516 research outputs found
A new framework for estimating noise impact of novel aircraft
No full textAir traffic demand is forecast to significantly grow during the next few years. To compensate for the associated potential increase of aviation environmental impact, ambitious aircraft noise and emissions reduction goals have been set by several organisations worldwide. Accommodating these goals requires planning new mitigation strategies involving technological advances, optimised flight operations, and novel aircraft concepts. Methods for predicting the impact of potential mitigation strategies is vital to support effective planning.This thesis presents a new framework for estimating the noise impact of mitigation strategies (i.e. involving each or both of technological and operational changes) aspiring to: a) bypass the dependance on empirical flyover data and hence enable impact assessment of novel aircraft and operations, b) be independent of specific noise prediction methods and confidential inputs that are normally required by many noise prediction tools, c) have low computational requirements and thus be efficient in parametric studies, and d) provide inputs to emissions prediction tools, facilitating a more holistic strategic mitigation that considers various environmental concerns.The crux of the framework developed is that rather than seeking absolute noise values, it computationally estimates the noise impact of mitigation strategies, starting from a baseline scenario for which noise levels are known. This eliminates the need for measurements whilst minimising complexity and dependance on confidential inputs. Noise and emissions interdependencies are incorporated by expressing noise changes as a function of thrust, which is a common influencing parameter. In addition, the framework provides means for deriving purely computational NPD curves, enabling the construction of noise exposure contour maps for future aircraft and contemporary operations.The framework’s applicability on innovative flight operations and its capability of including the interdependencies between noise and emissions is demonstrated by estimating the environmentally-optimum approach and takeoff angles for civil aircraft of different sizes. The applicability to novel aircraft is displayed through noise estimations (including noise exposure contours) for various electric aircraft featuring Distributed Electric Propulsion (DEP), as well as for a Blended-Wing-Body (BWB) aircraft.The results obtained for future scenarios generally conform with the expected trends (deriving from e.g. higher-fidelity tools or historical trends) highlighting the framework’s great potential and usefulness in contributing in effective planning and decision-making
Noise assessment of aircraft with distributed electric propulsion using a new noise estimation framework
No full textFuture aircraft are envisioned to have significantly smaller noise footprint and emissions impact in order to satisfy the ambitious long-term aircraft noise and emissions goals set by several organisations worldwide, for example ACARE and NASA. Distributed electric propulsion (DEP) is anticipated as one of the most suitable and efficient options for powering these aircraft. DEP is the dispersion of thrust among multiple propulsors that are driven electrically rather than mechanically. This paper presents preliminary noise estimations for a civil aircraft that uses various DEP architectures (e.g. different number of electric propulsors, powered by either batteries or gas turbine engines), obtained through a new noise estimation framework that estimates noise variations arising from technological and/or operational changes with respect to a baseline scenario, where the noise levels are known. The aim of the paper is therefore twofold; investigate the possible noise benefits of DEP aircraft, whilst on the other hand demonstrate the core methodology and capabilities of our framework for estimating the noise impact of future aircraft concepts. This preliminary study indicates the framework’s potential in correctly capturing trends
Evaluation of environmentally optimal descent and take-off slopes for existing and novel aircraft
No full textDescent and takeoff slopes of civil aircraft influence the associated noise and emissions impact around airports. Steep take-off and approach procedures are expected to reduce the noise footprint around airports whereas they could offer local air quality benefits as well. This paper appraises the optimal descent and take-off slopes in terms of noise and emissions for existing civil aircraft, as well as fora future blended wing-body (BWB) concept aircraft. The effect of the interdependencies between noise and emissions is demonstrated, whereas estimated Noise-Power-Distance (NPD) curves for the steep operations are presented. It is shown that a common optimum slope for both environmental concerns is unlikely to occur and that generally, noise benefits come to the expense of increased fuel consumption. However, it is also highlighted that new, more flexible ways of expressing the noise and emissions interdependencies may be required in order to determine optimum slopes more realistically
Framework for predicting Noise-Power-Distance curves for novel aircraft designs
No full textAlong with flight profiles, Noise-Power-Distance (NPD) curves are the key input variable for computing noise exposure contour maps around airports. With the development of novel aircraft designs (incorporating noise reduction technologies) and new noise abatement procedures, NPD datasets will be required for assessing their potential benefit in terms of noise reduction around airports. NPD curves are derived from aircraft flyover noise measurements taken for a range of aircraft configurations and engine power settings. Clearly then, empirical NPD curves will be unavailable for novel aircraft designs and novel operations. This paper presents a generic framework for computationally generating NPD curves for novel aircraft and situations. The new framework derives computationally the NPD noise levels that are normally derived experimentally, by estimating noise level variations arising from technological and operational changes with respect to a baseline scenario, where the noise levels are known, or otherwise estimated. The framework is independent of specific prediction methods and can use any potential new model for existing or new noise sources. The paper demonstrates the methodology of the framework, discusses its benefits and illustrates its applicability by deriving NPD curves for an unconventional approach operation and for a future concept blended-wing-body (BWB) aircraft
A new method for estimating community noise changes due to aircraft technology variations
No full textFuture air traffic growth forecasts underline the need for new environmental abatement strategies for aviation, involving, among others, the adoption of new aircraft designs and technologies. Accurately predicting the noise impact of these strategies is therefore a matter of significance. The reliability of existing tools is governed by tradeoffs between parameters such as their fidelity level, their dependence on confidential data, as well as the cost and accuracy of experimental data. This paper proposes an innovative, flexible and simplified method for aircraft noise prediction that by-passes the difficulties of existing models. Based on scenarios where community noise levels are known through existing tools or publicly available databases, the proposed method determines variations resulting from aircraft technology changes, such as the increase of the bypass ratio of a turbofan engine. The method shows promise of being applicable to new designs like the wing body aircraft, whereas, by adapting the input variables, it can also estimate the noise impact of changes at operational level. To illustrate the proposed method, which is part of a wider effort to better understand environmental and economic interdependencies, noise estimations are compared to existing NPD data
Estimating variation in community noise due to variation in aircraft operations
No full textNotwithstanding considerable effort by many researchers world-wide, the estimation of community noise due to changes in aircraft fleets and operations remains subject to considerable uncertainty. This paper describes a new taxonomical architecture for aircraft noise prediction models that can be adapted to differing levels of input data and required outputs. Sound levels on the ground are estimated at base level using existing tools (such as INM or ANCON). The aim then is to determine variations on this base level depending upon differences in known input data whilst by-passing the full complexity of engineering models for which the necessary inputs can often only be assumed or are not even available for particular cases. The architecture is well-adapted for estimating incremental change associated with single input variables, such as approach glide slope angle, or flight track concentration associated with performance based radio navigation. The research is being carried out as part of a wider effort to better understand environmental and economic interdependencies, for which taxonomical models can be highly beneficial. To illustrate the approach, the model is compared against empirical data collected from trials of steeper approach glide slope angle
Preliminary noise assessment of aircraft with distributed electric propulsion
No full textElectric and hybrid-electric propulsion technologies are an increasingly attractive option for aviation stakeholders, providing more reliable and efficient power plants than traditional internal combustion engines, while reducing the dependency on fossil fuels, such as oil, whose value is volatile and availability uncertain. Combined with distributed electric propulsion (DEP), these propulsion technologies have shown significant potential in reducing civil aircraft noise emissions and are therefore viable candidates for delivering the strict mid-to-longterm environmental goals set by aviation organisations worldwide, such as ACARE and NASA. This paper examines the noise emission of a concept tube and wing aircraft that falls in the A320 category and features DEP systems using two different power supply units (turboshaft engines or batteries) and a varying number of propulsors. The transition of conventional propulsory systems to electric and hybrid systems is discussed, with Noise-Power-Distance (NPD) curves and noise exposure contour maps computed for several DEP systems and propulsor number configurations. Noise benefits of DEP especially at takeoff are demonstrated, whereas it is shown that based on predicted year 2035 entry into service technology, All Electric aircraft exhibit a larger noise footprint than aircraft using hybrid electric propulsion systems. Finally, our analysis indicates that the number of propulsors is a key parameter that may be used to optimise the environmental performance and noise benefits of DEP aircraft.</p
Towards estimating noise-power-distance curves for propeller powered zero emission hydrogen aircraft
No full textAs part of the UK Research and Innovation project New Aviation, Propulsion, Knowledge and Innovation Network (NAPKIN), a high-level framework was developed for the assessment of the noise impact of the proposed regional-sized hydrogen-powered aircraft. This study consists of the methodology used to generate the industry-standard noise–power–distance (NPD) curves from individual component noise analysis, specifically propeller tonal noise. The model is based on an asymptotic analysis of a frequency domain propeller tonal noise model combined with a linear approximation, taking advantage of the logarithmic nature of noise. An error analysis on the linear approximation assumption proves that the relative error between predicted and actual values of the noise remains below 10% for appropriately chosen baseline points. Verification of the framework was achieved through a bench-marking procedure that compared predictions of departure NPD curves for current technology regional aircraft against published ones over a range of operational power settings. Finally, departure and approach NPD predictions for three of the NAPKIN hydrogen concept aircraft are presented. Concepts featuring a larger, slower-rotating propeller with an increased number of blades relative to the reference aircraft showed benefits over the reference aircraft, despite, in some cases, increases in maximum takeoff weight
Closed-form analytical approach for calculating noise contours of directive aircraft noise sources
No full textThe Δρομοδείχτης της Ελλάδος of 1824 and Athanasios Stageirites (Τίτλος περίληψης)
No full textσ. [281]-290Κείμενο στα ελληνικά με περίληψη στα αγγλικά με τον τίτλο: The Δρομοδείχτης της Ελλάδος of 1824 and Athanasios StageiritesThe article first examines the close relationship between the publication “Δρομοδείχτης της Ελλάδος” [1824] and the publication “Ηπειρωτικά” (1819) by Athanasios Stageirites and then suggests that Athanasios Stageirites is the likeliest author of the “Δρομοδείχτης της Ελλάδος”.Δωδώνη: Τεύχος Πρώτο: επιστημονική επετηρίδα του Τμήματος Ιστορίας και Αρχαιολογίας της Φιλοσοφικής Σχολής του Πανεπιστημίου Ιωαννίνων; Τόμ. 43-44 (2014-2015
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