Abstract: A liquid-sealed vane oscillator includes a housing defining a cavity corresponding to part of a virtual annulus centered around, and extending at least 180.degree. about, an axis of rotation and delimited by first and second ends. A vane is mounted rotatably within the cavity. The vane includes a first seal and a second seal carried with the vane and deployed so as to subdivide the cavity into a first chamber of variable volume between the first end and the first seal, a second chamber of variable volume between the second end and the second seal, and an intermediate volume between the first seal and the second seal. At least one port is provided in fluid communication with each of the first and second chambers. The oscillator also has an axial shaft, penetrating and extending from the cavity, which is mechanically coupled to the vane so as to allow exchange of mechanical power with an external device.