The Measurement of Turbomachinery Stator-to-Drum Running Clearances

Abstract

The clearance between a compressor or turbine case and rotating blades or shrouds has been measured in a variety of ways over the years with varying degrees of accuracy. However, one critical clearance which has defied active measurement heretofore has been that between the tip of a cantilevered stator vane and an adjacent drum rotor. A significant number of turbomachines under development, representing many millions of dollars, have met an inglorious end through unanticipated rubs which were experienced in this area. The present paper describes how a device which was introduced by its manufacturer for conventional rotor tip or shroud clearance measurements was applied to measure stator-vane-to-drum clearance. The installation technique is explained, and the results of vane-to-drum measurements made with a research compressor are presented. Adaptations of the same technique should permit similar measurements to be made within a turbine, and possibly on rotating seals buried deep within a turbomachine.

A High Speed Capacitance Based System for Gauging Turbomachinery Blading Radius During the Tip Grind Process

“…(1) An electromechanical measurement system originally developed by Davidson et al [1983] has been successfully used for over five years on manual grinding machines to enable bladed rotors to be machined to an accuracy of +0.025 mm on radius.…”

“…A Stepper Motor driven Probe (an SMP) utilising a spark/discharge principle of operation was originally developed by Davidson et al [1983] for clearance measurement in gas turbines. The development of a miniaturised SMP and a detailed description of its principle of operation are given by Sheard & Turner [1992].…”

Development of the PGT 25 High Efficiency Gas Turbine: Part 3 — Experimental Program and Testing

“…20). (10) Each system comprises a capacitive transducer, an electronically controlled actuator and a bent adaptor that connects the actual probe to the actuator. The transducer is formed of two concentric, mutuallyinsulated, electrodes, the inside of which is the probe electrode.…”

Design, Fabrication and Testing of a High-Sensitive Fibre Sensor for Tip Clearance Measurements

“…Microwave sensors are robust and insensitive to contamination, but the hollow waveguides at submillimeter wavelengths are impractical, and the corresponding circuitry complex [ 16 , 17 ]. Finally, electromechanical systems belong to the oldest tip clearance measurement systems [ 18 ]. They benefit from their high resolution over the entire measurement range, but their main drawbacks are that they only measure the clearance of the longest blade and the slow response time.…”