Gas-liquid multiphase pump numerical prediction method considering bubble deformation and size change

Abstract

The invention discloses a gas-liquid multiphase pump numerical prediction method considering bubble deformation and size change, which comprises the following steps of: 1, establishing a resistance coefficient model, and calculating to obtain a corrected resistance coefficient; and 2, setting a numerical simulation calculation scheme, performing numerical calculation on an internal flow field of the gas-liquid multiphase pump, setting related conditions, determining a bubble size model, and obtaining a numerical prediction result of the gas-liquid multiphase pump. The invention belongs to the technical field of gas-liquid mixed transportation fluid machinery, and discloses a gas-liquid mixed transportation fluid mechanical simulation method which comprises the following steps: on the basis of a bubble multi-size group model MUSIG model, considering bubble deformation and size change caused by bubble breaking and coalescence behaviors, correcting a resistance coefficient model Schiller Namann model, carrying out numerical research on the operation characteristics of a gas-liquid mixed transportation pump, and calculating the gas-liquid mixed transportation fluid mechanical simulation model. And the performance prediction precision of the gas-liquid multiphase pump under the conditions of low gas content and high gas content is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of gas-liquid mixed transmission fluid machinery, and relates to a numerical prediction method for a gas-liquid mixed transmission pump taking into account bubble deformation and size change. Background Art

[0002] As a key equipment in deepwater oil and gas exploitation and transportation systems, the gas-liquid mixed pump usually contains gas phase (bubbles) and liquid phase when deepwater oil and gas resources are exploited, and the bubbles flow with the liquid phase. Due to the complex structure of the impeller flow channel and the rotation effect of the impeller, the bubbles produce transient dynamic phenomena such as collision, crushing, and aggregation, which increase the complexity of fluid flow, and then cause the pressure rise of the gas-liquid mixed pump to drop sharply, accompanied by transient instability problems such as strong pressure pulsation and vibration, which deteriorates the pump's delivery capacity.

[0003] At present, most of the numerical simulation studies on gas-liquid mixed flow pumps are carried out under the condition of relatively small inlet gas content, using the Eulerian-Eulerian multiphase flow model, fixed bubble size and Schiller Naumann resistance model for prediction and analysis, and rarely consider the influence of bubble size distribution and the resistance model in the gas-liquid phase force model. Especially at high gas content, the bubble aggregation and breakup effects inside the pump are often ignored, resulting in underestimation of gas-liquid interaction and overestimation of pump performance to a certain extent.

[0004] Therefore, it is crucial to develop a numerical prediction method for gas-liquid mixed pumps that takes into account bubble deformation and size change. Summary of the invention

[0005] The purpose of the present invention is to provide a numerical prediction method for a gas-liquid mixed flow pump taking into account bubble deformation and size change, thereby solving the problem that the prior art does not take into account the influence of bubble deformation and size change, resulting in inaccurate performance prediction of the gas-liquid mixed flow pump under low gas content and high gas content conditions.

[0006] The technical solution adopted by the present invention is a numerical prediction method for a gas-liquid mixed transmission pump considering bubble deformation and size change, which is implemented according to the following steps: Step 1: Establish a drag coefficient model and calculate the corrected drag coefficient; Step 2: Set up the numerical simulation calculation scheme, first perform numerical calculation on the internal flow field of the gas-liquid mixed flow pump, set relevant conditions, determine the bubble size model, and obtain the numerical prediction results of the gas-liquid mixed flow pump.

[0007] The beneficial effect of the present invention is that the method, based on the bubble multi-size group model (MUSIG model), fully considers the bubble deformation and size change caused by the bubble breakage and aggregation behavior, corrects the resistance coefficient model (SchillerNaumann model), improves the performance prediction accuracy of the gas-liquid mixed flow pump under low gas content and high gas content conditions, and meets the needs of engineering technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a comparison chart of the values ​​predicted by the method of the present invention and the pump pressure rise obtained by the test; Figure 2 is a comparison diagram of gas phase distribution in Example 1 of the method of the present invention when IGVF = 5%; Figure 3 is based on Figure 2 Electronic schematic diagram of gas content distribution in CFD cross section when Span = 0.5 in the state; Figure 4 is based on Figure 2 Electronic schematic diagram of CFD gas volume fraction isosurface (value ≥ 0.9) in the state; Figure 5 is a comparison diagram of gas phase distribution in Example 5 of the method of the present invention when IGVF = 25%; Figure 6 is based on Figure 5 Electronic schematic diagram of gas content distribution in CFD cross section when Span = 0.5 in the state; Figure 7 is based on Figure 5 Electronic schematic diagram of CFD gas volume fraction isosurface (value ≥ 0.9) under the state. DETAILED DESCRIPTION

[0009] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0010] The numerical prediction method of the gas-liquid mixed transmission pump considering the bubble deformation and size change of the present invention is implemented according to the following steps: Step 1: Establish a drag coefficient model and calculate the modified drag coefficient. The specific process is: According to existing technical conditions, under low Reynolds number conditions, it is mainly viscous flow, Re<<1, under this condition, the resistance coefficient C D =24 / Re; when the Reynolds number is large enough, that is, 1000 ≤ Re ≤ (1 ~ 2)×10 5 , the inertial effect is greater than the viscous effect, then C D= 0.44; When the Reynolds number is in the transition region between the viscous effect and the inertial effect, i.e., 0.1 < Re < 1000, both effects are important, and the drag coefficient is a complex function of the Reynolds number and must be determined through experiments.

[0011] The existing drag coefficient models mainly include the Schiller Naumann model, the Ishii Zuber model, and the Grace model. Among them, the Schiller Naumann model is derived for the flow over a single spherical particle, so it is applicable to the mixed medium with a relatively small particle phase volume fraction. Its expression is as follows: (1) (2) In the formula, C D is the drag coefficient; Re is the Reynolds number; d is the bubble diameter; w is the velocity; μ is the dynamic viscosity; the subscripts g , l represent the gas phase and the liquid phase respectively; At larger Reynolds numbers, in the inertial or distorted state, the surface tension effect becomes more important. Fluid particles such as bubbles first appear approximately elliptical and then develop into a spherical cap shape; considering the transient behaviors such as bubble coalescence and breakup in the gas-liquid mixed transportation pump when the inlet gas volume fraction is relatively high (IGVF ≥ 5%), the surface tension effect deforms the bubbles, forming irregular shapes, elliptical shapes, or spherical cap shapes; in such distorted states, the drag coefficient is independent of the Reynolds number.

[0012] The drag coefficient model adopted in this step is to give multiple sets of bubble diameters in the bubble size model to simulate the bubble coalescence and breakup behaviors in the gas-liquid mixed transportation pump. As the bubbles deform, the drag coefficient changes with the change of the bubble diameter; However, the Schiller Naumann model is derived for a single bubble and cannot consider the influence of the change in bubble diameter. Therefore, in this step, the Tomiyama model is used to correct the Schiller Naumann model to fully consider the factors of bubble deformation and size change. The drag coefficient with a higher value calculated according to the two formulas is automatically selected as the drag coefficient of the gas-liquid interfacial force. The expression of the final corrected drag coefficient is as follows: (3) (4) (5) (6) (7) In various To correct the drag coefficient; To calculate the drag coefficient expression based on the Tomiyama model; To calculate the drag coefficient expression based on the Schiller-Naumann model; ρ l and ρ g are the density of liquid and the density of gas respectively; Eo is the ratio of gravity to surface tension; N i For the i The number of bubbles in the group; d b is the Sauter mean bubble diameter, in mm; d i is the diameter of the ith bubble. Step 2: Set up the numerical simulation calculation scheme, first perform numerical calculation on the internal flow field of the gas-liquid mixed flow pump, set relevant conditions, determine the bubble size model, and obtain the numerical prediction results of the gas-liquid mixed flow pump. The specific process is: The commercial software ANSYS CFX is used to perform numerical calculations on the internal flow field of the gas-liquid mixed flow pump. In order to facilitate the calculation of the gas-liquid flow in the pump, the basic assumptions are as follows: (1) The flow type in the inlet pipe is bubbly flow; (2) The bubbles are set as spherical bubbles; (3) The gas and liquid flow rates in the inlet pipe are equal and evenly distributed; (4) Both the gas and liquid phases are incompressible fluids; (5) The gas and liquid phases do not dissolve in each other and there is no interphase mass transfer. During the numerical calculation, the working media are water and air, the inlet boundary condition is set to total pressure, the outlet boundary condition is set to mass flow, the impeller is a rotating domain, the inlet pipe, guide vanes and outlet pipe are stationary domains, and the wall is set to a no-slip boundary. The specific settings are as follows: Working medium: liquid phase is water, gas phase is air, air temperature is 25 degrees Celsius; Inlet boundary conditions: total pressure, inlet gas fraction IGVF, bubble size distribution; Outlet boundary conditions: gas-liquid mixed phase mass flow rate; Turbulence model: Liquid phase is SST Turbulence model, gas phase is a dispersed phase zero equation model; Surface tension coefficient: 0.072N / m; Resistance model: Modified Schiller Naumann model; Lift model: Legendre Magnaudet model; Virtual mass force model: coefficient is 0.5; Bubble breakup model: Lou and Svendsen model; Bubble coalescence model: Prince and Blanch model; Dynamic and static interface: Teansient Rotor stator; Discrete format of convection term: High solution; Turbulence term discretization format: first order; Time term discrete format: first order backward; Convergence criterion: Maximum residual 10 -4 ; Maximum number of iterations: 10; Time step: 1 / 2n, the impeller rotates 3°, n is the speed; Calculation time: 900 / n, the impeller rotates 15 times.

[0013] The homogeneous MUSIG model is selected as the bubble size model. Considering the calculation cost and calculation accuracy, 10 groups of bubbles of different sizes are used in this step, and the bubble size ranges from 0.1 mm to 10 mm.

[0014] Diameters of ten size groups d (mm) are set as follows: 0.10, 0.17, 0.28, 0.46, 0.77, 1.29, 2.15, 3.59, 5.99, 10.0. Among them, bubble size group 5 and group 6 are selected as the imported bubble size, both accounting for 50%.

[0015] Considering the complexity of the internal flow of the mixed-flow gas-liquid mixed pump, the present invention first performs steady-state calculation under single-phase pure water conditions before carrying out unsteady calculation, and then uses the steady-state result as the initial value of the two-phase unsteady calculation, so as to ensure that the initial conditions before the unsteady calculation are good, reduce the calculation divergence or result deviation caused by unreasonable initial settings, and improve the stability and reliability of the calculation. Finally, the most reasonable numerical prediction result of the gas-liquid mixed pump is obtained.

[0016] Example 1 The preparation process for the test verification is: build a visual test bench for the gas-liquid mixed pump, design a single-stage gas-liquid mixed pump, and conduct a gas-liquid two-phase test as a comparison group. In the gas-liquid two-phase working condition, the multiphase flow model is selected as the Euler-Euler heterogeneous model and the MUSIG bubble size distribution model. At the same time, the Schiller Naumann model is modified to a new resistance model that considers bubble deformation. The relevant equations and settings refer to steps 1 and 2, and the modified resistance model is implemented in the settings by writing CEL language.

[0017] When the speed of the gas-liquid mixed transport pump is 1200rpm and the inlet gas content is 5%, referring to the above steps 1-2, the implementation process is as follows: The Tomiyama model is used to modify the Schiller Naumann model to fully consider the factors of bubble deformation and size change. The resistance coefficient with a higher value calculated according to the two formulas is automatically selected as the gas-liquid phase force resistance coefficient. By selecting the larger value of the drag coefficients calculated by the two formulas as the final corrected drag coefficient, a more realistic drag coefficient can be obtained under different working conditions (such as different bubble sizes and deformation conditions).

[0018] The commercial software ANSYS CFX is used to numerically calculate the internal flow field of the gas-liquid mixed flow pump. In order to facilitate the calculation of the gas-liquid flow in the pump, the basic assumptions are as follows: (1) The flow type in the inlet pipe is bubbly flow; (2) The bubbles are set as spherical bubbles; (3) The gas and liquid flow rates in the inlet pipe are equal and evenly distributed; (4) Both the gas phase and the liquid phase are incompressible fluids; (5) The gas and liquid phases do not dissolve in each other and there is no interphase mass transfer. During the numerical calculation, the working medium is water and air, the inlet boundary condition is set to total pressure, the outlet boundary condition is set to mass flow, the impeller is a rotating domain, the inlet pipe, guide vane and outlet pipe are stationary domains, and the wall is set to a no-slip boundary.

[0019] After setting the modified resistance model in step 1 and performing numerical calculations in step 2, the error between the calculated results and the experimental results was 5.68% under the conditions of a rotation speed of 1200 rpm and an inlet air content of 5%.

[0020] Example 2 Refer to the preparation process of the test verification of Example 1: build a visual test bench for the gas-liquid mixed delivery pump, design a single-stage gas-liquid mixed delivery pump, and conduct a gas-liquid two-phase test as a comparison group.

[0021] Referring to the background parameters of Example 1, when the speed of the gas-liquid mixed transport pump is 1200 rpm and the inlet gas content is 10%, the above-mentioned steps 1-2 are implemented.

[0022] After setting the modified resistance model in step 1 and performing numerical calculations in step 2, due to the different gas content in step 2, under the conditions of a rotation speed of 1200 rpm and an inlet gas content of 10%, the error between the calculated result and the test result was 6.07%.

[0023] Example 3 Refer to the preparation process of the test verification of Example 1: build a visual test bench for the gas-liquid mixed delivery pump, design a single-stage gas-liquid mixed delivery pump, and conduct a gas-liquid two-phase test as a comparison group.

[0024] Referring to the background parameters of Example 1, when the speed of the gas-liquid mixed transport pump is 1200 rpm and the inlet gas content is 15%, the above-mentioned steps 1-2 are implemented.

[0025] The commercial software ANSYS CFX is used to numerically calculate the internal flow field of the gas-liquid mixed flow pump. In order to facilitate the calculation of the gas-liquid flow in the pump, the basic assumptions are as follows: (1) The flow type in the inlet pipe is bubbly flow; (2) The bubbles are set as spherical bubbles; (3) The gas and liquid flow rates in the inlet pipe are equal and evenly distributed; (4) Both the gas phase and the liquid phase are incompressible fluids; (5) The gas and liquid phases do not dissolve in each other and there is no interphase mass transfer. During the numerical calculation, the working medium is water and air, the inlet boundary condition is set to total pressure, the outlet boundary condition is set to mass flow, the impeller is a rotating domain, the inlet pipe, guide vane and outlet pipe are stationary domains, and the wall is set to a no-slip boundary.

[0026] After setting the modified resistance model in step 1 and performing numerical calculations in step 2, due to the different gas content in step 2, under the conditions of a rotation speed of 1200 rpm and an inlet gas content of 15%, the error between the calculated result and the test result was 6.78%.

[0027] Example 4 Refer to the preparation process of the test verification of Example 1: build a visual test bench for the gas-liquid mixed delivery pump, design a single-stage gas-liquid mixed delivery pump, and conduct a gas-liquid two-phase test as a comparison group.

[0028] Referring to the background parameters of Example 1, when the speed of the gas-liquid mixed delivery pump is 1500 rpm and the inlet gas content is 20%, the implementation process is as follows with reference to the aforementioned steps 1-2: The Tomiyama model is used to modify the Schiller Naumann model to fully consider the factors of bubble deformation and size change. The resistance coefficient with a higher value calculated according to the two formulas is automatically selected as the gas-liquid phase force resistance coefficient. By selecting the larger value of the drag coefficients calculated by the two formulas as the final corrected drag coefficient, a more realistic drag coefficient can be obtained under different working conditions (such as different bubble sizes and deformation conditions).

[0029] The commercial software ANSYS CFX is used to numerically calculate the internal flow field of the gas-liquid mixed flow pump. In order to facilitate the calculation of the gas-liquid flow in the pump, the basic assumptions are as follows: (1) The flow type in the inlet pipe is bubbly flow; (2) The bubbles are set as spherical bubbles; (3) The gas and liquid flow rates in the inlet pipe are equal and evenly distributed; (4) Both the gas phase and the liquid phase are incompressible fluids; (5) The gas and liquid phases do not dissolve in each other and there is no interphase mass transfer. During the numerical calculation, the working medium is water and air, the inlet boundary condition is set to total pressure, the outlet boundary condition is set to mass flow, the impeller is a rotating domain, the inlet pipe, guide vane and outlet pipe are stationary domains, and the wall is set to a no-slip boundary.

[0030] After setting the modified resistance model in step 1 and performing numerical calculations in step 2, due to the different gas content in step 2, under the conditions of a rotation speed of 1500 rpm and an inlet gas content of 20%, the error between the calculated result and the test result was 7.05%.

[0031] Example 5 Refer to the preparation process of the test verification of Example 1: build a visual test bench for the gas-liquid mixed delivery pump, design a single-stage gas-liquid mixed delivery pump, and conduct a gas-liquid two-phase test as a comparison group.

[0032] Referring to the background parameters of Example 1, when the speed of the gas-liquid mixed delivery pump is 1500 rpm and the inlet gas content is 25%, refer to the above steps 1-2 for implementation: The Tomiyama model is used to modify the Schiller Naumann model to fully consider the factors of bubble deformation and size change. The resistance coefficient with a higher value calculated according to the two formulas is automatically selected as the gas-liquid phase force resistance coefficient. By selecting the larger value of the drag coefficients calculated by the two formulas as the final corrected drag coefficient, a more realistic drag coefficient can be obtained under different working conditions (such as different bubble sizes and deformation conditions).

[0033] The commercial software ANSYS CFX is used to numerically calculate the internal flow field of the gas-liquid mixed flow pump. In order to facilitate the calculation of the gas-liquid flow in the pump, the basic assumptions are as follows: (1) The flow type in the inlet pipe is bubbly flow; (2) The bubbles are set as spherical bubbles; (3) The gas and liquid flow rates in the inlet pipe are equal and evenly distributed; (4) Both the gas phase and the liquid phase are incompressible fluids; (5) The gas and liquid phases do not dissolve in each other and there is no interphase mass transfer. During the numerical calculation, the working medium is water and air, the inlet boundary condition is set to total pressure, the outlet boundary condition is set to mass flow, the impeller is a rotating domain, the inlet pipe, guide vane and outlet pipe are stationary domains, and the wall is set to a no-slip boundary.

[0034] After setting the modified resistance model in step 1 and performing numerical calculations in step 2, due to the different gas content in step 2, at a speed of 1500 rpm and an inlet gas content of 25%, the error between the calculated result and the test result was 7.58%.

[0035] Example 6 Refer to the preparation process of the test verification of Example 1: build a visual test bench for the gas-liquid mixed delivery pump, design a single-stage gas-liquid mixed delivery pump, and conduct a gas-liquid two-phase test as a comparison group.

[0036] Referring to the background parameters of Example 1, when the speed of the gas-liquid mixed delivery pump is 1500 rpm and the inlet gas content is 30%, the above-mentioned steps 1-2 are implemented, and the process is as follows: The Tomiyama model is used to modify the Schiller Naumann model to fully consider the factors of bubble deformation and size change. The resistance coefficient with a higher value calculated according to the two formulas is automatically selected as the gas-liquid phase force resistance coefficient. By selecting the larger value of the drag coefficients calculated by the two formulas as the final corrected drag coefficient, a more realistic drag coefficient can be obtained under different working conditions (such as different bubble sizes and deformation conditions).

[0037] The commercial software ANSYS CFX is used to numerically calculate the internal flow field of the gas-liquid mixed flow pump. In order to facilitate the calculation of the gas-liquid flow in the pump, the basic assumptions are as follows: (1) The flow type in the inlet pipe is bubbly flow; (2) The bubbles are set as spherical bubbles; (3) The gas and liquid flow rates in the inlet pipe are equal and evenly distributed; (4) Both the gas phase and the liquid phase are incompressible fluids; (5) The gas and liquid phases do not dissolve in each other and there is no interphase mass transfer. During the numerical calculation, the working medium is water and air, the inlet boundary condition is set to total pressure, the outlet boundary condition is set to mass flow, the impeller is a rotating domain, the inlet pipe, guide vane and outlet pipe are stationary domains, and the wall is set to a no-slip boundary.

[0038] After setting the modified resistance model in step 1 and performing numerical calculations in step 2, due to the different gas content in step 2, under the conditions of a rotation speed of 1500 rpm and an inlet gas content of 30%, the error between the calculated result and the test result was 7.21%.

[0039] Only the relevant data of the aforementioned Example 1 and Example 5 are analyzed below.

[0040] Figure 1 The calculated values ​​of the modified resistance model and the pump pressure rise results (Δ P); the error between the calculated results and the test results is expressed in numbers, which represent the relative error between the calculated value and the test value of the modified resistance model. The calculation results of the Schiller Naumann model at 1500 rpm are also given. The change law of the pump pressure rise curve predicted by numerical calculation is basically consistent with the test results. With the increase of the inlet gas content, the pump pressure rise value decreases.

[0041] In particular, when the inlet gas content increases from 5% to 15%, the pump pressure rise drops sharply, which is called surge phenomenon. Before and after this phenomenon, the internal flow conditions of the gas-liquid mixed flow pump are quite different. Before the surge phenomenon occurs, the pump pressure rise drops less than that of the single-phase pure water condition, and the internal flow field is close to that of the single-phase pure water condition; after the surge phenomenon occurs, the internal flow is extremely complex, and the influence of gas plays a dominant role, causing the pressure rise of the gas-liquid mixed flow pump to drop sharply to 50% of the pump pressure rise under the single-phase pure water condition. The more complex the internal flow of the gas-liquid mixed flow pump, the greater the numerical calculation error. Before the surge phenomenon occurs, the error is basically around 5%, while after the surge phenomenon occurs, the error increases to 6% to 10%. Considering the complexity of the gas-liquid flow behavior in the gas-liquid mixed flow pump, the error is acceptable, so the numerical prediction method under gas-liquid two-phase conditions has been experimentally verified.

[0042] In order to further verify the accuracy of the numerical prediction method under gas-liquid two-phase conditions, the gas phase distribution cloud map calculated numerically considering the modified resistance model was compared with the gas phase distribution picture taken by the high-speed camera during the test. Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 Compared with the gas phase distribution image, the numerical calculation also predicts the air mass and air pockets in the guide vane of the gas-liquid mixed pump and the air-entrapped blade tip leakage vortex in the impeller. However, the shape and distribution position of the air pockets are slightly deviated, see Figure 2 and Figure 5 As shown, SS and PS represent the suction side and pressure side of the blade respectively.

[0043] When the inlet gas content is 5% (corresponding to Figure 2 , Figure 3 , Figure 4 , before the surge phenomenon occurs), the impeller and guide vane flow channel of the gas-liquid mixed flow pump is a water-gas mixture, and some small air pockets appear near the suction surface of the guide vane blade; the gas content cloud map at the height of the pump half blade also shows that the gas gathers on the suction surface of the guide vane blade. Combined with the gas volume fraction isosurface, the spatial distribution of the air pockets can be observed, and the position is basically consistent with the photographed picture. However, the numerical calculation prediction results underestimate the shape of the air pockets and the distribution of the water-gas mixture, which causes the pressure rise value of the pump to be higher than the experimental value ( Figure 1 ).

[0044] When the inlet gas content increases to 25% (corresponding to Figure 5 , Figure 6 , Figure 7 After the surge phenomenon occurs, the size and number of air pockets in the guide vanes of the gas-liquid mixed flow pump increase significantly, accompanied by more severe air-entrapped blade tip leakage vortices. Under this condition, there is a slight deviation between the numerically calculated gas phase distribution and the test photos, resulting in an error of about 8% between the calculated pump pressure rise and the test value. In short, the numerical prediction method for gas-liquid two-phase working conditions can accurately predict the performance and gas phase distribution characteristics of the gas-liquid mixed flow pump at low and high gas content.

[0045] In summary, after the numerical prediction method of the gas-liquid mixed flow pump of the present invention takes into account the deformation and size change of bubbles, the error between the calculated pressure rise of the gas-liquid mixed flow pump and the test result under the gas-liquid two-phase working condition is within 10%, and the gas phase distribution in the pump is basically consistent with the test image, which improves the performance prediction accuracy of the gas-liquid mixed flow pump under low and high gas content rates, and fully proves that the method of the present invention is feasible and effective.

Claims

1. A numerical prediction method for a gas-liquid mixed flow pump considering bubble deformation and size change, characterized in that: Follow these steps to implement: Step 1: Establish a drag coefficient model and calculate the corrected drag coefficient; Step 2: Set up the numerical simulation calculation scheme, first perform numerical calculation on the internal flow field of the gas-liquid mixed flow pump, set relevant conditions, determine the bubble size model, and obtain the numerical prediction results of the gas-liquid mixed flow pump.

2. The numerical prediction method for a gas-liquid mixed flow pump considering bubble deformation and size change according to claim 1 is characterized in that: In step 1, the specific process is: The resistance coefficient model used is to give multiple groups of bubble diameters in the bubble size model to simulate the bubble aggregation and breakup behavior in the gas-liquid mixed delivery pump. As the bubble deforms, the resistance coefficient changes with the change of bubble diameter. The Schiller Naumann model is derived for a single bubble and cannot consider the influence of bubble diameter change. Therefore, this step uses the Tomiyama model to correct the Schiller Naumann model to fully consider the factors of bubble deformation and size change. The resistance coefficient calculated according to the two formulas automatically selects the resistance coefficient with a higher value as the gas-liquid phase force resistance coefficient. The final expression of the corrected resistance coefficient is as follows: （3） （4） （5） （6） （7） In various To correct the drag coefficient; To calculate the drag coefficient expression based on the Tomiyama model; To calculate the drag coefficient expression based on the Schiller-Naumann model; ρ l and ρ g are the density of liquid and the density of gas respectively; Eo is the ratio of gravity to surface tension; N i For the i The number of bubbles in the group; d b is the Sauter mean bubble diameter, in mm; d i is the diameter of the ith bubble.

3. The numerical prediction method for a gas-liquid mixed flow pump considering bubble deformation and size change according to claim 1 is characterized in that: In step 2, the software ANSYS CFX is used to perform numerical calculations on the internal flow field of the gas-liquid mixed flow pump. The basic assumptions are as follows: (1) The flow pattern in the inlet pipe is bubbly flow; (2) The bubbles are set to spherical bubbles; (3) The gas and liquid flow rates in the inlet pipe are equal and evenly distributed; (4) Both the gas phase and the liquid phase are incompressible fluids; (5) The gas and liquid phases do not dissolve in each other, and there is no interphase mass transfer. In numerical calculations, the working media are water and air, the inlet boundary condition is set to total pressure, the outlet boundary condition is set to mass flow, the impeller is a rotating domain, the inlet pipe, guide vane and outlet pipe are stationary domains, and the wall is set to a no-slip boundary.

4. The numerical prediction method for a gas-liquid mixed flow pump considering bubble deformation and size change according to claim 1, characterized in that: In step 2, the specific settings are as follows: Working medium: liquid phase is water, gas phase is air, air temperature is 25 degrees Celsius; Inlet boundary conditions: total pressure, inlet gas fraction IGVF, bubble size distribution; Outlet boundary conditions: gas-liquid mixed phase mass flow rate; Turbulence model: Liquid phase is SST Turbulence model, gas phase is a dispersed phase zero equation model; Surface tension coefficient: 0.072N / m; Resistance model: Modified Schiller Naumann model; Lift model: Legendre Magnaudet model; Virtual mass force model: coefficient is 0.5; Bubble breakup model: Lou and Svendsen model; Bubble coalescence model: Prince and Blanch model; Dynamic and static interface: Teansient Rotor stator; Discrete format of convection term: High solution; Turbulence term discretization format: first order; Time term discrete format: first order backward; Convergence criterion: Maximum residual 10 -4 ; Maximum number of iterations: 10; Time step: 1 / 2n, the impeller rotates 3°, n is the speed; Calculation time: 900 / n, the impeller rotates 15 times.

5. The numerical prediction method for a gas-liquid mixed flow pump considering bubble deformation and size change according to claim 1, characterized in that: In step 2, the bubble size model selects the homogeneous MUSIG model.

6. The numerical prediction method for a gas-liquid mixed flow pump considering bubble deformation and size change according to claim 1, characterized in that: In step 2, when the homogeneous MUSIG model is used, 10 groups of bubbles of different sizes are used to optimize the model.

7. The numerical prediction method for a gas-liquid mixed flow pump considering bubble deformation and size change according to claim 6, characterized in that: The bubble size range is 0.1mm~10mm.

8. The method for numerical prediction of a gas-liquid mixed flow pump considering bubble deformation and size change according to claim 1, characterized in that: In step 2, considering the complexity of the internal flow of the mixed-flow gas-liquid mixed flow pump, this step first performs a steady-state calculation under single-phase pure water conditions before carrying out unsteady calculations, and then uses the steady-state results as the initial values ​​of the two-phase unsteady calculations to facilitate subsequent calculations, and finally obtain the numerical prediction results of the gas-liquid mixed flow pump.

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