Optimisation du carénage d’aube de turbine intégré dans la phase de conception préliminaire

Abstract

The turbine blade shroud increases the aerodynamic efficiency of the rotor by reducing the leakage flow at the blade tip. The larger the shroud, between the leading and trailing edges, the more the flow is weakened, but the greater the mechanical stresses. Two stresses in particular are impacted: the stress concentration in the fillet of the connection between the shroud and the blade and the stress on the tip surface of the blade due to the mass of the rotating shroud. To reduce this first stress it is possible to increase the value of the fillet, however this increases the mass at the blade tip and therefore the associated stress. In this context, this master work has allowed the development of a method to quickly evaluate an optimal point, for the values of the size of the shroud and the fillet, respecting the associated stress, and this for any model of rotor having a shrouded blade. This method is adapted to the development framework, i.e. the preliminary design automation software environment implemented at Pratt & Whitney Canada. The process is as follows: from rotor geometry, the algorithm performs several mechanical analyses in CATIA, allowing interpolations to be performed and the space of admissible assemblies to finally extract the point corresponding to the largest shroud size. The simulations are based on lighter rotor geometry: the blade and its shroud. The results of these simulations were compared with the results obtained with the usual procedure: the relative deviations do not exceed 4%, which is satisfactory for the preliminary design phase. In addition, the time saved is considerable: 10 minutes for the usual process as opposed to 1 minute for the lighter simulations. The process developed shows that a local and targeted dimensioning, limiting the number of parameters and constraints, responds quickly and precisely to the problem. However, the choice of variable parameters is crucial, hence the importance of the study of the influence of the parameters presented in this paper. This optimization method contributes to the preliminary design phase of the shroud to reduce the design time and gain in accuracy while ensuring the robustness of the process.

Date	3 Aug 2020
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Saïd Hany Moustapha (Supervisor) & Marlène Sanjosé (Co-supervisor)