Conference Paper

System Analysis and Design Space Exploration of Regional Aircraft with Electrified Powertrains

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View Video Presentation: This paper explores the design spaces of a thin-haul and a regional aircraft with parallel hybrid electric propulsion architectures and an entry into service date of 2030. Notional technology reference aircraft models were developed for a 19- and a 50-passenger aircraft based on publicly available data on the Beechcraft 1900D and ATR 42-600, respectively. Advanced technology aircraft models were developed by infusing the reference aircraft models with a set of selected airframe and propulsion system technologies projected to reach maturity by2030. Matlab and NPSS-based parametric, physics-based models were created for the charge depleting parallel hybrid electric propulsion system architecture. Different modes of operation were identified and parametrized with a basket of design variables to investigate the feasibility and trade space for peak power shaving, climb power boosting, electric taxi, battery usage schedules, and in-flight battery recharge strategies. A design of experiments with thousands of data points was conducted for the 19- and 50-passenger electrified aircraft propulsion vision systems. The vision systems were sized for the same point and mission performance requirements as their conventional counterpart. Artificial Neural Network models were fit toa set of subsystem, system, and mission level metrics of interest. An extensive trade study was performed to identify the fuel burn, weight, and efficiency trends and sensitivities as a function of different modes of operation as well as the electric powertrain key performance parameters and technology projections for 2030 and onward. The resulting multidisciplinary design space exploration environment was used to identify the optimum vision system designs and modes of operation for the minimum block fuel burn objective. It was found that both vehicle classes with the charge depleting parallel hybrid electric architecture provided fuel burn benefits over their 2030 advanced technology counterparts under certain modes of operation.

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... Improvements in airframe and engine, the deployment of sustainable aviation fuels, the introduction of government regulations and economic measures to discourage activities that produce CO 2 emissions, and improved operations and air traffic management are the four main research areas regarding attempts to attain net-zero CO 2 emissions by 2050 [3]. Improvements in aircraft fuel efficiency can be made by designing more-electric architectures [4,5] or hybrid-electric powertrains [6,7]. However, these concepts are likely to take decades, due to issues with battery energy densities [8] and safety and reliability considerations [9,10]. ...
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With the growth in commercial aviation traffic and the need for improved environmental performance, strategies to lower emissions that can be implemented in the near term are necessary. Since novel technology takes time to enter the market, operational improvements that employ existing aircraft and require no new infrastructure are fit for this goal. While quantified data collected throughout aviation, such as arrival/departure statistics and flight data, have been well-utilized, text data collected through safety reports have not been leveraged to their full extent. In this paper, a methodology is presented that can use aviation text data to identify high-level causes of flight delays and cancellations, using delays as a metric of operational inefficiency. The dataset is extracted from the Aviation Safety Reporting System (ASRS), which includes voluntary safety incident reports in text narrative and metadata formats. The methodology uses natural language processing tools, K Means clustering, and dimensionality reduction by t-Distributed Stochastic Neighbor Embedding (t-SNE) to categorize and visualize narratives. The method identified 7 major clusters and a total of 23 sub-clusters. A comparison between the subclusters’ topics and the causes of flight delays revealed by the quantified data shows that the ASRS database provides a unique safety perspective to delay cause identification, as illustrated by the method’s identification of maintenance as the main cause of delays, rather than weather.
... V), which will serve as the baseline models in future studies of powertrain electrification. The work presented in this paper builds on previous work by Cinar et al. [1], who explored the design space for similar thin-haul regional aircraft with EAP. This paper improves the results of the baseline modeling which align better with the scope of the Electrified Powertrain Flight Demonstration Program. ...
Conference Paper
This paper presents a parametric modeling and integrated sizing approach for a charge-depleting parallel hybrid electric aircraft. The hybrid powertrain model is integrated within a regional aircraft with an entry-into-service of 2030-2035. In addition to the physical architecture, different operational modes enabled by the hybridization of the propulsion system are modeled parametrically. The modes of operation presented in this paper are peak power shaving, climb power electric boost, in-flight battery recharging, and electric taxi. The aircraft and powertrain sizing is 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 to other aircraft classes. The work is done as part of the Electrified Powertrain Flight Demonstration program.
Conference Paper
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View Video Presentation: Distributed propulsion systems are enabled by electrified aircraft and can provide aero-propulsive benefits. The magnitude and impact of these benefits rely on the location of propulsors on the vehicle, the amount of propulsive force generated by those propulsors, vehicle geometry, and the extent of hybridization of the propulsion system. With an increased number of degrees of freedom over conventionally electrified aircraft, the full extent of the impacts of this technology have not yet been explored, especially for military applications. This study builds on a previous one that implemented a series hybrid and turboeletric propulsion architecture on a turboprop UAV, by introducing a distributed electric propulsion system on the same vehicle. The previous study showed that with a hybrid architecture, the same performance, in terms of range and endurance, could not be achieved for a fixed gross take-off weight. This study investigates the impact of the distributed propulsion system with the goal of identifying the benefits over the previous vehicle and determining the level of technology required to break even with the conventional propulsion UAV. In incorporating the new propulsion system, the engine and main motor are resized, leading edge wing mounted propellers and motors are added to the configuration, and a new battery sizing strategy is implemented. Preliminary results show that, although this new system shows increased range and endurance over the series hybrid vehicle, it still falls short compared to the conventional vehicle with current levels of technology. Although improvements are needed to the electrical system technology to reduce the weight enough to break even with the conventional system, the new vehicle shows increased performance during climb, and has the capability to store energy during the mission. With the proper power management and battery utilization strategies, this system can provide reduction in fuel burn and improved performance during certain phases of the mission which could be beneficial for military applications.
Conference Paper
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General Aviation (GA) is likely to be at the forefront of a paradigm change in aviation, where the introduction of novel concepts such as Urban Air Mobility (UAM), architectures like e−VTOL, and technologies like Distributed Electric Propulsion (DEP) are expected to make aircraft more efficient and reduce their environmental footprint. However, these architectures carry with them an uncertainty related to the off-nominal operational risk they pose. The limitations and off-nominal operational considerations generally postulated during traditional safety analysis may not be complete or correct for new technologies. While a lot of the literature surveyed focuses on improving traditional methods of safety analysis, it still does not completely address the limitations caused due to insufficient knowledge and experience with transformative technologies. The research objective of the present work is to integrate the Bayesian safety assessment framework developed previously by the authors with conceptual and 6-DoF performance models for DEP aircraft to evaluate off-nominal performance and reliability using information that is typically available in conceptual or preliminary design phases. A case study on the electric power architecture of the the NASA Maxwell X-57 Mod. IV is provided. A maximum potential flight path angle metric, as well as trimmability considerations using a 6-DoF model constructed using available literature help determine hazard severity of power degradation scenarios. Bayesian failure rate posteriors are constructed for the different components in the traction power system, which are used in a Bayesian decision framework. The results indicate that while most of the components in the traction power architecture of the X-57 Mod. IV are compliant with failure rate requirements generated, the batteries, cruise motors, and cruise motor-inverters do not meet those requirements.
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In this engineering note we derive a simple range equation for hybrid-electric aircraft with a constant power split. The equation is shown to be identical to the traditional Breguet range equation for the limit case of zero supplied power ratio. Analogously, for fully-electric configurations, the equation matches the expressions found in literature. A simple demonstration exercise shows that the equation can provide insight into the effect of battery technology level and other design considerations of hybrid-electric aircraft, without requiring detailed knowledge of the aircraft configuration. The equation can be combined with methods capable of estimating the installed power and empty weight of hybrid-electric aircraft, in order to analyze the design space or to provide initial values for more advanced design routines.
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The potential environmental benefits of hybrid electric regional turboprop aircraft in terms of fuel consumption are investigated. Lithium–air batteries are used as energy source in combination with conventional fuel. A validated design and analysis framework is extended with sizing and analysis modules for hybrid electric propulsion system components. In addition, a modified Bréguet range equation, suitable for hybrid electric aircraft, is introduced. The results quantify the limits in range and performance for this type of aircraft as a function of battery technology level. A typical design for 70 passengers with a design range of 1528 km, based on batteries with a specific energy of 1000 Wh/kg, providing 34% of the shaft power throughout the mission, yields a reduction in emissions by 28%.
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This paper presents an improved and easy-to-use battery dynamic model. The charge and the discharge dynamics of the battery model are validated experimentally with four batteries types. An interesting feature of this model is the simplicity to extract the dynamic model parameters from batteries datasheets. Only three points on the manufacturer's discharge curve in steady state are required to obtain the parameters. Finally, the battery model is included in the SimPowerSystems simulation software and used in a detailed simulation of an electric vehicle based on a hybrid fuel cell-battery power source. The results show that the model can accurately represent the dynamic behaviour of the battery.
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The Strategic Research and Innovation Agenda andNASA N = 3 goals have set new challenges for the aeronautical community via declaration of dramatic efficiency improvements. Because further evolutionary improvements do not appear to be sufficient, envisioning disruptive technologies turn out to be essential to reach the set of future targets. The design of innovative integrated energy-power systems is certainly a major promising element as can be shown by the increasing interest toward hybrid energy and universally electric aircraft. The consideration of these new types of aircraft represents a new challenge for conventional aircraft sizing and performance methods. As an extension of the conventional methods used for fuel-energy aircraft, a sizing and performance methodology for hybrid-energy aircraft is proposed. A design study of a battery and fuel hybrid-energy single-aisle retrofit is conducted to demonstrate the methodology and to analyze the implications of the associated new design variables on the sizing and performance. The benchmark against a conventional reference aircraft shows a potential block fuel-burn reduction up to 16% for a 900 n mile off-design mission stage length (using a mix of fuel energy to electrical energy of 82:18%). Clean sheet designs will be part of future work to assess the full potential of hybrid-energy aircraft. Copyright © 2014 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
To achieve improvements in aircraft efficiency and reduced environmental footprint, aircraft must incorporate novel concepts, architectures, and technologies, such as distributed electric propulsion. These new concepts, architectures, and technologies pose an uncertainty related to risk associated with off-nominal operation due to limitations of traditional safety analysis applied to new technologies. Surveyed literature does not completely address the limitations caused by insufficient knowledge and experience with transformative technologies. The present work proposes an integrated safety assessment framework developed previously by the authors to evaluate off-nominal performance and reliability using information that is typically available in conceptual or preliminary design phases. A case study on the electric power architecture of a test distributed electric propulsion aircraft inspired by the NASA Maxwell X-57 Mod-IV is provided. A maximum potential flight-path angle metric and trimmability considerations using a six-degree-of-freedom model help determine hazard severity of power degradation scenarios. Bayesian failure rate posteriors are constructed for the different components in the traction power system, which are used in a Bayesian decision framework to make a compliance assessment.
Conference Paper
View Video Presentation: An electrified aircraft propulsion (EAP) design exploration study was performed to determine the impact of EAP technologies on a set of regional transport aircraft concepts. A range of aircraft sizes were included in the study, including 18, 48, and 70 passenger turboprops, as well as 50 and 78passenger turbofan aircraft configurations. The motivation for this research was to better understand some of the design trades associated with EAP aircraft by performing a series of parametric studies that explored the performance impact of battery size, motor size, range, and amount of electrification. The study team had to establish a concept of operations for the vehicles, establish metrics to compare the EAP aircraft to conventional baseline aircraft, determine modeling strategies, and design the trade studies. This paper documents the approaches, technology assumptions, and tools used to carry out this research. A separate upcoming paper will report the results from this design exploration study.
One of the barriers to the development of novel aircraft architectures and technologies is the uncertainty related to their reliability and the safety risk they pose. In the conceptual and preliminary design stages, traditional system safety techniques rely on heuristics, experience, and historical data to assess these requirements. The limitations and off-nominal operational considerations generally postulated during traditional safety analysis may not be complete or correct for new concepts. Additionally, dearth of available reliability data results in poor treatments of epistemic and aleatory uncertainty for novel aircraft architectures. Two performance-based methods are demonstrated to solve the problem of improving the identification and characterization of safety related off-nominal requirements in early design. The problem of allocating requirements to the unit level is solved using a network-based bottom-up analysis algorithm combined with the Critical Flow Method. A Bayesian probability approach is utilized to better deal with epistemic and aleatory uncertainty while assessing unit level failure rates. When combined with a Bayesian decision theoretic approach, it provides a mathematically backed framework for compliance finding under uncertainty. To estimate multi-state reliability of complex systems, this dissertation contributes a modified Monte-Carlo algorithm that uses the Bayesian failure rate posteriors previously generated. Finally, multi-state importance measures are introduced to determine the sensitivity of different hazard severity to unit reliability. The developed tools, techniques, and methods of this dissertation are combined into an integrated framework with the capability to perform trade-studies informed by safety and reliability considerations for novel aircraft architectures in early preliminary design. A test distributed electric propulsion (T-DEP) aircraft inspired by the X-57 is utilized as a test problem to demonstrate this framework
Purpose The purpose of this paper was to create a generic and flexible framework for the exploration, evaluation and side-by-side comparison of novel propulsion architectures. The intent for these evaluations was to account for varying operation strategies and to support architectural design space decisions, at the conceptual design stages, rather than single-point design solutions. Design/methodology/approach To this end, main propulsion subsystems were categorized into energy, power and thrust sources. Two types of matrices, namely, the property and interdependency matrices, were created to describe the relationships and power flows among these sources. These matrices were used to define various electrified propulsion architectures, including, but not limited to, turboelectric, series-parallel and distributed electric propulsion configurations. Findings As a case study, the matrices were used to generate and operate the distributed electric propulsion architecture of NASA’s X-57 Mod IV aircraft concept. The mission performance results were acceptably close to the data obtained from the literature. Finally, the matrices were used to simulate the changes in the operation strategy under two motor failure scenarios to demonstrate the ease of use, rapidness and automation. Originality/value It was seen that this new framework enables rapid and analysis-based comparisons among unconventional propulsion architectures where solutions are driven by requirements.
Conference Paper
Traditional aircraft conceptual design primarily involves determination of top-level sizing parameters, resulting in an initial design which satisfies specified point-performance constraints while flying the so-called design mission. In practical scenarios, commercial aircraft are also expected to operate optimally in the actual missions they fly which may drastically differ from the design mission. To improve performance and reduce operating costs, optimization shall be performed using specific objectives from the on-design mission and from one or more representative off-design reference mission(s). Such multi-mission optimizations may result in different designs for the same performance constraints. Moreover, the size of aircraft and choice of reference mission(s) may also have an effect in the difference resulting from such multi-mission optimizations. This paper solves a series of multi-objective on-design and multimission optimization problems in the conceptual design phase on aircraft spanning a range of size-classes, using the Non-dominated Sorting Genetic Algorithm II (NSGA-II). Results shed light on the design differences between formulations that exclusively consider design mission metrics of interest from the ones that consider metrics of interest from disparate missions. In addition, results also reveal the impact of off-design mission weightings on the designs obtained from the optimization problems.
A feasibility study of a hybrid-electric commercial transport aircraft was conducted by analyzing the simulated performance and lifecycle carbon dioxide (CO2) emissions of a conventional single-aisle aircraft and an aircraft with a modified parallel hybrid-electric propulsion system. A flight performance simulation was developed in a MATLAB/Simulink environment using publicly available aircraft data for the Boeing 737-700 commercial transport aircraft and the CFM56-7B26 turbofan engine. A parallel hybrid drivetrain was integrated into the aircraft performance model. Various missions with different degrees of hybridization and battery specific energy densities were simulated and compared to the conventional turbofan case. CO2 emissions associated with fuel burn and electricity generation for charging battery systems were modeled for each hybrid aircraft configuration. The results indicated that reductions in CO2 emissions per passenger mile were achievable using a parallel hybrid propulsion system as compared to conventional systems of equivalent range. A candidate propulsion system configuration was defined, which used a 50% electrical-power drivetrain and a battery specific energy density of 1000 (W⋅h)/kg. This configuration was estimated to produce 49.6% less lifecycle CO2 emissions than a modern conventional aircraft, with a maximum range equivalent to that of the average of all global flights, making it a viable option for environmentally responsible aviation.
A number of topics that involve the selection and performance of propellers are presented in the chapter. These range from fundamentals of propeller installation and regulatory aspects, to design and thrust generation. A section is dedicated to discussing a number of peculiar effects the propeller has on the aircraft and the aircraft designer must be aware of. Generally referred to as the P-factor, these effects include gyroscopic precession, normal and yaw force, angular momentum, as well as asymmetric thrust effects for multi-engine aircraft and A·q loads for turboprops. This is followed by a number of tips to help the designer select the right propeller, ranging from initial estimation of suitable diameter and pitch, to basics of thrust and power related coefficients, to methods helpful when selecting the number of blades. Then several procedures to estimate propeller thrust are presented. These include methods developed based on industry experience, as well as standard methods, such as the Rankine-Froude Momentum and Blade Element theories. These can be used to estimate thrust, induced airspeed in the streamtube going through the propeller, propeller efficiency, and power required to rotate the propeller.
Conference Paper
Textron Lycoming of Stratford, Connecticut is incorporating the latest in advanced technology into turboshaft and turboprop engines for near term commercial service. The level of cold section technology being incorporated is the already demonstrated next generation of axi-centrifugal compressor beyond that which was developed for the U.S. Army T800, 0.9 MW turboshaft engine in the late 1980s. The compressor evolution is given special emphasis. The hot section technology is a robust, simplified, low cost, commercial endurance derate of the tri-service; US Army, US Navy, US Air Force and Textron Lycoming joint core engine [1] now on test. The new 2 MW commercial engine has substantially reduced fuel consumption, is lighter, and is smaller than today’s best engines. Engineering development is now underway and certification is slated to be completed in 1996. Copyright © 1993 by ASME Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
IntroductionBattery ParametersLead Acid BatteriesNickel-based BatteriesSodium-based BatteriesLithium BatteriesMetal Air BatteriesBattery ChargingThe Designer's Choice of BatteryUse of Batteries in Hybrid VehiclesBattery ModellingIn Conclusion References
Gas turbine engines for aircraft applications are required to meet multiple performance and sizing requirements, subject to constraints established by the best available technology level. The performance requirements and limiting values of constraints that are considered by the cycle analyst conducting an engine cycle design occur at multiple operating conditions. The traditional approach to cycle analysis chooses a single design point with which to perform the on-design analysis. Additional requirements and constraints not transpiring at the design point must be evaluated in off-design analysis and therefore do not influence the cycle design. Such an approach makes it difficult to design the cycle to meet more than a few requirements and limits the number of different aerothermodynamic cycle designs that can reasonably be evaluated. Engine manufacturers have developed computational methods to create aerothermodynamic cycles that meet multiple requirements, but such methods are closely held secrets of their design process. This thesis presents a transparent and publicly available on-design cycle analysis method for gas turbine engines which generates aerothermodynamic cycles that simultaneously meet performance requirements and constraints at numerous design points. Such a method provides the cycle analyst the means to control all aspects of the aerothermodynamic cycle and provides the ability to parametrically create candidate engine cycles in greater numbers to comprehensively populate the cycle design space from which a "best" engine can be selected. This thesis develops the multi-design point on-design cycle analysis method labeled simultaneous MDP. The method is divided into three different phases resulting in an 11 step process to generate a cycle design space for a particular application. Through implementation of simultaneous MDP, a comprehensive cycle design space can be created quickly for the most complex of cycle design problems. Furthermore, the process documents the creation of each candidate engine providing transparency as to how each engine cycle was designed to meet all of the requirements. The simultaneous MDP method is demonstrated in this thesis on a high bypass ratio, separate flow turbofan with up to 25 requirements and constraints and 9 design points derived from a notional 300 passenger aircraft. Ph.D. Committee Chair: Mavris, Dimitri; Committee Member: Gaeta, Richard; Committee Member: German, Brian; Committee Member: Jones, Scott; Committee Member: Schrage, Daniel; Committee Member: Tai, Jimmy
Advances in computational technology and in physics-based modeling are making large-scale, detailed simulations of complex systems possible within the design environment. For example, the integration of computing, communications, and aerodynamics has reduced the time required to analyze major propulsion system components from days and weeks to minutes and hours. This breakthrough has enabled the detailed simulation of major propulsion system components to become a routine part of designing systems, providing the designer with critical information about the components early in the design process. This paper describes the development of the numerical propulsion system simulation (NPSS), a modular and extensible framework for the integration of multicomponent and multidisciplinary analysis tools using geographically distributed resources such as computing platforms, data bases, and people. The analysis is currently focused on large-scale modeling of complete aircraft engines. This will provide the product developer with a "virtual wind tunnel" that will reduce the number of hardware builds and tests required during the development of advanced aerospace propulsion systems.
An algorithm is presented for calculating both the quantity of compressor bleed flow required to cool the turbine and the decrease in turbine efficiency caused by the injection of cooling air into the gas stream. The algorithm, which is intended for an axial flow, air routine in a properly written thermodynamic cycle code. Ten different cooling configurations are available for each row of cooled airfoils in the turbine. Results from the algorithm are substantiated by comparison with flows predicted by major engine manufacturers for given bulk metal temperatures and given cooling configurations. A list of definitions for the terms in the subroutine is presented.
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