Virtual-real combined bearing dynamic thermal resistance measuring method

Abstract

The invention discloses a virtuality and reality combined bearing dynamic thermal resistance measuring method which comprises the following steps: an experiment part: electrifying until the temperature is constant, recording the temperature of an inner ring surface and an outer ring surface of a bearing, and calculating the static radial thermal resistance of the bearing according to a formula # imgabs0 # by the power shown by a metering socket; in the simulation part, the geometric model of the bearing is simplified, and a multiphase flow simulation model for bearing lubrication and heat transfer is established; setting multiple reference systems for inner and outer rings and balls of the bearing in the simulation model, setting two side surfaces of the bearing to be insulated, setting temperatures of inner and outer ring surfaces to be fixed values, and simulating radial heat transfer; monitoring the heat flow of the inner and outer ring surfaces, calculating the heat resistance, and adjusting the volume ratio of the lubricating grease in the bearing cavity at an extremely low rotating speed until the heat resistance value is equal to the experimental value, thereby calibrating the bearing simulation model; different rotating speeds are set for the bearing, and the thermal resistance under different rotating speeds and lubricating grease distribution can be calculated. According to the technical scheme, the simulation result has good precision, and the thermal resistance values of the bearing under different rotating speed conditions can be accurately simulated.

Description

Technical Field

[0001] The invention relates to the technical field of bearing performance testing, and in particular to a virtual-real combined method for measuring dynamic thermal resistance of a bearing. Background Art

[0002] Bearings are key supporting and rotating parts in mechanical equipment, and their thermal performance has a vital impact on the overall operation of the equipment. However, existing methods for determining bearing thermal resistance have many limitations and shortcomings.

[0003] Theoretical calculation methods are often based on simplified model structures and idealized assumptions, which makes it difficult to fully consider the bearing lubrication medium and operating conditions. For example, under actual operating conditions, the grease distribution and temperature gradient distribution are complex and changeable, which are often simplified or ignored in theoretical calculation models, resulting in a large deviation between the calculation results and the actual thermal resistance. Simulation is also one of the commonly used methods to calculate bearing thermal resistance, but because the grid deformation needs to be implemented in the CFD simulation of multiphase flow in the lubrication state to adapt to the fast-moving fluid boundary, convergence problems are usually encountered in CFD simulation. Regardless of theoretical calculation or numerical simulation, the results need to be verified by experiments.

[0004] However, experimental measurement methods also face many challenges and limitations. Traditional contact temperature sensors, such as thermal resistors or thermocouples, can accurately measure the temperature of the outer ring of the bearing, but are not suitable for the inside of the bearing. The measurement of the inner ring temperature also requires special connection devices such as slip rings. Inductively coupled wireless temperature sensors are susceptible to signal interference and have a short coupling distance. Although fiber Bragg grating sensors can measure the temperature inside the bearing, they also face challenges such as difficult wiring and complex demodulation equipment.

[0005] More importantly, most of the existing bearing thermal resistance determination methods lack effective coordination and deep integration between experiments and simulations. Experiments can provide accurate data, but they have limitations in analyzing the internal heat transfer mechanism of bearings and are difficult to implement; although simulations can simulate various complex situations, they require experimental data for verification and calibration to ensure the accuracy of the model. Therefore, there is an urgent need for an innovative bearing thermal resistance determination method that can combine the advantages of experiments and simulations. This virtual-real combination method can reduce the difficulty of experimental implementation and improve the in-depth understanding of the heat transfer mechanism while ensuring the accuracy of bearing thermal resistance measurement. Summary of the invention

[0006] The core of the present invention is to overcome the limitations of the existing technology and provide a comprehensive method for confirming the thermal resistance of bearings that combines experiments and simulations, thereby achieving high-precision measurement of the thermal resistance of bearings, and especially being able to accurately grasp the changing law of the thermal resistance of bearings under different working conditions, thus providing solid technical support for the optimal design of bearings, performance improvement, and reliable application in various types of mechanical equipment.

[0007] According to the technical solution of the present invention, a method for measuring the dynamic thermal resistance of a bearing by combining virtual and real is provided, comprising the following steps:

[0008] The experimental part includes:

[0009] Attach thermocouples to the inner and outer ring surfaces of the bearing, attach thermal insulation materials to both ends of the bearing, apply thermal conductive silicone grease evenly to the inner and outer ring surfaces of the bearing, put the heating ring on the outer ring surface of the bearing and fix it, and install the bearing on one end of the expansion shaft;

[0010] Power on until the temperature is constant, record the temperature of the inner and outer ring surfaces of the bearing, and calculate the power from the data of the metering socket according to the formula Calculate the static radial thermal resistance of the bearing, where is the thermal resistance, is the temperature difference between the inner and outer ring surfaces, is the heating power;

[0011] Simulation part:

[0012] Draw or download the 3D model of the bearing, simplify the 3D model of the bearing, set the material properties according to the manufacturer's data, and establish a multiphase flow simulation model for bearing lubrication and heat transfer;

[0013] Set up multiple reference systems for the inner and outer races of the bearing and the balls in the multiphase flow simulation model;

[0014] Set the two sides of the multiphase flow simulation model to be insulated, and set the inner and outer ring surface temperatures to fixed values ​​so that heat is transferred along the radial direction of the bearing;

[0015] Monitor the heat of the inner and outer ring surfaces, calculate the thermal resistance, and adjust the grease volume ratio in the bearing cavity at a speed lower than 10 rpm until the simulated thermal resistance value is equal to the measured static thermal resistance value, thereby calibrating the multiphase flow simulation model;

[0016] In the multiphase flow simulation model, different speeds are set for the bearings, and the thermal resistance at different speeds is calculated.

[0017] Beneficial effects:

[0018] Since the CFD simulation model is calibrated using the static thermal resistance measurement results of the bearing, the simulation results have good accuracy and can accurately simulate the thermal resistance value of the bearing under different speed conditions. The method disclosed in the present invention is easy to implement, while ensuring the accuracy of the bearing thermal resistance measurement, it eliminates the dependence on complex measurement devices, effectively reduces the experimental cost, and has broad application prospects in the field of thermal management technology of transmission systems with high-speed bearings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A flow chart of a method for measuring dynamic thermal resistance of a bearing by combining virtual and real elements provided in an embodiment of the present invention;

[0020] Figure 2 This is the general diagram of the experimental device;

[0021] Figure 3 This is a partial diagram of the bearing of the experimental device;

[0022] Figure 4 Schematic diagram of multi-reference frame (MRF) modeling;

[0023] Figure 5 This is the distribution diagram of grease in the bearing at 3000rpm;

[0024] Figure 6 is the bearing thermal resistance at different speeds. DETAILED DESCRIPTION

[0025] Figure 1 The flowchart of the method for measuring the dynamic thermal resistance of a bearing by combining virtual and real methods provided in an embodiment of the present invention. Figure 1 As shown, the method includes:

[0026] The experimental part, its equipment is as follows Figure 2 As shown, including:

[0027] Stick patch thermocouples on the inner and outer ring surfaces of the bearing, stick thermal insulation materials on both ends of the bearing, and evenly apply thermal conductive silicone grease on the inner and outer ring surfaces of the bearing. Figure 3 As shown;

[0028] Put the heating ring on the outer ring surface of the bearing and fix it, and install the bearing on one end of the expansion shaft;

[0029] Power on until the temperature is constant, record the temperature of the inner and outer ring surfaces of the bearing, and calculate the power from the data of the metering socket according to the formula Calculate the static radial thermal resistance of the bearing, where is the thermal resistance, is the temperature difference between the inner and outer ring surfaces, is the heating power;

[0030] Simulation part:

[0031] Draw or download the 3D model of the bearing, simplify the 3D model of the bearing, set the material properties according to the manufacturer's data, and establish a multiphase flow simulation model for bearing lubrication and heat transfer;

[0032] In the multiphase flow simulation model, multiple reference systems are set for the inner and outer rings of the bearing and the balls, such as Figure 4 As shown, the rotation speed of each reference frame is;

[0033]

[0034]

[0035]

[0036] In the formula, is the bearing rotation speed, is the ball diameter, is the bearing pitch diameter, and , , They are the rotational speeds of the bearing inner ring reference system, the bearing outer ring reference system and the rotational speeds of each ball reference system.

[0037] Set the two sides of the multiphase flow simulation model to be insulated, and set the inner and outer ring surface temperatures to fixed values ​​so that heat is transferred along the radial direction of the bearing;

[0038] The heat of the inner and outer ring surfaces is monitored to calculate the thermal resistance. The grease volume ratio in the bearing cavity is adjusted at a speed lower than 10 rpm until the thermal resistance value calculated by simulation is equal to the measured static thermal resistance value, thereby calibrating the multiphase flow simulation model.

[0039] In the multiphase flow simulation model, different speeds are set for the bearings, and the thermal resistance at different speeds is calculated.

[0040] Figure 5 This is the grease distribution diagram in the bearing at 3000rpm. Figure 6 is the bearing thermal resistance at different speeds.

[0041] Among them, in the experimental part, the thermal insulation material is made of high-temperature resistant insulation tape, which is cut and pasted on the bearing end face for insulation to reduce axial heat loss.

[0042] In the experimental part, an expansion shaft is used to install the bearing to ensure close contact between the bearing and the shaft to ensure effective heat transfer. The shaft is a conventional component in this field, and the bearing is used to support and fix the shaft.

[0043] In the experimental part, the outer ring of the bearing is heated by an electric heating ring, the inner ring of the bearing is cooled by heat conduction through the expansion shaft, and ice water is used to provide constant temperature cooling conditions for the expansion shaft.

[0044] Among them, the outer ring is a bearing component, the outer ring surface is the ring surface of the outer ring of the bearing (also the radial outermost surface of the bearing). The inner ring is also a bearing component, and the "inner ring surface" is the ring surface of the inner ring of the bearing (also the radial innermost surface of the bearing).

[0045] In the simulation part, the multi-reference system dynamic and static method is used, including: creating rotating reference systems for the inner and outer rings of the bearing and the ball, and the rotation speeds are:

[0046]

[0047]

[0048]

[0049] In the formula, is the bearing rotation speed, is the ball diameter, is the bearing pitch diameter, and , , They are the rotational speeds of the bearing inner ring reference system, the bearing outer ring reference system and the rotational speeds of each ball reference system.

[0050] In the simulation part, the calibration of the bearing three-dimensional model includes: comparing the simulated thermal resistance value at a speed lower than 10 rpm with the measured static thermal resistance value, and eliminating the deviation between the simulation result and the measured value by fine-tuning the grease volume ratio or other key model parameters that cannot be accurately determined, thus completing the calibration of the bearing three-dimensional model.

[0051] An example is described below.

[0052] 1. Experimental

[0053] 1) Preparation of experimental materials:

[0054] Ice water bucket: Choose an iron bucket or wooden bucket with appropriate capacity, avoid using plastic buckets with poor heat resistance, and use a mixture of ice and water to maintain a constant cooling temperature.

[0055] Expansion shaft: Select a stainless steel expansion shaft of appropriate diameter range to install and tighten the bearing being measured.

[0056] Insulation support frame: A suitable design of the support frame, the fixture of which is made of materials with good thermal insulation properties, is used to fix the expansion shaft.

[0057] Electric heating ring: can be fastened to the outer ring surface of the bearing to achieve uniform heating.

[0058] Power supply: Choose a power supply or metered socket that can accurately set the output power.

[0059] Thermometer: It has multi-channel acquisition function and is equipped with thin-film thermocouple or thermal resistor.

[0060] Thermal grease and high-temperature glue: required to be suitable for the temperature range of the experiment.

[0061] Insulation material: Use high temperature resistant insulation tape for the bearing end surface to avoid axial heat loss.

[0062] Protective gloves: Choose high temperature resistant and scald-proof gloves to ensure safe operation.

[0063] 2) Assembly of experimental device:

[0064] Paste the thin-film thermocouple or thermal resistor: first, thoroughly clean the inner and outer ring surfaces of the bearing to ensure the surface is clean; then use high-temperature glue to firmly paste the thin-film thermocouple or thermal resistor on the inner and outer ring surfaces of the bearing, and press gently to ensure that there are no bubbles between the contact surfaces; finally, evenly apply thermal conductive silicone grease on the inner and outer ring surfaces of the bearing.

[0065] Install the heating ring: Put the heating ring on the outer ring surface of the bearing and clamp it to ensure that the heating ring covers and fits tightly to the entire outer ring surface of the bearing.

[0066] Install the bearing: Put the inner ring of the bearing in the middle of the expansion shaft, and tighten the expansion shaft so that there is no gap between it and the annular surface of the inner ring of the bearing.

[0067] Paste the thermal insulation material: Cut the thermal insulation tape and stick it on the bearing end face, making sure it fits neatly with the bearing end face; minimize heat loss from the bearing end face.

[0068] Fix the expansion shaft: Use the heat-insulating clamp of the support frame to clamp one end of the expansion shaft to fix the expansion shaft upright, and extend the other end of the expansion shaft into the ice water bucket.

[0069] Connect the power supply and the temperature meter: connect the thin-film thermocouple or thermal resistor attached to the bearing to the temperature meter; when the power is disconnected, connect the heating ring wire to the power supply device or metering socket.

[0070] 3) Data measurement and recording:

[0071] Check before power on: Before turning on the power, check all experimental equipment to ensure that the connections are correct and firm. In particular, check whether the bearings, heating rings, expansion shafts and brackets are firmly installed, whether the connection between the heating ring and the power supply is safe and correct, and whether the temperature meter connected to the thermocouple or thermal resistor displays the correct reading.

[0072] Temperature monitoring and recording: After the heating ring is powered on, the experimenter needs to pay close attention to the temperature changes displayed on the thermometer and adjust the heating power to prevent excessive temperature rise. Record the temperature data of the inner and outer ring surfaces of the bearing in a timely manner. When the temperature does not change for several consecutive minutes, it can be determined that the bearing has reached thermal equilibrium.

[0073] Power calculation and recording: When the bearing temperature stabilizes, record the heating power data displayed on the power supply or metering socket to obtain the accurate heating power.

[0074] Thermal resistance bearing calculation: According to the formula Calculate the static thermal resistance of the bearing, where is the thermal resistance between the inner and outer ring surfaces of the bearing, is the temperature difference between the inner and outer ring surfaces, For the heating power.

[0075] 2. Simulation part

[0076] 1) Bearing model simplification and error elimination

[0077] In the geometry creation of the simulation model, appropriate simplification can be performed, the bearing support frame can be removed, and the clearance between each ball and the inner and outer raceways can be kept the same. The overall model error caused by the simplification of geometry and boundary conditions and other uncertain factors can be eliminated by adjusting a single model parameter in the subsequent model calibration.

[0078] 2) Dynamic and static modeling of bearing rotation

[0079] Based on the multi-reference frame (MRF) dynamic and static method, a rotating reference coordinate system is created for the inner and outer rings of the bearing and the ball respectively, such as Figure 4 As shown, the speed settings of each reference frame are as follows:

[0080]

[0081]

[0082]

[0083] In the formula, is the bearing rotation speed, is the ball diameter, is the bearing pitch diameter, and , , They are the rotational speeds of the bearing inner ring reference system, the bearing outer ring reference system and the rotational speeds of each ball reference system.

[0084] In the simulation model, a corresponding rotating reference system is set for each fixed component area, and a rotating reference system that is the same as the contacted solid is set for each boundary of the fluid area.

[0085] 3) Thermal boundary conditions of bearing model

[0086] In line with the heat insulation treatment of experimental measurement, the two axial end faces of the bearing model are set as adiabatic boundary conditions. The annular surfaces of the inner and outer rings of the bearing are set as fixed temperature boundary conditions.

[0087] 4) Thermal resistance calculation and model correction

[0088] Thermal resistance calculation: Monitor the heat flux curves of the inner and outer ring surfaces over time in real time during the simulation. When the simulation reaches thermal equilibrium, the heat flux of the inner and outer ring surfaces tends to be stable and basically equal. Divide the temperature difference set between the inner and outer ring surfaces by the steady-state heat flux to obtain the total radial thermal resistance of the bearing.

[0089] Model calibration: Compare the thermal resistance simulation calculation results at extremely low speeds with the static experimental measurement results. By fine-tuning the grease volume ratio or other key model parameters that cannot be accurately determined, the deviation between the simulation results and the measured values ​​is eliminated to complete the model calibration.

[0090] 4) Simulation of different working conditions

[0091] According to the set speed, select the appropriate time step to perform simulation calculation of thermal resistance at different speeds, and draw a curve of thermal resistance changing with speed.

[0092] In summary, at present, the widely used experimental measurement method of bearing thermal resistance requires the use of wireless sensors or slip rings to arrange temperature sensors for the moving parts of the bearing, which is very difficult to implement. The numerical simulation method requires experimental confirmation of its accuracy, and the multiphase flow simulation of grease is also difficult to converge due to the presence of moving parts. The present invention adopts a virtual-real combination scheme: first, a simple device is used to measure and obtain the static thermal resistance of the bearing in the experimental link; then, a multiphase flow computational fluid dynamics (CFD) thermal simulation model of the bearing is established, and the static simulation of the bearing motion is realized based on the dynamic and static method of the multi-reference frame (MRF). Since the CFD simulation model is calibrated using the static thermal resistance measurement results of the bearing, its simulation results have good accuracy and can accurately simulate the thermal resistance value of the bearing under different speed conditions. The method disclosed in the present invention is easy to implement, while ensuring the accuracy of the bearing thermal resistance measurement, it eliminates the dependence on complex measurement devices, effectively reduces the experimental cost, and has broad application prospects in the field of thermal management technology of transmission systems with high-speed bearings.

Claims

1. A virtual and real combined bearing dynamic thermal resistance measurement method, characterized in that: The following steps are involved: The experimental part includes: Attach thermocouples to the inner and outer ring surfaces of the bearing, attach thermal insulation materials to both ends of the bearing, apply thermal conductive silicone grease evenly to the inner and outer ring surfaces of the bearing, put the heating ring on the outer ring surface of the bearing and fix it, and install the bearing on one end of the expansion shaft; Power on until the temperature is constant, record the temperature of the inner and outer ring surfaces of the bearing, and calculate the power from the data of the metering socket according to the formula Calculate the static radial thermal resistance of the bearing, where is the thermal resistance, is the temperature difference between the inner and outer ring surfaces, is the heating power; Simulation part: Draw or download the 3D model of the bearing, simplify the 3D model of the bearing, set the material properties according to the manufacturer's data, and establish a multiphase flow simulation model for bearing lubrication and heat transfer; Set up multiple reference systems for the inner and outer races of the bearing and the balls in the multiphase flow simulation model; Set the two sides of the multiphase flow simulation model to be insulated, and set the inner and outer ring surface temperatures to fixed values ​​so that heat is transferred along the radial direction of the bearing; Monitor the heat flow of the inner and outer ring surfaces to calculate the thermal resistance, and adjust the grease volume ratio in the bearing cavity at a speed lower than 10 rpm until the simulated thermal resistance value is equal to the measured static thermal resistance value, thereby calibrating the multiphase flow simulation model; In the multiphase flow simulation model, different speeds are set for the bearings, and the thermal resistance at different speeds is calculated.

2. The virtual-real combined bearing dynamic thermal resistance measurement method according to claim 1 is characterized in that: The thermal insulation material is made of high temperature resistant insulation tape, which is cut and affixed to the bearing end face for thermal insulation.

3. The virtual-real combined bearing dynamic thermal resistance measurement method according to claim 1, characterized in that: Installing the bearing on one end of the expansion shaft includes: ensuring close contact between the bearing and the shaft.

4. The virtual-real combined bearing dynamic thermal resistance measurement method according to claim 1, characterized in that: The outer ring of the bearing is heated by an electric heating ring, and the inner ring of the bearing is cooled by heat conduction through an expansion shaft.

5. The virtual-real combined bearing dynamic thermal resistance measurement method according to claim 1, characterized in that: Ice water is used to provide constant temperature cooling conditions for the expansion shaft.

6. The virtual-real combined bearing dynamic thermal resistance measurement method according to claim 1, characterized in that: The simulation model uses the multi-reference frame dynamic and static method to create rotating reference frames for the inner and outer rings of the bearing and the ball respectively, and the rotation speeds are: In the formula, is the bearing rotation speed, is the ball diameter, is the bearing pitch diameter, and , , They are the rotational speeds of the bearing inner ring reference system, the bearing outer ring reference system and the rotational speeds of each ball reference system.

7. The virtual-real combined bearing dynamic thermal resistance measurement method according to claim 1, characterized in that: The calibration of the bearing lubrication heat transfer simulation model includes: comparing the simulated thermal resistance value at a speed lower than 10 rpm with the measured static thermal resistance value, and eliminating the deviation between the simulation result and the measured value by fine-tuning the grease volume ratio to complete the model calibration.

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