Oil Friction Loss Evaluation of Oil-Immersed Cooling In-Wheel Motor Based on Improved Analytical Method and VOF Model
Abstract
:1. Introduction
2. Methods
2.1. An Improved Analytical Derivation
- (1)
- The rotor and stator are both simplified to cylinders, as shown in Figure 1. The oil friction loss is divided into two parts: oil friction loss generated in air gap and oil friction loss generated at both ends of the bottom of the cylinder, which are calculated respectively.
- (2)
- The fluid motion in the air gap is considered as circular steady laminar flow, so the axial and radial velocities are approximately 0. The mass force is ignored, and there is no pressure difference in the axial direction.
- (3)
- The fluid flow at the end of the cylinder is assumed to be a steady flow, the velocity does not change with θ, and the mass force is ignored.
2.2. Numerical Analysis Procedure
2.2.1. Model Definition and Mesh
2.2.2. Governing Equation
2.2.3. Sliding Mesh Method and Boundary Conditions
2.2.4. Convergence Criteria
2.3. Experimental Procedure
2.3.1. Setup
2.3.2. Loss Measurement
- (1)
- Test the loss with a fixed oil-soaked depth inside the motor. Pour 1500 mL of ATF cooling oil into the testing motor, which is equivalent to the oil-soaked depth of 112.5 mm. The equivalent method can be followed as formula (23), which is obtained by numerical fitting of the fifth-degree polynomial. Record the stable torque with different speeds.
- (2)
- Testing the loss with different oil-soaked depths. Set a fixed speed of 1000 rpm, pour 800 mL of ATF cooling oil into the testing motor firstly, and record the stable torque. Then, change the oil quantity and record the stable torque:
2.3.3. Uncertainly Analysis
3. Results
4. Conclusions
- The improved method analytical has higher computational accuracy than those previously studied. It is suitable for the early design of an oil-immersed cooling motor. When the design parameters need to be adjusted, the designer can quickly calculate the oil friction loss.
- The VOF model can accurately reflect the law of oil friction loss under the rotation speed and oil-soaked depth. The maximum error between theoretical calculation and testing data is less than 10%. It is useful in the later optimization design of the oil-immersed cooling motor, and the oil friction loss caused by the variation of local structure can be calculated by the model.
- The oil friction loss is proportional to the first power of the oil-soaked depth and the 2nd–3rd power of the rotational speed.
Author Contributions
Funding
Conflicts of Interest
References
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Parameter | Value |
---|---|
Rated power/kW | 200 |
Peak power/kW | 445 |
Rated power/rpm | 1000 |
Maximum speed/rpm | 5000 |
Slots | 36 |
Stator Diameter/mm | 430 |
Air gap/mm | 2 |
Rotor Diameter/mm | 316 |
Axial length of iron core/mm | 104 |
inner cavity volume/mL | 8300 |
Medium | Density (kg/m3) | Dynamic Viscosity (Pa × s) |
---|---|---|
Oil-ATF220 | 867.2 | 0.07805 |
air | 1.205 | 1.81 × 10−5 |
Speed (rpm) | 1000 | 2000 | 3000 | 4000 | 5000 |
---|---|---|---|---|---|
Kori’s method/kW [Error/%] | 0.31 [42] | 1.24 [33] | 2.80 [47] | 4.97 [54] | 7.77 [55] |
Improved method/kW [Error/%] | 0.46 [13] | 2.06 [−11] | 5.04 [4.0] | 9.56 [12] | 15.8 [8.7] |
VOF model/kW [Error/%] | 0.52 [1.8] | 1.70 [8.6] | 4.78 [8.9] | 11.5 [−5.2] | 16.1 [6.9] |
Testing value/kW | 0.53 | 1.86 | 5.25 | 10.93 | 17.3 |
h (m) | 0.0843 | 0.1014 | 0.1125 | 0.2125 |
---|---|---|---|---|
Kori’s method/kW [Error/%] | 0.22 [30] | 0.28 [36] | 0.31 [42] | 0.55 [54] |
Improved method/kW [Error/%] | 0.28 [12] | 0.39 [11] | 0.46 [13] | 1.12 [6.7] |
VOF model/kW [Error/%] | 0.29 [9.0] | 0.41 [6.8] | 0.52 [1.8] | 1.16 [3.3] |
Testing value/kW | 0.32 | 0.44 | 0.53 | 1.20 |
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Yin, Y.; Li, H.; Xiang, X. Oil Friction Loss Evaluation of Oil-Immersed Cooling In-Wheel Motor Based on Improved Analytical Method and VOF Model. World Electr. Veh. J. 2021, 12, 164. https://doi.org/10.3390/wevj12040164
Yin Y, Li H, Xiang X. Oil Friction Loss Evaluation of Oil-Immersed Cooling In-Wheel Motor Based on Improved Analytical Method and VOF Model. World Electric Vehicle Journal. 2021; 12(4):164. https://doi.org/10.3390/wevj12040164
Chicago/Turabian StyleYin, Yi, Hui Li, and Xuewei Xiang. 2021. "Oil Friction Loss Evaluation of Oil-Immersed Cooling In-Wheel Motor Based on Improved Analytical Method and VOF Model" World Electric Vehicle Journal 12, no. 4: 164. https://doi.org/10.3390/wevj12040164