CHAPTER 4. Engine turbines

A turbine is a vane assembly which converts thermal, kinetic and pressure energy into mechanical work.

There are two turbines on the engine – a compressor turbine and free turbine and they have no kinetic connection.

4.1. COMPRESSOR TURBINE

It is an axial-flow, two-stage turbine (fig. 4.1, suppl. fig. 4.2). Its purpose is to produce power which is transmitted to the compressor rotor and for the engine accessories.

The compressor turbine consists of a nozzle assembly casing 2, two nozzle assemblies 11, 12, a rotor 13 and the III support of the engine.

The casing of welded construction and it is common for the nozzle assemblies of the I and II stages. There are 14 thermocouples 4 in the casing and holders 6, 9 with a honey comb seal 7.

Nozzle assemblies are used to accelerate the gas stream and to direct it to the rotor vanes with a designed angle. The nozzle assembly of the I stage comprises an outer holder, vanes of the nozzle assembly, an inner holder and a rotor labyrinth (the honey comb seal).

The vanes of the nozzle assembly are cast, hollow (to be cooling with the secondary air). They are installed on the shaped slots in the holders.

The nozzle assembly of the II stage is all-cast and hollow. It is centered in the casing on the rectangular pins.

The rotor of the turbine takes up the force of the gas pressure, i.e. it converts thermal energy of the gas flow into the mechanical force.

It consists of a hollow shaft, two discs with vanes and 4 covering discs. These units are interconnected by means of splines and bolts. The vanes have locks of “Christmas tree” shape which are used to enlarge the heat emission area. On the tips of the vanes there are shelves with sealing labyrinths forming an annular rim which makes them vibration-proof. The sealing labyrinths are located on the shaft and over all the covering discs.

The turbine shaft is located on the turbo compressor rotor supports: in the front part it rests upon the II support through the compressor rotor, and the tail part of it rests upon the III support. The III support (see suppl. fig. 4.6) consists of the casing (jack) of the support, a ball bearing and a graphite sealing.

The support jack is connected to the inner rim of the nozzle assembly of the III support. The support is pressurized from the VII stage of the compressor. The oil is supplied through the external pipe from МА-78 oil pump.

Рис. 4.1. Турбина компрессора

1 – корпус камеры сгорания; 2 –корпус сопловых аппаратов; 3 – жаровая труба;

4 – термопара; 5,6 – обойма; 7, 17, 19, 20 – сотовое уплотнение; 8 – корпус соплового аппарата свободной турбины; 10 – лабиринт уплотнения; 11, 12 – сопловая лопатка;

13 – рабочая лопатка (ротор); 14 – внутренний обод; 15 – диафрагма; 16 – покрывающий диск; 18 – корпус лабиринта; 21 – внутренний диффузор камеры сгорания.

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