Theoretical Design And System Development Of A Hydraulic Levitation Micropump

Electronic devices are developing towards high power and high integration.Due to high heat flux,flexible regulation and long heat transmission distance,active liquid cooling system is increasingly applied to electronic cooling.Micropump is the core driving component of active liquid cooling system,and determines system operating performance and reliability.This thesis aims at developing a high power density and high reliability micropump for board level liquid cooling system.Hydraulic components in microscale are designed and optimized.A hydraulic levitation shafting is developed for high-speed micropump rotor.Achievements are as follows:1)Based on velocity coefficient method and partial emission pump theory,micropump hydraulic components are designed to generate 2L/min flow rate,90kPa head at 22000RPM.According to computational fluid dynamic and experiment analysis,open impeller shows superior performance to closed impeller in micro scale and is selected for micropump scheme.Moreover,a multi-objective optimization algorithm combined with neural network is applied to open impeller structure optimization,and improves the pressure head and hydraulic efficiency 20%,6%respectively.2)A hydraulic levitation shafting comprised of hydraulic thrust bearing and journal bearing is proposed.Accordingly,a systematic design method is established.Based on Muijderman theory,the hydraulic thrust bearing is designed to generate 2.15N carrying capacity.We analysis the pressure distribution and thrust characteristic by using finite element method(FEM).Similarly,the journal bearing is designed and numerically analysised.Besides,influences of installation precision and shafting deflection are also investigated.3)2 versions of micropump prototype MT1 and MT2 are fabricated.MT1 is length 69mm,weight 150 grams and generates 2L/min flow rate,90kPa head.MT2 is height 25mm,weight 60 grams and generates 1L/min flow rate,45kPa head.The power density of MT2 is 86 kW/m3.A hydraulic performance test bench is built to validate hydraulic model.A hydraulic thrust bearing test bench is built to test carrying capacity in different condition and validate calculation accuracy of FEM.A shafting levitation test bench is built.The starting time of rotor levitation is measure to be 600ms,and stable levitation height is 48?m±5.Meanwhile,influences of temperature and rotation speed on rotor levitation are also studied.4)An active liquid cooling system intergrated with micropump is developed.The system maintains 60 ? heat source temperature under q=120W/cm2.The system running characteristic and cooling performance are tested under different thermal loads and working conditions.