Research On The Micro-cooling Fan Aerodynamic Performance Testing Techniques

With the miniaturization of electronic devices,the size and volume of cooling fans are required to be smaller and smaller.The emergence of micro-fans has put forward new requirements for fan aerodynamic performance testing technology.The original technical standards and measurement techniques cannot meet the measurement requirements of small flow.Based on the theory of fluid mechanics,this thesis studies the aerodynamic performance testing techniques for micro-miniature axial flow and centrifugal cooling fans of different specifications.The main research contents and results are as follows:(1)Analysis of the aerodynamic performance test model of a small cooling fan based on a nozzle.For fans with a flow greater than 15.6 CFM,the test system can use the nozzle as the flow standard table.Referring to the American standard AMCA210,the appropriate test pipeline was selected,and the flow and pressure calculation model in the measurement data processing was obtained.The calculation and verification method of the flow nozzle outflow coefficient was proposed,and the calculation formula of the fan pressure head was proposed.(2)Micro-cooling fan aerodynamic performance testing technology based on Laminar flow sensing element.For a cooling fan with a flow rate less than 20 CFM,a laminar flow sensing element is used as a standard meter.Aiming at the actual laminar flow measurement pipeline,considering the local loss of the Laminar flow sensing element and the inlet section effect in the capillary,the flow calculation model of the conventional capillary Laminar flow sensing element is derived.The differential and pressure differential capillary laminar flow sensing elements and their working principles are proposed and verified by experiments.The results are satisfactory.The pressure differential type laminar flow sensing element can eliminate the local loss of capillary inlet and outlet and the Flow-differential pressure nonlinear factor caused by the flow of the laminar inlet section,and the advantages are obvious.(3)Micro-cooling fan pneumatic performance test device design.A miniature cooling fan performance test device based on flow nozzle and laminar flow sensing element is designed,including measurement pipeline structure design,flow measurement unit design,measurement instrument selection,measurement control hardware and software development.The micro-cooling fan performance test system based on nozzle and laminar flow sensing elements has a flow range of 15.6-70 CFM and 0.1-20 CFM,respectively.(4)Micro-cooling fan pneumatic performance test system calibration evaluation.Flow calibration and performance evaluation for the developed test system.Flow nozzles and laminar flow sensing elements are calibrated using standard methods and bell jar flow standard device.Flow-nozzle-based test systems have measurement accuracy within ±1%;flow rates based on conventional laminar flow sensing element test systems The measurement accuracy is within ±1.5%;the flow measurement accuracy of the test device based on the pressure difference method laminar flow sensing element is within ±1.0%.