EP0046698B1 - Means and method for detecting rotating stall - Google Patents

Description

The present invention relates to a method for detecting a rotating detachment in a turbomachine having two rotating bodies: a high pressure body and a low pressure body, method of the type according to which the speed of rotation of each of said bodies is measured.

The gas turbine engine illustrated in Figure 1 is an example of the different types of engines for which the present invention can be used.

The invention also relates to a rotating detachment detection device.

• - chute brutale de la pression de sortie du compresseur 2,4 suivie d'une croissance de cette pression inférieure au taux de croissance normal;
• - augmentation brutale de la température T du flux de gaz à l'entrée des turbines 5, 3, se traduisant parfois par une cassure dans la pente de la courbe de cette température en fonction du temps, et une stabilisation de cette température à des niveaux plus élevés que le niveau normal de consigne;
• - une croissance du régime de rotation N_HP du corps haute pression 4a, 5 inférieure au taux de croissance normal;
• - une stabilisation instantanée du régime de rotation N_BP du corps basse pression 2a, 3, suivie d'une croissance faible de ce régime N_BP;
• - parfois des grondements et une inversion de fonctionnement dite »pompage« du compresseur 2, 4.

Rotary detachment is a phenomenon that affects all turbomachinery at various operating speeds. If the causes are still poorly understood, the effects on double-barrel motors almost always manifest themselves in the same way:

• - sudden drop in the output pressure of the compressor 2,4 followed by a growth of this pressure lower than the normal growth rate;
• - sudden increase in the temperature T of the gas flow at the inlet of the turbines 5, 3, sometimes resulting in a break in the slope of the curve of this temperature as a function of time, and a stabilization of this temperature at levels higher than the normal setpoint level;
• a growth in the rotation regime N _HP of the high pressure body 4a, 5 lower than the normal growth rate;
• an instantaneous stabilization of the rotation regime N _BP of the low pressure body 2a, 3, followed by a weak growth of this regime N _B P;
• - sometimes rumblings and an inversion of operation called "pumping" of the compressor 2, 4.

After a time interval of several seconds, these parameters T, N _HP , N _BP stabilize at values different from those corresponding to normal stabilization, but, under certain conditions, serious accidents can occur suddenly: extinction at the level of the combustion device 6, rupture of blades, etc.

Document US-A-2 918 790 thus describes a system for regulating a turbomachine of the double body type in which the input parameters are the rotational speeds of the low-pressure and high-pressure bodies, but also the temperature d 'turbine inlet, which leads to a very complex method or device of implementation where inter-actions are provided between these parameters and others such as the fuel flow rate or the nozzle opening section. The operating laws adopted are also complex and must be translated by particular profiles of the connecting cam in the device. The invention aims to reduce the number of parameters used and to define simple relationships between them which facilitate implementation.

Document FR-A-2 332 427 relates to a blockage warning detector and a blockage detection method for a turbomachine in which various parameters are also associated: turbine temperature (inlet or outlet), speed reduction speed of the compressor (high or low pressure), position of the compressor relief valves. Document GB-A-1 492 924 relates to a fuel flow control device for a turbomachine in which the parameters chosen are a speed of rotation (possibly of high-pressure body) and another parameter increasing with speed but decreasing in case of rotary detachment which is the outlet pressure of the compressor. GB-A-1 422 572 also relates to a control device using an electronic tachometer. In one embodiment, a comparator receiving two shaft speed signals is associated with a speed differentiator and a threshold switch, the output signals being supplied to an AND gate.

It is therefore important that the pilot or other user be promptly informed of the appearance of the revolving take-off or of the imminence of its triggering in order to be able to take timely measures to prevent it.

This is why an object of the invention is to propose a method for investigating the operating parameters of a turbomachine, evolving before the appearance of rotary detachment, in a characteristic manner.

According to this method, a law of constant evolution is used for several pairs of parameters, this law being characteristic of the appearance of separation.

Another object of the invention consists in making a device capable of using the data coming from appropriate sensors, of processing them in a function generator, of discriminating if two conditions are met, and of triggering an alarm in the cockpit of the turbomachine.

de la vitesse de rotation N_HP du corps haute pression et on génère un signal de commande dès que l'on a:

et

où A, B et C sont des valeurs constantes.For these effects, the method according to the invention, according to which the speed of rotation N _HP , N _BP of each of the rotating bodies is measured, is characterized in that the derivative with respect to time is deduced

of the rotation speed N _HP of the high pressure body and a control signal is generated as soon as we have:

and

where A, B and C are constant values.

• A est compris entre 1 et 1,5, B est compris entre 8 et 30, C est compris entre -0,6 et - 0,2 et dans un cas particulier, A est égal à 1,26; B est égal à 18,2 et C est égal à - 0,4.

Thus, in a particular application of the invention to a known motor, the following values are determined, when the rotational speeds occur as a% of the nominal value:

• A is between 1 and 1.5, B is between 8 and 30, C is between -0.6 and - 0.2 and in a particular case, A is 1.26; B is 18.2 and C is - 0.4.

When the speeds of rotation intervene in absolute value, we choose A equal to 1.62; B equal to 4106 rpm and C equal to - 250 rpm.

For example, said control signal is used to trigger an alarm.

Alternatively or simultaneously, according to one aspect of the invention, said control signal serves to trigger an operation making it possible to return to normal operating conditions of the turbomachine.

) fourni par le déri- vateur avec un deuxième signal de référence (C) fourni par une deuxième source de signal de référence, les premier et second comparateurs étant chacun du type fournissant un signal logique »0« ou »1 selon que le signal de référence reçu par ce comparateur est supérieur ou inférieur à l'autre signal appliqué à ce comparateur; et une porte ET à deux entrées recevent chacune le signal de sortie d'un comparateur respectif, et dont la sortie délivre un signal de commande.The detection device according to the invention is due to type comprising a first detector measuring the speed of rotation (N _HP ) of the high pressure body and a second detector measuring the speed of rotation (N _BP ) of the low pressure body; this detection device is characterized in that it further comprises: a multiplier by a constant A, this multiplier receiving the signal (N _BP ) emitted by the second detector; a subtractor subtracting from the signal (N _HP ) emitted by the first detector, the signal (A - N _BP ) supplied by the multiplier; a first comparator comparing the signal (Nnp ― A · N _BP ) supplied by the subtractor with a reference signal (B) supplied by a reference signal source; a derivative receiving the signal (N _HP ) emitted by the first detector; a second comparator comparing the signal (

) supplied by the diverter with a second reference signal (C) supplied by a second reference signal source, the first and second comparators each being of the type providing a logic signal "0" or "1 depending on whether the signal reference received by this comparator is higher or lower than the other signal applied to this comparator; and an AND gate with two inputs each receives the output signal from a respective comparator, and the output of which delivers a control signal.

• - la figure 1 est une coupe axiale schématique à travers un moteur à turbine à gaz double flux; et
• - la figure 2 est un schéma synoptique d'un dispositif de détection selon un mode de réalisation de l'invention.

The characteristics and advantages of the invention will be better understood on reading the description which follows of an embodiment of the invention, description made with reference to the annexes in which:

• - Figure 1 is a schematic axial section through a double flow gas turbine engine; and
• - Figure 2 is a block diagram of a detection device according to an embodiment of the invention.

The gas turbine engine illustrated in FIG. 1 is a double flow axial flow motor comprising an engine casing 1 in which are mounted, as is known, a low pressure compressor 2 and its drive turbine 3 , as well as a high pressure compressor 4 and its drive turbine 5. A combustion device 6 burns the fuel it receives from a command (not shown) by releasing drive gas from the turbines 3, 5, these gases then being evacuated by a nozzle in order to produce the thrust.

Thus, according to the invention, the parameters used are the rotational speeds of the high pressure and low pressure bodies. The law for the correct adaptation of these regimes is established in the form:

A discriminating criterion eliminates the normal deceleration phases of the engine in the form of a test on the derivative of the rotation regime of the high pressure body with respect to time:

• A = 1,26;
• B = 18,2;
• C = -0,4.

A particular case of application of this process gives the following values, the values of N _HP and N _BP being expressed in% of the nominal speeds of the high pressure and low pressure bodies and the time dt expressed in seconds:

• A = 1.26;
• B = 18.2;
• C = -0.4.

• A = 1,62;
• B = 4106tours/mn;
• C = 250tours/mn/s.

When N _HP and N _BP are expressed in revolutions per minute and the time dt in seconds, we choose:

• A = 1.62;
• B = 4106 revolutions / min;
• C = 250tours / mn / s.

• - les paramètres N_HP et N_BP sont obtenus avec une grande precision et présentent une dispersion faible;
• - les conditions ISA (International Standard Atmosphère) ont une faible influence sur ces paramètres;
• - le temps maximal de détection est de l'ordre de 3 secondes;
• - ces paramètres nécessaires à la détection sont déjà utilisés la régulation normale.

This detection method has many advantages:

• the parameters N _HP and N _BP are obtained with great precision and have a low dispersion;
• - ISA (International Standard Atmosphere) conditions have little influence on these parameters;
• - the maximum detection time is around 3 seconds;
• - these parameters necessary for detection are already used for normal regulation.

) fourni par le dérivateur 13 avec un deuxième signal de référence (C) fourni par une deuxième source de signal de référence 15, les premier 11 et second 14 comparateurs étant chacun du type fournissant un signal logique »0« ou »1« selon que le signal de référence reçu par ce comparateur est, respectivement, inférieur ou supérieur à l'autre signal appliqué à ce comparateur; et une porte ET, 16 à deux entrées 16a, 16b recevant chacune le signal de sortie d'un comparateur respectif 11, 14. A partir des détecteurs de régime HP et BP 7 et 8, les divers générateurs de fonction 9, 10 et 13 calculent les valeurs de NHP-A · N_BP et

dtThe device for detecting a rotating detachment shown in FIG. 2 comprises: a first detector 7 measuring the speed of rotation (N _H p) of the high pressure body 4a, 5 and a second detector 8 measuring the speed of rotation (N _BP ) of the low pressure body 2a, 3; a multiplier by a constant A, 9, this multiplier receive the signal (N _BP ) emitted by the second detector 8; a subtractor 10 subtracting from signal (N _HP ) emitted by the first detector 7, the signal (A · N) supplied by the multiplier 9, a first comparator 11 comparing the signal (NHP-A · N _BP ) supplied by the subtractor 10 with a reference signal (B) provided by a reference signal source 12; a shunt 13 receiving the signal (N _HP ) emitted by the first detector 7; a second comparator 14 comparing the signal (

) supplied by the differentiator 13 with a second reference signal (C) supplied by a second reference signal source 15, the first 11 and second 14 comparators each being of the type providing a logic signal "0" or "1" depending on whether the reference signal received by this comparator is, respectively, lower or higher than the other signal applied to this comparator; and an AND gate, 16 with two inputs 16a, 16b each receiving the output signal from a respective comparator 11, 14. From the speed sensors HP and BP 7 and 8, the various function generators 9, 10 and 13 calculate the NHP-A · N _BP values and

dt

sont réunies, le circuit logique 11, 12, 14, 15, 16 entraîne le fonctionnement d'un système d'alarme optique ou sonore (ou les deux) 17 qui prévient le pilote que le moteur est en décollement tournant. Celui-ci peut alors appliquer une consigne permettant de revenir à des conditions normales de fonctionnement du moteur.When the two conditions:

are combined, the logic circuit 11, 12, 14, 15, 16 causes the operation of an optical or audible alarm system (or both) 17 which warns the pilot that the engine is in revolving take-off. The latter can then apply a setpoint making it possible to return to normal engine operating conditions.

The detection device 7 to 16 can optionally control the automatic execution of a maneuver making it possible to find these normal operating conditions (for example, programming a negative flow step) and a gradual return to the initial operating point.

The device shown in Figure 2 can use conventional electronic components; however, other elements, for example fluidics, can be used. It may be advantageous to use for the detection of N _HP and N _BP the detectors already existing in the regulator; alternatively, these detectors can also be specific to the device.

Claims (7)

1. Method for detecting rotating stall in a turbo-machine having two rotary spools; a high pressure spool (4a, 5) and a low pressure spool (2a, 3), of the type in accordance with which the rotary speed (N_HP, N_BP) of each of the said spools is measured, characterised in this that the derivative with respect to time

of the rotary speed N_HP of the high pressure spool is calculated and a control signal is generated whenever

and

where A, B and C are constant values.

2. Method according to claim 1, characterised in this that when the rotary speeds intersect at a percentage of the nominal value, the coefficients are calculated so that A lies between 1 and 1.5, B lies between 8 and 30 and C lies between - 0.6 and - 0.2.

3. Method according to claim 2, characterised in this that substantially, A is equal to 1.26; B is equal to 18.2 and C to - 0.4.

4. Method according to claim 1, characterised in this that when the rotary speeds intersect at an absolute value, the coefficients are calculated so that substantially A is equal to 1.62; B is equal to 4106 RPM and C is equal to-250 RPM/sec.

5. Method according to one of the preceding claims characterised in this that said control signal serves to initiate an alarm.

6. Method according to one of the preceding claims, characterised in this that said control signal serves to initiate an operation serving to return to normal the functional conditions of the turbo-machine.

7. Detection device for putting into practice the detection method of rotating stall in a turbo- machine according to claim 1 and comprising a high-pressure rotary spool (4a, 5) and a low-pressure rotary spool (2a, 3) of the type comprising a first detector (7) measuring the rotational speed (N_HP) of the high-pressure spool and a second detector (8) measuring the rotational speed (N_BP) of the low-pressure spool, characterised in this that it comprises in addition: a multiplier by a constant A, (9), this multiplier receiving the signal (N_BP) emitted by the second detector (8); a subtractor (10) subtracting from the signal (N_HP) emitted by the first detector (7), the signal (A - N_BP) supplied by the multiplier (9); a first comparator (11) comparing the signal (N_HP-A - N_BP) supplied by the subtractor (10) with a reference signal (B) supplied by a first reference signal source (12); a differentiator (13) receiving the signal (N_HP) emitted by the first detector (7); a second comparator (14) comparing the signal

supplied by the differentiator (13) with a second reference signal (C) supplied by a second reference signal source (15), the first (11) and second (14) comparators each being of a type supplying a logic signal »0« and »1« according to whether the reference signal receiving by the comparator is less than or greater than the other signal applied to this comparator; and an AND gate (16) with two inputs (16a, 16b) each receiving the output signal of a respective comparator (11, 14) and the output of which delivers a control signal.

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