Shock tube test section structure and ignition observation system

Abstract

The invention discloses a shock tube test section structure and an ignition observation system, and relates to the technical field of fuel combustion experiments.The shock tube comprises a shock tube test section body, a reaction cavity is formed in the shock tube test section body, and a butt joint structure is arranged at one end of the shock tube test section body; the butt joint structure is used for butt joint of a shock tube high-voltage driving section capable of forming shock waves; the side surface of the shock tube test section body and the other end of the shock tube test section body are both provided with the visual structures, and the visual structure located on the side surface of the shock tube test section body extends from one end of the shock tube test section body to the other end of the shock tube test section body. Visual structures are arranged on the side face and the end portion of the shock tube testing section body, the visual structures are matched with a visual module to directly shoot the fuel self-ignition combustion process of a reaction cavity in the shock tube testing section body, an image is formed, and the self-ignition process of the reaction cavity in the shock tube is recorded. And the ignition homogeneity on the radial section of the shock tube and the ignition homogeneity and the ignition position on the axial surface in the tube can be conveniently judged.

Description

Technical Field

[0001] The present application relates to the technical field of fuel combustion experiments, and in particular to a shock tube test section structure and a fire observation system. Background Art

[0002] There are two types of fuel ignition, one is forced ignition, such as ignition using a spark plug, and the other is spontaneous ignition, such as when a combustible mixture is compressed to a certain temperature and pressure to ignite. For compression ignition engines, spontaneous ignition is the main method. The length of the fuel self-ignition time has an important influence on the engine operation and the selection of structural parameters. Therefore, it is necessary to study and measure the fuel self-ignition time. The so-called self-ignition time, that is, the ignition delay time of the fuel, refers to the time when the mixture of fuel and oxidant reaches the self-ignition condition, it will not ignite immediately, but will go through a chemical preparation period, and then start a violent combustion chemical reaction process. There are two commonly used devices in the laboratory to measure the fuel ignition delay time, namely shock tubes and fast compressor devices, corresponding to the measurement of fuel ignition time at medium and high temperatures and low temperatures. Among them, the shock tube mainly uses the shock wave formed by the pressure difference to compress the mixture of fuel, oxidant and diluent to the specified temperature and pressure conditions, and then the combustible mixture begins to self-ignite. Combined with the observation data of the fuel self-ignition process, data information about the fuel ignition delay time can be extracted.

[0003] The ideal ignition process of fuel is homogeneous ignition, but due to the existence of non-ideal factors in the actual shock tube, the degree of homogeneity of the actual ignition process is yet to be determined, and ensuring the homogeneity of the ignition process is very important for judging the validity of the ignition delay time test data. The existing method of measuring the fuel ignition delay time based on pressure signals or a combination of pressure and light signals has the following disadvantages: only collecting pressure or pressure and light signals cannot intuitively reflect whether the ignition process occurring in the low-pressure end wall test area in the shock tube is homogeneous, making it difficult to judge the validity of the ignition delay time test data; at the same time, it cannot provide more information for studying the influence of non-ideal factors in the shock tube on the fuel self-ignition process, making the understanding of the fuel ignition process in the shock tube relatively single. Summary of the invention

[0004] The present application aims to solve one of the above technical problems in the prior art. To this end, an embodiment of the present application provides a shock tube test section structure.

[0005] An embodiment of the present application also provides a fire observation system.

[0006] According to an embodiment of the first aspect of the present application, a shock tube test section structure is provided, including a shock tube test section body, a reaction chamber is arranged in the shock tube test section body, a docking structure is arranged at one end of the shock tube test section body, and the docking structure is used to dock with a shock tube high-voltage driving section that can form a shock wave; a visualization structure, the visualization structure is arranged on the side of the shock tube test section body and the other end of the shock tube test section body, and the visualization structure located on the side of the shock tube test section body extends from one end of the shock tube test section body to the other end.

[0007] The above-mentioned shock tube has at least the following beneficial effects: compared with the prior art, in terms of structure, a visualization structure is provided on the side and end of the shock tube test section body, and in terms of testing technology, the self-ignition and combustion process of the fuel in the reaction chamber in the shock tube test section body is directly photographed in cooperation with the visual module to form an image and record the self-ignition process of the reaction chamber in the shock tube. According to the ignition image taken from the end visualization structure, the homogeneity of the ignition on the radial cross section in the shock tube can be judged, and the ignition image taken from the side visualization structure can be used to judge the ignition homogeneity and ignition position on the axial surface in the tube. On the one hand, these image data can be used to judge whether the ignition in the shock tube is a homogeneous process, thereby improving the accuracy of the fuel ignition delay time data measured based on pressure and light signals, and on the other hand, it can provide a basis for studying the influence of non-ideal factors in the shock tube on the ignition process, so as to deepen the understanding of the ignition process in the shock tube.

[0008] According to the shock tube test section structure described in the embodiment of the first aspect of the present application, grooves connected to the reaction chamber are provided on the sides and ends of the shock tube test section body, and the two ends of the groove on the side of the shock tube test section body are respectively close to the two ends of the shock tube test section body, and the visualization structure is fixed to the groove.

[0009] According to the shock tube test section structure described in the embodiment of the first aspect of the present application, the visualization structure includes a fire barrier and a clamping assembly, the fire barrier is made of a transparent material, and the clamping assembly fixes the fire barrier to the groove from the outside of the shock tube test section body.

[0010] According to the shock tube test section structure described in the embodiment of the first aspect of the present application, a boss is arranged in the groove, and the clamping assembly includes a pressure plate and a fastener. The middle part of the pressure plate is hollowed out, and the pressure plate has a clamping portion that can enter the groove. The fastener locks the pressure plate to the side of the shock tube test section body so that the clamping portion can clamp the fire isolation member placed on the boss.

[0011] According to the shock tube test section structure described in the embodiment of the first aspect of the present application, sealing gaskets are arranged between the fire isolation member and the boss and between the fire isolation member and the pressing portion.

[0012] According to the shock tube test section structure described in the embodiment of the first aspect of the present application, the shock tube also includes a first flange portion, which is arranged at the end of the shock tube test section body, and the first flange portion has the groove, wherein the diameter of the first flange portion is larger than the diameter of the shock tube test section body.

[0013] According to the shock tube test section structure described in the embodiment of the first aspect of the present application, a reinforcement portion is provided on the side of the shock tube test section body, the reinforcement portion extends from one end of the shock tube test section body to the other end, and the groove is provided on the reinforcement portion.

[0014] According to the shock tube test section structure described in the embodiment of the first aspect of the present application, the material of the shock tube test section body is stainless steel, and the material of the fire isolation component is quartz glass.

[0015] According to the shock tube test section structure described in the embodiment of the first aspect of the present application, the docking structure includes a second flange portion, and the diameter of the second flange portion is larger than the shock tube test section body.

[0016] According to an embodiment of the second aspect of the present application, a fire observation system is provided, comprising:

[0017] A shock tube, the shock tube comprising the shock tube test section structure described in the first aspect above;

[0018] a first visual module, wherein the first visual module obtains the ignition reaction condition in the reaction chamber through the visual structure on the side of the shock tube test section body;

[0019] a second visual module, wherein the second visual module obtains the ignition reaction condition in the reaction chamber through the visual structure at the end of the shock tube test section body;

[0020] A pressure sensor is arranged on the shock tube test section body, and the pressure sensor is used to detect the pressure condition in the reaction chamber.

[0021] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present application is further described below with reference to the accompanying drawings and embodiments;

[0023] Figure 1The structure of the fire observation system of the embodiment of the present application is shown in FIG. Figure 1 ;

[0024] Figure 2 The structure of the fire observation system of the embodiment of the present application is shown in FIG. Figure 2 ;

[0025] Figure 3 The structure of the fire observation system of the embodiment of the present application is shown in FIG. Figure 3 ;

[0026] Figure 4 The structure of the fire observation system of the embodiment of the present application is shown in FIG. Figure 4 ;

[0027] Figure 5 It is a schematic diagram of the structure of the shock tube test section body in an embodiment of the present application.

[0028] Reference numerals:

[0029] Shock tube 100, reaction chamber 101, mounting hole 102, shock tube test section body 110, groove 111, first flange 120, second flange 130, reinforcement 140;

[0030] Visualization structure 200, sealing gasket 210, fireproof member 220, pressing plate 240, pressing portion 241, hollow hole 242, fastener 250;

[0031] A first visual module 400;

[0032] Second vision module 500 . DETAILED DESCRIPTION

[0033] This section will describe in detail the specific embodiments of the present application. The preferred embodiments of the present application are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present application, but it cannot be understood as a limitation on the scope of protection of the present application.

[0034] In the description of the present application, it should be understood that descriptions involving orientation, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0035] In the description of this application, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0036] In the description of this application, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in this application based on the specific content of the technical solution.

[0037] The shock tube is divided into a high-pressure driving section and a low-pressure driven section. The driving section is filled with high-pressure driving gas, and the driven section is filled with a mixture of fuel, oxidant, and diluent. The driving section and the driven section are separated by a diaphragm. When the diaphragm ruptures, a shock wave will be formed due to the inconsistent pressure between the driving section and the driven section. This pressure wave will compress the combustible mixture in the driven section.

[0038] During the self-ignition process of the fuel in the shock tube, the pressure will rise due to ignition and combustion after a plateau period. The time span of the plateau period corresponds to the ignition delay time of the fuel. At the same time, the combustion of the fuel will also emit a light signal. According to the pressure and light signal characteristics during the ignition process of the fuel in the shock tube, there are currently two common methods for monitoring the self-ignition process of the fuel. One is to monitor pressure changes. When the shock wave in the tube reaches the test area on the end wall of the low-pressure section of the shock tube, the combustible mixture in this area will successively experience compression of the incident shock wave and the reflected shock wave, and then reach the specified temperature and pressure conditions. The time starting point is the compression of the reflected shock wave and the formation of a high-pressure environment. The subsequent pressure changes in the test area, including the plateau period and the pressure rise period after ignition, are recorded using a dynamic pressure sensor to define the end point of the fuel ignition process, and then the ignition delay time of the fuel can be determined. Another method is to combine the pressure signal with the light signal. As described in the first method, the pressure signal is used to define the starting point of the fuel ignition, but a monochromator and other devices are used to record the light signal emitted by the fuel self-ignition process, such as the OH* signal, and the end point of the ignition process is defined by the light signal, thereby calculating the self-ignition delay time of the fuel.

[0039] The ideal self-ignition process of fuel is homogeneous ignition, that is, after the combustible mixture reaches the self-ignition condition, the chemical preparation process begins everywhere in space, and then ignition and combustion begin. Corresponding to the monitoring signal, the pressure signal remains stable and unchanged during the ignition delay period, and the optical signal changes significantly. At this time, the measured fuel ignition delay time can accurately reflect the self-ignition characteristics of the fuel under given temperature and conditions. However, the actual ignition in the shock tube is affected by various factors, such as the existence of a boundary layer near the inner wall of the tube, where the temperature inside is inconsistent with the temperature in the center area of ​​the tube; the presence of impurity particles in the tube, the high temperature points formed can cause the combustible mixture to ignite in advance; the uneven speed shock wave compresses the combustible mixture to form an uneven temperature. These factors will cause the ignition in the shock tube to deviate from the ideal homogeneous ignition, so that the measured fuel ignition delay time cannot accurately reflect the ignition characteristics of the fuel under given initial conditions, and the experimental data is invalid.

[0040] However, when determining the fuel ignition delay time based on the existing pressure and light signals, it is not easy to determine whether the self-ignition process in the shock tube is a homogeneous process, especially within the transition initial conditions between homogeneous and heterogeneous ignitions, when the pressure signal change during the plateau period is not very obvious. The self-ignition process of the fuel in the shock tube mainly occurs in the end wall test area. Therefore, this application aims to design a set of shock tubes that are easy to observe, and use a high-speed camera to directly record the ignition process of the end wall test area of ​​the low-pressure section of the shock tube to form a visual image to determine whether the ignition is homogeneous, thereby providing support for determining the validity of the ignition delay time data.

[0041] Specifically, Figures 1 to 5 As shown, the present application provides a shock tube test section structure 100 , which includes a shock tube test section body 110 and a visualization structure 200 .

[0042] Among them, a reaction chamber 101 is arranged in the shock tube test section body 110, a docking structure is arranged at one end of the shock tube test section body 110, and the docking structure is used to dock with the shock tube high-voltage driving section that can form a shock wave, and a visualization structure 200 is arranged on the side of the shock tube test section body 110 and the other end of the shock tube test section body 110, and the visualization structure 200 located on the side of the shock tube test section body 110 extends from one end of the shock tube test section body 110 to the other end.

[0043] When in use, the visualization structure 200 is installed on the side of the shock tube test section body 110 and the other end of the shock tube test section body 110, and the docking structure of the shock tube 100 is connected to the shock tube high-voltage driving section. The reaction chamber 101 in the shock tube test section body 110 is used as the test area. At the beginning of the experiment, a mixture of fuel, oxidant and diluent is injected into the reaction chamber 101, and is compressed twice by the incident and reflected shock waves generated in the shock tube high-voltage driving section. After the pressure in the reaction chamber 101 reaches a certain value, the fuel self-ignites. The self-ignition and combustion process of the fuel in the reaction chamber 101 in the shock tube test section body 110 is directly photographed with the visual module to form an image and record the self-ignition process of the reaction chamber 101 in the shock tube 101. According to the ignition image taken from the end visualization structure 200, the homogeneity of the ignition on the radial cross section inside the shock tube 100 can be determined, and according to the ignition image taken from the side visualization structure 200, the ignition homogeneity and ignition position on the axial surface inside the tube can be determined. On the one hand, these image data can be used to determine whether the ignition in the shock tube 100 is a homogeneous process, thereby improving the accuracy of the fuel ignition delay time data measured based on the pressure and light signals. On the other hand, it can provide a basis for studying the influence of non-ideal factors in the shock tube 100 on the ignition process, so as to deepen the understanding of the ignition process in the shock tube 100.

[0044] In some embodiments, the shock tube test section body 110 is columnar, and the sides and ends of the shock tube test section body 110 are provided with grooves 111 connected to the reaction chamber 101. The two ends of the side groove 111 of the shock tube test section body 110 are respectively close to the two ends of the shock tube test section body 110, and the visualization structure 200 is fixed to the groove 111. The setting of the groove 111 facilitates the installation and maintenance of the visualization structure 200. In addition, the two ends of the side groove 111 of the shock tube test section body 110 are respectively close to the two ends of the shock tube test section body 110, and the groove 111 is set long enough to enable a relatively complete observation of the fuel combustion conditions at various locations in the reaction chamber 101.

[0045] In some embodiments, Figures 2 to 4 As shown, the visualization structure 200 includes a fire-shielding piece 220 and a clamping assembly. The fire-shielding piece 220 is made of a transparent material. The clamping assembly fixes the fire-shielding piece 220 to the groove 111 from the outside of the shock tube test section body 110 to facilitate the installation and removal of the fire-shielding piece 220.

[0046] In some embodiments, a boss is provided in the groove 111, and the clamping assembly includes a pressing plate 240 and a fastener 250. The middle portion of the pressing plate 240 is hollowed out, and the pressing plate 240 has a clamping portion 241 that can enter the groove 111. The fastener 250 locks the pressing plate 240 to the side of the shock tube test section body 110 so that the clamping portion 241 can clamp the fire isolation member 220 placed on the boss.

[0047] Specifically, the middle of the pressing plate 240 has a hollow hole 242 to make the pressing plate 240 annular, and the outer contour of the pressing plate 240 is similar to the shape of the groove 111, but the outer contour of the pressing plate 240 is larger than the contour of the groove 111. After the fireproof member 220 is placed in the groove 111, the pressing portion 241 of the pressing plate 240 is inserted into the groove 111 to press against the fireproof member 220, and the fasteners 250 are arranged at intervals along the edge of the pressing plate 240, wherein a portion of the fasteners 250 penetrates the pressing plate 240 and is threadedly connected to the shock tube test section body 110. In the embodiment of the present application, the fasteners 250 are bolts.

[0048] In some embodiments, a sealing gasket 210 is provided between the fireproof member 220 and the boss and between the fireproof member 220 and the pressing portion 241 to improve the sealing between the visualization structure 200 and the shock tube test section body 110. At the same time, the provision of the sealing gasket 210 can also prevent the fireproof member 220 from being crushed. In the embodiment of the present application, the sealing gasket 210 is made of polytetrafluoroethylene.

[0049] In some embodiments, the shock tube 100 further includes a first flange portion 120, which is disposed at the end of the shock tube test section body 110, and has a groove 111, wherein the diameter of the first flange portion 120 is greater than the diameter of the shock tube test section body 110. The provision of the first flange enhances the strength of the end of the shock tube test section body 110, and also facilitates the provision of the groove 111 and the provision of the visualization structure 200.

[0050] In some embodiments, a reinforcement portion 140 is provided on the side of the shock tube test section body 110, and the reinforcement portion 140 extends from one end of the shock tube test section body 110 to the other end. The groove 111 is provided in the reinforcement portion 140, and the reinforcement portion 140 can strengthen the structural strength of the shock tube test section body 110 where the groove 111 is opened.

[0051] In some embodiments, the shock tube test section body 110 and the pressure plate 240 are both made of stainless steel, and the fireproof member 220 is made of quartz glass.

[0052] In some embodiments, the docking structure includes a second flange portion 130, and the diameter of the second flange portion 130 is larger than the shock tube test section body 110. The second flange portion 130 is used for docking with the shock tube high voltage driving section.

[0053] The present application also provides a fire observation system, which includes a shock tube 100. The shock tube 100 includes the above-mentioned shock tube test section structure, a first vision module 400, a second vision module 500, and a pressure sensor.

[0054] Among them, the first visual module 400 obtains the ignition reaction conditions in the reaction chamber 101 through the visualization structure 200 on the side of the shock tube test section body 110; the second visual module 500 obtains the ignition reaction conditions in the reaction chamber 101 through the visualization structure 200 at the end of the shock tube test section body 110; the pressure sensor is arranged on the shock tube test section body 110, and the shock tube test section body 110 is provided with a mounting hole 102 for mounting the pressure sensor, and the pressure sensor is used to detect the pressure conditions in the reaction chamber 101.

[0055] The ignition observation system of the present application can directly provide image information of the ignition process in the shock tube 100, and can be used to determine the degree of homogeneity of fuel ignition and test and study the factors affecting homogeneous and inhomogeneous ignition processes.

[0056] In the embodiment of the present application, the first visual module 400 and the second visual module 500 are high-speed cameras, and the high-speed cameras are equipped with lenses.

[0057] In addition to the first visual module 400, the second visual module 500 and the pressure sensor, the shock tube test section body 110 is equipped with a dynamic pressure sensor for measuring the shock wave velocity, a pressure sensor and a monochromator for respectively measuring the pressure and light signal during the ignition process.

[0058] During the experiment, the combustible mixture in the reaction chamber 101 is compressed twice by the incident and reflected shock waves to reach the temperature and pressure conditions for ignition. This process is accompanied by a rapid increase in pressure. The rising pressure is used as a trigger signal to trigger the high-speed camera to start working. The recording time of the high-speed camera depends on its memory size, which is generally in the order of seconds. The ignition process in the shock tube 100 lasts from microseconds to milliseconds, so the ignition process in the shock tube 100 can be fully recorded using a high-speed camera.

[0059] The ignition observation system of the present application can record the process of fuel self-ignition in the reaction chamber 101 in the shock tube 100 in the form of images through an optical shooting system combined with the end wall and the side wall. On the one hand, it can be used to clarify whether the ignition in the tube is a homogeneous process at this time, and provide a basis for judging the validity of the fuel ignition delay time test results defined based on pressure and light signals; on the other hand, it can provide a basis for studying the mechanism of action of non-ideal factors that affect the actual self-ignition process of the fuel in the shock tube 100.

[0060] The embodiments of the present application are described in detail above in conjunction with the accompanying drawings, but the present application is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the technical field without departing from the purpose of the present application.

Claims

1. A shock tube test section structure, characterized in that: include A shock tube test section body, wherein a reaction chamber is arranged in the shock tube test section body, and a docking structure is arranged at one end of the shock tube test section body, wherein the docking structure is used for docking with a shock tube high-voltage driving section capable of forming a shock wave; A visualization structure is provided on the side of the shock tube test section body and the other end of the shock tube test section body, and the visualization structure located on the side of the shock tube test section body extends from one end to the other end of the shock tube test section body.

2. The shock tube test section structure according to claim 1, characterized in that: The sides and ends of the shock tube test section body are provided with grooves connected to the reaction chamber, and the two ends of the groove on the side of the shock tube test section body are respectively close to the two ends of the shock tube test section body, and the visualization structure is fixed to the groove.

3. The shock tube test section structure according to claim 2, characterized in that: The visualization structure includes a fireproof member and a clamping assembly, wherein the fireproof member is made of a transparent material, and the clamping assembly fixes the fireproof member to the channel from the outside of the shock tube test section body.

4. The shock tube test section structure according to claim 3, characterized in that: A boss is arranged in the groove, and the clamping assembly includes a pressing plate and a fastener. The middle part of the pressing plate is hollowed out, and the pressing plate has a clamping portion that can enter the groove. The fastener locks the pressing plate to the side of the shock tube test section body so that the clamping portion can clamp the fire isolation member placed on the boss.

5. The shock tube test section structure according to claim 4, characterized in that: Sealing pads are arranged between the fire isolation member and the boss, and between the fire isolation member and the pressing portion.

6. The shock tube test section structure according to any one of claims 2 to 5, characterized in that: The shock tube further includes a first flange portion, which is disposed at the end of the shock tube test section body, and has the groove, wherein the diameter of the first flange portion is greater than the diameter of the shock tube test section body.

7. The shock tube test section structure according to any one of claims 2 to 5, characterized in that: A reinforcement portion is arranged on the side of the shock tube test section body, the reinforcement portion extends from one end of the shock tube test section body to the other end, and the groove is arranged on the reinforcement portion.

8. The shock tube test section structure according to any one of claims 2 to 5, characterized in that: The material of the shock tube test section body is stainless steel, and the material of the fireproof component is quartz glass.

9. The shock tube test section structure according to claim 1, characterized in that: The docking structure includes a second flange portion, and a diameter of the second flange portion is larger than the shock tube test section body.

10. A fire observation system, characterized in that: include A shock tube, the shock tube comprising the shock tube test section structure according to any one of claims 1 to 9; a first visual module, wherein the first visual module obtains the ignition reaction condition in the reaction chamber through the visual structure on the side of the shock tube test section body; a second visual module, wherein the second visual module obtains the ignition reaction condition in the reaction chamber through the visual structure at the end of the shock tube test section body; A pressure sensor is arranged on the shock tube test section body, and the pressure sensor is used to detect the pressure condition in the reaction chamber.

Images