An experimental centrifugal compressor is fitted with free-vortex guide vanes to reduce the relative air speed at inlet to the impeller. At the outer radius of the eye, air leaving the guide vanes has a velocity of 91.5 m/s at 20 to the axial direction. Determine the inlet relative Mach number, assuming frictionless flow through the guide vanes, and the impeller total-tototal efficiency. Other details of the compressor and its operating conditions are:

Radial vanes at impeller exit

Radial vanes at impeller exit

Impeller entry tip diameter, 0.457 m;

Impeller exit tip diameter, 0.762 m;

Slip factor, 0.9 radial blades at impeller exit;

Radial component of velocity at impeller exit, 53.4 m/s;

Rotational speed of impeller, 11,000 rev/min;

Static pressure at impeller exit, 223 kPa (abs).