CN111898308A - Design scheme for optimizing air nozzle of paint spray gun by using response surface method - Google Patents
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Abstract
The invention discloses a design scheme for optimizing an air nozzle of a paint spray gun by using a response surface method, which comprises the steps of establishing an air nozzle numerical model and experimental verification, selecting characteristic parameters to be optimized of the air nozzle, establishing a test scheme and a response surface model, diagnosing errors and inspecting the significance of the response surface model, analyzing a response surface diagram, establishing a solution optimization model, and analyzing and comparing results before and after optimization. On the basis that the numerical model is verified through experiments, a central composite test of key factors is designed, a response surface regression model and a mathematical optimization model are established, the air nozzle structural parameters and the working condition parameters serve as design variables, the central pressure of a spraying surface serves as a target variable, the structural parameters and the working condition parameters of the nozzle are optimized, and the optimal combination of the nozzle characteristic parameters is obtained. The optimization design of the characteristic parameters of the air nozzle can reduce the central pressure of a spraying surface, improve the atomization flow field of the nozzle and improve the spraying performance; the design and development period of the air nozzle is shortened, and the efficiency is improved.
Description
Technical Field
The invention relates to the technical field of design of air nozzles of paint spray guns, in particular to a design scheme for optimizing the air nozzles of the paint spray guns by using a response surface method.
Background
The air atomization paint spray gun is widely applied to the spraying fields of industrial manufacturing, surface coating, novel special materials and the like with high-quality atomization performance, the air spray nozzle is a core component of the paint spray gun, and structural parameters and working condition parameters of the air spray nozzle directly influence the form and distribution of an atomization flow field between the spray nozzle and a spraying surface, so that the spraying performance and the working efficiency of the spray gun are influenced, and the design and optimization of the air spray nozzle play a crucial role in atomization spraying. The distribution and the control of the gas outlet direction of the shaping air hole to the spraying surface atomization flow field have great influence, the crushing and the atomization degree of the liquid coating can be directly influenced by the size of the annular air hole inlet pressure and the shaping air hole inlet pressure, improper control can cause overlarge pressure or uneven spraying of the spraying surface, the defects of overspray, coating sagging and the like are generated, the function of the auxiliary air hole is to carry out secondary atomization on coating droplets, the surface of the nozzle is kept clean, and the diameter of the liquid outlet hole is selected to be related to the viscosity of the coating. For an atomization flow field of an air nozzle, the spraying effect on a spraying surface has a great relation with the central pressure on the spraying surface, the splashing and the sagging of paint droplets are easily caused by overlarge gas phase pressure, the adhesion force between the paint droplets and the spraying surface is insufficient due to the overlarge gas phase pressure, the fog droplets float, the environment pollution is caused, and the transmission efficiency of a spray gun is reduced.
The atomization flow field of the air nozzle is very complex, and the phenomena of collision, fusion, deposition and the like are also generated in the spraying process of the liquid coating which is deformed and broken into liquid drops, so that the atomization flow field and the spraying performance of the air nozzle are influenced interactively between different structural parameters and working condition parameters of the air nozzle. At present, aiming at the optimization design of an air nozzle of a paint spray gun, the atomization flow field and the spraying performance are improved only when a certain structural parameter or a working condition parameter of the air nozzle is changed, the improvement is made aiming at a certain single variable factor, the atomization spraying performance of the nozzle is difficult to control on the whole, the interaction influence rule of the multi-factor coupling parameters cannot be separated out, the global optimization design of the structure and the working condition of the air nozzle is not considered, the design period is long, and the cost is high.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a design scheme for optimizing the air nozzle of the paint spray gun by using a response surface method, so that the air nozzle obtains the optimal combination of structural parameters and working condition parameters, and the atomization spraying performance of the air nozzle is improved.
In order to achieve the purpose, the invention provides the following technical scheme: a design scheme for optimizing an air nozzle of a paint spray gun by using a response surface method comprises the following steps of establishing an air nozzle numerical model and experimental verification thereof; selecting characteristic parameters to be optimized of the air nozzle; step three, establishing a test scheme and a response surface model; step four, diagnosing errors and detecting significance of the response surface model; analyzing the response surface graph and establishing a solving mathematical optimization model; and sixthly, analyzing and comparing results before and after the air nozzle is optimized.
Further, the air nozzle structure includes that coating goes out liquid hole, annular gas pocket, four auxiliary atomization gas pockets and four moulding gas pockets, and moulding gas pocket is located the nozzle both sides horn mouth, is symmetrical 180 diagonal distributions.
Further, the numerical model in the first step comprises a three-dimensional geometric model and a calculation model, the three-dimensional geometric model is constructed by Solidworks software, a non-structural grid method is adopted for grid division, and local encryption is carried out near the axis of the air nozzle and the spraying surface; the calculation model adopts a readable k-turbulence model, and the transport equations of turbulence kinetic energy k and turbulence dissipation rate are respectively
Wherein the content of the first and second substances,
in the formula: gkFor turbulent kinetic energy terms produced by laminar velocity gradients，GbFor the kinetic energy term of turbulence generated by buoyancy, YMContribution of turbulent pulsating expansion to the global dissipation ratio for compressible flows, G1、G2、G3Is a constant value, σkAnd σThe k equation and the Prandtl constant of the turbulence of the equation, v being the velocity component of the fluid parallel to gravity, mutIs the turbulent viscosity coefficient.
By the design, the atomization flow field between the air nozzle and the spraying surface can be accurately simulated by adopting the Realizable k-turbulence model, and the complicated and changeable gas phase flow under the interaction of the annular air hole, the auxiliary atomization air hole and the shaping air hole spraying gas is simulated and calculated.
Further, the experiment in the first step verifies that the speed measurement experiment table using the hot-wire anemometer comprises an air source system, the hot-wire anemometer and a coordinate support, wherein the air source system comprises an air compressor, a valve, a pressure gauge and a flowmeter, and the hot-wire anemometer comprises a host, a support and a probe; firstly, setting boundary conditions and inlet pressure by using Ansys Fluent software, carrying out simulation calculation on the speed and pressure of an atomizing flow field of an air nozzle, and then comparing the speed and the pressure with the speed of the atomizing flow field measured by an experiment under the same conditions, thereby verifying the accuracy of a numerical model; and if the numerical model is accurate, performing the step two, otherwise, performing the step one again.
By means of the design, the accuracy of the numerical model of the air nozzle is quantitatively verified by comparing the velocity distribution of the atomizing flow field obtained through simulation and experiments, and the numerical model is proved to be used for carrying out subsequent optimization design on the air nozzle.
Further, the characteristic parameters to be optimized selected in the second step comprise air nozzle structure parameters and working condition parameters; one, more or all of the diameter of the coating liquid outlet hole, the diameter of the annular air hole, the diameter of the shaping air hole, the inclined angle of the shaping air hole and the diameter of the auxiliary atomization air hole are selected as structural parameters, and one, more or all of the flow rate of the coating liquid outlet hole, the pressure of the annular air hole inlet, the pressure of the shaping air hole inlet and the pressure of the auxiliary atomization air hole inlet are selected as working condition parameters.
By the design, the multi-factor coupling parameters can be brought into the interaction influence on the spraying performance of the air nozzle, and the optimal design of the structure and the working condition of the air nozzle is carried out globally.
Further, the test scheme in the third step adopts a rotatable center composite design; the response surface model is a second-order response surface regression equation which is established according to the least square theory and takes characteristic parameters of the air nozzle as design variables and the central pressure of the spraying surface as a target variable, and is expressed as
In the formula: pcIs the central pressure of the spraying surface, beta0、βi、βii、βijFor unknown coefficients, xi、xjN is the number of design variables for the air nozzle.
By the design, according to the Weierstress polynomial optimal approximation theorem, the functional relation between the characteristic parameters of the air nozzle and the central pressure of the spraying surface can be approximately fitted by using a second-order regression equation, and the regression model is more accurate.
Further, the reasonable index for diagnosing the error of the response surface model in the fourth step is as follows: the correlation coefficient, the correction correlation coefficient and the prediction correlation coefficient are all close to 1; the signal-to-noise ratio is greater than 4; the difference between the corrected correlation coefficient and the predicted correlation coefficient is less than 0.2; the internal student residual error of the central pressure of the spraying surface follows normal distribution; the predicted value of the response surface of the central pressure of the spraying surface is close to the numerical value; and if the error diagnosis is reasonable, performing the fifth step, otherwise, performing the third step again.
By the design, whether the response surface model can replace numerical calculation to carry out relevant prediction on the central pressure of the spraying surface is judged; and the significance of the influence of each characteristic parameter and the interactive item thereof on the central pressure of the spraying surface is judged through significance test.
Further, the response surface map of the step five comprises a surface map and a contour map; and determining constraint conditions of each characteristic parameter of the air nozzle, establishing a mathematical optimization model by taking the minimum central pressure of a spraying surface as an optimization target, and solving by using a numerical optimization module in Design Expert software based on a satisfaction function method.
By means of the design, through analysis of the curved surface diagram and the contour diagram, the influence rule of interaction among all characteristic parameters of the air nozzle on the central pressure of the spraying surface can be summarized; the minimum central pressure of the spraying surface is taken as an optimization target, and local over-spraying, paint liquid drop splashing and sagging caused by overlarge gas phase pressure can be prevented.
And further, analyzing, comparing and optimizing the central pressure of the atomizing flow field of the air nozzle on the spraying surface before and after the step six, and judging whether the uniform spraying of the spraying surface is facilitated.
By the design, the results before and after optimization are compared to judge whether the local action of the atomization flow field on the spraying surface is reduced or not and whether the spraying performance of the air nozzle is improved or not, so that whether the optimization design of the characteristic parameters of the air nozzle of the paint spray gun is effective or not by using a response surface method or not can be known, and the efficiency is improved.
Compared with the prior art, the invention has the following beneficial effects: according to the invention, by using the optimal design scheme of the response surface method for the characteristic parameters of the air nozzle, not only can the influence rule of interaction among the characteristic parameters of the air nozzle on the central pressure of the spraying surface be analyzed, but also the optimal combination of the characteristic parameters of the nozzle can be obtained, the central pressure of the spraying surface is reduced, the atomization flow field of the air nozzle is improved, and the spraying performance is improved; and greatly shortens the period of designing and researching the air nozzle and improves the efficiency.
Drawings
FIG. 1 is a flow chart of the present invention for optimizing the design of a paint spray gun air nozzle using a response surface method;
FIG. 2(a) is an isometric and semi-sectional view of an air nozzle of the present invention;
FIG. 2(b) is a schematic diagram of the air nozzle numerical model calculation domain of the present invention;
FIG. 3 is a schematic diagram of a hot-wire anemometer speed measurement experiment table;
FIG. 4(a) is a cloud chart of the velocity of the atomizing flow field in the YZ plane of the calculation domain of the air nozzle;
FIG. 4(b) is a cloud of atomizing flow field velocities for the air nozzle calculation domain ZX plane;
FIG. 4(c) is a cloud of atomizing flow field pressures for an air nozzle spray face EFGH;
FIG. 5 is a graph comparing simulated and experimental velocity distributions of an air nozzle atomizing flow field ZX in-plane distance d from a nozzle;
FIG. 6(a) is a residual probability distribution diagram of the center pressure of the spraying surface in the embodiment of the invention;
FIG. 6(b) is a comparison graph of the predicted value and the calculated value of the response surface of the central pressure of the spraying surface in the embodiment of the present invention;
FIG. 7 is a graph of a response curve and a contour plot of the interaction of the inclination of the shaped vent slope and the pressure at the annular vent inlet on the center pressure of the spray surface in an embodiment of the present invention;
FIG. 8 is a graph of a response curve and a contour plot of the interaction of the tilt angle of the shaping vent slope and the shaping vent inlet pressure on the center pressure of the spray surface in an embodiment of the present invention;
FIG. 9 is a graph of the response curve and contour plot of the interaction of annular vent inlet pressure and shaping vent inlet pressure on the center pressure of the spray surface in an embodiment of the present invention.
In the figure: the device comprises a coating liquid outlet hole 1, an annular air hole 2, an auxiliary atomizing air hole 3, a shaping air hole 4, an air source system 5, an air compressor 51, a valve 52, a pressure gauge 53, a flow meter 54, a hot wire anemoscope 6, a host 61, a support 62, a probe 63 and a coordinate support 7.
Detailed Description
The present invention will be described in detail below with reference to the drawings and specific examples, but the embodiments of the present invention are not limited to the scope of the examples.
As shown in FIG. 1, the invention provides a design scheme for optimizing an air nozzle of a paint spray gun by using a response surface method, which comprises the steps of firstly, establishing a numerical model of the air nozzle and experimental verification thereof; selecting characteristic parameters to be optimized of the air nozzle; step three, establishing a test scheme and a response surface model; step four, diagnosing errors and detecting significance of the response surface model; analyzing the response surface graph and establishing a solving mathematical optimization model; and sixthly, analyzing and comparing results before and after the air nozzle is optimized.
As shown in fig. 2(a), the air nozzle structure includes a paint liquid outlet 1, an annular air hole 2, four auxiliary atomization air holes 3 and four shaping air holes 4, the shaping air holes 4 are located on the bell mouths at two sides of the nozzle and are symmetrically distributed at 180 ° diagonal angles, and the initial relevant structural parameters of the air nozzle are as follows: the diameter of a coating liquid outlet hole 1 is 0.8mm, the diameter of an annular air hole 2 is 2.8mm, the diameter of an auxiliary atomization air hole 3 is 0.56mm or 0.7mm, the diameter of a shaping air hole 4 is 1.3mm, and the inclined angle alpha of a shaping air hole inclined plane is 21 degrees. As shown in fig. 2(b), the calculation field of the air nozzle numerical model is a rectangular parallelepiped model having dimensions of 400mm × 200mm × 200mm, and the air nozzle is located at the center of the face ABCD.
Step one, establishing an air nozzle numerical model and experimental verification thereof.
The numerical model in the first step comprises a three-dimensional geometric model and a calculation model, the three-dimensional geometric model is constructed by Solidworks software, a non-structural grid method is adopted for grid division, and local encryption is carried out near the axis of the air nozzle and the spraying surface EFGH; the calculation model adopts a readable k-turbulence model, and the transport equations of turbulence kinetic energy k and turbulence dissipation rate are respectively
Wherein the content of the first and second substances,
in the formula: gkFor the turbulent kinetic energy term produced by the laminar velocity gradient, GbFor the kinetic energy term of turbulence generated by buoyancy, YMContribution of turbulent pulsating expansion to the global dissipation ratio for compressible flows, G1、G2、G3Is a constant value, σkAnd σThe k equation and the Prandtl constant of the turbulence of the equation, v being the velocity component of the fluid parallel to gravity, mutIs the turbulent viscosity coefficient.
As shown in fig. 3, the experimental verification in the first step uses a hot-wire anemometer speed measurement experiment table, which includes an air source system 5, a hot-wire anemometer 6 and a coordinate support 7, wherein the air source system 5 includes an air compressor 51, a valve 52, a pressure gauge 53 and a flow meter 54, and the hot-wire anemometer 6 includes a host 61, a support 62 and a probe 63. A pressure-based solver and a SIMPLE algorithm are adopted in Ansys Fluent software, a first-order windward format is used for turbulent kinetic energy and turbulent kinetic energy dissipation rate, a second-order windward format is used for other variables, and the main phase is air. The boundary conditions of the annular air hole 2, the auxiliary atomizing air hole 3 and the shaping air hole 4 are all pressure inlets, the spraying surface EFGH and the surface of the nozzle are set to be non-slip wall surface boundaries, and other planes ABFE, CDHG, ADHE, BCGF and ABCD of the calculation domain are pressure outlets. Setting initial working condition and annular air hole inlet pressure according to air nozzle spraying work in laboratory1250000Pa, 250000Pa for the inlet pressure of the auxiliary atomization air hole, and P for the inlet pressure of the shaping air hole2The simulated calculation of the cloud image of the atomizing flow field velocity of the YZ plane of the air nozzle calculation domain, the cloud image of the atomizing flow field velocity of the ZX plane of the air nozzle calculation domain and the cloud image of the atomizing flow field pressure of the spraying surface EFGH of the air nozzle are respectively shown in fig. 4(a), (b) and (c), high-speed air flows are sprayed from each air hole and then mutually intersect, spread to the spraying surface EFGH in a flat elliptic cone shape, then flow out along the wall surface to the periphery, finally an elliptic pressure action area is formed on the wall surface, and the central pressure P of the spraying surface iscThe size was 308.27 Pa.
As shown in fig. 5, the velocity distribution comparison diagram at positions d 60mm, 120mm, and 180mm away from the nozzle in the ZX plane of the atomizing flow field measured by simulation and experiment under the same condition is shown.
And step two, selecting characteristic parameters to be optimized of the air nozzle.
The characteristic parameters to be optimized selected in the second step comprise air nozzle structure parameters and working condition parameters; the structural parameter selects the inclined angle alpha of the inclined plane of the shaping air hole, and the working condition parameter selects the inlet pressure P of the annular air hole1Moulding gas hole inlet pressure P2. A, B, C respectively represent the inclination angle alpha of the shaping air hole slope and the pressure P of the annular air hole inlet1Moulding gas hole inlet pressure P2The code of (2) is represented by-1, 0 and 1 respectively for three levels of three factors, and the code and level value of each characteristic parameter of the air nozzle are shown in table 1.
TABLE 1 coding and horizon table of characteristic parameters
And step three, establishing a test scheme and a response surface model.
The test scheme in the third step adopts a rotatable three-factor center composite design, and totally comprises 20 test points, wherein 8 cause analyzing points, 6 asterisk points and 6 central points are used, and the central pressure P of each group of spraying surfaces iscThe results of the calculations are recorded and the resulting test protocol and response values are shown in table 2.
TABLE 2 test protocol and response values
Taking characteristic parameters of the air nozzle as design variables and the central pressure P of a spraying surfacecEstablishing a second-order response surface regression model according to the least square theory for the target variable, wherein the regression equations of the coding factor and the real factor are respectively
Pc＝311.43+68.02A+179.93B-128.34C+0.67AB+28.52AC-106.74BC+16.90A2+11.67B2+101.11C2
Pc＝417.34997-12.41742α+3.80989×10-3P1-6.50250×10-3P2+7.43056×10-7αP1+4.52679×10-5αP2-1.52480×10-8P1P2+0.20865α2+1.16677×10-9P1 2+2.06346×10-8P2 2
Step four, error diagnosis and significance test of the response surface model.
As shown in table 3, the correlation index of the error diagnosis of the response surface model in the fourth step is obtained, the correlation coefficient, the corrected correlation coefficient and the predicted correlation coefficient are all close to 1, the signal-to-noise ratio is greater than 4, and the difference between the corrected correlation coefficient and the predicted correlation coefficient is less than 0.2; as shown in fig. 6(a) and (b), the internal student chemical residual points of the center pressure of the spray surface are distributed on a substantially straight line, and follow a normal distribution, and the predicted value of the response surface of the center pressure of the spray surface approaches the numerical value. The above shows that the response surface model has good correlation and small error, and can replace numerical calculation to calculate the central pressure P of the spraying surfacecAnd (6) performing relevant prediction.
TABLE 3 response surface model error diagnosis correlation index
As shown in Table 4, which is a significance test table of the response surface model, it can be seen that the regression terms A, B and C are very significant (P < 0.01), indicating the inclination angle α of the inclined surface of the shaping air hole and the inlet pressure P of the annular air hole1And shaping air hole inlet pressure P2To the central pressure P of the spraying surfacecAll had significant effects; interaction term BC and squared term C2Is also very significant (P < 0.01), indicating an annular gas orifice inlet pressure P1And the pressure P of the inlet of the shaping air hole2To the central pressure P of the spraying surfacecThe interaction of (a) is very significant. In the experimental design range, p of the whole model is less than 0.0001, so that the response surface model reaches an extremely significant level, the fitting precision is good, and the approximate model is reasonable and effective.
Table 4 significance test of response surface model
And step five, analyzing the response surface graph and establishing a solving mathematical optimization model.
FIG. 7 shows the inclination angle α of the inclined plane of the shaping air hole and the inlet pressure P of the annular air hole in the fifth step1To the central pressure P of the spraying surfacecAnd (4) a response surface map and a contour map of the interaction effect. The inclined angle alpha of the inclined plane of the air hole and the pressure P of the annular air hole along with the shaping1Increase of (2) center pressure P of the sprayed surfacecThe pressure P of the annular air hole is increased along with the gradual increase of the inclined angle alpha of the inclined plane of the shaping air hole1The increasing effect on the central pressure value of the spraying surface is more and more obvious.
FIG. 8 shows the molding gas hole slope inclination angle α and the molding gas hole inlet pressure P2To the central pressure P of the spraying surfacecAnd (4) a response surface map and a contour map of the interaction effect. Shaping air hole inclined plane inclination angle alpha and shaping air hole pressure P2Has obvious interaction, when the inclined angle alpha of the shaping air hole inclined plane is kept unchanged, the pressure P of the shaping air hole is along with the pressure P of the shaping air hole2Is continuously increased, and the central pressure P of the spraying surfacecIt decreases significantly and then increases slightly, especially when the shaping vent slope angle α is at a lower level. When the pressure P of the shaping air hole2At a certain time, obviously the central pressure P of the spraying surfacecThe inclination angle alpha of the inclined plane of the shaping air hole is increased, and the pressure P of the shaping air hole can be seen from a contour diagram2At higher levels, this effect is stronger.
FIG. 9 shows the annular vent inlet pressure P1And the pressure P of the inlet of the shaping air hole2To the central pressure P of the spraying surfacecAnd (4) a response surface map and a contour map of the interaction effect. Annular vent pressure P1And molding air hole pressure P2The interaction between the two is very obvious, and the central pressure P of the spraying surface is changedcThe influence trend of (c). When the annular air hole pressure P1At a lower level, following the shaping of the pressure P of the air hole2Increase inCenter pressure P of the sprayed surfacecWill decrease first and then increase; when the annular air hole pressure P is reached1At a higher level, the shaping vent pressure P2The increase of the pressure will cause the center pressure P of the spraying surfacecThe negative correlation change is presented, and the local acting force of the gas phase flow field of the annular air hole on the spraying surface can be greatly relieved. When the pressure P of the shaping air hole2Held at a constant, apparently following annular vent pressure P1Increase of (2) center pressure P of the sprayed surfacecIt will increase with the pressure of the shaping air hole P, and the contour diagram shows that the phenomenon is in the shaping air hole pressure P2Particularly at lower levels.
In order to prevent the influence of local over-spraying, paint liquid drop splashing and sagging caused by overlarge gas phase pressure of an atomizing flow field of an air nozzle on the spraying performance, the minimum central pressure of a spraying surface is taken as an optimization target, the constraint conditions of all characteristic parameters are determined, and a mathematical optimization model is established as
find x＝[α,P1,P2]T
min Pc(x)
A numerical optimization module in Design Expert software is used, solving is carried out based on the satisfaction function method principle to obtain three groups of optimal solution combinations and response surface predicted values thereof shown in the table 5, and the three groups of optimal solution combinations and the response surface predicted values are respectively compared with values obtained through numerical calculation. The relative error between the predicted value of the central pressure of the spraying surface obtained by the response surface model and the value obtained by numerical calculation is within 7 percent, and the established response surface regression model is further shown to be accurate and can approximately replace numerical calculation for prediction.
TABLE 5 comparison of predicted and calculated values under optimal parameter combinations
And sixthly, analyzing and comparing results before and after the air nozzle is optimized.
Considering the complexity of the air nozzle structure and the controllability of machining and working condition parameter adjustment, on the basis of the three groups of optimization schemes listed in table 5, the final optimization result of determining the nozzle structure parameters and the working condition parameters is that the inclination angle alpha of the inclined plane of the shaping air hole is 25 degrees and the pressure P of the inlet of the annular air hole is 25 degrees1145000Pa, shaping air hole inlet pressure P2186000Pa, the central pressure P of the spraying surface under the optimization scheme is calculated by a numerical modelcIt was 130.69 Pa. Characteristic parameters before and after optimization of air nozzle and corresponding central pressure P of spraying surfacecAs shown in table 6, it can be seen that the pressure ratio of the air nozzle optimized by using the response surface method to the center action of the spray surface is reduced by 57.6% before the optimization, the local action of the atomization flow field to the spray surface is effectively reduced, and the uniform spraying of the spray surface is facilitated.
TABLE 6 characteristic parameters before and after optimization of the air nozzle and center pressure of the sprayed surface
The above embodiments are merely specific examples for further details of the purpose, technical steps and advantages of the present invention using a response surface approach to optimize a paint spray gun air nozzle design, and the present invention is not limited thereto. Any modification, equivalent replacement, or improvement made within the scope of the present disclosure is included in the protection scope of the present disclosure.
Claims (9)
1. A design for optimizing a paint spray gun air nozzle using a response surface method, comprising the steps of:
establishing an air nozzle numerical model and experimental verification thereof;
selecting characteristic parameters to be optimized of the air nozzle;
step three, establishing a test scheme and a response surface model;
step four, diagnosing errors and detecting significance of the response surface model;
analyzing the response surface graph and establishing a solving mathematical optimization model;
and sixthly, analyzing and comparing results before and after the air nozzle is optimized.
2. The design according to claim 1 wherein said air nozzle structure comprises a paint outlet, an annular air hole, four auxiliary atomizing air holes and four shaping air holes, said shaping air holes being located on the bell mouths of the nozzle at opposite sides and being symmetrically distributed at 180 ° diagonal.
3. The design solution according to claim 1 for optimizing an air nozzle of a paint spray gun by using a response surface method, wherein the numerical model in the first step comprises a three-dimensional geometric model and a calculation model, the three-dimensional geometric model is constructed by using solid works software, a non-structural grid method is adopted for grid division, and local encryption is performed near the axis of the air nozzle and a spray surface; the calculation model adopts a readable k-turbulence model, and the transport equations of turbulence kinetic energy k and turbulence dissipation rate are respectively
Wherein the content of the first and second substances,
in the formula: gkFor the turbulent kinetic energy term produced by the laminar velocity gradient, GbFor the kinetic energy term of turbulence generated by buoyancy, YMContribution of turbulent pulsating expansion to the global dissipation ratio for compressible flows, G1、G2、G3Is a constant value, σkAnd σThe k equation and the Prandtl constant of the turbulence of the equation, v being the velocity component of the fluid parallel to gravity, mutIs the turbulent viscosity coefficient.
4. The design scheme as claimed in claim 1, wherein the experiment in the first step verifies that the speed measurement experiment table using the hot wire anemometer comprises an air source system, the hot wire anemometer and a coordinate support, wherein the air source system comprises an air compressor, a valve, a pressure gauge and a flow meter, and the hot wire anemometer comprises a host, a support and a probe; firstly, setting boundary conditions and inlet pressure by using Ansys Fluent software, carrying out simulation calculation on the speed and pressure of an atomizing flow field of an air nozzle, and then comparing the speed and the pressure with the speed of the atomizing flow field measured by an experiment under the same conditions, thereby verifying the accuracy of a numerical model; and if the numerical model is accurate, performing the step two, otherwise, performing the step one again.
5. The design scheme according to claim 1 wherein the characteristic parameters selected in step two to be optimized include structural parameters and operating parameters of the air nozzle; one, more or all of the diameter of the coating liquid outlet hole, the diameter of the annular air hole, the diameter of the shaping air hole, the inclined angle of the shaping air hole and the diameter of the auxiliary atomization air hole are selected as structural parameters, and one, more or all of the flow rate of the coating liquid outlet hole, the pressure of the annular air hole inlet, the pressure of the shaping air hole inlet and the pressure of the auxiliary atomization air hole inlet are selected as working condition parameters.
6. The design of claim 1 for optimizing air jets of paint spray guns using the response surface method, wherein the test in step three is a rotatable center compound design; the response surface model is a second-order response surface regression equation which is established according to the least square theory and takes characteristic parameters of the air nozzle as design variables and the central pressure of the spraying surface as a target variable, and is expressed as
In the formula: pcIs the central pressure of the spraying surface, beta0、βi、βii、βijFor unknown coefficients, xi、xjN is the number of design variables for the air nozzle.
7. The design scheme as claimed in claim 1, wherein the index of reasonable error diagnosis of the response surface model in the fourth step is as follows: the correlation coefficient, the correction correlation coefficient and the prediction correlation coefficient are all close to 1; the signal-to-noise ratio is greater than 4; the difference between the corrected correlation coefficient and the predicted correlation coefficient is less than 0.2; the internal student residual error of the central pressure of the spraying surface follows normal distribution; the predicted value of the response surface of the central pressure of the spraying surface is close to the numerical value; and if the error diagnosis is reasonable, performing the fifth step, otherwise, performing the third step again.
8. The design of claim 1 wherein said response surface map of step five comprises a curved surface map and a contour map; and determining constraint conditions of each characteristic parameter of the air nozzle, establishing a mathematical optimization model by taking the minimum central pressure of a spraying surface as an optimization target, and solving by using a numerical optimization module in Design Expert software based on a satisfaction function method.
9. The design scheme as claimed in claim 1 wherein, in step six, the central pressure of the atomized flow field of the air nozzle acting on the spray surface before and after optimization is analyzed and compared to determine whether uniform spraying of the spray surface is facilitated.
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