A simulation method and system for blowing air on the surface of a blade

Abstract

The present invention relates to a simulation method and system for blowing air on the blade surface. The method includes obtaining the configuration parameters of the rotor to be simulated; constructing a grid system according to the configuration parameters, the grid system including blade grids and background grids; obtaining the jet velocity and the grid motion velocity; the grid motion velocity includes: the motion velocity of the blade grids and the motion velocity of the background grids; calculating the grid velocity on the jet orifice surface according to the jet velocity and the grid motion velocity; and performing a blowing air simulation by blowing air simultaneously at the jet orifices on the upper surface and the lower surface of the grid system according to the grid velocity on the jet orifice surface. The present invention can reduce the blade-vortex interaction noise.

Description

Technical Field

[0001] The present invention relates to the technical field of helicopters, and particularly to a simulation method and system for blowing air on the blade surface. Background Art

[0002] As one of the most important noises of helicopters, the problem of high-intensity and pulsed blade-vortex interaction (BVI) noise has received extensive attention. The BVI phenomenon occurs when a helicopter is flying forward in a low-speed oblique descent. The tip vortices shed from the rotor blade tips approach and directly collide with other rotor blades or even the blade itself, causing the aerodynamic load on the blade surface to fluctuate impulsively in a short time, and at the same time, it will also cause strong blade-vortex interaction aerodynamic noise. As an active control method for blade-vortex interaction noise, the rotor tip mass jet technology refers to arranging jet pipes at the rotor blade tip ends or on the blade surface and blowing out air. This technology has initially shown the ability to change the flow field tip vortices and reduce blade-vortex interaction noise in a series of experiments, but the simulation research has not been well developed. On the one hand, because the blade-vortex interaction state is quite complex, it is limited by the insufficient prediction accuracy of blade-vortex interaction noise; on the other hand, due to the complexity of simulating the blowing flow control under the blade-vortex interaction state, the previous simulation results of blowing air on the blade surface show that blowing air may cause a decrease in the rotor thrust performance, and the noise reduction effect at the expense of rotor thrust is not ideal.

[0003] The current simulation research work on rotor mass jet control mainly focuses on studying the influence of blowing control on the generation and intensity of tip vortices in the rotor hover flow field. Some existing technologies have numerically simulated the influence of blowing air on the blade surface on changing the tip vortices of the hovering rotor, not only demonstrating the effectiveness of blowing air in changing the tip vortex structure and intensity, but also finding that blowing air is superior to passive control methods such as installing flow deflectors, but blowing air will also reduce the rotor thrust coefficient. There are also existing technologies that analyze the influence of spanwise blowing and chordwise blowing on the generation and evolution of tip vortices of a single hovering rotor blade, showing that blowing control significantly reduces the tip vortex flow velocity and increases the vortex core radius. There are also existing technologies that analyze the influence of parameters such as jet velocity and jet angle in spanwise jet control on the tip vortex intensity and rotor aerodynamic characteristics for the Caradonna-Tung rotor hover flow field. The above research on blowing control in the hover flow field is of great significance, but there is a lack of simulation research on the influence of blowing control on the rotor blade-vortex interaction flow field and noise control. Summary of the Invention

[0004] The purpose of the present invention is to provide a simulation method and system for blowing air on the blade surface, which can reduce blade-vortex interaction noise.

[0005] To achieve the above purpose, the present invention provides the following solutions:

[0006] A method for simulating air blowing on the surface of a blade, comprising:

[0007] Obtaining the configuration parameters of the rotor to be simulated;

[0008] Constructing a grid system according to the configuration parameters, the grid system including blade grids and background grids;

[0009] Obtaining the jet velocity and the grid movement velocity; the grid movement velocity includes: the movement velocity of the blade grids and the movement velocity of the background grids;

[0010] Calculating the grid velocity on the surface of the jet orifice according to the jet velocity and the grid movement velocity;

[0011] Performing air blowing simulation by simultaneously blowing air at the jet orifices on the upper surface and the lower surface of the grid system according to the grid velocity on the surface of the jet orifice.

[0012] Optionally, the calculating the grid velocity on the surface of the jet orifice according to the jet velocity and the grid movement velocity specifically includes:

[0013] Calculating the grid velocity on the surface of the jet orifice corresponding to the blade grids according to the jet velocity and the movement velocity of the blade grids;

[0014] Calculating the grid velocity on the surface of the jet orifice corresponding to the background grids according to the jet velocity and the movement velocity of the background grids.

[0015] Optionally, the performing air blowing simulation by simultaneously blowing air at the jet orifices on the upper surface and the lower surface of the grid system according to the grid velocity on the surface of the jet orifice specifically includes:

[0016] Performing air blowing simulation by simultaneously blowing air at the jet orifices on the upper surface and the lower surface of the blade grids according to the grid velocity on the surface of the jet orifice corresponding to the blade grids;

[0017] Performing air blowing simulation by simultaneously blowing air at the jet orifices on the upper surface and the lower surface of the background grids according to the grid velocity on the surface of the jet orifice corresponding to the background grids.

[0018] Optionally, the blade grids are blade grids with a three-dimensional C-O type topology, and the background grids are Cartesian background grids.

[0019] A system for simulating air blowing on the surface of a blade, comprising:

[0020] A first obtaining module, configured to obtain the configuration parameters of the rotor to be simulated;

[0021] A grid system construction module, configured to construct a grid system according to the configuration parameters, where the grid system includes a blade grid and a background grid;

[0022] A second acquisition module, configured to acquire the jet velocity and the grid motion velocity; the grid motion velocity includes: the motion velocity of the blade grid and the motion velocity of the background grid;

[0023] A jet orifice surface grid velocity calculation module, configured to calculate the jet orifice surface grid velocity according to the jet velocity and the grid motion velocity;

[0024] A blowing simulation module, configured to perform a blowing simulation by blowing air simultaneously at the jet orifices on the upper surface and the lower surface of the grid system according to the jet orifice surface grid velocity.

[0025] Optionally, the jet orifice surface grid velocity calculation module specifically includes:

[0026] A blade grid jet orifice surface grid velocity calculation unit, configured to calculate the jet orifice surface grid velocity corresponding to the blade grid according to the jet velocity and the motion velocity of the blade grid;

[0027] A background grid jet orifice surface grid velocity calculation unit, configured to calculate the jet orifice surface grid velocity corresponding to the background grid according to the jet velocity and the motion velocity of the background grid.

[0028] Optionally, the blowing simulation module specifically includes:

[0029] A blade grid blowing simulation unit, configured to perform a blowing simulation by blowing air simultaneously at the jet orifices on the upper surface and the lower surface of the blade grid according to the jet orifice surface grid velocity corresponding to the blade grid;

[0030] A background grid blowing simulation unit, configured to perform a blowing simulation by blowing air simultaneously at the jet orifices on the upper surface and the lower surface of the background grid according to the jet orifice surface grid velocity corresponding to the background grid.

[0031] Optionally, the blade grid is a blade grid with a three-dimensional C-O type topology, and the background grid is a Cartesian background grid.

[0032] According to the specific embodiments provided by the present invention, the following technical effects are disclosed: The present invention acquires the configuration parameters of the rotor to be simulated; constructs a grid system according to the configuration parameters; acquires the jet velocity and the grid motion velocity; calculates the jet orifice surface grid velocity according to the jet velocity and the grid motion velocity; and performs a blowing simulation by blowing air simultaneously at the jet orifices on the upper surface and the lower surface of the grid system according to the jet orifice surface grid velocity. Blowing air simultaneously on the upper and lower surfaces can reduce the blade-vortex interaction noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0034] Figure 1 It is a flowchart of a method for simulating blowing on the surface of a blade provided by an embodiment of the present invention;

[0035] Figure 2 It is a schematic diagram of a two-dimensional airfoil grid provided by an embodiment of the present invention;

[0036] Figure 3 It is a schematic diagram of a grid system using a moving nested grid system and uniformly encrypted spanwise nodes provided by an embodiment of the present invention;

[0037] Figure 4 It is a schematic diagram of a blade grid provided by an embodiment of the present invention;

[0038] Figure 5 It is a schematic diagram of a background grid provided by an embodiment of the present invention;

[0039] Figure 6 It is a partial schematic diagram when blowing air on both the upper and lower surfaces of the blade provided by an embodiment of the present invention;

[0040] Figure 7 It is a schematic diagram of the surface grid of the jet orifice provided by an embodiment of the present invention;

[0041] Figure 8 It is an overall schematic diagram when blowing air on both the upper and lower surfaces simultaneously provided by an embodiment of the present invention;

[0042] Figure 9 It is a comparison diagram of the distribution of the sectional pressure coefficient of the rotor blade for the example of blowing air on both the upper and lower surfaces of the blade;

[0043] Figure 10 It is an isovorticity diagram of the rotor flow field showing the influence of the example of blowing air on both the upper and lower surfaces of the blade on the structure and trajectory of the rotor blade tip vortex in the blade-vortex interaction flow field;

[0044] Figure 11 It is a result diagram showing the influence of the example of blowing air on both the upper and lower surfaces of the blade on the time history of the noise sound pressure at the microphone. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0046] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0047] There are numerical simulation studies on reducing blade-vortex interaction noise by blowing air on the upper surface of the blade in the prior art. It is found that while blowing air on the upper surface reduces noise, it will cause an adverse effect of rotor thrust loss. Therefore, this blowing method is not conducive to being carried out in actual engineering applications. The requirement of engineering applications is to reduce noise on the premise of not significantly reducing the rotor thrust performance. Based on this, the present invention establishes a feasible numerical simulation method for simultaneously blowing air on the upper and lower surfaces of the blade applicable to reducing blade-vortex interaction noise. This method uses the Reynolds-averaged Navier-Stokes (RANS) equation based on the fifth-order accurate WENO-Z scheme and the Farassat's Formulation 1A (F1A formula) based on the Ffowcs Williams-Hawkings (FW-H) equation to perform high-resolution CFD / acoustic analogy numerical simulations of the blade-vortex interaction flow field and noise, and models the jet surface boundary conditions to simulate the influence of simultaneously blowing air on the upper and lower surfaces of the blade on the blade-vortex interaction noise. When the blade-vortex interaction occurs, the blade-vortex interaction noise is reduced by simultaneously blowing air at equal jet velocities through jet orifices at the same spanwise and chordwise positions on the upper and lower surfaces of the blade, and the rotor thrust performance can be maintained basically unchanged. Therefore, this method has potential effectiveness in engineering design applications.

[0048] The blade surface blowing simulation method provided by the embodiment of the present invention, as Figure 1 shown, includes:

[0049] Step 101: Obtain the configuration parameters of the rotor to be simulated.

[0050] Step 102: Construct a grid system according to the configuration parameters, and the grid system includes blade grids and background grids.

[0051] Step 103: Obtain the jet velocity and the grid motion velocity; the grid motion velocity includes: the motion velocity of the blade grids and the motion velocity of the background grids.

[0052] Step 104: Calculate the grid velocity on the surface of the jet orifice according to the jet velocity and the grid movement velocity.

[0053] Step 105: Perform a blowing simulation by blowing air simultaneously at the jet orifices on the upper surface and the lower surface of the grid system according to the grid velocity on the surface of the jet orifice.

[0054] In practical applications, the calculation of the grid velocity on the surface of the jet orifice according to the jet velocity and the grid movement velocity specifically includes:

[0055] Calculate the grid velocity on the surface of the jet orifice corresponding to the blade grid according to the jet velocity and the movement velocity of the blade grid.

[0056] Calculate the grid velocity on the surface of the jet orifice corresponding to the background grid according to the jet velocity and the movement velocity of the background grid.

[0057] In practical applications, the performance of the blowing simulation by blowing air simultaneously at the jet orifices on the upper surface and the lower surface of the grid system according to the grid velocity on the surface of the jet orifice specifically includes:

[0058] Perform a blowing simulation by blowing air simultaneously at the jet orifices on the upper surface and the lower surface of the blade grid according to the grid velocity on the surface of the jet orifice corresponding to the blade grid.

[0059] Perform a blowing simulation by blowing air simultaneously at the jet orifices on the upper surface and the lower surface of the background grid according to the grid velocity on the surface of the jet orifice corresponding to the background grid.

[0060] In practical applications, the blade grid is a blade grid with a three-dimensional C-O type topology, and the background grid is a Cartesian background grid.

[0061] In practical applications, the calculation of the grid velocity on the surface of the jet orifice corresponding to the blade grid according to the jet velocity and the movement velocity of the blade grid specifically includes:

[0062] Construct a blowing model on the blade surface.

[0063] Input the jet velocity and the movement velocity of the blade grid into the blowing model on the blade surface to obtain the grid velocity on the surface of the jet orifice corresponding to the blade grid.

[0064] In practical applications, the calculation of the grid velocity on the surface of the jet orifice corresponding to the background grid according to the jet velocity and the movement velocity of the background grid specifically includes:

[0065] Construct a blowing model on the blade surface.

[0066] Input the jet velocity and the movement velocity of the background grid into the blade surface blowing model to obtain the jet orifice surface grid velocity corresponding to the background grid.

[0067] The present invention also provides a more specific blade surface blowing simulation method for reducing rotor blade-vortex interaction noise, which is a numerical simulation method for reducing rotor blade-vortex interaction noise by blowing air simultaneously on the upper and lower surfaces of the rotor blade. The high-resolution computational fluid dynamics (CFD) / acoustic analogy numerical method is used to simulate the rotor flow field and noise in the blade-vortex interaction state, and the active flow control of the blade-vortex interaction flow field and noise by blowing air simultaneously on the upper and lower surfaces of the blade is simulated. In the CFD method, a jet blowing model (referred to as a jet boundary condition) of the upper and lower surfaces of the blade that takes into account the jet velocity is established through a mass flow outlet boundary condition. The grids on the upper and lower surfaces of the blade near the blade tip are specified as the jet orifice positions and the same jet velocity is applied for blowing simultaneously, so as to improve the intensity of the blade tip vortex in the blade-vortex interaction state and change the trajectory of the blade tip vortex, thereby reducing the blade-vortex interaction noise and keeping the rotor thrust performance basically unchanged. It mainly includes four aspects: "generating a grid system for jet blowing control according to the rotor configuration parameters", "a high-precision CFD method for solving the rotor blade-vortex interaction flow field and blowing control considering the jet influence", "using a noise program to process and calculate the BVI noise of the unsteady aerodynamic load", and "comparison of the aerodynamic force, flow field and noise results between the non-blowing reference case and the blowing control case". Around these contents, the technical solution of this embodiment is as follows:

[0068] (1) Use a self-written grid generation program to generate a grid system according to the rotor configuration parameters (the airfoil distribution of the blade, the chord length and radius of the blade, the twist distribution, the three-dimensional changes at the blade tip (sweeping, tapering and dihedral, etc.)). The grid system includes the rotor blade grid and the background grid. When generating the blade grid, first generate the corresponding two-dimensional airfoil grid according to the airfoil coordinate points; and according to the chord length and radius, the twist distribution and the change of the 1 / 4 chord line, perform operations such as folding, tiling and refolding on the two-dimensional airfoil grid in sequence as Figure 2 shown to obtain the blade grid.

[0069] The generation of the background grid is very simple. Just knowing the radius R of the rotor, the length, width, and height of the cube of the background grid can be calculated. Once the dimensions are determined, the nodes can be directly divided along the length, width, and height. Specifically: Generate a cube with a length, width, and height of 7R (R represents the blade radius), 5.5R, and 6R respectively, and divide the grid points on each edge. A high-resolution grid is the key to accurately predicting the blade-vortex interaction noise and simulating the blowing control on the blade surface. For the blowing simulation, 15 nodes are uniformly encrypted at the distribution position of the jet orifice (92%-95% of the radius in the spanwise direction) on the blade grid.

[0070] (2) Model the blowing model on the blade surface. Establish the jet boundary condition through the mass flow outlet boundary condition to account for the influence of jet blowing in the CFD method; adopt the RANS equation based on the fifth-order accurate WENO format for high-precision simulation of the rotor blade-vortex interaction flow field.

[0071] When modeling the blowing on the blade surface, note that a reasonable CFD modeling is carried out without considering the influence of some practical problems, such as compressed air needs to be supplied by an engine or an independent compressor, and at the same time, the blown air needs to be supplied to the blade surface by the pipeline system inside the blade. In the simulation study, the surface blowing is appropriately simulated as the mass flow outlet boundary condition of the surface grid at the position of the jet orifice defined in (1) on the blade surface. The blade surface blowing model is where u represents the component of the jet orifice surface grid velocity in the x direction, v represents the component of the jet orifice surface grid velocity in the y direction, w represents the component of the jet orifice surface grid velocity in the z direction, u mesh represents the component of the grid movement velocity in the x direction, v mesh represents the component of the grid movement velocity in the y direction, w mesh represents the component of the grid movement velocity in the z direction, Flag is a control parameter. When Flag is set to 0, the incident jet velocity is not considered, and only the grid movement velocity is considered, which is the wall boundary condition; when Flag is set to 1, the jet velocity is considered, and the jet orifice surface grid velocity is the vector sum of the grid movement velocity and the jet velocity, which is the jet boundary condition. n x represents the unit normal vector of the coordinate system in the x direction, n y represents the unit normal vector of the coordinate system in the y direction, n y represents the unit normal vector of the coordinate system in the z direction, V jetDenote the jet velocity. For the velocity components in the flow field, the velocities in the three directions are as follows: Since the rotor itself is in motion, it has a grid motion velocity, which is determined by the rotor motion parameters (rotation speed, advance ratio, etc.). Because it is a numerical simulation, the actual motion of the rotor blades is simulated by the motion of the blade grids. By setting the rotation speed and forward flight speed, the grids have a motion velocity. After applying the jet (the jet velocity is defined by the user), there is a jet velocity, and the total velocity is the superposition of the two. The jet velocity + the grid motion velocity is the grid velocity on the jet orifice surface.

[0072] Specifically, the modeling of surface blowing is carried out by applying the jet surface boundary condition on the grid cell surface at the jet orifice position defined in (1), and setting the magnitude of the jet velocity on the jet orifice surface. According to the blowing model, the grid velocity on the jet orifice surface is solved, and the blade is blown with the grid velocity on the jet orifice surface perpendicular to the blade surface, keeping other flow conditions of the blowing control case exactly the same as those of the non-blowing reference case.

[0073] The solution of the rotor blade-vortex interaction flow field uses the RANS equation in the inertial coordinate system as the governing equation, and its expression is

[0074]

[0075] In the formula, V and S represent the control volume and surface area respectively, and W is the conserved variable vector [ρ, ρu, ρv, ρw, ρE]. T , F c and F v represent the inviscid flux and viscous flux respectively. The finite volume method with a cell-centered format is used for spatial discretization of the governing equation. Among them, the inviscid term is calculated using the Roe flux difference splitting format developed based on the approximate Riemann solution. In this work, the reconstruction of the state variables on both sides of the interface flux uses the improved fifth-order weighted essentially non-oscillatory format (WENO-Z format); the calculation of the viscous flux uses the second-order central difference format; the time marching applies the dual-time iterative stepping method, and the calculation of the pseudo-time step uses the efficient implicit LU-SGS marching format. The Spalart-Allmaras (S-A) turbulence model is modeled to simulate turbulence. The self-developed CFD program is used to solve the flow field and aerodynamic load data of the non-blowing reference case and the blowing control case respectively under the rotor blade-vortex interaction state. u, v, w and the conserved variable vector W in the RANS equation, the inviscid flux F c and the viscous flux F v are all related. Therefore, during the flux calculation, due to the velocity change, these fluxes need to be taken into account and modified.

[0076] Based on the solution of the rotor BVI flow field by the CFD method, the calculation model of BVI noise selects the blade surface as the sound source integration surface. The blade surface grid coordinates and the pressure on the blade surface obtained in (2) (by applying the jet velocity, the surface grid velocity at the jet orifice is the vector sum of the grid motion velocity and the jet velocity, and the normal component of the surface velocity is obtained by decomposing along the normal vectors in each direction of the coordinate system. The density on the surface grid of the jet orifice is extrapolated by interpolation from the internal cells of the flow field, and the pressure is calculated using the normal momentum equation containing the surface velocity) are used as the input parameters of the self-written noise program. The calculation of rotor aerodynamic noise uses the F1A formula of the FW-H equation based on the "Lighthill acoustic analogy method". The blowing has been simulated in CFD, and the noise is a post-processing of the CFD calculation results. The noise only requires the grid coordinates and the pressure calculated by CFD

[0077] p'(x,t) = p' T (x,t) + p' L (x,t)

[0078] where x represents the position vector coordinate of the observation point, t represents the observation time, p' T and p' L represent the thickness noise and loading noise of the blade respectively, and their expressions are

[0079]

[0080] In the formula, c0 and ρ0 represent the sound speed and density in the undisturbed medium, r is the distance from the sound source surface to the observation point, v n represents the normal velocity of the sound source surface, denotes the first derivative of v n with respect to velocity, denotes the first derivative of v n with respect to the coordinate vector, M r is the component of the source surface motion Mach number along the propagation direction, l r represents the loading component of the sound source surface along the propagation direction, i r denotes l r with respect to the first derivative of time, l M represents the component of the loading along the source surface motion Mach number. The superscript "" represents the time derivative of the variable, and the subscript ret represents the retarded time.

[0081] By integrating and solving the above formula at the retarded time, the noise information at the observation point can be obtained. The self-written noise program is used to calculate the BVI noise results at the observation point for the non-blowing baseline case and the blowing control case respectively.

[0082] (4) Compare the aerodynamic forces, flow fields, and noise results of the non-blowing reference case and the blowing control case to compare the influence of simultaneous blowing on the upper and lower surfaces of the blade on the rotor blade-vortex interaction flow field and noise control. The main data for comparison include: the distribution of blade section pressure coefficients, the structure and trajectory of the tip vortices in the flow field, the vorticity intensity map of the flow field cross-section, the time history of the noise sound pressure at the observation point, and the peak sound pressure and sound pressure level at the observation point.

[0083] The embodiment of the present invention further provides a blowing control simulation of the blade-vortex interaction aerodynamic / noise test in the "10014" state of the OLS rotor as an example to further elaborate on the above method in detail.

[0084] (1) Generate a grid system for jet blowing control according to the rotor configuration parameters:

[0085] The blade-vortex interaction aerodynamic / noise test in the "10014" state of the OLS rotor was carried out in the German-Dutch Wind Tunnel (DNW). The OLS test rotor has two rectangular straight blades, the section airfoil adopts the OLS airfoil, the rotor radius is 0.958 m, the chord length is 0.1039 m, and the blade has a negative twist of 8.2°. The "10014" state is a typical blade-vortex interaction state in the OLS rotor series tests. The corresponding rotor tip Mach number for this test condition is 0.664 (tip speed is 226.0 m / s), the advance ratio is 0.164, and the thrust coefficient is 0.0054. The moving nested grid method is used to simulate the movement of the rotor blade, and a self-developed grid generation program is used to generate the grid system according to the rotor configuration parameters. The grid system includes two C-O type body-fitted blade structure grids (as shown in Figure 4 shown, Figure 4 (b) is Figure 4 (a)'s partial enlarged view), and a Cartesian background grid (as shown in Figure 5 shown, Figure 5 (b) is Figure 5 (a)'s partial enlarged view, the square represents the jet orifice), as shown in Figure 3 shown, the center of the rotor hub is located at the origin of the coordinate system, the oncoming flow direction points to the positive x-axis direction, the vertical direction is the y direction, and the lateral direction is the z direction. For blowing simulation, 15 nodes were uniformly encrypted at the distribution position of the jet orifices (92%-95% radius in the spanwise direction) on the blade grid. The positions of the jet orifices are on the upper and lower surfaces of the blade near the trailing edge near the tip, at two 15×5 (spanwise and chordwise) grid cell surfaces with the same spanwise and chordwise positions (as shown in Figure 7 shown), the length is between 92%-95% radius in the spanwise direction of the rotor blade surface, and the width is between 84%-90% chord length.

[0086] (2) High-precision CFD method for solving the rotor blade-vortex interference flow field considering the influence of the jet and blowing control:

[0087] In the simulation study of the blowing case, surface blowing is appropriately modeled by imposing boundary conditions at the mass flow outlet on the surface grid of the blade at the defined jet orifice positions. By imposing the blowing jet velocity, the density on the surface grid of the jet orifice is extrapolated by interpolation from the internal cells of the flow field. The velocity on the surface of the jet orifice is the vector sum of the blade rotational linear velocity and the blowing jet velocity, and the normal component of the velocity is obtained by decomposing along the normal vectors in each direction of the coordinate system. The pressure is calculated using the normal momentum equation containing the surface velocity.

[0088] For the blowing case simulation of the OLS rotor (see Figure 6 and Figure 8 ), the modeling of surface blowing is carried out by imposing jet surface boundary conditions on the 15×5 (spanwise and chordwise) grid cell surfaces on the upper and lower surfaces near the trailing edge of the airfoil near the blade tip of the rotor blade, and specifying the jet blowing velocity on the surface of the jet orifice as 20% of the rotor blade tip velocity (i.e., 45.2 m / s; the blowing velocity direction is perpendicular to the blade surface), keeping other flow conditions exactly the same as those of the non-blowing benchmark case.

[0089] The solution of the rotor blade-vortex interference flow field uses the RANS equation in the inertial coordinate system as the governing equation, and the finite volume method with a cell-centered grid is used for spatial discretization of the governing equation. Among them, the inviscid term is calculated using the Roe flux difference splitting scheme developed based on the approximate Riemann solution, and the reconstruction of the state variables on both sides of the interface flux uses the improved fifth-order weighted essentially non-oscillatory scheme (WENO-Z scheme); the calculation of the viscous flux uses the second-order central difference scheme; the time marching applies the dual-time iteration stepping method, and the calculation of the pseudo-time step uses the efficient implicit LU-SGS marching scheme. The Spalart-Allmaras (S-A) turbulence model is modeled to simulate turbulence. The self-developed CFD program is used to solve the flow field and aerodynamic load data of the non-blowing benchmark case and the blowing control case under the rotor blade-vortex interference state respectively.

[0090] (3) Using a noise program to process and calculate the BVI noise for unsteady aerodynamic loads:

[0091] Based on the solution of the rotor BVI flow field by the CFD method, the calculation model of BVI noise selects the blade surface as the sound source integration surface. The blade surface grid coordinates and the pressure on the blade surface grid obtained in (2) for the non-blowing case and the blowing control case are used as the input parameters of the self-written noise program. By integrating and solving the F1A formula at the delay time, the noise information at the observation point can be obtained. The self-written noise program is used to calculate the BVI noise results at the observation point for the non-blowing reference case and the blowing control case respectively.

[0092] (4) Comparison of aerodynamic forces, flow fields and noise results between the non-blowing reference case and the blowing control case:

[0093] The aerodynamic forces, flow fields and noise results of the non-blowing reference case and the blowing control case of the OLS rotor blade-vortex interaction state are compared to compare the influence of blowing on both the upper and lower surfaces of the blade on the blade-vortex interaction flow field and noise control. The main data for comparison include: the distribution of blade section pressure coefficients, the structure and trajectory of the tip vortex in the flow field, the vorticity intensity map of the flow field cross-section, the noise sound pressure time history at microphones 3 and 9 in the experiment, and the sound pressure peak values and sound pressure levels at microphones 3 and 9.

[0094] Figure 9 The comparison results of the sectional pressure coefficient distributions at the blade spanwise position of 0.955R at azimuth angles of 0°, 90° and 180° simulated by the non-blowing case and the blade surface blowing case are shown. Figure 9 (a) is the comparison diagram of the sectional pressure coefficient distribution at the blade spanwise position of 0.955R at the azimuth angle of 0°. Figure 9 (b) is the comparison diagram of the sectional pressure coefficient distribution at the blade spanwise position of 0.955R at the azimuth angle of 90°. Figure 9 (c) is the comparison diagram of the sectional pressure coefficient distribution at the blade spanwise position of 0.955R at the azimuth angle of 180°. It can be seen that the blowing method provided by the present invention has a good agreement between the calculated value and the experimental value for the non-blowing case; and compared with the non-blowing case, the presence of surface blowing significantly affects the distribution of the surface pressure coefficient, and pressure coefficient oscillations occur near the trailing edge. Blowing on both the upper and lower surfaces does not cause a significant change in the pressure difference between the upper and lower surfaces, that is, the rotor thrust coefficient remains basically unchanged. The comparison of the calculated thrust coefficients in Table 1 will also illustrate this point. Taking the rotor thrust coefficient of 0.00539 of the non-blowing case as a reference (the experimental value is 0.0054), the rotor thrust coefficient corresponding to the case of blowing on both the upper and lower surfaces with a jet velocity of 20% of the tip speed is also 0.00539.

[0095] Table 1 Comparison of thrust coefficient and noise calculation results between non-blowing and blowing cases

[0096]

[0097] Figure 10 The comparative results of the vortex structures and vortex trajectories captured in the rotor flow field for the non-blowing case and the blowing case at an azimuth angle of 90° are presented. Figure 10 (a) is the top-view result diagram of the vortex structures and vortex trajectories captured in the rotor flow field for the non-blowing case. Figure 10 (b) is the side-view result diagram of the vortex structures and vortex trajectories captured in the rotor flow field for the non-blowing case. Figure 10 (c) is the top-view result diagram of the vortex structures and vortex trajectories captured in the rotor flow field for the blowing case. Figure 10 (d) is the side-view result diagram of the vortex structures and vortex trajectories captured in the rotor flow field for the blowing case. The flow separation caused by the presence of the jet leads to vortex shedding. The blowing makes the vortex roll up within the blade disk plane, and a part of it mixes with the tip vortex. Moreover, the blowing on the surface of the rotor blade causes larger-scale vortex roll-up and greater vortex dissipation in the axial direction of the vortex motion on the blade disk plane for the vortex generated by the rotor compared to the non-blowing reference case. Periodically formed and rolled-up vortices that move along the tip vortex trajectory appear. It can be seen that under the action of blowing, the intensity of the tip vortex at the No. 1 interference position does not change, and the tip vortex still approaches the blade, but the intensities at the No. 2 and No. 3 positions change significantly.

[0098] Figure 11 The calculation results of the noise sound pressure time histories at microphones 3 and 9 for the blowing case are presented. Figure 11 (a) is the calculation result of the noise sound pressure time history at microphone 3 for the blowing case. Figure 11 (b) is the calculation result of the noise sound pressure time history at microphone 9 for the blowing case. It can be seen that the calculated values of the present method for the non-blowing case are in good agreement with the experimental values of the sound pressure time history, especially the calculated results of the noise sound pressure peak are quite close to the experimental values. Compared with the non-blowing case, the blowing plays a certain role in weakening the impulsive sound pressure amplitude of the BVI noise, and the sound pressure peaks at both microphones decrease. The calculated values of the sound pressure peak and sound pressure level at the two microphones are given in Table 1. Compared with the non-blowing case, in the case where the upper surface and the lower surface jet simultaneously and the rotor thrust coefficient remains the same, the sound pressure peaks at microphones 3 and 9 decrease by as much as 13.9% and 24.5% respectively, and their sound pressure levels also decrease by 0.3 dB and 1.5 dB. Considering the change in the blade-vortex interaction and the noise reduction effect comprehensively, the method of blowing on the upper surface and the lower surface of the blade proposed in the present invention reduces the blade-vortex interaction noise and keeps the rotor thrust performance unchanged, overcomes the adverse effect that blowing will reduce the rotor thrust performance in previous studies, and enhances the feasibility of blowing control in engineering practice.

[0099] The present invention also provides a blade surface blowing simulation system corresponding to the above method, and the system includes:

[0100] A first acquisition module for acquiring configuration parameters of a rotor to be simulated.

[0101] A grid system construction module for constructing a grid system according to the configuration parameters, the grid system including blade grids and background grids.

[0102] A second acquisition module for acquiring jet velocity and grid motion velocity; the grid motion velocity includes: the motion velocity of the blade grids and the motion velocity of the background grids.

[0103] A jet orifice surface grid velocity calculation module for calculating the jet orifice surface grid velocity according to the jet velocity and the grid motion velocity.

[0104] A blowing simulation module for performing blowing simulation by blowing air simultaneously at the jet orifices on the upper surface and the lower surface of the grid system according to the jet orifice surface grid velocity.

[0105] As an optional implementation manner, the jet orifice surface grid velocity calculation module specifically includes:

[0106] A blade grid jet orifice surface grid velocity calculation unit for calculating the jet orifice surface grid velocity corresponding to the blade grid according to the jet velocity and the motion velocity of the blade grid.

[0107] A background grid jet orifice surface grid velocity calculation unit for calculating the jet orifice surface grid velocity corresponding to the background grid according to the jet velocity and the motion velocity of the background grid.

[0108] As an optional implementation manner, the blowing simulation module specifically includes:

[0109] A blade grid blowing simulation unit for performing blowing simulation by blowing air simultaneously at the jet orifices on the upper surface and the lower surface of the blade grid according to the jet orifice surface grid velocity corresponding to the blade grid.

[0110] A background grid blowing simulation unit for performing blowing simulation by blowing air simultaneously at the jet orifices on the upper surface and the lower surface of the background grid according to the jet orifice surface grid velocity corresponding to the background grid.

[0111] As an optional implementation manner, the blade grid is a blade grid with a three-dimensional C-O type topology, and the background grid is a Cartesian background grid.

[0112] The present invention has the following technical effects:

[0113] 1. The present invention is based on the jet boundary model, the fifth-order WENO-Z format and the high-resolution grid system. The CFD / acoustic analogy simulation method based on the RANS / FW-H equations can accurately simulate the rotor blade-vortex interference flow field and noise as well as the blade surface blowing control.

[0114] 2. The present invention reveals the control mechanism of air blowing on the blade surface through simulation: under the influence of air blowing, the downflow deviates from the airfoil, and the vortex rolled up in the impeller disk surface and the rotor tip vortex are mixed. Compared with the rotor tip vortex flow in the non-blowing benchmark example, the blowing example produces a larger-scale vortex roll-up and greater vortex dissipation in the axial direction of the vortex motion.

[0115] 3. The simultaneous blowing of air on the upper and lower surfaces of the blades proposed in the present invention changes the rotor tip vortex strength and the staggered distance between the blade and the tip vortex under the blade-vortex interference state, reduces the blade-vortex interference noise, and maintains the rotor thrust performance unchanged, overcoming the adverse effect of air blowing on reducing the rotor thrust performance in previous studies, and enhancing the feasibility of air blowing control in engineering practice.

[0116] 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 system 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.

[0117] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A simulation method for blowing air on the surface of a blade, characterized in that, Including: Obtain the configuration parameters of the rotor to be simulated; Construct a grid system according to the configuration parameters, the grid system including blade grids and background grids; Obtain the jet velocity and the grid motion velocity; The grid motion velocity includes: the motion velocity of the blade grids and the motion velocity of the background grids; Calculate the grid velocity on the jet orifice surface according to the jet velocity and the grid motion velocity; Perform blowing simulation by blowing air simultaneously at the jet orifices on the upper surface and the lower surface of the grid system according to the grid velocity on the jet orifice surface; The calculating the grid velocity on the jet orifice surface according to the jet velocity and the grid motion velocity specifically includes: Calculate the grid velocity on the jet orifice surface corresponding to the blade grids according to the jet velocity and the motion velocity of the blade grids; Calculate the grid velocity on the jet orifice surface corresponding to the background grids according to the jet velocity and the motion velocity of the background grids; The performing blowing simulation by blowing air simultaneously at the jet orifices on the upper surface and the lower surface of the grid system according to the grid velocity on the jet orifice surface specifically includes: Perform blowing simulation by blowing air simultaneously at the jet orifices on the upper surface and the lower surface of the blade grids according to the grid velocity on the jet orifice surface corresponding to the blade grids; Perform blowing simulation by blowing air simultaneously at the jet orifices on the upper surface and the lower surface of the background grids according to the grid velocity on the jet orifice surface corresponding to the background grids; According to the formula Calculate the grid velocity on the jet orifice surface. Here, u represents the component of the grid velocity on the jet orifice surface in the x direction, v represents the component of the grid velocity on the jet orifice surface in the y direction, w represents the component of the grid velocity on the jet orifice surface in the z direction, u mesh represents the component of the motion velocity in the x direction, v mesh represents the component of the motion velocity in the y direction, w mesh represents the component of the motion velocity in the z direction. Flag is a control parameter. When Flag is set to 0, the incident jet velocity is not considered, and only the motion velocity is considered, which is the wall boundary condition; when Flag is set to 1, the jet velocity is considered, and the grid velocity on the jet orifice surface is the vector sum of the motion velocity and the jet velocity, which is the jet boundary condition; n x represents the unit normal vector of the coordinate system in the x direction, n y represents the unit normal vector of the coordinate system in the y direction, n y represents the unit normal vector of the coordinate system in the z direction, V jet represents the jet velocity.

2. The simulation method of blowing air on the blade surface according to claim 1, wherein The blade grids are blade grids with a three-dimensional C-O type topology, and the background grids are Cartesian background grids.

3. A blade surface blowing simulation system, characterized in that, Including: A first obtaining module, configured to obtain the configuration parameters of the rotor to be simulated; A grid system construction module, configured to construct a grid system according to the configuration parameters, the grid system including blade grids and background grids; A second obtaining module, configured to obtain the jet velocity and the grid motion velocity; The grid motion velocity includes: the motion velocity of the blade grids and the motion velocity of the background grids; A jet orifice surface grid velocity calculation module, configured to calculate the grid velocity on the jet orifice surface according to the jet velocity and the grid motion velocity; A blowing simulation module, configured to perform blowing simulation by blowing air simultaneously at the jet orifices on the upper surface and the lower surface of the grid system according to the grid velocity on the jet orifice surface; The jet orifice surface grid velocity calculation module specifically includes: A blade grid jet orifice surface grid velocity calculation unit, configured to calculate the grid velocity on the jet orifice surface corresponding to the blade grids according to the jet velocity and the motion velocity of the blade grids; A background grid jet orifice surface grid velocity calculation unit, configured to calculate the grid velocity on the jet orifice surface corresponding to the background grids according to the jet velocity and the motion velocity of the background grids; The blowing simulation module specifically includes: A blade grid blowing simulation unit, configured to perform blowing simulation by blowing air simultaneously at the jet orifices on the upper surface and the lower surface of the blade grids according to the grid velocity on the jet orifice surface corresponding to the blade grids; The background grid blowing simulation unit is used to perform blowing simulation by blowing air simultaneously at the jet ports on the upper surface and the lower surface of the background grid according to the surface grid velocity of the jet ports corresponding to the background grid; According to the formula calculate the grid velocity on the jet orifice surface. Here, u represents the component of the grid velocity on the jet orifice surface in the x direction, v represents the component of the grid velocity on the jet orifice surface in the y direction, w represents the component of the grid velocity on the jet orifice surface in the z direction, u mesh represents the component of the motion velocity in the x direction, v mesh represents the component of the motion velocity in the y direction, w mesh represents the component of the motion velocity in the z direction. Flag is a control parameter. When Flag is set to 0, the incident jet velocity is not considered and only the motion velocity is considered, which is the wall boundary condition; when Flag is set to 1, the jet velocity is considered and the grid velocity on the jet orifice surface is the vector sum of the motion velocity and the jet velocity, which is the jet boundary condition; n x represents the unit normal vector of the coordinate system in the x direction, n y represents the unit normal vector of the coordinate system in the y direction, n y represents the unit normal vector of the coordinate system in the z direction, V jet represents the jet velocity.

4. The blade surface blowing simulation system according to claim 3, characterized in that, The blade grid is a blade grid with a three-dimensional C-O type topology, and the background grid is a Cartesian background grid.

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