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An Electric Motor Thermal Bus Cooling System for Vehicle Propulsion – Design and Test

CCDC Ground Vehicle Systems Center-Katherine Sebeck
Clemson University-Shervin Shoai Naini, Richard Miller, John Wagner
  • Technical Paper
  • 2020-01-0745
To be published on 2020-04-14 by SAE International in United States
Automotive and truck manufacturers are introducing electric propulsion systems into their ground vehicles to reduce fossil fuel consumption and harmful tailpipe emissions. The mobility shift to electric motors requires a compact thermal management system that can accommodate heat dissipation demands with minimum energy consumption in a confined space. An innovative cooling system design, emphasizing passive cooling methods coupled with a small liquid system, using a thermal bus architecture will be explored. The laboratory experiment features an emulated electric motor interfaced to a thermal cradle and multiple heat rejection pathways to evaluate the transfer of generated heat to the ambient surroundings. The thermal response of passive (e.g., carbon fiber, high thermal conductivity material, thermosyphon) and active cooling systems are investigated for two operating scenarios. The test results demonstrate significant improvements can be achieved in cooling system energy consumption while maintaining a target e-motor temperature of 70℃. The governing thermal system dynamics will be reviewed in discussion of the experimental observations.
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Machine Learning Based Optimal Energy Storage Devices Selection Assistance for Vehicle Propulsion Systems

Clemson University-Bin Xu
Stanford University-Simona Onori
  • Technical Paper
  • 2020-01-0748
To be published on 2020-04-14 by SAE International in United States
This study investigates the vehicle propulsion system energy storage devices selection. In recent years, powertrain electrification has been popular in all kinds of vehicles such as commercial vehicles and military utility vehicles. Energy storage devices are necessary for all levels of electrification. However, due to the large number of available energy storage devices (e.g. chemistry, size, energy density, and power density), and various class of vehicles (e.g. weight, range, acceleration, operating road environment), the energy storage devices selection process requires tremendous work if using traditional method. This study aims to assist the energy storage devices selection using the data sets collected from existing vehicles that equipped with energy storage devices. Machine Learning models are used to extract the relationship between the vehicles and the corresponding energy storage devices. After the training, the Machine Learning models can predict the ideal energy storage devices given the target vehicles design parameters as the inputs. The predicted ideal energy storage devices can be treated as the initial design and modification can be made based on the validation results. With…
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An Innovative Electric Motor Cooling System for Hybrid Vehicles - Model and Test

Clemson University-Shervin Shoai Naini, Junkui (Allen) Huang, Richard Miller, John R. Wagner
US Army TARDEC-Denise Rizzo, Katherine Sebeck, Scott Shurin
Published 2019-04-02 by SAE International in United States
Enhanced electric motor performance in transportation vehicles can improve system reliability and durability over rigorous operating cycles. The design of innovative heat rejection strategies in electric motors can minimize cooling power consumption and associated noise generation while offering configuration flexibility. This study investigates an innovative electric motor cooling strategy through bench top thermal testing on an emulated electric motor. The system design includes passive (e.g., heat pipes) cooling as the primary heat rejection pathway with supplemental conventional cooling using a variable speed coolant pump and radiator fan(s). The integrated thermal structure, “cradle”, transfers heat from the motor shell towards an end plate for heat dissipation to the ambient surroundings or transmission to an external thermal bus to remote heat exchanger. A complete lumped parameter numerical modelling was implemented to estimate the thermal behavior of the corresponding electric motor cooling system. Experimental and numerical results compare the temperature, heat flux, and cooling power measurements. For 250VA thermal load applied, the hybrid heat rejection strategy could save up to 33% of the power consumption while the operating…
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A Hybrid Thermal Bus for Ground Vehicles Featuring Parallel Heat Transfer Pathways

SAE International Journal of Commercial Vehicles

Clemson Unversity-Shervin Shoai Naini, Junkui (Allen) Huang, Richard Miller, John R. Wagner
US Army TARDEC-Denise Rizzo, Katherine Sebeck, Scott Shurin
  • Journal Article
  • 2018-01-1111
Published 2018-04-03 by SAE International in United States
Improved propulsion system cooling remains an important challenge in the transportation industry as heat generating components, embedded in ground vehicles, trend toward higher heat fluxes and power requirements. The further minimization of the thermal management system power consumption necessitates the integration of parallel heat rejection strategies to maintain prescribed temperature limits. When properly designed, the cooling solution will offer lower noise, weight, and total volume while improving system durability, reliability, and power efficiency. This study investigates the integration of high thermal conductivity (HTC) materials, carbon fibers, and heat pipes with conventional liquid cooling to create a hybrid “thermal bus” to move the thermal energy from the heat source(s) to the ambient surroundings. The innovative design can transfer heat between the separated heat source(s) and heat sink(s) without sensitivity to gravity. A case study examines the thermal stability, heat dissipation capabilities, power requirements, and system weights for several driving cycles. Representative numerical results show that the HTC materials and carbon fibers offer moderate cooling while loop heat pipes provide significant improvements for passive cooling.
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An Integrated Cooling System for Hybrid Electric Vehicle Motors: Design and Simulation

SAE International Journal of Commercial Vehicles

Clemson University-Junkui (Allen) Huang, Shervin Shoai Naini, Richard miller, John R. Wagner
US Army TARDEC-Denise Rizzo, Katherine Sebeck, Scott Shurin
  • Journal Article
  • 2018-01-1108
Published 2018-04-03 by SAE International in United States
Hybrid electric vehicles offer the advantages of reduced emissions and greater travel range in comparison to conventional and electric ground vehicles. Regardless of propulsion strategy, efficient cooling of electric motors remains an open challenge due to the operating cycles and ambient conditions. The onboard thermal management system must remove the generated heat so that the motors and other vehicle components operate within their designed temperature ranges. In this article, an integrated thermal structure, or cradle, is designed to efficiently transfer heat within the motor housing to the end plates for transmission to an external heat exchanger. A radial array of heat pipes function as an efficient thermal connector between the motor and heat connector, or thermal bus, depending on the configuration. Cooling performance has been evaluated for various driving cycles. Numerical results show that 1.3 kW of peak heat wattage can be accommodated with free convection while 3.2 kW is obtained by adding forced convection using 13.7 W of electric power. The internal motor temperature is maintained within the prescribed limits of 75°C and 55°C…
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Cooling Parasitic Considerations for Optimal Sizing and Power Split Strategy for Military Robot Powered by Hydrogen Fuel Cells

US Army TARDEC-Denise Rizzo
University of Michigan-Jason B. Siegel, Anna G. Stefanopoulou, Niket Prakash
Published 2018-04-03 by SAE International in United States
Military vehicles are typically armored, hence the open surface area for heat rejection is limited. Hence, the cooling parasitic load for a given heat rejection can be considerably higher and important to consider upfront in the system design. Since PEMFCs operate at low temp, the required cooling flow is larger to account for the smaller delta temperature to the air. This research aims to address the combined problem of optimal sizing of the lithium ion battery and PEM Fuel Cell stack along with development of the scalable power split strategy for small a PackBot robot. We will apply scalable physics-based models of the fuel cell stack and balance of plant that includes a realistic and scalable parasitic load from cooling integrated with existing scalable models of the lithium ion battery. This model allows the combined optimization that captures the dominant trends relevant to component sizing and system performance. The baseline optimal performance is assessed using dynamic programming for a reduced order model, by assuming a static cooling load required to maintain the stack at the…
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Computationally-Efficient Heat Convection Model for Electric Machines

US Army TARDEC-Denise Rizzo, Scott Shurin
University of Michigan-Yuanying Wang, Heath Hofmann
Published 2017-03-28 by SAE International in United States
This paper presents a computationally-efficient model of heat convection due to air circulation produced by rotor motion in the air gap of an electric machine. The model calculates heat flux at the boundaries of the rotor and stator as a function of the rotor and stator temperatures and rotor speed. It is shown that, under certain assumptions, this mapping has the homogeneity property. This property, among others, is used to pose a structure for the proposed model. The coefficients of the model are then determined by fitting the model to the results of a commercial Computational Fluid Dynamics (CFD) simulation program. The accuracy of the new model is compared to the CFD results, shown an error of less than 0.3% over the studied operating range.
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A Thermal Bus for Vehicle Cooling Applications - Design and Analysis

SAE International Journal of Commercial Vehicles

Clemson University-Shervin Shoai Naini, Junkui (Allen) Huang, Richard Miller, John R. Wagner
TARDEC-Katherine Sebeck
  • Journal Article
  • 2017-01-0266
Published 2017-03-28 by SAE International in United States
Designing an efficient cooling system with low power consumption is of high interest in the automotive engineering community. Heat generated due to the propulsion system and the on-board electronics in ground vehicles must be dissipated to avoid exceeding component temperature limits. In addition, proper thermal management will offer improved system durability and efficiency while providing a flexible, modular, and reduced weight structure. Traditional cooling systems are effective but they typically require high energy consumption which provides motivation for a paradigm shift. This study will examine the integration of passive heat rejection pathways in ground vehicle cooling systems using a “thermal bus”. Potential solutions include heat pipes and composite fibers with high thermal properties and light weight properties to move heat from the source to ambient surroundings. An initial case study focuses on the integration of heat pipes in a thermal bus to transfer heat from the thermal load (e.g., internal combustion engine, electric motor, battery pack, power electronic, etc.) to the heat exchanger. A mathematical U-shaped pulsating heat pipe model is used to numerically describe…
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Optimal Power Management of Vehicle Sourced Military Outposts

SAE International Journal of Commercial Vehicles

Michigan Technological University-Robert Jane, Gordon G. Parker, Wayne Weaver, Ronald Matthews, Michael Cook
US Army TARDEC-Denise Rizzo
  • Journal Article
  • 2017-01-0271
Published 2017-03-28 by SAE International in United States
This paper considers optimal power management during the establishment of an expeditionary outpost using battery and vehicle assets for electrical generation. The first step in creating a new outpost is implementing the physical protection and barrier system. Afterwards, facilities that provide communications, fires, meals, and moral boosts are implemented that steadily increase the electrical load while dynamic events, such as patrols, can cause abrupt changes in the electrical load profile. Being able to create a fully functioning outpost within 72 hours is a typical objective where the electrical power generation starts with batteries, transitions to gasoline generators and is eventually replaced by diesel generators as the outpost matures. Vehicles with power export capability are an attractive supplement to this electrical power evolution since they are usually on site, would reduce the amount of material for outpost creation, and provide a modular approach to outpost build-up. Military vehicles have the attributes of a microgrid and when connected produce a scalable power generation capability [1]. For example, each vehicle could power a subset of the outpost’s build-up…
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