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Flow measurements related to gas exchange applications
KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
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.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , viii, 197 p.
Series
Trita-MEK, ISSN 0348-467X ; 2012:08
Keyword [en]
Flow meters, vortex flow meters, compressible flow, pulsating flow, hot-wire anemometry, cold-wire anemometry, time resolved measurements, wavelet analysis
National Category
Applied Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-94133ISBN: 978-91-7501-385-5 (print)OAI: oai:DiVA.org:kth-94133DiVA: diva2:525408
Public defence
2012-06-01, E2, Lindstedtsvägen 3, KTH, Stockholm, 10:15 (English)
Opponent
Supervisors
Note
QC 20120510Available from: 2012-05-10 Created: 2012-05-07 Last updated: 2012-05-10Bibliographically approved
List of papers
1. A flow facility for the characterization of pulsatile flows
Open this publication in new window or tab >>A flow facility for the characterization of pulsatile flows
2012 (English)In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 26, 10-17 p.Article in journal (Refereed) Published
Abstract [en]

In this paper a new flow facility for studies of pulsating flows is described. The pulsating flow is generated by means of a rotating valve and the flow is quantified through a newly developed flow measurement module accurately measuring the phase averaged flow distribution. The measuring probe of the module consists of a hot/cold-wire pair that enables both the mass flux and recovery temperature to be measured simultaneously. Calibrations of both the hot and cold wire are done in-situ in steady flow by means of a Pitot tube and a thermocouple. Moreover, the phase averaged flow distribution can be obtained by an automatic traverse of the measuring probe across the pipe cross section in both the radial and azimuthal directions. In the paper we exemplify and describe the flow properties, using the new flow measurement module, both in steady and pulsating flow.

Keyword
Hot-wire anemometry, Cold-wire anemometry, Pulsating flow, Pipe flow, Mass flowmeter, Time resolved measurements
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-94753 (URN)10.1016/j.flowmeasinst.2012.04.009 (DOI)000306886200002 ()2-s2.0-84861759857 (Scopus ID)
Funder
StandUp
Note

QC 20120903. Updated from accepted to published.

Available from: 2012-05-10 Created: 2012-05-10 Last updated: 2017-12-07Bibliographically approved
2. 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
3. Experimental analysis of turbocharger interaction with a pulsatile flow through time-resolved flow measurements upstream and downstream of the turbine
Open this publication in new window or tab >>Experimental analysis of turbocharger interaction with a pulsatile flow through time-resolved flow measurements upstream and downstream of the turbine
Show others...
2012 (English)In: Institution of Mechanical Engineers - 10th International Conference on Turbochargers and Turbocharging, 2012, 405-415 p.Conference paper, Published paper (Refereed)
Abstract [en]

The inflow to and outflow from turbochargers are highly complex and, in particular, pulsating. Nevertheless, most studies of turbocharger performance are conducted under steady conditions. Hence, there is a great interest in determining and understanding turbocharger performance maps under pulsatile conditions. The highly complex flow field constitutes a challenge for time-resolved flow measurements by means of conventional measurement techniques. In a recent paper by Laurantzon et al [Meas. Sci. Technol. 20 123001 (2010)], time-resolved bulk flow measurements under pulsatile conditions have been obtained via wavelet analysis of the signal from a vortex flow meter. Here, this method has been used in order to obtain time-resolved performance maps based on the mass flow both upstream and down-stream of the turbine. The results show that the turbine has a large damping effect on the mass flow pulsations, but that the pulse shape is to a high degree preserved while passing through the turbine, and that the time-dependent filling and emptying of the turbine case make the quasi-steady assumption invalid, if the whole turbine stage is considered.

Keyword
Flow measurement, Flow of fluids, Mass transfer, Turbines, Wavelet analysis
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-94757 (URN)2-s2.0-84865469576 (Scopus ID)978-085709209-0 (ISBN)
Conference
10th International Conference on Turbochargers and Turbocharging; London; 15 May 2012 through 16 May 2012
Funder
StandUp
Note

QC 20121018

Available from: 2012-05-10 Created: 2012-05-10 Last updated: 2013-04-16Bibliographically approved
4. Vortex shedding flow meters: accuracy assessment and extension towards industrial configurations
Open this publication in new window or tab >>Vortex shedding flow meters: accuracy assessment and extension towards industrial configurations
Show others...
(English)Article in journal (Other academic) Submitted
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-94758 (URN)
Note
QS 2012Available from: 2012-05-10 Created: 2012-05-10 Last updated: 2012-05-10Bibliographically approved
5. Response of common flowmeters to unsteady flow
Open this publication in new window or tab >>Response of common flowmeters to unsteady flow
2012 (English)Report (Other academic)
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-94760 (URN)
Funder
StandUp
Note

QC 20120510

Available from: 2012-05-10 Created: 2012-05-10 Last updated: 2013-04-18Bibliographically approved
6. 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
7. What does the hot-wire measure?
Open this publication in new window or tab >>What does the hot-wire measure?
2012 (English)Report (Refereed)
Abstract [en]

 

National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-94828 (URN)
Conference
9th International Conference on Turbochargers and Turbocharging
Funder
StandUp
Note

QC 20120510

Available from: 2012-05-10 Created: 2012-05-10 Last updated: 2013-04-18Bibliographically approved

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