EPFD Technical Papers
2023 Publications
Impedance Measurements of Motor Drives and Supplies in NASA NEAT Facility
Many electrified aircraft configurations consist of a number of power components operating on the same shared electrical bus. Understanding the impedance performance of electrical loads and sources is key to understanding, and designing for, acceptable overall vehicle power quality and power system stability. This paper discusses impedance measurements made on the NASA Electric Aircraft Testbed (NEAT) Electrical Power System (EPS) at NASA Glenn Research Center. First, an overall discussion of the NEAT facility configuration during testing is presented. Then, details of the impedance measurement approach and the various testing configurations are discussed. Next, input impedance measurements at NEAT, including sources (DC supplies) and loads (multiple motor drives, electric machines, and resistive load banks, with long interconnecting cable leads), are performed under a number of conditions and results, including load model comparisons and stability analysis, are presented and discussed.
Read it here: https://ntrs.nasa.gov/citations/20230006175
Impedance Measurements of Motor Drive and Supply in SPEED Testbed
Many electrified aircraft configurations consist of a number of power components operating on the same shared electrical bus. Understanding the impedance performance of electrical loads and sources is key to understanding, and designing for, acceptable overall vehicle power quality and power system stability. To enable these measurements, personnel at NASA’s Glenn Research Center have designed and built the Scaled Power Electrified Drivetrain (SPEED) Testbed. This paper will present data taken in the SPEED lab, including impedance measurements of a DC supply (source) and a motor drive and electric machine (load) under a number of conditions. Impacts of load power, drive controller tuning, and field-weakening on load impedance are measured, presented, and discussed; as are source impedance data, stability, and DC bus current spectra at different loading levels.
Read it here: https://ntrs.nasa.gov/citations/20230006178
The Electric Aircraft EcoSystem: Performance Potential, Economics and Societal Impact in the Age of Sustainable Air Travel
Presentation by Gaudy Bezos-O’Connor: Project Manager, Electrified Powertrain Flight Demonstration Project
Read it here: https://ntrs.nasa.gov/citations/20230008870
2022 Publications
Advanced 2030 Single Aisle Aircraft Modeling for the Electrified Powertrain Flight Demonstration Program
The NASA Electrified Powertrain Flight Demonstration Program is aimed at advancing electrified powertrains for future aircraft platforms through flight demonstrations for various passenger classes and power levels. The objective of this paper is to establish non-electrified reference models for 2030 aircraft with advanced technologies for the large single aisle (150 passenger) and small single aisle (100 passenger) vehicle classes. Current state-of-art aircraft are first identified and modeled using a proprietary design tool called Environmental Design Space. Next, through a comprehensive literature review, engine, airframe and composite material technologies that are expected to be available by 2030 are identified, and their respective benefits are applied to the 2030 vehicles. The engine cycle and the aircraft design are then optimized to provide the maximum fuel burn benefit while meeting all the specified aircraft requirements. While the large single aisle aircraft range requirement is kept the same as the current state-of-art aircraft, the small single aisle aircraft is optimized for a reduced range of 1000 nmi. Expected fuel burn benefit from these technologies along with any propulsive, aerodynamic and weight benefit will be summarized in this paper.
Read it here: https://ntrs.nasa.gov/citations/20230002464
Advanced 2030 Turboprop Aircraft Modeling for the Electrified Powertrain Flight Demonstration Program
Electrified aircraft propulsion concepts are rapidly emerging due to their huge potential in fuel saving and mitigating negative environmental impact. In order to perform a linear technology progression and fairly assess the impacts of powertrain electrification, it is important to first establish parametric state-of-the-art baseline vehicle models with advanced technologies matured by 2030. For a regional turboprop (50-passenger) size class and a thin haul (19-passenger) turboprop size class, a current state-of-the-art technology reference aircraft (TRA) is identified and modeled using a multi-disciplinary analysis and optimization environment. Viable technologies for airframe and conventional propulsion system are then identified which are expected to be available by 2030. These technologies are parametrically infused in the TRA models to create advanced technology aircraft models, which will serve as the baseline models for future studies of powertrain electrification.
Read it here: https://ntrs.nasa.gov/citations/20230003230
An MBSE Framework to Identify Regulatory Gaps for Electrified Transport Aircraft
A typical aircraft certification process consists of obtaining a type, production, airworthiness, and continued airworthiness certificates. During this process, a type certification plan is created that includes the intended regulatory operating environment, the proposed certification basis, means of compliance, and a list of documentation to show compliance. Earlier work by the authors demonstrated a model-based framework for the management of these certification artifacts for normal category airplanes. Presently, it is expanded and adapted to consider certification for transport category airplanes regulated under 14 CFR Part 25, providing clear transparency and traceability between the text of the regulations and imposed requirements, contextual information, and specified test activities. In particular, a capability to identify potential gaps in the applicability of regulations for novel architectures such as electrified aircraft is proposed. This capability, based on mismatches between the functional intent and the corresponding prescribed physical implementation, is developed. A sample implementation of the proposed capability is presented for a notional electrified powertrain aircraft architecture.
Read it here: https://ntrs.nasa.gov/citations/20230003302
Modeling and Simulation of a Parallel Hybrid Electric Regional Aircraft for the Electrified Powertrain Flight Demonstration (EPFD) Program
This paper presents a parametric modeling and integrated aircraft sizing and synthesis approach for a charge depleting parallel hybrid electric architecture. The developed models are integrated within the baseline thin-haul and regional aircraft. In addition to the physical architecture, different modes of operation enabled by propulsion system electrification are also modeled parametrically. The modes of operation presented in this paper are the peak power shaving, climb power electric boost, in-flight battery recharging, and electric taxi. The sizing of the powertrain and the aircraft are performed within the multidisciplinary analysis and optimization environment, E-PASS. The consideration of the physical system and its operation together provides a holistic approach where the propulsion system and the airframe are designed under an optimized power and energy management strategy. The parametric nature of the work enables the design space exploration for electrification and lays the groundwork for future technology projection and uncertainty quantification studies. The developed capability is generic and can be applied on other aircraft classes. The work is done as part of the Electrified Powertrain Flight Demonstration program.
Read it here: https://ntrs.nasa.gov/citations/20230003923
Modeling and Simulation of a Parallel Hybrid-Electric Propulsion System – Electrified Powertrain Flight Demonstration (EPFD) Program
Electrified aircraft propulsion concepts have been proposed to meet aggressive future performance and environmental goals for the next generation of aircraft. However, electrified aircraft present a unique modeling and simulation challenge as they introduce multiple energy sources to the propulsion system, providing various means to meet thrust requirements, compared to conventional gas turbine propulsion architectures where only fuel is available. Additionally, the introduction of an electric powertrain to the existing system enables multiple electrified flight modes to exist (i.e. eTaxi, climb boost, takeoff boost, etc.), further increasing the complexity of the modeling environment. As part of the Electrified Powertrain Flight Demonstration program, this paper presents a modeling and simulation framework for a parallel hybrid-electric propulsion concept using the Environmental Design Space simulation tool. Electrical components are modeled in NPSS, and an overall sizing methodology is introduced. Finally, various operational modes of the electric powertrain are modeled and tested and their impact on key performance parameters is evaluated.
Read it here: https://ntrs.nasa.gov/citations/20230003929
Projecting Power Converter Specific Power Through 2050 for Aerospace Applications
In order to analyze the potential fuel burn benefit from the electrification of aircraft powertrains, it is important to quantify the amount of weight that will be added to the aircraft for each additional component of the electric powertrain. This paper provides a projection of the specific power and efficiency of power converters, (AC-DC, DC-AC, or DC-DC), through the year 2050. Data was first collected on state of the art power converters in multiple application areas, creating a power converter database. Relevant specific powers were added to a set of historical data from 1976-2020, and then three different logistic curves were fit through the historical data to represent S-curve shaped growth through the year 2050. The three curves were differentiated by conservative, nominal, and aggressive assumptions for the year in which the logistic curve begins to bend down towards slower growth. With a 30% knockdown factor accounting for the additional weight required for a high altitude converter, projections range from the aggressive specific power projection of 52.9 kW/kg in 2050 to a much more conservative specific power of 12 kW/kg in which growth is limited due to certifiability concerns. Little historical data was found on converter efficiencies to project efficiency based on historical trends. Projections are based on expert opinion on yearly decreases in converter losses. 2050 projections range from 0.987 to 0.997.
Read it here: https://ntrs.nasa.gov/citations/20230004083
Specific Power and Efficiency Projections of Electric Machines and Circuit Protection Exploration for Aircraft Applications
The purpose of this paper is to generate specific power and efficiency projections through the year 2050 for electric machines for aircraft applications. A general literature review was performed to identify the types of electric machines that are commonly used and which types have the biggest potential for future aircraft applications due to their high specific power and efficiency. A database with historical data was built to include parameters such as weight [kg], rated power [kW], specific power [kW/kg], RPM, efficiency, year, motor cooling type, application type and motor type to allow for trend identification and accurate projections. Once the data was gathered, multiple curve fits on the historical data were generated and extrapolated to produce the projections for specific power according to conservative, nominal and aggressive projection scenarios. A different process was followed for the efficiency projections due to the scattered nature of the data. A state of the art (SoA) value for efficiency was identified through literature review and was used to create the conservative, nominal and aggressive projections for the time frames of 2030, 2040, and 2050. The efficiency and the specific power projections of EMs for 2050 are 0.989 and 50kW/kg respectively. This paper will also be examining circuit protection as it is an additional component of electric powertrains.
Read it here: https://ntrs.nasa.gov/citations/20230004087
