Numerical Investigation into the Cooling Process of Conventional Engine Oil and Nano-Oil Inside the Piston Gallery
A numerical simulation model has been developed for the transient flow and heat transfer problems of oil inside the piston gallery using a coupled VOF/Level Set method. Detailed cooling processes of Cu-oil nanofluids, with the nanoparticle size of 50 nm a
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Abstract A numerical simulation model has been developed for the transient flow and heat transfer problems of oil inside the piston gallery using a coupled VOF/ Level Set method. Detailed cooling processes of Cu-oil nanofluids, with the nanoparticle size of 50 nm and the volume fractions of 1, 2 and 3 %, have been investigated. The oil fill ratio (OFR) and heat transfer coefficients (HTC) variations at different crank angles have been examined as well. The results have demonstrated that the nano-oil is able to improve the heat transfer capacity by a large margin. Compared with the conventional engine oil, the overall average heat transfer coefficients of the nano-oil, with the volume fractions of 1, 2 and 3 %, increase by 5.80, 14.51 and 28.11 % respectively.
Keywords Piston cooling gallery Nanofluids Multiphase flow VOF Level set
1 Introduction Over the years in the past, the overall heat loading of internal combustion engines increases rapidly with the special power rising. In a variety of high-temperature components, the working condition of piston is the worst due to prolonged exposure to the combustion chamber. The piston suffers periodic mechanical and thermal loadings. The cooling gallery inside the piston head is commonly adopted to optimize the heat extraction. The heat flux removed by the cooling gallery can F2012-A07-002 P. Wang (&) J. Lv M. Bai C. Hu L. Zhang H. Liu Dalian University of Technology, Dalian, China e-mail: [email protected]
SAE-China and FISITA (eds.), Proceedings of the FISITA 2012 World Automotive Congress, Lecture Notes in Electrical Engineering 190, DOI: 10.1007/978-3-642-33750-5_26, Ó Springer-Verlag Berlin Heidelberg 2013
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Fig. 1 Schematics of piston gallery oil flow
occupy as much as 45 * 75 % of the total heat passed to the piston from the combustion gases, so heat transfer coefficient of this region is of great importance to the accurate calculation of piston temperature. However, the structure of cooling gallery limits the piston strength to some extent. With the peak cylinder pressure in diesel engines steadily increased, simply extending or modifying the cooling gallery configuration may be insufficient when power rating is above a certain level and additional cooling measures are quite necessary. In 1995, Choi [1] proposed the concept of nanofluids, which is a new type of heat transfer medium. It contains nanoparticles of metal or metal oxides with dimensions smaller than 100 nm, suspended uniformly and stably in base fluid. Inclusion of solid particles in liquid will greatly enhance the overall average thermal conductivity due to high thermal conductivity and large specific surface area of solid particles. Therefore, if nanofluids can be used in the heat transfer process of engine piston, especially as the cooling medium of piston gallery, the heat transfer efficiency will be effectively improved. Due to small space and complicated structure of the piston gallery, it is quite difficult through experiments to gain accurate vi
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