Dynamic mesh simulation flow field and micro-filling experiment analysis of viscous medium transported by two- lobe rotary pump

The current study aimed to explore the conveyance properties exhibited by the rotary lobe pump.To simulate the flow field of a two-lobe rotary pump, the K-ε turbulence model was employed in conjunction with the dynamic mesh technique, and the micro-filling accuracy of pure water and syrup with different viscosity were tested by servo control technique. 3D model of the two-lobe rotary pump was established by CREO, 2D model was meshed by ICEM, and the area near the rotor was meshed encrypted. The effects of medium viscosity on outlet flow characteristics, volumetric efficiency and medium viscosity on pump efficiency and micro-filling accuracy at low rotating speed were discussed. The results show that when the rotor speed is at 25.58 rpm, the flow pulsation is minimal; And the outlet flow rate is increased by 0.533kg/s when the rotor speed increased by 10 rpm. For fluids with low viscosity (ranging from 1 to 100cP), there is a notable increase in volumetric efficiency as the rotational speed rises. Conversely, the volumetric efficiency of medium-viscosity and high-viscosity fluids (spanning 250 to 850cP) is relatively insensitive to changes in rotor speed; When the inlet pressure is increased by 1kPa, the flow rate is increased by 0.127kg/s. In the viscosity range of 1cP-250cP, the flow non-uniformity coefficient decreases continuously, and when the viscosity reaches 450cP, the flow non-uniformity coefficient is almost not affected by the medium viscosity. According to the numerical simulation results, rotor lobe pump is used to carry out the micro-filling accuracy experiment. When filling 25g syrup, the optimal precision could be controlled within 0.6g, and when filling 500ml pure water, the precision could be controlled within 1.2ml. Therefore, the rotor lobe pump driven by servo motor is suitable for the micro-filling requirements of the milk tea industry.