Method and apparatus for compressor surge control

Claim 3

A method in accordance with claim 1 including the step of bleeding off a portion of the boundary layer at the compressor outlet back into the compressor inlet in response to detected flow reversal in order to delay the onset of surge.

Claim 4

A method in accordance with claim 1 including the step of operating a back pressure valve in response to detected flow reversal so that the compressor is bypassed by the flowing material prior to the onset of surge.

Claim 5

A method in accordance with claim 1 including the step of operating a back pressure valve in response to detected flow reversal so that high pressures are relieved at the outlet side of the compressor to eliminate flow reversal in the boundary layer and thereby delay the onset of surge.

Claim 6

A method in accordance with claim 2 in which 5 percent or less of the output of the compressor is bled back into the input in order to delay the onset of surge.

Claim 7

In a compressor including a stage having an inlet and an outlet and adapted for fluid flow through the compressor, a surge detecting system comprising: a velocity probe mounted to the compressor adjacent a wall thereof near its outlet, said velocity probe having a flow direction sensing ability at a predetermined portion thereof, said predetermined portion being disposed within the boundary layer of material flowing through the compressor at the compressor outlet adjacent said wall, said predetermined portion also having a predetermined orientation with respect to the expected downstream direction of material flow in said boundary layer under nonsurge conditions to cause a detectable output indication from said velocity probe whenever said material flow substantially reverses in direction from said expected downstream direction, and indicating means connected with said probe for detecting an impending compressor surge condition in response to said output indication from said velocity probe indicating flow reversal of direction in said boundary layer which is, in turn, indicative of impending surge condition.

Claim 8

In a compressor including a stage having an inlet and an outlet and adapted for fluid flow through the compressor, a surge detecting system comprising: a velocity probe mounted to the compressor adjacent a wall thereof near its outlet, said velocity probe having a flow direction sensing ability at a predetermined portion thereof, said predetermined portion being disposed within the boundary layer of material flowing through the compressor at the compressor outlet adjacent said wall, said predetermined portion also having a predetermined orientation with respect to the expected downstream direction of material flow in said boundary layer under nonsurge conditions to cause a detectable output indication from said velocity probe whenever said material flow substantially reverses in direction from said expected downstream direction, and indicating means connected with said probe for detecting an impending compressor surge condition in response to said output indication from said velocity probe indicating flow reversal of direction in said boundary layer which is, in turn, indicative of impending surge condition.

Claim 9

Apparatus in accordance with claim 6 including a bleed line extending between the compressor stage outlet and the compressor stage inlet, said bleed line having a valve positioned therein, said flow reversal indicating means functioning to operate said valve to bleed back a portion of the fluid at the outlet of the compressor back into the inlet when flow reversal occurs so as to eliminate flow reversal and delay the onset of surge conditions.

Claim 10

Apparatus in accordance with claim 6 including means responsive to said flow reversal indicating means for operating a back pressure valve for relieving high pressure conditions at the compressor stage outlet.

Claim 11

Apparatus in accordance with claim 6 wherein said velocity probe comprises a pressure sensing tube having an aperture therein oriented facing downstream of the desired flow in the compressor and wherein said flow reversal indicating means comprises a pressure sensing apparatus.

Claim 12

Apparatus in accordance with claim 6 wherein said compressor stage is a centriFugal compressor stage and wherein said velocity probe is mounted adjacent the impeller exit of the compressor stage.

Claim 13

Apparatus in accordance with claim 6 wherein said compressor stage is an axial flow compressor stage and wherein said velocity probe is mounted adjacent the exit side of the rotor blade tips.