12 research outputs found

    Measurement techniques for mode detection in aeroengine inter-stage sections

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    The sound field within an aeroengine duct can be expressed as a superimposition of acoustic modes. Knowledge of the modal pressure amplitude is useful for providing insight into the noise generation mechanism, assist in the design of sound absorbing liners, and is invaluable for determining the sound power. In-duct modal analysis allows the amplitude of each modal component to be determined from the sound pressure measured at the duct wall. Previous research has demonstrated the feasibility of using axial microphone arrays to detect the modes in the tonal and broadband sound fields. Broadband noise generally comprises all propagating modes, which would require at least as many microphones to deduce the amplitude for each mode index pair (m,n). Most existing studies have focussed on the modal analysis of broadband noise at the inlet or bypass sections of aeroengines. Meanwhile, all existing modal analysis techniques assume that the modes in the sound field are mutually uncorrelated. It is commonly believed that the broadband noise is mainly generated from the interaction of wake turbulence from the rotor with the leading edge of the Outlet Guide Vane (OGV), and the interaction of the boundary turbulence with the trailing edge of rotor blade. However, no work has been undertaken into modal analysis based on measurements in the engine inter-stage section aimed at understanding this interaction noise mechanism. The space restriction of the inter-stage section constrains the number of microphones that can be used. Therefore, innovative measurement techniques must be developed which can detect the modes in the limited spacing between the rotor and the OGV. This paper investigates two different measurement techniques suitable for this purpose. The first is based on measurements of the coherence function of the acoustic pressure between two measurement positions at the duct wall. The second uses a beamformer formed from an axial array of microphones at the duct wall. In this paper we present a simple acoustic model for the sound field in the engine inter-stage due to a rotating fan and an OGV. The model has a number of simplifying assumptions but includes realistic spanwise correlation characteristics through the use of simple semi-empirical turbulence models, which is necessary for predicting the correct modal correlation behaviour. The swirl is treated simply as a rigid body rotation. Based on the simulated acoustic pressure at the duct wall, the actual mode amplitude distribution and the estimated mode amplitude distribution from two techniques are compared. The modal information is obtained in the form of the mode amplitude versus modal cuton ratio for both rotor and OGV. Thus, the methods are effective as a means of determining the dominant noise source in the engine. The relationship between the two methods is explored

    Experimental investigation of a new two-microphone method for the determination of broadband noise radiation from ducts

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    This paper experimentally investigates a new technique for measuring the modal amplitude distribution, sound power transmission and radiation, and far field directivity of the broadband noise from hard walled ducts. The innovative aspect of this method is that it only requires the measurements of the two-point complex coherence function between the acoustic pressures at two closely spaced points on the duct wall. This method is therefore very useful when direct measurements of sound power and directivity are not possible. This paper describes detailed measurements of the sound power spectrum and coherence function from a hard walled circular duct excited at one end by a diffuse sound field. The other open end is terminated within an anechoic chamber with which to measure the radiated sound field at 11 microphones distributed over a polar arc. Measurements of the complex coherence were made at the duct and used to infer the sound power spectrum and far field directivity. This paper demonstrates generally good agreement between direct measurements of sound power and directivity and those inferred from the coherence function. The method is restricted to broadband noise in large ducts in the frequency range where many modes are able to propagate and the modal amplitudes are mutually uncorrelated

    Yale school of medicine IRB consent.

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    IntroductionElectronic cigarette (EC) use has increased rapidly in the last decade, especially among youth. Regulating nicotine delivery from ECs could help curb youth uptake and leverage EC use in harm reduction yet is complicated by varying device and liquid variables that affect nicotine delivery. Nicotine flux, the nicotine emission rate, is a parameter that incorporates these variables and focuses on the performance rather than the design of an EC. Nicotine flux therefore could be a powerful regulatory tool if it is shown empirically to predict nicotine delivery and subjective effects related to dependence.Methods and analysisThis project consists of two complementary clinical trials. In Trial I, we will examine the relationship between nicotine flux and the rate and dose of nicotine delivery from ECs, hence, impacting abuse liability. It will also examine the extent to which this relationship is mediated by nicotine form (i.e., freebase versus protonated). At Yale School of Medicine (YSM), study participants will puff EC devices under conditions that differ by flux and form, while arterial blood is sampled in high time resolution. In Trial II, we will assess the relationship between nicotine flux, form, and subjective effects. At the American University of Beirut (AUB), participants will use EC devices with varying nicotine fluxes and forms, while dependency measures, such as the urge to use ECs, nicotine craving, and withdrawal symptoms, will be assessed. We will also monitor puffing intensity and real-time exposure to toxicants.Ethics and disseminationThe protocol of Trial I and Trial II was approved by YSM and AUB IRBs, respectively. We will disseminate study results through peer-reviewed publications and conference presentations.Trial registrationNCT05706701 for Trial I and NCT05430334 for Trial II.</div

    Yale school of medicine IRB protocol.

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    IntroductionElectronic cigarette (EC) use has increased rapidly in the last decade, especially among youth. Regulating nicotine delivery from ECs could help curb youth uptake and leverage EC use in harm reduction yet is complicated by varying device and liquid variables that affect nicotine delivery. Nicotine flux, the nicotine emission rate, is a parameter that incorporates these variables and focuses on the performance rather than the design of an EC. Nicotine flux therefore could be a powerful regulatory tool if it is shown empirically to predict nicotine delivery and subjective effects related to dependence.Methods and analysisThis project consists of two complementary clinical trials. In Trial I, we will examine the relationship between nicotine flux and the rate and dose of nicotine delivery from ECs, hence, impacting abuse liability. It will also examine the extent to which this relationship is mediated by nicotine form (i.e., freebase versus protonated). At Yale School of Medicine (YSM), study participants will puff EC devices under conditions that differ by flux and form, while arterial blood is sampled in high time resolution. In Trial II, we will assess the relationship between nicotine flux, form, and subjective effects. At the American University of Beirut (AUB), participants will use EC devices with varying nicotine fluxes and forms, while dependency measures, such as the urge to use ECs, nicotine craving, and withdrawal symptoms, will be assessed. We will also monitor puffing intensity and real-time exposure to toxicants.Ethics and disseminationThe protocol of Trial I and Trial II was approved by YSM and AUB IRBs, respectively. We will disseminate study results through peer-reviewed publications and conference presentations.Trial registrationNCT05706701 for Trial I and NCT05430334 for Trial II.</div

    American University of Beirut protocol.

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    IntroductionElectronic cigarette (EC) use has increased rapidly in the last decade, especially among youth. Regulating nicotine delivery from ECs could help curb youth uptake and leverage EC use in harm reduction yet is complicated by varying device and liquid variables that affect nicotine delivery. Nicotine flux, the nicotine emission rate, is a parameter that incorporates these variables and focuses on the performance rather than the design of an EC. Nicotine flux therefore could be a powerful regulatory tool if it is shown empirically to predict nicotine delivery and subjective effects related to dependence.Methods and analysisThis project consists of two complementary clinical trials. In Trial I, we will examine the relationship between nicotine flux and the rate and dose of nicotine delivery from ECs, hence, impacting abuse liability. It will also examine the extent to which this relationship is mediated by nicotine form (i.e., freebase versus protonated). At Yale School of Medicine (YSM), study participants will puff EC devices under conditions that differ by flux and form, while arterial blood is sampled in high time resolution. In Trial II, we will assess the relationship between nicotine flux, form, and subjective effects. At the American University of Beirut (AUB), participants will use EC devices with varying nicotine fluxes and forms, while dependency measures, such as the urge to use ECs, nicotine craving, and withdrawal symptoms, will be assessed. We will also monitor puffing intensity and real-time exposure to toxicants.Ethics and disseminationThe protocol of Trial I and Trial II was approved by YSM and AUB IRBs, respectively. We will disseminate study results through peer-reviewed publications and conference presentations.Trial registrationNCT05706701 for Trial I and NCT05430334 for Trial II.</div
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