Research On Aerodynamic Characteristics And Aeroacoustics For Cooling Fan Of Construction Machinery

With the constant improvement of construction machinery technology level andurgent request of environment，construction machinery products pay more and moreattention to solutions of the thermal equilibrium problem and noise problem.Construction machinery cooling fan is an important part of the cooling system，itdrives the cold air to overcome the resistance of the system through the rotarymotion，makes the cold air constantly flowing through the radiators and takes away alot of heat from radiators，then makes the temperature of the cooling fluid，hydraulicoil and transmission oil reduced to guarantee the normal work of the whole machine.At the same time of cooling，cooling fan noise has become an important noisesource in engine compartment，especially its aerodynamic noise. In order to solvethe thermal equilibrium and noise problem of construction machinery，the thesisresearched aerodynamic characteristics and aeroacoustics of cooling fan withNational Science and Technology Support Programme Project “Energy-saving andsafety-oriented， integrated engineering machinery and equipment research anddevelopment”（project number：2013BAF07B04）.Firstly，according to the performance testing using standardized airways，thethesis used some softwares including FLUENT software to do numerical simulationof the arc plate airfoil cooling fan performance for a construction machinery，Itshowed that the numerical error of the aerodynamic characteristics and aeroacousticsis small，so it can be used to study the fan performance.Secondly，the thesis analyzed some factors of aerodynamic characteristics andaeroacoustics of cooling fan. The performance of cooling fan is mainly influencedby the blade structure parameters and the relative position of parts in the enginecompartment. Taking the original arc plate airfoil cooling fan as the research object， the thesis analyzed variation regularity of the cooling fan performance affected byblade installation Angle，blade chord length，blade radius，blade number and speedin the virtual standardized airways；Based on the original arc plate airfoil coolingfan，the thesis studied how four type blades including NACA9502airfoil blades，blades with deflectors，blades distributed nonuniformly and blades with circularshroud affect the fan performance；Another study is in the virtual wind chamber，therelative position relations among cooling fan， air director and radiators areresearched for aerodynamic characteristics and aeroacoustics of cooling fan.Finally，under the stationary test condition，the thesis used CFD method toanalyze the internal flow field of engine compartment and exterior noise spectrumemitted to environment for a construction machinery. In the aspect of noise reductionin propagation path， closed six ventilation openings on the hood of enginecompartment and then calculated，the contrast showed this solution can reduce2dBA，but the flow rate of cooling air is relatively reduced，then changed the fan tosuction fan，and found that the effect does not be improved. Then the thesisimproved the performance of engine compartment according to the above stud iedblades style with good fan performance and a reasonable relative position for partsin engine compartment，found the exterior fan noise reduced4dBA，so it showedthat the improved scheme is better，based on the improved scheme，studied threekinds of solutions including removing the ring part of air director，closing theclearance between cooling fan and air director and reducing one-third the width ofcircular shroud，the result showed the solution of reducing one-third the width ofcircular shroud with removing the ring part of air director is the best.