Pumps – With condition responsive pumped fluid control – Fluid flow rate responsive
Reexamination Certificate
1999-12-22
2001-09-25
Ryznic, John E. (Department: 3745)
Pumps
With condition responsive pumped fluid control
Fluid flow rate responsive
C417S282000, C417S295000
Reexamination Certificate
active
06293766
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to a compressor with a downstream user with variable gas output. The present invention also pertains to a unit operating according to this process with a compressor and a downstream user. The present invention is applicable preferably but not exclusively to a fuel gas compressor unit connected to a pipeline, which supplies a gas turbine with compressed fuel gas.
BACKGROUND OF THE INVENTION
It is necessary in many compressor applications to maintain both the intake pressure (inlet pressure) and the end pressure (outlet pressure) of the compressor at a constant value. The control elements used for this are a throttling member on the intake side of the compressor as well as control units, with which the position of the guide vanes and/or the speed of rotation of the compressor can be changed. The compressor delivers the compressed gas with an end pressure that is to be held at an essentially constant pressure to a user or to a process in which the gas is processed. This user of this process usually has control units of its own for changing or controlling the gas throughput, e.g., a throttling member at the inlet of the user or process.
It has been known that the compressor may be equipped with at least three control circuits to maintain the intake pressure and the end pressure at a constant value and to prevent the flow instabilities. An end pressure controller usually acts on the guide vanes of the compressor and/or on a means for adjusting the speed of rotation. An intake pressure controller acts on the throttling member on the intake side of the compressor. Furthermore, a pump surge limiter is provided, which acts on a blow-by valve connecting the outlet side to the intake side of the compressor in order to ensure a minimum flow rate through the compressor in the case of excessively low flow rate of the compressor by blowing over flow media from the delivery side to the intake side.
Each of these three control circuits affects the other. The absence of instabilities is ensured only by a careful and mutually coordinated design of the control circuits.
The working points and the dynamic behavior of the control circuits are designed for a normal value of the flow rate of the compressor and consequently of the gas throughput at the outlet of the compressor. Even though the control circuits are able, if a sudden change occurs in the gas throughput needed on the user side, to follow such changes in the gas flow rate to a certain extent, they are inherently able to do so with a sluggish time response only, which it not sufficient for a rapid elimination of changes or disturbances in the user-side gas output and may also cause the control circuits to mutually affect one another and to engage in an undesired interaction.
SUMMARY AND OBJECTS OF THE INVENTION
The primary object of the present invention is to operate a compressor with a downstream user such that its control can respond sufficiently rapidly to changes in the user-side gas output.
According to the invention a process is provided for operating a compressor with variable gas output and with a downstream user. A throttling member is arranged on the intake side of the compressor and is controlled as a function of the gas consumption of the user. A cross section of the throttling member is reduced when the gas consumption decreases.
The throttling member may additionally be controlled as a function of the gas pressure on the intake side of the compressor. The intake-side throttling member may be controlled by an intake pressure controller such that the intake-side pressure at the compressor inlet is maintained at a constant value, and such that a signal representing the value of the gas consumption at the user is additionally sent to said intake pressure controller.
The intake-side throttling member may be controlled by an adjusting signal, which is formed by linking a signal corresponding to the intake pressure of the compressor with the gas consumption at the user. This linkage may be performed by addition and/or by multiplication. The signal representing the gas consumption may be changed by a nonlinear member.
The end pressure at the outlet of the compressor may be maintained at an essentially constant value by a pressure controller, which acts on the position of the guide vanes and/or on the speed of rotation of the compressor drive.
A blow-by section connecting the outlet of the compressor to the intake side of the compressor may be controlled by a pump surge limiter such that the flow rate of the compressor does not drop below a minimum.
Time constants of the controller controlling the intake-side throttling member may be selected to be such that the throttling member responds more rapidly to changes in the user-side gas consumption than to changes in the pressure on the intake side of the compressor.
The intake side of the compressor may be connected to a pipeline. The user may be a gas turbine, which burns the gas compressed by the compressor.
According to another aspect of the invention a unit or system is provided with a compressor and with a downstream user. The system has a throttling member on the intake side of the compressor and with a control unit for changing the gas throughput through the user. The controller controls the intake-side throttling member as a function of the gas throughput of the user.
A throttling member arranged on the intake side of the compressor is controlled according to the present invention as a function of the user-side gas discharge, preferably such that the throttling member is adjusted proportionally to a reduction in the user-side gas throughput such that the pressure loss over the intake-side throttling member remains constant even at reduced flow. An undesired interaction with the other control circuits is thus reduced to a minimum.
One embodiment of the present invention will be explained in greater detail below on the basis of a flow and control chart of a compressor with downstream gas turbine, which compressor is connected to a gas pipeline.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawing and descriptive matter in which a preferred embodiment of the invention is illustrated.
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F. Kluge, Mar. 19, 1941, Regelung Von Kreiselverdichtern, German.
Man Turbomaschinen AG GHH Borsig
McGlew and Tuttle , P.C.
Ryznic John E.
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