A noncatalytic coating for platinum-rhodium thermocouples

Kint, Jeroen

doi:10.1016/s0010-2180(70)80040-2

Cited by 215 publications

(59 citation statements)

References 2 publications

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“…The main addition to the reactions of allene was to consider the reactions of abstraction of a hydrogen atom by H atoms and OH, CH 3 , C 2 H, C 2 H 3 , C 2 H 5 and a-C 3 H 5 radicals (reactions [15][16][17][18][19][20][21][22]. These reactions, involving the abstraction of vinylic H-atoms, had been neglected in our previous work in shock tube conditions [8], but were found important here to correctly reproduce the profile of allene in the flame doped with this compound.…”

Section: Table Imentioning

confidence: 99%

“…The thermocouple wire was sustained by a fork and crosses the flame horizontally to avoid conduction heat losses. The junction was located at the centre of the burner.The thermocouple was coated with an inert layer of BeO-Y 2 O 3 to prevent catalytic effects [16].The ceramic layer was obtained by damping in a hot solution of Y 2 (CO 3 ) 3 (93% mass.) and BeO (7% mass.)…”

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confidence: 99%

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Rich methane premixed laminar flames doped with light unsaturated hydrocarbonsI. Allene and propyne

Gueniche

Glaude

Dayma

et al. 2006

Combustion and Flame

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The structure of three laminar premixed rich flames have been investigated: a pure methane flame and two methane flames doped by allene and propyne, respectively. The gases of the three flames contain 20.9% (molar) of methane and 33.4 % of oxygen corresponding to an equivalent ratio of 1.25 for the pure methane flame. In both doped flames, 2.49 % of C 3 H 4 was added, corresponding to a ratio C 3 H 4 / CH 4 of 12 % and an equivalent ratio of 1.55. The three flames have been stabilized on a burner at a pressure of 6.7 kPa using argon as dilutant, with a gas velocity at the burner of 36 cm/s at 333 K. The concentration profiles of stable species were measured by gas chromatography after sampling with a quartz microprobe. Quantified species included carbon monoxide and dioxide, methane, oxygen, hydrogen, ethane, ethylene, acetylene, propyne, allene, propene, propane, 1,2-butadiene, 1,3-butadiene, 1-butene, iso-butene, 1-butyne, vinylacetylene and benzene. The temperature was measured using a thermocouple in PtRh (6%)-PtRh (30%) settled inside the enclosure and ranged from 700K close to the burner up to 1850K. In order to model these new results, some improvements have been made to a mechanism previously developed in our laboratory for the reactions of C 3 -C 4 unsaturated hydrocarbons. The main reaction pathways of consumption of allene and propyne and of formation of C 6 aromatic species have been derived from flow rate analyses.Keywords : Premixed laminar flame, methane, allene, propyne, modeling. 3 INTRODUCTIONSoots and polyaromatic hydrocarbons (PAH), which are present in the exhaust gas of diesel engine, represent a high part of the urban pollution. Many efforts have then been focused on reducing the emissions of these compounds. The formation of soot precursors and PAH in combustion involves small unsaturated hydrocarbons, the chemistry of which is still very uncertain. Different reaction pathways have been proposed for the formation and the oxidation of the first aromatic compounds, involving the reactions of C 2 (acetylene), C 3 or C 4 unsaturated species [1][2][3][4][5].As the determinant role of propargyl radicals in forming benzene, the first aromatic ring, is now well accepted, it is important to better understand their reactions. With that purpose, the oxidation of allene (propadiene) and propyne has been already studied in several oxidation conditions: shock tubes [6][7][8], flow reactor [9,10], jet-stirred reactor [7,11] and premixed flames [10,11]. Previous works in flames include studies of the influence of the addition of allene on The purpose of the present paper is to experimentally investigate the structures of two premixed laminar methane flames containing propadiene and propyne, respectively, and to compare them with that of a pure methane flame containing the same mole fractions of methane and oxygen. The use of a methane flame will allow us to have a reactive mixture rich in methyl radicals and to be more representative of combustion mixtures containing larger hydrocarbons than hydrogen or ...

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Section: Table Imentioning

confidence: 99%

mentioning

confidence: 99%

Rich methane premixed laminar flames doped with light unsaturated hydrocarbonsI. Allene and propyne

Gueniche

Glaude

Dayma

et al. 2006

Combustion and Flame

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“…Any reactions on the surface of the junction will increase the temperature, which deviates from the true flame temperature. As described by Kent [62], a catalytically active thermocouple should be insulated from the flame with an inert coating. Secondly, platinum-rhodium alloys may be contaminated at high temperatures by elements, such as hydrogen and carbon, which are naturally found in flames.…”

Section: Coated Thermocouplesmentioning

confidence: 99%

“…However, silica coatings have been reported to react with hydrogen at high temperatures (>1400 K) to form platinum silicide on the thermocouple surface and this silicide causes embrittlement of the thermocouple wire [62]. There are other types of coating materials that could be used, such as a beryllium-yttrium oxide (BeO/Y 2 O 3 ) ceramic coating and an alumina-based ceramic.…”

Section: Thermocouple Coatingsmentioning

confidence: 99%

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Experimental and kinetic modeling study of 1-hexanol combustion in an opposed-flow diffusion flame

Yeung

Thomson

2013

Proceedings of the Combustion Institute

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Optical methods and results of dew point and deposition rate measurements in salt/ash‐containing combustion gases—B₂O₃(I) deposition rates by interference methods and comparisons with theory

Seshadri

Rosner

1984

AIChE Journal

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"hot corrosion" in fossil-fuel-fired furnaces and engines. The inorganic compounds which deposit on heat exchanger surfaces and blades are formed in combustion product gases when the fuel and/or ingested air contains inorganic impurities. An improved understanding of the coupled thermodynamic, kinetic, and transport processes governing the deposition rate of inorganic oxides and salts from hot gases containing these compounds (or their precursors) can suggest more efficient test strategies and control measures. Accordingly, an optical interference method for accurately measuring the growth rate of deposits well before the onset of run-off under laboratory burner conditions has been developed.To demonstrate the technique and provide data suitable for theoretical model development, a deliberately simple chemical system and target geometry are used. BCl3(g) is introduced into a premixed C&-air flat flame at atmospheric pressure. The growth rate of B203(I) on an electrically heated platinum ribbon is then measured interferometrically over a range of fuel/air ratios and seed levels. However, the very existence of Bz03(I) deposition at the present seed levels and surface temperatures (about 1,200-1,300 K) clearly demonstrates the importance of kinetic restrictions on Bz03(1) gasification reactions. Optically measured film growth rates are obtained at film thicknesses small enough to neglect condensate run-off, hence they yield vapor deposition rates directly. These deposition rates are found to be in good agreement with the predictions of a recently developed multicomponent mass-transfer boundary layer (BL) theory, with a constrained equilibrium ((HB02)3 precluded) boundary condition. Remarkably, at a constant value of the BC13 flow rate, the Pt ribbon temperature above which there is no Bz03 condensate (i.e., the so-called dew point) is observed to depend on the fuel/air ratio. Whereas previous equilibrium-based deposition models cannot embrace such phenomena, a semiquantitative argument, based on the nonequilibrium chemistry of B203 precursor formation and (HBO&-formation barriers, explains these potentially significant trends. These encouraging results suggest a more general applicability for the optical methods and chemically frozen (Cfl BL theory described herein, and demonstrate the important role of heterogeneous and homogeneous kinetic barriers in determining dew points and deposition rates in combustion systems. SCOPEWith increased interest in the combustion of minimally processed coal-derived fuels and lower grade residual fuel oils, the problems attending inorganic salt and ash deposition on heat exchanger surfaces, turbine blades, etc. assume greater importance. However, an understanding of the laws governing deposition has been impeded by the lack of precise and rapid methods of deposition rate measurement-with some experiments lasting more than 12 hours each and yet being clouded by the effects of liquid condensate runaff. To provide improved methods and the data to test recently developed multicomponent ...

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A noncatalytic coating for platinum-rhodium thermocouples

Cited by 215 publications

References 2 publications

Rich methane premixed laminar flames doped with light unsaturated hydrocarbonsI. Allene and propyne

Rich methane premixed laminar flames doped with light unsaturated hydrocarbonsI. Allene and propyne

Experimental and kinetic modeling study of 1-hexanol combustion in an opposed-flow diffusion flame

Optical methods and results of dew point and deposition rate measurements in salt/ash‐containing combustion gases—B₂O₃(I) deposition rates by interference methods and comparisons with theory

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A noncatalytic coating for platinum-rhodium thermocouples

Cited by 215 publications

References 2 publications

Rich methane premixed laminar flames doped with light unsaturated hydrocarbonsI. Allene and propyne

Rich methane premixed laminar flames doped with light unsaturated hydrocarbonsI. Allene and propyne

Experimental and kinetic modeling study of 1-hexanol combustion in an opposed-flow diffusion flame

Optical methods and results of dew point and deposition rate measurements in salt/ash‐containing combustion gases—B2O3(I) deposition rates by interference methods and comparisons with theory

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Optical methods and results of dew point and deposition rate measurements in salt/ash‐containing combustion gases—B₂O₃(I) deposition rates by interference methods and comparisons with theory