Stall characteristic comparison device

Abstract

The utility model discloses a stall characteristic comparison device and a demonstration method thereof, and the device comprises an airplane model without wings, a straight wing, a trapezoidal wing, a sweepback wing, a delta wing, a force measurement balance, a supporting mechanism, a wind speed generation device, a smoke generator, a laser, and a support. The airplane model is fixed on the force measuring balance, the force measuring balance is connected with the supporting mechanism, the wind speed generating device is arranged in front of the airplane model, the smoke generator is arranged at an outlet of the wind speed generating device, and the laser is arranged on the upper portion of the airplane model and connected with the supporting seat. The device can well perform stall characteristic contrast experiments and teaching demonstration of wings with different plane shapes, vividly presents stall characteristics of low-speed to high-speed airplanes, has the characteristics of convenience in observation, good demonstration effect, low cost, simplicity in operation, good portability and the like, and can well meet experiment and teaching requirements.

Description

Technical Field

[0001] The utility model belongs to the teaching field of aircraft aerodynamics and flight mechanics, relates to experiments and simulation demonstrations, which are important means of teaching and research of aircraft aerodynamics and flight mechanics, and specifically relates to a stall characteristic comparison device. Background Art

[0002] Experiments and simulation demonstrations are important means to enhance students' intuitive and perceptual understanding, help students verify, digest and consolidate basic theories and principles, and learn and apply theories to solve practical problems. Experiments are an important means of teaching and research. They are a series of operations or activities to test relevant theories, and simulation demonstrations are to make some physical objects realistic. Due to objective reasons, flight students cannot vividly describe some important phenomena that occur during the actual flight of the aircraft in classroom teaching, and watching videos lacks a sense of substitution. Experiments allow students to personally reproduce some phenomena that occur in actual flights and enhance intuitive cognition. Simulation demonstrations can combine classroom teaching with real-time teaching of some important flight phenomena, concepts, and definitions, which has a significant effect on improving the quality of classroom teaching. At the same time, every theoretical breakthrough in the development of fluid mechanics (aerodynamics) and its application in engineering almost all start from relevant experiments and demonstration observations of flow phenomena. For example, the Reynolds transition experiment in 1880, the Mach shock wave experiment in 1888, Prandtl's boundary layer concept in 1904, von Karman's analysis of vortex streets around cylinders in 1912, and the new winglet proposed by Whitcomb, director of the Langley Aeronautical Laboratory in 1976, were all based on experiments and demonstration observations. In the history of aerodynamics, there has been a research and development process from low-speed airflow characteristics to high-speed airflow characteristics. With the Wright brothers driving the "Flyer One" to achieve the first powered, manned, continuous, stable and controllable flight in human history, human aviation has entered a new era. The development of various types of aircraft has also experienced a development process from low speed to high speed. During this process, the plane shape of the wing has also experienced many types of development and changes, such as straight wings, trapezoidal wings, swept wings and delta wings. Although humans have long entered the supersonic era, the training of flight talents has always followed the path from low speed to high speed, that is, primary trainer aircraft (low speed), intermediate / advanced trainer aircraft (subsonic / transonic), and then assigned to the corresponding aircraft models. In this process, they will experience aircraft with wings of different plane shapes, and the stall characteristics of the wings (aircraft) will also be different. Aerodynamics is the first flight principle course that flight students come into contact with to learn subsequent flight knowledge and skills. It lays the foundation in the entire system. Understanding and mastering the flow and stall characteristics of wings of different plane shapes plays an important role in students' subsequent understanding of many flight phenomena in flight, mastering the actual operation in flight training, and countermeasures when encountering special situations. In traditional classroom teaching, students see or hear video animations or theoretical explanations, and it is difficult to have an intuitive understanding and perception of different forms of stall characteristics. On-site teaching is limited by many conditions and faces difficulties in implementation.

[0003] In view of this, it is of great significance to design a stall characteristics comparison device that is practical, simple, convenient, easy to use, and has good effects and methods. Utility Model Content

[0004] The purpose of the utility model is to overcome the shortcomings of the above-mentioned prior art and provide a stall characteristic comparison device, which is not only suitable for relevant experiments and classroom simulation demonstration teaching, but also can realize the comparison of stall characteristics of low-speed to high-speed aircraft on the same device. In addition, the obscure but very important concepts - wing root effect and wing tip effect and their influence can be intuitively displayed to students by means of flow display, and at the same time, it also has practical value for reference and learning for popular science teaching.

[0005] The utility model discloses a stall characteristic comparison device, which is special in that the device comprises: an aircraft model without wings, a straight wing, a trapezoidal wing, a swept wing, a delta wing, a force measuring balance, a supporting mechanism, a wind speed generating device, a smoke generator, a laser, and a support. The aircraft model is respectively connected with wings of different plane shapes under different conditions, the aircraft model is fixed on the force measuring balance, the force measuring balance is connected with the supporting mechanism, the wind speed generating device is arranged in front of the aircraft model, the smoke generator is arranged at the outlet of the wind speed generating device, and the laser is arranged on the upper part of the aircraft model and connected with the support. Through flow display, combined with dynamometer balance data, continuous adjustment of the angle of attack and replacement of wings with different planar shapes, the stall process and principles of wings with different planar shapes can be clearly and intuitively presented to students, allowing them to master the stall characteristics of aircraft under different wings. This not only allows students to have a deep understanding of the stall characteristics of low-speed and high-speed aircraft and related measures to improve the stall characteristics of aircraft, but also has a good boosting effect on avoiding stalls, stall recovery, special situation response, and tactical training in subsequent actual flights.

[0006] Preferably, the wing is any one of a straight wing, a trapezoidal wing, a swept wing, and a delta wing. The connection mode between the aircraft model and the above-mentioned wings of different plane shapes is a slide slot type. The stall characteristics of wings of different plane shapes are different. For example, the straight wing stalls first at the wing root due to the decrease in the effective angle of attack caused by the downwash of the wingtip airflow, and the trapezoidal wing will gradually move from the wing root to the wing tip as the root-tip ratio (the ratio of the chord length at the wing root to the chord length at the wing tip) increases. The swept wing and delta wing represented by high-speed wings will stall first at the wing tip due to the wing root and wing tip effects, which will then have an adverse effect on flight control. Through the slide-type connection, the opening of a groove in the middle of the aircraft model fuselage and the processing of matching bosses on the wings, not only can the stall characteristic experiment and simulation demonstration of wings with different plane shapes be carried out on the same aircraft model, thus greatly reducing the device cost, but also the experiments and simulation demonstrations on the same aircraft model can ensure the consistency of many geometric parameters of the aircraft model, eliminate the interference of irrelevant variables, and enhance the pertinence and accuracy of the demonstration effect.

[0007] Preferably, the span and airfoil of the straight wing, trapezoidal wing, swept wing, and delta wing are the same and have no geometric and aerodynamic twist. Although the plane shapes of the wings of each aircraft are different in practice and the parameters such as span and airfoil are also different, the design is mainly considered from the perspective of aerodynamics and improving stall, and the stall characteristics of wings with different plane shapes cannot be fundamentally changed. Wings with different plane shapes have different stall characteristics due to their different flow characteristics, and the span and airfoil of each wing are the same and have no geometric and aerodynamic twist, which can fully eliminate irrelevant variables and enhance the pertinence and accuracy of the demonstration effect.

[0008] Preferably, the dynamometer is a dynamometer that can measure force and torque. When an aircraft is flying, there are not only various aerodynamic forces, but also torques generated by these aerodynamic forces. When the aircraft stalls, the aerodynamic forces and corresponding aerodynamic torques of the aircraft will change significantly. Qualitative display combined with quantitative data can help students understand the relevant abstract theoretical knowledge more deeply.

[0009] Preferably, the support mechanism includes a vertical rod and an oblique support rod, and the oblique support rod and the vertical rod are fastened by screws. Through this form of connection, the angle of attack of the aircraft model can be easily adjusted, and the entire process from the beginning of the aircraft to the stall and the evolution of the flow on the wing surface can be fully displayed, thereby providing guidance and help for mastering the stall characteristics and principles of wings with different plane shapes.

[0010] Preferably, the wind speed generating device is an adjustable speed device. The wind speed generating device is specifically a small or micro axial flow fan or a small or micro centrifugal fan. The use of a small or micro axial flow fan or a small or micro centrifugal fan can effectively reduce costs on the one hand, and also take into account the portability when used as a teaching aid. Of course, wind speed generating devices such as electric fans can also be used.

[0011] Preferably, the smoke from the smoke generator is colored. When the aircraft is flying, as the angle of attack gradually increases to the stall (critical) angle of attack, how does the flow pattern on the aircraft surface change? What is the "S"-shaped flow on the wing surface under the effects of the swept wing and delta wing at the wing root and wing tip? Under the combined effect of colored smoke and the light emitted by the laser, the surface and space flow can be clearly and intuitively presented to the trainees.

[0012] Preferably, the roller at the bottom of the support can move the laser along the longitudinal axis of the aircraft model, that is, the laser can move back and forth from the nose to the tail of the aircraft. Since the laser emits a sheet of light and can only illuminate one plane, the reciprocating movement of the laser can illuminate the entire flow condition around the wing, so that the flow state on the wing surface and the evolution of the aircraft model during the increase of the angle of attack, especially the "S"-shaped flow on the surface of the swept wing and delta wing, the judgment of the stall position, the flow state, etc. are presented to the trainees in a three-dimensional form, so that they can have a deeper grasp of the knowledge and theories related to stall.

[0013] The utility model provides a demonstration method for a stall characteristic comparison device, which is special in that it comprises the following steps:

[0014] During the demonstration, the straight wing is fixed at the corresponding position of the aircraft model, the support mechanism is adjusted to make the aircraft model at an angle of attack of 0°, the speed of the wind speed generator is fixed and the corresponding outlet wind speed is recorded, the wind speed generator is placed in front of the aircraft model, the outlet axis of the wind speed generator is collinear with the longitudinal axis of the aircraft model, the sheet of light emitted by the laser is placed at the leading edge of the wing by adjusting the support, smoke is released in front of the aircraft model, and while observing the flow field, the support mechanism is gradually adjusted to increase the angle of attack of the aircraft model. During this process, attention should be paid to observing and recording the force balance data. When the lift data increases and becomes gentle, the laser is slowly moved toward the tail of the wing. When the lift data begins to decrease, the position of the support mechanism is fixed, and the flow on the wing surface illuminated by the laser is observed. At this time, the flow near the wing tip is still relatively regular and most of it is attached to the wing surface. The smoke separation is not serious, while the separation is serious at the wing root. The smoke flow is relatively turbulent and stall occurs. Then the straight wing is removed and replaced with a trapezoidal wing, and the above operation is repeated;

[0015] The wings are replaced with swept wings and delta wings, and the wind speed generating device uses a micro axial flow fan. During the demonstration, the swept wings are fixed at the corresponding position of the aircraft model, and the supporting mechanism is adjusted to make the aircraft model at an angle of attack of 0°. The wind speed at the outlet of the wind speed generating device is the same as mentioned above. The wind speed generating device is placed in front of the aircraft model so that the outlet axis of the wind speed generating device is collinear with the longitudinal axis of the aircraft model. By adjusting the support, the sheet of light emitted by the laser is placed at the leading edge of the wing, and smoke is released in front of the aircraft model. While observing the flow field, the supporting mechanism is gradually adjusted to increase the angle of attack of the aircraft model. During this process, it is necessary to observe and record the force balance data. When the increase in lift data becomes gentle, the laser is slowly moved toward the tail of the wing. At this time, it will be found that the smoke flow on the wing surface shows a certain left and right curvature, that is, "S"-shaped flow. This flow characteristic is exactly the mechanism by which the swept wing produces the "wing root effect" and "wing tip effect", which leads to The swept wing stall presents different characteristics. Through intuitive and visual demonstration, students can master these two abstract concepts; then, when the lift data begins to decrease, fix the position of the support mechanism and observe the flow on the wing surface under laser illumination. At this time, it will be found that the smoke near the wing tip flows fast and is relatively chaotic, the separation is serious, and the wing tip shakes. The dynamometer rolling moment is sometimes large and sometimes small, while at the wing root, the smoke separation is not serious and is still relatively regular, and most of it is attached to the wing surface; then remove the swept wing and replace it with a delta wing, and repeat the above operation; combine the quantitative data of the dynamometer balance with the qualitative display of the flow field and the wingtip shake to explain in detail the stall characteristics of high (subsonic) speed aircraft represented by swept wings and delta wings and the adverse effects on flight control during stall, so as to better understand and master the stall characteristics of advanced trainer aircraft and some fighters, and the fundamental principles that cause such stall characteristics, and strengthen students' connection and application of knowledge points with actual flight.

[0016] The utility model provides a stall characteristic comparison device, including an aircraft model without wings, a straight wing, a trapezoidal wing, a swept wing, a delta wing, a dynamometer, a support mechanism, a wind speed generating device, a smoke generator, a laser, and a support, which can well conduct stall characteristic comparison experiments and teaching demonstrations of wings with different plane shapes. Through flow display, combined with dynamometer data, continuous adjustment of the angle of attack, and replacement of wings with different shapes, the stall process and principle of wings with different plane shapes are clearly and intuitively presented to students, so that students can master the stall characteristics of aircraft under different wings, which not only allows students to have a profound understanding of the stall characteristics of low-speed and high-speed aircraft and the relevant measures to improve the stall characteristics of aircraft, but also has a good boosting effect on avoiding stalls, stall recovery, special situation response, and tactical training in subsequent actual flights. The device has the characteristics of convenient observation, good demonstration effect, low cost, simple operation, good portability, etc., and can well meet the requirements of experiments and teaching. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1The utility model is a schematic structural diagram of a stall characteristic comparison device. DETAILED DESCRIPTION

[0018] The specific implementation of the present utility model is described in detail below in conjunction with the accompanying drawings. Example 1

[0019] A stall characteristic comparison device of this embodiment, such as Figure 1 As shown, it specifically includes: an aircraft model 1 without wings, a straight wing 2, a trapezoidal wing 3, a force measuring balance 6, a supporting mechanism 7, a wind speed generating device 8, a smoke generator 9, a laser 10, and a support 11. The aircraft model 1 can be connected to wings of different plane shapes. The aircraft model 1 is fixed on the force measuring balance 6, the force measuring balance 6 is connected to the supporting mechanism 7, the wind speed generating device 8 is placed in front of the aircraft model 1, the smoke generator 9 is placed at the outlet of the wind speed generating device 8, and the laser 10 is placed on the upper part of the aircraft model 1 and connected to the support 11. The wind speed generating device 8 adopts a small centrifugal fan.

[0020] During the demonstration, the straight wing 2 is fixed at the corresponding position of the aircraft model 1, and the support mechanism 7 is adjusted to make the aircraft model at an angle of attack of 0°. The speed of the wind speed generating device 8 is fixed and the corresponding outlet wind speed is recorded, that is, the incoming flow speed is constant or the flight speed is constant. The wind speed generating device 8 is placed in front of the aircraft model so that the outlet axis of the wind speed generating device 8 is collinear with the longitudinal axis of the aircraft model 1. By adjusting the support, the sheet of light emitted by the laser 10 is placed at the leading edge of the wing, and smoke is released in front of the aircraft model 1. While observing the flow field, the support mechanism 7 is gradually adjusted to increase the angle of attack of the aircraft model 1. When adjusting, it is necessary to operate gently and avoid roughness. During this process, pay attention to observe and record the data of the force balance. When the lift data increases and becomes flat, slowly move the laser 10 toward the tail of the wing. When the lift data begins to decrease, fix the position of the support mechanism 7 and observe the flow on the wing surface illuminated by the laser. At this time, you will find that the flow near the wing tip is still relatively regular and most of it is attached to the wing surface. The smoke separation is not serious, but at the wing root, the separation is serious, and the smoke flow is relatively disordered, which means stall. Then remove the straight wing 2 and replace it with the trapezoidal wing 3, and repeat the above operation. Combined with the quantitative data of the force balance 6 and the qualitative display of the flow field, the stall characteristics of low-speed aircraft represented by the straight wing 2 and the trapezoidal wing 3 are described in detail, so as to better understand and master the stall characteristics of a certain primary trainer aircraft to be used in flight training, and strengthen the students' connection and application of knowledge points with actual flight. Example 2

[0021] A stall characteristic comparison device in this embodiment has a structure that is basically the same as that of Embodiment 1, with the main differences being: (1) the straight wing or trapezoidal wing is replaced with a swept wing 4 or a delta wing 5; and (2) the wind speed generating device 8 uses a micro axial flow fan, which can further reduce the size of the fan and increase the maximum wind speed of the fan.

[0022] During the demonstration, the swept wing 4 is fixed at the corresponding position of the aircraft model 1, and the support mechanism 7 is adjusted to make the aircraft model 1 at an angle of attack of 0°. The outlet wind speed of the wind speed generating device 8 is the same as that of Example 1, that is, the incoming flow speed is constant or the flight speed is constant. The wind speed generating device 8 is placed in front of the aircraft model 1, so that the outlet axis of the wind speed generating device 8 is collinear with the longitudinal axis of the aircraft model 1. By adjusting the support, the sheet of light emitted by the laser 10 is placed at the leading edge of the wing, and smoke is released in front of the aircraft model 1. While observing the flow field, the support mechanism 7 is gradually adjusted to increase the angle of attack of the aircraft model 1. When adjusting, it is necessary to operate gently and avoid roughness. During this process, pay attention to observe and record the data of the force balance. When the lift data increases and becomes flat, slowly move the laser 10 toward the tail of the wing. At this time, you will find that the smoke flow on the wing surface shows a certain left and right bend, that is, "S"-shaped flow. This flow characteristic is exactly the mechanism of the "wing root effect" and "wing tip effect" produced by the swept wing, which leads to different characteristics of the swept wing stall. Through intuitive and vivid demonstration, let the students better grasp these two abstract concepts. Then fix the position of the support mechanism when the lift data begins to decrease, and observe the flow on the wing surface illuminated by the laser. At this time, you will find that the smoke flow near the wing tip is fast and relatively chaotic, the separation is serious, and the wing tip is shaking. The rolling torque of the force balance is sometimes large and sometimes small, while at the wing root, the smoke separation is not serious and is still relatively regular, and most of it is attached to the wing surface. Then remove the swept wing and replace it with a delta wing, and repeat the above operation. Combining the quantitative data of the dynamometer with the qualitative display of the flow field and wingtip flutter, the course explains in detail the stall characteristics of high (subsonic) speed aircraft represented by swept wings and delta wings, as well as the adverse effects on flight control during stall. This course helps students better understand and master the stall characteristics of advanced trainer aircraft and some fighter aircraft, as well as the fundamental principles that cause such stall characteristics, and strengthens the connection and application of knowledge points with actual flight practice.

[0023] Finally, it should be noted that the above description is only a preferred embodiment of the utility model and is not intended to limit the utility model. Although the utility model is described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions recorded in the above embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model shall be included in the protection scope of the utility model.

Claims

1. A stall characteristics comparison device, It is characterized in that include: An aircraft model (1) without wings, a wing, a force measuring balance (6), a supporting mechanism (7), a wind speed generating device (8), a smoke generator (9), a laser (10), and a support (11), wherein the aircraft model (1) is connected to wings of different plane shapes under different conditions, the aircraft model (1) is fixed on the force measuring balance (6), the force measuring balance (6) is connected to the supporting mechanism (7), the wind speed generating device (8) is placed in front of the aircraft model (1), the smoke generator (9) is arranged at the outlet of the wind speed generating device (8), and the laser (10) is placed on the upper part of the aircraft model (1) and connected to the support (11).

2. A stall characteristics comparison device as claimed in claim 1, It is characterized in that The wing is any one of a straight wing (2), a trapezoidal wing (3), a swept wing (4), and a delta wing (5).

3. A stall characteristics comparison device as claimed in claim 1, It is characterized in that The connection between the aircraft model (1) and the wing is a sliding groove type.

4. A stall characteristics comparison device as claimed in claim 2, It is characterized in that The straight wing (2), the trapezoidal wing (3), the swept wing (4), and the delta wing (5) have the same span and airfoil and have no geometric or aerodynamic twist.

5. A stall characteristics comparison device as claimed in claim 1, It is characterized in that The force measuring balance (6) is a force measuring balance capable of measuring force and torque.

6. A stall characteristics comparison device as claimed in claim 1, It is characterized in that The support mechanism (7) comprises a vertical rod and an oblique support rod, and the oblique support rod and the vertical rod are fastened by screws.

7. A stall characteristics comparison device as claimed in claim 1, It is characterized in that The wind speed generating device (8) is a speed-adjustable device.

8. A stall characteristics comparison device as claimed in claim 1, It is characterized in that The smoke generated by the smoke generator (9) is colored.

9. A stall characteristics comparison device as claimed in claim 1, It is characterized in that A roller is provided at the bottom of the support (11), and the support (11) is pushed to move the laser (10) along the longitudinal axis direction of the aircraft model (1).

Images