Nozzle replaceable fuel injection system for constant volume bomb experiment and experimental method

Abstract

The application discloses a replaceable nozzle fuel injection system and experimental method for constant volume bomb experiment, and belongs to the technical field of internal combustion engines. The system comprises an oil circuit module, a jet control module, a constant volume bomb module and an air circuit module; the oil circuit module is used for providing fuel with preset pressure, flow and temperature; the jet control module comprises a solenoid valve, a detachable nozzle, an electronic control unit and a host computer, the solenoid valve is connected with the host computer through the electronic control unit, and the fuel of the oil circuit module is sprayed out through the detachable nozzle according to preset injection parameters through the solenoid valve; the constant volume bomb module comprises a constant volume bomb body and an adapter connected with the constant volume bomb body, the solenoid valve is installed at the top opening of the constant volume bomb body through the adapter, and the three are matched to form a coaxial sealing structure; the air circuit module is used for adjusting the back pressure of the constant volume bomb and providing an air source for a gas-liquid booster pump. The system has the advantages of low cost, high flexibility, reliable sealing and convenience for quantitative research on the atomization characteristics of different nozzles.

Description

Technical Field

[0001] The application relates to the field of internal combustion engine technology, and more specifically, to a nozzle-replaceable fuel injection system and experimental method for constant volume bomb experiments. Background Technology

[0002] Fuel injection systems are key components of various combustion devices, including internal combustion engines, gas turbines, industrial burners, and aero engines. Their performance directly determines fuel atomization quality, fuel-air mixing efficiency, and the level of combustion pollutant generation. Especially in engine development and fundamental combustion research, it is necessary to conduct systematic testing and comparative analysis of different nozzle structures under a wide range of operating conditions (temperature, pressure, back pressure) to understand the influence of nozzle geometry parameters on spray characteristics and combustion performance. This will provide a basis for nozzle optimization design and combustion system matching.

[0003] Currently, commercially available integrated nozzles or pre-made injectors are commonly used in combustion experiments and injection tests. These nozzles typically integrate the solenoid valve and orifice structure into a non-removable unit, with fixed orifice geometry. When studying the impact of different orifice structures on injection and atomization, it often requires replacing the entire nozzle or relying on expensive custom machining, making it difficult to achieve rapid, flexible, and low-cost nozzle structure switching. It also makes it difficult to ensure fair comparisons under the same driving and operating conditions. For example, typical commercially available injectors such as gasoline direct injection injectors and diesel common rail injectors employ highly integrated structures, integrating the solenoid valve assembly, valve needle, valve seat, internal flow channel, and orifice structure into a single unit. The orifices are directly machined to the nozzle end or formed as a non-removable connection through welding, laser processing, or other methods. The number of orifices, orifice diameter, orifice shape, and spray angle are fixed during the manufacturing stage and cannot be individually replaced or adjusted during use. When research or development requires testing the impact of different orifice parameters, the entire injector must be replaced, significantly increasing experimental costs and extending the customization cycle, failing to meet the needs of rapid iteration and multi-solution comparisons during R&D. Meanwhile, frequent disassembly and reassembly increase the risk of system seal failure and may introduce unnecessary experimental variables due to installation differences, affecting the fairness and consistency of comparative experiments between different nozzle structures.

[0004] Furthermore, when comparing the performance of nozzle structures, ideally only the nozzle geometry parameters should be changed, while keeping all other conditions, such as drive parameters and cavity structure, strictly consistent. However, in existing schemes, the drive parameters of the injection end, such as injection pulse width, frequency, and drive voltage, as well as the cavity geometry, are often fixed or have limited adjustment ranges, and are inconvenient to adjust. When using different integral nozzles, their built-in solenoid valve characteristics and flow chamber dimensions may vary, resulting in differences in injection waveform, opening and closing response, and intracavity flow field. These uncontrolled variables are intertwined with the influence of nozzle geometry, making it difficult to effectively separate the effects of the nozzle structure itself, thus reducing the accuracy of experimental results and the credibility of conclusions.

[0005] Fuel properties are significantly affected by temperature, and injection pressure and back pressure environment also play a crucial role in spray development. Existing experimental systems often disperse functional modules such as pressurization, heating, flow measurement, and injection control. When conducting tests under different oil temperatures, injection pressures, and back pressures, system configuration and parameter adjustment become cumbersome, and ensuring consistency between modules is difficult, affecting the repeatability and comparability of experimental results. For example, existing fuel injection devices and constant-volume cartridges often employ a separate assembly structure. The valve body and the top of the constant-volume cartridge are typically connected via multi-stage joints, flanges, or transition pieces, resulting in dispersed sealing surfaces and force paths, making it difficult to form an integrated sealing structure between the valve body and the constant-volume cartridge. Under high pressure or temperature fluctuations, this easily leads to the risk of micro-leakage and repeated assembly deviations. Simultaneously, fuel heating and temperature sensing elements are often located in external pipelines to the valve body or far from the injection inlet, resulting in significant heat loss and temperature lag. Oil temperature control and status monitoring are difficult to perform close to the critical areas of the injection inlet and back pressure chamber. During the switching process of multiple operating conditions with wide oil temperature, wide injection pressure, and wide back pressure, the above-mentioned decentralized connection and temperature and pressure measurement methods will bring problems such as long debugging time, long stabilization time, and difficulty in ensuring parameter consistency, which will reduce the repeatability and comparability of experimental data, and thus affect experimental efficiency and the reliability of results.

[0006] In summary, there is an urgent need in this field for a fuel injection experimental device that can support rapid replacement of nozzle geometry, integrate fuel temperature and pressure control and flow monitoring, and facilitate visualization experiments under controlled back pressure conditions, so as to improve the efficiency, flexibility and data reliability of nozzle structure research. Summary of the Invention

[0007] This application provides a replaceable nozzle fuel injection system and experimental method for constant volume bomb experiments. It can flexibly adjust the injection pulse width, injection interval and injection voltage to simulate a wide range of oil temperature, injection pressure and back pressure environments. It solves the problems of existing technologies where replacing nozzles requires replacing the entire expensive commercial fuel injector and the assembly repeatability is poor. It has the advantages of low cost, high flexibility, reliable sealing and convenient quantitative study of the atomization characteristics of different nozzles.

[0008] The specific technical solution is as follows: In a first aspect, embodiments of this application provide a nozzle-replaceable fuel injection system for constant-volume projectile experiments, comprising: The fuel circuit module includes a heating device and a fuel tank, a first control valve, a gas-liquid booster pump, and a flow meter connected in sequence, for providing fuel at preset pressure, flow rate, and temperature; The injection control module includes a solenoid valve, a detachable nozzle, an electronic control unit, and a host computer. The detachable nozzle is mounted to the outlet end of the solenoid valve via a detachable mechanical connection structure. The solenoid valve is electrically connected to the host computer via the electronic control unit. Fuel from the fuel circuit module is injected through the solenoid valve and then through the detachable nozzle according to preset injection parameters. The preset injection parameters include injection pulse width, injection interval, and injection voltage. Furthermore, a sealing gasket is sandwiched between the solenoid valve and the detachable nozzle. The volumetric ammunition module includes a volumetric ammunition body and an adapter connected thereto. The solenoid valve is installed at the top opening of the volumetric ammunition body through the adapter. The three components cooperate to form a coaxial sealing structure, and the detachable nozzle is located in the cavity of the volumetric ammunition body. The gas path module includes a nitrogen cylinder and a vacuum pump that are respectively connected to the cavity of the constant volume bomb body to adjust the back pressure of the constant volume bomb, and the nitrogen cylinder also provides a gas source for the gas-liquid booster pump.

[0009] In some embodiments of this application, the volumetric projectile body includes a volumetric projectile shell, a volumetric projectile base, and a viewing window; two viewing windows are symmetrically arranged on the side wall of the volumetric projectile shell along its radial direction; the volumetric projectile base is disposed at one end of the volumetric projectile shell along its central axis, and the solenoid valve and the detachable nozzle are disposed at the other end of the volumetric projectile shell along its central axis via the adapter, and sealing elements are provided between the solenoid valve and the adapter, between the adapter and the volumetric projectile shell, and between the volumetric projectile shell and the volumetric projectile base, so as to jointly enclose and form a sealed structure with an internal cavity.

[0010] In some embodiments of this application, the adapter includes an integrally formed mounting portion and a fixing portion; the mounting portion is a cylindrical structure, the fixing portion is an annular structure, the fixing portion is sleeved on the end of the mounting portion away from the volume-regulating cartridge body, and the fixing portion is symmetrically provided with two arc-shaped adjustment slots; a mounting cavity is provided on the end face of the mounting portion away from the volume-regulating cartridge body, a positioning shoulder is provided on the inner sidewall of the mounting cavity, the shape and size of the mounting cavity and the positioning shoulder match the shape and size of the solenoid valve, and a communication channel for the volume-regulating cartridge is provided on the bottom end face of the mounting cavity. The body has a stepped through groove in its cavity; the volume-regulating cartridge module also includes a clamping plate, the solenoid valve is housed in the mounting cavity and abuts against the positioning shoulder to achieve positioning, the clamping plate is fastened to the end face of the mounting part away from the volume-regulating cartridge body by bolts, axially pressing and fixing the solenoid valve in the mounting cavity, and the detachable nozzle is fixed through the stepped through groove and passes through the cavity of the volume-regulating cartridge body; the mounting part is embedded in the top opening of the volume-regulating cartridge shell and is connected to the volume-regulating cartridge shell by bolts through the two arc-shaped adjusting slots of the fixing part; The solenoid valve is a normally closed solenoid valve. When energized, the valve core actuates to open the oil passage between the detachable nozzle and the oil passage module. When de-energized, the oil passage between the detachable nozzle and the oil passage module is closed under the action of spring force.

[0011] In some embodiments of this application, the constant volume spring module further includes a pressure table, the pressure table having a through hole extending through both ends therethrough, and the two ends of the through hole having internal threads for screwing in a ferrule connector, which is connected to the oil circuit pipeline of the oil circuit module and the inlet of the solenoid valve through the ferrule connector. The heating device includes two first electric heating tubes, a first K-type thermocouple, two second electric heating tubes, and a second K-type thermocouple. The two first electric heating tubes are symmetrically embedded inside the pressure platform about the central axis of the pressure platform, and are used to heat the fuel flowing in the through hole. The first K-type thermocouple is installed inside the pressure platform and is used to monitor the temperature of the fuel flowing in the through hole in real time. The two second electric heating tubes are symmetrically embedded inside the fixing part about the central axis of the mounting cavity, and the second K-type thermocouple is installed inside the fixing part, and is used to compensate for heating and monitor the temperature of the fuel entering the detachable nozzle in real time.

[0012] In some embodiments of this application, the constant-volume projectile body further includes four first connecting blocks, four second connecting blocks, four first connecting gaskets, and two first side cover plates; the constant-volume projectile shell is cuboid in shape, with a first circular through hole on each of its four side walls; the first connecting block includes a first snap-fit ​​portion and a first connecting portion, the first snap-fit ​​portion being an annular plate structure and the first connecting portion being a cylindrical ring structure, the first connecting portion being integrally connected to one side of the first snap-fit ​​portion; the second connecting block includes a second snap-fit ​​portion and a second connecting portion, the second snap-fit ​​portion being an annular plate structure and the second connecting portion being a cylindrical ring structure, the second snap-fit ​​portion being integrally connected to one end of the inner side wall of the second connecting portion; the inner and outer diameters of the first connecting portion and the second connecting portion are the same, and the outer diameter of the first connecting portion and the second connecting portion is the same as the diameter of the first circular through hole, the inner diameter of the first snap-fit ​​portion is the same as the diameter of the first circular through hole. The inner diameter of the second snap-fit ​​part is the same, and the outer diameter of the first snap-fit ​​part is larger than the diameter of the first circular through hole. The sum of the lengths of the first connecting part and the second connecting part is the same as the length of the first circular through hole. The second connecting part and the first connecting part are bolted together. The four second connecting blocks are respectively connected to the four first connecting blocks one by one. The first connecting gasket is disposed between the second connecting part and the first connecting part. The first snap-fit ​​part and the second snap-fit ​​part form a fixed snap-fit ​​groove for snapping the first side cover plate or the viewing window. The first connecting part and the second connecting part are embedded in the first circular through hole and are bolted to the volume-regulating bullet body through the first snap-fit ​​part. The first connecting block and the second connecting block are fixedly installed on the volume-regulating bullet body. A sealing element is also provided between the first connecting block and the volume-regulating bullet body.

[0013] In some embodiments of this application, the constant volume projectile module further includes a pressure sensor and a third type K thermocouple. The pressure sensor and the third type K thermocouple are both installed on one of the first side cover plates. The pressure sensor is used to monitor the back pressure of the constant volume projectile in real time, and the third type K thermocouple is used to monitor the temperature inside the cavity of the constant volume projectile body in real time.

[0014] In some embodiments of this application, the constant-volume projectile body further includes a third connecting block, a fourth connecting block, a second connecting gasket, and a second side cover plate; a second circular through hole is provided on the bottom wall of the constant-volume projectile shell; the third connecting block includes a third snap-fit ​​portion and a third connecting portion, the third snap-fit ​​portion being an annular plate structure and the third connecting portion being a cylindrical ring structure, the third connecting portion being integrally connected to one side of the third snap-fit ​​portion; the fourth connecting block includes a fourth snap-fit ​​portion and a fourth connecting portion, the fourth snap-fit ​​portion being an annular plate structure and the fourth connecting portion being a cylindrical ring structure, the fourth snap-fit ​​portion being integrally connected to one end of the inner side wall of the fourth connecting portion; the inner and outer diameters of the third connecting portion and the fourth connecting portion are the same, and the outer diameter of the third connecting portion and the fourth connecting portion is the same as the diameter of the second circular through hole; the inner diameter of the third snap-fit ​​portion is the same as the diameter of the fourth snap-fit ​​portion. The inner diameters of the three parts are the same, and the outer diameter of the third snap-fit ​​part is larger than the diameter of the second circular through hole. The sum of the lengths of the third connecting part and the fourth connecting part is not greater than the length of the second circular through hole. The fourth connecting part and the third connecting part are bolted together. The fourth connecting block is connected to the third connecting block. The second connecting gasket is disposed between the fourth connecting part and the third connecting part. The third snap-fit ​​part and the fourth snap-fit ​​part form a fixing snap-fit ​​groove for snapping the second side cover plate. The third connecting part and the fourth connecting part are embedded in the second circular through hole and bolted to the volume-regulating bullet body by the third snap-fit ​​part. The third connecting block and the fourth connecting block are fixedly installed on the volume-regulating bullet body. A sealing element is also provided between the third connecting block and the volume-regulating bullet body. The volume-regulating bullet base covers the bottom of the volume-regulating bullet shell.

[0015] In some embodiments of this application, the detachable mechanical connection structure includes mating external and internal threads. The external thread is disposed on the outer side wall of the detachable nozzle, and the internal thread is disposed at the outlet end of the solenoid valve. The detachable nozzle and the outlet end of the solenoid valve are threadedly connected; or, The detachable mechanical connection structure includes mating external and internal threads, as well as a bayonet protrusion and a bayonet groove. The external thread is located on the outer side wall of the detachable nozzle, and the internal thread is located on the inner circumferential surface of the outlet end of the solenoid valve. The detachable nozzle is threadedly connected to the outlet end of the solenoid valve. The bayonet protrusion is located on the inner circumferential surface of the outlet end of the solenoid valve, and the bayonet groove is located on the outer side wall of the detachable nozzle. When the detachable nozzle is tightened, the bayonet protrusion and the bayonet groove engage. Alternatively, The detachable mechanical connection structure includes mating external and internal threads, as well as an external and internal conical surface. The external conical surface is disposed on the outer side wall of the detachable nozzle, and the external thread is disposed on the external conical surface. The internal conical surface is disposed on the inner circumferential surface of the outlet end of the solenoid valve, and the internal thread is disposed on the internal conical surface. The detachable nozzle and the outlet end of the solenoid valve are axially locked together by the external and internal threads, and the external and internal conical surfaces abut and seal against each other; or, The detachable mechanical connection structure includes mating external and internal threads, a split clamping ring, and a locking nut. The split clamping ring is located at the outlet end of the solenoid valve and is radially divided into at least two arc-shaped lobes. The arc-shaped lobes enclose a clamping hole for accommodating the detachable nozzle. The internal thread is located on the inner wall of the arc-shaped lobes, and the external thread is located on the outer wall of the detachable nozzle. The detachable nozzle is threadedly connected to the split clamping ring, and the locking nut is threadedly connected to the outside of the split clamping ring. When the locking nut is tightened, it axially pushes the arc-shaped lobes to contract radially to clamp the detachable nozzle.

[0016] In some embodiments of this application, the gas path module further includes a main gas path pipe, a first branch gas path pipe, a second branch gas path pipe, a second control valve, a third control valve, and a fourth control valve. One end of the main gas path pipe is connected to the outlet of the nitrogen cylinder, and the other end of the main gas path pipe is connected to one end of the first branch gas path pipe and one end of the second branch gas path pipe, respectively. The other end of the first branch gas path pipe is connected to the inlet of the gas-liquid booster pump, and the other end of the second branch gas path pipe is connected to the nitrogen inlet of the constant volume bomb body. The second control valve is disposed on the main gas path pipe, the third control valve is disposed on the first branch gas path pipe, and the fourth control valve is disposed on the second branch gas path pipe.

[0017] Secondly, embodiments of this application provide an experimental method for a nozzle-replaceable fuel injection system for a constant-volume projectile experiment based on the first aspect, the experimental method comprising: S1. Connect the detachable nozzle to be tested to the outlet end of the solenoid valve, check the seal, and then open the first control valve of the fuel tank; S2. Start the gas-liquid booster pump to boost the fuel to the preset pressure value, and at the same time start the heating device to stabilize the fuel temperature to the target temperature value; S3. Adjust the cavity pressure of the constant volume bomb body to the preset back pressure value using a nitrogen cylinder or vacuum pump; S4. Set the preset injection parameters of the solenoid valve via the host computer; wherein, the preset injection parameters include injection pulse width, injection interval and injection voltage; S5. The solenoid valve is controlled by the electronic control unit to spray fuel into the cavity of the constant volume bomb body through the detachable nozzle for atomization experiment, and the fuel flow data is recorded by the flow meter. S6. Determine whether to replace the detachable nozzle. If so, perform the depressurization and disassembly of the original detachable nozzle, and repeat steps S1–S5. Otherwise, end the experiment.

[0018] The beneficial effects of the embodiments of this application are as follows: 1. Efficient and repeatable nozzle replacement: The detachable nozzle is connected to the downstream outlet of the solenoid valve via a threaded connection. The detachable nozzle can be replaced simply by screwing it in / out. The sealing gasket ensures the repeatability of the nozzle's axial position and coaxiality, reducing the risk of errors caused by frequent injector replacements.

[0019] 2. Low cost and support for any nozzle structure: Detachable nozzles can be fabricated using simple machining or additive manufacturing methods; as long as they have threaded connection ends, they can be matched with the system, avoiding reliance on expensive dedicated commercial nozzles and long-term custom machining.

[0020] 3. Adjustable solenoid valve drive parameters: The solenoid valve, adapter, and constant volume spring are integrated and sealed. The parameters of the solenoid valve drive are adjustable and can be recorded through the electronic control unit and host computer. At least parameterized control of injection pulse width, injection interval, and injection voltage can be achieved. At the same time, online monitoring and recording of fuel injection flow can be achieved, which facilitates quantitative comparison of different nozzle structures.

[0021] 4. Wide range of temperature / pressure / back pressure conditions adaptability: Integrated heating, pressure stabilization and flow monitoring can maintain stable fuel supply and quantitative traceability under varying fuel temperature and injection pressure conditions; and optional constant volume spring can realize a controllable back pressure environment, achieving stable fuel injection and rapid switching under a wide range of fuel temperature, injection pressure and back pressure.

[0022] 5. Modular structure, easy maintenance and scalability: Each module can be upgraded and replaced independently; it does not rely on specific model-specific parts and is suitable for long-term, repeated use and continuous iteration in the laboratory. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1A schematic diagram of the composition of a nozzle-replaceable fuel injection system for a constant volume bomb experiment provided in an embodiment of this application; Figure 2 This is a partial cross-sectional schematic diagram of a fuel injection device provided in an embodiment of this application; Figure 3 This is a cross-sectional schematic diagram of a fuel injection device provided in an embodiment of this application; Figure 4 This is a schematic diagram of a fuel injection device without a pressure plate, provided in an embodiment of this application. Figure 5 This is a schematic diagram of the structure of an adapter provided in an embodiment of this application; Figure 6 A half-sectional view of an adapter provided in an embodiment of this application; Figure 7 This is a schematic diagram of a detachable nozzle provided in an embodiment of this application, wherein (a) is a structural schematic diagram of the detachable nozzle, and (b) is a cross-sectional schematic diagram of the detachable nozzle; Figure 8 A schematic flowchart illustrating an experimental method based on a nozzle-replaceable fuel injection system for a constant-volume projectile experiment, provided for an embodiment of this application. Explanation of reference numerals in the attached drawings: 1 is the fuel tank; 2 is the first control valve; 3 is the gas-liquid booster pump; 4 is the flow meter; 5 is the solenoid valve; 6 is the detachable nozzle; 7 is the electronic control unit; 8 is the host computer; 9 is the volumetric projectile body; 91 is the volumetric projectile shell; 92 is the volumetric projectile base; 93 is the viewing window; 94 is the first connecting block; 941 is the first snap-fit ​​part; 942 is the first connecting part; 95 is the second connecting block; 951 is the second snap-fit ​​part; 952 is the second connecting part; 96 is the first connecting gasket; 97 is the first side cover; 98 is the first circular through hole; 99 is the fixing snap-fit ​​groove; 910 is the third connecting block; 9101 is the third snap-fit ​​part; 9102 is the third connecting part; 911 is the fourth connecting block; 9111 is the fourth snap-fit ​​part; 9112 is the fourth connecting part; 912 is the second connecting gasket; 913 is the second side cover. Plate, 914 is the second circular through hole, 10 is the adapter, 101 is the mounting part, 102 is the fixing part, 103 is the arc-shaped adjustment slot, 104 is the mounting cavity, 105 is the positioning shoulder, 106 is the stepped through groove, 11 is the nitrogen cylinder, 12 is the vacuum pump, 13 is the sealing element, 14 is the clamping plate, 15 is the pressure table, 151 is the straight through hole, 152 is the internal thread part, 16 is the oil pipeline, 17 is the first electric heating tube, 18 is the first K-type thermocouple, 19 is the second electric heating tube, 20 is the second K-type thermocouple, 21 is the pressure sensor, 22 is the third K-type thermocouple, 23 is the main air pipeline, 24 is the first branch air pipeline, 25 is the second branch air pipeline, 26 is the second control valve, 27 is the third control valve, 28 is the fourth control valve, 29 is the fuel injection device, 30 is the nitrogen inlet, and 31 is the exhaust port. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The terms "comprising" and "having," and any variations thereof, in the embodiments and drawings of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0027] This application discloses a replaceable nozzle fuel injection system for constant volume bomb experiments. It employs a modular design combining a solenoid valve and a detachable nozzle. The detachable nozzle is installed at the solenoid valve outlet via a detachable mechanical connection structure, supporting rapid replacement of different nozzle structures. Simultaneously, a specific adapter structure achieves coaxial integration and sealing between the solenoid valve and the constant volume bomb. These will be described in detail below.

[0028] Figure 1 – Figure 7 A nozzle-replaceable fuel injection system for a constant-volume projectile experiment is shown according to an embodiment of this application. Figure 1 – Figure 7 As shown, the system mainly includes: an oil circuit module, an injection control module, a constant volume projectile module, and an air circuit module.

[0029] Specifically, the fuel system module includes a heating device and, in sequence, a fuel tank 1, a first control valve 2, a gas-liquid booster pump 3, and a flow meter 4. The fuel tank 1, the gas-liquid booster pump 3, and the flow meter 4 are all connected via fuel line pipes 16. The first control valve 2 is located on the fuel line pipe 16 between the fuel tank 1 and the gas-liquid booster pump 3, thereby providing the system with fuel at a preset pressure, flow rate, and temperature through the fuel system module. The fuel tank 1 stores fuel and transmits it through the fuel line pipes 16. The main function of the fuel line pipes 16 is to transmit a high-pressure liquid jet; the liquid flow through the pipes forms a high-pressure jet, and it can also modify fuel properties, such as by using biomass fuels or clean fuels as alternative fuels. The first control valve 2 controls the opening and closing of the fuel line pipe 16 between the fuel tank 1 and the gas-liquid booster pump 3. The gas-liquid booster pump 3 is a key component for increasing fuel pressure; driven by an external air source, it boosts the fuel from the fuel tank 1 to the set pressure required for the experiment. The gas-liquid booster pump 3 supports a wide range of pressure regulation, meeting the needs of different injection conditions from low to high pressure, ensuring that the fuel has sufficient kinetic energy to achieve effective atomization upon injection. Simultaneously, the integrated design of the gas-liquid booster pump 3 and the fuel circuit reduces the risk of external connections and leaks, improving the system's compactness and reliability. A flow meter 4 is installed downstream of the gas-liquid booster pump 3 and upstream of the fuel injection device 29 (i.e., the core device for the injection experiment, consisting of the heating device, solenoid valve 5, detachable nozzle 6, constant volume ejector body 9, and its connected adapter 10), used to monitor and record the transient and cumulative fuel flow rate in real time. This flow meter 4 features high precision and rapid response, accurately measuring fuel consumption under different injection parameters, providing a quantitative comparison of the atomization efficiency and flow characteristics of different nozzle structures. Furthermore, the heating device is used to heat the fuel entering the fuel injection device 29 and monitor its temperature in real time.

[0030] The fuel circuit module is installed in the fuel circuit of the fuel injection system. The high-pressure room temperature liquid fuel stored in the fuel tank 1 will first pass through the gas-liquid booster pump 3 in the fuel circuit pipeline 16 to increase the pressure, and then pass through the flow meter 4 to measure the flow rate after boosting. Then it enters the fuel injection device 29, and then the fuel that has been preheated and boosted to the set state is injected into the constant volume bomb in the set back pressure environment according to the set injection parameters and is broken and atomized.

[0031] The injection control module includes a solenoid valve 5, a detachable nozzle 6, an electronic control unit 7, and a host computer 8. The detachable nozzle 6 is mounted to the outlet end of the solenoid valve 5 via a detachable mechanical connection structure. The solenoid valve 5 is electrically connected to the host computer 8 via the electronic control unit 7. Fuel from the fuel circuit module is injected through the solenoid valve 5 and then through the detachable nozzle 6 according to preset injection parameters. Furthermore, a sealing gasket (not shown in the figure) is sandwiched between the solenoid valve 5 and the detachable nozzle 6 to ensure sealing and axial positioning between them. The coaxiality between the solenoid valve 5 and the detachable nozzle 6 is also ensured through the machining process of the mechanical connection structure. The preset injection parameters include injection pulse width, injection interval, and injection voltage (also known as drive voltage). In addition, the solenoid valve 5 is a normally closed solenoid valve. When energized, the valve core actuates to open the fuel circuit between the detachable nozzle 6 and the fuel circuit module, allowing fuel to be injected through the nozzle under pressure differential. When de-energized, the fuel circuit between the detachable nozzle 6 and the fuel circuit module is closed by spring force. The solenoid valve 5 is the core component controlling the timing and action of fuel injection. It receives commands from the host computer 8 via the electronic control unit 7, enabling precise adjustment of multiple parameters such as injection pulse width, injection interval, and drive voltage. The valve body outlet has a standard threaded interface, supporting direct or adapter connection to various detachable nozzles 6, ensuring flexibility and consistency in injection control. The solenoid valve 5 is connected to the electronic control unit 7 via a control signal line, and the electronic control unit 7 is connected to the host computer 8 via a data line. The electronic control unit 7 is configured to receive control commands from the host computer 8 and control the on / off state of the solenoid valve 5 accordingly. This system can directly control the automatic opening and closing of the solenoid valve 5 and continuous injection from the host computer 8, changing the injection pulse width, injection interval, and injection voltage of the solenoid valve 5, thereby achieving flexible and variable injection through the host computer 8 and the electronic control unit 7.

[0032] The volumetric cartridge module includes a volumetric cartridge body 9 and an adapter 10 connected thereto. A solenoid valve 5 is installed at the top opening of the volumetric cartridge body 9 via the adapter 10. The three components cooperate to form a coaxial sealing structure. When the solenoid valve 5 is installed on the volumetric cartridge body 9 via the adapter 10, the detachable nozzle 6 connected to the solenoid valve 5 is located in the cavity of the volumetric cartridge body 9. In some embodiments, the volumetric cartridge body 9 includes a volumetric cartridge housing 91, a volumetric cartridge base 92, and a viewing window 93. Two viewing windows 93 are symmetrically arranged on the side wall of the volumetric cartridge housing 91 along its radial direction. The volumetric cartridge base 92 is located at one end of the volumetric cartridge housing 91 along its central axis. The solenoid valve 5 and the detachable nozzle 6 are located at the other end of the volumetric cartridge housing 91 along its central axis via the adapter 10. Sealing elements 13 are provided between the solenoid valve 5 and the adapter 10, between the adapter 10 and the volumetric cartridge housing 91, and between the volumetric cartridge housing 91 and the volumetric cartridge base 92, to jointly enclose and form a sealing structure with an internal cavity. The constant-volume projectile body 9 provides a sealed, controllable, and optically measurable experimental environment for the fuel spray and atomization process. It consists of a constant-volume projectile shell 91 and a constant-volume projectile base 92, with quartz viewing windows 93 on both sides for easy visualization of the spray pattern using high-speed photography, laser diagnostics, and other optical methods. Furthermore, the constant-volume projectile body 9 is connected to a nitrogen cylinder 11 and a vacuum pump 12 via a nitrogen inlet 30 and an exhaust port 31, respectively, enabling precise back pressure control over a wide range from vacuum to high pressure. This simulates the gas environment inside a real engine cylinder or under specific operating conditions, supporting basic spray research and performance evaluation. The adapter 10 is the core component in the fuel injection device 29 that enables the installation and fixation of the solenoid valve 5 and the sealing of the constant-volume projectile environment. It has a mounting cavity 104 that matches the solenoid valve 5 and is securely locked with bolts to suppress injection vibration. As the top sealing interface structure of the constant-volume projectile, the adapter 10 is connected to a flange and pressed against a sealing ring to ensure the long-term stability and reliability of the back pressure environment inside the constant-volume projectile.

[0033] The gas path module includes a nitrogen cylinder 11 and a vacuum pump 12, both connected to the cavity of the constant-volume projectile body 9, to regulate the back pressure of the projectile. The nitrogen cylinder 11 also provides a gas source for the gas-liquid booster pump 3. The nitrogen cylinder 11 stores nitrogen, providing it to the cavity of the constant-volume projectile body 9 to regulate the back pressure environment inside the projectile, and also providing a gas source for the gas-liquid booster pump 3. The vacuum pump 12 is mainly used to regulate the back pressure environment inside the constant-volume projectile. Connected to the exhaust port 31 on the side of the projectile, the vacuum pump 12 can extract gas from the projectile, achieving a wide range of back pressure conditions from atmospheric pressure to vacuum, simulating the spray behavior under low pressure in an engine cylinder or in special environments. The vacuum pump 12, used in conjunction with the intake valves (i.e., the second control valve 26 and the fourth control valve 28), can quickly and accurately establish and maintain the target back pressure, ensuring the consistency and repeatability of the experimental environment.

[0034] In some embodiments, such as Figure 2 , Figure 3 , Figure 5 and Figure 6 As shown, the adapter 10 includes an integrally formed mounting part 101 and a fixing part 102. The mounting part 101 is mainly used for mounting the solenoid valve 5, and the fixing part 102 is mainly used for fixing the adapter 10 to the volume-regulating cartridge body 9. Specifically, the mounting part 101 has a cylindrical structure, and the fixing part 102 has a ring-shaped structure. The fixing part 102 is sleeved on the end of the mounting part 101 away from the volume-regulating cartridge body 9. The mounting part 101 is embedded in the top opening of the volume-regulating cartridge body 9, and the fixing part 102 abuts against the top end face of the volume-regulating cartridge body 9. Two arc-shaped adjustment slots 103 are symmetrically provided on the fixing part 102. The arc-shaped adjustment slots 103 provide bolt mounting positions for the bolt connection between the adapter 10 and the volume-regulating cartridge body 9. A mounting cavity 104 is provided on the end face of the mounting part 101 away from the volume-regulating bullet body 9 to provide a mounting position for the solenoid valve 5. A positioning shoulder 105 is provided on the inner wall of the mounting cavity 104 to enable quick positioning and installation of the solenoid valve 5. The shape and size of the mounting cavity 104 and the positioning shoulder 105 match the shape and size of the solenoid valve 5. Additionally, a stepped through groove 106 is provided on the bottom end face of the mounting cavity 104, connecting to the cavity of the volume-regulating bullet body 9. The stepped through groove 106 provides a positioning mounting position for the detachable nozzle 6. Furthermore, the volume-regulating bullet module also includes a clamping plate 14. The solenoid valve 5 is housed within the mounting cavity 104 and abuts against the positioning shoulder 105 for positioning. The clamping plate 14 is fastened to the end face of the mounting part 101 away from the volume-regulating bullet body 9 by bolts, axially pressing and fixing the solenoid valve 5 within the mounting cavity 104. Simultaneously, the detachable nozzle 6 is fixed through the stepped through groove 106 and passes into the cavity of the volume-regulating bullet body 9. In addition, the mounting part 101 is embedded in the top opening of the constant volume cartridge housing 91 and is bolted to the constant volume cartridge housing 91 through the two arc-shaped adjustment slots 103 of the fixing part 102.

[0035] In other embodiments, such as Figure 1 , Figure 2 and Figure 3As shown, the constant volume spring module also includes a pressure table 15. The pressure table 15 has a through hole 151 extending through both ends. The two ends of the through hole 151 are respectively provided with internal threads 152 for screwing on the ferrule connector (not shown in the figure). The ferrule connector is connected to the oil circuit pipe 16 of the oil circuit module and the inlet of the solenoid valve 5 respectively. Furthermore, the heating device includes two first electric heating tubes 17, a first K-type thermocouple 18, two second electric heating tubes 19, and a second K-type thermocouple 20. The two first electric heating tubes 17 are symmetrically embedded inside the pressure platform 15 about the central axis of the pressure platform 15, and are used to heat the fuel flowing in the through hole 151. The first K-type thermocouple 18 is installed inside the pressure platform 15 and is used to monitor the temperature of the fuel flowing in the through hole 151 in real time. The two second electric heating tubes 19 are symmetrically embedded inside the fixing part 102 about the central axis of the mounting cavity 104, and the second K-type thermocouple 20 is installed inside the fixing part 102, and is used to provide compensatory heating and real-time temperature monitoring for the fuel entering the detachable nozzle 6. By embedding the electric heating tubes and thermocouples inside the adapter 10, i.e., close to the detachable nozzle 6, auxiliary heating and real-time temperature measurement of the flowing fuel can be performed, improving the overall temperature control accuracy of the system. The pressure station 15 is the main module for fuel heating and temperature monitoring. It integrates a first electric heating element 17 and a first K-type thermocouple 18, located between the fuel flow meter 4 and the solenoid valve 5. It is responsible for heating the flowing fuel and measuring its temperature in real time, ensuring that the fuel reaches and stabilizes at the set temperature value before injection. Furthermore, in this embodiment, the pressure station 15 uses a compression fitting and a straight-through adapter to connect to the upstream and downstream fuel lines, ensuring a tight seal while facilitating disassembly and maintenance.

[0036] In other embodiments, such as Figure 2 , Figure 3 and Figure 4As shown, the constant-volume projectile body 9 also includes four first connecting blocks 94, four second connecting blocks 95, four first connecting gaskets 96, and two first side cover plates 97. The constant-volume projectile shell 91 is rectangular, and each of its four side walls is provided with a first circular through hole 98. Each first circular through hole 98 is provided with a first connecting block 94, a second connecting block 95, and a first connecting gasket 96. In detail, the first connecting block 94 includes a first latching portion 941 and a first connecting portion 942. The first latching portion 941 is an annular plate structure, and the first connecting portion 942 is a cylindrical ring structure. The first connecting portion 942 is integrally connected to one side of the first latching portion 941. The second connecting block 95 includes a second latching portion 951 and a second connecting portion 952. The second latching portion 951 is an annular plate structure, and the second connecting portion 952 is a cylindrical ring structure. The second latching portion 951 is integrally connected to one end of the inner sidewall of the second connecting portion 952. The inner and outer diameters of the first connecting portion 942 and the second connecting portion 952 are the same, and the outer diameter of the first connecting portion 942 and the second connecting portion 952 is the same as the diameter of the first circular through hole 98. The inner diameter of the first latching portion 941 is the same as the inner diameter of the second latching portion 951, and the outer diameter of the first latching portion 941 is larger than the first circular through hole 98. The diameter of the first connecting part 942 and the length of the second connecting part 952 are the same as the length of the first circular through hole 98. The second connecting part 952 and the first connecting part 942 are bolted together. The four second connecting blocks 95 are respectively connected to the four first connecting blocks 94 one by one. The first connecting gasket 96 is disposed between the second connecting part 952 and the first connecting part 942. The first snap-fit ​​part 941 and the second snap-fit ​​part 951 form a fixed snap-fit ​​groove 99 for snapping the first side cover plate 97 or the viewing window 93. The first connecting part 942 and the second connecting part 952 are embedded in the first circular through hole 98 and are bolted to the volume-regulating bullet body 9 through the first snap-fit ​​part 941. The first connecting block 94 and the second connecting block 95 are fixedly installed on the volume-regulating bullet body 9. A sealing element 13 is also provided between the first connecting block 94 and the volume-regulating bullet body 9. Thus, the first side cover 97 and the viewing window 93 can be detachably installed through the setting of the first connecting block 94 and the second connecting block 95, and the sealing of the internal cavity of the constant volume bullet body 9 is ensured through the setting of the first connecting gasket 96 and the sealing element 13.

[0037] In this embodiment, the constant volume projectile module further includes a pressure sensor 21 and a third K-type thermocouple 22. The pressure sensor 21 and the third K-type thermocouple 22 are both mounted on one of the first side cover plates 97. The pressure sensor 21 is used to monitor the back pressure of the constant volume projectile in real time, and the third K-type thermocouple 22 is used to monitor the temperature inside the cavity of the constant volume projectile body 9 in real time.

[0038] Furthermore, the constant-volume projectile body 9 also includes a third connecting block 910, a fourth connecting block 911, a second connecting gasket 912, and a second side cover plate 913. A second circular through hole 914 is provided on the bottom wall of the constant-volume projectile casing 91 to provide mounting positions for the third connecting block 910, the fourth connecting block 911, the second connecting gasket 912, and the second side cover plate 913. Specifically, the third connecting block 910 includes a third latching portion 9101 and a third connecting portion 9102. The third latching portion 9101 is an annular plate structure, and the third connecting portion 9102 is a cylindrical ring structure. The third connecting portion 9102 is integrally connected to one side of the third latching portion 9101. The fourth connecting block 911 includes a fourth latching portion 9111 and a fourth connecting portion 9112. The fourth latching portion 9111 is an annular plate structure, and the fourth connecting portion 9112 is a cylindrical ring structure. The fourth engaging portion 9111 is integrally connected to one end of the inner wall of the fourth connecting portion 9112. The inner and outer diameters of the third connecting portion 9102 and the fourth connecting portion 9112 are the same, and the outer diameters of the third connecting portion 9102 and the fourth connecting portion 9112 are the same as the diameter of the second circular through hole 914. The inner diameter of the third engaging portion 9101 is the same as the inner diameter of the fourth engaging portion 9111, and the outer diameter of the third engaging portion 9101 is larger than the diameter of the second circular through hole 914. The sum of the lengths of the third connecting part 9102 and the fourth connecting part 9112 is not greater than the length of the second circular through hole 914. The fourth connecting part 9112 and the third connecting part 9102 are bolted together. The fourth connecting block 911 is connected to the third connecting block 910. The second connecting gasket 912 is disposed between the fourth connecting part 9112 and the third connecting part 9102. A fixed snap-fit ​​groove 99 is also formed between the third snap-fit ​​part 9101 and the fourth snap-fit ​​part 9111 for snapping the second side cover plate 913. The third connecting part 9102 and the fourth connecting part 9112 are embedded in the second circular through hole 914 and bolted to the volume-regulating bullet body 9 through the third snap-fit ​​part 9101. The third connecting block 910 and the fourth connecting block 911 are fixedly installed on the volume-regulating bullet body 9. A sealing element 13 is also provided between the third connecting block 910 and the volume-regulating bullet body 9. The volume-regulating bullet base 92 covers the bottom of the volume-regulating bullet shell 91. Furthermore, the second side cover plate 913 can be detachably installed by setting the third connecting block 910 and the fourth connecting block 911, and the sealing of the internal cavity of the volume-fixed projectile body 9 is ensured by setting the second connecting gasket 912 and the sealing element 13. Thus, the setting of the third connecting block 910, the fourth connecting block 911 and the second side cover plate 913 makes it easier to replace and repair the components inside the cavity of the volume-fixed projectile body 9.

[0039] In other embodiments, such as Figure 1As shown, the gas path module also includes a main gas path pipe 23, a first branch gas path pipe 24, a second branch gas path pipe 25, a second control valve 26, a third control valve 27, and a fourth control valve 28. One end of the main gas path pipe 23 is connected to the outlet of the nitrogen cylinder 11, and the other end of the main gas path pipe 23 is connected to one end of the first branch gas path pipe 24 and one end of the second branch gas path pipe 25, respectively. The other end of the first branch gas path pipe 24 is connected to the inlet of the gas-liquid booster pump 3, and the other end of the second branch gas path pipe 25 is connected to the nitrogen inlet 30 of the constant volume bomb body 9. The second control valve 26 is installed on the main gas path pipe 23, the third control valve 27 is installed on the first branch gas path pipe 24, and the fourth control valve 28 is installed on the second branch gas path pipe 25.

[0040] In some specific implementation processes, the detachable mechanical connection structure includes mutually mating external threads and internal threads. The external thread is set on the outer side wall of the detachable nozzle 6, and the internal thread is set on the outlet end of the solenoid valve 5. The detachable nozzle 6 and the outlet end of the solenoid valve 5 are threadedly connected.

[0041] In some other specific implementations, the detachable mechanical connection structure includes mutually mating external and internal threads, as well as a bayonet protrusion and a bayonet groove. The external thread is provided on the outer side wall of the detachable nozzle 6, and the internal thread is provided on the inner circumferential surface of the outlet end of the solenoid valve 5. The detachable nozzle 6 is threadedly connected to the outlet end of the solenoid valve 5, and the bayonet protrusion is provided on the inner circumferential surface of the outlet end of the solenoid valve 5, and the bayonet groove is provided on the outer side wall of the detachable nozzle 6. When the detachable nozzle 6 is tightened, the bayonet protrusion and the bayonet groove engage.

[0042] In some other specific implementations, the detachable mechanical connection structure includes mutually mating external and internal threads, as well as an external conical surface and an internal conical surface. The external conical surface is located on the outer side wall of the detachable nozzle 6, and the external thread is located on the external conical surface. The internal conical surface is located on the inner circumferential surface of the outlet end of the solenoid valve 5, and the internal thread is located on the internal conical surface. The detachable nozzle 6 and the outlet end of the solenoid valve 5 are axially locked through the external and internal threads, and the external conical surface and the internal conical surface abut and seal.

[0043] In other specific implementations, the detachable mechanical connection structure includes mating external and internal threads, a split clamping ring, and a locking nut. The split clamping ring is located at the outlet end of the solenoid valve 5 and is radially divided into at least two arc-shaped lobes. The arc-shaped lobes enclose a clamping hole that accommodates the detachable nozzle 6. The internal thread is located on the inner wall of the arc-shaped lobes, and the external thread is located on the outer wall of the detachable nozzle 6. The detachable nozzle 6 is threadedly connected to the split clamping ring, and the locking nut is threadedly connected to the outside of the split clamping ring. When the locking nut is tightened, it axially pushes the arc-shaped lobes to contract radially to clamp the detachable nozzle 6.

[0044] In this embodiment, the fuel system module mainly includes a fuel tank 1, a fuel line 16, a gas-liquid booster pump 3, a flow meter 4, and a heating device. The fuel to be tested is typically stored in the high-pressure, room-temperature fuel tank 1. During the injection experiment, the valve of the fuel tank 1 is opened. The fuel flows from the fuel line 16 through the first control valve 2, and then is pressurized to a set pressure by the gas-liquid booster pump 3. It then enters the flow meter 4 for flow measurement and reaches the fuel injection device 29. The fuel injection device 29 has a fuel heating function and can also measure the temperature of the fuel before injection. When the set parameters are reached, the fuel is injected into the constant-volume cartridge through the nozzle according to a certain injection pulse width and interval. The high-pressure fuel liquid is ejected in a jet manner, forming a jet or spray.

[0045] The heating device is responsible for heating the fuel in the fuel circuit module and measuring its real-time temperature to ensure the fuel injection temperature reaches the set value. Its main components and functions are concentrated in the pressure station 15. The heating device includes a first electric heating element 17 and a first K-type thermocouple 18 within the pressure station 15. Furthermore, to improve the heating rate and temperature measurement accuracy, a second electric heating element 19 and a second K-type thermocouple 20 are also arranged near the injection inlet within the adapter 10 to provide compensating heating and temperature measurement. The upstream of the pressure station 15 is connected to the fuel line via a compression fitting to a straight-through threaded connection, while the downstream of the pressure station 15 is connected to the fuel line via a straight-through to a compression fitting threaded connection to ensure connection reliability and airtightness under high-pressure conditions. The solenoid valve 5 and the removable nozzle 6 are the main devices for fuel injection. The fuel line 16 is connected upstream of the solenoid valve 5 via a compression fitting to a straight-through connector, while the downstream of the solenoid valve 5 is connected to the removable nozzle 6 via a threaded connection. As the solenoid valve 5 opens and closes, fuel is injected through the removable nozzle 6 under the action of pressure differential, thus atomizing. Figure 7 As shown, by ensuring the threaded interface size of the detachable nozzle 6, and by replacing the detachable nozzle 6 with one of different structures or types, rapid switching of different nozzle spray characteristics can be achieved. The solenoid valve 5 is connected to the host computer 8 via the electronic control unit 7. The host computer 8 transmits data to the electronic control unit 7, and the electronic control unit 7 transmits control signals to the solenoid valve 5. This enables direct control of the automatic opening and closing of the solenoid valve 5 and continuous spraying on the host computer 8, changing the spray pulse width, spray interval, and spray voltage of the solenoid valve 5 to achieve flexible and variable spraying.

[0046] The constant-volume projectile device serves as a test environment for fuel injection experiments, providing a sealed, controllable, and optically measurable back pressure environment for the fuel injection and atomization process. Specifically, it consists of a constant-volume projectile housing 91, a constant-volume projectile base 92, and a viewing window 93. The internal back pressure is precisely set and stably maintained through a nitrogen inlet 30, an exhaust port 31, and a pressure sensor 21, thereby simulating spray behavior under engine cylinder conditions or specific pressure conditions. Simultaneously, quartz windows (viewing windows 93) are designed on both sides of the constant-volume projectile housing 91, allowing for the direct placement of optical measurement equipment such as high-speed cameras and laser diagnostics, enabling visual observation and quantitative analysis of spray morphology, particle size distribution, and the evaporative combustion process.

[0047] The solenoid valve 5 is preferably installed in the adapter 10 in an embedded manner. The adapter 10 is then connected to the top of the volume-regulating cartridge in a fitted manner, forming a coaxial integrated installation and sealing structure of the valve body, adapter, and volume-regulating cartridge. Specifically, the adapter 10 is provided with a mounting cavity 104 and a positioning shoulder 105 that match the shape of the solenoid valve 5. After the solenoid valve 5 is installed, it is pre-tightened and locked by the clamping plate 14 with bolts, so that the solenoid valve 5 maintains axial position stability and suppresses vibration and loosening under injection pulse load. At the same time, an annular sealing ring is used to seal the end face between the solenoid valve 5 and the adapter 10 to isolate the high-pressure fuel passage from the outside. The adapter 10 is connected to the top of the volume-regulating cartridge by bolts and is provided with an annular sealing ring, so that the back pressure space inside the volume-regulating cartridge is reliably isolated from the outside. Thus, the high-pressure fuel sealing and the back pressure sealing of the volume-regulating cartridge are completed in the same coaxial assembly system, reducing the sealing surface dispersion and assembly deviation caused by traditional multi-stage joints, and realizing the integrated configuration of the solenoid valve 5 and the volume-regulating cartridge, as well as the integrated sealing of the valve body, adapter, and volume-regulating cartridge.

[0048] The detachable nozzle 6 supports modular replacement of nozzles with different structures and types. These detachable nozzles 6 can be categorized by the number of nozzle holes (single-hole, multi-hole) or by the internal structure of the nozzle holes (straight-hole, countersunk, stepped-hole, or other types). Different structures correspond to different flow separation and atomization mechanisms, resulting in different liquid ejection methods and atomization processes, which significantly influence the final atomization characteristics. In a preferred embodiment of this application, multiple detachable nozzles 6 can be replaced modularly. Quick replacement can be achieved by ensuring the specifications of the detachable nozzle 6 connection port or by connecting a suitable adapter according to the experimental setup requirements. Installation and removal of the detachable nozzle 6 only require screwing it into or out of the corresponding threaded hole. A sealing section ensures reliable sealing under high-pressure jet conditions, thereby enabling rapid switching and reconfigurable assembly of different nozzle structures.

[0049] The gas circuit module mainly consists of a nitrogen cylinder 11, a vacuum pump 12, a main gas circuit pipe 23, a first branch gas circuit pipe 24, a second branch gas circuit pipe 25, a second control valve 26, a third control valve 27, and a fourth control valve 28. One side of the nitrogen cylinder 11 is connected to a gas-liquid booster pump 3, which provides the gas source and is responsible for pressurizing the fuel. The other side of the nitrogen cylinder 11 is connected to the nitrogen inlet 30 on the side of the constant-volume bomb, and the air intake can be manually controlled. Simultaneously, the exhaust port 31 installed on the side of the constant-volume bomb is connected to the vacuum pump 12, and the exhaust can be manually controlled. A high back pressure environment can be achieved by filling the sealed constant-volume bomb with nitrogen, and a vacuum environment can be achieved by evacuating the gas, thus establishing a flexible and controllable back pressure environment within the constant-volume bomb. Nitrogen gas is stored in a high-pressure, room-temperature nitrogen cylinder 11. Two pressure-reducing valves, namely the second control valve 26 and the fourth control valve 28, are installed in the gas pipeline between the nitrogen cylinder 11 and the nitrogen inlet 30 of the constant-volume bomb. These valves reduce the nitrogen pressure in the inlet pipeline to a lower level before it enters the constant-volume bomb through the nitrogen inlet 30. This not only alters the internal gas environment of the constant-volume bomb but also increases the back pressure to a certain extent. The nitrogen in the gas pipeline can also pass through valves directly into the gas-liquid booster pump 3, providing it with a gas source. The nitrogen cylinder 11 is connected to the nitrogen inlet 30 of the constant-volume bomb, and the vacuum pump 12 is connected to the exhaust port 31 of the constant-volume bomb. Opening the valve between the nitrogen cylinder 11 and the nitrogen inlet 30 allows nitrogen to directly enter the constant-volume bomb with its lower environmental pressure, thereby increasing its internal environmental pressure. Starting the vacuum pump 12 and opening its exhaust port 31 reduces the internal environmental pressure of the constant-volume bomb.

[0050] The above describes the various components and their connections in the replaceable nozzle fuel injection system and experimental method for constant volume projectile experiments provided in this embodiment. The following section will discuss these components in conjunction with... Figure 1 – Figure 7 The complete structure and working principle of the nozzle-replaceable fuel injection system used in constant volume bomb experiments are described in detail.

[0051] This embodiment provides a fuel injection device with a variable nozzle structure, which can be used to systematically study the fuel spray atomization characteristics and combustion performance of different nozzles under a wide range of oil temperature, pressure, and back pressure conditions. The device adopts a modular integrated design, in which fuel pressurization, heating, flow monitoring, and controllable injection functions are coordinated and unified. A quick-change interface structure enables convenient replacement and precise positioning of the nozzle components. This device mainly involves a fuel supply and control module, a parameter-adjustable and precise electromagnetic injection module, and an optional optical constant volume spring back pressure module, supporting comparative experiments of different nozzle structures under precise control and simultaneous monitoring of multiple parameters.

[0052] High-pressure, ambient-temperature fuel oil flows from fuel line 16, first passing through a valve, then being pressurized to a set pressure by the gas-liquid booster pump 3. It then enters the flow meter 4 for flow measurement, followed by initial heating and temperature measurement at the pressure plate 15. Upon reaching the solenoid valve 5, it undergoes a second heating and temperature measurement via an electric heating element and thermocouple mounted on the adapter 10. With the opening and closing of the solenoid valve 5, the high-pressure fuel oil, under the influence of the pressure difference, is sprayed through a nozzle connected to the solenoid valve 5, interacting with the ambient gas within the constant-volume chamber, resulting in atomization and fragmentation. Ensuring that the nozzle thread interface specifications are identical allows for the replacement of nozzles with different structures or types, enabling rapid switching between different nozzle spray characteristics.

[0053] When the temperature and pressure of the fuel in solenoid valve 5 reach the set value, the valve core remains closed under the action of spring force because solenoid valve 5 is de-energized, thus solenoid valve 5 is in a normally closed state, and fuel cannot pass through. When solenoid valve 5 is energized, the coil generates electromagnetic force, attracting the valve core to move against the spring force, solenoid valve 5 is in a normally open state, and fuel can flow. Solenoid valve 5 is connected to the host computer 8 through electronic control unit 7, and its injection mode (manual or automatic), injection frequency, injection pulse width, injection interval, and drive voltage can all be directly controlled by the host computer 8. The outlet of solenoid valve 5 has a fixed internal thread structure, and any nozzle with the same external thread structure or a nozzle with a conversion interface can be directly connected to solenoid valve 5, achieving high-precision and wide-range adjustment of injection parameters for nozzles of any structure.

[0054] After passing through the pressure reducing valve, part of the nitrogen gas is directly connected to the gas-liquid booster pump 3 to provide a gas source for pressurizing the fuel, and the other part is connected to the side interface of the constant volume bomb to pressurize the constant volume bomb and change its internal environment. Both pipelines are controlled by valves, allowing for on / off switching. The vacuum pump 12 is connected to another interface on the side of the constant volume bomb to create a vacuum and low-pressure environment inside the bomb. The direct intake of nitrogen gas and the evacuation of vacuum pump 12 can conveniently and efficiently change the environment and back pressure inside the constant volume bomb, while also solving the problem of environmental changes inside the constant volume bomb caused by repeated fuel injection experiments. The switches for nitrogen gas intake and vacuum pump 12 are directly integrated into the control panel via relevant wiring, further improving the convenience of the experiment.

[0055] A constant-volume bomb confines the interaction between fuel and ambient gases within its internal space. The bomb maintains a stable internal temperature and modulates the pressure of the ambient gases, thus enabling the interaction between different fuel temperatures and pressures and varying ambient gas pressures. The spatial arrangement within the constant-volume bomb supports testing techniques such as backlighting, laser-induced fluorescence, Mie scattering imaging, and schlieren imaging.

[0056] Based on the replaceable fuel injection system for constant volume projectile experiments described in the above embodiments, another embodiment of this application provides an experimental method, such as... Figure 8 As shown, the experimental method includes the following steps: S1. Thread the detachable nozzle to be tested to the outlet end of the solenoid valve, check the seal, and then open the first control valve of the fuel tank.

[0057] S2. Start the gas-liquid booster pump to boost the fuel to the preset pressure value, and at the same time start the heating device to stabilize the fuel temperature to the target temperature value.

[0058] S3. Adjust the cavity pressure of the constant volume bomb body to the preset back pressure value using a nitrogen cylinder or vacuum pump.

[0059] S4. Set the preset injection parameters of the solenoid valve via the host computer.

[0060] The preset injection parameters include injection pulse width, injection interval, and injection voltage.

[0061] S5. The solenoid valve is controlled by the electronic control unit to spray fuel into the cavity of the constant volume bomb body through the detachable nozzle for atomization experiment, and the fuel flow data is recorded by the flow meter.

[0062] S6. Determine whether to replace the detachable nozzle.

[0063] If a replacement is needed, perform the depressurization and disassembly of the original detachable nozzle, and repeat steps S1–S5; otherwise, end the experiment.

[0064] In summary, this application discloses a replaceable nozzle fuel injection system and experimental method for constant volume bomb experiments. It features a maintainable and scalable structure, with each functional module capable of independent upgrades and replacements without relying on specific models of dedicated components, making it highly suitable for long-term repeated use and continuous iteration in the laboratory. Regarding nozzle replacement, the system achieves efficient and repeatable operation. The nozzle is connected to the downstream outlet of the solenoid valve via a threaded connection, requiring only screwing in or out for replacement. Furthermore, the related connection structure effectively ensures the repeatability of the nozzle's axial position and coaxiality, significantly reducing the error risk caused by frequent injector replacements. Simultaneously, the system can support any nozzle orifice structure at low cost. Nozzles can be fabricated through simple machining or additive manufacturing, requiring only a threaded connection end for compatibility with the device, avoiding reliance on expensive dedicated commercial nozzles and long-term custom machining limitations. In terms of drive control, the solenoid valve's drive parameters are adjustable and recordable, enabling parameterized control of injection pulse width, injection interval, and drive voltage. In addition, the system is adaptable to a wide range of temperature, pressure and back pressure conditions. By integrating heating, pressure stabilization and flow monitoring functions, it can maintain stable and quantitatively traceable fuel supply under varying fuel temperature and injection pressure conditions. It can also be equipped with a constant volume cartridge to achieve a controllable back pressure environment.

[0065] It will be understood by those skilled in the art that the accompanying drawings are merely schematic diagrams of one embodiment, and the components shown in the drawings are not necessarily essential for implementing the invention. It should also be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0066] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, in the description of the embodiments of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention.

[0067] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of protection described in the claims.

Claims

1. A nozzle-replaceable fuel injection system for constant-volume projectile experiments, characterized in that, include: The fuel circuit module includes a heating device and a fuel tank, a first control valve, a gas-liquid booster pump, and a flow meter connected in sequence, for providing fuel at preset pressure, flow rate, and temperature; The injection control module includes a solenoid valve, a detachable nozzle, an electronic control unit, and a host computer. The detachable nozzle is installed at the outlet end of the solenoid valve via a detachable mechanical connection structure. The solenoid valve is electrically connected to the host computer via the electronic control unit. Fuel from the fuel circuit module is injected through the solenoid valve and then through the detachable nozzle according to preset injection parameters. The preset injection parameters include injection pulse width, injection interval, and injection voltage. The volumetric ammunition module includes a volumetric ammunition body and an adapter connected thereto. The solenoid valve is installed at the top opening of the volumetric ammunition body through the adapter. The three components cooperate to form a coaxial sealing structure, and the detachable nozzle is located in the cavity of the volumetric ammunition body. The gas path module includes a nitrogen cylinder and a vacuum pump that are respectively connected to the cavity of the constant volume bomb body to adjust the back pressure of the constant volume bomb, and the nitrogen cylinder also provides a gas source for the gas-liquid booster pump.

2. The nozzle-replaceable fuel injection system for constant-volume projectile experiments according to claim 1, characterized in that, The constant-volume projectile body includes a constant-volume projectile shell, a constant-volume projectile base, and a viewing window; two viewing windows are symmetrically arranged on the side wall of the constant-volume projectile shell along its radial direction; the constant-volume projectile base is located at one end of the constant-volume projectile shell along its central axis, and the solenoid valve and the detachable nozzle are located at the other end of the constant-volume projectile shell along its central axis via the adapter, and sealing elements are provided between the solenoid valve and the adapter, between the adapter and the constant-volume projectile shell, and between the constant-volume projectile shell and the constant-volume projectile base, so as to jointly enclose and form a sealed structure with an internal cavity.

3. The nozzle-replaceable fuel injection system for constant-volume projectile experiments according to claim 2, characterized in that, The adapter includes an integrally formed mounting part and a fixing part; the mounting part is a cylindrical structure, and the fixing part is an annular structure. The fixing part is sleeved on the end of the mounting part away from the volume-regulating cartridge body, and the fixing part has two symmetrically arranged arc-shaped adjustment slots; a mounting cavity is provided on the end face of the mounting part away from the volume-regulating cartridge body, and a positioning shoulder is provided on the inner sidewall of the mounting cavity. The shape and size of the mounting cavity and the positioning shoulder match the shape and size of the solenoid valve, and a cavity communicating with the volume-regulating cartridge body is provided on the bottom end face of the mounting cavity. The stepped through groove; the volume-regulating cartridge module also includes a clamping plate, the solenoid valve is housed in the mounting cavity and abuts against the positioning shoulder to achieve positioning, the clamping plate is fastened to the end face of the mounting part away from the volume-regulating cartridge body by bolts, axially pressing and fixing the solenoid valve in the mounting cavity, while the detachable nozzle is fixed through the stepped through groove and passes through the cavity of the volume-regulating cartridge body; the mounting part is embedded in the top opening of the volume-regulating cartridge housing and is bolted to the volume-regulating cartridge housing through the two arc-shaped adjusting slots of the fixing part; The solenoid valve is a normally closed solenoid valve. When energized, the valve core actuates to open the oil passage between the detachable nozzle and the oil passage module. When de-energized, the oil passage between the detachable nozzle and the oil passage module is closed under the action of spring force.

4. The nozzle-replaceable fuel injection system for constant-volume projectile experiments according to claim 3, characterized in that, The constant volume spring module also includes a pressure table, which has a through hole extending through both ends. The two ends of the through hole are respectively provided with internal threads for screwing in a ferrule connector. The ferrule connector is connected to the oil circuit pipeline of the oil circuit module and the inlet of the solenoid valve. The heating device includes two first electric heating tubes, a first K-type thermocouple, two second electric heating tubes, and a second K-type thermocouple. The two first electric heating tubes are symmetrically embedded inside the pressure platform about the central axis of the pressure platform, and are used to heat the fuel flowing in the through hole. The first K-type thermocouple is installed inside the pressure platform and is used to monitor the temperature of the fuel flowing in the through hole in real time. The two second electric heating tubes are symmetrically embedded inside the fixing part about the central axis of the mounting cavity, and the second K-type thermocouple is installed inside the fixing part, and is used to compensate for heating and monitor the temperature of the fuel entering the detachable nozzle in real time.

5. The nozzle-replaceable fuel injection system for constant-volume projectile experiments according to claim 2, characterized in that, The constant-volume projectile body further includes four first connecting blocks, four second connecting blocks, four first connecting gaskets, and two first side cover plates. The constant-volume projectile shell is rectangular, with a first circular through hole on each of its four side walls. Each first connecting block includes a first snap-fit ​​portion and a first connecting portion. The first snap-fit ​​portion is an annular plate structure, and the first connecting portion is a cylindrical ring structure. The first connecting portion is integrally connected to one side of the first snap-fit ​​portion. Each second connecting block includes a second snap-fit ​​portion and a second connecting portion. The second snap-fit ​​portion is an annular plate structure, and the second connecting portion is a cylindrical ring structure. The second snap-fit ​​portion is integrally connected to one end of the inner side wall of the second connecting portion. The inner and outer diameters of the first and second connecting portions are the same, and the outer diameters of the first and second connecting portions are the same as the diameter of the first circular through hole. The inner diameter of the first snap-fit ​​portion is the same as the diameter of the second snap-fit ​​portion. The inner diameters of the parts are the same, and the outer diameter of the first snap-fit ​​part is larger than the diameter of the first circular through hole. The sum of the lengths of the first connecting part and the second connecting part is the same as the length of the first circular through hole. The second connecting part and the first connecting part are bolted together. The four second connecting blocks are respectively connected to the four first connecting blocks one by one. The first connecting gasket is disposed between the second connecting part and the first connecting part. The first snap-fit ​​part and the second snap-fit ​​part form a fixed snap-fit ​​groove for snapping the first side cover plate or the viewing window. The first connecting part and the second connecting part are embedded in the first circular through hole and are bolted to the volume-regulating bullet body through the first snap-fit ​​part. The first connecting block and the second connecting block are fixedly installed on the volume-regulating bullet body. A sealing element is also provided between the first connecting block and the volume-regulating bullet body.

6. The nozzle-replaceable fuel injection system for constant-volume projectile experiments according to claim 5, characterized in that, The constant volume projectile module also includes a pressure sensor and a third type K thermocouple. The pressure sensor and the third type K thermocouple are both installed on one of the first side cover plates. The pressure sensor is used to monitor the back pressure of the constant volume projectile in real time, and the third type K thermocouple is used to monitor the temperature inside the cavity of the constant volume projectile body in real time.

7. The nozzle-replaceable fuel injection system for constant-volume projectile experiments according to claim 5, characterized in that, The constant-volume projectile body further includes a third connecting block, a fourth connecting block, a second connecting gasket, and a second side cover plate. A second circular through hole is provided on the bottom wall of the constant-volume projectile shell. The third connecting block includes a third snap-fit ​​portion and a third connecting portion. The third snap-fit ​​portion is an annular plate structure, and the third connecting portion is a cylindrical ring structure. The third connecting portion is integrally connected to one side of the third snap-fit ​​portion. The fourth connecting block includes a fourth snap-fit ​​portion and a fourth connecting portion. The fourth snap-fit ​​portion is an annular plate structure, and the fourth connecting portion is a cylindrical ring structure. The fourth snap-fit ​​portion is integrally connected to one end of the inner side wall of the fourth connecting portion. The inner and outer diameters of the third and fourth connecting portions are the same, and the outer diameter of the third and fourth connecting portions is the same as the diameter of the second circular through hole. The inner diameter of the third snap-fit ​​portion is the same as the inner diameter of the fourth snap-fit ​​portion. Furthermore, the outer diameter of the third snap-fit ​​portion is larger than the diameter of the second circular through hole, and the sum of the lengths of the third connecting portion and the fourth connecting portion is not greater than the length of the second circular through hole. The fourth connecting portion and the third connecting portion are bolted together, the fourth connecting block is connected to the third connecting block, and the second connecting gasket is disposed between the fourth connecting portion and the third connecting portion. The third snap-fit ​​portion and the fourth snap-fit ​​portion form a fixing snap-fit ​​groove for snapping the second side cover plate. The third connecting portion and the fourth connecting portion are embedded in the second circular through hole and bolted to the volume-regulating bullet body through the third snap-fit ​​portion. The third connecting block and the fourth connecting block are fixedly installed on the volume-regulating bullet body, and a sealing element is also provided between the third connecting block and the volume-regulating bullet body. The volume-regulating bullet base covers the bottom of the volume-regulating bullet shell.

8. The replaceable nozzle fuel injection system for constant volume bomb experiments according to claim 1, characterized in that, The detachable mechanical connection structure includes mating external and internal threads. The external thread is located on the outer side wall of the detachable nozzle, and the internal thread is located at the outlet end of the solenoid valve. The detachable nozzle and the outlet end of the solenoid valve are threadedly connected; or... The detachable mechanical connection structure includes mating external and internal threads, as well as a bayonet protrusion and a bayonet groove. The external thread is located on the outer side wall of the detachable nozzle, and the internal thread is located on the inner circumferential surface of the outlet end of the solenoid valve. The detachable nozzle is threadedly connected to the outlet end of the solenoid valve. The bayonet protrusion is located on the inner circumferential surface of the outlet end of the solenoid valve, and the bayonet groove is located on the outer side wall of the detachable nozzle. When the detachable nozzle is tightened, the bayonet protrusion and the bayonet groove engage. Alternatively, The detachable mechanical connection structure includes mating external and internal threads, as well as an external and internal conical surface. The external conical surface is disposed on the outer side wall of the detachable nozzle, and the external thread is disposed on the external conical surface. The internal conical surface is disposed on the inner circumferential surface of the outlet end of the solenoid valve, and the internal thread is disposed on the internal conical surface. The detachable nozzle and the outlet end of the solenoid valve are axially locked together by the external and internal threads, and the external and internal conical surfaces abut and seal against each other; or, The detachable mechanical connection structure includes mating external and internal threads, a split clamping ring, and a locking nut. The split clamping ring is located at the outlet end of the solenoid valve and is radially divided into at least two arc-shaped lobes. The arc-shaped lobes enclose a clamping hole for accommodating the detachable nozzle. The internal thread is located on the inner wall of the arc-shaped lobes, and the external thread is located on the outer wall of the detachable nozzle. The detachable nozzle is threadedly connected to the split clamping ring, and the locking nut is threadedly connected to the outside of the split clamping ring. When the locking nut is tightened, it axially pushes the arc-shaped lobes to contract radially to clamp the detachable nozzle.

9. The nozzle-replaceable fuel injection system for constant-volume projectile experiments according to claim 1, characterized in that, The gas path module further includes a main gas path pipe, a first branch gas path pipe, a second branch gas path pipe, a second control valve, a third control valve, and a fourth control valve. One end of the main gas path pipe is connected to the outlet of the nitrogen cylinder, and the other end of the main gas path pipe is connected to one end of the first branch gas path pipe and one end of the second branch gas path pipe, respectively. The other end of the first branch gas path pipe is connected to the inlet of the gas-liquid booster pump, and the other end of the second branch gas path pipe is connected to the nitrogen inlet of the constant volume bomb body. The second control valve is located on the main gas path pipe, the third control valve is located on the first branch gas path pipe, and the fourth control valve is located on the second branch gas path pipe.

10. An experimental method for a nozzle-replaceable fuel injection system for a constant-volume projectile experiment based on any one of claims 1-9, characterized in that, The experimental methods include: S1. Connect the detachable nozzle to be tested to the outlet end of the solenoid valve, check the seal, and then open the first control valve of the fuel tank; S2. Start the gas-liquid booster pump to boost the fuel to the preset pressure value, and at the same time start the heating device to stabilize the fuel temperature to the target temperature value; S3. Adjust the cavity pressure of the constant volume bomb body to the preset back pressure value using a nitrogen cylinder or vacuum pump; S4. Set the preset injection parameters of the solenoid valve via the host computer; wherein, the preset injection parameters include injection pulse width, injection interval and injection voltage; S5. The solenoid valve is controlled by the electronic control unit to spray fuel into the cavity of the constant volume bomb body through the detachable nozzle for atomization experiment, and the fuel flow data is recorded by the flow meter. S6. Determine whether to replace the detachable nozzle. If so, perform the depressurization and disassembly of the original detachable nozzle, and repeat steps S1–S5. Otherwise, end the experiment.

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