Objective of this thesis work is the validation of a CFD numerical model applied to the detailed study of a single operative point (2000 x 4.3) relative to a CNG lightduty engine, designed and manufactured by FPT Industrial. This engines series has been specifically designed for light commercial vehicles and the NG version is a Dieselderived version fuelled by natural gas. The numerical model used for the scope relies on Lib-ICE, a complete library developed and continuously kept up to date by Politecnico di Milano internal combustion engines ICE Group for the open-source computational fluid dynamics software OpenFOAM, while information regarding the engine and experimentally measured data were directly provided by FPT Industrial. Firstly, a cold-flow simulation has been performed so as to understand whether boundary and initial conditions were coherently and opportunely set-up, to analyse air fluxes during the whole cycle and to initialize the flow for the subsequent combustion simulation. Incylinder pressure was compared with the corresponding experimental profile to validate the computation. After that, combustion reaction was simulated (fuel injection process was not taken into account): model validation was performed by comparison with experimental measurements in terms of in-cylinder pressure, heat release rate, burned mass fraction, exhaust pollutants emission and performance parameters. In general, simulations results were in good agreement with experimental data; only minor differences emerged during the analysis and the main reason resides in the simplifications introduced in the calculation.
L’obiettivo di questo lavoro di tesi `e la valizione di un modello numerico CFD applicato allo studio dettagliato di un singolo punto operativo (2000 x 4.3) relativo ad un motore CNG light-duty, progettato e prodotto da FPT Industrial. Questa serie di motori `e stata progettata specificamente per i veicoli commerciali leggeri e la versione NG `e una versione derivata dal Diesel, alimentata a gas naturale. Il modello numerico utilizzato per lo scopo si basa sulla Lib-ICE, una libreria completa sviluppata e continuamente aggiornata dal gruppo di motori a combustione interna ICE Group del Politecnico di Milano per il software open-source di fluidodinamica computazionale OpenFOAM, mentre le informazioni riguardanti il motore e i dati misurati sperimentalmente sono stati forniti direttamente da FPT Industrial. Prima di tutto, `e stata realizzata una simulazione cold-flow al fine di comprendere se le condizioni al contorno e iniziali fossero coerentemente e opportunamente imposte, per analizzare i flussi d’aria durante l’intero ciclo e per inizializzare correttamente il flusso per la successiva simulazione di combustione. La pressione all’interno del cilindro `e stata confrontata con il corrispondente profilo sperimentale per validare il calcolo. Dopodich´e, la reazione di combustione `e stata simulata (il processo di iniezione non `e stato considerato): la validazione del modello `e stata eseguita per mezzo di un confronto con le misure sperimentali in termini di pressione nel cilindro, curva di rilascio termico, frazione di massa combusta, emissione di inquinanti allo scarico e parametri prestazionali. In generale, le simulazioni sono risultate essere in buon accordo con i dati sperimentali; solo lievi differenze sono emerse durante l’analisi e la ragione principale risiede nelle semplificazioni che sono state introdotte nel calcolo.
CFD analysis of the combustion process in a light-duty CNG engine
FRONGILLO, GIANLUCA
2017/2018
Abstract
Objective of this thesis work is the validation of a CFD numerical model applied to the detailed study of a single operative point (2000 x 4.3) relative to a CNG lightduty engine, designed and manufactured by FPT Industrial. This engines series has been specifically designed for light commercial vehicles and the NG version is a Dieselderived version fuelled by natural gas. The numerical model used for the scope relies on Lib-ICE, a complete library developed and continuously kept up to date by Politecnico di Milano internal combustion engines ICE Group for the open-source computational fluid dynamics software OpenFOAM, while information regarding the engine and experimentally measured data were directly provided by FPT Industrial. Firstly, a cold-flow simulation has been performed so as to understand whether boundary and initial conditions were coherently and opportunely set-up, to analyse air fluxes during the whole cycle and to initialize the flow for the subsequent combustion simulation. Incylinder pressure was compared with the corresponding experimental profile to validate the computation. After that, combustion reaction was simulated (fuel injection process was not taken into account): model validation was performed by comparison with experimental measurements in terms of in-cylinder pressure, heat release rate, burned mass fraction, exhaust pollutants emission and performance parameters. In general, simulations results were in good agreement with experimental data; only minor differences emerged during the analysis and the main reason resides in the simplifications introduced in the calculation.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/146206