Internal flow gap design method for thermal control mechanical pump

Abstract

A thermal control mechanical pump internal flow clearance design method comprises the steps that firstly, initial values of all clearances in a mechanical pump are set, then a full-basin simulation calculation model of a mechanical pump rotor is established to carry out CFD simulation calculation, and pressure distribution, temperature distribution and cooling flow of cooling fluid in the mechanical pump at all positions of a cooling flow channel and axial force borne by a bearing are obtained; and then the fatigue life and the abrasion life of the bearing, the operation efficiency of the mechanical pump and the supercooling degree of the working medium on the leeside of the rear bearing are sequentially compared with design requirements, and the final gap design is completed by continuously adjusting all gap values. According to the mechanical pump, fine control over cooling flow and pressure distribution is achieved through clearance control over the cooling flow channels in the pump, the efficient cavitation resistance of the mechanical pump can be ensured, and the reliability of the mechanical pump is improved.

Description

Technical Field

[0001] This invention belongs to the field of aerospace thermal control technology and relates to a mechanical pump used in the thermal control pump drive fluid circuit of a spacecraft. Background Technology

[0002] To meet the application requirements of high power, high heat flux density, and long-distance heat transport in future space missions, pump-driven fluid loop systems have unique technological advantages. The mechanical pump (hereinafter referred to as the mechanical pump) in the pump-driven fluid loop is the core component of the spacecraft thermal control pump-driven fluid loop and the only high-speed moving device, providing driving force for the flow of the working fluid and possessing a certain degree of cavitation resistance.

[0003] Based on the current development of mechanical pump products or prototypes in various countries around the world, the overall characteristics of mechanical pumps can be summarized as follows: 1) In terms of overall structure and rotary seal treatment, to ensure safety, reliability and maintenance-free operation, a leak-free pump structure with magnetic drive or shielded structure is adopted. 2) Due to the shielded structure, the motor rotor is completely immersed in the working fluid. On the one hand, the heat of the motor needs to be dissipated through heat exchange via convection of the working fluid. On the other hand, the working fluid acts as a lubricating medium to provide auxiliary lubrication for the bearings. 3) In terms of impeller and related flow-through component structure, considering the adaptability to small flow and high head and the cavitation problem, a composite impeller structure with a combination of long and short blades is generally adopted, and an inducer is used in some cases to improve the cavitation resistance.

[0004] Since mechanical pumps are all canned motor pumps, their entire rotor shaft is immersed in the working fluid. A portion of the pump's flow enters the shaft system along the impeller back clearance, providing auxiliary lubrication for the bearings and carrying away the heat generated by the motor. This cooling flow returns from inside the shaft to the impeller inlet, forming a cycle. The cooling flow must at least meet the motor's heat dissipation requirements to prevent the motor temperature from becoming too high; at the same time, the temperature rise from the cooling flow should not be too high, otherwise the working fluid used in the mechanical pump is prone to cavitation at the lower bearing. However, the cooling flow should also not be too large, as this portion of the cooling flow is actually an internal circulation within the pump and does not perform external work. Excessive flow will lead to problems such as decreased pump efficiency and increased axial force. Therefore, precise control of the internal cooling flow and pressure distribution of the mechanical pump is necessary.

[0005] During on-orbit operation, there have been several cases of mechanical pumps failing due to improper internal flow design. On July 31, 2010, a power control unit on the International Space Station shut down during a high-current surge, causing the mechanical pump in the main circuit to stop. The problem was identified as follows: the cooling fluid inside the pump motor had only one drain hole at the rear bearing, and the cooling fluid jetted through this hole onto the shaft. Analysis revealed that at 12,500 rpm, the radial imbalance force caused by this jet exceeded the radial bearing capacity, ultimately leading to bearing wear and failure.

[0006] Another example is the mechanical pump used in AMS02, launched and put into orbit in 2011. The pump's bearings were initially designed for long lifespan, using sliding bearings. After the journal of the sliding bearing rotates at high speed, the internal working fluid creates dynamic pressure, supporting the journal. However, after four years of operation in orbit, due to coating degradation leading to insufficient supercooling of the inlet working fluid, the local pressure of the liquid inside the sliding bearing fell below the saturated vapor pressure, causing cavitation. This prevented the formation of a stable liquid film within the sliding bearing, resulting in wear and failure of the bearing's moving and stationary rings. Summary of the Invention

[0007] The technical problem solved by this invention is: to address the issue of precise control of cooling flow rate and pressure distribution inside a mechanical pump, a design method for the internal flow clearance of a mechanical pump is proposed. By designing the internal flow channel and shaft clearance, precise control of cooling flow rate and internal pressure distribution can be achieved, thereby improving the operating efficiency and cavitation resistance of the mechanical pump and ensuring the reliable and stable operation of the mechanical pump and the pump-driven fluid circuit system.

[0008] The technical solution of this invention is: a method for designing the internal flow clearance of a thermally controlled mechanical pump, comprising the following steps: (1) Set the clearance between the inner blades of the mechanical pump stator-rotor gap Shaft end clearance Reflux orifice diameter jet orifice diameter and jet orifice angle The initial value; (2) Establish a full-domain simulation calculation model of the mechanical pump rotor; (3) Use the model to perform computational fluid dynamics simulation to obtain the pressure distribution, temperature distribution, cooling flow rate, and axial force on the bearing of the cooling fluid in the cooling channel of the mechanical pump. (4) Check whether the bearing fatigue life and wear life meet the requirements based on the axial force on the bearing. If they meet the requirements, proceed to step (5); if they do not meet the requirements, return to step (1) to adjust the initial values ​​until the bearing fatigue life and wear life meet the requirements. (5) Analyze whether the mechanical pump operating efficiency meets the requirements based on the cooling flow rate. If it does, proceed to step (6); if it does not, return to step (1) to adjust the initial value until the mechanical pump operating efficiency meets the requirements. (6) Analyze the subcooling of the working fluid at the leeward side of the rear bearing based on the pressure and temperature at the leeward side of the rear bearing. If the requirements are met, the clearance design is complete; otherwise, return to step (1) to adjust the initial value until the working fluid subcooling at the leeward side of the rear bearing is reached. The requirements are met.

[0009] Preferably, the blade back gap The design value range is 0.5~2mm, and the stator-rotor gap is... The design value range is 0.2~2mm, shaft end clearance. The design value range is 0.5~3mm, and the reflux orifice diameter is... The design value range is 1~2mm, and the jet orifice diameter is... The design value range is 0.5~1mm, and the jet orifice angle is... The design value range is 30°~60°.

[0010] Furthermore, the method for obtaining the axial force on the bearing is as follows: taking the impeller, guide cap, and shaft as the analysis objects, the force exerted by the fluid on each component is calculated by the fluid pressure acting on the surface of each component. The component of this force along the axial direction of the shaft is the axial force exerted by the fluid on the component. The axial forces exerted on each component are combined to obtain the axial force exerted on the impeller, guide cap, and shaft as a whole. The axial force exerted on the whole is finally applied to the bearing and is the axial force exerted on the bearing.

[0011] Furthermore, in step (4), if returning to step (1), the corresponding adjustment method is: reduce the impeller back clearance. To reduce axial force or reduce impeller back clearance. To reduce axial force, the bearing diameter is increased to increase the bearing's load-bearing capacity.

[0012] Furthermore, in step (5), if returning to step (1), the corresponding adjustment method is: adjust the diameter of the return hole. and jet orifice diameter This increases the pressure drop of the leaking fluid as it passes through the return hole, thus reducing the leakage amount.

[0013] Preferably, the cooling flow rate is when the total flow rate is... At that time, the cooling flow rate is taken as the total flow rate. And when the total flow At that time, the cooling flow rate is taken as the total flow rate. .

[0014] Furthermore, the subcooling of the working fluid at the leeward side of the rear bearing... Specifically ,in The temperature at the leeward side of the rear bearing. The pressure at the leeward side of the rear bearing was obtained by consulting the working fluid property handbook. The corresponding saturation temperature of the working fluid.

[0015] Preferably, the working fluid subcooling at the leeward side of the rear bearing... ,satisfy Celsius.

[0016] Furthermore, in step (6), if returning to step (1), the corresponding adjustment method is: increase the stator-rotor gap. Or reduce the shaft end clearance. .

[0017] Preferably, the verification of bearing fatigue life and wear life is performed using the LP equation or the ANSI equation.

[0018] The advantages of this invention compared to the prior art are: 1) Existing designs for the internal flow clearance of thermally controlled mechanical pumps primarily rely on the designer's personal experience to select parameter values, lacking quantitative design calculation criteria for the internal flow clearance, thus failing to achieve precise control over cooling leakage and pressure distribution. The internal flow clearance design method proposed in this invention establishes a quantitative correlation between the leakage channel clearance distribution and pressure drop distribution, resulting in more accurate and standardized design results.

[0019] 2) Existing thermally controlled mechanical pump internal flow clearance designs lack control and evaluation of bearing cavitation resistance. The internal flow clearance design method proposed in this invention provides a criterion for determining the cavitation resistance margin of the bearing based on the pressure and temperature values ​​of the working fluid at the leeward side of the rear bearing, thereby enabling the clearance design results to effectively control the bearing's cavitation resistance.

[0020] 3) This invention provides a standard process for iterative design of internal flow gaps, which is applicable to the design calculation of internal flow gaps of thermally controlled mechanical pumps of different specifications and has broad engineering application value. Attached Figure Description

[0021] Figure 1 is a schematic diagram of the mechanical pump structure, where Figure 1(a) shows the internal structure and Figure 1(b) shows the external structure; in the figure, 1 is the pump inlet, 2 is the volute, 3 is the guide cap, 4 is the jet hole, 5 is the impeller, 6 is the bearing cover, 7 is the adjusting ring, 8 is the front bearing, 9 is the rotating shaft, 10 is the stator, 11 is the rear bearing, 12 is the return hole, and 13 is the pump outlet; Figure 2 This is a schematic diagram of the cooling flow path inside a mechanical pump. Figure 3 Schematic diagram of the critical clearance in the cooling channel of a mechanical pump; Figure 4 for Figure 3 A magnified view of a portion of the image; Figure 5 This is a schematic diagram of the pressure drop along the cooling flow path. Figure 6This is a flowchart of the method of the present invention; Figure 7 This is a schematic diagram of the internal flow clearance design of the mechanical pump in an embodiment of the present invention; Figure 8 This is a schematic diagram of a global computational model with cooling channels in an embodiment of the present invention; Figure 9 This is a schematic diagram of the pressure distribution within the cooling channel in an embodiment of the present invention. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the accompanying drawings.

[0023] I. Cooling Channel Design and Optimization Target Parameters The internal and external structures of the mechanical pump and the cooling flow path inside the pump are shown in Figures 1(a), (b), and 1, respectively. Figure 2 As shown, the mechanical pump mainly consists of a volute 2, a guide cap 3, an impeller 5, a bearing cover 6, an adjusting ring 7, a front bearing 8, a rotating shaft 9, a stator 10, and a rear bearing 11. The liquid working fluid enters the mechanical pump through the pump inlet 1, is pressurized by the rotation of the impeller 5, and most of the working fluid flows out from the impeller 5 outlet to the pump outlet 13. The remaining working fluid, which is the cooling fluid, flows through the back of the impeller 5, the stator-rotor gap, the shaft end gap, and the return hole 12, finally returning to the inlet of the mechanical pump impeller 2 through the jet hole 4 of the guide cap 3, mixing into the main flow area, completing the cooling flow process for motor cooling and bearing lubrication.

[0024] 1. Design input parameters Design input parameters include: rated flow rate of the mechanical pump. , Yangcheng m; rotational speed rpm; motor heat generation W; working fluid density , .

[0025] 2. Optimize design parameters Optimized design parameters include: internal flow clearances at various points within the pump, such as... Figure 3 , Figure 4 As shown, including the blade back gap stator-rotor gap Shaft end clearance Reflux orifice diameter and jet orifice diameter All units are in mm.

[0026] 3. Optimize target parameters Optimization target parameters include: cooling flow rate , Pressure on the leeward side of the rear bearing ,Pa.

[0027] Design parameters are the design parameters that need to be iteratively adjusted during the internal flow clearance design process, while target parameters are the objectives of the iterative design and are used to evaluate whether the design results meet the requirements during the iterative design process.

[0028] II. Cooling Flow Control Method Cooling flow Pressure difference between the inlet and outlet of the cooling channel and resistance Decide:

[0029] In the formula, Pa The pressure at the inlet of the cooling channel (i.e., the outlet of the pump impeller) This refers to the pressure at the outlet of the cooling channel (i.e., at the inlet of the pump impeller). The drag coefficient is expressed in units of... . It is the acceleration due to gravity. .

[0030] drag coefficient The resistance is determined by the gaps at various points in the cooling channel. By controlling the size of these gaps, the pressure drop at each point can be controlled, thereby controlling the resistance. (Resistance coefficient) Obtained through numerical simulation calculations. For example... Figure 5 The diagram shows the pressure drop along the cooling flow path. The cooling medium flows from the impeller outlet, passing through the blade back clearance. stator-rotor gap Shaft end clearance Reflux orifice diameter and jet orifice diameter Afterwards, the pressure decreased to , , , , The pressure drop in each section is as follows: , , , , The pressure drop in each section is affected by... , , , as well as The direct impact is that the pressure drop is negatively correlated with the clearance.

[0031] The selection principle for each gap is as follows: 1. Too small, will lead to Too large; on the contrary, when When it is too big, The reduction in bearing life leads to an increase in the axial force of the impeller, which has an adverse effect on bearing life. 2. Too small, will lead to Too large; on the contrary, when When it is too big, This reduction leads to a decrease in the magnetic transmission efficiency of the stator and rotor, and an increase in motor losses. 3. At the shaft end clearance, the cooling medium undergoes a convex-contractor throttling process, resulting in a significant pressure drop. 4. Reflux orifice diameter If it is too small, it cannot be processed; if it is too large, it will affect the strength of the shaft. 5. Jet orifice diameter At this point, the cooling working fluid forms a jet, resulting in a significant pressure drop.

[0032] Pressure reduction is underway at various locations. , , The proportion is relatively large. and The proportion is relatively small.

[0033] After design, cooling flow rate The objective is:

[0034]

[0035] Total flow At that time, the cooling flow rate is taken as the total flow rate. And when the total flow At this time, the cooling flow rate can be appropriately increased to a certain percentage of the total flow rate. .

[0036] III. Rear Bearing Backwind Side Pressure Control Method The cooling medium inside the mechanical pump absorbs heat and its temperature rises after passing through the motor. At the same time, the pressure drops due to flow resistance. Therefore, the design must ensure that cavitation does not occur at the bearing.

[0037] The mechanical pump's internal bearing consists of a front bearing and a rear bearing. The most demanding operating conditions are found on the leeward side of the rear bearing; ensuring no cavitation occurs in this area will prevent cavitation in the front bearing as well. The pressure on the leeward side of the rear bearing is... Through the working fluid pressure at this location You can consult the working fluid property handbook to obtain the saturated vapor pressure of the working fluid at this pressure. .

[0038] Temperature of the working fluid on the leeward side of the rear bearing for:

[0039] In the formula, The temperature of the working fluid at the inlet of the cooling channel is ℃. The specific heat capacity of the working fluid, .

[0040] supercooling for: , ℃.

[0041] To ensure that cavitation does not occur at the bearing and that there is sufficient margin, the following must be met: .

[0042] because ,therefore by and The direct impact, The proportion is relatively large, therefore in the process During the design phase, the bearing's axial force should be maximized as much as possible while ensuring that the bearing's axial force meets the tolerance range. To increase This is to ensure that the bearing does not cavitate.

[0043] IV. Jet Orifice Design At the outlet of the cooling channel, the cooling medium forms a jet through the jet orifice and mixes into the mainstream region. The design of the jet orifice must follow the following principles: 1. There must be at least two jet holes, not just one, and they must be evenly distributed circumferentially. The jet will generate a reaction force on the rotating shaft. If there is only one jet hole or it is not evenly distributed, it may cause an imbalance of radial force on the rotating shaft, leading to accelerated bearing failure. 2. Angle between the centerline of the jet orifice and the centerline of the rotating shaft It should be 30°~60°. Angles such as Figure 4 As shown, if the angle is too small, it is not conducive to processing and will increase the length of the shaft; if it is too large, the jet will have too much impact on the mainstream area and will be detrimental to the flow at the pump inlet.

[0044] V. Design Process Based on the above-mentioned cooling flow rate and pressure distribution control methods, this invention proposes the entire design process for the internal flow gap, as follows: Figure 6 As shown.

[0045] 1. Based on the empirical parameter range, initially set the internal flow clearance values ​​at various points inside the pump.

[0046] The following are the empirical values ​​for the design parameters: blade back clearance (0.5~2mm) Stator-rotor gap (0.2~2mm) Shaft end clearance (0.5~3mm), reflux hole diameter (1~2mm) and jet orifice diameter (0.5~1mm) and jet orifice angle (30°~60°). The empirical parameter values ​​can be adjusted appropriately according to the actual pump operating flow range, but they should not be too small, as this would place too high demands on product processing and assembly, which would be detrimental to product realization.

[0047] 2. Establish a full-domain simulation model of the pump rotor. This model includes the pump inlet flow channel, pump outlet flow channel, impeller, impeller back, flow channel between stator and rotor, return flow hole inside the shaft, jet hole, etc. The schematic diagram of the calculation model is shown below. Figure 3 As shown.

[0048] Considering the computational complexity, the calculation model is simplified, including: the bearing is simplified to an annular throttling area based on the actual flow area, that is, the area between the inner and outer rings of the bearing minus the cross-sectional area of ​​the ball is equivalent to an annular flow area.

[0049] 3. Perform CFD (Computational Fluid Dynamics) simulations to obtain the flow state at various points within the cooling channels, including the pressure and velocity distribution of the cooling fluid. The cooling flow rate can also be calculated based on the simulation results. In the CFD simulation, the impeller, guide cap, and shaft are used as the analysis objects. By analyzing the fluid pressure acting on the surfaces of each component, the force exerted by the fluid on each component can be calculated. The axial component of this force along the shaft is the axial force exerted by the fluid on the component. The axial forces acting on each component are then combined to obtain the axial force acting on the entire rotor (impeller, guide cap, and shaft). This axial force ultimately acts on the bearings.

[0050] 4. Based on the axial force acting on the bearing, check whether the bearing fatigue life and wear life meet the requirements. If they do, proceed to the next step; if not, reduce the impeller back clearance. To reduce axial force. If reducing the impeller back clearance still does not meet the bearing life requirements, the bearing diameter can be increased to increase the bearing's load-bearing capacity until the bearing life meets the requirements. However, it should be noted that reducing the impeller back clearance will also reduce leakage; the impeller back clearance should not be too small to ensure assembly manufacturability.

[0051] The assessment of bearing fatigue life and wear life can be based on the national standards GB / T 24607-2009 "Rolling Bearings - Life and Reliability Testing and Evaluation" and GB / T 6391-2010 "Rolling Bearings - Rated Dynamic Load and Rated Life". Both standards provide widely used life calculation formulas for bearing life and reliability verification and assessment.

[0052] 5. Based on cooling flow rate Analyze the size of the cooling flow rate to determine if the overall pump efficiency meets the requirements. Excessive cooling flow will lead to low pump efficiency. If the cooling flow rate is sufficient, proceed to the next step; otherwise, adjust the diameter of the return flow orifice. and jet orifice diameter This increases the pressure drop of the leaking fluid as it passes through the return hole, thus reducing the leakage amount.

[0053] The cooling flow rate criterion is: when the total flow rate... At that time, cooling flow rate Take the total flow And when the total flow At this time, the cooling flow rate can be appropriately increased to a certain percentage of the total flow rate. .

[0054] 6. Cooling fluid passes through the blade back gap. and stator-rotor clearance Afterwards, the fluid pressure decreased to... and That is, the fluid pressure at the leeward side of the rear bearing decreases to By consulting the working fluid property handbook, the saturated vapor pressure of the working fluid at this pressure is obtained as follows: The temperature of the fluid at the leeward side of the rear bearing, obtained from CFD calculations, is... Thus, the subcooling degree of the fluid at that location is obtained as follows: ( Analysis of the subcooling of the working fluid on the leeward side of the bearing. Does it meet the requirements? For example, subcooling? Insufficient cooling will lead to the risk of cavitation at the bearing and undercooling. The temperature should not be less than 3℃. If this requirement is not met, the stator-rotor clearance should be increased appropriately. Reduce shaft end clearance The adjustment criteria are: ensuring cooling flow rate. While ensuring the size meets requirements, minimize the pressure drop at the blade back as much as possible. Voltage drop between stator and rotor This results in undercooling of the working fluid at the bearing. It is high enough to ensure the safe operation of the bearing.

[0055] 7. If the bearing is undercooled If the requirements are met, the subsequent verification of the rotor critical speed and strength can continue, and the entire design work of the internal flow clearance is completed.

[0056] Example This example uses a mechanical pump with a rated flow rate of 20 L / h and a head of 8 m to illustrate how the internal flow clearance design method is specifically implemented.

[0057] I. Impeller Design Before carrying out the internal flow clearance design, based on the classic design theory of centrifugal pumps and according to the hydraulic performance requirements in the mechanical pump design parameters, the hydraulic design including the impeller and volute was completed, including the number of impeller blades, impeller inlet and outlet installation angles, blade tip clearance, impeller diameter, etc.; the main parameter design of the volute flow channel (including volute profile, throat diameter, etc.) was completed.

[0058] Table 1 Main Design Parameters of the Impeller

[0059] II. Setting the internal flow gap like Figure 7 As shown, initial values ​​are selected for each gap based on empirical parameter ranges. The iterative calculation process is omitted here, and the final optimized gap values ​​are given. , , , , .

[0060] like Figure 8 As shown, a global 3D mesh model of the impeller and cooling channels was established with a total mesh size of 9.17 million. Axial force and leakage were calculated. The impeller region was configured as follows: the impeller fluid domain rotated, while the blades and impeller hub surface were stationary relative to the fluid domain. The cooling channel fluid domain was set to non-rotating, while the blade back surface and shaft wall were set as rotating walls at a rotation speed of 11,000 rpm. The walls were designed as no-slip walls, and an enhanced wall function was used near the wall. The SIMPLEC algorithm was used to solve the pressure-velocity coupling equations. The convection terms of the momentum, turbulent kinetic energy, and turbulent dissipation rate equations were discretized using a second-order upwind scheme.

[0061] III. Bearing Fatigue Life Verification The axial force consists of two parts: the axial force between the impeller and the guide cap, and the axial force of the shaft. Simulation results show that under rated operating conditions, the axial force between the impeller and the guide cap is 38 N, the axial force of the shaft is -48.3 N, and the resultant force is -10.3 N, directed towards the impeller inlet. The radial force of the impeller, calculated, is 0.0115 N.

[0062] National standards GB / T 24607-2009 "Rolling Bearings - Life and Reliability Testing and Evaluation" and GB / T 6391-2010 "Rolling Bearings - Rated Dynamic Load and Rated Life" provide widely used life calculation formulas (LP equations) for bearing life and reliability verification and evaluation.

[0063] With the development of bearing manufacturing technology, ISO proposed a modified rolling bearing life calculation equation based on L10 (ANSI equation):

[0064] P r —Equivalent dynamic load, for ball bearings In the formula For the axial load of the bearing, For radial load, X and Y are the radial load and axial load coefficients, respectively. These coefficients are related to the contact angle and the axial relative load coefficient, which can be found in the table. , .

[0065] According to the above formula, the fatigue life of the bearing is calculated. The front bearing is calculated as a single bearing. The calculation results show that when the axial force is controlled below 10.3N and the radial force is below 0.0115N, the bearing life can meet the requirement of 5 years of use.

[0066] IV. Pressure Drop Distribution and Leakage Cooling channel pressure distribution as follows Figure 9 As shown in Tables 2 and 3, the pressure distribution at various points and the pressure drop percentage of each section are presented. It can be seen that the pressure drop across the entire cooling channel is 82 kPa, or 6.9 m, approximately equal to the pressure drop at the impeller inlet and outlet. The cooling channel pressure drop consists of five sections, including the pressure drop on the back of the blades. and reflux inlet pressure drop It occupies a dominant position.

[0067] Cooling leakage The flow rate is 0.00258 kg / s, or 7.7 L / h, accounting for a certain percentage of the total flow rate. 36% of the target is met, satisfying the design requirements.

[0068] The motor has a rated shaft power of 1.38W, and the total power consumption of the motor and control system is approximately 7.3W. The heat loss of the motor mainly includes: core loss, armature copper loss, wind friction and stray loss, and housing eddy current loss, totaling approximately 2W.

[0069] The working fluid temperature at the inlet of the cooling channel is 20℃. What is the specific heat capacity of R22 at 20℃? J / (kg·K), density =1210 kg / m 3 Therefore, after passing through the motor, the temperature of the cooling medium is:

[0070] The pressure at the rear bearing leeward side is Corresponding saturation temperature Therefore, supercooling for:

[0071] The working fluid at the bearing reaches a subcooling of 7.9℃, which ensures safe operation.

[0072] Table 2 Pressure values ​​at various points in the cooling channel

[0073] Table 3 Pressure drop distribution and percentage of each section of the cooling channel

[0074] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for designing the internal flow clearance of a thermally controlled mechanical pump, characterized in that: Includes the following steps: (1) Set the clearance between the inner blades of the mechanical pump stator-rotor gap Shaft end clearance Reflux orifice diameter jet orifice diameter and jet orifice angle The initial value; (2) Establish a full-domain simulation calculation model of the mechanical pump rotor; (3) Use the model to perform computational fluid dynamics simulation to obtain the pressure distribution, temperature distribution, cooling flow rate, and axial force on the bearing of the cooling fluid in the cooling channel of the mechanical pump. (4) Check whether the bearing fatigue life and wear life meet the requirements based on the axial force on the bearing. If they meet the requirements, proceed to step (5); if they do not meet the requirements, return to step (1) to adjust the initial values ​​until the bearing fatigue life and wear life meet the requirements. (5) Analyze whether the mechanical pump operating efficiency meets the requirements based on the cooling flow rate. If it does, proceed to step (6); if it does not, return to step (1) to adjust the initial value until the mechanical pump operating efficiency meets the requirements. (6) Analyze the subcooling of the working fluid at the leeward side of the rear bearing based on the pressure and temperature at the leeward side of the rear bearing. If the requirements are met, the clearance design is complete; otherwise, return to step (1) to adjust the initial value until the working fluid subcooling at the leeward side of the rear bearing is reached. The requirements are met.

2. The method for designing the internal flow clearance of a thermally controlled mechanical pump according to claim 1, characterized in that: The blade back gap The design value range is 0.5~2mm, and the stator-rotor gap is... The design value range is 0.2~2mm, shaft end clearance. The design value range is 0.5~3mm, and the reflux orifice diameter is... The design value range is 1~2mm, and the jet orifice diameter is... The design value range is 0.5~1mm, and the jet orifice angle is... The design value range is 30°~60°.

3. The method for designing the internal flow clearance of a thermally controlled mechanical pump according to claim 1, characterized in that: The method for obtaining the axial force on the bearing is as follows: taking the impeller, guide cap, and shaft as the analysis objects, the force exerted by the fluid on each component is calculated by the fluid pressure acting on the surface of each component. The component of this force along the axial direction of the shaft is the axial force exerted by the fluid on the component. The axial forces exerted on each component are combined to obtain the axial force exerted on the impeller, guide cap, and shaft as a whole. The axial force exerted on the whole is finally applied to the bearing and is the axial force exerted on the bearing.

4. The method for designing the internal flow clearance of a thermally controlled mechanical pump according to claim 1, characterized in that: In step (4), if returning to step (1), the corresponding adjustment method is: reduce the impeller back clearance. To reduce axial force or reduce impeller back clearance. To reduce axial force, the bearing diameter is increased to increase the bearing's load-bearing capacity.

5. The method for designing the internal flow clearance of a thermally controlled mechanical pump according to claim 1, characterized in that: In step (5), if returning to step (1), the corresponding adjustment method is: adjust the diameter of the return hole. and jet orifice diameter This increases the pressure drop of the leaking fluid as it passes through the return hole, thus reducing the leakage amount.

6. The method for designing the internal flow clearance of a thermally controlled mechanical pump according to claim 1, characterized in that: The cooling flow rate, when the total flow rate At that time, the cooling flow rate is taken as the total flow rate. And when the total flow At that time, the cooling flow rate is taken as the total flow rate. .

7. The method for designing the internal flow clearance of a thermally controlled mechanical pump according to claim 1, characterized in that: The working fluid subcooling at the leeward side of the rear bearing Specifically ,in The temperature at the leeward side of the rear bearing. The pressure at the leeward side of the rear bearing was obtained by consulting the working fluid property handbook. The corresponding saturation temperature of the working fluid.

8. The method for designing the internal flow clearance of a thermally controlled mechanical pump according to claim 7, characterized in that: The working fluid subcooling at the leeward side of the rear bearing ,satisfy Celsius.

9. The method for designing the internal flow clearance of a thermally controlled mechanical pump according to claim 1, characterized in that: In step (6), if returning to step (1), the corresponding adjustment method is: increase the stator-rotor gap. Or reduce the shaft end clearance. .

10. The method for designing the internal flow clearance of a thermally controlled mechanical pump according to claim 1, characterized in that: The verification of bearing fatigue life and wear life is performed using the LP equation or the ANSI equation.

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