17 research outputs found
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
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
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 textTechnological, economic, and environmental prospects of all-electric aircraft
No full textEver since the Wright Brothers’ first powered flight in 1903, commercial aircraft have relied on liquid hydrocarbon fuels. However, the need for greenhouse gas emission reductions along with recent progress in battery technology for automobiles has generated strong interest in electric propulsion in aviation. This work provides a first-order assessment of the energy, economic, and environmental implications of all-electric aircraft. We show that batteries with significantly higher specific energy and lower cost, coupled with further reductions of costs and CO2 intensity of electricity, are necessary for exploiting the full range of economic and environmental benefits provided by all-electric aircraft. A global fleet of all-electric aircraft serving all flights up to a 400-600 nmi (741-1,111 km) distance would demand an equivalent of 0.6-1.7% of worldwide electricity consumption in 2015. Whereas lifecycle CO2 emissions of all-electric aircraft depend on the power generation mix, all direct combustion emissions and thus direct air pollutants and direct non-CO2 warming impacts would be eliminated
Closed-form analytical approach for calculating noise contours of directive aircraft noise sources
No full textThis paper extends the simplified airport noise model Rapid Aviation Noise Evaluator (RANE) [Torija et al., Journal of the Acoustical Society of America, Vol. 141, No. 2, 2017, pp. 981–995], adding capability of including fully nonisotropic noise sources. This extended tool, RANE v2, is developed as a part of multidisciplinary acoustic assessment of novel aircraft, in order to produce ground contours around airports and helipads. Version 2 extends the capability of RANE to accommodate predictions of future air vehicles implementing propulsion systems solution with inherent directional properties. The model uses three-dimensional noise emission surfaces around a series of discretized segments that represent the aircraft flightpath. The main inputs are the sources’ sound power level, the distance from the flightpath at which a level is observed, and the source three-dimensional directivity. The directivity function may take analytical or numerical form, allowing for experimental data inputs. This paper demonstrates the use of spherical harmonics as a form of directivity function with a closed-form analytical solution for calculating the noise exposure contours. Results and comparison against the Federal Aviation Administration’s Aviation Environmental Design Tool module for helicopter community noise indicate that exposure contour coordinates can be estimated for high and low noise exposure levels. The incorporation of source directivity allows for the assessment of lateral attenuation, engine installation effects, and transition operations (for vertical to horizontal flight and vice versa) via the assumption of individual source directivities and, therefore, complex noise surfaces. As a consequence of the analytical nature of the model, low computational requirements allow for fast exploration of the design space and parametric studies, with minimal input requirements. The capabilities of RANE v2 are demonstrated by predicting noise footprints for three helicopters, each of different size, performance, and directivity characteristics.AIAA Journa
Toward 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
ESHRE PGD consortium best practice guidelines for organization of a PGD centre for PGD/preimplantation genetic screening
No full textIn 2005, the European Society for Human Reproduction and Embryology (ESHRE) PGD Consortium published a set of Guidelines for Best Practice PGD to give information, support and guidance to potential, existing and fledgling PGD programmes. Subsequent years have seen the introduction of new technologies as well as the evolution of current techniques. Additionally, in light of recent advice from ESHRE on how practice guidelines should be written/formulated, the Consortium believed it was timely to update the PGD guidelines. Rather than one document that covers all of PGD, the new guidelines are separated into four documents, including one relating to organization of the PGD centre and three relating to the methods used: DNA amplification, fluorescence in situ hybridization and biopsy/embryology. Here, we have updated the sections on organization of the PGD centre. One area that has continued to expand is Transport PGD, in which patients are treated at one IVF centre, whereas their gametes/embryos are tested elsewhere, at an independent PGD centre. Transport PGD/preimplantation genetic screening (PGS) has a unique set of challenges with respect to the nature of the sample and the rapid turn-around time required. PGS is currently controversial. Opinions of laboratory specialists and clinicians interested in PGD and PGS have been taken into account here. Current evidence suggests that PGS at cleavage stages is ineffective, but whether PGS at the blastocyst stage or on polar bodies might show improved delivery rates is still unclear. Thus, in this revision, PGS has been included. This document should assist everyone interested in PGD/PGS in developing the best laboratory and clinical practice possible. © 2010 The Author
ESHRE PGD Consortium data collection XII: Cycles from January to December 2009 with pregnancy follow-up to October 2010
No full textSTUDY QUESTION: How do data in the 12th annual data collection (Data XII) of the European Society of Human Reproduction and Embryology Preimplantation Genetic Diagnosis (PGD) Consortium compare with the cumulative data for collections I-XI? SUMMARY ANSWERS: ince the beginning of the data collections, there has been a steady increase in the number of cycles, pregnancies and babies reported annually.WHAT IS KNOWN ALREADYThe PGD Consortium has collected, analysed and published 11 previous data sets since 1997. STUDY DESIGN, SIZE, DURATION: Data were collected from each participating centre using a pre-designed FileMaker Pro database (versions 5-10). Separate FileMaker Pro files were used for the cycles, pregnancies and baby records. The study documented cycles performed during the calendar year 2009 and follow-up of the pregnancies and babies born which resulted from these cycles (until October 2010). PARTICIPANTS/MATERIALS, SETTING, METHODS: Data were submitted by 60 centres (full PGD Consortium members), and the blank files were distributed to each PGD Consortium member centre at the end of 2008. The submitted data were thoroughly analysed to identify incomplete data entries and corrections were requested from the participating centres. Records remaining with incomplete data were excluded from the calculations. Corrections, tables and calculations were made by expert co-authors. MAIN RESULTS AND THE ROLE OF CHANCE: For data collection XII, 60 centres reported data for 6160 cycles with oocyte retrieval (OR), along with details of the follow-up on 1607 pregnancies and 1238 babies born. A total of 870 OR were reported for chromosomal abnormalities, 113 OR for sexing for X-linked diseases, 1597 OR for monogenic diseases, 3551 OR for preimplantation genetic screening and 29 OR for social sexing. LIMITATIONS, REASONS FOR CAUTION: These data cannot include every PGD cycle performed annually, and only indicate the trends in PGD worldwide. WIDER IMPLICATION OF THE FINDINGS: The annual data collections provide an extremely valuable resource for data mining and for following trends in PGD practice. © 2014 The Author
Carbon nanoparticles in lateral flow methods to detect genes encoding virulence factors of Shiga toxin-producing Escherichia coli
No full textThe use of carbon nanoparticles is shown for the detection and identification of different Shiga toxin-producing Escherichia coli virulence factors (vt1, vt2, eae and ehxA) and a 16S control (specific for E. coli) based on the use of lateral flow strips (nucleic acid lateral flow immunoassay, NALFIA). Prior to the detection with NALFIA, a rapid amplification method with tagged primers was applied. In the evaluation of the optimised NALFIA strips, no cross-reactivity was found for any of the antibodies used. The limit of detection was higher than for quantitative PCR (q-PCR), in most cases between 10 4 and 10 5 colony forming units/mL or 0.1-0.9 ng/¿L DNA. NALFIA strips were applied to 48 isolates from cattle faeces, and results were compared to those achieved by q-PCR. E. coli virulence factors identified by NALFIA were in very good agreement with those observed in q-PCR, showing in most cases sensitivity and specificity values of 1.0 and an almost perfect agreement between both methods (kappa coefficient larger than 0.9). The results demonstrate that the screening method developed is reliable, cost-effective and user-friendly, and that the procedure is fast as the total time required is <1 h, which includes amplification. © 2010 The Author(s).This work was partially supported by the Generalitat Valenciana (BEST/2009/026), the Universidad Politecnica de Valencia (PAID-00-09-2837), and by the Dutch Ministry of Agriculture, Nature and Food Quality (KennisBasis 6 programme). The authors would like to thank Dr. Eva Moller Nielsen at the Danish Veterinary Institute (Copenhagen, Denmark) for providing E. coli control strains and Dr. Lutz Geue (Friedrich-Loeffler-Institut, Wusterhausen, Germany) and Dr. Dorte Dopfer (School of Veterinary Medicine, University of Wisconsin, Madison, WI, USA) for field isolates.Noguera Murray, PS.; Posthuma-Trumpie, G.; Van Tuil, M.; Van Der Wal, F.; De Boer, A.; Moers, A.; Van Amerongen, A. (2011). Carbon nanoparticles in lateral flow methods to detect genes encoding virulence factors of Shiga toxin-producing Escherichia coli. 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