The vortex-ingesting stirred tank reactor uses a combination of a helical screw impeller and concentric draft-tube to entrain and recycle headspace gas and disperse it as bubbles in a liquid reaction solvent. This study presents an experimental characterisation of a 0.29 m diameter vortex-ingesting gas-liquid stirred reactor, operated with solids mass fractions from 0 to 25%, over a range of sp...

The key parameters of the inner structure of a cylindrical airlift bioreactor, including the ratio of the cross-section area of the downcomer to the cross-section area of the riser, clearance from the upper edge of the draft tube to the water level, and clearance from the low edge of the draft tube to the bottom of the reactor, significantly affected the biomass production of Botryococcus braun...

In the present study, numerical investigations of a Francis turbine at model scale are performed. A part load operating point is selected for the analysis with a focus on the cavitating draft tube vortex rope. For three σ-levels, different aspects are investigated. First, the extension of the vapor volume is analyzed and compared to high-speed visualization recordings from the measurements. Fur...

Six laboratory scale biogas mixed anaerobic digesters were operated to study the effect of biogas recycling rates and draft tube height on their performance. The digesters produced methane at 0.40-0.45 L per liter of digester volume per day. A higher methane production rate was observed in unmixed digesters, while increased biogas circulation rate reduced methane production. However, different ...

The optimization of kernel parameters is an important step in the application of the Relevance Vector Machine (RVM) for many real-world problems. In this paper, firstly we have developed an improved anisotropic Gaussian kernel as the kernel function of the RVM model, whose parameters are optimized by Bacterial Foraging Optimization (BFO). Then the proposed method is applied to describing the pr...

Gas holdup, mixing, liquid circulation and gas–liquid oxygen transfer were characterized in a large (∼1.5 m3) draft-tube airlift bioreactor agitated with Prochem® hydrofoil impellers placed in the draft-tube. Measurements were made in water and in cellulose fiber slurries that resembled broths of mycelial microfungi. Use of mechanical agitation generally enhanced mixing performance and the oxyg...

Under low flow-rate conditions, a Francis turbine exhibits precession of vortex rope with pressure fluctuations in the draft tube. These undesirable flow phenomena can lead to deterioration performance as manifested by torque and power output fluctuations. In order suppress swirl component tube, use anti-swirl fins was investigated previous study. However, generation still occurred near cone th...

Abstract We performed Large-eddy simulations of the flow in a model air Francis turbine range low-load regimes with swirler rotating at fixed frequency. All investigated revealed presence coherent helical vortex structure draft tube: precessing core. identified frequency this instability and obtained mean velocity fields to be utilized further works.