A method and device for diagnosing high-temperature self-ignition of droplets under shock wave thermal loading

Abstract

The invention discloses a shock wave heat-loaded droplet high-temperature self-ignition diagnosis method and device, comprising a shock tube body, an intake and exhaust system, a pressure acquisition system, and an injection system; the shock tube body comprises a driving section, a film section and a driven section, the film section is arranged between the driving section and the driven section, an experimental section is arranged at the end of the driven section, a pressure acquisition system is arranged at the front end of the experimental section, the pressure acquisition system signal is transmitted to the injection system, and the injection system is connected to the experimental section; the method is as follows: after vacuum treatment of the tube body, the driving section and the driven section are filled with experimental gas; the signal is transmitted to the injection system through the pressure acquisition system, and the shock tube is injected with oil; the self-ignition characteristics of a single droplet of liquid phase fuel under a static environment are studied in a shock tube device, the strong physical action between the single droplet of liquid phase fuel and the primary shock wave and the secondary shock wave is avoided, and the influence of the evaporation characteristics and chemical reaction kinetic characteristics of the single droplet of liquid phase fuel on its self-ignition characteristics is accurately characterized.

Description

Technical Field

[0001] The invention relates to the field of gas-liquid two-phase shock tube experiments, and in particular to a shock wave heat-loaded droplet high-temperature self-ignition diagnosis method and device. Background Art

[0002] The combustion process in the combustion chamber of a real internal combustion engine or aircraft engine involves complex physical and chemical processes, including but not limited to atomization behavior, evaporation behavior, and self-ignition behavior. The two-phase self-ignition behavior of the fuel has an important impact on the engine's operating efficiency. Therefore, as an important basis for guiding the design and optimization of the combustion chamber of an internal combustion engine or aircraft engine, the development of a quantitative measurement of the fuel gas-liquid two-phase self-ignition delay time is critical for the development of a new generation of engine combustion chambers. However, the real spray combustion process is affected by many factors such as the injector structure, the shape of the combustion chamber, and the fuel atomization characteristics. It is difficult to develop a two-phase combustion reaction model that couples physical spray and chemical reactions, which limits the independent development and research of the combustion chamber. In a steady-state environment, the single droplet self-ignition behavior is the core process of gas-liquid two-phase self-ignition and is also the focus of research. It is the key to accurately characterize the contribution of the fuel evaporation characteristics and reaction kinetics characteristics to its self-ignition behavior.

[0003] Conventional single-droplet fuel combustion diagnostic equipment, such as hot furnaces and fast compressors, are difficult to match the characteristic size of fuel droplets in real sprays, and are difficult to simulate the instantaneous high temperature and high pressure environment of a real combustion chamber. The experimental temperature is difficult to reach the real temperature of a real combustion chamber, especially the real temperature of an afterburner. As the mainstream device for studying the self-ignition characteristics of fuels in the world, the shock tube can generate a momentary high temperature and high pressure nearly adiabatic experimental environment in the experimental area through secondary shock waves, induce the self-ignition behavior of the fuel, and can well simulate the real environment in the combustion chamber.

[0004] The shock tube device is widely used in the self-ignition experiment of gas phase fuel. However, in the study of gas-liquid two-phase fuel, due to its short effective experimental time of only milliseconds, it is difficult to introduce a single droplet of liquid phase fuel instantly. The general methods of introducing single droplet of liquid phase fuel in shock tubes are: using suspended droplet technology to suspend the fuel droplet on the fiber filament in advance to fix the fuel in the predetermined experimental position, or using free fall to continuously drip monodisperse droplets to the experimental position after the experiment begins. However, these two methods of introducing liquid phase fuel cannot avoid the strong physical interaction between the fuel and the primary shock wave and the secondary shock wave, which makes it difficult to accurately characterize the self-ignition characteristics of single droplet liquid phase fuel. How to introduce a single droplet of liquid phase fuel after the secondary shock wave and avoid the physical interaction between the single droplet of liquid phase fuel and the shock wave is a difficulty that needs to be overcome when using shock tube devices to study the self-ignition characteristics of gas-liquid two-phase fuels. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a shock wave heat-loaded droplet high-temperature self-ignition diagnosis method and device, so as to realize the study of the self-ignition characteristics of a single droplet of liquid phase fuel in a static environment in a shock tube device, avoid the strong physical interaction between the single droplet of liquid phase fuel and the primary shock wave and the secondary shock wave, and accurately characterize the influence of the evaporation characteristics and chemical reaction kinetics characteristics of the single droplet of liquid phase fuel on its self-ignition characteristics.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A shock wave heat-loaded droplet high-temperature self-ignition diagnostic device comprises a shock tube body, an intake and exhaust system, a pressure collection system, and an injection system; the shock tube body comprises a driving section, a membrane section, and a driven section, the membrane section is arranged between the driving section and the driven section, the driving section, the membrane section, and the driven section are connected in sequence, an experimental section is arranged at the end of the driven section, a pressure collection system is arranged at the front end of the experimental section, the pressure collection system transmits a collection signal to the injection system, and the injection system is connected to the experimental section.

[0008] Furthermore, the driven section also includes a transition section; the transition section is arranged between the driven section and the test section.

[0009] Furthermore, the air intake and exhaust system includes a gas pipeline, a high-pressure gas cylinder, a gas mixing tank and a vacuum pump. The high-pressure gas cylinder contains different types of gases, and there are multiple high-pressure gas cylinders; the high-pressure gas cylinder is connected to the gas pipeline, and the gas pipeline is connected to the shock tube body; there are at least two gas pipelines, one of which is for inputting driving gas to the driving section, and a gas mixing tank is connected between the other gas pipeline and the high-pressure gas cylinder, and the gas mixing tank is used to prepare the gas in the high-pressure gas cylinder into a test gas and connect it to the driven section; multiple gas pipelines are connected to each other, and multiple valves are provided on the gas pipeline; the gas pipeline is also connected to the outdoor atmospheric environment.

[0010] Furthermore, the pressure acquisition system includes a pressure sensor, a signal converter and a data collector; the pressure sensor is arranged on the shock tube body, the pressure sensor is connected to the data collector through the signal converter, and the data collector is connected to the droplet generator controller.

[0011] Furthermore, there are multiple pressure sensors, one of which is symmetrically arranged on the lower wall of the test section with respect to the position of the droplet generator, and the remaining pressure sensors are arranged on the upper wall of the test section and the axial distances between the pressure sensors are equal.

[0012] Furthermore, the fuel injection system includes a droplet generator, a droplet generator controller, a high-pressure oil pump, a fuel tank and an oil pipeline. The droplet generator controller is connected to the droplet generator through a control cable, and the droplet generator is connected to the experimental section; the droplet generator is also connected to a high-pressure oil pump through an oil pipeline, and the high-pressure oil pump is connected to the fuel tank.

[0013] Furthermore, a vacuum pump is provided on the gas transmission pipeline, and the vacuum pump draws a vacuum on the shock tube body through the gas transmission pipeline.

[0014] Furthermore, a plurality of gas pressure gauges are provided on the gas transmission pipeline, the first gas pressure gauge is connected to the driving section via a monitoring pipeline, and the second gas pressure gauge provided on the gas transmission pipeline is connected to the driven section via a monitoring pipeline.

[0015] Furthermore, two visualization windows are arranged on the side wall surface of the experimental section, and a large-size visualization end cover window is arranged on the end surface, and a high-speed camera can shoot the experimental process through the visualization windows in two directions.

[0016] The present invention also provides a high-temperature self-ignition diagnosis method for droplets based on shock wave thermal loading. After the shock tube body is vacuum treated, the gas required for the experiment is filled into the driving section and the driven section; the pressure inside the shock tube body is collected by a pressure collection system; the collected signal is then transmitted to the fuel injection system, and the fuel injection system injects fuel into the experimental section of the shock tube according to the received signal.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects:

[0018] The present invention proposes a shock wave heat-loaded droplet high-temperature self-ignition diagnosis method and device, which triggers a droplet generator to spray oil according to a pressure transition signal induced by a secondary shock wave, and introduces a single droplet of liquid-phase fuel into a static experimental environment after reflecting the secondary shock wave, thereby avoiding the strong physical interaction between the shock wave and the single droplet of liquid-phase fuel, and can accurately characterize the self-ignition characteristics of the single droplet of liquid-phase fuel, providing a theoretical basis for constructing a combustion model of actual engine fuel; in the device provided by the present invention, the pressure change curve in the tube obtained by the pressure acquisition system is used to trigger a high-speed camera to start shooting; when the experimentally characterized reflected shock wave passes through the experimental site, a delicate high-temperature and high-pressure environment is formed, triggering the injection system.

[0019] Furthermore, the device provided by the present invention is provided with a transition section, and the cross-sectional shape of the shock tube pipeline of the driving section, the membrane section and the driven section is circular. The circular pipeline is beneficial to the stability of the shock wave surface and reduces the influence of the boundary layer effect on the experimental results; and the main purpose of designing the experimental section pipeline as a square is to increase the window size and facilitate visualization experiments. If a window is designed on a circular pipeline, the window size will be reduced by 30%-40%; therefore, a transition section is provided between the driven section and the experimental section of the device; because when the shock wave transitions from the circular pipeline to the square pipeline, the shock wave has an expansion process, and the setting of the transition section is beneficial to the stability of the shock wave surface; it can effectively realize the smooth transition between the circular pipeline of the driven section and the square pipeline of the experimental section.

[0020] Furthermore, the device is provided with multiple high-pressure gas cylinders, and the gas in the gas cylinders can be mixed in multiple ways or can be a single gas experiment. The setting of this step can effectively increase the utilization rate of the device and improve the use effect of the device. At the same time, the separate setting of multiple gas cylinders is also conducive to the replacement of high-pressure gas cylinders; and a mixing tank is also provided on the summer pipeline connected to the driven section. The mixing tank is used to configure and store experimental gases. During the experiment, it can effectively improve the experimental efficiency and effectively increase the experimental accuracy of the device, which is the basis for ensuring the safety of the experiment; multiple gas pipelines are provided on the device, and multiple valves are provided on the gas pipelines, which can effectively control the flow of high-pressure gas; the gas pipeline is also connected to the outdoor atmospheric environment for exhausting the shock tube body.

[0021] Furthermore, the pressure sensor is used to collect the pressure change curve of the test section, and the signal output of the pressure sensor is connected to the data collector through a signal converter, and the pressure sensor is used to collect the pressure change curve of the test section; the data collector is used to store the voltage signal collected by the pressure sensor, and is used to trigger the droplet generator controller to control the droplet generator to spray oil; the pressure sensor can detect whether the shock wave returns to a stable plane after passing through the transition section. At the same time, the speed of the incident shock wave can be measured and the test pressure and temperature can be calculated through the shock wave equation.

[0022] Furthermore, there are multiple pressure sensors. The more pressure sensors there are, the more detailed the detection of the pressure environment in the tube is. The pressure sensor is used to collect the gas pressure changes in the experimental section and output them to the data collector, and can reduce the calculation error of the incident shock wave velocity. The shock wave velocity, experimental temperature and pressure can be obtained based on the analysis of the pressure signal, and the output secondary pressure transition signal is also used to trigger the droplet generator controller to control the droplet generator to spray oil.

[0023] Furthermore, a droplet generator controller is used to control the droplet injection timing and the amount of oil injection; the oil tank supplies oil to the droplet generator through an oil pipeline and a high-pressure oil pump; the droplet generator is used to spray oil into the experimental section; it is the key to ensuring the accuracy of the experimental results, and at the same time, it can effectively solve the problems existing in the prior art.

[0024] Furthermore, the first gas pressure gauge is connected to the driving section through a monitoring pipeline for monitoring the intake pressure of the driving section, and the second gas pressure gauge arranged on the gas transmission pipeline is connected to the driven section through a monitoring pipeline for monitoring the intake pressure of the driven section, which can effectively ensure the accuracy of the experimental results.

[0025] Furthermore, two visualization windows are set on the side wall of the experimental section; at the same time, in the present device, the main purpose of designing the experimental section pipeline as a square is to increase the window size and facilitate visualization experiments. For example, if a window is designed on a circular pipeline, the window size will be reduced by 30%-40%; the side wall windows are relatively set, and a background parallel light source needs to be set when shooting with a high-speed camera or using a schlieren system. The light source needs to be set relative to the camera, so the two side wall windows are relatively set and have the same size; the end window is used for chemical spontaneous luminescence imaging, which does not require a background light source, so it can be set separately, which simplifies the complexity of the device; using a shock wave heat-loaded droplet high-temperature self-ignition diagnostic method and device provided by the present invention, through the large-size windows on the side wall and end face of the test section, the high-speed camera can clearly capture the introduction, falling, evaporation and self-ignition process of a single droplet of liquid phase fuel, and can accurately characterize the influence of the evaporation characteristics of the single droplet of liquid phase fuel and the chemical reaction kinetics characteristics on its self-ignition characteristics, providing a factual basis for the single droplet of liquid phase fuel combustion reaction model. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or technical descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 A schematic diagram of the structure of the present invention

[0028] Among them, there are driving section 1, membrane section 2, driven section 3, transition section 4, experimental section 5, gas pipeline 6, helium cylinder 7, nitrogen cylinder 8, oxygen cylinder 9, gas cylinder 10, mixing tank 11, vacuum pump 12, pressure sensor 13, signal converter 14, data acquisition device 15, droplet generator 16, droplet generator controller 17, high-pressure oil pump 18, oil tank 19, oil pipeline 20, end cover window 21, atmospheric environment 22, first gas pressure gauge 23, and second gas pressure gauge 24. DETAILED DESCRIPTION

[0029] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0030] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0031] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0032] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0034] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0035] A shock wave heat-loaded droplet high-temperature self-ignition diagnostic device, in a specific embodiment of the device, includes a shock tube body, an intake and exhaust system, a pressure acquisition system, and an injection system. The shock tube body includes a coaxially connected driving section 1, a diaphragm section 2, and a driven section 3; the diaphragm section 2 is arranged between the driving section 1 and the driven section 3, and two diaphragms are arranged on both sides of the diaphragm section 2 to separate the driving section 1, the diaphragm section 2 and the driven section 3; the transition section 4 is arranged between the driven section 3 and the test section 5, It is used to achieve a smooth transition between the circular pipeline of the driven section 3 and the square pipeline of the test section 5; the intake and exhaust system includes a gas pipeline 6, a high-pressure gas cylinder, a gas mixing tank 11 and a vacuum pump 12, the gas pipeline 6 is connected to the shock tube body, the high-pressure gas cylinder can include a helium cylinder 7, a nitrogen cylinder 8, an oxygen cylinder 9 and a gas cylinder 10, or only one high-pressure gas cylinder is provided with only one gas; the helium cylinder 7 and the nitrogen cylinder 8 convey the driving gas to the driving section through the gas pipeline, and the gas mixing tank 11 conveys the driving gas to the driving section through the gas pipeline. 6 is for conveying experimental gas to the driven section 3, the transition section 4 and the test section 5. The vacuum pump 12 draws vacuum for the shock tube body through the gas pipeline 6. The pressure acquisition system includes a pressure sensor 13, a signal converter 14 and a data collector 15. The pressure sensor 13 is used to collect the pressure change curve of the test section, and the signal output of the pressure sensor 13 is connected to the data collector 15 through the signal converter 14. The data collector 15 is used to store the voltage signal collected by the pressure sensor 13 and to trigger the droplet generator controller 17 to control the droplet generator 16 to spray oil. The oil injection system includes the droplet generator 16, the droplet generator controller 17, a high-pressure oil pump 18, an oil tank 19 and an oil pipeline 20. The droplet generator 16 is used to spray oil to the test section 5. The oil tank 19 supplies oil to the droplet generator 16 through the oil pipeline 20 and the high-pressure oil pump 18. The droplet generator controller 17 is connected to the droplet generator 16 through a control cable to control the droplet injection timing and the amount of oil injection.

[0036] The driving section 1, the clamping section 2 and the driven section 3 are round tubes with the same inner diameter, the experimental section 5 is a square tube, and a transition section 4 is arranged between the driven section 3 and the experimental section 5 to achieve a smooth transition of the inner wall of the shock tube; two visualization windows are arranged on the walls on both sides of the horizontal direction of the experimental section, and a large-size visualization end cover window 21 is arranged on the end face, and a high-speed camera can shoot the experimental process through the visualization windows in two directions; the high-pressure gas cylinders include but are not limited to helium cylinders 7, nitrogen cylinders 8, oxygen cylinders 9, and gas cylinders 10, and the helium cylinders 7 or the helium cylinders 7 and the nitrogen cylinders 8 are transported through The gas pipeline 6 is connected to the driving section 1 and the membrane section 2, and serves as a driving gas source to supply gas to the driving section 1 and the membrane section 2. The nitrogen cylinder 8, oxygen cylinder 9 and gas cylinder 10 are connected to the mixing tank 11 through the gas pipeline 6, and are used to prepare experimental gas in the mixing tank 11. The mixing tank 11 is used to configure and store experimental gas, and is connected to the driven section 3 through the gas pipeline 6 to supply gas to the driven section 3, the transition section 4 and the test section 5. The gas pipeline 6 is connected to the outdoor atmospheric environment 22, and is used to exhaust the shock tube body. A plurality of valves are arranged on the gas pipeline 6 to control the flow of high-pressure gas.

[0037] The vacuum pump 12 is connected to the driving section 1, the diaphragm section 2 and the driven section 3 through the air supply pipeline 6, and is used to evacuate the driving section 1, the diaphragm section 2, the driven section 3, the transition section 4 and the test section 5; a first gas pressure gauge 23 is arranged on the air supply pipeline 6 and is connected to the driving section 1 and the diaphragm section 2 through a monitoring pipeline, and is used to monitor the intake pressure of the driving section 1 and the diaphragm section 2; a second gas pressure gauge 24 is arranged on the air supply pipeline 6 and is connected to the driven section 3 through a monitoring pipeline, and is used to monitor the intake pressure of the driven section 3, the transition section 4 and the test section 5.

[0038] There are six pressure sensors 13, five of which are arranged on the upper wall of the test section, and one is symmetrically arranged on the lower wall of the test section with respect to the droplet generator 16, and the axial distances between the pressure sensors 13 are equal. The pressure sensors 13 are used to collect the gas pressure changes in the test section and output them to the data acquisition device 15. The shock wave velocity, experimental temperature and pressure can be obtained based on the analysis of the pressure signal. The output secondary pressure transition signal is also used to trigger the droplet generator controller 17 to control the droplet generator 16 to spray oil.

[0039] The present invention also provides a shock wave heat loading droplet high temperature self-ignition diagnosis method:

[0040] In a specific embodiment, the valve of the gas mixing tank 11 is opened to allow air to flow into the gas mixing tank 11, and after the air intake is completed, the valves are closed and left to stand, waiting for the experimental gas in the gas mixing tank 11 to stabilize; diaphragms are installed on both sides of the membrane section 2; the valve of the vacuum pump 12 and the valves of the driving section 1, the membrane section 2 and the driven section 3 are opened to evacuate the shock tube body; the target pressures of the driving section 1, the membrane section 2 and the driven section 3 are calculated according to the target working conditions and the shock wave equation; the valve of the membrane section 2 is closed after the membrane section 2 reaches the target pressure; the valve of the driving section 1 is kept open to continue to allow air to flow into the driving section 1 until the target pressure is reached, the valve of the driving section 1 is opened, and nitrogen is input into the driving section; the valve of the gas mixing tank 11 and the valve of the driven section 3 are opened; the experimental gas is input into the driven section 3 until the target pressure is reached; the data acquisition device 15, the droplet generator controller 17 and the high-speed camera are set to the triggering mode, ready to receive the pressure transition signal to start collecting data, control the droplet generator 16 to spray oil and shoot the experimental phenomenon.

[0041] In a specific embodiment of a shock wave heat loading droplet high temperature self-ignition diagnosis method provided by the present invention:

[0042] The experimental gas composition is designed according to the target working condition. The valve of the gas mixing tank 11 is opened, and the valves of the nitrogen cylinder 8, the oxygen cylinder 9 or the gas cylinder 10, the nitrogen cylinder 8 and the oxygen cylinder 9 are opened in sequence. The embodiment provided in this embodiment is only a preferred embodiment. In the specific experimental process, there are also different experimental gas compositions, or single gas experiments; the gas is introduced into the gas mixing tank 11, and after the gas introduction is completed, the valves are closed and left to stand, waiting for the experimental gas in the gas mixing tank 11 to stabilize; diaphragms are installed on both sides of the membrane section 2 to separate the driving section 1, the membrane section 2 and the driven section 3 cavity, and the valve of the vacuum pump 12 is opened to connect the driving section 1, the membrane section 2 and the driven section 3. Valve, evacuate the shock tube body, and when the shock tube body reaches vacuum, turn off the vacuum pump 12; calculate the target pressures of the driving section 1, the membrane section 2 and the driven section 3 according to the target working condition and the shock wave equation, open the valves of the helium bottle 7 and the nitrogen bottle 8 and the valves of the driving section 1 and the membrane section 2, input driving gas to the driving section 1 and the membrane section 2, and close the valve of the membrane section 2 after the membrane section 2 reaches the target pressure, keep the valve of the driving section 1 open and continue to feed air to the driving section 1 until the target pressure is reached, open the valve of the mixing tank 11 and the valve of the driven section 3, and input experimental gas to the driven section 3, the transition section 4 and the experimental section 5 until the target pressure is reached.

[0043] The data acquisition device 15, the droplet generator controller 17 and the high-speed camera are set to the triggering mode, ready to receive the pressure jump signal to start collecting data, control the droplet generator 16 to spray oil and shoot the experimental phenomenon, open the exhaust pipe valve connected to the atmospheric environment 22, and then instantly open the valve of the diaphragm section 2. The driving gas in the diaphragm section 2 is discharged, resulting in a sudden drop in the pressure in the diaphragm section 2 and a huge pressure difference with the driving section 1. The pressure difference between the driving section 1 and the diaphragm section 2 exceeds the allowable pressure of the diaphragm, causing the diaphragm to rupture and break through the diaphragm between the diaphragm section 2 and the driven section 3 to form a shock wave. At this time, the shock wave propagates toward the experimental section 5, and at the same time, a sparse wave is generated to propagate toward the driving section 1. At the moment of rupture, the contact surface between the driving gas and the experimental gas and the shock wave surface basically coincide. During the propagation process, the movement speed of the contact surface is less than the propagation speed of the shock wave, so the distance between the contact surface and the shock wave surface continues to expand. When the incident shock wave propagates to the end face of the experimental section 5, it will be reflected, generating a secondary reflected shock wave that propagates toward the driving section 1, and again increasing the temperature and pressure of the experimental part of the gas to achieve the designed target working conditions; the effective experimental time of the shock tube is different in the two different working modes. In the non-stitching mode, the contact surface continues to propagate toward the experimental section 5 after contacting with the reflected shock wave. When the contact surface flows through the experimental section 5, the temperature and pressure of the experimental section 5 decrease, resulting in the end of the experiment. In the stitching mode, the contact surface is stationary after contacting with the reflected shock wave and no longer propagates toward the experimental section 5. The experimental section 5 will maintain a high temperature and high pressure environment for a long time until the secondary rarefaction wave generated after the rarefaction wave contacts the end face of the driving section 1 flows through the experimental section 5, causing the temperature and pressure of the experimental section 5 to decrease, resulting in the end of the experiment. It can be seen that when operating in the stitching mode, the effective experimental time of the shock tube is greatly increased.

[0044] For the suturing mode operation, it is required that the gas pressure on both sides of the contact surface is balanced after the membrane is broken, and the suturing contact surface relationship equation is satisfied. In actual experimental operation, the suturing contact surface relationship equation can be satisfied by changing the ratio of helium and nitrogen in the driving gas components in the driving segment 1, thereby achieving the suturing mode conditions. In the non-suturing mode, in the near term, it is only necessary to open the driving segment 1 valve and the helium bottle 7 valve to input single-component helium into the driving segment. In the suturing mode, it is necessary to open the driving segment 1 valve and the helium bottle 7 and nitrogen bottle 8 valves to input a certain ratio of helium and nitrogen mixed gas into the driving segment. The ratio of helium and nitrogen is determined by the suturing contact surface relationship equation. When the primary shock wave flows through the pressure sensor 13 after the membrane breaks, the pressure sensor 13 senses the sudden change in pressure in the tube and outputs a pressure transition signal, triggering the data acquisition device 15 to continue data acquisition, obtaining the pressure change curve in the tube, and triggering the high-speed camera to start shooting. When the primary shock wave is reflected to form a secondary shock wave, the secondary shock wave propagates in the direction of the driving section 1 and flows through the pressure sensor 13 opposite to the droplet generator 16. The pressure sensor 13 outputs a secondary pressure transition signal, indicating that the reflected shock wave passes through the experimental site, and a static high-temperature and high-pressure environment is formed, triggering the droplet generator controller 17 to control the droplet generator 16 to spray oil once, and a single droplet of liquid-phase fuel is sprayed into the experimental site in a vertical direction and performs free fall motion. The high-speed camera can record the introduction, falling, evaporation and self-ignition process of the single droplet of liquid-phase fuel.

[0045] According to the pressure change curve collected by the data acquisition device 15, the actual pressure of the experiment can be obtained, and the incident shock wave velocity can be calculated, and then the actual temperature of the experiment can be calculated. According to the experimental phenomena captured by the high-speed camera, the ignition delay time of the single droplet of liquid phase fuel can be obtained: the moment when the single droplet of liquid phase fuel is introduced into the experimental section to the moment when the single droplet of liquid phase fuel has obvious ignition behavior.

[0046] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0047] In addition, it should be understood that although this specification is described in accordance with the implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A shock wave heat loading droplet high temperature self-ignition diagnostic device, characterized in that: The invention comprises a shock tube body, an intake and exhaust system, a pressure collection system and an injection system; the shock tube body comprises a driving section (1), a diaphragm section (2) and a driven section (3); the diaphragm section (2) is arranged between the driving section (1) and the driven section (3); the driving section (1), the diaphragm section (2) and the driven section (3) are connected in sequence; an experimental section (5) is arranged at the end of the driven section (3); a pressure collection system is arranged at the front end of the experimental section (5); the pressure collection system transmits a collection signal to the injection system; and the injection system is connected to the experimental section (5); The driven section (3) further comprises a transition section (4); the transition section (4) is arranged between the driven section (3) and the test section (5); The pressure acquisition system comprises a pressure sensor (13), a signal converter (14) and a data collector (15); the pressure sensor (13) is arranged on the shock tube body, the pressure sensor (13) is connected to the data collector (15) via the signal converter (14), and the data collector (15) is connected to a droplet generator controller (17); The fuel injection system comprises a droplet generator (16), a droplet generator controller (17), a high-pressure oil pump (18), an oil tank (19) and an oil pipeline (20); the droplet generator controller (17) is connected to the droplet generator (16) via a control cable, and the droplet generator (16) is connected to the experimental section (5); the droplet generator (16) is also connected to the high-pressure oil pump (18) via an oil pipeline, and the high-pressure oil pump (18) is connected to the oil tank (19); The side wall of the experimental section (5) is provided with two visualization windows, and the end face is provided with a large-size visualization end cover window (21). A high-speed camera can shoot the experimental process through the visualization windows in two directions.

2. The shock wave heat loading droplet high temperature self-ignition diagnostic device according to claim 1, characterized in that: The air intake and exhaust system comprises a gas pipeline (6), a high-pressure gas cylinder, a gas mixing tank (11) and a vacuum pump (12). The high-pressure gas cylinder contains different types of gas, and a plurality of the high-pressure gas cylinders are provided. The high-pressure gas cylinder is connected to the gas pipeline (6), and the gas pipeline (6) is connected to the shock tube body. At least two gas pipelines (6) are provided, one of which is used to input driving gas to the driving section (1), and a gas mixing tank (11) is connected between the other gas pipeline (6) and the high-pressure gas cylinder. The gas mixing tank (11) is used to prepare the gas in the high-pressure gas cylinder into test gas and connect it to the driven section. The plurality of gas pipelines (6) are connected to each other, and a plurality of valves are provided on the gas pipeline (6). The gas pipeline (6) is also connected to the outdoor atmospheric environment (22).

3. The shock wave heat loading droplet high temperature self-ignition diagnostic device according to claim 1, characterized in that: A plurality of pressure sensors (13) are provided, wherein one pressure sensor (13) is symmetrically arranged on the lower wall surface of the test section (5) with respect to the position of the droplet generator (16), and the remaining pressure sensors are arranged on the upper wall surface of the test section, and the axial distances between the pressure sensors (13) are equal.

4. The shock wave heat loading droplet high temperature self-ignition diagnostic device according to claim 2, characterized in that: The gas transmission pipeline (6) is also provided with a vacuum pump (12), and the vacuum pump (12) evacuates the shock tube body through the gas transmission pipeline (6).

5. The shock wave heat loading droplet high temperature self-ignition diagnostic device according to claim 2, characterized in that: A plurality of gas pressure gauges are arranged on the gas delivery pipeline (6); the first gas pressure gauge (23) is connected to the driving section (1) via a monitoring pipeline; and the second gas pressure gauge (24) arranged on the gas delivery pipeline (6) is connected to the driven section (3) via a monitoring pipeline.

6. The method for diagnosing high temperature self-ignition of droplets based on shock wave heat loading according to the device of claim 1, characterized in that: After the shock tube body is vacuum treated, the gas required for the experiment is filled into the driving section (1) and the driven section (2); the pressure inside the shock tube body is collected by a pressure collection system; the collected signal is then transmitted to the fuel injection system, and the fuel injection system injects fuel into the experimental section (5) of the shock tube according to the received signal.

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