Ground test system and design method for liquid oxygen-methane semi-system engine capable of safe treatment of methane-rich gas

Abstract

This invention relates to ground testing of liquid oxygen-methane semi-system engines, specifically to a ground testing system and design method for liquid oxygen-methane semi-system engines capable of safely handling methane-rich fuel gas. Based on a traditional test rig, this system innovatively integrates a methane-rich fuel gas outlet pipeline optimized through fluid-structure interaction simulation and an igniter precisely positioned based on flow field simulation and minimum ignition energy theory. By optimizing the structure of the outlet pipeline to ensure safe delivery, and by accurately simulating the outlet flow field and combining it with theoretical calculations, the optimal installation position and angle of the igniter are determined, thereby achieving reliable ignition and safe disposal of methane-rich fuel gas in open spaces. This invention effectively solves the safety emission problem caused by the high chemical reactivity and unstable state of methane-rich fuel gas in ground testing of liquid oxygen-methane semi-system engines, significantly improving the safety and reliability of the test rig.

Description

Technical Field

[0001] This invention relates to a ground test device for a liquid oxygen-methane semi-system engine, specifically to a ground test system for a liquid oxygen-methane semi-system engine capable of safely processing methane-rich combustion gases and its design method. Background Technology

[0002] With the continuous development of aerospace technology and the increasingly urgent need for efficient and environmentally friendly propellants, liquid oxygen-methane semi-system engines, due to their excellent comprehensive performance, have become an important direction in aerospace propulsion system research. During ground tests of liquid oxygen-methane semi-system engines, a large amount of high-temperature, high-pressure methane-rich gas is generated. Methane-rich gas has extremely high chemical reactivity and potential hazards; its state is extremely unstable and prone to deflagration or even detonation. Improper handling will pose a serious threat to the safety of test facilities and personnel, leading to safety accidents and significant economic losses.

[0003] Chinese patent CN211234965U discloses a test rig for supersonic engine testing. Its core functionality involves setting up a main test rig structure, exhaust gas treatment equipment, and auxiliary systems to verify engine operation on the ground. This device primarily focuses on the overall layout of the test rig and conventional exhaust gas guidance and noise reduction, but it does not address the safety issues of high-temperature, high-pressure combustion gases rich in unburned methane during emission, nor does it resolve the risk of forming an explosive limit mixing zone during the diffusion of combustible gases under supersonic jets. Furthermore, this patent does not consider the fluid-structure interaction response of the exhaust pipeline under high thermal loads, lacking optimized design for pipeline thermal stress, thermal deformation, and structural safety. Chinese patent CN103743572A discloses a spray device for a small rocket engine test rig. This device includes a water supply system and an engine exhaust flame guidance system, spraying water mist through a spray ring towards the engine extension section to cool the exhaust flame and guide the exhaust gas. However, this method mainly achieves passive cooling and dilution, and the spray system has limited impact on the combustion gas concentration. For methane-rich, high-temperature, and high-pressure exhaust gases, water spraying may not be able to adequately dilute the combustible mixture, nor can it actively ignite unburned gases, resulting in a weak safety handling capability.

[0004] Therefore, existing technologies have not solved the problems of safe emission of high-temperature and high-pressure methane-rich gas, reliable supersonic ignition, and pipeline structure optimization in the ground test of liquid oxygen methane semi-system engines. There is an urgent need for a ground test system and its design method for liquid oxygen methane semi-system engines that can safely handle methane-rich gas. Through systematic design, a set of safe handling procedures for the characteristics of methane-rich gas can be formed to solve the problem of safe emission in semi-system tests and improve the safety margin of the test bench. Summary of the Invention

[0005] To address the challenges of safe emission of methane-rich fuel gas in existing technologies, particularly the insufficient ignition reliability under supersonic jets and the lack of systematic optimization design for the safety of emission pipeline structures, this invention provides a ground test system and design method for a liquid oxygen-methane semi-system engine capable of safely treating methane-rich fuel gas.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A ground test system for a liquid oxygen-methane semi-system engine capable of safely processing methane-rich fuel gas includes a load-bearing structure, a gas supply and distribution system, a measurement and control system, a liquid oxygen-methane semi-system engine, and a test stand guide channel. The load-bearing structure is used to mount the liquid oxygen-methane semi-system engine under test. The gas supply and distribution system supplies gas to the test liquid oxygen-methane semi-system engine and is controlled and monitored by the measurement and control system. The test stand guide channel extends obliquely to guide and discharge the combustion products after ignition. Its unique feature is that it also includes a methane-rich fuel gas outlet pipeline and an igniter.

[0008] The inlet of the methane-rich gas outlet pipeline is connected to the gas outlet of the liquid oxygen methane semi-system engine, and is used to guide the methane-rich gas generated by the liquid oxygen methane semi-system engine to the area below the horizontal plane of the test stand, and to direct the gas jet toward the obliquely extending test stand guide groove.

[0009] The geometry and support arrangement of the methane-rich gas outlet pipeline are optimized based on fluid-structure interaction simulation to reduce the thermal stress and thermal deformation of the pipeline system.

[0010] The installation position and injection angle of the igniter are determined based on the computational fluid dynamics simulation results of the flow field at the outlet of the methane-rich gas extraction pipe and the minimum ignition energy theory. This is used to reliably ignite the methane-rich gas under supersonic jet conditions. The installation position and injection angle of the igniter are determined using Le Chatelier's rule and the minimum ignition energy formula, combined with the computational fluid dynamics simulation results of the flow field at the outlet of the methane-rich gas extraction pipe. By using computational fluid dynamics to simulate and analyze the supersonic flow field in the outlet region of the extraction pipe, the velocity, concentration, and temperature distributions are obtained, thereby determining the combustible mixture region where the methane concentration is above the lower explosive limit. The installation position and injection angle of the igniter are optimized based on this flow field result and combined with the minimum ignition energy theory to ensure that the ignition flame can stably couple with the combustible mixture region, achieving reliable ignition of the methane-rich gas under supersonic jet conditions.

[0011] Furthermore, the optimized design of the geometric orientation and support arrangement of the methane-rich gas outlet pipeline is determined by adopting the third strength theory, stiffness and strength condition formulas, and combined with the results of fluid-structure interaction simulation.

[0012] Furthermore, the igniter is a coaxial DC igniter; the flame length of the igniter is 600mm, ensuring sufficient contact time between the flame and the methane-rich gas, thereby eliminating the risk of unburned mixture accumulation; the installation position is 0.35 meters away from the center axis of the methane-rich gas outlet pipeline, the angle between the axis of the igniter and the plane perpendicular to the center axis of the methane-rich gas outlet pipeline is 55°, and the methane concentration at the contact point between the flame and the methane-rich gas is 20%~70%, achieving reliable ignition under supersonic conditions.

[0013] Meanwhile, this invention also provides a ground test design method for a liquid oxygen-methane semi-system engine capable of safely processing methane-rich gas. Its unique feature is that it employs the aforementioned ground test system for a liquid oxygen-methane semi-system engine capable of safely processing methane-rich gas, and includes the following steps:

[0014] Step 1: Based on the third strength theory, complete the strength verification of the methane-rich gas outlet pipeline. Perform fluid-structure interaction simulation on the methane-rich gas outlet pipeline to obtain the internal flow field, thermal strain and thermal stress distribution. Based on the simulation results, verify and optimize the geometric direction of the pipeline and the support constraint position. Finally, calculate the support spacing of the methane-rich gas outlet pipeline according to the stiffness condition and the strength condition respectively, and take the smaller value of the two to comprehensively determine the geometric direction and support arrangement scheme of the methane-rich gas outlet pipeline.

[0015] Step 2: Establish a fluid dynamics model including the outlet region of the methane-rich gas outlet pipeline, perform supersonic jet simulation, and obtain the temperature, Mach number, velocity, and methane concentration distribution of the flow field;

[0016] Step 3: Based on the flow field temperature, Mach number, velocity, and methane concentration distribution obtained from the flow field simulation in Step 2, and combined with the minimum ignition energy theory, calculate the lower explosion limit of methane-rich gas and the required minimum ignition energy, and optimize and determine the installation position and injection angle of the igniter accordingly.

[0017] Step 4: Based on the simulation results of Step 1, optimize and determine the geometric direction and support arrangement of the methane-rich gas outlet pipeline, the installation position and injection angle of the igniter determined in Step 3, and arrange the load-bearing structure, gas supply and distribution system, measurement and control system, liquid oxygen methane semi-system engine and test bench guide channel to complete the design of the ground test system of liquid oxygen methane semi-system engine that can safely handle methane-rich gas.

[0018] Furthermore, in step 1, the calculation formula for the strength verification of the methane-rich gas outlet pipeline using the third strength theory is as follows:

[0019]

[0020]

[0021]

[0022] In the formula: σ θ For circumferential stress, σ z For axial stress, σ r Where is the radial stress, P is the internal pressure of the pipe, r is the pipe radius, and t is the pipe wall thickness;

[0023] The yield criterion is:

[0024]

[0025] In the formula, σ1 is the maximum principal stress, σ2 is the minimum principal stress, and σ y Where n is the yield strength of the pipe material, and n is the safety factor, which is 2.5 for thin-walled pipes.

[0026] Further, in step 1, the support spacing of the methane-rich gas outlet pipeline is calculated according to the stiffness condition and the strength condition respectively, and the smaller value of the two is taken.

[0027] The stiffness condition is calculated using the following formula:

[0028]

[0029] In the formula: L1 is the span calculated from the stiffness condition, E t Let E be the elastic modulus of the pipe at the design temperature. t =2×10 5 MPa, I is the moment of inertia of the pipe section after deducting the negative deviation of the corrosion allowance level, and q is the weight of the pipe per meter;

[0030]

[0031]

[0032] In the formula: D0 is the outer diameter of the pipe, D i p is the inner diameter of the pipe. L For pipe density;

[0033] The strength condition is calculated using the following formula:

[0034]

[0035] In the formula: L2 is the span calculated from the strength condition, [σ] t The allowable stress of the pipe at room temperature is taken as 137 MPa, and W is the section modulus of the pipe after deducting the negative deviation of the corrosion allowance level.

[0036] Furthermore, in step 3, to ensure reliable ignition of the methane-rich gas under high-speed jet conditions, based on the composition of the methane-rich gas, Le Chatelier's rule is applied, and the lower explosive limit (LFL) of the mixture is calculated according to the following formula. mix :

[0037]

[0038] In the formula: y i LFL is the volume fraction of the i-th component in the mixture. i Let be the lower explosive limit of the i-th component in the mixture;

[0039] The minimum ignition energy (MIE) of this methane-rich gas is calculated using the following formula:

[0040]

[0041] Where: MIE ch4 The minimum ignition energy of pure methane, LFL ch4 The lower explosive limit (LFL) for pure methane. mix This is the lower explosive limit of the gas mixture.

[0042] Furthermore, in step 3, the specific method for optimizing and determining the installation position and injection angle of the igniter is as follows: Based on the flow field temperature, Mach number, velocity, and methane concentration distribution obtained from the flow field simulation in step 2, and combined with the minimum ignition energy theory, the combustibility of the methane-rich gas-air mixture at different spatial locations and the required minimum ignition energy are analyzed. Regions with suitable methane concentration and relatively low flow velocity are selected, and the optimal injection angle suitable for supersonic jet conditions is determined to ensure that the igniter reliably releases ignition energy.

[0043] Furthermore, in step 1, in order to ensure the structural reliability of the discharge pipeline under high temperature, high pressure and supersonic conditions, the fluid-structure interaction simulation adopts a three-dimensional model. The simulation results are used to determine the pipe bend angle, length and support constraint position, so as to reduce thermal stress, reduce thermal deformation and improve the system strength margin.

[0044] Furthermore, in step 2, in order to accurately grasp the flow characteristics of methane-rich gas ejected from the outlet of the emission pipeline, a computational fluid dynamics model including the pipeline outlet area and its surrounding space is established. The fluid dynamics simulation uses a density-based solver and a large eddy simulation turbulence model to simulate the velocity field, temperature field, concentration field and jet diffusion characteristics of methane-rich gas under supersonic conditions.

[0045] Compared with the prior art, the beneficial effects of the present invention are:

[0046] 1. This invention guides high-temperature, high-pressure methane-rich gas to an open area outside the test stand's horizontal plane and directs its emission towards the guide channel, thereby reducing the risk of combustible mixtures accumulating near the test stand at the source. Combined with a pipeline structure optimized based on fluid-structure interaction analysis, it effectively reduces the risk of leakage and rupture caused by thermal stress concentration and thermal deformation, giving the emission system a higher structural safety margin and improving the overall safety of methane-rich gas emissions.

[0047] 2. This invention employs computational fluid dynamics to simulate and analyze the supersonic flow field in the outlet region of the lead-in pipe, accurately obtaining the velocity, concentration, and temperature distributions, thereby determining the combustible mixture region where the methane concentration is above the lower explosive limit. The igniter's installation position and injection angle are optimized based on this flow field result and combined with the minimum ignition energy theory, ensuring stable coupling between the ignition flame and the combustible mixture region, achieving reliable ignition of methane-rich gas under supersonic jet conditions.

[0048] 3. The methane-rich gas outlet pipeline of this invention is designed using three-dimensional fluid-structure interaction simulation, comprehensively considering the internal flow field, thermal strain, and thermal stress of the pipeline, achieving quantitative optimization of the bend angle, length, and support arrangement. By using a support arrangement that meets the stiffness and strength requirements, pipeline vibration and deformation under thermal load can be effectively suppressed, extending the structural lifespan, achieving quantitative optimization design of the emission pipeline, and improving the system's adaptability to different engine models and operating conditions.

[0049] 4. The design method proposed in this invention integrates three-dimensional fluid-structure interaction simulation, computational fluid dynamics simulation, lower explosion limit calculation, and minimum ignition energy analysis to form a structured design process that can be directly applied to the construction of a liquid oxygen-methane semi-system engine test rig. This method can not only be used for the implementation of the system of this invention, but also provide design references for other types of liquid rocket engines or similar gas treatment systems, demonstrating good versatility and engineering application value. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the overall layout of an embodiment of the liquid oxygen-methane semi-system engine ground test system that enables safe treatment of methane-rich gas according to the present invention;

[0051] Figure 2 This is a three-dimensional model diagram of the methane-rich gas emission pipeline in step 1 of the embodiment of the design method of the ground test system of the liquid oxygen methane semi-system engine that can realize the safe treatment of methane-rich gas of the present invention;

[0052] Figure 3 This is a schematic diagram of the grid division of the methane-rich gas emission pipeline in step 1 of the embodiment of the design method of the ground test system of the liquid oxygen methane semi-system engine that can realize the safe treatment of methane-rich gas of the present invention;

[0053] Figure 4 This is a schematic diagram of the constraint settings of the methane-rich gas emission pipeline in step 1 of the embodiment of the design method of the ground test system of the liquid oxygen methane semi-system engine that can realize the safe treatment of methane-rich gas of the present invention;

[0054] Figure 5 This is the maximum principal stress cloud diagram of the methane-rich gas emission pipeline in step 1 of the embodiment of the design method of the ground test system of the liquid oxygen methane semi-system engine that can realize the safe treatment of methane-rich gas of the present invention.

[0055] Figure 6 This is the minimum principal stress cloud diagram of the methane-rich gas emission pipeline in step 1 of the embodiment of the design method of the ground test system of the liquid oxygen methane semi-system engine that can realize the safe treatment of methane-rich gas of the present invention.

[0056] Figure 7 This is a modeling diagram of the methane-rich gas outlet flow field calculation region in step 2 of the embodiment of the design method of the ground test system for the liquid oxygen-methane semi-system engine capable of safe treatment of methane-rich gas of the present invention.

[0057] Figure 8 This is a schematic diagram of the mesh division and boundary condition setting of the methane-rich gas outlet flow field calculation region in step 2 of the embodiment of the design method of the ground test system of the liquid oxygen methane semi-system engine that can realize the safe treatment of methane-rich gas.

[0058] Figure 9 This is a temperature cloud map of the methane-rich gas outlet flow field in step 2 of the embodiment of the design method of the ground test system for the liquid oxygen-methane semi-system engine that enables safe treatment of methane-rich gas according to the present invention.

[0059] Figure 10 This is a Mach number cloud map of the flow field at the outlet of the liquid oxygen-methane semi-system engine in step 2 of the embodiment of the design method of the ground test system of the liquid oxygen-methane semi-system engine that can realize the safe treatment of methane-rich gas of the present invention.

[0060] Figure 11 This is a velocity cloud map of the flow field at the outlet of the methane-rich gas in step 2 of an embodiment of the design method for a ground test system of a liquid oxygen-methane semi-system engine capable of safely handling methane-rich gas, as described in this invention.

[0061] Figure 12 This is a methane concentration cloud map of the methane-rich gas outlet flow field in step 2 of the embodiment of the design method of the ground test system of the liquid oxygen methane semi-system engine that can realize the safe treatment of methane-rich gas of the present invention.

[0062] Figure 13 This is a schematic diagram of the igniter installation position in step 3 of the embodiment of the design method of the ground test system for the liquid oxygen methane semi-system engine that enables safe treatment of methane-rich gas according to the present invention.

[0063] Figure 14 This is a diagram showing the methane concentration distribution along the igniter flame axis in step 3 of the embodiment of the design method for a ground test system of a liquid oxygen-methane semi-system engine capable of safely handling methane-rich gas, as described in this invention.

[0064] The attached figures are labeled as follows:

[0065] 1-Supporting structure, 2-Gas supply and distribution system, 3-Measurement and control system, 4-Liquid oxygen methane semi-system engine, 5-Methane-rich gas outlet pipeline, 6-Test bench horizontal plane, 7-Igniter, 8-Test bench guide channel. Detailed Implementation

[0066] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0067] This invention provides a ground test system for a liquid oxygen-methane semi-system engine capable of safely processing methane-rich combustion gases, such as... Figure 1 As shown, it includes a load-bearing structure 1, a gas supply and distribution system 2, a measurement and control system 3, a liquid oxygen methane semi-system engine 4, a methane-rich gas outlet pipeline 5, an igniter 7, and a test bench guide channel 8.

[0068] The liquid oxygen-methane semi-system engine 4 is fixedly mounted on the load-bearing structure 1. The gas supply and distribution system 2 is connected to the propellant inlet of the liquid oxygen-methane semi-system engine 4 via a supply pipeline and is controlled and monitored by the measurement and control system 3. The inlet of the methane-rich gas outlet pipeline 5 is connected to the gas outlet of the liquid oxygen-methane semi-system engine 4, and the outlet extends to a safe area outside the test stand horizontal plane 6, pointing towards the test stand guide channel 8, thereby reducing the accumulation of combustible mixture near the test stand. Igniters 7 are arranged in the open area for controlled ignition of the emitted methane-rich gas, preventing unburned gas from spreading and forming an explosive gas cloud.

[0069] This invention also provides a ground test design method for a liquid oxygen-methane semi-system engine capable of safely processing methane-rich gas. Its key feature is that it employs the aforementioned ground test system for the liquid oxygen-methane semi-system engine capable of safely processing methane-rich gas, and includes the following steps:

[0070] Step 1: Perform a strength check on the methane-rich gas outlet pipeline 5 based on the third strength theory. The calculation formula for the strength check of the methane-rich gas outlet pipeline 5 using the third strength theory is as follows:

[0071]

[0072]

[0073]

[0074] In the formula: σ θ For circumferential stress, σ z For axial stress, σ r Where is the radial stress, P is the internal pressure of the pipe, r is the pipe radius, and t is the pipe wall thickness;

[0075] The yield criterion is:

[0076]

[0077] In the formula, σ1 is the maximum principal stress, σ2 is the minimum principal stress, and σ y Where n is the yield strength of the pipe material, and n is the safety factor, which is 2.5 for thin-walled pipes.

[0078] Substituting the data, the maximum and minimum principal stress differences are calculated as follows:

[0079]

[0080] Therefore, the methane-rich gas emission pipeline meets the requirements of the third strength theory.

[0081] Based on the fluid-structure interaction simulation method, a three-dimensional model of the methane-rich gas outlet pipeline 5 was created, such as... Figure 2 As shown in the figure, this model accurately reflects the key features of the pipeline, such as its geometric orientation and bend angles, laying the foundation for subsequent simulation analysis.

[0082] Import the 3D model into the Static Structure module of Ansys Workbench and perform high-quality mesh generation, such as... Figure 3 As shown, the average mesh distortion is 0.11, indicating good quality and ensuring computational accuracy.

[0083] Based on the installation method of the methane-rich gas outlet pipeline 5 on the actual test bench, its constraint conditions are set, such as... Figure 4 As shown, these constraints realistically simulate the fixing and limiting effect of pipe supports on pipes.

[0084] Static analysis was performed after applying the working pressure load to obtain the maximum principal stress contour maps and minimum principal stress contour maps of the pipeline, as shown below. Figure 5 , Figure 6 As shown. The difference between the maximum and minimum principal stresses is calculated as follows:

[0085]

[0086] The difference between the maximum and minimum principal stresses of the pipeline system satisfies the yield criterion of the third strength theory, proving that the pipeline structure has sufficient safety margin after fluid-structure interaction simulation optimization.

[0087] Meanwhile, the spacing of the pipe supports was calculated and verified. The calculation was based on the stiffness conditions of a three-span continuous bridge under uniform load, and the strength conditions were checked. The smaller value between the two was taken.

[0088] The stiffness condition is calculated using the following formula:

[0089]

[0090] In the formula: L1 is the span calculated from the stiffness condition, E t Let E be the elastic modulus of the pipe at the design temperature. t =2×10 5 MPa, I is the moment of inertia of the pipe section after deducting the negative deviation of the corrosion allowance level, and q is the weight of the pipe per meter;

[0091]

[0092]

[0093] In the formula: D0 is the outer diameter of the pipe, D i p is the inner diameter of the pipe. L For pipe density;

[0094] The strength condition is calculated using the following formula:

[0095]

[0096] In the formula: L2 is the span calculated from the strength condition, [σ] t The allowable stress of the pipe at room temperature is taken as 137 MPa, and W is the section modulus of the pipe after deducting the negative deviation of the corrosion allowance level.

[0097] Calculations show that the stiffness condition span L1 = 16.99m and the strength condition span L2 = 13.94m. In practice, the support installation spacing is 3m, 2.5m, 4m and 2m, all of which are less than 13.94m. Therefore, the pipe support setting meets the strength and stiffness requirements.

[0098] Step 2: Establish a refined fluid dynamics model including the outlet region of methane-rich gas extraction pipeline 5, such as... Figure 7 , 8 As shown, a density-based solver and a large eddy simulation turbulence model were used to simulate a supersonic jet, obtaining the temperature, Mach number, velocity, and methane concentration distribution of the flow field. Figure 9-12 As shown, this provides a basis for the design of the igniter 7 position.

[0099] First, Ansys SpacesClaim is used to perform a two-dimensional model of the flow field at the outlet of the methane-rich gas, establishing the computational domain, such as... Figure 7 As shown in the figure, the model includes the emission outlet and the surrounding key areas.

[0100] The computational domain is meshed and boundary conditions are set, such as... Figure 8 As shown.

[0101] The calculations were performed using a density-based solver and a large eddy simulation turbulence model. After simulation convergence, the temperature and Mach number contour maps of the flow field were obtained, as shown below. Figure 9 , Figure 10 As shown in the figure, analysis reveals that a complex shock wave structure was formed near the exhaust port, with a maximum Mach number of 2.2, clearly defining the range of the supersonic core region.

[0102] Further analysis yielded velocity contour maps and methane concentration contour maps of the flow field, as shown below. Figure 11 , Figure 12 As shown in the diagrams, these cloud maps clearly demonstrate the diffusion patterns of the jet and the spatial distribution of combustible gas concentration, providing a direct basis for identifying the optimal ignition zone.

[0103] Step 3: Based on the flow field simulation results of Step 2, the installation position and injection angle of the igniter 7 are optimized and determined by combining the minimum ignition energy theory.

[0104] Based on the composition of the methane-rich gas, the lower explosive limit (LFL) of the mixture is calculated using Le Chatelier's rule. mix :

[0105]

[0106] In the formula: y i LFL is the volume fraction of the i-th component in the mixture. i Let be the lower explosive limit of the i-th component in the mixture;

[0107] The lower explosive limit (LFL) of the gas mixture was calculated. mix =7.6%.

[0108] Calculate the minimum ignition energy (MIE) of this methane-rich gas:

[0109]

[0110] In the formula: MIE is the minimum ignition energy of pure methane, LFL ch4 The lower explosive limit (LFL) for pure methane. mix This is the lower explosive limit of the gas mixture;

[0111] The minimum ignition energy (MIE) of the methane-rich gas was calculated to be 0.123 mJ.

[0112] The chemical equation for the complete combustion of methane is:

[0113]

[0114] Given a methane flow rate of 0.08 kg / s and an oxygen flow rate of 0.04 kg / s, these translate to molar flow rates of 5 mol / s and 1.25 mol / s, respectively. Therefore, the maximum molar flow rate of combustible methane is 0.625 mol / s. The heat of combustion of methane is 802.3 kJ / mol, resulting in a calculated energy release of 501.4375 kW. This energy is significantly higher than the minimum ignition energy of methane-rich fuel gas (0.123 mJ). Therefore, in regions where the methane concentration reaches or exceeds the lower explosive limit (7.6%), the combustion energy is sufficient to ignite methane-rich fuel gas.

[0115] Based on the design results of igniter 7, the flame length of igniter 7 is approximately 600 mm. Figure 13 As shown, igniter 7 is installed 0.35 meters from the center axis of the discharge pipe outlet, at an angle of 55°. Figure 14 As shown, the methane concentration at the contact point between the flame of igniter 7 and the methane-rich gas is 20%-70%, which is much greater than the lower explosive limit (7.6%), providing a certain ignition margin and improving the ignition success rate and combustion stability.

[0116] Step 4: Based on the simulation results of Step 1, optimize and determine the geometric direction and support arrangement of the methane-rich gas outlet pipeline 5, the installation position and injection angle of the igniter 7 determined in Step 3, and arrange the load-bearing structure 1, gas supply and distribution system 2, measurement and control system 3, liquid oxygen methane semi-system engine 4 and test bench guide channel 8 to complete the design of the ground test system for the liquid oxygen methane semi-system engine that can safely handle methane-rich gas.

[0117] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present invention should 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 the claims.

Claims

1. A ground test system for a liquid oxygen-methane semi-system engine capable of safely processing methane-rich combustion gases, comprising: The test bench includes a load-bearing structure (1), a gas supply and distribution system (2), a measurement and control system (3), and a test bench guide channel (8). The load-bearing structure (1) is used to install the liquid oxygen methane semi-system engine (4) to be tested. The gas supply and distribution system (2) is used to supply gas to the liquid oxygen methane semi-system engine (4) to be tested, and is controlled and monitored by the measurement and control system (3). The test bench guide channel (8) is arranged in an oblique direction to guide the discharge of combustion products after ignition. The test bench is characterized by including a methane-rich gas outlet pipeline (5) and an igniter (7). The inlet of the methane-rich gas outlet pipeline (5) is connected to the gas outlet of the liquid oxygen methane semi-system engine (4) to guide the methane-rich gas generated by the liquid oxygen methane semi-system engine (4) to the area below the test bench horizontal plane (6) and to direct the gas jet toward the obliquely extending test bench guide groove (8). The geometric orientation and support arrangement of the methane-rich gas outlet pipeline (5) are determined by optimization design based on fluid-structure interaction simulation in order to reduce the thermal stress and thermal deformation of the pipeline system. The installation position and injection angle of the igniter (7) are determined based on the computational fluid dynamics simulation results of the flow field at the outlet of the methane-rich gas outlet pipe (5) and the minimum ignition energy theory. It is used to reliably ignite the methane-rich gas under supersonic jet conditions. The installation position and injection angle of the igniter (7) are determined by adopting the Le Chatelier rule and the minimum ignition energy formula, combined with the computational fluid dynamics simulation results of the flow field at the outlet of the methane-rich gas outlet pipe (5). By using computational fluid dynamics to simulate and analyze the supersonic flow field in the outlet area of ​​the outlet pipe, the velocity, concentration and temperature distribution are obtained, thereby determining the combustible mixture area where the methane concentration is above the lower explosive limit. The installation position and injection angle of the igniter are optimized based on the flow field results and combined with the minimum ignition energy theory, so that the ignition flame can be stably coupled with the combustible mixture area, and the reliable ignition of the methane-rich gas under supersonic jet conditions is achieved.

2. The ground test system for a liquid oxygen-methane semi-system engine capable of safely processing methane-rich combustion gas according to claim 1, characterized in that: The geometric orientation and support arrangement of the methane-rich gas outlet pipeline (5) were optimized by using the third strength theory, stiffness and strength condition formulas, and combined with the results of fluid-structure interaction simulation.

3. The ground test system for a liquid oxygen-methane semi-system engine capable of safely processing methane-rich combustion gas according to claim 1, characterized in that: The igniter (7) is a coaxial DC igniter; The igniter (7) is installed 0.35 meters away from the center axis of the outlet of the methane-rich gas outlet pipe (5), and the angle between the axis of the igniter (7) and the plane perpendicular to the center axis of the outlet of the methane-rich gas outlet pipe (5) is 55°.

4. A design method for a ground test system for a liquid oxygen-methane semi-system engine capable of safely processing methane-rich combustion gases, as described in any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Based on the third strength theory, complete the strength verification of the methane-rich gas outlet pipeline (5), perform fluid-structure interaction simulation on the methane-rich gas outlet pipeline (5), obtain the internal flow field, thermal strain and thermal stress distribution of the pipeline, and verify and optimize the geometric direction of the pipeline and the support constraint position based on the simulation results. Finally, calculate the support spacing of the methane-rich gas outlet pipeline (5) according to the stiffness condition and the strength condition, and take the smaller value of the two to comprehensively determine the geometric direction and support arrangement scheme of the methane-rich gas outlet pipeline (5). Step 2: Establish a fluid dynamics model including the outlet region of the methane-rich gas outlet pipeline (5), perform supersonic jet simulation, and obtain the temperature, Mach number, velocity, and methane concentration distribution of the flow field; Step 3: Based on the flow field temperature, Mach number, velocity, and methane concentration distribution obtained from the flow field simulation in Step 2, calculate the lower explosion limit of methane-rich gas and the required minimum ignition energy using the minimum ignition energy theory, and optimize and determine the installation position and injection angle of the igniter (7) accordingly. Step 4: Based on the simulation results of Step 1, optimize and determine the geometric direction and support arrangement of the methane-rich gas outlet pipeline (5), the installation position and injection angle of the igniter (7) determined in Step 3, and arrange the load-bearing structure (1), gas supply and distribution system (2), measurement and control system (3), liquid oxygen methane semi-system engine (4) and test bench guide channel (8) to complete the design of the ground test system of liquid oxygen methane semi-system engine that can realize the safe treatment of methane-rich gas.

5. The method of designing a ground test system for a semi-system engine capable of safe handling of methane-rich gas according to claim 4, wherein: In step 1, the calculation formula for the strength verification of the methane-rich gas outlet pipeline (5) using the third strength theory is as follows: ； ； ； Where: σ θ For circumferential stress, σ z For axial stress, σ r Where is the radial stress, P is the internal pressure of the pipe, r is the pipe radius, and t is the pipe wall thickness; The yield criterion is: ； In the formula, σ1 is the maximum principal stress, σ2 is the minimum principal stress, and σ y Where n is the yield strength of the pipe material, and n is the safety factor, which is 2.5 for thin-walled pipes.

6. The design method of the ground test system for a liquid oxygen-methane semi-system engine capable of safely processing methane-rich gas according to claim 4, characterized in that: In step 1, the support spacing of the methane-rich gas outlet pipeline (5) is calculated according to the stiffness and strength conditions respectively, and the smaller value of the two is taken. The stiffness condition is calculated using the following formula: ； In the formula: L1 is the span calculated from the stiffness condition, E t Let E be the elastic modulus of the pipe at the design temperature. t =2×10 5 MPa, I is the moment of inertia of the pipe section after deducting the negative deviation of the corrosion allowance level, and q is the weight of the pipe per meter; ； ； wherein: D0 is the outside diameter of the pipe, D i is the inside diameter of the pipe, p L is the density of the pipe material; The strength condition is calculated using the following formula: ； In the formula: L2 is the span calculated from the strength condition, [σ] t The allowable stress of the pipe at room temperature is taken as 137 MPa, and W is the section modulus of the pipe after deducting the negative deviation of the corrosion allowance level.

7. The method of designing a ground test system of a semi-system engine capable of safe handling of methane-rich gas according to claim 4, wherein, In step 3, the specific method for calculating the lower explosive limit and minimum ignition energy required for methane-rich gas is as follows: According to the Le Chatelier rule, the lower flammable limit LFL of the mixed gas is calculated according to the following formula mix : ； where: y i Volumetric fraction of the i-th component in the mixture, LFL i Lower explosive limit of the i-th component in the mixture; The minimum ignition energy (MIE) of this methane-rich gas is calculated using the following formula: ； Where: MIE ch4 The minimum ignition energy of pure methane, LFL ch4 The lower explosive limit (LFL) for pure methane. mix This is the lower explosive limit of the gas mixture.

8. The method of designing a ground test system of a semi-system engine capable of safe handling of methane-rich gas according to claim 7, wherein, In step 3, the specific method for optimizing and determining the installation position and injection angle of the igniter (7) is as follows: Based on the flow field temperature, Mach number, velocity, and methane concentration distribution obtained from the flow field simulation in step 2, and combined with the minimum ignition energy theory, the combustibility of the methane-rich gas-air mixture at different spatial locations and the minimum ignition energy required are analyzed. Areas with suitable methane concentration and relatively low flow velocity are selected, and the optimal injection angle suitable for supersonic jet conditions is determined to ensure that the igniter (7) reliably releases ignition energy.

9. The method of designing a ground test system of a semi-system engine capable of safe handling of methane-rich gas according to claim 4, wherein: In step 1, the fluid-structure interaction simulation uses a three-dimensional model, and the simulation results are used to determine the pipe bend angle, length, and support constraint position.

10. The method of designing a ground test system of a semi-system engine capable of safe handling of methane-rich gas according to claim 4, wherein: In step 2, the fluid dynamics simulation uses a density-based solver and a large eddy simulation turbulence model.

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