A staged air intake device and method for inducing strong shock waves

Abstract

The present invention discloses a staged air intake device and method for inducing strong shock waves, a staged air intake device for inducing strong shock waves, comprising an expansion section, a driving section, a diaphragm section and an experimental section which are connected in sequence and coaxially arranged, the expansion section and the driving section are connected through a valve, the diaphragm section is arranged between the driving section and the experimental section, and a diaphragm for separating the chamber is arranged between the diaphragm section and the driving section and between the diaphragm section and the experimental section, respectively, the signal output end of the pressure sensor is connected to a data collector through a signal converter, the data collector is used to collect voltage signals collected by the pressure sensor, the expansion section, the driving section, the diaphragm section and the experimental section are respectively connected to a gas pipeline through a valve, and the gas pipeline is connected to an expansion gas tank for inflating the expansion section. The present invention can greatly reduce the use of rare resource helium, save experimental costs, and significantly broaden the physical boundaries of shock tube high-pressure experimental measurements.

Description

Technical Field

[0001] The invention relates to the field of shock tube experiments, and in particular to a staged air intake device and method for inducing strong shock waves. Background Art

[0002] Modern engine design methods based on computational fluid dynamics (CFD) simulation have been widely used in the development of new products by enterprises and model research institutes. As a necessary chemical source for CFD simulation, the reliability and accuracy of the combustion reaction model will directly affect the design and optimization of the combustion chamber structure. As an important basic combustion parameter, the accurate experimental characterization of the ignition delay period under a wide range of operating conditions is particularly critical for the development of combustion reaction models. The shock tube device can generate strong shock waves to induce the experimental fluid to reach high temperature and pressure instantly, and maintain a near-adiabatic environment with constant temperature and pressure within milliseconds. It is the mainstream device for ignition delay period measurement in the world.

[0003] The shock tube generates shock waves through the pressure difference between the high-value driving gas on both sides of the membrane section and the experimental gas to be tested, and induces ignition of the combustible mixture through the energy transfer between the shock wave and the fluid medium. Among them, the length of the driving section of the shock tube and the diameter of the experimental section both significantly affect its performance. Specifically: the longer the driving section length, the longer the effective experimental time and the wider the measurable temperature range; the larger the diameter of the experimental section, the smaller the boundary layer, and the more ideal the experimental data obtained. The driving section, membrane section, and experimental section of the traditional shock tube all adopt a coaxial equal cross-sectional structure. By increasing the length of the driving section and the diameter of the experimental section, its performance is improved and its measurable range is expanded, but at the same time, the consumption of the driving gas will be greatly increased. Generally speaking, gases with smaller molecular weight and larger adiabatic index, such as hydrogen and helium, are more ideal strong shock wave driving gases. However, hydrogen has high diffusivity and strong explosiveness, and has potential safety issues. Therefore, helium as a driving gas is the mainstream research method internationally. However, helium is a rare strategic material that is indispensable for national defense, military industry and high-tech development. my country's helium resources are quite scarce, with low content, high dependence on foreign countries and high prices. It is imperative to solve the problem of balancing the cost of using helium in shock tubes and the generation of strong shock waves. Summary of the invention

[0004] The purpose of the present invention is to solve the above problems and provide a staged air intake device and method for inducing strong shock waves, so as to solve the problem of high cost of existing shock tube technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A staged air intake device for inducing strong shock waves comprises an expansion section, a driving section, a diaphragm section and an experimental section which are connected in sequence and arranged coaxially, the expansion section and the driving section are connected via a valve, and diaphragms for separating the diaphragm section and the driving section and between the diaphragm section and the experimental section are respectively arranged, the end of the experimental section is connected to a pressure sensor, the signal output end of the pressure sensor is connected to a data collector via a signal converter, the data collector is used to collect voltage signals collected by the pressure sensor, the expansion section, the driving section, the diaphragm section and the experimental section are respectively connected to a gas pipeline via valves, and the gas pipeline is connected to an expansion gas tank for inflating the expansion section.

[0007] Furthermore, the inner diameter of the valve (2) is the same as the inner diameter of the expansion section (1) and the inner diameter of the driving section (3).

[0008] Furthermore, the pressure sensor includes a first pressure sensor and a second pressure sensor, wherein a plurality of the first pressure sensors are provided, and the first pressure sensors are provided on the side wall of the experimental section, and the second pressure sensors are provided at the end of the experimental section.

[0009] Furthermore, the gas pipeline is connected to a gas mixing tank, a nitrogen tank, and a helium tank through valves respectively. The helium tank or the helium tank and the nitrogen tank are used as driving gas to inflate the driving section. The gas mixing tank is used to store the gas to be tested to inflate the experimental section. The gas pipeline is connected to the atmosphere through a ventilation pipe, and a valve is provided on the ventilation pipe.

[0010] Furthermore, a vacuum pump is connected to the gas pipeline, and the vacuum pump is used to evacuate the expansion section, the driving section, the clamping section and the experimental section.

[0011] Furthermore, a second pressure gauge for monitoring the gas pressure in the gas pipeline and in the expansion section, the driving section and the clamping section is connected to the gas pipeline through a valve, and a first pressure gauge for monitoring the gas pressure in the experimental section is connected to the experimental section through a valve.

[0012] Furthermore, the inner diameters of the expansion section, the driving section, the clamping section and the experimental section are the same.

[0013] Furthermore, the expansion gas tank contains air, nitrogen or carbon dioxide.

[0014] Furthermore, the first pressure sensor adopts PCB 113B22, and the second pressure sensor adopts PCB113B03.

[0015] The present invention also provides a working method of a staged air intake device for inducing a strong shock wave, comprising the following steps:

[0016] 1) According to the experimental requirements, the required driving gas pressure and experimental gas pressure under the target working condition are calculated by the shock wave equation, and the gas pressure value of the membrane clamping section is determined according to the driving gas pressure and the experimental gas pressure; a diaphragm is sandwiched between the membrane clamping section and the driving section and between the membrane clamping section and the experimental section, the valve is opened, and the expansion section, the driving section, the membrane clamping section and the experimental section are evacuated to a vacuum state by a vacuum pump, and then the valve is closed;

[0017] 11) Introduce driving gas into the membrane section and the driving section. During the introduction process, ensure that the pressure difference between the membrane section and the driving section and between the membrane section and the test section is less than the allowable pressure difference. When the gas pressure of the membrane section reaches the gas pressure value of the membrane section, close the air intake of the membrane section, and continue to enter the driving section until the driving gas pressure required under the target working condition is reached and the air intake is stopped;

[0018] 12) Introduce expansion gas into the expansion section until the pressure of the expansion section is the same as that of the driving section; then, let the experimental gas in the mixing tank enter the experimental section until the experimental gas pressure is reached and then stop ventilation, and then adjust the data acquisition device to the automatic data recording state;

[0019] 2) Open the valve and connect the diaphragm section to the atmosphere. The diaphragm ruptures because the pressure change exceeds the allowable pressure. At this time, a shock wave is generated and propagates toward the experimental section along the axis of the driving section. When the shock wave passes through the pressure sensor of the experimental section, the pressure sensor captures the pressure rise signal, and then converts the signal through the signal converter. The converted signal enters the data acquisition device, and the data acquisition device begins to record the pressure change signal of the experimental gas in the experimental section over time. When the shock wave reaches the end of the experimental section and is reflected by the end face, the temperature and pressure of the experimental gas in the experimental section once again meet the experimental requirements. Then the voltage signal of the data acquisition device is processed to obtain the self-ignition time, ignition temperature and pressure of the experimental gas.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects:

[0021] The present invention proposes a staged air intake device for inducing strong shock waves, which uses a valve to separate an expansion section and a driving section. The driving section is filled with helium or helium and nitrogen as driving gas, which increases the effective experimental time while ensuring the intensity of the shock wave. The temperature requirement range of the experiment is larger. The expansion section is equivalent to further extending the total length of the driving section, and the expansion section is filled with expansion gas with lower value than helium, which can greatly reduce the use of rare resource helium and save experimental costs. In addition, the experimental device of the present invention is safe and simple, easy to operate, has a wider experimental range, and is more economical.

[0022] The present invention also provides a staged air intake method for inducing a strong shock wave, wherein a gas volume that meets the experimental requirements is filled into each chamber, and then the valves of the expansion section and the driving section are opened while the diaphragm section is connected to the atmosphere, so that the diaphragm of the diaphragm section is ruptured due to the pressure difference, thereby achieving the experimental purpose. Compared with the traditional helium filling method of the integral driving section, the present invention adopts the method of filling the driving section with helium or helium and nitrogen, and filling the expansion section with expansion gas, so that the present invention can increase the effective time while ensuring the shock wave intensity, thereby saving costs, and the higher the experimental pressure of the present invention, the more significant the effect, which can significantly broaden the physical boundary of shock tube high-pressure experimental measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the present invention;

[0024] In the attached figure: 1- expansion section, 2- valve, 3- driving section, 4- membrane section, 5- experimental section, 6- first pressure sensor, 7- second pressure sensor, 8- signal converter, 9- data acquisition device, 10- gas mixing tank, 11- vacuum pump, 12- nitrogen tank, 13- helium tank, 14- expansion gas tank, 15- first pressure gauge, 16- second pressure gauge, 17- gas pipeline, 18- ventilation pipe. DETAILED DESCRIPTION

[0025] The present invention will be further described in detail below with reference to the accompanying drawings.

[0026] like Figure 1 A staged air intake device for inducing strong shock waves is shown, comprising an expansion section 1, a driving section 3, a diaphragm section 4 and an experimental section 5 which are connected in sequence and coaxially arranged, the expansion section 1 and the driving section 3 are connected via a valve 2, the diaphragm section 4 is arranged between the driving section 3 and the experimental section 5, and diaphragms for separating chambers are respectively arranged between the diaphragm section 4 and the driving section 3 and between the diaphragm section 4 and the experimental section 5, a pressure sensor is connected to the end of the experimental section 5, a signal output end of the pressure sensor is connected to a data acquisition device 9 via a signal converter 8, the data acquisition device 9 is used to convert the voltage signal converted by the signal converter 8 into a pressure signal, the expansion section 1, the driving section 3, the diaphragm section 4 and the experimental section 5 are respectively connected to a gas pipeline 17 via valves, and the gas pipeline 17 is connected to an expansion gas tank 14 for inflating the expansion section 1.

[0027] Furthermore, the expansion section, the driving section, the diaphragm section and the experimental section have the same inner diameter, the inner diameter of the valve (2) is the same as the inner diameter of the expansion section (1) and the inner diameter of the driving section (3), and the valve 2 is preferably a high-pressure turbine ball valve.

[0028] Furthermore, the pressure sensor includes a first pressure sensor 6 and a second pressure sensor 7 , wherein a plurality of the first pressure sensors 6 are provided, and the first pressure sensors 6 are provided on the side wall of the experimental section 5 , and the second pressure sensor 7 is provided at the end of the experimental section 5 .

[0029] Furthermore, the gas pipeline 17 is connected to a gas mixing tank 10, a nitrogen tank 12, and a helium tank 13 through valves, respectively. The helium tank 13 or the nitrogen tank 12 and the helium tank 13 are used as driving gas to inflate the driving section 3. The gas mixing tank 10 is used to store the gas to be tested to inflate the experimental section 5. The gas pipeline 17 is connected to the atmosphere through a ventilation pipe 18, and a valve is provided on the ventilation pipe 18.

[0030] Furthermore, a vacuum pump is connected to the gas pipeline 17, and the vacuum pump is used to evacuate the expansion section 1, the drive section 3, the membrane section 4 and the experimental section 5. When the vacuum pump is preparing to evacuate, the internal spherical space of the valve body of the valve 2 also needs to be evacuated to a vacuum, so the valve 2 needs to be opened.

[0031] The present invention opens the valve 2 between the expansion section 1 and the driving section 3 and then connects the diaphragm section 4 to the atmosphere through the vent pipe 18. Then the pressure difference between the driving section 3 and the experimental section 5 breaks through the diaphragms at both ends of the diaphragm section 4, generating an incident compression shock wave that propagates toward the experimental section 5. The temperature and pressure of the fluid to be measured rise instantly after the wave. At the same time, a fan-shaped rarefaction expansion wave is generated in the opposite direction of the positive pressure difference and propagates toward the driving section 3 along the axis of the experimental section 5. In a certain embodiment of the present invention, the valve 2 is opened and then the diaphragm section 4 is connected to the atmosphere through the vent pipe 18 within 5S.

[0032] Since there is no mass exchange between the driving gas and the experimental gas during the operation of the shock tube, a contact surface will be formed after the membrane is broken. At the beginning, the contact surface and the shock wave basically coincide, but because its movement speed is less than the shock wave propagation speed, the distance between the contact surface and the shock wave will continue to expand as the flow distance increases. The incident shock wave is reflected at the end of the experimental section 5 to form a secondary reflected shock wave, which again increases the temperature and pressure of the experimental gas, and the experimental gas is pressurized and heated for a second time. The pressure and temperature after the secondary wave are regulated by the pressure of the driving gas and the experimental gas to achieve the preset experimental conditions. A pressure sensor is installed at the end of the gas in the experimental section 5. When the incident shock wave passes through the first pressure sensor 6, the ignition diagnosis system is triggered, and the data acquisition device 9 starts to record the output signals of each sensor; the incident shock wave velocity can be obtained by the time interval of the shock wave reaching each sensor of the first pressure sensor 6 and the installation position of each sensor, and then the self-ignition temperature is calculated by the one-dimensional shock wave equation; the pressure and self-ignition time can be obtained by the pressure rise signal captured by the second pressure sensor 7. At this point, the self-ignition time of the fuel under the set pressure and temperature conditions can be obtained. For the rarefaction expansion wave, reflection also occurs after reaching the end face of the driving section 3, causing the rarefaction wave head to propagate toward the direction of the experimental section 5 at the speed of sound and catch up with the contact surface.

[0033] From the above analysis, it can be seen that the longest effective experimental time that can be achieved by the shock tube is subject to the time that the high-pressure and high-temperature state of the gas in the experimental section 5 can be maintained after the secondary reflected shock wave. The main factor affecting this state is the gas state after the secondary reflected shock wave or rarefaction wave contacts the contact surface and reflects the unsteady wave interference wave again. For this effect, the stitched contact surface operation mode is usually used, that is, mixing helium and nitrogen, matching the driving gas molecular weight and adiabatic index in a certain proportion, so that the secondary reflected shock wave contacts the contact surface and is completely projected without any reflection. Obviously, under the stitching condition, the state of the experimental gas after the wave only depends on the time when the reflected rarefaction expansion wave head reaches the contact surface. The effective experimental time is significantly improved by adopting the stitching contact surface operation mode. Therefore, increasing the length of the shock tube driving section 3 is the most effective way to extend the effective experimental time. However, the increase in the volume of the driving section 3 will inevitably lead to an increase in the amount of helium used, which is particularly significant under the stitching condition.

[0034] The present invention uses a valve 2 to separate the expansion section 1 and the driving section 3; the expansion section 1 is filled with an expansion gas with a lower value than helium, which significantly reduces the cost of helium use and can be used to extend the total length of the driving section 3 to increase the effective experimental time; the driving section 3 is filled with helium or helium and nitrogen as the driving gas, and the driving gas in the driving section 3 must meet the requirement of being able to generate strong shock waves. Helium has a large adiabatic index and a small molecular weight, and can generate strong shock waves. Nitrogen can be mixed into the helium, and the mixed gas can more effectively extend the effective experimental time and obtain a larger experimental temperature range.

Claims

1. A staged air intake device for inducing strong shock waves, characterized in that: The invention comprises an expansion section (1), a driving section (3), a diaphragm section (4) and a test section (5) which are connected in sequence and arranged coaxially. The expansion section (1) and the driving section (3) are connected via a valve (2). Diaphragms for separating the diaphragm section (4) and the test section (5) are respectively arranged between the diaphragm section (4) and the driving section (3) and between the diaphragm section (4) and the test section (5). The end of the test section (5) is connected to a pressure sensor. The signal output end of the pressure sensor is connected to a data acquisition device (9) via a signal converter (8). The data acquisition device (9) is used to acquire a voltage signal collected by the pressure sensor. The expansion section (1), the driving section (3), the diaphragm section (4) and the test section (5) are respectively connected to a gas pipeline (17) via valves. The gas pipeline (17) is connected to an expansion gas tank (14) for inflating the expansion section (1).

2. A staged air intake device for inducing strong shock waves according to claim 1, characterized in that: The inner diameter of the valve (2) is the same as the inner diameter of the expansion section (1) and the inner diameter of the drive section (3).

3. The staged air intake device for inducing strong shock waves according to claim 1, characterized in that: The pressure sensor comprises a first pressure sensor (6) and a second pressure sensor (7), wherein a plurality of the first pressure sensors (6) are provided, and the first pressure sensor (6) is provided on the side wall of the experimental section (5), and the second pressure sensor (7) is provided at the end of the experimental section (5).

4. The staged air intake device for inducing strong shock waves according to claim 1, characterized in that: The gas transmission pipeline (17) is also connected to a gas mixing tank (10), a nitrogen tank (12), and a helium tank (13) through valves, respectively. The helium tank (13) or the nitrogen tank (12) and the helium tank (13) are used as driving gas to inflate the driving section (3). The gas mixing tank (10) is used to store gas to be tested to inflate the experimental section (5). The gas transmission pipeline (17) is connected to the atmosphere through a ventilation pipe (18), and a valve is provided on the ventilation pipe (18).

5. The staged air intake device for inducing strong shock waves according to claim 1, characterized in that: The gas delivery pipeline (17) is also connected to a vacuum pump (11), and the vacuum pump (11) is used to evacuate the expansion section (1), the drive section (3), the film clamping section (4) and the experimental section (5).

6. The staged air intake device for inducing strong shock waves according to claim 1, characterized in that: The gas pipeline (17) is connected to a second pressure gauge (16) via a valve for monitoring the gas pressure in the gas pipeline and in the expansion section (1), the drive section (3) and the clamping section (4), and the experimental section (5) is connected to a first pressure gauge (15) via a valve for monitoring the gas pressure in the experimental section.

7. The staged air intake device for inducing strong shock waves according to claim 1, characterized in that: The expansion section (1), the driving section (3), the clamping section (4) and the experimental section (5) have the same inner diameter.

8. The staged air intake device for inducing strong shock waves according to claim 1, characterized in that: The expansion gas tank (14) contains air, nitrogen or carbon dioxide.

9. The staged air intake device for inducing strong shock waves according to claim 3, characterized in that: The first pressure sensor (6) adopts PCB 113B22, and the second pressure sensor (7) adopts PCB 113B03.

10. The working method of the air intake device according to any one of claims 1 to 9, characterized in that: The steps include: 1) According to the experimental requirements, the driving gas pressure and experimental gas pressure required to achieve the target working condition are calculated by the shock wave equation, and the gas pressure value of the membrane clamping section (4) is determined according to the driving gas pressure and the experimental gas pressure; a diaphragm is inserted between the membrane clamping section (4) and the driving section (3) and between the membrane clamping section (4) and the experimental section (5), the valve (2) is opened, and the expansion section (1), the driving section (3), the membrane clamping section (4) and the experimental section (5) are evacuated to a vacuum state, and then the valve (2) is closed; 2) introducing driving gas into the diaphragm section (4) and the driving section (3), during which the pressure difference between the diaphragm section (4) and the driving section (3) and between the diaphragm section (4) and the test section (5) is ensured to be less than the allowable pressure difference; when the gas pressure of the diaphragm section (4) reaches the gas pressure value of the diaphragm section (4), the diaphragm section (4) stops taking in gas, and the driving section (3) continues to take in driving gas until the driving gas pressure required under the target working condition is reached; 3) introducing expansion gas into the expansion section (1) until the pressure of the expansion section (1) is the same as that of the driving section (3); then, introducing experimental gas into the experimental section (5) until the experimental gas pressure is reached and then stopping the ventilation, and then adjusting the data acquisition device (9) to the automatic data recording state; 4) Open the valve (2), and then connect the diaphragm section (4) to the atmosphere. The diaphragm ruptures because the pressure change exceeds the allowable pressure. At this time, a shock wave is generated and propagates along the axis of the driving section (3) to the experimental section (5). When the shock wave passes through the pressure sensor of the experimental section (5), the pressure sensor captures the pressure rise signal, and then converts the signal through the signal converter (8). The converted signal enters the data acquisition device (9). The data acquisition device (9) starts to record the pressure change signal of the experimental gas in the experimental section (5) over time. When the shock wave reaches the end of the experimental section (5) and is reflected by the end face, the temperature and pressure of the experimental gas in the experimental section (5) once again reach the experimental requirements. Then, the voltage signal of the data acquisition device (9) is processed to obtain the self-ignition time, ignition temperature and pressure of the experimental gas.

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