Turbojet engine

General characteristic of the engine design

Small-sized turbojet engine for the aircraft model with a thrust of 15 kgf, air flow rate at the inlet of 0.34 kg/s. Structurally, the engine consists of an inlet fairing, a centrifugal compressor with a pressure increase of 3.25, an annular combustion chamber with a rotating nozzle, a single-stage centripetal turbine and a jet nozzle. On the front of the shaft there is an electric brushless high-speed starter-generator on permanent magnets. The rotor rests on two gas bearings: thrust and radial. Bearings are located between compressor and turbine and in front of compressor. The bearings are cooled by air.

II.Construction of units

Input part

The fairing and the inlet part of the engine are made of composite material - fiberglass by injection molding. Radial inlet part design includes inner and outer shells connected by shaped aerodynamic struts. At the rear end of the outer shell there is a flange for attachment to the compressor housing, at the front end there is a flange for attachment of the air intake device (not shown), and a flange for the starter. Attachment of inlet fairing is performed by means of bolts and self-locking nuts.

Compressor

The compressor rotor is a centrifugal wheel, which is carried out by powder technology. The centrifugal wheel sits on the shaft, and the torque is transmitted by means of a pin connection between them. In the stator above the compressor impeller there is an annular element made of aluminum coated with ALK500 material to minimize damage to the impeller when it hits the housing. Compressor diffuser blades are cast together with rotary channel. The rotary channel itself is made of sheet material. All compressor parts are made of aluminium.

Combustion chamber

The combustion chamber consists of three parts: the inner and outer walls of the flame tube and the fuel sprayer (rotating fuel nozzle). The outer wall is welded to the outer casing of the turbine nozzle apparatus and is attached to the housing by means of an elastic cone with a flange. Spark plugs are installed in two holes in outer wall. Inner wall of flame tube is welded to turbine nozzle unit. Flame tube elements are made of EP648 material and combustion chamber casing is made of titanium. Rotary fuel nozzle made of EI961 material is made in shaft. Torque from the impeller is transmitted by means of a pin connection. On the shaft in the zone of the rotating nozzle there are labyrinth seals, above which ring inserts with sprayed ALK500 material are made in the stator.

Turbine

Centripetal turbine consists of nozzle apparatus cast from VX4L material and impeller made from HLP12 alloy, disk and blades of which are made as a whole. The nozzle unit is welded to the flame tube, and it is attached to the combustion chamber casing by means of an elastic cone. Torque from turbine is transmitted to shaft through pin joint. The shaft is hollow inside, made of pipe made of material EI961. The turbine uses ceramic seals (silicon carbide).

Jet nozzle

The jet nozzle is a separate annular element and can easily be replaced during delivery tests to provide a given amount of thrust.

Fuel system

Fuel is supplied through a pipeline through the front of the shaft. It enters the hollow shaft, under a pressure of 3 atm. The fuel reaches the plug. Plugs are attached to shaft by means of pin joint. Then, under the influence of centrifugal force, fuel is supplied to the rotating nozzle. In order that fuel does not go into the rear part of the shaft, a plug is installed inside it, and a bead is made in the front part on the shaft wall.

Start

On the front of the shaft there is an electric brushless high-speed starter-generator on permanent magnets. Material of magnets neodium + iron + boron (NeFeBr). With its right part, it rests on the collar of the shaft, and on the left it is pressed by a self-locking nut screwed onto the shaft. The starter generator serves both to start the engine and to generate electric current to power the engine units. For example, the generator generates current for an electric motor that drives a fuel pump and aircraft units.

Analytical study of completed structures

In this course project, I used materials to study the design of the following engines: Microturbo TR6020, NPT 171 ENGINE DESCRIPTION, NPT 754 TURBOFAN, NPT 051 ENGINE DESCRIPTION, NPT 100, NPT et 301 TurboJ.

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