Objectives  Buoyancy regulating system is a key component of an underwater glider for controlling submerging and surfacing statuses and gliding speed of the underwater glider. To further study the buoyancy regulating system,

  Methods  we carry out theoretical analysis and CFD for the underwater glider and its buoyancy regulating system to obtain the buoyancy regulating value, which is an important design parameter; develop a buoyancy regulating system with both oil outlet and oil return passages, that is, a high-pressure plunger pump for oil outlet in deep water and a low-energy gear pump for oil return in shallow water. We conduct the tests for the oil outlet and oil return characteristics and the energy consumption under different pressure conditions.

  Results  The results show that the oil outlet is normal under the pressure of 2.5 MPa and the oil return is normal under atmospheric pressure. The developed test device can simulate the marine pressure in the actual operating environment of the underwater glider.

  Conclusions  The study results can provide useful references for the engineering application of the buoyancy regulating system.