Numerical Analysis of a Supersonic Turbine for Novel Propulsion Systems
Tutor / directorGressier, Jérémie
Document typeMaster thesis (pre-Bologna period)
Rights accessRestricted access - author's decision
Current state-of-the-art supersonic turbines have been conceived to work under supersonic ow conditions where the inlet axial velocity is subsonic. For the present case, an extreme ow situation has been studied, where the inlet axial velocity component is supersonic. After the literature, it can be stated that the performance achieved by conventional turbines working under axial supersonic conditions is extremely low (e - ciencies of the order of 27%). As an answer to this challenge, this master thesis presents, for the rst time in the open literature, the aerodynamic performance study of a new supersonic turbine blade design intended to work under inlet axial supersonic conditions. For this purpose, an accurate 3-D Navier-Stokes analysis of the blade performance has been conducted, for both design and o -design conditions . At rst, the in uence of the inlet ow angle on the blade performance at a given Mach number was parametrized through steady-state simulations. In a second step, an implicit time-marching method was used to solve the unsteady Reynolds-Averaged Navier-Stokes equations. This transient analysis of the turbine performance considered a sinusoidal inlet angle variation at a frequency of 100 Hz. Finally, in order to study the in uence of the inlet Mach number on the establishment of supersonic ow within the blade passage, a steady state parametrization of the inlet Mach number for the given geometry was performed. Steady state results highlight important drawbacks on the blade performance due to the nature of the inlet supersonic axial ow. Oblique shocks are created and ingested by the turbine blade passage. As a result, large stagnation losses occur, due to the presence of shocks and its interaction with the blade's boundary layers. By the same way, the transient analysis points out the importance of the frequency at which the inlet conditions vary. As the frequency rises, increasingly signi cant hysteresis-like behaviour of the ow variables is seen at the outlet of the turbine. Finally, the blade passage's converging geometry has remarked the importance of the inlet Mach number in order to correctly establish a supersonic ow within the passage. For the studied geometry, a lower limit on Mach number is identi ed, below which the turbine enters into an unstarted condition, where supersonic ow could not be established in the passage.
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