1. From the history of aeroengines development. Classification of air gas turbine engines

Since the middle of the ХIХ-th century the attempts to create aircraft without engines had been made in many countries. At the end of the XIХ-th century (1881) A.F. Mozhaysky got the patent and constructed an airplane with steam engines. In 1894 an Englishman Х. Maxim created a giant airplane. In France the inventor К. Ader designed and created airplanes. Nevertheless, the steam engines turned out to be heavy and unwieldy, and attempts to fly with such engines sailed. The first successful flight was made on the 17 th of December, 1903 on an airplane with an internal-combustion engine by the Wright brothers in the USA. At about the same time airplanes having similar engines are created one after another in Europe, mainly in France (L. Blerio, F. Ferber and A. Santos-Dumon).

A considerable stimulus for development of aircraft and engine building, in particular, was given by the World War I. Nevertheless, there was no domestic airmotor industry either in Russia, or in Ukraine at that time. And only in 1921 the aircraft designer A.D. Shvetsov created in the USSR an air-cooled engine M-11 with the power of 100 hp, which had been in serial production since 1924. It was mounted on airplanes По-2 (У-2) and Як‑18, which had served in aviation for more than forty years. In 1950s in an experimental-design office of the General designer A.G. Ivchenko (now Zaporozhye motor-building design office – ЗМКБ) the piston air-cooled aeroengine AИ-14 with the power of 360 hp was created, which became the basis for the whole family of engines for light airplanes and helicopters.

Nevertheless in 1920s and 1930s there exists a new direction in development of aeroengines. The projects of the first jet engines appear.

The jet engines of aircraft are subdivided into air-breathing and rocket engines.

In air-breathing engines (ABEs) an atmospheric air is used for jet formation. In rocket engines the gases are used for this purpose. They are yields of a chemical reaction of a propellant.

The air-breathing engines are subdivided into three main types:

- ram jet air-breathing engines (RABEs);

- pulsatory (pulse) air-breathing engines (PABEs);

- gas turbine engines (GTEs).

Dependence of working process parameters on atmospheric parameters (temperature of surroundings, altitude and flight speed) is typical of all these engines.

The classification of rocket engines is grounded on physical properties of fuel before they enter a chemical reaction inside the engine. From this point of view the rocket engines are subdivided into two main types:

- liquid-rocket engines (LREs), in which propellant components are liquid before entering the combustion chamber;

- rocket engines of solid fuel (REsSF), in which propellant components are solid before the beginning of a chemical reaction.

The working process parameters and rocket engines characteristics depend little on flight conditions of an aircraft.

To use technical advantages of engines of different types in a unified power plant, and therefore, to improve the characteristics of aircraft, sometimes combined power plants are applied. They include air-breathing and rocket engines or hybrid engines, which use manifold principles of working process formation, for example, turbo/ram jet, rocket/ram jet, turbo-rocket engines, etc.

Each type of engine has a particular area of possible and optimal application.

In the manned aircraft power plants of military and civil aviation the most widespread types of gas turbine engines are:

- turbojet engines (TJEs);

- turbofan engines (TFEs);

- turboprop engines (TPEs);

- turboshaft engines with free turbine (free-power turbine) (TSEsF);

- turbopropfan engines (TPFEs).

In turbojet engines practically all excessive potential energy of a gas flow, coming out of a turbine, transforms into kinetic energy as gas expands in a jet nozzle. It provides the acceleration of a gas flow up to a high speed and creation of thrust. The afterburner (AB) is applied if it is necessary to supply a short-lived increase in engine thrust without a considerable increase of overall dimensions and weight of a power plant. It is set between turbine and jet nozzle. The overload fuel moves to AB at a reheat starting. After it is burnt the temperature of gases rises, and therefore, the speed of gas efflux from a jet nozzle and an engine thrust increase. Such type of afterburning is used in some turbojet and turbofan engines, which in this case are called afterburning turbojet engines (ATJEs) and afterburning turbofan engines (ATFEs).

Modern TJEs without afterburning provide reaching of flight speeds corresponding to Mach number (М) not larger than 1,3...1,4 at altitudes up to 12...14 km. The augmented engines ATJE allow to develop airplane flight speeds corresponding to М numbers 3...3,5 at altitudes up to 30...35 km. The afterburning turbojet engines of considerable and mean thrusts are set in fighters and bombers, while low-powered TJEs and ATJEs are used on training airplanes. Besides, in 1950s TJEs have been set in the first jet passenger airplanes: Tу-104 (USSR), Boeing-707 (USA), "Comet" (England), "Caravelle" (France). Later the TJEs were not used in civil aviation airplanes owing to their low fuel profitability.

The turbofan engines have two flows – primary and secondary. In such engines a part of fuel combustion energy, submitted to the primary flow is transformed into mechanical energy for the fan drive of the secondary flow.

The TFE primary flow is an air-gas channel that houses working devices of compressor, combustion chamber, turbine and jet nozzle, i. e. this flow is the turbojet engine air-gas channel of a common scheme.

The TFE secondary flow is an annulus channel with a fan in it. Only air passes through the secondary flow. It receives an impulse of motion from the fan. This air passes outside the combustion chamber and the turbine. It is exhausted from the engine in parallel to gases flow, that comes out of the turbine.

The TFE thrust consists of gas flow reaction forces in the primary flow and air flow in the secondary flow.

The TFEs are more effective than single-flow TJEs as far as subsonic flight speeds are concerned, and they have lower noise level. The high profitability is provided with a high bypass ratio, which is characterized by relation of the mass air flow in the secondary flow to the mass air flow in the primary flow.

The TFE bypass ratio (m) varies from 0,7 to 10.

The TFEs with highly thrust effectiveness and low specific fuel consumption are the main type of engines of long-haul passenger airplanes, that fly with speeds corresponding to Mach number M=0,75...0,9.

In turboprop engines (TPEs) thrust is formed by air masses. They are accelerated by a propeller, that rotates with the help of a gas turbine. The TPEs are applied in power plants of passenger and transport airplanes with flight speeds corresponding to M=0,4...0,7. Within this air speed range the TPE efficiency is higher than in engines of other types. Therefore the airplanes with TPEs are more effective than the airplanes with TJEs and TFEs.

The most popular power plants of modern helicopters include the turboshaft engine with free-power turbine. The free-power turbine, which is not mechanically connected with the compressor turbine in engines of such type, provides the drive of lifting and antitorque propellers of the helicopter through reduction gear (main and tail) and other transmission devices. Having high power at small overall dimensions and weight, turboshaft engines with a free-power turbine have allowed to create helicopters with weight-lifting capacity of some dozens of tons. Such are giant helicopters created in М.L. Mil design bureau: Ми‑6, Ми‑10, Ми‑12, Ми‑26.

The perspective type of engines for a new generation of passenger airplanes is a turbopropfan engine (TPFE). By its specifications TPFE takes an intermediate position between TPE and TFE. Having multiblade propfans as a mover (“thrust provider”), engines of such type are highly efficient. Modern techniques of propfan contouring and manufacturing permit to use them at flight speeds, which correspond to Mach number M=0,7...0,8. This provides a high economic efficiency of passenger traffic at short stage and average stage distances. A "Super-fan" class engine is one of the TPFE varieties. They have ducted fans. They work in a case like TFE fans. The "Super-fan" engines provide airplane cruising speeds of flight corresponding to Mach number M=0,75...0,82 with fuel consumption 15...20 % less than airplanes with TFE have. The engines of such class are intended for long-distance passenger and transport airplanes.

The modern scheme of the turbojet engine was offered by a French researcher Gillome in 1922. For the first time turbojet engine was practically used by the inventor Frank Whittle, who received the patent on the 11th of January, 1930. Frank Whittle constructed the first turbojet engine in 1937, and the first flight with this engine was made in England on an airplane "Gloster" in May 1941.

In Germany turbojet engines have been developed since 1930s, and on the 27th of August, 1939 German pilots made first flight on an airplane with a turbojet engine.

In the USSR first design developments of air-breathing engines were proposed by V.I. Bazarov (TPE with a centrifugal compressor, 1923) and A.M. Lyulka (TFE with an axial-flow compressor, 1937). Since 1932 V.V. Uvarov had been working on TPE creation. In 1946 the first TJE (TP-1) constructed by A.M Lyulka was tested.

The experience of the first foreign engines development was used in the USSR along with designing of new domestic engines. Production of the РД-10 and РД‑20 engines with axial-flow compressors after the pattern of German UMO-004 and BMW‑003 engines was set going. During 1947...1949, the aircraft industry of the USSR mastered production of РД-45 and РД-500 turbojet engines on the basis of the licensed English “Nene 1” and “Derwent 5” turbojet engines, respectively. These engines allowed to create and to begin operation of the first Soviet jet airplanes: Як‑15, МиГ‑9, МиГ‑15, Як‑23, Ил‑28, Ла‑15, etc.

The main specifications for gas turbine engines, serial production of which began before 1950, are given in Tab. 1.1.

After this, creation of more perfect engines started in the USSR. Soviet designers and scientists V.Y. Klimov, A.A. Mikulin, S.K. Tumansky, A.M. Lyulka, M.D. Kuznetsov, V.A. Dobrynin, A.G. Ivchenko, P.A. Solovyov, S.P. Izotov, V.A. Lotarev, V.A. Glushenkov contributed a lot to new engines development.

As a result, a lot of gas turbine engines had been created and put in a serial production by the beginning of 1950s in the USSR.

So, the ВК-1 (1949) and the ВК-1Ф (1951) engines with centrifugal compressors have been successfully used for a long time (Ил-20 mail-carrying airplane and МиГ-17 front fighter).

AM-3 engine, which had been in serial production since 1949, had thrust of 85,2 kN. At that time it was the most powerful TJE with an axial-flow compressor in the world. It was set in Tу-16 long-distance bombers and in the first passenger airplanes Ту‑104 (1956), which initiated jet aviation for passenger traffic. The modified version of this engine РД3М‑500 with thrust of 93,1 kN has been still used in airplanes Tу‑16. Two ATJEs РД­-9Б with afterburning rating thrust of 32,2 kN were set in the first serial supersonic fighter МиГ‑19 (1954).

While creating new, more powerful and efficient engines the necessity to increase the compressor pressure ratio arose. Nevertheless, the use of high-head axial-flow compressors in TJE design created difficulties for provision of a necessary reserve of compressor gas-dynamic stability (surge reserve of compressor). The search for optimum solutions of this problem caused creation of two-shaft engines. In the second half of 1950s Р11Ф-300 two-shaft ATJE with maximum non-augmented rating thrust of 39 kN for МиГ-21 supersonic fighters and Як‑28 was created and put in serial production. It became the basis model for designing high-performance, reliable and efficient engines.