Method of controlling the surge limit of turbocompressors

Claim 1

A method of controlling a gas conveying turbocompressor having a suction side, an outlet side and a relief valve connected to the outlet side which can be opened and closed as a function of the distance between a working point and at least one of a surge limit line and a blow-off line which are plotted on a characteristic graph, the turbocompressor operating at a momentary working point lying at a point in the characteristic graph, the blow-off line and surge limit line of the characteristic graph being plotted using predetermined theoretical coordinates which are a function of theoretical flow parameters including suction gas temperature, suction gas pressure, volumetric flow rate, outlet gas pressure and gas composition at the suction and outlet sides of the compressor, the method comprising: continuously measuring the suction gas pressure and suction gas temperature at the suction side and outlet gas pressure at the outlet side of the compressor; calculating the actual characteristic graph coordinates at the gas composition using the continuously measured pressures and tempertures representing a momentary working point of the turbocompressor; continuously measuring the actual value of the speed of the compressor, which is used to define a family of characteristic lines on the characteristic graph; obtaining a set point value for the speed on the characteristic graph using a characteristic line generated by the speed which passed through the momentary working point of the compressor as it appears on the characteristic graph; comparing the actual value of the speed to the set point value therefor; and generating a correction signal indicating a change in gas composition if the actual value of the monitoring parameter deviates from the set point value therefor.

Claim 2

A method of controlling a gas conveying turbocompressor having a suction side, an outlet side and a relief valve connected to the outlet side which can be opened and closed as a function of the distance between a working point and at least one of a surge limit line and a blow-off line which are plotted on a characteristic graph, the turbocompressor operating at a momentary working point lying at a point in the characteristic graph, the blow-off line and surge limit line of the characteristic graph being plotted using predetermined theoretical coordinates which are a function of theoretical flow parameters including suction gas temperature, suction gas pressure, volumetric flow rate, outlet gas pressure and gas composition at the suction and outlet sides of the compressor, the method comprising: continuously measuring the suction gas pressure and suction gas temperature at the suction side and outlet gas pressure at the outlet side of the compressor; calculating the actual characteristic graph coordinates at the gas composition using the continuously measured pressures and tempertures representing a momentary working point of the turbocompressor; continuously measuring the actual value of the speed of the compressor, which is used to define a family of characteristic lines on the characteristic graph; obtaining a set point value for the speed on the characteristic graph using a characteristic line generated by the speed which passed through the momentary working point of the compressor as it appears on the characteristic graph; comparing the actual value of the speed to the set point value therefor; and generating a correction signal indicating a change in gas composition if the actual value of the monitoring parameter deviates from the set point value therefor.

Claim 12

An apparatus for controlling a gas conveying turbocompressor having a suction side, an outlet side and a relief valve connected to the outlet side which can be opened and closed the turbocompressor operating at a momentary working point and having a surge limit line and a blow-off line on a characteristic graph having characteristic theoretical graph coordinates which are calculated based on theoretical flow parameters at the suction and outlet sides of the compressor, the apparatus comprising: pressure and temperature sensors for sensing the temperature and pressure values at the suction and outlet sides of the compressor; first calculating means connected to the sensor for calculating one of the actual characteristic graph coordinates; second calculator means connected to the sensors for calculating a second actual characteristic graph coordinate; means for comparing one of said first and second actual characteristic graph coordinate with the blow-off line and outputting a set point signal representing a theoretical corresponding characteristic graph coordinate; means for comparing said set point signal with the other of said one of said first and second actual characteristic graph coordinates to produce a control input signal; a monitoring parameter sensor for sensing a parameter of the compressor which is independent of the pressures and temperatures sensed by the pressure and temperature sensors; third calculator means connected to the monitoring parameter sensor for calculating a family of characteristic lines on the characteristic graph, one of which passes through the working point of the compressor; and means for comparing the actual monitoring parameter as measured by the monitoring parameter sensor with a monitoring parameter set point for the monitoring parameter which is taken from a characteristic line of the monitoring parameter on the characteristic graph which passes through the working point and outputting a correction signal representative of the difference; means for combining said control input signal with said correction signal; control means for generating a control signal based on said input control signal and said correction signal for opening and closing the relief valve.

Claim 13

An apparatus for controlling a gas conveying turbocompressor having a suction side, an outlet side and a relief valve connected to the outlet side which can be opened and closed the turbocompressor operating at a momentary working point and having a surge limit line and a blow-off line on a characteristic graph having characteristic theoretical graph coordinates which are calculated based on theoretical flow parameters at the suction and outlet sides of the compressor, the apparatus comprising: pressure and temperature sensors for sensing the temperature and pressure values at the suction and outlet sides of the compressor; first calculating means connected to the sensor for calculating one of the actual characteristic graph coordinates; second calculator means connected to the sensors for calculating a second actual characteristic graph coordinate; means for comparing one of said first and second actual characteristic graph coordinate with the blow-off line and outputting a set point signal representing a theoretical corresponding characteristic graph coordinate; means for comparing said set point signal with the other of said one of said first and second actual characteristic graph coordinates to produce a control input signal; a monitoring parameter sensor for sensing a parameter of the compressor which is independent of the pressures and temperatures sensed by the pressure and temperature sensors; third calculator means connected to the monitoring parameter sensor for calculating a family of characteristic lines on the characteristic graph, one of which passes through the working point of the compressor; and means for comparing the actual monitoring parameter as measured by the monitoring parameter sensor with a monitoring parameter set point for the monitoring parameter which is taken from a characteristic line of the monitoring parameter on the characteristic graph which passes through the working point and outputting a correction signal representative of the difference; means for combining said control input signal with said correction signal; control means for generating a control signal based on said input control signal and said correction signal for opening and closing the relief valve.

Claim 16

A method of controlling the pumping limit of a gas conveying turbocompressor having a suction side, an outlet side and a relief valve connected to the outlet side which can be opened and closed with the turbocompressor operating at a momentary working point and having a surge limit line and a blow-off line which are plotted on a characteristic graph, the momentary working point of the compressor lying at a point in the characteristic graph, the blow-off line and surge limit line of the characteristic graph being plotted using predetermined theoretical coordinates which are calculated as a function of theoretical flow parameters measured including suction gas temperature, suction gas pressure, volumetric flow rate, outlet gas pressure and gas composition at the suction and outlet sides of the compressor, the method comprising: continuously measuring the suction gas pressure and suction gas temperature at the suction side and outlet gas pressure at the outlet side of the compressor; calculating the actual characteristic graph coordinates using the continuously measured pressures and temperatures representing a momentary working point of the turbocompressor; comparing one of the coordinates of the calculated characteristic graph coordinates with one of the blow-off line and the sure limit line on the characteristic graph to obtain a set point value corresponding with the calculated graph coordinate; comparing said set point value corresponding to the calculated characteristic graph coordinate with another calculated characteristic graph coordinate to form a controller input signal; controlling the relief valve based on said controller input signal; continuously measuring the actual value of the speed of the compressor, which monitoring parameter is used to define a family of characteristic lines on the characteristic graph; obtaining a set point value for the speed on the characteristic graph using a characteristic line generated by the speed which passed through the momentary working point of the compressor as it appears on the characteristic graph; comparing the actual value of the speed to the set point value therefor; and generating a correction signal if the actual value of the monitoring parameter deviates from the set point value therefor thereby indicating a change in the composition of the conveyed gas.

Claim 17

A method of controlling the pumping limit of a gas conveying turbocompressor having a suction side, an outlet side and a relief valve connected to the outlet side which can be opened and closed with the turbocompressor operating at a momentary working point and having a surge limit line and a blow-off line which are plotted on a characteristic graph, the momentary working point of the compressor lying at a point in the characteristic graph, the blow-off line and surge limit line of the characteristic graph being plotted using predetermined theoretical coordinates which are calculated as a function of theoretical flow parameters measured including suction gas temperature, suction gas pressure, volumetric flow rate, outlet gas pressure and gas composition at the suction and outlet sides of the compressor, the method comprising: continuously measuring the suction gas pressure and suction gas temperature at the suction side and outlet gas pressure at the outlet side of the compressor; calculating the actual characteristic graph coordinates using the continuously measured pressures and temperatures representing a momentary working point of the turbocompressor; comparing one of the coordinates of the calculated characteristic graph coordinates with one of the blow-off line and the sure limit line on the characteristic graph to obtain a set point value corresponding with the calculated graph coordinate; comparing said set point value corresponding to the calculated characteristic graph coordinate with another calculated characteristic graph coordinate to form a controller input signal; controlling the relief valve based on said controller input signal; continuously measuring the actual value of the speed of the compressor, which monitoring parameter is used to define a family of characteristic lines on the characteristic graph; obtaining a set point value for the speed on the characteristic graph using a characteristic line generated by the speed which passed through the momentary working point of the compressor as it appears on the characteristic graph; comparing the actual value of the speed to the set point value therefor; and generating a correction signal if the actual value of the monitoring parameter deviates from the set point value therefor thereby indicating a change in the composition of the conveyed gas.