Dual-adjustable angle inlet adjustable guide vanes for widening the fan bypass ratio operating range

Abstract

This invention provides a dual-adjustable-angle inlet guide vane for widening the bypass ratio operating range of a fan, comprising: a first main blade, a second main blade, an auxiliary blade, a main shaft A, and an auxiliary shaft B. The second main blade and the auxiliary blade are respectively disposed on one side of the first main blade. The auxiliary blade is located below the blade base of the second main blade and contacts an arc-shaped groove on the first main blade. The main shaft A is disposed on the blade base of the first main blade, and the auxiliary shaft B is disposed on the blade base of the auxiliary blade and located within the hollow cylinder of the main shaft A. The main shaft A drives the first and second main blades to rotate, and the auxiliary shaft B drives the auxiliary blade to rotate. By adjusting the first main blade, the second main blade, and the auxiliary blade through the main shaft A and the auxiliary shaft B, the flow field at the fan inlet can be adjusted in zones, providing different degrees of pre-swirl for the inlet airflow at different fan blade heights, improving the quality of the fan inlet airflow, increasing the working efficiency of adaptive startup, and expanding the bypass ratio variation range of the adaptive fan.

Description

Technical Field

[0001] This invention belongs to the technical field, specifically relating to a dual-adjustable-angle inlet adjustable guide vane for widening the working range of a fan bypass ratio. Background Technology

[0002] With the rapid development of aviation technology, higher requirements have been placed on the combat capabilities of military aircraft. In order to meet the dual performance requirements of high thrust-to-weight ratio and low fuel consumption for the next generation of fighter jets, and to meet the new characteristics of modern local wars such as rapid search and strike capabilities, it has become an inevitable trend to develop aero-engine technology with higher economic efficiency, all-weather capability, multi-purpose capability, long range, high maneuverability, thrust vectoring capability, and vertical take-off and landing capability.

[0003] In the design of aircraft engines, different flight missions have different design requirements. When the aircraft is in cruise mode, a low fuel consumption rate is required to ensure a long cruise time. When the aircraft is climbing or in supersonic mode, a greater specific thrust is required to meet mission requirements. However, conventional engines seem to be unable to meet both of these requirements.

[0004] The emergence of the Variable Cycle Engine (VCE) has solved this problem and plays a significant role in modern weaponry. The VCE integrates the performance advantages of a medium-bypass turbofan engine in subsonic flight and a turbojet engine in supersonic flight, combining the two into one. It allows for flexible adjustment of the engine's bypass ratio, pressure ratio, flow rate, and cycle operating mode, enabling the aircraft to maintain high performance across a wider flight envelope. This balances the diverse engine requirements of different flight missions.

[0005] Adaptive cycle engines and variable cycle engines are inextricably linked, with the latter being a development and extension of the former. Currently, the United States leads in research on adaptive variable cycle engines, and this research has primarily progressed through the following stages.

[0006] The adaptive cycle engine was first researched in 2007 as a project of the U.S. Air Force Research Laboratory (AFRL) called the ADVENT program. Its goal was to develop technology that could independently change the fan / core engine flow rate and pressure ratio for the development of a new generation of military aircraft. GE and Rolls-Royce, as contractors for the project, conducted two years of testing and verification on key components such as the engine's fan, compressor, and variable flow turbine. The main structural feature of GE's ADVENT model is that it has three bypass ducts. The inner and second bypass ducts are similar to the YF120 twin-bypass variable cycle engine. The third bypass duct is unique in that its airflow always remains within the outer bypass duct and does not enter the core engine. The flow rate in the third bypass duct can be changed according to different mission requirements to adjust the engine's bypass ratio, and it can also serve as a cooling airflow.

[0007] In 2009, based on the research results of the first phase, the ADVENT project carried out the second phase of technology verification, further improved the key technical solutions of engine components, and designed an adaptive cycle engine with variable fan pressure ratio and flow rate. Later, the full-scale ground test of the engine demonstrator was successfully carried out.

[0008] In 2012, in order to further develop adaptive cycle engine technology and to develop a more complete propulsion system for the next generation of fighter jets, the U.S. Air Force formulated the four-year AETD program. The initial goal of the program was to test and verify key components such as engine fans and core engines. The ultimate goal was to complete the whole-aircraft test by 2017. GE and PW were both designated to participate in the AETD program.

[0009] In 2019, GE unveiled the basic structure of its next-generation adaptive engine. Public information shows that the engine compresses gas using a three-stage fan and a seven-stage high-pressure compressor, and does not have a core drive fan. It relies solely on the fan and high-pressure compressor for pressurization, suggesting a high pressure ratio. According to GE's website, this engine has two operating modes: high thrust and high efficiency. In high thrust mode, the second bypass and inner bypass ducts receive a larger flow to generate greater thrust, while the third bypass duct receives very little flow. In high efficiency mode, the flow in the third bypass duct increases, while the flow in the second bypass duct is very small, thereby improving the engine's fuel efficiency.

[0010] On the other hand, adaptive engine technology has been demonstrated by researchers both at home and abroad, who have pointed out that the adaptive fan component is one of the key technologies for achieving its comprehensive performance. In addition to completing the pressurization function of a traditional fan, it also needs to complete the unique functions of flow regulation and variable bypass ratio of the adaptive variable cycle engine, achieve good matching of multiple operating points, operate stably during the switching of operating modes, and be strongly coupled with the entire adaptive variable cycle engine. It can be seen that the performance requirements of the adaptive fan are stringent, and it is difficult to meet the new performance requirements by relying solely on traditional imported adjustable guide vanes. Therefore, in view of the complex radial changes in the internal flow field when the adaptive fan switches from the design bypass ratio condition (small bypass ratio condition) to the large bypass ratio condition, it is necessary to develop and design a new type of imported adjustable guide vane suitable for the variable bypass ratio mode of the adaptive fan to ensure the stable operation of the adaptive fan. This is a key technology for achieving multiple performance requirements. Summary of the Invention

[0011] The purpose of this invention is to address the complex radial changes in the internal flow field of an adaptive fan when it transitions from a low bypass ratio to a high bypass ratio operating condition. This invention designs a fully three-dimensional adjustable guide vane technology based on dual-adjustment angles to change the blade profile and achieve zoned control, thereby significantly improving the combat capability of the adaptive variable cycle engine. It also provides a dual-adjustment angle inlet adjustable guide vane for widening the fan bypass ratio operating range.

[0012] To achieve the above objectives, the present invention adopts the following technical solution: a dual-adjustable angle inlet adjustable guide vane for widening the working range of the fan bypass ratio, comprising: a first main blade, a second main blade, an auxiliary blade, a main shaft A, and an auxiliary shaft B;

[0013] A second main blade and an auxiliary blade are respectively provided on one side of the first main blade. The auxiliary blade is located below the blade base of the second main blade and is in contact with the arc-shaped groove on the first main blade. The main shaft A is provided on the blade base of the first main blade, and the auxiliary shaft B is provided on the blade base of the auxiliary blade and is located inside the hollow cylinder of the main shaft A.

[0014] The main shaft A is used to drive the first main blade and the second main blade to rotate, and the secondary shaft B is used to drive the secondary blade to rotate.

[0015] Furthermore, the first main blade and the second main blade are connected as a whole by a trapezoidal keyway.

[0016] Furthermore, the height at the intersection of the trailing edges of the second main blade and the secondary blade is the height corresponding to the dividing point where the change in the airflow angle at the fan rotor inlet is relatively large and relatively small.

[0017] Furthermore, the leading edge of the secondary blade is located at 35%-45% of the chord length of the entire fan blade.

[0018] Furthermore, one-quarter radius of the main shaft A is connected to the base of the first main blade, and the other three-quarter radius is in contact with the base of the secondary blade.

[0019] Furthermore, the secondary shaft B is located at the leading edge of the secondary blade, and the perpendicular line from the center of the inscribed circle of the blade at this position is the secondary shaft B.

[0020] Furthermore, the main shaft A, with the central arc of the initial blade shape as the reference point, rotates within a range of -20° to 20° around the axis.

[0021] Furthermore, the secondary shaft B, with the central arc of the initial blade shape as the reference point, rotates within a range of -30° to 30° around the shaft.

[0022] Beneficial effects: This invention inherits the advantages of traditional adjustable guide vanes while also being able to adjust the flow field at the fan inlet in different zones, providing different degrees of pre-swirl for the inlet airflow at different fan blade heights, improving the quality of the fan inlet airflow, increasing the working efficiency of adaptive engines, and increasing the bypass ratio variation range of adaptive fans, providing a wider working range for variable cycle engines and significantly enhancing the combat capability of variable cycle engines. Attached Figure Description

[0023] Appendix Figure 1 This is a three-dimensional structural diagram of a dual-adjustable-angle inlet adjustable guide vane that widens the working range of the fan bypass ratio.

[0024] Appendix Figure 2 It features a dual-adjustable-angle inlet adjustable guide vane with a radial direction pattern, which widens the working range of the fan bypass ratio.

[0025] Appendix Figure 3 This is a diagram showing the relationship between the fan blade inlet angle parameters and the velocity triangle.

[0026] Appendix Figure 4 This is a schematic diagram of the radial distribution of the inlet airflow angle of the fan under low bypass ratio and high bypass ratio conditions.

[0027] Appendix Figure 5 This is a schematic diagram showing the change in blade profile at the small blade height section of the adjustable guide vane with dual adjustable angle inlet.

[0028] Appendix Figure 6 This is a schematic diagram showing the change in blade profile due to the adjustment of the main shaft rotation angle by the dual-adjustment angle inlet adjustable guide vanes and the high cross-section of the large blade.

[0029] Appendix Figure 7 This is a schematic diagram showing the changes in blade height and cross-section of the dual-adjustable inlet guide vanes, which adjust the rotation angle of the main shaft and the secondary shaft. Detailed Implementation

[0030] The invention will now be further explained with reference to the accompanying drawings.

[0031] Under the minimum bypass ratio design at a fixed flow rate, with the inlet adjustable guide vanes maintaining their initial airfoil shape and no adjustment or only minor changes, the airflow entering the fan flows well along the airfoil profile and decelerates and pressurizes, with almost no flow separation at the blade suction surface. As the fan's bypass ratio increases, the throttling effect of the inner duct increases, reducing the inner duct flow rate. This leads to a decrease in the flow rate at the fan blade base corresponding to the inner duct, resulting in an increased inlet angle of attack. A larger low-speed region appears at the rotor trailing edge of the fan's small blades. Therefore, the inlet adjustable guide vanes are needed to provide appropriate airflow pre-swirl for the fan, i.e., to provide a suitable angle of attack for the fan inlet airflow, thus reducing the range of the low-speed region. Simultaneously, the blade mid-section and tip also need adjustment. When shifting to a larger bypass ratio, the strong throttling of the inner duct also affects the throttling effect of the large-blade high outer bypass duct, resulting in a relatively smaller flow rate at the fan's large blade high. Therefore, the airflow angle of attack at the fan blade tip inlet increases slightly, but less than the change in the blade root region. Thus, the inlet adjustable guide vanes are needed to adjust the airflow pre-swirl in the large-blade high region to provide a suitable angle of attack for the airflow at the blade tip.

[0032] Based on the above research, such as Figure 1 As shown, the present invention provides a dual-adjustable angle inlet adjustable guide vane for widening the working range of fan bypass ratio, comprising: a first main blade 1, a second main blade 2, an auxiliary blade 3, a main shaft A, and an auxiliary shaft B.

[0033] A second main blade 2 and an auxiliary blade 3 are respectively provided on one side of the first main blade 1. The auxiliary blade 3 is located below the blade bottom of the second main blade 2 and is in contact with the arc-shaped groove on the first main blade 1. The main shaft A is set on the blade bottom of the first main blade 1, and the auxiliary shaft B is set on the blade bottom of the auxiliary blade 3 and is located inside the hollow cylinder of the main shaft A.

[0034] Main shaft A is used to drive the first main blade 1 and the second main blade 2 to rotate, and secondary shaft B is used to drive the secondary blade 3 to rotate.

[0035] In the above scheme, rotating the main shaft A drives the first main blade 1 and the second main blade 2 to rotate, providing a suitable angle of attack for the fan inlet to eliminate flow separation in the tip range of the fan blades. Rotating the secondary shaft B drives the secondary blade 3 to rotate, thereby reducing the angle of attack of the airflow at the fan inlet, so that the airflow flows along the back of the blades as much as possible, reducing the low-speed range at the trailing edge.

[0036] like Figure 3 As shown, in the fan inlet velocity triangle, the angle of attack i = β k-β, an excessively large angle of attack will cause the airflow in the fan to deviate from the flow along the blade surface, resulting in significant flow separation at the back of the fan rotor blades. This leads to substantial flow blockage and losses within the blade passage. Therefore, reducing the relative airflow angle at the fan inlet can decrease the inlet angle of attack, thereby reducing flow separation at the back of the fan rotor blades and widening the fan's surge boundary. Thus, the fundamental theory in the design of adjustable guide vanes at the inlet is to apply different degrees of inlet pre-swirl based on the fan inlet velocity triangle to improve airflow.

[0037] Based on the above-mentioned basic theory, the design idea of ​​this scheme is to add an adjustable secondary shaft B to the original single-angle adjustable guide vane profile. The blades are divided into main blades and secondary blades 3 along the secondary shaft, which can apply different degrees of pre-rotation to different blade heights.

[0038] The main blades include a first main blade 1 and a second main blade 2. The first main blade 1 and the second main blade 2 are connected as a whole by a trapezoidal keyway, which facilitates overall assembly.

[0039] The main shaft A is a hollow cylindrical shaft. One-quarter radius of one end of the main shaft A is connected to the blade base of the first main blade 1 as a whole, and the other three-quarter radius is in contact with the blade base of the secondary blade 3. The secondary shaft B is located inside the hollow cylinder of the main shaft A, and is located at the perpendicular line from the center of the inscribed circle of the leading edge of the secondary blade 3, and is connected to the blade base of the secondary blade 3 as a whole. This main and secondary shaft layout can effectively reduce interference between the actuating mechanisms.

[0040] The main shaft A is also connected to the main blade rocker arm, and the secondary shaft B is also connected to the secondary blade rocker arm. The main blade rocker arm and the secondary blade rocker arm are respectively connected to the corresponding drive rings through joint bearings. Under the action of the drive rings, the main blade rocker arm can drive the main shaft A to rotate, and the secondary blade rocker arm can drive the secondary shaft B to rotate. In order to solve the problem that the throttling intensity of the fan inner duct increases when switching from a small bypass ratio to a large bypass ratio, resulting in a large change in the angle of attack of the inlet airflow at the high point of the fan blades, the main shaft A is adjusted to rotate around the shaft within a range of -20° to 20° with the middle arc line of the initial blade profile as the reference point, and the secondary shaft B is adjusted to rotate around the shaft within a range of -30° to 30° with the middle arc line of the initial blade profile as the reference point, so as to increase the upper limit of the fan bypass ratio.

[0041] The adjustment process involves two-stage adjustment of the main blade and the secondary blade 3. An overly complex three-dimensional blade profile will increase the difficulty of guide vane adjustment. In order to make the adjustment mechanism simpler and more efficient, the initial blade profile of the dual-adjustment angle inlet guide vane will adopt an axisymmetric initial three-dimensional blade profile without sweep. This blade profile configuration is simple and can play a good role in rectification.

[0042] like Figure 2 and Figure 4As shown, when the variable circulation fan changes from a fixed flow rate and low bypass ratio design state to a high bypass ratio state, the radial variation of the relative airflow angle at the rotor inlet is inconsistent. This leads to inconsistent radial pre-selection of the fan by the inlet guide vanes when expanding the fan's bypass ratio variation range. Therefore, when the fan transitions from a fixed flow rate and low bypass ratio design state to a high bypass ratio state, the throttling degree of the fan's internal duct increases, and the airflow angle change at the high inlet of the fan rotor blades will be greater. Point a is the dividing point between a large and a relatively small change in the airflow angle at the fan rotor inlet. The dividing point is determined flexibly according to the inlet airflow conditions of different fan rotors. Therefore, after determining the initial blade profile, the regions of the main blade and the secondary blade 3 are divided. The division method is as follows: the height corresponding to point a is taken as the height of the intersection of the main blade and the secondary blade at the trailing edge of the guide vane. That is, a to the blade tip b is the main blade, and a to the blade root c is the secondary blade 3. In order to enhance the control capability of the guide vanes on the airflow, the leading edge of the secondary blade 3 is located at 35%-45% of the fan blade chord length.

[0043] like Figure 5-6 As shown, this illustrates the guide vane adjustment angles required at the fan rotor blade root and tip when the fan transitions from a fixed flow rate, low bypass ratio design to a high bypass ratio design.

[0044] like Figure 7 This is a comprehensive adjustment method for dual-angle adjustable inlet guide vanes, which coordinates the adjustment angles for different blade heights.

[0045] Example 1

[0046] For a variable circulation fan with a bypass ratio ranging from 0.07 to 0.9, the performance requirements are that the fan design point efficiency is not less than 86% at any bypass ratio, the boost ratio is not less than 1.7, and the stability margin decrease is not more than 8%. In a variable cycle fan with a bypass ratio of 0.07 (a low-bypass turbofan engine), flow separation occurs only at the blade tip and mid-section during throttling. This separation can be eliminated or reduced by adjusting the pre-spinning of the main blades via the main shaft A, thus expanding the fan's stability margin at this bypass ratio. As the bypass ratio of the variable cycle fan gradually increases, the relative airflow angle at the fan inlet varies radially, with smaller changes at the blade tip and larger changes at the blade root. Therefore, in a variable cycle fan with a bypass ratio of 0.9, the relative airflow angle at the blade tip and mid-section changes less, which can be adjusted by slightly adjusting the main shaft A. The relative airflow angle at the blade root changes more significantly, which can be adjusted by adjusting the secondary shaft B. The coordinated adjustment of the two shafts improves the quality of the inlet airflow, achieving both stability enhancement and an expanded bypass ratio range, thereby improving the operational capability of the variable cycle engine. In the 0.07–0.9 bypass ratio mode, the secondary shaft controls the secondary blades to adjust their angles to meet the high inlet flow field requirements of the downstream rotor blades, while the main shaft controls the main blades to meet the high inlet flow field requirements of the downstream rotor blades. By coordinating the adjustment of the two shafts, the fan design point efficiency is maintained at 87.8%–90.2%, the boost ratio is as high as 1.81–1.93, and the stability margin decrease is less than 6.8%.

[0047] This invention, when the fan transitions from a low bypass ratio operating condition to a high bypass ratio operating condition, coordinates the main shaft A and the secondary shaft B to adjust the first main blade 1, the second main blade 2, and the secondary blade 3. This achieves zoned adjustment of the flow field at the fan inlet, providing different degrees of pre-swirl for the inlet airflow at different blade heights, improving the quality of the fan inlet airflow, increasing the working efficiency of the adaptive engine fan, and expanding the bypass ratio variation range of the adaptive fan. This provides a wider operating range for the variable cycle engine and significantly enhances the combat capability of the adaptive engine.

[0048] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A dual-adjustable-angle inlet adjustable guide vane for widening the working range of a fan's bypass ratio, characterized in that, include: First main blade (1), second main blade (2), auxiliary blade (3), main shaft A and auxiliary shaft B; A second main blade (2) and a secondary blade (3) are respectively provided on one side of the first main blade (1). The secondary blade (3) is located below the blade bottom of the second main blade (2) and is in contact with the arc-shaped groove on the first main blade (1). The main shaft A is provided on the blade bottom of the first main blade (1), and the secondary shaft B is provided on the blade bottom of the secondary blade (3) and is located inside the hollow cylinder of the main shaft A. The main shaft A is used to drive the first main blade (1) and the second main blade (2) to rotate, and the secondary shaft B is used to drive the secondary blade (3) to rotate. The height at the intersection of the trailing edges of the second main blade (2) and the secondary blade (3) is the height corresponding to the dividing point where the airflow angle at the fan rotor inlet changes significantly and relatively little. The leading edge of the secondary blade (3) is located at 35%-45% of the chord length of the entire fan blade.

2. The dual-adjustable-angle inlet adjustable guide vane for widening the fan bypass ratio operating range according to claim 1, characterized in that, The first main blade (1) and the second main blade (2) are connected as a whole by a trapezoidal keyway.

3. The dual-adjustable-angle inlet adjustable guide vane for widening the fan bypass ratio operating range according to claim 1, characterized in that, One-quarter radius portion of the main shaft A is connected to the bottom of the first main blade (1), and the other three-quarter radius portion is in contact with the bottom of the secondary blade (3).

4. The dual-adjustable-angle inlet adjustable guide vane for widening the fan bypass ratio operating range according to claim 1, characterized in that, The secondary shaft B is located at the leading edge of the secondary blade, and the perpendicular line from the center of the inscribed circle of the blade at this position is the secondary shaft B.

5. The dual-adjustable-angle inlet adjustable guide vane for widening the fan bypass ratio operating range according to claim 1, characterized in that, The main shaft A is adjusted to rotate around the axis within a range of -20° to 20°, with the central arc of the initial blade shape as the reference point.

6. The dual-adjustable-angle inlet adjustable guide vane for widening the fan bypass ratio operating range according to claim 1, characterized in that, The adjustment range of the secondary shaft B, with the central arc of the initial blade shape as the reference point, is within -30° to 30° around the rotating shaft.

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