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Time-resolved measurements with a vortex flowmeter in a pulsating turbulent flow using wavelet analysis
KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strömningsfysik. KTH, Skolan för teknikvetenskap (SCI), Centra, Centrum för förbränningsteknik, CICERO.
KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strömningsfysik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Skolan för teknikvetenskap (SCI), Centra, Centrum för förbränningsteknik, CICERO.ORCID-id: 0000-0002-1663-3553
KTH, Skolan för teknikvetenskap (SCI), Mekanik, Stabilitet, Transition, Kontroll. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.ORCID-id: 0000-0001-8667-0520
KTH, Skolan för teknikvetenskap (SCI), Mekanik, Strömningsfysik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Skolan för teknikvetenskap (SCI), Centra, Centrum för förbränningsteknik, CICERO.ORCID-id: 0000-0002-1146-3241
2010 (engelsk)Inngår i: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 21, nr 12, s. 123001-Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
2010. Vol. 21, nr 12, s. 123001-
Emneord [en]
vortex flowmeter, wavelet analysis, Kármán vortex street, pulsatile flow
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-26336DOI: 10.1088/0957-0233/21/12/123001ISI: 000284261900002Scopus ID: 2-s2.0-78649894956OAI: oai:DiVA.org:kth-26336DiVA, id: diva2:371865
Merknad
QC 201012008Tilgjengelig fra: 2010-11-23 Laget: 2010-11-23 Sist oppdatert: 2022-06-25bibliografisk kontrollert
Inngår i avhandling
1. Flow Measuring Techniques in Steady and Pulsating Compressible Flows
Åpne denne publikasjonen i ny fane eller vindu >>Flow Measuring Techniques in Steady and Pulsating Compressible Flows
2010 (engelsk)Licentiatavhandling, med artikler (Annet vitenskapelig)
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.

sted, utgiver, år, opplag, sider
Stockholm: KTH, 2010. s. 89
Serie
Trita-MEK, ISSN 0348-467X ; 2010:09
Emneord
Flow measuring, compressible flow, steady flow, pulsating flow, hot-wire anemometry, cold-wire anemometry
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-26344 (URN)978-91-7415-824-3 (ISBN)
Presentation
2010-12-12, Sal S40, KTH, Teknikringen, Stockholm, 15:12
Opponent
Veileder
Merknad
QC 20101208Tilgjengelig fra: 2010-12-08 Laget: 2010-11-23 Sist oppdatert: 2022-06-25bibliografisk kontrollert
2. Flow measurements related to gas exchange applications
Åpne denne publikasjonen i ny fane eller vindu >>Flow measurements related to gas exchange applications
2012 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

This thesis deals with flow measuring techniques applied to steady and pulsating gas flows relevant to gas exchange systems for internal combustion engines. Gas flows in such environments are complex, i.e. they are inhomogeneous, three-dimensional, unsteady, non-isothermal and exhibit significant density changes. While a variety of flow metering devices are available and have been devised for such flow conditions, the performance of these flow metersis to a large extent undocumented when a strongly pulsatile motion is superposed on the already complex flow field. Nonetheless, gas flow meters are commonly applied in such environments, e.g. in the measurement of the air flow to the engine or the amount of exhaust gas recirculation. The aim of the present thesis is therefore to understand and assess, and if possible to improve the performance of various flow meters under highly pulsatile conditions as well as demonstrating the use of a new type of flow meter for measurements of the pulsating mass flow upstream and downstream the turbine of a turbocharger.

The thesis can be subdivided into three parts. The first one assesses the flow quality of a newly developed flow rig, designed for measurements of steady and pulsating air flow at flow rates and pulse frequencies typically found in the gas exchange system of cars and smaller trucks. Flow rates and pulsation frequencies achieved and measured range up to about 200 g/s and 80 Hz, respectively. The time-resolved mass flux and stagnation temperature under both steady and pulsating conditions were characterized by means of a combined hot/cold-wire probe which is part of a newly developed automated measurement module. This rig and measurement module were used to create a unique data base with well-defined boundary conditions to be used for the validation of numerical simulations, but in particular, to assess the performance of various flow meters.

In the second part a novel vortex flow meter that can measure the timedependent flow rate using wavelet analysis has been invented, verified and extensively tested under various industrially relevant conditions. The newly developed technique was used to provide unique turbine maps under pulsatile conditions through time-resolved and simultaneous measurements of mass flow, temperature and pressure upstream and downstream the turbine. Results confirm that the quasi-steady assumption is invalid for the turbine considered as a whole.

In the third and last part of the thesis, two basic fundamental questions that arose during the course of hot/cold-wire measurements in the aforementioned high speed flows have been addressed, namely to assess which temperature a cold-wire measures or to which a hot-wire is exposed to in high speed flows as well as whether the hot-wire measures the product of velocity and density or total density. Hot/cold-wire measurements in a nozzle have been performed to test various hypothesis and results show that the recovery temperature as well as the product of velocity and stagnation density are measured.

sted, utgiver, år, opplag, sider
Stockholm: KTH Royal Institute of Technology, 2012. s. viii, 197
Serie
Trita-MEK, ISSN 0348-467X ; 2012:08
Emneord
Flow meters, vortex flow meters, compressible flow, pulsating flow, hot-wire anemometry, cold-wire anemometry, time resolved measurements, wavelet analysis
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-94133 (URN)978-91-7501-385-5 (ISBN)
Disputas
2012-06-01, E2, Lindstedtsvägen 3, KTH, Stockholm, 10:15 (engelsk)
Opponent
Veileder
Merknad
QC 20120510Tilgjengelig fra: 2012-05-10 Laget: 2012-05-07 Sist oppdatert: 2022-06-24bibliografisk kontrollert

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