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Thermal Analysis of Parallel Connected Li-Ion Batteries For Hybrid Aircraft

Anadolu University-Hikmet Karakoç
Howard University-Nadir Yilmaz
  • Technical Paper
  • 2020-01-0891
To be published on 2020-04-14 by SAE International in United States
Improving the energy performance of batteries will certainly increase the reliability of electric aircraft and thus their penetration into the market. To achieve this goal, battery management systems are required to keep the temperature below the safety limits and make the temperature distribution as even as possible within the battery pack and cells. Li-ion batteries are suitable for electric aircraft due to their high specific energy and advantage of energy density. In this study, 20 14.6 Ah prismatic batteries were connected in 2 parallel 10 series. Three-dimensional thermal analysis was performed for forced and natural transport conditions under 4 different discharge rates (0.5C, 1C, 2C, 2.5C) of the batteries. The study was conducted with Ansys Fluent. The NTGK Empirical model was chosen and a simple algorithm was used. A second order upwind method was chosen for pressure, momentum and energy equations. Batteries were tested for mesh independency. When the number of nodes in natural transport was increased from 43,204 to 345,560, the change in heat transfer was 0.1%. As the current rate given to the…
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Unsettled Domains Concerning Electric Propulsion Technology for Commercial Aircraft

drR2 Consulting-Ravi Rajamani
  • Research Report
  • EPR2019006
Published 2019-12-30 by SAE International in United States
According to some, electric propulsion is already on its way down the “trough of disillusionment.” This report argues that while there are some concerns with associated technologies, such pessimism is unwarranted. Yes, battery systems can be more energy dense; charging standards are late in being developed; it is not clear what technologies and architectures will win out for which sectors; we still have to figure out how to deal with thermal management issues at all levels in future designs; and what might be the certification standards for electric aircraft. But that does not mean that these issues will not be addressed. Yes, these unsettled questions may take a little longer to solve than originally estimated, but there is full expectation within the industry that electric propulsion for commercial aircraft will succeed. In this SAE EDGE Research Report we present points of view from leading researchers in the industry who are thinking deeply about solving these problems.NOTE: SAE EDGE™ Research Reports are intended to identify and illuminate key issues in emerging, but still unsettled, technologies of…
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SAE Aerospace Applied Thermodynamics Manual Aerothermodynamic Systems Engineering and Design

AC-9 Aircraft Environmental Systems Committee
  • Aerospace Standard
  • AIR1168/3A
  • Current
Published 2019-09-24 by SAE International in United States
This section presents methods and examples of computing the steady-state heating and cooling loads of aircraft compartments. In a steady-state process the flows of heat throughout the system are stabilized and thus do not change with time. In an aircraft compartment, several elements compose the steady-state air conditioning load. Transfer of heat occurs between these sources and sinks by the combined processes of convection, radiation, and conduction in the following manner: 1 Convection between the boundary layer and the outer airplane skin. 2 Radiation between the external skin and the external environment. 3 Solar radiation through transparent areas directly on flight personnel and equipment and on the cabin interior surfaces. 4 Conduction through the cabin walls and structural members. 5 Convection between the interior cabin surface and the cabin air. 6 Convection between cabin air and flight personnel or equipment. 7 Convection and radiation from internal sources of heat such as electrical equipment. The subsequent paragraphs discuss methods of determining each of the heat transfer rates listed above, as well as the physiological considerations involved…
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Gradationally Controlled Voltage Inverter for More Electric Aircrafts

IHI Corporation-Hitoshi Oyori
Mitsubishi Electric Corp.-Tetsuya Kojima, Masahiro Sugahara, Yusuke Shirouchi, Hisatoshi Fukumoto, Akihiko Iwata
Published 2019-09-16 by SAE International in United States
The more electric aircraft (MEA) concept has been attracting attention over recent decades to reduce emissions and fuel consumption. In MEAs, many subsystems that previously used hydraulic or pneumatic power have been replaced by electrical systems, and hence the weight of inverters has significant importance. The weight of inverters is largely attributed to passive filters that reduce the derivative of output voltages dv/dt and electromagnetic interference noises caused by common-mode voltages. To reduce the size of passive filters, multilevel inverters with 5 or more voltage steps are preferred. However, classic multilevel inverters have some challenges to achieve these step numbers without using plural dc power supplies that require massive transformers. In this work, a gradationally controlled voltage (GCV) inverter is proposed for MEAs. The GCV inverter can supply gradational quasi-sinusoidal voltages with 7 voltage steps, combining two different voltages from a three-level (main) inverter and H-bridge (sub) inverters. In addition, only one dc power supply is required for the main inverter. Furthermore, when sub inverters have faults, the GCV inverter can continue operation using the…
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Design and Experimental Verification of a High Force Density Tubular Permanent Magnet Linear Motor for Aerospace Application

Daido University-Yoshiaki Kano
KYB Corporation-Kousuke Satou
Published 2019-09-16 by SAE International in United States
This paper presents the design and construction of a high force density tubular permanent-magnet (PM) linear motor. A strut structure of a tubular PM linear motor developed to improve resistance to impurities and structural rigidity is described.In the design, computationally efficient two-dimensional finite-element analysis is used to estimate the motor force density. The motor’s design is optimized for the major pole number/slot number combinations of 8/24, 16/24, 20/24, 28/24, 32/24, and 40/24. The optimized motor design of a three-phase 16/24 combination with one-layer winding achieved the highest force-to-mass density. The force-to-mass density of the designed motor is higher than that of the first prototype motor by a factor of 5. The validity of the proposed design method and the expected drive characteristics are experimentally verified using the prototype.
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Flight Optimization Model on Global and Interval Ranges for Conceptual Studies of MEA Systems

Akita University-Yotsugi Shibuya
IHI Corporation-Hitoshi Oyori, Hirotaka Sugawara, Naoki Seki
Published 2019-09-16 by SAE International in United States
In development of more electric aircraft applications, it is important to discuss aircraft energy management on various level of aircraft operation. This paper presents a computationally efficient optimization model for evaluating flight efficiency on global and interval flight ranges. The model is described as an optimal control problem with an objective functional subjected to state condition and control input constraints along a flight path range. A flight model consists of aircraft point-mass equations of motion including engine and aerodynamic models. The engine model generates the engine thrust and fuel consumption rate for operation condition and the aerodynamic model generates the drag force and lift force of an aircraft for flight conditions. These models is identified by data taken from a published literature as an example. First, approximate optimization process is performed for climb, cruise, decent and approach as each interval range path. Next, optimization for global range path involves whole flight path to find optimal operation condition in the flight. In aircraft energy management, fuel consumption converts into not only thrust power, but power of…
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Electromagnetic Characteristic Comparison of Superconducting Synchronous Motor Characteristics for Electric Aircraft Propulsion Systems

IHI Corporation-Hitoshi Oyori
The University of Tokyo-Yutaka Terao, Yusuke Ishida, Hiroyuki Ohsaki
Published 2019-09-16 by SAE International in United States
This paper describes the comparison of electromagnetic characteristics of two different superconducting-motor structures for electrified aircraft propulsion systems. Future electrified aircraft demand higher output (over 16 kW/kg) and higher efficiency (> 98%) for their motors in comparison with current ones. To satisfy the demands, two kinds of superconducting motors are dealt in this study: one is partially superconducting motors (PSCMs), made of superconducting field coils and copper armature windings; the other is the fully superconducting motors (FSCMs) made of superconducting field/armature windings. They are cooled at 20 K with liquid hydrogen. We designed these two motors with finite element method to obtain the output density of 16-20 kW/kg for future electrified propulsion systems. We selected 3.0- and 5.0 MW superconducting motors, considering the application to aircraft for almost 180 passengers and 44 MW rated power for take-off. Also, we evaluated the motor weight using two kinds of cryostat materials: stainless steel (SUS) and fiber-reinforced plastic (FRP). The results show that the 5.0 MW PSCM using FRP achieved the output density of 16.9 kW/kg and the…
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Preventing Ice Buildup on Electric Aircraft

  • Magazine Article
  • TBMG-34869
Published 2019-08-01 by Tech Briefs Media Group in United States

Fuel economy is one of the biggest challenges facing the aviation industry. To overcome these challenges, researchers are working on next generation aviation systems.

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Preventing Ice Buildup on Electric Aircraft

Aerospace & Defense Technology: August 2019

  • Magazine Article
  • 19AERP08_04
Published 2019-08-01 by SAE International in United States

Fuel economy is one of the biggest challenges facing the aviation industry. To overcome these challenges, researchers are working on next generation aviation systems. Next generation aircraft will be either hybrid power, or all-electric power, which would help with fuel consumption. But electric aircraft present challenges in other areas such as the prevention of ice formation. Ice formation on aircraft can degrade the aerodynamic performance significantly by reducing lift while increasing drag. Tech Briefs Media Group (TBMG) editor, Billy Hurley, interviewed researcher Afaq Ahmed Abbasi of Northwestern Polytechnical University's Department of Fluid Mechanics to learn more about these challenges.

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A Predictive Reference Governor for Synchronous Generator Regulation with a Pulsed Constant Power Load

US Air Force Research Laboratory-Jon Zumberge, Brandon Hencey
University of Dayton-Raul Ordonez
Published 2019-03-19 by SAE International in United States
In this paper, first an analytical model of a synchronous generator with a pulsed constant power load (CPL) is developed and numerically compared with a detailed simulation model. The analytical model is shown to possess good predictive abilities, thus enabling its use for control purposes. Second, the generator has a proportionalintegral (PI) control inner-loop, whose task is to regulate the generator’s output voltage to a desired reference. A novel outer-loop predictive reference governor (PRG) is designed and tested via simulation. The PRG uses the analytical model to predict the output behavior of the generator over a short time window, and continuously modifies the reference given to the inner-loop in order to maintain stringent steady-state requirements, in spite of demanding power requirements at the CPL. Simulation results illustrate the significant performance advantages of using the PRG versus using the inner-loop PI controller alone. The paper also discusses challenges of implementing standard model predictive control (MPC) on this problem, thus further strengthening the case for the potential usefulness of the PRG.
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