Primary Analysis of Effective Permeability of the Flame in Burning Natural Gas

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1 Jornal of etals, aterials and inerals. Vol.7 No. pp rimary Analysis of Effective ermeability of the Flame in Brning Natral Gas Rakoš JAROSAV * and Repasova AGDAENA * Department of Thermal Technology, Faclty of etallrgy, Technical University in Kosice, Slovak Repblic Abstract Received Sept. 8, 007 Accepted Nov. 9, 007 This paper presents a method of analysis of effective permeability of the flame in brning natral gas. In order to condct a complex analysis, it is necessary to determine this parameter as a special case of the process of qasi-plasma natre for the prpose of investigating the options for application of sitable indstrial methods applied in similar cases. We observed the synergy of solenoid parameters of the plasma part of the flame with ceramic materials withot any special additional cstomization of the measrement device. The processed reslts of measrement demonstrate additional reqirements necessary for measrement technology. The method was applied for varios cases of energy of plse signals and for two types of finalized sensors. The method ses a definite marker in observed voltages, which is realized after exceeding the gate voltage in the forward direction of the fast semicondctor valve. Reslts of measrement show that the vales of effective permeability can be measred via this method with acceptable sensitivity. Key words : Effective permeability, roperties of flame, Natral gas Introdction easrement of ionization of the flame which was pblished in () shows that the first operations for describing the natral gas flame can be carried ot also for frther parameters of the qasi-plasma natre of the flame. roperties of arc excitation and high-temperatre applications sch as devices for plasma breakdowns in pblications (-4) or special plasma applications for frnaces (3, 4) are all sbject to Sach s law. (5-7) Extreme cases were examined in the past for devices of type Tokamak bt qasi-plasma non-arc excitation was not examined becase from the energy perspective, aside from generation of heat, it did not have any special application. Sach s law is sable for measrement of the degree of ionization only while sing a modified approximation. Therefore, examination of frther properties of the natral gas flame is important in this context as well. easrement of the flame for temperatres p to 700 C can be accomplished even in laboratory conditions and ths it is possible to predict the properties of the flame almost p to arc excitation. The method was focsed on stating the effective permeability of the natral gas flame in the first approximation. Theoretical Basis By introdcing the flame into a system of solenoids, the flame is manifested as a solenoid parameter and in a favorable case, a feedback manifesting itself in the change of self indction, or respectively, in the change of mtal indction, which characterizes the copling to the secondary system. If we direct the flame in the axis of the solenoid, the inflence derived from the theory of the electromagnetic field, is mainly of magnetic natre, becase the intensity of the electric field generated by self indction processes in the solenoid s axis is zero. As far as the inner side of the solenoid, vales of both intensities are comparable. Therefore, in case of sing a solenoid skeleton made ot of cemaric material with ε r >, for a given range of freqencies, one can expect a synergic effect of the impact on the solenoid. It is advantageos to minimize all parasitic reactions in the measrement parimeter of the excitation generator in sch a way that the properties of the measrement sensor dominate. Then, all relaxation times will depend on the vale of the energy of the implses and reactance properties of the solenoid. The process of marking of the corse of discharging the solenoid s energy takes place after address : Jaroslav.rakos@tke.sk address : agdalena.repasova@tke.sk

Slovak Repblic Abstract Received Sept. 8, 007 Accepted Nov. 9, 007 This paper presents a method of analysis of effective permeability of the flame in brning natral gas.

2 64 JAROSAV, R. and AGDAENA, R. completion of the relaxation process by physically reversing the direction of the crrent flowing throgh the solenoid via blocking the crrent on the edge of non-linearity of the fast semicondctor diode. The location of the marker in the corse of the voltage when sing a long enogh discharging period allows finding the change of indction even at small relative changes. Chosen ethods of rocessing To condct the measrement, a circit as per Figre was sed. At zero inpt, the generator s internal resistance is infinitely large. eriod of 47μs was sed, with plse width of approx..5 μs. The generator had these properties at the resistance load. In Figre, vales R of the resistor were sed sch that a voltage limitation wold not occr and so that limitation wold occr for the prpose of increasing the energy of the plses. Where (t) is the corse of the voltage on the secondary solenoid. From the defining relations for circit elements of a system with mtal feedback indctance, the following eqation is obtained: ( t) d ( t) ( t) di t = = becase dt dt () d ( t) i = (3) R dt For general corse of voltages (t) and (t), we then obtain ( t) = = [ - ] (4) p If we se Nagaoka s coefficients for describing indctances and sing α a α, at n a n of coil trns we will se an alternative expression of the vale of indctance μ [H] and = μ α n [H] (5) = α n G R S D i B A OSC where μ is absolte coil-permeability. Indctances are chosen so that the relaxation process takes place in the gaps between implses. Typical corse of the voltage and crrent on the primary solenoid is depicted in Figre Withot the presence of a flame, expression of the secondary voltage (t) is identical to that of (t). (t) i (t) Figre. easrement circit A For crrent i (t) within the circit, the following holds: i (t) R [ U ] i = [A] () t imp (t) t where (t) and i (t) are voltage and crrent of the primary solenoid ( ) a R is the limiting resistor in the perimeter of the generator as per Figre. The following relation holds for ratio p of the transformation system according to Figre p = R = d dt [ - ] () T Figre. Relaxation process After disconnecting the semicondctor valve S, voltage on the indctance decreases into negative vales, while the direction of the crrent with indctance does not change even after disconnecting the generator. The discharging phase dring the time period T is done via diode D and ends with the first marker of relaxation on the non-

diode. The location of the marker in the corse of the voltage when sing a long enogh discharging period allows finding the change of indction even at small relative changes.

3 rimary Analysis of Effective ermeability of the Flame in Brning Natral Gas 65 linear part of the diode s transition. For small differences in vale T before and after application of the flame, it is possible to se the relations for the ratio between indctance with the flame and withot the flame in the explanation of the response to the signal with a fnctionally defined corse or for harmonic signal. Then, it can be claimed that: R d = μ dt = R d dt π ω = π ω T T [-] (6) From Table, it is evident that in case of self-spporting air-cored coils, the vales of the effective permeability of the flame is μ within an interval <.03 ;.035 > [ - ] and in case of a sensor with a ceramic tbe, is μ within an interval <.08 ;.50 > [ - ], depending on the energy of the plse. The reslt with the ceramic tbe illstrates synergy of ceramics. Figre 3 shows an example of a typical corse from an oscilloscope recording obtained when sing a generator constrcted for a laboratory experiment. where μ is the soght effective relative permeability of the flame. In relation (6), we have set for the aplace transform in case of a harmonic corse p = jω and sbstitted relations o (5). If we denote the amplitdes of the voltage plses A a A for (t) and (t), then sing expression (4), it is possible, withot any loss to the generality of the relation, to state: p A A = μ [-] (7) A A Figre 3. Sample of the measred process where and are mtal feedback indctance and this vale withot flame, A and A are secondary voltage amplitde with flame on the coil and, A and A are secondary and primary amplitde withot flame. Evalating Reslts of the easrement Reslts of the measrements obtained sing relations o (7) are smmarized in Table. Reslts were obtained based on processing oscilloscopic data (Tektronix TDS 0). Table. ROBE IUSES T [μs] T [μs] / [-] μ [-] SATURATED CERAICS NOT SATURATED SATURATED AIR-COI NOT SATURATED Conclsion Reslts of the effective measrement point ot the fact that for frther analysis, it will be necessary to se an oscilloscope with a significantly higher freqency range (p to 0 GHz). easred vales of the effective magnetic permeability of the flame are measrable with satisfactory sensitivity and favorable. Synergy of the ceramics was also confirmed for solenoid parameters of the measrement sensor. References. Rakos, J. and Repasova, Ionisation and thermal field of diffsion flame of natral gas. Acta echanica Slovaca. 3-A. 8 : Holbecky, Constrction of plasma offen for gasification of waste. Acta echanica Slovaca. 3-A. 8 :

the response to the signal with a fnctionally defined corse or for harmonic signal.

4 66 JAROSAV, R. and AGDAENA, R. 3. olcan,., Klenovcanova, A. and Imris, I Engineering of plasma offen for casting and gasification of waste. In: VII. International conference: Combstion and enviroment. 003, SjF VSB TU 7-8 th Jne 003, Ostrava : olcan, Comparison of the experimental and theoretical reslts after gasification of waste in plasma frnace. Acta echanica Slovaca. 3-A. 8 : Novak,. 99. Electrical frnaces and warmers. Kosice. 6. Novak,. and Kolesar, J Elektrothermal technicqe. Alfa : Bratislava. 7. Rada, J Electrothermal techniqe. SNT/AFA, rage.

Comparison of the experimental and theoretical reslts after gasification of waste in plasma frnace. Acta echanica Slovaca. 3-A. 8 : 337-346. 5. Novak,.

5 rimary Analysis of Effective ermeability of the Flame in Brning Natral Gas 67

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