the characteristics of a soft start． nate the friction discs have different hydro—viscous system，since the surface of the friction us has surface friction disc used Considering roughness grooves．The by disc．we have and radial surface a investigated numerically analyti— grooves。For convenience，only part and transfer characte— of the ana． the load friction three cally capacity torque disc，including grooves，is ristics of the film the AD is the inlet BC is oil 1yzed(see Fig．2)毕业论文http://www.751com.cn/in order to reveal the temperature—viscosity equation the belt mechanism of the soft start of hydro—viscous C to facilitate tIle of the conveyor and conceptual design soft starter and the control hydro—viscous system． ＼ ＼ 2 Softstart A soft start means that a belt can conveyor start the iner- smoothly by progressively overcoming Calculation model Fig．2 tia even under the condition of a full load．In order to reduce the of the should be no damage impact，there Since the load of the oil film in a capacity hy． sudden in acceleration．So a change during perfect dro—viscous clutch is much less than that in a hydro． the should from zero to the startup process speed vary lubrication radial flow induced dynamic bearing．the value to a curve．Both rating according given starting all role the force and centrifugal plays important by the Harrision and Nordell curves are commonly used cannot be is modified neglected，Reynolds equation as and are shown in V is curves starting Fig．1．where the of the our effect force in calcula． by centrifugal the rated and Z Harrision speed starting time．e tion model．In our Cartesian coordinate system，the curve is more and is US to investigate popular the friction disc surface and the use。d，by xoy plane represents the characteristics of a soft start¨II． oil film thickness is the direction． z represented along the friction disc surface Considering roughness and a flow mod— model，the by using Patir-Cheng average ified be derived as follows： Reynolds equation can 0 0 TJ2 t t (a)Harrision CBI'VC (b)Nordell curve U。，' and Harrison Nordell CUWCS 2 Fig．1 starting ．Ul。一U2， The transferred the oil film between fric· torque by dx z 2 tion discs Call be definition： calculated．By‰t, where M is transferred oil torque by film，∥dy— namic viscosity,以andare input speed and ④ is oil film thickness． output speed respectively,h] the inner outer radius of the fric． ，；and‘are and flow factors pressure along whereandare tion discs respectively． It from the cor- can be seen Fig．1a and Eq．f1)that the x and direction the shear Y respectivelyandis and oil film thickness responding speed，acceleration the flow of components factor．Uh，(f-l，2)are at Call be these results moment any calculatedand of the friction disc the x and direction． velocity along the basic data for further calculation of load Y provide oil film oil film at the real is transfer of the capacity and torqHe any k=h-I-d+ is thickness，h moment the during startup process． the nominal oil film thickness，i．e．，thedistance be— the two“middle surfaces”．one the tween rough sur— 3 the the Fundamental equations face of the friction disc and other of separator, the surface each roughness by taking 4 andare 3．1 Modmed Reynolds equation “middlesurface”as refe‘rence respectively．hT is It is to of a the characteristics preferable investigate the oil film thicknessand the mathematical average soft start a Cartesiancoordi-- hydro··viscous by using