Multi-objective optimization method for liquid-ring combined pump

Abstract

Disclosed in the present invention is a multi-objective optimization method for a liquid-ring combined pump. By taking a head coefficient of a main centrifugal pump and the stress of an impeller as constraints and taking the highest hydraulic efficiency of the main centrifugal pump, the minimum deformation of the impeller and the lightest weight as objectives, multi-objective optimization is performed on the impeller of the main centrifugal pump of the liquid-ring combined pump on the basis of an intelligent optimization algorithm. On this basis, by taking self-priming time and shaft power of a liquid-ring pump as evaluation indexes and taking the number of vanes of a liquid-ring impeller, the width of the liquid-ring impeller, a vane outlet inclination angle of the liquid-ring impeller, an eccentricity of the liquid-ring impeller and a hub inclination angle of the liquid-ring impeller as test factors, multi-objective optimization is performed on the liquid-ring impeller of the liquid-ring pump on the basis of a genetic algorithm. The feasibility of the multi-objective optimization method is verified on the basis of tests. A Z-G-B cavitation model is modified by taking thermodynamic effects and centrifugal pump rotational dynamics and geometric characteristics into consideration, and a cavitation characteristic curve, a vapor volume fraction and a pressure pulsation characteristic of the liquid-ring combined pump before and after optimization are analyzed. The weight of the pump is reduced, and the self-priming performance of the pump is improved while meeting the requirements for the efficiency and the strength of the vanes.

Description

A multi-objective optimization method for liquid ring combination pump Technical Field

[0001] The invention belongs to the field of centrifugal pump design, and in particular relates to a multi-objective optimization method for a liquid ring combination pump. Background Art

[0002] The liquid ring combination pump is a self-priming pump composed of a main centrifugal pump and a liquid ring pump, and is a type of specialty pump. The main centrifugal pump's impeller and the liquid ring pump's liquid ring wheel are coaxially arranged. The liquid ring wheel of the liquid ring pump is placed eccentrically above and below its annular pump chamber. When the liquid ring wheel rotates, it drives the liquid in the pump chamber to rotate at high speed, forming a liquid ring concentric with the pump chamber. There is a crescent-shaped air chamber on each side of the liquid ring wheel's axis. One side is a low-pressure area, which gradually expands with the direction of rotation, and the other side is a high-pressure area, which gradually contracts with the direction of rotation. The low-pressure area is the liquid ring pump's suction area and is connected to the main centrifugal pump inlet at the front end. The high-pressure area is the liquid ring pump's exhaust area, which is connected to the outside atmosphere and discharges gas out of the pump. When the liquid ring combination pump is turned on, the motor drives the liquid ring wheel and impeller to rotate at high speed. The liquid ring pump will discharge the gas in the main centrifugal pump and the inlet pipe out of the pump. There is a one-way valve at the outlet of the main centrifugal pump impeller. When the outlet pressure of the main centrifugal pump is greater than the spring pressure of the one-way valve, the one-way valve opens, thereby completing the self-priming of the liquid ring combination pump.

[0003] The liquid ring combination pump boasts a simple structure, compact size, and lightweight, making it easy to install and maintain. It can adapt to diverse operating environments and requirements, both on the ground and at high altitudes, making it a highly desirable self-priming pump structure for aviation fuel systems. However, maintaining the original performance parameters of the liquid ring combination pump while improving its self-priming performance has become a new challenge. Therefore, a multi-objective optimization method for liquid ring combination pumps that simultaneously considers both efficiency and self-priming performance is urgently needed. To date, no such multi-objective optimization method has been reported for liquid ring combination pumps.

[0004] Summary of the Invention

[0005] In view of the shortcomings in the prior art, the present invention provides a multi-objective optimization method for a liquid ring combination pump, thereby achieving the goals of satisfying efficiency and blade strength while reducing the weight of the combination pump and improving its self-priming performance.

[0006] In order to achieve the above objectives, the following technical solutions are adopted:

[0007] A multi-objective optimization method for a liquid ring combination pump is disclosed. The liquid ring combination pump is a self-priming pump composed of a main centrifugal pump and a liquid ring pump. The impeller of the main centrifugal pump and the liquid ring wheel of the liquid ring pump are coaxial. The multi-objective optimization method for the liquid ring combination pump comprises the following steps:

[0008] Step 1: Taking the main centrifugal pump head coefficient and impeller stress as constraints, and aiming at maximizing the main centrifugal pump hydraulic efficiency, minimizing the impeller deformation, and minimizing the weight, a multi-objective optimization of the main centrifugal pump impeller of the liquid ring combination pump was performed based on an intelligent optimization algorithm.

[0009] Step 2: Based on the optimization results of the main centrifugal pump, the self-priming time and shaft power of the liquid ring pump are used as evaluation indicators, and the number of liquid ring impeller blades, liquid ring impeller width, liquid ring impeller blade outlet inclination angle, liquid ring impeller eccentricity and liquid ring impeller hub inclination angle are used as experimental factors. A regression model of the main geometric parameters of the liquid ring impeller and the self-priming time and shaft power of the liquid ring pump is established, and a multi-objective optimization model of the liquid ring pump liquid ring impeller is performed based on the genetic algorithm;

[0010] Step 3: Build a liquid ring combination pump test bench to test and verify the feasibility of the multi-objective optimization method of the liquid ring combination pump;

[0011] Step 4: Considering the thermodynamic effects and the rotational motion and geometric characteristics of the centrifugal pump, the Zwart-Gerber-Belamri (ZGB) cavitation model is improved, and the cavitation flow in the liquid ring combination pump before and after optimization is numerically calculated. The cavitation characteristic curve, cavitation volume ratio and outlet pressure pulsation characteristics of the liquid ring combination pump before and after optimization are analyzed.

[0012] Preferably, in step 1, the steps of multi-objective optimization of the impeller of the main centrifugal pump of the liquid ring combination pump are specifically as follows:

[0013] (1) The parametric modeling of the main centrifugal pump impeller of the liquid ring combination pump is realized based on the five-point quartic Bezier curve, and a multi-objective optimization design platform for the main centrifugal pump impeller of the liquid ring combination pump is built based on ANSYS optiSLang;

[0014] (2) A multi-objective optimization mathematical model for the impeller of the main centrifugal pump of a liquid ring combination pump was constructed, which used 10 blade angle control points and 10 blade thickness control points in the five-point quartic Bezier curve as design variables, the main centrifugal pump head coefficient and impeller stress as constraints, and the main centrifugal pump hydraulic efficiency, minimum impeller deformation, and lightest weight as optimization objectives;

[0015] (3) Generate the sample space of multi-objective optimization design of the main centrifugal pump impeller of the liquid ring combination pump based on the optimal Latin hypercube method;

[0016] (4) Based on the intelligent optimization algorithm, the multi-objective optimization mathematical model of the impeller of the main centrifugal pump of the liquid ring combination pump is globally optimized to obtain the optimal solution set for the impeller optimization.

[0017] Preferably, the constraint of the head coefficient is that the head coefficient of the main centrifugal pump fluctuates within a range of 3%, that is, Where ψ0 is the head coefficient of the main centrifugal pump before optimization, ψ(x) To optimize the head coefficient of the main centrifugal pump.

[0018] Preferably, the constraint of impeller stress is the maximum stress σ that the main centrifugal pump impeller is subjected to after optimization. max Lower than or equal to the maximum stress on the main centrifugal pump impeller before optimization Right now

[0019] Preferably, the intelligent optimization algorithm is an adaptive simulated annealing algorithm, a genetic algorithm, an ant colony algorithm, or a particle swarm algorithm.

[0020] Preferably, in step 2, the steps of multi-objective optimization of the liquid ring wheel of the liquid ring pump are specifically as follows:

[0021] S1: Based on the optimization results of the main centrifugal pump, the self-priming time and shaft power of the liquid ring pump are used as evaluation indicators, and the main geometric parameters of the liquid ring wheel, such as the number of liquid ring wheel blades, liquid ring wheel width, liquid ring wheel blade outlet inclination angle, liquid ring wheel eccentricity and liquid ring wheel hub inclination angle, are used as test factors. An orthogonal test is carried out on the liquid ring wheel of the liquid ring pump, and the influence of each test factor on the evaluation indicators is obtained by using range analysis and variance analysis.

[0022] S2: Orthogonal polynomial regression analysis is used to determine the regression model of the main geometric parameters of the liquid ring wheel and the self-priming time and shaft power of the liquid ring pump;

[0023] S3: Genetic algorithm is used to perform multi-objective optimization on the regression model of the self-priming time and shaft power of the liquid ring wheel to determine the optimal structure of the liquid ring wheel.

[0024] Preferably, in step 3, the steps of experimentally verifying the feasibility of the multi-objective optimization method for the liquid ring combination pump are specifically as follows:

[0025] (1) Build a closed test bench for liquid ring combination pumps, which simulates the performance test and cavitation test of liquid ring combination pumps in ground environment and high altitude environment, and obtains the flow rate, head, efficiency, power, required NPSH, and outlet pulsating pressure of the liquid ring combination pumps;

[0026] (2) Use an electronic scale to weigh the weight of the main centrifugal pump impeller of the liquid ring combination pump, and compare and analyze the weight of the main centrifugal pump impeller before and after optimization;

[0027] (3) The head, efficiency, power, outlet pulsation pressure and self-priming time of the liquid ring combination pump at the rated flow rate were measured experimentally, and the required cavitation margin of the liquid ring combination pump at the rated flow rate was measured by vacuuming with a vacuum pump. At the same time, the head coefficient, efficiency, power, average value of outlet pulsation pressure, required cavitation margin and self-priming time of the liquid ring combination pump before and after optimization at the rated flow rate were analyzed, thereby verifying the feasibility of the multi-objective optimization method of the liquid ring combination pump.

[0028] Preferably, the steps of improving the ZGB cavitation model in step 4 are as follows:

[0029] S1: Considering the rotational motion and geometric characteristics of the centrifugal pump, the bubble diameter R is proposed b Calculation formula, Where C is the constant coefficient, which is obtained by fitting the centrifugal pump visualization test data; z is the number of blades of the main centrifugal pump impeller; k is the turbulent kinetic energy; ρ l is the liquid phase density; n is the speed of the liquid ring combination pump;

[0030] S2: Considering the thermodynamic effect, the ZGB cavitation model is improved, and the evaporation source term of the improved ZGB cavitation model is Expressions and condensation source terms The expression is:

[0031] Where: C evap is the evaporation coefficient; α v is the vapor phase volume fraction; ρ v is the gas phase density; P v is the pressure inside the bubble (assuming it is the saturated vapor pressure at the operating temperature of the pump); P is the pressure of the liquid around the bubble; C pl is the constant pressure specific heat of the liquid phase; α l is the thermal diffusion of the liquid, α l =λ l / ρ l C pl ;λ l is the thermal conductivity of the liquid phase; t is any time; T ∞ is the far-field temperature; T is the temperature at any time t; L ev is the latent heat of vaporization; C cond is the condensation coefficient.

[0032] S3: The various physical parameters in the improved ZGB cavitation model are fitted as functions of temperature using the least squares method;

[0033] S4: The improved ZGB cavitation model is embedded into CFX through CFX Expression Language (CEL), and the thermal conductivity λ not included in the formula v Specific heat capacity at constant pressure C pv Parameters that also vary with temperature are also fitted as functions of temperature and input into the corresponding positions in the CFX pre-processing.

[0034] The advantages of the present invention are:

[0035] (1) The multi-objective optimization method for a liquid ring combination pump proposed in the present invention achieves the goal of satisfying both efficiency and blade strength while reducing the weight of the liquid ring combination pump and improving its self-priming performance.

[0036] (2) The present invention develops a ZGB cavitation model that takes into account the thermodynamic effects and the rotational motion and geometric characteristics of the centrifugal pump, which improves the calculation accuracy of the cavitation flow in the liquid ring combination pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG1 is a flow chart of a multi-objective optimization method for a liquid ring combination pump;

[0038] FIG2 is a flow field calculation model of a liquid ring combination pump in a specific embodiment;

[0039] FIG3 is a diagram showing the control points of the impeller profile of the main centrifugal pump of the liquid ring combination pump in a specific embodiment;

[0040] FIG4 is a diagram showing the initialization state of the self-priming calculation of the liquid ring combination pump in a specific embodiment;

[0041] FIG5 is a schematic diagram of a closed test bench for a liquid ring combination pump according to a specific embodiment;

[0042] FIG6 is a cavitation characteristic curve of the liquid ring combination pump before and after optimization under rated working conditions in a specific embodiment;

[0043] Description of the drawings: 1-Liquid ring combination pump, 2-Separator, 3-Controller, 4-Valve 1, 5-Vacuum pump, 6-Valve 2, 7-Flow meter, 8-Electric regulating valve, 9-Thermometer, 10-Liquid level gauge, 11-Outlet pressure sensor, 12-Outlet pressure pulsation sensor. DETAILED DESCRIPTION

[0044] The present invention will be further described below with reference to Figures 1-6 and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0045] Example 1

[0046] A multi-objective optimization method for a liquid ring combination pump is characterized in that the liquid ring combination pump is a self-priming pump composed of a main centrifugal pump and a liquid ring pump, the impeller of the main centrifugal pump and the liquid ring wheel of the liquid ring pump are coaxial, and its flow field calculation model is shown in Figure 2.

[0047] The multi-objective optimization method of liquid ring combination pump includes the following steps:

[0048] (1) Multi-objective optimization of the main centrifugal pump impeller of a liquid ring combination pump

[0049] ① Based on the five-point quartic Bezier curve, the parametric modeling of the main centrifugal pump impeller of the liquid ring combination pump is realized, and a multi-objective optimization design platform for the main centrifugal pump impeller of the liquid ring combination pump is built based on ANSYS optiSLang.

[0050] ② A multi-objective optimization mathematical model for the impeller of the main centrifugal pump of the liquid ring combination pump was constructed. The 10 blade angle control points (see Table 1) and 10 blade thickness control points (see Table 2) in the five-point quartic Bezier curve were used as design variables (as shown in Figure 3). The head coefficient and impeller stress of the main centrifugal pump were used as constraints. The optimization objectives were to maximize the hydraulic efficiency of the main centrifugal pump, minimize the impeller deformation, and minimize the weight.

[0051] Table 1 Upper and lower limits of angle control point parameters

[0052] Table 2 Upper and lower limits of thickness control point parameters

[0053] The head coefficient constraint is that the head coefficient fluctuation of the main centrifugal pump should be within 3%, that is, Where ψ0 is the head coefficient of the main centrifugal pump before optimization.

[0054] The impeller stress constraint is that the maximum stress on the main centrifugal pump impeller after optimization should be lower than the maximum stress on the main centrifugal pump impeller before optimization, that is,

[0055] ③Generate the sample space of multi-objective optimization design of the main centrifugal pump impeller of liquid ring combination pump based on the optimal Latin hypercube method;

[0056] ④ Based on the particle swarm algorithm, the multi-objective optimization mathematical model of the impeller of the main centrifugal pump of the liquid ring combination pump is globally optimized to obtain the optimal solution set of the impeller optimization.

[0057] Tables 3 and 4 give the comparison of the angle control point parameters and thickness control point parameters before and after optimization, respectively. Table 5 gives the performance comparison of the main centrifugal pump before and after optimization.

[0058] Table 3 Comparison of angle control point parameters

[0059] Table 4 Comparison of thickness control point parameters

[0060] Table 5 Performance comparison of main centrifugal pump before and after optimization

[0061] (2) Multi-objective optimization of liquid ring pump and liquid ring wheel of liquid ring combination pump

[0062] ① Based on the optimization results of the main centrifugal pump, the self-priming time and shaft power of the liquid ring pump are used as evaluation indicators, and the main geometric parameters such as the number of liquid ring impeller blades, liquid ring impeller width, liquid ring impeller blade outlet inclination angle, liquid ring impeller eccentricity and liquid ring impeller hub inclination angle are used as test factors to carry out orthogonal tests on the liquid ring pump liquid ring impeller.

[0063] To ensure the accuracy of the calculation results, a monitoring surface is set at the outlet of the main centrifugal pump to monitor the outlet gas content. When the outlet gas content of the main centrifugal pump is less than 0.2%, the self-priming is considered to have ended. Figure 4 shows the initialization state diagram of the self-priming calculation of the liquid ring combination pump.

[0064] The influence of each experimental factor on the self-priming time based on the range analysis and variance analysis is: the number of liquid ring wheel blades > liquid ring wheel liquid ring wheel width > liquid ring wheel eccentricity > liquid ring wheel blade outlet inclination angle > liquid ring wheel hub inclination angle. The influence of each experimental factor on the shaft power based on the range analysis is: liquid ring wheel width > liquid ring wheel eccentricity > liquid ring wheel number of blades > liquid ring wheel blade outlet inclination angle > liquid ring wheel hub inclination angle, while the influence of each experimental factor on the shaft power based on the range analysis is: liquid ring wheel width > liquid ring wheel blade outlet inclination angle > liquid ring wheel number of blades > liquid ring wheel eccentricity > liquid ring wheel hub inclination angle. It can be seen that the liquid ring wheel hub inclination angle is a minor influencing factor on the self-priming time and shaft power. In the future, only four influencing factors will be considered: the number of liquid ring wheel blades, liquid ring wheel width, liquid ring wheel blade outlet inclination angle, and liquid ring wheel eccentricity.

[0065] ② Orthogonal polynomial regression analysis was used to determine the regression model of the number of liquid ring wheel blades, liquid ring wheel width, liquid ring wheel blade outlet angle, liquid ring wheel eccentricity and liquid ring pump self-priming time and shaft power.

[0066] ③ A genetic algorithm was used to perform multi-objective optimization on the regression model of the liquid ring impeller's self-priming time and shaft power to determine the optimal liquid ring impeller structure. The optimal liquid ring impeller structural parameters were: 10 liquid ring impeller blades, 19.1 mm liquid ring impeller width, 155° liquid ring impeller blade outlet inclination, and 3.6 mm liquid ring impeller eccentricity.

[0067] The CFD calculation results show that under rated flow, the self-priming time of the optimized liquid ring combination pump is 0.20s shorter than that before optimization, and the shaft power of the optimized liquid ring combination pump is also reduced by 1.57kW.

[0068] (3) Experimental verification of the feasibility of the multi-objective optimization method for liquid ring combination pumps

[0069] ① Build a closed test bench for liquid ring combination pumps (see Figure 5). This test bench can simulate the performance test and cavitation test of liquid ring combination pumps in ground and high-altitude environments to obtain the flow rate, head, efficiency, power, required cavitation margin, and outlet pulsating pressure of the liquid ring combination pumps.

[0070] ② An electronic scale was used to weigh the impeller of the main centrifugal pump of the liquid ring combination pump, and the weight of the main centrifugal pump impeller before and after optimization was compared and analyzed. The results showed that the weight of the main centrifugal pump impeller before and after optimization was 131.24g and 123.79g, respectively.

[0071] ③ The test measures the head, efficiency, power, outlet pulsating pressure and self-priming time of the liquid ring combination pump at the rated flow rate, and measures the required NPSH of the liquid ring combination pump at the rated flow rate by vacuuming with a vacuum pump. At the same time, the head coefficient, efficiency, power, average outlet pulsating pressure, required NPSH and self-priming time of the liquid ring combination pump before and after optimization at the rated flow rate are analyzed.

[0072] Table 6 shows a performance comparison of the liquid ring combination pump before and after optimization. It can be seen that the efficiency of the liquid ring combination pump increased by 2.55 percentage points, the power decreased by 5.26%, the average outlet pulsation pressure decreased by 4.29%, the required NPSH decreased by 9.59%, and the self-priming time decreased by 6.52%. Therefore, the multi-objective optimization method for the liquid ring combination pump proposed in this patent is feasible.

[0073] Table 6 Performance comparison of liquid ring combination pump before and after optimization

[0074] (4) Improve the ZGB cavitation model and conduct a comparative analysis of the cavitation flow in the liquid ring combination pump before and after optimization

[0075] ① Considering the rotational motion and geometric characteristics of the centrifugal pump, the bubble diameter R is proposed b Calculation formula, Where C is the constant coefficient, which is obtained by fitting the centrifugal pump visualization test data; z is the number of blades of the main centrifugal pump impeller; k is the turbulent kinetic energy; ρ l is the liquid phase density; n is the speed of the liquid ring combination pump;

[0076] ② Considering the thermodynamic effect, the ZGB cavitation model is improved, and the evaporation source term of the improved ZGB cavitation model is Expressions and condensation source terms The expression is:

[0077] Where: C evap is the evaporation coefficient; α v is the vapor phase volume fraction; ρ v is the gas phase density; P v is the pressure inside the bubble (assuming it is the saturated vapor pressure at the operating temperature of the pump); P is the pressure of the liquid around the bubble; C pl is the constant pressure specific heat of the liquid phase; αl is the thermal diffusion of the liquid, α l =λ l / ρ l C pl ;λ l is the thermal conductivity of the liquid phase; t is any time; T ∞ is the far-field temperature; T is the temperature at any time t; L ev is the latent heat of vaporization; C cond is the condensation coefficient.

[0078] ③The least squares method is used to fit all the physical parameters in the improved ZGB cavitation model as functions of temperature;

[0079] ④ The improved ZGB cavitation model is embedded into CFX through CFX Expression Language (CEL), and the thermal conductivity λ not included in the formula is v Specific heat capacity at constant pressure C pv Parameters that also vary with temperature are also fitted as functions of temperature and input into the corresponding positions in the CFX pre-processing.

[0080] ⑤ Based on the improved ZGB cavitation model, the cavitation flow in the liquid ring combination pump before and after optimization was numerically calculated, and the cavitation characteristic curve, cavitation volume ratio and pressure pulsation characteristics of the liquid ring combination pump before and after optimization were analyzed.

[0081] Figure 6 shows the cavitation characteristic curves of the liquid ring combination pump before and after optimization under rated operating conditions. It can be seen that the critical cavitation coefficient of the optimized solution decreased by 15.18%. Therefore, cavitation in the optimized fuel centrifugal pump has been suppressed to a certain extent.

[0082] The contents described in the embodiments of this specification are merely an enumeration of the implementation forms of the inventive concept. The scope of protection of the present invention should not be regarded as limited to the specific forms described in the embodiments. The scope of protection of the present invention also includes equivalent technical means that can be thought of by those skilled in the art based on the inventive concept.

Claims

1. A multi-objective optimization method for a liquid ring combined pump, characterized in that, The liquid-ring combined pump is a self-priming pump composed of a main centrifugal pump and a liquid-ring pump. The impeller of the main centrifugal pump and the liquid-ring wheel of the liquid-ring pump are coaxial. The multi-objective optimization method of the liquid-ring combined pump includes the following steps: Step 1: With the head coefficient of the main centrifugal pump and the impeller stress as constraints, and with the highest hydraulic efficiency of the main centrifugal pump, the minimum impeller deformation, and the lightest weight as objectives, multi-objective optimization of the impeller of the main centrifugal pump of the liquid-ring combined pump is carried out based on an intelligent optimization algorithm; Step 2: On the basis of the optimization results of the main centrifugal pump, taking the self-priming time and shaft power of the liquid-ring pump as evaluation indexes, and taking the number of blades of the liquid-ring wheel, the width of the liquid-ring wheel, the outlet angle of the liquid-ring wheel blades, the eccentricity of the liquid-ring wheel, and the hub angle of the liquid-ring wheel as test factors, a regression model of the main geometric parameters of the liquid-ring wheel and the self-priming time and shaft power of the liquid-ring pump is established, and multi-objective optimization of the liquid-ring wheel of the liquid-ring pump is carried out based on the genetic algorithm; Step 3: Build a test bench for the liquid-ring combined pump, and experimentally verify the feasibility of the multi-objective optimization method of the liquid-ring combined pump; Step 4: Considering the thermodynamic effect and the rotational motion and geometric characteristics of the centrifugal pump, improve the Zwart-Gerber-Belamri cavitation model, that is, the Z-G-B cavitation model, and numerically calculate the cavitation flow in the liquid-ring combined pump before and after optimization, and analyze the cavitation characteristic curves, the proportion of cavitation volume, and the pressure pulsation characteristics of the liquid-ring combined pump before and after optimization.

2. The multi-objective optimization method of a liquid-ring combined pump according to claim 1, characterized in that, In the said Step 1, the steps of multi-objective optimization of the impeller of the main centrifugal pump of the liquid-ring combined pump are as follows: (1) Realize the parametric modeling of the impeller of the main centrifugal pump of the liquid-ring combined pump based on the five-point and fourth-degree Bezier curve, and build a multi-objective optimization design platform for the impeller of the main centrifugal pump of the liquid-ring combined pump based on ANSYS optiSLang; (2) Construct a multi-objective optimization mathematical model for the impeller of the main centrifugal pump of the liquid-ring combined pump, that is, take 10 blade angle control points and 10 blade thickness control points in the five-point and fourth-degree Bezier curve as design variables, take the head coefficient of the main centrifugal pump and the impeller stress as constraints, and take the highest hydraulic efficiency of the main centrifugal pump, the minimum impeller deformation, and the lightest weight as optimization objectives; (3) Generate a sample space for the multi-objective optimization design of the impeller of the main centrifugal pump of the liquid-ring combined pump based on the optimal Latin hypercube method; (4) Carry out global optimization solution of the multi-objective optimization mathematical model of the impeller of the main centrifugal pump of the liquid-ring combined pump based on an intelligent optimization algorithm, so as to obtain the optimal solution set of the impeller optimization.

3. A multi-objective optimization method for a liquid ring combined pump according to claim 1 or 2, characterized in that, The constraint on the head coefficient is that the head coefficient fluctuation of the main centrifugal pump is within 3%, that is where ψ0 is the head coefficient of the main centrifugal pump before optimization, and ψ (x) is the head coefficient of the main centrifugal pump after optimization.

4. A multi-objective optimization method for a liquid ring combined pump according to claim 1 or 2, characterized in that The constraint on the impeller stress is the maximum stress σ that the main centrifugal pump impeller experiences after optimization max is less than or equal to the maximum stress that the main centrifugal pump impeller experienced before optimization i.e.

5. A multi-objective optimization method for a liquid ring combined pump according to claim 1 or 2, characterized in that, The said intelligent optimization algorithm is an adaptive simulated annealing algorithm, or a genetic algorithm, or an ant colony algorithm, or a particle swarm algorithm.

6. The multi-objective optimization method of a liquid ring type combined pump according to claim 1, characterized in that, In the said Step 2, the steps of multi-objective optimization of the liquid-ring wheel of the liquid-ring pump are as follows: (1) On the basis of the optimization results of the main centrifugal pump, taking the self-priming time and shaft power of the liquid-ring pump as evaluation indexes, and taking the main geometric parameters such as the number of blades of the liquid-ring wheel, the width of the liquid-ring wheel, the outlet angle of the liquid-ring wheel blades, the eccentricity of the liquid-ring wheel, and the hub angle of the liquid-ring wheel as test factors, conduct an orthogonal test on the liquid-ring wheel of the liquid-ring pump, and obtain the influence degree of each test factor on the judgment index according to the range analysis and variance analysis; (2) Use orthogonal polynomial regression analysis to determine the regression model of the main geometric parameters of the liquid-ring wheel and the self-priming time and shaft power of the liquid-ring pump; (3) Use the genetic algorithm to perform multi-objective optimization on the regression models of the self-priming time and shaft power of the liquid ring wheel to determine the optimal structure of the liquid ring wheel.

7. A multi-objective optimization method for a liquid ring combined pump according to claim 1, characterized in that, In the third step described above, the steps to experimentally verify the feasibility of the multi-objective optimization method for the liquid ring type combined pump are as follows: (1) Build a closed test bench for the liquid ring type combined pump. This test bench simulates the performance test and cavitation test of the liquid ring type combined pump under ground environment and high altitude environment, and obtains the flow rate, head, efficiency, power, required net positive suction head (NPSH), and pulsating pressure of the liquid ring type combined pump. (2) Use an electronic scale to weigh the impeller of the main centrifugal pump of the liquid ring type combined pump, and compare and analyze the weights of the impellers of the main centrifugal pump before and after optimization. (3) Experimentally measure the head, efficiency, power, outlet pulsating pressure, and self-priming time of the liquid ring type combined pump at the rated flow rate, and measure the required net positive suction head (NPSH) of the liquid ring type combined pump at the rated flow rate by means of vacuum pumping with a vacuum pump. At the same time, analyze the head coefficient, efficiency, power, average value of the outlet pulsating pressure, required net positive suction head (NPSH), and self-priming time of the liquid ring type combined pump before and after optimization at the rated flow rate, so as to verify the feasibility of the multi-objective optimization method for the liquid ring type combined pump.

8. A multi-objective optimization method for a liquid ring combined pump according to claim 1, characterized in that (6) In the fourth step described above, the steps to improve the Z-G-B cavitation model are as follows: (1) Considering the rotational motion and geometric characteristics of a centrifugal pump, the bubble diameter R b calculation formula In the formula, C is the constant term coefficient, which is obtained by fitting the visualized test data of the centrifugal pump; z is the number of blades of the main centrifugal pump impeller; k is the turbulent kinetic energy; ρ l is the liquid phase density; n is the rotational speed of the liquid-ring combined pump; (2) Considering the thermodynamic effect, improve the Z - G - B cavitation model, then the evaporation source term of the improved Z - G - B cavitation model Expression and condensation source term The expression is: Where: C evap is the evaporation coefficient; α v is the vapor volume fraction; ρ v is the gas-phase density; P v is the pressure inside the bubble (assumed to be the saturation vapor pressure at the temperature of the operating medium in the pump); P is the pressure of the liquid surrounding the bubble; C pl is the specific heat at constant pressure of the liquid phase; α l is the thermal diffusivity of the liquid, α l = λ l / ρ l C pl ; λ l is the thermal conductivity of the liquid phase; t is any moment; T ∞ is the far-field temperature; T is the temperature at any moment t; L ev is the latent heat of vaporization; C cond is the condensation coefficient; (3) Use the least squares method to fit each physical property parameter in the improved Z-G-B cavitation model as a function of temperature. (4)Embed the improved Z-G-B cavitation model into CFX through the CFX expression language. The thermal conductivity λ not included in the formula v , the specific heat capacity at constant pressure C pv and other parameters that also vary with temperature are also fitted as functions of temperature and input into the corresponding positions in the CFX preprocessing.

Images