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Flow Measuring Techniques in Steady and Pulsating Compressible Flows
KTH, School of Engineering Sciences (SCI), Mechanics.
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with flow measuring techniques applied on steady and pulsatingflows. Specifically, it is focused on gas flows where density changes canbe significant, i.e. compressible flows. In such flows only the mass flow ratehas a significance and not the volume flow rate since the latter depends onthe pressure. The motivation for the present study is found in the use of flowmeters for various purposes in the gas exchange system for internal combustionengines. Applications can be found for instance regarding measurements of airflow to the engine, or measurements of the amount of exhaust gas recirculation.However the scope of thesis is wider than this, since the thesis aims toinvestigate the response of flow meters to pulsating flows. The study is mainlyexperimental, but it also includes an introduction and discussion of several inindustry, common flow measuring techniques.The flow meters were studied using a newly developed flow rig, designedfor measurement of steady and pulsating air flow of mass flow rates and pulsefrequencies typically found in the gas exchange system of cars and smallertrucks. Flow rates are up to about 200 g/s and pulsation frequencies from 0 Hz(i.e. steady flow) up to 80 Hz. The study included the following flow meters:hot-film mass flow meter, venturi flowmeter, Pitot tube, vortex flowmeter andturbine flowmeter. The performance of these meters were evaluated at bothsteady and pulsating conditions. Furthermore, the flow under both steady andpulsating conditions were characterized by means of a resistance-wire basedmass flow meter, with the ability to perform time resolved measurements ofboth the mass flux ρu, and the stagnation temperature T0.Experiments shows that, for certain flow meters, a quasi-steady assumptionis fairly well justified at pulsating flow conditions. This means that thefundamental equations describing the steady flow, for each instant of time,is applicable also in the pulsating flow. In the set-up, back-flow occurred atcertain pulse frequencies, which can result in highly inaccurate output fromcertain flow meters, depending on the measurement principle. For the purposeof finding means to determine when back flow prevails, LDV measurementswere also carried out. These measurements were compared with measurementsusing a vortex flow meter together with a new signal processing technique basedon wavelet analysis. The comparison showed that this technique may have apotential to measure pulsating flow rates accurately.Descriptors: Flow measuring, compressible flow, steady flow, pulsating flow,hot-wire anemometry, cold-wire anemometry.

Place, publisher, year, edition, pages
Stockholm: KTH , 2010. , 89 p.
Series
Trita-MEK, ISSN 0348-467X ; 2010:09
Keyword [en]
Flow measuring, compressible flow, steady flow, pulsating flow, hot-wire anemometry, cold-wire anemometry
National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-26344ISBN: 978-91-7415-824-3 (print)OAI: oai:DiVA.org:kth-26344DiVA: diva2:371890
Presentation
2010-12-12, Sal S40, KTH, Teknikringen, Stockholm, 15:12
Opponent
Supervisors
Note
QC 20101208Available from: 2010-12-08 Created: 2010-11-23 Last updated: 2010-12-08Bibliographically approved
List of papers
1. The corona mass flow meter
Open this publication in new window or tab >>The corona mass flow meter
2008 (English)Conference paper, Published paper (Refereed)
Identifiers
urn:nbn:se:kth:diva-26338 (URN)
Conference
The 19th Symposium on Measuring Techniques in Transonic and Supersonic Flow in Cascades and Turbomachines
Note
QC 20101208Available from: 2010-11-23 Created: 2010-11-23 Last updated: 2010-12-08Bibliographically approved
2. A pulsating flow rig for analyzing turbocharger performance
Open this publication in new window or tab >>A pulsating flow rig for analyzing turbocharger performance
2010 (English)Conference paper, Published paper (Refereed)
Abstract [en]

 

Drastic improved performance of IC-engines requires efforts along many lines, where gas management is one important area. Although simulation intensive research and design tools are becoming more and more in use, they still need to be verified through accurate experiments. This is especially so for the turbocharger, an essential component for improved performance that is working in a highly complex environment. In this paper we describe a new test facility where a pulsed flow can be generated and the pulses accurately quantified trough a traversed hot-wire flow meter.

National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-26340 (URN)2-s2.0-78649850841 (Scopus ID)
Conference
9th International Conference on Turbochargers and Turbocharging
Note
QC 20101208Available from: 2010-11-23 Created: 2010-11-23 Last updated: 2010-12-08Bibliographically approved
3. Time-resolved measurements with a vortex flowmeter in a pulsating turbulent flow using wavelet analysis
Open this publication in new window or tab >>Time-resolved measurements with a vortex flowmeter in a pulsating turbulent flow using wavelet analysis
2010 (English)In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 21, no 12, 123001- p.Article in journal (Refereed) Published
Abstract [en]

Vortex flowmeters are commonly employed in technical applications and are obtainable in a variety of commercially available types. However their robustness and accuracy can easily be impaired by environmental conditions, such as inflow disturbances and/or pulsating conditions. Various post-processing techniques of the vortex signal have been used, but all of these methods are so far targeted on obtaining an improved estimate of the time-averaged bulk velocity. Here, on the other hand, we propose, based on wavelet analysis, a straightforward way to utilize the signal from a vortex shedder to extract the time-resolved and thereby the phase-averaged velocity under pulsatile flow conditions. The method was verified with hot-wire and laser Doppler velocimetry measurements.

Keyword
vortex flowmeter, wavelet analysis, Kármán vortex street, pulsatile flow
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-26336 (URN)10.1088/0957-0233/21/12/123001 (DOI)000284261900002 ()2-s2.0-78649894956 (Scopus ID)
Note
QC 201012008Available from: 2010-11-23 Created: 2010-11-23 Last updated: 2017-12-12Bibliographically approved
4. Review on the sensed temperature in cold-wire and hot-wire anemometry
Open this publication in new window or tab >>Review on the sensed temperature in cold-wire and hot-wire anemometry
2010 (English)Report (Other academic)
Abstract [en]

Instantaneous velocity and temperature measurements by means of hot-wire and coldwires have become a standard technique used in almost every fluid dynamic research laboratory. Nonetheless, when it comes to compressible flows in applied fields, there seems to remain a need for clarification on which temperature is actually measured by a cold-wire and which temperature a hot-wire senses as its fluid temperature. The present paper reviews the view present in the literature and presents additional experimental evidence, that it is indeed the recovery temperature that is measured by a cold-wire and that this is also the temperature needed to compensate hot-wire readings in nonisothermal compressible flows

Publisher
11 p.
Keyword
hot-wire anemometry, cold-wire anemometry, recovery temperature, temperature
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-26343 (URN)
Note
QC 20101208Available from: 2010-11-23 Created: 2010-11-23 Last updated: 2012-05-10Bibliographically approved

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