Design of High Speed Rotary Valves for Pneumatic Applications

Valves based on rotating geometry have long been sought by designers for their simplicity, compactness, and desirable dynamic properties. Unfortunately, they generally involve tight sealing surfaces with significant relative motion, making them particularly prone to problems of wear, leakage, and seizure. These inherent weaknesses are easily overcome in applications involving low pressures or low actuation speeds but become more significant in applications with high pressures and/or high speeds. In this paper, a new high speed, high pressure rotary valve design for an experimental reciprocating compressor-expander is presented. A physical prototype is created, and leakage and valving experiments are performed. Sealing performance is verified and shown to be on the order of piston ring leakage, making it suitable for compressor use. Although not intended for combustion applications, it is possible that a modified version of this design could function in that capacity. As shown, this design is useful in pneumatic applications in which temperatures are lower and oil leakage is tolerable.