Overall hydraulic performance prediction method for sink-type dishwasher

Abstract

Method for predicting the overall hydraulic performance of a sink-type dishwasher. Process begins with unsteady numerical computation on a dishwasher pump under static conditions to obtain a characteristic pump curve. Using this curve, rotation velocity adaptation coefficient (A.sub.d) and axial velocity coefficient (B.sub.d) are determined. Mapping relationship is established between composite superposition virtual impeller and composite impeller. Passive rotation velocity of the volute and the nozzle flow rate are calculated using GMO model and virtual impeller. A jet mass source is established, using the nozzle flow rate and the volute's passive rotation velocity as boundary conditions. This leads to a non-submerged rotating jet flow computation with a multi-nozzle setup using the VOF method. This approach streamlines the dishwasher's intricate multi-physics, conserves computing resources, and effectively resolves issues related to free surface divergence and estimating the volute's passive rotation speed, leading to an accurate prediction of the dishwasher's overall hydraulic performance.

Claims

1. An overall hydraulic performance prediction method for a sink-type dishwasher, comprising following steps: step 1: constructing models of a composite impeller and a twin-volute spraying arm within a dishwasher based on the composite impeller and the twin-volute spraying arm within the dishwasher in a real operational condition, and conducting numerical simulations based on the models to obtain a pump characteristic curve for a new type of dishwasher pump under a static condition of a volute; step 2: obtaining a full-open flow rate Q.sub.0 from the pump characteristic curve, obtaining a rotation velocity adaptation coefficient A.sub.d and an axial velocity coefficient B.sub.d, performing unsteady simulation on a passive rotation of the volute using a GMO-TruVOF method, and obtaining a passive rotation velocity of the volute and a flow rate at an exit of each nozzle; and step 3: taking the passive rotation velocity of the volute and the flow rate at the exit of each nozzle as initial conditions, conducting non-submerged rotational unsteady computation on nozzles based on FAVOR-TruVOF to obtain flow parameters of the dishwasher, and estimating a hydraulic washing capacity of the dishwasher according to the flow parameters.

2. The overall hydraulic performance prediction method for a sink-type dishwasher according to claim 1, wherein the constructing models of a composite impeller and a twin-volute spraying arm within a dishwasher based on the composite impeller and the twin-volute spraying arm within the dishwasher in a real operational condition, and conducting numerical simulations based on the models to obtain the pump characteristic curve for the new type of dishwasher pump under the static condition of the volute comprises following processes: process 1.1: constructing a water body of the new type of dishwasher pump based on models of the composite impeller and a volute type spraying arm, meshing by using ICEM software, and performing unsteady simulation of the new type of dishwasher pump with Fluent software; and process 1.2: conducting numerical simulation predictions of the pump characteristic curve by using a RANS method, computing a head at a minimum of five different flow rates under the static condition of the volute, and plotting the pump characteristic curve.

3. The overall hydraulic performance prediction method for a sink-type dishwasher according to claim 2, wherein the obtaining the full-open flow rate Q.sub.0 from the pump characteristic curve, obtaining the rotation velocity adaptation coefficient A.sub.d and the axial velocity coefficient B.sub.d, performing unsteady simulation on the passive rotation of the volute using the GMO-TruVOF method, and obtaining the passive rotation velocity of the volute and the flow rate at the exit of each nozzle comprises following processes: process 2.1: determining the full-open flow rate Q.sub.0 using the pump characteristic curve obtained in process 1.2, acquiring the rotation velocity adaptation coefficient A.sub.d, and the axial velocity coefficient B.sub.d suitable for the new type of dishwasher pump, constructing a virtual impeller model within the FLOW-3D software, and establishing a mapping relationship between parameters of a virtual impeller and the composite impeller; process 2.2: constructing near-field computational domains at the exit of each nozzle, conducting Cartesian meshing on the virtual impeller, a volute spraying arm, and a near field of a nozzle jet flow domain based on FAVOR technology, and selecting an appropriate mesh resolution to ensure effective analysis of a computational domain; and process 2.3: enabling fluid-structure interaction and free surface computation of the new type of dishwasher pump based on the virtual impeller and the GMO-TruVOF method to realize a numerical simulation of the passive rotation of the volute, and monitoring the passive rotation velocity of the volute and the flow rate at the exit of each nozzle.

4. The overall hydraulic performance prediction method for a sink-type dishwasher according to claim 3, wherein the taking the passive rotation velocity of the volute and the flow rate at the exit of each nozzle as initial conditions, conducting non-submerged rotational unsteady computation on the nozzles based on the FAVOR-TruVOF to obtain flow parameters of the dishwasher, and estimating the hydraulic washing capacity of the dishwasher according to the flow parameters comprises following processes: process 3.1: constructing a gas-liquid two-phase non-submerged jet flow computational domain with a free surface in a sink of the dishwasher, and setting a jet mass source in the gas-liquid two-phase non-submerged jet flow computational domain; process 3.2: computing a complex non-submerged rotating jet flow field of a multi-nozzle combination based on the FAVOR-TruVOF by taking the flow rate at the exit of each nozzle and the passive rotation velocity of the volute obtained in process 2.3 as boundary conditions of the jet mass source; and process 3.3: post-processing non-submerged rotating jet flow computation results, which comprises analyzing distribution laws of jet flow impact pressure, vorticity, and other flow parameters, as well as evaluating the overall hydraulic performance of the dishwasher.

5. The overall hydraulic performance prediction method for a sink-type dishwasher according to claim 4, wherein in process 3.1, the setting of the jet mass source in the gas-liquid two-phase non-submerged jet flow computational domain comprises defining an inflow source in the computational domain, comprising a setting of position, direction, geometry, and flow velocity of the inflow source, and a distance between the jet mass source and the exit of each nozzle is 1.5 times the nozzle diameter, in particular, the flow rate is set as a function of time, and a data aligns with the flow rate of each nozzle obtained in process 2.3.

6. The overall hydraulic performance prediction method for a sink-type dishwasher according to claim 3, wherein in process 2.1, the constructing the virtual impeller model comprises: innovating the rotation velocity adaptation coefficient A.sub.d and the axial velocity coefficient B.sub.d for the new type of dishwasher pump, and constructing, in combination with the mapping relationship of parameters between the composite impeller and the virtual impeller, a virtual impeller assembly, namely, two cylinders stacked up and down, to respectively replace a forward curved axial flow cascade and a centrifugal radial blade of impeller, outer diameters and heights of the cylinders describing a region swept by the blade, a size of an inner diameter being set, a region fluid flowing out of the cylinders at a certain vortex and an axial velocity being defined, and rotation axes of the cylinders being determined using a two-point method.

7. The overall hydraulic performance prediction method for a sink-type dishwasher according to claim 3, wherein in process 2.2, the near-field computational domains at outlets of nozzles are obtained by selecting a non-submerged nozzle jet flow height, the non-submerged nozzle jet flow height is required to ensure that water flows out from nozzles without impacting monitoring of nozzle flow rate, and is also required to have no effect or negligible effect on a setting of a jet mass source in step 3, and a near-field height of a jet flow domain is 1-2 times a nozzle diameter of a highest point at a top of a nozzle opening.

8. The hydraulic performance prediction method for a sink-type dishwasher based on a multi-physics coupling simulation strategy according to claim 2, wherein in process 1.2, heads under the five flow rates exclude conditions of flows less than 0.2 Q.sub.d, while a resultant five groups of data undergo linear approximation fitting.

9. The hydraulic performance prediction method for a sink-type dishwasher based on the multi-physics coupling simulation strategy according to claim 8, wherein the linear approximation fitting comprises fitting the pump characteristic curve to obtain the full-open flow rate Q.sub.0, and determining the rotation velocity adaptation coefficient A.sub.d and the axial velocity coefficient B.sub.d suitable for the new type of dishwasher pump by using Q.sub.0 and a parameter relationship between the composite impeller and the virtual impeller, a fitted linear expression being as follows: $h=aQ+Q_0$ wherein h represents a head of a pump, with a unit of m; a represents a slope of a straight line; Q represents the flow rate, with a unit of 1/min; Q.sub.0 represents both a horizontal axis intercept of a fitted straight line and a full-open flow rate of the pump; a mapping relationship between parameters of the composite impeller and the virtual impeller is as follows: $\begin{array}{c}{H}_{y1}=L\cos {}_L\\ H_{y2}=H+b_2-0.3D\\ D_{y1}=D\\ D_{y2}=D_2\\ D_{y3}=d_h\end{array}$ wherein left side of above equations shows geometric parameters of the virtual impeller, and right side of above equations shows geometric parameters of the composite impeller; H.sub.y1 is a height of a virtual impeller I, with a unit of m; D.sub.y1 is an outer diameter of the virtual impeller I, with a unit of m; H.sub.y2 is a height of a virtual impeller II, with a unit of m; D.sub.y2 is an outer diameter of the virtual impeller II, with a unit of m; D.sub.y3 is a hub diameter of the virtual impeller, with a unit of m; L is an airfoil chord length of the composite impeller, with a unit of m; .sub.L is an airfoil angle of the composite impeller, with a unit of degree; H is a height of a back cover plate of the composite impeller, with a unit of m; b.sub.2 is an outlet width of the composite impeller, with a unit of m; D is a minimum outer diameter of the composite impeller, with a unit of m; D.sub.2 a maximum outer diameter of the composite impeller, with a unit of m; d.sub.h is a hub diameter of the composite impeller, with a unit of m; the rotation velocity adaptation coefficient A.sub.d and the axial velocity coefficient B.sub.d for the new type of dishwasher pump obtained according to the full-open flow rate Q.sub.0 and the parameter relationship between the virtual impeller and the composite impeller being as follows: $A_d=\frac{{\mathrm{gn}}^2{D}_2^2\left(C_1{D}^2+C_2{D}_2^2\right)}{4Q_0\left(L\cos {}_L+H+b_2-0.3D\right)}$ $B_d=\frac{12Q_0}{n\left(D_2^3-D^3\right)}$ wherein C.sub.1=.sup.2/3600 g(=0.92-0.98), and C.sub.2=.sup.2/3600 g(=0.67-0.75).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is the flowchart of simulation prediction of a dishwasher.

(2) FIG. 2 is the new type of dishwasher pump model of a dishwasher and a water body computational domain.

(3) FIG. 3 is the pump characteristic curve prediction (solid line) of the new type of dishwasher pump and a fitting approximate value (dashed line).

(4) FIG. 4 is the geometric model of the virtual impeller.

(5) FIG. 5 is the structural diagram of the radial-type blade of the composite impeller.

(6) FIG. 6 is the plan view of the forward curved axial flow cascade of the composite impeller.

(7) FIG. 7 is the Cartesian coordinate division diagram of the new type of dishwasher pump.

(8) FIG. 8 shows the variation of the volute passive rotation velocity.

(9) FIGS. 9(a)-9(m) show the fluid velocity of the monitoring point at the exit of each nozzle.

(10) FIG. 10 shows the arrangement of the mass source on volute.

(11) FIG. 11 shows the variation of mean pressure on the top surface of the tank over time.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(12) Hereinafter, the technical solutions of the present invention will be described in detail with reference to the accompanying drawings and specific embodiments. (1) The hydraulic performance prediction of a dishwasher under a multi-physics coupling simulation strategy is achieved using a geometric model of a new type of dishwasher pump of the dishwasher. The whole prediction flow is illustrated in FIG. 1. (2) The multi-physics problems of the dishwasher are primarily concentrated on a volute type spraying arm. To accurately obtain the heads of the dishwasher pump under different flow rates without computational divergence, a static state simulation of the volute is conducted. A structural diagram of the pump model and its computational domain are depicted in FIG. 2. (3) The meshing process is conducted using ICEM software, employing hexahedral structure meshes. The computational domain is segmented into four computational regions: an inlet flow channel, a diversion loop flow channel, an impeller flow channel, and a volute flow channel. Additionally, a boundary layer is incorporated into the wall surface for localized refinement. (4) Fluent software is employed for performing the external characteristic simulation computation. The k-co turbulence model is adopted for steady computation. The inlet uses the flow inlet boundary condition with a specified flow rate setting. The outlet adopts the pressure outlet boundary condition with ambient atmospheric pressure. The wall surface is subject to a non-slip boundary condition. The impeller domain and the diversion loop water domain have a rotation velocity of n, while other components are set as static domains. The computation is performed using the SIMPLE algorithm, and a second-order upwind difference scheme is employed in the discrete process. (5) The performance curve based on RANS numerical simulation prediction is depicted as the solid line in FIG. 3. As simulation errors are considerable under extreme conditions, linear fitting is conducted based on a minimum 0.5 Q.sub.d condition, resulting in the fitting result shown as the dotted line in FIG. 4. Through the linear fitting curve, an approximate equation of the pump characteristic curve may be derived:

(13) $\begin{array}{cc}h=aQ+Q_0& \left(\mathrm{Equation}1\right)\end{array}$ where a is the slope of the fitted straight line, and Q.sub.0 represents the horizontal axis intercept of the fitted straight line and serves as the full-open flow rate of the pump.

(14) A maximum head and the full-open flow rate may be respectively expressed as:

(15) $\begin{array}{cc}h=\frac{L_0}{g}.Math.\frac{Q_0}{R^{*2}}.Math.A_d& \left(\mathrm{Equation}2\right)\end{array}$$\begin{array}{cc}{Q}_0=\frac{2}{3}\left(R^{*3}-r^3\right)n{B}_d& \left(\mathrm{Equation}3\right)\end{array}$ where h represents the maximum head, L.sub.0 is the total height of the impeller, g is gravitational acceleration, Q.sub.0 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 rotation velocity of the impeller. (6) The virtual impeller geometry is shown in FIG. 4. Two hollow cylinders have the same inner diameter. D.sub.y3 is the hub diameter, D.sub.y2 is the impeller diameter, D.sub.y1 is the minimum impeller diameter, H.sub.y1 is the height of impeller I, H.sub.y2 is the height of impeller II, and the heights of the impellers have the following relationship:

(16) $\begin{array}{cc}{H}_{y1}+H_{y2}=L_0& \left(\mathrm{Equation}4\right)\end{array}$ (7) The structural diagram of a centrifugal radial impeller of a composite impeller is depicted in FIG. 5, with the primary parameters encompassing D as the inlet diameter of the impeller, D.sub.2 as the outlet diameter of the impeller, b.sub.2 as the outlet width of the impeller, d.sub.h as the hub diameter of the impeller, H as the height of a back cover plate of the impeller, and as the blade thickness. (8) FIG. 6 shows the plan view of a forward curved axial flow cascade of a composite impeller, where the main geometric parameters include L as the airfoil chord length, d.sub.h as the hub diameter of the impeller, .sub.L as the airfoil angle, z as the number of blades, t as a grid distance (calculated as t=2R/z), R as the radius of a cylindrical laminar flow surface, and as the attack angle, namely, the angle between an incoming flow direction and a chord. (9) The radial blade illustrated in FIG. 5 and the forward curved axial flow cascade depicted in FIG. 6 together constitute the original composite impeller. The mapping relationship between the partial parameters of the composite impeller and the parameters of the virtual impeller is established:

(17) $\begin{array}{cc}{H}_{y1}=L\cos {}_L& \left(\mathrm{Equation}5\right)\end{array}$$\begin{array}{cc}{H}_{y2}=H+b_2-0\text{.3}D& \left(\mathrm{Equation}6\right)\end{array}$$\begin{array}{cc}{D}_{y1}=D& \left(\mathrm{Equation}7\right)\end{array}$$\begin{array}{cc}{D}_{y2}=D_2& \left(\mathrm{Equation}8\right)\end{array}$$\begin{array}{cc}{D}_{y3}=d_h& \left(\mathrm{Equation}9\right)\end{array}$ (10) By employing the mapping relationship between the geometric parameters of the composite impeller model and the virtual impeller, and in conjunction with the full-open flow rate Q.sub.0 obtained by fitting the head flow curve of the new type of dishwasher pump, a simultaneous relationship of the rotation velocity adaptation coefficient A.sub.d and the axial velocity coefficient B.sub.d with the full-open flow rate Q.sub.0 and the parameters of the composite impeller can be derived from (Equation 2) to (Equation 9):

(18) $\begin{array}{cc}{A}_d=\frac{g{n}^2{D}_2^2\left(C_1{D}^2+C_2{D}_2^2\right)}{4Q_0\left(L\cos {}_L+H+b_2-0.3D\right)}& \left(\mathrm{Equation}10\right)\end{array}$

(19) The axial velocity coefficient is:

(20) $\begin{array}{cc}{B}_d=\frac{12Q_0}{n\left(D_2^3-D^3\right)}& \left(\mathrm{Equation}11\right)\end{array}$ where C.sub.1=.sup.2/3600 g (=0.92-0.98), and C.sub.2=.sup.2/3600 g (=0.67-0.75). (11) Based on the parameter mapping relationship between the original impeller and the virtual impeller as stated in (Equation 5) to (Equation 9), specific values of the parameters of the composite impeller of the new type of dishwasher pump, the rotation velocity adaptation coefficient A.sub.d, and the axial velocity coefficient B.sub.d are imported into a setting interface of the virtual impeller in FLOW-3D, where a virtual impeller model and the spraying arm are subsequently constructed. (12) Adhering to the meshing principle of the FAVOR technology, Cartesian meshing is executed on the overall model using FLOW-3D. As exemplified in FIG. 7, the distance between the top surface of the jet flow near-field computational domain and the nozzle is approximately 1-2 times the nozzle diameters. To circumvent the tracking of jet flow fields of the whole nozzles, the required outlet flow velocity of each nozzle and the passive rotation velocity of the volute are simultaneously monitored. A mesh resolution is set to be no more than 1/20 of the minimum nozzle diameter. Specific computation and time steps are determined, and the requisite hydraulic computation data is verified. (13) A GMO coupling motion option in a Moving and Simple Deforming Objects model of a physics interface in FLOW-3D is enabled, and a baffle is inserted near the exit of the nozzle, specifically establishing a flow velocity monitoring surface at each outlet of the volute. The passive rotation of the volute is simulated using a TruVOF method, and the variation of the rotation velocity of the volute and the flow velocity at each nozzle exit over time are closely monitored, as depicted in FIG. 8 and FIGS. 9(a)-9(m). (14) The construction of the dishwasher sink is accomplished using Creo software, with particular attention paid to creating the top surface of the sink body and embedding a volute model into the sink model. (15) The work completed in (12) are replicated in the FLOW-3D simulation software. An overall jet inflow source is configured, ensuring that the shape of the mass source aligns with the nozzle exit. To address the complex issue of determining the direction of the mass source, the mass source is horizontally embedded above each nozzle, with the distance between the mass source and the exit of the nozzle set at 1.5 times the nozzle diameter, as illustrated in FIG. 10. Additionally, the outlet flow velocity of each nozzle obtained through monitoring in step (13) is inputted accordingly. (16) The data obtained by monitoring in step (13) is integrated into the mass source, facilitating the simulation of nozzle jet flow under the passive rotation of the volute using the TruVOF method. (17) Subsequently, the simulation results of the non-submerged rotating jet flow are subjected to post-processing, encompassing the evaluation of the variation pattern of the average water pressure on the top surface of the sink body over time. The computation of the water pressure adheres to the formulas detailed in Equation (12) and Equation (13).

(21) 0$\begin{array}{cc}\stackrel{}{P}={\stackrel{}{P}}_t\mathrm{dt}/t& \left(\mathrm{Equation}12\right)\end{array}$$\begin{array}{cc}{\stackrel{}{P}}_t=\mathrm{PdA}/dA& \left(\mathrm{Equation}13\right)\end{array}$ where A is the area of a stress surface, m.sup.2; t is time, s; P is an average pressure per unit of time, N; P.sub.t is the average pressure of the plate at different moments, N. (18) The ultimate prediction outcome regarding the washing capacity of the dishwasher is depicted in FIG. 11. Moreover, the estimation of the maximum impact force and the average impact force is conducted by observing the fluctuation pattern of stress on a top plate over time.