Proximity sensing

Claim 2

A turbine blade proximity indicating system for providing an indication of the proximity of blades of a turbine to a reference location, the system being of the kind including probe means, means mounting said probe means with the turbine, and a microwave oscillator that supplies microwave energy to said probe means, the improvement wherein said probe means is positioned and operative to direct propagating microwave energy towards the blades of the turbine and to receive microwave energy reflected by said blades, said system including means mounted remote from said probe means for mixing microwave energy reflected from said blades with microwave energy reflected from a part of said probe means, the said mixing means being operative to produce interference dependent upon the phase difference between the energy reflected by said blades and the energy from said probe means, and said system including means responsive to said phase difference for deriving an indication of the proximity of the blades to the reference location.

Claim 3

A system according to claim 1, wherein said mixing means includes a magic tee assembly.

Claim 4

A system according to claim 1, wherein said system includes a circuit that compares a first output, derived when said blades are positioned such that said probe means receives energy reflected from the blades, with a second output, derived when the said blades are positioned such that the probe means receives substantially no energy reflected from the blades.

Claim 5

A system according to claim 1, wherein said system includes two detectors, and means mounting said detectors in spaced relation to one another so as to provide signals that are in quadrature with one another, said system including a divider circuit, and means supplying signals derived from said two detectors to said divider circuit.

Claim 8

A system according to claim 1, including a microwave reflector post, and solenoid means moveably mounting said microwave reflector post intermediate the end of said probe means and said microwave oscillator, said solenoid means being actuable to move said microwave reflector post to a position in which said microwave reflector post reflects microwave energy to said mixing means for comparison with microwave energy from said probe means.

Claim 9

A system according to claim 1, including an assembly surrounding said turbine blades, actuator means, and means supplying signals in accordance with said indication of proximity to said actuator means to cause said actuator means to control the proximity of said turbine blades to said surrounding assembly.

Claim 10

A system according to claim 7, wherein the internal diameter of said surrounding assembly varies along its length, said system including means mounting said surrounding assembly for displacement along its length, and means coupling said actuator means to said surrounding assembly such that said actuator means controls said proximity by displacing the assembly along its length.

Claim 15

A gas-turbine engine system comprising: a turbine including turbine blades, an outer assembly, and means mounting said outer assembly in close proximity with the outer tips of said blades; and means for controlling the clearance between said blades and said outer assembly comprising: probe means, means mounting said probe means with said outer assembly to direct propagating microwave energy towards said blades and to receive microwave energy reflected by said blades, oscillator means supplying microwave energy to said probe means, means mounted remote from said probe means that mixes microwave energy reflected from said blades with microwave energy reflected from a part of said probe means, the mixing means being operative to produce interference dependent on the phase difference between the energy reflected by said blades and the energy from said probe means, means responsive to said phase difference for deriving an indication of the proximity of the blades to the probe means, and actuator means for displacing said outer assembly relative to said blades in accordance with said indication of proximity.

Claim 16

A gas-turbine engine system comprising: a turbine including turbine blades, an outer assembly, and means mounting said outer assembly in close proximity with the outer tips of said blades; and means for controlling the clearance between said blades and said outer assembly comprising: probe means, means mounting said probe means with said outer assembly to direct propagating microwave energy towards said blades and to receive microwave energy reflected by said blades, oscillator means supplying microwave energy to said probe means, means mounted remote from said probe means that mixes microwave energy reflected from said blades with microwave energy reflected from a part of said probe means, the mixing means being operative to produce interference dependent on the phase difference between the energy reflected by said blades and the energy from said probe means, means responsive to said phase difference for deriving an indication of the proximity of the blades to the probe means, and actuator means for displacing said outer assembly relative to said blades in accordance with said indication of proximity.

Claim 17

A system according to claim 1, wherein the said part of the probe means is the tip of the probe means.