Gas-Liquid-Solid Three Phase Flow in Cesspipe of Vacuum Toilet: A Simulation Study

The gas-liquid-solid three-phase flow in the cess-pipe of vacuum toilet was empirically approximated,mathematically formulated in standard k-ε turbulence model,theoretically analyzed,numerically simulated with FLUENT software and experimentally evaluated.The influence of the air volume-fraction and outlet pressure on cavitation of the simplified gas-liquid two-phase flow was investigated.The simulated results show that the air volume-fraction has a major impact.For example,as the air-content increases,the cavitation changes in an increase-decrease mode,maximizing at an air-content in 40%~45% range,possibly because of air-entrainment effect on cavitation alleviation; whereas an increase of the outlet pressure weakly affects the cavitation because a higher induced velocity markedly alleviate cavitation.The simulated and measured results were found to be in good agreement.We suggest that the optimized conditions may include an air-content of 45% and an outlet pressure of 65 kPa.