EP2805058B1 - Method for reducing pumps in a compressor - Google Patents

Description

The invention relates to a method for avoiding pump surges in a compressor, in which a plurality of characteristics of the compressor is monitored during operation and a setpoint range for the plurality of characteristics is predetermined, wherein when exceeding or falling below a number of parameters from the setpoint range a counteracting the pump surge reaction is triggered. It further relates to a compressor and a turbomachine with a compressor and a control device, which is connected to the data input side with a plurality of sensors, which are designed to detect characteristics during operation.

Compressors, especially gas turbines, tend to pump under certain operating conditions. If the counter-pressure in the direction of flow becomes too great, then the compressor can no longer convey air and the direction of flow reverses locally or even completely. With local backflow, a portion of the air trapped in the compressor and rotates with the blades with. One speaks of a rotating separation of the flow (rotating stall). In contrast, in the so-called compressor surge (deep surge) the medium completely flows back - it comes to a vehement shock opposite to the thrust direction.

Both aerodynamic effects can have serious consequences. While rotating separations can lead to material fractures due to strong vibrations, the spontaneous tearing off of entire blades in the event of a pump surge threatens. In any case, the air flow is interrupted to the combustion chamber of the gas turbine, which leads to switching off the same.

The compressor map, which typically represents the pressure ratio between inlet and outlet pressures versus flow rate, is divided by the surge line into a stable and an unstable region. Pumping occurs when the operating points of the compressor fall into the unstable range by reducing the flow rate (throughput) or by increasing the final pressure (delivery head).

Usually, a surge margin is defined in the control electronics or software of a control device of the turbomachine, which is sufficiently far away from the surge limit in operation at design conditions. Under real conditions, such as. B. with decreasing power frequency, high ambient temperatures and / or air humidity, low calorific values of fuels, but also by aging, contamination or damage to the compressor, it may happen that the surge line reaches the operating characteristic or even falls below. This then leads to immediate pumping of the compressor.

At the inlet of the compressor (suction cone) often one or more sensors designed as differential pressure switches are installed, which, as soon as the flow through the compressor is interrupted during pumping, fall below a certain limit and cause the immediate shutdown of the gas turbine by closing the fuel valves. The anti-pumping pressure switches, however, do not recognize an approach to the surge limit, but only prevent the pumping of the compressor again and possibly the mechanical damage to the compressor by the immediate interruption of the fuel supply.

In a further development, a compressor pressure ratio limiting regulator is therefore often used. Such a controller looks at characteristics of the compressor (pressure ratio, line frequency, Vorleitschaufelstellung and ambient conditions such as temperature and humidity) and compares these with allowable values from a compressor-specific Surge limit map. If the current operating point of the surge limit approaches, ie if it exceeds or falls below a predetermined setpoint range, a reaction counteracting the pump surge is triggered.

The US 2009/055071 is considered to be the closest prior art and discloses all features of the preamble of claims 1 and 6.

A disadvantage of both mentioned methods, however, is that they do not take into account aging, massive contamination or damage to the compressor and thus can no longer reliably prevent pumping of the compressor as the running time of the turbomachine increases.

Next it is for example from the US 2009/0055071 A1 known to arrange pressure sensors and / or microphones in a space upstream of the burner, which detect the states of the compressed air in the room. Their signals are then evaluated to analyze an impending pumping event. Likewise, the beats EP2375081 A2 to use shockwaves and other acoustic phenomena of compressed air for pump prediction. Again, microphones or similar pressure sensors are used. The disadvantage, however, is that such sensors only have a limited service life at higher ambient temperatures.

The invention is therefore based on the object to provide a method for preventing pump surges in a compressor, a compressor or a turbomachine, which reliably prevent pumping of the compressor even at relatively high mileage.

With regard to the method, the object is achieved according to the invention in that the plurality of parameters comprises a parameter associated with the rotary sound of the compressor.

The invention is based on the consideration that for a higher mileage of the turbomachine reliable prevention of pump surges should not be used exclusively on predetermined maps and controllable operating variables, but rather current, for preventive detection of impending surge should be used appropriate measures. Predictive detection would be possible if an approximation to the surge limit in the form of the rotating stall, ie the rotating flow separation, could already be detected by appropriate measurements. It was recognized that such a flow separation generates vibrations in the compressor stages, which lead to increased pressure pulsations and further vibrations. These pressure pulsations and vibrations change the rotational sound of the compressor, so that a change in the rotary sound indicates predictive an imminent pumping. Therefore, a characteristic associated with the rotational sound of the compressor should be measured and used to avoid pump surges.

To detect a change in the rotary sound, a variety of parameters and a variety of sensors can be used, which are able to display vibrations in the compressor. For example, highly dynamic pressure sensors can be used with which the described pressure pulsations can be detected. However, it is disadvantageous here that such pressure sensors are not suitable for long-term stability and are not suitable for all operating conditions of the turbomachine (increased contamination, moisture, increased hum, compressor washing, etc.). Therefore, the measured characteristic assigned to the rotary sound of the compressor is advantageously a vibration amplitude and / or frequency of a component of the turbomachine. The pressure pulsations are also transmitted to the components of the turbomachine. Thus, the rotational sound on the mechanical vibrations of corresponding components of the gas turbine can be determined. The suitable sensors and encoders are less sensitive to the operating conditions mentioned and thus more durable.

Advantageously, provided with the corresponding sensors component is the shaft and / or the housing of the turbine and / or the compressor. Based on the housing and / or shaft vibrations of turbine and / or compressor, the rotary sound can be determined particularly well with regard to an imminent approach to the surge line particularly well.

Advantageously, the characteristics used further include the shaft speed, the compressor discharge pressure and / or the Vorleitschaufelstellung. In this way, the predictive recognition of the pumping can be further improved since the rotary sound can be determined particularly well with the aid of these additional parameters, for example in a computer provided with special evaluation algorithms specifically for the measurement.

In a particularly advantageous embodiment, the counteracting the pump surge reaction comprises a reduction of the target value of the turbine outlet temperature and / or a reduction of the fuel mass flow. As part of the regulation of the turbomachine, a reduction of the setpoint value of the turbine outlet temperature results in the fact that the adjustable pilot vanes of the compressor are opened. This increases the distance to the surge line. By reducing the fuel mass flow, the compressor discharge pressure and thus the compressor pressure ratio are reduced as quickly as possible. As a further measure z. B. through the anti-icing valve of the compressor at the compressor end air are removed. Improving then the air removal via the anti-icing valve can be re-introduced at the compressor inlet. This also reduces the compressor pressure ratio.

Advantageously, a turbomachine with a compressor and a control device for carrying out the method described is formed.

With regard to the turbomachine with a compressor and a control device, which is connected to the data input side with a plurality of sensors, which are designed to detect characteristics during operation, the Problem solved in that one of the sensors for detecting a rotational sound of the compressor associated characteristic is formed.

Advantageously, the respective sensor is a vibration sensor. This is advantageously designed as a vibrometer. Particularly advantageous here are vibrometers which measure accelerations on a piezoelectric basis, such as, for example, the piezoelectric accelerometer CA 901 from Meggitt. This is particularly durable and robust against high temperatures, soiling and compressor washes.

In an advantageous embodiment, the respective sensor of the shaft and / or the housing of the turbine and / or the compressor is assigned. In this case, corresponding sensors are advantageously mounted at several points on the circumference of the compressor, ideally in Klingelbohrungen outside, d. H. not in the flow path.

A power plant advantageously comprises a turbomachine described.

The advantages achieved by the invention are in particular that can be seen by the targeted measurement of the rotational sound of the compressor of a turbomachine approach to the surge line or a rotating stall before an actual pumping occurs. This can be achieved particularly easily by means of corresponding vibration sensors which measure pressure changes of rotating compressor rotor blades of one stage. With the help of other donors (shaft speed, compressor discharge, Vorleitschaufelstellung) can be the rotational sound of the compressor in a control device such. B. determine a computer with special evaluation algorithms. This also makes it possible to detect foreign objects that can damage the compressor flow path and its parts. Namely, such foreign bodies also lead to a change of the rotary sound. Subsequent damage to components downstream of the compressor can thus be avoided.

The invention will be explained in more detail with reference to a drawing. Therein, the figure shows schematically a section through the upper half of a compressor of a gas turbine.

The turbomachine 1, which is shown in detail in FIG. 1, is designed as a gas turbine. From the gas turbine, only the compressor 2 is shown. The compressor 2 comprises guide vanes 6 fixed to a housing 4 and thus fixed, which are located in a flow channel 8 between the compressor inlet 10 and the compressor outlet 12. The first vane 6 in the flow direction of the air is designed as an adjustable guide vane 14. As a result, the air supply can be regulated and throttled in the flow channel 8.

In the flow direction of the air behind each vane 6, 14 16 blades 18 are each arranged on a shaft. The blades 18 and the guide vanes 6, 14 are each arranged in a star shape in rings in the flow channel 8. A ring of guide vanes 6, 14 together with the following in the flow direction ring of blades 18 each one stage of the compressor. 2

For the early detection of impending pumping, a large number of sensors, not shown in detail, are arranged in the compressor 2. In particular, designed as piezoelectric acceleration sensors vibration sensors 20 are mounted in each 90 ° angularly mounted bell holes that detect mechanical vibrations and thus allow an image of the rotational sound of the compressor 2.

The rotary sound is determined by means of an evaluation algorithm 22, which as software on a control device, not shown, for. B. a computer is implemented. In the evaluation algorithm go next to the vibration data the vibration sensors 20, the data of further corresponding sensors or sensors. These include the shaft speed, the compressor pressure ratio between compressor inlet 10 and compressor outlet 12, the vane position, the shaft vibration, and the housing vibration at the compressor and turbine.

If, due to approaching the surge line, the rotational sound or the waveform of the existing vibration meters changes, the computer sends signals (binary or analog) to perform appropriate responses to prevent pumping.

The reactions include opening the anti-icing valve 24, lowering the turbine exit temperature 26 and reducing the amount of fuel 28. Other measures may also be provided. The reactions can be triggered as needed as a function of the results determined by the evaluation algorithm 22. Thus, for example, only a few of the reactions mentioned can take place or else a majority. Furthermore, messages can be sent to operating personnel 30.

Should a foreign body fly through the flow channel 8 of the compressor 2, this can also be determined by the rotary sound change. Foreign object impacts also trigger messages to the operations control system or to the operating personnel 30. The operations control or personnel can then decide on the measures to be taken, for. B. Shutdown and Diagnosis of the Compressor 2 or the Turbomachine 1. Foreign object impacts that can lead to secondary damage or damage to compressor components can - if they do not occur spontaneously - be detected and reported. On the other hand, spontaneous, severe damage leads to automatic measures in the case of FOD 32 (Foreign Object Detection), such as the shutdown of the gas turbine.

Claims (9)

1. Method for avoiding pump surges in a compressor (2), in which a plurality of parameters of the compressor (2) are monitored during the operation and a desired value range for the plurality of parameters is predetermined,
   wherein a reaction (24, 26, 28) that counteracts the imminent pump surge is triggered if a number of parameters from the desired value range are exceeded or fallen below, and wherein the plurality of parameters comprises a parameter assigned to the rotational noise of the compressor (2), and
   the parameter assigned to the rotational noise of the compressor (2) is a vibration amplitude and/or frequency of a component of the fluid-flow machine (2), and the component is the shaft (16) and/or the housing (4) of the compressor (2),
   characterized in that
   sensors are fitted at multiple points on the circumference of the compressor and detect mechanical vibrations.
2. Method according to Claim 1,
   in which, in order to determine the rotational noise, the accelerations of the component are detected.
3. Method according to one of the preceding claims,
   in which the plurality of parameters comprises the shaft rotational speed, the compressor final pressure and/or the pre-rotation vane position.
4. Method according to one of the preceding claims,
   in which the reaction counteracting the pump surge comprises a reduction in the desired value of the turbine outlet temperature (26) and/or a reduction in the fuel mass flow (28).
5. Method according to one of the preceding claims,
   in which the compressor (2) is part of a fluid-flow machine (1).
6. Compressor (2) and a control device
   which, on the data input side, is connected to a plurality of sensors which are designed to detect parameters during the operation,
   wherein
   a plurality of sensors is designed to detect a parameter assigned to the rotational noise of the compressor (2), and wherein these sensors are vibration sensors (20) which are arranged on the compressor (2) of the gas turbine and by means of which mechanical vibrations of the components can be determined, characterized in that the sensors are arranged at multiple points on the circumference of the compressor.
7. Compressor according to Claim 6,
   in which the plurality of sensors are configured as acceleration sensors.
8. Fluid-flow machine (1) having a compressor (2) according to Claim 6 or 7.
9. Power plant having a fluid-flow machine (1) according to Claim 8.

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