A method for judging stall based on static pressure coefficient threshold and a PSJ control method

Abstract

The application discloses a method for judging stall based on a static pressure coefficient threshold value and a PSJ control method, S1: acquiring a real-time attack angle alpha of an airfoil, a constant pressure, a real-time pressure of a leading edge pressure measuring hole on the upper surface of the airfoil, a static pressure of a flow and a dynamic pressure of the flow; S2: calculating a real-time static pressure coefficient C of the leading edge pressure measuring hole p_L , and updating a minimum real-time static pressure coefficient C of the leading edge pressure measuring hole before stall in real time p_m and an attack angle alpha0 corresponding to the minimum real-time static pressure coefficient C p_m ; S3: when C p_L ≥ a leading edge threshold value C p_L0 and alpha is greater than or equal to alpha0, it is judged that the airfoil has stalled. By C L , many pressure points are needed to judge stall by a lift coefficient, and the calculation is complex, while the present scheme only needs to compare the leading edge pressure measuring point with the leading edge threshold value to judge whether stall occurs, and the calculation is simple; and by adding the attack angle limit, the judgment is more accurate.

Description

Technical Field

[0001] The present invention relates to the field of flight equipment, and in particular to a method for determining stall based on a static pressure coefficient threshold and a PSJ control method. Background Art

[0002] A plasma synthetic jet (PSJ) is an exciter that uses spark discharge to generate a high-speed pulsed jet of high-temperature plasma as the excitation source. It typically consists of a pair of electrodes and a discharge chamber with a jet orifice. The electrodes break down the gas, generating a spark discharge. The generated heat rapidly heats the gas within the chamber, causing a sudden increase in pressure within the chamber and generating a high-speed jet. The plasma synthetic jet generation cycle primarily proceeds through three phases. The first phase is the energy deposition phase. A high-voltage pulse is applied between the cathode and anode via a power supply. Energy is deposited between the exciter's electrodes. When the voltage exceeds the breakdown voltage of the gas within the chamber, an arc discharge forms within the chamber, generating plasma and converting electrical energy into thermal energy. The second phase is the jet ejection phase. After the energy deposition phase, the gas within the chamber is heated, causing a sharp increase in pressure, creating a pressure differential between the inside and outside of the chamber. Ultimately, the gas within the chamber is ejected through the jet orifice, forming a plasma synthetic jet. The third stage is the air intake recovery phase. After the second stage of jet ejection, the gas and temperature in the cavity drop rapidly, causing the pressure inside the cavity to be lower than the external pressure. The gas will then refill the cavity through the jet orifice, preparing for the next discharge. In recent years, domestic and foreign experts and researchers have conducted extensive research in basic research and engineering applications, achieving fruitful results. This type of control technology aims to influence the motion characteristics of the aircraft by changing the flow environment. This not only improves the aerodynamic characteristics and safety performance of the aircraft / engine, but also reduces noise and environmental pollution, and has broad application prospects.

[0003] In the prior art, the lift coefficient of an airfoil is usually calculated by the pressure distribution on the upper and lower surfaces of the airfoil. Confirm whether stall occurs, where C pl is the pressure coefficient of the lower surface of the airfoil, C pu It is the pressure coefficient of the airfoil upper surface. It requires many pressure points to be sampled and the calculation is complicated. Summary of the Invention

[0004] The object of the present invention is to overcome the above-mentioned defects or problems existing in the background technology and to provide a method for determining stall based on a static pressure coefficient threshold and a PSJ control method.

[0005] To achieve the above objectives, the present invention and its preferred embodiments adopt the following technical solutions, but the embodiments are not limited to the following solutions: Solution 1, a method for determining stall based on a static pressure coefficient threshold, comprising the following steps:

[0006] S1: Obtain the real-time attack angle α of the airfoil, the constant pressure, the real-time pressure of the pressure measuring hole on the leading edge of the airfoil upper surface, the static pressure of the incoming flow, and the flowing pressure of the incoming flow;

[0007] S2: Calculate the real-time static pressure coefficient C of the leading edge pressure measuring hole p_L , and update the minimum real-time static pressure coefficient C of the leading edge pressure measuring hole in real time p_m and the minimum real-time static pressure coefficient C p_m The corresponding angle of attack α0; where the real-time static pressure coefficient C of the leading edge pressure measuring hole p_L According to the real-time pressure, constant pressure, incoming static pressure and incoming flow pressure of the leading edge pressure measuring hole, the real-time static pressure coefficient C of the pressure measuring hole is obtained. p When it is reduced due to stall, the pressure tap is the leading edge pressure tap;

[0008] S3: When C p_L ≥ leading edge threshold C p_L0 And when α≥α0, it is judged that the airfoil is stalled.

[0009] Solution 2, based on Solution 1, S1 further includes the following steps: measuring the real-time pressure of the pressure measuring hole on the trailing edge of the upper surface of the airfoil;

[0010] S2 also includes the following steps: calculating the real-time static pressure coefficient C of the trailing edge pressure measuring hole p_T ; Among them, the real-time static pressure coefficient C of the trailing edge pressure measuring hole p_T It is obtained based on the real-time pressure, constant pressure, incoming static pressure and incoming flow pressure of the pressure measuring hole at the trailing edge; when the real-time static pressure coefficient C of the pressure measuring hole is p When it increases due to stall, the pressure tap is the trailing edge pressure tap;

[0011] S3 also includes the following steps: p_T ≤ trailing edge threshold C p_T0 It is determined that the airfoil has stalled.

[0012] Solution 3, based on Solution 2, before S1, obtain the leading edge threshold C according to the following steps: p_L0 :

[0013] Under the condition of keeping the incoming wind speed V and Reynolds number Re constant, according to the real-time static pressure coefficient C of the leading edge pressure measuring hole p_L and the relationship diagram of the real-time attack angle α, determine the real-time static pressure coefficient Cp_a before the leading edge pressure measuring hole separation and the real-time static pressure coefficient Cp_s during separation;

[0014] Determine the leading edge threshold C p_L0 =C p_m +(Cp_s-Cp_a).

[0015] Solution 4: Based on Solution 3, before S1, obtain the trailing edge threshold C according to the following steps: p_T0 :

[0016] Under the condition of keeping the incoming wind speed V and Reynolds number Re constant, according to the real-time static pressure coefficient C of the pressure measuring hole at the trailing edge p_L and the real-time attack angle α, determine the real-time static pressure coefficient Cp_a before the separation of the trailing edge pressure measuring hole and the real-time static pressure coefficient Cp_s during separation;

[0017] Determine the trailing edge threshold C p_T0 =(Cp_s+Cp_a)*coefficient, 0<coefficient<1.

[0018] Option 5, based on Option 4, the leading edge pressure measuring hole x / c = 0.05, the trailing edge pressure measuring hole x / c = 0.8, where x is the distance from the pressure measuring hole to the leading edge of the airfoil, and c is the total length of the airfoil.

[0019] Option 6, a PSJ control method, including a method for judging stall based on a static pressure coefficient threshold as described in any one of Option 2 to Option 5 and the following steps: S3 also includes the following steps: turning on the PSJ when it is determined that the airfoil is stalled.

[0020] Scheme 7, based on Scheme 6, also includes S4: When C p_L <C p_L0 And α<α0 and C p_T >C p_T0 Close PSJ when α0 is the minimum real-time static pressure coefficient C of the leading edge pressure measuring hole before opening PSJ. p_m The corresponding angle of attack.

[0021] Solution 8, based on Solution 6, S5: re-execute steps S1 and S2 after S3 or S4.

[0022] Solution 9: A control system comprising

[0023] A pressure scanning valve is used to measure the constant pressure and the real-time pressure of the leading edge pressure measuring holes and the trailing edge pressure measuring holes on the upper surface of the airfoil;

[0024] Pressure anemometer, which is used to measure the static pressure and the flowing pressure of the incoming flow;

[0025] An angle sensor, which is used to measure the real-time angle of attack α of the airfoil;

[0026] An actuator suitable for controlled opening and closing of the PSJ;

[0027] A controller is electrically connected to the pressure scanning valve, the angle sensor and the actuator, and is suitable for determining whether the airfoil stalls and the stall ends according to a PSJ control method described in any one of Schemes 6 to 8, and controlling the actuator to open the PSJ when it is determined that the airfoil stalls, and controlling the actuator to close the PSJ when it is determined that the airfoil stall ends.

[0028] Solution 10: A flying device comprising an airfoil and a control system as described in Solution 9;

[0029] The upper surface of the airfoil is provided with a jet hole, a leading edge pressure measuring hole and a trailing edge pressure measuring hole;

[0030] The control system is installed on the airfoil, and the PSJ is suitable for being ejected from the jet hole.

[0031] From the above description of the present invention and its preferred embodiments, it can be seen that compared with the prior art, the technical solution of the present invention and its preferred embodiments have the following beneficial effects due to the adoption of the following technical means:

[0032] 1. In solution 1 and its preferred embodiment, a method for determining stall based on a static pressure coefficient threshold comprises the following steps:

[0033] S1: Obtain the real-time attack angle α of the airfoil, the constant pressure, the real-time pressure of the pressure measuring hole on the leading edge of the airfoil upper surface, the static pressure of the incoming flow, and the flowing pressure of the incoming flow;

[0034] S2: Calculate the real-time static pressure coefficient C of the leading edge pressure measuring hole p_L , and update the minimum real-time static pressure coefficient C of the leading edge pressure measuring hole in real time p_m and the minimum real-time static pressure coefficient C p_m The corresponding angle of attack α0; where the real-time static pressure coefficient C of the leading edge pressure measuring hole p_L According to the real-time pressure, constant pressure, incoming static pressure and incoming flow pressure of the leading edge pressure measuring hole, the real-time static pressure coefficient C of the pressure measuring hole is obtained. p When it is reduced due to stall, the pressure tap is the leading edge pressure tap;

[0035] S3: When C p_L ≥ leading edge threshold C p_L0 And when α≥α0, it is judged that the airfoil is stalled;

[0036] By C L The lift coefficient requires many pressure points to determine whether a stall occurs, and the calculation is complicated. However, this solution only needs to measure the leading edge pressure point and compare it with the leading edge threshold to determine whether a stall occurs, which is simple to calculate. In addition, the static pressure coefficient C of the leading edge pressure hole is taken into account. p The value decreases gradually with the increase of the angle of attack α, and increases gradually when stall occurs. If the angle of attack is not restricted, it is possible to meet C in the process of decreasing the angle of attack α. p_L ≥ leading edge threshold C p_L0 However, no stall occurs at this time, and the judgment is inaccurate. Therefore, adding α≥α0 as a limit makes the judgment more accurate.

[0037] 2. Scheme 2 and its preferred embodiment, due to the low Reynolds number Re cIn the case of a stall, the pressure change starts from the leading edge. At this time, the leading edge pressure tap is more suitable for determining the stall. As the Reynolds number increases, the pressure will start to change from the trailing edge. At this time, the leading edge pressure tap is more suitable for determining the stall. Therefore, this embodiment simultaneously determines whether the leading edge and the trailing edge meet the threshold conditions. When either of the two meets the threshold condition, it is determined that a stall has occurred and the PSJ is opened to meet the different Reynolds numbers. c Use below.

[0038] The static pressure coefficient C of the pressure tap at the trailing edge increases with the angle of attack before the stall. p The change is not obvious. When stall occurs, the static pressure coefficient C p Decreases rapidly, so C p_T ≤ trailing edge threshold C p_T0 To determine whether a stall has occurred.

[0039] 3. In the third solution and its preferred embodiment, before step S1, the leading edge threshold C is obtained according to the following steps: p_L0 :

[0040] Under the condition of keeping the incoming wind speed V and Reynolds number Re constant, according to the real-time static pressure coefficient C of the leading edge pressure measuring hole p_L and the relationship diagram of the real-time attack angle α, determine the real-time static pressure coefficient Cp_a before the leading edge pressure measuring hole separation and the real-time static pressure coefficient Cp_s during separation;

[0041] Determine the leading edge threshold C p_L0 =C p_m +(Cp_s-Cp_a).

[0042] At the leading edge pressure tap, as the airfoil angle of attack α decreases, the static pressure coefficient C p Increase, if a fixed value is taken as the leading edge threshold C p_L0 , when α decreases, the static pressure coefficient C p will meet the leading edge threshold C p_L0 When the PSJ is automatically turned on, and it is within the safe attack angle range at this time, the judgment is inaccurate. Therefore, the leading edge threshold C p_L0 Desirable C p_m + constant, constant = (C p_s -C p_a ), although (C p_s -C p_a ) is a constant, but since C p_m It changes in real time, so the leading edge threshold C p_L0 , also changes in real time, making the judgment more accurate. If there is no such constant, C p_L0 =C p_m In fact, stall is only judged by α≥α0, which is also inaccurate.

[0043] 4. In the fourth solution and its preferred embodiment, the trailing edge threshold C p_T0 =(Cp_s+Cp_a)*coefficient, 0<coefficient<1. Multiplying by the coefficient is to ensure that the stall occurs before the stall. Since the pressure tap hole at the trailing edge increases with the angle of attack before the stall, its static pressure coefficient C p The change is not obvious. When stall occurs, the static pressure coefficient C p It decreases rapidly, which is different from the variable situation of the leading edge pressure measuring hole. Therefore, a constant can be selected as the threshold, which is simple and convenient.

[0044] 5. In the fifth scheme and its preferred embodiment, the leading edge pressure measuring hole x / c=0.05, and the trailing edge pressure measuring hole x / c=0.8, which facilitates the judgment of stall.

[0045] 6. In the sixth solution and its preferred embodiment, a PSJ control method is provided, which turns on the PSJ when it is determined that the airfoil is stalled, so as to delay the stall angle of attack.

[0046] 7. Scheme 7 and its preferred embodiment, when C p_L <C p_L0 And α<α0 and C p_T >C p_T0 The PSJ can be automatically closed when the PSJ is turned off, saving energy. Among them, α0 is the minimum real-time static pressure coefficient C of the leading edge pressure measuring hole before the PSJ is turned on. p_m The corresponding angle of attack, since α0 corresponds to the minimum real-time static pressure coefficient C before stall p_m , that is, the minimum real-time static pressure coefficient C before opening PSJ p_m Even after stall, the static pressure coefficient C of the leading edge pressure tap p Less than the minimum real-time static pressure coefficient C before stall p_m , α0 will not change either.

[0047] 8. In the eighth solution and its preferred embodiment,

[0048] S5: After S3 or S4, steps S1 and S2 are re-executed to realize a cycle and achieve closed-loop control.

[0049] 9. Option 9 and its preferred embodiments provide a control system, wherein a pressure scanning valve is used to measure a constant pressure and the real-time pressure of the leading edge pressure measuring holes and the trailing edge pressure measuring holes on the upper surface of the airfoil; a pressure anemometer is used to measure the static pressure and the flowing pressure of the incoming flow; an angle sensor is used to measure the real-time angle of attack α of the airfoil; an actuator is suitable for controlled opening and closing of the PSJ; a controller is electrically connected to the pressure scanning valve, the angle sensor, and the actuator, and is suitable for determining the occurrence and end of stall of the airfoil according to one of the above-mentioned PSJ control methods, and controlling the actuator to open the PSJ when it is determined that the airfoil has stalled, and to control the actuator to close the PSJ when it is determined that the airfoil has ended stall. The control system has the beneficial effects brought by the above-mentioned PSJ control method.

[0050] 10. A flying device comprising an airfoil and a control system as described above; the upper surface of the airfoil is provided with a jet hole, a leading edge pressure measuring hole and a trailing edge pressure measuring hole; the control system is mounted on the airfoil, and the PSJ is adapted to be ejected from the jet hole, which has the beneficial effects brought by the above control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0052] Figure 1 Flowchart of the PSJ control method in Example 1;

[0053] Figure 2 is the Reynolds number Re in Example 1 c =1.00×10 5 When , the static pressure coefficient at different positions on the airfoil changes with the angle of attack;

[0054] Figure 3 The static pressure coefficient and control signal of the PSJ closed-loop flow control airfoil in the increasing angle of attack mode in Example 1;

[0055] Figure 4 The velocity cloud diagram of the flow field on the upper surface of the unexcited airfoil in Example 1;

[0056] Figure 5 The velocity cloud diagram of the airfoil flow field under closed-loop feedback control with variable angle of attack in Example 1;

[0057] Figure 6 The static pressure coefficient and control signal of the PSJ closed-loop flow control airfoil in the decreasing angle of attack mode in Example 1;

[0058] Figure 7 It is a plasma synthetic jet open-loop flow control system in the prior art;

[0059] Figure 8 This is a schematic diagram of the closed-loop flow control experiment layout of Example 2;

[0060] Figure 9 To implement a two-loop closed-loop flow control system structure;

[0061] Figure 10 A top view of the sensor in Example 2;

[0062] Figure 11 Schematic diagram of the airfoil. DETAILED DESCRIPTION

[0063] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are preferred embodiments of the present invention and should not be regarded as excluding other embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0064] In the claims, description and drawings of the present invention, unless otherwise clearly defined, the use of terms such as "first", "second" or "third" is for the purpose of distinguishing different objects rather than for describing a specific order.

[0065] In the claims, specification and the above-mentioned drawings of the present invention, unless otherwise expressly defined, directional words such as the terms "center", "transverse", "longitudinal", "horizontal", "vertical", "top", "bottom", "inside", "outside", "up", "down", "front", "back", "left", "right", "clockwise", "counterclockwise" and the like indicating directions or positional relationships are based on the directions and positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the specific scope of protection of the present invention.

[0066] In the claims, description and above-mentioned drawings of the present invention, unless otherwise expressly defined, the terms "fixed connection" or "fixed connection" should be understood in a broad sense, that is, any connection method without displacement relationship and relative rotation relationship between the two parties, that is, including non-detachable fixed connection, detachable fixed connection, integral connection and fixed connection through other devices or elements.

[0067] In the claims, description and drawings of the present invention, if the terms "include", "have" and their variations are used, they are intended to mean "including but not limited to".

[0068] refer to Figures 1-6 , a PSJ control method comprising the following steps:

[0069] S1: Obtain the real-time attack angle α of the airfoil, the constant pressure, the real-time pressure of the leading edge pressure measuring hole and the trailing edge pressure measuring hole on the upper surface of the airfoil, the static pressure of the incoming flow, and the flowing pressure of the incoming flow;

[0070] S2: Calculate the real-time static pressure coefficient C of the leading edge pressure measuring hole p_L , the real-time static pressure coefficient C of the trailing edge pressure measuring hole p_T , and update the minimum real-time static pressure coefficient C before the leading edge pressure measuring hole stalls in real time p_m and the minimum real-time static pressure coefficient Cp_m The corresponding angle of attack α0; where the real-time static pressure coefficient C of the leading edge pressure measuring hole p_L The real-time static pressure coefficient C of the pressure measuring hole at the trailing edge is obtained based on the real-time pressure, constant pressure, incoming static pressure and incoming flow pressure of the pressure measuring hole at the leading edge. p_T It is obtained based on the real-time pressure, constant pressure, incoming static pressure and incoming flow pressure of the pressure measuring hole at the trailing edge; among them, the real-time static pressure coefficient C of the pressure measuring hole is defined p When the pressure tap is reduced due to stall, the pressure tap is the leading edge pressure tap, and the real-time static pressure coefficient C of the pressure tap is p When it increases due to stall, the pressure tap is the trailing edge pressure tap;

[0071] S3: When C p_L ≥ leading edge threshold C p_L0 and α≥α0 or C p_T ≤ trailing edge threshold C p_T0 When the airfoil is judged to be stalled, the PSJ is opened;

[0072] S4: When C p_L <C p_L0 And α<α0 and C p_T >C p_T0 Close PSJ when α0 is the minimum real-time static pressure coefficient C of the leading edge pressure measuring hole before opening PSJ. p_m The corresponding angle of attack;

[0073] S5: Re-execute steps S1 and S2 after S3 or S4.

[0074] The closed-loop control of PSJ is realized by the above cycle, which can automatically open or close PSJ, has good adaptability to the environment, good control effect, high control efficiency, and can realize opening and closing on demand, saving energy. It should be understood that after step S2, the judgment of S3 and S4 can be carried out simultaneously. Among them, before S1, the leading edge threshold C is obtained according to the following steps p_L0 and trailing edge threshold C p_T0 :

[0075] Under the condition of keeping the incoming wind speed V and Reynolds number Re constant, according to the real-time static pressure coefficient C of the leading edge pressure measuring hole p_L and the real-time attack angle α, and determine the real-time static pressure coefficient C before the leading edge pressure tap is separated p_a (angle of attack approaching stall) and the real-time static pressure coefficient C at separation p_s ;

[0076] Determine the leading edge threshold C p_L0 =C p_m +(C p_s -C p_a ).

[0077] Under the condition of keeping the incoming wind speed V and Reynolds number Re constant, according to the real-time static pressure coefficient C of the pressure measuring hole at the trailing edge p_L and the real-time attack angle α, and determine the real-time static pressure coefficient C before the trailing edge pressure tap is separated p_a (angle of attack approaching stall) and the real-time static pressure coefficient C at separation p_s ;

[0078] Determine the trailing edge threshold C p_T0 =(C p_s +C p_a )*coefficient, 0<coefficient<1.

[0079] refer to Figure 2 In this embodiment, the leading edge pressure measuring hole x / c=0.05, and the trailing edge pressure measuring hole x / c=0.8. The following explains why these two pressure measuring holes are selected as the collection points;

[0080] At the incoming wind speed V = 7m / s and the Reynolds number Re c =1.00×10 5 When , the collection points at different positions (x / c = 0.05, 0.15, 0.4, 0.6, 0.8) on the upper surface of the airfoil are selected, such as Figure 11 , x is the distance from the pressure tap to the leading edge of the airfoil, c is the total length of the airfoil; each acquisition point is set along the center line of the airfoil, and the center line of the airfoil is located in the middle position perpendicular to the x-axis and y-axis directions. Get the real-time static pressure coefficient C of the pressure tap p and the real-time angle of attack α.

[0081] When the airfoil angle of attack α≤16° (stall angle of attack), the static pressure coefficient C of the pressure tap near the leading edge of the airfoil (x / c=0.05, 0.15) p The negative pressure increases with the increase of α, and the closer to the leading edge (x / c = 0.05), the greater the negative pressure. The static pressure coefficient C of the pressure tap near the trailing edge of the airfoil (x / c = 0.6, 0.8) p The static pressure coefficient C remains almost unchanged, and the closer to the trailing edge (x / c=0.8) p The closer to 0.

[0082] When α>16°, the two-dimensional airfoil stalls and a large range of flow separation occurs. The static pressure coefficient C near the leading edge of the airfoil p The curve drops suddenly, the negative pressure decreases, and the static pressure coefficient C of the pressure measuring hole closer to the leading edge of the airfoil p Compared with the working condition of α=16°, at the position of x / c=0.05, the static pressure coefficient C p The largest decrease is 55.7%. Therefore, the pressure acquisition point at x / c = 0.05 is suitable as one of the key feedback pressure signal acquisition positions for judging whether the airfoil has flow separation leading to stall.p The curve suddenly rises, the negative pressure increases, and the static pressure coefficient C of the pressure measuring hole closer to the trailing edge p Compared with the working condition of α=16°, at the position of x / c=0.8, the static pressure coefficient C p The increase is the largest, reaching 189.0%. It can be seen that the pressure collection point at x / c = 0.8 should also be used as another key feedback pressure signal collection position.

[0083] refer to Figure 2 , below, for the leading edge threshold C p_L0 and trailing edge threshold C p_T0 Provide explanation.

[0084] At the trailing edge x / c = 0.8, when no stall occurs (angle of attack α = 16°), the real-time static pressure coefficient Cp_a before the separation of the trailing edge pressure tap is -0.209. When stall occurs (angle of attack α = 17°), the real-time static pressure coefficient Cp_a when the trailing edge pressure tap is separated is -0.209. p_s =-0.604, trailing edge threshold C p_T0 = coefficient × (C p_s +C p_a ), in this embodiment, the coefficient is selected as 0.5, and the trailing edge threshold C p_T0 =-0.4.

[0085] At the leading edge x / c = 0.05, as the airfoil angle of attack α decreases, the static pressure coefficient C p Increase, if a fixed value is taken as the leading edge threshold C p_L0 , when α decreases, the static pressure coefficient C p will meet the leading edge threshold C p_L0 When the PSJ is automatically turned on, and it is within the safe attack angle range at this time, the judgment is inaccurate. Therefore, the leading edge threshold C p_L0 The real-time static pressure coefficient C before the leading edge pressure tap is separated needs to be dynamically changed. p_a =-2.069 (corresponding to angle of attack α = 16°), when the leading edge pressure tap stalls, C p_s =-0.916 (corresponding to angle of attack α = 17°), leading edge threshold C p_L0 Desirable C p_m +(C p_s -C p_a )=C p_m +0.57, due to C p_m It changes in real time, so the leading edge threshold C p_L0 , which also changes in real time. In addition, the restriction of α≥α0 is added to make the judgment of whether stall occurs more accurate.

[0086] In summary, the leading edge threshold C p_L0 =C p_m +0.57, determine the trailing edge threshold Cp_T0 is -0.4, the leading edge threshold C can be used p_L0 and trailing edge threshold C p_T0 As a general judgment condition, of course, it can also be based on different incoming wind speeds V and different Reynolds numbers Re c To determine the judgment conditions in different situations.

[0087] Because at low Reynolds numbers Re c In the case of a stall, the pressure change starts from the leading edge. At this time, the leading edge pressure tap is more suitable for determining the stall. As the Reynolds number increases, the pressure will start to change from the trailing edge. At this time, the leading edge pressure tap is more suitable for determining the stall. Therefore, this embodiment simultaneously determines whether the leading edge and the trailing edge meet the threshold conditions. When either of the two meets the threshold condition, it is determined that a stall has occurred and the PSJ is opened to meet the different Reynolds numbers. c Use below.

[0088] The static feasibility of the plasma synthetic jet closed-loop flow control system has been verified under the condition of constant angle of attack. The dynamic feasibility of the system will be verified under the condition of variable angle of attack. The PSJ excitation electrical parameters, structural parameters and control positions used in the experiment are consistent with the fixed angle of attack experiment. The incoming flow condition is still maintained at V = 7m / s, Re c =1.00×10 5 , select the pressure measuring holes at x / c=0.05 and x / c=0.8 as monitoring points.

[0089] Angle of attack increasing mode:

[0090] refer to Figure 3-Figure 5 In the dynamic change process of gradually increasing angle of attack α, when the airfoil is about to stall, the PSJ is automatically turned on according to the control law command, suppressing the flow separation on the airfoil surface and restoring the suction peak on the upper surface of the airfoil, thereby increasing the stall angle of attack by 4° and delaying the stall.

[0091] refer to Figure 3 Before the airfoil stalls, that is, when α≤16°, the airfoil does not stall. At this time, the closed-loop control system does not turn on the PSJ according to the control law, which can save energy consumption in this stage compared to the open-loop control. The static pressure coefficient C of the leading edge pressure measuring hole and the trailing edge pressure measuring hole in this stage p Basically the same as the uncontrolled state. x / c=0.8 static pressure coefficient C p As the angle of attack α increases, it remains basically unchanged, while the static pressure coefficient C at x / c = 0.05 p As the angle of attack α increases, the negative pressure increases and the suction peak at the leading edge strengthens.

[0092] When the airfoil is about to stall, that is, when α>16°, the static pressure coefficient C at x / c=0.05 pThe first to drop, x / c = 0.8 static pressure coefficient C p This is because the flow separation occurs at low Reynolds numbers and starts directly from the leading edge of the airfoil, resulting in the leading edge static pressure coefficient C p Changes before the trailing edge. p_L ≥ leading edge threshold C p_L0 and α≥α0 or C p_T ≤ trailing edge threshold C p_T0 When the static pressure coefficient C in the closed-loop control state is p It is basically the same as the uncontrolled state. But when the static pressure coefficient C at x / c = 0.05 p First drop to meet C p_L ≥C p_L0 When the attack angle α≈16.5° and α≥α0 is satisfied, the closed-loop control system automatically turns on the PSJ and keeps it turned on during the dynamic change of α. After turning on the PSJ, the static pressure coefficient C at x / c=0.8 is p The static pressure coefficient Cp at x / c = 0.05 remains essentially unchanged, with a rapid rise. The jet's ability to suppress flow separation persists up to α = 20°, where the upper airfoil flow completely reattaches to the airfoil surface, resulting in a higher leading edge suction peak compared to α = 16°. The static pressure coefficient at x / c = 0.8 remains essentially unchanged at approximately -0.25.

[0093] When the airfoil enters the deep stall state, that is, when α>20°, PSJ is not enough to completely suppress the flow separation, and the static pressure coefficient C at x / c=0.8 p Rapidly rising, static pressure coefficient C at x / c = 0.05 p It descends and becomes consistent with the static pressure coefficient in the uncontrolled state, and the airfoil is in a stall state.

[0094] Angle of attack decreasing mode:

[0095] refer to Figure 6 After the airfoil angle of attack α increases to 24°, the closed-loop feedback control system with reduced angle of attack is experimentally verified. According to the control law, PSJ is instructed to operate at a speed of 100 km / h when the angle of attack α≥α0 (since α0 corresponds to the minimum real-time static pressure coefficient C before stalling). p_m , that is, the minimum real-time static pressure coefficient C before opening PSJ p_m Even after stall, the static pressure coefficient C p Less than the minimum real-time static pressure coefficient C before stall p_m , α0 will not change), it will remain in the open state and will automatically close after entering the safe angle of attack range.

[0096] When the airfoil is in deep stall, that is, when the angle of attack α is greater than 20°, PSJ is insufficient to completely suppress flow separation, and the static pressure coefficient C pThe change pattern is basically the same as when the angle of attack is increased. When the angle of attack α is close to 20°, the static pressure coefficient C at x / c = 0.8 p Rapidly decreases, and the static pressure coefficient C at x / c = 0.05 p Rising rapidly.

[0097] When the airfoil is about to stall, that is, when α>16°, and the PSJ remains open, the static pressure coefficient C p The change rule is basically the same as that of increasing the angle of attack α. When α<α0, the static pressure coefficient C p Satisfy C p_L <C p_L0 And C p_T >C p_T0 And α<α0, the closed-loop control system automatically closes PSJ, and the closing angle of attack α≈16°. At this time, the static pressure coefficient C at the position x / c=0.05 p There is no extreme drop, but a basically linear drop. The static pressure coefficient Cp at the position of x / c=0.8 remains basically unchanged. This is because the airflow has a hysteresis effect. After closing the PSJ, the airflow will still adhere to the upper surface of the airfoil for a period of time. As the angle of attack α continues to decrease, the airfoil enters the safe angle of attack range, and the upper wing surface remains in an attached flow state.

[0098] Subsequently, the airfoil enters the pre-stall stage, that is, when α≤16°, the closed-loop flow control system has automatically closed the PSJ, and it remains closed during this stage. The static pressure coefficient C p The change curve is basically the same as that without excitation. The static pressure coefficient C at x / c=0.8 p Basically remains unchanged, the static pressure coefficient C at x / c=0.05 p As the angle of attack decreases, the negative pressure decreases.

[0099] Experiments at both constant and variable angles of attack demonstrate that a closed-loop PSJ flow control system based on a dual-hole static pressure coefficient threshold monitors the airfoil's upper surface for stall. It automatically opens the PSJ when stall is imminent (or before stall) to prevent the airfoil from stalling. However, the PSJ automatically closes when the airfoil is slightly below the stall angle of attack. By combining the trailing edge (x / c = 0.8) and leading edge (x / c = 0.05) as stall detection criteria, the closed-loop feedback control system's ability to sense stall is further enhanced. Adjusting the PSJ threshold allows for control of the timing of PSJ opening. Compared to open-loop flow control, this significantly reduces PSJ operating time, lowers discharge power, conserves plasma discharge system energy, and improves flow control efficiency.

[0100] It should be understood that in order to reduce the amount of calculation, when judging whether to turn off PSJ, it is possible to first determine that α<α0, and then turn on C if the above conditions are met. p_L <C p_L0And C p_T >C p_T0 Make a judgment.

[0101] Example 2:

[0102] like Figure 7 It is an open-loop flow control system for plasma synthetic jets in the prior art. Most experimental results of plasma synthetic jets in open-loop flow control systems are obtained by open-loop control under certain specific experimental conditions, that is, the PSJ is kept open at the beginning of the experiment. The flow state in the actual working environment is very complex, and the open-loop active flow control technology is difficult to make self-adjustments to the changing environmental dynamics. The poor adaptability to the environment leads to unsatisfactory control effects and low control efficiency. It cannot be opened on demand when a stall occurs, which brings great challenges to the practical application of flow control technology.

[0103] like Figure 8 、 Figure 9 Compared to open-loop control, this closed-loop control system can achieve closed-loop control and dynamically adjust to changing environments. It has good adaptability, effective control, and high control efficiency, enabling on-demand opening and closing, saving energy. Specifically, a control system includes a load cell, an angle sensor, an actuator, a controller, a pressure anemometer, and a programmable high-voltage pulse power supply.

[0104] The pressure measuring piece is used to measure the constant pressure and the real-time pressure of each pressure measuring hole distributed along the leading edge to the trailing edge of the airfoil on the upper surface of the airfoil; specifically, the pressure measuring piece is a pressure sensor, such as Figure 10 The pressure sensor has two pressure nozzles and a pressure sensitive chip. The two pressure nozzles are port1 and port2, which are used to measure the constant pressure and the real-time pressure of the pressure measuring holes. The pressure nozzle used to measure the real-time pressure of the pressure measuring holes is connected to each pressure measuring hole through a pipe. The constant pressure can be standard atmospheric pressure. The chip senses different pressures through the pressure nozzles to form an electrical signal corresponding to the pressure. Through the pressure difference between the two, the controller can calculate p i The measurement and calculation process is prior art and will not be elaborated on here. The pressure sensor can have multiple sensors and be integrated into a pressure scanning valve to achieve multi-channel pressure synchronous acquisition.

[0105] Pressure anemometer is used to measure the static pressure p of the incoming flow ∞ and incoming flow pressure q ∞ ;

[0106] The angle sensor is used to measure the real-time angle of attack α of the airfoil;

[0107] The actuator is suitable for controlled opening and closing of PSJ;

[0108] The controller (including a small industrial computer and a single-chip microcomputer) is electrically connected to the pressure measuring piece, the angle sensor and the actuator, and is suitable for determining the occurrence and end of the airfoil stall according to the PSJ control method described in the first embodiment, and controlling the actuator to open the PSJ when the airfoil stall is determined, and controlling the actuator to close the PSJ when the airfoil stall is determined.

[0109] A programmable high-voltage pulse power supply is used to drive the actuator, and the programmable signal is output by an industrial computer through a control program based on LabVIEW.

[0110] Example 3:

[0111] A flying device includes an airfoil and a control system according to the second embodiment. The upper surface of the airfoil is provided with a jet hole, a leading edge pressure measuring hole, and a trailing edge pressure measuring hole. The control system is mounted on the airfoil, and the PSJ is adapted to be ejected from the jet hole.

[0112] The above description and embodiments are intended to explain the scope of protection of the present invention, but do not constitute a limitation thereto. Modifications, equivalent substitutions, or other improvements to the embodiments of the present invention or portions thereof that can be obtained by a person of ordinary skill in the art through logical analysis, reasoning, or limited experimentation based on the teachings of the present invention or the above embodiments, combined with common knowledge, ordinary technical knowledge in the field, and / or prior art, should all be included within the scope of protection of the present invention.

Claims

1. A method for determining stall based on a static pressure coefficient threshold, characterized by: The following steps are involved: S1: Obtain the real-time attack angle α of the airfoil, the constant pressure, the real-time pressure of the pressure measuring hole on the leading edge of the airfoil upper surface, the static pressure of the incoming flow, and the flowing pressure of the incoming flow; S2: Calculate the real-time static pressure coefficient C of the leading edge pressure measuring hole p_L , and update the minimum real-time static pressure coefficient C of the leading edge pressure measuring hole in real time p_m and the minimum real-time static pressure coefficient C p_m The corresponding angle of attack α0; where the real-time static pressure coefficient C of the leading edge pressure measuring hole p_L According to the real-time pressure, constant pressure, incoming static pressure and incoming flow pressure of the leading edge pressure measuring hole, the real-time static pressure coefficient C of the pressure measuring hole is obtained. p When it is reduced due to stall, the pressure tap is the leading edge pressure tap; S3: When C p_L ≥ leading edge threshold C p_L0 And when α≥α0, it is judged that the airfoil is stalled.

2. The method for determining stall based on a static pressure coefficient threshold according to claim 1, wherein: S1 also includes the following steps: measuring the real-time pressure of the pressure measuring hole on the trailing edge of the upper surface of the airfoil; S2 also includes the following steps: calculating the real-time static pressure coefficient C of the trailing edge pressure measuring hole p_T ; Among them, the real-time static pressure coefficient C of the trailing edge pressure measuring hole p_T It is obtained based on the real-time pressure, constant pressure, incoming static pressure and incoming flow pressure of the pressure measuring hole at the trailing edge; when the real-time static pressure coefficient C of the pressure measuring hole is p When it increases due to stall, the pressure tap is the trailing edge pressure tap; S3 also includes the following steps: p_L ≥ leading edge threshold C p_L0 and α≥α0 or C p_T ≤ trailing edge threshold C p_T0 It is determined that the airfoil has stalled.

3. The method for determining stall based on a static pressure coefficient threshold according to claim 2, wherein: Before S1, the leading edge threshold C is obtained according to the following steps p_L0 : Under the condition of keeping the incoming wind speed V and Reynolds number Re constant, according to the real-time static pressure coefficient C of the leading edge pressure measuring hole p_L and the relationship diagram of the real-time attack angle α, determine the real-time static pressure coefficient Cp_a before the leading edge pressure measuring hole separation and the real-time static pressure coefficient Cp_s during separation; Determine the leading edge threshold C p_L0 =C p_m +(Cp_s-Cp_a).

4. The method for determining stall based on a static pressure coefficient threshold according to claim 3, wherein: Before S1, the trailing edge threshold C is obtained according to the following steps: p_T0 : Under the condition of keeping the incoming wind speed V and Reynolds number Re constant, according to the real-time static pressure coefficient C of the pressure measuring hole at the trailing edge p_L and the real-time attack angle α, determine the real-time static pressure coefficient Cp_a before the separation of the trailing edge pressure measuring hole and the real-time static pressure coefficient Cp_s during separation; Determine the trailing edge threshold C p_T0 =(Cp_s+Cp_a)*coefficient, 0<coefficient<1.

5. The method for determining stall based on a static pressure coefficient threshold according to claim 4, wherein: The leading edge pressure tap is x / c=0.05, and the trailing edge pressure tap is x / c=0.8, where x is the distance from the pressure tap to the leading edge of the airfoil, and c is the total length of the airfoil.

6. A PSJ control method, characterized in that: The method comprises a method for judging stall based on a static pressure coefficient threshold as described in any one of claims 2 to 5 and the following steps: S3 also comprises the following steps: turning on the PSJ when it is determined that the airfoil is stalled.

7. A PSJ control method according to claim 6, characterized in that: Also includes S4: When C p_L <C p_L0 And α<α0 and C p_T >C p_T0 Close PSJ when α0 is the minimum real-time static pressure coefficient C of the leading edge pressure measuring hole before opening PSJ. p_m The corresponding angle of attack.

8. A PSJ control method according to claim 6, characterized in that: S5: Re-execute steps S1 and S2 after S3 or S4.

9. A control system, characterized in that: include A pressure scanning valve is used to measure the constant pressure and the real-time pressure of the leading edge pressure measuring holes and the trailing edge pressure measuring holes on the upper surface of the airfoil; Pressure anemometer, which is used to measure the static pressure and the flowing pressure of the incoming flow; An angle sensor, which is used to measure the real-time angle of attack α of the airfoil; An actuator suitable for controlled opening and closing of the PSJ; a controller electrically connected to the pressure scanning valve, the angle sensor, and the actuator, and adapted to determine the occurrence and end of stall of the airfoil according to a PSJ control method according to any one of claims 6 to 8, and to control the actuator to open the PSJ when it is determined that the airfoil has stalled, and to control the actuator to close the PSJ when it is determined that the airfoil has ended stall.

10. A flying device, characterized in that: comprising an airfoil and a control system as claimed in claim 9; The upper surface of the airfoil is provided with a jet hole, a leading edge pressure measuring hole and a trailing edge pressure measuring hole; The control system is installed on the airfoil, and the PSJ is suitable for being ejected from the jet hole.

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