The present work deals with the fluid-dynamic and mechanical design of an innovative Stirling engine characterized by a rotary architecture. The layout of the machine allows for an high specific work with compact dimension, avoiding the use of crankshaft and exploiting the advantages of arbitrary law for the volume chamber variation. As a preliminary step, the adopted numerical methodology is described, ranging from simple thermodynamic simulation to complete 3D CFD thermo-fluid dynamic model. The effect of volumes law, compression ratio and dead spaces repartition are analysed; moreover also the heat exchangers geometrical specifications, including the regenerator, have been detailed investigated, deriving guidelines for their design. On the basis of thermo-fluid dynamic results, the mechanical design of the machine has been assessed, in view of the manufacturing of a prototype to be adopted for the experimental campaign. Guidelines of this design process were components modularity and manufacturing simplicity. Simple analytical models were applied to verify all the components. The manufacturing process of the prototype was designed in order to exploit standard industrial technologies which could be the basis for a future scaling up of the product. Finally, a cost analysis was performed pointing out the existing margins of cost lowering for future production series.
Nel presente lavoro di tesi è presentato il dimensionamento termofluidodinamico di un innovativo motore Stirling basato su un'architettura rotante, che evita l'utilizzo di bielle e alberi a gomito. Il risultato è stato l'ottenere una macchina compatta, capace di alti lavori specifici derivanti dallo sfruttamento dei vantaggi di un'arbitraria legge di variazione dei volumi. Sono quindi descritti i modelli numerici che verranno utilizzati, partendo da una semplice simulazione termodinamica a modelli fluidodinamici CFD completi. Verrà quindi analizzato come la legge dei volumi, il rapporto di compressione e gli spazi morti influenzino il ciclo; unitamente ad un'analisi sulle caratteristiche degli scambiatori di calore e del rigeneratore, estrapolando linee guida per il loro dimensionamento. Sulla base dei risultati del dimensionamento termofluidodinamico è stata effettuata la progettazione meccanica, nell'ottica di modularità e semplicità costruttiva richiesti da un prototipo. Sono stati inoltre sottoposti a verifica strutturale gli elementi maggiormente sollecitati, mediante semplici modelli analitici. Inoltre, il design degli elementi, permette l'utilizzo di tecnologie standard, gettando le basi per una successiva scalabilità del prodotto. In ultima analisi, una basilare analisi economica evidenzia margini di risparmio per una futura produzione in serie.
Thermo-fluid dynamic and mechanical design of a novel rotary Stirling engine
Cristani, Luigi
2021/2022
Abstract
The present work deals with the fluid-dynamic and mechanical design of an innovative Stirling engine characterized by a rotary architecture. The layout of the machine allows for an high specific work with compact dimension, avoiding the use of crankshaft and exploiting the advantages of arbitrary law for the volume chamber variation. As a preliminary step, the adopted numerical methodology is described, ranging from simple thermodynamic simulation to complete 3D CFD thermo-fluid dynamic model. The effect of volumes law, compression ratio and dead spaces repartition are analysed; moreover also the heat exchangers geometrical specifications, including the regenerator, have been detailed investigated, deriving guidelines for their design. On the basis of thermo-fluid dynamic results, the mechanical design of the machine has been assessed, in view of the manufacturing of a prototype to be adopted for the experimental campaign. Guidelines of this design process were components modularity and manufacturing simplicity. Simple analytical models were applied to verify all the components. The manufacturing process of the prototype was designed in order to exploit standard industrial technologies which could be the basis for a future scaling up of the product. Finally, a cost analysis was performed pointing out the existing margins of cost lowering for future production series.File | Dimensione | Formato | |
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2022_07_Cristani_executive_summary.pdf
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2022_07_Cristani_Thesis.pdf
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https://hdl.handle.net/10589/190153