Study On High Pressure Water Jet Cleaning Mechanism And Technology For Machine Parts

The fouling layer breakage and its micro-structure damage are under the effect of factors including viscosity,mechanical properties,particle size of fouling layer and adherence between material and fouling layer.Normally kinds of theoretical analysis describing high pressure water jet cleaning mechanism are based on giant amount of experiments and conclusions of others,methods of indirect way.Imparities in simplified model building in experiment process,postulated conditions in analyzing different matters would make different results.Thereby the high pressure water jet cleaning mechanism is complexly described.Three kinds of nozzles normally used in industrial production are numerically simulated,and the structure of nozzle with the best jetting performance out of the three nozzles is optimized.The R90 nozzle displays the most optimal jetting properties.A new helix nozzle structure is presented based on the analysis results.Simulation results of all sample nozzles in this study show that the helix nozzle ultimately displays the best jetting performance.Jetting velocity magnitude along Y and Z coordinates is not symmetrical for the helix nozzle.Compared to simply changing the jetting angle,revolving the jet issued from the helix nozzle creates a grinding wheel on the cleaning surface,which makes not only an impact effect but also a shearing action on the cleaning object.Jet issuing from this particular structure impacts indirectly on fouling layer surface,the shearing action concentrates strong turbulence,which is the largest near the axial line,spiral line and boundary between jet medium and environment medium.Entrainment is produced on the fouling layer surface cased by axial impacting force and spiral shearing force.Considering the interaction of these two forces,flow on the cleaning surface is complex;thereby the environment phenomenon is difficult to be described.The velocity,momentum and dynamic pressure of the impacting jet change obviously on the fouling layer surface,where the energy loss transmits to.The dynamic pressure,a defined property of a moving flow of gas,could accurately reflect the cleaning ability,instead of the total impacting force.One of the traditional common nozzles,cylindrical contracting nozzle,which is used for high pressure water jet cleaning,issues cylindrical jet on the fouling layer surface,the largest dynamic pressure at the center of the axial jet,a small area where the jet concentrates upon.Another kind of nozzle,external helix nozzle,which is used for dusting,issues spacious jet in the air,functions in large area but losses the ability of cleaning fouling layer.The boundary shearing jet issuing from our optimized helix nozzle completely makes up for the lack of functional area and cleaning ability.The friction between boundary shearing jet and intimal jet caused by the viscosity property of jet medium(water or other detergents)functions on jet from nozzle wall surface to axial center.And the moving flow including impacting force and shearing action produces high level cleaning ability and considerable cleaning area.In designing the high pressure water jet cleaning experiment system,experiment principle and measuring variables,water jet booster devices and control system are analyzed.Components including scavenging pump,filter pump,flow meter,butterfly valve and energy accumulator form the water jet booster devices.Components including PLC,kinds of sensors,PC and industrial camera form the control system.Then the waterway schematic diagram of high pressure water jet experiment,high pressure water jet experiment system silhouette and electrical system chart are designed.