The use of numerical techniques is widely accepted by manufactures in order to increase engine durability and performances and reduce emissions. The effective thermal load prediction is always considered a nodal point to correctly assess the coolant mass flow rate and jackets arrangement.
In literature many approaches used to analyzed the in-cylinder heat transfer can be found and they can be classified as follows: methods based on the steady convective heat transfer, approaches based on the solution of the unsteady heat conduction equation by means of the knowledge of the temperature profile, approaches based on the energy conservation for the whole mass contained inside the cylinder.
The purpose of this paper is to define a proper methodology to evaluate the thermal flow distribution and intensity inside the engine liner, head and coolant channel. In facts, this work shows the analysis of the cooling circuit of a small single-cylinder, four-stroke, high power density engine carried out with a numerical, three-dimensional CFD analysis using a commercial CFD 3D code.
A numerical conjugate analysis is presented in this work and a particular attention was used to define realistic boundary conditions. Furthermore, a sensitivity study on mesh was also carried out.
This study is based on the knowledge of the mean steady heat flow and takes into consideration the following topics:
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the evaluation of the needed coolant mass flow by means of an analysis based on the Woschni approach;
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the analysis of the velocity and temperature field by means of a conjugate heat transfer simulation of the whole head and cylinder group.
This work includes the comparison of the numerical results with data collected by literature and experiments.