Segment V12.5: Dental Drill

(Related to Textbook Section 12.8.1 - Impulse Turbine)

In an impulse turbine, there is essentially no pressure drop across the turbine rotor. The pressure drop occurs in the nozzles just upstream of the rotor and produces the high speed jet that impinges upon the rotor.

A dental drill is driven by a small diameter, high speed impulse turbine. Because of the small diameter of the rotor, the angular velocity must be very large (i.e., 300,000 rpm) if the blade speed is to be of the same order as the air speed from the nozzles. Small, precision ball bearings and precise machining of the rotor are needed.