WO2009041851A1

WO2009041851A1 - Method for monitoring the operating modes of a compressor and a device for carrying out said method

Info

Publication number: WO2009041851A1
Application number: PCT/RU2008/000257
Authority: WO
Inventors: Nataliya Nikolaevna Ledovskaya
Original assignee: Central Institute Of Aviation Motors (Ciam)
Priority date: 2007-09-24
Filing date: 2008-05-21
Publication date: 2009-04-02
Also published as: RU2354851C1

Abstract

The invention relates to aircraft and compressor engineering. The inventive method for monitoring the operating modes of a compressor consists in measuring the pressure pulsation parameters and the rotor wheel rotation frequency, forming an operating mode control signal and in comparing said signal with a threshold value. The device comprises a sensor (1) for measuring the total pressure and the pulsations thereof, a sensor (2) for measuring the static pressure and the pulsations thereof, a digital recorder, a sensor (4) for measuring the rotor wheel (3) rotational frequency, an identifier (6) of the rotor wheel (3) rotational frequency and velocity, a spectrum analyser (7), a flow parameter identifier (8), a data bank (9), an analyser (10) and a control signal former (11). Said invention makes it possible to increase the compressor reliability, to maintain the operational stability thereof by adjusting the operating mode when the evidence of the approaching rotating stall is detected.

Description

METHOD FOR MONITORING COMPRESSOR OPERATING MODES AND DEVICE FOR ITS IMPLEMENTATION

The invention relates to the field of aircraft engine manufacturing, compressor engineering, and the operation of compressor systems, in particular, to their regulation and protection.

In systems containing a compressor, it is important to ensure the gas-dynamic stability of the working process at maximum efficiency. For this purpose, active monitoring and control of the compressor system operating modes is carried out. The need for active control is due to the danger of the destruction of blade machines due to low-frequency fluctuations in flow with loss of flow stability, whether it is a rotating stall or surge. An increase in the requirements for compressor reliability and, accordingly, for expanding the range of its stable operation, makes us look for new approaches to recognizing the pre-surge and premature compressor condition. Based on an experimental study of the unsteady flow structure in a compressor, it is known that when the air flow through the compressor decreases at the same speed, the flow in the impeller gradually loses stability, i.e. there is a destabilization of the flow in the interscapular channels of the compressor impeller. The first signs of destabilization of the flow occur when approaching a rotating stall, when the angles of attack on the leading edges of the blades in the impeller increase above acceptable values. In this case, there is a change in pressure pulsations measured on

SUBSTITUTE SHEET (RULE 26) wall above the impeller. Pulsation sensors show that, simultaneously with a change in the high-frequency part of the spectrum, which can be manifested in an increase in the amplitudes of the harmonics of the repetition frequency of the blades A _n i and its multiple frequencies: A _P2 , A _n s ... A _n i, the pulsation spectrum changes in the frequency band from 0 to the blades repetition rate A _n ]. In this case, the standard deviation of the pressure in this frequency region increases. A further decrease in the flow rate leads to a redistribution of the pulsation energy in this frequency band to the low frequency region, which is manifested in a change in the ratio of the amplitudes of rotor harmonics with numbers from Ai to 0.5 A _n i. The occurrence of flow destabilization, due to a decrease in flow rate, is accompanied by the appearance in the spectrum of harmonics in the frequency band 0 ... Ai ^{at the} frequency of the rotating stall, which indicates its (nucleation) occurrence. The development of stalling phenomena with a decrease in flow rate after the initiation of a rotating stall leads to a decrease in the frequency of flow pulsations and the further development of a rotating stall and the occurrence of surging. To date, the detection and recognition schemes for the compressor’s pre-surge state are built on the basis of preliminary tests with the definition of the boundary of steady operation in the event of surge. In this case, the range of stable operation is determined by the flow rate and the stability margin is moved away from the surging margin by 10% upward. Currently, proposals are being made to diagnose the compressor's pre-surge state for the occurrence of a rotating stall.

The well-known “Method for stabilizing the gas-dynamic stability of a turbocompressor)), patent RU Na 2098669, F04D 27/2 of 08/21/1995, in which are used as a pressure parameter

SUBSTITUTE SHEET (RULE 26) spectral components of pressure pulsations, measured at least at two points along the circumferential direction of the turbocompressor flow path through which a control signal is generated, compared with a threshold value. The frequencies of the spectral components are compared with the rotor speed, after which the amplitude-frequency characteristics, the frequency of which is a multiple of the rotor speed, are used as the first component of the control signal, and the phase shift between the spectral components not multiple of the rotor speed is used as the second signal component control, the received two-component control signal is then compared with a threshold value, which is a function of the rotor speed.

The well-known “Method for controlling operating modes of the compressor”, patent RU JY ° 2230939, F04D 27/02 of 04.24.2002, which consists in measuring the parameter of pressure fluctuations in its flow part and generating control signals, where it is proposed to determine in the range of possible compressor operation modes in gas coordinates

dynamic characteristics (abscissa) and (ordinate)

TT / V indicates the occurrence of a rotating stall _baz ⁼ f (bases), using the maximum of the autocorrelation function of the pressure fluctuation parameter as a signal for the rotating stall, and then after an interval

time ( ^τ ), which is selected according to the operating conditions of the compressor in the range

~ Psekund - Shchasovj determine the shift of the mode of occurrence of a rotating stall relative to the base border by the ratio

SUBSTITUTE SHEET (RULE 26) Δosj = (Xi - αg _al (πj) and then abscissa point operating mode and system configuration line antisurge control and protection, which occurred at i - that call, is displaced by an amount Δαi = f (πi), corresponding to a change in stall margin, who had place at offset Δαj.

The well-known "Method of monitoring the operating conditions of the compressor system and device for its implementation", patent RU Na 2246640, F04D 27/02, 07/22/2003, which consists in the fact that they are installed downstream of the throat of the interscapular channel of the straightening apparatus of the last stage of the nozzle compressor to measure the total and bottom pressures, measure the difference between the total and bottom pressures, determine the mathematical expectation of the bottom pressure from the averaging time 0.1–0.2 τ _p0c , where τ is the _percentage time constant of the controlled transient.

The disadvantage of these technical solutions is that control signals are generated after the appearance of signs of the onset of loss of flow stability in the compressor, i.e. the beginning of the formation of a rotating stall in it, manifested in the spectrum in the form of harmonics at a frequency less than and not a multiple of the frequency of rotation of the impeller. The formation of control signals requires a time comparable to the time of occurrence and existence of stall phenomena in the compressor, in particular a rotating stall. This creates the possibility of loss of gas-dynamic stability of the compressor.

The objective of the proposed technical solution is to increase the reliability of the compressor, ensuring the maintenance of its stable operation by correcting the operating mode in case of detection of a sign indicating the approach of the occurrence of a rotating stall.

SUBSTITUTE SHEET (RULE 26) The technical result is achieved in the inventive method of controlling the compressor operating modes, which consists in measuring pressure pulsation parameters in its flow part, measuring the speed of the compressor impeller, generating a control signal for the compressor operating mode and comparing it with a threshold value, with pressure use the spectral components of its pulsations, and the frequencies of the spectral components are compared with the rotational speed of the impeller of the compressor, after which the amplitude -frequency characteristics of spectral components, the frequency of which is a multiple of the frequency of rotation of the impeller of the compressor, is used as a component of the control signal, and at the inlet of the compressor in front of the leading edge of its impeller synchronously and continuously at different rotation frequencies measure the total pressure and pulsation of the total pressure, static pressure and pulsations of static pressure, and at the same time determine the main parameters of the inlet flow:

- reduced peripheral speed of the impeller U _{to p} ;

- reduced axial flow velocity λ in _x .

Then, a spectral analysis of pressure pulsations is carried out, and harmonic amplitudes are used as a control signal, the frequencies of which are a multiple of the frequency of rotation of the impeller of the compressor and do not exceed 0.5 of the repetition frequency of the blades of the impeller of the compressor. Using the values of the amplitudes and the values of the main flow parameters at the inlet to the impeller of the compressor, a control signal is generated, it is compared with a threshold value, which prevents the appearance of signs of a rotating stall and surge. The threshold value of the control signal is a function of the impeller speed and the reduced

SUBSTITUTE SHEET (RULE 26) axial flow velocity at the inlet, and is determined under conditions of stable operation of the compressor, to ensure recognition of its emergency state.

The inventive device for monitoring compressor operating modes that implements the inventive method, comprises a full pressure pulsation sensor and a static pressure pulsation sensor, which are installed in the compressor flow path, a compressor impeller, a compressor impeller speed sensor, a digital recorder, a speed and peripheral speed determiner wheels, spectrum analyzer, determinant of flow parameters, data bank for preliminary tests at different speeds, analyzer, etc. comparing the measured and preliminary data, the shaper of the control signal. In front of the leading edge of the compressor impeller, a sensor for full pressure and pulsations of full pressure, and a sensor for static pressure and pulsations of static pressure are installed for synchronous, continuous measurement of total and static pressures and pulsations of full and static pressures at different speeds of rotation of the compressor impeller. The outputs of the full pressure sensor and pulsation of the full pressure, the static pressure sensor and pulsation of static pressure, the speed sensor of the impeller of the compressor are connected to a digital recorder, which is connected to an analyzer that compares the measured and preliminary data. Through the determinant of the rotational speed and peripheral speed of the impeller, the digital recorder is connected to a data bank for preliminary tests at different rotational speeds. At the same time, the digital recorder is connected through a spectrum analyzer and through a flow parameter determiner with a data bank according to preliminary

SUBSTITUTE SHEET (RULE 26) torture at different speeds. The database of preliminary tests at different rotational speeds has feedback from the spectrum analyzer to ensure its continuous operation. A digital recorder, a determinant of the rotational speed and peripheral speed of the impeller, a spectrum analyzer, a determinant of flow parameters and a database of preliminary tests at different rotational speeds have a direct connection with the analyzer, which compares the measured and preliminary data and recognizes its pre-disruptive state. An analyzer comparing the measured and preliminary data and recognizing its pre-disruptive state is connected to a control signal shaper, where a compressor mode control signal is generated, which ensures its stable operating state. The analyzer, which compares the measured and preliminary data and recognizes its pre-disruptive state, has feedback from the spectrum analyzer, which, in the case of stable operation of the compressor, provides a signal to the spectrum analyzer to continue its operation.

Thus, measurements of the total pressure and pulsations of the total pressure, static pressure and pulsations of the static pressure are performed synchronously and continuously at different frequencies of rotation of the impeller of the compressor, and at the same time they are processed throughout its operation.

At each of the fixed operating modes of the compressor, a spectral analysis of the measurement results is performed, compared with the results of preliminary tests. Based on a sample of harmonics amplitudes at frequencies that are multiple of the impeller rotation frequency, which are rotor harmonics, and do not exceed 0.5

SUBSTITUTE SHEET (RULE 26) the repetition rates of the impeller blades form a control signal for the compressor operation mode and compare it with the threshold value determined during preliminary tests of the compressor under conditions of its stable operation during throttling and at the same compressor rotor speed.

The main flow parameters are determined:

- reduced axial velocity λ in _x ,

- peripheral speed U _k - on the periphery of the impeller in front of the leading edge, and compare with their values at the optimum point of the throttle characteristic of the compressor. Based on the results of the comparison, commands are issued to the actuators that regulate the operation mode of the entire compressor system.

Recognition of the compressor pre-failure state by the main flow parameters and the sample of rotor harmonic amplitudes provides the ability to fine-tune the inventive device to the parameters of a specific compressor, which increases the accuracy of determining the boundaries of stable operation of the compressor, and extends the compressor operating area with the highest efficiency values.

The performance of the claimed device is enhanced by the use of high-frequency sensors and a spectral analysis algorithm with short averaging periods.

Preventing the appearance of a rotating stall in the impeller of the compressor, the claimed device does not allow the occurrence of vibrations that occur in the scapular machine due to inhomogeneities that occur during the formation of a rotating stall.

SUBSTITUTE SHEET (RULE 26) Figure 1 presents a diagram of a device for monitoring the operating modes of the compressor.

Figure 2 presents the algorithm for implementing the method of monitoring the operating modes of the compressor according to the claimed device.

A device for monitoring compressor operating conditions shown in FIG. 1 comprises:

1 - sensor full pressure P * and pulsations of the total pressure (P *) ';

2 - static pressure sensor P and static pressure pulsations

(P) ';

3 - the impeller of the compressor;

4 - speed sensor f _{pk the} impeller of the compressor;

5 - digital recorder;

6 - determinant of the rotational speed f _pк and _peripheral speed U ^ of the compressor impeller;

7 - spectrum analyzer;

8 - determinant of flow parameters (peripheral velocity U ^; reduced axial flow velocity λ _vx ; reduced flow velocity in relative motion X _wl at the input);

9 - a database of preliminary tests at different frequencies of rotation of the impeller of the compressor;

10 - analyzer, comparing the measured and preliminary data;

11 - driver signal control.

To ensure the implementation of the algorithm for monitoring the compressor operating modes according to the claimed device, the elements of the device for monitoring the compressor operating modes are interconnected, as shown in figure 2, namely: sensor 1 of the total pressure and pulsations

SUBSTITUTE SHEET (RULE 26) full pressure and static pressure sensor 2 and static pressure pulsations are installed in front of the leading edge of the compressor impeller 3 for synchronous and continuous measurement of total and static pressure and their pulsations, while the outputs of sensor I _{5 of} sensor 2 are connected to a digital recorder 5, which records the measured values full and static pressures and their pulsation and forms temporary implementations. At the same time, the digital recorder 5 registers the readings of the sensor 4 of the rotational speed of the impeller 3 of the compressor. The obtained temporary realizations from the digital recorder 5 are transferred to the determinant 6 of the rotational speed and peripheral speed of the impeller 3 of the compressor, to the spectrum analyzer 7 and the determinant 8 of the flow parameters. The results of operation of the determinant 6 of the rotational speed and peripheral speed of the impeller of the compressor and the determinant 8 of the flow parameters, as well as the spectrum analyzer 7, which calculates the spectra of pressure pulsations, are transmitted to the input of the data bank 9 on preliminary tests at different rotational speeds. The data bank 9 for preliminary tests at different rotational speeds has feedback with the spectrum analyzer 7, which, after the calculation of the spectra of pressure pulsations and transmission of a signal about it to the data bank 9, receives a command to continue the calculation of the spectra of pressure pulsations. Data from Bank 9 data on preliminary tests at different rotational speeds, spectra of pressure pulsations from the output of the analyzer 7, as well as data on the peripheral speed and the values of the reduced flow velocity of the impeller 3 at the input λ _vx , the reduced flow velocity in relative motion ^ ₁ Ha at the entrance to the impeller 3 are fed to the input of the analyzer 10, which compares the measured and preliminary data, where

SUBSTITUTE SHEET (RULE 26) plateau of harmonics whose frequencies are a multiple of the rotational speed of the impeller 3 of the compressor and do not exceed 0.5 the repetition frequency of the blades of its impeller. After that, they are compared with the data of preliminary tests. If the threshold value obtained from the data bank 9 on preliminary tests at different speeds of rotation of the impeller of the compressor is exceeded, the signal is transmitted to the shaper 11 of the control signal, where the control signal of the compressor operating mode is generated and it is transferred to a more favorable mode. If, according to the results of the sample, the amplitudes of harmonics, whose frequencies are multiples of the rotational speed of the compressor impeller, do not exceed the threshold value, a signal about the continuation of operation is fed to the spectrum analyzer 7 for feedback, the control signal is not generated and the compressor continues to operate in stable operation mode. An analyzer 10 comparing the measured and preliminary data has feedback with a spectrum analyzer 7, which, in the case of stable operation of the compressor, provides a signal to the spectrum analyzer 7 to continue its operation.

The inventive device for monitoring the operating modes of the compressor according to the claimed method works as follows.

The sensor 1 of the total pressure and pulsations of the total pressure and the sensor 2 of the static pressure and pulsations of the static pressure are placed at the compressor inlet in front of the leading edge of the compressor impeller 3, and the averaged flow and pulsation parameters are measured at different frequencies of rotation of the compressor impeller. The sensor 4 rotational speed of the impeller of the compressor measure the frequency of its rotation.

SUBSTITUTE SHEET (RULE 26) The measured parameters P * and (P *) ', converted into electrical signals, are recorded using a digital recorder 5, where temporary realizations are formed, which are transmitted to the inputs of the determiner 6 of the speed and peripheral speed of the compressor impeller 3, a spectrum analyzer 7, and determinant 8 flow parameters.

From the output of the determinant 6 of the rotation frequency and peripheral speed of the impeller of the compressor, the obtained values of the frequency of its rotation are transmitted to the spectrum analyzer 7 to calculate the spectral composition of the pulsations of static and total pressure. The values of the peripheral speed from the determinant 6 of the speed of rotation and the peripheral speed of the impeller of the compressor are transmitted to the data bank 9 for preliminary tests at different frequencies of rotation of the impeller of the compressor. Databank 9 is a program containing the values of the flow parameters and its pulsations obtained as a result of preliminary tests of the compressor at different speeds under conditions of its stable and unstable operation to select parameter values at the optimal characteristics points and near the stability boundary for the corresponding speed values and peripheral speed. The data bank 9 has feedback with the spectrum analyzer 7, which allows, after transmitting data from the spectrum analyzer 7 to the data bank 9, to resume the operation of the spectrum analyzer 7 for calculating the pressure fluctuation spectra.

From the outputs of the determinant 6 of the rotational speed and peripheral speed of the compressor impeller, the spectrum analyzer 7, the determinant 8 of the flow parameters and the data bank 9 for preliminary tests at different rotational speeds of the compressor impeller 3, the data obtained using them are transmitted to the analyzer 10, which

SUBSTITUTE SHEET (RULE 26) compares the measured data and the data obtained during preliminary tests at the same impeller speed and reduced inlet flow rate.

An analyzer 10 comparing the measured and preliminary data has feedback with a spectrum analyzer 7, which, in the case of stable operation of the compressor, provides a signal to the spectrum analyzer 7 to continue its operation.

According to the comparison results, if the threshold value of the parameter is exceeded, a control signal is generated in the control signal generator 11, which recognizes the compressor pre-failure state, for the formation of which harmonic amplitudes are used, at frequencies that are a multiple of the frequency of the impeller rotation and do not exceed 0.5 the repetition frequency of the working blades compressor wheels.

The inventive method of monitoring the compressor mode and the device for its implementation allow for stable operation of the compressor, since the control signal is generated in conditions of stable operation and does not allow signs of the occurrence of a rotating stall and surge.

Thus, increasing the reliability of the compressor, ensuring its stable operation by correcting the operation mode in case of detection of a sign indicating the approach of the occurrence of a rotating stall, allows for stable operation of the compressor, since the control signal is formed in conditions of stable operation and does not allow the appearance of signs of the occurrence of a rotating disruption and surge.

SUBSTITUTE SHEET (RULE 26)

Claims

CLAIM

1. The method of monitoring the compressor operating modes, namely, that pressure pulsation parameters are measured in its flow part, the compressor impeller rotational speed is measured, a compressor operation mode control signal is generated, and it is compared with a threshold value, using pressure parameter the spectral components of its pulsations, and the frequencies of the spectral components are compared with the rotational speed of the compressor impeller, after which the amplitude-frequency characteristics of the spectral components total frequency of the compressor impeller is used as a component of the control signal, DIFFERENT in that at the inlet of the compressor in front of the leading edge of its impeller synchronously and continuously at different rotation frequencies they measure the total pressure and pulsations of the total pressure, static pressure and pulsations of static pressure, and at the same time determine the main parameters of the inlet flow:

- reduced peripheral speed of the impeller U _{to p} ;

- the reduced axial flow velocity λ _vx , a spectral analysis of pressure pulsations is carried out, and the harmonic amplitudes are used as a control signal, the frequencies of which are multiple of the compressor rotor speed and do not exceed 0.5 of the compressor impeller blades repetition rate, according to the amplitudes and values of the main flow parameters

SUBSTITUTE SHEET (RULE 26) at the entrance to the impeller of the compressor, a control signal is generated, it is compared with a threshold value, which prevents the appearance of signs of rotating stall and surge, and the threshold value of the control signal is a function of the rotor speed and the reduced axial flow rate at the input, and is determined in conditions of stable operation of the compressor, to ensure recognition of its pre-disruption state.

2. A device for monitoring the compressor operating modes, comprising a full pressure pulsation sensor and a static pressure pulsation sensor, which are installed in the compressor flow path, a compressor impeller, a compressor impeller speed sensor, a digital recorder, a speed and peripheral speed determiner, spectrum analyzer, determinant of flow parameters, a database of preliminary tests at different rotational speeds, an analyzer that compares measured and preliminary It is DIFFERENT that, in front of the leading edge of the compressor impeller, a sensor for full pressure and pulsations of full pressure and a sensor for static pressure and pulsations of static pressure are installed for synchronous, continuous measurement of total and static pressures and pulsations of total and static pressures different frequencies of rotation of the impeller of the compressor, while the outputs of the full pressure sensor and full pulsation

SUBSTITUTE SHEET (RULE 26) pressure, static pressure sensor and static pressure pulsation, compressor rotor speed sensor are connected to a digital recorder, which is connected to an analyzer that compares measured and preliminary data, and through the determinant of speed and peripheral speed of the impeller, the digital recorder is connected to a data bank preliminary tests at different rotational speeds, at the same time the digital recorder is connected through a spectrum analyzer and through a parameter determinant in a stream with a data bank for preliminary tests at different speeds, and a data bank for preliminary tests at different speeds has feedback from the spectrum analyzer to ensure its continuous operation, moreover, a digital recorder, a determinant of the rotational speed and peripheral speed of the impeller, a spectrum analyzer, a determinant flow parameters and a database of preliminary tests at different rotational speeds have a direct connection with an analyzer that compares measured and preliminary data and recognizes its pre-disruptive state, which is connected to the control signal generator, where the compressor control signal is generated, which ensures its stable state, while the analyzer comparing the measured and preliminary data has feedback from the spectrum analyzer, which in the case of stable compressor operation signal transmission to the spectrum analyzer to continue its work.

SUBSTITUTE SHEET (RULE 26)