Research On Optimization Design System Of External Gear Pumps With Ultra Low Viscosity Medium Equipped In Spacecraft

External gear pumps are a kind of power tools of pumping working oil,owing to theiradvantages in prices,reliability,lifetime and many more,therefore,they are widely used in conventional oil medium.Subject to the restriction of installation space size and maintenance,quality of driven component in the space environment,these pumps have been widely used in ultra low viscosity mediumhydraulic system of large foreign spacecraft,because of their characteristics is simple instructure,small size,light weight,high reliability,long lifetime,good self-absorption properties,etc.External gear pumps with ultra low viscosity medium and their related technologys become the cutting-edgeresearch of hydraulic international community gradually too.The internal leakage of conventional external gear pumps will increase substantially when ultra low viscosity mediums are used in them,so this paper must do targeted optimization design of their gears and construction.Based on the typical physical and chemical properties of ultra low viscosity medium,this paper designs and developments a NX/CAD system of external gear pumps with ultra low viscosity medium with considering the focus on reducing leakage,improving volumetric efficiency,achieving the volume and flow pulsation minimum of external gear pumps and reducing the radial force which has important theoretical significance and practical value.Based on learning and analyzing domestic and foreign research results deeply,considering the ultra-low viscosity of the medium,this paper probed the contact ratio formula of gear pairs of external gear pumps with ultra low viscosity medium emphatically,created a new contact ratio formula for gear pairs with undercut in external gear pumps.With using larger safety factor,this paper created the constraint function of gear strength;based on analyzing and researching the leakage and effective volume ratio of gear pumps,the power loss and the viscous friction loss of medium and many more,this paper created the corresponding objective function and constraint function,the expression of the best axial and radial clearance.This paper created a weighted linear optimization model under multi objective function of these pumps,this paper optimizated with the algorithm of Global Simplex and Powell synthetically after uniting dimensionless.These make theoretical preparations for the design optimization and system development of gear pumps with ultra low viscosity medium.With referencing the related optimization design theory and system development methodology of hydraulic gear pumps,this paper put forward a integral NX/CAD system design program of external gear pumps with ultra low viscosity medium,realized the optimization of core parameters and 3D model-driven of gear pairs of these gear pumps under NX software,provided the optimized realization of this system under EXCEL software also.The achievements of these researches are actions of enormous importance in promoting the efficiency and quality of development and design and reducing the costs of development of gear pumps with ultra low viscosity medium(equipped in spacecraft),provided an important reference for the wider range of applications in the ultra-low viscosity hydraulic field of external gear pumps.