A waveform, amplitude and duration adjustable pulse excitation device and method

Abstract

The present application relates to a kind of adjustable waveform, amplitude and duration of pulse excitation device and method, belong to pulse excitation generator technical field, solve the technical problem that pulse excitation device waveform and duration cannot be adjusted, its pulse excitation device includes supply system and shock tube, supply system includes gas source, pressure reducing valve, third steady pressure sensor, high-pressure gas exported from gas source enters shock tube by pressure reducing valve.Shock tube includes shock tube main body, diaphragm, first dynamic pressure sensor, second dynamic pressure sensor, shock tube can also include piston, baffle.Pulse excitation method is according to the state that shock tube has piston and has no piston, generates pulse excitation, including pulse excitation waveform adjustment, pulse excitation duration adjustment, pulse excitation amplitude adjustment.The present application is used in the situation that combustion chamber pressure is lower, and pulse excitation is generated in combustion chamber.

Description

Technical Field

[0001] This invention belongs to the field of pulse excitation generator technology, specifically relating to a pulse excitation device and method with adjustable waveform, amplitude, and duration. Background Technology

[0002] Pulse excitation devices are commonly used to evaluate the combustion stability margin of rocket engines, such as most large liquid rocket engines abroad, including the LE-7, RD-0120, RD-120, and RD-170, as well as a series of conventional propellant engines in China (YF-X1 to X5). Pulse excitation is also used in the combustion response measurement of solid rocket engines (T-type burners) and in full-scale engine stability tests. Pulse excitation has two effects on the combustion chamber: one is the shock wave propagating within the combustion chamber, and the other is the transfer of momentum to the gas within the combustion chamber. The disturbance results of pulse excitation in the combustion chamber (such as the maximum impact amplitude) are determined by the characteristics of the pulse excitation itself, the conditions under which the pulse excitation is introduced, and the operating parameters of the combustion chamber. The characteristics of the pulse excitation itself include the waveform (half-sine wave, triangular wave, etc.), duration (shock wave duration), and amplitude (the maximum amplitude in the waveform).

[0003] Some have pointed out that pulse excitation must have a specific form and duration. The pulse excitation should have a sufficiently strong energy distribution within the frequency range of interest, even in combustion chambers with acoustic cavities. It has been mentioned that the type and weight of the explosive charge affect the shape and amplitude of the pulse excitation, thus influencing the input energy to a specific acoustic mode. According to mechanical shock theory, the form (waveform) and duration of the pulse excitation have a significant impact on the shock response spectrum. If the acoustic mode of interest in the combustion chamber is in the low-amplitude band of the pulse shock response spectrum, it may be impossible to excite oscillations in the mode of interest, or its response amplitude may be significantly lower than that in the high-amplitude band, resulting in incorrect results when using decay time to assess the stability margin of the combustion chamber. Therefore, it is necessary to impose requirements on the perturbation form and duration of the pulse excitation to ensure a sufficiently strong energy distribution within the frequency range of interest.

[0004] Simultaneously, requirements should be set for the amplitude range of the pulse excitation. The maximum impact amplitude of the pulse excitation should be greater than the maximum disturbance value that may occur inside the combustion chamber during operation, with a certain margin. Regarding the upper limit of the maximum impact amplitude, some tests show that for higher excitation amplitudes, the maximum impact amplitude of the combustion chamber actually decreases. Other tests show that excessively large excitation amplitudes can seriously affect the combustion process, producing "over-explosion" (the excitation amplitude is very large, severely disrupting propellant injection. Before the re-injected propellant begins to burn, the impact amplitude in the combustion chamber may have already stabilized), resulting in incorrect information. Some believe that the maximum impact amplitude generated by pulse excitation should ideally be 2 to 4 times the steady-state chamber pressure. Russia requires that the maximum impact amplitude in the combustion chamber or generator be 15 to 25 times the root mean square value of the combustion noise.

[0005] Although the waveform and duration of the pulse excitation have a significant impact on the perturbation results, in most applications, only the maximum impact amplitude generated by the pulse excitation in the combustion chamber is considered. This is mainly because designing the excitation waveform and duration of a solid propellant pulse gun is not easy to achieve. The few existing gas reaction shock tube experiments show that the duration of the pulse excitation depends on the ratio of the initial pressure of the shock tube mixture to the chamber pressure, the shock tube volume, and the shock tube outlet area. Summary of the Invention

[0006] To overcome the problem that the waveform and duration of existing pulse excitation devices cannot be adjusted, this invention proposes a pulse excitation device and method with adjustable waveform, amplitude, and duration.

[0007] The technical solution adopted by this invention to solve its technical problem is:

[0008] A pulse excitation device with adjustable waveform, amplitude, and duration includes a supply system and a shock tube.

[0009] The supply system includes a gas source, a pressure reducing valve, and a third steady-state pressure sensor; the high-pressure gas output from the gas source enters the shock tube through the pressure reducing valve, the third steady-state pressure sensor is used to measure the gas pressure before entering the shock tube, and the gas source stores inert high-pressure gas.

[0010] The shock tube includes a shock tube body, a diaphragm, a first dynamic pressure sensor, a second dynamic pressure sensor, a first flange, and a second flange; the diaphragm, the first flange, and the second flange are located on the shock tube body. The shock tube body is divided into a high-pressure section before the diaphragm, a middle section, and a low-pressure section connected sequentially. The high-pressure section and the middle section are connected via the first flange and the second flange, and the middle section and the low-pressure section are connected via a compression fitting. The first dynamic pressure sensor and the second dynamic pressure sensor are connected to the low-pressure section via a dynamic sensor connector, and are spaced a certain distance apart, used to measure the gas pressure within the low-pressure section at a certain distance.

[0011] The shock tube may further include a piston and a baffle. When the shock tube includes a piston and a baffle, the intermediate section includes a front intermediate section, a rear intermediate section, and a piston section, which are connected sequentially. The piston can move within the piston section, and the baffle is used to define the movement boundary of the piston. The front intermediate section is connected to the high-pressure section via a first flange and a second flange, the piston section is connected to the rear intermediate section via a third flange, and the rear intermediate section is connected to the low-pressure section via a compression fitting.

[0012] The aforementioned pulse excitation device, including its supply system, further comprises a first shut-off valve, a first steady-state pressure sensor, a second steady-state pressure sensor, a second shut-off valve, and an exhaust valve. High-pressure gas from the gas source sequentially passes through the first shut-off valve, the pressure reducing valve, and the second shut-off valve before entering the shock tube. The first and second steady-state pressure sensors measure the gas pressure before and after the pressure reducing valve. The exhaust valve, located after the second shut-off valve, is used to release gas when the pulse excitation generates a shock wave.

[0013] In the aforementioned pulse excitation device, the inert high-pressure gas stored in the gas source is nitrogen.

[0014] The aforementioned pulse excitation device, the supply system further includes an orifice plate, which is located after the second shut-off valve. The orifice plate has a diameter smaller than the inner diameter of the supply system pipeline, in order to improve the gas pressure control accuracy.

[0015] In the aforementioned pulse excitation device, the first and second shut-off valves are both solenoid valves used for remote control, and the exhaust valve is an electric pneumatic valve or a solenoid valve.

[0016] In the aforementioned pulse excitation device, the high-pressure section before the diaphragm is made of stainless steel. The diaphragm is located between the first flange and the second flange. A first O-ring is installed between the diaphragm and the first flange, and a second O-ring is installed between the diaphragm and the second flange. The first and second O-rings are used to seal the diaphragm and the shock tube body. The low-pressure section is made of industrial seamless stainless steel.

[0017] In the aforementioned pulse excitation device, the diaphragm is a polyimide film with a thickness of 0.1 mm.

[0018] In the aforementioned pulse excitation device, the piston is made of aluminum alloy.

[0019] In the aforementioned pulse excitation device, both the first dynamic pressure sensor and the second dynamic pressure sensor are piezoelectric dynamic pressure sensors.

[0020] A pulse excitation method with adjustable waveform, amplitude, and duration, generating pulse excitation in two states: with and without a piston in the shock tube, includes the following steps:

[0021] Step S1, Pulse excitation waveform adjustment

[0022] Adjusting the shock tube piston setting results in different pulse excitation waveforms depending on whether the shock tube has a piston or not, thus achieving pulse excitation waveform adjustment.

[0023] When the shock tube has no piston, the diaphragm ruptures to generate a shock wave; when the shock tube has a piston, the shock wave generated by the diaphragm rupture pushes the piston to accelerate, and the piston's movement generates a shock wave.

[0024] The shock wave velocity, shock wave Mach number, and shock wave amplitude are calculated using the distance between the first dynamic pressure sensor and the second dynamic pressure sensor, the displayed pressure, and the time difference between the shock wave passing through the first dynamic pressure sensor and the second dynamic pressure sensor.

[0025] Step S2, Pulse excitation duration adjustment

[0026] When the shock tube has no piston, the volume of the high-voltage section in front of the diaphragm is adjusted to regulate the duration of the pulse excitation.

[0027] When the shock tube has a piston, the duration of pulse excitation can be adjusted by adjusting the piston mass or piston movement distance.

[0028] Step S3, Pulse excitation amplitude adjustment

[0029] When the shock tube has no piston, the diaphragm thickness is adjusted to regulate the pulse excitation amplitude.

[0030] When the shock tube has a piston, the pulse excitation amplitude can be adjusted by adjusting the piston mass, the volume of the high-voltage section in front of the diaphragm, and the piston movement distance.

[0031] The beneficial effects of this invention are:

[0032] A pulse excitation device with adjustable waveform, amplitude, and duration is disclosed, which achieves adjustment of the pulse excitation waveform through piston-equipped and pistonless shock tubes. In the pistonless shock tube, the pulse excitation duration is adjusted by changing the volume in front of the diaphragm. In the piston-equipped shock tube, the pulse excitation duration is adjusted by changing the piston mass or piston travel distance. In the pistonless shock tube, the pulse excitation amplitude is adjusted by changing the diaphragm rupture pressure. In the piston-equipped shock tube, the pulse excitation amplitude is adjusted by changing the piston mass, the volume in front of the diaphragm, or the piston travel distance.

[0033] A pulse excitation device with adjustable waveform, amplitude, and duration can be applied to combustion chambers with low pressure to generate pulse excitation and assess the combustion stability margin of the combustion chamber. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the pulse excitation device according to Embodiment 1 of the present invention;

[0035] Figure 2 This is a schematic diagram of the shock tube structure according to Embodiment 1 of the present invention;

[0036] Figure 3 In Embodiment 1 of the present invention, when there is no piston shock tube, pulse excitation is generated by a diaphragm with a thickness of 0.1 mm polyimide film.

[0037] Figure 4 In Embodiment 1 of the present invention, when a piston shock tube is present, the pulse excitation generated by the pulse excitation device is under the conditions of three piston masses m1 = 0.92g, m2 = 1.27g, and m3 = 2.12g.

[0038] Figure 5 In Embodiment 1 of the present invention, when a piston shock tube is present, the pulse excitation generated by the pulse excitation device is under the conditions of three diaphragm front volumes V1 = 79 mL, V2 = 157 mL, and V3 = 236 mL.

[0039] Figure 6 In Embodiment 1 of the present invention, when a piston shock tube is present, the pulse excitation generated by the pulse excitation device is under three conditions: piston movement distance L1 = 50 mm, L2 = 100 mm, and L3 = 150 mm.

[0040] Reference numerals: 1. First flange, 2. Second flange, 3. Third flange, 4. Baffle, 5. Piston, 6. Dynamic sensor connector, 8. Pipe connector, 9. First O-ring seal, 10. Second O-ring seal, 11. Compression fitting straight connector, 12. Diaphragm, 13. Shock tube body, 14. First dynamic pressure sensor, 15. Second dynamic pressure sensor, 17. Gas source, 18. First shut-off valve, 19. First steady-state pressure sensor, 20. Pressure reducing valve, 21. Second steady-state pressure sensor, 22. Second shut-off valve, 23. Third steady-state pressure sensor, 24. Supply system, 25. Shock tube. Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0042] Example 1

[0043] A pulse excitation device with adjustable waveform, amplitude, and duration includes a supply system 24 and a shock tube 25, such as Figure 1As shown. The gas supply system 17 uses a high-pressure gas cylinder containing nitrogen or other inert gases. A pressure reducing valve 20 reduces the high-pressure gas to the target pressure. A first shut-off valve 18 and a second shut-off valve 22 control the on / off of the gas supply. A first steady-state pressure sensor 19, a second steady-state pressure sensor 21, and a third steady-state pressure sensor 23 monitor the pressure before, after, and before the shock tube diaphragm 12 of the pressure reducing valve 20, respectively. The structure of the shock tube 25 is as follows. Figure 2 As shown, the system includes three types of flanges (first flange 1, second flange 2, and third flange 3), a baffle 4, a piston 5, a dynamic sensor connector 6, a pipe connector 8, a first O-ring 9, a second O-ring 10, a compression fitting straight connector 11, and a diaphragm 12. The high-pressure section before the diaphragm 12 is made of stainless steel and connected via flanges. The low-pressure section is made of seamless industrial stainless steel and connected via compression fittings. The diaphragm 12 is made of polyimide film, the piston 5 is made of aluminum, and the first dynamic pressure sensor 14 and the second dynamic pressure sensor 15 are piezoelectric dynamic pressure sensors.

[0044] The shock tube 25 has two states: 1) a pistonless shock tube: the diaphragm 12 ruptures to generate a shock wave; 2) a piston-equipped shock tube: the shock wave generated by the rupture of the diaphragm 12 pushes the piston 5 to accelerate, and the movement of the piston 5 causes a shock wave to be generated at its front end. The implementation methods of the pulse excitation device in both states are as follows:

[0045] (1) Pistonless shock tube 25: The structure of pistonless shock tube 25 is as follows: Figure 2 Based on this, remove baffle 4 and piston 5. Open the first shut-off valve 18 and adjust the pressure reducing valve 20 so that the pressure after the pressure reducing valve 20 reaches the target pressure P2 (the value monitored by the second steady-state pressure sensor 21). Open the second shut-off valve 22, and the pressure P3 (the value monitored by the third steady-state pressure sensor 23) rises slowly at a rate less than 0.1 MPa / s until the diaphragm 12 ruptures. Close the second shut-off valve 22 to complete one shock wave experiment. The shock wave generated after the diaphragm 12 ruptures is measured by the first dynamic pressure sensor 14 and the second dynamic pressure sensor 15 (p1 and p2) downstream of the diaphragm. Using the distance between the first dynamic pressure sensor 14 and the second dynamic pressure sensor 15 and the time difference of the shock wave passing through the first dynamic pressure sensor 14 and the second dynamic pressure sensor 15, the shock wave velocity, shock wave Mach number, and shock wave amplitude can be calculated.

[0046] (2) With piston shock tube 25: The structure of piston shock tube 25 is as follows Figure 2As shown. Open the first shut-off valve 18 and adjust the pressure reducing valve 20 until the pressure after the pressure reducing valve 20 reaches the target pressure P2 (the value monitored by the second steady-state pressure sensor 21). Open the second shut-off valve 22, and the pressure P3 (the value monitored by the third steady-state pressure sensor 23) rises slowly at a rate less than 0.1 MPa / s until the diaphragm 12 ruptures. The shock wave generated after the diaphragm 12 ruptures, along with the high-pressure gas, pushes the piston 5 downstream, generating a compression wave in the downstream gas. As the piston 5 accelerates, the compression waves continuously superimpose, increasing in intensity to form a shock wave. The piston 5 is eventually blocked by the second baffle 4 (the baffle 4 in the second flange). The distance between the two baffles 4 minus the length of the piston is called the piston 5's movement distance. Close the second shut-off valve 22 and open the exhaust valve to complete one shock wave experiment. The shock wave generated by piston 5 is measured by the first dynamic pressure sensor 14 and the second dynamic pressure sensor 15 (p1 and p2) downstream of the second baffle 4. The shock wave velocity, shock wave Mach number and shock wave amplitude can be calculated by using the distance between the first dynamic pressure sensor 14 and the second dynamic pressure sensor 15 and the time difference of the shock wave passing through the first dynamic pressure sensor 14 and the second dynamic pressure sensor 15.

[0047] To control the pressure rise rate before diaphragm 12 and ensure consistent diaphragm 12 rupture pressure, a smaller orifice plate can be added after the second shut-off valve 22 to improve pressure control accuracy. For remote control, the first shut-off valve 18, the second shut-off valve 22, and the exhaust valve can all be electric or solenoid valves.

[0048] Based on the two shock tube states, the pulse excitation waveform, duration, and amplitude can be adjusted. Specifically:

[0049] (1) Adjust the pulse excitation waveform

[0050] The pistonless shock tube 25 generates a trapezoidal pulse excitation with a steep leading edge, such as... Figure 3 As shown.

[0051] A piston shock tube 25 generates a pulse excitation similar to a sine wave, such as... Figure 4 As shown.

[0052] (2) Adjust the pulse excitation duration

[0053] In the pistonless shock tube 25, the pulse excitation duration can be shortened by reducing the volume in front of the diaphragm 12, that is, the volume from the shut-off valve to the diaphragm 12.

[0054] In a piston shock tube 25, the duration of pulse excitation can be increased by either reducing the piston mass or increasing the piston travel distance. Figure 4 and Figure 6 As shown.

[0055] (3) Adjust the pulse excitation amplitude

[0056] In the pistonless shock tube 25, the pulse excitation amplitude can be increased by increasing the rupture pressure of the diaphragm 12, that is, by increasing the thickness of the diaphragm 12.

[0057] In the piston shock tube 25, the pulse excitation amplitude can be increased in three ways: reducing the piston mass, increasing the volume in front of the diaphragm 12, and increasing the piston movement distance. Figures 4-6 As shown.

Claims

1. A waveform, amplitude and duration adjustable pulsed excitation device, characterized in that, The supply system (24) and the shock tube (25) are included. The supply system (24) includes a gas source (17), a pressure reducing valve (20) and a third steady pressure sensor (23); high-pressure gas output by the gas source (17) enters the shock tube (25) through the pressure reducing valve (20), and the third steady pressure sensor (23) is used for measuring the gas pressure before entering the shock tube (25); the gas source (17) stores inert high-pressure gas. The shock tube (25) includes a shock tube body (13), a diaphragm (12), a first dynamic pressure sensor (14), a second dynamic pressure sensor (15), a first flange (1) and a second flange (2); the diaphragm (12), the first flange (1) and the second flange (2) are located on the shock tube body (13); the shock tube body (13) is divided into a high-pressure section before the diaphragm, an intermediate section and a low-pressure section in sequence; the high-pressure section and the intermediate section are connected through the first flange (1) and the second flange (2); the intermediate section and the low-pressure section are connected through a sleeve joint (11); the first dynamic pressure sensor (14) and the second dynamic pressure sensor (15) are connected to the low-pressure section through a dynamic sensor joint (6); the first dynamic pressure sensor (14) and the second dynamic pressure sensor (15) are spaced apart at a certain distance and used for measuring the gas pressure at the certain distance in the low-pressure section.

2. The pulse excitation device of claim 1, wherein The shock tube (25) further includes a piston (5) and a baffle (4); when the shock tube (25) includes the piston (5) and the baffle (4), the intermediate section includes an intermediate front section, an intermediate rear section and a piston section; the intermediate front section, the baffle (4), the piston section, the baffle (4) and the intermediate rear section are connected in sequence; the piston (5) can move in the piston section; the baffle (4) is used for defining the moving boundary of the piston (5); the intermediate front section and the high-pressure section are connected through the first flange (1) and the second flange (2); the piston section and the intermediate rear section are connected through a third flange (3); and the intermediate rear section and the low-pressure section are connected through the sleeve joint (11).

3. The pulse excitation device of claim 1, wherein The supply system (24) further includes a first stop valve (18), a first steady pressure sensor (19), a second steady pressure sensor (21), a second stop valve (22) and an exhaust valve; high-pressure gas output by the gas source (17) enters the shock tube (25) through the first stop valve (18), the pressure reducing valve (20) and the second stop valve (22) in sequence; the first steady pressure sensor (19) and the second steady pressure sensor (21) are used for measuring the gas pressure before and after the pressure reducing valve (20); and the exhaust valve is located behind the second stop valve (22) and used for exhausting gas when the pulse excitation generates a shock wave.

4. The pulse excitation device of claim 1, wherein The inert high-pressure gas stored in the gas source (17) is nitrogen.

5. The pulse excitation device of claim 3, wherein The supply system (24) further includes a hole plate; the hole plate is located behind the second stop valve (22); the diameter of the hole plate is smaller than the inner diameter of the supply system pipeline; and the hole plate is used for improving the gas pressure control precision.

6. The pulse excitation device of claim 3, wherein The first stop valve (18) and the second stop valve (22) are both electromagnetic valves and are used for realizing remote control; and the exhaust valve is an electric air valve or an electromagnetic valve.

7. The pulse excitation device of claim 1, wherein The high-pressure section in front of the diaphragm (12) is made of stainless steel material, the diaphragm (12) is located between the first flange (1) and the second flange (2), a first O-shaped sealing ring (9) is arranged between the diaphragm (12) and the first flange (1), a second O-shaped sealing ring (10) is arranged between the diaphragm (12) and the second flange (2), the first O-shaped sealing ring (9) and the second O-shaped sealing ring (10) are used for sealing the diaphragm (12) and the shock tube main body (13), and the low-pressure section is made of industrial seamless stainless steel.

8. The pulse excitation device of claim 1, wherein The diaphragm (12) is a polyimide film with a thickness of 0.1 mm.

9. The pulse excitation device of claim 2, wherein The piston (5) is made of aluminum alloy.

10. The pulse excitation device of claim 1, wherein The first dynamic pressure sensor (14) and the second dynamic pressure sensor (15) are both piezoelectric dynamic pressure sensors.

11. A method for generating a pulse excitation with adjustable waveform, amplitude and duration, using the pulse excitation device according to any one of claims 1 to 10, characterized in that, According to the two states of the shock tube (25) with the piston (5) and without the piston (5), pulse excitation is generated, including the following steps: Step S1, pulse excitation waveform adjustment: Adjust the setting of the shock tube piston (5), the shock tube (25) has two states of no piston (5) and with piston (5), the generated pulse excitation waveforms are different, and the adjustment of the pulse excitation waveform is realized; When the shock tube (25) has no piston (5), the diaphragm (12) breaks to generate a shock wave; when the shock tube (25) has a piston (5), the diaphragm (12) breaks to generate a shock wave to push the piston to accelerate, and the piston (5) moves to generate a shock wave; The distance between the first dynamic pressure sensor (14) and the second dynamic pressure sensor (15), the displayed pressure, and the time difference of the shock wave passing through the first dynamic pressure sensor (14) and the second dynamic pressure sensor (15) are used to calculate the shock wave speed, the shock wave Mach number and the shock wave amplitude; Step S2, pulse excitation duration adjustment: When the shock tube (25) has no piston (5), the volume of the high-pressure section in front of the diaphragm (12) is adjusted to realize the adjustment of the pulse excitation duration; When the shock tube (25) has a piston (5), the piston mass or the piston (5) movement distance is adjusted to realize the adjustment of the pulse excitation duration; Step S3, pulse excitation amplitude adjustment: When the shock tube (25) has no piston (5), the thickness of the diaphragm (12) is adjusted to realize the adjustment of the pulse excitation amplitude; When the shock tube (25) has a piston (5), the piston (5) mass, the volume of the high-pressure section in front of the diaphragm (12), and the piston (5) movement distance are adjusted to realize the adjustment of the pulse excitation amplitude.

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