Patent ID: 9074606
Filing Date: 2015-07-07
Classification: F04D

Abstract:
1. A method of controlling surge in a multi-stage compressor comprising: (a) providing a compressor system feed to a compressor having a first stage and a second stage; (b) discharging a compressor discharge stream from the compressor; (c) combining a first portion of the compressor discharge stream with the compressor system feed to create a first stage compressor feed having a first volumetric flow rate; (d) feeding the first stage compressor feed into the first stage; (e) combining a second portion of the compressor discharge stream with a discharge stream from the first stage at a location within the compressor between the first stage and the second stage to create a second stage compressor feed having a second volumetric flow rate; (f) feeding the second stage compressor feed into the second stage; (g) calculating the first volumetric flow rate; (h) controlling the first portion of the compressor discharge stream such that the first volumetric flow rate is maintained near or above a first set point and such that the first volumetric flow rate is maintained above a first stage surge point; (i) calculating the second volumetric flow rate; and (j) controlling the second portion of the compressor discharge stream such that the second volumetric flow rate is maintained near or above a second set point and such that the second volumetric flow rate is maintained above a second stage surge point; (k) wherein the calculating of the second volumetric flow rate includes a calculation of a first stage effective head; (l) wherein the first stage effective head is calculated as a function of a first stage compressor speed and the first volumetric flow rate; and (m) wherein the function is specific to an impeller geometry of the first stage.