Stator and rotor structure based inlet passage test exit pulsating back pressure generating device

Abstract

The application discloses an inlet passage test outlet pulse back pressure generating device based on a stator and a rotor structure, which comprises an inlet passage outlet section, a stator with a flow guide cone and blades, a rotor with blades and a driving mechanism. The rotor blades rotate under the driving of the driving mechanism, and the periodic change of the relative position of the rotor and the stator can realize periodic throttling, thereby generating periodic pulse back pressure. Compared with the throttling blade method adopted in the prior art, the pulse back pressure generating device is directly installed downstream of the inlet passage outlet, has higher integration degree with the inlet passage, has obviously reduced volume, reduces the plugging degree in the wind tunnel, is more favorable for carrying out inlet passage related tests in the wind tunnel, the blades are more uniformly stressed, the pulse back pressure generating device is more stable in the rotating process, the pulse back pressure generating structure is simpler, the stator and the rotor structure are more convenient to replace, and the test cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of inlet duct testing technology, and more specifically to an inlet duct test outlet pulsating back pressure generating device based on stator and rotor. Background Technology

[0002] The scramjet engine mainly consists of an intake, an isolator, a combustion chamber, and a tail nozzle. Since the outlet of the isolator is directly connected to the combustion chamber, and unstable combustion usually occurs in the combustion chamber, the back pressure at the outlet of the isolator will pulsate. The pulsation frequency ranges from 100Hz to 500Hz. Directly integrating the intake, isolator and combustion chamber is not only costly and unsafe, but also makes it difficult to control the pulsation pattern. Therefore, it is necessary to develop a simple and reliable outlet pulsation back pressure generating device in the intake test.

[0003] There are currently three main methods for generating pulsed back pressure at the intake duct test outlet. The first method is to control the throttling device through a stepper motor at the intake duct outlet to achieve periodic back pressure. However, its pulse frequency is low, usually below 100Hz, which cannot meet the requirements of high-frequency pulsed back pressure.

[0004] The second method is to achieve this by rotating rods of different shapes. Currently, the widest frequency range of the commonly used elliptical rods is 12Hz to 124Hz, which still cannot cover the frequency range of the actual intake outlet pulsating back pressure.

[0005] The third method involves installing throttling blades downstream of the intake outlet. These blades periodically block the outlet airflow, creating pulsating back pressure. Xiong Bing's doctoral dissertation, "Study on Forced Oscillation Characteristics of Shock Trains in the Isolation Section," details this pulsating back pressure generating device, demonstrating a frequency range of 15Hz to 300Hz. Figure 1 This is a schematic diagram of the device. Although it can achieve high-frequency pulsation, this scheme still has the following drawbacks. First, because the blades need to block the entire inlet outlet, and the size of a single blade is roughly the same as the size of the inlet outlet, the entire pulsating back pressure generating device is relatively large. If inlet tests are conducted in a wind tunnel, the wind tunnel may not start due to excessive blockage. Second, because each throttling operation involves a single blade blocking the airflow at the inlet outlet, the blades experience uneven stress, which can lead to vibration problems under high-frequency conditions. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides an inlet test outlet pulsating back pressure generating device based on a stator and rotor structure. The aim is to reduce the volume of the pulsating back pressure generating device and ensure uniform stress on the blades while achieving high-frequency pulsating excitation, thus providing a new method for inlet wind tunnel related tests.

[0007] Technical solution: To achieve the above objectives, the present invention may adopt the following technical solution:

[0008] An inlet test outlet pulsating back pressure generating device based on a stator and rotor structure includes an inlet outlet section, a stator, a rotor, and a drive mechanism for driving the rotor to rotate. The stator is installed at the end of the inlet outlet section and includes a guide cone extending into the inlet outlet section and an outlet end located at the end of the inlet outlet section. The outlet end includes several openings and a guide cone surface. Each opening has the same area and shape and is uniformly arranged around the central axis of the stator. The rotor is coaxially mounted with the stator and has several blades. Each blade has the same shape and size and is uniformly arranged around the central axis of the rotor. During the rotation of the rotor, the relative position of the rotor and the stator changes periodically.

[0009] Furthermore, the intake duct outlet section is an expansion section, and the outlet is circular.

[0010] Furthermore, the stator has a guide cone with a semi-cone angle of 15° to 25°, and the outlet end facing the airflow has a guide cone surface with an included angle of 50° to 60° between the cone surfaces. The blade end facing away from the airflow is flat and parallel to the outlet end face of the air inlet.

[0011] Furthermore, the number of stator blades is greater than 2 and they are distributed in a circular pattern at equal angles, with a cylindrical blind hole at the center of each blade.

[0012] Furthermore, the rotor has more than 2 openings that are circumferentially distributed at equal angles, and a threaded hole is present at the center of the rotor.

[0013] Furthermore, the central axes of the stator and the rotor coincide, and both the stator and the rotor have a central ring at their center. The outer diameter of the rotor's central ring is smaller than that of the stator's central ring. Reducing the distance between the rotor and the stator increases the amplitude of the pulsating back pressure. Increasing the outer diameter or width of the rotor blades also increases the amplitude of the pulsating back pressure.

[0014] Furthermore, the drive mechanism is a model aircraft brushless motor. The rotor blade center is connected to the drive shaft of the model aircraft brushless motor by a thread and locked with nuts installed at the front and rear. The rotation speed of the motor is controlled by adjusting the given voltage value, and the rotation direction is changed by adjusting the wiring method. Changing the blade rotation speed realizes the adjustment of the pulsating back pressure frequency.

[0015] Furthermore, the intake outlet section is connected to the intake isolation section.

[0016] Furthermore, the opening shape of the stator is fan-shaped.

[0017] Furthermore, the rotor blades are cuboids, and adjacent blades form a triangular angle.

[0018] Compared with the throttling blades used in the prior art, the main advantages of the present invention are:

[0019] (1) The pulse back pressure generating device of the present invention is directly installed downstream of the intake outlet, and has a higher degree of integration with the intake. The volume of the pulse back pressure generating device is significantly reduced, which reduces the blockage in the wind tunnel and is more conducive to carrying out intake-related tests in the wind tunnel.

[0020] (2) The blades are subjected to more uniform force, and the pulsating back pressure generating device is more stable during rotation;

[0021] (3) The structure for generating pulsating back pressure is simpler, and the replacement of stator and rotor structures is more convenient;

[0022] (4) Lower testing costs. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a pulsed back pressure generating device (throttling blade structure) in the prior art;

[0024] Figure 2 This is a schematic diagram of the pulsating back pressure generating device based on the stator and rotor structure of the present invention;

[0025] Figure 3 This is a schematic diagram of the stator and rotor structure of the present invention;

[0026] Figure 4 This is a schematic diagram of the semi-cone angle of the stator guide cone and the surface angle of the guide cone at the outlet end of the present invention;

[0027] Figure 5 This is a schematic diagram of the pressure pulsation and spectrum analysis results measured at a point inside a pipe under wind tunnel test conditions with a blade speed of 680 rpm.

[0028] Figure 6 This is a schematic diagram of the pressure pulsation and spectrum analysis results measured at a point inside a pipe under wind tunnel test conditions with a blade speed of 4170 rpm. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0030] refer to Figures 2 to 3The diagram shows the inlet outlet pulsating back pressure generating device based on a stator and rotor structure according to the present invention. It includes an inlet outlet section 1, a stator 2, a rotor 3, and a drive mechanism 4 for rotating the rotor. The stator 2 is installed at the end of the inlet outlet section 1. The stator 2 includes a guide cone 21 extending into the inlet outlet section 1 and an outlet end 22 located at the end of the inlet outlet section 1. The outlet end 22 includes several openings 23, each with the same area and shape, uniformly arranged around the central axis of the stator 2. In this embodiment, there are 8 rotor blades 31, and 8 openings 23 in the stator 2, distributed in an equiangular circumferential pattern. The rear end face of the stator 2 and the front end face of the rotor blades 31 are both planar and parallel to the inlet outlet end face. The openings 23 of the stator are fan-shaped. The rotor blades 31 are cuboids, and adjacent blades 31 form a triangular angle.

[0031] The rotor and stator are coaxially mounted. The rotor has several blades 31, each with the same shape and size, evenly arranged around the central axis of the rotor 31. The drive mechanism uses a model aircraft brushless motor. The center of the rotor blades 31 is threaded to the drive shaft of the model aircraft brushless motor 4 and locked with nuts at the front and rear. The rotational speed of the motor is controlled by a given voltage value, and the rotational direction is changed by adjusting the wiring. Changing the rotational speed of the blades 31 can adjust the frequency of the pulsating back pressure. Wind tunnel tests show that the pulsating back pressure frequency range that can be generated in this example is 90.2Hz to 556.1Hz, which completely covers the frequency range of the outlet pulsating back pressure under real combustion conditions.

[0032] In this example, the stator's guide cone has a half-cone angle of 15 degrees, and there is a guide cone surface at the outlet end facing the airflow. The included angle between the cone surfaces is 58.5°. The blade end facing away from the airflow is flat and parallel to the outlet end face of the inlet. The central axes of the stator and the rotor coincide. Both the stator and the rotor have a central ring at their center. The outer diameter of the rotor's central ring is smaller than the outer diameter of the stator's central ring. The current blade arrangement makes the rotor blade 31 more uniformly stressed during rotation and significantly reduces the size of a single blade 31.

[0033] During the rotation of the rotor blades, when the area of ​​the stator opening 23 blocked by the rotor blades 31 is at its maximum, the blockage of the outlet airflow is at its highest and the pulsating pressure reaches its peak. When the area of ​​the stator opening 23 blocked by the rotor blades 31 is at its minimum, the blockage of the outlet airflow is at its lowest and the pulsating pressure reaches its trough.

[0034] In this example, the brushless motor 4 of the model aircraft is a Langyu series V2216-KV800 brushless motor with an outer diameter of only 27.5mm, which greatly reduces the size of the pulse back pressure generating device.

[0035] In this example, reducing the distance between the rotor blade 31 and the stator opening 23 increases the amplitude of the pulsating back pressure; increasing the outer diameter or width of the rotor blade 31 also increases the amplitude of the pulsating back pressure.

[0036] Figure 4 and Figure 5 The paper presents the pulsating pressure and its corresponding spectral characteristics measured at a point in the inlet channel under wind tunnel test conditions at motor speeds of 680 rpm and 4170 rpm for the model aircraft. Firstly, observing the pulsating pressure changes reveals that the pressure variation within each cycle is essentially consistent, facilitating fundamental experimental research on the inlet. Furthermore, based on the number of blades, the corresponding frequencies at the two speeds can be calculated to be 90.7 Hz and 556.0 Hz, respectively, which are very close to the experimentally measured 90.2 Hz and 556.1 Hz. This indicates that adjusting the rotor speed can yield the expected outlet pulsating frequency.

[0037] There are many specific applications of this invention, and the above description is only a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention.

Claims

1. An inlet test outlet pulsating back pressure generating device based on a stator and rotor structure, characterized in that, The system includes an intake duct outlet section (1), a stator (2), a rotor (3), and a drive mechanism (4) for rotating the rotor. The stator (2) is installed at the end of the intake duct outlet section. The stator includes a guide cone (21) extending into the intake duct outlet section and an outlet end (22) located at the end of the intake duct outlet section. The outlet end includes several openings (23) and a guide cone surface (24). Each opening has the same area and shape and is uniformly arranged around the central axis of the stator. The rotor is coaxially installed with the stator. The rotor has several blades (31). Each blade has the same shape and size and is uniformly arranged around the central axis of the rotor. During the rotation of the rotor, the relative position of the rotor and the stator changes periodically. The drive mechanism (4) is a brushless motor for model aircraft; The stator (2) has a guide cone (24) at the air outlet facing the airflow, and the blade end facing away from the airflow is flat and parallel to the air inlet outlet end face; the rotor blades are cuboids, and there is a triangular angle between adjacent blades.

2. The inlet test outlet pulsating back pressure generating device according to claim 1, characterized in that: The intake duct outlet section is an expansion section, and the outlet is circular.

3. The inlet test outlet pulsating back pressure generating device according to claim 1, characterized in that: The stator (2) has a guide cone (21) with a semi-cone angle of 15° to 25°.

4. The inlet test outlet pulsating back pressure generating device according to claim 3, characterized in that: The number of stator blades is greater than 2 and they are distributed in a circular pattern at equal angles, with a cylindrical blind hole at the center of each blade.

5. The inlet test outlet pulsating back pressure generating device according to claim 1, characterized in that: The rotor (3) has more than 2 openings that are circumferentially distributed at equal angles, and there is a threaded hole at the center of the rotor.

6. The inlet test outlet pulsating back pressure generating device according to claim 5, characterized in that: The central axes of the stator and the rotor coincide, and both the stator and the rotor have a central ring. The outer diameter of the rotor's central ring is smaller than that of the stator's central ring. Reducing the distance between the rotor and the stator increases the amplitude of the pulsating back pressure. Increasing the outer diameter or width of the rotor blades also increases the amplitude of the pulsating back pressure.

7. The inlet test outlet pulsating back pressure generating device according to claim 1, characterized in that: The rotor blade center is connected to the drive shaft of the model aircraft brushless motor by a thread and locked with nuts installed at the front and rear. The rotation speed of the motor is controlled by adjusting the given voltage value, and the rotation direction is changed by adjusting the wiring method. Changing the blade rotation speed achieves the adjustment of the pulsating back pressure frequency.

8. The inlet test outlet pulsating back pressure generating device according to claim 1, characterized in that: The intake outlet section is connected to the intake isolation section.

9. The inlet test outlet pulsating back pressure generating device according to claim 1, characterized in that: The opening shape of the stator is fan-shaped.

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