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Exercise 2. Read and translate the following word – combinations.
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A.
- air-breathing engine, type of an air-breathing engine, the simplest type of air-breathing engines;
- wide application, wide application in aviation, wide application in military aviation;
- fuel consumption, high fuel consumption, low fuel consumption, turbojets’ high fuel consumption;
- rocket engine, liquid-propellant rocket engine, modern liquid-propellant rocket engine, solid-propellant rocket engine.
- complete supply, fuel supply system, oil supply system, rocket propulsion system;
- gas turbine engine, pilotless military weapons, fuel - air mixture, auxiliary power plant, conventional power plant;
- high speed military aircraft, low speed military aircraft, large multi-engine
aircraft, high pressure gases.
B.
- flight time, wing design, engine characteristics, helicopter engine, pressure rise, cooling system;
- aircraft wing load, shaft rotation speed, ballistic rocket trajectory, aircraft steam engine, better engine performances, gas turbine installation, turbine inlet temperature;
- solar ultra-violet radiation, high temperature and high-pressure gases, a nine-pressure compressor, high thrust-to-weight ratio, improved supersonic specific fuel consumption.
Text: Aircraft Engines
One of the most essential parts of any airplane is its power plant. The heart of the power plant is the engine. There must also be fuel supply and oil supply system, engine control system, cooling and starting systems.
Types of engines, their number and location on the airplane depend on the airplane performances, namely, its speed, altitude, range, load-carrying capacity and so on. Engines may be mounted on the wings, on the fuselage (forward or aft) or under the wings on pylons.
There are many types of aircraft engines in use: piston engines for low-speed aircraft and some types of jet engines.
Jet engines fall into two main classes: air-breathing engines and rocket engines. The engines of the first class utilize air from the atmosphere together with the combustion of fuel to produce the jet for propulsive purposes. Pay attention that the jet engine is not a modern development.
When used a jet engine produces high pressure, high temperature gas, which is ejected rearwards with great force named thrust. The thrust is the reaction of the flow or the jet of hot gases ejected from the rear. The jet is produced by the combustion of the fuel in the compressed air which is supplied by the atmospheric air that enters through the front opening.
For getting the required air into the combustion chamber a compressor is mounted in the front opening. The air is sucked in the compressor and then is used to burn the fuel.
Although a rocket engine is a jet engine it differs from other jet propulsion systems considered in that it does not use atmospheric air as the propulsive fluid stream. It carries the complete supply of working fluid or propellants (oxidizer and fuel) and can operate outside the earth’s atmosphere. Therefore when used in the vacuum the rocket engine can produce its thrust and so provides a possible means of propulsion for interplanetary vehicles. The rocket engine is suitable for operation over short periods.
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There are two basic types of rocket engines: liquid-propellant and solid-propellant rocket engines. Rockets find extensive use. They are used as boosters for missiles and research rockets, and as main power plants of guided missiles. A rocket propulsion system may also be used as a primary or an auxiliary power plant of an airplane.
The simplest type of air-breathing engines is the ramjet engine. It has no major rotating parts. The main components of the ramjet are: the diffuser, the combustion chamber and the jet nozzle. A ramjet is often the power plant for missiles and target vehicles. The ramjet can operate at high flight speeds and altitudes but is unsuitable as an aircraft power plant because it requires forward motion imparting to it before any thrust is produced, that is, it must be boosted to a high speed before the initial starting of the engine. Up to now the ramjet has not yet found wide application in aviation.
The pulsejet is more complicated than the ramjet; however, its flight velocity is considerably lower. The pulsejet is unsuitable as an aircraft power plant because it has high fuel consumption and is unable to equal the performance of the modern gas turbine engines. Possible application of the pulsejet is to propel pilotless military weapons. The main limitation of the pulsejet is the following one: it produces great noise during its operation.
Turbojet, turboprop and turbofan belong to the family of gas-turbine engines. Any type of the gas-turbine engines comprises the inlet assembly (diffuser), the compressor, the combustion chamber, the gas turbine and exhaust nozzle.
In a turbojet engine the diffuser takes the air and delivers it to the compressor. The mechanical compressor further compresses the air and delivers it to the combustion chamber, where the fuel-air mixture burns. The high temperature and high pressure gases enter the turbine. The turbine is connected with the compressor. The main function of the turbine is to provide power for the compressor. Then the combustion products expand in the exhaust nozzle and are ejected with high velocity producing thrust.
The turbojets are classified into 2 groups according to the kind of compressors which they use, that is, centrifugal and axial compressors. The majority of modern turbojets are equipped with axial compressors. At present the turbojet engine has become a conventional power plant for nearly all high-speed military aircraft.
The turboprop engine is very similar to the turbojet. The difference is that it uses propeller to provide most of its thrust. It is heavier than a turbojet of equivalent size and power. However, its fuel consumption is lower in comparison with a turbojet. A variation of the turboprop engine is known as the turboshaft engine. It is often used for powering helicopters.
The turbofan engine combines the features of both the turbojet and turboprop engines. In the turbofan the propeller is replaced by an axial-flow fan. The turbofan is lighter than a turboprop; it has relatively low fuel consumption. The turbofan as well as the turboprop produces more thrust than the turbojet during take-off. Turbofans are widely used in aviation, especially in large multi-engine aircraft.
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