Adjustable tandem fan structure capable of realizing continuous wide-speed-range operation of propulsion system

Abstract

The application discloses a kind of adjustable tandem fan structures that can realize the continuous wide speed range operation of propulsion system, for optimizing the efficiency of propulsion system under the condition of variable incoming flow, including tandem rotor and tandem stator, tandem rotor includes rotor front blade and rotor rear blade, these blades are designed as adjustable angle, to adapt to different incoming flow speed from subsonic to supersonic speed.The stator also includes stator front blade and stator rear blade with variable camber, wherein the adjustable angle of stator front blade and the variable camber of stator rear blade further optimize airflow guide, ensure that the fan outlet airflow angle is close to axial, reduce energy loss.The fan of the application can directly accept wide speed range incoming flow, significantly shorten the length of inlet duct, reduce the structure mass of engine, solve the problem of "dead weight" of traditional fan in hypersonic flight state, while ensuring high efficiency and margin in full speed range, effectively solve the technical problem of fan low-speed starting and accelerating in prior art.

Description

Technical Field

[0001] This invention belongs to the field of compressor technology for aero-engine systems, and relates to the design of fans / compressors in propulsion systems. Specifically, it relates to an adjustable tandem fan structure that enables continuous wide-speed-range operation of the propulsion system. By adjusting the blade angle, it can adapt to different incoming flow conditions from subsonic to supersonic speeds, thereby achieving continuous wide-speed-range operation of the propulsion system and optimizing the performance and efficiency of the propulsion system. Background Technology

[0002] In modern aero-engine systems, fans / compressors, as key components of the propulsion system, are widely used in various types of aero-engines, such as combined-spindle engines and ATR engines, to assist in starting and acceleration, and to provide necessary aerodynamic support for the propulsion system under various flight conditions. During different flight phases of an aircraft, the efficiency of the fan / compressor directly affects the performance and energy efficiency of the propulsion system.

[0003] However, most current fans / compressors can only accept axial subsonic incoming air. Therefore, in order to bring the incoming air to this speed range, a long air intake is usually required to reduce the incoming air to subsonic speed. The large size and low efficiency of the air intake have become important factors restricting engine development. At the same time, when a propulsion system similar to a combined engine enters hypersonic flight, the fan will no longer work, which will lead to the problem of "dead weight" in the propulsion system.

[0004] In recent years, with the continuous development of aviation technology, the single-stage boosting capacity of fans has been continuously improved, and the number of stages has been continuously reduced. This has also become one of the research directions for reducing the structural weight of fans. However, with the development of active / passive control technology, the potential of traditional fans will be pushed to its limit, and the weight reduction benefits brought by fan pressure ratio will tend to a threshold. To overcome these limitations, existing technologies have proposed ultrasonic flow fans (such as...) Figure 1 As shown in the diagram (1 is the supersonic inlet, 2 is the single-stage fan, and 3 is the core engine), this type of fan can directly accept axial supersonic airflow, thus eliminating the need for a longer inlet and reducing the structural weight of the propulsion system. Its inlet Mach number reaches over Mach 2, giving it extremely strong work-capability. However, like traditional turbofan engines, the inlet Mach number of turbine engines equipped with this fan structure is still limited to below Mach 3.5.

[0005] To achieve higher flight speeds, existing technologies, building upon ultrasonic flow fan technology, have proposed the concept of adjustable tandem blades (such as...). Figure 2As shown in Figures (a) to (c), which correspond to the transonic mode, supersonic flow mode, and high-speed windmill mode, respectively, this design aims to achieve continuous operation of the advanced propulsion system across a wide speed range. This design seeks to adapt to different incoming flow conditions by adjusting the blade angle and position, thereby improving the fan's adaptability and efficiency. However, existing adjustable tandem blade schemes still have significant limitations. In particular, because the trailing blade is not adjustable, it operates at a maximum positive angle of attack during transonic operation, causing flow separation at the suction front edge of the trailing blade, resulting in flow blockage, extremely high losses, and difficulty in achieving reliable operation, thus reducing the feasibility of this scheme.

[0006] In summary, while the solutions proposed in the existing technologies are theoretically forward-looking, they still face challenges in practical applications, such as the angle-of-attack mismatch caused by the non-adjustable rotor trailing blades and the inability of supersonic fans to fully adapt to different incoming flow conditions. Therefore, to address the limited range of acceptable incoming flow for traditional turbine engine fans, and the fact that most traditional fans can only accept axial subsonic incoming flow and require longer inlets, as well as to resolve the angle-of-attack mismatch caused by the non-adjustable rotor trailing blades in the original adjustable tandem blade design under transonic modes, it is necessary to further explore and develop adjustable tandem blade structures that adapt to different incoming flow conditions. This would enable the propulsion system to operate continuously across a wider speed range, meeting the needs of future aero-engine systems. Summary of the Invention

[0007] (I) Purpose of the Invention

[0008] To address the shortcomings of existing propulsion systems, such as insufficient adaptability of fans / compressors across different flight speed ranges, the need for long inlets to accommodate axial subsonic inflow leading to "dead weight" issues during hypersonic flight, and the non-adjustable rear blades of rotors and stators in existing adjustable tandem fans (resulting in mismatches between the airflow angle and geometry of the rear blades under various operating conditions), this invention proposes an adjustable tandem fan structure capable of continuous wide-speed-range operation of the propulsion system. This structure utilizes an adjustable front blade-adjustable rear blade rotor and an adjustable front blade-variable camber rear blade stator. The adjustable front blade adapts to inflow at different speeds to ensure the inlet operates at the optimal angle of attack. The adjustable rear blade further matches the front blade, ensuring the rear blade also operates near the optimal angle of attack, preventing significant flow separation due to angle-of-attack mismatch. Simultaneously, the variable camber design ensures the stator outlet remains close to the axial direction. The adjustable tandem fan layout of the present invention can balance the blade geometry requirements under different incoming flow conditions, realize the continuous wide speed range operation of the advanced propulsion system, and also ensure the fan's pressurization capability in subsonic, transonic and supersonic flow modes, as well as the function similar to the air intake in high-speed windmill mode, so that the fan can play a role in the full speed range and has extremely high application potential.

[0009] (II) Technical Solution

[0010] To achieve the objective of this invention and solve its technical problems, the present invention adopts the following technical solution:

[0011] The first objective of this invention is to provide an adjustable tandem fan structure capable of continuous wide-speed-range operation of a propulsion system, used to ensure effective operation of the propulsion system under varying incoming flow conditions, comprising at least a tandem rotor disposed on the upstream side and a tandem stator disposed on the downstream side, wherein:

[0012] The tandem rotors are located at the fan inlet and include at least a front rotor blade and a rear rotor blade arranged adjacent to each other in the meridional direction. Each front rotor blade and each rear rotor blade are configured with an adjustable blade installation angle. The blade installation angle of the front rotor blade is adjusted to adapt to different inflow conditions at the fan inlet, and the blade installation angle of the rear rotor blade is adjusted to match the airflow angle at the outlet of the front rotor blade.

[0013] The tandem stators are located downstream of the tandem rotor and include at least a stator front blade and a stator rear blade arranged adjacent to each other in the meridional direction. Each stator front blade is configured with an adjustable blade installation angle, and each stator rear blade is configured with a variable camber. The blade installation angle of the stator front blade is adjusted to match the airflow angle at the outlet of the tandem rotor, and the camber of the stator rear blade is adjusted to match the airflow angle at the outlet of the stator front blade, ensuring that the airflow angle at the fan outlet remains near the axial direction.

[0014] Preferably, the tandem rotor is further provided with an independent rotor front blade installation angle adjustment mechanism and a rotor rear blade installation angle adjustment mechanism. The rotor front blade changes its blade installation angle within a preset range through its adjustment mechanism to adapt to different incoming flow conditions at the fan inlet. The rotor rear blade changes its blade installation angle within a preset range through its adjustment mechanism to achieve matching with the airflow angle at the rotor front blade outlet.

[0015] Furthermore, the tandem stator is also provided with a stator front blade installation angle adjustment mechanism and a stator rear blade curvature adjustment mechanism. The stator front blade changes its blade installation angle within a preset range through its adjustment mechanism to match the airflow angle at the outlet of the tandem rotor. The stator rear blade changes its blade curvature within a preset range through its adjustment mechanism to match the airflow angle at the outlet of the stator front blade, and ensures that the airflow angle at the fan outlet remains near the axial direction.

[0016] Preferably, the high-speed wind turbine mode with a fan operating Mach number of 3.5 or higher is the mode corresponding to the design point, and the blade profile design of each blade in the tandem rotor and tandem stator will comprehensively consider the performance requirements under each mode.

[0017] Furthermore, in the tandem rotor, the front blades of each rotor adopt a transonic small-angle blade profile to reduce shock wave loss and adapt to transonic operating conditions, while the rear blades of each rotor adopt a large-angle blade profile to ensure the fan's power-adding capacity under supersonic flow mode.

[0018] Furthermore, in the tandem stators, the front and rear blades of each stator adopt a small bend angle blade profile, and the bend angle ratio is arbitrarily allocated according to the flow channel requirements under the high-speed wind turbine mode, so as to ensure that the flow channel of each blade in the tandem stator can be approximately straight under the high-speed wind turbine mode, thereby reducing the aerodynamic losses under this mode.

[0019] Furthermore, in the transonic mode, the fan operates at Mach number between 0.8 and 1.6. At this time, the tandem rotor and tandem stator significantly adjust each blade through the adjustment mechanism, so that after adjusting the installation angle of each blade of the rotor front blade, the relative airflow angle at the rotor inlet is relatively large. The rotor front blade utilizes its transonic airfoil to minimize aerodynamic losses while keeping the airflow speed down to subsonic. After adjusting the installation angle of each blade of the rotor rear blade and stator front blade, the decelerated subsonic incoming flow completes further deceleration and diffusion of the airflow after passing through the rotor rear blade. The stator front blade ensures that the airflow can be reduced to subsonic speed again. The camber of the stator rear blade is adjusted to ensure that the airflow turns to the axial direction at the stator rear blade to maintain an effective diffusion and rectification process.

[0020] Furthermore, in the ultrasonic flow mode, the fan operates at a Mach number between 1.5 and 3.5. At this time, the tandem rotor and tandem stator adjust each blade slightly through the adjustment mechanism. The rotor trailing blade is based on its large camber angle airfoil to adapt to the large airflow turning angle requirement of the high Mach number incoming flow and ensure the fan's work capacity in the ultrasonic flow mode. The camber of the stator trailing blade is adjusted to ensure that the airflow turns to the axial direction at the stator trailing blade and further reduces aerodynamic losses during the turning process to the axial direction.

[0021] Furthermore, in the high-speed wind turbine mode, the fan operates at a Mach number above 3.5. At this time, the tandem rotor and tandem stator adjust each blade slightly through the adjustment mechanism, so that the tandem rotor and tandem stator form a nearly straight direct flow channel, thus playing a role similar to an air intake. When the gas enters the tandem rotor blade channel, the rotor does almost no work or only a small amount of work on the gas. When the gas enters the tandem stator blade channel, no deceleration and diffusion occur, and there is a low aerodynamic loss.

[0022] The second objective of this invention is to provide a propulsion system, characterized in that the propulsion system is provided with the adjustable tandem fan structure provided in the first objective of this invention.

[0023] (III) Technical Effects

[0024] Compared with existing technologies, the adjustable tandem fan proposed in this invention, which enables continuous wide-speed-range operation of advanced propulsion systems, has the following beneficial and significant technical effects:

[0025] (1) The adjustable tandem fan structure of the present invention enables the fan to directly adapt to incoming flow conditions over a wide speed range. The fan rotor of the present invention adopts an adjustable front blade-adjustable rear blade layout, and the fan stator blades adopt an adjustable front blade-variable camber rear blade layout. The adjustable front and rear blade design of the present invention allows for dynamic adjustment of the blade angle at various stages of the aircraft from subsonic to supersonic speeds to adapt to different incoming flow conditions and achieve optimal aerodynamic performance across the entire flight speed range. This structure allows the fan to directly accept incoming flow over a wide speed range, eliminating the need for a long air intake, thereby significantly shortening the air intake length, reducing structural complexity, and resulting in a reduction in engine structural weight.

[0026] (2) The adjustable tandem fan of the present invention can operate across the entire speed range of the engine, solving the problem of "dead weight" of the fan. In traditional propulsion systems, the fan often fails to function under hypersonic flight conditions, becoming an ineffective weight in the system. However, the adjustable tandem fan structure of the present invention can work effectively at all speed stages, including hypersonic cruise, through adjustable blades, avoiding ineffective loads in any flight state. This is of great significance for improving propulsion efficiency and reducing energy consumption.

[0027] (3) This invention significantly improves the adaptability and efficiency of the propulsion system under different flight conditions. Although existing advanced propulsion systems can achieve cruise flight at high Mach numbers, their low-speed start-up and acceleration process is a major technical challenge. The adjustable tandem fan used in this invention can directly accept a wide range of incoming flow, meeting the performance requirements of the fan under different incoming flow conditions, and ensuring the high efficiency and margin of the propulsion system fan across the entire speed range from ground to hypersonic speeds.

[0028] (4) The adjustable tandem fan structure of the present invention optimizes aerodynamic performance at different flight speeds by precisely controlling the angle and camber of the rotor and stator blades. In subsonic, transonic, supersonic and even hypersonic flight states, the adjustable blade design enables effective control and compression of airflow, improves propulsion efficiency and reduces energy loss. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of an existing ultrasonic flow fan engine.

[0031] Figure 2The diagram shows an existing adjustable tandem blade scheme, where the front blade is adjustable and the rear blade is not. (a) shows the transonic mode, (b) shows the supersonic flow mode, and (c) shows the high-speed wind turbine mode.

[0032] Figure 3 This is a schematic diagram of the adjustable tandem fan layout and speed triangle (transonic mode) of the present invention;

[0033] Figure 4 This is a schematic diagram of the adjustable tandem fan layout and velocity triangle (ultrasonic flow mode) of the present invention;

[0034] Figure 5 This is a schematic diagram of the adjustable tandem fan layout and speed triangle of the present invention (high-speed windmill mode).

[0035] Explanation of reference numerals in the attached figures:

[0036] 1-Supersonic air intake, 2-Single-stage fan, 3-Core engine, 11-Rotor front blade, 12-Rotor rear blade, 21-Stator front blade, 22-Stator rear blade. Detailed Implementation

[0037] To better understand the present invention, the following embodiments further illustrate its content. Throughout the accompanying drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions. The described embodiments are some, but not all, of the embodiments of the present invention. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The structure and technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings, providing one embodiment of the present invention.

[0038] This invention discloses an adjustable tandem fan structure that enables continuous wide-speed-range operation of a propulsion system. It is used to optimize the efficiency of the propulsion system under varying incoming flow conditions. It can directly accept wide-speed-range incoming flow, significantly shorten the intake length, reduce the engine structural mass, solve the "dead weight" problem of traditional fans in hypersonic flight, and at the same time ensure high efficiency and margin in the full speed range. It effectively solves the technical problem of low-speed start-up and acceleration of fans in the prior art.

[0039] As a specific example, such as Figures 3-5As shown, the adjustable tandem fan structure of the present invention, which enables continuous wide-speed-range operation of the propulsion system, includes a tandem rotor on the upstream side and a tandem stator on the downstream side. The tandem rotor is located at the fan inlet and includes a rotor front blade 11 and a rotor rear blade 12 arranged adjacent to each other in the meridional direction. Each rotor front blade and each rotor rear blade is configured with an adjustable blade installation angle. By adjusting the blade installation angle of the rotor front blade, different inflow conditions at the fan inlet are adapted; by adjusting the blade installation angle of the rotor rear blade, the airflow angle at the rotor front blade outlet is matched. The tandem stator is located downstream of the tandem rotor and includes a stator front blade 21 and a stator rear blade 22 arranged adjacent to each other in the meridional direction. Each stator front blade is configured with an adjustable blade installation angle, and each stator rear blade is configured with a variable camber. By adjusting the blade installation angle of the stator front blade, the airflow angle at the tandem rotor outlet is matched; by adjusting the camber of the stator rear blade, the airflow angle at the stator front blade outlet is matched, ensuring that the airflow angle at the fan outlet remains near the axial direction.

[0040] In the adjustable tandem fan structure of this invention, by setting an adjustable front blade-adjustable rear blade rotor and an adjustable front blade-variable camber rear blade stator, the adjustable front blade can adapt to incoming flow at different speeds to achieve the optimal angle of attack at the inlet. The adjustable rear blade is further matched with the front blade to ensure that the rear blade also operates near the optimal angle of attack, preventing significant flow separation due to mismatch in angle of attack. Simultaneously, the variable camber design ensures that the stator outlet is close to the axial direction. This adjustable tandem fan layout can balance the blade geometry requirements under different incoming flow conditions, enabling continuous wide-speed-range operation of advanced propulsion systems. It also ensures the fan's pressurization capability in subsonic, transonic, and supersonic flow modes, as well as its function similar to an inlet in high-speed windmill mode, allowing the fan to function effectively across the entire speed range.

[0041] In the adjustable tandem fan structure of this invention, the rotor employs adjustable front blades to adapt to different inflow conditions at the fan inlet; the rotor's rear blades employ an adjustable structure to match the airflow angle at the front blade outlet. The stator employs adjustable front blades to match the airflow angle at the rotor outlet; the stator's rear blades employ variable camber rear blades, which can both match the airflow angle at the stator's front blade outlet and keep the fan outlet airflow angle near the axial direction. As the advanced propulsion system starts from the ground and enters hypersonic cruise mode, the rotor and stator blades of the adjustable tandem fan rotate to different installation angles through their adjustable structures, sequentially adapting to and experiencing subsonic mode, transonic mode, supersonic flow mode, and high-speed windmill mode (at which point the engine enters hypersonic cruise mode), thereby achieving the purpose of continuous wide-speed-range operation of this invention.

[0042] When the fan operates at Mach 3.5 or higher, it enters the high-speed windmill mode. This mode corresponds to the design point, and the adjustable tandem fan rotor and stator blades are designed based on this mode. The rotor's leading blade is designed as a transonic airfoil (small bend angle) to adapt to performance under transonic conditions. The rotor's trailing blade is designed as a large bend angle blade to ensure the fan's work capacity under the supersonic flow mode. The stator tandem blades adopt a small bend angle design (the bend angle ratio can be arbitrarily allocated), thus ensuring that the flow path of the stator tandem blades is approximately straight under the high-speed windmill mode, reducing aerodynamic losses in this mode. When gas enters the blade passage, the rotor does almost no work or only a small amount of work on the gas, functioning similarly to an air intake.

[0043] When the fan operates at a Mach number between 1.5 and 3.5, and the axial component of the Mach number is supersonic, it enters the supersonic flow mode. At this time, the rotor and stator blades rotate slightly. In the supersonic flow mode, the incoming flow Mach number is high, therefore the throat Mach number is greater than 1, and the airflow accelerates within the expansion channel. The large bend angle design of the rotor's rear blades ensures the large airflow turning angle required in the supersonic flow mode, giving the fan extremely strong acceleration capability in this mode to increase the kinetic energy of the airflow.

[0044] When the fan operates at Mach 0.8-1.5, and the axial component of the Mach number is subsonic, it enters the transonic mode. At this time, the rotor and stator blades rotate significantly. At the design pressure ratio for the transonic mode, the airflow passes through the rotor's adjustable front blade, and is reduced to subsonic speed by the leading-edge bow shock wave and the normal shock wave flow within the channel. Due to the transonic airfoil design, the rotor's adjustable front blade does not incur high losses during this process. The subsonic flow passes through the rotor's rear blade, completing the deceleration and diffusion of the airflow. Finally, the flow passes through the stator for further diffusion and rectification.

[0045] like Figures 3-5 The blade arrangement and velocity triangle distribution of a medium-adjustable tandem fan under different operating modes, in transonic modes (such as...) Figure 3 As shown, the flow inside the rotor is similar to that of a conventional transonic tandem blade. The relative airflow angle at the rotor inlet is relatively large. As the flow enters the front blade, it forms a leading-edge bow shock wave and a channel shock wave, reducing the relative velocity to subsonic. The subsonic airflow is further decelerated and diffused through the rear blade. The flow enters the stator at subsonic speed (potentially generating a local ultrasonic region, but it can be reduced to subsonic again at the front blade). The stator rear blade bend angle increases, and as the flow progresses downstream, the airflow is further decelerated and turns axially at the rear blade.

[0046] In ultrasonic flux modes (such as...) Figure 4 As shown), the large bend angle of the rotor's rear blades ensures the rotor's added power in this mode. The flow in the channel completes the turning through the shock wave system and enters the stator at supersonic speed. The bend angle of the stator's rear blades increases, and it further completes the turning through the shock wave system in the stator to the axial direction.

[0047] In high-speed windmill mode (e.g.) Figure 5 As shown, the rotor's front and rear blades form a "direct flow path," meaning the flow within the rotor experiences almost no deflection or deceleration. Therefore, the rotor's ability to perform work on the airflow is very weak, or even nonexistent. The flow then enters the stator, where the rear blade angle remains unchanged, forming an approximately direct flow path. The airflow in the stator experiences almost no deceleration or diffusion. Combining these two points, in high-speed windmill mode, the fan functions similarly to an air intake. This fan blade layout can meet the performance requirements of the fan under different incoming flow conditions, thus ensuring high efficiency and margin for advanced propulsion system fans across a wide speed range. Simultaneously, the fan is no longer a component for starting and accelerating at low speeds, but rather operates across the entire speed range of the propulsion system, solving the "dead weight" problem of the fan under hypersonic flight conditions.

[0048] In summary, the adjustable tandem fan structure of this invention, through its innovative adjustable blade design, achieves efficient operation of the propulsion system across a wide speed range, effectively solving the "dead weight" problem of traditional fans in hypersonic conditions and improving performance across the entire speed range. This structure not only reduces the weight and size of the engine but also enhances its adaptability to varying incoming flow conditions, meeting the future demands of aerospace propulsion systems for high performance, high adaptability, and wide speed range operation. It possesses significant practical value and broad application prospects.

[0049] The objectives of this invention have been fully and effectively achieved through the above embodiments. Those skilled in the art will understand that this invention includes, but is not limited to, the contents described in the accompanying drawings and the specific embodiments described above. Although the invention has been described with reference to what is currently considered the most practical and preferred embodiments, it should be understood that the invention is not limited to the disclosed embodiments, and any modifications that do not depart from the functional and structural principles of the invention will be included within the scope of the claims.

Claims

1. An adjustable tandem fan structure capable of continuous wide-speed-range operation of a propulsion system, used to ensure effective operation of the propulsion system under varying incoming flow conditions, comprising at least a tandem rotor disposed on the upstream side and a tandem stator disposed on the downstream side, characterized in that: The tandem rotors are located at the fan inlet and include at least rotor front blades and rotor rear blades arranged adjacent to each other in the meridional direction. Each rotor front blade and each rotor rear blade are configured with an adjustable blade installation angle. By adjusting the blade installation angle of the rotor front blade, different inflow conditions at the fan inlet can be adapted. By adjusting the blade installation angle of the rotor rear blade, the airflow angle at the rotor front blade outlet can be matched. Furthermore, each rotor front blade adopts a transonic small-angle blade profile to reduce shock wave loss and adapt to transonic conditions, and each rotor rear blade adopts a large-angle blade profile to ensure the fan's work capacity in the supersonic flow mode. The tandem stators are located downstream of the tandem rotor and include at least stator front and rear blades arranged adjacent to each other in the meridional direction. Each stator front blade is configured with an adjustable blade installation angle, and each stator rear blade is configured with a variable camber. By adjusting the blade installation angle of the stator front blade, the airflow angle at the outlet of the tandem rotor is matched. By adjusting the camber of the stator rear blade, the airflow angle at the outlet of the stator front blade is matched, ensuring that the airflow angle at the fan outlet remains near the axial direction. Furthermore, each stator front and rear blade adopts a small camber angle blade profile, and the camber ratio is arbitrarily allocated according to the flow channel requirements under the high-speed wind turbine mode, so as to ensure that the flow channel of each blade of the tandem stator forms an approximately straight shape under the high-speed wind turbine mode, thereby reducing the aerodynamic losses under this mode.

2. The adjustable tandem fan structure for realizing continuous wide-speed-range operation of a propulsion system according to claim 1, characterized in that, The tandem rotor is also provided with an independent rotor front blade installation angle adjustment mechanism and a rotor rear blade installation angle adjustment mechanism. The rotor front blade changes its blade installation angle within a preset range through its adjustment mechanism to adapt to different incoming flow conditions at the fan inlet. The rotor rear blade changes its blade installation angle within a preset range through its adjustment mechanism to achieve matching with the airflow angle at the rotor front blade outlet.

3. The adjustable tandem fan structure for realizing continuous wide-speed-range operation of the propulsion system according to claim 2, characterized in that, The tandem stator is also equipped with a stator front blade installation angle adjustment mechanism and a stator rear blade curvature adjustment mechanism. The stator front blade changes its blade installation angle within a preset range through its adjustment mechanism to match the airflow angle at the outlet of the tandem rotor. The stator rear blade changes its blade curvature within a preset range through its adjustment mechanism to match the airflow angle at the outlet of the stator front blade, and ensures that the airflow angle at the fan outlet remains near the axial direction.

4. The adjustable tandem fan structure for realizing continuous wide-speed-range operation of the propulsion system according to claim 3, characterized in that, The high-speed wind turbine mode with a fan operating Mach number of 3.5 or higher is the design point corresponding mode. The blade profile design of each blade in the tandem rotor and tandem stator will comprehensively consider the performance requirements under each mode.

5. The adjustable tandem fan structure for realizing continuous wide-speed-range operation of the propulsion system according to claim 4, characterized in that, In transonic mode, the fan operates at Mach numbers between 0.8 and 1.

6. At this time, the tandem rotor and tandem stator significantly adjust each blade through the adjustment mechanism, so that after adjusting the installation angle of each blade of the rotor front blade, the relative airflow angle at the rotor inlet is relatively large. The rotor front blade reduces the incoming flow to subsonic speed through the leading edge shock wave and the normal shock wave in the channel. By using transonic airfoils, aerodynamic losses can be minimized while maintaining the airflow speed at subsonic speed. After adjusting the installation angle of each blade of the rotor rear blade and stator front blade, the subsonic incoming flow after deceleration completes further deceleration and diffusion of the airflow after passing through the rotor rear blade. The stator front blade ensures that the airflow can be reduced to subsonic speed again. The camber of the stator rear blade is adjusted to ensure that the airflow turns to the axial direction at the stator rear blade to maintain an effective diffusion and rectification process.

6. The adjustable tandem fan structure for realizing continuous wide-speed-range operation of a propulsion system according to claim 4, characterized in that, In the ultrasonic flow mode, the fan operates at a Mach number between 1.5 and 3.

5. At this time, the tandem rotor and tandem stator adjust each blade slightly through the adjustment mechanism. The rotor trailing blade is based on its large camber angle airfoil to adapt to the large airflow turning angle requirement of the high Mach number incoming flow and ensure the fan's work capacity in the ultrasonic flow mode. The camber of the stator trailing blade is adjusted to ensure that the airflow turns to the axial direction at the stator trailing blade and further reduces aerodynamic losses during the turning process to the axial direction.

7. The adjustable tandem fan structure for realizing continuous wide-speed-range operation of a propulsion system according to claim 4, characterized in that, In the high-speed wind turbine mode, the fan operates at a Mach number above 3.

5. At this time, the tandem rotor and tandem stator adjust each blade slightly through the adjustment mechanism, so that the tandem rotor and tandem stator form a nearly straight direct flow channel, which plays a similar role to the air intake channel. When the gas enters the tandem rotor blade channel, the rotor does almost no work or a small amount of work on the gas. When the gas enters the tandem stator blade channel, there is no deceleration and diffusion and there is low aerodynamic loss.

8. A propulsion system, characterized in that, The propulsion system is provided with the adjustable tandem fan structure as described in any one of claims 1 to 7.

Images