An adjustable stator vane in an aircraft engine inlet casing and its design method

Abstract

This application belongs to the technical field of aircraft engine inlet casing design, and specifically relates to an adjustable stator vane in an aircraft engine inlet casing and its design method. Among them, the adjustable stator vane in the aircraft engine inlet casing includes a blade body, an upper journal and a lower journal connected to the blade body; the blade body includes an inner load-bearing structure and an outer wave-absorbing layer; the inner load-bearing structure is a plate-like structure; the outer wave-absorbing layer is coated on the outside of the inner load-bearing structure and is made of a material with wave-absorbing ability; the material with wave-absorbing ability can be a composite material with wave-absorbing ability or a wave-absorbing coating; the material types and thickness distributions at different positions of the outer wave-absorbing layer are different, so that the radar wave-absorbing abilities at different positions of the adjustable stator vane are different, so as to be able to match the tasks performed by the aircraft and specifically absorb the radar waves with low detectability requirements.

Description

Technical Field

[0001] This application belongs to the technical field of aircraft engine inlet casing design, and specifically relates to an adjustable stator vane in an aircraft engine inlet casing and its design method. Background Art

[0002] The engine is the main power source of the aircraft and also an important radar reflection source of the aircraft. To reduce the detectability of the aircraft, relevant designs are usually carried out on the engine inlet casing, mainly using the following three technical solutions.

[0003] Solution 1:

[0004] An absorbing coating with the function of absorbing radar waves is coated on the inner and outer flow path surfaces of the engine inlet casing and the outside of the struts.

[0005] Within the flight envelope, when the aircraft performs different tasks, the requirements for detectability are different, and the targeted radar bands are different. To ensure the low detectability of the aircraft within the full flight envelope, the absorbing coating needs to be able to absorb radar waves within a relatively wide band, and also needs to meet requirements such as strength and bonding force. The design update is difficult, the price is high, the engineering implementation is difficult, and the absorbing coating usually has a large density. Extensive use will significantly increase the weight of the engine, reduce the engine inlet flow rate, affect the aerodynamic performance of the engine, resulting in a reduction in engine thrust and affecting the thrust-to-weight ratio of the engine.

[0006] Solution 2:

[0007] An absorbing waveguide fluid that can absorb radar waves is provided in the aircraft inlet duct at the front end of the engine inlet casing.

[0008] The absorbing waveguide fluid has a complex structure and large size and weight, which will cause significant losses in many key indicators of the engine such as weight, size, and thrust. In addition, the absorbing waveguide fluid is provided at a certain axial distance at the front end of the engine, which affects the compact design of the engine, will greatly increase the distance from the inspection and maintenance operation position at the front end of the engine to the first-stage rotor of the fan, greatly increasing the difficulty of inspecting and maintaining the fan, and increasing the required axial space for engine installation. This not only affects the space utilization of the aircraft equipped, but also severely restricts the universality of the engine for different types of aircraft, and will greatly affect the reduction of the flow field quality at the engine inlet, increasing the aerodynamic loss of the engine, affecting the thrust of the engine, and reducing the thrust-to-weight ratio of the engine.

[0009] Solution 3:

[0010] An S-shaped inlet duct coated with an absorbing coating is added at the front end of the engine inlet casing, and the S-shaped inlet duct is used to refract and absorb radar waves repeatedly.

[0011] The S-bend inlet is arranged at the front end of the engine inlet casing. It also has relatively large size and weight, which will cause significant losses in many key indicators of the engine such as weight, size, and thrust, affect the compact design of the engine, greatly increase the distance from the inspection and maintenance operation position at the front end of the engine to the first-stage rotor of the fan, extremely increase the difficulty of inspecting and maintaining the fan, and bring an increase in the axial space required for engine installation. This not only affects the space utilization of the equipped aircraft but also severely limits the universality of the engine for different types of aircraft. Moreover, due to its complex bending structure, it will seriously affect the flow field quality at the engine inlet, increase the aerodynamic losses of the engine, affect the thrust of the engine, and reduce the thrust-to-weight ratio of the engine.

[0012] The above three technical solutions are of fixed structure design and cannot adaptively adjust the absorption of radar waves in corresponding bands according to the tasks performed by the aircraft. To ensure the low detectability requirements within the full flight envelope of the aircraft, it is only possible to take into account all possible radar bands and their required levels as much as possible. In this way, over-design for detectability often occurs. For example, the thickness of the radar-absorbing coating is relatively thick, the axial length of the radar-absorbing fluid guide is relatively long, and the bending degree of the S-bend inlet is relatively large, etc., which further exacerbates the technical problems.

[0013] In view of the existence of the above technical defects, this application is proposed. Summary of the Invention

[0014] The purpose of this application is to provide an adjustable stator vane in the engine inlet casing of an aircraft and its design method to overcome or mitigate at least one aspect of the known technical defects.

[0015] The technical solution of this application is as follows:

[0016] On the one hand, an adjustable stator vane in the engine inlet casing of an aircraft is provided, which includes a blade body, and an upper journal and a lower journal connected to the blade body;

[0017] The blade body includes an inner load-bearing structure and an outer radar-absorbing layer;

[0018] The inner load-bearing structure is a plate-like structure;

[0019] The outer radar-absorbing layer is coated on the outside of the inner load-bearing structure and is made of a material with radar-absorbing ability;

[0020] The material with radar-absorbing ability is a composite material with radar-absorbing ability or a radar-absorbing coating;

[0021] The material types and thickness distributions at different positions of the outer radar-absorbing layer are different, so that the radar-absorbing abilities at different positions of the adjustable stator vane are different, so as to be able to match the tasks performed by the aircraft and specifically absorb the radar waves with low detectability requirements.

[0022] Optionally, in the adjustable stator vanes in the aircraft engine inlet casing described above, the inner load-bearing structure is made of fiber-reinforced composite material or lightweight metal material.

[0023] Optionally, in the adjustable stator vanes in the aircraft engine inlet casing described above, the upper journal and the lower journal are connected to the inner load-bearing structure.

[0024] Optionally, in the adjustable stator vanes in the aircraft engine inlet casing described above, the upper journal and the lower journal are made of the same material as the inner load-bearing structure and are integrally formed on the inner load-bearing structure.

[0025] On the other hand, a design method for the adjustable stator vanes in the aircraft engine inlet casing is provided, which is used to design the adjustable stator vanes in the aircraft engine inlet casing described above, including:

[0026] Step 1: Preliminarily design the vane profile of the adjustable stator vane and its adjustment angle.

[0027] Step 2: Analyze the requirements for low observability of the aircraft performing various tasks within the flight envelope, including the radar bands targeted by low observability and their required levels.

[0028] Step 3: Identify the adjustment angles of the adjustable stator vanes when the aircraft performs various tasks, and then determine the corresponding low observability requirements.

[0029] Step 4: Design the material types and thickness distributions at different positions of the outer wave-absorbing layer according to the adjustment angles of the adjustable stator vanes and the corresponding low observability requirements.

[0030] Step 5: Analyze whether the detectability of each adjustable stator vane adjustment angle under the engine operating conditions under the whole aircraft conditions meets the corresponding low observability requirements.

[0031] If there is a situation where the detectability of the adjustable stator vane adjustment angle under the engine operating conditions does not meet the corresponding low observability requirements, then optimize the vane profile of the adjustable stator vane and its adjustment angle, and repeat Steps 3 to 5 until the detectability of each adjustable stator vane adjustment angle under the engine operating conditions meets the corresponding low observability requirements.

[0032] The present application has at least the following beneficial technical effects:

[0033] The adjustable stator vane in the aircraft engine inlet casing and its design method disclosed in the above embodiments utilize the tasks performed by the aircraft within the flight envelope, the radar bands targeted by its low detectability and the required levels, the engine operating conditions, and the one-to-one correspondence between the adjustment angles of the adjustable stator vane in the inlet casing and the reflection paths of radar waves. The adjustable stator vane is designed to have radar wave absorbing capabilities, and the radar wave absorbing capabilities at different positions are different. It can be realized that within the entire flight envelope, according to the tasks performed by the aircraft, the absorption of radar waves with requirements for low detectability can be adjusted specifically and reach the level of low detectability requirements, thereby reducing the requirements for the related designs of the existing inlet casing, avoiding over-design for detectability, and achieving the purpose of reducing the severity of related technical problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 FIG. is a schematic diagram of the radar wave reflection path when the adjustable stator vane in the aircraft engine inlet casing provided by the embodiment of the present application is at the open angle;

[0035] Figure 2 FIG. is a schematic diagram of the radar wave reflection path when the adjustable stator vane in the aircraft engine inlet casing provided by the embodiment of the present application is at the closed angle;

[0036] Figure 3 FIG. is a schematic diagram of the adjustable stator vane in the aircraft engine inlet casing provided by the embodiment of the present application;

[0037] Figure 4 FIG. is a schematic cross-sectional view of the blade body provided by the embodiment of the present application;

[0038] Figure 5 FIG. is a schematic diagram of the design method of the adjustable stator vane in the aircraft engine inlet casing provided by the embodiment of the present application;

[0039] Wherein:

[0040] 1 - blade body; 2 - upper journal; 3 - lower journal;

[0041] 11 - inner load-bearing structure; 12 - outer radar wave absorbing layer.

[0042] For better illustrating this embodiment, some contents in the drawings are omitted, enlarged or reduced, and are only used for exemplary illustration and should not be construed as a limitation to the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] To make the technical solutions and their advantages of this application clearer, the following will further clearly and completely describe the technical solutions of this application in conjunction with the accompanying drawings. It can be understood that the specific embodiments described herein are only partial embodiments of this application, which are only used to explain this application and not to limit this application. It should be noted that for the convenience of description, only the parts related to this application are shown in the drawings, and other related parts can refer to the general design.

[0044] In addition, unless otherwise defined, the technical terms or scientific terms used in the description of this application should be the ordinary meanings understood by those of ordinary skill in the art to which this application belongs. The "including" used in the description of this application means that the concept appearing before this word covers the concepts listed after this word and their equivalents, without excluding other related concepts.

[0045] In addition, the words indicating directions used in the description of this application are only used to indicate relative directions or positional relationships. When the absolute position of the object being described changes, its relative positional relationship may also change accordingly. It should also be noted that unless otherwise clearly specified and limited, the terms such as "installation" and "connection" used in the description of this application should be understood in a broad sense. For example, connection can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. Those skilled in the art can understand their specific meanings in this application according to the specific situation.

[0046] Within the flight envelope, when the aircraft performs different tasks, its low detectability targets different radar bands, and the requirements for detectability are different. For example, when the aircraft performs a cruise mission, its low detectability mainly targets radar waves in the low-frequency band and has relatively high requirements for low detectability; when performing a maneuver mission, its detectability mainly targets radar waves in the high-frequency band and has relatively low requirements for low detectability. Also, when performing takeoff and landing missions, the radar bands targeted by low detectability and their required levels are also different.

[0047] When the aircraft performs different tasks, it needs to match different engine operating conditions. For example, when the aircraft performs a cruise mission, it requires less thrust and only needs the engine to operate at a lower operating condition; when the aircraft performs a maneuver mission, it requires greater thrust and needs the engine to operate at a higher operating condition.

[0048] An adjustable stator vane is arranged inside the engine inlet casing. The angle of the adjustable stator vane is adjusted accordingly according to the operating conditions of the engine to meet the requirements for the inlet flow rate of the engine under different operating conditions. When the engine operates at a lower operating condition, the requirement for the inlet flow rate is lower, and the adjustable stator vane is adjusted to a partially closed angle; when the engine operates at a higher operating condition, the requirement for the inlet flow rate is higher, and the adjustable stator vane is adjusted to a partially open angle. When the adjustable stator vane is at different open angles, in cooperation with the struts inside the inlet casing and the electromagnetic reflection surface inside the engine, the reflection paths of radar waves are different, such as Figure 1 - Figure 2 as shown. At the same time, the airfoil of the adjustable stator vane will also affect the reflection path of radar waves, and when the airfoils of the adjustable stator vanes are different, the opening angles required when the engine is at different operating conditions are also different.

[0049] As can be seen from the above, within the flight envelope, the missions performed by the aircraft, the radar bands and the required levels of its low detectability, are in one-to-one correspondence with the engine operating conditions, the adjustment angles of the adjustable stator vanes inside the inlet casing and the reflection paths of radar waves. Therefore, under the condition that the airfoil of the adjustable stator vane is determined, by designing the adjustable stator vane to have radar wave absorbing ability and different radar wave absorbing abilities at different positions, it is possible to adjust the absorption of radar waves required for low detectability according to the missions performed by the aircraft within the entire flight envelope and meet the requirements for low detectability, thereby reducing the requirements for the related designs of the existing inlet casing, avoiding over-design for detectability, and further reducing the severity of related technical problems.

[0050] Based on the above, the present application embodiment provides an adjustable stator vane inside an aircraft engine inlet casing, such as Figure 3 as shown, which includes a blade body 1, and an upper journal 2 and a lower journal 3 connected to the blade body 1.

[0051] The blade body 1 includes an inner load-bearing structure 11 and an outer wave-absorbing layer 12, such as Figure 4 shown.

[0052] The inner load-bearing structure 11 is a plate-like structure, made of fiber-reinforced composite materials with high specific strength and high specific stiffness, such as carbon fiber-reinforced composite materials, or made of lightweight metal materials, such as T800 grade carbon fiber-reinforced bis-maleimide resin matrix composite materials, or TC4 titanium alloy, and has a high load-bearing capacity to effectively transfer the aerodynamic loads borne by the adjustable stator vane and maintain the shape of the adjustable stator vane, avoiding serious deformation or damage of the adjustable stator vane under aerodynamic loads.

[0053] The upper journal 2 and the lower journal 3 can be connected to the inner load-bearing structure 11, are made of the same material as the inner load-bearing structure 11, and can be integrally formed on the inner load-bearing structure 11.

[0054] The outer wave-absorbing layer 12 is coated on the outside of the inner load-bearing structure 11 and is made of a material with wave-absorbing ability.

[0055] The material with wave-absorbing ability can be a composite material with wave-absorbing ability, such as a glass fiber-reinforced resin-based composite material added with carbonyl iron powder wave-absorbing particles, or a wave-absorbing coating, such as a wave-absorbing coating of ferrite, barium titanate, etc.

[0056] The material types and thickness distributions at different positions of the outer wave-absorbing layer 12 are different, so that the radar wave-absorbing abilities at different positions of the adjustable stator vane are different, so as to be able to match the tasks performed by the aircraft, specifically absorb the radar waves with low detectability requirements, and reach the level of low detectability requirements.

[0057] In order to quickly design an adjustable stator vane that meets the usage requirements, the present application provides the following design method for the adjustable stator vane in the aircraft engine inlet casing disclosed in the above embodiments, as Figure 5 shown.

[0058] Step 1: Preliminary design the airfoil of the adjustable stator vane and its adjustment angle.

[0059] Preliminarily design the airfoil and adjustment angle of the adjustable stator vane to provide an initial scheme for the airfoil of the adjustable stator vane and its usage angles under various engine operating conditions. The design can be carried out with reference to the existing conventional design methods for the airfoil and adjustment angle of the adjustable stator vane.

[0060] Step 2: Analyze the requirements for low detectability of the aircraft performing various tasks within the flight envelope, including the radar bands targeted by low detectability and the required degree.

[0061] The required degree of low detectability mentioned above can mainly refer to the required degree of low detectability in the forward direction of the engine.

[0062] Step 3: Identify the adjustment angles of the adjustable stator vane when the aircraft performs various tasks, and then determine the corresponding low detectability requirements.

[0063] Step 4: Design the material types and thickness distributions at different positions of the outer wave-absorbing layer according to the adjustment angle of the adjustable stator vane and the corresponding low detectability requirements.

[0064] When the adjustment angle of the adjustable stator vane is determined, the reflection path of the radar wave is also determined accordingly. Based on this, wave-absorbing enhancement design can be carried out for the radar bands targeted by the corresponding low detectability in the reflection area, and the corresponding wave-absorbing materials can be selected and the material thickness can be increased to meet the required degree of the corresponding low detectability.

[0065] Since the purpose of designing this type of adjustable stator blades is to reduce the requirements for the existing air intake casing related design, avoid over-design of detectability, and reduce the severity of related technical problems, we can focus on the situation when the low detectability requirements are high, and design the material type and thickness distribution at different positions of the external absorbing layer.

[0066] Step 5: Analyze the detectability of the adjustable stator blade adjustment angles under the whole machine conditions corresponding to the engine operating conditions to see whether they meet the corresponding low detectability requirements. The specific analysis can be carried out by experimental or simulation methods.

[0067] If there is a situation where the detectability of the adjustable stator blade adjustment angle under the engine operating condition does not meet the corresponding low detectability requirement, identify the key factors that do not meet the corresponding low detectability requirement, optimize the adjustable stator blade profile and its adjustment angle, and repeat steps three to five until the detectability of each adjustable stator blade adjustment angle under the engine operating condition meets the corresponding low detectability requirement.

[0068] The adjustable stator blades in the air intake casing of the engine disclosed in the above-mentioned embodiment and the design method thereof utilize the one-to-one correspondence between the missions performed by the aircraft within the flight envelope, the radar bands and requirements for its low detectability, the engine operating conditions, the adjustment angles of the adjustable stator blades in the air intake casing, and the reflection paths of the radar waves, and design the adjustable stator blades to have radar absorbing capabilities, and the radar absorbing capabilities at different positions are different, so that within the entire flight envelope, the radar waves required for low detectability can be absorbed in a targeted manner according to the missions performed by the aircraft, and the required degree of low detectability can be achieved, thereby reducing the requirements for the existing air intake casing related designs, avoiding over-design of detectability, and achieving the purpose of reducing the severity of related technical problems.

[0069] So far, the technical solution of the present application has been described in conjunction with the preferred embodiments shown in the accompanying drawings. Those skilled in the art should understand that the scope of protection of the present application is obviously not limited to these specific embodiments. Without departing from the principles of the present application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the scope of protection of the present application.

Claims

1. An adjustable stator blade in an aircraft engine air intake casing, characterized in that: It comprises a blade body (1), and an upper journal (2) and a lower journal (3) connected to the blade body (1); The blade body (1) comprises an inner load-bearing structure (11) and an outer wave-absorbing layer (12); The inner bearing structure (11) is a plate-shaped structure; The outer wave absorbing layer (12) is coated on the outer side of the inner bearing structure (11) and is made of a material having wave absorbing capability; The material with microwave absorption capability is a composite material with microwave absorption capability, or a microwave absorption coating; The material type and thickness distribution of the outer absorbing layer (12) at different positions are different, so that the radar absorbing capabilities of the adjustable stator blades at different positions are different, so as to match the mission performed by the aircraft and absorb radar waves with low detectability requirements in a targeted manner.

2. The adjustable stator blade in the air intake casing of an aircraft engine according to claim 1, characterized in that: The inner load-bearing structure (11) is made of fiber-reinforced composite material or lightweight metal material.

3. The adjustable stator blade in the air intake casing of an aircraft engine according to claim 2, characterized in that: The upper journal (2) and the lower journal (3) are connected to the inner bearing structure (11).

4. The adjustable stator blade in the air intake casing of an aircraft engine according to claim 3, characterized in that: The upper journal (2) and the lower journal (3) are made of the same material as the inner bearing structure (11) and are integrally formed on the inner bearing structure (11).

5. A method for designing adjustable stator blades in an aircraft engine air intake casing, used for designing the adjustable stator blades in an aircraft engine air intake casing according to claim 4, characterized in that: include: Step 1: Preliminary design of the blade profile and adjustment angle of the adjustable stator blade; Step 2: Analyze the low-observability requirements of the aircraft for various missions within the flight envelope, including the radar bands targeted by low-observability and the required degree; Step 3: Identify the adjustment angle of the adjustable stator blades when the aircraft performs various tasks, and then determine the corresponding low detectability requirements; Step 4: Design the material type and thickness distribution at different positions of the external absorbing layer according to the adjustment angle of the adjustable stator blades and the corresponding low detectability requirements; Step 5: Analyze the detectability of the adjustable stator blade adjustment angles under the whole machine condition and the corresponding engine operating conditions to see whether they meet the corresponding low detectability requirements; If there is a situation where the detectability of the adjustable stator blade adjustment angle under the engine operating condition does not meet the corresponding low detectability requirement, the adjustable stator blade profile and its adjustment angle are optimized, and steps three to five are repeated until the detectability of each adjustable stator blade adjustment angle under the engine operating condition meets the corresponding low detectability requirement.

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