Riassunto analitico
The internal combustion engine simulation is a relevant phase of a powertrain development.
Once the first design step of an engine is terminated, fluid-dynamics and finite element simulation departments cooperate trying to reach the desired target with an iterative procedure that may bring back to the design phase to review some geometrical aspects.
In particular CFD simulation provides the boundary condition for the FEA thermal and thermo-structural analysis which has the aim to verify how much the engine is stressed.
This work is focused on the engine head and in particular on valves behavior during a whole engine cycle. First of all a steady state thermal analysis has been realized setting the cycle averaged boundary condition, and then a transient heat transfer thermal analysis has been done, simulating different engine cycles and so setting instantaneous (time dependent) boundary condition always provided by CFD simulation.
The realization of a transient analysis leads also to the creation of different contact status for the valves which open and close during the engine cycle implying a not trivial setting of the complete simulation.
The standard simulation procedure for the engine is generally the steady state thermal analysis that gives as output the temperature field applied to the structural subsequent analysis. Steady state thermal analysis is an approximation of the engine cycle thermal behavior, especially for valves which are moving reaching maximum lift and changing contacts and contact areas with seat and guides. The need of approximation comes from the complexity to implement a transient analysis which requires lot of setting time and computational cost.
For all these reasons the interest of this work is the comparison between transient and steady state final results to highlight its sensitivity. If the difference between the results of the steady state and the averaged output of the transient is negligible the rightness of the steady state approximation usually employed will be confirmed.
This thesis has been possible thanks to the company HPE COXA S.R.L. with a six months internship. This company is specialized in automotive, motorsport, automation, aerospace and defence applications and so makes available materials and tools to realize the following analysis. The society was born from the union of the engineering knowhow of HPE, founded in 1998 by Piero Ferrari, and the workforce of COXA born in 1985 and specialized on high precision production and prototypes for niche components. HPE COXA S.R.L. represents also a partner of Motorvehicle University of Emilia Romagna which is the promoter of Advanced Automotive Engineering courses.
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