Method and apparatus for noninteracting control of a dynamic compressor having rotating vanes

Claim 3

A control apparatus for controlling a system including a dynamic compressor with rotating vanes having suction and discharge ports and a safe operating zone, a turbine driver, a pipeline connecting said discharge port to a user of a compressed gas, control members capable of moving an operating point of the compressor along its operating line by changing its performance, a fluid relief means connected to said pipeline, a flow measuring device installed in said suction port of the compressor, a pressure differential transmitter measuring the pressure differential across said flow measuring device, transmitters measuring suction pressure and temperature, a speed transmitter, calculating means for defining an actual mass flow rate and a volumetric flow rate through the compressor, a process control means for maintaining a constant mass flow rate through the compressor, a performance control means for controlling the speed of rotation of the compressor, and a protective control means for keeping the operating point of the compressor inside of its safe operating zone, the improvement comprising: a function generator means for controlling the position of the rotating vanes to maintain a constant optimum relationship between the vanes position and the volumetric flow rate through the compressor; a summer means for summarizing an output signal of said process control means with a signal proportional to an output signal of said function generator means in order to compensate for an influence of the rotating vanes position change on the compressor's performance until the operating point of compressor reaches a line limiting its safe operating zone; a high signal limiter means for receiving its input signal from said summer means and limiting the maximum permissible speed of rotation; and a low signal limiter means for controlling the outflow through said fluid relief means in response to a change of an output signal of the summer means, said output signal from the summer means being dependent on changes of both the volumetric flow rate through the compressor and an output signal of said process control means; said low signal limiter means being adjustable whereby under an increase of the output signal of said process control means, the summer means output signal appears simultaneously with a beginning of limitation of an output signal of said high signal limiter means; said low signal limiter means in conjunction with said summer means and said function generator means thereby providing for a noninteracting control of flow through the compressor and protection of the compressor from surge.

Claim 4

A control apparatus for controlling a system including a dynamic compressor with rotating vanes having suction and discharge ports and a safe operating zone, a turbine driver, a pipeline connecting said discharge port to a user of a compressed gas, control members capable of moving an operating point of the compressor along its operating line by changing its performance, a fluid relief means connected to said pipeline, a flow measuring device installed in said suction port of the compressor, a pressure differential transmitter measuring the pressure differential across said flow measuring device, transmitters measuring suction pressure and temperature, a speed transmitter, calculating means for defining an actual mass flow rate and a volumetric flow rate through the compressor, a process control means for maintaining a constant mass flow rate through the compressor, a performance control means for controlling the speed of rotation of the compressor, and a protective control means for keeping the operating point of the compressor inside of its safe operating zone, the improvement comprising: a function generator means for controlling the position of the rotating vanes to maintain a constant optimum relationship between the vanes position and the volumetric flow rate through the compressor; a summer means for summarizing an output signal of said process control means with a signal proportional to an output signal of said function generator means in order to compensate for an influence of the rotating vanes position change on the compressor's performance until the operating point of compressor reaches a line limiting its safe operating zone; a high signal limiter means for receiving its input signal from said summer means and limiting the maximum permissible speed of rotation; and a low signal limiter means for controlling the outflow through said fluid relief means in response to a change of an output signal of the summer means, said output signal from the summer means being dependent on changes of both the volumetric flow rate through the compressor and an output signal of said process control means; said low signal limiter means being adjustable whereby under an increase of the output signal of said process control means, the summer means output signal appears simultaneously with a beginning of limitation of an output signal of said high signal limiter means; said low signal limiter means in conjunction with said summer means and said function generator means thereby providing for a noninteracting control of flow through the compressor and protection of the compressor from surge.