Research On Ethylene Glycol/Water-Based Nanofluid Heat Transfer Performance And Its Influence On Engine Performance

Engine heat dissipation performance has an important impact on enhancing engine power.Nanofluid exhibits excellent heat transfer performance as a new heat transfer effort due to high thermal conductivity,thus has a good application prospect in automotive heat dissipation.The stability of nanofluid is affected by the comprehensive role of particulate properties and basic liquid properties,which has been a significant reason that restricts its application in industrial production.The reinforcing heat transfer effect of the nanofluid is related to a variety of factors,and its mechanism is not fully clear.Therefore,preparing nanofluids with good stability and exploring their effects of being engine cooling media on engine performance,is of great significance to the application of nanofluid in automobiles.In this thesis,graphene/alumina-ethylene glycol/water based hybrid nanofluid was first prepared by using ethylene glycol and deionized water as basic fluid.Then the effects of sodium dodecyl sulfate,sodium dodecyl benzene sulfonate,and polyvinyl pyrrolidone as dispersants on stability of hybrid nanofluid were investigated based on natural settlement,UV–vis spectrometry method and Zeta potential method,found that nanofluid performed better stability when using sodium dodecyl benzene sulfonate as dispersant.Meanwhile,hybrid nanofluid maintained better stability when the mixing ratio of dispersant and hybrid nanoparticles was 4:1.Then,according to the stability experiment,graphene/alumina-ethylene glycol/water-based hybrid nano-coolant was prepared by using sodium dodecyl benzene sulfonate as dispersant and ethylene glycol/water-based coolant as base fluid.The effects of dispersant concentration,particle mass fraction,and mixing ratio on the thermal conductivity of hybrid nano-coolant were investigated,and the graphene/alumina hybrid nanoparticles were found to significantly increase the thermal conductivity of the coolant,the enhancement effect increased with temperature,and the maximum thermal conductivity of the hybrid nanofluid increased by 10% when the mass ratio of graphene and alumina was 1:1.The influence of the concentration of dispersant and hybrid nanoparticles,and the mixing ratio of the hybrid nanoparticles on the rheological characteristic of nano-coolant were analyzed by using viscometer.It was found that the hybrid nanoparticles increased the viscosity of the coolant but the increasing ratio decreased with the temperature rise.Finally,the engine cold start,warming and load characteristic tests were carried out based on engine test bench using ethylene glycol/water-based coolant and graphene/alumina-ethylene glycol/water-based hybrid nano-coolant.Moreover,the effects of hybrid nano-coolant on engine performance were analyzed.The engine cooling system model was established by GT-Suite software,based on the viscosity of the two coolants,the thermal conductivity and other physical parameters,and the effect of using the mixed nano-coolant on the cold start process of the engine cycle condition is analyzed.The result showed that the hybrid nano coolant exhibited good heat transfer characteristics in the engine,promoted the heating rate of the engine idle cooling activation,and the time when engine coolant temperature rose from 20°C to 60°C was shortened for 2 min,the fuel consumption rate was reduced by 3.9% under 1400 rpm.