Modelling and optimization of rotary vane seals

The present study deals with the formulation of the mechanics and elastohydrodynamics, and performance of composite vane seals of rectangular cross-section and goalpost shape, such as those used in rotary vane actuators in aviation, automotive, and industrial applications. After constructing the mathematical and computational model of such seals, results are obtained for an application involving a rotary vane actuator for aircraft wing control surfaces. Examples are presented for both steady-state and transient conditions (steady and unsteady motion). These are followed by an extensive parametric study to establish the effects of various parameters on sealing performance, such as the effects of the seal interferences, sealed pressure, speed, design clearances, operating temperature, and the degree of lubricant starvation. Sealing performance is assessed on the grounds of the mass leakage rate, hydrodynamic friction force and extrusion size during operation. The parametric study resulted in the construction of 144 diagrams with 432 performance curves in total. Based on this, the design and operational sealing parameters were optimized to maximize sealing performance, that is, to minimize leakage, friction, and extrusion. There was an excellent agreement between the theoretically derived optimum values and those recommended semi-empirically by the seal and actuator manufacturers as initial estimates. The parametric study showed that vane seals are objects of complex mechanical behaviour, requiring attention to details in their design and application, not only to maximize performance, but, primarily, to establish sufficient sealing and avoid premature failure that could prove very costly indeed.