Improvement of cooling efficiency of electric motors by utilizing internal magnetic field and magnetic fluids

Abstract

The invention relates to the improvement of the cooling efficiency of electric motors by utilizing the internal magnetic field and magnetic fluids, aiming to enhance convective heat transfer for improved cooling performance. In this invention, cooling channels are positioned near the coil windings and stator regions—where heat generation is most intense—by making use of the magnetic field already present within the motor. Magnetic fluids (magnetic liquid metals or magnetic nanofluids) are employed as the coolant, and magnetohydrodynamic (MHD) effects are induced through the Lorentz forces exerted by the magnetic field, which alter the flow velocity profile and enhance convective heat transfer. By this method, while the motor temperature is reduced, its cooling capacity is significantly increased. The invention comprises the components rotor (1), stator (2), shaft (3), coil windings (4), housing (5), magnets (6), and cooling channels (7).

Description

[0001] IMPROVEMENT OF COOLING EFFICIENCY OF ELECTRIC MOTORS BY UTILIZING INTERNAL MAGNETIC FIELD AND MAGNETIC FLUIDS

[0002] Technical Field

[0003] The invention relates to the improvement of the cooling efficiency of electric motors used in electric land, air, and marine vehicles within the automotive sector, by utilizing the internal magnetic field already existing in the motor itself. This approach enhances the cooling performance of the motor without adversely affecting the vehicle's range and, on the contrary, contributes to extending it.

[0004] Background of the Invention

[0005] An electric motor is a machine that converts electrical energy into mechanical energy. Its fundamental operating principle is based on the force generated by the movement of electric current within a magnetic field, which causes a rotor to rotate. These machines are widely used in various fields, such as electric vehicles, household appliances, industrial machinery, and energy systems.

[0006] Climate change and global warming have led to a significant shift in engineering applications toward technologies aimed at reducing carbon emissions [1]. In recent years, there has been a growing interest in electric vehicles, particularly in the land transportation sector, which accounts for 49% of global fuel consumption [2, 3]. While Andersen et al. demonstrated that the transition from gasoline- powered to electric vehicles could reduce greenhouse gas emissions by up to 20% [4], Endo [5] projected a substantial reduction— up to one-third— in CO2emissions between 1990 and 2050 through the advancement of electric vehicle technologies. Many governments plan to implement tax regulations to prevent the excessive use of carbon-based fuels in vehicles, thereby encouraging the adoption of electric vehicles. With the increasing prevalence of electric vehicles, electric motors with higher power capacities and longer ranges are being developed each day. A similar situation applies to electric motors used in air and marine vehicles. The rise in motor performance consequently increases the cooling load required for these motors. If the thermal load cannot be adequately dissipated from the system, the efficiency of the electric motor decreases, its service life and durability are reduced, and maintenance costs rise. In currently used electric motors, when heat transfer remains limited, the motor operates at relatively high temperatures. And this may result in a shorter lifespan for the motor, a reduced level of mechanical endurance, and higher level of maintenance expenses. When the motor cannot be effectively cooled, its operating capacity must be reduced to ensure that it functions safely within permissible temperature limits, which in turn negatively affects vehicle performance.

[0007] The invention titled "ig Rotorlu Elektrik Motoru igin Bir Kanalli SIVI Sogutma Sistemi" with application number 2017 / 16470, owned by Aselsan Elektronik Sanayi ve Ticaret Anonim §irketi, is considered the closest prior art. However, it differs significantly from the present invention titled "Improvement of Cooling Efficiency of Electric Motors by Utilizing Internal Magnetic Field and Magnetic Fluids." In the invention with application number 2017 / 16470, cooling is achieved by integrating and positioning cold cooling channels and manifolds within the motor. However, the use of the magnetic field inside the motor or magnetohydrodynamic (MHD) effects has not been considered, which limits the capacity of the cooling system. In that design, the direction of the fluid flow is achieved through the use of inlet and outlet manifolds, channels, and couplings.

[0008] The invention titled "Versatile Cooling Housing for an Electrical Motor" with publication number EP2879278A1, owned by SKF Magnetic Mechatronics, is considered the second closest prior art. However, it also differs from the invention titled "Improvement of Cooling Efficiency of Electric Motors by Utilizing Internal Magnetic Field and Magnetic Fluids." The invention disclosed in the publication number EP2879278A1 provides effective heat dissipation by using cooling fins and liquid cooling paths. This process is achieved through the use of fins and liquid cooling channels placed on the outer surface of the housing. However, in this invention as well, neither the utilization of the internal magnetic field of the motor nor the application of magnetohydrodynamic (MHD) effects for cooling has been considered.

[0009] The fundamental methods applied to improve the cooling of electric motors include increasing the flow rate of the coolant, enlarging the surface area where heat transfer occurs, and using coolants with higher thermal conductivity. The increase in the flow rate of the coolant is limited by the flow capacity and power of the pumps or fans used. When a pump or fan with higher power consumption is employed, the required energy is drawn from the vehicle's battery, which consequently reduces the driving range.

[0010] It is possible to enhance heat transfer by increasing the surface area in contact with the coolant— such as by passing the fluid through a greater number of channels or by adding fins to existing channels in this way. However, as the contact surface area between the fluid and the surface increases, friction and the resulting pressure drop also increase. Therefore, greater pump or fan power is required to maintain the same flow rate. Moreover, since the available space within a vehicle for the electric motor is limited, it is not always feasible to add fins of the desired shape or size.

[0011] Increasing the thermal conductivity of the coolant enhances the cooling performance of the electric motor. For this reason, replacing air-cooling systems with liquid-cooling circuits improves cooling performance. However, even in liquid- cooled systems, the thermal conductivity of the conventional cooling fluids may limit overall cooling effectiveness. Therefore, the thermal conductivity may be increased by mixing the coolant with another fluid of higher thermal conductivity to form an emulsion. Similarly, the thermal conductivity can also be improved by dispersing solid-phase nanoparticles with high thermal conductivity, at nanometer scale, into the coolant to obtain a colloid. This technique is widely applied in the literature, and numerous studies have implemented it.

[0012] In the study conducted by Deriszadeh and Monte, a cooling jacket design using an AI2O3-water nanofluid was developed. For the electric motor used in their research, under constant heat flux conditions, the convective heat transfer coefficient was increased by up to 64.7% with a 4% volume fraction of AI2O3[6]. In another study by Pandey et al., heat transfer analyses of an induction motor were performed using various nanofluids composed of AI2O3, ZnO, and CuO nanoparticles, with water as the base fluid. In the most critical motor component (the coil windings), temperature reductions of only 2%, 4%, and 3% were observed, respectively [7,8].

[0013] In the current state of the art, three approaches are used to achieve the necessary performance improvement for effective liquid cooling of the motor. These approaches are as follows: 1. Increasing the flow rate of the cooling fluid: When the flow rate of the cooling fluid increases, convective heat transfer is enhanced, resulting in more effective cooling. However, in this case, the power consumed by the pump that circulates the cooling fluid also increases, and since this power is supplied by the vehicle's battery, this approach consequently reduces the vehicle's driving range.

[0014] 2. Increasing the surface area: It is possible to enhance heat transfer by increasing the surface area in contact with the cooling fluid— such as by routing the fluid through a greater number of channels or by adding fins to existing channels where heat transfer occurs. However, in all these approaches, as the contact surface area between the fluid and the surface increases, the friction and corresponding pressure drop also increase. Consequently, greater pump power is required to maintain the same flow rate. In addition, the extra material used to enlarge the surface area increases the weight of both the motor and the vehicle. In either case, as previously noted, the vehicle's driving range is negatively affected.

[0015] 3. Enhancing the thermal conductivity of the cooling fluid: One of the commonly used methods in prior art is to increase the thermal conductivity of the coolant by adding solid-phase nanoparticles with relatively high thermal conductivity, thereby forming fluids with improved heat transfer properties. However, in this approach, along with the increase in thermal conductivity, the viscosity of the fluid also rises. This, in turn, requires the pump circulating the cooling fluid to consume more power to maintain a given flow rate, which negatively affects the vehicle's driving range. Furthermore, the improvement in cooling performance achieved solely through enhanced thermal conductivity remains limited.

[0016] The invention in question eliminates the disadvantages described above, based on the known situation. In this invention, the cooling channels are positioned in regions where the existing internal magnetic field of the motor is effective, and a magnetic fluid is used as the coolant. By doing so, a magnetohydrodynamic (MHD) effect is generated within the flow of the cooling system's channels, thereby enhancing the heat transfer from the motor to the cooling fluid. The potential outcomes of the increased heat transfer achieved through this approach are as follows: 1. Enhanced cooling efficiency allows the motor to be cooled even when the pump operates at a lower flow rate. As the pump's energy consumption decreases, the vehicle's driving range is extended.

[0017] 2. More effective motor cooling corresponds to an increase in the overall cooling capacity of the cooling system. This enables proper cooling even when the motor operates at higher power outputs, thereby improving motor performance.

[0018] 3. Efficient cooling of the motor reduces the motor's operating temperature, which prolongs its service life and, consequently, extends the vehicle's lifespan while reducing maintenance costs.

[0019] The structural and characteristic features and all the advantages of the invention will be more clearly understood due to the figures shown below and, the details referring to these figures and, thus the assessment should be made considering these figures and the details.

[0020] Figures Helping to Understand the Invention

[0021] The invention will be explained with reference to the attached figures so that the features of the invention will be understood more clearly. However, it is not intended to limit the invention to these particular embodiments. On the contrary, it is intended to cover all the alternatives, modifications and equivalents which may be included within the scope of the invention as defined by the appended claims. It is to be understood that the details shown are presented solely for the purpose of illustrating preferred embodiments of the present invention and are presented for the purpose of providing the most useful and easily understandable description of both the embodiment of the methods and the rules and conceptual features of the invention. In these drawings;

[0022] Figure 1: Detailed illustration of the electric motor

[0023] Figure 2: View of the electric motor with axial cooling channels

[0024] Figure 3: Comparison of velocity profiles along the X-axis

[0025] Figure 4: Comparison of velocity profiles along the Y-axis

[0026] Figure 5: View of the magnetic field observed in the cross-section References Helping to Understand the Invention

[0027] 1. Rotor

[0028] 2. Stator

[0029] 3. Shaft

[0030] 4. Coil windings

[0031] 5. Housing

[0032] 6. Magnets

[0033] 7. Cooling channels

[0034] A: Water-ethylene glycol mixture

[0035] B: 1% Cu and water-ethylene glycol mixture

[0036] Detailed Description of the Invention

[0037] In this detailed description, the invention relates to the improvement of the cooling efficiency of electric motors by utilizing the internal magnetic field and magnetic fluids, and it is provided solely for the purpose of better understanding the subject matter without imposing any limiting effect.

[0038] The invention in question consists of:

[0039] • a rotor (1), which is the rotating part of the motor and converts electrical energy into mechanical energy;

[0040] • a stator (2), which is the stationary part of the motor that generates a magnetic field to drive the rotor (1);

[0041] • a shaft (3), which is the rotating element of the motor that transmits the mechanical energy of the rotor (1) outward;

[0042] • coil windings (4), which generate a magnetic field and contribute to the operation of the motor;

[0043] • a housing (5), which protects the internal components of the motor from external factors and ensures operational safety;

[0044] • magnets (6), located on the stator (2) or rotor (1), which create a magnetic field enabling the motor's rotation; and

[0045] • cooling channels (7), which provide the flow of the coolant to prevent overheating and transfer heat from the motor to the cooling fluid in this way. In the invention, the electric motor generates mechanical work through the rotation of the rotor (1) under the influence of the magnetic field formed in the coil windings (4). The stator (2), which is fixed to the vehicle body, remains stationary around the rotor (1), contains the coil windings that generate the motor's magnetic field, and enables the rotor (1) to rotate. When electric current passes through the coil windings (4), a magnetic field is produced, which causes the movement of the rotor (1). During motor operation, both the coil windings (4) and the stator (2) generate a significant amount of heat. To effectively dissipate this heat, cooling channels (7) are placed within the motor. These cooling channels (7) are positioned between the coil windings (4) and the stator (2) in regions of high heat generation to ensure more efficient heat removal. In the invention, magnetohydrodynamic (MHD) effects are induced by using magnetic fluids as the coolant flowing through the cooling channels positioned in regions where the magnetic field is most intense. Through the Lorentz forces exerted by the magnetic field on the fluid, the velocity of the coolant increases, the flow profile changes, and these effects enhance heat transfer. Such interactions improve the motor's temperature regulation, allowing it to operate safely at lower temperatures. Consequently, the cooling capacity of the motor is increased, and its overall performance is improved.

[0046] In this invention, the primary objective is to enhance the cooling efficiency of electric motors by increasing convective heat transfer. The targeted improvement in convective heat transfer is achieved by utilizing the magnetic field that already exists within the motor. The fundamental operating principle of electric motors is the generation of mechanical work through the rotation of the shaft, which results from the interaction between the permanent magnets (6) and the electric current passing through the coil windings (4). In electric motors, the regions with the high heat generation are the coil windings (4), which produce heat due to the current flowing through them, and the stator (2), where iron losses are concentrated, especially in high-speed motors. For this reason, the cooling channels (7) are positioned between the coil windings (4), in close proximity to both the coil windings (4) and the permanent magnets (6), where heat generation is most intense and the magnetic field is strongest. Figures 1 and 2 illustrate the electric motor and the positioning of the axial cooling channels (7). With this arrangement, the channels are located nearer to the components that heat up more significantly, which positively contributes to the overall cooling efficiency of the motor. Furthermore, since the magnetic forces are relatively stronger in these regions, the use of magnetic fluids as the coolant enables the utilization of magnetohydrodynamic (MHD) effects. These fluids consist of magnetic liquid metals (such as gallium and its alloys, mercury, and similar substances) or magnetic fluids (magnetic nanofluids or magnetic colloids). Magnetic fluids are liquids that can be influenced by magnetic forces and possess high electrical conductivity. In addition to liquid metals, the base fluid— such as water, ethylene glycol, a water / ethylene glycol mixture, or oil-can be ionically doped to enhance electrical conductivity and combined with nanoparticles exhibiting high thermal and electrical conductivity (for example, CuO - copper oxide, Fe2O4- magnetite ferrite, MnZnFe2O4- manganese-zinc ferrite, NiZnFe2O4- nickel-zinc ferrite, and all materials with similar properties).

[0047] In this invention, the magnetohydrodynamic (MHD) effects activated are based on the Lorentz forces exerted by the magnetic field on the fluid, which increase the velocity of the fluid— particularly near the wall regions— and thereby enhance the effectiveness of convective heat transfer in these areas. While the average velocity of the fluid increases due to the MHD effect, the flow profile also changes accordingly. This phenomenon is illustrated in Figures 3 and 4, which show the velocity profiles of the magnetic fluid (B) influenced by the magnetic field, compared to the non-magnetic fluid (A) that has similar flow and thermal properties. The distribution of the magnetic field in this region is shown in Figure 5. In particular, in areas where the magnetic field is stronger, the axial velocities increase, leading to an enhancement of the convective heat transfer coefficient, which indicates the effectiveness of convective heat transfer. As a result of the significant improvement in convective heat transfer, the motor temperature is considerably reduced under a constant thermal load, while for a specified maximum temperature, the motor's cooling capacity is substantially increased.

[0048] The technical features mentioned in each claim are follows by the reference numbers, which are used only to facilitate the understanding of the claims, therefore it should not be considered that the procedure steps indicated by these reference numbers for the purpose of sampling limit the respective scope.

[0049] It is obvious that a person specialized about the technique may reveal the innovation specified in this invention by means of using similar structures and / or implements this structure in other areas with similar purposes used in the respective technique. Therefore, it is also obvious that such structures would lack of innovation and, in particular, the criterion to exceed the known condition of the technique.

Claims

CLAIMS1. The invention relates to the improvement of the cooling efficiency of electric motors by utilizing the internal magnetic field and magnetic fluids, and it is characterized by the following components:• a rotor (1), which is the rotating part of the motor and converts electrical energy into mechanical energy;• a stator (2), which is the stationary part of the motor that generates a magnetic field to drive the rotor (1);• a shaft (3), which transmits the mechanical energy of the rotor (1) outward and forms the rotating element of the motor;• coil windings (4), which generate a magnetic field and contribute to the operation of the motor;• a housing (5), which protects the internal components of the motor from external factors and ensures operational safety;• magnets (6), located on the stator (2) or rotor (1), which create a magnetic field enabling the motor's rotation; and• cooling channels (7), which provide the flow of the coolant to prevent overheating and transfer heat from the motor to the cooling fluid in this way.

2. According to Claim 1, the invention relates to the improvement of the cooling efficiency of electric motors by utilizing the internal magnetic field and magnetic fluids, and it is characterized in that the cooling channels (7) are positioned near the coil windings (4) and the permanent magnets (6), where heat generation is intense and the magnetic field is strong.

3. According to Claim 1, the invention relates to the improvement of the cooling efficiency of electric motors by utilizing the internal magnetic field and magnetic fluids, and it is characterized in that, in regions where convective heat transfer is intense and magnetic forces are relatively strong, the magnetohydrodynamic (MHD) effect in cooling is achieved by using magnetic fluids— such as magnetic liquid metals (gallium and its alloys, mercury, etc.) or magnetic fluids (magnetic nanofluids or magnetic colloids, etc.)— as the coolant.

4. The invention relates to the improvement of the cooling efficiency of electric motors by utilizing the internal magnetic field and magnetic fluids, and it is characterized in that, in addition to liquid metals, the coolant comprises a base fluid with enhanced electrical conductivity through ionic doping, containing nanoparticles with both thermal and electrical conductivity.

5. According to Claim 4, the invention relates to the improvement of the cooling efficiency of electric motors by utilizing the internal magnetic field and magnetic fluids, and it is characterized in that the base fluid with enhanced electrical conductivity through ionic doping comprises water, ethylene glycol, a water / ethylene glycol mixture, oil, or similar substances.

6. According to Claim 4, the invention relates to the improvement of the cooling efficiency of electric motors by utilizing the internal magnetic field and magnetic fluids, and it is characterized in that the coolant contains one or more types of nanoparticles selected from copper oxide, magnetite ferrite, manganese-zinc ferrite, and nickel-zinc ferrite.

Images