The effect of speed variation on in-duct source data determination
2014 (English)In: 21st International Congress on Sound and Vibration 2014, ICSV 2014, 2014, 2395-2401 p.Conference paper (Refereed)
Experimental acoustic source characterization is used for IC-engines and fluid machines connected to duct or pipe systems. Information about the engine as an acoustic source is needed to calculate insertion loss of mufflers or the level of radiated sound. The source model used in the low frequency plane wave range is often the linear time invariant 1 -port model. The acoustic source data is obtained from experimental tests or from 1 -D CFD codes describing the engine gas exchange process. Multi-load methods and especially the two-load method are most commonly used to extract the source data. The IC-engine is a high level acoustic source and in most cases not completely linear. The real part of the measured source impedance sometimes has negative values which is un-physical. This effect has been attributed to non-linearity and source time variation. Another possible explanation could be speed variation giving measurement errors especially for higher harmonics. In the present paper this effect is studied by re-visiting source data experiments for IC-engine exhausts and comparing the outcome of different methods for extracting the amplitude and phase of the pressure in terms of frequency components or engine orders.
Place, publisher, year, edition, pages
2014. 2395-2401 p.
Acoustic impedance, Acoustic noise measurement, Acoustics, Computational fluid dynamics, Engines, Exhaust systems (engine), Internal combustion engines, Measurement errors, Acoustic sources, Experimental test, Frequency components, Gas exchange process, Higher harmonics, Linear time invariant, Source impedance, Speed variations, Ducts
IdentifiersURN: urn:nbn:se:kth:diva-167520ScopusID: 2-s2.0-84922654411ISBN: 9781634392389OAI: oai:DiVA.org:kth-167520DiVA: diva2:819728
21st International Congress on Sound and Vibration 2014, ICSV 2014, 13 July 2014 through 17 July 2014
QC 201506112015-06-112015-05-222015-06-11Bibliographically approved