|
|
Calculation of Standard Thermodynamic Functions of Simple Compounds under Thermal Plasma Conditions
Živný, Oldřich ; Bartlová, Milada (referee) ; Křenek, Petr (referee) ; Krčma, František (advisor)
The substance of present work is to provide standard thermodynamic functions (STF) of small size molecules for the calculation of the composition and thermodynamic properties of low-temperature plasma, and also method for such a calculation applying obtained STF under non-ideal plasma conditions. With a view to further application in modelling the phenomena in thermal plasma the range of pressures is limited to the region from 0.01 bar to 100 bar, and that of temperature to 298.15–50 kK. To obtain STF the method of partition function resulting from statistical mechanics was proposed. State of art in the given scientific area and theoretical basis of the statistical mechanics required for establishing of the proposed method together with discussion of partition function divergence problem have been reviewed. For the calculation of STF of diatomic molecules the method of direct summation has been employed, whereas, as for the larger size molecules, the rigid rotor and harmonic oscillator model have been generally adopted. The spectral data required for the calculations have been taken from literature, or, in selected cases, these have been computed by quantum chemistry ab initio techniques. The resulting STF have been included into already existing database system of thermodynamic properties and those can serve as input data for subsequent thermodynamic calculations. A general method has been worked out for the purpose of the computation of thermodynamic properties and composition of non-ideal homogenous plasma system in thermodynamic equilibrium. The method is based on minimizing total Gibbs energy to compute at constant pressure or Helmholtz energy to compute at constant volume. The computation algorithm was implemented into computer program and subsequently applied to the computation of the composition and thermodynamic properties of SF6 dissociation and ionization products using obtained STF.
|
|
|
Enthalpy Probe Diagnostics of Steam/Argon Plasma Jet
Hlína, Michal ; Hrabovský, Milan
DC plasma torch with argon/water stabilization features extreme properties of the exiting plasma jet. The plasma mass flow rate is very low while the temperature reaches very high values. Plasma properties were measured by enthalpy probe connected to a mass spectrometer. The measurements of enthalpy, temperature, density and dynamic pressure were carried out for three different arc currents and at atmospheric pressure. The dependences of plasma characteristics on arc current were shown.
|
|
|
Calculation of Standard Thermodynamic Functions of Simple Compounds under Thermal Plasma Conditions
Živný, Oldřich ; Bartlová, Milada (referee) ; Křenek, Petr (referee) ; Krčma, František (advisor)
The substance of present work is to provide standard thermodynamic functions (STF) of small size molecules for the calculation of the composition and thermodynamic properties of low-temperature plasma, and also method for such a calculation applying obtained STF under non-ideal plasma conditions. With a view to further application in modelling the phenomena in thermal plasma the range of pressures is limited to the region from 0.01 bar to 100 bar, and that of temperature to 298.15–50 kK. To obtain STF the method of partition function resulting from statistical mechanics was proposed. State of art in the given scientific area and theoretical basis of the statistical mechanics required for establishing of the proposed method together with discussion of partition function divergence problem have been reviewed. For the calculation of STF of diatomic molecules the method of direct summation has been employed, whereas, as for the larger size molecules, the rigid rotor and harmonic oscillator model have been generally adopted. The spectral data required for the calculations have been taken from literature, or, in selected cases, these have been computed by quantum chemistry ab initio techniques. The resulting STF have been included into already existing database system of thermodynamic properties and those can serve as input data for subsequent thermodynamic calculations. A general method has been worked out for the purpose of the computation of thermodynamic properties and composition of non-ideal homogenous plasma system in thermodynamic equilibrium. The method is based on minimizing total Gibbs energy to compute at constant pressure or Helmholtz energy to compute at constant volume. The computation algorithm was implemented into computer program and subsequently applied to the computation of the composition and thermodynamic properties of SF6 dissociation and ionization products using obtained STF.
|
|
|
Electric Probe Diagnostic of Supersonic Thermal Plasma Jet
Hurba, Oleksiy ; Hrabovský, Milan
This paper describes how electric probes can be used as relatively simple and efficient tool for investigation of structure of flow field in thermal plasma jet at the low pressure. A boundary of plasma jet between nozzle of plasma torch and ambient air was investigated by means of array of moving electric probes. Were defined boundaries of the conducting region and their change with pressure change
|
|
|
Thermal plasma gasification of organic waste and biomass
Hrabovský, Milan
The paper presents description of thermal plasma gasification processes. Analysis of energy balances of plasma gasification is presented, kinetics of the gasification process is discussed and relations between particle size, reaction temperature and gasification rate are analyzed. Examples of results of gasification of biomass and pyrolysis oil from used tires are given. Syngas with high heating value, high hydrogen content and low tar contamination is produced by plasma gasification.
|
|
|
Dependence of Thermal Plasma Flow Velocity on Arc Current Determined by Correlation Analysis of Optical Records
Gruber, Jan ; Šonský, Jiří ; Hlína, Jan
Optical radiation of thermal plasma jet was recorded in two parallel cross-sections perpendicular to the jet axis and separated by 3.5 mm. Sufficient sampling rate was a prerequisite to obtain detectable shift between the time-series recorded in closer and farther cross-sections. We have determined time lags between the recorded signals both in the core and boundary regions by correlation analysis and subsequently determined associated velocities of plasma flow. Arc current was gradually increased in respective measurements, gas flow was fixed. Determined flow velocities are in the range 140 m/s - 280 m/s in the jet core and 110 m/s – 220 m/s in the boundary region. This is in agreement with the results obtained for similar plasma torches by other methods in the past. Velocity increases with arc current almost linearly and this dependence and velocity profile in the plasma jet cross-section are presented in this paper.
|
|
|
Prostorové rozložení oscilací v modulovaném proudu plazmatu
Gruber, Jan ; Šonský, Jiří
Electric current in a vertically oriented DC plasma torch was modulated with frequencies varying in the range 15 Hz ? 7.5 kHz. Resulting plasma jet optical radiation was recorded by the high-speed CCD camera. The length of the record and the time resolution were sufficient for the application of the FFT yielding a detailed view of the oscillation phenomena in the plasma flow. Significant oscillations were identified and their distributions in the jet plane examined. In this work we show influence of current modulation on the dominant frequencies of oscillations and their spatial distributions.
|
|
|
Procesy difuze v H2O-Ar plazmovém hořáku
Křenek, Petr
In the hybrid water/argon plasma torch [2] the arc column is composed of argon-stabilized section followed by a section stabilized by water vortex, where argon plasma is mixed with steam evaporated from the stabilizing water wall. At the nozzle outlet the H2O & Ar mixture is supposed. For modelling the mixing processes in the torch composition and diffusion coefficients of steam-argon gas mixtures are needed. In this introductory study the composition and the diffusion coefficients of H2O-Ar plasma were computed in the temperature range 300 K to 50 000 K and pressure 0.1 MPa under the assumption of local thermodynamic equilibrium. The composition was calculated using mass action laws and particle and charge balance equations. Following components were considered: e, H, H+, H-, H2, H2+, H3+, O, O+, O2+, O3+, O4+, O5+, O6+, O-, O2, O2+, O2-, O3, OH, OH+, OH-, HO2, HO2-, H2O, H2O+, H2O2, H3O+, Ar, Ar+, Ar2+, Ar3+.
|
|
|
Zplynování biomasy v termickém plazmatu
Hrabovský, Milan
The gasification of biomass in thermal plasma is discussed and the processes are analyzed. Heat needed for production of syngas was determined from heats of wood combustion and thermodynamic analysis of all processes in the reactor. The kinetics of the process of gasification in plasma flow is analyzed. Experiments with biomass treatment in plasma reactor with hybrid gas/water-stabilized arc are described. Effects of plasma power, material feed rate and flow rate of reaction gases were studied. Syngas with high content of hydrogen and carbon monoxide was produced. No presence of complex hydrocarbons or tar was detected.
|
|
|
Výzkum vlivu množství argony na stabilitu proudu Ar-H-O plazmatu
Chumak, Oleksiy ; Kavka, Tetyana ; Hrabovský, Milan
The paper examines an effect of an argon amount on the thermal plasma jet generated from water/argon mixture in a dc arc plasma torch. In spite of an increase of plasma velocity with an addition of argon a decrease of plasma jet length is observed for bigger argon amount in the plasma. The investigation was based on an analysis of a jet structure based on imaging of the plasma jet by a CCD camera. Statistical processing of plasma jet photographs provided information about a jet shape and its fluctuations space distribution. It was found that an argon amount increase caused significant intensification of the plasma jet fluctuations.
|
guest ::
