A microwave double-focusing ignition test device

Abstract

The application discloses a microwave double-focusing ignition test device, which comprises a microwave ignition cavity, a microwave energy feeding probe and a sample table. The microwave ignition cavity is used for resonating microwave energy so that the microwave energy is reflected and propagated back and forth in the cavity, thereby increasing the energy and amplitude. The microwave energy feeding probe is used for transmitting and focusing the microwave energy. The sample table is located below the output end of the microwave energy feeding probe, and the top of the sample table is provided with an energetic material. The microwave energy is first transmitted and focused by the microwave energy feeding probe, enters the microwave ignition cavity through the microwave energy feeding probe, resonates in the microwave ignition cavity, is again gathered to the needle tip by the microwave resonance cavity, and is focused and enhanced again, so that the energetic material is ignited.

Description

Technical Field

[0001] This invention relates to the field of microwave ignition technology, and in particular to a microwave dual-focusing ignition test device. Background Technology

[0002] With the development of science and technology, microwave ignition technology has been widely used in civilian and military fields due to its advantages such as speed, safety and environmental protection.

[0003] Currently available microwave ignition testing devices for energetic materials in China suffer from high ignition power, low microwave energy utilization, and insufficient consideration of protection against explosive impacts and electromagnetic radiation, which may cause damage to operators and valuable instruments. Summary of the Invention

[0004] To address at least one of the problems in existing microwave ignition test devices, namely high ignition power, low microwave energy utilization, and insufficient protection against explosion impact and electromagnetic radiation, this invention provides a microwave dual-focusing ignition test device.

[0005] The technical solution adopted in this invention is:

[0006] A microwave dual-focus ignition test device includes: a microwave ignition cavity, a microwave energy feed probe, and a sample stage;

[0007] A microwave ignition cavity is used to generate a resonance effect on microwave energy, so that the microwave energy is reflected and propagated back and forth inside the cavity, thereby increasing the energy and amplitude.

[0008] A microwave energy feed probe is used to transmit and focus microwave energy. The input end of the microwave energy feed probe is located on the top outer side of the microwave ignition cavity, and the output end of the microwave energy feed probe passes through the top of the microwave ignition cavity and extends outward.

[0009] A sample stage is located below the output end of the microwave energy feed probe, and an energetic material is disposed on the top of the sample stage.

[0010] Preferably, the microwave energy feed probe includes: a coaxial line and a needle tip;

[0011] A coaxial cable, comprising an outer conductor and an inner conductor, wherein polycarbonate is filled between the inner conductor and the outer conductor;

[0012] A needle, which is connected to the inner conductor.

[0013] Preferably, the sample stage includes: a base, a screw sleeve, a screw, and a support platform;

[0014] The base is located at the bottom end of the microwave ignition cavity;

[0015] A threaded sleeve, one end of which is connected to the base;

[0016] The screw is threadedly connected to the screw sleeve;

[0017] A support platform is provided on top of the screw.

[0018] Preferably, an observation window is provided on the side wall of the microwave ignition cavity, and the observation window is provided with a waveguide.

[0019] Preferably, the inner diameter of the waveguide is the same as the radius of the observation window, and the length of the waveguide is 2 cm.

[0020] Preferably, the side wall of the microwave ignition cavity 1 is provided with an electromagnetic shielding door.

[0021] Preferably, the outer conductor has a radius of 5.167 mm, the inner conductor has a radius of 1.25 mm, and the coaxial cable has a length of 29.5 mm.

[0022] The total length of the needle is 31mm, the radius of the needle is 1.25mm, and the length of the needle tip is 4mm.

[0023] Preferably, the length of the microwave ignition cavity 1 is 20.5cm, and the width and height of the microwave ignition cavity 1 are both 17cm.

[0024] The beneficial effects of this invention are as follows: The microwave ignition cavity concentrates microwave energy to the microwave energy feed probe for a second time as follows: The microwave energy first enters the microwave ignition cavity from the microwave source through the input end of the microwave energy feed probe and is focused at the tip. Then, it is reflected and propagated back and forth inside the microwave ignition cavity, generating a resonance effect, thereby further increasing the microwave energy and amplitude at the tip, thus igniting the energetic material and improving the utilization rate of microwave energy. Attached Figure Description

[0025] Figure 1 This is a three-dimensional structural diagram of the experimental device in an embodiment of the present invention;

[0026] Figure 2 This is a front view schematic diagram of the experimental device in an embodiment of the present invention;

[0027] Figure 3 This is a front view schematic diagram of the microwave energy feeding probe in an embodiment of the present invention;

[0028] Figure 4 This is a schematic diagram of the front cross-sectional structure of the microwave energy feed probe in an embodiment of the present invention;

[0029] Figure 5 This is a schematic diagram of the electric field strength at the needle tip after changing the radius of the inner conductor in an embodiment of the present invention;

[0030] Figure 6 This is a schematic diagram of the electric field strength at the needle tip after adjusting the inner radius of the outer conductor in an embodiment of the present invention;

[0031] Figure 7 This is a schematic diagram of the electric field strength at the needle tip after changing the needle tip length in an embodiment of the present invention;

[0032] Figure 8 This is a schematic diagram of the electric field strength at the needle tip after changing the needle length in an embodiment of the present invention;

[0033] Figure 9 This is a schematic diagram of the electric field strength at the needle tip after changing the length of the coaxial line in an embodiment of the present invention;

[0034] Figure 10 This is a schematic diagram of the electric field strength at the tip of the microwave probe after adding a resonant cavity in an embodiment of the present invention;

[0035] Figure 11 This is a schematic diagram of the structure in which an observation window is provided on the side wall of the microwave ignition cavity in an embodiment of the present invention;

[0036] Figure 12 This is a frontal cross-sectional view of the waveguide structure with the observation window provided in an embodiment of the present invention;

[0037] Figure 13 This is a schematic diagram of the electric field intensity at the outer port of the waveguide in an embodiment of the present invention;

[0038] Figure 14 This is a schematic diagram of the sample stage in an embodiment of the present invention.

[0039] Reference numerals: 1. Microwave ignition cavity; 11. Observation window; 2. Microwave energy feed probe; 21. Outer conductor; 22. Inner conductor; 23. Needle; 3. Sample stage; 31. Base; 32. Screw sleeve; 33. Screw; 34. Support platform; 4. Waveguide; 5. Electromagnetic shielding door. Detailed Implementation

[0040] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0041] Example:

[0042] To address at least one of the problems in existing microwave ignition test devices, such as high ignition power, low microwave energy utilization, and insufficient consideration of protection against explosive impact and electromagnetic radiation, such as... Figure 1 and Figure 2 As shown, this embodiment provides a microwave dual-focus ignition test apparatus, including:

[0043] Microwave ignition cavity 1, the microwave ignition cavity is used to generate a resonance effect on microwave energy so that microwave energy is reflected and propagated back and forth inside the cavity;

[0044] A microwave energy feed probe 2 is used to transmit and focus microwave energy. The input end of the microwave energy feed probe 2 is located on the top outer side of the microwave ignition cavity 1, and the output end of the microwave energy feed probe 2 passes through the top of the microwave ignition cavity 1 and extends thereafter.

[0045] Sample stage 3 is located below the output end of microwave energy feed probe 2, and energetic material is disposed on the top of sample stage 3.

[0046] The side wall of the microwave ignition cavity 1 is equipped with an electromagnetic shielding door 5. It is understood that the input end of the microwave energy feed probe 2 is connected to an external microwave source.

[0047] Energetic materials refer to substances that can absorb microwave energy and generate chemical reactions, thereby releasing large amounts of heat and pressure. For example, thermite, a mixture of metal and oxidant powder, is a high-energy material characterized by high energy density and fast reaction speed. In microwave ignition devices, thermite can act as an igniter, providing a high-energy reaction process. Another example is nanomaterials, a novel type of energetic material characterized by extremely high surface area and activity, enabling efficient energy release. In microwave ignition devices, nanomaterials can act as an igniter, improving ignition efficiency and energy density.

[0048] Considering that metal materials would reflect and interfere with microwaves if sample stage 3 were made of metal, it is made of high-transmittance polytetrafluoroethylene (PTFE). High-transmittance PTFE provides excellent microwave penetration, allowing microwave energy to be better applied to the sample, thus improving the efficiency and reliability of microwave ignition. High-transmittance PTFE also has higher high-temperature resistance, maintaining stability and reliability at higher temperatures.

[0049] To further prevent the energetic material from damaging the sample stage 3 during combustion, a glass slide or ceramic tube is placed between the energetic material and the sample stage 3. The sample amount of the energetic material is in the milligram range and is placed on the glass slide or in the ceramic tube.

[0050] In this embodiment, the process by which the microwave ignition cavity 1 refocuses microwave energy onto the microwave energy feed probe 2 is as follows: Microwave energy first enters the microwave ignition cavity 1 from the microwave source through the input end of the microwave energy feed probe 2, and is focused at the tip to form a high-energy microwave field. Inside the microwave ignition cavity 1, the microwave energy resonates and reflects and propagates back and forth within the cavity 1, further enhancing the microwave energy and amplitude at the tip of the probe 2. During this process, the microwave energy is refocused and amplified, thereby igniting the energetic material on the sample stage 3.

[0051] The electromagnetic shielding door 5 is designed to prevent microwave energy from leaking out of the cavity and affecting personnel and the environment. The electromagnetic shielding door 5 is typically made of conductive material that can reflect and absorb microwave energy, thus preventing microwave energy leakage from the cavity.

[0052] Furthermore, in order to improve the utilization rate of microwave energy, it is necessary to design the dimensions of the microwave energy feed probe 2 and the microwave ignition cavity 1.

[0053] Among them, such as Figure 3 and Figure 4 As shown, the microwave energy feed probe 2 includes: an outer conductor 21; an inner conductor 22, wherein polycarbonate is filled between the inner conductor 22 and the outer conductor 21; and a needle 23, wherein the needle 23 is connected to the inner conductor 22.

[0054] In this embodiment, the microwave source frequency is 2.45 GHz, and the design process of the coaxial cable and microwave needle tip is as follows:

[0055] Given a microwave source frequency of 2.45 GHz, the wavelength can be obtained.

[0056]

[0057] Initially, let the outer conductor radius R be 5mm and the characteristic impedance be 50Ω. Therefore, the inner conductor radius r1 should satisfy:

[0058]

[0059] The inner and outer conductors of the coaxial line are filled with polycarbonate (PC) with a relative permittivity of 2.9, resulting in an inner conductor radius r1 = 1.2 mm.

[0060] The preliminary design specifies the outer conductor radius R = 5mm, the inner conductor radius r1 = 1.2mm, the coaxial cable length l = λ / 4 = 30.6mm, and the total microwave needle length h = λ / 4 = 30.6mm, where the needle tip length A = 3mm. The microwave needle radius is equal to the inner conductor radius r1. The coaxial cable is connected to the microwave source via a feed port, with the average input power at the feed port set to 30W.

[0061] An electric field probe is placed at the tip of the needle, and the radius r1 of the inner conductor is changed. Figure 5 To change the electric field strength at the needle tip after changing the inner conductor radius, r1 = 1.25 mm was selected, and R = 5.167 mm was calculated. Figure 6 To adjust the electric field strength at the needle tip after adjusting the inner radius of the outer conductor.

[0062] Change the needle tip length A, Figure 7 To change the electric field strength at the needle tip after adjusting the needle tip length, considering factors such as effect and process, A = 4mm was selected.

[0063] Change the needle length h, Figure 8 To change the electric field strength at the needle tip after adjusting the needle length, a needle length of h = 31 mm was chosen.

[0064] Change the length l of the coaxial line, Figure 9 To change the electric field strength at the needle tip after adjusting the length of the coaxial line, l = 29.5 mm was chosen.

[0065] In summary, the selection of coaxial cable and needle parameters is as follows:

[0066] The coaxial cable is 29.5 mm long, with an outer conductor radius of 5.167 mm and an inner conductor radius of 1.25 mm.

[0067] The total length of the needle is 31mm, the radius is 1.25mm, and the needle tip length is 4mm.

[0068] At this point, the probe model's S-parameters at 2.45 GHz are -12.051 dB. This value represents the efficiency of microwave energy transmission from the probe to the ignition region. -12.051 dB is a relatively low value, indicating high transmission efficiency.

[0069] Furthermore, to improve microwave energy utilization, the dimensions of the microwave ignition cavity 1 are optimized. In this embodiment, the microwave ignition cavity 1 is a rectangular resonant cavity with a resonant mode of TE. 103 The resonant mode mnp = 10³, a = 15cm, b = 15cm, d = 20cm, and the resonant frequency f satisfies the formula:

[0070]

[0071] The calculated value is f = 2462 MHz. Since the size of the resonant cavity will need to be adjusted later, the resonant frequency does not need to be exactly 2.45 GHz initially.

[0072] At this time, the resonant cavity TE 103 The electric field of the resonant mode is

[0073]

[0074] In the resonant cavity, a microwave source is used to excite the coupling. Common excitation methods include electrical excitation, magnetic excitation, and hybrid electromagnetic excitation. Using a coaxial microwave energy feed into probe 2 to excite the electromagnetic field is an example of electrical excitation, also known as probe excitation. Since the resonant cavity mode is set to TE... 103 The probe is placed at the location of maximum electric field strength, parallel to the direction of the electric field, so it is placed at the center of the upper surface of the rectangular resonant cavity. Literature review indicates that the insertion of the probe will cause a change in the cavity's resonant frequency.

[0075] By changing the length of the resonant cavity, choosing a = 18.5 cm, the resonant frequency of the rectangular resonant cavity excited by the coaxial microwave energy feed into probe 2 is around 2.45 GHz. At this time, the electric field strength at the probe tip is 123.66 dBV / m = 1524 kV / m.

[0076] At this time, the dimensions of the microwave ignition cavity 1 are 20.5cm in length, and 17cm in width and height (taking into account a thickness of 1cm).

[0077] Figure 10 The field strength at the tip of the microwave probe is 110.48 dBV / m = 334 kV / m for a standalone antenna. Adding the resonant cavity increases the field strength by 13.18 dBV / m.

[0078] In one possible implementation, such as Figure 11 As shown, an observation window 11 is provided on the side wall of the microwave ignition cavity 1. Through the observation window, the operator can view the microwave ignition process in real time, such as whether ignition is successful and the ignition effect. This helps ensure the accuracy and safety of the experiment. The observation window also allows the operator to closely monitor the microwave ignition process, for example, to observe changes in the sample to determine whether ignition is successful. In some cases, microwave ignition may produce unexpected situations, such as sample deflagration or equipment malfunction. Through the observation window, the operator can promptly detect these situations and take corresponding safety measures to avoid injury or damage to personnel and equipment. The observation window also allows the operator to record the results of microwave ignition, such as ignition time and ignition effect, which is helpful for the recording and analysis of experimental results.

[0079] Considering the electromagnetic leakage problem at the window, such as Figure 12 As shown, a waveguide 4 with an inner diameter a and the same window radius is proposed to be used as an attenuator to achieve electromagnetic shielding effect.

[0080] For the dominant mode TE11 of the circular waveguide, the cutoff frequency is...

[0081]

[0082] The calculated value is fc = 11.7 GHz. (Cutoff wavelength) The wavelength of the 2.45 GHz microwave source is λ = 122.45 mm, which is greater than the cutoff wavelength. Therefore, the attenuation constant for propagation in the waveguide is...

[0083]

[0084] The calculated value is α = 240 / m. Electromagnetic waves with frequencies below the cutoff frequency exhibit exponential attenuation along the waveguide in a circular waveguide.

[0085] E1=E0e -αL

[0086] Figure 13 The electric field strength is at the outer port of the waveguide. To achieve electromagnetic shielding, the length of the external waveguide 4 is chosen to be 2cm.

[0087] Among them, the dominant mode TE11 of a circular waveguide refers to a specific mode within the waveguide, in which the field components vary periodically along the circular edge of the transverse cross-section. It is the longest cutoff wavelength and the lowest second mode, thus possessing unique properties and importance in circular waveguides.

[0088] In one possible implementation, such as Figure 14 As shown, in order to facilitate experimental operation and ensure that microwave energy can be effectively fed into the sample, the sample stage 3 includes: a base 31, which is disposed at the bottom end of the microwave ignition cavity 1; a screw sleeve 32, one end of which is connected to the base 31; a screw 33, which is threadedly connected to the screw sleeve 32; and a support platform 34, which is disposed at the top of the screw 33.

[0089] It should be noted that, to ensure precise height adjustment of sample stage 3, a micrometer screw is used. A portion of the screw sleeve is machined with a 0.5mm pitch thread, and the perimeter of the screw is divided into 50 equal divisions. This allows for precise adjustment and measurement of even minute heights of the sample stage.

[0090] The overall height of the sample stage 3 was set to 8cm, and the distance between the support stage 34 and the needle tip was 0.5mm. Then, the overall simulation was performed. At this time, the electric field strength at the needle tip was 116dBV / m = 630.96kV / m. This shows that the electric field strength at the needle tip inside the microwave ignition cavity 1 reached 630.96kV / m, which is a relatively high value. This indicates that there is enough microwave energy at the needle tip to be used for ignition or to trigger other high-energy reactions.

[0091] The embodiments described above are merely illustrative of specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A microwave dual-focusing ignition test device, characterized in that, include: Microwave ignition cavity (1), the microwave ignition cavity is used to generate a resonance effect on microwave energy so that microwave energy is reflected and propagated back and forth inside the cavity; A microwave energy feed probe (2) is used to transmit and focus microwave energy. The input end of the microwave energy feed probe (2) is located on the top outside of the microwave ignition cavity (1), and the output end of the microwave energy feed probe (2) extends through the top of the microwave ignition cavity (1). The sample stage (3) is located below the output end of the microwave energy feed probe (2), and the top of the sample stage (3) is used to place energetic materials. The microwave energy feed probe (2) includes: A coaxial cable comprising an outer conductor (21) and an inner conductor (22), wherein polycarbonate is filled between the inner conductor (22) and the outer conductor (21); The needle (23) is connected to the inner conductor (22); The outer conductor (21) has a radius of 5.167 mm, the inner conductor (22) has a radius of 1.25 mm, and the coaxial line has a length of 29.5 mm; The total length of the needle (23) is 31 mm, the radius of the needle (23) is 1.25 mm, and the needle tip length of the needle (23) is 4 mm. The length of the microwave ignition cavity (1) is 20.5cm, and the width and height of the microwave ignition cavity (1) are both 17cm.

2. The microwave dual-focusing ignition test device according to claim 1, characterized in that: The sample stage (3) includes: The base (31) is disposed at the bottom end inside the microwave ignition cavity (1); A threaded sleeve (32), one end of which is connected to the base (31); A screw (33) is threadedly connected to a screw sleeve (32); A support platform (34) is disposed on top of the screw (33).

3. The microwave dual-focusing ignition test device according to claim 2, characterized in that: An observation window (11) is provided on the side wall of the microwave ignition cavity (1): Waveguide (4), which is connected to the observation window (11).

4. The microwave dual-focusing ignition test device according to claim 3, characterized in that, The inner diameter of the waveguide (4) is the same as the radius of the observation window (11), and the length of the waveguide is 2cm.

5. A microwave dual-focusing ignition test apparatus according to any one of claims 1-4, characterized in that: The side wall of the microwave ignition cavity (1) is provided with an electromagnetic shielding door (5).

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