Experimental Investigation On Impinging Jet Cooling For Simulation Of Internal Combustion Engine Piston Underside

With the development of modern internal combustion engine,the operation parameters and the overall structure and material of the piston have been deeply optimized.It is obviously not enough to reduce the piston's thermal load from the design characteristics of the engine itself.The piston is vulnerable in continuous high temperatures.Therefore,nanoparticles were added to the lubricating oil to cool the piston cooling oil chamber whose results show that the cooling effect is better.To ensure the advantage of simple structure and low cost,we proposed the experiment of adding nanoparticles to the jet impact of piston underside.This paper simulates the bottom surface of the piston of internal combustion engine.The jet impact cooling experiment was carried out with nano-fluid as heat transfer medium.To explore the influence of different conditions on jet impact cooling,this article mainly carries on the following work:SiO₂-water nanofluids with different volume fractions were prepared by using the‘two-step method'.Then the suspension stability experiment and electron microscope scanning experiment were carried out by sampling the prepared liquid.The stability is good and the particle size and particle shape.The experimental stage was designed and established to simulate the jet heat transfer at the bottom of the internal combustion engine piston.The basic experiment was carried out with deionized water first.Then,SiO₂-water nanofluids with different volume fractions were tested as heat transfer medium for heat transfer.The influence of volume fraction,jet impact angle,jet height and jet Re on the average heat transfer coefficient of jet impact cooling is investigated.The radial temperature distribution of the heat transfer surface in different working conditions was recorded as well.It can be found that the addition of nanoparticles can significantly improve the average heat transfer coefficient of jet impact cooling by comparing the obtained images with reference to different heat exchanges.The influence of volume fractions,jet height and jet impact angle on the average heat transfer coefficient is not linear and the effect of jet Re is linear growth trend.These effects are basically the same as the heat transfer work in deionized water and the radial temperature distribution of the heat surface in steady state is basically the same.The optimal solution of this simulation experimental can be obtained from many experimental conditions of this experiment.When the maximum jet cooling coefficient is obtained under the same experimental background,the corresponding volume fraction,jet fraction,jet height,impact angle,and Re parameter are the relative optimal conditions.With the optimal solution is the fixed experimental condition,the experiment was carried with the same concentration of Al₂O₃-water and SiO₂-water.Then the relative optimal solutions including the species of nanofluids are obtained.According to the experimental data obtained,we modified and improved the previous empirical correlation.In this paper,we propose a simulation of the empirical correlation of the jet flow in the simulated internal combustion engine with the jet height,the impact angle and volume fraction of the nanofluids.The correlation between data value and empirical fitting was96.166%,which means that the empirical correlation is relatively high and it has considerable reliability.