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Author:Virtanen, Roy
Title:Black liquor spray model validation with particle image velocimetry measurements
Svartlut spraymodell validering med particle image velocimetry mätningar
Mustalipeäruiskumallin validointi particle image velocimetry mittauksilla
Publication type:Master's thesis
Publication year:2014
Pages:82 s. + liitt. 8      Language:   eng
Department/School:Energiatekniikan laitos
Main subject:Energiatekniikka   (K3007)
Supervisor:Järvinen, Mika
Instructor:Kankkunen, Ari
Electronic version URL: http://urn.fi/URN:NBN:fi:aalto-201410312964
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  4679   | Archive
Keywords:black liquor spray
spray modeling
particle image velocimetry
mustalipeän ruiskutus
ruiskumalli
Abstract (eng):Black liquor - the main by-product of pulp industries utilizing the kraft process - is generally combusted in recovery boilers in order to recover energy and most of the chemicals required for the pulping process.
In recovery boilers, black liquor is sprayed into the recovery boiler mostly with splash plate nozzles.
The spray tends to flash due to the high temperature required, because of the high viscosity of black liquor, which causes a two-phase flow.
Flashing increases the velocity of the spray, and generally also reduces the size of the droplets.
The velocity and the droplet size of the black liquor exiting the spray nozzles are of great importance, as they decide where and how combustion is taking place.

In this work the results from two different versions of a one-dimensional plug-flow spray model were compared to experimental measurements in order to validate the models.
Mainly the velocities were compared, but the pressures were also compared in some cases.
Model 1 accounts e.g. for two-phase flows and also possible non-Newtonian effects, while model 2 - in addition to this - also considers the pressure drop caused by the splash plate.
Two different sets of black liquor spray experiments were used for validation.
Case 1: Rauma 2000 measurements were conducted using a camera capturing multiple exposure images, and the Fast Fourier Transformation (FFT) method to solve the velocity.
Case 2: Rauma 2012 experiments were conducted using a high-speed camera and Particle Image Velocimetry (PIV) to obtain the velocity.
This included the use of PIV-software DaVis - by LaVision - and a self-made Microsoft® Excel spreadsheet to solve the velocity.
In both cases the centerline velocity was used to represent the measured velocity.

When comparing the velocity results obtained by simulations to the experimental results, it seemed like model 1 provided more accurate results compared to model 2.
However, when comparing the pressures; model 2 seemed to be more accurate in this regard, in comparison to model 1.
Both models had more or less deviations from the experiments, as could be expected.
The most likely reasons to the deviations would be the initial parameters used in the simulations.
Another cause to the differences in the velocities could be the usage of centerline velocity to represent the experimental velocity.
Using an adapted average velocity instead, could possibly even out the differences somewhat.
Errors in the measured velocities were also calculated, but were deemed minimal.
Abstract (fin):Mustalipeä on sellutuotannon sivutuote joka syntyy kun sellua tuotetaan sulfaattimenetelmällä.
Mustalipeä poltetaan yleisesti soodakattilassa jotta energiasisältö voitaisiin hyödyntää, ja sammalla suurin osa kemikaaleista voidaan myös kierrättää.
Mustalipeä ruiskutetaan useimmiten lusikkasuuttimilla tulipesään.
Mustalipeän korkean viskositeetin takia, lämpötila on pidettävä korkealla; jolloin lipeä kiehuu ja poistuu suuttimesta kaksifaasivirtauksena.
Kiehuminen nostaa ruiskun nopeutta, ja yleisesti myös pienentää pisarankokoa.
Mustalipeäruiskun pisaran nopeus ja koko ovat tärkeitä, sillä ne ratkaisevat missä ja miten palaminen tapahtuu.

Tässä työssä kahden eri mallien ennustuksia verrattiin kokeellisiin mittauksiin mallien validoimiseksi.
Ensisijaisesti verrattiin nopeuksia, mutta myös paineet muutamissa tapauksissa.
Malli 1 huomioi muun muassa mustalipeän kiehumisen sekä mustalipeän mahdollisen ei- Newtonilaisen käyttäytymisen.
Malli 2 huomioi tämän lisäksi painehäviön lusikassa.
Kaksi eri mustalipeän ruiskutus mittaussarjaa käytettiin tämän työn validoimiseen.
Tapaus 1: Rauma 2000 mittauksissa käytettiin kameraa joka tallensi monta kuvaa samaan kuvaan (päällekkäisvalotus), ja käytettiin Fast Fourier Transformation (FFT) menetelmää nopeuden ratkaisemiseen.
Tapaus 2: Rauma 2012 mittauksissa taas käytettiin suurnopeuskameraa ja Particle Image Velocimetry (PIV) menetelmää.
Tähän käytettiin myös LaVisionin DaVis PIVohjelmaa, sekä omatekoista Microsoft® Excel taulukkoa nopeuden laskemiseen.
Kummassakin tapauksessa keskilinjan nopeus edusti mittaus-nopeuksia.

Kokeellisiin tuloksiin verrattuna malli 1 näytti ennustavan nopeuden paremmin kuin malli 2.
Malli 2 kuitenkin ennusti paineet paremmin kuin malli 1.
Odotetusti, molempien mallien ennustukset erosivat kokeellisista tuloksista jossakin määrin.
Todennäköisin syy eroavaisuuksiin on malleissa käytetyt alkuparametrit.
Toinen mahdollinen syy nopeuksien eroavaisuuksiin voisi olla keskilinjan nopeuden käyttö.
Mukautetun keskinopeuden käyttö keskilinjan nopeuden sijaan voisi mahdollisesti pienentää eroavaisuuksia nopeuksissa.
Mittaustuloksien nopeuksien virheet laskettiin myös, mutta katsottiin minimaalisiksi.
ED:2014-11-02
INSSI record number: 49993
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