Method for detecting the occurrence of surge in a centrifugal compressor by detecting the change in the mass flow rate
First Claim
1. A method for detecting the change in the compressible fluid mass flow rate that accompanies surge in a compressor, the compressor having means for sensing a first fluid temperature, means for sensing a first pressure, means for sensing a second pressure, and means for measuring current drawn by a compressor prime mover, the method comprising the steps of:
- (A) calculating the time rate of change of the first fluid temperature for a time interval by sensing a present first fluid temperature and subtracting a previous value first fluid temperature from the present first fluid temperature;
(B) calculating the time rate of change of the first fluid pressure for a time interval by sensing a present first fluid pressure and subtracting a previous value first fluid pressure from the present first fluid pressure;
(C) calculating the time rate of change of the second fluid pressure for a time interval by sensing a present second fluid pressure and subtracting a previous value second fluid pressure from the present second fluid pressure;
(D) calculating the time rate of change of current drawn by the compressor prime mover by sensing a present drawn current and subtracting a previous value prime mover current drawn;
(E) calculating the mass flow rate by combining the rates of change calculated in steps (A), (B), (C), and (D); and
(F) comparing the calculated mass flow rate to a predetermined acceptable mass flow rate to determine if surge is present.
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Abstract
A method for controlling working fluid surge in a centrifugal compressor. According to the method, surge detection is accomplished by calculating the change in the compressible fluid mass flow rate that accompanies surge in a compressor, the compressor having means for sensing a first fluid temperature, means for sensing a first pressure, means for sensing a second pressure, and means for measuring current drawn by a compressor prime mover, the method comprising the steps of: calculating the time rate of change of the first fluid temperature; calculating the time rate of change of the first fluid pressure; calculating the time rate of change of the second fluid pressure; calculating the time rate of change of current drawn by the compressor prime mover; calculating the mass flow rate by combining the calculated rates of change; and comparing the calculated mass flow rate to a predetermined acceptable mass flow rate to determine if surge is present.
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Citations
6 Claims
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1. A method for detecting the change in the compressible fluid mass flow rate that accompanies surge in a compressor, the compressor having means for sensing a first fluid temperature, means for sensing a first pressure, means for sensing a second pressure, and means for measuring current drawn by a compressor prime mover, the method comprising the steps of:
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(A) calculating the time rate of change of the first fluid temperature for a time interval by sensing a present first fluid temperature and subtracting a previous value first fluid temperature from the present first fluid temperature;
(B) calculating the time rate of change of the first fluid pressure for a time interval by sensing a present first fluid pressure and subtracting a previous value first fluid pressure from the present first fluid pressure;
(C) calculating the time rate of change of the second fluid pressure for a time interval by sensing a present second fluid pressure and subtracting a previous value second fluid pressure from the present second fluid pressure;
(D) calculating the time rate of change of current drawn by the compressor prime mover by sensing a present drawn current and subtracting a previous value prime mover current drawn;
(E) calculating the mass flow rate by combining the rates of change calculated in steps (A), (B), (C), and (D); and
(F) comparing the calculated mass flow rate to a predetermined acceptable mass flow rate to determine if surge is present. - View Dependent Claims (3, 4, 5, 6)
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2. The method of detecting surge wherein in step (E) the mass flow rate is calculated by adding the rates of change calculated in steps (A), (B), (C), and (D).
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