consumption to consume to burn to reduce reduction flexibility overhaul steam engine двигать движение источник производить прибор, агрегат требовать надежный надежность полезная нагрузка позволять касаться, иметь дело получать тяга удельный расход топлива потреблять, расходовать гореть уменьшать уменьшение гибкость капитальный ремонт паровой двигатель

Text: The Propulsion System

In order to propel an airplane through the air the force is required. This force must be rather intensive and is provided by the propulsion system.

Every propulsion system consists of:

- the fuel which is the energy source from which the force is produced for the required time;

- the engine which is the mechanical device by which the energy of the fuel is transformed into the propulsive force. The word "engine" originally meant any “ingenious” device, and came from the Greek word "ingenious", clever.

Any aircraft propulsion system must meet certain requirements. First is low weight; second, the system must be reliable; third, the cost of the system must be sufficiently low

The total weight of the airplane can be divided among the airframe, the propulsion system and the payload. The payload consists of the crew, equipment and cargo. The weight of the propulsion system must be so divided between fuel and engine as to permit the airplane to fly a desirable distance without landing.

It must be stated that engines present one of the most interesting groups of problems considered in the engineering field. The problems dealt with are different. One of the main problems worked at by the designers is receiving the maximum possible power or thrust for minimum weight.

Another important problem dealt with is that of fuel. Both in the past and today the designers work at the problem of getting lower specific fuel consumption. Specific fuel consumption is obtained by dividing the weight of the fuel burned per hour by the horse power developed.

Probably the reduction of fuel consumption can be solved when a nuclear reactor is used. If used as a source of power the nuclear process gives the most energy per unit of mass of any source known. It must be noted that controlled atomic energy has already produced electric power and marine propulsion power.

Another possible problem considered in any engine is its flexibility. Flexibility is the ability of the engine to run smoothly and perform properly at all speeds and through all variations of atmospheric conditions.

One more important problem worked at by the designers is the engine reliability. The engine is to have a long life, with maximum of time between overhaul periods. Overall propulsion system reliability is increased by using more than one engine. At present the preferred number of engines varies from one engine on small airplanes to eight on large military bombers. In transports the use of four engines predominates. Reliability is determined by the length of time the engine can run without major overhaul. The time varies with the use of the airplane.

It must be emphasized that in some cases the problem of balance is one of the main. Balance has several possible meanings but the principal factor is freedom from vibration.

Besides any engine must be started easily and carry its full load in a few minutes.

The necessity of carrying away excess heat developed by the engine has always been a problem of first importance too.

Nowadays there exist many types of engines used for various purposes. There are gasoline engines, diesel engines, gas turbines, steam engines, steam turbines, jet engines and rocket engines.

Each of them has certain advantages and disadvantages over other forms of power plants.

Exercise 2. Read and translate the adverbs. Name the adjectives from which the adverbs are formed.

Fully, originally, smoothly, considerably, recently, deeply, highly, heavily, principally, properly, definitely

Exercise 3. Translate the nouns formed from the verbs in the left column.

ignition heat consumption inclusion operation performance accomplishment improvement driver expression mixture rise requirement supply

to ignite - зажигать to heat - нагревать to consume - потреблять to include - включать to operate - действовать to perform - выполнять to accomplish - достигать, выполнять to improve - улучшать to drive - водить, управлять to express - выражать to mix - смешивать to rise - поднимать to require - требовать to supply - снабжать

Exercise 4. Find the Russian equivalents.

to propel source to produce device to require reliable reliability payload to receive specific fuel consumption to consume to reduce flexibility overhaul

гибкость двигать источник капитальный ремонт надежность надежный полезная нагрузка получать потреблять прибор, агрегат производить требовать удельный расход топлива уменьшать

Exercise 5 . Match the columns.

A.

to propel the airplane to consist of to transform into must meet can be divided among to receive the maximum possible power to get lower to increase the reliability by to produce

using more than one engine through the air the propulsive force the fuel and the engine specific fuel consumption for minimum weight certain requirements electrical power the airframe, the propulsion system and the payload

B.

propulsion energy propulsive engineering fuel specific nuclear atomic engine overhaul

consumption energy field force fuel consumption period process reliability source system xercise Answer the Questions:

Exercise 6. Read the text “Air propulsion” and answer the questions:

1. What does an aircraft propulsion system consists of?

2. What are the aims of propulsion system?

3. Why do cargo planes have turboprops?

4. What airplanes do require very high excess thrust and why?

5. What does thrust depend on?