No abstract

A three-dimensional computational fluid dynamics (CFD) model of flow through cyclones was developed to obtain the pressure drop and flow profiles. The CFD results agreed very well with the experimental data obtained by Bohnet (Chem. Eng. Process. 1995, 34, 151) and Boysan et al. (Inst. Chem. Eng. Symp. Ser. 1983, 69, 305). CFD simulations were also performed at various flow rates, temperatures, and pressures. A fictitious fluid was used to observe the separate effects of density and viscosity on the flow pattern. The influence of density on the pressure profiles in the cyclone is significant, but that of viscosity is negligible. The results indicate that decreasing gas density and increasing gas viscosity can similarly reduce the magnitude of the tangential velocity in the region of the outer vortex at the same inlet volumetric flow rate. A first-order logarithmic equation was derived to correlate the ratio of the maximum tangential velocity to the inlet velocity with the Reynolds number for predicting the tangential velocity at high temperatures and high pressures.

The present study was focused on the turbulent L = Q~*~ Qair.st velocity field of a central annular natural gas jet which d, m = d T 0 penetrated a strongly swirling air flow. Due to the high p swirl number S = 0.95 and the high momentum ratio, the fuel jet was almost immediately integrated into the air Q stream. High rates of shear resulted in an intensive turRe bulent mixing process between natural gas and air. The central hub of the fuel exit annulus stabilized the reverse flow zone at a fixed location. The present nozzle configuration resulted in a very stable and symmetric flame. 6esch wincligkeitsmessungen in einer stark verdrallten ErdgasflammeZusammenfassung In der vorliegenden Arbeit wird das Geschwindigkeitsfeld einer stark verdrallten Erdgasflamme vorgestellt. Es bildet die Basis ffir die intensive turbulente Durchmischung zwischen Brennstoff und Verbrennungsluft, die ffir Drallflammen charakteristisch ist. Aus einem zentralen Ringspalt tritt Erdgas aus und wird sofort in den stark verdrallten Luftstrahl integriert. Die Flamme stabilisiert sich nahe/fiber dem Brenneraustritt und brennt symmetrisch. Als Mefldaten werden Mittelwerte f/fir Axial-und Umfangsgeschwindigkeit zur Verffigung gestellt, sowie die Standardabweichungen und die Reynolds-Stress-Tensor Komponenten des Geschwindigkeitsvektors. Aufgrund der Kleinheit der mittleren Radialgeschwindigkeit werden diese Mefldaten nicht gezeigt. Die vorgestellten Ergebnisse dienen als Basis zur Validierung yon Turbulenzmodellen. List of symbols b width of fuel nozzle annulus d diameter D diameter, without index: air nozzle, 60 mm f focal length I momentum ratio