A method of acoustic network construction for a piping system

Abstract

The application belongs to the field of multi-branch flow pipeline, and relates to a method for constructing an acoustic network of a pipeline system, which is used for segmenting and discretizing a complex pipeline system, determining all component units of the pipeline system, including a sound source end, a node and a middle section component, correlating all sound source ends and middle section components with each other through the node to form an acoustic network diagram, discretizing the complex pipeline system into component units and connecting the component units in the form of nodes to form the acoustic network diagram, adopting an acoustoelectric analogy mechanism, constructing a scattering relationship between sound pressure in a single pipeline in the complex pipeline system and global sound pressure of the system under the premise of known transfer matrix and sound source characteristics of the component units, establishing a mapping matrix of the global sound pressure of the pipeline system and each sound source, and obtaining an internal sound field of the pipeline, so that defects of classical pipeline acoustic theory and numerical methods are avoided, and a simple and effective means for rapid prediction of complex pipeline noise is provided.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of multi-branch flow pipe, and particularly relates to a method for constructing an acoustic network of a pipe system. BACKGROUND

[0002] Multi-branch flow pipes have important application value and research significance in industrial gas transportation, heating, ventilation and air conditioning systems, and aerospace fields. The acoustic problems therein are diverse and complex. Sound waves propagate along different paths in the pipe system, producing multiple reflections. Reflections in the pipe can cause standing wave phenomena. Corners, branches and special components of the pipe can cause scattering, further causing polymorphic propagation of sound waves. Long-distance propagation inevitably causes attenuation of sound waves during propagation. The gas flow in the pipe affects the propagation characteristics of sound waves, and also induces flow-induced noise sources at special components. The interaction and coupling between multiple noise sources also affect the overall sound field distribution in the pipe.

[0003] Traditional classical pipe acoustics theory is based on too many ideal condition assumptions (such as no friction, uniform material and simple geometric shape, etc.), which is often quite different from the actual complex pipe situation, and does not consider the complex coupling effects of fluid and sound wave propagation.

[0004] Numerical simulation methods, such as finite element, can meet the prediction needs of the pipe flow field to some extent, but for industrial-level, large-scale and highly complex pipe systems, simulation requires a large amount of computing resources and time, which is not conducive to rapid design and optimization, and the flow-induced noise induced by special components cannot be accurately analyzed or numerically described.

[0005] Therefore, an accurate and fast complex pipe noise prediction method needs to be developed to lay a theoretical foundation for low-noise pipe system design. SUMMARY

[0006] The purpose of the present application is to provide a method for constructing an acoustic network of a pipe system to solve the problem of large resource occupation and long time of existing complex pipe noise prediction methods.

[0007] The technical solution of the present application is: a method for constructing an acoustic network of a pipe system, comprising:

[0008] The complex pipe system is segmented and discretized, all component units of the pipe system are determined, the component units include sound source ends, nodes and middle section components, all sound source ends and middle section components are associated with each other through the nodes to form an acoustic network graph, all acoustic characteristic data of the middle section components of the acoustic network graph are obtained, and all discretized middle section components are simplified as two-port models;

[0009] All acoustic characteristic data of the sound source ends are obtained, and all discretized sound source ends are simplified as one-port models.

[0010] obtaining acoustic characteristic data of each node, the acoustic characteristic data including volume flow and cross-sectional area, numbering each two-port model, one-port model and node, and then establishing a node scattering matrix according to the volume flow and cross-sectional area of each node;

[0011] obtaining two-direction pressure amplitudes of all two-port component units, converting the two-direction pressure amplitudes of all two-port component units into a pressure matrix, and then constructing a scattering matrix S of the two-port component units through the pressure matrix c ;

[0012] associating all two-port pressure amplitudes with the node scattering matrix to construct a mapping matrix

[0013] according to all acoustic characteristic data of the one-port component units and the two-port component units, associating all two-port component units and one-port component units with each other through the mapping matrix to form a sound pressure scattering relationship matrix.

[0014] Preferably, in the two-port model, two ports are an inlet end and an outlet end respectively, indicating the direction of each port connection and the direction of acoustic mass flow, each port includes pressure amplitudes of the inlet end and the outlet end, and each pressure amplitude is represented as:

[0015]

[0016] wherein p 1- , p 2- are output pressure amplitudes of the inlet end and the outlet end respectively; p 1+ , p 2+ are input pressure amplitudes of the inlet end and the outlet end respectively; and are self-noise pressure amplitudes of the inlet end and the outlet end respectively; S m represents a scattering relationship of the pressure amplitudes in the two ports.

[0017] Preferably, the one-port model is:

[0018]

[0019] wherein is a constant pressure source, Z ns is an acoustic source impedance, is a constant current source.

[0020] Preferably, the node scattering matrix includes a positive scattering matrix and a negative scattering matrix, and the specific acquisition method of the positive scattering matrix and the negative scattering matrix is:

[0021] Assume that the inlet port and the outlet port of a node have the same total area; in this case the volume flow q n is defined as:

[0022]

[0023] where p + is the input pressure amplitude of the two-port component unit, p - is the output pressure amplitude of the two-port component unit, and the characteristic impedance Z = p0c / A; where c is the local sound speed, A is the cross-sectional area of the plane wave propagation, and p0is the medium density in the tube;

[0024] Since the sum of the volume flows of all the two-port component units connected to a node equals the total volume flow of the node, we obtain:

[0025]

[0026] where There are m n two-port component units connected to node n, is the cross-sectional area of the two-port component unit m connected to node n, is the input pressure amplitude of the two-port component unit m connected to node n, is the output pressure amplitude of the two-port component unit m connected to node n; from equations (5) and (6) we obtain:

[0027]

[0028] Since the pressure is continuous at all nodes, we obtain:

[0029]

[0030] Equations (7) and (8) together give:

[0031]

[0032] where is the input pressure amplitude of any two-port component unit connected to node n, is the output pressure amplitude of the same two-port component unit connected to node n;

[0033] Combining equations (7) and (9) gives:

[0034]

[0035] In matrix form we obtain:

[0036]

[0037] wherein and are the positive and negative scattering matrices of node n respectively:

[0038]

[0039] and are the pressure amplitudes of the two directions into and out of node n respectively, is the source strength of a port connected to the node.

[0040] Preferably, the sound pressure scattering relationship matrix is:

[0041]

[0042] wherein and contain all acoustic feature data from one-port component units and two-port component units, is the acoustic network matrix, is the two-port source matrix.

[0043] Preferably, the pressure amplitudes of the two-port component units include the acoustic network matrix a [2M x 1] matrix and the two-port source matrix wherein c represents that the matrix is a complete acoustic network matrix; s represents that it is a source strength in two ports; cs represents that it is a source strength of a complete network.

[0044] The acoustic network construction method of the pipeline system of the present application discretizes a complex pipeline system into component units and connects the component units in the form of nodes to form an acoustic network graph. Using an acoustoelectric analogy mechanism, the scattering relationship between the sound pressure in a single pipeline in a complex pipeline system and the global sound pressure of the system is constructed under the premise that the transfer matrix and the source feature of the component units are known. The mapping matrix of the global sound pressure of the pipeline system and each source is established, and the internal sound field of the pipeline is obtained, avoiding the defects of the classical pipeline acoustics theory and numerical methods, and providing a simple and effective means for rapid prediction of complex pipeline noise. BRIEF DESCRIPTION OF DRAWINGS

[0045] In order to more clearly illustrate the technical solutions provided by the present application, the following will briefly introduce the drawings. Obviously, the drawings described below are only some embodiments of the present application.

[0046] Figure 1 is a schematic diagram of the overall process of the present application;

[0047] Figure 2 is a schematic diagram of a four-source, four-node, five-element pipeline system of the present application;

[0048] Figure 3 for the acoustic network graph of the pipeline system of the present application;

[0049] Figure 4 for the acoustic scattering relation of the two-port element of the present application numbered m. DETAILED DESCRIPTION

[0050] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0051] A method for constructing an acoustic network of a pipeline system, as shown in Figure 1 , specifically comprising the following steps:

[0052] Step S100, segmenting and discretizing a complex pipeline system to determine all component units of the pipeline system, the component units including a sound source end, nodes and middle section components, all sound source ends and middle section components being associated with each other through the nodes to form an acoustic network graph;

[0053] obtaining all acoustic characteristic data of the middle section components of the acoustic network graph, simplifying all discretized middle section components into two-port models, and the specific judgment standard is that a component unit capable of acting on the acoustic network through two ports is simplified into a two-port model, and component units such as straight pipes, variable cross-section pipes and valves can be represented as two ports, a total of M two-port component units are generated, numbered as m=1, 2, …M, and each component unit interacts with the entire pipeline network through two ports. The two ports are an inlet end and an outlet end, representing the direction of each port connection and the direction of acoustic mass flow. Each port has two state variables, which are the pressure amplitudes of the inlet and outlet ports, respectively. Each pressure amplitude is represented as:

[0054]

[0055] wherein p 1- and p 2- are the output pressure amplitudes of the inlet end and the outlet end, respectively, p 1+ and p 2+ are the input pressure amplitudes of the inlet end and the outlet end, respectively, and are passive and unknown variables. and are the self-noise pressure amplitudes of the inlet end and the outlet end, respectively, and flow out of the two ports, and are active known variables. mrepresents the scattering relation of pressure amplitude in two ports, i.e. transmission and reflection. There is a necessary passive part and a possible active part in the inlet and outlet ends.

[0056] In step S200, all acoustic characteristic data of the sound source end is obtained, and all discretized sound source ends are simplified into one-port models

[0057] One port means only containing one port and acting on the whole acoustic network through the single port, i.e. the sound source end. One port means an element, such as a power device or an exhaust end. Similar to two ports, one port is described by two state variables, but in this case they are pressure p and volume flow q. The pressure amplitude p n Two different models, constant pressure source and constant flow source, can be used for description.

[0058] The constant pressure source model is described as:

[0059]

[0060] The constant flow source model is described as:

[0061]

[0062] wherein is the constant pressure source (active part of one port), Z ns is the sound source acoustic impedance, q n is the volume flow, is the constant flow source. The combination of formula (2) and formula (3) obtains:

[0063]

[0064] In step S300, acoustic characteristic data of each node is obtained, the acoustic characteristic data including volume flow and cross-sectional area, each two-port model, one-port model and node is numbered, and then node scattering matrices including positive scattering matrices and negative scattering matrices are respectively established according to the volume flow and cross-sectional area of each node;

[0065] The node is the connection point of each component unit in the acoustic network, and can be connected with any number of one-port models and two-port models. The node determines how to divide the acoustic mass flow among the ports connected to the node.

[0066] Preferably, the specific acquisition method of the positive scattering matrix and the negative scattering matrix is that it is assumed that the inlet port and the outlet port of the node have the same total area. At this time, the volume flow q n is defined as:

[0067]

[0068] where p + is the input pressure amplitude of the two-port component unit, p - is the output pressure amplitude of the two-port component unit, the characteristic impedance Z = p0c / A; where c is the local sound speed, A is the cross-sectional area of the plane wave propagation, and p0is the medium density in the pipe.

[0069] Since the sum of the volume flow rates of all the two-port component units connected to a node equals the total volume flow rate of the node, we have:

[0070]

[0071] where There are m n two-port component units connected to node n, is the cross-sectional area of the two-port component unit m connected to node n, is the input pressure amplitude of the two-port component unit m connected to node n, is the output pressure amplitude of the two-port component unit m connected to node n; from equations (5) and (6) we have:

[0072]

[0073] Since the pressure is continuous at all nodes, we have:

[0074]

[0075] Equations (7) and (8) together give us:

[0076]

[0077] where is the input pressure amplitude of any two-port component unit connected to node n, is the output pressure amplitude of the same two-port component unit connected to node n.

[0078] Combining equations (7) and (9) gives us:

[0079]

[0080] In matrix form, we have:

[0081]

[0082] where and are the positive and negative scattering matrices of node n, respectively:

[0083]

[0084] and are the two-directional pressure amplitudes of the node n respectively, is the source strength of a port connected to the node.

[0085] Step S400, obtaining all two-directional pressure amplitudes of the two-port component units, and converting all two-directional pressure amplitudes of the two-port component units into a pressure matrix: the two-directional pressure amplitudes of the two-port component units are expressed as an acoustic network matrix a [2Mx1] matrix and a two-port sound source matrix where c represents that the matrix is a complete acoustic network matrix, s represents that it is a source strength in the two-port. cs represents that it is a source strength of the complete network.

[0086] Then a scattering matrix S of the two-port component units is constructed through the pressure matrix c , S c is a diagonal matrix with a dimension of [2Mx2M]. At this time, equation (11) is converted into a correlation matrix

[0087]

[0088] for describing the correlation of each pressure amplitude in the entire sound source network.

[0089] The one-port model does not need to construct a scattering matrix additionally due to its simple working principle.

[0090] Step S500, correlating all two-port pressure amplitudes with the node scattering matrix to construct a mapping matrix; according to all acoustic characteristic data of the one-port component units and the two-port component units, all two-port component units and one-port component units are correlated with each other through the mapping matrix to form a sound pressure scattering relationship matrix

[0091] In order to be able to connect all two-port component units to each other through the node, the method introduces a mapping matrix which contains the key information of whether the node n is connected to the two-port. The information in the mapping matrix also contains whether the node is an outlet or an inlet, and describes the relationship between the local pressure amplitude and the entire network pressure amplitude. The mapping matrix should satisfy:

[0092]

[0093] wherein, represents or The value of each position is 0 or 1, 1 if the node is connected to two ports, otherwise 0. At this time, It can be expressed as:

[0094]

[0095] The equation of all nodes is transformed into the sound pressure scattering relationship matrix:

[0096]

[0097] The above formula describes the sound pressure scattering relationship in the complete acoustic network, a total of 2M equations are formed. And Containing all the acoustic feature data from one-port component units and two-port component units, it can be calculated by understanding the geometry of the acoustic network body. Combined with formula (1), M two-port local scattering equations are constructed, forming another 2M equations, which can form 4M equations to obtain the p 1+ ,p 1- ,p 2+ ,p 2- At this time, the sound field solution of the entire complex pipeline system is completed.

[0098] As a specific embodiment, the following is described with a specific example:

[0099] 1) The complex pipeline system is divided, such as Figure 2 The pipeline system contains four sound source ends, four nodes, and five middle section "two-port" components, which can be simplified as Figure 3 The pipeline system acoustic network diagram;

[0100] For a two-port model, each element interacts with the entire pipeline network through two ports. The two ports are divided into inlet and outlet ends, representing the direction of each port connection and the direction of sound mass flow. Each port has two state variables, which are the pressure amplitude of the inlet and outlet ports, as shown in Figure 4 , where the output p 1- , p 2- and the input p 1+ , p 2+ are the pressure amplitudes in the pipe, which are passive terms and unknown variables. and are the source pressure amplitudes, which flow out of the two ports, and are active terms and known variables.

[0101] 2) Simplify the pipeline sound source end and outlet end as a "one-port" model. The acoustic feature data of the one-port model includes sound mass flow information, sound source intensity (unique to the sound source end), and port impedance. The one-port model is connected to a node, as shown in Figure 3 .

[0102] 3) Number each two-port model, one-port model and each node, get the positive scattering matrix and negative scattering matrix of each node. Establish the global sound pressure scattering relationship Global scattering matrix S c [2Mx2M] is a diagonal matrix, and the diagonal elements are S1, S2, …, S M ;

[0103] 4) Construct the node scattering matrix, to Figure 3 Take node three in as an example, its scattering matrix P 3 is as follows:

[0104]

[0105] If the connection is an inlet end, the first number in the index is 1, and if it is an outlet end, it is 2. The second number describes which two-port is connected to. For example, p 2,5+ is the sound pressure amplitude from node (+), through the outlet end (2) and connected to two-port 5. The mapping matrix can be expressed as follows

[0106]

[0107] 6) Bring the node scattering matrix, global scattering matrix and mapping matrix into For a pipeline system containing M two-port elements, 4M equations are constructed at this time, and each two-port element corresponding p 1+ , p 1- , p 2+ , p 2- is solved, and the sound field of the pipeline system is solved.

[0108] Through the above design, the complex pipeline system is discretized into component units and connected in the form of nodes to form an acoustic network diagram. By using the acoustoelectric analogy mechanism, the scattering relationship between the sound pressure in a single pipeline and the global sound pressure in the system is constructed under the premise that the transfer matrix and the sound source characteristics of the component units are known, the mapping matrix between the global sound pressure of the pipeline system and each sound source is established, and the internal sound field of the pipeline is obtained. The defects of the classical pipeline acoustics theory and the numerical method are avoided, and a simple and effective means for rapid prediction of complex pipeline noise is provided.

[0109] Finally, it should be noted that: the drawings of the disclosed embodiments only involve the structures involved in the disclosed embodiments, other structures can refer to the usual design, and under the condition of no conflict, the same embodiments and different embodiments of the present application can be combined with each other;

[0110] Finally: the above only for the preferred embodiments of the present application, and not for limiting the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application, should be included in the scope of protection of the present application.

Claims

1. A method of constructing an acoustic network of a piping system, characterized by, Comprise: Segment and discretize the complex pipeline system, determine all component units of the pipeline system, the component units include sound source end, node and middle section component, all sound source ends and middle section components are associated with each other through the node to form an acoustic network diagram; obtain all acoustic characteristic data of the middle section component of the acoustic network diagram, and simplify all discretized middle section components into two-port models; Obtain all acoustic characteristic data of the sound source end, and simplify all discretized sound source ends into one-port models; Obtain acoustic characteristic data of each node, the acoustic characteristic data includes volume flow and cross-sectional area, number each two-port model, one-port model and node, and then respectively establish node scattering matrices according to the volume flow and cross-sectional area of each node; Obtaining two-direction pressure amplitude of all two-port component units, converting the two-direction pressure amplitude of all two-port component units into a pressure matrix; and then constructing a scattering matrix S of the two-port component units through the pressure matrix c ; Correlate pressure amplitudes of all two-port models with the node scattering matrices to construct a mapping matrix Based on all the acoustic characteristic data of the one-port component units and the two-port component units, a mapping matrix is established All the two-port component units and the one-port component units are correlated with each other to form a sound pressure scattering relationship matrix.

2. The method of claim 1, wherein: In the two-port model, two ports are an inlet end and an outlet end respectively, representing the direction of each port connection and the direction of acoustic mass flow, each port includes pressure amplitudes of inlet and outlet ports, and each pressure amplitude is represented as: where p 1- , p 2- are the output pressure amplitudes at the inlet and outlet ends, respectively; p 1+ , p 2+ are the input pressure amplitudes at the inlet and outlet ends, respectively; and are the self-noise pressure amplitudes at the inlet and outlet ends, respectively; S m denotes the scattering relation of the pressure amplitudes in the two ports.

3. The method of claim 1, wherein, The one-port model is: wherein is a constant voltage source, Z ns is the acoustic impedance of the sound source, is a constant current source.

4. The method of constructing an acoustic network of a piping system according to claim 3, characterized by: The node scattering matrix includes a positive scattering matrix and a negative scattering matrix, and the specific obtaining method of the positive scattering matrix and the negative scattering matrix is: Suppose that the inlet port and the outlet port of the node have the same total area; The volumetric flow rate q at this time n is defined as: where p + is the input pressure amplitude of the two-port component cell, p - is the output pressure amplitude of the two-port component cell, the characteristic impedance Z = p0c / A; where c is the local sound speed, A is the cross-sectional area of the planar wave propagation, and p0is the medium density in the tube. Since the sum of all volume flows connected to a certain node is equal to the total volume flow of the node, the following is obtained: wherein the total m n two-port component units connected to node n, is the cross-sectional area of two-port component unit m connected to node n, is the input pressure amplitude of two-port component unit m connected to node n, is the output pressure amplitude of two-port component unit m connected to node n; obtained from the combination of equations (5) and (6): Since the pressure is continuous on all nodes, it is transformed into: Equations (7) and (8) together obtain: wherein is the input pressure amplitude of an arbitrary two-port component unit connected to the node n, is the output pressure amplitude of the same two-port component unit connected to the node n; Equations (7) and (9) are combined to obtain: The matrix form is: where and are the positive and negative scattering matrices of node n, respectively: and are the pressure amplitude in the two directions into and out of node n, respectively, is the source strength of a port connected to the node.

5. The method of claim 4, wherein: The sound pressure scattering relationship matrix is: wherein and comprising all acoustic feature data from one-port component units and two-port component units, is an acoustic network matrix, is a two-port sound source matrix.

6. The method of claim 2, wherein: The pressure amplitude of the two-port component unit comprises an acoustic network matrix One [2M x 1] matrix and a two-port sound source matrix where c denotes that the matrix is a complete acoustic network matrix; s denotes that it is a source strength in two ports; cs denotes that it is a source strength of a complete network.

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