MULTI-STAGE COMPRESSION SYSTEM AND METHOD OF OPERATING THE SAME
A multi-stage compression system includes a plurality of centrifugal compression stages. Each stage includes an impeller and a variable speed motor coupled to the impeller. Each variable speed motor is operable at a speed between a first speed and a second speed. The multi-stage compression system also includes a control system that is connected to each of the variable speed motors and is operable to vary the speed of each motor. The speed of each motor is varied simultaneously such that a ratio of the speed of any two variable speed motors remains constant.
1 . A multi-stage compression system comprising:
a plurality of centrifugal compression stages, each stage including an impeller and a variable speed motor coupled to the impeller, each variable speed motor operable at a speed between a first speed and a second speed; and
a control system connected to each of the variable speed motors and operable to vary the speed of each motor, the speed of each motor being varied simultaneously such that a ratio of the speed of any two variable speed motors remains constant.
2 . The multi-stage compression system of claim 1 , wherein a fluid flow passes through the plurality of centrifugal compression stages sequentially.
3 . The multi-stage compression system of claim 1 , wherein the plurality of centrifugal compression stages are mechanically de-coupled from each other.
4 . The multi-stage compression system of claim 1 , further comprising at least one heat exchanger, the at least one heat exchanger positioned to receive a fluid flow from at least one of the plurality of centrifugal compression stages.
5 . The multi-stage compression system of claim 1 , wherein the control system includes at least one sensor positioned to measure a parameter of a fluid flow passing through the plurality of centrifugal compression stages.
6 . The multi-stage compression system of claim 5 , further comprising a valve disposed between the plurality of centrifugal compression stages and a gas utilization system, the valve operable to discharge a portion of the fluid flow from the multi-stage compression system.
7 . The multi-stage compression system of claim 6 , wherein the control system varies the speed of the variable speed motor and operates the valve at least partially in response to the measured parameter.
8 . The multi-stage compression system of claim 5 , wherein the parameter is at least one of a pressure, a temperature, and a mass flow rate.
9 . The multi-stage compression system of claim 1 , wherein a mass flow rate of the plurality of centrifugal compression stages is substantially constant.
10 . The multi-stage compression system of claim 1 , wherein a mass flow rate of the plurality of centrifugal compression stages is variable in response to use of a fluid flow at a gas utilization system.
11 . The multi-stage compression system of claim 1 , wherein a first variable speed motor operates at a different speed than a second of the variable speed motors.
12 . A multi-stage compression system comprising:
a first centrifugal compressor stage including a first impeller and a first variable speed motor, the first variable speed motor operable at a first speed between a low speed and a high speed;
a second centrifugal compressor stage including a second impeller and a second variable speed motor, the second variable speed motor operable at a second speed between a low speed and a high speed, the first speed and the second speed defining a first ratio;
a third centrifugal compressor stage including a third impeller and a third variable speed motor, the third variable speed motor operable at a third speed between a low speed and a high speed, the first speed and the third speed defining a second ratio and the second speed and the third speed defining a third ratio; and
a control system operable to synchronously vary the first speed, the second speed, and the third speed such that the first ratio, the second ratio, and the third ratio remain constant.
13 . The multi-stage compression system of claim 12 , wherein the first centrifugal compressor stage, the second centrifugal compressor stage, and the third centrifugal compressor stage are arranged in series.
14 . The multi-stage compression system of claim 12 , wherein the centrifugal compressor stages are mechanically de-coupled from each other.
15 . The multi-stage compression system of claim 12 , further comprising a first heat exchanger positioned between the first centrifugal compression stage and the second centrifugal compression stage, a second heat exchanger positioned between the second centrifugal compression stage and the third centrifugal compression stage, and a third heat exchanger positioned between the third centrifugal compression stage and an air utilization system.
16 . The multi-stage compression system of claim 12 , wherein the control system includes at least one sensor positioned to measure a parameter of a fluid flow passing through the centrifugal compression stages.
17 . The multi-stage compression system of claim 16 , further comprising a valve disposed between the third centrifugal compression stage and an air utilization system, the valve operable to discharge a portion of the fluid flow from the multi-stage compression system.
18 . The multi-stage compression system of claim 17 , wherein the control system varies the speed of the first variable speed motor, the second variable speed motor, and the third variable speed motor and operates the valve in response to the measured parameter.
19 . The multi-stage compression system of claim 16 , wherein the parameter is at least one of a temperature, a pressure, and a mass flow rate.
20 . The multi-stage compression system of claim 12 , wherein a mass flow rate of the centrifugal compression stages is substantially constant.
21 . The multi-stage compression system of claim 12 , wherein a mass flow rate of the centrifugal compression stages is variable in response to use of a fluid flow at a gas utilization system.
22 . The multi-stage compression system of claim 12 , wherein the first speed does not equal the second speed and the third speed.
23 . A method of controlling a multi-stage compression system to deliver gas to a gas utilization system that uses the gas at a variable rate, the method comprising:
operating a first centrifugal compressor stage at a first speed to produce a fluid flow;
directing the fluid flow to a second centrifugal compressor stage;
operating the second centrifugal compressor stage at a second speed; and
varying the first speed and the second speed in response to the variable rate and in unison such that a ratio between the first speed and the second speed remains constant.
24 . The method of claim 23 , further comprising directing the fluid flow from the second centrifugal compressor stage to a third centrifugal compressor stage, and operating the third centrifugal compressor stage at a third speed.
25 . The method of claim 24 , further comprising varying the third speed in unison with the first speed and the second speed such that a second ratio between the first speed and the third speed and a third ratio between the second speed and the third speed remain constant.
26 . The method of claim 23 , further comprising monitoring a property of the fluid flow, and varying the first speed and the second speed in unison in response to the monitored property.
27 . The method of claim 23 , wherein the first speed does not equal the second speed.