Mavris, Dimitri N.

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Now showing 1 - 10 of 314
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    Framework for the Assessment of Capacity and Throughput Technologies
    (Georgia Institute of Technology, 2000-10) Garcia, Elena ; Mavris, Dimitri N.
    The demand for air travel is expanding beyond the capacity of existing airports and air traffic control. This excess traffic often results in delays and compromised safety. Therefore, a number of initiatives to improve airport capacity and throughput have been proposed. However, in order to assess the impact of these technologies on commercial air traffic one must move beyond the vehicle to a system-of-systems point of view. This top-level point of view must include consideration of the aircraft, airports, air traffic management and airlines that make up the airspace system. In addition to the analyses of each of these components and their interactions, a thorough investigation of capacity and throughput technologies requires due consideration of other pressures such as economics, safety and government regulations. Furthermore, the air traffic system is inherently variable with constant changes in everything from fuel prices to the weather. Thus, the development of a modeling environment that encompasses all these sources of uncertainty and the methodology to be used in a probabilistic evaluation of technological impacts are the subject of this paper.
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    Conceptual Design of a BLI Propulsor Capturing Aero-Propulsive Coupling and Distortion Impacts
    (Georgia Institute of Technology, 2019) Pokhrel, Manish ; Shi, Mingxuan ; Ahuja, Jai ; Gladin, Jonathan ; Mavris, Dimitri N. ; Georgia Institute of Technology. Aerospace Systems Design Laboratory
    Boundary Layer Ingestion (BLI) appears to be a promising solution to meet aggressive aviation fuel burn and environmental goals defined by NASA and other entities. Propulsion-airframe integration plays a critical role in BLI vehicle design given the strong coupling between the airframe and the propulsion system. Several studies have focused on flow field impacts on the propulsion system performance, but have ignored the effect of the propulsor on the flow field. Recent studies, however, have focused on both aspects, highlighting the need for capturing this interdisciplinary coupling. Multidisciplinary analyses (MDA), especially those involving CFD, are computationally expensive and are not suitable in the conceptual design of BLI propulsion systems. This paper aims to provide a less expensive approach by developing a parametric formulation for the effect of the propulsion system on the flow field, which can then be used in BLI propulsor conceptual design. This paper quantifies the sensitivity of the changes in the flow field due to the on-design and off-design parameters of the propulsion system. In addition, it also illustrates the difference in propulsion system design and performance when the throttle dependent effects on the flow field is captured, to the case where it is not. Distortion impacts on engine sizing and performance are also considered in this paper.
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    Performance Assessment of a Distributed Electric Propulsion System for a Medium Altitude Long Endurance Unmanned Aerial Vehicle
    (Georgia Institute of Technology, 2021-08) Markov, Alexander A. ; Cinar, Gokcin ; Gladin, Jonathan C. ; Garcia, Elena ; Denney, Russell K. ; Mavris, Dimitri N. ; Patnaik, Sounya S. ; Georgia Institute of Technology. Aerospace Systems Design Laboratory ; Air Force Research Laboratory. Aerospace Systems Directorate
    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.
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    Conceptual Design of Current Technology and Advanced Concepts for an Efficient Multi-Mach Aircraft
    (Georgia Institute of Technology, 2005) Jiménez, Hernando ; Mavris, Dimitri N. ; Georgia Institute of Technology. Aerospace Systems Design Laboratory
    A design process is formulated and implemented for the taxonomy selection and system-level optimization of an Efficient Multi-Mach Aircraft Current Technology Concept and an Advanced Concept. Concept space exploration of taxonomy alternatives is performed with multi-objective genetic algorithms and a Powell’s method scheme for vehicle optimization in a multidisciplinary modeling and simulation environment. A dynamic sensitivity visualization analysis tool is generated for the Advanced Concept with response surface equations.
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    A Bayesian Approach to Non-Deterministic Hypersonic Vehicle Design
    (Georgia Institute of Technology, 2001-09) Mantis, George C. ; Mavris, Dimitri N.
    Affordable, reliable endo- and exoatmospheric transportation, for both the military and commercial sectors, grows in importance as the world grows smaller and space exploration and exploitation increasingly impact our daily lives. However, the impact of disciplinary, operational, and technological uncertainties inhibit the design of the requisite hypersonic vehicles, an inherently multidisciplinary and non-deterministic process. Without investigation, these components of design uncertainty undermine the designers decision-making confidence. In this paper, the authors propose a new probabilistic design method, using Bayesian Statistics techniques, which allows assessment of the impact of disciplinary uncertainty on the confidence in the design solution. The proposed development of a two-stage reusable launch vehicle configuration highlights the means to first quantify the fidelity of the disciplinary analysis tools utilized, then propagate such to the vehicle system level.
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    Development of an Open Rotor Propulsion System Model and Power Management Strategy
    (Georgia Institute of Technology, 2023-01) Clark, Robert A. ; Perron, Christian ; Tai, Jimmy C. M. ; Airdo, Benjamin ; Mavris, Dimitri N. ; Georgia Institute of Technology. Aerospace Systems Design Laboratory
    The development of an open rotor propulsion system architecture model and fuel burn-minimizing power management strategy is investigated. The open rotor architecture consists of a single-rotor open rotor (SROR) connected to the low speed shaft of a traditional turbojet engine in a puller configuration. The proposed architecture is modeled in the Numerical Propulsion System Simulation (NPSS) tool, and performance is evaluated across a complete flight envelope typical for a narrow body commercial airliner. Rotor performance maps are generated using a custom blade element momentum theory (BEMT) code, while compressor performance maps are created using CMPGEN. The performance of the overall propulsion system is detailed in the context of a notional 150 passenger aircraft mission, and a method for scheduling rotor power across the flight envelope is developed in order to minimize aircraft mission fuel burn. It is demonstrated that the power absorbed by the rotor can be optimized by scheduling rotor blade pitch angle versus fan speed. A power management technique using the optimal blade pitch angle at only six points in the flight envelope was shown to provide significant computational benefits without sacrificing any fuel burn when compared to a method using a schedule generated from data across the complete flight envelope.
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    Energy-Constrained Multi-UAV Coverage Path Planning for an Aerial Imagery Mission Using Column Generation
    (Georgia Institute of Technology, 2019-03) Choi, Younghoon ; Choi, Youngjun ; Briceno, Simon ; Mavris, Dimitri N. ; Georgia Institute of Technology. Aerospace Systems Design Laboratory
    This paper presents a new Coverage Path Planning (CPP) method for an aerial imaging mission with multiple Unmanned Aerial Vehicles (UAVs). In order to solve a CPP problem with multicopters, a typical mission profile can be defined with five mission segments: takeoff, cruise, hovering, turning, and landing. The traditional arc-based optimization approaches for the CPP problem cannot accurately estimate actual energy consumption to complete a given mission because they cannot account for turning phases in their model, which may cause non-feasible routes. To solve the limitation of the traditional approaches, this paper introduces a new route-based optimization model with column generation that can trace the amount of energy required for all different mission phases. This paper executes numerical simulations to demonstrate the effectiveness of the proposed method for both a single UAV and multiple UAV scenarios for CPP problems.
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    Defining and Parameterizing the Design Space for Cislunar PNT Architectures
    ( 2023-01) Bender, Theresa ; Gabhart, Austin ; Steffens, Michael ; Mavris, Dimitri N.
    Operations in cislunar space are expected to greatly increase over the next decade, which will place a heightened demand on position, navigation, and timing (PNT) architectures. Existing PNT systems will be unable to support this growth, evidencing the need for a new cislunar PNT infrastructure. This study defines and parameterizes the design space for cislunar PNT architecture development, with the goal of enabling design space exploration and architecture trade studies. Design choices such as orbit type, architecture symmetry, and preferred design variables and their ranges are discussed. An environment for modeling and evaluating PNT architectures is developed and demonstrated on a subset of the defined design space. Preliminary results are shown to exhibit the type of data and trends to be expected from these studies. A discussion of optimization algorithms that can leverage this environment to fully explore the defined design space and identify optimal designs is presented.
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    Analysis of Advanced Technology Impact on HSCT Engine Cycle Performance
    (Georgia Institute of Technology, 1999-06) Roth, Bryce Alexander ; Mavris, Dimitri N.
    The objective of this paper is to describe and apply methods that could assist the propulsion system designer in the evaluation and selection of propulsion technologies. The focus here is on the aerothermo-dynamic aspects of the problem, particularly estimation of engine internal losses. This is accomplished by leveraging developments in second law analysis methods that are able to quantify the theoretical work potential as well as the loss in work potential. Two basic methods, exergy and suitability of each for propulsion systems analysis is discussed. These are used to develop a simple approach to engine internal loss estimation, and are then demonstrated on several basic technology scenarios for a High Speed Civil Transport Propulsion System. The various sources of loss for each concept are examined in detail, and the results for the two methods are compared.
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    Aircraft Flight Plan Optimization with Dynamic Weather and Airspace Constraints
    (Georgia Institute of Technology, 2020) Ramee, Coline ; Junghyun, Kim ; Deguignet, Marie ; Justin, Cedric ; Briceno, Simon ; Mavris, Dimitri N. ; Georgia Institute of Technology. Aerospace Systems Design Laboratory
    Flight planning is the process of producing a flight plan which describes a proposed aircraft trajectory. This task is typically performed ahead of departure with the intent of minimizing operating costs, while accounting for weather, airspace, traffic, and comfort considerations. Recent improvements in cockpit connectivity present new opportunities for flight crews to continuously re-assess the trajectories once in the air using the latest information sets (weather observations and forecasts, traffic). In turn, this enables flight crews to proactively respond to the uncertain evolution of the weather by steering the aircraft along optimal trajectories. This also brings new challenges as flight crews are ill-equipped to continuously process vast amount of information to perform the trajectory optimization. A framework is therefore proposed to automate the fusion of various sources of information (severe weather, winds aloft, restricted airspace) to feed a trajectory optimizer that continuously updates the aircraft trajectory. This relies on the implementation of the A* algorithm with the objective to minimize cruise fuel burn and emissions. Use-cases are investigated by comparing continuously updated trajectories with actual flight trajectories retrieved from the FAA Traffic Flow Management Systems through consumer-oriented websites. Promising results are observed with fuel burn savings reaching 8%.