A method for predicting the overall hydraulic performance of a sink-type dishwasher

Abstract

The present invention discloses a method for predicting the overall hydraulic performance of a sink-type dishwasher. Under the condition of a stationary volute, unsteady numerical calculation is carried out on an open pump to obtain the external characteristic curve; the external characteristic curve of the open pump is fitted to obtain its rotational speed adaptation coefficient A d and the axial velocity coefficient B d , establish the mapping relationship between the composite superposition virtual impeller and the compound impeller, realize the passive rotation of the volute spray arm based on the GMO model and the virtual impeller, and obtain the passive rotational speed of the volute and the nozzle flow rate; set the nozzle mass source with the nozzle flow rate and the passive rotational speed of the volute spray arm as boundary conditions, and perform non-submerged rotating jet calculation of multiple nozzles in combination based on the VOF method to realize the simulation of the overall performance of the dishwasher. The present invention subdivides and simplifies the complex multi-physical fields of the dishwasher, greatly reduces the computing resources, and at the same time solves the problems such as the easy divergence of the free surface in the dishwasher and the difficulty in predicting the passive rotational speed of the volute, and realizes the prediction of the overall hydraulic performance of the dishwasher.

Description

Technical Field

[0001] The present invention relates to a method for simulating and predicting the internal hydraulic cleaning mechanism of a dishwasher, in particular to a method for predicting the hydraulic performance of a dishwasher based on a multi-physical field coupling simulation strategy, which solves the problems that the turbulence model is difficult to accurately describe, the residual curve is not easy to converge, the passive rotation speed of the volute makes the dynamic mesh prone to negative angles, and the free surface causes mass non-conservation when directly simulating the internal turbulence mechanism of the dishwasher, resulting in ineffective control of the calculation process and excessive demand for computing resources. Technical Background

[0002] As a household kitchen appliance, the dishwasher has successfully liberated people's hands from the repetitive and boring dishwashing work.

[0003] In recent years, Fotile has developed a sink-type dishwasher, which uses a new type of dishwasher pump, that is, a double-tongue volute spray arm. The volute in the working state will rotate passively, thereby inducing a rotating jet. The passive rotation involves problems such as gas-liquid two-phase flow, free surface flow, six-degree-of-freedom motion, and fluid-structure interaction; the rotating jet belongs to the category of non-submerged jets and also involves problems such as free surface and gas-liquid two-phase flow. It can be seen that the passive rotation of the volute is an extremely complex multi-physical field problem. It is still difficult to truly simulate it using existing simulation technologies, mainly manifested in that the turbulence model is difficult to accurately describe, consuming huge simulation computing resources, the passive rotation speed of the volute makes the dynamic mesh prone to negative angles, and the free surface causes mass non-conservation and other problems, making the calculation not easy to converge and control. Therefore, creating a method for simulating and predicting the real machine of the sink-type dishwasher has become an important problem to be solved urgently for the sink-type dishwasher.

[0004] After retrieval, there is no relevant report on the method for simulating and predicting the real machine of the sink-type dishwasher based on the multi-physical field coupling strategy. Summary of the Invention

[0005] Aiming at the problems existing in the existing simulation technologies, the purpose of the present invention is to overcome the complex simulation problems of multiple physical fields brought about by the passive rotation of the volute inside the dishwasher, and provide a step-by-step simulation and prediction method for the real machine of the dishwasher, which can solve the problems that the turbulence model is difficult to accurately describe the flow field and the calculation is extremely difficult to converge, save computing resources, and the simulation results are closer to the real situation.

[0006] To solve the above technical problems, the specific technical solutions adopted by the present invention are as follows:

[0007] A method for predicting the overall hydraulic performance of a sink-type dishwasher, comprising the following steps:

[0008] Step 1: Numerically simulate the compound impeller and double - tongue volute spray arm in the dishwasher to obtain the flow - head characteristic curve of the open - type water pump under the condition of a stationary volute;

[0009] Step 2: Obtain the full - open flow rate Q0 from the flow - head characteristic curve, and obtain the rotational speed adaptation coefficient A d and the axial velocity coefficient B d , and based on the GMO - TruVOF method, conduct an unsteady simulation of the passive rotation of the volute to obtain the rotational speed of the passive rotation of the volute and the flow rate at each nozzle outlet;

[0010] Step 3: Taking the passive rotational speed of the volute and the flow rate at each nozzle outlet as the initial conditions, conduct a non - submerged rotational unsteady calculation of the nozzle based on the FAVOR - TruVOF method to obtain flow parameters such as the hydraulic cleaning pressure of the dishwasher, and estimate the hydraulic cleaning ability of the dishwasher.

[0011] The specific process of Step 1 includes the following:

[0012] Process 1.1: Based on the compound impeller and volute spray arm model, construct the water body of the open - type water pump, divide the grid using ICEM software, and perform unsteady simulation calculations of the open - type water pump using Fluent software;

[0013] Process 1.2: Numerically simulate and predict the performance curve of the open - type pump based on the RANS method. Under the condition of a stationary volute, calculate the head at at least 5 groups of flow conditions respectively, and draw the flow - head curve;

[0014] The specific process of Step 2 includes the following:

[0015] Process 2.1: Use the flow - head curve drawn in Process 1.2 to obtain the full - open flow rate Q0, and obtain the rotational speed adaptation coefficient A d and the axial velocity coefficient B d , construct a new type of compound virtual impeller model in the FLOW - 3D software, and establish a mapping relationship between the parameters of the virtual impeller and the compound impeller;

[0016] Process 2.2: Construct the near - field calculation domain of the nozzle outlet, conduct Cartesian grid division on the near - field of the virtual impeller, volute spray arm, and nozzle jet domain based on the FAVOR technology, select an appropriate grid resolution to ensure that the calculation domain can be effectively analyzed;

[0017] Process 2.3: Based on the virtual impeller and the GMO - TruVOF method, establish the fluid - structure interaction and free - surface calculation of the open - type water pump, realize the simulation calculation of the passive rotation of the volute, and monitor the passive rotational speed of the volute and the flow rate at each nozzle outlet;

[0018] The specific process of Step 3 includes the following:

[0019] Process 3.1: Construct a gas-liquid two-phase non-submerged jet calculation domain with a free surface in the dishwasher sink, and set the nozzle mass source in the calculation domain.

[0020] Process 3.2: Use the outlet flow rate of each nozzle and the passive rotational speed of the volute obtained in Process 2.3 as the boundary conditions of the nozzle mass source, and calculate the complex non-submerged rotating jet flow field of the multi-nozzle combination based on the FAVOR-TruVOF method.

[0021] Process 3.3: Post-process the calculation results of the non-submerged jet, including the distribution laws of flow parameters such as jet impact pressure and vorticity, and evaluate the hydraulic performance of the whole dishwasher.

[0022] In Process 1.3, the RANS method is used to simulate the external characteristics of the open pump. To reduce the simulation error, the small flow rate conditions are not simulated, and at least 5 sets of data on the head and flow rate should be obtained and linearly approximated. The linear approximation fitting is characterized by fitting the head-flow rate curve of the pump to obtain the full-open flow rate Q0, and using Q0 and the parameter relationship between the original impeller and the virtual impeller to solve the rotational speed adaptation coefficient A d and the axial velocity coefficient B d . The expression of the fitted straight line is as follows:

[0023] h = aQ + Q0

[0024] In the formula:

[0025] h represents the head of the pump, m;

[0026] a represents the slope of the straight line;

[0027] Q represents the flow rate, l / min;

[0028] Q0 represents the abscissa intercept of the fitted straight line and is also the full-open flow rate of the pump.

[0029] The following geometric relationships exist between the original impeller and the virtual impeller:

[0030] H y1 = Lcosβ L

[0031] H y2 = H + b2 - 0.3D

[0032] D y1 = D

[0033] D y2 = D2

[0034] D y3 = d h

[0035] In the formula, the left side of the equation represents the geometric parameters of two virtual impellers, and the right side represents several geometric parameters of the original impeller.

[0036] H y1 is the height of virtual impeller I, in m;

[0037] D y1 is the outer diameter of virtual impeller I, in m;

[0038] H y1 is the height of virtual impeller II, in m;

[0039] D y2 is the outer diameter of virtual impeller II, in m;

[0040] D y2 is the hub diameter of the virtual impeller, in m;

[0041] L is the chord length of the airfoil of the original impeller, in m;

[0042] β L is the setting angle of the airfoil of the original impeller, in °;

[0043] H is the height of the rear shroud of the original impeller, in m;

[0044] b2 is the outlet width of the original impeller, in m;

[0045] D is the minimum outer diameter of the original impeller, in m;

[0046] D2 is the maximum outer diameter of the original impeller, in m;

[0047] d h is the hub diameter of the original impeller, in m.

[0048] According to the full-open flow rate Q0 and the parameter relationship between the virtual impeller and the compound impeller, the new rotational speed adaptation coefficient A d and the axial velocity coefficient B d of the open-type water pump can be obtained as follows:

[0049]

[0050]

[0051] In the formula, where C2 = ψπ 2 / 3600g, where ψ = 0.67 - 0.75.

[0052] In process 2.1, the construction of the compound superposition virtual impeller model is achieved by innovating the rotational speed adaptation coefficient A d and the axial velocity coefficient B d, and in combination with the parameter mapping relationship between the compound impeller and the virtual impeller, a virtual impeller assembly is constructed, which is two cylinders stacked on top of each other, respectively replacing the forward-curved axial flow cascade and the centrifugal radial blades of the impeller. The outer diameter and height of the cylinder can describe the area swept by the blades. The size of the inner diameter is set and it is defined that the fluid in the inner diameter area flows out of the cylinder with a certain vortex and axial velocity. The rotation axis of the cylinder is set by the two-point method.

[0053] In Process 2.2, the construction of the near field of the non-submerged jet domain is the selection of the non-submerged nozzle jet height. The jet height needs to ensure that the water body flows out of the nozzle without affecting the monitoring of the nozzle flow rate, and at the same time, it needs to meet the requirement that there is no influence or the influence is negligible on the setting of the nozzle mass source in Step 3. It is recommended that the height of the near field of the jet domain is 1 to 2 times the nozzle diameter of the highest point at the top of the nozzle orifice.

[0054] In Process 3.1, the setting of the mass source is to define the inflow source within the computational domain, including the setting of the position, direction, geometry, and flow velocity of the inflow source, and the distance between the mass source and the nozzle outlet is 1.5 times the nozzle diameter. In particular, the flow velocity is set as a function of time, and the data is kept consistent with the flow velocities of each nozzle obtained in Process 2.3.

[0055] The beneficial effects of the present invention are as follows: By applying the multi-physical field step-by-step coupling simulation strategy to the simulation of the real dishwasher, the present invention saves simulation computing resources, and its simulation results are closer to the actual operation of the dishwasher, and can avoid problems such as the passive rotation speed of the volute causing the dynamic grid to easily become a negative angle and the free surface causing mass non-conservation in direct simulation. In the present invention, when performing the external characteristic numerical simulation under different flow rate conditions under the static condition of the open-type water pump model, the simulation of the non-submerged jet with a free surface involved in the volute-type spray arm nozzle is avoided; the construction of the virtual impeller can comprehensively and three-dimensionally simulate the flow characteristics of the impeller on the basis of simplifying the impeller model, and at the same time reduce the number of Cartesian orthogonal grids; the setting of the jet mass source can simplify the six-degree-of-freedom physical field of simulating the non-submerged jet of the volute-type spray arm. Taking the open-type water pump model of the dishwasher as the research object, adopting a new step-by-step coupling simulation strategy and setting the jet mass source, the present invention can simplify the complex model, subdivide the complex superimposed physical fields, and transfer the simulation data and results of the previous step to the next step. Compared with direct simulation, the calculation amount is greatly reduced and the calculation is easy to converge, improving the accuracy and fidelity of the prediction of the hydraulic performance of the dishwasher. Description of the Drawings

[0056] Figure 1 is the flow chart for dishwasher simulation prediction;

[0057] Figure 2 is the open-type water pump model of the dishwasher and the water body computational domain;

[0058] Figure 3For the external characteristic curve prediction (solid line) of an open pump and its fitting approximation (dashed line);

[0059] Figure 4 For the virtual impeller geometric model;

[0060] Figure 5 For the radial blade structure diagram of the compound impeller;

[0061] Figure 6 For the plane development diagram of the forward-curved axial flow cascade of the compound impeller;

[0062] Figure 7 For the Cartesian coordinate division diagram of the open pump;

[0063] Figure 8 For the diagram of the variation law of the rotational speed of the passive rotation of the volute;

[0064] Figure 9 For the variation law of the fluid velocity at the monitoring points at the outlets of the nozzles;

[0065] Figure 10 For the layout of the mass source on the volute;

[0066] Figure 11 For the variation law of the average water pressure on the top surface of the tank with time at different times. Specific implementation mode

[0067] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0068] (1) Predict the hydraulic performance of the dishwasher under the multi-physical field coupling simulation strategy using the geometric model of the open pump of the dishwasher. The entire prediction process is as Figure 1 shown.

[0069] (2) The multi-physical field problems of the dishwasher mainly focus on the volute spray arm. In order to obtain the head of the dishwasher pump under different flow conditions on the premise that the calculation results do not diverge, simulate the static state of the volute water body. The schematic diagram of the structure of the open pump model and the water body calculation domain are as Figure 2 shown.

[0070] (3) Use ICEM software for mesh generation. The mesh adopts a hexahedral structured mesh. The water body is divided into 4 calculation regions, namely the inlet flow channel, the guide circulation channel, the impeller flow channel and the volute flow channel, and a boundary layer is added to the wall surface for local refinement.

[0071] (4) The external characteristic simulation calculation is carried out using Fluent software, and the k-ω model is adopted for steady-state calculation of the turbulence model; the flow inlet boundary condition is used at the inlet, the inlet working condition flow rate is set, the pressure outlet boundary condition is used at the outlet, and it is set to the ambient atmospheric pressure, and the no-slip boundary condition is used for the wall surface; the rotational speed of the impeller domain and the guide ring water domain is n, and the other components are all set as stationary domains; the SIMPLE algorithm is used for the calculation, and the second-order upwind difference format is adopted during the discretization process.

[0072] (5) The performance curve predicted based on the RANS numerical simulation is as Figure 3 shown by the solid line. Since the simulation error is relatively large under the extreme working conditions, a linear fitting is performed based on the minimum 0.5Q d working condition, and the fitting result is as Figure 4 shown by the dashed line. The approximate equation of the flow rate-head curve can be obtained through the linear fitting curve as

[0073] h = aQ + Q0 (Equation 1)

[0074] where a is the slope of the fitting straight line, Q0 is the horizontal axis intercept of the fitting straight line, and also the full-open flow rate of the pump.

[0075] The maximum head and the full-open flow rate can be respectively expressed as

[0076]

[0077]

[0078] where Δh represents the maximum head, L0 is the total height of the impeller, g is the acceleration due to gravity, Q0 is the full-open flow rate, R * is the outer radius of the impeller, r represents the minimum radius of the impeller, and n represents the rotational speed of the impeller.

[0079] (6) The virtual impeller geometry is as Figure 4 shown. The inner diameters of the two hollow cylinders are the same, both are D y3 which is the hub diameter, D y2 is the impeller diameter, D y1 is the minimum diameter of the impeller, H y1 is the height of impeller I, H y2 is the height of impeller II, and there is the following relationship for the impeller height:

[0080] H y1 + H y2 = L0 (Equation 4)

[0081] (7) Figure 5 Shown is the structural diagram of the centrifugal radial impeller of the compound impeller. The main parameters are: D is the impeller inlet diameter, D2 is the impeller outlet diameter, b2 is the impeller outlet width, d his the impeller hub diameter, H is the height of the impeller rear cover, and δ is the blade thickness.

[0082] (8) Figure 6 The figure shows the planar development of the forward-curved axial flow blade cascade of the composite impeller. Its main geometric parameters are: L is the chord length of the airfoil; d h is the impeller hub diameter, β L is the blade chord placement angle, z is the number of blades, t is the pitch (t=2πR / z), R is the radius of the cylindrical laminar surface, and Δα is the angle of attack, that is, the angle between the infinitely far incoming flow direction and the chord.

[0083] (9) Figure 5 The radial blades shown and Figure 6 The forward curved axial flow blade cascade shown constitutes the original compound impeller. The mapping relationship between some parameters of the compound impeller and the parameters of the virtual impeller is as follows:

[0084] H y1 =Lcosβ L (Formula 4)

[0085] H y2 =H+b2-0.3D (Formula 5)

[0086] D y1 =D (Formula 6)

[0087] D y2 =D2 (Formula 7)

[0088] D y3 =d h (Formula 8)

[0089] (10) According to the mapping relationship between the composite impeller model and the virtual impeller geometric parameters, combined with the full-open flow rate Q0 obtained by fitting the head flow curve of the open pump, the speed adaptation coefficient A can be obtained by combining (Equation 2) to (Equation 8): d and axial velocity coefficient B d Regarding the relationship between the full-open flow rate Q0 and the compound impeller parameters:

[0090]

[0091] The axial velocity coefficient is:

[0092]

[0093] In the formula, in C2=ψπ 2 / 3600g, where ψ=0.67~0.75.

[0094] (11) According to the parameter mapping relationships between the original impeller and the virtual impeller in (Equation 4) - (Equation 8), input the specific values of the open - type water pump compound impeller parameters and the rotational speed adaptation coefficient A d and the axial velocity coefficient B d into the setting interface of the virtual impeller in FLOW - 3D to construct the virtual impeller model and the volute - type spray arm housing;

[0095] (12) Based on the FAVOR technology grid - division principle, use FLOW - 3D to perform Cartesian grid division on the real - machine model. As Figure 7 shown, the ratio of the distance between the top surface of the jet near - field calculation domain and the nozzle to the nozzle diameter is about 1 - 2. Without tracking the jet flow fields of multiple nozzles, it can simultaneously monitor the outlet flow velocities of each required nozzle and the passive rotational speed of the volute. Set the grid resolution, whose value shall not be greater than 1 / 20 of the smallest jet hole, set the calculation time and the minimum time step size, and check the required hydraulic calculation data;

[0096] (13) Check the GMO coupling motion option in the Moving and Simple Deforming Objects model on the physics interface of FLOW - 3D; insert a baffle near the nozzle outlet, that is, set the monitoring surfaces for the outlet flow velocities of each nozzle of the real - machine volute spray arm; use the TruVOF method to simulate the passive rotation of the volute and monitor the variation laws of the volute rotational speed and the outlet flow velocities of each nozzle over time, as Figure 8 and Figure 9 shown;

[0097] (14) Use Creo software to construct the dishwasher sink, especially the construction of the top surface of the tank body, and embed the volute spray arm model into the sink model;

[0098] (15) Repeat the work in (12) in the FLOW - 3D simulation software, set the real - machine jet inflow source, and ensure that the shape of the mass source is consistent with the nozzle outlet shape. To solve the complex problem of determining the mass - source direction, horizontally embed the mass source above each nozzle, and the distance between the mass source and the nozzle outlet is 1.5 times the nozzle diameter, as Figure 10 shown, and correspondingly input the outlet flow velocities of each nozzle monitored in step (13);

[0099] (16) Import the data monitored in step (13) into the mass source and use the TruVOF method to simulate the nozzle jet under the passive rotation of the volute;

[0100] (17) Post - process the simulation results of the non - submerged rotating jet. The post - processing includes the variation law of the average water pressure on the top surface of the tank body over time, and the formula forms for water - pressure calculation are as in Equation (11) and Equation (12);

[0101]

[0102]

[0103] where A is the area of the force-bearing surface, m 2 ; t is time, s; is the average pressure on the force-bearing surface per unit time, N; is the average pressure on the plate at different times, N.

[0104] (18) The predicted effect of the final dishwasher cleaning ability is as Figure 11 shown. By observing the variation law of the force on the top plate with time, the maximum impact force and average impact force are estimated, etc.

Claims

1. A method for predicting the overall hydraulic performance of a sink-type dishwasher, characterized in that, It includes the following steps: Step 1, perform numerical simulation calculations on the composite impeller and double-separated tongue volute spray arm in the dishwasher to obtain the flow head characteristic curve of the open pump under the condition of a stationary volute; Step 2: Obtain the full-open flow rate Q0 from the flow head characteristic curve and acquire the rotational speed adaptation coefficient A d and the axial velocity coefficient B d , perform an unsteady simulation on the passive rotation of the volute based on the GMO-TruVOF method to obtain the rotational speed of the passive rotation of the volute and the flow rate at the outlet of each nozzle; Step 3, taking the passive rotation speed of the volute and the flow rate at each nozzle outlet as the initial conditions, perform non-submerged rotational unsteady calculations on the nozzles based on the FAVOR-TruVOF method to obtain the flow parameters of the hydraulic cleaning pressure of the dishwasher and estimate the hydraulic cleaning capacity of the dishwasher.

2. The method for predicting the overall hydraulic performance of a sink-type dishwasher according to claim 1, wherein: Performing numerical simulation calculations on the composite impeller and double-separated tongue volute spray arm in the dishwasher to obtain the flow head characteristic curve of the open pump under the condition of a stationary volute includes the following processes: Process 1.1, based on the composite impeller and volute spray arm model, construct the water body of the open pump, divide the grid using ICEM software, and perform unsteady simulation calculations on the open pump using Fluent software; Process 1.2, numerically simulate and predict the performance curve of the open pump based on the RANS method. Under the condition of a stationary volute, calculate the head at least five groups of flow conditions respectively, and draw the flow head curve.

3. The method for predicting the overall hydraulic performance of the sink-type dishwasher according to claim 2, wherein: Obtain the full-open flow rate Q0 from the flow head characteristic curve and acquire the rotational speed adaptation coefficient A d and the axial velocity coefficient B d , and conduct unsteady simulation of the passive rotation of the volute based on the GMO-TruVOF method to obtain the rotational speed of the passive rotation of the volute and the flow rates at the outlets of each nozzle, including the following processes: Process 2.1: Obtain the full-open flow rate Q0 by using the flow-head curve plotted in Process 1.2, and obtain the rotational speed adaptation coefficient A applicable to the open-type water pump d and the axial velocity coefficient B d , construct a composite virtual impeller model in the FLOW-3D software, and simultaneously establish the mapping relationship between the parameters of the virtual impeller and the composite impeller Process 2.2, construct the near-field calculation domain of the nozzle outlet, perform Cartesian grid division on the virtual impeller, volute spray arm, and the near field of the nozzle jet domain based on the FAVOR technology, and select an appropriate grid resolution to ensure that the calculation domain can be effectively analyzed; Process 2.3, establish the fluid-structure interaction and free surface calculation of the open pump based on the virtual impeller and GMO-TruVOF method to realize the simulation calculation of the passive rotation of the volute, and monitor the passive rotation speed of the volute and the flow rate at each nozzle outlet.

4. The method for predicting the overall hydraulic performance of the sink-type dishwasher according to claim 3, wherein: Taking the passive rotation speed of the volute and the flow rate at each nozzle outlet as the initial conditions, perform non-submerged rotational unsteady calculations on the nozzles based on the FAVOR-TruVOF method to obtain the flow parameters of the hydraulic cleaning pressure of the dishwasher and estimate the hydraulic cleaning capacity of the dishwasher, including the following processes: Process 3.1, construct the gas-liquid two-phase non-submerged jet calculation domain with a free surface in the dishwasher sink, and set the nozzle mass source in the calculation domain; Process 3.2, take the flow rate at each nozzle outlet and the passive rotation speed of the volute obtained in Process 2.3 as the boundary conditions of the nozzle mass source, and calculate the complex non-submerged rotating jet flow field of the multi-nozzle combination based on the FAVOR-TruVOF method; Process 3.3, post-process the calculation results of the non-submerged jet, including the distribution laws of the jet impact pressure and vorticity flow parameters, and evaluate the hydraulic performance of the whole dishwasher.

5. The method for predicting the overall hydraulic performance of a sink-type dishwasher according to claim 2, wherein: In Process 1.2, the head under five groups of flow conditions does not include the condition where the flow rate is less than 0.2Q d For the five groups of data, a linear approximation fit is performed.

6. The method for predicting the overall hydraulic performance of a sink-type dishwasher according to claim 5, wherein: The linear approximation fitting includes obtaining the full-open flow rate Q0 by fitting the head-flow curve of the pump, and obtaining the rotational speed adaptation coefficient A suitable for the open-type water pump by using Q0 and the parameter relationship between the original impeller and the virtual impeller d and the axial velocity coefficient B d ; The expression of the fitted straight line is as follows: h = aQ + Q0; In the formula: h represents the head of the pump, m; a represents the slope of the straight line; Q represents the flow rate, l / min; Q0 represents the abscissa intercept of the fitted straight line and is also the full-open flow rate of the pump; The mapping relationship between the parameters of the composite impeller and the virtual impeller is: H y1 = L cos β L ; H y2 = H + b2 - 0.3D; D y1 = D; D y2 = D2; D y3 = d h ; In the formula, the left side of the equation is the geometric parameter of the composite superposed virtual impeller, and the right side of the equation is the geometric parameter of the composite impeller; H y1 is the height of the virtual impeller I, m; D y1 is the outer diameter of the virtual impeller I, in m; H y2 is the height of the virtual impeller II, m; D y2 is the outer diameter of the virtual impeller II, m; D y3 is the hub diameter of the virtual impeller, m; L is the chord length of the airfoil of the original impeller, m; β L is the installation angle of the original impeller airfoil, °; H is the height of the rear cover plate of the original impeller, m; b2 is the outlet width of the original impeller, m; D is the minimum outer diameter of the original impeller, m; D2 is the maximum outer diameter of the original impeller, m; d h is the hub diameter of the original impeller, m; According to the parameter relationship between the full-open flow rate Q0 and the virtual impeller and the compound impeller, the open-type water pump speed adaptation coefficient A d and the axial velocity coefficient B d are as follows: In the formula, where C2 = ψπ 2 / 3600g, where ψ = 0.67 - 0.75; g represents the acceleration due to gravity; n represents the impeller rotational speed.

7. The method for predicting the overall hydraulic performance of a sink-type dishwasher according to claim 3, wherein: In Process 2.1, a composite virtual impeller model is constructed by innovating the rotational speed adaptation coefficient A of an open pump d and the axial velocity coefficient B d , and combining the parameter mapping relationship between the composite impeller and the virtual impeller, a virtual impeller assembly is constructed, which is two cylinders stacked on top of each other, respectively replacing the forward-curved axial flow cascade and the centrifugal radial blades of the impeller; the outer diameter and height of the cylinder can describe the area swept by the blades, the size of the inner diameter is set and it is defined that the fluid in the inner diameter area flows out of the cylinder with a certain vortex and axial velocity, and the rotation axis of the cylinder is set by the two-point method.

8. The method for predicting the overall hydraulic performance of a sink-type dishwasher according to claim 3, characterized in that: In Process 2.2, the near-field calculation domain of the nozzle outlet is the selection of the jet height of the non-submerged nozzle. The jet height should ensure that the water body flows out of the nozzle without affecting the monitoring of the nozzle flow rate. It is recommended that the near-field height of the jet domain be 1 to 2 times the nozzle diameter at the highest point of the nozzle tip.

9. The method for predicting the overall hydraulic performance of a sink-type dishwasher according to claim 4, characterized in that: In Process 3.1, setting the nozzle mass source in the calculation domain means defining the inflow source in the calculation domain, including the settings of the inflow source position, direction, geometry, and flow velocity. The distance between the mass source and the nozzle outlet is 1.5 times the nozzle diameter. In particular, the flow velocity is set as a function of time, and the data is consistent with the flow velocities of each nozzle obtained in Process 2.3.

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