A device and method for measuring gas phase ignition delay time of self-igniting propellant

Abstract

This invention discloses a device and method for measuring the gas-phase ignition delay time of a self-igniting propellant. An aluminum diaphragm divides the combustion reaction chamber of the self-igniting propellant into two chambers: the first chamber is located near the compression cylinder of a rapid compressor, and the second chamber is located further away. Rapid compression by a piston heats and pressurizes the gas inside the first chamber. When the gas pressure in the first chamber reaches a certain level, the aluminum diaphragm ruptures under the pressure difference. The gases in the two chambers rapidly and uniformly mix under the influence of a high pressure gradient and strong turbulence generated by the rupture, with a mixing time scale of less than 1.5 ms. This time scale is significantly smaller than the 10 ms required for the gas-phase ignition delay time of the self-igniting propellant being studied. 1 -10 2 The time is on the order of milliseconds, thus enabling the decoupling of the self-igniting propellant mixing and chemical reaction ignition processes, resulting in a near-complete ignition delay time for both fuel and oxidizer.

Description

Technical Field

[0001] This invention relates to the field of experimental apparatus technology for combustion chemical reaction kinetics, specifically to a device and method for measuring the gas phase ignition delay time of a self-igniting propellant. Background Technology

[0002] Using computational fluid dynamics (CFD) coupled with chemical reaction kinetics to simulate propellant flow and combustion is a growing trend in aerospace propulsion design. Accurate chemical reaction kinetics are crucial for high-precision simulation of propellant combustion, and the reliability of these mechanisms needs verification through fundamental combustion experiments, such as ignition delay times measured by shock tubes and rapid compressors. These fundamental combustion experiments typically require the preparation of premixed fuel and oxidizer gases to eliminate the influence of component transport during the chemical reaction. However, the inherent "contact-based reaction" nature of self-igniting propellants at ambient temperature and pressure renders traditional premixing methods unsuitable. Even with significant dilution, fuel and oxidizer can still undergo significant chemical reactions at relatively low temperatures and pressures. Existing experimental methods for studying the fundamental combustion characteristics of self-igniting propellants suffer from a high degree of coupling between physical mixing and chemical reaction processes, making them unsuitable for studying propellant chemical reaction kinetics. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a device and method for measuring the gas phase ignition delay time of self-igniting propellants, thereby decoupling the mixing and chemical reaction ignition processes of self-igniting propellants and obtaining the ignition delay time of fuel and oxidizer.

[0004] This invention is achieved through the following technical solution:

[0005] A device for measuring the gas phase ignition delay time of a self-igniting propellant includes a compression cylinder with a piston inside. A combustion reaction chamber is provided at the end of the compression cylinder. A diaphragm is provided in the combustion reaction chamber to divide the combustion reaction chamber into two chambers. The two chambers are used to inject propellant fuel and oxidant respectively. When the diaphragm ruptures, the fuel and oxidant in the two chambers mix and burn.

[0006] Preferably, the combustion reaction chamber includes a first chamber plate, a second chamber plate, and an end cap arranged coaxially;

[0007] A first chamber is provided in the first cavity plate, and a second chamber is provided in the second cavity plate. One side of the first cavity plate is sealed and fixed to the end of the compression cylinder. A diaphragm seal is press-fitted between the first cavity plate and the second cavity plate, making the first chamber and the second chamber independent of each other. An end cap is sealed at the end of the second cavity plate.

[0008] Preferably, the diaphragm is an aluminum diaphragm.

[0009] Preferably, the diaphragm has slits to control the direction of diaphragm rupture.

[0010] Preferably, pressure sensors are provided on both the first cavity plate and the second cavity plate to measure the pressure of their respective chambers.

[0011] Preferably, heating devices are also embedded in the first cavity plate and the second cavity plate respectively, for controlling the temperature of the corresponding cavity.

[0012] Preferably, the fuel is a mixture of fuel and dilution gas; the oxidant is a mixture of oxidant and dilution gas.

[0013] A method for measuring the gas phase ignition delay time of a self-igniting propellant using a measuring device includes the following steps:

[0014] Step 1: Inject the prepared mixture of oxidant and dilution gas into the first chamber, and inject the mixture of fuel and dilution gas into the second chamber. Record the initial parameters of the two chambers at this moment.

[0015] Step 2: Apply pressure to the first chamber to rupture the diaphragm, allowing the fuel and oxidizer to mix and burn rapidly;

[0016] Step 3: Obtain the time from time 0 in the second chamber to the time corresponding to the maximum slope of the pressure rise in the second chamber, and obtain the ignition delay time of the self-igniting propellant gas phase under the initial parameters of the chamber.

[0017] The time 0 is the moment corresponding to the highest value of the first sharp rise in pressure in the second chamber after the diaphragm ruptures.

[0018] Preferably, the initial parameters of the chamber include the temperature, volume, and pressure of the chamber.

[0019] Preferably, the method further includes the following step: obtaining the pressure value of the second chamber at time 0. p c By combining the ideal gas law, the average temperature in the combustion reaction chamber at time 0 was determined. T c ;

[0020]

[0021] in, T 0 represents the initial temperature of the two chambers. p 0-1 The initial pressure of the first chamber. p 0-2 The initial pressure of the second chamber. V 1. Initial volume of the first chamber V 2. Initial volume of the second chamber.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] This invention provides a device for measuring the gas-phase ignition delay time of a self-igniting propellant. An aluminum diaphragm divides the combustion reaction chamber of the self-igniting propellant into two chambers. The first chamber is located near the compression cylinder of a rapid compressor, where the gas inside is heated and pressurized by the rapid compression of the piston. The second chamber is located further away from the piston. When the gas pressure in the first chamber reaches a certain level, the aluminum diaphragm ruptures under the pressure difference. The gas in the two chambers rapidly and uniformly mixes under the influence of a high pressure gradient and the strong turbulence generated by the ruptured diaphragm. The mixing time is less than 1.5 ms. This timescale is much smaller than the 10 ms required for the gas-phase ignition delay time of the self-igniting propellant being studied. 1 -10 2 The time delay is on the order of milliseconds. Then, based on the time from the 0th moment of the second chamber to the moment corresponding to the maximum slope of the pressure rise in the second chamber, the gas phase ignition delay time of the self-igniting propellant under the initial parameter conditions of the chamber is obtained. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the measuring device of the present invention;

[0025] Figure 2 This is a schematic diagram of the internal structure of the measuring device of the present invention;

[0026] Figure 3 This is a schematic diagram of the combustion reaction chamber of the measuring device of the present invention;

[0027] Figure 4 This is the pressure curve of the combustion reaction chamber of the dual-chamber rapid compressor of the present invention;

[0028] Figure 5 This is a temperature distribution diagram of the membrane rupture process in the dual-cavity rapid compressor of the present invention;

[0029] Figure 6 This is a graph showing the pressure / temperature / component concentration changes of the dual-chamber rapid compressor of the present invention.

[0030] In the diagram: 1. Pressure sensor; 2. Diaphragm; 3. End cap; 4. Sealing ring; 5. Radial window; 6. Piston; 7. First chamber plate; 8. Second chamber plate; 9. Compression cylinder; 10. End cap window. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings. These descriptions are intended to explain the invention and not to limit it.

[0032] See Figure 1-3A device for measuring the gas phase ignition delay time of a self-igniting propellant includes a compression cylinder 9, inside which a piston 6 is installed. A combustion reaction chamber is installed at the end of the compression cylinder 9. A diaphragm is installed in the combustion reaction chamber to divide the combustion reaction chamber into two chambers. The two chambers are used to inject propellant fuel and oxidant respectively. When the diaphragm is damaged, the two chambers are connected and the fuel and oxidant are rapidly mixed.

[0033] The combustion reaction chamber includes a first chamber plate 7, a second chamber plate 8, and an end cap. A first chamber is provided in the first chamber plate 7, and a second chamber is provided in the center of the second chamber plate 8. The first chamber plate 7, the second chamber plate 8, and the end cap are coaxially arranged at the end of the compression cylinder. One side of the first chamber plate 7 is fixedly connected to the end of the compression cylinder. A diaphragm is arranged between the first chamber plate 7 and the second chamber plate 8, and sealing rings 4 are provided on both sides of the diaphragm. The end cap, the second chamber plate 8, and the first chamber plate 7 are connected by bolts.

[0034] Pressure sensors 1 are provided on both the first cavity plate 7 and the second cavity plate 8 to measure the pressure of their respective chambers. Radial viewing windows 5 are provided on the side walls of the first cavity plate 7 and the second cavity plate 8 for observing the chambers. An end cap viewing window 10 is provided at the center of the end cap. The chambers can be observed from multiple directions through the radial viewing windows 5 and the end cap viewing window 10. Both the first cavity plate and the second cavity plate are provided with feed inlets that communicate with the chambers to realize the separate injection of fuel and oxidant.

[0035] Heating rods are also embedded in the first cavity plate 7 and the second cavity plate 8, respectively, to heat the gaseous combustion and oxidizing agents and prevent them from turning into liquid.

[0036] The diaphragm is made of aluminum and has slits. The thickness of the aluminum film and the depth of the slits together determine the pressure difference required when the film breaks. At the same time, the slits play a guiding role when the aluminum film breaks. During the test, the direction and depth of the slits are controlled to guide the diaphragm to break towards the area without the optical window, so as to avoid interfering with the observation optical path of the radial window.

[0037] For example, a star-shaped cut is provided on the diaphragm, and one of the cuts is parallel to the axis of the radial window 5. Under pressure, the diaphragm breaks along the cut from the center to the edge, thus preventing the aluminum film from blocking the radial window 5 after it breaks.

[0038] The following is a detailed description of a method for measuring the gas-phase ignition delay time of a self-igniting propellant, specifically including the following steps:

[0039] Step 1: Inject the prepared mixture of oxidant and dilution gas into the first chamber, and inject the mixture of fuel and dilution gas into the second chamber, and record the initial temperature of the two chambers at this moment. T 0 and the initial pressure of the first chamber p0-1 Initial pressure of the second chamber p 0-2 .

[0040] In this step, the heating rods on the first and second chamber plates are activated to heat the mixed gas, ensuring that the fuel and oxidant do not liquefy. A PID temperature controller is used to accurately adjust the initial temperature before the experiment. The intake volume of each component is calculated based on the chamber volume, intake pressure, and temperature.

[0041] Step 2: Start the rapid compressor. The piston pressurizes the first chamber, causing a rapid increase in pressure and temperature. When the pressure in the first chamber reaches a certain value, the diaphragm ruptures in a predetermined direction, connecting the first and second chambers to form a combustion reaction chamber. Simultaneously, the fuel and oxidizer mix and ignite rapidly, with a mixing time not exceeding 1.5 ms. After the diaphragm ruptures, the pressure in the first chamber drops rapidly, while the pressure in the second chamber rises rapidly, quickly reaching the same pressure value. The pressure value of the second chamber at time 0 is obtained using a pressure sensor. p c .

[0042] definition:

[0043] 1. The moment corresponding to the highest value of the first sharp rise in pressure in the second chamber after the diaphragm ruptures is defined as moment 0;

[0044] 2. The ignition moment, i.e., the ignition delay time, is defined as the point where the slope of the pressure rise in the second chamber due to the heat released by the chemical reaction of fuel and oxidant.

[0045] 3. The ignition temperature condition is defined as the average temperature inside the combustion reaction chamber at time 0. T c .

[0046] For research conditions where the chemical reaction releases heat slowly, a photomultiplier tube-fiber optic connection can be used to connect to the visualization window. The maximum value of the light signal measured by the photomultiplier tube is defined as the ignition moment.

[0047] Step 4: Based on the initial temperature, initial pressure, and volume of the first and second chambers, and the pressure value of the second chamber at time 0. p c By combining the ideal gas law, the average temperature in the combustion reaction chamber at time 0 was determined. T c ;

[0048]

[0049] in, T 0 represents the initial temperature; the initial temperatures of both chambers are the same. p0-1 The initial pressure of the first chamber. p 0-2 The initial pressure of the second chamber. V 1. Initial volume of the first chamber V 2. Initial volume of the second chamber.

[0050] Step 5: Determine the ignition delay time based on the time at moment 0 in the second chamber and the time corresponding to the maximum slope of the pressure rise in the second chamber, thus obtaining the ignition delay time under the set fuel and oxidizer concentrations, initial pressure, and average temperature of the combustion reaction chamber. T c The ignition delay time.

[0051] Step 6: By changing the fuel and oxidizer concentrations and the initial pressure p 0-1 and p 0-2 Initial temperature T Repeat steps 1-5 to obtain the self-igniting propellant under different oxygen-fuel ratios and pressures. p c and the average temperature of the combustion reaction chamber T c The ignition delay time.

[0052] During the test, the gas in the first chamber experienced a rapid increase in pressure and temperature under piston compression, with 50% of the pressure rise concentrated in the last 2 ms. Near the end of compression, the pressure difference between the first and second chambers reached the predetermined design value, causing the aluminum membrane to rupture. The high-temperature, high-pressure gas in the first chamber and the low-temperature, low-pressure gas in the second chamber underwent strong turbulent mixing under the pressure and temperature gradient. Simultaneously, the rupture of the membrane also provided some stirring for the gas in both chambers. Due to the small chamber size (inner diameter < 50 mm, axial length < 50 mm), the gas mixing process was very rapid. The time from the start of mixing to the cessation of drastic temperature fluctuations in most areas of the combustion reaction chamber was controlled within 1.5 ms. After the gas in both chambers ruptured and mixed, it reached the set characteristic temperature and pressure, and a chemical reaction occurred. After a certain period, the pressure in the combustion reaction chamber increased due to the exothermic chemical reaction. The time interval from the moment the pressure signal first experienced a sharp rise / fall due to membrane rupture to the moment the pressure rose again to its maximum slope was defined as the ignition delay time, as shown in Figure 2. In cases where weak ignition may result in a slight pressure rise, a photomultiplier device is used to measure the light signal of a specific wavelength in the gas mixture to determine the ignition moment.

[0053] The following is a detailed explanation of the simulation results of the diaphragm rupture process and gas mixing process of the dual-chamber rapid compressor using CFD simulation.

[0054] Under a pressure differential of 20 bar, the aluminum diaphragm ruptures completely in less than 0.5 ms. The temperature and component equilibrium times in the central region of the combustion chamber are approximately 1–1.5 ms, as shown in Figure 3. At the moment of rupture, a significant pressure / density / temperature gradient at the dual-chamber interface of the combustion reaction chamber generates a shock wave. Under the influence of this shock wave, the temperature of the gas in the second chamber rises instantaneously, while the gas in the first chamber cools due to the expansion wave. Subsequently, the gas diffuses and mixes under strong turbulence. Related studies with combustion reaction chamber dimensions similar to those of fast compressors show that when the Reynolds number is greater than 800, the homogeneity of mixing can be guaranteed. Furthermore, the Reynolds number after rupture in a dual-chamber fast compressor can be maintained at 10 within the range of 0–5 ms. 5 -10 3 On the order of magnitude, turbulent kinetic energy can reach as high as 10 3 m 2 / s 2 Therefore, it can ensure that the gas is mixed quickly and evenly.

[0055] Two characteristic points were selected in the first and second chambers, respectively, and their temperature, pressure, and component concentration histories were plotted as shown in Figure 4. After membrane rupture, the pressure in the two chambers rapidly balanced (<1 ms), and the temperature and component concentration (CO2 as an example) gradually stabilized within 1.5 ms, reaching the theoretical level of thorough mixing. Therefore, this method can be used to measure 10 1 -10 2 The ignition delay time is on the order of milliseconds, and it can satisfy the requirement that the gas mixing timescale is much smaller than the chemical reaction timescale.

[0056] This invention provides a device for measuring the gas-phase ignition delay time of a self-igniting propellant. An aluminum diaphragm (aluminum membrane) divides the combustion reaction chamber of the self-igniting propellant into two chambers. The first chamber is located near the compression cylinder of a rapid compressor, where the gas inside is heated and pressurized by the rapid compression of the piston. The second chamber is located further away from the piston. When the gas pressure in the first chamber reaches a certain level, the aluminum membrane ruptures under the pressure difference. The gas in the two chambers rapidly and uniformly mixes under the influence of a high pressure gradient and the strong turbulence generated by the membrane rupture, with a mixing time scale of less than 1.5 ms. This time scale is much smaller than the gas-phase ignition delay time of the self-igniting propellant studied (10 ms). 1 -10 2 The time is on the order of milliseconds, thus enabling the decoupling of the self-igniting propellant mixing and chemical reaction ignition processes, resulting in a near-complete ignition delay time for both fuel and oxidizer.

[0057] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A device for measuring gas phase ignition delay time of self-igniting propellant, characterized by, The application relates to a self-ignition propellant gas phase combustion reaction device, which comprises a compression cylinder, a piston arranged in the compression cylinder, a combustion reaction cavity arranged at the end of the compression cylinder, a diaphragm arranged in the combustion reaction cavity, two chambers divided by the diaphragm, and fuel and oxidant respectively injected into the two chambers. The maximum value of the slope of the pressure rise of the second chamber caused by the heat release of the chemical reaction of the fuel and the oxidant is defined as the ignition delay time. The combustion reaction cavity comprises coaxially arranged first and second cavity plates and an end cover. The first cavity plate is provided with a first chamber, the second cavity plate is provided with a second chamber, one side of the first cavity plate is sealingly and fixedly connected with the end of the compression cylinder, the diaphragm is sealingly arranged between the first and second cavity plates and makes the first and second chambers independent of each other, and the end cover is sealingly arranged at the end of the second cavity plate. Pressure sensors are arranged on the first and second cavity plates and used for measuring the pressure of the respective chambers. The diaphragm is an aluminum diaphragm, and a notch is arranged on the diaphragm and used for controlling the breaking direction of the diaphragm.

2. The device according to claim 1, wherein Heating devices are respectively arranged in the first and second cavity plates and used for controlling the temperature of the corresponding chambers.

3. The device according to claim 1, wherein The fuel is a mixed gas of fuel and dilution gas, and the oxidant is a mixed gas of oxidant and dilution gas.

4. A measuring method of the apparatus for measuring the gas phase ignition delay time of the hypergolic propellant according to any one of claims 1 to 3, characterized in that, The application further discloses a combustion reaction method of the self-ignition propellant gas phase combustion reaction device. Step 1: injecting the mixed gas of the prepared oxidant and dilution gas into the first chamber and injecting the mixed gas of the fuel and dilution gas into the second chamber, and recording the initial parameters of the two chambers at this moment, wherein the initial parameters include the temperature, volume and pressure of the chambers. Step 2: applying pressure to the first chamber to break the diaphragm, and rapidly mixing and combusting the fuel and the oxidant. Step 3: obtaining the time from the 0 moment of the second chamber to the moment corresponding to the maximum value of the slope of the pressure rise of the second chamber, and obtaining the ignition delay time of the self-ignition propellant gas phase under the condition of the set initial parameters of the chamber. The 0 moment is the moment corresponding to the highest value of the first steep rise of the pressure of the second chamber after the diaphragm is broken.

5. The measurement method of the self-combustion type propellant gas phase ignition delay time measurement device according to claim 4, characterized by, Further comprising the step of obtaining a pressure value of the second chamber at time 0 p c And in combination with the ideal gas state equation, determine the average temperature in the combustion reaction chamber at time 0 T c ; wherein T 0 is the initial temperature of the two chambers, p 0-1 P0 is the initial pressure of the first chamber, p 0-2 P1 is the initial pressure of the second chamber, V 1 the initial volume of the first chamber, V 2 the initial volume of the second chamber.

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