Renewable energy sources are increasingly gaining importance among the power production sector nowadays and are expected to continuously establish themselves in the years to come. Fossil fuel power plants are progressively employed as peaking plants, gradually substituted by renewable power sources to fulfill base load energy demand, a task historically entrusted to the former. Moreover, coal-fed plants are being replaced with NG fueled systems, to pursue a decarbonization process. This is enhanced by means of specific policies such as the implementation of a Carbon Tax, whose value is expected to grow in the years to come. Simultaneously NG fuel cost is forecast to progressively decrease, making interesting the option to generate power by means of NGCC, at times working in Open Cycle configuration in order to have a flexible and reliable power plant. The present work focuses on the CFD analysis of the thermal release from the by-pass stack situated in a CC. The two power plant stacks are designed with different heights, namely a higher HRSG tower and a lower by-pass tower. This solution is adopted in order to reduce the amount of material required for the construction of the by-pass stack, inducing a remarkable cost reduction. The objective of the study is to perform a technical and economic analysis and identify the ideal height for the by-pass tower, considering a sensitivity analysis on its height. The economic aim is to reduce costs as much as possible. The technical aim is to study the trajectory and cooling pattern of hot flue gas emitted by the by-pass stack, in the case in which an external wind condition pushes the plume in the direction of the higher HRSG stack. The thermal profile of flue gas is surveyed by means of a CFD analysis in order to evaluate the temperature reached by gas hitting the upwind external surface of the HRSG tower and establish whether or not they cool down below the material safety temperature - in order not to damage them. The CFD study is performed on a student version of ANSYS Fluent 2019 R2 software. The outcomes prove that either during nominal operating conditions and at the minimum environmental load, considering a summertime or winter ambient temperature, flue gas impact the HRSG external surface below the safety temperature limit. The thesis work was performed in partnership with Enel S.p.A. .
Le risorse energetiche rinnovabili stanno progressivamente acquisendo importanza al giorno d'oggi nel settore di produzione dell'energia ed è prevista una loro continua affermazione negli anni a venire. Gli impianti alimentati a combustibili fossili sono sempre più utilizzati per la copertura dei picchi della richiesta energetica, gradualmente sostituiti dalle fonti rinnovabili che si occupano di gestire il carico di base, un compito storicamente affidato ai primi. Inoltre gli impianti alimentati a carbone sono sostituiti da sistemi alimentati a GN, in un'ottica di progressiva decarbonizzazione. Questo processo è favorito dall'adozione di determinate politiche, come ad esempio l'implementazione della Carbon Tax, per la quale si prevede un aumento di imposta nei prossimi anni. Parallelamente il costo del GN diminuirà gradualmente, rendendo interessante l'opzione di produrre energia per mezzo di NGCC, talvolta operanti in ciclo aperto così da avere un impianto flessibile e sempre disponibile. Il lavoro di tesi si focalizza sull'analisi CFD del rilascio termico dal camino di by-pass di un CC. I due camini dell'impianto sono stati progettati con differenti altezze, ovvero un camino del GVR più alto rispetto al camino di by-pass. Tale soluzione è adottata per ridurre la quantità di materiale richiesta per la costruzione del camino più basso, con una conseguente significativa riduzione nei costi. L'obiettivo dello studio è condurre un'analisi tecnico-economica ed identificare l'altezza ideale per il camino di by-pass, considerando un'analisi di sensitività sulla sua altezza. L'intento economico è ridurre il più possibile i costi. Lo scopo tecnico è studiare la traiettoria ed il profilo di raffreddamento dei gas emessi ad alta temperatura dal camino di by-pass, nel caso in cui una condizione di vento esterno sospinga il pennacchio esattamente nella direzione del camino del GVR. Il profilo termico dei gas di scarico è ispezionato mediante un'analisi CFD con lo scopo di valutare la temperatura raggiunta dai gas che colpiscono la superficie esterna della torre del GVR e stabilire se essi si raffreddano al di sotto della temperatura di sicurezza dei materiali, evitandone il danneggiamento. Lo studio CFD è stato condotto su una versione accademica del software ANSYS Fluent 2019 R2. I risultati mostrano che sia in condizioni operative nominali sia al minimo tecnico ambientale i gas impattano la superficie del camino più alto con una temperatura inferiore rispetto a quella limite. Il lavoro è stato svolto in collaborazione con Enel S.p.A. .
CFD analysis of the thermal release from the by-pass stack of an H-class gas turbine
Carbotti, Filippo
2019/2020
Abstract
Renewable energy sources are increasingly gaining importance among the power production sector nowadays and are expected to continuously establish themselves in the years to come. Fossil fuel power plants are progressively employed as peaking plants, gradually substituted by renewable power sources to fulfill base load energy demand, a task historically entrusted to the former. Moreover, coal-fed plants are being replaced with NG fueled systems, to pursue a decarbonization process. This is enhanced by means of specific policies such as the implementation of a Carbon Tax, whose value is expected to grow in the years to come. Simultaneously NG fuel cost is forecast to progressively decrease, making interesting the option to generate power by means of NGCC, at times working in Open Cycle configuration in order to have a flexible and reliable power plant. The present work focuses on the CFD analysis of the thermal release from the by-pass stack situated in a CC. The two power plant stacks are designed with different heights, namely a higher HRSG tower and a lower by-pass tower. This solution is adopted in order to reduce the amount of material required for the construction of the by-pass stack, inducing a remarkable cost reduction. The objective of the study is to perform a technical and economic analysis and identify the ideal height for the by-pass tower, considering a sensitivity analysis on its height. The economic aim is to reduce costs as much as possible. The technical aim is to study the trajectory and cooling pattern of hot flue gas emitted by the by-pass stack, in the case in which an external wind condition pushes the plume in the direction of the higher HRSG stack. The thermal profile of flue gas is surveyed by means of a CFD analysis in order to evaluate the temperature reached by gas hitting the upwind external surface of the HRSG tower and establish whether or not they cool down below the material safety temperature - in order not to damage them. The CFD study is performed on a student version of ANSYS Fluent 2019 R2 software. The outcomes prove that either during nominal operating conditions and at the minimum environmental load, considering a summertime or winter ambient temperature, flue gas impact the HRSG external surface below the safety temperature limit. The thesis work was performed in partnership with Enel S.p.A. .| File | Dimensione | Formato | |
|---|---|---|---|
|
Tesi_Carbotti.pdf
accessibile in internet per tutti
Descrizione: CFD Analysis of the Thermal Release from the By-pass Stack of an H-Class Gas Turbine
Dimensione
5.21 MB
Formato
Adobe PDF
|
5.21 MB | Adobe PDF | Visualizza/Apri |
I documenti in POLITesi sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
https://hdl.handle.net/10589/165281