Tracer-dilution method indicates flow-rate through compressor

A technique for measuring compressor flowrate through an operating natural-gas centrifugal compressor has been tested and found to have a precision approaching ± 1.5%. The technique employs constant-flow tracer dilution. Testing demonstrated that use of a critical-flow nozzle to inject a constant, know flow of tracer into a flowing natural-gas stream is feasible. Effects of potential pulsation on a tracer flow measurement appear to be eliminated by this technique. With experimental and operational streamlining, the constant-flow tracer dilution technique is capable of being used to measure the flowrate through operating centrifugal compressors with sufficient precision and accuracy to allow actual compressor operating characteristics to be determined. This technique is especially useful in situations in which an orifice-flow measurement cannot be performed because of physical space limits or economic considerations.