In this thesis work, a flow analysis was carried out inside the collectors and the chamber of an internal combustion engine with canted valves through the computational fluid dynamics approach (CFD acronym for Computational Fluid Dynamics) in order to evaluate the intake air flow and the turbulent motions that characterize its operation. After an introduction on the theory of internal combustion engines, we have moved on to the description of the engine on which all the simulations were carried out. The engine was a 4 strokes single-cylinder internal combustion engine with controlled ignition. Before proceeding with the simulations, it was necessary to generate the computational domain starting from the engine mesh, supplied by the manufacturer. A reverse-engineering process was performed using the Rhinoceros 3D CAD modeling software. Once the computational domain was generated, an optimal hybrid moving mesh was built to solve the Navier-Stokes equations and the other conservation equations. In order to deal with the simulations, the Ansys Fluent solver was used to solve the Reynolds (RANS) mediated equations with a segregated approach based on the PISO (Pressure Implicit with Splitting of Operators) algorithm, using a Finite Volume discretization. The software used to generate the grid was Ansys Meshing. Subsequently, simulations of a complete motor cycle have been set and carried out for different engine speeds. The simulations reproduced the motoring cycles recorded in the experiments. Finally, the results from the calculation were analyzed; the evolution of the in-cylinder pressure and the motion fields were observed. These results were then compared with the experimental data.
In questo lavoro di tesi è stata effettuata un’analisi del flusso all’interno dei collettori e della camera di un motore a combustione interna a valvole inclinate attraverso l’approccio della fluidodinamica computazionale (CFD acronimo di Computational Fluid Dynamics) al fine di valutare la portata d’aria aspirata e i moti turbolenti che ne caratterizzano il funzionamento. Dopo un’introduzione sulla teoria dei motori a combusione interna, si è passato alla descrizione del motore su cui verranno effettuate tutte le simulazioni ossia un motore a combustione interna monocilindrico 4T ad accensione comandata. Prima di procedere alle simulazioni è stato necessario generare il volume di flusso a partire dalla mesh del motore, fornita dalla casa costruttrice. È stato, effettuato un processo di reverse-engineering utilizzando il software di modellazione CAD 3D Rhinoceros. Generato il volume di flusso, è stata costruita una mesh ibrida ottimale del motore per poter risolvere le equazioni di Navier-Stokes e le altre equazioni di conservazione. Per affrontare le simulazioni è stato usato il solver Ansys Fluent grazie al quale vengono risolte le equazioni mediate di Reynolds (RANS) con un approccio segregato basato sull’algoritmo PISO (Pressure Implicit with Splitting of Operators), utilizzando una discretizzazione a Volumi Finiti. Il software utilizzato per la generazione della griglia è stato Ansys Meshing. Successivamente, sono state impostate ed eseguite le simulazioni di un ciclo motore completo, per diversi regimi di rotazione. Le simulazioni sono state eseguite su cicli trascinati in funzione dei dati sperimentali a disposizione. Infine, sono stati studiati i risultati provenienti dal calcolo; sono stati posti sotto osservazione l’andamento della pressione del cilindro e dei campi di moto. Questi risultati sono stati, poi, confrontati con i dati sperimentali.
CARATTERIZZAZIONE FLUODINAMICA 3D DELLA FASE DI ASPIRAZIONE DI UN MOTORE 4 TEMPI.
CARRIERI, FRANCESCO
2017/2018
Abstract
In this thesis work, a flow analysis was carried out inside the collectors and the chamber of an internal combustion engine with canted valves through the computational fluid dynamics approach (CFD acronym for Computational Fluid Dynamics) in order to evaluate the intake air flow and the turbulent motions that characterize its operation. After an introduction on the theory of internal combustion engines, we have moved on to the description of the engine on which all the simulations were carried out. The engine was a 4 strokes single-cylinder internal combustion engine with controlled ignition. Before proceeding with the simulations, it was necessary to generate the computational domain starting from the engine mesh, supplied by the manufacturer. A reverse-engineering process was performed using the Rhinoceros 3D CAD modeling software. Once the computational domain was generated, an optimal hybrid moving mesh was built to solve the Navier-Stokes equations and the other conservation equations. In order to deal with the simulations, the Ansys Fluent solver was used to solve the Reynolds (RANS) mediated equations with a segregated approach based on the PISO (Pressure Implicit with Splitting of Operators) algorithm, using a Finite Volume discretization. The software used to generate the grid was Ansys Meshing. Subsequently, simulations of a complete motor cycle have been set and carried out for different engine speeds. The simulations reproduced the motoring cycles recorded in the experiments. Finally, the results from the calculation were analyzed; the evolution of the in-cylinder pressure and the motion fields were observed. These results were then compared with the experimental data.I documenti in UNITESI sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
https://hdl.handle.net/20.500.14253/82680