international jurnal of thermodinamika

JURNAL INTERNASIONAL
THERMODINAMIKA
TUGAS KIMIA








Disusun oleh :
AHMAD JAZULI
10 09 1 0002
PETERNAKAN










FAKULTAS PERTANIAN
UNIVERSITAS MAJALENGKA
2010 - 2011

1. JURNAL INTERNASIONAL

*Corresponding Author Vol. 13 (No. 4) / 119
International Journal of Thermodynamics Vol. 13 (No. 4), pp. 119-125, 2010
ISSN 1301-9724 www.icatweb.org/ijot
A Thermodynamic Model for Argon Plasma Kernel Formation
Kian Eisazadeh-Far1, Farzan Parsinejad2, Hameed Metghalchi1*
James C. Keck3
1Northeastern University, Mechanical and Industrial engineering Department, Boston, MA 02115
2Chevron Oronite Company LLC, Richmond, CA 94801
3Massachusetts Institute of Technology, Cambridge, MA 02139
metghalchi@coe.neu.edu

Abstract
Plasma kernel formation of argon is studied experimentally and theoretically. The experiments have beenperformed in a constant volume cylindrical vessel located in a shadowgraph system. The experiments have beendone at constant pressure. The energy of plasma is supplied by an ignition system using two electrodes located in the vessel. The experiments have been done with two different spark energies to study the effect of input energy on kernel growth and its properties. A thermodynamic model employing mass and energy balances was developed to predict the experimental data. The agreement between the experiments and model prediction is very good. The effect of various parameters such as initial temperature, initial radius of the kernel, and the radiation loss have been investigated and it has been concluded that the initial condition is very important on the formation and expansion of the kernel.
Keywords: Argon plasma; kernel formation; thermodynamic model; ionization.












1. Introduction
Since plasma kernel formation is the beginning of flamepropagation in many systems, understanding this process isvery important. In plasma kernel formation of a noncombustiblegas by an external energy source like a spark,there are two important processes: The first part which is very short (microseconds) is the formation of a spark channel between two electrodes. The second part which is longer (milliseconds) is the conversion of electrical energy to thermal energy and consequently ionization and plasma kernel expansion. In the case of the existence of a combustible gas, the third stage will be evolution of the plasma kernel to a self sustained flame. There are numerous theoretical and experimental studies on the first and third stages (Bradley et al., 2004; Kravchik & Sher, 1994; Lee et al. ,2000; Maly, 1981; Mantel, 1992; Pischinger & Heywood, 1991; Sher & Keck, 1986; Sher et al., 1992; Yossefi et al., 1993; Ziegler et al, 1985). Maly and Vogel (1979) in a theoretical and experimental study determined that the most important part of spark discharge is the breakdown process. They mentioned that the other processes including arc and glow discharge are less important because their electrical energy is dissipated into the electrodes. Sher et al (1992) did a fundamental study on spark formation in air and proposed a model to calculate the spark kernel temperature after breakdown. They concluded that the initial spark kernel is a very high temperature region, but the temperature drops rapidly due to energy dissipation. They stated that beyond a specific limit of temperature, the energy of spark affects the flame kernel size, and not the temperature. They concluded that the spark kernel is grown in two steps. The first, shorter stage consists of a pressure wave emission. This is followed by a longer period, in which constant pressure ionization starts. Chen and Ju (2007) studied the evolution of the ignition kernel to a flame ball and they concluded that radiation plays a very important role in transition of initial flame kernel to the actual self-sustained flame. Most of the cited studies focus on the first and third stage of ignition and a semi-quantitative understanding of these stages has been achieved. In this paper we will focus on the second part of ignition which is the formation and expansion of the plasma kernel by adding electrical energy. We will study the plasma kernel of an inert gas, argon, to avoid the complexities of a reacting gas mixture and multicomponent species.










2. Experimental System
Figure 1 shows the sketch of the experimental system. The experimental system includes a cylindrical vessel. It is fitted with two extended spark plug electrodes which provide a central point ignition source for the chamber. The thickness of electrode (de) is 0.381 mm. A shadowgraph system is used with the cylindrical system to take images of kernel growth. A CMOS camera with the capability of taking pictures up to 40,000 frames per second has been
used in these experiments. Additional information about the experimental facility can be found in previous publications (Eisazadeh-Far, Moghaddas, Al-Mulki, & Metghalchi, 2010; Eisazadeh-Far, Parsinejad, & Metghalchi, 2010; Eisazadeh-Far, Parsinejad, Metghalchi, & Keck, 2010; Parsinejad, Arcari, & Metghalchi, 2006; Parsinejad, Keck, & Metghalchi, 2007; Rahim, Eisazadeh-Far, Parsinejad, Andrews, & Metghalchi, 2008).

120 / Vol. 13 (No. 4) Int. Centre for Applied Thermodynamics (ICAT)
Figure 1: The experimental set up of the system.
Ignition system: An important detail of the ignition system is the 5 select-switch, which allows the energy stored in the capacitors to be varied. The capacitors storing this energy discharge to a transformer and therefore to spark plugs. Voltage and current across the spark plug gap during the electrical discharge have been measured to calculate the discharge energy. This has been achieved by setting up a detection circuit employing two resistors. The resistors are placed in parallel to the spark plugs to allow only a very small but measurable portion of the current to flow through the detection circuit. These small portions were then sampled by an oscilloscope. In this system the voltage difference across one of the resistors in the detection circuit
is 1/201 of the voltage across the spark plugs. Another similar method was used to calculate the current across the spark plug, which in this case is exactly equal to the amperage flowing through the parallel circuit.













3. Experimental Results
3.1. Discharge energy (DE): Using a voltage divider
circuit, the voltage and current across the gap were measured. Figure 2 shows the experimentally determined voltages and currents across the spark plug gap for each voltage setting on the ignition system in argon. The spike, approximately at 5-10 microseconds in duration, shows the breakdown stage which is the beginning of spark discharge. In this stage the gap is bridged by the avalanche of electrons flowing from cathode to anode. Figure 3 shows the discharged power calculated by the product of the measured values of current (I) and voltage (V) for two different stored energies in the ignition system. Discharged energy, DE, can be calculated as DE=∫VI dt. It
should be noted that discharged energy is different from the electrical energy converted to the thermal energy in the gas. A portion of the discharged energy is dissipated by conduction into the electrodes.

3.2. Image capturing: Figures 4 shows the snapshot of an argon plasma kernel. It can be seen that the boundary layer surrounding the plasma kernel is very thin. Figure 5 shows the radii of a kernel at two different spark energies. It can be seen that spark energy has a remarkable effect on the size of the kernel.
Time (ms)
Voltage (V)
0 0.5 1 1.5 2 2.5
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
DE = 46 mJ
DE = 26 mJ
Breakdown mode: 0.25 mJ
Time (ms)
current (A)
0 0.5 1 1.5 2 2.5
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
DE = 46 mJ
DE = 26 mJ
Figure 2: Voltage and current versus time for low and high discharge energies.
Int. J. of Thermodynamics (IJoT) Vol. 13 (No. 4) / 121
Time (ms) Power (W)
0 1 2 3
0
10
20
30
40
50
DE = 26 mJ
DE = 46 mJ
Figure 3: Spark discharge power of argon at low and high discharge energies. Figure 4: Argon plasma kernel, P = 1 atm, DE = 46 mJ.
Time (ms) r (mm)
0 0.5 1 1.5
0
0.5
1
1.5
argon, DE = 46 mJ
argon, DE = 26 mJ
Figure 5: Argon radii at two different spark discharge energies (DE = 26 and 46 mJ).

4. Thermodynamic Model
In this section the thermodynamic model for predicting the growth of argon plasma kernel will be described.Figure 6 shows the schematic diagram of the control mass and energy transformation across the boundary.
Figure 6: the sketch of the model.
The major assumptions are as following:
1- It is assumed that the plasma kernel is spherical.
2- All calculations start after the breakdown stage. It is assumed that the shock wave is emitted and pressure is constant.
3- Since the relaxation time scale of different energy modes (translational, rotational, vibrational, electronic) are too small (O~10-9 s), all species are in local thermodynamic equilibrium (Maly, 1981; Maly & Vogel, 1979; Sher et al, 1992; Sher & Keck, 1986).
4- There is no mass transport processes involved in the model. It is assumed that the plasma kernel is a constant-mass system and expands in a constant pressure process.
5- Energy losses are due to radiation, cathode-anode fall dissipations, and conduction through the thermal boundary layer to the electrodes. The governing equations are, equation of state, mass conservation, and energy balance. The equation of state is given as
pV =nRT (1)
where p is the pressure, V is the volume of the kernel, n is number of moles, R is the universal gas constant, and T is the temperature. Total number of moles is determined by:
Σ=
=
z
i
n ni
1
(2)
where z is the number of species. The number of elemental atom number is then given by
0
z
EAr Arε
ε =
= Σ ε = 0, 1, 2, 3,…z (3)
In this equation, ε is the charge of ions.




122 / Vol. 13 (No. 4) Int. Centre for Applied Thermodynamics (ICAT)
The equation for energy balance is given by:
ncv (T − T0 ) = DE − p(V − V0 ) −Qrad −Qcond (4)
Eq. (4) can be rewritten as:
0 p ( )
rad cond
c
p V V DE Q Q
R
− = − − (5)
where T is the temperature, cv and cp are the heat capacities, 0 V is the initial volume of the kernel, Qrad is the radiation energy loss, and Qcond is the conduction energy loss to the electrodes through the thermal boundary layer. It should be noted that for each step the increment of temperature is chosen to be too small throughout the solution. This is the reason for integration of equations (4) and (5) versus temperature and appearance of constant specific heat capacities. It means that at each step it is assumed that the specific heat capacity is constant. In Eqn. (5):
0
0
( ) ( ) b t t
b fall b colbca
DE IVdt IV dt IV dt
IVdt Q SE
= + +
= + +
∫ ∫ ∫
∫
(6)
In this equation, t is time, ∫b IVdt
0
is the breakdown energy, ca Q is the cathode-anode fall dissipation by conduction into the electrodes, and SE is the net spark energy converted to thermal energy in the plasma. Conduction to electrodes in the thermal boundary layer is:
0 2 T e ( )
cond
Q k A T T dt
αt
−
= ∫ (7)
where kT is the thermal conductivity of the gas; Ae is the contact area of electrodes with the gas, T0 is the temperature of the electrode, and α is the thermal diffusivity of argon. Experimental data of Wilbers, Beulens, & Schram (2002), which have been collected at high temperatures under optically thin conditions, have been used to model radiation losses.

4.1. Thermodynamic properties: The thermodynamic properties of argon have been calculated by statistical thermodynamic methods. These parameters include cp and the enthalpy of the mixture. For argon the species are Ar, Ar+, Ar2+, Ar3+, Ar4+, Ar5+, Ar6+and e (electron). Additional information can be found in (Eisazadeh-Far, Metghalchi, & Keck, 2010). In the theoretical model, the values of specific heat are needed at very high temperatures of 300 – 100,000 K. Figure 7 shows the heat capacity of argon in this temperature range. Figure 8 shows the normalized number of species of argon. The results of Eq. (2) have been normalized by the sum of the elemental atom numbers defined in Eq. (3). It can be seen that number of particles increase as the temperature of the gas increases.
Temperature (K)
cp (kJ/kg.K)
20000 40000 60000 80000 100000
0
5
10
15
20
25
30
Figure 7: Specific heat capacity of argon at high temperatures.
T (K)
Normalized particle numbers
25000 50000 75000 100000
0
3
6
9
12
15
Figure 8: Particle numbers of argon normalized by elemental atom numbers.


5. Results and Discussion
Eqs. (1)–(7) have been solved to determine the radii and temperature of plasma kernel for different initial temperatures and volumes of the kernel and input electrical energies. The values of initial radius and initial temperature depend on the discharged energy, pressure, gas type and energy losses during the breakdown. The effect of initial parameters on the size and temperature of the kernel is investigated in the following Section.
5.1. Initial radius: Figures 9 and 10 demonstrate the effect of the initial radius of the plasma kernel on growth and temperature of the plasma kernel. It can be seen that the size of the plasma kernel is not dependent on the initial radius but the temperature of the kernel is very sensitive to the initial radius.
5.2. Initial temperature: Figures 11 and 12 show the effect of initial temperature on plasma kernel growth and its temperature. It is shown that initial temperature does not have a major effect on the size of the kernel but it can change the temperature of the hot plasma strikingly. Initial temperature depends on breakdown energy and breakdown
Int. J. of Thermodynamics (IJoT) Vol. 13 (No. 4) / 123
duration. The range of initial temperature for plasma is 5,000-7,000 K.
5.3. Best fit to the model: Figure 13 shows the results of the calculations and the comparison with the experimental data. There are two curves in each figure which are the calculations with and without radiation. As can be seen, radiation is a major source of energy loss. The radiation becomes important especially when the temperature is high. It can also be concluded that the decrease of argon plasma radii is due to radiation energy losses. At higher discharged energies not only the temperature of the kernel but also the volume of kernel increases and it causes higher radiation energy losses.
Table 1 shows the summary of fractional energy terms. It can be seen that a large part of energy is dissipated by cathode-anode fall conduction dissipations. Clearly, the amount of radiation loss depends on the value of discharged energy. This percentage is strongly a function of the current and the temperature of the arc (Hermann & Schade, 1970).
Table 2 shows that approximately 3-5 % of discharged energy is converted to thermal energy. The results presented in Table 1 are in good agreement with experimental measurements of Teets & Sell (1988).
Time (ms)
r (mm)
0 0.5 1 1.5 2 2.5 3
0
0.5
1
1.5
2
2.5
ri = 0.32 mm
ri = 0.34 mm
ri = 0.38 mm
Figure 9: The effect of initial radius on kernel size of
argon, Ti = 7000 K, DE = 46 mJ, Qrad = 0.
Time (ms)
Temperature (K)
0 0.5 1 1.5 2 2.5 3
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
100000
110000
ri = 0.32 mm
ri = 0.34 mm
ri = 0.38 mm
Figure 10: The effect of initial radius on kernel temperature
of argon, Ti = 7000 K, DE = 46 mJ, Qrad = 0.
Time (ms)
r (mm)
0 0 0.5 1 1.5 2 2.5 3
0.5
1
1.5
2
2.5
Ti = 5000 K
Ti = 6000 K
Ti = 7000 K
Figure 11: The effect of initial temperature on argon kernel
growth, Ti = 7000 K, ri = 0.34 mm, DE = 46 mJ, Qrad = 0.
Time (ms)
Temperature (K)
0 0.5 1 1.5 2 2.5 3
0
20000
40000
60000
80000
100000
120000
Ti = 5000 K
Ti = 6000 K
Ti = 7000 K
Figure 12: The effect of initial temperature on argon kernel
temperature, Ti = 7000 K, ri = 0.34 mm, DE = 46 mJ, Qrad
= 0.

124 / Vol. 13 (No. 4) Int. Centre for Applied Thermodynamics (ICAT)
Time (ms)
r (mm)
0 0.5 1 1.5 2 2.5 3
0
0.5
1
1.5
2
2.5
3
with radiation
zero radiation
Experiment
DE = 26 mJ
Ti = 5000 K
ri = 0.25 mm
Qrad = 6% ofDE
de = 0.381 mm
(a)
Time (ms)
r (mm)
0 0.5 1 1.5 2 2.5 3
0
0.5
1
1.5
2
2.5
3
with radiation
zero radiation
Experiment
DE = 46 mJ
Ti = 7000 K
ri = 0.34 mm
Qrad = 27% of DE
de = 0.381 mm
(b) Figure 13: Argon plasma radii and comparison with experiments: a) DE = 26 mJ; b) DE = 46 mJ.


















6. Conclusions
Formation of an argon plasma kernel has been studied experimentally and theoretically. The experiments were performed at constant pressure in a shadowgraph system. They have been performed with two different discharged energies to investigate the effect of spark energy. Radii of the argon plasma kernel were measured optically. A thermodynamic model was developed to predict the expansion of the kernel under initial conditions of experiments. The major conclusions are: 1- It can be assumed that the plasma kernel expands in a constant pressure and constant mass condition.
2- Total number of moles increases as the temperature of the gas increases and it is the main source of kernel expansion at constant pressure and constant mass condition.
3- Increase of heat capacity of the plasma gases at high temperatures plays a very important role on the temperature and growth mechanism of the kernel.
4- Initial volume and initial temperature of the kernel have a great effect on the temperature of the kernel. However, they do not have a major effect on the size of the kernel.
5- Cathode-anode falls are the major source of energy losses. Radiation is another source of energy losses which becomes more important at higher discharge energies due to higher kernel temperatures. A small portion of discharged energy is converted to thermal energy which depends on the discharged energy amount. This portion is less than 10%.
6- This model can be extended to combustible mixtures toinvestigate the spark ignition and flame formation mechanism of engines and other combustors.
Acknowledgment
This work has been partially supported by Office of Naval Research (ONR), grant number N00010-09-1-0479, under technical monitoring of Dr. Gabriel Roy.















References
Bradley, D., Sheppard, C. G. W., Suardjaja, I. M., Woolley, R. 2004. Fundamentals of high-energy spark ignition with lasers, Combustion and Flame, 138(1-2),55-77.
Chen, Z., and Ju., Y. 2007. Theoretical analysis of the evolution from ignition kernel to flame ball and planar flame. Combustion Theory and Modeling, 11(3), 427 – 453.
Eisazadeh-Far, K., Metghalchi, H., and Keck, J. C. 2010. Thermodynamic Properties of Ionized Gases at High Temperatures. Submitted to Journal of Energy Resources and Technology.
Eisazadeh-Far, K., Moghaddas, A., Al-Mulki, J., Metghalchi, H. 2010. Laminar Burning Speeds of Ethanol/Air/Diluent Mixtures. Proc. Combust. Inst. (2010), doi:10.1016/j.proci.2010.05.105.
Eisazadeh-Far, K., Parsinejad, F., and Metghalchi, H. 2010. Flame structure and laminar burning speeds of JP-8/air premixed mixtures at high temperatures and pressures. Fuel, 89, 1041–1049.
Eisazadeh-Far, K., Parsinejad, F., Metghalchi, H., Keck. J. C. 2010. On Flame Kernel Formation and Propagation in Premixed Gases, Combustion and Flame, 157, 2211–2221. Table 1: Summary of fractional energy terms Argon (DE = 26 mJ) Argon (DE = 46 mJ) Cathode-anode fall losses 88.80% 68.20% Thermal boundary layer conduction 0.20% 0.30% Radiation losses 6% 27% Converted to thermal energy (present study) 5% 3.50% Converted to thermal energy (Teets and Sell (1988)) 7%
Int. J. of Thermodynamics (IJoT) Vol. 13 (No. 4) / 125
Hermann, W., Schade, E. 1970. Transportfunktionen von Stickstoff bis 26000 K. A. Physik. 233, 333-350.
Kravchik, T., Sher, E. 1994. Numerical modeling of spark ignition and flame initiation in a quiescent methane-air mixture. Combustion and Flame, 99(3-4), 635-643.
Lee, Y. G., Grimes, D. A., Boehler, J. T., Sparrow, J., Flavin, C. 2000. A Study of the Effects of Spark Plug Electrode Design on 4-Cycle Spark-Ignition Engine Performance, SAE Paper 2000-01-1210.
Maly, R., Vogel, M. 1979. Initiation and propagation of flame fronts in lean CH4-air mixtures by the three modes of the ignition spark. Symposium (International) on Combustion. 17(1), 821-831.
Maly, R., 1981. Ignition model for spark discharges and the early phase of flame front growth. Symposium (International) on Combustion. 18(1), 1747-1754. Mantel, T. SAE Paper 920587.
Parsinejad, F., Arcari, C., Metghalchi, H. 2006. Flame Structure and Burning Speed of JP-10 Air Mixtures. Combustion Science and Technology. 178, 975-1000. Parsinejad, F., Keck, J. C., and Metghalchi, H. 2007. On the location of flame edge in Shadowgraph pictures of spherical flames: a theoretical and experimental study. Experiments in Fluids. 43(6), 887-894.
Pischinger, S., Heywood, J. B. 1991. A model for flame kernel development in a spark ignition engine. Symposium (International) on Combustion. 23(1), 1033-1040.
Rahim, F., Eisazadeh-Far, K., Parsinejad, F., Andrews, R. J., Metghalchi, H. 2008. A Thermodynamic Model toCalculate Burning Speed of Methane-Air- Diluent Mixtures, International Journal of Thermodynamics. 11, 151-161. Sher, E., Ben-Ya'Ish, J., Kravchik, T. 1992. On the birth of spark channels, Combustion and Flame, 89(2), 214-220.
Sher, E., Keck, J. C. 1986. Spark ignition of combustible gas mixtures. Combustion and Flame. 66(1), 17-25.
Teets, R. E., Sell, J. A. 1988. Calorimetry of Ignition Sparks, SAE Paper 880204.
Wilbers, A. T. M., Beulens, J. J., Schram, D. C. 2002. Radiative energy loss in a two-temperature argon plasma, Journal of Quantitative Spectroscopy and Radiative Transfer, 46(5), 385-392.
Yossefi, D., Belmont, R., Thurley, R., Thomas, J. C.,
Hacohen, J. 1993. A Coupled Experimental-Theoretical
Model of Flame Kernel Development in a Spark Ignition
Engine. SAE paper 932716.
Ziegler, G. F. W., Wagner E. P., Maly, R. 1985. Ignition of lean methane-air mixtures by high pressure glow and ARC discharges, Symposium (International) on Combustion, 20(1), 1817-1824.
















2. RESUME
Maly dan Vogel (1979) dalam studi teoritis dan eksperimental menetapkan bahwa bagian paling penting dari percikan debit adalah proses kerusakan. Mereka menyebutkan bahwa selain proses itu termasuk debit busur dan cahaya kurang penting karena energi listrik mereka hilang ke elektroda. Sher et al (1992) melakukan penelitian mendasar pada percikan formasi di udara dan mengusulkan model untuk menghitung percikan suhu kernel setelah rusak. dia menyimpulkan bahwa percikan awal kernel suhu wilayah yang sangat tinggi, tapi suhu turun dengan cepat karena energi disipasi. Mereka menyatakan bahwa di luar batas tertentu suhu, energi spark mempengaruhi kernel api ukuran, dan tidak suhu. Mereka menyimpulkan bahwa percikan kernel ditanam dalam dua langkah. Yang, pertama lebih pendek terdiri dari emisi gelombang tekanan. Hal ini diikuti oleh waktu yang lebih lama, di mana ionisasi tekanan konstan dimulai.
Chen dan Ju (2007) mempelajari evolusi mesin kernel untuk bola api dan mereka menyimpulkan bahwa radiasi memainkan peran yang sangat penting dalam transisi api awal kernel ke api berkelanjutan yang sebenarnya. Sebagian besar penelitian yang dikutip fokus pada pertama dan ketiga pengapian dan tahap pemahaman semi-kuantitatif tahap ini telah tercapai. Dalam tulisan ini kita akan fokus pada bagian kedua dari pengapian yang pembentukan dan perluasan kernel plasma dengan menambahkan energi listrik. Kami akan mempelajari inti plasma dari argon, gas inert, untuk menghindari kompleksitas dari campuran gas yang bereaksi dan multikomponen spesies.
Sistem pengapian: Sebuah detail penting dari sistem pengapian adalah 5 pilih-switch, yang memungkinkan energi yang tersimpan dalam kapasitor yang akan divariasikan. Kapasitor menyimpan energi ini dibuang ke transformator dan digunakan untuk busi. Tegangan dan arus di celah busi selama debit listrik telah diukur untuk menghitung pembuangan energi. Hal ini telah dicapai dengan mendirikan rangkaian deteksi mempekerjakan dua resistor. Resistor adalah ditempatkan di sejajar dengan busi untuk hanya mengijinkan yang sangat sebagian kecil tetapi dapat diukur dari arus mengalir melalui rangkaian deteksi. Porsi kecil ini kemudian sampel oleh osiloskop. Dalam sistem ini tegangan perbedaan di salah satu resistor dalam rangkaian deteksi adalah 1 / 201 dari tegangan di busi. metode Lain yang sama digunakan untuk menghitung arus di busi, yang dalam hal ini persis sama dengan ampere mengalir melalui rangkaian paralel.
Pada bagian ini model termodinamika untuk memprediksi pertumbuhan kernel argon plasma akan dijelaskan.
Asumsi utama adalah sebagai berikut:
1 - Hal ini diasumsikan bahwa kernel plasma bola.
2 - Semua perhitungan dimulai setelah tahap kerusakan. Hal ini diasumsikan bahwa gelombang kejut yang dipancarkan dan tekanan konstan.
3 - Sejak skala relaksasi saat energi yang berbeda mode (translasi, rotasi, getaran, elektronik) terlalu kecil (O ~ 10-9 s), semua spesies yang di lokal termodinamika ekuilibrium (Maly, 1981; Maly & Vogel, 1979; Sher et al, 1992; Sher & Keck, 1986).
4 - Tidak ada transportasi massal proses yang terlibat dalam model. Diasumsikan bahwa kernel plasma adalah sistem massa konstan dan proses tekanan berkembang secara konstan.
5 - kerugian Energi akibat radiasi, jatuh anoda katoda dissipations, dan konduksi termal melalui
batas layer ke elektroda. Persamaan pengatur tersebut, persamaan keadaan, massa konservasi, dan keseimbangan energi. Persamaananya adalah pV = nRT (1) di mana p adalah tekanan, V adalah volume kernel, n jumlah mol, R adalah konstanta gas universal, dan T adalah suhu.
Sifat argon telah dihitung dengan statistik metode termodinamika. Parameter ini meliputi cp dan
entalpi campuran. Untuk argon spesies adalah Ar, Ar +, Ar2 +, Ar3 +, Ar4 +, Ar5 +, Ar6 + dan e (elektron). Tambahan informasi dapat ditemukan dalam (Eisazadeh-Jauh, Metghalchi, & Keck, 2010). Dalam model teoritis, nilai-nilai tertentu panas yang sangat dibutuhkan di suhu tinggi 300 - 100.000 K.
Seperti dapat dilihat, radiasi merupakan sumber utama kehilangan energi. radiasi menjadi penting terutama ketika suhu tinggi. Hal ini juga dapat disimpulkan bahwa penurunan plasma argon jari-jari adalah karena kehilangan energi radiasi. Pada energi tinggi habis energi tidak hanya di pengaruhi oleh suhu kernel tetapi juga volume meningkat kernel dan hal itu menyebabkan kerugian energi radiasi yang lebih tinggi. jumlah kerugian radiasi tergantung pada nilai dibuang energi. Persentase ini sangat fungsi dari arus dan suhu busur (Hermann & Schade, 1970).











3. KESIMPULAN
Dalam pembentukan kernel plasma dari noncombustible gas dengan sumber energi eksternal seperti percikan, ada dua proses penting: Bagian pertama yang sangat singkat (mikrodetik) adalah pembentukan percikan saluran antara dua elektroda. Bagian kedua (milidetik) adalah konversi energi listrik untuk ionisasi energi panas dan akibatnya plasma kernel ekspansi. Dalam kasus adanya gas yang mudah terbakar, tahap ketiga akan evolusi plasma kernel untuk api berkelanjutan sendiri.
Penelitian tentang Pembentukan kernel argon plasma telah dipelajari eksperimen dan teoritis. Percobaan dilakukan pada tekanan konstan dalam suatu sistem shadowgraph.. Jari-jari dari kernel argon plasma diukur optik. Model termodinamika dikembangkan untuk memprediksi perluasan kernel dalam kondisi awal percobaan. Kesimpulan utama adalah:
1 - Hal ini dapat diasumsikan bahwa kernel plasma berkembang di tekanan konstan dan kondisi massa konstan.
2 - Jumlah mol meningkat sebagai peningkat suhu gas dan itu adalah sumber utama kernel ekspansi pada tekanan konstan dan kondisi massa konstan.
3 - Meningkatkan kapasitas panas dari gas plasma pada tingkat tinggi suhu memainkan peran yang sangat penting pada suhu dan pertumbuhan mekanisme kernel.
4 - volume awal dan suhu awal kernel telah menimbulkan efek yang besar pada suhu kernel. Namun, tidak memiliki pengaruh besar pada ukuran kernel.
5 - katoda-anoda jatuh adalah sumber utama energi kerugian. Radiasi merupakan sumber kehilangan energi yang menjadi lebih penting pada debit tinggi karena suhu kernel yang lebih tinggi energi. porsi energi dibuang dikonversi menjadi panas energi yang tergantung pada energi habis jumlah. Bagian ini kurang dari 10%.
6 - Model ini dapat diperluas untuk campuran mudah terbakar ke menyelidiki pembentukan pengapian dan percikan api mekanisme mesin dan pembakar lainnya.
7- energi dibuang berbeda dari energi listrik diubah menjadi energi panas dalam gas. Sebagian dari energi dibuang didisipasikan oleh konduksi ke elektroda.