Transfer function identification of POGO system device
Résumé
The future developments of the Ariane rockets make it necessary to improve the modeling of hydraulic behavior of cryogenic engines. For this, experimental studies of pressure and mass flow rate fluctuations at the inlet and the outlet of hydraulic components are needed to estimate their dynamic transfer functions. The present study concerns the POGO phenomenon observed in the rockets engines. This phenomenon is related to the interactions between the engine’s thrust fluctuations, the flow rate and pressure oscillations of the power supply and the modal vibration of the rocket structure. To control the system stability, two hydraulic components are important: the LOX turbo pump and the corrective system POGO (also named POGO accumulator, which should absorb the hydraulic dynamic fluctuations).The article presents the corrective system POGO, as well as the identification methodology of the characteristic transfer functions applied. Experimental study has been performed in the CREMHyG’s hydro-acoustic test rig, with POGO accumulator geometries developed by SNECMA. Several configurations at different operating points have been tested. Experimental results have been compared to models and theoretical approaches available. An analogy with classical hydraulic accumulator has been also proposed. This work is the first step of a study aiming to more complex hydraulic systems analyses, associating the turbo pump and the POGO accumulator.