Exhaust system and design method of axial flow compressor test stand

Abstract

This invention discloses an exhaust system and design method for an axial compressor test bench. The exhaust system, suitable for installation at the exhaust end of the axial compressor test bench, includes: a volute connected to the exhaust end to receive the gas to be treated discharged from the exhaust end; a delivery pipe connected to the volute, with an exhaust valve installed on the delivery pipe, the delivery pipe including: a direct discharge group configured to deliver the gas to be treated; an ejector group configured to deliver the gas to be treated, with an ejector nozzle installed at the outlet end of the ejector group to draw in atmospheric air at the outlet end of the ejector group to cool the gas to be treated; a mixing pipe installed at the outlet end of the delivery pipe to deliver the gas to be treated; and an expansion pipe installed at the outlet end of the mixing pipe, configured to deliver the gas to be treated into an exhaust tower.

Description

Technical Field

[0001] At least one embodiment of this disclosure relates to the field of exhaust system technology, and more particularly to an exhaust system and design method for an axial compressor test bench. Background Technology

[0002] The exhaust system is one of the core systems of the axial compressor test bench. Its main function is to guide the high-temperature and high-pressure gas from the exhaust end of the axial compressor test bench to be discharged.

[0003] Exhaust systems with wide flow rate adjustment ranges are complex in aerodynamic and structural design, requiring overcoming difficulties such as ejecting and cooling high-temperature, high-pressure gases and achieving a large flow coefficient coverage range. Currently, exhaust systems for axial compressor test benches generally consist of a set of exhaust pipes and adjustment devices. While structurally simple, their flow rate adjustment range is small and unsuitable for high-power axial compressor test benches with wide flow rate adjustment ranges, thus lacking a large flow coefficient coverage range. Summary of the Invention

[0004] To address the existing technical problems, this disclosure provides an exhaust system and design method for an axial compressor test bench, which at least partially solves the above-mentioned technical problems. By adjusting the number and opening degree of the exhaust valves that need to be opened, a wide flow rate adjustment range can be obtained.

[0005] The first aspect of this disclosure provides an exhaust system for an axial compressor test bench, suitable for installation at the exhaust end of an axial compressor test bench, comprising: a volute connected to the exhaust end to receive the gas to be treated discharged from the exhaust end; a delivery pipe connected to the volute, the delivery pipe having an exhaust valve, the delivery pipe comprising: a direct discharge assembly configured to deliver the gas to be treated; an ejector assembly configured to deliver the gas to be treated, the outlet end of the ejector assembly having an ejector nozzle for drawing in atmospheric air at the outlet end of the ejector assembly to cool the gas to be treated; a mixing pipe installed at the outlet end of the delivery pipe to deliver the gas to be treated; and an expansion pipe installed at the outlet end of the mixing pipe, configured to deliver the gas to be treated into an exhaust tower.

[0006] The first aspect of this disclosure provides a design method for the exhaust system of an axial compressor test bench, comprising: determining the group of the gas to be treated flowing through the delivery pipeline based on the total gas flow temperature at the exhaust end, wherein the group of the delivery pipeline includes a direct exhaust group and an ejector group; estimating the target flow coefficient of the delivery pipeline based on the total gas flow pressure and volumetric flow rate of the gas to be treated at the exhaust end and the total gas flow temperature, thereby obtaining the number and diameter of exhaust valves on the delivery pipeline; and obtaining the cross-sectional area of ​​the pipeline before the valve based on the gas velocity in the pipeline before the valve, the total gas flow temperature, the total gas flow pressure, and the mass flow rate of the gas to be treated at the exhaust end, wherein the cross-sectional area of ​​the pipeline before the valve is determined. The pipeline represents the delivery pipeline located at the front end of the exhaust valve; based on the preset diameter of the pipeline downstream of the valve, the target diameter of the pipeline downstream of the valve is obtained according to the total outlet pressure, the Mach number before the shock wave, and the Mach number after the shock wave of the pipeline downstream of the valve, wherein the pipeline downstream of the valve represents the delivery pipeline located at the rear end of the exhaust valve; based on the preset diameter of the exhaust system end, the preset total outlet airflow pressure and preset total outlet airflow temperature at the outlet end of the expansion pipeline of the exhaust system are obtained, wherein the exhaust system end includes the ejector nozzle, the mixing pipeline, and the expansion pipeline; if the preset total outlet airflow pressure and the preset total outlet airflow temperature meet the preset limiting conditions and conform to the ejection calculation, the preset diameter is determined as the target diameter.

[0007] Based on the exhaust system and design method of the axial compressor test bench provided in this disclosure, the diameter of the exhaust system terminal, the cross-sectional area of ​​the pre-valve pipeline, and the cross-sectional area of ​​the post-valve pipeline are determined to meet preset limiting conditions. Based on the total gas flow temperature of the gas to be treated at the exhaust end of the axial compressor, the group of the delivery pipeline through which the gas to be treated flows is determined, so that gases of different temperatures can be processed through either the direct exhaust group or the ejector group. Based on the total gas flow pressure, volumetric flow rate, and total gas flow temperature at the exhaust end, the target flow coefficient of the delivery pipeline is estimated to determine the number and opening degree of the exhaust valves that need to be opened on the delivery pipeline, thereby obtaining a wide flow rate adjustment range suitable for a high-power axial compressor test bench with a wide flow rate adjustment range. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the exhaust system of an axial compressor test bench according to an embodiment of the present disclosure;

[0009] Figure 2 This is a flowchart illustrating the design method of the exhaust system for an axial compressor test bench according to an embodiment of the present disclosure; and

[0010] Figure 3 This is a flowchart illustrating the number and diameter of exhaust valves on a delivery pipeline according to an embodiment of this disclosure.

[0011] Figure Labels

[0012] 1. Snail shell;

[0013] 2. Delivery pipelines;

[0014] 21. Straight-line group;

[0015] 22. Ejector Group;

[0016] 221. Ejector nozzle;

[0017] 23. Exhaust valve;

[0018] 24. Piping upstream of the valve;

[0019] 25. Piping downstream of the valve;

[0020] 3. Mixed pipelines;

[0021] 4. Expand the pipeline. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0023] However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of this application. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of this application for ease of explanation. However, it will be apparent that one or more embodiments may be implemented without these specific details. Furthermore, descriptions of well-known technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this application.

[0024] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0025] When using expressions such as "at least one of A, B, and C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). Similarly, when using expressions such as "at least one of A, B, or C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0026] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0027] The present invention is described herein with respect to structural embodiments and methods. It should be understood that this is not intended to limit the invention to the specific disclosed embodiments; the invention can be practiced using other features, elements, methods, and embodiments. Similar elements in different embodiments are typically designated with similar numbers.

[0028] Multistage axial compressors are key components commonly found in aero engines and other turbomachinery, used to increase gas pressure. The exhaust system's primary function is to guide the high-temperature, high-pressure gas from the exhaust end of the axial compressor test bench. The exhaust system typically consists of a set of exhaust pipes and regulating devices; its structure is simple, but its flow rate adjustment range is small, making it unsuitable for axial compressor test benches with wide flow rate adjustment ranges and high power requirements.

[0029] Figure 1 This is a schematic diagram of the exhaust system of an axial compressor test bench according to an embodiment of the present disclosure.

[0030] The embodiments of this disclosure provide an exhaust system for an axial compressor test bench, suitable for installation at the exhaust end of the axial compressor test bench, such as... Figure 1 As shown, the exhaust system includes a volute 1, a delivery pipe 2, a mixing pipe 3, and an expansion pipe 4. The volute 1 is connected to the exhaust end to receive the gas to be treated discharged from the exhaust end.

[0031] The conveying pipe 2 is connected to the volute 1. An exhaust valve 23 is installed on the conveying pipe 2. The conveying pipe 2 includes a direct discharge assembly and an ejector assembly. The direct discharge assembly is configured to convey the gas to be treated; the ejector assembly is configured to convey the gas to be treated, and an ejector nozzle 221 is installed at the outlet end of the ejector assembly to draw in atmospheric air and cool the gas to be treated. Figure 1 In the diagram, those marked with serial numbers ①②⑤⑥ are the straight-line group, and those marked with serial numbers ③④ are the ejection group.

[0032] A mixing pipe 3 is installed at the outlet end of the conveying pipe 2 to convey the gas to be treated. An expansion pipe 4 is installed at the outlet end of the mixing pipe 3 and is configured to convey the gas to be treated into the exhaust tower.

[0033] In one exemplary embodiment, such as Figure 1 As shown, the exhaust valve 23 is located in the middle of the conveying pipe 2. The conveying pipe 2 located in front of the exhaust valve 23 is the pre-valve pipe 24, and the conveying pipe 2 located behind the exhaust valve 23 is the post-valve pipe 25. The straight discharge group and the ejector group are two types of groups in the conveying pipe 2. There are multiple straight discharge groups and multiple ejector groups, and they are all connected in parallel.

[0034] The two ends of the straight-out assembly are connected to the volute 1 and the mixing pipe 3, respectively. The inlet end of the ejector assembly is connected to the volute 1. A slot is provided at the position opposite to the outlet end of the ejector assembly in the mixing pipe 3. The outlet end of the ejector assembly is inserted into the slot. There is a gap between the pipe wall of the delivery pipe 2 of the ejector assembly and the slot. When the high-temperature and high-pressure gas to be treated is ejected from the ejector nozzle 221, the atmosphere around the mixing pipe 3 flows into the mixing pipe 3 from the gap in the slot and mixes with the high-temperature and high-pressure gas to be treated to cool down the gas to be treated.

[0035] The embodiments of this disclosure also propose a design method for the exhaust system of an axial compressor test bench.

[0036] Figure 2 This is a flowchart of a design method for the exhaust system of an axial compressor test bench according to an embodiment of the present disclosure.

[0037] like Figure 1 and 2 As shown, the design method of the exhaust system in this embodiment includes operations S110 to S150:

[0038] In operation S110, the group of the gas to be treated flowing through the conveying pipe 2 is determined according to the total temperature of the gas flow at the exhaust end. The conveying pipe 22 includes the direct discharge group 21 and the ejector group 22.

[0039] According to an embodiment of this disclosure, a high-temperature, high-pressure gas to be treated is discharged from the exhaust end of an axial compressor test bench. Based on the total temperature of the gas flow, the group of the gas to be treated flowing through the delivery pipe 2 is determined, so as to classify and process the gas to be treated at different flow temperatures.

[0040] According to an embodiment of this disclosure, in operation S110, determining the group of the gas to be treated flowing through the conveying pipe 2 based on the total temperature of the gas flow at the exhaust end includes: determining the ejector group 22 through the conveying pipe 2 when the total gas flow temperature is greater than a preset temperature; and determining the direct exhaust group 21 through the conveying pipe 2 when the total gas flow temperature is less than or equal to the preset temperature. The preset temperature represents the maximum temperature that the exhaust tower can withstand.

[0041] According to the embodiments of this disclosure, when the total temperature of the gas flow to be treated is greater than the preset temperature, it is necessary to cool down the gas to be treated. The exhaust valve 23 is controlled so that the gas to be treated flows through the ejector group 22 of the conveying pipe 2. The outlet end of the ejector group 22 draws in the atmosphere to cool down the gas to be treated, so that the gas to be treated can be delivered to the exhaust tower, thereby treating gases of different temperatures and improving the applicability of the exhaust system.

[0042] In operation S120, the target flow coefficient of the conveying pipeline 2 is estimated based on the total pressure and volumetric flow rate of the gas to be treated at the exhaust end and the total temperature of the gas flow, and the number and diameter of the exhaust valves 23 on the conveying pipeline 2 are obtained.

[0043] According to embodiments of this disclosure, given the target flow coefficient of the conveying pipeline 2, the valve opening degree of the exhaust valve 23 can be determined, whereby the valve opening degree represents the sum of the valve opening degrees of multiple conveying pipelines 2. By determining the target flow coefficient and the valve opening degree, the number and diameter of the exhaust valves 23 on the conveying pipeline 2 can be obtained.

[0044] In operation S130, the cross-sectional area of ​​the inlet pipe 24 is obtained based on the gas flow rate, total gas temperature, total gas pressure, and mass flow rate of the gas to be treated at the exhaust end of the inlet pipe 24. The inlet pipe 24 represents the delivery pipe 2 located at the front end of the exhaust valve 23.

[0045] According to embodiments of this disclosure, the cross-sectional area of ​​the pre-valve pipe 24 represents the sum of the cross-sectional areas of the pre-valve pipes 24 of the plurality of conveying pipes 2. The cross-sectional area of ​​a single pre-valve pipe 24 and the number of pre-valve pipes 24 can be determined based on the cross-sectional area of ​​the pre-valve pipe 24.

[0046] In operation S140, based on the preset diameter of the downstream pipe 25, the target diameter of the downstream pipe 25 is obtained according to the total outlet pressure of the downstream pipe 25, the Mach number before the shock wave, and the Mach number after the shock wave. The downstream pipe 25 represents the delivery pipe 2 located at the rear end of the exhaust valve 23.

[0047] According to embodiments of this disclosure, the cross-sectional area of ​​the downstream conduit 25 represents the sum of the cross-sectional areas of the downstream conduits 25 of the plurality of delivery conduits 2. The cross-sectional area of ​​a single downstream conduit 25 and the number of downstream conduits 25 can be determined based on the cross-sectional area of ​​the downstream conduit 25.

[0048] In operation S150, based on the preset diameter of the exhaust system end, the preset total pressure and preset total temperature of the exhaust gas flow at the outlet end of the expansion pipe 4 of the exhaust system are obtained. The exhaust system end includes an ejector nozzle 221, a mixing pipe 3 and an expansion pipe 4.

[0049] In operation S160, if the preset total pressure and preset total temperature of the outlet airflow meet the preset limiting conditions, the preset diameter is determined as the target diameter.

[0050] According to an embodiment of this disclosure, in operation S160, the preset limiting conditions are that the total pressure of the outlet gas flow of the expansion pipe 4 is greater than 1.05 bar, and the total temperature of the outlet gas flow of the expansion pipe 4 is less than the limit temperature that the exhaust tower can withstand. Based on the preset diameter of the ejector nozzle 221, the preset diameter of the mixing pipe 3, and the preset diameter of the expansion pipe 4, the preset total pressure and preset total temperature of the outlet gas flow of the expansion pipe 4 of the exhaust system are obtained. Under the condition that the total pressure of the outlet gas flow of the expansion pipe 4 is greater than 1.05 bar and the total temperature of the outlet gas flow of the expansion pipe 4 is less than the limit temperature that the exhaust tower can withstand, the preset diameter is determined as the target diameter, and the target diameters of the ejector nozzle 221, the mixing pipe 3, and the expansion pipe 4 are obtained.

[0051] Figure 3 This is a flowchart illustrating the number and diameter of the exhaust valves 23 on the conveying pipeline 2 according to an embodiment of this disclosure.

[0052] like Figure 3 As shown, the method for obtaining the number and diameter of the exhaust valves 23 on the conveying pipeline 2 in this embodiment includes operations S210 to S240.

[0053] In operation S210, the flow state of the airflow in the delivery pipeline 2 is determined based on the pressure difference ratio of the exhaust valve 23, wherein the flow state includes blocked flow and non-blocked flow.

[0054] According to embodiments of this disclosure, in operation S210, if the pressure differential ratio is greater than the critical pressure differential ratio, the flow state is determined to be choked flow. If the pressure differential ratio is less than or equal to the critical pressure differential ratio, the flow state is determined to be non-choked flow.

[0055] In operation S220, based on the flow state, the target flow coefficient is obtained according to the total air temperature, total air pressure and volumetric flow rate.

[0056] According to an embodiment of this disclosure, in operation S220, when the flow state is determined to be a non-blocked flow, the expression (1) for the first target flow coefficient is obtained as follows:

[0057]

[0058] Among them, K V Q is the flow coefficient. p Volumetric flow rate, The total pressure of the airflow. ρ is the total temperature of the airflow. N =1.29kg / m 3 Density under standard conditions Z is the coefficient of thermal expansion, Z is a function of specific pressure and specific temperature, and X is the valve differential pressure ratio.

[0059] Based on the first target flow coefficient expression (1), the first target flow coefficient is obtained according to the total air temperature, the total air pressure and the volumetric flow rate.

[0060] Given that the flow state is determined to be choked flow, the expression for the second target flow coefficient (2) is obtained as follows:

[0061]

[0062] Among them, K V Q is the flow coefficient. p Volumetric flow rate, The total pressure of the airflow. ρ is the total temperature of the airflow. N =1.29kg / m 3 Let Z be the density under standard conditions, Z be a function of specific pressure and specific temperature, and X be the density. T is the critical differential pressure ratio of the valve, and k is the gas adiabatic index;

[0063] Based on the expression for the second target flow coefficient (2), the second target flow coefficient is obtained according to the total temperature of the airflow, the total pressure of the airflow, and the volumetric flow rate.

[0064] In operation S230, the valve opening of exhaust valve 23 is determined based on the target flow coefficient.

[0065] According to an embodiment of this disclosure, the target flow coefficient K of the conveying pipeline 2 is... V There is a corresponding relationship between the valve opening degree θ and the valve opening degree θ, the relationship being θ = f(K V This allows for the determination of valve opening based on the target flow coefficient. For example, the relationship between the valve opening and the flow coefficient for a DN400 valve is shown in Table 1 below.

[0066] Table 1

[0067] CL900 DN400 262 568 882 1348 1995 3054 4101 4530 4740

[0068] According to embodiments of this disclosure, C V =1.156K V Calculations revealed that the flow coefficient C on the axial compressor test bench was... V When the value is between 1488 and 1649, the corresponding valve opening is between 40° and 50°, therefore the DN400 valve meets the requirements.

[0069] In operation S240, the number of exhaust valves 23 and their valve diameter are determined based on the valve opening.

[0070] According to embodiments of this disclosure, the valve opening degree represents the sum of the valve opening degrees of multiple exhaust valves 23. The requirement is met when all valve opening degrees are within the optimal operating range of the valves. If the valve opening degree is too large, the valve diameter or the number of valves needs to be increased; if the valve opening degree is too small, the valve diameter or the number of valves needs to be reduced.

[0071] According to embodiments of this disclosure, the test parameters for the axial compressor test bench, including rotational speed, mass flow rate, total gas pressure, total gas temperature, and outlet diameter at the exhaust end, are shown in Table 2 below:

[0072] Table 2

[0073] 110％ 87.15 2621.00 845.26 0.75 / 0.71 100％ 95.81 2626.20 774.90 0.75 / 0.71 90％ 62.80 1510.10 664.10 0.75 / 0.71 80％ 33.51 701.30 559.76 0.75 / 0.71 70％ 23.33 453.05 493.78 0.75 / 0.71 60％ 18.02 334.76 447.80 0.75 / 0.71

[0074] According to an embodiment of this disclosure, the cross-sectional area of ​​the upstream pipeline 24 is obtained based on the gas flow rate of the upstream pipeline 24, the flow rate function of the gas in the upstream pipeline 24, the total temperature of the gas flow, the total pressure of the gas flow, and the mass flow rate of the gas to be treated at the exhaust end.

[0075] The expression (3) relating the flow rate function of the gas in the inlet pipe 24, the total temperature of the gas flow, the total pressure of the gas flow, the mass flow rate of the gas to be treated at the exhaust end, and the cross-sectional area of ​​the inlet pipe 24 is as follows:

[0076]

[0077] Where q(λ2) is the flow function of the pipeline upstream of the valve, and G p For quality flow, The total temperature of the airflow. A1 is the total air pressure, A2 is the cross-sectional area of ​​the pipe before the valve, and K = 0.0404 for air.

[0078] Furthermore, based on the velocity coefficient of the gas in the upstream pipeline 24, the flow rate function of the gas in the upstream pipeline 24 is obtained. The expression (4) relating the velocity coefficient of the gas in the upstream pipeline 24 to the flow rate function of the gas in the upstream pipeline 24 is as follows:

[0079]

[0080] Where q(λ2) is the flow function, λ2 is the velocity coefficient of the gas in the pipeline before the valve, and k is the gas adiabatic index.

[0081] Furthermore, based on the gas velocity and total gas temperature in the upstream pipeline 24, the velocity coefficient of the gas in the upstream pipeline 24 is obtained. The expression (5) relating the gas velocity, total gas temperature, and velocity coefficient of the gas in the upstream pipeline 24 is as follows:

[0082]

[0083] Where v2 is the gas velocity in the upstream pipeline, λ2 is the gas velocity coefficient in the upstream pipeline, and R is the gas constant. Let be the total temperature of the airflow, and k be the adiabatic index of the gas, k = 1.4.

[0084] According to the embodiments of this disclosure, the gas flow velocity of the inlet pipe 24 generally meets the range of 24-29 m / s, which is not limited here. Based on the gas flow velocity v2 of the inlet pipe 24, the velocity coefficient λ2 of the gas inlet pipe 24 is obtained through expression (5). Then, through expressions (4) and (3), the cross-sectional area A2 of the inlet pipe 24 is obtained, and the cross-sectional diameter of the inlet pipe 24 can also be known.

[0085] According to embodiments of this disclosure, the total pressure before the valve is equal to the total outlet pressure of the axial compressor test bench, and the total pressure after the valve is equal to the total outlet pressure of the downstream pipe 25. When the total pressure ratio between the total pressure before and after the valve reaches the critical pressure ratio, the valve is in a blocked state, a shock wave is generated after the valve, and the total pressure decreases; when the total pressure ratio between the total pressure before and after the valve is less than the critical pressure ratio, the gas flow at both the valve and the downstream pipe 25 is subsonic. The valve can be equivalent to a Laval nozzle, and the outlet of the downstream pipe 25 (the outlet of the ejector nozzle 221) is subsonic, with an outlet static pressure approximately equal to atmospheric pressure. The larger the cross-sectional area of ​​the downstream pipe 25, the lower the gas velocity and the smaller the pressure loss. Due to structural limitations, the minimum cross-sectional area of ​​the downstream pipe 25 needs to be calculated.

[0086] According to an embodiment of this disclosure, based on the preset diameter of the downstream pipe 25, the target diameter of the downstream pipe 25 is obtained according to the total outlet pressure of the downstream pipe 25, the Mach number before the shock wave, and the Mach number after the shock wave.

[0087] According to an embodiment of this disclosure, based on the Mach number after the shock wave, the iterative diameter of the downstream pipe 25 is obtained according to the mass flow rate, total gas temperature, and total outlet pressure of the downstream pipe 25. Under the condition that the ejection calculation is satisfied, the iterative diameter of the downstream pipe 25 is determined as the target diameter of the downstream pipe 25.

[0088] Among them, the expressions (6) and (7) for the relationship between the Mach number after the shock wave, the total outlet pressure of the downstream pipeline 25, the mass flow rate, and the total gas temperature are:

[0089]

[0090]

[0091] Among them, G p For mass flow rate, air K = 0.0404. The total temperature of the airflow. Let A' be the total outlet pressure of the downstream pipeline, Ma′2 be the Mach number after the shock wave, and A′ be the cross-sectional area of ​​the shock wave, which is equivalent to the cross-sectional area of ​​the downstream pipeline (the diameter of the downstream pipeline can be determined from the cross-sectional area of ​​the downstream pipeline).

[0092] Furthermore, the Mach number after the shock is obtained based on the Mach number before the shock. The expression (8) relating the Mach number before and after the shock is as follows:

[0093]

[0094] Where Ma′2 is the Mach number after the shock wave, Ma′1 is the Mach number before the shock wave, and k is the gas adiabatic index, k = 1.4.

[0095] Furthermore, the Mach number before the shock wave is obtained based on the total outlet pressure and total gas flow pressure of the downstream pipe 25. The expression (9) relating the total outlet pressure, total gas flow pressure, and Mach number before the shock wave of the downstream pipe 25 is as follows:

[0096]

[0097] in, This refers to the total outlet pressure of the pipeline downstream of the valve. Here, Ma′1 is the total pressure of the gas flow, Ma′1 is the Mach number before the shock wave, and k is the gas adiabatic index, k = 1.4.

[0098] Furthermore, based on the velocity coefficient of the gas at the outlet of the downstream pipeline and the static pressure at the outlet of the downstream pipeline, the total outlet pressure of the downstream pipeline is obtained. The expression (10) relating the velocity coefficient of the gas at the outlet of the downstream pipeline, the static pressure at the outlet of the downstream pipeline, and the total outlet pressure of the downstream pipeline is as follows:

[0099]

[0100] in, P5 is the total outlet pressure of the downstream pipeline, P5 is the outlet static pressure of the downstream pipeline, λ5 is the velocity coefficient of the gas at the outlet of the downstream pipeline, and k is the gas adiabatic index, k = 1.4.

[0101] Furthermore, based on the preset diameter of the downstream pipe 25, the preset cross-sectional area of ​​the downstream pipe 25 can be determined. The velocity coefficient of the gas at the outlet of the downstream pipe 25 is obtained based on the outlet static pressure, mass flow rate, and total gas temperature of the downstream pipe 25. The expression (11) relating the preset cross-sectional area of ​​the downstream pipe 25, the outlet static pressure, mass flow rate, total gas temperature, and the velocity coefficient of the gas at the outlet of the downstream pipe 25 is as follows:

[0102]

[0103] Among them, G p For mass flow rate, K = 0.0404 for air, and P5 is the outlet static pressure of the downstream pipeline. λ5 is the outlet temperature of the exhaust end of the axial compressor, which is the same as the total gas temperature. A5 is the preset cross-sectional area of ​​the downstream pipeline, and λ5 is the velocity coefficient of the gas at the outlet of the downstream pipeline.

[0104] According to an embodiment of this disclosure, based on the preset diameter of the downstream pipe 25, the preset cross-sectional area of ​​the downstream pipe 25 is known. Based on expression (11), the velocity coefficient λ5 of the gas at the outlet of the downstream pipe 25 is obtained. Based on the velocity coefficient λ5 of the gas at the outlet of the downstream pipe 25, the total outlet pressure of the downstream pipe 25 is obtained based on expression (10). Based on the total outlet pressure of the downstream pipe 25, the pre-shock Mach number is obtained based on expression (9). Based on the pre-shock Mach number, the post-shock Mach number is obtained based on expression (8). Based on the post-shock Mach number, based on expressions (7) and (6), the cross-sectional area of ​​the downstream pipe 25 is obtained, and the iterative diameter of the downstream pipe 25 is known. If the ejection calculation is satisfied, the iterative diameter of the downstream pipe 25 is determined as the target diameter of the downstream pipe 25. On the other hand, if the ejection calculation is not satisfied, the preset diameter of the downstream pipe 25 is updated, and the above process is repeated for iterative calculation until the ejection calculation is satisfied, and the iterative diameter of the downstream pipe 25 is determined as the target diameter of the downstream pipe 25.

[0105] Specifically, when the gas to be treated flows through the ejector assembly 22 of the conveying pipeline 2, the preset diameter of the downstream pipeline 25 is the preset diameter of the ejector nozzle 221 of the ejector assembly 22, and the calculated target diameter of the downstream pipeline 25 is greater than the preset diameter of the ejector nozzle 221. When the gas to be treated flows through the direct discharge assembly 21 of the conveying pipeline 2, the preset diameter of the downstream pipeline 25 is the diameter of the downstream pipeline 25 of the direct discharge assembly 21, and the calculated target diameter of the downstream pipeline 25 is equal to the preset diameter of the downstream pipeline 25.

[0106] According to an embodiment of this disclosure, taking the ejector assembly as an example, assuming the diameter of the ejector nozzle 221 is 0.8m, then based on expression (11), we can obtain:

[0107]

[0108] We can obtain λ5 = 0.75, and based on expression (10), we can obtain the total outlet pressure of the ejector nozzle. for:

[0109]

[0110] Based on expressions (9) and (8), the Mach number before the shock wave is 5.21, and the Mach number after the shock wave is 0.41. Then, based on expressions (6) and (7), the shock wave cross-sectional area is 0.73 m², the equivalent cross-sectional area of ​​the downstream pipe 25 is 0.73 m², and the iterative diameter of the downstream pipe 25 is 0.9 m. The final diameter of the downstream pipe 25 still needs to be confirmed by ejection calculation. If the ejection calculation is successful, the iterative diameter of the downstream pipe 25 is determined as the target diameter of the downstream pipe 25, and the cross-sectional area of ​​the downstream pipe 25 is obtained. If the ejection calculation is unsuccessful, the preset diameter of the ejector nozzle 221 is updated, and the above process is repeated for iterative calculation until the ejection calculation is successful, and the iterative diameter of the downstream pipe 25 is determined as the target diameter of the downstream pipe 25.

[0111] According to embodiments of this disclosure, a preset total outlet airflow pressure of the ejector nozzle 221 is obtained based on a preset diameter of the ejector nozzle 221; a preset ejected airflow flow rate is obtained based on the preset total outlet airflow pressure of the ejector nozzle 221; and a preset total outlet airflow pressure and a preset total outlet airflow temperature of the exhaust system are obtained based on the preset ejected airflow flow rate and the preset diameters of the mixing pipe 3 and the expansion pipe 4.

[0112] If the preset total pressure and temperature of the outlet gas flow meet the preset limiting conditions and conform to the ejection calculation, the preset diameter is determined as the target diameter. Among them, the preset limiting conditions are that the total pressure of the outlet gas flow of the expansion pipe 4 is greater than 1.05 bar, and the total temperature of the outlet gas flow of the expansion pipe 4 is less than the limit temperature that the exhaust tower can withstand.

[0113] Based on the exhaust system and design method of the axial compressor test bench provided in this disclosure, the diameter of the exhaust system end, the cross-sectional area of ​​the pre-valve pipe 24, and the cross-sectional area of ​​the post-valve pipe 25 that meet the preset limiting conditions are determined. Based on the total gas flow temperature of the gas to be treated at the exhaust end of the axial compressor, the group of the gas to be treated flowing through the delivery pipe 2 is determined, so that gases of different temperatures can be treated by flowing through the direct exhaust group 21 or the ejector group 22. Based on the total gas flow pressure, volumetric flow rate, and total gas flow temperature at the exhaust end, the target flow coefficient of the delivery pipe 2 is estimated to determine the number and opening degree of the exhaust valves 23 that need to be opened on the delivery pipe 2, thereby obtaining a wide flow adjustment range suitable for a high-power axial compressor test bench with a wide flow adjustment range.

[0114] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of designing an exhaust system of an axial compressor test stand, characterized in that, The exhaust system is suitable for installation at the exhaust end of an axial compressor test bench and includes: The volute (1) is connected to the exhaust end to receive the gas to be treated discharged from the exhaust end; A conveying pipe (2) is connected to the volute (1), and an exhaust valve (23) is provided on the conveying pipe (2). The conveying pipe (2) includes: The direct-flow assembly (21) is configured to convey the gas to be processed; The ejector assembly (22) is configured to deliver the gas to be treated. The outlet end of the ejector assembly (22) is provided with an ejector nozzle (221) to draw in atmospheric air at the outlet end of the ejector assembly (22) to cool the gas to be treated. A mixing pipe (3) is installed at the outlet end of the conveying pipe (2) to convey the gas to be treated; and An expansion pipe (4) is installed at the outlet end of the mixing pipe (3) and is configured to transport the gas to be treated into the exhaust tower. The design method includes: Based on the total temperature of the gas to be treated at the exhaust end, the group of the gas to be treated flowing through the conveying pipe (2) is determined, wherein the group of the conveying pipe (2) includes a straight discharge group (21) and an ejector group (22). Based on the total pressure and volumetric flow rate of the gas to be treated at the exhaust end and the total temperature of the gas flow, the target flow coefficient of the conveying pipeline (2) is estimated, and the number and valve diameter of the exhaust valves (23) on the conveying pipeline (2) are obtained. The cross-sectional area of ​​the pipe before the valve (24) is obtained based on the gas flow rate of the pipe before the valve (24), the total temperature of the gas flow, the total pressure of the gas flow and the mass flow rate of the gas to be treated at the exhaust end, wherein the pipe before the valve (24) represents the conveying pipe (2) located at the front end of the exhaust valve (23); Based on the preset diameter of the downstream pipe (25), the target diameter of the downstream pipe (25) is obtained according to the total outlet pressure, the Mach number before the shock wave and the Mach number after the shock wave of the downstream pipe (25), wherein the downstream pipe (25) represents the conveying pipe (2) located at the rear end of the exhaust valve (23). Based on the preset diameter of the exhaust system end, the preset total pressure of the outlet airflow and the preset total temperature of the outlet airflow at the outlet end of the expansion pipe of the exhaust system are obtained, wherein the exhaust system end includes the ejector nozzle (221), the mixing pipe (3) and the expansion pipe (4). If the preset total pressure and the preset total temperature of the outlet airflow meet the preset limiting conditions and conform to the ejection calculation, the preset diameter is determined as the target diameter.

2. The design method of an exhaust system according to claim 1, characterized by, The step of determining the group of the gas to be treated flowing through the delivery pipe (2) based on the total temperature of the gas flow at the exhaust end includes: When the total temperature of the gas flow is greater than the preset temperature, the gas to be treated is determined to flow through the ejector assembly (22) of the delivery pipe (2); If the total temperature of the airflow is less than or equal to the preset temperature, the gas to be treated is determined to flow through the direct discharge group (21) of the conveying pipe (2); The preset temperature represents the maximum temperature that the exhaust tower can withstand.

3. The design method for the exhaust system according to claim 1, characterized in that, The step of estimating the target flow coefficient of the conveying pipeline (2) based on the total pressure and volumetric flow rate of the gas to be treated at the exhaust end and the total temperature of the gas flow, and obtaining the number and valve diameter of the exhaust valves (23) on the conveying pipeline (2), includes: Based on the pressure difference ratio of the exhaust valve (23), the flow state of the airflow in the delivery pipe (2) is determined, wherein the flow state includes blocked flow and non-blocked flow; Based on the flow state, the target flow coefficient is obtained according to the total air temperature, the total air pressure, and the volumetric flow rate. Based on the target flow coefficient, determine the valve opening of the exhaust valve (23); Based on the valve opening, the number of valves and the valve diameter of the exhaust valve (23) are determined.

4. The design method of the exhaust system according to claim 3, characterized in that, The step of determining the flow state of the airflow in the conveying pipeline (2) based on the pressure difference ratio of the exhaust valve (23) includes: If the pressure differential ratio is greater than the critical pressure differential ratio, the flow state is determined to be choked flow. When the pressure differential ratio is less than or equal to the critical pressure differential ratio, the flow state is determined to be non-blocked flow.

5. The design method of the exhaust system according to claim 3, characterized in that, The step of obtaining the target flow coefficient based on the flow state, according to the total air temperature, the total air pressure, and the volumetric flow rate, includes: Given that the flow state is determined to be non-blocked flow, the expression for the first target flow coefficient is obtained as follows: ； in, For flow coefficient, Volumetric flow rate, The total pressure of the airflow. The total temperature of the airflow. Density under standard conditions The coefficient of thermal expansion is 1 / 3. It is a function of specific pressure and specific temperature. Valve differential pressure ratio; Based on the first target flow coefficient expression, the first target flow coefficient is obtained according to the total air temperature, the total air pressure, and the volumetric flow rate; Given that the flow state is determined to be choked flow, the expression for the second target flow coefficient is obtained as follows: ； in, For flow coefficient, Volumetric flow rate, The total pressure of the airflow. The total temperature of the airflow. Density under standard conditions It is a function of specific pressure and specific temperature. This is the critical differential pressure ratio of the valve. The gas adiabatic index; Based on the expression for the second target flow coefficient, the second target flow coefficient is obtained according to the total air temperature, the total air pressure, and the volumetric flow rate.

6. The design method of the exhaust system according to claim 1, characterized in that, The step of obtaining the cross-sectional area of ​​the inlet pipe (24) based on the gas flow rate of the inlet pipe (24), the total temperature of the gas flow, the total pressure of the gas flow, and the mass flow rate of the gas to be treated at the exhaust end includes: Based on the gas flow rate in the upstream pipeline (24) and the total temperature of the gas flow, the velocity coefficient of the gas in the upstream pipeline is obtained; Based on the velocity coefficient of the gas in the upstream pipeline, the flow function value corresponding to the velocity coefficient of the gas in the upstream pipeline is obtained; Based on the flow function value, the cross-sectional area of ​​the inlet pipe (24) is obtained according to the mass flow rate, the total temperature of the airflow, and the total pressure of the airflow.

7. The design method for the exhaust system according to claim 1, characterized in that, The target diameter of the downstream pipeline (25) is obtained based on the preset diameter of the downstream pipeline (25), according to the total outlet pressure of the downstream pipeline (25), the Mach number before the shock wave, and the Mach number after the shock wave, including: Based on the preset diameter of the downstream pipe (25), the velocity coefficient of the gas at the outlet of the downstream pipe (25) is obtained according to the outlet static pressure of the downstream pipe (25), the mass flow rate, and the total temperature of the gas flow. The total outlet pressure of the downstream pipeline (25) is obtained based on the velocity coefficient of the gas at the outlet of the downstream pipeline (25) and the static pressure at the outlet of the downstream pipeline (25). The Mach number before the shock wave is obtained based on the total outlet pressure of the downstream pipe (25) and the total airflow pressure. Based on the Mach number before the shock wave, the Mach number after the shock wave is obtained; Based on the Mach number after the shock wave, the iterative diameter of the downstream pipe (25) is obtained according to the mass flow rate, the total temperature of the airflow, and the total outlet pressure of the downstream pipe (25). Under the condition of conforming to the ejection calculation, the iterative diameter of the downstream pipe (25) is determined as the target diameter of the downstream pipe (25).

8. The design method for the exhaust system according to claim 1, characterized in that, The method of obtaining the preset total pressure and preset total temperature of the exhaust gas flow at the end of the exhaust system based on the preset diameter includes: Based on the preset diameter of the ejector nozzle (221), the preset total pressure of the outlet airflow of the ejector nozzle (221) is obtained; The preset ejected airflow flow rate is obtained based on the preset total outlet airflow pressure of the ejector nozzle (221); Based on the preset ejected airflow rate, and according to the preset diameter of the mixing pipe (3) and the preset diameter of the expansion pipe (4), the preset outlet airflow total pressure and preset outlet airflow total temperature of the exhaust system are obtained.

9. The design method for the exhaust system according to claim 1, characterized in that, The preset limiting conditions are that the total pressure of the outlet airflow of the expansion pipe (4) is greater than 1.05 bar, and the total temperature of the outlet airflow of the expansion pipe (4) is less than the limit temperature that the exhaust tower can withstand.

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