Device for measuring spraying oil cooling heat transfer coefficient of motor stator winding

Abstract

The invention discloses a device for measuring the spraying oil cooling heat transfer coefficient of a motor stator winding, which comprises a sealed cavity, a cushion block is fixed in the center of the inner bottom surface of the sealed cavity, and a simulation winding is arranged above the cushion block; an oil outlet is formed in the side wall of the sealed cavity, an oil inlet is formed in the center of the top surface of the sealed cavity, a hose with a peristaltic pump is connected between the oil inlet and the oil outlet, and the peristaltic pump pumps cooling oil in the sealed cavity to the oil inlet and sprays the cooling oil on the simulation winding; a heating plate is attached to the simulation winding, the heating plate is connected with a power controller, and the power controller controls the output power of the heating plate; temperature sensors are respectively arranged on the surface of the heating plate and the bottom of the sealed cavity; and substituting the readings of the power controller, the temperatures of the simulation winding and the cooling oil and the surface area of the simulation winding into a Newton convection cooling law calculation formula to obtain a convection heat transfer coefficient of spray cooling of the motor stator winding. According to the invention, the convective heat transfer coefficient of spray cooling of the motor stator winding can be simulated and calculated, so that the jet impact enhanced heat transfer rule and characteristics can be explored.

Description

Technical Field

[0001] This invention belongs to the field of motor and heat and mass transfer technology, specifically relating to a device for measuring the heat transfer coefficient of motor stator winding spray oil cooling. Background Technology

[0002] With the rapid development of modern technology and the increasingly severe energy problem, the research and development of high-performance, low-emission, and multi-energy-utilizing electric vehicles is of great strategic significance and has received high attention from countries around the world. The drive motor is one of the core components of an electric vehicle. In recent years, scholars both domestically and internationally have increasingly focused on improving the power density of drive motors to achieve higher performance. However, due to losses, motor operation is often accompanied by temperature increases, and the higher the power density, the higher the temperature rise. Excessive temperature accelerates the aging of insulation materials and shortens the motor's lifespan, which limits the further development of drive motors. Therefore, it is urgent to solve the technical challenge of efficient heat dissipation for motors.

[0003] Currently, the main motor cooling methods include air cooling, water cooling, and oil cooling. The main research goals are to increase the heat dissipation area, expand the heat dissipation path, and improve the heat dissipation structure. Among these, oil cooling is currently the most efficient cooling method and is more suitable for high-power-density motors compared to other methods. Oil cooling takes various forms. For stator winding cooling, the most common method is to spray cooling oil onto the end windings through nozzles for direct cooling, which is essentially a type of jet impact convection heat transfer. Jet impact heat transfer refers to using circular or slit-shaped nozzles to spray a fluid (gas, liquid, water mist, etc.) under certain pressure vertically or at a certain angle onto the heat exchange surface, achieving enhanced cooling of the impact surface. Jet impact generally has a large impact pressure, and the fluid at the heat exchange surface has the characteristics of high flow velocity and a thin boundary layer, thus achieving a large heat transfer capacity, making it an extremely effective heat transfer method. Furthermore, the cooling intensity can be effectively controlled by adjusting parameters such as jet pressure, jet distance, jet angle, and jet layout. Studying the heat transfer characteristics of jet impingement heat transfer is a prerequisite for its better application in production practice. The heat transfer characteristics of jet impingement are related to many factors, such as nozzle shape, jet surface roughness, jet distance, jet pressure, jet medium, and nozzle spacing. Furthermore, the pressure, velocity, and direction of the jet change drastically after impacting the heat transfer surface, leading to varying heat transfer intensities at different locations on the surface. Therefore, the study of the laws and characteristics of jet impingement-enhanced heat transfer has always been a research hotspot. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a measuring device for the heat transfer coefficient of spray oil cooling of motor stator windings, which can simulate and calculate the convective heat transfer coefficient of spray cooling of motor stator windings, and then explore the heat transfer law and characteristics of jet impact enhancement.

[0005] Technical Solution: This invention provides a measuring device for the cooling heat transfer coefficient of a motor stator winding sprayed with oil. The device includes a sealed cavity with a pad fixed at the center of the bottom surface inside the cavity. A simulated winding for simulating a motor stator winding is fixed above the pad. An oil outlet is opened on the side wall of the sealed cavity, and an oil inlet is opened at the center of the top surface. A flexible hose connects the oil outlet and the oil inlet, and a peristaltic pump is installed on the hose. The peristaltic pump draws cooling oil from the sealed cavity to the oil inlet, achieving oil circulation. The cooling oil is sprayed onto the simulated winding from the oil inlet. A heating plate is attached to the upper surface of the simulated winding, applying a heat source to it. The heating plate is connected to a power controller, which controls the output power of the heating plate. Temperature sensors are respectively installed on the surface of the heating plate and the bottom of the sealed cavity to measure the temperature of the simulated winding and the cooling oil. The cooling heat transfer coefficient of the motor stator winding sprayed with oil is obtained by substituting the power controller reading, the temperature of the simulated winding and the cooling oil, and the surface area of ​​the simulated winding into Newton's law of convection cooling.

[0006] Furthermore, the effect of gravity on the spray nozzles at different positions along the circumference of the motor stator winding is simulated by changing the tilt angle of the sealed cavity.

[0007] Furthermore, the diameter of the oil inlet is equal to the diameter of the spray nozzle, and spray nozzles of different diameters can be simulated by changing the diameter of the oil inlet.

[0008] Furthermore, the distance between the oil inlet and the heating plate is equal to the radial distance between the spray nozzle and the motor stator winding; the flow rate of the peristaltic pump is equal to the flow rate of the spray nozzle.

[0009] Furthermore, the effect of the number of spray nozzles on the spray heat transfer intensity of the stator winding was simulated by controlling the flow rate of cooling oil in the peristaltic pump.

[0010] Furthermore, the upper surface of the simulated winding is designed as an arc surface to simulate the curved shape of the motor stator winding.

[0011] Furthermore, multiple temperature sensors are pre-embedded at different positions on the surface of the heating plate, and the average value of the multiple temperature sensors is taken as the temperature of the simulated winding.

[0012] Furthermore, the heating plate is a flexible silicone heating plate.

[0013] Furthermore, an outlet is provided on the top surface of the sealed cavity, through which the power controller cable passes and connects to the heating plate.

[0014] Furthermore, the sealed cavity includes a transparent box and a transparent cover, forming a transparent sealed cavity.

[0015] Beneficial effects: Compared with the prior art, the significant technical effects of the present invention are as follows: (1) The present invention has a simple and reliable structure, the required instruments are easy to obtain, the cost is low, and the heat transfer coefficient of the stator winding spray cooling can be measured quickly and efficiently; (2) The cold heat transfer coefficient is calculated based on the analytical formula, and the parameters of the formula are all obtained by measurement, the uncertainty of the experiment is low, and the heat transfer coefficient data obtained is more reliable; (3) Various influencing factors in jet impact heat transfer are fully considered, including cooling oil flow rate, nozzle size, gravity, etc. These parameters can be freely adjusted in the experiment, which is conducive to a comprehensive and extensive study of the relationship between the stator winding spray cold heat transfer coefficient and these parameters. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the present invention;

[0017] Figure 2 This is a schematic diagram of the structure of the sealed cavity in this invention;

[0018] Figure 3 This is a schematic diagram of the interior of the sealed cavity in this invention;

[0019] Figure 4 This is a schematic diagram of the motor stator spray oil cooling structure simulated by the present invention. Detailed Implementation

[0020] The technical solution of the present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0021] This invention provides a measuring device for the heat transfer coefficient of motor stator winding spray oil cooling, used to simulate the actual physical scenario of a motor stator oil cooling structure. For example... Figure 4 As shown, the motor stator oil-cooling structure includes a stator winding 1, a stator core 2, and an oil collecting ring 3. The yoke of the stator core 2 has several cooling oil channels, namely stator yoke oil passages 21. Cooling oil flows through the stator yoke oil passages 21 to the oil collecting ring 3. The oil collecting ring has several circular oil spray nozzles 31 arranged circumferentially. The cooling oil is pressurized through the oil spray nozzles 31 and sprayed onto the surface of the stator winding 1 for direct cooling. This convective cooling method is, in principle, a jet impingement heat transfer. Based on the principle of symmetry, this invention modularizes the above physical scenario, extracts a model of one of the oil spray nozzles and the stator winding, and designs an experimental device (i.e., a device for measuring the heat transfer coefficient of the motor stator winding sprayed with oil) based on the above model to simulate the actual physical scenario.

[0022] Since the heat transfer intensity at a certain location on the jet impact heat transfer interface is generally characterized by the Nusselt number (Nu), which is a dimensionless number in fluid mechanics and heat transfer, the formula for its calculation is: In the formula, L is the geometric characteristic length of the heat transfer surface; k is the thermal conductivity of the stationary fluid; and h is the surface convective heat transfer coefficient of the fluid, characterizing the heat transfer capacity between the fluid and the solid surface, and is calculated as follows: In the formula, q represents the heat exchanged between a unit area of ​​solid surface and fluid per unit time, called heat flux density, and t represents the heat exchange rate. w t ∞ These are the temperatures of the solid surface and the fluid, respectively. Therefore, by continuously supplying heat to the workpiece while performing surface jet heat exchange, and ensuring that the supplied heat and the heat carried away by the jet reach a stable equilibrium, the convective heat transfer coefficient can be calculated by measuring the input heat flux density q and the temperature of the heat exchange surface, and thus the heat transfer intensity can be calculated.

[0023] In view of this, the present invention provides a measuring device for the heat transfer coefficient of motor stator winding spray oil cooling, used to simulate stator winding spray cooling scenarios under multiple operating conditions, thereby guiding the design of oil-cooled motors and improving and solving motor heat dissipation problems. Figures 1 to 3 As shown, the present invention discloses a measuring device for the heat transfer coefficient of motor stator winding sprayed with oil, comprising a main body and external equipment. The main body includes a sealed cavity, a pad 61, and a simulated winding 62. The external equipment includes a heating plate 63, a power controller 7, a temperature sensor 8, and a peristaltic pump 9. In this embodiment, the sealed cavity includes a transparent box 4 and a transparent cover 5, forming a transparent sealed cavity.

[0024] The transparent cover 5 is placed on the transparent box 4 and sealed. The design of the transparent box 4 and the transparent cover 5 allows the tester to clearly observe the flow of the oil from the outside, facilitating judgment and adjustment. The transparent cover 5 can be opened at any time, making it easier to perform operations such as wire feeding and oiling compared to an integrated design. The transparent box 4 and the transparent cover 5 can be made of acrylic material, which has the advantages of being lightweight and high-strength.

[0025] A narrow pipe opening, designated as an oil outlet 41, is provided on the side wall of the sealed cavity. The outlet 41 is positioned near the bottom, below the surface of the oil accumulation at the bottom of the transparent box 4, to prevent pump cavitation and ensure stable flow. An oil inlet 52 is located in the center of the top surface of the sealed cavity, directly above the simulated winding 62. A flexible hose connects the outlet 41 and the inlet 52, with a peristaltic pump 9 mounted on it. The peristaltic pump 9 controls the flow of cooling oil, drawing it from the sealed cavity and delivering it to the inlet 52 for oil circulation. The flow rate of the peristaltic pump 9 should be accurately read and adjustable. Cooling oil is sprayed from the inlet 52 onto the simulated winding 62. In a real-world scenario, with a constant total flow rate, the flow rate of a single spray nozzle 31 is linearly inversely proportional to the number of spray nozzles in the oil collecting ring 3. Therefore, the effect of the number of spray nozzles in the oil collecting ring 3 on the heat transfer intensity of the stator winding can be simulated by controlling the flow rate of cooling oil from the peristaltic pump 9. The cable outlet 51 is designed for easy cable connection.

[0026] A pad 61 is fixed in the center of the bottom surface inside the sealed cavity. A simulated winding 62 is fixed above the pad 61 to simulate the stator winding 1 of the motor. The pad 61 needs to be high enough to avoid direct contact between the simulated winding and the oil accumulation at the bottom of the transparent box, which would cause measurement errors. At the same time, the pad cannot be too high to avoid the simulated winding touching the transparent cover, which would also cause measurement errors. In addition, the distance from the surface of the simulated winding 62 to the oil inlet 52 can be controlled by adjusting the height of the pad 61, which can be used to investigate the effect of different distances between the oil nozzle 31 and the surface of the stator winding 1 on the cooling intensity. The upper surface of the simulated winding 62 is designed as an arc surface with a certain curvature to simulate the curved shape of the stator winding 1 of the motor. The outer side of the stator winding 1 of the motor is curved. A hole is opened at an appropriate position next to the oil inlet 52 on the top surface of the sealed cavity as a cable outlet 51. The cable of the power controller 7 passes through the cable outlet 51 and connects to the heating plate 63. The cable of the temperature sensor 8 also exits through the cable outlet 51.

[0027] A heating plate 63 is attached to the upper surface of the simulated winding 62. The heating plate 63 applies heat to the simulated winding 62. The heating plate 63 is connected to a power controller 7, which quantitatively controls the output power of the heating plate 63. In this embodiment, the heating plate 63 is a flexible silicone heating plate, which is fixed in close contact with the upper surface of the simulated winding 62 as a heat source.

[0028] A flexible silicone heating plate is a soft heating device with silicone as its base material, possessing excellent flexibility and heating performance. It mainly consists of a heating element and an insulating layer. The heating element is typically composed of nickel-chromium alloy resistance wire wound around fiberglass cloth or formed into a sheet-like heating element using an etching circuit method, providing a uniform heat field. The insulating layer is a composite of silicone rubber and fiberglass cloth. The silicone rubber covers the surface of the heating element, serving to insulate, conduct heat, and protect, ensuring safe use. When current passes through the built-in heating wire or carbon fiber heating element, the resistance converts electrical energy into heat energy. The silicone material, with its excellent thermal conductivity, evenly transfers heat to the surface of the heating plate, thereby heating the object in contact with it.

[0029] Flexible silicone heating plates possess excellent flexibility, allowing them to bend and conform to irregular surfaces, adapting to the heating needs of different shapes and surfaces. They can also be manufactured into arbitrary shapes. This characteristic enables them to adhere well to the simulated winding surface, better simulating the heating of stator winding 1 compared to other heating devices. Furthermore, flexible silicone heating plates have excellent thermal conductivity, enabling rapid and uniform heat transfer, avoiding localized overheating or uneven heating. They offer high thermal efficiency, achieving rapid heating rates and high temperature control accuracy. The silicone material itself also has good waterproof and corrosion-resistant properties, making it suitable for oil-cooled experiments. Solid surface roughness is also a factor affecting jet impingement heat transfer; therefore, optionally, a layer of material similar to the surface of stator winding 1 can be attached to the heating plate 6, making their surface roughness identical, thus avoiding the influence of this factor on the accuracy of the heat transfer coefficient.

[0030] The power controller 7 is a power regulation device specifically designed for heating plates. Its core function is to achieve stable regulation of heating temperature and heating power by precisely controlling the input power of the heating plate, while ensuring the safety and energy efficiency of the heating process. The controller needs to be adapted to the purely resistive characteristics of the heating plate to avoid a decrease in control accuracy due to inductive or capacitive interference. Experimental data needs to be read when the temperature rise reaches a steady state, but the heating plate's temperature rise has a lag; therefore, the controller must have dynamic adjustment capabilities to avoid temperature overshoot or excessive fluctuations. In addition, the controller needs to support compatibility with temperature sensors such as thermocouples to achieve closed-loop "power-temperature" control.

[0031] Temperature sensors 8 are installed on the surface of the heating plate 63 and at the bottom of the sealed cavity to measure the temperature of the simulated winding 62 and the cooling oil. The probes of the temperature sensors 8 need to be placed on the surface of the heating plate 63 and in the oil accumulation at the bottom of the transparent box 4. Multiple temperature sensors 8 are pre-embedded at different locations on the surface of the heating plate 63, and the average value of the readings from these multiple temperature sensors 8 is taken as the temperature of the simulated winding 62. A temperature sensor 8 is installed in the oil accumulation at the bottom of the sealed cavity to measure the temperature of the cooling oil.

[0032] Temperature sensor 9 is a device that converts the physical quantity of temperature into a measurable and processable electrical signal, and is the core component for temperature monitoring. Temperature sensors are mainly divided into contact and non-contact types. This experiment requires high accuracy in temperature measurement, therefore a contact temperature sensor is required. Considering the non-uniformity of temperature distribution, multiple temperature sensors need to be embedded at different locations on the surface of the heating plate 6 and in the oil accumulation at the bottom of the transparent box 4, and the average temperature is taken as a parameter for calculating the heat transfer coefficient.

[0033] The peristaltic pump 10 is a positive displacement pump that compresses an elastic hose to direct fluid flow in a specific direction. The core structure of the peristaltic pump includes a drive mechanism and an elastic hose. During operation, multiple rollers (or pressure blocks) on the drive mechanism rotate along a fixed trajectory, sequentially compressing the hose. When a roller passes over the hose, the hose's inner cavity is temporarily sealed, pushing the internal fluid forward. After the roller moves away, the hose returns to its original shape due to its elasticity, creating a partial vacuum and drawing in new fluid from the inlet. The volume of fluid compressed by the rollers per revolution is constant; therefore, the flow rate is directly proportional to the rotational speed of the drive mechanism's motor. The flow rate can be precisely controlled by adjusting the motor speed, and fine-tuning of the flow rate is supported. Since the flow rate required in this experiment is very small, this characteristic makes it an ideal choice for the oil circulation system of this experimental setup.

[0034] Regarding the input parameters and parameters to be tested in this application, such as Figure 1 As shown in Table 1, the dashed lines represent pipelines or cables. By changing the combination of input parameters, the oil injection situation under different design conditions can be simulated, and the convective heat transfer coefficient can be directly calculated from the parameters to be measured.

[0035] Table 1 Input parameters and parameters to be measured

[0036]

[0037] As shown in the table, the distance h between the oil inlet 52 and the heating plate 63 is equal to the radial distance between the spray nozzle 31 and the motor stator winding 1. The flow rate f of the peristaltic pump 9 is equal to the flow rate of the spray nozzle 31. All relevant parameters in the experiment can be freely changed. Specifically, the heat source power can be adjusted using the flexible silicone heating plate and the power controller connected to it; the cooling oil flow rate can be adjusted using the peristaltic pump 9; the diameter of the oil inlet 52 is equal to the diameter of the spray nozzle 31, and different diameters of the spray nozzle 31 can be simulated by changing the diameter of the oil inlet 52. The size of the spray nozzle 31 can be adjusted using the hose diameter; the tilt angle of the sealed cavity simulates the effect of gravity when spraying from the spray nozzles 31 at different positions upwards around the motor stator winding 1.

[0038] Therefore, by substituting the readings of the power controller 7, the temperatures of the simulated winding 62 and the cooling oil, and the surface area of ​​the simulated winding 62 into the calculation formula of Newton's law of convection cooling, the convective heat transfer coefficient of the motor stator winding 1 under spray cooling is obtained.

[0039] The technical solution of this invention can accurately measure the heat transfer coefficient of the motor stator winding spray oil cooling. It can also explore the relationship between the jet impact heat transfer coefficient of the motor stator winding spray cooling and factors such as the orifice diameter of the oil spray nozzle, the number of oil spray nozzles and the flow rate of cooling oil by changing the experimental parameter settings. This can guide the stator spray design of oil-cooled motors and improve and solve the motor heat dissipation problem.

Claims

1. A measuring device for the heat transfer coefficient of sprayed oil cooling in motor stator windings, characterized in that: It includes a sealed cavity, and a pad (61) is fixed in the center of the bottom surface inside the sealed cavity. A simulated winding (62) for simulating the stator winding (1) of the motor is fixed above the pad (61). An oil outlet (41) is provided on the side wall of the sealed cavity, and an oil inlet (52) is provided in the center of the top surface of the sealed cavity. A hose is connected between the oil outlet (41) and the oil inlet (52). A peristaltic pump (9) is provided on the hose. The peristaltic pump (9) is used to draw the cooling oil in the sealed cavity to the oil inlet (52) to realize the oil circulation. The cooling oil is sprayed from the oil inlet (52) onto the simulated winding (62). A heating plate (63) is attached to the upper surface of the simulated winding (62). The heating plate (63) applies a heat source to the simulated winding (62). The heating plate (63) is connected to a power controller (7). The power controller (7) is used to control the output power of the heating plate (63). Temperature sensors (8) are respectively installed on the surface of the heating plate (63) and the bottom of the sealed cavity to measure the temperature of the simulated winding (62) and the cooling oil; Substituting the readings of the power controller (7), the temperatures of the simulated winding (62) and the cooling oil, and the surface area of ​​the simulated winding (62) into the calculation formula of Newton's law of convection cooling, the cold heat transfer coefficient of the motor stator winding (1) spray cooling is obtained.

2. The measuring device for the heat transfer coefficient of motor stator winding sprayed with oil according to claim 1, characterized in that: The effect of gravity on the spray nozzles (31) at different positions in the circumferential direction of the motor stator winding (1) is simulated by changing the tilt angle of the sealed cavity.

3. The measuring device for the heat transfer coefficient of motor stator winding sprayed with oil according to claim 1, characterized in that: The diameter of the oil inlet (52) is the same as the diameter of the spray nozzle (31), and the diameter of the oil inlet (52) is changed to simulate spray nozzles (31) of different diameters.

4. The measuring device for the heat transfer coefficient of motor stator winding sprayed with oil according to claim 1, characterized in that: The distance between the oil inlet (52) and the heating plate (63) is equal to the radial distance between the spray nozzle (31) and the motor stator winding (1); the flow rate of the peristaltic pump (9) is equal to the flow rate of the spray nozzle (31).

5. The measuring device for the heat transfer coefficient of motor stator winding sprayed with oil according to claim 1, characterized in that: The effect of the number of spray nozzles (31) on the spray heat transfer intensity of the stator winding is simulated by controlling the flow rate of cooling oil in the peristaltic pump (9).

6. The measuring device for the heat transfer coefficient of motor stator winding sprayed with oil according to claim 1, characterized in that: The upper surface of the simulated winding (62) is designed as an arc surface to simulate the curved shape of the motor stator winding (1).

7. The measuring device for the heat transfer coefficient of motor stator winding sprayed with oil according to claim 1, characterized in that: Multiple temperature sensors (8) are embedded at different positions on the surface of the heating plate (63), and the average value of the multiple temperature sensors (8) is taken as the temperature of the simulated winding (62).

8. The measuring device for the heat transfer coefficient of motor stator winding sprayed with oil according to claim 1, characterized in that: The heating plate (63) is a flexible silicone heating plate.

9. The measuring device for the heat transfer coefficient of motor stator winding sprayed with oil according to claim 1, characterized in that: The sealed cavity has a cable outlet (51) on its top surface, through which the cable of the power controller (7) passes and connects to the heating plate (63).

10. The measuring device for the heat transfer coefficient of motor stator winding sprayed with oil according to claim 1, characterized in that: The sealed cavity includes a transparent box (4) and a transparent cover (5) to form a transparent sealed cavity.

Images