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Measuring with pressure sensitive paint in time-varying flows
KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics. (CCGEx, FLOW)
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Increasingly tougher legislation on internal combustion engine emissions drives the development towards smaller engines with higher efficiency where an important component is the gas-exchange system and especially the turbocharger. The flow in the gas-exchange system is inherently pulsating and unsteady and the present thesis aims at investigating if and how pressure sensitive paint (PSP) can be used for internal unsteady flows of relevance for engine applications. PSP is an optical non-intrusive technique for pressure measurements on surfaces and in the thesis different acquisition, evaluation and signal-to-noise-raising methods have been evaluated and developed with focus on unsteady internal flow. In particular it describes a path towards measurements of unsteady pressure distributions on the impeller blades of turbocharger compressors appearing in compressors at surge.

As a first step, dynamic calibration of a polymer/ceramic pressure sensitive paint (PC-PSP) was made using a shock tube. The cut-off frequency for the tested ruthenium-based formulation was found to be a few kilohertz; sufficient for resolving unsteady compressor behaviour such as surge and rotating stall.

The same PC-PSP was used for measurements of the pressure on the inside wall of a y-junction sized to resemble the exhaust manifold of a car engine. The intensity method was used where a LED array provided excitation light and luminescent intensities was acquired using a CCD camera. Phase averaging was made in-camera by summing the intensity from several LED flashes phase locked to the flow pulses.

A filtering technique based on singular value decomposition (SVD) was also developed. As a test case the fluctuating pressure field due to unsteady vortex shedding on the side of a square cylinder was evaluated. The data was captured using a high speed CMOS camera and continuous LED light. The result was a reduction of pixel noise on the order of two magnitudes that made it possible to recover vortex shedding behaviour otherwise submerged in noise.

Due to complex geometries and high rotational speeds, pressure measurements on the impeller blades are unfeasible using traditional pressure taps and transducers and here the pressure was measured with PSP on the impeller blades of a rotating compressor. For this study, point measurements using a scanning laser for excitation and a photomultiplier tube for the acquisition of the luminescence was used and evaluated with the so called lifetime method. The measurements were able to capture the surge frequency as well as its spatial distribution.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. , viii, 54 p.
Series
TRITA-MEK, ISSN 0348-467X ; 2014.18
Keyword [en]
Pressure sensitive paint, fluid mechanics, internal flow, pulsating flow
National Category
Applied Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-149576ISBN: 978-91-7595-246-8 (print)OAI: oai:DiVA.org:kth-149576DiVA: diva2:740366
Public defence
2014-09-26, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 14:15 (English)
Opponent
Supervisors
Note

QC 20140901

Available from: 2014-09-01 Created: 2014-08-25 Last updated: 2014-09-01Bibliographically approved
List of papers
1. Dynamic Calibration of Polymer/Ceramic Pressure Sensitive Paint Using a Shock Tube
Open this publication in new window or tab >>Dynamic Calibration of Polymer/Ceramic Pressure Sensitive Paint Using a Shock Tube
2010 (English)In: Seventh International Conference on Flow Dynamics: Proceedings, 2010, 132-133 p.Conference paper, Published paper (Refereed)
Abstract [en]

This work deals with the topic of dynamic calibration of pressure sensitive paint (PSP) using methods of system identification in z-space, suitable for discrete time analysis. The aim is to be able to reconstruct time varying pressures from (phase and amplitude distorted) measurement data. The calibration method is useful when a well known pressure source is available, such as moving shock in a shock tube. 

National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-49107 (URN)
Conference
Seventh International Conference on Flow Dynamics
Note

QC 20111208

Available from: 2011-12-08 Created: 2011-11-25 Last updated: 2014-09-01Bibliographically approved
2. Wall Pressure Measurements in a Y-Junction at Pulsating Flow using Polymer/Ceramic Pressure Sensitive Paint
Open this publication in new window or tab >>Wall Pressure Measurements in a Y-Junction at Pulsating Flow using Polymer/Ceramic Pressure Sensitive Paint
2011 (English)In: Proceedings of the 10th International Symposium on Experimental and Computational Aerothermodynamics of Internal Flows, 2011, 1-6 p.Conference paper, Published paper (Refereed)
Abstract [en]

In this experiment ruthenium based polymer/ceramic pressure sensitive paint (PC-PSP) has been used to study the pressure inside a y-junction at pulsating flow conditions. Pressure has been measured using the intensity based method and through phase locked averages. The aim has been to investigate the potential of PC-PSP at mass flows and pulse frequencies typical of those in the exhaust manifold of internal combustion engines. 

Keyword
time resolved PSP, PC-PSP, y-junction, internal flow, pulsating flow
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-49123 (URN)
Conference
10th International Symposium on Experimental and Computational Aerothermodynamics of Internal Flows
Note
QC 20111208Available from: 2011-12-08 Created: 2011-11-25 Last updated: 2014-09-01Bibliographically approved
3. Enhancing the signal-to-noise ratio of pressure sensitive paint data by singular value decomposition
Open this publication in new window or tab >>Enhancing the signal-to-noise ratio of pressure sensitive paint data by singular value decomposition
2013 (English)In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 24, no 7, 075301- p.Article in journal (Refereed) Published
Abstract [en]

When using pressure sensitive paint under unsteady conditions in low-speed applications, the signal-to-noise ratio is usually low and may hinder the proper evaluation of the acquired data. Here, we propose a new noise-filtering scheme that is based on singular value decomposition. As a test case, we evaluate the fluctuating pressure field due to unsteady vortex shedding on the side of a square cylinder. The proposed scheme resulted in a reduction of pixel noise of the order of two magnitudes which made it possible to obtain results regarding the spatial form of flow structures as well as the shedding frequency.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2013
Keyword
pressure sensitive paint, singular value decomposition, proper orthogonal decomposition, square cylinder, vortex shedding, noise filtering
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-124966 (URN)10.1088/0957-0233/24/7/075301 (DOI)000320449100045 ()2-s2.0-84879974682 (Scopus ID)
Funder
Swedish Energy Agency
Note

QC 20130805

Available from: 2013-08-05 Created: 2013-08-02 Last updated: 2017-12-06Bibliographically approved
4. Pressure and velocity field measurements of pulsating flow in a square channel y-junction
Open this publication in new window or tab >>Pressure and velocity field measurements of pulsating flow in a square channel y-junction
2013 (English)In: Bulletin of the American Physical Society 58, 2013Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

The pressure and velocity fields in a y-junction of a square (40×40 mm²) cross-section channel were investigated during pulsating flow. One of the sides of the channel was covered with fast responding pressure sensitive paint (PSP) whereas the velocity field at the channel center parallel to the PSP surface was measured using particle image velocimetry (PIV). The flow conditions, in terms of mass flow rate and pulsation frequency, were selected to resemble the flow inside an exhaust manifold of a small internal combustion engine, although the gas was at room temperature. The mass flow was varied between 10 and 130 g/s with pulsations between 0 and 80 Hz. For both the PSP and the PIV measurements images were acquired unsynchronized to the pulses using a high-speed camera and phase averages were formed a posteriori. The use of PSP together with PIV demonstrates how the two techniques can be used to verify and complement each other, PIV excelling at the lower mass flow rates and PSP at the higher. It is shown that the signal-to-noise ratio for PSP at low velocities can be enhanced using a technique based on singular value decomposition.

National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-143946 (URN)
Conference
66th Annual Meeting of the APS Division of Fluid Dynamics; Pittsburgh, Pennsylvania, November 24–26, 2013
Note

QC 20140626

Available from: 2014-04-03 Created: 2014-04-03 Last updated: 2014-09-01Bibliographically approved

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