The current work focuses on the flow capacity and efficiency analysis and modelling of twin-entry radial turbines under unequal admission conditions. These conditions are the most common in real operation, so they must be properly assessed. A thorough analysis of the flow patterns I would like to thank Antonio Gil and Pau Raga for their assistance in the CFD meshing. Also, Rafael Carrascosa, Ali Abbad, Adolfo Guzmán "Fito", Valentín Ucedo and Miguel Ángel Ortiz for helping me to perform reliable experimental measurements and Amparo Cutillas for her never-ending assistance with all the paperwork. I would also acknowledge Andrés Tiseira and José Ramón Serrano for their advice during these years. Specially, I would like to thank my fellow PhD students Pau, Alberto, Lucas, Fabio, Juancho, Miguel Ángel, Guille and Miguel for making my daily work more enjoyable and support me in the best and worst moments.I would like to acknowledge Gianluca Montenegro and all the staff at the Dipartimento di Energia for receiving me and make me feel like I was in home during my doctoral stay at Politecnico di Milano.Finally, the people that more deserve my gratitude are my parents, my brother, my grandmothers and all my family. They have always supported me in all decisions I've made and this PhD thesis could not be concluded without them. Also, I wish to thank all my friends, specially Sergio, Inés and Paula, for giving me the energy I needed to finish this work. ix