Research On Jet Cleaning Of Sewage Settling Tank

Aiming at the problem of lag in sewage settling tank cleaning technology, low Equipment utilization rate and ineffectiveness, in this paper a new sewage settling tank cleaning method by water jet technology is designed. The technology is controlling a cleaning cars moving in the tank bottom, through water jet beating and provoking the sediment, finally using siphon or other way output tank outside. This paper mainly through numerical simulation and experiment, study the nozzle of the jet characteristics and optimize nozzle structure, complete preliminary research work jet cleaning equipments.Through the research of water jet and nozzle jet theoretical, preliminary analysis the effect of nozzle structure,jet hydraulic parameters and operating parameters on jet cleaning. Analysising the correlation literature, points out the rectangular nozzles excellent of jet characteristics.Through the establishment of the 3d model of rectangular nozzles on free submerged water jet, the numerical simulation of internal and external jet flow field of nozzle were carried out,and stydied the effect of the convergence angle, length-diameter ratio on water jet,compared with the round nozzle of the same structure. Point out the initial period of rectangular nozzles jet, the jet diffusion angle of length and breadth side,nozzle flow field speed decay laws all conform to axisymmetric submerged jets theory,and convergence angle and length-diameter ratio mainly affect the hydraulic losses and jet cluster property of the nozzle .The water jet experiment device using rectangular nozzles and round nozzle with convergence angle 13°and length-diameter ratio 3,was established, and studied the relationship of water jet characteristic and these factors such as the export shapeof the nozzle, jet pressure, micro-injection distance. Results show that the hydraulic losses of rectangular nozzle is lower than round nozzle, and the flow coefficient of rectangular nozzle is higher than round nozzle,so rectangular nozzles has higher energy transmission efficiency than round nozzle and has characteristics of energy saving.Choosing rectangular nozzle with better jet characteristics as jet device cleaning nozzle, four nozzle are symmetrically placed on the both sides of clening car. Calculating the hydraulic losses of whole cleaning hose, finally determined the cleaning pressure 3.5MPa, the flow 20L/min, the stand-off distance 20cm, the impact angle 45°, the forward speed 2m/s, cleaner model PX-40A, the high-pressure hoses XPU-10 type.