A nanobubble generator with honeycomb structures producing a large amount of water including large nanobubble density in a short time is described. The nanobubble-generating performance is investigated for large and small apparatus having different honeycomb cell dimensions by applying computational fluid dynamics (CFD) coupled with a population balance model (PBM). The CFD simulation shows that a significant pressure drop and shear stress occur in the bubbly flow in the honeycomb cell. The numerical model is based on the Eulerian multiphase model and the PBM is used to calculate the bubble size distribution. The obtained CFD-PBM results are compared with the experimental results for large and small apparatus. Bubble size distributions in the honeycomb structure under different inlet absolute pressure can be predicted by the PBM. The maximum shear stress is determined as the main controlling factor for nanobubble generation.

No abstract

This paper presents a new estimation method of rotor position to achieve a position sensorless control for surface permanent magnet synchronous motor. DC current adds to SPMSM and nonlinear observer is applied to the torque equation to estimate the rotor position from the induced voltage while the motor is vibrating. When the error of the measured and calculated induced voltage is converged, the estimated rotor position is converged to the real value. The validity of the proposed method is verified by the experiment.

In this study, nanobubble generator using a honeycomb structure is investigated towards producing a large amount of water including large nanobubble density. Our previous study showed that the pressure reduction and shear stress are involved in the honeycomb cell flow. In this study, the nanobubble generating performance is studied experimentally for honeycomb structures by varying the cell size and the flow velocity. Then, the small-scale honeycomb cell structure is studied for the broader industrial applications. Computational Fluid Dynamics analysis is also performed to simulate the experiment to find out the efficient nanobubble generation. The results show that the maximum shear stress is the main controlling factor of the nanobubble generation for small and large apparatuses.

No abstract