A Magnetic-Fluid Seal for Measurement of Aerodynamic Surface Pressure.

摘要

A magnetic-fluid sliding seal was designed, fabricated, and tested for application in a special instrumentation arrangement to measure the aerodynamic surface pressure on a spinning wind tunnel model. The seal was intended to provide a low-friction, airtight linear seal between stationary and rotating model components. A series of laboratory tests was conducted to evaluate the performance of the seal in relation to anticipated wind tunnel test conditions and possible model configurations. These tests involved measuring the maximum pressure that the seal was capable of holding a various model spin rates. The effects of certain seal parameters were investigated including: gap distance between stationary and moving components, magnetic-fluid properties (i.e., magnetization strength and viscosity), and ferrous versus nonferrous moving component material. These tests demonstrated that the seal was capable of holding a nominal pressure of 1 psi at a maximum sustained spin rate of 1250 rpm. This relates to a relative velocity between the moving and stationary components of 27 ft/sec. Higher pressures could be held at lower sustained spin rates and even under impulsive rotational conditions. The current seal design would appear to be applicable for this wind tunnel test techniques where extremely low friction is required. However, it would be limited to spin rates under 1000 rpm. Design trends are indicated to increase the seal performance for future applications. (Author)