System and method for controlling compressor flow

Abstract

A system for controlling air flow comprises an inlet, a first compressor, a first pressure sensor, a second pressure sensor, a first temperature sensor, and a first controller. The inlet is configured to direct a first stream of air into the system. The first compressor is configured to pull in the first stream of air through the inlet and compress the first stream of air. The first pressure sensor senses a first pressure of the first stream of air prior to compression in the first compressor, the second pressure sensor senses a second pressure of the first stream of air after compression in the first compressor, and the first temperature sensor senses a temperature of the first stream of air after compression in the first compressor. The controller adjusts a speed of the first compressor based upon a comparison between a desired flow rate and a calculated flow rate.

1 . A system for controlling air flow, the system comprising:
 an inlet configured to direct a first stream of air into the system;   a first pressure sensor for sensing a first pressure of the first stream of air;   a first compressor configured to pull in the first stream of air through the inlet and compress the first stream of air;   a second pressure sensor for sensing a second pressure of the first stream of air;   a first temperature sensor for sensing a temperature of the first stream of air after compression in the first compressor; and   a first controller for controlling a speed of the first compressor as a function of a desired flow rate of the first stream of air and a calculated flow rate of the first stream of air.   
   
   
       2 . The system of  claim 1 , wherein the first controller determines the calculated flow rate of the first stream of air using the first pressure, the second pressure, the temperature, and an initial speed of the first stream of air. 
   
   
       3 . The system of  claim 2 , wherein the first compressor is an electric compressor. 
   
   
       4 . The system of  claim 3 , wherein the first controller is configured to control rotation of a plurality of fan blades disposed within the first compressor. 
   
   
       5 . The system of  claim 4 , wherein the first compressor further includes a variable diffuser, and wherein a position of the variable diffuser is also used to determine the calculated flow rate. 
   
   
       6 . The system of  claim 1 , and further comprising:
 a third pressure sensor for sensing a first pressure of a second stream of air directed into the system by the inlet;   a second compressor configured to pull in the second stream of air through the inlet and compress the second stream of air;   a fourth pressure sensor for sensing a second pressure of the second stream of air;   a second temperature sensor for sensing a temperature of the second stream of air after compression in the second compressor; and   a second controller for controlling a speed of the second compressor as a function of a desired flow rate of the second stream of air and a calculated flow rate of the second stream of air.   
   
   
       7 . The system of  claim 6 , wherein the first and second compressors are electric compressors. 
   
   
       8 . The system of  claim 7 , wherein the first and second streams of air merge together to form a combined stream of air. 
   
   
       9 . The system of  claim 8 , and further comprising a flow sensor configured to determine a flow rate of the combined stream of air. 
   
   
       10 . A method of controlling air flow in a system, the method comprising the steps of:
 calculating a flow rate of a stream of air exiting a compressor;   comparing the calculated flow rate with a desired flow rate of the stream of air exiting the compressor to determine a difference; and   controlling speed of the compressor based upon the difference to adjust the speed of the compressor so that the calculated flow rate is substantially equivalent to the desired flow rate.   
   
   
       11 . The method of  claim 10 , wherein the step of calculating a flow rate is based upon a speed of the stream of air entering the compressor, a pressure drop of the stream of air within the compressor, and a temperature of the stream of air after compression within the compressor. 
   
   
       12 . The method of  claim 11 , wherein the compressor includes a variable diffuser, and wherein a position of the variable diffuser is a component of the calculated flow rate of the stream of air exiting the compressor. 
   
   
       13 . The method of  claim 12 , wherein the steps are repeated at a defined frequency. 
   
   
       14 . The method of  claim 13 , wherein the frequency is about 20 Hz. 
   
   
       15 . A method of controlling air flow in a system, the method comprising:
 directing a first stream of uncompressed air into the system through an inlet;   determining an initial speed of the first stream of uncompressed air;   sensing a first pressure of the first stream of uncompressed air;   compressing the first stream of uncompressed air in a first compressor and discharging a first stream of compressed air from the compressor;   sensing a pressure of the first stream of compressed air;   determining a pressure drop by calculating the difference between the first and second pressures;   sensing a temperature of the first stream of compressed air;   calculating a flow rate of the first stream of compressed air based upon the initial speed of the first stream of uncompressed air, the pressure drop, and the temperature of the first stream of compressed air;   comparing the calculated flow rate with a desired flow rate to determine a difference; and   controlling speed of the first compressor based upon the difference to adjust the speed of the first compressor so that the calculated flow rate of the first stream of compressed air is substantially equivalent to the desired flow rate of the first stream of compressed air.   
   
   
       16 . The method of  claim 15 , wherein the steps are repeated at a defined frequency. 
   
   
       17 . The method of  claim 15 , wherein the first compressor is an electric compressor. 
   
   
       18 . The method of  claim 15 , and further comprising:
 directing a second stream of uncompressed air into the system through the inlet;   determining an initial speed of the second stream of uncompressed air;   sensing a first pressure of the second stream of uncompressed air;   compressing the second stream of uncompressed air in a second compressor and discharging a second stream of compressed air from the compressor;   sensing a pressure of the second stream of compressed air;   determining a pressure drop by calculating the difference between the first and second pressures;   sensing a temperature of the second stream of compressed air;   calculating a flow rate of the second stream of compressed air based upon the initial speed of the second stream of uncompressed air, the pressure drop, and the temperature of the second stream of compressed air;   comparing the calculated flow rate with a desired flow rate of the second stream of compressed air to determine a difference; and   controlling speed of the second compressor based upon the difference to adjust the speed of the second compressor so that the calculated flow rate of the second stream of compressed air is substantially equivalent to the desired flow rate of the second stream of compressed air.   
   
   
       19 . The method of  claim 18 , and further comprising the step of merging the first and second streams of compressed air to form a combined stream of compressed air. 
   
   
       20 . The method of  claim 19 , and further comprising the steps of:
 sensing a flow rate of the combined stream of compressed air with a flow sensor;   comparing the flow rate of the combined stream of compressed air with the desired flow rates of the first and second streams of compressed air to determine an error; and   using the error to adjust the desired flow rates of the first and second streams of compressed air.