Method for calculating flow rate of single compressor in continuous wind tunnel parallel compressor system

Abstract

The application discloses a method for calculating the flow of a single compressor in a continuous wind tunnel parallel compressor system, and relates to the field of supersonic wind tunnel operation debugging.The mass flow of a wind tunnel nozzle is measured as a total flow benchmark;the equal-speed total pressure ratio performance curves of each single compressor are measured in advance and are parameterized into a continuous equal-speed total pressure ratio performance mathematical model;the speed and total pressure ratio of each compressor are measured in real time when the wind tunnel is operated;the equivalent flow is obtained by solving the inverse function or the iterative method; the initial mass flow of each compressor is calculated in combination with the inlet total pressure and the inlet total temperature;finally, the actual mass flow of each compressor is obtained by correcting the deviation between the mass flow of the nozzle and the sum of the initial mass flow of each compressor, so that the accurate determination of the flow of each single compressor in parallel operation is realized, and the establishment and operation safety of the target flow field of the test section of the wind tunnel are ensured.

Description

Technical Field

[0001] This invention relates to the field of supersonic wind tunnel operation and commissioning, specifically to a method for calculating the flow rate of a single compressor in a continuous wind tunnel parallel compressor system. Background Technology

[0002] Continuous wind tunnels are indispensable ground-based testing facilities supporting the development of aerospace vehicles. The compressor system is the heart of a continuous wind tunnel, and precise control of the compressor system is crucial for establishing the target flow field and ensuring safe operation. Accurately measuring the compressor's mass flow rate during operation is fundamental to achieving precise compressor control; compressor flow rate is a core control parameter for the compressor.

[0003] Due to factors such as the size and spatial layout of continuous wind tunnels, it is often impossible to directly and accurately measure the compressor mass flow rate. Since the mass flow rate through all sections of a continuous wind tunnel is equal during operation, and considering that the flow field is most uniform in the nozzle section, current technology usually uses the measured mass flow rate of the nozzle section as the compressor mass flow rate, and uses it as the core control parameter of the wind tunnel compressor.

[0004] A single large / ultra-large compressor driving a continuous wind tunnel is a conventional technical solution in the design of continuous wind tunnel compressor systems. In recent years, to effectively reduce the technical risks and development costs of continuous wind tunnel compressor systems, a compressor system based on multiple small compressors connected in parallel has become a common technical solution for many ongoing continuous wind tunnel compressor systems (referred to as the multi-parallel wind tunnel compressor system technical solution, such as...). Figure 1 (As shown). The technical solution of optimizing a single large / ultra-large compressor into multiple small compressors connected in parallel effectively reduces the technical risks in compressor structural design, processing and manufacturing, and external components, but it brings new challenges to the control of the wind tunnel compressor system.

[0005] Because of the differences in the overall performance of individual compressors (even when multiple compressors of the same model are connected in parallel, they are affected by various factors such as processing and installation), and because of the differences in the inlet and outlet pipelines of each compressor, the mass flow rate flowing through each compressor in the parallel compressor system varies. Therefore, it is impossible to accurately determine the mass flow rate of each compressor in the parallel compressor system by simply measuring the mass flow rate of a single section of the wind tunnel nozzle. This leads to an inability to precisely control each compressor, thus posing challenges to the achievement of the target flow field and operational safety in the wind tunnel test section.

[0006] In summary, using the mass flow rate of the wind tunnel nozzle section as the core control parameter of the wind tunnel compressor is only applicable to a single wind tunnel compressor system and cannot meet the practical needs of accurately measuring the compressor flow rate for precise control of parallel wind tunnel compressor systems. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a method for determining the flow rate of a single compressor in a continuous wind tunnel parallel compressor system. This method addresses the problem that the existing technology, which measures the mass flow rate of the wind tunnel nozzle section and uses it as the core control parameter of the wind tunnel compressor, cannot meet the practical requirement of accurately measuring the compressor flow rate of the parallel wind tunnel compressor system, thus affecting the establishment of the target flow field in the wind tunnel test section and the safety of wind tunnel operation.

[0008] To achieve the above-mentioned objective, this invention provides a method for calculating the flow rate of a single compressor in a continuous wind tunnel parallel compressor system, the method comprising:

[0009] Step 1: Obtain the total pressure and temperature of the wind tunnel's steady section, as well as the static pressure at the nozzle outlet. Calculate the mass flow rate through the nozzle based on the total pressure of the steady section and the static pressure at the nozzle outlet.

[0010] Step 2: Pre-determine the total pressure ratio performance curve of each compressor in the parallel compressor system at constant speed, parameterize the discrete total pressure ratio performance curve at constant speed, and construct a continuous mathematical model of total pressure ratio performance at constant speed with the reduced flow rate and reduced speed as independent variables;

[0011] Step 3: During wind tunnel operation, measure the total inlet pressure, total inlet temperature, speed, and total pressure ratio of each compressor in the parallel compressor system in real time;

[0012] Step 4: Based on the continuous constant speed total pressure ratio performance mathematical model, calculate the corresponding reduced flow rate according to the speed and total pressure ratio of each individual compressor;

[0013] Step 5: Calculate the initial mass flow rate through each individual compressor based on the converted flow rate, the total inlet pressure, and the total inlet temperature.

[0014] This method describes a complete calculation process, including five core steps: obtaining stable section parameters and calculating nozzle mass flow rate; pre-determining compressor performance curves and constructing a mathematical model; real-time measurement of compressor operating parameters; calculation of converted flow rate based on the mathematical model; and calculation of initial mass flow rate based on the converted flow rate. This solves the problem that existing technologies cannot determine the flow rate of each individual compressor in a parallel compressor system, leading to inaccurate control of each compressor and affecting the establishment of the target flow field and operational safety in the wind tunnel test section. Through the design of the overall process, it realizes the indirect measurement from measurable parameters to the flow rate of individual compressors, providing a foundation for subsequent precise control.

[0015] Preferably, the calculation of the mass flow rate through the nozzle based on the total pressure of the stable section and the static pressure at the nozzle exit includes:

[0016] Calculate the nozzle exit Mach number based on the total pressure of the stabilization section and the static pressure at the nozzle exit.

[0017] If the nozzle exit Mach number is less than or equal to 1, the mass flow rate of the nozzle is calculated using the subsonic nozzle flow rate formula.

[0018] If the nozzle exit Mach number is greater than 1, the mass flow rate of the nozzle is calculated using the supersonic nozzle flow rate formula.

[0019] This method specifies the concrete steps for calculating the nozzle mass flow rate: first, the nozzle exit Mach number is calculated; then, depending on whether the Mach number is greater than 1, either the subsonic flow rate formula or the supersonic flow rate formula is used for calculation. Using appropriate calculation formulas for different flow conditions ensures the accuracy of the nozzle mass flow rate calculation and provides a reliable benchmark value for subsequent correction steps.

[0020] Preferably, in the step of parameterizing the discrete constant-speed total pressure ratio performance curve, the continuous constant-speed total pressure ratio performance mathematical model is specifically: the total pressure ratio of the compressor is a function of the reduced flow rate and the reduced speed. ,in, The total pressure ratio of the compressor. To convert the flow rate, This is the converted rotational speed.

[0021] Among them, the discrete performance curve is transformed into a continuous analytical function through parametric modeling, so that the corresponding total pressure ratio can be obtained at any speed and flow rate, which lays the foundation for solving the inverse function or iterative calculation.

[0022] Preferably, the solution to obtain the corresponding reduced flow rate includes: by adjusting the function... Solving for the inverse function yields the inverse functional expression of the reduced flow rate with respect to the reduced speed and the compressor's total pressure ratio. The reduced flow rate is calculated by substituting the real-time measured rotational speed and the total pressure ratio of the compressor into the inverse function expression.

[0023] In this method, the inverse function of the mathematical model is solved, and the real-time measured speed and total pressure ratio are substituted into the inverse function expression to calculate the equivalent flow rate. Solving the inverse function provides the most direct and fastest calculation method, which can quickly obtain the equivalent flow rate and meet the needs of real-time control.

[0024] Preferably, when the inverse function expression cannot be parsed, the reduced flow rate is calculated by using an iterative method to solve the function. The corresponding reduced flow rate is calculated. This method provides an alternative when the inverse function cannot be obtained, ensuring the universality and robustness of the method, and can obtain the desired results regardless of the complexity of the mathematical model.

[0025] Preferably, the formula for calculating the initial mass flow rate is:

[0026] ;

[0027] in, Let be the initial mass flow rate of the i-th compressor. Let i be the converted flow rate of the i-th compressor. Let be the total inlet pressure of the i-th compressor. Let be the total inlet temperature of the i-th compressor.

[0028] By transforming the formula for reduced flow rate, the conversion from reduced parameters to actual physical quantities was achieved, and the initial mass flow rate of each individual compressor was obtained.

[0029] Preferably, after calculating the initial mass flow rate of each individual compressor, this method further includes an initial mass flow rate correction step:

[0030] The total mass flow rate of the parallel compressor system is obtained by summing the initial mass flow rates of all individual compressors.

[0031] Based on the deviation between the mass flow rate of the nozzle and the total mass flow rate of the parallel compressor system, the initial mass flow rate of each individual compressor is corrected to obtain the actual mass flow rate of each individual compressor.

[0032] The flow rate of each compressor is corrected by applying the principle of mass conservation, which ensures the accuracy of the calculation results and eliminates the cumulative error that may be caused by single-point calculation.

[0033] Preferably, the formula for correcting the initial mass flow rate of each individual compressor is:

[0034] ;

[0035] in, Let i be the actual mass flow rate of the i-th compressor. The mass flow rate of the nozzle. Sum the initial mass flow rates of all individual compressors, where N is the number of compressors in parallel. Let be the initial mass flow rate of the i-th compressor.

[0036] Preferably, in the step of pre-determining the total pressure ratio performance curve of each individual compressor in the parallel compressor system at constant speed, the mass flow rate of the compressor (i.e., the compressor flow rate data used to construct the performance curve) is determined by measuring the mass flow rate of the wind tunnel nozzle under the performance test conditions.

[0037] Preferably, the rotational speed is a reduced rotational speed. The reduced rotational speed The calculation method is as follows: ; This refers to the compressor speed. Total inlet temperature of the compressor, converted to flow rate The calculation method is as follows: ;in, For compressor mass flow rate, This is the total inlet pressure of the compressor.

[0038] One or more technical solutions provided by this invention have at least the following technical effects or advantages:

[0039] Accurate measurement of the flow rate of a single compressor in a parallel compressor system has been achieved: by using an indirect measurement method, the problem of not being able to directly measure the compressor flow rate has been solved, providing basic parameters for the precise control of parallel compressor systems.

[0040] The problem of controlling parallel compressor systems has been solved: by accurately acquiring the real-time flow of each individual compressor, precise control of each compressor can be achieved, ensuring the establishment of the target flow field in the wind tunnel test section and the safe operation of the wind tunnel.

[0041] Make full use of measurable parameters: Only easily measurable parameters such as wind tunnel stable section parameters, nozzle outlet static pressure, compressor inlet and outlet total pressure, inlet total temperature, and rotational speed need to be measured, without the need to add complex flow measurement equipment, resulting in low implementation costs.

[0042] The method is highly versatile: it is applicable to any number of compressors connected in parallel, and is not limited by differences in compressor model, specifications, or performance, thus exhibiting good versatility and adaptability.

[0043] High accuracy: The mass conservation correction step eliminates the influence of calculation errors and measurement differences, ensuring the accuracy and continuity of the calculation results. Attached Figure Description

[0044] The accompanying drawings, which are provided to further illustrate embodiments of the invention and constitute a part of this invention, are not intended to limit the scope of the invention.

[0045] Figure 1 A schematic diagram of a continuous wind tunnel parallel compressor system;

[0046] Figure 2 A flowchart illustrating the method for calculating the flow rate of a single compressor in a continuous wind tunnel parallel compressor system;

[0047] Figure 3 This is a schematic diagram of the total pressure ratio performance curve of a single compressor at constant speed in a continuous wind tunnel parallel compressor. Detailed Implementation

[0048] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, where there is no conflict, the embodiments of the present invention and the features thereof can be combined with each other.

[0049] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0050] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0051] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0052] Example 1;

[0053] Please refer to Figure 2 , Figure 2 This invention provides a flowchart illustrating the calculation method for the flow rate of a single compressor in a continuous wind tunnel parallel compressor system. The method indirectly determines the flow rate of each compressor in the parallel wind tunnel compressor system based on easily measurable wind tunnel nozzle mass flow rate, total pressure and temperature in the steady-state section, and total pressure at the compressor inlet and outlet. It first measures the comprehensive aerodynamic performance of each compressor in the parallel wind tunnel compressor system and then parameterizes the obtained accurate, discrete isodynamic performance curves into a continuously analytical mathematical model of the isodynamic total pressure ratio performance. The flow rate of each compressor in the parallel compressor system is calculated by solving the inverse function of the continuously analytical mathematical model or by using an iterative method to solve the original function. This addresses the problem that existing methods, which use the measured mass flow rate of the wind tunnel nozzle section as the core control parameter of the wind tunnel compressor, cannot meet the practical requirements for accurate flow rate measurement in precise control of parallel wind tunnel compressor systems, thus affecting the establishment of the target flow field in the wind tunnel test section and the safety of wind tunnel operation. Specific methods include:

[0054] Step 1: Obtain the total pressure and temperature of the wind tunnel's steady section, as well as the static pressure at the nozzle outlet. Calculate the mass flow rate through the nozzle based on the total pressure of the steady section and the static pressure at the nozzle outlet.

[0055] Step 2: Pre-determine the total pressure ratio performance curve of each compressor in the parallel compressor system at constant speed, parameterize the discrete total pressure ratio performance curve at constant speed, and construct a continuous mathematical model of total pressure ratio performance at constant speed with the reduced flow rate and reduced speed as independent variables;

[0056] Step 3: During wind tunnel operation, measure the total inlet pressure, total inlet temperature, speed, and total pressure ratio of each compressor in the parallel compressor system in real time;

[0057] Step 4: Based on the continuous constant speed total pressure ratio performance mathematical model, calculate the corresponding reduced flow rate according to the speed and total pressure ratio of each individual compressor;

[0058] Step 5: Calculate the initial mass flow rate through each individual compressor based on the converted flow rate, the total inlet pressure, and the total inlet temperature.

[0059] The initial mass flow rate is calculated using the following formula:

[0060] ;

[0061] in, Let be the initial mass flow rate of the i-th compressor. Let i be the converted flow rate of the i-th compressor. Let be the total inlet pressure of the i-th compressor. Let be the total inlet temperature of the i-th compressor.

[0062] The technical principle of this invention is as follows:

[0063] During continuous wind tunnel operation, the mass flow rate through each section of the wind tunnel is equal. Therefore, the mass flow rate through the nozzle is equal to the total mass flow rate through the parallel compressor system. Each compressor has inherent aerodynamic performance characteristics, meaning that at a given speed and flow rate, the compressor can provide a definite total pressure ratio. By pre-determining the compressor's constant-speed total pressure ratio performance curve, a functional relationship between the compressor's total pressure ratio and its equivalent flow rate and equivalent speed can be established. While it's impossible to directly measure the mass flow rate through each compressor, the compressor's speed, inlet and outlet total pressure (thus obtaining the total pressure ratio), inlet total temperature, and inlet total pressure can be conveniently measured. Using a pre-established performance mathematical model, the compressor's equivalent flow rate can be derived from the measurable parameters (speed and total pressure ratio). Combined with the inlet total pressure and inlet total temperature, the actual mass flow rate of the compressor can be calculated. Summing the calculated mass flow rates of each compressor yields the total mass flow rate of the parallel compressor system. This calculated value may slightly deviate from the measured mass flow rate at the nozzle; proportional correction ensures mass continuity and improves calculation accuracy.

[0064] In this embodiment of the invention, the parallel compressor system refers to a system in which two or more compressors are connected in parallel through pipelines, share intake and exhaust pipes, and work together to provide the required airflow for a continuous wind tunnel. In this system, the compressors can be of the same model or different models, and they share the load to improve the overall air supply capacity, operational reliability, and adjustment flexibility of the system.

[0065] The continuous constant-speed total pressure ratio performance mathematical model refers to: obtaining discrete total pressure ratio and flow rate relationship data (i.e., constant-speed total pressure ratio performance curves) at different constant speeds by conducting aerodynamic performance tests on a single compressor in a parallel compressor system; then, using parametric modeling methods, fitting these discrete data into a continuous analytical function, which can express the total pressure ratio at a reduced speed. and equivalent flow The total pressure ratio of the compressor is expressed continuously and accurately as the independent variable. Characteristics, in their general form are This model serves as a bridge connecting the measurable parameters of the compressor (speed, total pressure ratio) with the parameters to be determined (reduced flow rate). It is used in wind tunnel operation to determine the corresponding reduced flow rate by solving an inverse function or using an iterative method based on the real-time measured reduced speed and total pressure ratio, and then calculate the mass flow rate through a single compressor.

[0066] The specific steps of this method are as follows:

[0067] (1) A calibrated total temperature probe and total pressure probe are installed in the stable section of the wind tunnel, and a calibrated static pressure measuring hole is installed at the nozzle outlet. A measurement system is also provided to accurately obtain the total pressure in the stable section of the wind tunnel. Total temperature in the stable section and nozzle outlet static pressure The measurement system refers to a complete set of equipment used to acquire key parameters of wind tunnel operation. It typically includes: sensors such as calibrated total temperature probes, total pressure probes, and static pressure orifices, used to sense and convert physical quantities; data acquisition equipment such as pressure scanning valves, temperature acquisition modules, and A / D converters, used to convert sensor signals into recordable data; and a data processing unit such as a computer and accompanying software, used to process, calculate, and store the acquired data. The measurement system is a commonly used measurement device in this invention, and will not be described in detail in this embodiment. It should be noted that in a continuous wind tunnel, the stable section is connected to the compressor inlet via a pipe. The total temperature remains constant as the airflow passes through this pipe section, i.e., the total temperature of the stable section remains constant. Equal to the total temperature at the compressor inlet Therefore, in subsequent calculations, using This represents the total temperature at the compressor inlet, the value of which is taken from the total temperature in the steady-state section measured in step (1). .

[0068] (2) Total pressure in the steady section obtained by measurement and nozzle outlet static pressure Calculate the nozzle exit Mach number Calculate the mass flow rate of the nozzle (the mass flow rate passing through the nozzle) based on whether the Mach number at the nozzle exit is greater than 1. The formula for calculating the Mach number is shown in equation (1). When the nozzle exit Mach number is less than or equal to 1 (subsonic operating condition), the formula for calculating the nozzle mass flow rate (subsonic nozzle flow rate formula) is shown in equation (2); when the nozzle exit Mach number is greater than 1 (supersonic operating condition), the formula for calculating the nozzle mass flow rate (supersonic nozzle flow rate formula) is shown in equation (3).

[0069] (1)

[0070] (2)

[0071] (3)

[0072] In equations (1) to (3) , , and The specific heat ratio, working gas constant, nozzle area (subscript outlet and throat represent the nozzle outlet and nozzle throat areas, respectively) and correction factor (subscript sub and sup represent subsonic and supersonic conditions, respectively) of the working fluid are respectively identified.

[0073] (3) Before the wind tunnel is put into operation, each individual compressor in the parallel wind tunnel compressor system (the number of parallel compressors is...) should be tested. In each parameter, the subscript i represents the parameter corresponding to the i-th compressor in the parallel compressor system. For simplification, the subscripts of all parameters in steps (3) to (5) are omitted. Conduct aerodynamic performance tests (similar to the technical solution of a single wind tunnel compressor system, the nozzle mass flow rate can be used to replace the compressor mass flow rate) to obtain accurate and discrete iso-speed total pressure ratio performance curves for each compressor (the properties of the performance test itself determine that the iso-speed performance curves of the compressor can only be measured at a limited speed), that is, given the compressor speed. and compressor mass flow rate The total pressure ratio that the lower compressor can provide .

[0074] The aerodynamic performance test circuit uses a wind tunnel circuit. The wind tunnel compressor is generally driven by a frequency converter, and the compressor speed is... The mass flow rate of the compressor can be accurately measured using the signal feedback from the frequency converter. Since only a single unit in the parallel compressor system is measured during commissioning, the mass flow rate of the compressor can be calculated by measuring the mass flow rate of the nozzle. The total pressure ratio is determined by measuring the compressor inlet total pressure using total pressure probes / frames placed at the compressor inlet and outlet. and total export pressure Calculated, i.e., total pressure ratio In practice, the equivalent rotational speed is commonly used. , and equivalent flow , Replace compressor speed and compressor mass flow rate To obtain more universal performance standards. However, in actual compressor control, the equivalent speed is generally used, even in wind tunnel testing. and equivalent flow As a control parameter, where This refers to the total temperature at the compressor inlet.

[0075] (4) Based on the obtained accurate and discrete (within the range of 0%-100% speed, select a finite number of speed points) total pressure ratio performance data at equal speeds, perform parameterized modeling (the specific modeling method can be the modeling method in CN120874403A or other commonly used modeling methods in this field, and this method does not impose any restrictions or elaborate on them), obtain a relatively accurate and continuous parameterized mathematical model of the total pressure ratio performance at equal speeds of a compressor in a parallel compressor system. The model can be represented by mathematical functions as shown in equation (4).

[0076] (4)

[0077] (5) Based on the parameterized isostatic total pressure ratio performance parameterized mathematical function obtained in steps (3) and (4), the function is derived and calculated. inverse function The calculation function for the reduced flow rate of a compressor in a parallel compressor system, expressed in terms of reduced speed and total pressure ratio, is shown in equation (5). The reduced flow rate of a compressor can be calculated based on the measured reduced speed and total pressure ratio. .

[0078] (5)

[0079] In practical application, when the function inverse function When the value cannot be directly derived, an iterative solution method (such as Newton's iteration method) can be used to calculate the equivalent rotational speed according to equation (4). Total pressure ratio of the compressor The equivalent flow rate of a certain compressor in the corresponding parallel compressor system Based on the total temperature of the stable section obtained by synchronous measurement and compressor inlet total pressure Calculate the mass flow rate of a compressor in a parallel compressor system. .

[0080] (6) Assuming the measurement The first of the parallel compressors The mass flow rate of the compressor is The total mass flow rate through the parallel compressor system Taking into account the influence of measurement differences, calculation errors, and other factors, the total mass flow rate is calculated. It may not be strictly equal to the nozzle mass flow rate calculated in step (2). To ensure continuous quality, the mass flow rate of a single compressor in the parallel compressor system is corrected, and the calculation expression of the mass flow rate of a certain compressor is shown in equation (6).

[0081] (6)

[0082] in, Let i be the actual mass flow rate of the i-th compressor. The mass flow rate of the nozzle. Sum the initial mass flow rates of all individual compressors, where N is the number of compressors in parallel. Let be the initial mass flow rate of the i-th compressor.

[0083] This invention employs an indirect measurement approach. While compressor flow rate cannot be directly measured, compressor speed, inlet and outlet total pressure, and inlet total temperature can be conveniently measured. This invention utilizes an inverse function or iterative solution method. Based on the mathematical model established in step 4, its inverse function is derived. When the inverse function cannot be directly expressed analytically, an iterative method is used. During actual wind tunnel operation, the speed and total pressure ratio of each compressor are measured in real time. Substituting these values ​​into the inverse function or through iterative calculation yields the reduced flow rate of each compressor. This invention utilizes the definition of reduced flow rate for transformation. Based on the definition of reduced flow rate, the formula for calculating the actual mass flow rate can be derived. Substituting the reduced flow rate calculated in step 4 with the real-time measured inlet total pressure and inlet total temperature into this formula yields the initial mass flow rate of each compressor. This invention employs a mass conservation correction step. The total mass flow rate is obtained by summing the initial mass flow rates of each compressor. This is compared with the nozzle mass flow rate measured in step 1, and the initial mass flow rates of each compressor are corrected proportionally to obtain the final actual mass flow rate. This correction ensures mass continuity and improves calculation accuracy.

[0084] Example 2;

[0085] Based on Embodiment 1, Embodiment 2 of the present invention will be described in conjunction with specific examples:

[0086] Taking a continuous wind tunnel driven by two identical axial compressors in parallel as an example (the two compressors are named compressor #1 and compressor #2, respectively), this invention calculates the mass flow rate of each compressor in the parallel compressor system during wind tunnel operation. The specific implementation steps are as follows:

[0087] (1) During wind tunnel operation, the total pressure and total temperature of the wind tunnel stable section, obtained by the total pressure and total temperature racks arranged in the wind tunnel stable section, are 100.00 kPa and 300.00 K, respectively. The static pressure at the nozzle outlet, obtained by the static pressure measurement and control system arranged at the nozzle outlet, is 27.24 kPa.

[0088] (2) The Mach number at the nozzle exit is calculated as Ma1.5 based on formula (1) in step (2). Since the exit Mach number is greater than Ma1.0, the flow rate at the nozzle exit is calculated as 0.85022 (divided by the dimensionless value obtained by mass flow rate corresponding to the nozzle exit Mach number of Ma1.0) using formula (3) in step (2).

[0089] (3) Conduct aerodynamic performance tests on each individual compressor in the parallel wind tunnel compressor system, and obtain the constant speed total pressure ratio performance curve of each individual compressor (see Figure 3 Since all compressors in a parallel compressor system are of the same model, their constant-speed total pressure ratio performance curves are identical. Figure 3This is a schematic diagram of the total pressure ratio performance curve of a single compressor operating at constant speed in a continuous wind tunnel parallel compressor system. The horizontal axis represents the reduced flow rate (dimensionless), and the vertical axis represents the total pressure ratio. Solid lines represent experimentally measured values, and dashed lines represent fitted analytical values.

[0090] (4) Based on the total pressure ratio performance curves of each compressor at constant speed obtained in step (3), a relatively accurate and continuous total pressure ratio parameterized mathematical model of a certain compressor at constant speed in the parallel compressor system is obtained by parametric modeling, as shown in equation (7). The inverse function of equation (7) is derived as shown in equation (8). k in equations (7) and (8) and The calculation expressions are shown in equations (9) to (11), where k, and All of these are dimensionless coefficients obtained by fitting compressor performance test data.

[0091] (7) (8)

[0092] (9)

[0093] (10)

[0094] (11)

[0095] (5) Based on step (4), obtain the mathematical model (equation (7)) and derive and calculate the inverse function of equation (7). As shown in equation (8). Given an equivalent rotational speed of 0.85, k is obtained. and The values ​​were 5.8117, 90.6972, and 0.0037, respectively. When the wind tunnel compressor system was running in parallel, the measured total pressure ratios of compressor #1 and compressor #2 were 3.5255 and 3.5609, respectively. The total inlet temperature for both was 300K, and the total inlet pressures were 28364.77 Pa and 28222.95 Pa, respectively. The dimensionless mass flow rates through compressors #1 and #2 were calculated to be 0.4270 and 0.4234, respectively (divided by the dimensionless values ​​obtained by dividing by the mass flow rate corresponding to a nozzle exit Mach number of Ma1.0).

[0096] (6) Based on the mass flow rate obtained in step (5), the dimensionless mass flow rates flowing through each compressor are calculated according to formula (6) as 0.42691 and 0.42331.

[0097] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0098] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for calculating the flow rate of a single compressor in a continuous wind tunnel parallel compressor system, characterized in that, The method includes: Step 1: Obtain the total pressure and temperature of the wind tunnel's steady section, as well as the static pressure at the nozzle outlet. Calculate the mass flow rate through the nozzle based on the total pressure of the steady section and the static pressure at the nozzle outlet. Step 2: Pre-determine the total pressure ratio performance curve of each compressor in the parallel compressor system at constant speed, parameterize the discrete total pressure ratio performance curve at constant speed, and construct a continuous mathematical model of total pressure ratio performance at constant speed with the reduced flow rate and reduced speed as independent variables; Step 3: During wind tunnel operation, measure the total inlet pressure, total inlet temperature, speed, and total pressure ratio of each compressor in the parallel compressor system in real time; Step 4: Based on the continuous constant speed total pressure ratio performance mathematical model, calculate the corresponding reduced flow rate according to the speed and total pressure ratio of each individual compressor; Step 5: Calculate the initial mass flow rate through each individual compressor based on the converted flow rate, the total inlet pressure, and the total inlet temperature; After calculating the initial mass flow rate of each individual compressor, this method also includes an initial mass flow rate correction step: The total mass flow rate of the parallel compressor system is obtained by summing the initial mass flow rates of all individual compressors. Based on the deviation between the mass flow rate of the nozzle and the total mass flow rate of the parallel compressor system, the initial mass flow rate of each individual compressor is corrected to obtain the actual mass flow rate of each individual compressor. The formula for correcting the initial mass flow rate of each individual compressor is as follows: ； in, Let i be the actual mass flow rate of the i-th compressor. The mass flow rate of the nozzle. Sum the initial mass flow rates of all individual compressors, where N is the number of compressors in parallel. Let be the initial mass flow rate of the i-th compressor.

2. The method for calculating the flow rate of a single compressor in a continuous wind tunnel parallel compressor system according to claim 1, characterized in that, The calculation of the mass flow rate through the nozzle based on the total pressure of the stable section and the static pressure at the nozzle exit includes: Calculate the nozzle exit Mach number based on the total pressure of the stabilization section and the static pressure at the nozzle exit. If the nozzle exit Mach number is less than or equal to 1, the mass flow rate of the nozzle is calculated using the subsonic nozzle flow rate formula. If the nozzle exit Mach number is greater than 1, the mass flow rate of the nozzle is calculated using the supersonic nozzle flow rate formula.

3. The method for calculating the flow rate of a single compressor in a continuous wind tunnel parallel compressor system according to claim 1, characterized in that, In the step of parameterizing the discrete constant-speed total pressure ratio performance curve, the continuous constant-speed total pressure ratio performance mathematical model is specifically as follows: the total pressure ratio of the compressor is a function of the reduced flow rate and the reduced speed. ,in, The total pressure ratio of the compressor. To convert the flow rate, This is the converted rotational speed.

4. The method for calculating the flow rate of a single compressor in a continuous wind tunnel parallel compressor system according to claim 3, characterized in that, The solution to obtain the corresponding reduced flow rate includes: by applying the function... Solving for the inverse function yields the inverse functional expression of the reduced flow rate with respect to the reduced speed and the compressor's total pressure ratio. The reduced flow rate is calculated by substituting the real-time measured rotational speed and the total pressure ratio of the compressor into the inverse function expression.

5. The method for calculating the flow rate of a single compressor in a continuous wind tunnel parallel compressor system according to claim 4, characterized in that, When the inverse function expression cannot be parsed, the reduced flow rate is calculated by using an iterative method to solve the function. The corresponding equivalent flow rate is calculated.

6. The method for calculating the flow rate of a single compressor in a continuous wind tunnel parallel compressor system according to claim 4, characterized in that, The formula for calculating the initial mass flow rate is: ； in, Let be the initial mass flow rate of the i-th compressor. Let i be the converted flow rate of the i-th compressor. Let be the total inlet pressure of the i-th compressor. Let be the total inlet temperature of the i-th compressor.

7. The method for calculating the flow rate of a single compressor in a continuous wind tunnel parallel compressor system according to claim 1, characterized in that, In the step of pre-determining the total pressure ratio performance curve of each individual compressor in a parallel compressor system at constant speed, the mass flow rate of the compressor is determined by measuring the mass flow rate of the wind tunnel nozzle under performance test conditions.

8. The method for calculating the flow rate of a single compressor in a continuous wind tunnel parallel compressor system according to claim 1, characterized in that, The rotational speed is a reduced rotational speed. The reduced rotational speed The calculation method is as follows: ; This refers to the compressor speed. Total inlet temperature of the compressor, converted to flow rate The calculation method is as follows: ;in, For compressor mass flow rate, This is the total inlet pressure of the compressor.

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