Taewoo Nam

Next Generation More-Electric Aircraft: A Potential Application for HTS Superconductors

Sustainability in the aviation industry calls for aircraft that are significantly quieter and more fuel efficient than todays fleet. Achieving this will require revolutionary new concepts, in particular, electric propulsion. Superconducting machines offer the only viable path to achieve the power densities needed in airborne applications. This paper outlines the main issues involved in using superconductors for aeropropulsion. We review our investigation of the feasibility of superconducting electric propulsion, which integrate for the first time, the multiple disciplines and areas of expertise needed to design electric aircraft. It is shown that superconductivity is clearly the enabling technology for the more efficient turbo-electric aircraft of the future.

A Generalized Aircraft Sizing Method and Application to Electric Aircraft

Internal combustion (IC) engines, which consume hydrocarbon fuels, have dominated the propulsion systems of air-vehicles during a century of aviation history. In the past decade, however, a combination of environmental, technological, and socio-economic changes have stimulated the search for new, alternative sources of power that could challenge the dominance of the IC engine. In particular, fuel cells are increasingly being considered as an alternate power source due to their potential advantages over the traditional power system. Nevertheless, traditional aircraft sizing methods currently employed in the conceptual design phase are not immediately applicable to such revolutionary power drive aircraft designs. Motivated by such deficiencies in state-of-the art sizing methods, a generalized aircraft sizing method has been developed as a solution to this challenge. A brief outline of the method and preliminary results from its application to an electric high altitude long endurance (HALE) configuration are provided in this paper.

Power Based Sizing Method for Aircraft Consuming Unconventional Energy

Presented at the 43rd AIAA Aerospace Sciences Meeting and Exhibit, Reno, Nevada, Jan. 10-13, 2005.

Superconducting Ducted Fan Design for Reduced Emissions Aeropropulsion

This article introduces a new conceptual design tool for an environmentally sustainable method of aeropropulsion: a ducted fan system driven by a fully superconducting electrical machine. Such a system could help mitigate aviations contribution to global climate change by enabling the reduction of greenhouse gas emissions from aircraft. An electro-thermal motor sizing model was coupled with cycle analysis and weight estimation routines to create an automated environment for rapid design trade studies. The resulting parametric cycle analysis and sizing outcomes revealed the systems operational boundaries for a given aspiration space.

Multidisciplinary Design Optimization of a Truss Braced Wing Aircraft

†‡ § ¶ This paper focuses on establishing the po tential benefits of a truss-braced wing aircraft configuration as compared to the current generation cantilever wing aircraft, as well as a strut-braced wing. Mu ltidisciplinary Design Optimization is used to design aircraft with three diffe rent wing configurations with increasing complexity of structural topology: cantilever, 1-member truss (strut) and 3-member truss. Three different objective functions are studied: minimum takeoff gross weight, minimum fuel consumption and emissions, and maximum lift to drag ratio. The results show the significant advantage of strut and simple truss configurations over the conventional cantilever configuration. They also indicate that a truss-braced wing has a greater potential for improved aerodynamic performance than has been reported for other innovative aircraft configurations. In addition, the comparison between the various design objective functions shed light on their effect on the resulting configurat ions. Some initial aeroelastic analyses are then presented and discussed. Further studies will consider the inclusion of more complex truss topologies and other innovative technologies which are judged to be synergistic with truss-braced wing configurations.

Comparative Assessment of Strut-Braced and Truss-Braced Wing Configurations Using Multidisciplinary Design Optimization

This paper presents a study of aircraft featuring truss-braced wing configurations that have been optimized for minimum fuel consumption using multidisciplinary design optimization. The investigation proceeds following an earlier Boeing Subsonic Ultra Green Aircraft Research N+3 study, which selected the truss-braced wing concept as the most promising of several N+3 concept vehicles. This comes from the fact that a significantly higher-aspect-ratio wing could achieve substantial reductions in induced drag but requires major structural changes to support such a large span. This problem was explored through the use of a multidisciplinary design and analysis environment implemented in ModelCenter®. Optimization was performed using ModelCenter’s Design Explorer and Darwin genetic algorithm optimizers. Using the multidisciplinary environment, a large multidimensional design space, featuring design variables spread across the major aircraft design disciplines, was explored. Configurations featuring a strut-brac...

Analysis of the Effect of Cruise Speed on Fuel Efficiency and Cost for a Truss-Braced Wing Concept

Modern day commercial aviation has a strong incentive to pursue the design of advanced aircraft concepts, motivated both by growing environmental concerns and more challenging airline economics. In this regard, the Truss-Braced Wing concept has significant potential to achieve appreciable improvements with regard to fuel efficiency, emissions, noise, and operating cost, but without entailing as much technological risk and uncertainty as more exotic designs. The performance advantage of a Truss-Braced Wing design over a conventional cantilever wing design stems from the fact that the truss allows a wing of much higher aspect ratio, and thus higher aerodynamic efficiency, to be achieved without a correspondingly high weight penalty. In a previous investigation by the authors, a Multidisciplinary Design Optimization was performed to identify the most promising TrussBraced Wing architecture from among candidates that included a Strut-Braced Wing design in addition to one-jury and two-jury Truss-Braced Wing designs. The insights gained from that investigation are built on in this paper, which analyzes the mission-level impact of the aircraft’s cruise speed. A lower cruise speed may allow a reduction in mission fuel consumption, but this is not the only concern as airline operators must also consider the aircraft utilization. In this work therefore, consideration is given to both mission block fuel and the operating cost, and both fuel-optimal and cost-optimal designs are arrived at for a range of potential cruise speeds. The fuel and cost-optimal designs for a single aisle N+3 Truss-Braced Wing concept at the same Mach numbers were contrasted, and impact of cruise speed on operating costs was quantified.

Assessment of Environmental and Regulatory Uncertainty Impacts on Propulsion System Design

The objective of this paper is to discuss a new structured methodology developed for assisting in engine architecture selection to provide the maximum probability of success of the program under uncertain future environmental regulations. This method integrates a probabilistic analysis technique with the response surface method and an optimization solution technique to enable the designers to rapidly construct the design space and find the optimum design under regulation variations. The response surface method (RSM) approximates the system level responses with a set of quadratic equations as functions of the propulsion system design variables which can capture the primary characteristics of the candidate engine architectures. These equations are fed into the objective function and a series of constraints of an optimization tool. The uncertainty of future regulations is modeled as variations of the regulatory constraint values in the optimization problem. The optimization tool, wrapped with a Monte-Carlo simulation (MCS), solves optimization problems that are set up with randomly selected values of the regulatory constraints. Such a statistical simulation combined with the optimization solution technique provides useful information to the decision maker: the probability of success and estimated ranges of the objective function value for each candidate. A practical demonstration of the method and the accompanying results are given for assessing regulatory uncertainty associated with a Supersonic Business Jet (SBJ) engine development.

Multistage Reliability-Based Design Optimization and Application to Aircraft Conceptual Design

A new proposal for formulating reliability-based design optimization problems, named the multistage reliability-based design optimization approach, is presented. The classical reliability-based des...

Reduced-Order Modeling of a High-Fidelity Propulsion System Simulation via Probabilistic Principal Component Analysis and Neural Networks

Ever stringent aircraft design requirements on simultaneous reduction in fuel consumption, emissions, and noise necessitate innovative, integrated airframe designs that require concurrent engine designs. In order to ful ll these design challenges, aerospace engineers have relied on a physics-based engine modeling environment such as the numerical propulsion system simulation (NPSS). To expedite the use of NPSS in aircraft design, this research proposes a methodology for the reduced-order modeling (ROM) of NPSS by incorporating the following two techniques: probabilistic principal component analysis (PPCA) for basis extraction and neural networks for weighting coe cient prediction. To e ciently achieve an empirical orthogonal basis, this research capitalizes on an EM algorithm for PPCA (EM-PCA) to handle NPSS engine decks that typically lack some data due to failed o -design performance analyses. In addition, to e ectively explore a weighting coe cient space, this research utilizes neural networks to deal with six NPSS engine modeling parameters. As a proof of concept, the proposed NPSS ROM method is applied to an NPSS turbofan engine model usually employed for conventional civil transport aircraft. Comprehensive prediction quality investigations reveal that engine performance metrics estimated by the reduced-order NPSS model show considerably good agreement with those directly obtained by NPSS. Furthermore, the reduced NPSS engine model is integrated with the ight optimization system (FLOPS) in lieu of directly using NPSS as an illustration of the utility of NPSS ROM for aircraft design research.