The present thesis work discusses the execution and the results of an experimental campaign where independent measurements of temperature, pressure and velocity are made in a non-ideal high temperature compressible flow. The investigation has been carried out on the Test Rig for Organic VApors (TROVA), located at the Laboratory of Compressible fluid-dynamics for Renewable Energy Applications (CREA Lab). The Laser Doppler Velocimetry (LDV) technique has been implemented and adopted to directly measure the velocity of an expanding non-ideal flow of organic vapor, representative of those occurring in Organic Rankine Cycle (ORC) applications. The tested fluid is the siloxane MM (Hexamethyldisiloxane), a high molecular complexity organic compound, widley used in high temperature ORCs. Depending on the test operating conditions, the fluid under scrutiny expands in a converging or in a converging-diverging noozle, starting from non ideal condition and, because of the blow down nature of the TROVA, ending in an almost ideal condition. In order to properly inseminating the flow, to perform the LDV measurement, a suspension of tracer particles (titanium dioxide) is injected ahead of the noozle inlet, without altering the flow properties. Due to the flow thermodynamic conditions, the spray evaporates leaving the titanium dioxide particle free to follow the current. The provided measurements of pressure, temperature and velocity allow a complete assessment of CFD for non-ideal flows, making this work one of the first complete characterization of the thermo-fluid dynamic of these flows.
Il presente lavoro di tesi illustra l'esecuzione ed i risultati di una campagna sperimentale dove misure indipendenti di temperatura, pressione e velocità sono state effettuate in un flusso comprimibile non ideale ad alta temperatura. La ricerca è stata svolta sul TROVA (Test Rig for Organic VApors), situato presso il laboratorio CREALab (Laboratory of Compressible fluid dynamics for Renewable Energy Applications) del Politecnico di Milano. La tecnica LDV (Laser Doppler Velocimetry) è stata implementata e adottata per misurare direttamenta la velocità di un flusso non-ideale rappresentativo dei canali interpalari delle turbine per Cicli Rankine Organici (ORC). Il fluido testato è il silossano MM (Esametildisilossano), un composto organico ad alta complessità molecolare, largamente usato in applicazioni ORC ad alte temperature. In base alle condizioni operative dei test, il fluido espande in un ugello convergente o convergente-divergente, partendo da una condizione termodinamica non ideale a inizio test, per poi terminare in condizioni di fluido ideale. Per inseminare correttammente il flusso, in modo da effettuare le misurazioni LDV, una sospensione di particelle traccianti (diossido di titanio) è iniettata a monte dell'ugello, senza alterarne le proprietà. La fase liquida dello spary evapora grazie alle condizioni termodinamiche del flusso analizzato e le particelle di tracciante sono lasciate libere di seguire la corrente. Le misurazioni fornite di pressione, temperatura e velocità consentono una valutazione completa dei modelli CFD per flussi non ideali, consentendo una delle prime caratterizzazione complete della termofluidodinamica in questo tipo di flussi.
Direct velocity measurements in non-ideal high temperature flows
PEDRANA, MARCO
2018/2019
Abstract
The present thesis work discusses the execution and the results of an experimental campaign where independent measurements of temperature, pressure and velocity are made in a non-ideal high temperature compressible flow. The investigation has been carried out on the Test Rig for Organic VApors (TROVA), located at the Laboratory of Compressible fluid-dynamics for Renewable Energy Applications (CREA Lab). The Laser Doppler Velocimetry (LDV) technique has been implemented and adopted to directly measure the velocity of an expanding non-ideal flow of organic vapor, representative of those occurring in Organic Rankine Cycle (ORC) applications. The tested fluid is the siloxane MM (Hexamethyldisiloxane), a high molecular complexity organic compound, widley used in high temperature ORCs. Depending on the test operating conditions, the fluid under scrutiny expands in a converging or in a converging-diverging noozle, starting from non ideal condition and, because of the blow down nature of the TROVA, ending in an almost ideal condition. In order to properly inseminating the flow, to perform the LDV measurement, a suspension of tracer particles (titanium dioxide) is injected ahead of the noozle inlet, without altering the flow properties. Due to the flow thermodynamic conditions, the spray evaporates leaving the titanium dioxide particle free to follow the current. The provided measurements of pressure, temperature and velocity allow a complete assessment of CFD for non-ideal flows, making this work one of the first complete characterization of the thermo-fluid dynamic of these flows.| File | Dimensione | Formato | |
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2020_04_Pedrana.pdf
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https://hdl.handle.net/10589/154384