• test bench
• journal bearings
• banco di prova
• cuscinetti

The present work concerns the realization of a test bench to characterize liquid methane journal bearings. This technology promises a long-term lifetime for the turbopumps used in the launchers, permitting to use the same vector for multiple launches. The test article is a recessed journal bearing designed by the Departement of Civil and Industrial Engineering of Pisa for the European Space Research and Technology Center (ESTEC). The journal bearing is designed to support the shaft of liquid methane turbopump working at 20000 rpm at stationary operating conditions with a predicted bearing stiffness of 36 MN/m. At regime turbopump operating conditions, the journal bearing ensures to balance an estimated maximum static load of 600 N and a synchronous dynamic load having a maximum amplitude of 300 N. Start and stop transient represents the worse operating condition of journal bearings due to shaft tilting related to stick and slip on the bearing hub. So a test bench capable to reproduce the introduced operating conditions is necessary to assest the journal bearing life and load capacity. The test bench selected to accomplish the operating conditions has the test bearing mounted on a shaft supported by two pedestals. The static and dynamic loads are applied to the test article by two piezoelectric actuators using a housing made in AISI 316L. The shaft has been designed to reduce as much as possible the deformation introduced by the application of the loads and to avoid resonance with the rotational motion. During the tests pressure, displacements, and temperatures are monitored using sensors.