Date of Award

2014

Publication Type

Doctoral Thesis

Degree Name

Ph.D.

Department

Mechanical, Automotive, and Materials Engineering

Supervisor

Barron, Ronald

Supervisor

Balachandar, Ram

Rights

info:eu-repo/semantics/openAccess

Abstract

This computational study is concerned with oil jet impingement heat transfer with the aim to investigate and improve the heat transfer efficiency process of piston cooling. Finite volume based computations using CD-adapcofs STAR-CCM+ are performed in this study. One of the advantages of this commercial code is its ability to tackle problems involving multi-physics and complex geometries. Generic models with fixed and reciprocating moving discs are used in the first stage of this study to investigate the thermal characteristics of the jet impingement. Subsequently, the information that has been acquired from the first stage is used to successfully simulate a full-scale engine and estimate the temperature profile and heat dissipation from the pistons with and without a cooling oil jet. The computational results show that the radial extent of the stagnation region beneath the jet is not uniform as stated in the literature, but is a function of the radial velocity gradient (Ýu_r)⁄Ýr in this region. Correlations describing the stagnation zone and local Nusselt numbers have been developed, applicable over a wide range of Reynolds numbers and Prandtl numbers. The effect of nozzle geometry is found to be insignificant on thermal characteristics for long jets. For jet impingement onto a moving boundary, an innovative methodology to accelerate the computational solution and reduce the cost in term of CPU time has been developed and implemented. Finally, the piston cooling process due to oil jet impingement is evaluated for the Fiat-Chrysler full-scale 2.0 L Tigershark Inline 4-Cylinder gasoline engine. For this specific simulation, the cooling jet reduces the volume average temperature, the stagnation zone temperature, the maximum and minimum temperatures in the piston by 10%, 25%, 12% and 25%, respectively, in comparison with the no cooling jet case.

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