Gas turbine engine with an arrangement for measuring the shaft rotation speed

Abstract

A gas turbine engine includes an arrangement for measuring shaft rotation speed, including a laser source ( 10 ) for directing a laser beam ( 11 ) onto portions of rotor blades to either be reflected from or interrupted by the rotor blades to create light impulses as a function of the rotor rotation rate. A receiver diode ( 12 ) receives the light impulses and generates voltage impulses corresponding to the rotor or shaft rotation rate. An evaluation unit associated with the receiver diode measures the number of the voltage impulses generated per unit of time and calculates therefrom the rotation speed of the engine shaft connected to the rotor. The measurement arrangement is arranged in the engine housing to be easily accessible for mounting, maintenance and adjustment, is functionally reliable under robust engine operation and can detect the rotation of a low pressure shaft and connected fan.

1 . A gas turbine engine, comprising:
 an engine housing;   an engine shaft at least partly positioned within the engine housing;   a plurality of bladed rotors positioned within the engine housing and connected to the engine shaft;   a plurality of stators interspersed between the rotors;   an arrangement for measuring a rotation speed of the engine shaft, comprising:
 a laser source attached to the engine, for generating a laser beam toward portions of the rotating rotor blades to create light impulses having a frequency as a function of a rotation speed of the rotor; 
 a receiver diode attached to the engine for receiving the light impulses and generating voltage impulses corresponding to the rotation speed of the rotor; 
 an evaluation unit associated with the receiver diode for counting the voltage impulses and for calculating the rotation speed of the engine shaft. 
   
     
     
         2 . The gas turbine engine of  claim 1 , wherein the laser source and the receiver diode are arranged angled to each other in an engine housing section adjoining the blade tips, so that the laser beam is reflected from tips of the blades as light beams toward the receiver diode. 
     
     
         3 . The gas turbine engine of  claim 2 , wherein the laser source and the receiver diode are arranged in a wall recess of the engine housing. 
     
     
         4 . The gas turbine engine of  claim 3 , wherein the bladed rotor is a fan of the engine, the engine shaft is a low pressure shaft and the engine housing is a fan housing surrounding the fan. 
     
     
         5 . The gas turbine engine of  claim 1 , wherein the respective laser source and the respective receiver diode are aligned with respect to each other so that the laser beam is directed to pass between the rotor blades toward the receiver diode such that the rotating rotor blades interrupt the laser beam to create the light impulses impinging onto the receiver diode. 
     
     
         6 . The gas turbine engine of  claim 1 , wherein the laser source and the receiver diode are mounted respectively lying opposite on a stator arranged downstream and upstream of a rotor, wherein light impulses either passing through between the rotor blades or reflected therefrom impinge onto the receiver diode. 
     
     
         7 . The gas turbine engine of  claim 1 , wherein the laser source and the receiver diode are mounted jointly on a stator situated one of upstream and downstream from the rotor so that the receiver diode respectively receives light impulses reflected from the rotor blades. 
     
     
         8 . The gas turbine engine of  claim 1 , wherein the receiver diode is at least one of a photodiode and an optical sensor. 
     
     
         9 . The gas turbine engine of  claim 1 , and further comprising a filter associated with the receiver diode for filtering out intrusive light. 
     
     
         10 . The gas turbine engine of  claim 1 , wherein the bladed rotor is a fan of the engine, the engine shaft is a low pressure shaft and the engine housing is a fan housing surrounding the fan. 
     
     
         11 . The gas turbine engine of  claim 2 , wherein the bladed rotor is a fan of the engine, the engine shaft is a low pressure shaft and the engine housing is a fan housing surrounding the fan.