Planetary Rotor Concept
The planetary rotor expander involves four helical shaped rotors that interleave in such a way as to create an internal working cavity. Its namesake is derived from rotors (planets) sharing the same circle diameter (shown in red) about a central (sun) output shaft.
One of the many unique features of the design is its ability to self-clean rotor surfaces while in operation. The end view animation, to the right, shows the rotors sweeping past each other, removing any scale or ice build-up that may form from gas impurities such as water vapor. Also, because the rotors never touch they require no lubrication, permitting oil-free, total-flow operation with “wet” or dry gas.
Another benefit is the industry leading high pressure rating of 1,440 psi. Pressure forces from the working cavity push the rotors outward rather than inward, preventing rotor contact. In addition, twice as many rotors provide twice as many bearings to help carry the load.
How it works
High pressure gas enters the working cavity from one end of the expander and begins applying force against the rotors, causing them to rotate. Pressure in the cavity is maintained as it progresses through the stroke until the inlet is closed by the rotors themselves. Gas is then exhausted at the opposite end of the expander at lower pressure having produced work.
Torque is transmitted from the individual rotors to a central output shaft via Helidyne’s proprietary drive train. Because the drive train has zero backlash, it maintains perfect rotor timing and close running clearances for improved efficiency.