Centrifugal compressor impeller stall global stability prediction method and system based on leading edge overflow characteristics

Abstract

The invention discloses a centrifugal compressor impeller stall global stability prediction method based on front edge overflow characteristics. The method comprises the steps that a dimensionless two-dimensional N-S equation including vortex viscosity and molecular viscosity is established based on an impeller of a centrifugal compressor; decomposing based on the flow velocity of the inlet fluid of the impeller to obtain coherent structure items; obtaining a linear coherent perturbation equation based on coherent structure items and a dimensionless N-S equation; obtaining a pressure coherent disturbance item and a coherent structure item of the inlet fluid, and substituting the items into the linear coherent disturbance equation to obtain the linear disturbance equation; converting into a feature solving equation based on a linear disturbance equation; selecting a key surface of the impeller based on the front edge overflow characteristics; acquiring a fluid average velocity component based on the key surface; substituting the fluid average velocity component into a feature solving equation to obtain a feature value; and predicting the global stability of the impeller based on the magnitude of the characteristic value. The method achieves the precise prediction of the overall stability of the impeller of the centrifugal compressor.

Description

Technical Field

[0001] The present invention relates to the technical field of centrifugal compressor stability prediction, and more particularly to a centrifugal compressor impeller stall global stability prediction method and system based on leading edge overflow characteristics. Background Art

[0002] At present, centrifugal compressors are important equipment in national strategic fields such as micro-turbojet / turbofan engines, turbocharging, and fuel cell vehicles, and are widely used in various fields such as energy, aerospace, etc. Centrifugal compressor impeller leading edge overflow is a common phenomenon in centrifugal compressors or other rotating machinery, that is, air flow instability occurs in the leading edge area of ​​the impeller, causing the compressor impeller to stall, resulting in a decrease in compressor performance and even mechanical failure. Studying the stall mechanism of centrifugal compressor impellers and proposing a global stability prediction method for centrifugal compressor impeller stall are of great significance for improving the stability, safety and reliability of the compressor system.

[0003] However, most of the existing studies on the application of global stability to flow stability are based on the canonical mode method for stability prediction and mechanism analysis, but are rarely used in turbomachinery; existing methods are mainly used for transition prediction of classical flows such as cylindrical turbulence and airfoils, and cannot smoothly solve the difficult problems of prediction and analysis of turbulent instability in centrifugal compressors with complex geometric configurations and boundary conditions; (3) At present, there is no good solution to the problems of given boundary conditions, treatment of viscosity terms and treatment of compressible flow in the prediction of flow stability using global stability methods.

[0004] Therefore, how to achieve accurate prediction of the global stability of the centrifugal compressor impeller based on the leading edge overflow characteristics during the operation of the centrifugal compressor is an urgent problem that technical personnel in this field need to solve. Summary of the invention

[0005] In view of this, the present invention provides a method and system for predicting the global stability of a centrifugal compressor impeller stall based on leading edge overflow characteristics, thereby achieving accurate prediction of the global stability of the centrifugal compressor impeller.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A method for predicting the global stability of centrifugal compressor impeller stall based on leading edge overflow characteristics, comprising:

[0008] Based on the impeller of the centrifugal compressor, the dimensionless two-dimensional NS equations including eddy viscosity and molecular viscosity are established;

[0009] Decomposing the flow velocity of the inlet fluid of the impeller to obtain a coherent structure term;

[0010] A linear co-order perturbation equation is obtained based on the co-order structure term and the dimensionless NS equation;

[0011] Obtaining the pressure coherent disturbance term and the coherent structure term of the inlet fluid and substituting them into the linear coherent disturbance equation to obtain a linear disturbance equation;

[0012] Based on the linear perturbation equation, the linear perturbation equation is converted into a characteristic solution equation;

[0013] Selecting the key surface of the impeller based on the leading edge overflow characteristics;

[0014] Obtaining an average velocity component of the fluid based on the critical surface;

[0015] Substituting the average velocity component of the fluid into the characteristic solution equation to obtain a characteristic value;

[0016] The global stability of the impeller is predicted based on the magnitude of the eigenvalue.

[0017] Preferably, the dimensionless two-dimensional NS equation is:

[0018]

[0019] Where, u represents the dimensionless velocity of the impeller outlet fluid, t represents time, and p represents the dimensionless pressure of the impeller outlet fluid. represents the velocity gradient, represents the pressure gradient, Re represents the Reynolds number, and denote the gradient and Laplacian operators respectively, Represents velocity divergence.

[0020] Preferably, the pseudo-sequence structure item is obtained, specifically including:

[0021] Based on the classic three-part flow model, the flow velocity of the impeller inlet fluid is decomposed to obtain the time average term, the coherent structure term and the random turbulence disturbance term:

[0022]

[0023] Among them, u(x,t) represents the flow velocity of the impeller inlet fluid, represents the time average term, represents the co-order structure term, and u'(x,t) represents the random turbulence disturbance term.

[0024] Preferably, the linear quasi-order perturbation equation is obtained by:

[0025] Based on the time average term, the coherent structure term, the random turbulence disturbance term and the dimensionless two-dimensional NS equation, the coherent disturbance control equation is obtained:

[0026]

[0027] in, represents the pressure quasi-order disturbance term, represents the nonlinear term, represents the fluctuation of the turbulent random disturbance caused by the passage of the quasi-order disturbance, represents the time average term, represents the quasi-order structure term, u' represents the random turbulence disturbance term;

[0028] Based on the pseudo-order disturbance control equation, the infinitesimal disturbance hypothesis and the turbulent viscosity hypothesis theory are introduced to obtain the fluctuation and equivalent Reynolds number of the turbulent random disturbance caused by the passage of the pseudo-order disturbance.

[0029] The fluctuation of the turbulent random disturbance caused by the passage of the quasi-order disturbance and the equivalent Reynolds number are brought into the quasi-order disturbance control equation to obtain the linear quasi-order disturbance equation.

[0030] Preferably, the method for obtaining the quasi-sequential disturbance control equation is:

[0031] Based on the time average term, the coherent structure term, the random turbulence disturbance term and the dimensionless two-dimensional NS equation, a mean flow equation is obtained;

[0032] Based on the time average term, the coherent structure term and the dimensionless two-dimensional NS equation, a phase average control equation is obtained;

[0033] The pseudo-sequential disturbance control equation is obtained by subtracting the average flow equation from the phase average control equation.

[0034] Preferably, the fluctuation of turbulent random disturbance caused by the passage of quasi-sequential disturbance The acquisition method is:

[0035] Introducing the turbulent viscosity hypothesis theory, the pseudo-order perturbation control equation is closed, and the average term of the wave phase is:

[0036]

[0037] The fluctuation time average term is:

[0038]

[0039] Where k represents the turbulent kinetic energy, represents the phase average of the eddy viscosity coefficient, I represents the unit matrix, u represents the flow velocity of the impeller inlet fluid, is the time average of the turbulent kinetic energy, represents the time average of the eddy viscosity coefficient;

[0040] Based on the time average of the fluctuation phase average term and the fluctuation time average term, the identity is applied. get

[0041] Based on the equation Ignoring the superscript, and based on the fact that both the turbulent kinetic energy and the turbulent dissipation rate vary with the disturbance, the turbulent kinetic energy is obtained to be 0, and the fluctuation of the turbulent random disturbance caused by the passage of the quasi-order disturbance is obtained:

[0042]

[0043] Among them, μ t represents the eddy viscosity coefficient.

[0044] Preferably, obtaining the pressure coherent disturbance term and the coherent structure term of the inlet fluid specifically includes:

[0045] Based on the normal mode method, Laplace transform is applied to convert the disturbance into the normal mode form. The pressure pseudo-order disturbance term is:

[0046]

[0047] The proposed sequence structure item is:

[0048]

[0049] in, and represent the velocity disturbance amplitude and the pressure disturbance amplitude respectively, ω represents the complex frequency of the disturbance, and θ and z represent coordinate axes.

[0050] Preferably, the linear perturbation equation is specifically:

[0051]

[0052]

[0053] Among them, Re eff represents the equivalent Reynolds number.

[0054] Preferably, the characteristic solution equation is specifically:

[0055]

[0056] Where M represents the definition matrix, represents the flow parameter and i represents the imaginary unit.

[0057] A centrifugal compressor impeller stall global stability prediction system based on leading edge overflow characteristics, comprising: an equation building module, a structure term acquisition module, an equation conversion module, a parameter acquisition module and a result output module;

[0058] The equation building module uses a centrifugal compressor-based impeller to establish a dimensionless two-dimensional NS equation including eddy viscosity and molecular viscosity;

[0059] The structural item acquisition module is configured to decompose the flow velocity of the inlet fluid of the impeller to obtain the pseudo-sequence structural item;

[0060] The equation conversion module is used to obtain a linear coherent perturbation equation based on the coherent structure term and the dimensionless NS equation; obtain the pressure coherent perturbation term and the coherent structure term of the inlet fluid and bring them into the linear coherent perturbation equation to obtain a linear perturbation equation; and convert the linear perturbation equation into a characteristic solution equation based on the linear perturbation equation;

[0061] The parameter acquisition module is used to select the key surface of the impeller based on the leading edge overflow characteristics; and obtain the average velocity component of the fluid based on the key surface;

[0062] The result output module is used to bring the average velocity component of the fluid into the characteristic solution equation to obtain a characteristic value; and predict the global stability of the impeller based on the size of the characteristic value.

[0063] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a method and system for predicting the global stability of a centrifugal compressor impeller stall based on leading edge overflow characteristics, which has the following beneficial effects:

[0064] 1. The present invention applies the global stability prediction method to the impeller machinery, and innovatively provides a solution to the problems of given boundary conditions, processing of viscosity terms and processing of compressible flow in the impeller machinery.

[0065] 2. By constructing a two-dimensional stability method prediction model for a cylindrical surface taking into account eddy viscosity and molecular viscosity, the two-dimensional stability method prediction model constructed by the present invention can effectively predict the impeller inlet flow state, and at the same time can realize the accurate prediction of the global stability of the centrifugal compressor impeller.

[0066] 3. The existing methods are mainly used to predict the transition of classical flows such as cylindrical turbulence and airfoils, and the problem of predicting and analyzing turbulent instability in centrifugal compressors with complex geometric configurations and boundary conditions has been solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0068] Figure 1 A flow chart of a method for predicting the global stability of a centrifugal compressor impeller stall based on leading edge overflow characteristics provided by the present invention.

[0069] Figure 2 A schematic diagram of the θ-z cylindrical surface of the impeller inlet provided by the present invention.

[0070] Figure 3 This is a global stability characteristic spectrum diagram provided by the present invention.

[0071] Figure 4 A global modal schematic diagram of the impeller inlet disturbance provided by the present invention.

[0072] Figure 5 A schematic diagram of the structure of a centrifugal compressor impeller stall global stability prediction system based on leading edge overflow characteristics provided by the present invention. DETAILED DESCRIPTION

[0073] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0074] Example 1

[0075] like Figure 1 As shown, an embodiment of the present invention discloses a method for predicting the global stability of a centrifugal compressor impeller stall based on leading edge overflow characteristics, comprising:

[0076] Based on the impeller of the centrifugal compressor, the dimensionless two-dimensional NS equations including eddy viscosity and molecular viscosity are established;

[0077] Based on the flow velocity of the impeller inlet fluid, the coherent structure term is obtained;

[0078] Based on the co-order structure term and the dimensionless NS equation, the linear co-order perturbation equation is obtained;

[0079] Obtain the pressure pseudo-order disturbance term and pseudo-order structure term of the inlet fluid and bring them into the linear pseudo-order disturbance equation to obtain the linear disturbance equation;

[0080] Based on the linear perturbation equation, it is converted into a characteristic solution equation;

[0081] Select the key surface of the impeller based on the leading edge overflow characteristics;

[0082] Obtain the average velocity component of the fluid based on the critical surface;

[0083] Based on the average velocity component of the fluid, the characteristic value is obtained by substituting it into the characteristic solution equation;

[0084] The global stability of the impeller is predicted based on the magnitude of the eigenvalues.

[0085] Example 2

[0086] The embodiment of the present invention discloses a method for predicting the global stability of a centrifugal compressor impeller stall based on leading edge overflow characteristics, comprising:

[0087] Based on the impeller of the centrifugal compressor, the dimensionless two-dimensional NS equations including eddy viscosity and molecular viscosity are established:

[0088] Preferably, it is assumed that the working fluid at the impeller inlet of the centrifugal compressor is an incompressible fluid, and a dimensionless Navier-Stokes equation that considers both eddy viscosity and molecular viscosity is constructed.

[0089] Preferably, the dimensionless two-dimensional NS equation is:

[0090]

[0091] Where, u represents the dimensionless velocity of the impeller outlet fluid, t represents time, and p represents the dimensionless pressure of the impeller outlet fluid. represents the velocity gradient, represents the pressure gradient, Re represents the Reynolds number, and denote the gradient and Laplacian operators respectively, Represents velocity divergence.

[0092] Preferably, the flow parameters are dimensionless using the definitions shown in Table 1:

[0093] Table 1 Dimensionless impeller inlet flow and structural parameters

[0094]

[0095] The flow parameters with the superscript dim are dimensioned flow parameters, U ri represents the impeller outlet leading edge velocity, ri represents the bladeless diffuser inlet radius, ρ in Represents the density of the fluid.

[0096] Based on the decomposition of the flow velocity of the impeller inlet fluid, the coherent structure term is obtained:

[0097] Preferably, the pseudo-sequence structure item is obtained, specifically including:

[0098] Based on the classic three-part flow model, the flow velocity of the impeller inlet fluid is decomposed to obtain the time average term, the pseudo-order structure term and the random turbulence disturbance term:

[0099]

[0100] Among them, u(x,t) represents the flow velocity of the impeller inlet fluid, represents the time average term, represents the co-order structure term, and u'(x,t) represents the random turbulence disturbance term.

[0101] Preferably, the time average of the flow field data within the time scale T is defined as:

[0102]

[0103] Preferably, the phase average is defined as:

[0104]

[0105] Among them, γ represents the fluctuation period, and n and N represent the intermediate parameters used to calculate the phase average.

[0106] Preferably, in the stability problem, the quasi-sequential structure term To focus on the key points, the coherent structure terms are extracted based on the phase-averaged mean flow:

[0107]

[0108] Based on the co-order structure term and the dimensionless NS equation, the linear co-order perturbation equation is obtained:

[0109] Preferably, the linear quasi-order perturbation equation is obtained by:

[0110] Based on the time average term, co-order structure term, random turbulence disturbance term and dimensionless two-dimensional NS equation, the co-order disturbance control equation is obtained:

[0111]

[0112] in, represents the gradient of the pressure pseudo-order disturbance term, represents the nonlinear term, represents the fluctuation of the turbulent random disturbance caused by the passage of the quasi-order disturbance, represents the time average term, represents the quasi-order structure term, u' represents the random turbulence disturbance term;

[0113] Based on the pseudo-order disturbance control equation, the infinitesimal disturbance hypothesis and turbulent viscosity hypothesis theory are introduced to obtain the fluctuation and equivalent Reynolds number of the turbulent random disturbance caused by the passage of the pseudo-order disturbance.

[0114] The fluctuation of turbulent random disturbance caused by the passage of quasi-order disturbance and the equivalent Reynolds number are brought into the quasi-order disturbance control equation to obtain the linear quasi-order disturbance equation.

[0115] Preferably, the method for obtaining the quasi-sequential disturbance control equation is:

[0116] Based on the time average term, co-order structure term, random turbulence disturbance term and dimensionless two-dimensional NS equation, the mean flow equation is obtained;

[0117] Based on the time average term, the co-order structure term and the dimensionless two-dimensional NS equation, the phase average governing equation is obtained;

[0118] Based on the difference between the average flow equation and the phase average control equation, the quasi-sequential perturbation control equation is obtained.

[0119] Preferably, assumptions are made for the time average term and the co-order structure term: ① the average flow does not change with time, ② the average flow is uniform along the circumference, and based on the time average term, the co-order structure term, the random turbulence disturbance term and the dimensionless two-dimensional NS equation, the average flow equation is obtained:

[0120]

[0121] in, represents the gradient of the time-averaged pressure term, represents the Reynolds stress generated by the random turbulence disturbance term, It represents the stress generated by the coherent structure term, that is, the direct interaction between the mean flow and the coherent structure, and the mean flow and the random disturbance is already included in the mean flow field.

[0122] Preferably, the fluctuation of turbulent random disturbance caused by the passage of quasi-sequential disturbance The acquisition method is:

[0123] Introducing the turbulent viscosity hypothesis theory, the quasi-sequential perturbation control equation is closed, and the average term of the wave phase is:

[0124]

[0125] The fluctuation time average term is:

[0126]

[0127] Where k represents the turbulent kinetic energy, represents the phase average of the eddy viscosity coefficient, I represents the unit matrix, u represents the flow velocity of the impeller inlet fluid, is the time average of the turbulent kinetic energy, represents the time average of the eddy viscosity coefficient;

[0128] Based on the time average of the fluctuation phase average term and the fluctuation time average term, the identity is applied. At this time, the time average and phase average of the corresponding eddy viscosity coefficient are equal, and we can get

[0129] Based on the equation Ignore the superscript, then

[0130] in, represents the turbulent kinetic energy in the form of disturbance;

[0131] And based on the fact that both the turbulent kinetic energy and the turbulent dissipation rate vary with the disturbance, the turbulent kinetic energy is obtained to be 0, and the fluctuation of the turbulent random disturbance caused by the passage of the quasi-order disturbance is obtained:

[0132]

[0133] Among them, μ t represents the eddy viscosity coefficient.

[0134] Preferably, due to the introduction of the eddy viscosity coefficient, the equivalent Reynolds number is:

[0135] Re eff =ρ / d(μ+μ t )

[0136] Among them, ρ and μ represent the fluid density and fluid viscosity coefficient respectively, U and d represent the characteristic velocity and characteristic length of the flow field respectively.

[0137] Preferably, since the eddy viscosity coefficient is distributed in the flow field, the equivalent Reynolds number is also distributed in the flow field, and the linear quasi-sequential perturbation equation can be obtained:

[0138]

[0139] Simplified expression:

[0140]

[0141] Linear Operator for:

[0142]

[0143] Obtain the pressure coherent disturbance term and coherent structure term of the inlet fluid and bring them into the linear coherent disturbance equation to obtain the linear disturbance equation:

[0144] Preferably, obtaining the pressure coherent disturbance term and coherent structure term of the inlet fluid specifically includes:

[0145] Based on the normal mode method, Laplace transform is applied to convert the disturbance into the normal mode form. Based on the fact that the stability of the impeller θ-z plane is mainly affected by the axial disturbance, the pressure quasi-order disturbance term is:

[0146]

[0147] The pseudo-sequence structure items are:

[0148]

[0149] in, and Respectively represent the velocity disturbance amplitude and the pressure disturbance amplitude, ω=ω r +iω i represents the complex frequency of the disturbance, ω r and ω i represent the real frequency and the imaginary frequency respectively, and θ and z represent coordinate axes.

[0150] Preferably, the linear perturbation equation is specifically:

[0151]

[0152] Among them, Re eff represents the equivalent Reynolds number.

[0153] Based on the linear perturbation equation, it is converted into a characteristic solution equation:

[0154] Preferably, the linear perturbation equation is equivalent to a generalized eigenvalue problem, which is expressed in the form of an eigenvalue problem to obtain the characteristic solution equation:

[0155]

[0156] Where M represents the impeller inlet solution matrix, represents the flow parameter and i represents the imaginary unit.

[0157] Preferably, the matrix M is defined as:

[0158]

[0159] in, Indicates an operation symbol. represents the component of the average velocity of the fluid in the z-axis, It represents the component of the average velocity of the fluid on the θ axis.

[0160] Select the key surface of the impeller based on the leading edge overflow characteristics:

[0161] Preferably, the air flow fluctuation or instability in the compressor axis direction is the main reason for the overflow phenomenon at the leading edge of the impeller machine. Considering that the stall disturbance mainly occurs at the wheel rim, and the circumferential and axial disturbances of the tip clearance leakage flow have a dominant effect on the flow field stability, the key surface of this embodiment is the θ-z cylindrical surface of the impeller inlet, such as Figure 2 shown.

[0162] Get the average velocity component of the fluid based on the critical surface:

[0163] Preferably, the average fluid velocity component includes: the component of the average fluid velocity on the z-axis and the component of the average velocity of the fluid on the θ axis

[0164] Based on the average velocity component of the fluid, the eigenvalue of the impeller inlet solution matrix is ​​obtained by bringing it into the characteristic solution equation:

[0165] Preferably, the impeller inlet structure and flow parameters are obtained and substituted into the definition matrix M together with the average velocity component of the fluid to obtain the eigenvalues ​​and eigenvectors of the impeller inlet solution matrix, wherein the eigenvalues ​​reflect the stability of the system and the eigenvectors show the global modes of the impeller inlet disturbance.

[0166] Preferably, the impeller inlet structure and flow parameters include: the vaneless diffuser inlet radius ri, the impeller inlet axial position Zf1, the blade leading edge axial position Zf2 and the axial velocity v z .

[0167] Preferably, in this embodiment, the centrifugal compressor β is taken as the research object, the impeller operating speed is 80000r / min, the model used for calculation is the 99% blade height θ-z cylindrical surface of the impeller inlet area near the stall condition, and the impeller inlet structure and flow parameters are shown in Table 2:

[0168] Table 2 Impeller inlet structure and flow parameters

[0169]

[0170] Predict the global stability of the impeller based on the size of the eigenvalue:

[0171] Preferably, the stability of the predicted system is judged by the size of the largest imaginary part of the solved eigenvalue. The eigenvalue with the largest imaginary part is the most unstable eigenvalue. The larger the imaginary part, the more unstable the system. When the imaginary part is greater than 0, the disturbance mode is amplified on an infinite time scale, which will cause flow instability; when the imaginary part is equal to 0, the disturbance mode is neutrally stable; when the imaginary part is less than 0, the disturbance mode is attenuated on an infinite time scale, and the flow is stable.

[0172] The eigenvectors obtained by solving the matrix can show the flow state at the impeller inlet.

[0173] Preferably, Figure 3 As shown in the figure, the global stability characteristic spectrum of the near-stall condition is obtained based on the eigenvalue. The eigenvalue with the largest imaginary part in the characteristic spectrum is the most unstable eigenvalue, which determines the stability of the system. The global mode of the impeller inlet disturbance is obtained based on the eigenvector as shown in the figure. Figure 4 As shown in the figure, the global mode of the impeller inlet disturbance shows the flow state of the impeller inlet fluid. The disturbance characteristics at the 120° circumferential position of the impeller leading edge can be seen, the stall disturbance initial position point A (120° circumferential position of the blade leading edge), the disturbance propagation to the impeller inlet position point B, and the disturbance propagation again to the blade leading edge position point C, forming a triangular disturbance area between the three positions.

[0174] Example 3

[0175] like Figure 5 As shown, a centrifugal compressor impeller stall global stability prediction system based on leading edge overflow characteristics includes: an equation building module, a structure term acquisition module, an equation conversion module, a parameter acquisition module and a result output module;

[0176] Equation building module, which uses the impeller based on the centrifugal compressor to establish the dimensionless two-dimensional NS equations including eddy viscosity and molecular viscosity;

[0177] The structural term acquisition module uses the flow velocity of the impeller-based inlet fluid to decompose and obtain the pseudo-sequence structural term;

[0178] The equation conversion module is used to obtain the linear pseudo-order perturbation equation based on the pseudo-order structure term and the dimensionless NS equation; obtain the pressure pseudo-order perturbation term and the pseudo-order structure term of the inlet fluid and bring them into the linear pseudo-order perturbation equation to obtain the linear perturbation equation; convert the linear perturbation equation into a characteristic solution equation;

[0179] A parameter acquisition module is used to select a key surface of the impeller based on the leading edge overflow characteristics; and to obtain an average velocity component of the fluid based on the key surface;

[0180] The result output module is used to bring the average velocity component of the fluid into the characteristic solution equation to obtain the characteristic value; and predict the global stability of the impeller based on the size of the characteristic value.

[0181] Preferably, each of the above modules executes the method in Example 2 accordingly.

[0182] Example 4

[0183] Based on the same inventive concept, the present invention also provides a computer device, including a processor, a communication interface, a memory and a communication bus, wherein the processor, the communication interface and the memory communicate with each other via the communication bus;

[0184] Memory, used to store computer programs;

[0185] The processor, when used to execute the program stored in the memory, can implement a centrifugal compressor impeller stall global stability prediction method based on leading edge overflow characteristics as in Example 1 or 2.

[0186] The electronic device may include: a processor 41, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other via the communication bus. The processor may call the logic instructions in the memory to execute a centrifugal compressor impeller stall global stability prediction method based on leading edge overflow characteristics as in Embodiment 1 or 2.

[0187] In addition, the logic instructions in the above-mentioned memory can be implemented in the form of software functional units and can be stored in a computer-readable storage medium when sold or used as an independent product. Based on such an understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art or the part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods of each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0188] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a method and system for predicting the global stability of a centrifugal compressor impeller stall based on leading edge overflow characteristics, which has the following beneficial effects:

[0189] 1. The present invention applies the global stability prediction method to the impeller machinery, and innovatively provides a solution to the problems of given boundary conditions, processing of viscous terms and processing of compressible flow in the impeller machinery.

[0190] 2. By constructing a two-dimensional stability method prediction model for a cylindrical surface taking into account eddy viscosity and molecular viscosity, the two-dimensional stability method prediction model constructed by the present invention can effectively predict the impeller inlet flow state, and at the same time can realize the accurate prediction of the global stability of the centrifugal compressor impeller.

[0191] 3. The existing methods are mainly used to predict the transition of classical flows such as cylindrical turbulence and airfoils, and the problem of predicting and analyzing turbulent instability in centrifugal compressors with complex geometric configurations and boundary conditions has been solved.

[0192] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0193] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for predicting the global stability of centrifugal compressor impeller stall based on leading edge overflow characteristics, characterized in that: include: Based on the impeller of the centrifugal compressor, the dimensionless two-dimensional NS equations including eddy viscosity and molecular viscosity are established; Decomposing the flow velocity of the inlet fluid of the impeller to obtain a coherent structure term; A linear co-order perturbation equation is obtained based on the co-order structure term and the dimensionless NS equation; Obtaining the pressure coherent disturbance term and the coherent structure term of the inlet fluid and substituting them into the linear coherent disturbance equation to obtain a linear disturbance equation; Based on the linear perturbation equation, the linear perturbation equation is converted into a characteristic solution equation; Selecting the key surface of the impeller based on the leading edge overflow characteristics; Obtaining an average velocity component of the fluid based on the critical surface; Substituting the average velocity component of the fluid into the characteristic solution equation to obtain a characteristic value; The global stability of the impeller is predicted based on the magnitude of the eigenvalue.

2. The method for predicting global stability of centrifugal compressor impeller stall based on leading edge overflow characteristics according to claim 1, characterized in that: The dimensionless two-dimensional NS equation is: Where, u represents the dimensionless velocity of the impeller outlet fluid, t represents time, and p represents the dimensionless pressure of the impeller outlet fluid. represents the velocity gradient, represents the pressure gradient, Re represents the Reynolds number, and denote the gradient and Laplacian operators respectively, Represents velocity divergence.

3. The method for predicting global stability of centrifugal compressor impeller stall based on leading edge overflow characteristics according to claim 2, characterized in that: The pseudo-sequence structure items are obtained, including: Based on the classic three-part flow model, the flow velocity of the impeller inlet fluid is decomposed to obtain the time average term, the coherent structure term and the random turbulence disturbance term: Among them, u(x,t) represents the flow velocity of the impeller inlet fluid, represents the time average term, represents the co-order structure term, and u'(x,t) represents the random turbulence disturbance term.

4. The method for predicting global stability of centrifugal compressor impeller stall based on leading edge overflow characteristics according to claim 3, characterized in that: The linear quasi-sequential perturbation equation is obtained by: Based on the time average term, the coherent structure term, the random turbulence disturbance term and the dimensionless two-dimensional NS equation, the coherent disturbance control equation is obtained: in, represents the pressure quasi-order disturbance term, represents the nonlinear term, represents the fluctuation of the turbulent random disturbance caused by the passage of the quasi-order disturbance, represents the time average term, represents the quasi-order structure term, u' represents the random turbulence disturbance term; Based on the pseudo-order disturbance control equation, the infinitesimal disturbance hypothesis and the turbulent viscosity hypothesis theory are introduced to obtain the fluctuation and equivalent Reynolds number of the turbulent random disturbance caused by the passage of the pseudo-order disturbance. The fluctuation of the turbulent random disturbance caused by the passage of the quasi-order disturbance and the equivalent Reynolds number are brought into the quasi-order disturbance control equation to obtain the linear quasi-order disturbance equation.

5. The method for predicting global stability of centrifugal compressor impeller stall based on leading edge overflow characteristics according to claim 4, characterized in that: The method for obtaining the quasi-sequential disturbance control equation is: Based on the time average term, the coherent structure term, the random turbulence disturbance term and the dimensionless two-dimensional NS equation, a mean flow equation is obtained; Based on the time average term, the coherent structure term and the dimensionless two-dimensional NS equation, a phase average control equation is obtained; The pseudo-sequential disturbance control equation is obtained by subtracting the average flow equation from the phase average control equation.

6. The method for predicting global stability of centrifugal compressor impeller stall based on leading edge overflow characteristics according to claim 4, characterized in that: Fluctuation of turbulent random disturbances caused by the passage of quasi-sequential disturbances The acquisition method is: Introducing the turbulent viscosity hypothesis theory, the pseudo-order perturbation control equation is closed, and the average term of the wave phase is: The fluctuation time average term is: Where k represents the turbulent kinetic energy, represents the phase average of the eddy viscosity coefficient, I represents the unit matrix, u represents the flow velocity of the impeller inlet fluid, is the time average of the turbulent kinetic energy, represents the time average of the eddy viscosity coefficient; Based on the time average of the fluctuation phase average term and the fluctuation time average term, the identity is applied. get Based on the equation Ignoring the superscript, and based on the fact that both the turbulent kinetic energy and the turbulent dissipation rate vary with the disturbance, the turbulent kinetic energy is obtained to be 0, and the fluctuation of the turbulent random disturbance caused by the passage of the quasi-order disturbance is obtained: Among them, μ t represents the eddy viscosity coefficient.

7. The method for predicting global stability of centrifugal compressor impeller stall based on leading edge overflow characteristics according to claim 4, characterized in that: Obtaining the pressure coherent disturbance term and the coherent structure term of the inlet fluid specifically includes: Based on the normal mode method, Laplace transform is applied to convert the disturbance into the normal mode form. The pressure pseudo-order disturbance term is: The proposed sequence structure item is: in, and represent the velocity disturbance amplitude and the pressure disturbance amplitude respectively, ω represents the complex frequency of the disturbance, and θ and z represent coordinate axes.

8. The method for predicting global stability of centrifugal compressor impeller stall based on leading edge overflow characteristics according to claim 7, characterized in that: The linear perturbation equation is specifically: Among them, Re eff represents the equivalent Reynolds number.

9. The method for predicting global stability of centrifugal compressor impeller stall based on leading edge overflow characteristics according to claim 8, characterized in that: The characteristic solution equation is specifically: Where M represents the impeller inlet solution matrix, represents the flow parameter and i represents the imaginary unit.

10. A centrifugal compressor impeller stall global stability prediction system based on leading edge overflow characteristics, applied to the method according to any one of claims 1 to 9, characterized in that: include: Equation building module, structure term acquisition module, equation conversion module, parameter acquisition module and result output module; The equation building module uses a centrifugal compressor-based impeller to establish a dimensionless two-dimensional NS equation including eddy viscosity and molecular viscosity; The structural item acquisition module is configured to decompose the flow velocity of the inlet fluid of the impeller to obtain the pseudo-sequence structural item; The equation conversion module is used to obtain a linear co-order perturbation equation based on the co-order structure term and the dimensionless NS equation; Obtain the pressure pseudo-order disturbance term and the pseudo-order structure term of the inlet fluid and bring them into the linear pseudo-order disturbance equation to obtain a linear disturbance equation; convert the linear disturbance equation into a characteristic solution equation based on the linear disturbance equation; The parameter acquisition module is used to select the key surface of the impeller based on the leading edge overflow characteristics; Obtaining an average velocity component of the fluid based on the critical surface; The result output module is used to bring the average velocity component of the fluid into the characteristic solution equation to obtain a characteristic value; The global stability of the impeller is predicted based on the magnitude of the eigenvalue.

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