Title of Invention	"A PROTECTIVE DEVICE FOR CONTROLLING STALL AND SURGE IN COMPRESSORS"
Abstract	A protective device for controlling stall and surge in compressors, characterized by a pressure transducer (2) having a frequency response of at least 100 kHz mounted on to a compressor (1) which needs to be protected from stall and surge, the said compressor being also provided with an eddy current probe (3) capable of providing rotor triggered signal, the outputs of the said pressure transducer (2) and the eddy current probe (3) being connected to a microprocessor module-A (4) capable of processing at least one million samples/second and generating outputs of a pressure averaged (Pav) and real time pressure (Prt), the said outputs (Pav, Prt) being fed to a second microprocessor module-B (5) having a clock speed of at least 150 mega Hertz and random access memory (RAM) of at least 32 mega bytes and capable of generating a processed instability parameter output, the said outpyut being fed to a comparator and signal gernator module (6) capable of providing a triggered pulse to a control valve (7) connected to the compressor (1).

Title of Invention

"A PROTECTIVE DEVICE FOR CONTROLLING STALL AND SURGE IN COMPRESSORS"

Abstract

A protective device for controlling stall and surge in compressors, characterized by a pressure transducer (2) having a frequency response of at least 100 kHz mounted on to a compressor (1) which needs to be protected from stall and surge, the said compressor being also provided with an eddy current probe (3) capable of providing rotor triggered signal, the outputs of the said pressure transducer (2) and the eddy current probe (3) being connected to a microprocessor module-A (4) capable of processing at least one million samples/second and generating outputs of a pressure averaged (Pav) and real time pressure (Prt), the said outputs (Pav, Prt) being fed to a second microprocessor module-B (5) having a clock speed of at least 150 mega Hertz and random access memory (RAM) of at least 32 mega bytes and capable of generating a processed instability parameter output, the said outpyut being fed to a comparator and signal gernator module (6) capable of providing a triggered pulse to a control valve (7) connected to the compressor (1).

Full Text	This invention relates to a protective device for controlling stall and surge in compressors. The present invention particularly relates to a device that is not only capable of diagnosing inception of stall in a compressor but also capable of protecting the said compressor from stall and surge. The main usage of the device of this invention is to identify the inception of stall and control in order to avoid the mechanical failure of the compressor due to undesirably large excitation vibration. The device of the pre sent invention should find wide usage in industry wherever compressors are used. From extensive literature and patent search carried out by us we have found the following relevant prior art references: A device for controlling the surge in centrifugal compressor was developed by Hohlweg.,et. al.(US patent No. 4586870, 1986). This device energizes a blow off valve to prevent compressor operation under surge conditions. Adachi, et. al., (US patent No. 50957H, 1992) developed a device for predicting surge in the centrifugal compressor. This device compares the differential pressure from hub and shroud side wall to the set pressure value to trigger the onset of surge. Haugen (US patent No. 5520507, 1996) devised a method and an device to achieve passive damping of flow disturbances in a centrifugal compressor to control compressor surge. Beaverson, et. al., (US patent No. 5746062, 1998 and No. 5894736, 1999) devised a method and device for detecting surge in centrifugal compressor. The surge detection system comprises a means for sensing differential pressure developed across the compressor and a means for sensing current representing input power to the motor. In the entire above prior art references the devices detect the onset of surge and controlling it thereafter. Thus the draw back of detecting onset of stall leading to surge does not exists. In none of the said devices the inception of stall leading to the initiation of vibration exists. The main objective of the present invention is to provide a protective device for controlling stall and surge in compressors, which obviates the draw backs as detailed above. Another objective of the present invention is to provide a device capable of detecting inception of stall and controlling surge in a compressor just before the compressor goes into stall. Yet another objective of the present invention is to provide a device to protect the compressor from large excitations caused by vibrations, which lead to mechanical failure. Still another objective of present invention is to demarcate on the compressor characteristics the region of stable and unstable operation. In Figure-1 of the drawing accompanying this specification a schematic block diagram of an embodiment of the device of the present invention is depicted. In the figure Block (1) is the compressor which is to be protected from stall and surge. Block (2) is a pressure transducer mounted on to the said compressor. Block (3) is an eddy current probe capable of providing rotor triggered signal to block (4). Block (4) is a microprocessor module capable of acquiring and processing pressure signal to pressure average signal and real time pressure signal. Block (5) is a second microprocessor module capable of processing the pressure average and real time pressure signals to generate an aerodynamic parameter. Block (6) is a comparator and signal generator module capable of providing an output signal. Block (7) is a control valve capable of being actuated by the output signal of the Block (6). Accordingly the present invention provides a protective device for controlling stall and surge in compressors, characterized by a pressure transducer (2) having a frequency response of at least 100 kHz mounted on to a compressor (1) which needs to be protected from stall and surge, the said compressor being also provided with an eddy current probe (3) capable of providing rotor triggered signal, the outputs of the said pressure transducer (2) and the eddy current probe (3) being connected to a microprocessor module-A (4) capable of processing at least one million samples/second and generating outputs of a pressure averaged (Pav) and real time pressure (Prt), the said outputs (Pav, Prt) being fed to a second microprocessor module-B (5) having a clock speed of at least 150 mega Hertz and random access memory (RAM) of at least 32 mega bytes and capable of generating a processed instability parameter output, the said output being fed to a comparator and signal generator module (6) capable of providing a triggered pulse to a control valve (7) connected to the compressor (1). In an embodiment of present invention the pressure transducer used is compatible to the operating pressure levels of the compressor. In another embodiment of present invention the microprocessor module-A (4) has inbuilt analogue to digital converter and is capable of simultaneous acquisition and processing of signals. In yet another embodiment of present invention the microprocessor module-B (5) is conventional personnel computer. In another embodiment of present invention the triggered pulse from signal generator is connected to an alarm system. The device of the present invention provides for detecting the instability of flow in centrifugal compressors, which occurs just before the flow enters into unstable region. This is made possible by acquisition and processing the pressure signals and generating an aerodynamic parameter, called instability parameter, through a mathematical module embedded in the microprocessor, whose value and variation of it are used to determine the onset of stall inception, which occurs before compressor stall. The microprocessor is capable of generating at critical instant a control signal, which in turn provides an alarm and which further can be used to operate another device that would bring the compressor back to stable operating regime within a very short period thereby protecting the compressor from mechanical damage due to excitations caused by the instability stall or surge. In the present invention the device is capable of demarcation of stable and unstable operating regions of the compressor. In the device of present invention pressure signals and shaft rotational pulses are taken to the microprocessor. The embedded mathematical module evaluates an instability parameter online. If the measured value indicates detection of stall inception the signal generator module is energized and sends command out of the device to control valve provided in the compressor to open. The novelty of the device of the present invention is that the device is capable of proactively detecting and controlling stall and surge. The inventive step lies in the detection and processing of spatial and temporal disturbances that occur in a compressor stage and use it to detect stall inception and control surge. Another inventive step is in generating aerodynamic flow parameter which take into account the basic phenomena that is responsible for initiation of disturbances. This is done by taking the input from the pressure and rotation signals and evaluating an instability parameter within the device and generating a signal upon detection. The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention. EXAMPLE -1 The device was used to detect the inception of stall in centrifugal compressor stage. The pressure transducer was mounted at the exit of the centrifugal compressor and the eddy current probe was mounted below the rotating shaft of the compressor. The device was energized. The compressor was started and the speed was brought to steady level of 8000 rpm. In order to study the effectiveness of the device, the compressor was made go into stall by operating the control valve. It was found that the device successfully activated the control valve and thereby preempting the compressor going into stall and surge. The main advantages of the present invention are (1) The device is used to find the inception of stall in centrifugal compressor. It is also useful to control stall in centrifugal compressor. (2) Through this device the mechanical damage to impeller caused due to exitational vibrations due to stall could be avoided. (3) The identified parameter characterized through the device is ahead of the stalling of the compressor. (4) The timing for corrective action as well as mode of action by this device are well ahead of actual stall. (5) The device could be used in compressors to detect inception of stall and as a protective device against stall and surge. We Claim: 1. A protective device for controlling stall and surge in compressors, characterized by a pressure transducer (2) having a frequency response of at least 100 kHz mounted on to a compressor (1) which needs to be protected from stall and surge, the said compressor being also provided with an eddy current probe (3) capable of providing rotor triggered signal, the outputs of the said pressure transducer (2) and the eddy current probe (3) being connected to a microprocessor module-A (4) capable of processing at least one million samples/second and generating outputs of a pressure averaged (Pav) and real time pressure (Prt), the said outputs (Pav, Prt) being fed to a second microprocessor module-B (5) having a clock speed of at least 150 mega Hertz and random access memory (RAM) of at least 32 mega bytes and capable of generating a processed instability parameter output, the said outpyut being fed to a comparator and signal gernator module (6) capable of providing a triggered pulse to a control valve (7) connected to the compressor (1). 2. A protective device as claimed in claim 1 wherein the pressure transducer used is compatible to the operating level of the compressor. 3. A protective device as claimed in claims 1 and 2 wherein the microprocessor module-A (4) has in-built analogue to digital converter and is capable of simultaneous acquisition and processing of signals. 4. A protective device as claimed in claims 1-3 wherein the microprocessor module- B (5) is a conventional personnel computer. 5. A protective device as claimed in claims 1-4 wherein the triggered pulse from , the signal generator is connected to an alarm system. 6. A protective device for controlling stall and surge in compressors substantially as herein described with reference to the example and drawing accompanying this specification.

Full Text

This invention relates to a protective device for controlling stall and surge in compressors.
The present invention particularly relates to a device that is not only capable of diagnosing inception of stall in a compressor but also capable of protecting the said compressor from stall and surge.
The main usage of the device of this invention is to identify the inception of stall and control in order to avoid the mechanical failure of the compressor due to undesirably large excitation vibration. The device of the pre sent invention should find wide usage in industry wherever compressors are used.
From extensive literature and patent search carried out by us we have found the following relevant prior art references:
A device for controlling the surge in centrifugal compressor was developed by Hohlweg.,et. al.(US patent No. 4586870, 1986). This device energizes a blow off valve to prevent compressor operation under surge conditions.
Adachi, et. al., (US patent No. 50957H, 1992) developed a device for predicting surge in the centrifugal compressor. This device compares the differential pressure from hub and shroud side wall to the set pressure value to trigger the onset of surge.
Haugen (US patent No. 5520507, 1996) devised a method and an device to achieve passive damping of flow disturbances in a centrifugal compressor to control compressor surge.
Beaverson, et. al., (US patent No. 5746062, 1998 and No. 5894736, 1999) devised a method and device for detecting surge in centrifugal compressor. The surge detection system comprises a means for sensing differential pressure developed across the compressor and a means for sensing current representing input power to the motor.
In the entire above prior art references the devices detect the onset of surge and controlling it thereafter. Thus the draw back of detecting onset of stall leading to

surge does not exists. In none of the said devices the inception of stall leading to the initiation of vibration exists.
The main objective of the present invention is to provide a protective device for controlling stall and surge in compressors, which obviates the draw backs as detailed above.
Another objective of the present invention is to provide a device capable of detecting inception of stall and controlling surge in a compressor just before the compressor goes into stall.
Yet another objective of the present invention is to provide a device to protect the compressor from large excitations caused by vibrations, which lead to mechanical failure.
Still another objective of present invention is to demarcate on the compressor characteristics the region of stable and unstable operation.
In Figure-1 of the drawing accompanying this specification a schematic block diagram of an embodiment of the device of the present invention is depicted. In the figure Block (1) is the compressor which is to be protected from stall and surge. Block (2) is a pressure transducer mounted on to the said compressor. Block (3) is an eddy current probe capable of providing rotor triggered signal to block (4). Block (4) is a microprocessor module capable of acquiring and processing pressure signal to pressure average signal and real time pressure signal. Block (5) is a second microprocessor module capable of processing the pressure average and real time pressure signals to generate an aerodynamic parameter. Block (6) is a comparator and signal generator module capable of providing an output signal. Block (7) is a control valve capable of being actuated by the output signal of the Block (6).
Accordingly the present invention provides a protective device for controlling stall and surge in compressors, characterized by a pressure transducer (2) having a frequency response of at least 100 kHz mounted on to a compressor (1) which needs to be protected from stall and surge, the said compressor being also provided with an eddy

current probe (3) capable of providing rotor triggered signal, the outputs of the said pressure transducer (2) and the eddy current probe (3) being connected to a microprocessor module-A (4) capable of processing at least one million samples/second and generating outputs of a pressure averaged (Pav) and real time pressure (Prt), the said outputs (Pav, Prt) being fed to a second microprocessor module-B (5) having a clock speed of at least 150 mega Hertz and random access memory (RAM) of at least 32 mega bytes and capable of generating a processed instability parameter output, the said output being fed to a comparator and signal generator module (6) capable of providing a triggered pulse to a control valve (7) connected to the compressor (1).
In an embodiment of present invention the pressure transducer used is compatible to the operating pressure levels of the compressor.
In another embodiment of present invention the microprocessor module-A (4) has inbuilt analogue to digital converter and is capable of simultaneous acquisition and processing of signals.
In yet another embodiment of present invention the microprocessor module-B (5) is conventional personnel computer.
In another embodiment of present invention the triggered pulse from signal generator is connected to an alarm system.
The device of the present invention provides for detecting the instability of flow in centrifugal compressors, which occurs just before the flow enters into unstable region. This is made possible by acquisition and processing the pressure signals and generating an aerodynamic parameter, called instability parameter, through a mathematical module embedded in the microprocessor, whose value and variation of it are used to determine the onset of stall inception, which occurs before compressor stall. The microprocessor is capable of generating at critical instant a control signal, which in turn provides an alarm and which further can be used to operate another device that would bring the compressor back to stable operating regime within a very

short period thereby protecting the compressor from mechanical damage due to excitations caused by the instability stall or surge.
In the present invention the device is capable of demarcation of stable and unstable operating regions of the compressor.
In the device of present invention pressure signals and shaft rotational pulses are taken to the microprocessor. The embedded mathematical module evaluates an instability parameter online. If the measured value indicates detection of stall inception the signal generator module is energized and sends command out of the device to control valve provided in the compressor to open.
The novelty of the device of the present invention is that the device is capable of proactively detecting and controlling stall and surge. The inventive step lies in the detection and processing of spatial and temporal disturbances that occur in a compressor stage and use it to detect stall inception and control surge. Another inventive step is in generating aerodynamic flow parameter which take into account the basic phenomena that is responsible for initiation of disturbances. This is done by taking the input from the pressure and rotation signals and evaluating an instability parameter within the device and generating a signal upon detection.
The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention.
EXAMPLE -1
The device was used to detect the inception of stall in centrifugal compressor stage. The pressure transducer was mounted at the exit of the centrifugal compressor and the eddy current probe was mounted below the rotating shaft of the compressor. The device was energized. The compressor was started and the speed was brought to steady level of 8000 rpm. In order to study the effectiveness of the device, the compressor was made go into stall by operating the control valve. It was found that the device successfully activated the control valve and thereby preempting the compressor going into stall and surge.
The main advantages of the present invention are
(1) The device is used to find the inception of stall in centrifugal compressor. It is
also useful to control stall in centrifugal compressor.
(2) Through this device the mechanical damage to impeller caused due to exitational
vibrations due to stall could be avoided.
(3) The identified parameter characterized through the device is ahead of the stalling
of the compressor.
(4) The timing for corrective action as well as mode of action by this device are
well ahead of actual stall.
(5) The device could be used in compressors to detect inception of stall and as a
protective device against stall and surge.

We Claim:
1. A protective device for controlling stall and surge in compressors, characterized
by a pressure transducer (2) having a frequency response of at least 100 kHz
mounted on to a compressor (1) which needs to be protected from stall and
surge, the said compressor being also provided with an eddy current probe (3)
capable of providing rotor triggered signal, the outputs of the said pressure
transducer (2) and the eddy current probe (3) being connected to a
microprocessor module-A (4) capable of processing at least one million
samples/second and generating outputs of a pressure averaged (Pav) and real
time pressure (Prt), the said outputs (Pav, Prt) being fed to a second
microprocessor module-B (5) having a clock speed of at least 150 mega Hertz
and random access memory (RAM) of at least 32 mega bytes and capable of
generating a processed instability parameter output, the said outpyut being fed
to a comparator and signal gernator module (6) capable of providing a triggered
pulse to a control valve (7) connected to the compressor (1).
2. A protective device as claimed in claim 1 wherein the pressure transducer used
is compatible to the operating level of the compressor.
3. A protective device as claimed in claims 1 and 2 wherein the microprocessor
module-A (4) has in-built analogue to digital converter and is capable of
simultaneous acquisition and processing of signals.
4. A protective device as claimed in claims 1-3 wherein the microprocessor module-
B (5) is a conventional personnel computer.
5. A protective device as claimed in claims 1-4 wherein the triggered pulse from
, the signal generator is connected to an alarm system.
6. A protective device for controlling stall and surge in compressors substantially as
herein described with reference to the example and drawing accompanying this
specification.

Documents:

269-del-2000-abstract.pdf

269-del-2000-claims.pdf

269-del-2000-correspondence-others.pdf

269-del-2000-correspondence-po.pdf

269-del-2000-description (complete).pdf

269-del-2000-drawings.pdf

269-del-2000-form-1.pdf

269-del-2000-form-19.pdf

269-del-2000-form-2.pdf

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Patent Number

216819

Indian Patent Application Number

269/DEL/2000

PG Journal Number

13/2008

Publication Date

31-Mar-2008

Grant Date

19-Mar-2008

Date of Filing

16-Mar-2000

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI -110 001,INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	SRINIVASAN RAMAMURTHY	NATIONAL AEROSPACE LABORATORY BANGLORE (KARNATAK) INDIA
2	KULAVEERAN MURUGESAN	NATIONAL AEROSPACE LABORATORY BANGLORE (KARNATAK) INDIA
3	SUBRAMANI SANKARANARAYANAN	NATIONAL AEROSPACE LABORATORY BANGLORE (KARNATAK) INDIA
4	RAGHAVAN RAJENDRAN	NATIONAL AEROSPACE LABORATORY BANGLORE (KARNATAK) INDIA

PCT International Classification Number

G01H 3/04

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA