Compressed air ground starting system of small turbojet engine

Abstract

The utility model discloses a compressed air ground starting system of a small turbojet engine. The compressed air ground starting system comprises a high-pressure air supply unit arranged on a ground foundation; one end of the valve assembly is connected with the output end of the high-pressure gas supply unit; one end of the high-pressure electromagnetic valve is connected with the other end of the valve assembly; one end of the connecting pipe is connected with the other end of the high-pressure electromagnetic valve; one end of the air injection connector is detachably connected with the connecting pipe, the air injection connector penetrates through an air inlet channel of the small turbojet engine and is fixed to the air inlet channel, and the other end of the air injection connector is opposite to the air compressor blades. According to the utility model, the small turbojet engine can be simply started and is environment-friendly.

Description

Technical Field

[0001] The utility model relates to the technical field of small turbojet engines, and particularly relates to a compressed air ground starting system for a small turbojet engine. Background Art

[0002] When an aeroengine is designed, there is a working speed. The compressors and turbines of the engine are optimized for the working speed to obtain the optimal efficiency. Therefore, the starting process of the engine is to increase the rotor speed of the engine from zero to the working speed.

[0003] For aeroengines with relatively small power, such as the turboshaft engines used in general medium and small helicopters, and small and medium-sized turbojet engines, a basic starting system can be formed by adding a starting motor or a starting generator to the starting power supply.

[0004] For aeroengines with relatively larger power, such as turbofan engines, large and medium-sized turbojet engines, and some high-power turboprop and turboshaft engines, the starting process requires relatively large power and a relatively long rotation time. The direct use of a power supply and a starting motor can no longer meet the starting requirements, mainly due to factors such as the power consumption and weight of the motor. In this case, the starting method of the engine is generally to first start a small gas turbine by means of an electric motor, and then use this small gas turbine to start the large engine. This small gas turbine is generally called an auxiliary power unit (hereinafter referred to as APU).

[0005] There are currently three main methods to start a large engine through an APU. The main difference lies in the way the output of the APU is connected to the main engine. The first method is to generate electricity through the APU, and then use the APU as the power supply of the starting motor to drive the starting motor of the main engine to complete the starting and rotation. The second method is to draw a part of the air from the compressor of the APU through a mechanism or set up a separate load compressor for air extraction. The extracted air drives an air turbine starter through a pipeline. In the air turbine starter, the air flow drives the turbine to rotate and drives the rotor of the main engine to rotate, thereby completing the starting of the main engine. The third method is more direct. The power output shaft of the APU is directly connected to the rotor of the main engine through a speed reducer, and during starting, it is directly rotated by the shaft to the starting speed threshold of the main engine.

[0006] There are also some relatively rare starting methods, such as the starting method using a hydraulic motor, and for some engines used in cruise missiles, without considering multiple starts or in-air starts, a gunpowder starting method is generally used, where gunpowder combustion is used to directly push the turbine to start.

[0007] For some occasions with special starting requirements, especially when the engine of a single-engine fighter stops in the air, it is necessary to complete the starting work in a short time. An emergency power unit (EPU) can be used to complete the starting work. The EPU can provide sufficient compressed gas for the air turbine starter of the main engine in a short time.

[0008] In addition, for an engine in flight, the windmill starting method can also be adopted, using the ram air brought during flight to start the engine.

[0009] To sum up, there are mainly three mainstream ways to start a turbojet engine at present. One is to directly drive it with a starting motor, that is, the electric starting method. Another is to start it by using an air turbine starter, that is, the air starting method. The third is to directly drive it with shaft power through a reduction system. Each of the three has its own characteristics. When using the electric starting method, the structure is relatively simple, the position distribution of the power supply and the main engine is relatively flexible, and the mechanism of the entire starting part is relatively simple and compact. However, limited by the current technical level of the starting motor, a large amount of heat will be generated during the operation of the starting motor. Therefore, generally, the electric starting method has limitations for continuous starting. For the air starting method, there is no problem of motor heat dissipation. However, due to the layout and sealing of the air pipeline, the entire starting mechanism is much more complex than the electric starting method, and there are also limitations on the lubrication of the air turbine starter. When the shaft power is output, it is limited by the transmission system, and the distance between the APU and the main engine cannot be too long, otherwise the transmission efficiency is low. The first two methods are relatively common in the transport aircraft engine industry, and the third is more commonly used in fighter jets. The engine layout of fighter jets is very compact, which is convenient for direct drive.

[0010] For small turbojet engines, it is feasible to adopt the above starting methods, but it is necessary to select and apply them according to the characteristics of small turbojet engines. Compared with traditional aero-engines, small turbojet engines generally have relatively small volume and weight, and relatively high power density. There are strict requirements for the weight and volume of accessories outside the engine body. Therefore, it is imperative to select a starting system that suits the characteristics of small turbojet engines, is lightweight and feasible. Utility Model Content

[0011] The utility model provides a ground starting system for compressed air of a small turbojet engine, which can make the starting of the small turbojet engine simple and environmentally friendly.

[0012] The ground starting system for compressed air of a small turbojet engine includes:

[0013] A high-pressure air supply unit arranged on the ground foundation;

[0014] A valve assembly, one end of which is connected to the output end of the high-pressure air supply unit;

[0015] A high-pressure solenoid valve, one end of which is connected to the other end of the valve assembly;

[0016] A connecting pipe, one end of which is connected to the other end of the high-pressure solenoid valve;

[0017] An air injection joint, one end of which is detachably connected to the connecting pipe, the air injection joint passes through the air inlet duct of the small turbojet engine and is fixed to the air inlet duct, and the other end of the air injection joint faces the compressor blades.

[0018] Further, the valve assembly includes:

[0019] A shut-off valve for opening or closing the high-pressure gas output by the high-pressure gas supply unit, the shut-off valve is connected to the high-pressure gas supply unit;

[0020] A pressure reducing valve for reducing the pressure of the high-pressure gas output by the high-pressure gas supply unit, the input end of the pressure reducing valve is connected to the output end of the shut-off valve;

[0021] A pressure relief valve for releasing the pressure of the high-pressure gas to keep the air pressure constant, the pressure relief valve is connected to the output end of the pressure reducing valve.

[0022] Further, a check valve is provided in the air injection joint, and the check valve has a first position that makes the air injection joint in an open state after the high-pressure gas is turned on, and a second position that makes the air injection joint in a closed state after the high-pressure gas is cut off.

[0023] Further, a through hole is provided at a position corresponding to the compressor in the air inlet duct, the axis of the through hole forms an angle with the axis of the compressor, and the air injection joint passes through the through hole and is threadedly connected to the through hole.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: Compared with the traditional starting method, the compressed air starting system has higher driving efficiency, smaller system weight, cleaner and more environmentally friendly power output, more convenient power acquisition method, greatly improved engine starting efficiency, shorter starting time, faster starting speed, safe, fast and efficient starting operation, the engine can reach the specified operating speed in a short time, enabling the aircraft equipped with a small turbojet engine to enter the normal working state in a short time, effectively improving the system operation efficiency. Description of the Drawings

[0025] Figure 1 It is a schematic diagram of the connection between the compressed air ground starting system of a small turbojet engine and the small turbojet engine.

[0026] Figure 2 It is a schematic diagram of the compressed air ground starting system of a small turbojet engine.

[0027] Figure 3It is an assembly drawing of a small turbojet engine and a jet joint.

[0028] Markings in the attached drawings: high-pressure gas supply unit 1, valve assembly 2, shut-off valve 2a, pressure reducing valve 2b, pressure relief valve 2c, high-pressure solenoid valve 3, connecting pipe 4, jet joint 5, small turbojet engine A, air intake B. Specific implementation mode

[0029] The present utility model will be described in detail below with reference to the attached drawings.

[0030] As Figures 1 to 3 shown, the compressed air ground starting system of the small turbojet engine of the present utility model includes: a high-pressure gas supply unit 1, a valve assembly 2, a high-pressure solenoid valve 3, a connecting pipe 4, and a jet joint 5. The high-pressure gas supply unit 1 is arranged on the ground foundation, and one end of the valve assembly 2 is connected to the output end of the high-pressure gas supply unit 1; for example, the high-pressure gas supply unit 1 is a high-pressure tank filled with high-pressure gas (compressed air), and a control valve is provided on the high-pressure tank and is connected to the valve assembly 2 through the control valve. The pressure of the high-pressure gas is not less than 18 Mpa. Traditional high-pressure gas tanks are generally made of high-strength metals, but they are relatively heavy; with the development of new material technologies, composite materials have been widely used in various industries. The present utility model preferably uses carbon fiber composite materials to make the high-pressure gas tank, which can not only ensure the pressure resistance strength but also reduce the weight of the tank body.

[0031] In the present utility model, the valve assembly 2 includes a shut-off valve 2a, a pressure reducing valve 2b, and a pressure relief valve 2c. The shut-off valve 2a is used to open or close the high-pressure gas output by the high-pressure gas supply unit 1. The shut-off valve 2a is connected to the high-pressure gas supply unit 1, and the shut-off valve 2a is connected to the control valve on the high-pressure tank through a high-pressure pipeline. The pressure reducing valve 2b is used to reduce the pressure of the high-pressure gas output by the high-pressure gas supply unit 1. The input end of the pressure reducing valve 2b is connected to the output end of the shut-off valve 2a. The pressure relief valve 2c is used to release the pressure of the high-pressure gas to keep the air pressure constant. The pressure relief valve 2c is connected to the output end of the pressure reducing valve 2b.

[0032] Assume that the air pressure in the high-pressure tank is at the maximum value (equal to the maximum set value). After opening the shut-off valve 2a, the pressure reducing valve 2b, and the pressure relief valve 2c, the high-pressure gas flows through the shut-off valve 2a, the pressure reducing valve 2b, and the pressure relief valve 2c in sequence. The air pressure is reduced to the first set value through the pressure reducing valve 2b. After the pressure of the high-pressure gas is released through the pressure relief valve 2c, the pressure of the high-pressure gas is kept constant. In this way, the pressure of the air flow flowing into the air intake B is in a stable state, and the impact on the compressor impeller can also be kept stable.

[0033] One end of the high-pressure solenoid valve 3 is connected to the other end of the valve assembly 2. Since the opening and closing of the high-pressure solenoid valve 3 are adjusted by an electric signal, the high-pressure solenoid valve 3 can accurately control the on-off of the high-pressure gas flow.

[0034] The connecting pipe 4 is preferably a high-pressure pipe. One end of the connecting pipe 4 is connected to the other end of the high-pressure solenoid valve 3. One end of the jet connector 5 is detachably connected to the connecting pipe 4. The jet connector 5 passes through the air intake B of the small turbojet engine A and is fixed to the air intake. The other end of the jet connector 5 faces the compressor blades. A through hole is provided at the position of the air intake B corresponding to the compressor. The axis of the through hole forms an angle with the axis of the compressor. The jet connector 5 passes through the through hole and is threadedly connected to the through hole.

[0035] A check valve is provided in the jet connector 5. The check valve has a first position that keeps the jet connector 5 in an open state after the high-pressure gas is turned on, and a second position that keeps the jet connector 5 in a closed state after the high-pressure gas is cut off. There is a flow passage in the jet connector 5, and the check valve is installed in the flow passage. When the high-pressure gas passes through the jet connector 5, the high-pressure gas exerts a force on the check valve, causing the check valve to open the flow passage in the jet connector 5, and the high-pressure gas enters the air intake B to impact the impeller of the compressor. When no high-pressure gas is supplied to the jet connector 5, the check valve resets to close the flow passage.

[0036] Among the above-mentioned components, only the jet connector 5 is fixed to the air intake B of the small turbojet engine. The high-pressure gas supply unit 1, the valve assembly 2, the high-pressure solenoid valve 3, and the connecting pipe 4 are arranged on the ground foundation. The connecting pipe 4 and the jet connector 5 can be threadedly connected. The threaded connection facilitates the installation and disassembly of the connecting pipe 4 and the jet connector 5. Or the connecting pipe 4 and the jet connector 5 can be connected by a pneumatic quick connector with a safety structure, which can easily perform the quick installation and disassembly of the connecting pipe 4 and the jet connector 5.

[0037] When the utility model works, after high-pressure gas is released from the high-pressure gas supply unit 1, it flows through the valve assembly 2, high-pressure solenoid valve 3, connecting pipe 4, and jet joint 5 in sequence, and then enters the air inlet duct B. Since the axis of the jet joint 5 forms an angle with the axis of the compressor, the high-pressure gas impacts the impeller of the compressor at a corresponding inclined angle, and the impeller starts to rotate under the force. As the high-pressure air flow continuously impacts the impeller, the compressor impeller accelerates rotation. When the rotational speed of the compressor reaches the first set value, the small turbojet engine is controlled to enter the ignition start-up procedure. The fuel pump supplies fuel, the igniter is powered on to ignite, the fuel-air mixture is ignited and starts to burn in the combustion chamber. The air flow generated by the compressor increases the inlet pressure of the combustion chamber and at the same time increases the air flow rate, and the fuel in the combustion chamber burns more rapidly; the fuel burns in the combustion chamber to release energy to generate high-temperature and high-pressure gas, which expands and does work in the turbine through the guide vane. The internal energy of the gas is converted into the kinetic energy of the turbine, driving the compressor rotor to do work, and the engine enters the start-up and running state. At the same time, the high-pressure air flow continues to blow and rotate the compressor rotor, and accelerates rotation under the drive of the turbine. The compressor needs to consume the power obtained by the turbine from the gas to increase the rotational speed. When the rotational speed is relatively low, the power consumed by the compressor is greater than the power obtained by the turbine, and the engine itself alone cannot increase the rotational speed to the idle speed. At this time, compressed air is needed to blow and accelerate the rotor. While the compressed air blows and rotates the compressor rotor, it also provides additional air pressure for the engine, which helps to improve the working efficiency of the compressor. When the rotor rotational speed reaches the set threshold value, the power obtained from the turbine is greater than the power consumption of the compressor, and the extra power can support the continuous increase of the engine rotor rotational speed. After reaching the rated idle speed, the high-pressure solenoid valve and the valve assembly are closed, the connecting pipe 4 and the jet joint 5 are disassembled, the compressed air starting system is separated from the engine, the engine enters the normal running state, and the compressed air starting system has completed its work. Finally, the high-temperature and high-pressure gas generated by the internal combustion of the small turbojet engine is used to push the vehicle to the launch state and then launched.

[0038] The compressed air ground starting system of the small turbojet engine of the utility model is mainly used for the ground starting of the power systems of small unmanned aircraft such as unmanned aerial vehicles and target drones. It uses clean, safe, reliable and lightweight compressed air to replace the traditional electric starting system, and can quickly start the small turbojet engine in the wild or outdoor field. It can obtain the compressed air source for starting the engine in occasions where the power supply is scarce, and the actual application effect is very good.

[0039] The utility model uses compressed air to replace the complex starting system, making the starting of the small turbojet engine simpler and faster. Using clean compressed air as the energy source can be obtained more conveniently in remote places. Using compressed air as the power source to replace the electric starting system eliminates the need for a power supply and simplifies the system structure. The whole system is more energy-saving and environmentally friendly.

Claims

1. A small turbojet engine compressed air ground starting system, characterized in that: include: A high-pressure gas supply unit (1) arranged on a ground foundation; A valve assembly (2), one end of the valve assembly (2) being connected to an output end of the high-pressure gas supply unit (1); A high-pressure solenoid valve (3), one end of which is connected to the other end of the valve assembly (2); A connecting pipe (4), one end of which is connected to the other end of the high-pressure solenoid valve (3); A jet connector (5), one end of which is detachably connected to a connecting pipe (4), the jet connector (5) passes through an air inlet (B) of a small turbojet engine (A) and is fixed to the air inlet, and the other end of the jet connector (5) faces a compressor blade.

2. The small turbojet engine compressed air ground starting system according to claim 1, characterized in that: The valve assembly (2) comprises: A shut-off valve (2a) for opening or closing the high-pressure gas supply unit (1) outputting high-pressure gas, the shut-off valve (2a) being connected to the high-pressure gas supply unit (1); A pressure reducing valve (2b) for reducing the pressure of the high-pressure gas output by the high-pressure gas supply unit (1), wherein the input end of the pressure reducing valve (2b) is connected to the output end of the shut-off valve (2a); A pressure relief valve (2c) is used to release the pressure of high-pressure gas to keep the gas pressure constant, and the pressure relief valve (2c) is connected to the output end of the pressure reducing valve (2b).

3. The small turbojet engine compressed air ground starting system according to claim 1, characterized in that: A one-way valve is arranged inside the jet connector (5), and the one-way valve has a first position in which the jet connector (5) is in an open state after the high-pressure gas is opened, and a second position in which the jet connector (5) is in a closed state after the high-pressure gas is cut off.

4. The small turbojet engine compressed air ground starting system according to claim 1, characterized in that: A through hole is provided at a position of the air inlet (B) corresponding to the compressor, the axis of the through hole forms an angle with the axis of the compressor, and the jet connector (5) passes through the through hole and is threadedly connected to the through hole.

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