Analyse des vibrations et des instabilités de fonctionnement dans les turbines-pompes

¹ Ingénieurs Alsthom-Neyrpic, Grenoble
² Ingénieur, Bergeron S.A., Paris

Résumé

The hydraulic design and non-optimal operating characteristics of pump turbines differ appreciably in some respects from those of conventional turbines or pumps. To design these machines, one must know the unsteady hydrodynamic forces acting on the guide vanes or runner blades, especially at transient operating conditions. Like conventional turbomachines, these reversible machines are expected to give long, trouble-free operation and to require minimum development and maintenance.The authors analyse the hydrodynamic forces acting on these machines, especially unsteady forces liable to cause hydroelastic vibration. The main results of pump performance measurements for operation outside the optimum ranges (energy dissipation runaway condition, etc.) are discussed, also the possibility of flutter, stall flutter, buffeting or resonance occurring at these conditions. The analysis was based on theoretical blade cascade vibration research results applicable to the considered problems. Much additional knowledge on the subject of hydrodynamic vibration in turbomachines has been obtained from tests on models and large turbosets in operation. An extensive test programme is also in progress on prototypes. With our present knowledge and experience in producing turbines for very high outputs, we are in an excellent position to consider producing very large pump-turbines.