Conbustion And Convection In Microgravity

Conbustion And Convection In Microgravity

Naiara Barrado IzagirreEHU-UPV

Authors: Javier Rodríguez, Naiara Barrado, Daniel Fernández de Castillo, Leire Del Campo, Manuel J. Tello

Naiara Barrado Izagirre EHU-UPV Aalborg´05

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Index

What do we know about a candle in microgravity?Experiment Objectives.Experiment Description.Technical support.Outreach.


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COMBUSTION:The flame of a candle a non-propagating pure difusion flame.Many interesting results around flame:

EstructureSize

Differences under normal gravity or microgravity.

Althogh it may raise an eyebrow, the candle hides a complex physics

behind.

What Do We Know About A Candle?

aerodynamic featurechemistry and transport feature

ShapeColour

Candle under normal gravity

Candle under microgravity conditions

•Hemi spherical.•Dim blue.

•Tear-drop-like.•Yelow.

If anyone thinks about bringing a candle to the space in order to light up, it has been proved that he is wrong: The candle

doesn’t light in microgravity!!!!


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Why these tear-drop-like form?


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CONVECTION CURRENTS:Currents into the melted wax (in the top of the candle).Produced by temperature gradients between the flame base and the candle border. Very important in

order to avoid a very quickly candle melting the well base is an isothermal surface where the wax is contained.


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Experimet Objectives

The following experiment are proposed:1) Convection currents.

2) Behavior of the flame in presence of an electrical field.

3) Variation of the oxigen concentration.


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Experiment Description I

CONVECTIONCONVECTION CURRENTSCURRENTS:Study of the convection currents using sketchers.We were able to observe fluctuations in the currents under gravity conditions.Sketchers will follow the convection currents.Thermocouples: Allow registering the temperature changes at different points of the melted wax.

Hot focus

Isothermal surface

Convection currents followed by sketchers

Flame

Thermocouples

1)


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Experiment Description II

FLAME SHAPE IN AN FLAME SHAPE IN AN ELECTRICAL FIELDELECTRICAL FIELD:Study of the flame shape in an electrostatic field.Ifluence of the electrical field is due to the presence of some charged particles in the flame (soot).

Plane capacitor

2)


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Experiment Description III

OXIGEN CONCENTRATION:OXIGEN CONCENTRATION:Study the convection currents and the flame shape with and without electrical field changing the oxygen concentration.. Variation of oxygen will be made using a little oxygen container coupled to the boxes*.

3)


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Technical support I

Candles located in apropiate polycarbonate boxes (not flammable).


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Cameras

Technical support II

Location at the rack.Four cameras operating in the visible and ultraviolet.

Horizontal compensation mechanical system:

Allows to maintain the melted wax surface in the same position during the parabolic flight.


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Candles of different characteristics will be used :

diameterlengthtype of wicketc…

To see the influence of all these parameters in:flame shapecolour and dimensionssoot formationoxygen combustion


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Outreach

Experiments have scientificscientific, technologicaltechnological and educationaleducational objectives:Scientific: Writing an article.Tehnological: Application on candle production.Educational: Divulgation DVD.


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Bilbliography

1) J. Wisniak, “Candle: A light into the past”, Indian Journal of Chemical Technology 7 (2001) 319-326.

2) D.L. Dietrich, H.D. Ross, Y. Shu, P. Chang, J.S. Tien, “Candle flames in non-buoyant atmospheres”, Combustion Science & Technology 156 (200) 1-24.

3) X. Q. Zhang, W.F. Du, M.G. Wei, W.J. Kong, Y.Hua, “A study of candle flame in microgravity” (to be published).

4) Some internet pages.

Conbustion And Convection In Microgravity

Documents

flame base

flame shapecolour

flame soot

electrical field

candle border

candle doesnt light

electrostatic field

melted wax surface