Leakage and Frictional Characteristics of Turbulent Helical Flow in Fine Clearance

The leakage and frictional characteristics of helical flow in concentric cylinders with fine clearance have been studied for the ratio of clearance to radius from 0.0006 to 0.0127 and the ratio of length to clearance from 20 to 750. The Reynolds number based on the axial velocity was from zero to 10⁴ and the Reynolds number based on the radius and tangential velocity was from 10³ to 3 × 10⁵. These geometrical and kinematical conditions are usually encountered in the seal design of turbomachines. The leakage and the frictional torque have been measured with a 20 in. dia test rig for various pressure gradients and different rotational speeds of the inner cylinder. The case of zero pressure gradient has also been included. The experimental data and those published in the literature have been analyzed and correlated in the form of empirical equations.