Research On Rotor’s Profile Design And Processing Technology Of Marine Fuel Twin-Screw Pump

As a kind of external gearing screw pumps, twin-screw pumps have characteristicsof compact structure, Smaller pulsation, better suction capacity,a wide range of pumpedmedium’s viscosity, high flow transmission, stable and reliable, Long service life etc.Which have been widely used in shipbuilding, chemical, food, oil field, thermal powerplants, oil refineries, environmental protection and other fields. Along with the rapiddevelopment of our country industry, more and more Twin-screw pumps are demanded.However, on account of domestic manufacturers haven’t enough capacity to designtwin-screw pumps independently which result in singular tooth profile and poormachining uniformity. Domestic product quality still can’t meet the demand, whichmainly displays in the products have defects such as dynamic unbalance, large powerwear and tear, quick-wearing, not to reach the ideal use effect. Therefore, researching ontooth profile design and machining method of screw pumps’ rotors would havetheoretical and practical value to improve screw pump’s performance andself-developed products’ abilities.The research object is based on the marine fuel screw pump, which use principle ofgear meshing and the method of analytic geometry to analyze the relative movementsituations among screw pair and modify rotors’ tooth profile by straight line and arc.Three-dimensional models are built by Pro-E and analyzed no-load dynamicinterference after building the virtual assembly model of master-slave screw.Computer-aided design software on screw rotor’s profile design was developed. andthen, Based on the space envelop principle, form cutter dedicated to process screwmodified by straight line and arc is designed. The main research contents as follows：(1) Based on the fourth sealing requirements and meshing characteristics of theprofile, coordinate transformations equation is deduced between the master-slavescrews. Geometric method and conjugate design principle are used to deduce equationof the cycloid profile. Based on the relative movement situations among screw pair, theslave screw’s tooth profile is modified by straight line at first time, after then, modifiedby arc at the second time. Afterwards, the parameter equations of conjugate curvesabout master screw were deduced based on principles of gear connection.(2) Three-dimensional models of modified screws and the virtual assembly modelof master-slave screw are built by Pro-E. And then, dynamic contact condition among screw pair is analyzed under no-load condition to verify the rationality of profile design.To solve complex fuel screw’s tooth design calculation, visual computer aided designsoftware on screw pump is developed by using Visual Basic5.0.(3) According to principles of gear connection, coordinate transformationequations between meshing tool and screw was deduced. Under the design principles ofthe circle of milling cutter’s tangent overlaps with helix’s tangent in the sharp point,relative movement relationship between meshing tool and screw impact on the influencerule of setting angle and centre distance is analyzed. Contact condition equations of disccutter are obtained which is composed of discrete points. Cubic spline interpolationmethod is used to solve envelope equation to obtain tool profile of screw machiningdisc cutter. Finally, the sample rod is produced and tested.