| The goal of this research project is to attain a better understanding of the fluid mechanics associated with the high temperature jet of a thermal plasma torch. The analysis of a plasma, which has the ability to vaporize anything placed inside it without proper cooling, presents a unique research challenge. Several types of non-intrusive diagnostic techniques has been used to examine the jet from different perspectives.; To actually map out the mean gas velocities and turbulence intensities throughout the jet, laser Doppler anemometry has been employed. The plasma gas and entrained air has been seeded separately in order to conditionally sample the two fluids and attain information about the gas mixing process. Both radial and axial turbulence levels have been measured in order to analyze the non-isotropic nature of the jet.; A parabolic numerical code has been modified and compared with the obtained experimental results. Emphasis has been placed on how well the isotropic K-{dollar}varepsilon{dollar} turbulence model simulates the turbulence of the experimental data, which at this point is thought to be highly non-isotropic.; A new diagnostic technique for plasma torches, which involves the spectral analysis of voltage, optical (temperature), and acoustical (pressure) fluctuations, has been implemented. The acoustical spectrum can provide information about the existence of coherent structures in the flow while the cross correlation of the acoustical signal with the voltage fluctuations can tell one to what extent perturbations of the internal arc affect the external flow. Since temperature is a scalar that is dependent on the flow field, observing temperature fluctuations can likewise help one to understand the mechanics of the flow.; Flow visualization of the plasma jet using a high speed video camera has also been undertaken in order to better understand the entrainment process. |
