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Technical Paper

Heat Transfer Analysis of an Electric Motor Cooled by a Large Number of Oil Sprays Using Computational Fluid Dynamics

2022-03-29
2022-01-0208
This paper reports on an analytical study of the heat transfer and fluid flow in an electric vehicle e-Motor cooled by twenty five sprays/jets of oil. A three-dimensional, steady state, multi-phase, computational fluid dynamics (CFD) and conjugate heat transfer (CHT) model was created using a commercial CFD software. The transport equations of mass, momentum, energy and volume fraction were solved together with models for turbulence and wall treatment. An explicit formulation of the volume of fluid (VOF) technique was used to simulate the sprays, a time-implicit formulation was used for the flow-field and three dimensional conduction heat transfer with non-isotropic thermal conductivities was used to simulate the heat transfer in the windings.
Technical Paper

Multiphysics approach for thermal design of liquid cooled EV battery pack

2022-03-29
2022-01-0209
Thermal management of battery packs is essential to keep the cell temperatures within safe operating limits at all times and, hence, ensure the healthy functioning of an EV. The life cycle of a cell is largely influenced by its operating temperature, maintaining the cell temperature in its optimum range improves its longevity by decreasing its capacity fade rate and in turn extending the life of an EV. Liquid cooling techniques have proven to be cost-effective compared to other techniques such as air cooling, PCM-based in terms of performance in the given volumetric constraints. The battery thermal management solution being presented employs a tabbed type liquid cooling technology that achieves low-temperature differentials for an in-house designed battery pack consisting of 320 LFP cells (Size: 32700) with a total voltage and capacity of 27V and 240Ah respectively. Thermal design of the battery pack considers maximum dissipation when continuously operating at 1C-rate conditions.
Technical Paper

1D-3D Coupled Analysis for Motor Thermal Management in an Electric Vehicle

2022-03-29
2022-01-0214
Motor thermal management of electric vehicles (EVs) is becoming more significant due to its close relations to vehicle aerodynamic performance and energy consumption, while computer aided engineering (CAE) plays an important role in its development. A 1D-3D coupled model is established to characterize transient thermal performance of the motor in an electric vehicle on a high performance computer (HPC) platform. The 1D motor thermal management model is integrated with the 1D powertrain model, and a 3D thermal model is established for the motor, while online data exchange is realized between the 1D and 3D models. The 1D model gives boundaries such as inlet coolant temperature, mass flowrate and motor heat generation to the 3D model, while 3D gives back boundaries such as heat transfer to coolant simultaneously. Transient simulations are performed for the 140kph(20℃) driving cycle, and the model is calibrated with experimental data.
Technical Paper

Demonstrating UVC LED Inside Automobile HVAC Chambers for Clean Cabin Air and Airborne Transmission Risk Reduction

2022-03-29
2022-01-0197
The COVID-19 pandemic affected mobility in many ways- from changing business models of moving passenger to delivering packages and food, developing cleaning protocols for interiors and increasing the awareness of consumers to the hidden dangers of pathogens and viruses in an enclosed space. A trend towards healthy cars is believed to remain after the current pandemic and has led to the emergence of new safety features, from CO2 gas sensors, to antimicrobial fabrics, and enhanced air purifiers. While air purifiers trap contaminants using cartridge filters, they are not particularly efficient at removing viral particles and create large pressure drops, which must be compensated with larger fans, increasing noise and power consumption, both of which are not optimal for vehicle HVAC systems. However, air purifiers act as a pressure head, which limits their utility. UVC was not previously an option because mercury lamps pose their own electrical and chemical hazards.
Technical Paper

Use of Thermally Conductive Electrically Insulative (TCEI) Materials in E-motor Slot Liner Applications

2022-03-29
2022-01-0198
Slot liners are commonly used in electric motors to electrically insulate the motor windings from the laminated core. However, thermal conductivity of materials commonly used as slot liners is very low compared to other components in the motor thus creating a barrier for heat transfer. This thermal barrier affects overall motor performance and efficiency. Also, slot liners typically lack intimate contact with the laminated core resulting in air gaps which further increase thermal resistance in the system. Slot liners are traditionally made from high temperature films/papers that are cut and slid into slots of motors. The proposed work looks at developing an injection moldable slot liner to minimize air gaps. Additionally, use of TECI materials further lowers thermal resistance. A thermal finite element model has been developed to evaluate effects of slot liner thermal properties and air gaps on temperature distribution within the motor.
Technical Paper

Development of Vehicle Thermal Management Model for Improving the Energy Efficiency of Electric Vehicle

2022-03-29
2022-01-0201
Recently, automobile manufacturers are interested in the development of battery electric vehicle (BEV) having a longer mileage to satisfy customer needs. The BEV with high efficiency depends on the temperature of the electric components. Hence it is important to study the effect of the cooling system in electric vehicle in order to optimize efficiency and performance. In this study, we present a 1-D vehicle thermal management (VTM) simulation model. The individual vehicle subsystems were modeled including cooling, power electric (PE), mechanical, and control components. Each component was integrated into a single VTM model and it would be used to calculate energy transfer among electrical, thermal, and mechanical energy. As a result, this simulation model predicts a plenty of information including the state of each component such as temperature, energy consumption, and operating point about electric vehicle depending on driving cycles and environmental conditions.
Technical Paper

Adjoint method in optimizing conformal cooling channels of 3-D printed high-pressure tools for aluminium casting

2022-03-29
2022-01-0246
The emergence of additive manufacturing (AM) technology has enabled the internal cooling channel layout for high pressure aluminium die casting (HPADC) tools to be designed and modified without topological constraint. Optimisation studies of a full industrial HPADC mould for extending the tool service life has received limited attention due to the high geometrical complexity and the various physics with multi time and length scales in addition to the manufacturability limitations. In this work a new computational efficient algorithm that employs the adjoint optimization method has been developed to optimize the coolant channels layout in a complete mould with various 3D printed inserts. The algorithms reduced significantly the computational time and resources by decoupling the fluid flow in the coolant channels from the tool and simulating them separately.
Technical Paper

Non-destructive Evaluation of the Magnetic Quality of Electrical Steel Sheets by Magnetic Barkhausen Noise (MBN) Analysis

2022-03-29
2022-01-0235
Soft magnetic lamination core is a major component of all electric motors, and the magnetic quality of the lamination has a significant effect on the energy efficiency of the motor. The magnetic properties of electrical steel sheets, which are important design parameters for the manufacturing of electric motors, are normally measured on cut steel strips by standard Epstein frame method, which is destructive and is not suitable for the evaluation of magnetic anisotropy. This paper presents a relatively new technology, i.e., magnetic Barkhausen noise (MBN) analysis, to evaluate the magnetic quality of electrical steel sheets. This method is featured by non-destructive, simple measurement, short measuring time, and online/offline measurements, etc. In addition, it can be readily used to estimate the magnetic anisotropy of electrical steel sheets.
Technical Paper

Analysis on Irreversible Demagnetization Condition of Linear Oscillatory Actuator with Moving Magnets

2022-03-29
2022-01-0281
In this paper, a linear oscillatory actuator with moving magnets used in active engine mount is modeled and theoretically analyzed considering its performance decline at high temperature. Firstly, a finite element model of the linear oscillatory actuator with moving magnets is established. The actuator force is decomposed to ampere force and cogging force through formation mechanism analysis. By using the finite element model, ampere force and cogging force of the linear oscillatory actuator with moving magnets under different current loads and different mover positions are calculated. The finite element model and calculation method are validated by bench level test. The voice coil constant and cogging coefficient at room temperature are identified, which indicates the actuator force is a linear model related to the current and the mover position.
Technical Paper

Thermomechanical behavior of an automotive exhaust aftertreatment application

2022-03-29
2022-01-0277
An aftertreatment system is the back-end component of an automotive exhaust system, used mainly to reduce pollutant emissions. This system is exposed to high thermal loads which can exceed temperatures of 900 oC , usually they operate at temperatures under 600 oC - 700 oC, depending of the engine application. The durability assessment of a system under thermomechanical loads can be challenging due to the complexity of the technical problem, which involves complex material behavior at high temperatures and results in high thermomechanical strains and stresses. This study presents a computational approach for the lifetime assessment of an exhaust aftertreatment system subjected to thermomechanical loading. The method is composed of a fluid flow analysis to compute the temperature fields which are mapped to a mechanical analysis combined with a nonlinear elastoviscoplastic material behavior. Lastly, the lifetime of the overall assembly is assessed through a fatigue analysis.
Technical Paper

Effect of geometric parameters on folding of thin-walled steel tube under axial compression

2022-03-29
2022-01-0264
This study investigated the plastic deformation behavior of 304 stainless steel thin-walled tubes under axial compression by means of numerical calculation and theoretical analysis. It was found that the plastic deformation length of thin-walled tube determined the formability of folds and the work done in the whole axial compression process. To reveal the relation between the range of plastic deformation length and tube geometry parameters, regression equations were established using the quadratic regression orthogonal design method. Experiments were conducted to validate the equations. The process windows for forming a single fold and tube joining at ends had been printed ultimately. The results showed that the regression equations can accurately predict the range of plastic deformation length for forming a single fold.
Technical Paper

Remove unwanted Vibrations for HVAC by Altering Modal Frequency using Finite Element Modeling and Validating Experimentally

2022-03-29
2022-01-0316
The main Objective of this paper is to remove the abnormal noise by altering the modal frequency. From the numerical method, very high deflection is reported at HVAC assembly level, cause unwanted vibrations. Due to high deflection at low frequency (1st modal frequency), abnormal noise coming near blower assembly under experimentally dynamic conditions. Then, improved the design by adding the stiffeners on the flange to minimize unwanted vibrations and hence abnormal nose. Thereafter, modal frequency has been increased and reduced the high deflection. The same has been validated experimentally with proto sample and found no abnormal noise from the blower side. A good correlation between the numerical and experimental result is observed and matching numerical & experimental modal frequencies within the accuracy of ±10%.
Technical Paper

Numerical Investigation on the Internal Flow Field of Electronic Expansion Valve as the Throttle Element

2022-03-29
2022-01-0318
As one of the key components of the heat pump system, the electronic expansion valve mainly plays the role of throttling and reducing pressure in the heat pump system. The refrigerant flowing through the orifice will produce complex phase change. It is of great significance to study the internal flow field by means of CFD calculations. Firstly, a three-dimensional fluid model is established and the mesh is divided. Secondly, the phase change model is selected, the material is defined and the boundary conditions are determined. According to the principle of the fluid passing through thin-walled small holes, the flow characteristics of electronic expansion valve are theoretically analyzed. Then the flow characteristics of expansion valve are numerically calculated, and a bench for testing mass flow rate of the expansion valve is built. Then the theoretical value, CFD value and experimental value are compared to verify the correctness of the established three-dimensional fluid model.
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