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Drying of biomass
Gruber, Jan ; Baláš, Marek (referee) ; Pospíšil, Jiří (advisor)
This thesis deals with the drying of biomass, especially drying of small wood mass. The various drying methods, such as belt drying, fluidized bed drying and drum drying are compared including their advantages and disadvantages. It is suggested basic technological scheme of drying line. The last part of the thesis deals with a calculation of drum dryer of specified performance and economic balance is made.
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Cooperative Form of Financing of Housing Construction
Holý, Petr ; Gruber, Jan (referee) ; Breinek, Pavel (advisor)
The diploma thesis focus on evaluation of co-operative housing construction as one of the way from current credit crisis of financing of housing construction. Specifies and evaluate individual types of financig of new housing construction and apply it on model example. Evaluation is based on analysis of present circumstances of housing construction and trend of mortgage loans. In this evaluation also looks at subvene of new housing construction. At the same time looks on an alternative of non-profit co-operative housing construction.
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Analysis of thermal plasma radiation by Fourier transform, wavelet analysis and phase portraits
Gruber, Jan ; Šonský, Jiří ; Hlína, Jan
Combination of various methods for signal analysis, including Fourier transform, wavelet analysis and time-embeddings provide alternate views on thermal plasma dynamics. We have recorded and analyzed radiation of cutting plasma torch during the whole cathode life-cycle (from the new unworn cathode to the cathode failure). Changes in dynamics during cathode lifecycle lead to regular oscillations expressed in signal spectra, in sudden discontinuities caused by released molten particles detected by wavelet analysis and overall dynamics change expressed in reconstructed phase portraits by time-embeddings. We present all these various views on changing dynamics to illustrate complexity of this dynamics.
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Observation of HF Cathode and ARC Root Inside Cutting Plasma Torch
Šonský, Jiří ; Gruber, Jan
Electric arc and a cathode of a cutting plasma torch was observed through fused silica window in a specially modified nozzle. Sample rate of used high-speed camera was up to 120 kHz, sufficient for detecting high-frequency fluctuations in arc plasma intensity, produced mainly by current ripple. Fluctuations were examined up to 60 kHz by Fast Fourier Transformation (FFT). Increased cathode material loss at start-up and shut-down phase of the plasma torch was observed. At start up phase, large number of small particles are ejected from the cathode. After electric current shuts down, large droplets of molten material are usually detected.
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Influence of Cathode and Nozzle Wear on Distributions of Fluctuations in Cutting Arc
Gruber, Jan ; Šonský, Jiří ; Hlína, Jan
Electric arc produced by cutting plasma torch was observed by CCD camera. Fluctuations in arc plasma intensity were examined in several frequency intervals up to 50 kHz and distributions of their intensities were compared. Plasma torch was operated repeatedly in fixed-time cycles resulting in progressive wear of cathode and nozzle. Changes in distribution of overall arc intensity are rather small, showing compression and expansion zones. However, distributions of fluctuations intensities differ significantly during the nozzle lifecycle, exhibiting formation of double-layer structure and other noticeable changes. The fluctuation distributions are also influenced by frequency interval chosen for the analysis.
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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.
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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.
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Aplikace waveletové analýzy a Fournierovy transformace pro zkoumání časoprostorové dynamiky termického plazmatu
Gruber, Jan
Electric arc plasma generated by the plasma torch (plasmatron) was analyzed. Electric arc and resulting plasma jet were observed from four directions in two parallel planes perpendicular to the jet axis and arc current and voltage were also recorded synchronously. The record lengths and time resolution were sufficient for the application of the FFT yielding a detailed view of the oscillation phenomena in the plasma flow and for comparison with oscillations of voltage and current. Significant oscillations were identified and their planar distributions examined. Wavelet analysis was used for temporal dynamics investigation yielding information about structures dynamics. Different types of structures were identified and their mutual influence is described.
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