German, Brian J.

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Now showing 1 - 8 of 8
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    Power optimized battery swap and recharge strategies for electric aircraft operations
    (Georgia Institute of Technology, 2020-06) Justin, Cedric Y. ; Payan, Alexia P. ; Briceno, Simon I. ; German, Brian J. ; Mavris, Dimitri N.
    Electric propulsion for commuter air transportation is becoming promising because of significant strides in battery specific energy and motor specific power. Energy storage and rapid battery recharge remain nonetheless challenging owing to the significant energy and power requirements of even small aircraft. By modifying algorithms developed in the field of scheduling theory, we propose power optimized and power-investment optimized strategies for electric aircraft battery swaps and recharges. Several aspects are considered: electric energy expenditures, capital expenditures, and flight schedule integrity. The first strategy optimizes the swaps and recharges to minimize the peak-power draw from the grid and to reduce electric energy expenditures. The second strategy optimizes the swaps and recharges to minimize electricity expenditures and capital expenditures associated with battery and charger procurement. In both cases, the optimization is decomposed into two simpler problems. The first is a recharge schedule feasibility analysis given a number of chargers and batteries, which is based on a network flow representation of the battery swap and recharge. The second is a recharge schedule generation given a number of chargers and batteries. Both strategies are applied to the operations of two commuter airlines and are contrasted with a benchmark non-optimized power-as-needed strategy. Promising results are obtained with up to 61% reduction in peak-power draw and up to 25% reduction in electricity costs.
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    The Local Character of Urban Air Mobility: Opportunities and Challenges
    ( 2020-01-15) German, Brian J.
    Urban air mobility (UAM) with electric vertical takeoff and landing (eVTOL) aircraft is emerging as a promising aviation market for both cargo delivery and passenger travel. The rise of UAM is being driven by the convergence of two technologies: autonomy and electric aircraft propulsion. Although promising, these technologies place limits on the discovery of viable markets, the timeline of introduction, and the design of operational paradigms. In particular, electric propulsion—when achieved with battery energy storage—is highly constraining in terms of aircraft payload, range, and speed performance and in terms of operational tempo and ground infrastructure. This talk will discuss recent work in modeling aircraft performance and operations for UAM and will highlight the challenges and opportunities in particular urban markets.
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    Economics of Advanced Thin-Haul Concepts and Operations
    (Georgia Institute of Technology, 2016) Harish, Anusha ; Perron, Christian ; Bavaro, Daniel ; Ahuja, Jai ; Ozcan, Melek D. ; Justin, Cedric Y. ; Briceno, Simon ; German, Brian J. ; Mavris, Dimitri N.
    The thin-haul commuter concept refers to an envisioned class of four to nine passenger aircraft operating very short flights and providing scheduled and on-demand air services from smaller airports. Its objective is to enhance regional mobility reach by combining the flexibility of automobile travel with the shorter commute times associated with air travel. To achieve economic viability, the thin-haul commuter concept must provide appreciable economic advantages when compared to current commuter aircraft. This may be achieved by increasing the revenue potential through innovative pricing and scheduling, while drastically reducing operating costs, in particular, energy, maintenance, and labor costs. These ambitious objectives require the infusion of new cutting edge technologies. The use of distributed electric propulsion is investigated to reduce both energy and maintenance expenditures. New avionics systems are considered to enable simplified operations and thus to reduce both labor and training costs. The purpose of this on-going research is to assess the viability of the thin-haul aviation concept by investigating both the operational and economic impact of introducing a fleet of distributed electric propulsion aircraft into the operations of a commuter airline. This paper presents the development of an integrated economics and operations model that incorporates preliminary estimates of a distributed electric propulsion vehicle performance as well as some aspects of typical commuter operator schedules. The model helps compare advanced electric vehicles with more conventional commuters, and therefore enables a preliminary assessment of the expected cost savings.
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    On-demand aircraft conceptual design and development
    (Georgia Institute of Technology, 2013-01) German, Brian J.
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    Reconciling differences in post-flight trajectory reconstruction for EDL applications
    (Georgia Institute of Technology, 2011-07-31) Corman, Jason Andrew ; German, Brian J.
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    A Riemannian Geometric Mapping Technique for Identifying Incompressible Equivalents to Subsonic Potential Flows
    (Georgia Institute of Technology, 2007-04-05) German, Brian J.
    This dissertation presents a technique for the solution of incompressible equivalents to planar steady subsonic potential flows. Riemannian geometric formalism is used to develop a gauge transformation of the length measure followed by a curvilinear coordinate transformation to map a subsonic flow into a canonical Laplacian flow with the same boundary conditions. The method represents the generalization of the methods of Prandtl-Glauert and Karman-Tsien and gives exact results in the sense that the inverse mapping produces the subsonic full potential solution over the original airfoil, up to numerical accuracy. The motivation for this research was provided by the analogy between linear potential flow and the special theory of relativity that emerges from the invariance of the wave equation under Lorentz transformations. Whereas elements of the special theory can be invoked for linear and global compressibility effects, the question posed in this work is whether other techniques from relativity theory could be used for effects that are nonlinear and local. This line of thought leads to a transformation leveraging Riemannian geometric methods common to the general theory of relativity. The dissertation presents the theory and a numerical method for practical solutions of equivalent incompressible flows over arbitrary profiles. The numerical method employs an iterative approach involving the solution of the incompressible flow with a panel method and the solution of the coordinate mapping to the canonical flow with a finite difference approach. This method is demonstrated for flow over a circular cylinder and over a NACA 0012 profile. Results are validated with subcritical full potential test cases available in the literature. Two areas of applicability of the method have been identified. The first is airfoil inverse design leveraging incompressible flow knowledge and empirical data for the potential field effects on boundary layer transition and separation. The second is aerodynamic testing using distorted models.
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    An Evaluation of Green Propellants for an ICBM Post Boost Propulsion System
    (Georgia Institute of Technology, 2000-11) German, Brian J. ; Branscome, Ewell Caleb ; Frits, Andrew P. ; Yiakas, Nicholas C. ; Mavris, Dimitri N.
    Propellant toxicity is a major concern in storing, maintaining, and transporting strategic missiles. Many low toxicity green propellants have been developed which hold the potential of increasing the safety and lowering the operation and support costs of liquid-fuelled strategic missile propulsion systems. This study evaluates several green propellants for use in a notional next-generation post-boost propulsion system (PBPS). The mission and physical dimensions for this PBPS were defined by the requirements of the current Minuteman III propulsion system rocket engine (PSRE). Possible propellants were initially screened in terms of toxicity, performance, and technical feasibility for the PBPS application with a multi-attribute ranking method based on an overall evaluation criterion (OEC). Promising propellants were identified, and candidate PBPS concepts were developed and sized for each of these propellants. These concepts were evaluated in terms of weight, cost, and technical risk to determine which concepts, and hence propellants, show the most promise for the application. Probabilistic techniques were employed to explore the effects of uncertainty in the propellant performance and structural weight estimates. The results indicate that high-test peroxide (HTP) combined with either an ethanol-based nontoxic hypergolic miscible fuel (NHMF) or competitive impulse non-carcinogenic hypergol (CINCH) is a very viable propellant solution.