Manufacturing of a Radial Inflow Turbine for Microgas Turbine in a 3 Axis CNC Milling Machine

A micro gas turbine impeller is a highly challenging component to fabricate given the stringent tolerance requirements. This paper highlights and reports a novel process to machine and fabricate a SS 304 impeller using a 3 axis cnc milling machine with minimum usage of job overhead. The impeller chosen to demonstrate this process is a 12 vaned impeller with outside diameter of 110 mm with an elliptical hub surface and constant radius circular shroud surface. The blade thickness varies from 1.6 mm at tip and 3.5 mm at hub. The intersection region of the blade with the disk has a uniform fillet radius of 1.5 mm. The blade exit height is 16 mm. Blades are not perpendicular to the hub surface, intersecting angle is changing as you move down the blades. The height of the blade varies from exducer to inducer is 4.5 times. It is seen that a considerable saving in time and effort without a compromise on the dimensional tolerances is obtained with the above procedure.