Rotor unit assembly

A rotor unit assembly, comprising:

• a wall section of a housing which defines a chamber having a central axis and an inner surface, and the housing comprises an end plate to close the chamber, wherein the endplate defines a low pressure port, a first high pressure port, and a second high pressure port;
• a rotor located within the chamber and rotatable about the chamber central axis, the rotor having
• a main body having an outer surface, the outer surface being spaced apart from the wall section inner surface to define a clearance volume,
• a piston which extends radially outward from the main body, and
• a valve flange which extends radially from the main body, with an aperture provided in the valve flange;
• and
• a rotatable hub rotatable about a hub axis, with a cavity which extends radially inward from a hub outer surface, wherein the cavity is configured to receive the piston;
• wherein
• when the first high pressure port is open, the piston forms a seal with the inner surface of the chamber,
• when the second high pressure port is open, the piston is engaged with the cavity to provide a seal between the piston and the wall of the cavity,
• the wall section defines an opening having a first edge spaced apart from a second edge through which the hub extends to seal against the rotor, a seal being provided between the hub outer surface and the edge of the opening, and
• the cavity is configured to be isolated from the clearance volume when the piston has moved D degrees around the inner surface of the chamber away from the second edge of the opening through which the hub extends, to define an expansion region of the clearance volume between the piston and the hub, the expansion region thereby isolated from a remainder of the clearance volume, where D has a value of at least 8 but not more than 16.

A rotor unit assembly, comprising:

• a wall section of a housing which defines a chamber having a central axis and an inner surface, and the housing comprises an end plate to close the chamber, wherein the endplate defines a low pressure port, a first high pressure port, and a second high pressure port;
• a rotor located within the chamber and rotatable about the chamber central axis, the rotor having
• a main body having an outer surface, the outer surface being spaced apart from the wall section inner surface to define a clearance volume,
• a piston which extends radially outward from the main body, and
• a valve flange which extends radially from the main body, with an aperture provided in the valve flange;
• and
• a rotatable hub rotatable about a hub axis, with a cavity which extends radially inward from a hub outer surface, wherein the cavity is configured to receive the piston;
• wherein the first high pressure port, the second high pressure port, and the low pressure port are in fluid communication with a manifold;
• wherein the low pressure port is in fluid communication with a low pressure chamber of the manifold;
• wherein the first high pressure port and second high pressure port are in fluid communication with a high pressure chamber of the manifold;
• and
• wherein the low pressure chamber and high pressure chamber are separated from one another such that the low pressure chamber and the high pressure chamber are fluidly isolated from one another.