Avco Corporation

Alan R Duly

Zoltan L Libertini

Steven D White

A probe is constructed for placement in the hot turbine section of a gas turbine engine. A housing containing two electrodes extends through the turbine shroud into the tip clearance area of the turbine rotor. A voltage impressed across the electrodes will generate an electric field in the vicinity of the turbine blades which will be distorted as the blades pass, thereby generating a charge pulse at the output of the probe. The electrode conductors are imbedded in pins which are retained by insulating rings brazed in place. The electrodes extend slightly outward from the surrounding insulating surfaces to create an air gap around each electrode. This air gap provides additional insulation and prevents contamination.

Electrode structure for a high temperature capacitance probe for sensing

Apparatus is disclosed for the noncontact measurement of the clearance between the blade tips of a rotating turbine and the surrounding housing. Blade tip clearance is measured by placing a capacitance probe in the housing wall. The probe consists of two metallic conductors insulated one from the other and arranged to form the plates of a capacitor. Passing of a blade tip in close proximity to the two plates of the probe changes its capacitance. Electronic circuitry measures the change in capacitance and hence the clearance between blade tip and probe. Use of a balanced type input avoids the need for a ground return path and enables the use of a long sensor cable without degradation of results.

Growing community of inventors

Huntington, CT, United States of America

Alan R Duly