Pulse excitation device and method with adjustable waveform, amplitude and duration

Abstract

The invention relates to a waveform, amplitude and duration adjustable pulse excitation device and method, belongs to the technical field of pulse excitation generators, and solves the technical problem that the waveform and duration of a pulse excitation device cannot be adjusted. The supply system comprises a gas source, a pressure reducing valve and a third steady-state pressure sensor, and high-pressure gas output by the gas source enters the shock tube through the pressure reducing valve. The shock tube comprises a shock tube main body, a diaphragm, a first dynamic pressure sensor, a second dynamic pressure sensor, a piston and a baffle plate. According to the pulse excitation method, pulse excitation is generated according to the piston state and the piston-free state of the shock tube, and the pulse excitation method comprises pulse excitation waveform adjustment, pulse excitation duration adjustment and pulse excitation amplitude adjustment. The device is used for the condition that the combustion chamber pressure is low, and the combustion chamber generates pulse excitation.

Description

Technical Field

[0001] The present invention belongs to the technical field of pulse excitation generators, and in particular relates to a pulse excitation device and method with adjustable waveform, amplitude and duration. Background Art

[0002] Pulse excitation devices are often used to evaluate the combustion stability margin of rocket engines, such as most large liquid rocket engines abroad, such as LE-7, RD-0120, RD-120, RD-170, and a series of conventional propellant engines in China (YF-X1~X5). Pulse excitation methods are also used in solid rocket engine combustion response measurements (T-type burners) and full-scale engine stability tests. Pulse excitation has two effects on the excitation of the combustion chamber: one is the shock wave propagating in the combustion chamber, and the other is the transfer of momentum to the gas in 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 for the introduction of the pulse excitation, and the operating parameters of the combustion chamber. The characteristics of the pulse excitation itself include the waveform of the pulse excitation (half-sine wave, triangle wave, etc.), duration (duration of the shock wave), amplitude (the largest amplitude in the waveform), etc.

[0003] It has been pointed out that the pulse excitation must have a certain form and duration. The pulse excitation should have an energy distribution of sufficient intensity within the frequency range of interest, even in a combustion chamber with an acoustic cavity. It has been mentioned that the type and weight of the explosive charge will affect the shape and amplitude of the pulse excitation, and thus affect the input energy to a specific acoustic mode. According to the mechanical shock theory, the form (waveform) and duration of the pulse excitation have a great influence on the shock response spectrum. If the acoustic mode of the combustion chamber of interest is in the low-amplitude frequency band of the pulse shock response spectrum, it may not be possible to excite the oscillation of the acoustic mode of interest or its response amplitude may be significantly lower than the response amplitude of the high-amplitude frequency band, resulting in incorrect results when using the decay time to evaluate the stability margin of the combustion chamber. Therefore, it is necessary to put forward requirements on the disturbance form and duration of the pulse excitation so that it has an energy distribution of sufficient intensity within the frequency range of interest.

[0004] At the same time, requirements should be put forward for the amplitude range of pulse excitation. The maximum impact amplitude of pulse excitation should be greater than the maximum disturbance value that may occur inside the combustion chamber when it is working, and a certain margin should be left. For the upper limit of the maximum impact amplitude, some experiments have shown that for higher excitation amplitudes, the maximum impact amplitude of the combustion chamber is reduced. Other experiments have shown that excessive excitation amplitudes will seriously affect the combustion process and produce "overexplosion" (the excitation amplitude is very large, which seriously damages the injection of the propellant. Before the re-injected propellant begins to burn, the impact amplitude in the combustion chamber may have returned to stability), resulting in incorrect information. Some people believe that the maximum impact amplitude generated by pulse excitation should 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 pulse excitation have a great influence on the disturbance results, in most applications, only the maximum impact amplitude generated by pulse excitation in the combustion chamber is concerned. The main reason is that it is not easy to design the excitation waveform and duration of the solid powder pulse gun. The only gas reaction shock tube experiment shows that the duration of 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] In order to overcome the problem that the waveform and duration of the existing pulse excitation device cannot be adjusted, the present invention proposes a pulse excitation device and method with adjustable waveform, amplitude and duration.

[0007] The technical solution adopted by the present invention to solve the technical problem is:

[0008] A pulse excitation device with adjustable waveform, amplitude and duration comprises 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 by 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, a middle section, and a low-pressure section in front of the diaphragm, which are connected in sequence. The high-pressure section and the middle section are connected by a first flange and a second flange, and the middle section and the low-pressure section are connected by a ferrule-type joint. The first dynamic pressure sensor and the second dynamic pressure sensor are connected to the low-pressure section through a dynamic sensor joint. The first dynamic pressure sensor and the second dynamic pressure sensor are spaced a certain distance apart and are used to measure the gas pressure spaced a certain distance apart in the low-pressure section.

[0011] The shock tube may also include a piston and a baffle. When the shock tube includes a piston and a baffle, the middle section includes an intermediate front section, an intermediate rear section, and a piston section. The intermediate front section, the baffle, the piston section, the baffle, and the intermediate rear section are connected in sequence. The piston can move in the piston section, and the baffle is used to limit the movement boundary of the piston. The intermediate front section is connected to the high-pressure section through a first flange and a second flange, the piston section is connected to the intermediate rear section through a third flange, and the intermediate rear section is connected to the low-pressure section through a ferrule-type joint.

[0012] The pulse excitation device mentioned above, the supply system also includes a first stop valve, a first steady-state pressure sensor, a second steady-state pressure sensor, a second stop valve, and an exhaust valve; the high-pressure gas output by the gas source passes through the first stop valve, the pressure reducing valve, and the second stop valve in sequence into the shock tube. The first steady-state pressure sensor and the second steady-state pressure sensor are used to measure the gas pressure before and after the pressure reducing valve. The exhaust valve is located after the second stop valve and is used to release gas when the pulse excitation generates a shock wave.

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

[0014] The pulse excitation device mentioned above, the supply system also includes an orifice plate, which is located after the second stop valve, and the diameter of the orifice plate is smaller than the inner diameter of the supply system pipeline, which is used to improve the gas pressure control accuracy.

[0015] In the above-mentioned pulse excitation device, the first stop valve and the second stop valve are both solenoid valves for realizing remote control, and the exhaust valve is an electric valve or a solenoid valve.

[0016] In the above-mentioned pulse excitation device, the high-pressure section in front of the diaphragm is made of stainless steel material, the diaphragm is located between the first flange and the second flange, a first O-ring is arranged between the diaphragm and the first flange, and a second O-ring is arranged between the diaphragm and the second flange. The first O-ring and the second O-ring are used for sealing the diaphragm and the shock tube body, and the low-pressure section is made of industrial seamless stainless steel.

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

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

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

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

[0021] Step S1: Pulse excitation waveform adjustment

[0022] Adjust the setting of the shock tube piston. The shock tube has two states: without a piston and with a piston. The pulse excitation waveforms generated are different, so the pulse excitation waveform can be adjusted.

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

[0024] The shock wave velocity, shock wave Mach number and shock wave amplitude are calculated by 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-pressure section in front of the diaphragm is adjusted to adjust the duration of the pulse excitation;

[0027] When the shock tube has a piston, the piston mass or the piston movement distance is adjusted to achieve the regulation of the pulse excitation duration.

[0028] Step S3: pulse excitation amplitude adjustment

[0029] When the shock tube has no piston, the thickness of the diaphragm is adjusted to achieve the adjustment of the pulse excitation amplitude;

[0030] When the shock tube has a piston, the piston mass, the volume of the high-pressure section in front of the diaphragm and the piston movement distance are adjusted to achieve the regulation of the pulse excitation amplitude.

[0031] The beneficial effects of the present invention are:

[0032] A pulse excitation device with adjustable waveform, amplitude and duration is used to adjust the pulse excitation waveform through piston and pistonless shock tubes. In the pistonless shock tube, the pulse excitation duration is adjusted by adjusting the volume in front of the diaphragm. In the piston shock tube, the pulse excitation duration is adjusted by adjusting the piston mass or the piston movement distance. In the pistonless shock tube, the pulse excitation amplitude is adjusted by adjusting the diaphragm rupture pressure. In the piston shock tube, the pulse excitation amplitude is adjusted by adjusting the piston mass, the volume in front of the diaphragm or the piston movement distance.

[0033] A pulse excitation device with adjustable waveform, amplitude and duration can be used in the case of low combustion chamber pressure to generate pulse excitation to the combustion chamber and realize the evaluation of the combustion stability margin of the combustion chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the composition of a pulse excitation device according to an embodiment of the present invention;

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

[0036] Figure 3 In the case of the pistonless shock tube of the first embodiment of the present invention, a pulse excitation is generated by using a diaphragm of a polyimide film with a thickness of 0.1 mm;

[0037] Figure 4 The pulse excitation generated by the pulse excitation device in the first embodiment of the present invention when there is a piston shock tube and the three piston masses m1 = 0.92g, m2 = 1.27g, and m3 = 2.12g are used;

[0038] Figure 5 The pulse excitation device generates the pulse excitation when there is a piston shock tube in the first embodiment of the present invention and the three diaphragm front volumes V1=79mL, V2=157mL, and V3=236mL are used;

[0039] Figure 6 It is the pulse excitation generated by the pulse excitation device under the conditions of three piston movement distances L1=50mm, L2=100mm, and L3=150mm when there is a piston shock tube in the first embodiment of the present invention.

[0040] Figure markings: 1. first flange, 2. second flange, 3. third flange, 4. baffle, 5. piston, 6. dynamic sensor connector, 8. pipe connector, 9. first O-ring, 10. second O-ring, 11. ferrule-type straight connector, 12. diaphragm, 13. shock tube body, 14. first dynamic pressure sensor, 15. second dynamic pressure sensor, 17. air source, 18. first stop valve, 19. first steady-state pressure sensor, 20. pressure reducing valve, 21. second steady-state pressure sensor, 22. second stop valve, 23. third steady-state pressure sensor, 24. supply system, 25. shock tube. DETAILED DESCRIPTION

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

[0042] Embodiment 1

[0043] A pulse excitation device with adjustable waveform, amplitude and duration, comprising a supply system 24 and a shock tube 25, such as Figure 1The gas source 17 of the supply system adopts a high-pressure gas cylinder of nitrogen or other inert gas, the pressure reducing valve 20 reduces the high-pressure gas to the target pressure, the first stop valve 18 and the second stop valve 22 realize the on-off of the gas supply, the first steady-state pressure sensor 19, the second steady-state pressure sensor 21, and the third steady-state pressure sensor 23 respectively monitor the pressure before the pressure reducing valve 20, after the pressure reducing valve 20 and before the shock tube diaphragm 12. The structure of the shock tube 25 is as shown in FIG. Figure 2 As shown, it includes three flanges (first flange 1, second flange 2, third flange 3), baffle 4, piston 5, dynamic sensor joint 6, pipe joint 8, first O-ring 9, second O-ring 10, ferrule straight joint 11, and diaphragm 12. The high-pressure section in front of the diaphragm 12 is made of stainless steel and connected by flange, the low-pressure section is made of industrial seamless stainless steel and ferrule joint, 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) shock tube without piston: the diaphragm 12 ruptures to generate shock waves; 2) shock tube with piston: the shock wave generated by the rupture of the diaphragm 12 drives the piston 5 to accelerate, and the movement of the piston 5 causes a shock wave to be generated at the front end of the piston 5. The implementation methods of the pulse excitation device in the two states are as follows:

[0045] (1) Pistonless shock tube 25: The structure of the pistonless shock tube 25 is Figure 2 On the basis of , remove the baffle 4 and the piston 5. Open the first stop valve 18, adjust the pressure reducing valve 20, and make the pressure after the pressure reducing valve 20 reach the target pressure P2 (the monitoring value of the second steady-state pressure sensor 21). Open the second stop valve 22, and the pressure P3 (the monitoring value of the third steady-state pressure sensor 23) rises slowly at a rate less than 0.1MPa / s until the diaphragm 12 ruptures. Close the second stop 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. 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 between the shock wave passing through the first dynamic pressure sensor 14 and the second dynamic pressure sensor 15.

[0046] (2) With piston shock tube 25: The structure of piston shock tube 25 is as follows Figure 2As shown. Open the first stop valve 18 and adjust the pressure reducing valve 20 so that the pressure behind the pressure reducing valve 20 reaches the target pressure P2 (the monitoring value of the second steady-state pressure sensor 21). Open the second stop valve 22, and the pressure P3 (the monitoring value of the third steady-state pressure sensor 23) rises slowly at a rate less than 0.1MPa / s until the diaphragm 12 ruptures. The shock wave and high-pressure gas generated after the rupture of the diaphragm 12 push the piston 5 to move downstream, generating a compression wave in the downstream gas. As the piston 5 continues to accelerate, the compression waves continue to overlap, and the intensity increases 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 movement distance of the piston 5. Close the second stop valve 22, open the exhaust valve, and complete one shock wave experiment. The shock wave generated by the 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 between the shock wave passing through the first dynamic pressure sensor 14 and the second dynamic pressure sensor 15.

[0047] In order to control the pressure rising rate in front of the diaphragm 12 and achieve the consistency of the rupture pressure of the diaphragm 12, a small orifice plate can be added after the second stop valve 22 to improve the pressure control accuracy. To achieve remote control, the first stop valve 18, the second stop valve 22 and the exhaust valve can all be electric valves or solenoid valves.

[0048] Based on the two shock tube states, the pulse excitation waveform, duration and amplitude can be adjusted. The details are as follows:

[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 shown.

[0051] The piston shock tube 25 generates pulse excitation similar to the positive vector shape, such as Figure 4 shown.

[0052] (2) Adjust the pulse excitation duration

[0053] In the pistonless shock tube 25 , by reducing the volume before the diaphragm 12 , that is, the volume from the valve to the diaphragm 12 , the pulse excitation duration can be shortened.

[0054] In the piston shock tube 25, the pulse excitation duration can be increased by reducing the piston mass or increasing the piston movement distance, such as Figure 4 and Figure 6 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, increasing the thickness of the diaphragm 12 .

[0057] In the piston shock tube 25, the pulse excitation amplitude can be increased by three methods, namely, reducing the piston mass, increasing the volume in front of the diaphragm 12, and increasing the piston movement distance, such as Figure 4-Figure 6 shown.

Claims

1. A pulse excitation device with adjustable waveform, amplitude and duration, characterized in that: It includes a supply system (24) and a shock tube (25); The supply system (24) comprises a gas source (17), a pressure reducing valve (20), and a third steady-state pressure sensor (23); the high-pressure gas output by the gas source (17) enters the shock tube (25) through the pressure reducing valve (20); the third steady-state pressure sensor (23) is used to measure the gas pressure before entering the shock tube (25); the gas source (17) stores inert high-pressure gas; The shock tube (25) comprises 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, a middle section, and a low-pressure section which are connected in sequence, the high-pressure section and the middle section are connected by the first flange (1) and the second flange (2), and the middle section and the low-pressure section are connected by a ferrule-type joint (11); the first dynamic pressure sensor (14) and the second dynamic pressure sensor (15) are connected to the low-pressure section by a dynamic sensor joint (6), and the first dynamic pressure sensor (14) and the second dynamic pressure sensor (15) are spaced a certain distance apart and are used to measure the gas pressure spaced a certain distance apart in the low-pressure section; The shock tube (25) may further include a piston (5) and a baffle (4); when the shock tube (25) includes the piston (5) and the baffle (4), the middle 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 to limit the movement boundary of the piston (5); the intermediate front section is connected to the high-pressure section via a first flange (1) and a second flange (2); the piston section is connected to the intermediate rear section via a third flange (3); and the intermediate rear section is connected to the low-pressure section via a ferrule-type joint (11).

2. The pulse excitation device according to claim 1, characterized in that: The supply system (24) further comprises a first stop valve (18), a first steady-state pressure sensor (19), a second steady-state pressure sensor (21), a second stop valve (22), and an exhaust valve; the high-pressure gas output by the gas source (17) passes through the first stop valve (18), the pressure reducing valve (20), and the second stop valve (22) in sequence and enters the shock tube (25); the first steady-state pressure sensor (19) and the second steady-state pressure sensor (21) are used to measure the gas pressure before and after the pressure reducing valve (20); the exhaust valve is located after the second stop valve (22) and is used to release gas when the pulse excitation generates a shock wave.

3. The pulse excitation device according to claim 1, characterized in that: The inert high-pressure gas stored in the gas source (17) is nitrogen.

4. The pulse excitation device according to claim 2, characterized in that: The supply system (24) also includes an orifice plate, which is located behind the second stop valve (22) and has a diameter smaller than the inner diameter of the supply system pipeline, and is used to improve the gas pressure control accuracy.

5. The pulse excitation device according to claim 2, characterized in that: The first stop valve (18) and the second stop valve (22) are both solenoid valves for realizing remote control, and the exhaust valve is an electric valve or a solenoid valve.

6. The pulse excitation device according to claim 1, characterized in that: The high-pressure section in front of the diaphragm (12) is made of stainless steel. The diaphragm (12) is located between the first flange (1) and the second flange (2). A first O-type sealing ring (9) is arranged between the diaphragm (12) and the first flange (1), and a second O-type sealing ring (10) is arranged between the diaphragm (12) and the second flange (2). The first O-type sealing ring (9) and the second O-type sealing ring (10) are used for sealing the diaphragm (12) and the shock tube body (13). The low-pressure section is made of industrial seamless stainless steel.

7. The pulse excitation device according to claim 1, characterized in that: The diaphragm (12) is a polyimide film with a thickness of 0.1 mm.

8. The pulse excitation device according to claim 1, characterized in that: The piston (5) is made of aluminum alloy.

9. The pulse excitation device according to claim 1, characterized in that: The first dynamic pressure sensor (14) and the second dynamic pressure sensor (15) are both piezoelectric dynamic pressure sensors.

10. A pulse excitation method with adjustable waveform, amplitude and duration, using the pulse excitation device described in claims 1 to 9, characterized in that: According to the two states of the shock tube (25) with a piston (5) and without a 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: without the piston (5) and with the piston (5), The generated pulse excitation waveform is different, so as to realize the adjustment of the pulse excitation waveform; When the shock tube (25) has no piston (5), the diaphragm (12) ruptures to generate a shock wave; when the shock tube (25) has a piston (5), the shock wave generated by the rupture of the diaphragm (12) drives the piston to accelerate, and the movement of the piston (5) generates a shock wave; Calculating the shock wave velocity, the shock wave Mach number and the shock wave amplitude by using the distance between the first dynamic pressure sensor (14) and the second dynamic pressure sensor (15), the displayed pressure and the time difference between the shock wave passing through the first dynamic pressure sensor (14) and the second dynamic pressure sensor (15); 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 achieve the regulation of the pulse excitation duration; When the shock tube (25) has a piston (5), the piston mass or the moving distance of the piston (5) is adjusted to achieve the regulation 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 achieve the regulation of the pulse excitation amplitude; When the shock tube (25) has a piston (5), the mass of the piston (5), the volume of the high-pressure section in front of the diaphragm (12), and the movement distance of the piston (5) are adjusted to achieve the regulation of the pulse excitation amplitude.

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