Dual-angle adjustable inlet guide vanes for widening the stability margin of adaptive fans

Abstract

This invention provides a dual-angle adjustable inlet guide vane for expanding the stability margin of an adaptive fan, comprising: a main blade D1, a main blade D2, an auxiliary blade A, a profile compensation block B, a profile compensation block C, and a connecting mechanism. The main blade D2 is mounted on the main blade D1. The leading edge of the auxiliary blade A contacts an arc-shaped groove on one side of the main blade D1. The auxiliary blade A, profile compensation block B, profile compensation block C, and main blade D2 are sequentially connected to each other through the connecting mechanism. A hollow main shaft is also provided on the tip of the main blade D1, and a secondary shaft is provided inside the hollow main shaft. The secondary shaft is connected to the tip of the auxiliary blade A. The hollow main shaft and the secondary shaft drive the blades D1, D2, and A to rotate, adjusting the pre-rotation degree at different blade height positions, significantly expanding the stability margin and working performance of the adaptive fan under full bypass ratio conditions. When the auxiliary blade A rotates, it drives the profile compensation blocks B and C to move, thereby compensating for the area loss of the entire guide vane's outer surface caused by local deflection.

Description

Technical Field

[0001] This invention belongs to the field of aviation power plant technology, specifically relating to a dual-angle adjustable inlet guide vane for widening the stability margin of an adaptive fan. 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 latter. 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 functions of flow regulation and variable bypass ratio unique to 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 (high bypass ratio condition) to the low bypass ratio condition, the development and design of a new type of imported adjustable guide vane suitable for the variable bypass ratio mode of the adaptive fan is a key technology to ensure the stable operation of the adaptive fan and achieve multiple performance requirements. Summary of the Invention

[0011] The purpose of this invention is to solve the problem of area loss of the entire guide vane outer surface caused by adjusting the dual-angle inlet guide vane to widen the stability margin of adaptive fans, and to provide a novel dual-angle adjustable inlet guide vane for widening the stability margin of adaptive fans.

[0012] To achieve the above objectives, the present invention adopts the following technical solution: a dual-angle adjustable inlet guide vane for widening the stability margin of an adaptive fan, characterized in that it includes: a main blade D1, a main blade D2, an auxiliary blade A, a profile compensation block B, a profile compensation block C, and a connecting mechanism.

[0013] The main blade D2 is disposed on the main blade D1. The arc-shaped groove on one side of the auxiliary blade A is in contact with the main blade D1. The auxiliary blade A, the profile compensation block B, the profile compensation block C and the main blade D2 are sequentially connected to each other through a connecting mechanism.

[0014] A hollow main shaft is also provided on the tip of the main blade D1, and a secondary shaft is provided inside the hollow main shaft. The secondary shaft is connected to the tip of the secondary blade A.

[0015] Furthermore, the connecting mechanism includes a limiting slide groove and a rotating seat. The limiting slide groove is disposed on the profile compensation block C, and the rotating seat is disposed on the auxiliary blade A and the main blade D2 respectively.

[0016] Furthermore, the blade base of the secondary blade A is connected to the profile compensation block B via a rotating seat, the profile compensation block B is slidably connected to the limiting groove, and the profile compensation block C is connected to the blade tip of the main blade D2 via a rotating seat.

[0017] Furthermore, the trailing edge height of the profile compensation block B and profile compensation block C is 20% of the height of the main blade D2, which is used to avoid the inability to effectively compensate for the area when the adjustment angle of the main and auxiliary blades is large due to the area compensation block being too small.

[0018] Furthermore, the dividing point between the leading edge of the main blade D2 and the secondary blade A is the height corresponding to point a, which is the lowest height of the fan's high bypass ratio state separation zone.

[0019] Beneficial effects:

[0020] 1. This invention eliminates or reduces flow separation at the high blade height of the fan by adjusting the rotation angle of the secondary shaft to drive the secondary blade A to rotate. At the same time, it slightly adjusts the rotation angle of the hollow main shaft to drive the main blades D1 and D2 to rotate, thereby reducing the low-speed zone at the low blade height and blade back of the blades. This improves the uneven radial distribution of the rotor inlet airflow when the adaptive fan switches from high bypass ratio to low bypass ratio operation, significantly improves the stability margin and working performance of the widened adaptive fan across the full bypass ratio range, and enhances the quality of the rotor inlet airflow.

[0021] 2. When the auxiliary blade A of the present invention rotates, it will drive the profile compensation block B and profile compensation block C to move, thereby compensating for the area loss of the entire guide vane's outer surface caused by local deflection. Attached Figure Description

[0022] Appendix Figure 1 This is a three-dimensional structural diagram of the dual-angle adjustable inlet guide vanes that broaden the stability margin of the adaptive fan.

[0023] Appendix Figure 2 Design schematic diagram of fan separation zone distribution under high bypass ratio and low bypass ratio operating conditions.

[0024] In the diagram: 1. Hollow main shaft, 2. Secondary shaft, 3. Connecting mechanism, 3-1. Limiting groove, 3-2. Rotating seat. Detailed Implementation

[0025] The invention will now be further explained with reference to the accompanying drawings.

[0026] like Figure 1 As shown, the present invention provides a dual-angle adjustable inlet guide vane for widening the stability margin of an adaptive fan, comprising: a main blade D1, a main blade D2, an auxiliary blade A, a profile compensation block B, a profile compensation block C, and a connecting mechanism 3.

[0027] The main blade D2 is mounted on the main blade D1. The arc-shaped groove on one side of the auxiliary blade A is in contact with the arc-shaped groove on one side of the main blade D1. The auxiliary blade A, the profile compensation block B, the profile compensation block C and the main blade D2 are connected to each other in sequence through the connecting mechanism 3.

[0028] A hollow main shaft 1 is also provided on the tip of the main blade D1. A secondary shaft 2 is provided inside the hollow main shaft 1, and the secondary shaft 2 is connected to the tip of the secondary blade A.

[0029] The main blades D1 and D2 are connected as a whole by a trapezoidal keyway for easy assembly. The connecting mechanism 3 includes a limiting slide 3-1 and a rotating seat 3-2. The limiting slide 3-1 is set on the profile compensation block C, and the rotating seat 3-2 is set on the auxiliary blade A and the main blade D2 respectively. The blade bottom of the auxiliary blade A is connected to the profile compensation block B through the rotating seat 3-2. The profile compensation block B is slidably connected to the limiting slide 3-1. The profile compensation block C is connected to the blade tip of the main blade D2 through the rotating seat 3-2. The above configuration increases the flexibility of the profile compensation blocks B and C when the auxiliary blade is adjusted. During the rotation of the auxiliary blade A, the profile compensation block B will move through its rotating seat 3-2. Under the action of friction, the profile compensation block B will slide out part of the limiting slide 3-1 on the profile compensation block C, thereby compensating for the area loss caused by the local deflection on the outer surface of the guide vane.

[0030] The outer diameter of the hollow main shaft 1 is twice the radius of the secondary shaft 2. Approximately 25% of the radius of the hollow main shaft 1 is connected to the main blade D1, and 75% of the radius is in contact with the secondary blade A. The hollow main shaft 1 is also connected to the main blade rocker arm. The main blade rocker arm controls the main blade D1 through the hollow main shaft 1, and the main blade D1 drives the main blade D2 to rotate through the keyway, thus achieving the overall rotation of the main blade. The secondary shaft 2 is located at the tip of the secondary blade A and inside the hollow main shaft 1. The secondary shaft 2 is also connected to the secondary blade rocker arm. The secondary blade rocker arm controls the rotation of the secondary blade A through the secondary shaft 2. When the secondary blade A rotates, it will drive the profile compensation block B and profile compensation block C to move. The main blade rocker arm and the secondary blade rocker arm are respectively connected to their corresponding drive rings through spherical bearings, so that the entire guide vane can be rotated by simply pushing the drive ring.

[0031] When adjusting the hollow main shaft 1 and the secondary shaft 2, the limit adjustable angles of the two blades need to be fully considered. If the rotation angle of blade D1 and main blade D2 is too large, it will affect the flow at the tip of the blade in the adaptive fan. If the rotation angle of secondary blade A is too large, it will affect the flow at the root of the fan blade. However, if it is too small, it will not achieve a good control effect. Therefore, the limit adjustable angles of the hollow main shaft 1 and the secondary shaft 2 should be determined in conjunction with the actual engineering requirements.

[0032] like Figure 2 As shown, the separation region of an adaptive fan changes radially when transitioning from a high bypass ratio design to a lower bypass ratio. The separation region distribution of the fan in the high bypass ratio design state is shown in the figure. Figure 2 (a), where point a is the lowest height of the separation zone in the high bypass ratio state of the fan, while the distribution of the separation zone in the low bypass ratio state is shown in [reference needed]. Figure 2(b) Where point b is the lowest height of the fan's small bypass duct relative to the state separation zone, and point a is lower than point b, so considering all factors, the height corresponding to point a is taken as the dividing point between the leading edges of the main blade and the secondary blade A. Furthermore, to enhance the guide vane's control over airflow, the length of the secondary blade A is extended, positioned at 35%-45% of the total fan blade tip chord length. Then, 20% of the length of the main blade D2 is used as the trailing edge height of the profile compensation blocks B and C, thereby avoiding the inability to effectively compensate for area when the main and secondary blades have large zone adjustment angles due to the area compensation blocks being too small.

[0033] The transformation rules of the hollow main shaft 1 and secondary shaft 2 in this invention are as follows:

[0034] When the fan changes from a high bypass ratio design to a low bypass ratio: the flow separation vortex in the channel moves towards the high region of the fan blades, changing the rotation angle of the secondary shaft 2, so that the inlet guide vanes provide a suitable angle of attack for the fan inlet, eliminating or reducing flow separation at the high region of the fan blades, and improving the stability of the fan; while at the low region of the fan blades, the change in the angle of attack of the airflow is small, there is no large flow separation, the flow is relatively smooth, and the required control intensity is not large. Adjusting the rotation angle of the hollow main shaft 1 provides a suitable angle of attack for the airflow at the fan inlet, reducing the low-speed region at the back of the fan rotor blades.

[0035] Under a larger design bypass ratio, there is a small separation zone in the fan blades. By adjusting the hollow main shaft 1 to change the rotation angle of blades D1 and main blades D2, a suitable pre-rotation is applied to the fan inlet, which improves the airflow quality at the fan inlet and enhances the stability of the fan.

[0036] Based on the above-provided solution, specific implementation methods are as follows:

[0037] For a variable circulation fan with a bypass ratio ranging from 0.07 to 0.9, the performance requirements are as follows: after adjustment by the inlet guide vanes at any bypass ratio, the fan efficiency is not less than 86%, the boost ratio is not less than 1.7, and the stability margin increase is not less than 4%. When the fan operates at a bypass ratio of 0.9 (high bypass ratio turbofan engine mode), flow separation occurs only in a small area within the blades during throttling. This flow separation can be eliminated or reduced by adjusting the pre-swirl applied to blades D1 and D2 by adjusting the hollow main shaft 1, thereby increasing the fan's stability margin at this bypass ratio. As the bypass ratio gradually decreases, the relative airflow angle changes less at the fan inlet rotor blades and at the blade root, but more significantly at the blade tip, indicating that the flow separation vortex moves towards the blade tip. Therefore, when the variable cycle fan operates at a bypass ratio of 0.07 (turbojet engine mode), the relative airflow angle changes less at the blade root of the fan inlet blades. This can be adjusted by slightly adjusting the hollow main shaft 1 to regulate the flow field at the blade root. Conversely, the relative airflow angle changes more significantly at the blade tip, which can be adjusted by adjusting the secondary shaft 2. The two shafts work together to provide suitable airflow conditions for the fan, increasing its stability margin and improving the operational capability of the variable cycle engine. In the 0.07–0.9 bypass ratio mode, after coordinated adjustment of the hollow main shaft 1 and the secondary shaft 2, the fan efficiency is maintained at 87.8%–90.2%, the boost ratio is as high as 1.81–1.93, and the stability margin increases by more than 4% in each operating condition. During this coordinated adjustment process, the smaller the fan bypass ratio, the larger the flow vortex at the high blade back of the fan rotor, and of course, the larger the rotor inlet angle of attack. This is a continuously changing process, so the adjustment angle of the guide vanes also changes continuously in one direction.

[0038] This invention eliminates or reduces flow separation at the height of the large fan blades by adjusting the rotation angle of the secondary shaft, which drives the secondary blade A to rotate. At the same time, a slight adjustment of the rotation angle of the hollow main shaft drives the main blades D1 and D2 to rotate, thereby reducing the low-speed zone at the blade back. This improves the uneven radial distribution of the rotor inlet airflow when the adaptive fan switches from high bypass ratio to low bypass ratio operation. It significantly improves the stability margin and performance of the widened adaptive fan across the entire bypass ratio range, enhances the quality of the rotor inlet airflow, and the rotation of the secondary blade A drives the profile compensation blocks B and C to move, thereby compensating for the area loss of the entire guide vane profile caused by local deflection.

[0039] 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-angle adjustable inlet guide vane for widening the stability margin of an adaptive fan, characterized in that, include: Main blade D1, main blade D2, auxiliary blade A, profile compensation block B, profile compensation block C and connecting mechanism (3); The main blade D2 is disposed on the main blade D1. The arc-shaped groove on one side of the auxiliary blade A is in contact with the main blade D1. The auxiliary blade A, the profile compensation block B, the profile compensation block C and the main blade D2 are connected to each other in sequence through the connecting mechanism (3). A hollow main shaft (1) is also disposed on the tip of the main blade D1. A secondary shaft (2) is disposed inside the hollow main shaft (1). The secondary shaft (2) is connected to the tip of the auxiliary blade A. The connecting mechanism (3) includes: a limiting slide groove (3-1) and a rotating seat (3-2). The limiting slide groove (3-1) is set on the profile compensation block C, and the rotating seat (3-2) is set on the auxiliary blade A and the main blade D2 respectively. The blade base of the auxiliary blade A is connected to the profile compensation block B via a rotating seat (3-2). The profile compensation block B is slidably connected to the limiting groove (3-1). The profile compensation block C is connected to the blade tip of the main blade D2 via a rotating seat (3-2).

2. The dual-angle adjustable inlet guide vane for widening the stability margin of an adaptive fan according to claim 1, characterized in that, The trailing edge height of the profile compensation blocks B and C is 20% of the height of the main blade D2. This is to prevent the main and auxiliary blades from being unable to effectively compensate for the area when the adjustment angle of the main and auxiliary blades is too large due to the area compensation blocks being too small.

3. The dual-angle adjustable inlet guide vane for widening the stability margin of an adaptive fan according to claim 1, characterized in that, The dividing point between the leading edge of the main blade D2 and the secondary blade A is the height corresponding to point a, which is the lowest height of the fan's high bypass ratio state separation zone.

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