Studio e verifica delle performance di shroud block di turbina con ottimizzazione della geometria tramite analisi 3D CFD

Today gas turbines are subject of continuous studies aimed at optimizing performances, safety, reliability and efficiency. The current activity is carried out by a collaboration between the Politecnico of Torino and Ethos Energy Italia S.p.A., independent service provider working in the gas turbine field, operating also in design, maintenance and repair. The purpose of this thesis is to model leakage losses in correspondence of a gas turbine 1^st stage between stator and rotor, and to optimize the casing of the stator unit with the aid of\textit{ grooved shroud}, through Computational Fluid Dynamic (CFD) simulations. The grooved shroud, consisting of precisely engineered channels on the shroud surface, aims to control tip leakage flow and reduce mass flow losses. The abradable coating, applied to the shroud surface, allows for controlled wear during operation, maintaining an optimal clearance between the blade tip and shroud while accommodating thermal expansion and rotor dynamics. Through a series of closely spaced grooves, the new shroud create a path for the gas, reducing leakages from high-pressure to low-pressure areas. The efficiency of the grooves is strictly connected to their design, studied with the aim to induce turbulence and swirling in the gas, to break up the flow and dissipate the energy of the escaping gas. The thesis is divided in two parts. The first part is about the study of different configurations: one is a smooth stator layout and other is characterized by the presence of two different grooved shroud. First a sensitivity analysis is performed on the configuration without the sealings to guarantee the absence of any grid influence. Then, the second step of the analysis is followed by CFD simulations on the different cases to assess the grooved shroud effectiveness. The software used for CFD simulations is ANSYS - Fluent R22.2. The outcome of the thesis is the evaluation of performances change on the turbine in the two configurations, with and without the grooved shroud, also considering cooling flow, thus providing a clear overview of the advantages and challenges of this kind of solution.