Method for boosting a turbofan engine

Abstract

The invention relates to turbofan engines. A method for boosting a turbofan engine consists in increasing the volume of air fed by a fan of the engine into both the core and the bypass duct by briefly activating a brushless electric starter, thereby increasing the rotor speed of the turbofan engine by 5-10% for 10-30 seconds, with a simultaneous proportional increase in the amount of fuel fed into the combustion chamber of the engine. The method makes it possible to briefly increase thrust performance during the takeoff of an aircraft or during an aerial manoeuvre, without increasing the specific weight of the turbofan engine.

Description

[0001] Method of forcing a turbojet twin-circuit engine

[0002] The invention relates to afterburning systems for gas turbine twin-circuit engines.

[0003] Various methods of boosting gas turbine engines based on water injection into the flow path are widely known (patents RU 2284418 Cl, RU 2005109449 A, RU 2523510 C1). The methods consist of organizing water injection systems into the combustion chamber, compressor, before the compressor. In some variants of the solution, flammable liquid is added to the water.

[0004] The obvious disadvantage of these solutions is the need to carry on board the aircraft a supply of liquid to ensure the engine operates in afterburner mode and a system for supplying this liquid to the working tract of the gas turbine engine.

[0005] A method for feeding gas into the combustion chamber of a gas turbine engine is known (patent RU 2562822 C2). A gas generator is installed outside the housing, with oxidizer and fuel pipelines connected to the input, and a gas duct connected to the air duct of the main engine to the output.

[0006] The disadvantage of the given solution is that it is only suitable for use at high flight altitudes and the comparative complexity of its technical implementation.

[0007] A method of gas turbine engine afterburning is known (patent RU 2523510 C1) and is considered the closest analogue by a number of features. The method consists of feeding the combustion chamber or compressor with the amount of fuel necessary for its complete combustion. Additional fuel is also fed into the combustion chamber in the amount necessary to reduce the temperature of the gases in the combustion chamber to a safe limit (atmospheric afterburning). When the engine afterburning is turned on, an igniter of any type is simultaneously turned on at the outlet of the turbine into the atmosphere.

[0008] The disadvantage of this method is that combustion products during afterburning contain a large amount of toxic gases such as carbon monoxide, nitrogen oxides, unburned hydrocarbons and soot. The second disadvantage is a significant, up to several times, increase in the volume of fuel burned.

[0009] The objective of this invention is to develop a method for short-term increase in the power of a gas-turbine dual-circuit engine for up to 30 seconds without deterioration of the specific power of the engine and without the need to make significant changes to the engine design. The stated objective is achieved by equipping the gas-turbine engine with a starter of increased power compared to that required to start the engine by 40% - 60% with maximum operating speeds, allowing to increase the operating speed of the gas-turbine engine by 10%.This technical capability is provided by using a brushless DC motor with a rotor on high-energy magnets as a starter, complete with a starter speed controller based on low-resistance power field-effect transistors of the MOSFET or HEXFET type. At the same time, when the starter is briefly switched on for no more than 30 seconds, no additional measures for its cooling are required, and increasing the power of the brushless motor with such a formulation of the problem does not require a significant increase in its dimensions and weight, by no more than 30%. The weight of the starter based on a brushless motor does not exceed 2% of the weight of the gas-turbine dual-circuit engine structure.An increase in rotor speed leads to an increase in the amount of air supplied to the combustion chamber, the volume of fuel supplied to the combustion chamber increases proportionally due to an increase in the pressure drop on the fuel injectors, which results in an increase in the volume of combustion products. Excess volumes of combustion products supplied to the nozzle block of the inner circuit and an increased air flow through the nozzle of the outer circuit leads to an increase in the thrust of a dual-circuit gas turbine engine. An increase in the thermal power of the engine in the afterburner mode will lead to an increase in the temperature in the combustion chamber, in the turbine block and in the nozzle block of the inner circuit, this limits the engine operating time in the afterburner mode, approximately the afterburner duration is determined for a low-power gas turbine engine, a typical section of which is shown in Fig. 1, for this design the afterburner time should not exceed 0 sec.

[0010] The invention is explained by a drawing. Fig. 1 shows an axial section of a low-power dual-circuit gas-turbine engine equipped with a starter based on a brushless DC electric motor. The starter pos. 1 is connected to the rotor using a gearless scheme. The starter is located under the cowl pos. 2 of the fan pos. 3, which pumps air into both circuits. The outer circuit is marked pos. 5, the inner circuit pos. 4. Multistage axial compressor - pos. 6. Fuel manifold with injectors - pos. 7. Annular combustion chamber pos. 8. Nozzle block of the outer circuit pos. 9. Nozzle block of the inner circuit pos. 10. Turbine block - pos. 11.

[0011] The technical solution of the invention allows for a short-term, approximately for up to 30 seconds, increase in thrust of a gas-turbine dual-circuit engine up to 10% of the maximum working thrust, while the design of the engine as a whole is not complicated and the specific gravity of the engine changes insignificantly.

Claims

4 Invention formula A method for boosting a turbojet two-circuit engine, which consists of increasing the volume of air supplied by a fan to both circuits by briefly switching on an electric starter, using a brushless electric motor as a starter, thereby increasing the engine rotor speed by 5-10% over 10-30 seconds of operation of the turbojet engine with a simultaneous proportional increase in the amount of fuel supplied to the combustion chamber of the engine.

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