Flow Field Simulation Analysis of Train Siphon Toilet with Variable Pipe Diameter Based on the Investigation of Siphon Performance

The performance of siphon toilets in trains with varied pipe profiles were investigated. The profiles of the siphon pipe are varied based on the diameter of the pipe along the pipe length. The flushing process was simulated by using CFD method. The starting time, the duration, the siphon mass flow rate, the negative pressure in the siphon pipe were recorded and selected as siphon performance indexes. The results showed that for the same type of siphon pipe, the siphon performance becomes worse with the increase of the maximum pipe diameter as the minimum pipe diameter is 45mm. The simulation confirms that the performance of the siphon toilet with the pipe diameter varying from large to small then to large is the best; the performance of the siphon with a pipe diameter varying from small to large then to small is the worst. The qualitative results may provide some suggestions for relevant industrial designs.