Investigation on gas–liquid–solid three-phase flow characteristics in aircraft wastewater pipes

The aircraft wastewater system is an important system for civil aircraft. The wastewater is transported through the pipeline under the pressure difference between the cabin and the vacuum wastewater tank, and its flow time and characteristics are crucial for the system design. In this paper, the gas–liquid–solid flow of aircraft wastewater is investigated using the Euler–Euler–Euler multiphase flow numerical simulation method. The influencing factors of wastewater flow are analyzed. Afterward, the impact of different factors on the flow time and characteristics is analyzed, such as pressure differences between the cabin and the tank, pipeline length, pipeline inner diameter, and the disturbance for a straight long pipeline. The results show that the wastewater flow time is reduced from 6.4 to 2.6 s with the increase in the pressure difference from 20 to 60 kPa and increased from 3.4 to 10.2 s with the increase in the pipeline length from 30 to 70 m. The results obtained provide a modern theoretical basis for the design of such systems of vacuum wastewater and have a wide range of applications not only in aviation but also in other modern kinds of transport (rail, shipping), contributing to reducing their negative impact on the environment.