Axial flow-centrifugal combined type turbojet propulsion power device based on coupler coupling and operation method of axial flow-centrifugal combined type turbojet propulsion power device

Abstract

The invention discloses an axial flow-centrifugal combined type turbojet propulsion power device based on coupling of a coupler and an operation method of the axial flow-centrifugal combined type turbojet propulsion power device, and belongs to the technical field of aviation power, and the device is formed by coaxially connecting a centrifugal type core machine unit body and an axial flow type combined unit body through the coupler. An engine body extends forwards in the axis direction, an axial-flow type combined unit body is additionally arranged in the extending engine body through a coupler, and specifically components such as a fairing assembly, a fuel oil and lubricating oil combined pump, an axial-flow compressor assembly and a built-in generator are formed. The invention further provides a corresponding operation method which comprises the steps of starting, two-stage compressed air cooperation, ignition and self-sustaining switching, pressure ratio matching, fault response and the like, and efficient, safe and stable operation under all working conditions can be achieved. The invention has the functions of simplifying the engine structure, improving the supercharge ratio of the gas compressor, increasing the thrust of the engine and the like. After the thrust of the engine is increased, the load capacity and the flight speed of the unmanned aerial vehicle or the cruise missile can be effectively increased.

Description

Technical Field

[0001] The present invention belongs to the field of aviation power technology and relates to the optimization and improvement of the structure of traditional turbojet engines. Specifically, it is an axial-centrifugal composite turbojet propulsion power device based on coupling and its operation method, which can achieve an improved thrust-to-weight ratio, self-powered operation and compact structural design. Background Art

[0002] In recent years, the application areas and technical requirements for various high-performance small unmanned aerial vehicles (UAVs), such as long-endurance drones, high-altitude, high-speed target drones, and other high-subsonic aircraft, have continued to expand and improve. These aircraft place increasingly stringent demands on their powertrains, demanding not only high reliability and long lifespan but also high requirements for key performance indicators such as thrust, power-to-weight ratio, fuel economy, and high-altitude adaptability. Traditional piston internal combustion engines, due to their shortcomings such as short range, low power density, performance degradation at high altitudes, and inability to support high-speed flight, have proven difficult to meet the power requirements of these advanced aircraft.

[0003] Among existing small turbojet engine technologies, single-stage centrifugal turbojet engines have broad application value on small and medium-sized aviation platforms due to their compact structure, low manufacturing cost, and strong adaptability to the operating environment. In a typical centrifugal turbojet engine, the centrifugal compressor impeller rotates at high speed, pressurizing the inhaled air before sending it into the combustion chamber. This air mixes with the fuel and burns to form high-temperature, high-pressure combustion gas, which then drives the turbine to produce work and is ultimately ejected at high speed from the tail nozzle to generate thrust. However, as application requirements continue to escalate, the technical limitations of this type of single-stage centrifugal turbojet engine have become increasingly prominent.

[0004] First, since it relies solely on a single-stage centrifugal compressor for boosting, the compression ratio is small, making it difficult to provide sufficient thrust at high altitudes or high speeds. Secondly, this type of engine usually lacks a self-sustaining energy system and requires an external system to solve the supply of fuel / lubricating oil and onboard electricity. This not only makes the engine highly dependent on external systems, but also increases the overall structural complexity and system maintenance costs, and it is difficult to ensure that the engine can operate stably for a long time. In addition, in order to achieve energy transmission and functional coordination of various components, traditional structures often use complex transmission systems such as mechanical gears and couplings, which increases the weight of the entire machine and the probability of system failure. In terms of lubrication and cooling, most existing engines are equipped with independent lubricating oil circulation systems, which require additional oil tanks, coolers and pump groups, resulting in complex structures, high maintenance costs, and delayed system response, which is not conducive to the development of engines towards lightweight and high efficiency.

[0005] In the prior art, Chinese patent CN106939832A discloses an axial-flow-centrifugal integrally bladed disc combined compression system. While this system simplifies the structure, it still requires an external auxiliary system and offers limited improvement in boosting efficiency. CN118462613A discloses a counter-rotating axial-flow-centrifugal compressor. This scheme utilizes a counter-rotating structure, which improves the compressor's compression ratio to a certain extent. However, its planetary gear mechanism increases the structural complexity and weight, and the counter-rotating structure places higher demands on bearing performance.

[0006] In summary, existing small centrifugal turbojet engines still have limitations in terms of boost efficiency, thrust output, system integration, and high-altitude adaptability. Therefore, how to improve compression efficiency and thrust-to-weight ratio within a limited structural space, simplify engine structure, reduce engine weight, and improve engine independence and reliability are urgent technical challenges that need to be addressed in small aviation propulsion technology. Summary of the Invention

[0007] (1) Purpose of the invention In response to the above-mentioned defects and deficiencies in the prior art, the purpose of the present invention is to provide an axial-centrifugal composite turbojet propulsion power unit based on coupling coupling and its operation method. By integrating an axial-flow combined unit body at the front end of the centrifugal turbojet engine and using an involute internal and external spline coupling to achieve axial power coupling and torque synchronous transmission, a turbojet propulsion power unit with multi-stage compression capability and modular functional integration is constructed, significantly improving the overall compression efficiency and thrust-to-weight ratio. At the same time, by internally integrating the fuel / lubricating oil pump and generator, self-sustaining energy supply is achieved, eliminating dependence on external auxiliary systems, effectively simplifying the engine structure, reducing the weight of the entire machine, and improving the independence and reliability of the system, thereby meeting the comprehensive power requirements of small aviation flight platforms for high performance, long flight time and high-altitude operation capabilities.

[0008] (2) Technical solution In order to achieve the purpose of the invention and solve the technical problems, the present invention adopts the following technical solutions: The first object of the present invention is to provide an axial-flow-centrifugal composite turbojet propulsion power unit based on coupling, which is used to provide propulsion power with high thrust-to-weight ratio, high pressure ratio, self-powered capability and good system integration for small aviation platforms such as unmanned aerial vehicles and high-altitude aircraft. The power unit comprises a centrifugal core unit and an axial-flow combination unit arranged in sequence along the engine axis, with a coupling provided between the two, wherein: The centrifugal core engine unit comprises a centrifugal compressor component, an annular combustion chamber component, a turbine component, and a tail nozzle arranged in sequence from upstream to downstream along the engine axis, wherein the centrifugal compressor component and the turbine component are rotating parts and are coaxially connected to form a rotor shaft that passes through the annular combustion chamber and is rotatably supported in the engine casing by at least one pair of rolling bearings to form a 1-1 type simply supported beam structure, which is used to achieve radial compression of the intake air, fuel combustion and turbine work, and tail nozzle thrust increase; The axial-flow combined unit body is integrally arranged upstream of the centrifugal core engine unit body, and includes a fairing assembly, a fuel and lubricating oil combination pump, an axial-flow compressor assembly, and a built-in generator arranged in sequence from upstream to downstream along the engine axis, wherein the fairing assembly is a stationary structure located at the front end of the engine, and is used to guide and rectify the incoming gas flow; the fuel and lubricating oil combination pump is supported by sliding bearings in the internal space of the fairing assembly, and is used to achieve fuel injection and lubricating oil circulation supply; the axial-flow compressor assembly and the built-in generator share a rotor shaft, which is supported by a pair of rolling bearings in the axial stage casing to form a 0-1-1 cantilever beam structure; the axial-flow compressor assembly is used to perform axial multi-stage compression on the incoming gas flow, and the built-in generator is used to achieve independent supply of electricity for the propulsion power unit; The coupling is arranged between the axial-flow combined unit body and the centrifugal core engine unit body, and its upstream and downstream ends are respectively engaged with the rotor shafts of the two units to achieve coaxial coupling and power transmission between the two, so that the axial-flow compressor assembly, built-in generator, and fuel and lubricating oil combination pump in the axial-flow combined unit body rotate synchronously with the centrifugal compressor components and turbine components in the centrifugal core engine unit body, thereby constructing a turbojet propulsion power unit with multi-stage compression, energy self-sustaining and efficient transmission.

[0009] The second object of the present invention is to provide a method for operating the above-mentioned axial-centrifugal composite turbojet propulsion power plant based on coupling, comprising at least the following steps: SS1. Startup sequence initialization control: After receiving the start command, the working mode of the built-in generator is set to motor mode, and it outputs starting torque based on the onboard power supply, and synchronously drives the axial flow combination unit and the centrifugal core unit through the meshing transmission of the coupling; SS2. Compressed air path establishment and fuel ignition control: When the engine speed reaches the preset ignition speed threshold, the axial and centrifugal compression sections are controlled to achieve continuous airflow boosting, and the fuel output pressure of the fuel and lubricating oil combination pump is adjusted to ensure stable mixing of high-pressure air and fuel in the annular combustion chamber, and the ignition system is started. SS3. Successful ignition and self-sustaining operation transition control: After successful ignition, the exhaust temperature after the turbine or the rotor angular acceleration is monitored in real time to ensure stable pressure buildup in the combustion chamber. When the engine speed is detected to exceed the self-sustaining speed threshold, the onboard power supply is cut off and the built-in generator is switched to generator mode, using the engine's own power to generate electricity. SS4. Speed Establishment and Synchronous Matching Control: Real-time monitoring of the angular velocity and torque of the rotors on both sides of the coupling ensures that the two units maintain a synchronous speed relationship; monitoring and controlling the pressure ratio matching between the axial flow compressor assembly and the centrifugal compressor components to prevent compressor stall or surge; SS5. Steady-state operating parameter optimization control: After reaching the designed operating speed, the thrust output is precisely controlled by adjusting the fuel flow rate. At the same time, the compressor working status is monitored to ensure that the two-stage compression system operates near the optimal efficiency point. The power output is controlled by load regulation of the built-in generator. SS6. System integration operation monitoring: Continuously monitor the working status of the fuel and lubricating oil combination pump to ensure stable fuel pressure and effective circulation of the lubrication system. Use speed sensors and temperature sensors to monitor the operating parameters of each rotating component in real time. When abnormal operating conditions are detected, adjust the control strategy in time to ensure safe and reliable operation of the propulsion power unit.

[0010] (3) Technical effects Compared with the prior art, the coupling-based axial-flow-centrifugal composite turbojet propulsion power device and its operation method of the present invention have the following beneficial and significant technical effects: (1) The present invention integrates an axial-flow combined unit body at the front end of a centrifugal turbojet engine and adopts an involute internal spline coupling to achieve coaxial rigid coupling with the core engine, thereby constructing an axial-flow-centrifugal composite compression system with a compact structure and highly integrated functions. This design not only increases the engine's compression ratio, but also improves the fuel and lubricating oil supply and the local power generation system, making the engine structure perfect and simple, eliminating the traditional cumbersome and complicated gear transmission system; the present invention also uses fuel for cooling and lubrication, and simplifies the lubrication system and its structure, all of which reduce the weight of the engine itself and improve the thrust-to-weight ratio.

[0011] (2) The operating method proposed in the present invention integrates electric starting, self-powered switching, pressure ratio matching control and system collaborative anti-surge strategy, and establishes a closed-loop control logic throughout the entire process of starting and transition to steady state. It can realize the linkage adjustment and adaptive optimization of the working conditions among the various functional units of the engine, especially in complex high-altitude environments or high-speed cruising missions. It has good dynamic response capabilities and operating stability, and significantly improves the comprehensive efficiency and engineering adaptability of the propulsion system. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The figure shows the structural principle diagram of the axial-centrifugal composite turbojet propulsion power device based on coupling of the present invention; Figure 2 Shown is a flow chart of the operating method of the axial-centrifugal composite turbojet propulsion power device based on coupling of the present invention.

[0013] Description of reference numerals: Centrifugal core engine unit 10, centrifugal compressor component 11, annular combustion chamber component 12, turbine component 13, tail nozzle 14, rotor shaft 15, axial flow combined unit 20, fairing assembly 21, fuel and lubricating oil combination pump 22, axial flow compressor assembly 23, built-in generator 24, rotor shaft 25, involute internal spline coupling 30. DETAILED DESCRIPTION

[0014] The present invention aims to provide an axial-centrifugal composite turbojet propulsion power unit based on coupling and its operation method, which is used to provide propulsion power with high thrust-to-weight ratio, high pressure ratio, self-powered capability and good system integration for small aviation flight platforms such as unmanned aerial vehicles and high-altitude aircraft. In order to make the purpose, technical solutions and advantages of the implementation of the present invention clearer, the technical solutions in the embodiments of the present invention will be described in more detail below with reference to the drawings in the embodiments of the present invention. The described embodiments are part of the embodiments of the present invention, not all of the embodiments, and the described embodiments are exemplary and are intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0015] Example 1: Turbojet propulsion power plant As a specific example, see Figure 1 The axial-flow-centrifugal composite turbojet power unit based on coupling provided by an embodiment of the present invention is composed of an axial-flow combination unit body 20 and a centrifugal core engine unit body 10 combined through an involute internal spline coupling 30.

[0016] The centrifugal core engine unit 10 is used to achieve radial compression of the intake air, fuel combustion, turbine power generation, and tail jet thrust augmentation. It comprises a centrifugal compressor 11, an annular combustion chamber 12, a turbine 13, and a tail nozzle 14. These components are arranged from left to right along the engine axis, with the centrifugal compressor 11 located at the front (upstream) end of the unit 10, and the tail nozzle 14 located at the rightmost (downstream) end. The centrifugal compressor 11 and turbine 13 are the core rotating components. They are coaxial, with their shafts passing through the annular combustion chamber 9, forming the rotor shaft 15 of the centrifugal core engine unit 1. This shaft is rotatably supported on the engine casing by a pair of rolling bearings, forming a 1-1 simply supported beam structure. The rotor shaft 15 of the centrifugal core engine unit 10 extends to the left, with its end structured with an involute external spline that meshes with the internal spline at the right end of the involute internal spline coupling 30 to transmit power.

[0017] The axial-flow combined unit 20 is arranged as a whole upstream of the centrifugal core unit 10. It is a combined mechanism with an involute external spline shaft end, consisting of a coaxial fairing assembly 21, a fuel and lubricating oil combination pump 22, an axial-flow compressor assembly 23 and a built-in generator 24, a total of four mechanisms. These four mechanisms are arranged horizontally in a line from left to right along the engine axis; the axial-flow compressor assembly 23 and the built-in generator 24 are supported on the axial stage casing by a pair of rolling bearings, and the support type is a 0-1-1 cantilever beam structure; the fuel and lubricating oil combination pump 22 is supported in the internal space of the fairing assembly 21 by sliding bearings for realizing fuel injection and lubricating oil circulation supply; the fairing assembly Component 21 is a stator component, located at the leftmost end (upstream end) of the engine, and is used to guide the incoming gas and rectify it; the axial-flow compressor assembly 23 and the built-in generator 24 share a rotor shaft 25, and the rotor assembly formed by the two is located at the rightmost end (downstream end), and its rotor shaft end extends to the right. The shaft end structure is an involute external spline. The axial-flow compressor assembly 23 is used to perform axial multi-stage compression on the incoming gas, and the built-in generator 24 is used to achieve independent supply of electricity for the propulsion power unit; the right end shaft extension of the rotor assembly formed by the axial-flow compressor assembly 23 and the built-in generator 24 and the left end shaft extension of the rotor shaft 15 of the centrifugal core unit body 10 are engaged and connected through an involute internal spline coupling 30 to transmit power.

[0018] The involute internal spline coupling 30 is arranged between the axial-flow combination unit body 20 and the centrifugal core engine unit body 10, and its upstream and downstream ends are respectively engaged with the rotor shafts 15 and 25 of the two units 10 and 20 to achieve coaxial coupling and power transmission between the two, so that the axial-flow compressor assembly 23, the built-in generator 24, and the fuel and lubricating oil combination pump 22 in the axial-flow combination unit body 20 rotate synchronously with the centrifugal compressor component 11 and the turbine component 13 in the centrifugal core engine unit body 10, thereby constructing a turbojet propulsion power unit with multi-stage compression, energy self-sustaining and efficient transmission.

[0019] When the axial-flow-centrifugal turbojet propulsion system of the present invention is in operation, the turbine assembly 13, located at the second-rightmost position of the engine, drives the centrifugal compressor assembly 11, which in turn, through the involute internal spline coupling 30, drives the fuel and lubricating oil pump assembly 22, the axial-flow compressor assembly 23, and the internal generator 24 in synchronous operation. Air is introduced into the engine through the forward fairing assembly 21. After being supercharged twice by the axial-flow compressor assembly 23 and the centrifugal compressor assembly 11, its pressure and temperature are increased. The air then enters the annular combustion chamber assembly 12, mixes with the injected fuel, and combusts. The resulting high-temperature, high-pressure combustion gas flows out of the combustion chamber outlet and into the turbine assembly 13. The high-temperature, high-pressure combustion gas is further accelerated and directed within the turbine guide vane, directly propels the turbine rotor at high speed, and ultimately is ejected from the tail nozzle 14 at high speed. The high-speed ejected gas exerts a reaction force on the engine, which is the engine's forward thrust.

[0020] In an embodiment of the present invention, the coupling 30 is an involute internal spline coupling, and both upstream and downstream ends thereof are formed with internal spline sleeve structures; accordingly, the downstream end of the rotor shaft 25 of the axial-flow combination unit body 20 and the upstream end of the rotor shaft 15 of the centrifugal core unit body 10 have shaft end structures that are both set to involute external splines; the coupling 30 engages with the external splines of the rotor shaft ends of the two units through the internal spline sleeves at both ends thereof, thereby realizing rigid torque transmission with automatic centering, high load-bearing capacity and high transmission accuracy, ensuring that the axial-flow compressor assembly, built-in generator, fuel and lubricating oil combination pump and centrifugal compressor components and turbine components maintain the same speed operation, eliminating the complexity and weight burden of traditional gear transmission systems.

[0021] In an embodiment of the present invention, the engine body is extended upstream along the axial direction to accommodate the axial-flow combination unit body 20, and an installation space is formed inside the extended body, so that the axial-flow combination unit body 20 and the centrifugal core engine unit body 10 can be compactly integrated. After extension, the engine body maintains an aerodynamic shape to ensure the smoothness of the intake flow, and provides sufficient working space for the axial-flow compressor assembly to achieve efficient axial compression of the incoming air.

[0022] In an embodiment of the present invention, the axial-flow compressor assembly 23 and the built-in generator 24 share a rotor shaft 25, which passes through the axial casing and supports the two rotating assemblies at the same time. The upstream end of the rotor shaft 25 is coaxially connected to the rotating shaft of the fuel and lubricating oil combination pump 22, and the downstream end is provided with an involute external spline structure that is meshed with a coupling 30; and the rotor shaft 25 adopts a 0-1-1 cantilever beam support structure, including a radial rolling bearing located on the downstream side of the axial-flow compressor assembly 23 and a thrust rolling bearing located on the downstream side of the built-in generator 24. The two bearings work together to withstand the radial load, axial load and overturning moment of the rotor system, ensuring the stability and reliability of the rotor system under high-speed rotation. At the same time, the bearing configuration is simplified, the structural weight is reduced, and the power-to-weight ratio of the engine is improved.

[0023] Preferably, the fairing assembly 21 is a stationary component, fixed to the upstream end of the engine body by a supporting structure, and its outer wall is formed as an axisymmetric diffuser surface or a conical fairing guide surface, which is used to rectify the forward airflow and homogenize the flow field, thereby ensuring the directionality and flow uniformity of the incoming flow entering the axial compressor assembly 23, and its internal space is formed as a fuel and oil combination pump installation space.

[0024] In addition, the fuel and lubricating oil combination pump 22 is arranged in the internal structural space between the fairing assembly 21 and the axial flow compressor assembly 23 in a sliding bearing support manner, and is driven by the rotational power output by the axial flow combination unit rotor shaft 25. Its fuel pipeline and lubricating oil pipeline are combined and arranged, and fuel is used instead of lubricating oil for cooling and lubrication. The fuel sucked from the fuel tank and pressurized by the fuel and lubricating oil combination pump, the mainstream part is transported to the annular combustion chamber component to realize gas propulsion, and the rest is diverted to the lubricating oil pipeline for lubricating and cooling the various rotating parts of the engine.

[0025] It is worth noting that the present invention adopts a technical solution of fuel cooling and lubrication, which uses the flow of fuel to cool and lubricate key components of the engine, simplifying the traditional independent lubrication system configuration. During the circulation process, the fuel not only plays the role of a combustion medium, but also assumes the functions of a coolant and lubricant. The fuel supply and lubricating oil flow are precisely controlled through the unified adjustment of the fuel and lubricating oil combination pump, thereby omitting the oil tank, cooler and oil return system required by the traditional independent lubricating oil system, simplifying the overall structure of the engine, reducing the weight of the system, improving the thrust-to-weight ratio and system reliability, and avoiding the risk of lubrication failure caused by high temperature and high speed. It is suitable for continuous and stable operation under complex working conditions such as high altitude and long flight time.

[0026] Preferably, the axial flow compressor assembly 23 adopts a multi-stage axial flow compression structure, including compressor stages with multiple rows of stator blades and moving blades arranged alternately. Each compressor stage is composed of leading guide vanes, rotor blades and trailing guide vanes. The rotor blades are fixed on the rotor disk and rotate at high speed with the main shaft. The stationary blades are fixed on the casing to play a role in guiding and rectifying the flow. Through multi-stage compression, the intake air is pressurized step by step, effectively improving the compression efficiency and compression ratio, providing pre-compressed high-quality intake air for subsequent centrifugal compressor components, and realizing the synergistic effect of axial-centrifugal two-stage compression.

[0027] Preferably, the built-in generator 24 is integrated inside the axial-flow combination unit 20 and rotates coaxially with the axial-flow compressor assembly 23. The generator rotor assembly is axially supported by a thrust rolling bearing located on its downstream side, and together with the stator assembly in the casing, it constitutes a compact coaxial magnetoelectric conversion structure, which is used to provide a stable power supply for the engine control system, ignition system, fuel regulation system and airborne electronic equipment, and realize the self-power supply function of the engine system without relying on external power supply equipment, which simplifies the installation configuration of the engine, improves the overall independent operation capability, integration and adaptability of the propulsion system, and meets the self-sustaining requirements of the energy system of long-range and long-endurance flight platforms.

[0028] In an embodiment of the present invention, the axial flow combination unit 20 and the centrifugal core engine unit 10 are rigidly coupled through a coupling 30. When surge occurs in the axial flow compressor, the built-in generator 24 switches to the motor mode and injects reverse torque into the axial flow compressor assembly to suppress the development of surge. At the same time, the fuel and lubricating oil combination pump reduces the oil supply to reduce the turbine power, thereby realizing coordinated surge control across the units.

[0029] Example 2: Operation method Based on the detailed description of the structure and working principle of the propulsion power device of the present invention in Example 1, this Example 2 further combines the coordinated operation mechanism of the core components of the device to specifically explain the control method and operation steps from startup to steady-state operation, so as to reflect the practicality of the present invention at the dynamic execution level and the systematic nature of the control strategy. Specifically, Figure 2 As shown, the operation method mainly includes the following steps when implemented: SS1. Startup sequence initialization control: After receiving the start command, the working mode of the built-in generator is set to the motor mode, and the starting torque is output based on the onboard power supply, and the axial flow combination unit and the centrifugal core unit are synchronously driven through the meshing transmission of the coupling.

[0030] Preferably, the startup sequence initialization control process includes a pre-start system inspection phase, first performing an engine status self-check, including detecting the bearing lubrication status, fuel system pressure, electrical system connection status and static balance status of the rotor system, to confirm that each system is in a normal state; when the built-in generator is switched to the motor mode, by setting the target starting speed curve and adopting a progressive torque output control strategy, it starts with a lower torque in the initial stage to reduce the impact load on the coupling and rotor system, and then gradually increases the torque output until the preset starting speed establishment rate is reached, ensuring the smoothness and reliability of the entire startup process.

[0031] SS2. Compressed air path establishment and fuel ignition control: When it is monitored that the speed of the entire machine reaches the preset ignition speed threshold, the axial flow and centrifugal compression sections are controlled to achieve continuous airflow boosting, and the fuel output pressure of the fuel and lubricating oil combination pump is adjusted to ensure that the high-pressure air and fuel are stably mixed in the annular combustion chamber, and the ignition system is started.

[0032] Preferably, when it is monitored that the engine speed reaches a preset ignition threshold, the combined pump is started to form a high-pressure fuel passage in the fuel system, and the fuel is sprayed into the combustion chamber through the nozzle; at the same time, a stable airflow channel is established through the coordinated work of the axial compressor and the centrifugal compressor, so that the gas flow meets the turbine starting conditions; the ignition system is composed of a high-energy electronic igniter, and generates continuous sparks in the combustion chamber to achieve reliable ignition of high-pressure fuel and compressed air.

[0033] In addition, during the establishment of the compression path, a staged pressure ratio establishment strategy is adopted. First, the axial flow compressor components are controlled to establish the pressure ratio step by step. The static and dynamic pressure distributions at each stage are monitored to ensure the stable flow of the airflow in the axial flow compressor. Then, the centrifugal compressor components are controlled to establish radial compression. The optimal compression effect is achieved by adjusting the centrifugal impeller speed and the diffuser geometric parameters. During the establishment of the two-stage compressor pressure ratio, the total temperature and total pressure at the compressor outlet are continuously monitored to ensure that the temperature rise and pressure rise meet the design expectations. At the same time, by adjusting the working parameters of the fuel and lubricating oil combination pump, the fuel supply pressure and the compressed air pressure are kept dynamically matched, providing the optimal fuel-air ratio conditions for efficient combustion in the combustion chamber.

[0034] SS3. Successful ignition and self-sustaining operation transition control: After successful ignition, the exhaust temperature after the turbine or the rotor angular acceleration is monitored in real time to ensure stable pressure buildup in the combustion chamber. When the speed of the entire machine is detected to exceed the self-sustaining speed threshold, the onboard power supply is cut off and the built-in generator is switched to generator mode to use the engine's own power to generate electricity.

[0035] Preferably, a criterion for determining successful combustion is established through comprehensive multi-parameter monitoring. Successful ignition is confirmed when a continuous and stable combustion signal is detected and the rotor acceleration remains positive. When the speed exceeds the self-sustaining speed threshold, a progressive power cut-off and generator mode switching strategy is adopted. First, the motor torque output is gradually reduced and the fuel injection amount in the combustion chamber is increased. Then, the engine is smoothly switched to the generator mode to avoid speed fluctuations or power interruptions, thereby ensuring a seamless transition from external startup to autonomous operation.

[0036] SS4. Speed Establishment and Synchronous Matching Control: Real-time monitoring of the angular velocity and torque status of the rotors on both sides of the coupling upstream and downstream to ensure that the two units maintain a synchronous speed relationship; monitor and control the pressure ratio matching of the axial flow compressor assembly and the centrifugal compressor components to prevent compressor stall or surge.

[0037] Preferably, the synchronization monitoring of the rotors at both ends of the coupling includes real-time collection and analysis of the angular velocity difference, torque fluctuation rate and / or phase deviation. When it is detected that the speed deviation exceeds the allowable range, the speed synchronization correction is achieved by adjusting the fuel flow or motor load to avoid structural damage or power mismatch caused by inconsistent speeds; at the same time, a pressure ratio matching control algorithm for the axial flow compressor and the centrifugal compressor is established, and the operating point of the two-stage compressor is dynamically adjusted according to the intake conditions and speed status to ensure that the entire compression system operates in a high-efficiency area and avoid the occurrence of unstable working conditions such as stall and surge.

[0038] SS5. Steady-state operating parameter optimization control: After reaching the designed operating speed, precise control of thrust output is achieved through fuel flow regulation, while the compression working status is monitored to ensure that the two-stage compression system operates near the optimal efficiency point, and the power output is controlled through load regulation of the built-in generator.

[0039] SS6. System integration operation monitoring: Continuously monitor the working status of the fuel and lubricating oil combination pump to ensure stable fuel pressure and effective circulation of the lubrication system. Use speed sensors and temperature sensors to monitor the operating parameters of each rotating component in real time. When abnormal operating conditions are detected, adjust the control strategy in time to ensure safe and reliable operation of the propulsion power unit.

[0040] In summary, Example 2 details the operation method of a coupling-based axial-flow-centrifugal composite turbojet propulsion power plant, encompassing control strategies for key stages such as startup, compression, combustion, and power generation. Through precise control and coordinated optimization of each stage, the performance, reliability, and adaptability of the power plant can be effectively improved, meeting the propulsion power requirements of small aviation platforms.

[0041] The above embodiments fully and effectively achieve the objectives of the present invention. Those skilled in the art will appreciate that the present invention includes, but is not limited to, the contents described in the accompanying drawings and the above specific embodiments. Although the present invention has been described with reference to the embodiments currently considered to be the most practical and preferred, it should be understood that the present invention is not limited to the disclosed embodiments, and any modifications that do not deviate from the functional and structural principles of the present invention are intended to be included within the scope of the claims.

Claims

1. An axial-centrifugal composite turbojet propulsion power unit based on coupling, characterized in that: It includes a centrifugal core unit and an axial flow combination unit arranged in sequence along the engine axis, with a coupling provided between the two, wherein: The centrifugal core engine unit comprises a centrifugal compressor component, an annular combustion chamber component, a turbine component and a tail nozzle arranged in sequence along the engine axis, wherein the centrifugal compressor component and the turbine component are rotating parts and are coaxially connected to form a rotor shaft that passes through the annular combustion chamber and is rotatably supported in the engine casing by at least one pair of rolling bearings to form a 1-1 type simply supported beam structure; The axial-flow combined unit body is arranged upstream of the centrifugal core engine unit body, and includes a fairing assembly, a fuel and lubricating oil combination pump, an axial-flow compressor assembly, and a built-in generator arranged in sequence along the engine axis, wherein the fairing assembly is a stationary structure located at the front end of the engine, the fuel and lubricating oil combination pump is supported by a sliding bearing in the fairing assembly, and the axial-flow compressor assembly and the built-in generator share a rotor shaft, which is supported by a pair of rolling bearings in the axial stage casing to form a 0-1-1 cantilever beam structure; The coupling is arranged between the axial-flow combined unit body and the centrifugal core engine unit body, and its two ends are respectively engaged with the rotor shafts of the two units, so that the axial-flow compressor assembly, built-in generator, fuel and lubricating oil combination pump in the axial-flow combined unit body and the centrifugal compressor components and turbine components in the centrifugal core engine unit body are coaxially coupled and rotate synchronously.

2. The axial-centrifugal composite turbojet propulsion power device based on coupling according to claim 1, characterized in that: The coupling is an involute internal spline coupling, and both its upstream and downstream ends are formed with internal spline sleeve structures; accordingly, the downstream end of the axial flow combined unit rotor shaft and the upstream end of the centrifugal core unit rotor shaft have shaft end structures that are both configured as involute external splines; the coupling engages with the external splines at the ends of the two unit rotor shafts through the internal spline sleeves at its two ends.

3. The axial-centrifugal composite turbojet propulsion power device based on coupling according to claim 1, characterized in that: The engine body is extended upstream along the axial direction to accommodate the axial-flow combination unit body, and an installation space is formed inside the extended body, so that the axial-flow combination unit body and the centrifugal core engine unit body can be compactly integrated. After extension, the engine body maintains an aerodynamic shape to ensure the smoothness of the intake flow.

4. The axial-centrifugal composite turbojet propulsion power device based on coupling according to claim 1, characterized in that: The axial-flow compressor assembly and the built-in generator share a rotor shaft, which passes through the axial casing and supports two rotating assemblies at the same time, forming an integrated coaxial structure design. The upstream end of the rotor shaft is coaxially connected to the rotating shaft of the fuel and lubricating oil combination pump, and the downstream end is provided with an involute external spline structure that is meshed with a coupling; and the rotor shaft adopts a 0-1-1 cantilever beam support structure, including a radial rolling bearing located on the downstream side of the axial-flow compressor assembly and a thrust rolling bearing located on the downstream side of the built-in generator. The two bearings work together to withstand the radial load, axial load and overturning moment of the rotor system, ensuring the stability and reliability of the rotor system under high-speed rotation.

5. The axial-centrifugal composite turbojet propulsion power device based on coupling according to claim 1, characterized in that: The fairing assembly is fixed to the upstream end of the engine body through a supporting structure, and its outer wall is formed into an axisymmetric diffuser surface or a conical fairing guide surface, which is used to rectify the forward airflow and homogenize the flow field, and a fuel and lubricating oil combination pump installation space is formed inside it.

6. The axial-centrifugal composite turbojet propulsion power device based on coupling according to claim 1, characterized in that: The fuel and lubricating oil combination pump is arranged in the internal structural space between the fairing assembly and the axial compressor assembly in a sliding bearing support manner, and its fuel pipeline and lubricating oil pipeline are arranged together. The fuel and lubricating oil combination pump sucks and pressurizes the fuel from the fuel tank, and the mainstream part is delivered to the annular combustion chamber component to realize gas propulsion, and the remaining part is diverted to the lubricating oil pipeline for lubricating and cooling the various rotating parts of the engine.

7. The axial-centrifugal composite turbojet propulsion power device based on coupling according to claim 1, characterized in that: The axial flow compressor assembly adopts a multi-stage axial flow compression structure, including multiple rows of stationary blades and moving blades arranged alternately in a compressor stage. Each compressor stage is composed of leading guide vanes, rotor blades and trailing guide vanes. The rotor blades are fixed on the rotor disk and rotate at high speed with the main shaft. The stationary blades are fixed on the casing to play a role in guiding and rectifying the flow. The multi-stage compression achieves step-by-step pressurization of the intake air.

8. The axial-centrifugal composite turbojet propulsion power device based on coupling according to claim 1, characterized in that: The built-in generator is integrated inside the axial-flow combined unit body and rotates coaxially with the axial-flow compressor assembly. The generator rotor assembly is axially supported by a thrust rolling bearing located on its downstream side, and together with the stator assembly in the casing, it forms a compact coaxial magnetoelectric conversion structure, which is used to provide a stable power supply for the engine control system, ignition system, fuel regulation system and airborne electronic equipment, thereby realizing the self-power supply function of the engine system.

9. The axial-centrifugal composite turbojet propulsion power device based on coupling according to claim 1 or 8, characterized in that: The axial-flow combined unit body and the centrifugal core engine unit body are rigidly coupled through a coupling. When the axial-flow compressor surges, the built-in generator switches to electric motor mode and injects reverse torque into the axial-flow compressor assembly to suppress the development of surge. At the same time, the fuel and lubricating oil combined pump reduces the oil supply to reduce the turbine power, thereby realizing coordinated surge control across the units.

10. An operating method of an axial-centrifugal composite turbojet propulsion power plant based on coupling according to any one of claims 1 to 9, characterized in that: At least the following steps are included: Upon receiving the start command, SS1 switches the internal generator to motor mode, generating starting torque from the onboard power supply. This synchronously drives the axial-flow combined unit and centrifugal core unit through the meshing transmission of the coupling. SS2. When the engine speed reaches the preset ignition speed threshold, it controls the axial and centrifugal compression stages to achieve continuous airflow boosting, adjusts the fuel output pressure of the combined fuel and lubricating oil pump, and ensures stable mixing of high-pressure air and fuel in the annular combustion chamber. Ignition is then initiated. SS3. After successful ignition, the system monitors the exhaust temperature and rotor angular acceleration in real time to ensure stable combustion chamber pressure buildup. If the engine speed exceeds the self-sustaining speed threshold, the system shuts off the onboard power supply and switches the internal generator to generator mode, utilizing the engine's own power. SS4. Real-time monitoring of the angular velocity and torque of the rotors upstream and downstream of the coupling to ensure that the two units maintain a synchronous speed relationship; monitoring and controlling the pressure ratio matching between the axial-flow compressor assembly and the centrifugal compressor components to prevent compressor stall or surge; SS5. After reaching the designed operating speed, thrust output is precisely controlled by adjusting fuel flow. The compressor status is monitored to ensure the two-stage compression system operates near its optimal efficiency point. Power output is controlled by load regulation of the internal generator. SS6. Continuously monitor the operating status of the fuel and lubricating oil combination pump to ensure stable fuel pressure and effective circulation of the lubrication system. Use speed and temperature sensors to monitor the operating parameters of each rotating component in real time. When abnormal operating conditions are detected, promptly adjust the control strategy to ensure safe and reliable operation of the propulsion power unit.

11. The method for operating the axial-centrifugal composite turbojet propulsion power plant based on coupling according to claim 10, characterized in that: In step SS1, the startup sequence initialization control process includes a pre-start system check phase, which first performs an engine status self-check, including checking the bearing lubrication status, fuel system pressure, electrical system connection status, and static balance status of the rotor system; When the built-in generator switches to motor mode, a progressive torque output control strategy is adopted by setting the target starting speed curve. Initially, the engine starts with a lower torque to reduce the impact load on the coupling and rotor system, and then gradually increases the torque output until the preset starting speed establishment rate is reached.

Images