Analytical investigation of leakage flow in disk clearance of a magnetically suspended centrifugal impeller

Leakage flow through the disk clearance of a magnetically suspended centrif ugal blood pump is essential for a good washout. An analytical approach, ba sed on the theory of lubrication, is used to predict the leakage volume flo w rate, nondimensional radial velocity, nondimensional mean pressure distri bution, and comparative shear stress distribution for different disk cleara nce geometry under varying rotational speeds. The results showed that nondi mensional mean pressure distribution and nondimensional radial velocity dis tribution along the clearance are independent of rotational speed. The flow through the gap depends on a nondimensional parameter S that denotes the r atio of centrifugal forces to the head generating capability of the impelle r. It was found that an impeller having a lower S has less possibility of f low reversals in the gap, and gap with maximum height at the outside radius also is more susceptible to flow reversals at the impeller surface. The co mparative shear stress within the gap reveals that, in general, the scalar stress is below 500 N/m(2).