RU2241844C1 - Gas-turbine engine starting method - Google Patents

Abstract

FIELD: aircraft engineering.

SUBSTANCE: invention relates to methods of starting of aircraft turbojet engines. According to proposed method of starting of gas-turbine engine including starting of its rotor by one or several external power sources for engine with cooled turbine at its starting at flight or on ground under emergency conditions, rotor is started by delivering compressed air into cooling system of engine turbine, and at starting of engine of ground under standard conditions, simultaneously with delivery of compressed air into turbine cooling system, mechanical energy is supplied to engine rotor shaft. Proposed method considerably increases efficiency of engine starting owing to optimum combination of delivery of mechanical energy and energy of compressed air delivered into cooling system.

EFFECT: improved reliability of starting at emergency, provision of engine starting under conditions when starting cannot be effected earlier.

10 cl, 1 dwg

Description

The invention relates to the field of aviation technology, in particular to methods for starting aircraft turbojet engines.

A known method of starting a gas turbine engine, which consists in the promotion of its rotor from one or more external energy sources, in particular by supplying mechanical energy from a gas turbine and powder starters to the engine rotor (1).

The main disadvantage of this method is that the energy from an external source to the rotor is supplied only in the form of mechanical energy. At the same time, at the stage of ignition of the combustion chamber and the initial operation of the turbine, due to the low pressure level in the gas-air path of the engine, air is practically not supplied to the turbine cooling system, as a result of which there is no effective cooling of the main elements of the turbine - nozzle and rotor blades. In the process of starting the engine, this imposes a limitation on the temperature of the gases in front of the turbine, which reduces the possibility of reliable and quick starting of the engine, especially in extreme conditions for starting (at high ambient temperatures, high altitude conditions, etc.).

Another disadvantage of this method is the difficulty of spinning the rotor by supplying mechanical energy to it from an external source in flight conditions in autorotation modes, due to the high probability of failure of transmission elements, for example, couplings, springs, etc.

The elimination of these shortcomings is especially relevant for modern aircraft twin-rotor engines. In this case, as a rule, the high pressure rotor is unwound. The low-pressure rotor operates in turbine mode, as a result of which pressure decreases behind its impeller. In order to provide the pressure and temperature level necessary for igniting the combustion chamber, the high-pressure rotor must be additionally tightened, and this leads to an increase in the required power of external energy sources.

The objective of the invention is to increase the reliability of starting the engine on the ground and in flight, including in emergency situations and when starting in flight in autorotation mode, as well as reducing the time the engine starts.

The problem is solved in that in a method for starting a gas turbine engine, including spinning its rotor from one or more external energy sources, for an engine with a cooled turbine, when it is started in flight or on the ground in emergency conditions, the spinning of the rotor is carried out by supplying compressed air to the cooling system engine turbines, and when starting the engine on the ground under normal conditions simultaneously with the supply of compressed air to the cooling system of the engine turbine, mechanical energy is supplied to the engine rotor la.

In addition, an auxiliary power plant can be used as a source of mechanical energy, and either an auxiliary power plant, or a working engine of a nearby aircraft, or a ground-based power plant can be used as a source of compressed air. For a multi-engine aircraft, one of the working engines can be used as a source of compressed air.

For two-rotor gas turbine engines, mechanical energy can be supplied to the high-pressure rotor, and compressed air can be supplied either to the high-pressure turbine cooling system, or simultaneously to the high-pressure turbine cooling system and to the low-pressure turbine cooling system, or only to the low-pressure turbine cooling system .

When starting the engine in flight, simultaneously with the supply of compressed air to the cooling system of the engine turbine from an external energy source, it is possible to supply mechanical energy to the engine rotor.

The simultaneous supply of mechanical energy to the rotor and the supply of compressed air to the cooling system of the engine turbine can increase the reliability of start-up and reduce its time. The transfer of mechanical energy to the rotor allows you to intensively unwind the rotor at the initial stage of startup, and the main energy flow is spent on overcoming the moment of inertia of the rotor. The supply of compressed air to the turbine cooling system allows you to additionally tighten the rotor and reliably cool the turbine at the moment of ignition of the combustion chamber and supply energy to the rotor due to the operation of the turbine itself. With increasing rotor speed, the share of power from the supply of mechanical energy decreases, and the share of power from the supply of compressed air to the turbine cooling system increases.

The supply of mechanical energy and the energy of compressed air can be carried out both from one and from various external sources of energy. At the same time, the supply of mechanical energy and energy from compressed air from one external energy source reduces weight and simplifies the start-up system, and when supplied from various energy sources, the reliability of start-up under abnormal conditions increases.

When the engine is started in flight in autorotation modes, by supplying air to the turbine cooling system, an additional “soft” (without using overrunning clutches, etc.) twist the rotor to revolutions at which it is reliably started.

When starting the engine on the ground under abnormal conditions, for example, when it is impossible to bring mechanical energy to the rotor, the rotor is unwound only by supplying compressed air energy from an external source. Despite the increased start time, the engine will start.

Using an auxiliary power unit (hereinafter - APU) as a mechanical energy source allows you to place an external source directly in the engine area. The use of APU as a source of both mechanical energy and compressed air energy allows you to have an autonomous power source directly on the aircraft. In addition, the use of APU as a source of compressed air allows to reduce the weight and dimensions of air pipelines from the APU to the turbine cooling system.

Using as a source of compressed air a working engine of a nearby aircraft or a ground-based power plant or for a multi-engine installation of one of the working engines, expands the possibilities for starting the engine. At the same time, the selection of compressed air from several energy sources, for example, one of the above in combination with the APU, increases the starting efficiency and reliability of its system.

For two-rotor gas turbine engines, the simultaneous supply of mechanical energy and compressed air energy to the high-pressure rotor provides a more intensive promotion of the high-pressure rotor, which has a lower moment of inertia and a more developed turbine cooling system in comparison with the low-pressure rotor.

The supply of compressed air to the cooling system of the low pressure turbine allows additional twisting of the low pressure rotor, as a result of which the “turbine” effect on the low pressure compressor is reduced or completely removed.

In twin-rotor gas turbine engines, for example, if a low-pressure compressor has a small bypass ratio and a small compression ratio, it is more advisable to supply mechanical energy to the high-pressure rotor, and energy from compressed air to the low-pressure rotor.

If the engine has a coupling capable of connecting a source of mechanical energy, for example, APU, to a rotating rotor, in autorotation modes, both compressed air and mechanical energy can be simultaneously supplied to the rotor.

The proposed method is illustrated in the drawing, which shows a diagram of one of the options for starting the engine.

The engine starting system includes an APU 1 mechanically connected by means of gear 2 to a high-pressure rotor 3 of the engine. The APU 1 is connected by a pipeline 4 to the entrance to the nozzle vanes 5 of the high pressure turbine 6, and by a pipeline 7 to the nozzle vanes 8 of the low pressure turbine 9.

The method is as follows.

When starting the engine on the ground, under normal conditions for starting, the torque from the operating APU 1 is transmitted through a mechanical transmission 2 to the high pressure rotor 3. At the same time, compressed air is supplied through the pipe 4 from the same APU 1 to the cooling system of the high pressure turbine 6. Having entered the nozzle blades 5 and passing through their internal path, air flows from the slots of the outlet edges of the blades 5 and enters the working blades of the high pressure turbine 6, creating a torque on its impeller. Thus, the rotor 3 is transferred additional energy, increasing the efficiency of its promotion.

In some cases, compressed air from the APU 1 can also twist the rotor of the low pressure turbine 9, coming through the pipeline 7 through the internal path and the slots of the outlet edges of the nozzle blades 8 to the working blades of the low pressure turbine 9.

In emergency situations (extreme conditions for starting, emergency situations, etc.) and for starting the engine in flight in autorotation mode, the rotor is twisted by supplying compressed air to the working blades of the high pressure turbine 6 from the APU 1 or any other source of compressed air. To increase the starting efficiency, compressed air can be supplied simultaneously from several sources.

The proposed method can significantly increase the starting efficiency due to the optimal combination of the supply of mechanical energy and the supply of energy from compressed air to the cooling system, to increase the reliability of starting in emergency situations, as well as to ensure that the engine is started in conditions at which it was previously impossible to start.

(56) Patent RU No. 2196240 C1, F 02 C 7/26, publ. 2003, bull. No. 1.

Claims (10)

1. The method of starting a gas turbine engine, including the promotion of its rotor from one or more external energy sources, characterized in that for an engine with a cooled turbine when starting the engine in flight or on the ground in emergency conditions, the rotation of the rotor is carried out by supplying compressed air to the turbine cooling system engine, and when it starts on the ground under normal conditions, simultaneously with the supply of compressed air to the cooling system of the engine turbine, mechanical energy is supplied to the engine rotor. 2. The method according to claim 1, characterized in that an auxiliary power unit is used as a source of mechanical energy. 3. The method according to any one of claims 1 and 2, characterized in that an auxiliary power unit is used as a source of compressed air. 4. The method according to any one of claims 1 and 2, characterized in that a working engine of a nearby aircraft is used as a source of compressed air. 5. The method according to any one of claims 1 and 2, characterized in that a surface power plant is used as a source of compressed air. 6. The method according to any one of claims 1 and 2, characterized in that for a multi-engine aircraft, one of the working engines is used as a source of compressed air. 7. The method according to any one of claims 1 and 2, characterized in that for two-rotor gas turbine engines, mechanical energy is supplied to the high-pressure rotor, and compressed air is supplied to the cooling system of the high-pressure turbine. 8. The method according to any one of claims 1, 2, 7, characterized in that the compressed air is also supplied to the cooling system of the low pressure turbine. 9. The method according to any one of claims 1 and 2, characterized in that for two-rotor gas turbine engines, mechanical energy is supplied to the high-pressure rotor, and compressed air is supplied to the cooling system of the low-pressure turbine. 10. The method according to any one of claims 1 and 2, characterized in that when starting the engine in flight simultaneously with the supply of compressed air to the cooling system of the engine turbine from an external energy source, mechanical energy is supplied to the engine rotor.