Constant-volume optical test platform and test method suitable for ammonia-hydrogen stratified combustion

Abstract

The invention discloses a constant-volume optical test platform suitable for ammonia-hydrogen stratified combustion and a test method. The test platform comprises an experiment bench; the constant-volume combustion bomb is mounted on the experiment bench, and the interior of the constant-volume combustion bomb is divided into a combustion chamber and two heating chambers by two partition pieces; the ejector mounting seat is arranged at the top of the combustion chamber; the hydrogen ejector is mounted on the ejector mounting seat and is arranged towards the center of the combustion chamber; the two spark plugs are respectively arranged on the two separators and are arranged towards the center of the combustion chamber; the ammonia gas-air channel is arranged on the ejector mounting seat; the two first windows are symmetrically arranged on the two side faces, adjacent to the partition piece, of the combustion chamber. The second window is arranged on the bottom surface of the combustion chamber; the optical system is installed on the experiment bench, and the optical system and the constant volume combustion bomb form an optical path position required by a schlieren method and a direct shooting method; and the control system is electrically connected with the hydrogen ejector, the spark plug and the optical system.

Description

Technical Field

[0001] The present invention belongs to the technical field of ammonia-hydrogen combustion testing, and in particular relates to a constant-volume optical testing platform and a testing method suitable for ammonia-hydrogen stratified combustion. Background Art

[0004] Both hydrogen and ammonia are relatively clean energy sources. Ammonia has stable chemical properties, low storage and transportation costs, and can be cracked online to produce hydrogen. The advantages of hydrogen's fast laminar flame speed, low ignition energy, and wide combustion limit also solve the shortcomings of ammonia's slow flame propagation speed and poor combustion stability. Therefore, ammonia-hydrogen dual-fuel internal combustion engines have received widespread attention in the transportation field.

[0005] Currently, most research focuses on spark-ignition ammonia-hydrogen internal combustion engines, with studies on flame characteristics and combustion performance primarily based on a homogeneous premixed ammonia-hydrogen mixture. Considering processes such as fire nucleation, flame propagation, and heat transfer, different reaction zones within the cylinder have varying requirements for mixture composition. Furthermore, the composition of the ammonia-hydrogen mixture that optimizes combustion performance also varies under different operating conditions. Simply adjusting the ammonia-hydrogen ratio in a homogeneous mixture through low-degree-of-freedom control makes it difficult to achieve efficient combustion. To address this issue, the hydrogen injection strategy and the locally hydrogen-rich stratified mixture formed during the hydrogen-air mixing process can achieve both stable ignition and rapid flame propagation.

[0006] However, existing research rarely pays attention to the ammonia-hydrogen non-premixed stratified combustion mode, and the spray and flame propagation process cannot be observed through engine bench tests, making it difficult to elucidate the formation process of locally hydrogen-rich stratified mixtures and the flame propagation process and combustion performance under different stratification conditions. It is urgent to develop a dual-fuel constant-volume test platform with visualization functions that can observe the hydrogen spray process, the formation of ammonia-hydrogen stratified mixtures, and the flame propagation and combustion performance under different stratification conditions. Summary of the Invention

[0007] One of the objectives of the present invention is to provide a constant-volume optical testing platform suitable for ammonia-hydrogen stratified combustion, which can realize independent injection of hydrogen, thereby simulating different combustion modes through the control of hydrogen injection and spark plug ignition, and using an optical system to capture schlieren images and direct images of the hydrogen spray diffusion and hydrogen-ammonia combustion process to obtain more comprehensive image information.

[0008] Another object of the present invention is to provide a constant-volume optical testing method suitable for ammonia-hydrogen stratified combustion, which can change the ratio of ammonia, hydrogen and air, and realize active control of the ammonia-hydrogen stratified combustion mode by coupling spark plug ignition triggering, thereby realizing the simulation of multiple different combustion modes; and can obtain real-time images of the test process through an optical system.

[0009] The technical solution provided by the present invention is:

[0010] A constant volume optical test platform and test method suitable for ammonia-hydrogen stratified combustion, comprising:

[0011] Experimental bench;

[0012] A constant volume incendiary bomb, which is installed on the experimental bench, is provided with two partitions inside the constant volume incendiary bomb and is divided into a combustion chamber and two heating chambers by the two partitions;

[0013] Wherein, the two heating chambers are symmetrically arranged at both ends of the combustion chamber, and a heating device is provided in the heating chamber;

[0014] an injector mounting seat, which is arranged on the top of the combustion chamber;

[0015] a hydrogen injector mounted on the injector mounting seat and arranged toward the center of the combustion chamber;

[0016] two spark plugs, which are respectively mounted on the two partitions and arranged toward the center of the combustion chamber;

[0017] an ammonia-air passage, which is provided on the injector mounting seat and communicates with the combustion chamber;

[0018] two first viewing windows symmetrically arranged on two sides of the combustion chamber adjacent to the partition;

[0019] a second viewing window disposed on the bottom surface of the combustion chamber;

[0020] An optical system, which is installed on the experimental bench and is used to capture images inside the combustion chamber;

[0021] Wherein, the optical system and the two first windows form a schlieren shooting light path, and the optical system and the second window form a direct shooting light path;

[0022] A control system is electrically connected to the hydrogen injector, the spark plug and the optical system respectively.

[0023] Preferably, the heating device adopts a spiral heating tube.

[0024] Preferably, the center line of the spark plug is perpendicular to the center line of the hydrogen injector.

[0025] Preferably, the constant volume optical test platform suitable for ammonia-hydrogen stratified combustion further comprises:

[0026] a plurality of first temperature sensors mounted on the injector mounting base;

[0027] two sets of second temperature sensors, which are respectively mounted on the two partitions;

[0028] Each group of the second temperature sensors includes two second temperature sensors; the installation direction of the first temperature sensor is perpendicular to the installation direction of the second temperature sensor;

[0029] a pressure sensor mounted on the injector mounting seat for detecting the pressure in the combustion chamber;

[0030] Wherein, the temperature sensor and the pressure sensor are electrically connected to the control system respectively.

[0031] Preferably, the constant volume optical test platform suitable for ammonia-hydrogen stratified combustion further comprises:

[0032] An ammonia fuel supply system includes an ammonia-air bottle, an ammonia pressure reducing valve, an ammonia high-pressure ball valve, and a three-way joint that are connected in sequence;

[0033] Wherein, one interface of the three-way connector is communicated with the ammonia-air channel.

[0034] Preferably, the constant volume optical test platform suitable for ammonia-hydrogen stratified combustion further comprises:

[0035] A hydrogen fuel supply system comprising a hydrogen cylinder, a hydrogen pressure reducing valve, and a hydrogen high-pressure ball valve connected in sequence;

[0036] Wherein, the hydrogen high-pressure ball valve is connected to the hydrogen injector.

[0037] Preferably, the ignition gap of the spark plug is 2 mm.

[0038] A constant-volume optical testing method applicable to ammonia-hydrogen stratified combustion, using the constant-volume optical testing platform applicable to ammonia-hydrogen stratified combustion, comprises the following steps:

[0039] Step 1: Fill the combustion chamber of the constant volume combustion bomb with ammonia-air premixed gas until the pressure in the combustion chamber reaches the target pressure;

[0040] Step 2: starting the heating device in the heating chamber of the constant volume combustion bomb to heat the combustion chamber until the temperature in the combustion chamber reaches the target temperature;

[0041] Step 3: Turn on the hydrogen injector to inject hydrogen into the combustion chamber, and at the same time turn on the shooting device in the optical system;

[0042] Step 4: Determine the ignition timing, and start the spark plug to ignite at the determined ignition timing;

[0043] Repeat steps 1 to 4, and change the ratio of ammonia to air in the ammonia-air premix, the amount of hydrogen injected, and the interval between the ignition time and the start of hydrogen injection during each cycle to simulate different ratios of ammonia, hydrogen, and air and different hydrogen-ammonia stratified combustion modes;

[0044] In steps 3 and 4, the shooting device in the optical system continuously shoots to obtain hydrogen injection diffusion images and combustion process images in different stratified combustion modes.

[0045] Preferably, the constant volume optical testing method applicable to ammonia-hydrogen stratified combustion further comprises:

[0046] Before the test, the hydrogen injection amount corresponding to different hydrogen injection parameters was calibrated to obtain a MAP diagram of hydrogen injection parameters and hydrogen injection amount;

[0047] Wherein, the hydrogen injection parameters include: injection pressure, injection pulse width and injection times;

[0048] During the process of injecting hydrogen into the combustion chamber, the amount of hydrogen injected is controlled according to the MAP.

[0049] The beneficial effects of the present invention are:

[0050] The present invention provides a constant-volume optical test platform and test method suitable for ammonia-hydrogen stratified combustion. Based on the ammonia premixing and hydrogen direct injection method in a constant-volume combustion bomb, an ammonia-hydrogen dual-fuel mode is constructed inside the constant-volume bomb. The stratification state of the ammonia-hydrogen mixture can be regulated by controlling the hydrogen injection parameters and coordinating with the ignition timing: the ammonia-air premixed gas enters the bomb in advance and begins to diffuse and mix. After the mixture is evenly mixed, hydrogen is directly injected into the bomb. Active control of the ammonia-hydrogen stratified combustion is achieved by actively regulating the hydrogen injection parameters and coordinating with the control of the ignition timing. Combined with the synchronous shooting of the optical system, the schlieren image or the direct-shot image can be recorded in real time: the flow and combustion state of the mixture in the cylinder are judged by the images shot by the schlieren system at different stages of the hydrogen flow and the entire ammonia-hydrogen combustion process, and the flame shape is photographed by the direct-shot method through the bottom window; thereby, images of the combustion process are obtained in all directions, and the combustion test process is visualized. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a front view of the constant volume incendiary bomb described in the present invention.

[0052] Figure 2 for Figure 1 AA cross-sectional view.

[0053] Figure 3 for Figure 1 BB cross-sectional view.

[0054] Figure 4This is a front view of the constant volume incendiary bomb of the present invention installed on a laboratory bench.

[0055] Figure 5 It is a top view of the constant volume incendiary bomb described in the present invention.

[0056] Figure 6 This is a left view of the constant volume incendiary bomb of the present invention installed on a laboratory bench.

[0057] Figure 7 This is a framework diagram of the constant-volume optical test platform suitable for ammonia-hydrogen stratified combustion described in the present invention.

[0058] Figure 8 Light path diagram of the optical system according to the present invention.

[0059] Figure 9 This is a schematic diagram of the ammonia-hydrogen combustion mode control method described in the present invention.

[0060] Figure 10 This is a flow chart of the constant volume optical testing method applicable to ammonia-hydrogen stratified combustion according to the present invention. DETAILED DESCRIPTION

[0061] The present invention will be described in further detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0062] like Figure 1-7 As shown, the present invention provides a constant volume optical test platform suitable for ammonia-hydrogen stratified combustion, comprising: a test bench, a constant volume combustion bomb 110, an injector mounting seat 120, a hydrogen injector 130, a spark plug 140, an ammonia-air channel 150, a first window 160, a second window 170, an optical system and a control system.

[0063] The constant volume incendiary bomb 110 is a rectangular parallelepiped structure, mounted on a test bench. Two partitions 111 are spaced apart along its length, dividing the bomb into a combustion chamber 110a and two heating chambers 110b. The combustion chamber 110a has a cubic interior, and the two heating chambers 110b are symmetrically located at either end of the combustion chamber 110a. Each heating chamber 110b contains a heating device 112.

[0064] In this embodiment, the heating chamber cover plates 113 at both ends of the constant volume incendiary bomb 110 are configured as a separate structure from the main body of the constant volume incendiary bomb 110. The heating chamber cover plates 113 are connected to the ends of the main body of the constant volume incendiary bomb 110 via eight evenly distributed M12 bolts, thereby sealing the opening at the end of the main body of the constant volume incendiary bomb 110 (outside the heating chamber 110b). An annular limiting baffle 114 is provided on the inner wall of the constant volume incendiary bomb 110 at the separation between the combustion chamber 110a and the heating chamber 110b; the outer edge of the annular limiting baffle 114 is an integral structure with the inner wall of the constant volume incendiary bomb 110, and the annular limiting baffle 114 is arranged parallel to the partition 111.

[0065] As a preferred embodiment, the separator 111 is a cylindrical structure with one end open, the open end of the cylindrical structure abuts against the heating chamber cover 113, the bottom of the cylindrical structure abuts against the annular limit baffle 114, and the bottom edge of the cylindrical structure and the annular limit baffle 114 are sealed with a copper gasket 115; the outer wall of the cylindrical structure is gap-fitted with the inner wall of the constant volume combustion bomb 110. The separator 111 (cylindrical structure) is fixed by the heating chamber cover 113 and the annular limit baffle 114. In this embodiment, the internal cavity of the separator 111 (cylindrical structure) is set as a cylindrical cavity.

[0066] In this embodiment, the heating device 112 uses a 1KW spiral heating tube. The electrodes of the spiral heating tube are connected to two sets of independent heating tube voltage regulators via wires, and then connected to a 220V AC power supply through the heating tube voltage regulators. The spiral heating tubes are symmetrically arranged in the two heating chambers 110b of the constant volume combustion bomb 110, matched with the heating chamber cover 113 and with the electrodes exposed. The heating tube voltage regulators are placed on the experimental bench outside the constant volume combustion bomb 110, corresponding one to one with the spiral heating tubes.

[0067] The present invention adopts a large-volume medium heating solution. The heating device 112 is not in direct contact with the combustion chamber. The heating device 112 first heats the air in the heating chamber 110b and then uses the air to heat the combustion chamber 110a, which can minimize the problem of uneven heating of the combustion chamber 110a.

[0068] The top of the combustion chamber 110a has a reserved hole for the injector mounting seat. The disc-shaped injector mounting seat 120 is embedded in the top of the combustion chamber 110a. The contact point between the edge of the injector mounting seat 120 and the combustion chamber 110a is sealed by an injector mounting seat gasket 121. This gasket is made of copper.

[0069] The hydrogen injector 130 is mounted on the injector mount 120, perpendicular to the injector mount 120, and directed toward the center of the combustion chamber 110a. Two spark plugs 140 are mounted on two partitions 111, respectively, and are directed toward the center of the combustion chamber 110a. In this embodiment, the injector mount 120 is connected to the top of the constant volume combustion bomb 110 body via eight evenly distributed M12 bolts.

[0070] Preferably, the hydrogen injector 130 is mounted at the center of the injector mount 120 (i.e., at the center of the top of the combustion chamber 110a) via an injector guide 131, with the centerline of the hydrogen injector 130 perpendicular to the top of the combustion chamber 110a. Two spark plugs 140 are symmetrically mounted at the centers of the two partitions 111, with the centerlines of the spark plugs 140 perpendicular to the centerlines of the hydrogen injectors 130. This ensures that the ignition point during ignition is at the geometric center of the combustion chamber 110a and that the hydrogen spray exhibits a stratified concentration gradient around the spark plugs 140. The hydrogen injectors 130 are conventional automotive fuel injectors.

[0071] The hydrogen fuel supply system includes a hydrogen cylinder, a hydrogen pressure reducing valve, and a hydrogen high-pressure ball valve connected in sequence. The hydrogen high-pressure ball valve is connected to the hydrogen injector 130 to supply hydrogen to the hydrogen injector 130.

[0072] In one embodiment, the hydrogen supply system adopts an independent gas circuit design, and the outlet of the hydrogen cylinder is connected to a YQQ-370 type pressure reducing valve. After the hydrogen is reduced in pressure by the pressure reducing valve, it is controlled by a 304 stainless steel high-pressure ball valve and transported to the hydrogen injector 130 to achieve direct injection of hydrogen into the missile.

[0073] The ammonia-air channel 150 is arranged on the injector mounting seat 120 and is connected to the combustion chamber 110a. The ammonia fuel supply system includes an ammonia-air bottle, an ammonia pressure reducing valve, an ammonia high-pressure ball valve and a three-way joint that are connected in sequence; the ammonia-air bottle is used to store the ammonia-air premixed gas. Among them, one interface of the three-way joint is connected to the ammonia-air channel 150. The ratio of ammonia and air in the ammonia-air premixed gas stored in the ammonia-air bottle can be adjusted according to test requirements. The ammonia fuel supply system introduces the ammonia-air mixture into the combustion chamber 110a through the ammonia-air channel 150.

[0074] In one embodiment, in the ammonia fuel supply system, the outlet of the ammonia-air bottle is connected to a YQA-441 ammonia-specific pressure reducing valve. After the gas pressure is steadily reduced to the value required for the experiment, it is regulated by a 304 stainless steel high-pressure ball valve and connected to a three-way interface.

[0075] Among them, the three-way connector integrates the two major functions of ammonia-air premixed gas intake and exhaust gas discharge. The main passage is connected to the ammonia-air channel 150 on the injector mounting seat, one end of the bypass branch is for air intake, and the other end is connected to the pressure relief valve for exhaust, which greatly simplifies the complexity of pipeline installation.

[0076] The ignition point of the constant-volume incendiary bomb 110 is located at the geometric center of the bomb body. Considering the large internal space of the constant-volume bomb, to achieve the required ignition gap, an industrial furnace spark plug is used. Spark plug 140 is installed at the center of partition 111. The spark plug's ignition gap is adjusted by adjusting the thickness of the copper gasket 115 between partition 111 and annular limit baffle 114. In this embodiment, the spark plug's ignition gap is set to 2 mm.

[0077] The two first viewing windows 160 are symmetrically disposed on two side surfaces of the combustion chamber 110a adjacent to the partition 111. The second viewing window 170 is disposed on the bottom surface of the combustion chamber 110a.

[0078] In this embodiment, the combustion chamber 110a of the constant volume incendiary bomb is provided with window mounting slots (holes) on the sidewalls and bottom, respectively. A first window 160 and a second window 170 are respectively disposed in the corresponding window mounting slots. Furthermore, the first window 160 is secured to the sidewall of the combustion chamber 110a via a first window mounting seat 161 disposed on the exterior of the constant volume incendiary bomb, while the second window 170 is secured to the bottom of the combustion chamber 110a via a second window mounting seat 171 disposed on the exterior of the constant volume incendiary bomb. Both the first window 160 and the second window 170 are made of quartz glass, have a diameter of 140 mm, and a visible diameter of 120 mm after installation. They are also 50 mm thick.

[0079] A first inner sealing gasket 160a is provided on the inner side of the edge of the first window 160 for achieving sealing between the first window 160 and the combustion chamber 110a; a first outer sealing gasket 160b is provided on the outer side of the edge of the first window 160 for achieving sealing between the first window 160 and the first window mounting seat 161.

[0080] A second inner sealing gasket 170a is provided on the inner side of the edge of the second window 170 for achieving sealing between the second window 170 and the combustion chamber 110a; a second outer sealing gasket 170b is provided on the outer side of the edge of the second window 170 for achieving sealing between the second window 170 and the second window mounting seat 171.

[0081] As a preference, the first inner sealing gasket 160a, the first outer sealing gasket 160b, the second inner sealing gasket 170a and the second outer sealing gasket 170b are all made of polytetrafluoroethylene gaskets to take into account both sealing and optical component protection requirements.

[0082] The first window mounting seat 161 and the second window mounting seat 171 are respectively mounted on the main body of the constant volume incendiary bomb 110 through 8 evenly distributed M12 bolts.

[0083] like Figure 8 As shown, the optical system is fixedly mounted on the experimental bench and includes a schlieren system and a direct-viewing system. The schlieren system and the two first viewing windows 160 form a schlieren optical path, while the direct-viewing system and the second viewing window 170 form a direct-viewing optical path. The schlieren system includes an LED light source 310, an aperture 320, a first plane reflector 330 and its frame, a first concave reflector 340 and its frame, a second concave reflector 350 and its frame, a second plane reflector 360 and its frame, a knife edge 370, and a first high-speed camera 380, arranged sequentially on the experimental bench according to the schlieren optical path. The direct-viewing system includes a 45° reflector 410 and a second high-speed camera 420, arranged sequentially on the experimental bench according to the direct-viewing optical path. The 45° reflector 410 is positioned below the second viewing window 170 and forms a 45° angle with the second viewing window 170. The first and second high-speed cameras 380 and 420 are each electrically connected to the control system.

[0084] In this embodiment, the first high-speed camera 380 and the second high-speed camera 420 are both Phantom V611 models, and the parameter settings can be set separately according to the requirements of the schlieren method and the direct shooting method research.

[0085] Figure 8 This is the optical path diagram of the optical observation system of the present invention. An LED light source 310 is converted into a point light source after passing through the aperture in the aperture 320. The aperture opening is adjusted to the optimal opening for clear boundary imaging and sufficient brightness. After passing through the aperture 320, the point light source projects light onto a first concave reflector 340 via a first plane reflector 330, thereby generating parallel light. The test section is located between the first plane reflector 330 and the second concave reflector 350. This test section, in the present invention, is the spray flow area in a constant-volume incendiary bomb. After emitting the parallel light from the test section, it passes through the second concave reflector 350 and converges onto a second plane reflector 360. The light then passes through a knife edge 370 and enters a first high-speed camera 380. By adjusting the size of the light-blocking area of ​​the blade 370 and the relative position between the blade 370 and the second plane reflector 360, a clear and complete spray flow image can be observed in the high-speed camera; in terms of the optical path of the direct shooting method, the self-luminous light of the flame is emitted from the second window 170 at the bottom of the projectile in a vertical direction, and is reflected by the plane reflector 410 placed at a 45° angle below the projectile to become a horizontal light, which is directly projected into the second high-speed camera 420, so that a horizontal cross-section spray flow image can be obtained, which effectively makes up for the shortcomings of the Schlieren method in spatial representation.

[0086] The control system is electrically connected to the hydrogen injector 130 , the spark plug 140 and the first and second high-speed cameras 380 and 420 of the optical system, respectively, for controlling the working processes of the hydrogen injector 130 , the spark plug 140 and the optical system.

[0087] In this embodiment, the control system adopts the dSPACE system.

[0088] The injector mounting base 120 has three temperature sensor mounting holes, and the three first temperature sensors 211 are mounted in corresponding locations within the temperature sensor mounting holes on the injector mounting base 120. Each partition 111 has a set of temperature sensor mounting holes, each of which is mounted with a corresponding set of second temperature sensors 212. Each set of second temperature sensors 212 includes two second temperature sensors 212. The heating chamber cover 113 has temperature sensor wiring holes 113a, through which the temperature sensor wires pass.

[0089] Providing a plurality of first temperature sensors 211 and second temperature sensors 212 can detect the temperatures at different locations in the combustion chamber, thereby improving the accuracy of temperature detection.

[0090] In this embodiment, the three first temperature sensors 211 are evenly distributed on the injector mounting base 120. On the distribution circle, two groups of second temperature sensors 212 are symmetrically arranged on the partition 111 On the distribution circle, the installation directions of the first temperature sensor 211 and the second temperature sensor 212 are perpendicular.

[0091] The injector mounting base 120 is provided with a pressure sensor mounting hole, and the pressure sensor 220 is mounted in the pressure sensor mounting hole on the injector mounting base 120 to detect the pressure in the combustion chamber. The temperature sensor and the pressure sensor are electrically connected to the control system respectively.

[0092] In this embodiment, the first temperature sensor 211 and the second temperature sensor 212 are both K-type armored thermocouples, and the pressure sensor 220 is a high-temperature resistant pressure sensor.

[0093] like Figure 9-10 As shown, the present invention also provides a constant-volume optical testing method applicable to ammonia-hydrogen stratified combustion. Using the constant-volume optical testing platform applicable to ammonia-hydrogen stratified combustion, the specific testing method is as follows.

[0094] Figure 9The vertical axis is the hydrogen concentration near the spark plug when hydrogen is injected into the cylinder, the horizontal axis is time, and the origin O is the moment when hydrogen injection begins; t0 is the time from the start of hydrogen injection to the time when the front end of the hydrogen spray reaches the spark plug position under a certain back pressure and injection parameters, and the hydrogen concentration at this time is C0; t1 is the end of hydrogen injection, and the hydrogen concentration near the spark plug is C2; t8 corresponds to the time when the hydrogen concentration in the area near the spark plug reaches its peak, and the hydrogen diffusion rate in the area near the spark plug is equal to the replenishment rate of the area caused by the hydrogen jet; t2 is the time when hydrogen is completely premixed, and the concentration near the spark plug is C1; the pulse diagram corresponds to the three combustion modes described in the test method of the present invention: ignition at t3 indicates the hydrogen injection and combustion mode Formula, the ignition time is during the hydrogen injection process, at this time the hydrogen concentration near the spark plug shows an upward trend; ignition at time t4 indicates the stratified combustion mode after the hydrogen injection is completed, the ignition time is carried out after the hydrogen injection is completed, at this time the hydrogen presents a stratified concentration gradient distribution; ignition at time t5 indicates the combustion mode after the hydrogen premixing is completed, at this time the hydrogen is completely premixed, which belongs to the category of completely premixed combustion; ignition at time t7 indicates the ignition time between the completion of hydrogen injection and the completion of premixing, the earlier the ignition time, the lower the degree of hydrogen premixing and the higher the degree of stratification; the later the ignition time, the higher the degree of hydrogen premixing and the lower the degree of stratification; ignition at time t6 indicates that ignition at any time after the hydrogen is completely premixed is the completely premixed combustion mode;

[0095] Before the test, the hydrogen injection amount corresponding to different hydrogen injection parameters is calibrated to obtain a hydrogen injection parameter and hydrogen injection amount MAP diagram; wherein the hydrogen injection parameters include: injection pressure, injection pulse width and number of injections. During the process of injecting hydrogen into the combustion chamber, the hydrogen injection parameters are changed according to the MAP diagram to control the hydrogen injection amount. The ratio of ammonia and air in the premixed gas can also be adjusted according to the test needs. In this way, the ratio of hydrogen, ammonia and air in the combustion chamber can be adjusted. Afterwards, by changing the time interval between the spark plug ignition moment and the start of hydrogen injection, different stratified combustion modes can be controlled, specifically including:

[0096] Here we define Δt=t 点火 -t 喷射开始 ; where t 喷射开始It can be set to any moment after the intake of the ammonia-air mixture in the cylinder, and this moment is used as the reference moment for subsequent injection and ignition. From the spray calibration process, it can be known that the time (interval) from the start of hydrogen injection to the front of the hydrogen spray reaching the spark plug position (ignition point) is t0; when Δt < t0, the spray front has not reached the ignition point. When t0 ≤ Δt ≤ the hydrogen injection pulse width, it is equivalent to ignition during the period after the spray front reaches the spark plug position and before the injection ends, which belongs to the diffusion combustion mode, and the combustion is controlled by diffusion. When the hydrogen injection pulse width < Δt < the hydrogen injection pulse width + t0, some hydrogen in the constant volume bomb has participated in premixing, which belongs to the partial premixed combustion mode, and the combustion is controlled by both chemical kinetics and diffusion. When Δt > 600 s, that is, after the injection ends, it stands still for a period of time to wait for the hydrogen to be fully premixed, which belongs to the fully premixed combustion mode, and the combustion is controlled by chemical kinetic factors.

[0097] (1) Hydrogen diffusion combustion: Hydrogen participates in combustion immediately after being injected into the bomb. Ignition occurs during the hydrogen injection process, causing hydrogen to burn while being injected. At this time, the interval Δt between the ignition moment and the start of injection is very small, that is, t0 ≤ Δt ≤ the hydrogen injection pulse width. In this combustion mode, almost all hydrogen is in the hydrogen jet direction. Ignition starts when the spray front just reaches the spark plug position and has not been largely premixed with the ammonia-air in the bomb. Hydrogen burns while diffusing, belonging to the category of stratified combustion.

[0098] (2) Hydrogen partial premixed combustion: Ignition occurs after the hydrogen injection is completed. At this time, the injection end moment is earlier than the ignition moment and satisfies the hydrogen injection pulse width < Δt < the hydrogen injection pulse width + t0. The spray front has moved downward past the spark plug and there is partial premixing. Generally, it belongs to the category of partial premixed combustion and stratified combustion: The concentration of hydrogen is high near the spark plug and relatively low at the far end of the spark plug. The earlier the ignition moment, the lower the hydrogen premixing degree and the easier it is to achieve ammonia-hydrogen stratified combustion in the bomb by means of stratified combustion.

[0099] (3) Hydrogen fully premixed combustion: After a period of time after the hydrogen injection is completed, at this time the injection end moment is earlier than the ignition moment and Δt > 600 s. The spray front has long passed the spark plug and has diffused evenly. This mode is equivalent to ignition after hydrogen is premixed with ammonia. At this time, the concentration distribution of each component in the bomb is uniform, belonging to the fully premixed combustion mode.

[0100] Both diffusion combustion and partial premixed combustion belong to the stratified combustion mode. The earlier the ignition moment, the lower the hydrogen premixing degree and the higher the stratification degree; the later the ignition moment, the higher the hydrogen premixing degree and the lower the stratification degree; after the hydrogen is fully premixed, ignition at any moment is the fully premixed combustion mode.

[0101] Figure 10This is a flow chart of the constant volume optical test method for ammonia-hydrogen stratified combustion described in the present invention. After the ammonia-air premixed gas enters the interior of the bomb through the intake duct, hydrogen is directly injected into the constant volume combustion bomb. The hydrogen flow process is observed and recorded using optical equipment. The timing relationship between hydrogen injection and ignition is determined based on the target combustion mode: ignition during hydrogen injection belongs to the diffusion combustion mode, and ignition after injection but before hydrogen is fully premixed belongs to the partial premixed combustion mode. Both of the above combustion modes belong to stratified combustion, and the stratified state is affected by the degree of hydrogen premixing; ignition after hydrogen is fully premixed belongs to the ammonia-hydrogen fully premixed combustion mode. From the start of hydrogen injection to the complete premixing of hydrogen, the ignition time is continuously adjustable on the constant volume optical diagnostic platform, and multiple injections can be combined to achieve active control of the hydrogen concentration gradient distribution in the cylinder. From the time when hydrogen injection begins and the hydrogen concentration near the spark plug reaches the ignition range to the time when hydrogen injection is completed and ammonia and hydrogen are completely premixed, the constant volume combustion platform can achieve continuous adjustment of the ignition timing, thereby achieving the purpose of actively controlling whether the ammonia-hydrogen combustion is stratified and the degree of stratification.

[0102] Based on the different combustion modes of ammonia and hydrogen, the combustion flame is photographed through the optical diagnostic platform to realize the visualization of the test process.

[0103] The present invention can form a stratified mixture by directly injecting a small amount of hydrogen into the constant volume bomb combustion chamber, that is, forming a certain concentration gradient near the spark plug. This hydrogen distribution pattern helps to form a stable flame core near the spark plug and shorten the flame development period.

[0104] By igniting locally enriched hydrogen within the missile, a large amount of ammonia is ignited. The activated environment created by hydrogen combustion accelerates the chain reaction of the ammonia fuel, resulting in an orderly fuel energy release process. This combustion mode greatly utilizes the advantages of hydrogen's active chemical properties and easy ignition, as well as ammonia's high combustion calorific value and stable properties. It avoids many safety hazards in hydrogen storage and transportation, and does not require significantly increasing the ignition energy of the spark plug to directly ignite the ammonia.

[0105] The present invention is based on the constant-volume in-projectile composite injection technology and multiple injection technology to construct a flexible ammonia-hydrogen dual-fuel mode inside the combustion chamber, forming a controllable mixture stratification state inside the projectile: the ammonia-air premixed gas enters the combustion chamber in advance and begins to diffuse, and hydrogen is directly injected into the projectile at different times during the diffusion process. By actively adjusting parameters such as the hydrogen injection time, injection ratio, and injection pulse width, it is possible to control whether the hydrogen flow in the projectile is stratified and the degree of stratification. Coupling with the spark plug ignition trigger further realizes active control of the ammonia-hydrogen stratified combustion. Combined with the synchronous shooting of a high-speed camera, the schlieren image can be recorded in real time.

[0106] Subsequent researchers can process the obtained images, including hydrogen spray and flame images taken based on the schlieren optical path and flame images taken by the direct shooting method, and further extract characteristic parameters such as flame brightness, flame propagation speed, flame area, etc., combined with the temperature and pressure changes in the combustion chamber measured by the sensor, calculate the combustion temperature, pressure, heat release rate, flame propagation speed and other parameters, and then evaluate different ammonia-hydrogen combustion modes, which will help provide a reference for the combustion control method in the cylinder of ammonia-hydrogen engines.

[0107] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A constant volume optical test platform suitable for ammonia-hydrogen stratified combustion, characterized in that: include: Experimental bench; A constant volume incendiary bomb, which is installed on the experimental bench, is provided with two partitions inside the constant volume incendiary bomb and is divided into a combustion chamber and two heating chambers by the two partitions; Wherein, the two heating chambers are symmetrically arranged at both ends of the combustion chamber, and a heating device is provided in the heating chamber; an injector mounting seat, which is arranged on the top of the combustion chamber; a hydrogen injector mounted on the injector mounting seat and arranged toward the center of the combustion chamber; two spark plugs, which are respectively mounted on the two partitions and arranged toward the center of the combustion chamber; an ammonia-air passage, which is provided on the injector mounting seat and communicates with the combustion chamber; two first viewing windows symmetrically arranged on two sides of the combustion chamber adjacent to the partition; a second viewing window disposed on the bottom surface of the combustion chamber; An optical system, which is installed on the experimental bench and is used to capture images inside the combustion chamber; Wherein, the optical system and the two first windows form a schlieren shooting light path, and the optical system and the second window form a direct shooting light path; A control system is electrically connected to the hydrogen injector, the spark plug and the optical system respectively.

2. The constant volume optical test platform suitable for ammonia-hydrogen stratified combustion according to claim 1 is characterized in that: The heating device adopts a spiral heating tube.

3. The constant volume optical test platform suitable for ammonia-hydrogen stratified combustion according to claim 2, characterized in that: A center line of the spark plug is perpendicular to a center line of the hydrogen injector.

4. The constant volume optical test platform for ammonia-hydrogen stratified combustion according to any one of claims 1 to 3, characterized in that: Also includes: a plurality of first temperature sensors mounted on the injector mounting base; two sets of second temperature sensors, which are respectively mounted on the two partitions; Each group of the second temperature sensors includes two second temperature sensors; the installation direction of the first temperature sensor is perpendicular to the installation direction of the second temperature sensor; a pressure sensor mounted on the injector mounting seat for detecting the pressure in the combustion chamber; Wherein, the temperature sensor and the pressure sensor are electrically connected to the control system respectively.

5. The constant volume optical test platform suitable for ammonia-hydrogen stratified combustion according to claim 4, characterized in that: Also includes: An ammonia fuel supply system includes an ammonia-air bottle, an ammonia pressure reducing valve, an ammonia high-pressure ball valve, and a three-way joint that are connected in sequence; Wherein, one interface of the three-way connector is communicated with the ammonia-air channel.

6. The constant volume optical test platform suitable for ammonia-hydrogen stratified combustion according to claim 5, characterized in that: Also includes: A hydrogen fuel supply system comprising a hydrogen cylinder, a hydrogen pressure reducing valve, and a hydrogen high-pressure ball valve connected in sequence; Wherein, the hydrogen high-pressure ball valve is connected to the hydrogen injector.

7. The constant volume optical test platform for ammonia-hydrogen stratified combustion according to claim 6, characterized in that: The ignition gap of the spark plug is 2 mm.

8. A constant volume optical testing method for ammonia-hydrogen stratified combustion, using the constant volume optical testing platform for ammonia-hydrogen stratified combustion according to any one of claims 1 to 7, characterized in that: The steps include: Step 1: Fill the combustion chamber of the constant volume combustion bomb with ammonia-air premixed gas until the pressure in the combustion chamber reaches the target pressure; Step 2: starting the heating device in the heating chamber of the constant volume combustion bomb to heat the combustion chamber until the temperature in the combustion chamber reaches the target temperature; Step 3: Turn on the hydrogen injector to inject hydrogen into the combustion chamber, and at the same time turn on the shooting device in the optical system; Step 4: Determine the ignition timing, and start the spark plug to ignite at the determined ignition timing; Repeat steps 1 to 4, and change the ratio of ammonia to air in the ammonia-air premix, the amount of hydrogen injected, and the interval between the ignition time and the start of hydrogen injection during each cycle to simulate different ratios of ammonia, hydrogen, and air and different hydrogen-ammonia stratified combustion modes; In steps 3 and 4, the shooting device in the optical system continuously shoots to obtain hydrogen injection diffusion images and combustion process images in different stratified combustion modes.

9. The constant volume optical testing method for ammonia-hydrogen stratified combustion according to claim 8, characterized in that: Also includes: Before the test, the hydrogen injection amount corresponding to different hydrogen injection parameters was calibrated to obtain a MAP diagram of hydrogen injection parameters and hydrogen injection amount; Wherein, the hydrogen injection parameters include: injection pressure, injection pulse width and injection times; During the process of injecting hydrogen into the combustion chamber, the amount of hydrogen injected is controlled according to the MAP.

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