A Rotary Union to Provide Active Flow Control to a Mach Scale Rotor

A rotary union was developed and tested that allows for active flow control to be tested on the Army General Rotor Model System (GRMS) Mach scale rotor test stand. The union has a center pass through for the rotor shaft and control links. Three air channels formed by mortised seals allow air transit between the fixed frame and the rotating frame. Each channel can move 10 SCFM at 30 psi with a pressure loss of 0.2 psi. The union torque depends on seal differential pressure. The torque is 11 lbf-ft at 11 psi or 2.5 HP at 1250 RPM which is sufficient for a rotor tip Mach of 0.64. The union was tested on GRMS to 1250 RPM. The seals require differential pressure of 2 psid to engage and at 10 psid the leak rate was less than 0.5 SCFM. Considering future research, a non-dimensional flow control scaling parameter is derived which accounts for Coriolis effects.