Boundary layer control device and mobile unit
The boundary layer control device addresses the challenge of controlling friction and heat on high-speed moving bodies by managing gas flow and pressure, resulting in reduced friction and stabilized separation points.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- MITSUBISHI HEAVY IND LTD
- Filing Date
- 2022-05-20
- Publication Date
- 2026-07-09
AI Technical Summary
Existing cooling techniques for high-speed moving bodies fail to accurately control the boundary layer, leading to increased frictional resistance and frictional heat, which affects motion efficiency and pressure distribution non-uniformity.
A boundary layer control device comprising a porous member with outlets, pressure chambers, a gas supply unit, pressure adjustment unit, and a control unit to manage gas flow and pressure for precise control of the boundary layer.
The device effectively reduces frictional resistance and stabilizes separation points, enhancing motion efficiency and reducing pressure fluctuations.
Smart Images
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Abstract
Description
Technical Field
[0001] The present disclosure relates to a boundary layer control device and a moving body.
Background Art
[0002] Conventionally, as a cooling technique for cooling the surface of a moving body moving at high speed in the air, a film cooling device provided on the airframe is known to perform film cooling on the surface of the airframe by supplying a cooling gas (for example, see Patent Document 1).
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] As the speed of a moving body increases, the frictional resistance with the air generated on the surface of the moving body increases. When the frictional resistance increases, the motion efficiency of the moving body decreases or the frictional heat generated on the surface of the moving body increases. By the way, the pressure distribution of the airflow flowing along the surface of the moving body is not uniform, and the boundary layer formed on the surface of the moving body is non-uniform. In Patent Document 1, since the cooling gas is supplied uniformly from the film cooling device, although the surface of the airframe can be cooled, it is difficult to accurately control the boundary layer on the surface of the moving body. Therefore, in Patent Document 1, it was difficult to form a boundary layer capable of appropriately reducing the frictional resistance.
[0005] Therefore, an object of the present disclosure is to provide a boundary layer control device and a moving body that can appropriately reduce the frictional resistance on the surface of the moving body.
Means for Solving the Problems
[0006] The boundary layer control device of the present disclosure is a boundary layer control device for controlling a boundary layer formed on the surface of a moving body, comprising: a porous member provided on the surface of the moving body and having a plurality of outlets for blowing gas outwards; a plurality of pressure chambers provided on the back side of the porous member and provided according to a plurality of outlet regions partitioned on the surface of the porous member; a gas supply unit for supplying the gas to each of the plurality of pressure chambers; a pressure adjustment unit for adjusting the internal pressure of each of the plurality of pressure chambers; and a control unit for controlling the pressure adjustment unit.
[0007] The mobile body of this disclosure comprises a mobile body body and the boundary layer control device provided on the mobile body body. [Effects of the Invention]
[0008] According to this disclosure, frictional resistance on the surface of a moving object can be appropriately reduced. [Brief explanation of the drawing]
[0009] [Figure 1] Figure 1 shows a mobile body equipped with a boundary layer control device according to this embodiment. [Figure 2] Figure 2 is a schematic diagram of the boundary layer control device. [Figure 3] Figure 3 is an explanatory diagram regarding the boundary layer. [Figure 4] Figure 4 is an explanatory diagram regarding the delamination point in the boundary layer. [Figure 5] Figure 5 is an explanatory diagram regarding pressure control by the boundary layer control device. [Modes for carrying out the invention]
[0010] Embodiments relating to this disclosure will be described in detail below with reference to the drawings. However, the present invention is not limited by these embodiments. Furthermore, some of the components in the embodiments described below are substituted or substantially identical to those easily substituted by those skilled in the art. Moreover, the components described below can be combined as appropriate, and if there are multiple embodiments, each embodiment can be combined.
[0011] [This Circumstance] The mobile body 1 equipped with the boundary layer control device 10 of this disclosure is a spacecraft re-entering the atmosphere, or a mobile body flying at supersonic speed or faster. The mobile body 1 is not particularly limited and may be a transport vehicle such as an automobile, aircraft, or railway vehicle, or a mobile body moving at a speed slower than supersonic speed.
[0012] Figure 1 shows a mobile body equipped with a boundary layer control device according to this embodiment. Figure 2 is a schematic diagram of the boundary layer control device. Figure 3 is an explanatory diagram of the boundary layer. Figure 4 is an explanatory diagram of the separation point in the boundary layer. Figure 5 is an explanatory diagram of pressure control by the boundary layer control device. The mobile body 1 will be described with reference to Figure 1. In the following description, the mobile body 1 will be described in the context of an aircraft.
[0013] (Mobile) The mobile unit 1 comprises an airframe (mobile unit body) 5 and a boundary layer control device 10 that controls the boundary layer L formed on the surface of the airframe 5. The airframe 5 has a roll axis direction in the direction connecting its nose and tail, a pitch axis direction in the width direction connecting its left and right sides, and a yaw axis direction in the direction connecting its top and bottom. The roll axis direction, pitch axis direction, and yaw axis direction are orthogonal. During flight of the mobile unit 1, a boundary layer L is formed on the surface of the airframe 5.
[0014] Here, referring to FIG. 1, an example of the boundary layer L formed on the airframe 5 will be described. The boundary layer L is formed along the surface of the airframe 5 from the nose side to the tail side in the roll axis direction of the airframe 5. The boundary layer L includes a laminar boundary layer La that is formed in a layered shape on the nose side of the airframe 5 and a turbulent boundary layer Lb that is formed on the tail side of the airframe 5. The laminar boundary layer La is a layer with small fluctuations in the layer thickness of the boundary layer L, with a thinner layer thickness on the nose side and a thicker layer thickness on the tail side. The turbulent boundary layer Lb is a layer with large fluctuations in the layer thickness of the boundary layer L, and the layer thickness fluctuates due to the airflow (main flow) flowing along the surface of the airframe 5 becoming turbulent. Such a boundary layer L is controlled by the boundary layer control device 10 described below.
[0015] (Boundary layer control device) The boundary layer control device 10 is provided on the airframe 5 and controls the boundary layer L on the surface of the airframe 5. In FIG. 1, the boundary layer control device 10 is arranged to control the boundary layer L on the upper surface of the airframe 5, but it may also be arranged to control the boundary layer L on the lower surface of the airframe 5.
[0016] The boundary layer control device 10 includes a porous member 12, a plurality of pressure chambers 13, a pressure adjustment unit 14, a gas supply unit 15, an airflow sensor 17, an airframe sensor 18, and a control unit 20.
[0017] The porous member 12 is provided on the surface of the aircraft body 5 and has a plurality of blowout holes 19 that blow out gas toward the outside. The porous member 12 is a plate in which the blowout holes 19 are formed. The blowout holes 19 are through-holes on the order of micrometers. It is preferable that the opening diameter of the blowout holes 19 is 500 μm or less, and more preferably 100 μm or less. Also, the blowout holes 19 may have locally different opening diameters. The gas blown out from the blowout holes 19 has a blowing direction that is orthogonal to the mainstream. Also, the porous member 12 is partitioned into a plurality of blowout regions on its surface. The plurality of blowout regions are partitioned at predetermined intervals along the roll axis direction in FIG. 1. Note that the plurality of blowout regions may be partitioned at predetermined intervals along the pitch axis direction. The amount of gas blown out is adjusted in each of the plurality of blowout regions of the porous member 12. Note that the porous member 12 is a plate in which the blowout holes 19 are formed, but for example, a member using a porous material such as a foamed metal may also be used. Also, the blowout region may be provided on the tail side of the aircraft body. In this case, the separation point in the wake region at the rear end of the aircraft body can be moved or fixed.
[0018] The plurality of pressure chambers 13 are provided on the back side of the porous member 12. Also, the plurality of pressure chambers 13 are provided according to the plurality of blowout regions. As shown in FIG. 2, the pressure chamber 13 is partitioned by the porous member 12, the main structure 13a of the aircraft body 5, and the rib member 13b. The main structure 13a is, for example, the outer plate of the aircraft body 5. The rib member 13b is provided so as to protrude outward from the main structure 13a. That is, the lower side of the rib member 13b is connected to the main structure 13a. Also, the porous member 12 is provided above the rib member 13b. Thus, the plurality of pressure chambers 13 are formed by partitioning the space formed by the opposing main structure 13a and porous member 12 with the rib member 13b serving as a partition wall. Also, each pressure chamber 13 is provided with a gas supply port 13c to which a gas supply passage 22 described later is connected, and the gas supply port 13c is formed through the main structure 13a.
[0019] Furthermore, an insulating material 16 is provided inside the pressure chamber 13. The insulating material 16 is positioned on the main structure 13a side and is provided opposite the porous member 12. As a result, a space through which gas flows is formed between the porous member 12 and the insulating material 16. In the boundary layer control device 10, the insulating material 16 may be omitted, and the presence or absence of the insulating material 16 is not particularly limited.
[0020] The pressure adjustment unit 14 adjusts the internal pressure of each of the multiple pressure chambers 13. Specifically, the pressure adjustment unit 14 has multiple pressure adjustment valves 21 and multiple gas supply passages 22. The multiple gas supply passages 22 are passages that connect the multiple pressure chambers 13 and the gas supply unit 15 (its compressor 23). The multiple gas supply passages 22 are integrated on the gas supply unit 15 side. In other words, the multiple gas supply passages 22 are passages that branch out from the gas supply unit 15 side toward the multiple pressure chambers 13. The multiple pressure adjustment valves 21 are provided in each of the multiple gas supply passages 22. The pressure adjustment valves 21 change the internal pressure of the pressure chambers 13 by adjusting the flow rate of gas flowing through the gas supply passages 22. The pressure adjustment valves 21 are connected to the control unit 20, which adjusts the gas flow rate by controlling the opening degree of the pressure adjustment valves 21.
[0021] The gas supply unit 15 supplies gas to each of the multiple pressure chambers 13 via multiple gas supply passages 22. The gas supply unit 15 includes a compressor 23 and an outside air inlet 24. The outside air inlet 24 is formed on the surface of the machine body 5 and is an opening for taking in outside air. The outside air inlet 24 may be provided on the front of the machine body 5 or on the underside of the machine body 5, and is not particularly limited. For example, by providing the outside air inlet 24 on the front of the machine body 5, it is possible to promote the compression of the outside air taken in from the outside air inlet 24, thereby suppressing the compression performance of the compressor 23 and enabling miniaturization and weight reduction of the compressor 23. Alternatively, the outside air inlet 24 may be provided on the rear side of the machine body 5. The intake side of the compressor 23 is connected to the outside air inlet 24, and the delivery side is connected to the gas supply passage 22. The compressor 23 compresses the outside air taken in from the outside air inlet 24 and supplies the compressed outside air as gas to the pressure chamber 13 via the gas supply channel 22.
[0022] The gas supply unit 15 only needs to have an outside air inlet 24, and may be combined with a compressor 23 and a pressure regulating valve for supply as appropriate. In other words, the gas supply unit 15 may consist only of an outside air inlet 24, have an outside air inlet 24 and a compressor 23 (as shown in Figure 1), have an outside air inlet 24 and a pressure regulating valve for supply, or have an outside air inlet 24, a compressor 23 and a pressure regulating valve for supply. Furthermore, the gas supply unit 15 may be combined with an air storage device as appropriate. The air storage device may be provided in place of the compressor 23, or it may be provided connected to the gas discharge side of the compressor 23. This makes it possible to achieve boundary layer control even in thin air in the upper atmosphere or underwater.
[0023] The airflow sensor 17 is a sensor that measures the state of the airflow flowing over the surface of the aircraft 5. The airflow sensor 17 measures the state of the airflow, such as pressure, speed, and temperature. The airflow sensor 17 is connected to the control unit 20 and outputs the measurement results to the control unit 20.
[0024] The aircraft sensor 18 is a sensor that measures the state of the aircraft 5. The aircraft sensor 18 measures the state of the aircraft 5, for example, the altitude of the aircraft 5, the attitude of the aircraft 5, and the speed of the aircraft 5. The aircraft sensor 18 also acquires information that is the target of control for controlling the boundary layer L, namely the opening degree of the pressure regulating valve 21 of the pressure regulating unit 14, as part of the state of the aircraft 5. The aircraft sensor 18 is connected to the control unit 20 and outputs the measurement results to the control unit 20.
[0025] The control unit 20 controls each part of the boundary layer control device 10. The control unit 20 includes an integrated circuit such as a CPU (Central Processing Unit). As an example of control, the control unit 20 controls the boundary layer L by adjusting the gas blowout amount based on the chamber pressure. Specifically, the control unit 20 controls the internal pressure of the multiple pressure chambers 13 by controlling the pressure adjustment unit 14 based on the measurement results of the airflow sensor 17 and the aircraft sensor 18. By controlling the boundary layer L, the control unit 20 performs friction reduction control to reduce frictional resistance on the surface of the aircraft 5, and performs separation point fixing control to fix the separation points that occur on the surface of the aircraft 5.
[0026] Refer to Figure 3 to explain the friction reduction control. As shown in Figure 3, a main flow M flows along the surface of the aircraft body 5, and a boundary layer L is formed between the main flow M and the surface of the aircraft body 5. The greater the pressure P2 of the boundary layer L is compared to the pressure P1 of the main flow M, the thicker the boundary layer L becomes. In order to reduce the frictional resistance of the surface of the aircraft body 5, it is necessary to increase the thickness of the boundary layer L and make the pressure gradient from the surface of the boundary layer L to the main flow M gentler. In other words, the control unit 20 performs friction reduction control by increasing the thickness of the boundary layer L and making the pressure gradient of the boundary layer L gentler. At this time, the mass velocity ratio λ of the airflow flowing on the surface of the aircraft body 5 and the gas G blown out from the outlet 19 is applied as a parameter used in the friction reduction control performed by the control unit 20. Here, the mass velocity ratio λ is expressed by equation (1). Furthermore, the correlation between the amount of gas blown out from the outlet 19 and the gas supply flow rate supplied to the pressure chamber 13 or the internal pressure of the pressure chamber 13 may be measured in advance and obtained as a table, and this table may be incorporated into the control program.
[0027] λ = ρ c U c / ρ ∞ U ∞ ...(1) λ: mass flow rate ratio ρ c Density of gas G U c : Speed of gas G ρ ∞ : Mainstream M density U ∞ : Mainstream M speed
[0028] When the control unit 20 performs friction reduction control, it calculates the velocity of the main flow medium M using the airflow sensor 17 and the aircraft sensor 18. The density of the main flow medium M may be calculated using the correlation between altitude and atmospheric density from the aircraft sensor 18, such as an altimeter. After this, the control unit 20 calculates the amount of gas to be blown out so that the mass velocity ratio λ is predetermined to reduce frictional resistance. The correlation between the amount of gas to be blown out and the density and velocity of gas G has been obtained in advance by measurement. Therefore, based on the calculated amount of gas to be blown out, the control unit 20 can obtain the density and velocity of gas G from the correlation and calculate the mass velocity ratio λ.
[0029] Next, the separation point fixing control will be explained with reference to Figure 4. As shown in Figure 4, a separation point P of the boundary layer L occurs on the surface of the machine body 5. The separation point P is the boundary point where, due to the reverse pressure gradient, the velocity of the main flow M within the boundary layer L gradually decreases, and a reverse flow region R, which is a flow field in the opposite direction to the main flow M, is generated. Airflow separation occurs at the separation point P. The airflow flowing over the surface of the machine body 5 is more prone to separation as the thickness of the boundary layer L increases. Therefore, the control unit 20 blows gas G from the blowhole 19, which makes the velocity gradient near the surface of the machine body 5 gentler (the profile thins out), so that the reverse flow region in the reverse pressure gradient is more likely to occur upstream of the main flow M. And, by forming the reverse flow region upstream of the main flow M, the separation point P can be moved forward of the machine body 5, or the position of the oscillating separation point P can be uniquely fixed. Since airflow separation depends on the mass velocity ratio λ, it is necessary to control the mass velocity ratio λ when fixing the separation point P. In other words, the control unit 20 performs control to adjust the mass velocity ratio λ as separation point fixing control.
[0030] Specifically, when the control unit 20 performs separation point fixing control, it obtains the pressure distribution on the surface of the machine 5 using the airflow sensor 17. That is, the control unit 20 obtains the density and velocity of the main flow M as the pressure distribution. The control unit 20 also obtains the density and velocity of the gas G from the current control of the pressure adjustment unit 14 of the machine 5 using the machine sensor 18. Then, the control unit 20 controls the boundary layer L by adjusting the density and velocity of the gas G by controlling the pressure adjustment unit 14 so that the separation point P generated on the surface of the machine 5 changes to a predetermined mass velocity ratio λ in which the separation point P is fixed. The position of the fixed separation point P may be, for example, an impact-resistant area formed on the surface of the machine 5. The control unit 20 may also control the shock wave generation position by performing control to move the position of the separation point P upstream or downstream of the main flow M.
[0031] Next, with reference to Figure 5, the control unit 20 will specifically explain the control of the boundary layer L. When the control unit 20 performs control of the boundary layer L, it measures the state of the airflow (state of the flow field) using the airflow sensor 17 and the state of the aircraft 5 using the aircraft sensor 18. Based on the information obtained from the aircraft sensor 18, the control unit 20 performs a calculation of the flow field within the boundary layer L. Alternatively, the thickness of the boundary layer L and the separation point at each position corresponding to the flow field and the state of the aircraft 5 may be acquired in advance and stored in a database, and in the flow field calculation, the values may be obtained without relying on flow field analysis by calling up the boundary layer L thickness and separation point P that correspond to the conditions based on the information obtained from the airflow sensor 17 and the aircraft sensor 18.
[0032] Next, the control unit 20 calculates the amount of gas G discharged from each discharge region based on the calculated flow field within the boundary layer L. In this calculation, the discharge amount corresponding to the thickness of the boundary layer L may be acquired in advance, stored in a database, and incorporated. In this case, two types of databases are prepared: one with separation points and one without. Therefore, the calculation of the amount of gas G discharged is performed separately for the cases with and without separation points. The control unit 20 then controls each pressure regulating valve 21 to set the internal pressure of each pressure chamber 13 to a predetermined pressure so that the calculated amount of gas G discharged is achieved.
[0033] In this embodiment, the boundary layer L was controlled using the airflow sensor 17 and the aircraft sensor 18, but the boundary layer L may be controlled using at least one of the sensors. For example, instead of the airflow sensor 17, the airflow state may be obtained by calculating the airflow velocity and density around the aircraft 5 based on the speed, altitude, and acceleration of the aircraft 5, using standard atmospheric data, or by reading them from a table.
[0034] As described above, the boundary layer control device 10 and the mobile body 1 described in this embodiment can be understood, for example, as follows.
[0035] A boundary layer control device 10 according to the first embodiment controls a boundary layer L formed on the surface of a moving body 1, and comprises: a porous member 12 provided on the surface of the moving body 1 and having a plurality of outlet holes 19 for blowing gas outwards; a plurality of pressure chambers 13 provided on the back side of the porous member 12 and provided according to a plurality of outlet regions partitioned on the surface of the porous member 12; a gas supply unit 15 for supplying the gas to each of the plurality of pressure chambers 13; a pressure adjustment unit 14 for adjusting the internal pressure of each of the plurality of pressure chambers 13; and a control unit 20 for controlling the pressure adjustment unit 14.
[0036] With this configuration, the boundary layer L formed on the surface of the moving body 1 can be precisely controlled by adjusting the amount of gas blown out according to the blowing area. Therefore, a boundary layer that can appropriately reduce frictional resistance can be formed.
[0037] In a second embodiment, in the boundary layer control device 10 according to the first embodiment, the porous member 12 is a plate in which the blowout holes 19, which are on the order of micrometers, are formed.
[0038] This configuration allows the porous member 12 to be made of a thin material, thus reducing the weight.
[0039] In a third embodiment, in the boundary layer control device 10 according to the first or second embodiment, the pressure adjustment unit 14 includes a plurality of gas supply passages 22 connecting a plurality of pressure chambers 13 and a gas supply unit 15, and a plurality of pressure adjustment valves 21 provided in the plurality of gas supply passages 22.
[0040] With this configuration, the internal pressure of multiple pressure chambers 13 can be adjusted by controlling multiple pressure regulating valves 21.
[0041] In a fourth embodiment, in a boundary layer control device 10 according to any one of the first to third embodiments, the control unit 20 performs pressure control by the pressure adjustment unit 14 so as to change the mass velocity ratio λ between the airflow (main stream M) flowing over the surface of the moving body 1 and the gas G blown out from the outlet hole 19.
[0042] With this configuration, by using the mass velocity ratio λ as a control parameter, the boundary layer L can be controlled in a way that allows for precise reduction of frictional resistance.
[0043] In a fifth embodiment, in a boundary layer control device 10 according to any one of the first to third embodiments, the control unit 20 performs pressure control by the pressure adjustment unit 14 so that the separation point P where the airflow flowing over the surface of the moving body 1 separates is fixed.
[0044] With this configuration, since the separation point P is fixed, pressure fluctuations due to variations in the separation point P can be suppressed, thereby reducing vibration and noise.
[0045] In a sixth embodiment, in a boundary layer control device 10 according to any one of the first to fifth embodiments, the gas supply unit 15 includes an outside air inlet 24 for taking in the gas G from outside the moving body 1, and a compressor 23 for compressing the gas G taken in from the outside air inlet 24.
[0046] With this configuration, gas G can be taken in from outside the mobile unit 1, which allows for a smaller compressor 23 and a simplified gas supply unit 15.
[0047] In a seventh embodiment, the boundary layer control device 10 according to any one of the first to sixth embodiments further includes at least one of the following sensors: a sensor for measuring the state of the airflow flowing over the surface of the moving body 1 (airflow sensor 17) and a sensor for measuring the state of the moving body 1 (body sensor 18). The control unit 20 performs pressure control by the pressure adjustment unit 14 based on the measurement results of the sensors.
[0048] With this configuration, the state of the airflow over the surface of the moving body 1 and the state of the moving body 1 can be appropriately understood, thereby enabling precise control of the boundary layer L.
[0049] The mobile body 1 according to the eighth embodiment comprises a mobile body (machine 5) and a boundary layer control device 10 according to any one of the first to seventh embodiments provided on the mobile body.
[0050] This configuration makes it possible to provide a moving body 1 in which surface frictional resistance is appropriately reduced. [Explanation of Symbols]
[0051] 1 Mobile Unit 5 aircraft 10 Boundary layer control device 12. Perforated member 13 Pressure Chamber 14 Pressure adjustment section 15. Gas Supply Department 16. Insulation 17 Airflow Sensor 18. Aircraft sensors 19 Air outlet 20 Control Unit 21 Pressure regulating valve 22 Gas supply channel 23 Compressor 24. Outdoor air inlet L boundary layer G Gas P Peeling point
Claims
1. In a boundary layer control device that controls the boundary layer formed on the surface of a moving object, A porous member provided on the surface of the moving body, having multiple outlets for blowing gas outwards, A plurality of pressure chambers are provided on the back side of the porous member and are provided according to a plurality of blowing regions partitioned on the surface of the porous member, A gas supply unit that supplies the gas to each of the multiple pressure chambers, A pressure adjustment unit that adjusts the internal pressure of each of the multiple pressure chambers, A sensor for measuring the state of the airflow flowing over the surface of the moving body, and at least one of the sensors for measuring the state of the moving body, The system includes a control unit for controlling the pressure adjustment unit, The control unit is a boundary layer control device that performs pressure control by the pressure adjustment unit based on the measurement results of the sensor, so that the separation point where the airflow flowing over the surface of the moving body separates is formed on the surface and fixed to an impact-resistant portion that is resistant to shock waves generated at the separation point.
2. The boundary layer control device according to claim 1, wherein the porous member is a plate in which the blowout holes, which are on the order of micrometers, are formed.
3. The aforementioned pressure adjustment unit is Multiple gas supply channels connecting the multiple pressure chambers and the gas supply unit, The boundary layer control device according to claim 1, further comprising a plurality of pressure regulating valves provided in a plurality of gas supply passages.
4. The boundary layer control device according to claim 1, wherein the control unit performs pressure control by the pressure adjustment unit so as to change the mass velocity ratio between the airflow flowing over the surface of the moving body and the gas blown out from the outlet.
5. The aforementioned gas supply unit, The boundary layer control device according to claim 1, which has an outside air inlet for taking in the gas from outside the moving body.
6. The mobile unit body and A mobile body comprising a boundary layer control device according to claim 1, which is provided on the mobile body body.