纳米流体强化内燃机冷却系统流动的基础研究

利用高导热率、传热性能好的传热工质(纳米流体)替代传统冷却介质应用于内燃机冷却系统中,通过纳米流体流动特性的基础研究,为其在内燃机冷却系统中的应用提供理论基础支持.因此,利用试验方法对纳米流体在波壁管内的流动进行可视化研究,以期对纳米流体的流动机理进行详细的探讨,从而推动纳米流体在内燃机冷却系统中的应用.研究发现:纳米流体的黏度增加值不大,且随着温度的升高,增加值降低;而相同入口速度状态下,纳米流体在波壁管内的流动比纯水更为活跃,漩涡数量增多,质量传递特性增强,且随纳米颗粒浓度的增加,流动湍流效应增大.通过分子动力学方法发现纳米颗粒在纳米流体流动过程中存在强烈的旋转作用,从而出现微湍流流动效应,进一步强化了纳米流体的湍流流动效果.

Basic Research on Flow of Nanofluids in Cooling System of Internal Combustion Engine

As a substitute of traditional cooling medium,a heat transfer fluid with higher thermal conductivity and better heat transfer performance(nanofluids)was applied to the cooling system of internal combustion engine and the fundamental research on flow characteristics of nanofluids was performed to provide the theoretical support to its application.The present work made a visualization study on nanofluids flow in a waved-wall tube to clarify flow mechanism of nanofluids and promote the application of nanofluids in cooling system of internal combustion engine.Study found that the viscosity of nanofluids decreased as increasing temperature and conformed almost exactly to base liquid at high temperature.In the wavedwall tube and under the same inlet velocity condition,the flow of nanofluids is more active than that of the base liquid.The number of vortex is increased,mass transfer characteristic is strengthened and turbulence effect is increased with the increase of particle concentration.In addition,it is found by molecular dynamics analysis that there exists strong turning effort of nanoparticles in nanofluids flow and micro turbulent flow effect is promoted,leading to further strengthened turbulent flow effect of nanofluids.