RU2453733C2 - Compressor antisurge protection - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: proposed method comprises defining compressor flow rate variation speed or pressure difference variation rate at confuser and compressor rotor rpm acceleration. In case compressor rotor rpm acceleration ω_c exceeds preset ω_c-crit or compressor flow rate drop Q with inverse signal exceeds preset Q_crit, signal PRESURGE is generated to start count of said signal holding time. In case during said time another signal PRESURGE is generated, holding time is restarted. In case after termination of signal holding time count, count time is not counted to the end, signal SURGE is generated. Note here that signal SURGE may be generated if the number of n_nn occurrences of signal PRESURGE during preset time t_n after occurrence of first signal PRESURGE exceeds critical n_{nn_crit}.

EFFECT: reliable identification of surge at start of its origination.

2 cl, 3 dwg

Description

The invention relates to the field of protection of axial and centrifugal compressors against surge and can be used in the protection and control systems of gas pumping units for both a supercharger and axial compressors of gas-driven engines.

A known method of protecting the compressor from surge (AS USSR No. 985450, F04D 27/02, 1982), carried out by measuring the gas pressure at the compressor output and the rotational speed of its rotor, determining derivatives of the measured values, comparing the values of the derivatives with the settings , delays in the signal for exceeding the setpoint for the pressure derivative and generating a surge signal when the signal for exceeding the setpoint of the derivative of the speed and the delayed signal for exceeding the setpoint of the derivative of pressure coincides in time.

The disadvantage of this method is the low degree of protection of the compressor against surge losses, since the method determines surge only in the presence of surge fluctuations with a well-defined frequency at which the delay unit is set in advance.

A known method of protecting the compressor against surge (RF patent No. 2041398, F04D 27/02, 1995), implemented by measuring the pressure behind the compressor, determining the rate of change, comparing with a threshold value, signal delay, using it as the first protection parameter, measuring pressure behind the first group of compressor stages, gas pressure at the jet nozzle exit, forming a second protection parameter in case the threshold value exceeds the rate of change of the sum of pressure values behind the compressor, pressure behind the first group compressor stages and gas pressure at the jet nozzle exit, while having a common surge signal when the first or second protection parameter appears.

The disadvantage of this method is that it determines the surge only if the compressor load is a combustion chamber with a jet nozzle, as well as the use of a delay element, the value of which is set in advance and, therefore, requires preliminary knowledge about the dynamics of the surge.

A known method of protecting the compressor against surge (RF patent No. 2150611, F04D 27/02, 2000), where by measuring the gas pressure behind the compressor, in front of the compressor, the pressure drop across the confuser, the speed of its rotor and determine the pressure drop across the compressor, the initial the differential pressure values on the compressor, the differential pressure on the confuser and the rotor speed in the memory, then compare the current values of these parameters with the fixed values and, if the current value of the differential pressure on the compressor is higher than If these values are set, then these current values are recorded in the memory as new values, thus updating the memory, if the current value of the differential pressure on the compressor is not higher than the fixed value, the differential pressure value on the confuser is lower than the fixed value, and the value of the rotor speed is not lower than the fixed value, then the first protection signal, in the case of a decrease in the rotor speed, the difference between the current values and the fixed speeds and pressure drops across the confuser is continuously determined, determined from wearing the difference in pressure difference across the confuser to the difference in rotational speeds, after reducing the frequency by a threshold value, this ratio is fixed and then the current of this ratio is compared with it taking into account the curvature coefficient of the gas-dynamic characteristics at the surge boundary, when the current value of this function exceeds the difference ratio previously recorded in memory form a second protection signal, while having a common surge signal when the first or second signals.

The disadvantage of this method is the difficulty of tuning and the lack of satisfactory operation in the event of surge due to a pressure drop at the compressor inlet (for example, at a booster gas compressor station).

The technical result obtained during the implementation (manufacture) or use of means embodying the invention is expressed in increasing the reliability of recognizing surge at the very beginning of its generation for axial and centrifugal compressors, regardless of the type of load the compressor is working on and the type of compressor, as well as in case of compressor operation in the event of a surge as a result of an increase in the outlet pressure or a decrease in the inlet pressure (for example, at booster gas compressor stations where sharp th compressor pressure drop).

превышает заранее заданную

, либо скорость падения расхода через компрессор

с обратным знаком больше заранее заданной

формируют сигнал «Предпомпаж», после чего запускают отсчет времени сигнала помпажа и отсчет времени удержания сигнала предпомпажа, если в течение времени удержания сигнала «Предпомпаж» приходит новый сигнал «Предпомпаж» - время удержания перезапускается, в случае если к моменту окончания отсчета времени сигнала «Помпаж» время удержания сигнала предпомпажа ни разу не досчиталось до конца, формируют сигнал «Помпаж».This is achieved by the fact that in the method of protecting the compressor against surge by measuring the gas pressure behind the compressor, the gas pressure in front of the compressor, the pressure drop across the inlet constriction device (confuser), its rotor speed, the pressure drop across the confuser, comparing the current values of these parameters with the fixed the values determine the rate of change in the flow rate through the compressor or the rate of change of the differential pressure at the inlet constriction device (confuser) and the acceleration of the compressor rotor speed, in the case of if the acceleration of the compressor rotor speed

exceeds predetermined

or the rate of decrease in flow rate through the compressor

with a reverse sign greater than a predetermined

they generate the Pre-surge signal, after which the surge signal time countdown and the pre-surge signal retention time countdown are started, if a new Pre-surge signal arrives during the Pre-surge signal hold time, the retention time is restarted if, at the end of the “ Surge ”, the pre-surge signal holding time has never been counted to the end, the“ Surge ”signal is generated.

превышает заранее заданную

, и скорость падения расхода через компрессор

с обратным знаком больше заранее заданной

.In this case, the signal “Pre-Compression” can be generated only if the acceleration of the rotor speed of the compressor rotor

exceeds predetermined

, and the rate of decrease in flow rate through the compressor

with a reverse sign greater than a predetermined

.

, а также сигнал «Помпаж» могут формировать, если количество появления сигнала «Предпомпаж» n_nn в течение заданного времени t_n от появления первого сигнала «Предпомпаж» превышает критическое

.In this case, the “surge” signal can be generated if the number of occurrences of the “Pre-surge” signal n _nn for a predetermined time t _n from the appearance of the first “Pre-surge” signal exceeds the critical

, as well as the signal "surge" can generate if the number of occurrence of the signal "Pre-surge" n _nn for a given time t _n from the appearance of the first signal "Pre-surge" exceeds the critical

.

Figure 1 shows the change in the position of the operating point of the compressor when bypassing the pumped gas from the output to the compressor input by the signal "Pre-surge" or "Surge".

Figure 2 presents the timing diagram of the signal generation "Pre-surge".

Figure 3 presents the timing diagram of the signal generation "surge".

The method is carried out by measuring the flow rate of the medium through the compressor and the rotational speed of its rotor and determining the rate of change of these parameters. In some cases, instead of measuring and analyzing the flow rate of the medium, it is possible to measure and analyze the differential pressure at the inlet constriction device (confuser). The algorithm for determining the pre-surge state differs in the analysis of compression with the probability of surge due to an increase in the outlet pressure or a decrease in the inlet pressure. In the event that the occurrence of surge is assumed due to an increase in the outlet pressure, the pre-surge condition is diagnosed if one of two events occurs:

превышает заранее заданную

, то есть:1. acceleration of the compressor rotor speed

exceeds predetermined

, i.e:

с обратным знаком больше заранее заданной

, то есть:2. rate of drop in flow rate through the compressor

with a reverse sign greater than a predetermined

, i.e:

в формуле (2) можно использовать скорость изменения перепада на конфузоре

. Формула (2) в этом случае примет следующий вид:in some cases, if the flow rate through the compressor is determined by measuring the differential pressure on the narrowing device (confuser) instead of the rate of change of flow

in formula (2), you can use the rate of change of the differential on the confuser

. Formula (2) in this case will take the following form:

If the occurrence of surging is assumed due to a decrease in the inlet pressure, the pre-surge state is diagnosed in the case of the simultaneous presence of conditions (1) and (2) (or (1) and (2a)).

Upon receipt of the “Pre-Premage” signal, the design of the compressor unit should provide for a number of measures that contribute to the removal of the compressor from the pre-prestigious state. These measures include:

- opening of the anti-surge bypass valve, which bypasses part of the compressed medium from the compressor output to its input, while the pumped gas is partially transferred from the output to the compressor input, the gas flow through the compressor increases, which leads to a return to the stable operation zone (Fig. 1);

- an increase in the critical compression ratio of the compressor due to a sharp increase in compressor drive power;

- other measures.

In figure 1, line a-b is the boundary of the zone of stable operation and is called the boundary of the surge. The area to the left of line a-b is unstable. When the supercharger is operating, it should be prevented from working in the area to the left of the c-d line (control margin). Typically, the operating mode of the compressor station is chosen so that the superchargers operate in a zone of stable operation, however, various disturbing influences can cause the supercharger to approach the surge boundary. In order to keep the supercharger in the stable operation zone, the pumped gas is partially bypassed from the outlet to the supercharger inlet using an anti-surge valve with analog control, while the gas flow through the supercharger increases (line e-f), which leads to a return to the stable operation zone.

If such measures are provided for by the design of the compressor unit, its control system proceeds with their implementation. If such measures are not provided, the control system disconnects the compressor unit from the compression line and stops its drive.

In some cases, even taking measures to combat the precautionary condition is not able to remove the compressor from a dangerous state. To determine this state, a “surge” signal is provided. Based on this signal, the control system makes an emergency stop of the compressor unit with the compressor disconnected from the compression line. To determine the signal "surge", various algorithms are used for cases of a homogeneous and heterogeneous medium.

In the event that the occurrence of surging is assumed due to an increase in the outlet pressure, the control system (ACS) generates the “Surge” signal as follows.

1. When setting the “Pre-surge” signal to the self-propelled guns, two timers are started: the pre-surge signal hold timer and the “Surge” signal timer. The “Surge” signal timer is several times longer than the “Pre-surge” signal hold timer.

2. If a new “Pre-surge” signal arrives during the “Pre-Pomage” signal hold-down timer, the hold-down timer starts again.

3. If by the time the timer “Pomage” has finished, the signal hold-down timer has not counted the pre-surge to the end - the self-propelled gun generates the “Pompage” signal.

In the event that a surge is assumed due to a decrease in the inlet pressure, the control system (ACS) generates a “surge” signal as follows.

1. When the “Pre-surge” signal occurs, two timers are started: the “insensitivity” timer and the “Surge” timer. The "Surge" signal timer is several times longer than the "insensitivity" timer.

2. Upon occurrence of the “Over-surge” signal in the interval between the operation of the “insensitivity” timer and the “Surge” timer, the “Surge” signal is generated.

Means for implementing this method can be implemented on the basis of devices for integrated control systems of multiprocessor MSKU 5000-01, MSKU-SS 4510 manufactured by CJSC NPF Sistema-Service (St. Petersburg).

MSKU-5000 is built on the basis of software and hardware of Siemens Simatic S7. In this system, the computing core is implemented on the basis of processors of the CPU 4xx family. Input-output is carried out through distributed peripherals based on modules of the ET-200S, ET-200M family. Software method is implemented in Simatic S7-SCL language (language of IEC 61131-3 standard). MSKU-SS 4510 is built on the basis of Octagon and Fastwel hardware and proprietary software of NPF Sistema-Service CJSC. The computing core of the system is implemented on the basis of the Octagon 5066 processor module, input-output is carried out through the analog and discrete input-output modules manufactured by Octagon, Fastwel and in-house developed and manufactured by NPF Sistema-Service CJSC.

The present invention is suitable for protection against surging axial and centrifugal compressors, both turbo-driven and electric.

Compared with the prototype, the method has a higher accuracy and reliability of surge recognition and is suitable for compressors operating at any load, including capacitive, and not just a jet nozzle.

Claims (2)

1. A method of protecting the compressor against surge by measuring the gas pressure behind the compressor, the gas pressure in front of the compressor, the pressure drop across the inlet constrictor (confuser), the rotational speed of its rotor, the pressure drop across the confuser, comparing the current values of these parameters with the fixed values, characterized in that determine the rate of change in the flow rate through the compressor or the rate of change of the differential pressure on the input constriction device (confuser) and the acceleration of the rotor speed of the compressor rotor, in the case of and accelerating the compressor rotor speed

exceeds predetermined

and / or flow rate drop through the compressor

with a reverse sign greater than a predetermined

generate a signal “Pre-surge”, then start the countdown of the surge signal and the hold-down time of the pre-surge signal, if during the hold time of the signal “Pre-surge” a new signal “Pre-surge” arrives - the retention time is restarted, if at the end of the time “Surge” the pre-surge signal holding time was not counted to the end, the “Surge” signal is generated. 2. The method of protecting the compressor from surge according to claim 1, characterized in that the "Surge" signal is generated if the number of occurrences of the Pre-surge signal n _nn for a given time t _n from the appearance of the first Pre-Surge signal exceeds the critical n _{nn crit} .

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