Browsing by Author "Judt, David M."

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    Aircraft thermal management: Practices, technology, system architectures, future challenges, and opportunities
    (Elsevier, 2021-11-12) van Heerden, Albert S. J.; Judt, David M.; Jafari, Soheil; Lawson, Craig P.; Nikolaidis, Theoklis; Bosak, D.
    The provision of adequate thermal management is becoming increasingly challenging on both military and civil aircraft. This is due to significant growth in the magnitude of onboard heat loads, but also because of their changing nature, such as the presence of more low-grade, high heat flux heat sources and the inability of some waste heat to be expelled as part of engine exhaust gases. The increase in the use of composites presents a further issue to address, as these materials are not as effective as metallic materials in transferring waste heat from the aircraft to the surrounding atmosphere. These thermal management challenges are so severe that they are becoming one of the major impediments to improving aircraft performance and efficiency. In this review, these challenges are expounded upon, along with possible solutions and opportunities from the literature. After introducing relevant factors from the ambient environment, the discussion of the challenges and opportunities is guided by a simple classification of the elements involved in thermal management systems. These elements comprise heat sources, heat acquisition mechanisms, thermal transport systems, heat rejection to sinks, and energy conversion and storage. Heat sources include both those from propulsion and airframe systems. Heat acquisition mechanisms are the means by which thermal energy is acquired from the sources. Thermal transport systems comprise cooling loops and thermodynamic cycles, along with their associated components and fluids, which move the heat from the source to the sinks over potentially large distances. The terminal aircraft heat sinks include atmospheric air, fuel, and the aircraft structure. In addition to the discussions on these different elements of thermal management systems, several topics of particular priority in aircraft thermal management research are deliberated upon in detail. These are thermal management for electrified propulsion aircraft, ultra-high bypass ratio geared turbofans, and high power airborne military systems; environmental control systems; power and thermal management systems; thermal management on supersonic transport aircraft; and novel modelling and simulation processes and tools for thermal management.
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    Aircraft wing build philosophy change through system pre-equipping of major components
    (Society of Automotive Engineers, 2016-09-27) Judt, David M.; Forster, Kevin; Lockett, Helen L.; Lawson, Craig P.; Webb, Philip
    In the civil aircraft industry there is a continuous drive to increase the aircraft production rate, particularly for single aisle aircraft where there is a large backlog of orders. One of the bottlenecks is the wing assembly process which is largely manual due to the complexity of the task and the limited accessibility. The presented work describes a general wing build approach for both structure and systems equipping operations. A modified build philosophy is then proposed, concerned with large component pre-equipping, such as skins, spars or ribs. The approach benefits from an offloading of the systems equipping phase and allowing for higher flexibility to organize the pre-equipping stations as separate entities from the overall production line. Its application is presented in the context of an industrial project focused on selecting feasible system candidates for a fixed wing design, based on assembly consideration risks for tooling, interference and access. Further industrial, human and cost factors are discussed to establish project competiveness. The main findings show a potential to reduce assembly time of systems equipping operations by 30% together with a lower ergonomic impact score. The paper also presents design rules derived from the case study towards a system design for a pre-equipping build philosophy. Primarily, cross component interfaces should be avoided as much as possible. Access for phase one structural operations need to be considered as well as major component jig pickup points. To increase system installation independence, layout considerations of components should lead to sufficient access to all components at any installation stage.
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    Application of an automated aircraft architecture generation and analysis tool to unmanned aerial vehicle subsystem design
    (SAGE Publications, 2014-11-19) Judt, David M.; Lawson, Craig P.
    The work presents the application of a new computational framework, addressing future preliminary design needs for aircraft subsystems. The ability to investigate multiple candidate technologies forming subsystem architectures is enabled with the provision of automated architecture generation, analysis and optimisation. The core aspects involve a functional decomposition, coupled with a synergistic mission performance analysis on the aircraft, architecture and component level. This may be followed by a complete enumeration of architectures combined with a user-defined technology filtering and concept ranking procedure. In addition, a novel hybrid heuristic optimiser, based on ant colony optimisation and a genetic algorithm, is employed to produce optimal architectures in both component composition and design parameters. The framework is applied to the design of a regenerative energy system for a long endurance high altitude unmanned aerial vehicle, considering various emerging technologies. A comparison with the traditional design processes and certification requirements is made as well as technology trends summarised and substantiated.
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    Development of an automated aircraft subsystem architecture generation and analysis tool
    (Emerald, 2015-12-01) Judt, David M.; Lawson, Craig P.
    Purpose – The purpose of this paper is to present a new computational framework to address future preliminary design needs for aircraft subsystems. The ability to investigate multiple candidate technologies forming subsystem architectures is enabled with the provision of automated architecture generation, analysis and optimization. Main focus lies with a demonstration of the frameworks workings, as well as the optimizers performance with a typical form of application problem. Design/methodology/approach – The core aspects involve a functional decomposition, coupled with a synergistic mission performance analysis on the aircraft, architecture and component levels. This may be followed by a complete enumeration of architectures, combined with a user defined technology filtering and concept ranking procedure. In addition, a hybrid heuristic optimizer, based on ant systems optimization and a genetic algorithm, is employed to produce optimal architectures in both component composition and design parameters. The optimizer is tested on a generic architecture design problem combined with modified Griewank and parabolic functions for the continuous space. Findings – Insights from the generalized application problem show consistent rediscovery of the optimal architectures with the optimizer, as compared to a full problem enumeration. In addition multi-objective optimization reveals a Pareto front with differences in component composition as well as continuous parameters. Research limitations/implications – This paper demonstrates the frameworks application on a generalized test problem only. Further publication will consider real engineering design problems. Originality/value – The paper addresses the need for future conceptual design methods of complex systems to consider a mixed concept space of both discrete and continuous nature via automated methods.
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    Effects of more electric systems on fuel tank thermal behaviour
    (Société de l'Electricité, de l'Electronique et des Technologies de l'Information et de la Communication, 2019-12-31) van Heerden, Stevan; Judt, David M.; Lawson, Craig;; Bosak, David
    With the advent of more electric airframe systems and ultra-high bypass ratio turbofan engines, there is growing interest in the associated thermal implications. In this research project, an aircraft level model that is appropriate to enable investigations into novel thermal management solution on future aircraft is developed. In this paper, an investigation into the effects of more electric systems on the thermal behaviour of fuel tanks in civil transport aircraft is presented.Specifically, the influence of the heat generated by conventional and more electric systems on the fuel tank was modelled and simulated. A fuel thermal model was developed, which consists of a tank geometry representation, coupled to a module that calculates remaining mission fuel mass. The systems architectures are represented by connected thermal component models. Standard approaches were then employed to estimate convection and conduction heat transfer coefficients at the tank interfaces. The model solves 1-D transient heat equations, coupling heat transfer and material heat capacity via heat flux balances. The thermal and systems models were integrated into a baseline aircraft performance model, which was used to dynamically simulate the tank thermal behaviour during representative missions. The initial results indicate that switching to more electric environmental control and iceprotection systems likely have negligible thermal impact on the bulk fuel temperature. However, some benefits may be obtained regarding safety and certification, but this requires further study.
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    Experimental investigation into aircraft system manual assembly performance under varying structural component orientations
    (SAGE, 2019-10-18) Judt, David M.; Lawson, Craig;; Lockett, Helen L.
    Installation of aircraft wing systems is a bottleneck in the assembly process. This phase is typically composed of many work packages, taking hundreds of man-hours per wing. In addition to this volume of work, tasks are specialized and completed in a difficult environment in terms of access and visibility. In current industrial practice, the wing is mounted horizontally on a transport trolley, which exposes the workforce to prolonged periods of overhead working. Future wing designs may consider a pre-equipping build philosophy, where systems are installed to major structure assemblies before the wing box is assembled. This allows for a change in the orientation and position of the major structure and provides new freedoms in assembly station design and layout. This research presents results of experiments to investigate manual assembly performance of aircraft wing systems, under varying wing structure orientation. A mock-up of a section of an A320 aircraft wing front spar, mounted on a rotation device, functions as the testbed. Manual installation activities are then conducted to emulate real aircraft system equipping for electric harnesses, raceways and hot air ducts. The results show a best-case assembly performance change of 36% for electric system installation activities of cable harnesses and raceway housing components. Tilted and horizontal orientations of the structure show the highest time reductions, with the vertical orientation either non-conclusive or increasing the assembly time. The outcomes of this study are intended to aid in effective trade-off decision making for future wing systems and assembly station layouts from the perspective of structural orientation and assembly task interaction.
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    Framework for integrated dynamic thermal simulation of future civil transport aircraft
    (AIAA, 2020-01-05) van Heerden, Albert S. J.; Judt, David M.; Lawson, Craig P.; Jafari, Soheil; Nikolaidis, Theoklis; Bosak, David
    The development of increasingly more electric systems and ultra high bypass ratio turbofan engines for civil transport aircraft is projected to bring forth critical challenges regarding thermal management. To address these, it is required that the thermal behavior of the complete propulsion-airframe unit is studied in an integrated manner. To this purpose, a simulation framework for performing integrated thermal and performance analyses of the engines, airframe, and airframe systems, is presented. The framework was specifically devised to test novel integrated thermal management solutions for future civil aircraft. In this paper, the discussion focuses mainly on the thermal modeling of the wing and fuel. A highly flexible approach for creating wing thermal models by means of assembling generic thermal compartments is introduced. To demonstrate some of the capabilities, a case study is provided that involves thermal analysis of a single-aisle airplane with ultra high bypass ratio engines. Results are provided for fuel temperatures across flights in standard, hot, and cold days and for different airframe materials. Engine heat sink temperatures and input power to the engine gearboxes, both important parameters needed to design thermal management systems, are also presented.
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    Rapid design of aircraft fuel quantity indication systems via multi-objective evolutionary algorithms
    (IOS Press, 2020-12-11) Judt, David M.; Lawson, Craig; van Heerden, Albert S. J.
    The design of electrical, mechanical and fluid systems on aircraft is becoming increasingly integrated with the aircraft structure definition process. An example is the aircraft fuel quantity indication (FQI) system, of which the design is strongly dependent on the tank geometry definition. Flexible FQI design methods are therefore desirable to swiftly assess system-level impact due to aircraft level changes. For this purpose, a genetic algorithm with a two-stage fitness assignment and FQI specific crossover procedure is proposed (FQI-GA). It can handle multiple measurement accuracy constraints, is coupled to a parametric definition of the wing tank geometry and is tested with two performance objectives. A range of crossover procedures of comparable node placement problems were tested for FQI-GA. Results show that the combinatorial nature of the probe architecture and accuracy constraints require a probe set selection mechanism before any crossover process. A case study, using approximated Airbus A320 requirements and tank geometry, is conducted and shows good agreement with the probe position results obtained with the FQI-GA. For the objectives of accessibility and probe mass, the Pareto front is linear, with little variation in mass. The case study confirms that the FQI-GA method can incorporate complex requirements and that designers can employ it to swiftly investigate FQI probe layouts and trade-offs.