EP2075721A1 - Selection procedure for the arrangement of sectors of a stator ring for a turbomachine - Google Patents

Abstract

The method involves creating a database of three-dimensional numerical models of a valve sector (100) and lateral valve sectors (200, 300), by digitizing. A criterion to select an arrangement of the sectors is set, and a desired value for the criterion is set. Relative positions of the sectors are determined, for various evaluated arrangements, when the sectors are assembled together. A value of the criterion for the arrangement under evaluation, is determined according to the positions. The arrangement, in which the criterion has the value closest to the desired value, is retained. The criterion is a function of the shapes and the relative positions of the sectors.

Description

The present invention relates to a method for selecting a sector arrangement for a turbomachine distributor.

In a turbomachine distributor, a sector is a known part, comprising one or more blades connecting two platforms. The crowning of sectors is, for the most part, the distributor. In the distributor, each sector is positioned or puts itself in relative mounting position with respect to the two sectors located on either side, by abutting the contact surfaces of its platforms with those of the platforms of the adjacent sectors.

In a distributor, with exception, all sectors have the same geometry. The differences between sectors are difficult to measure and often undetectable to the naked eye. A fortiori, in general the quality of the relative positioning between adjacent sectors is not evaluated. For this reason, in general the optimization of the arrangement of the distributor sectors is not realized.

However, it appeared that due to variations in the manufacturing and use conditions of the sectors, there are significant geometric differences between them. These differences can lead to the appearance of geometrical defects such as asymmetries, which is very detrimental to the service life of the distributor, or even of the turbine engine in which it is mounted, because of the vibrations that these can cause. . Another unfortunate consequence is the decrease of the dispenser yield, or at least the achievement of a suboptimal yield.

The object of the present invention is to define a method for selecting a sector arrangement for a turbomachine distributor, which makes it possible to choose among different evaluated sector settings, the one that is optimal in terms of efficiency or operation of these machines. sectors once assembled. Of course, the method is more particularly intended to allow the choice of an arrangement of a set of sectors constituting a complete distributor.

1. A. on crée par digitalisation une base de données des modèles numériques tridimensionnels de secteurs ;
2. B. on fixe un critère de choix d'un arrangement de secteurs et une valeur souhaitée pour ce critère, le critère étant fonction de la géométrie et de la position relative des secteurs ;
3. C. pour différents arrangements évalués, on détermine par montage virtuel les positions relatives des secteurs montés ensemble, et en fonction de celles-ci, la valeur du critère de choix pour l'arrangement évalué ;
4. D. on retient l'arrangement pour lequel le critère de choix a la valeur la plus proche de la valeur souhaitée.

This objective is achieved by virtue of the fact that the method comprises the following steps:

1. A. digitalization is created of a database of three-dimensional numerical models of sectors;
2. B. a criterion for choosing an arrangement of sectors and a desired value for this criterion is fixed, the criterion being a function of the geometry and the relative position of the sectors;
3. C. for different evaluated arrangements, the relative positions of the sectors assembled together are determined by virtual editing, and according to these, the value of the criterion of choice for the evaluated arrangement;
4. D. the arrangement for which the selection criterion has the value closest to the desired value is retained.

In the foregoing, a sector arrangement for a turbomachine distributor designates the ordered sequence of the individual references of these assembled sectors in relative mounting position, that is to say in crown, to form a distributor. Thus, two arrangements are distinguished when the positions of the sectors inside the distributor are not the same, for example if the sectors have undergone a permutation. It should be noted that an arrangement of sectors may refer to the ordered sequence of individual references of a set of sectors that do not constitute an entire distributor but only a part of it.

The database formed in step A. contains a plurality of sector models, i.e. a collection of sector models, these models being broadly identical because they all represent sectors intended for a given sector. same distributor, but have secondary differences because they come from the digitization of different sectors. It is the existence of these differences that makes the whole point of choosing one arrangement rather than another.

In addition, the choice of an arrangement of a set of sectors concerns, on the one hand, the choice of sectors that make up the arrangement, but also on the respective positions of these in the arrangement.

The method of choosing a sector arrangement presented above makes it possible to optimize the choice of sectors and their relative positions in a distributor during the constitution of the distributor. As a result, a distributor with increased performance and increased service life is achieved. In addition, the use of a database of three-dimensional numerical models of distributor allows the control and the follow-up in time of a large number of geometrical characteristics of the sectors of the distributor.

It will be noted that digitization here denotes any method of recording three-dimensional coordinates on the part, whether by mechanical means using a touch point, or by optical means using a laser scanner or with structured light projection for example. In all cases, digitization involves the recording of a large number of three-dimensional coordinates, so as to obtain a "cloud of points", which makes it possible in particular to present on a computer screen the numerical model obtained in the form of mesh. .

For the step A. of creating a database of the three-dimensional numerical models of the sectors, each sector of distributor is measured in general disassembled, independently of the other sectors and without relative positioning with respect to these (which does not however, it does not prevent the use of means for securing or maintaining the sector during the measurement).

The use of digitalization, for parts such as distributor sectors, is a delicate operation, but one that has substantial advantages.

This operation is difficult firstly because of the shape of the surfaces of the dispenser sector. A dispenser sector is a complex shaped part, having many left surfaces, and whose normal directions are directed in all directions of space.

• Ce sont tout d'abord les surfaces dont le modèle numérique est nécessaire pour déterminer la valeur du critère de choix retenu. Naturellement, ces surfaces peuvent être localisées dans des emplacements difficiles d'accès. En effet, les surfaces fonctionnelles principales du secteur et qui sont les plus importantes sont les surfaces des aubes ; or, celles-ci sont disposées principalement dans le canal inter-aube. Ce canal est étroit, mesurant quelques millimètres à quelques centimètres de large ; l'introduction d'un outil de mesure dans cet espace est donc difficile. La mesure des surfaces du canal inter-aubes est donc particulièrement problématique ; et pour cette raison, dans le cas de nombreux critères, la digitalisation des surfaces nécessaires pour l'évaluation du critère est problématique.
• La seconde famille de surfaces dont la digitalisation est nécessaire, en vue du montage virtuel des secteurs réalisé à l'étape C., est celle des surfaces de référence nécessaires pour le montage virtuel. Ces surfaces de référence sont orientées de manière complètement différente des surfaces à mesurer. Il en résulte une difficulté de mesure supplémentaire.

Although it is not necessary to digitize all the external surfaces of the sector, it is necessary to digitize at least two families of surfaces:

• These are first the surfaces whose numerical model is necessary to determine the value of the selection criterion chosen. Naturally, these surfaces can be located in difficult to access locations. Indeed, the main functional surfaces of the sector and which are the most important are the surfaces of the blades; however, these are arranged mainly in the inter-blade channel. This canal is narrow, measuring a few millimeters to a few centimeters wide; the introduction of a measurement tool in this space so is difficult. The measurement of the surfaces of the inter-blade channel is therefore particularly problematic; and for this reason, in the case of many criteria, the digitization of the surfaces necessary for the evaluation of the criterion is problematic.
• The second family of surfaces whose digitization is necessary for the virtual editing of the sectors performed in step C., is that of the reference surfaces necessary for virtual editing. These reference surfaces are oriented completely differently from the surfaces to be measured. This results in an additional difficulty of measurement.

Finally, the accuracy that the digitization operation must have is important. Indeed, the admitted measurement uncertainty does not exceed the hundredth or even a few hundredths of a millimeter.

For the different reasons mentioned above, the digitization of the distributor sector is a difficult operation.

Conversely, digitalization provides a three-dimensional numerical model of the distributor sectors which contains a very large amount of information on them, namely, in practice, the possibly complete record of their external form. The exploitation of these digital models makes it possible to carry out the virtual assembly stages of the distributors, and to determine the value of the criterion for a set of assembled distributors, operations that are obviously impractical in the absence of a database of the digital models of the distributors. sectors of distributors.

Finally, the database constituted in the context of the method according to the invention consists of numerical models which make it possible to measure a large number of dimensions of the distributor sector and to verify their actual values with respect to their specified and toleranced values on the plan. The database thus allows powerful traceability operations.

Finally, the choice criterion set in step B) can take different values depending on the constraints considered most important for the optimization of the distributor. It is thus possible, for example, to seek to make the passage sections as close as possible to each other in the distributor, regardless of their respective dimensions; or any other criterion depending on geometries and relative positions in the arrangement of different sectors.

Depending on the computing power available, the method can be applied by evaluating a larger or smaller number of arrangements. If a large computing power is available, it is possible to test all the combinations of sectors of the database.

If the computing power is more modest, one can proceed as follows: in step C, an evaluated arrangement is the combination of an arrangement chosen by the method and another sector or another arrangement chosen using the method. The dispenser mounting algorithm is thus a recursive algorithm: the arrangement of the sectors comprising the distributor is gradually defined, optimizing at each step the addition of a new distributor sector with respect to the existing arrangement. The computing power consumed is much lower than in the previous case.

In addition, the database of three-dimensional models of distributor sectors can be used either to optimize the assembly of a single distributor or to optimize a fleet of distributor sectors making it possible to compose several distributors.

Thus according to the embodiment, in step A), the database used for the method may contain sectors coming from a single distributor, or sectors from at least two different distributors.

The method comprises an important step, in particular from the point of view of the measurement accuracy, which is that of the virtual assembly in assembled positions, of the numerical models of the sectors of the evaluated arrangement. (By virtual editing, here we mean the determination of the different three-dimensional reference changes, to be applied respectively to the three-dimensional numerical models of the sectors, to place these in mutual mutual mounting position, in a virtual space. in reference). For this virtual assembly, the registration is thus done digitally, on a computer, between the numerical models of the different sectors of the evaluated arrangement.
In the virtual editing step C., the virtual editing of the digital models of the distributor areas of an evaluated arrangement is done in the following manner. As has been written, the distributor sectors have contact surfaces, and are placed in relative position with respect to the adjacent distributor sectors by abutment of these contact surfaces.
According to one embodiment, in the database created in step A., the numerical models of the sectors comprise a modeling of the contact surfaces involved in their relative positioning position; and in step C the virtual editing of the numerical models of the sectors in an evaluated arrangement is made by mapping the contact surfaces of the adjacent sectors of said arrangement.

The digital registration thus follows the same rules, and thus provides the same results, as the real registration that could be achieved between the different distributor sectors of the evaluated arrangement.

It will further be noted that by simultaneously recalibrating a set of valve sectors, their passage sections (each being determined relative to the two adjacent sectors in the studied position) can be determined together.

According to one embodiment, the digitization step A. is carried out using a non-contact optical measurement means. The use of non-contact measurement or optical measurement is particularly advantageous in the case of distributor sectors because it avoids any scratching of these parts and any degradation of the surface thereof.

According to one embodiment, the creation of numerical models of the sectors, by digitalization, is automated. This result can be obtained in particular by embedding the digitalization sensor, like a 3D scanner with structured light projection, at the end of the arm of a robot. For the digitization of each sector, the arm of the robot travels a predetermined trajectory, including a certain number of stopping positions. When stopping the arm at these stopping positions, the digitizing sensor performs a data acquisition. In a known manner, the different acquisitions made at the different stopping positions are recalibrated with reference to the others automatically, by a calculator, so as to constitute the three-dimensional numerical model of the digitized sector. Digitization in automatic mode of a set of sectors can be done using a conveyor which places successively in front of the robotic arm carrying the digitization sensor, the different sectors to digitize.

According to one embodiment, the steps of determining a set of arrangements to be evaluated, virtual editing of the sectors of an evaluated arrangement, and / or determining the values of the selection criterion for the different evaluated arrangements, are automated. . A computer software used to perform the step C. of resetting and determining the passage sections is indeed programmed to perform these operations in sequence, without human intervention. The result obtained is a control report indicating the optimal arrangement and the criterion value of choice for this arrangement.

The advantages of automation are a saving of time, a reduction of operating errors, a reduction of labor time, and an increase in the reproducibility of the results, and ultimately a better accuracy of the measurement process.

In one embodiment, the selection criterion is a function of the respective passage sections of the distributor sectors. In a distributor, the overall performance depends in fact in particular the passage sections of the distributor, that is to say, the sum of the passage sections of the different sectors. The measurement of these passage sections is therefore an important operation.

For a given sector, the passage sections are the areas, measured perpendicularly to the flow direction, of the flow passing through the distributor sector. By extension, the passage sections can also more simply designate the passage widths of the flow through the distributor sector, measured in a perpendicular to the axis of the blades.

In what follows, the passage sections will be considered in their exact sense, that is to say flow passage sections that are areas. More generally, it will be understood that the present invention also aims at the case where the flow passage sections are only the passage widths of the flow as has been said previously.

In flow passage sections in a manifold sector, internal passage sections and external passage sections can be distinguished.

The internal passage sections, concerning only distributor sectors each having at least two vanes, are measured between adjacent vanes in pairs of the sector considered.

The external passage sections, two in number, are each half of the area formed between an end blade of the sector and the adjacent blade sector vis-à-vis in the distributor. In principle, the area between the end vane of the distributor sector and the adjacent vane must be determined with an adjacent vane that would be at the nominal dimensions; the nominal passage section at this end of the distributor sector is then obtained. By extension, it is possible to determine a real passage section for the end of the dispenser with respect to a blade of a given sector; in this case, the area between the end vane of the distributor sector and the latter vane is determined, and the passage section for this end of the distributor sector is half of this area.

According to one embodiment, to determine the passage section of a sector disposed at one end of the arrangement, a theoretical numerical model of a reference blade is also used. By theoretical numerical model, is meant here a model that has been generated by computer, typically using computer-aided design software (CAD); as opposed to a model resulting from digitization.

If the sectoral arrangement does not constitute a complete distributor, but only a part of it, the question arises, in the case where the criterion of choice concerns the sections of passage of the sectors, the measurement of passage sections of the two sectors at the ends of the arrangement. The numerical models of two reference vanes are then used. During the virtual assembly of the sectors, these vanes are positioned in relative mounting position at the ends of the arrangement. It is then possible to calculate the sections of passage of all the sectors, and thus to lead the process of choosing an arrangement to completion.

• la figure 1 est une vue en perspective de trois secteurs de distributeur présentés en position relative de montage ;
• la figure 2 est une vue en coupe circonférentielle en position relative de montage d'un secteur mesuré et de deux secteurs adjacents ;
• la figure 3 est une vue en coupe d'un secteur, faisant apparaître la section du canal inter-aubes dans lequelle est mesurée une section de passage entre deux aubes adjacentes ; et
• la figure 4 est une vue de face d'un ensemble de secteurs d'un distributeur, dont l'arrangement est optimisé grâce au procédé selon l'invention.

The invention will be better understood and its advantages will appear better on reading the detailed description which follows, of embodiments shown by way of non-limiting examples. The description refers to the accompanying drawings, in which:

• the figure 1 is a perspective view of three distributor sectors presented in relative mounting position;
• the figure 2 is a circumferential sectional view in relative mounting position of a measured sector and two adjacent sectors;
• the figure 3 is a sectional view of a sector, showing the section of the inter-blade channel in which is measured a passage section between two adjacent blades; and
• the figure 4 is a front view of a set of sectors of a dispenser, the arrangement is optimized by the method according to the invention.

It will be noted that when an element appears in several figures, either identically or in a similar form, it is described in relation to the first figure on which it appears; moreover, the description of the element is made only once.

With reference to figures 1 and 3 , a distributor sector will now be introduced. The meeting of such sectors makes it possible to compose a distributor, arranged around a distributor axis.

The sector of distributor 100 visible in figure 1 has two platforms 130, 140, substantially parallel. These platforms are substantially cylindrical in shape around the axis of the dispenser. These platforms 130, 140 comprise contact surfaces 131, 132, 141, 142, respectively directed towards the two sectors of distributors arranged on either side of the sector 100 measured (relative mounting position). The contact surfaces are designed to maintain the adjacent distributor sectors 200 and 300 in the relative position of contact. These lateral sectors 200, 300 respectively comprise two end vanes 220 and 310, which are arranged opposite the vanes. end of the sector 100 in the relative mounting position of the sectors.

The distributor sector 100 further comprises two blades 110, 120. Each of these blades has an aerodynamic profile and comprises a lower surface 111, 121, and an extrados 112, 122. As there are only two blades in the sector 100 , each of the vanes 110, 120 is a dawn end. Thus, each of these vanes is caused to be disposed vis-a-vis with an end vane of the adjacent distributor sector, in relative mounting position. More specifically, the intrados 111 is vis-à-vis the extrados 222 of the blade 220, and the extrados 122 is vis-à-vis the lower surface 311 of the blade 310.

Between the respective blades are formed inter-blade passages 101, 102, 103. The passage 102 is formed between the blades 110, 120 of the sector 100. In contrast, the inter-blade passages 101 and 103 are formed between, a a dawn (110 or 120) of the sector, and secondly the reference dawn vis-a-vis, 220 or 310.

In the embodiment of the method that will be presented in the following, the selection criterion chosen for an arrangement is a function of the passage sections in each sector. For this reason, before detailing the method according to the invention, the mode of determining the passage sections of a distributor sector will now be presented.

The passage sections are presented in relation to the figure 2 . This represents a section in a plane P, perpendicular to the axis of the vanes and substantially mid-height thereof, of the distributor sectors 100, 200, 300 showing in particular the reference vanes 220 and 310 (On was placed in the case where the blades would be full blades).

This section shows the sections of the various blades 220, 110, 120, 310; the mating contact surfaces 242, 141, 142, 341; and the inter-blade channels 101, 102, 103. By design, the nominal shape of the different channels is substantially the same.
As can be seen, in a given inter-blade channel, the distance between the vanes fluctuates as a function of the position in the channel. There is usually only one plane for which this distance is minimal. As the distance between the platforms 130, 140 is substantially constant, it is also in this plane that the passage section between the blades is minimal, for a given inter-blade channel. This plane of the channel corresponds respectively to the planes P1, P2, P3 for the channels 101, 102, 103; the distance between the blades in these sections is respectively D1, D2, D3. It will be noted that, advantageously, in the method according to the invention, it is possible to optimize for each inter-blade channel the position of the plane P1, P2, P3 section, thus determining the plane of the inter-blade channel in which the passage section is actually minimal.

• On définit tout d'abord une section de passage du flux entre deux aubes adjacentes comme étant sensiblement égale à l'aire minimale de passage du flux entre celles-ci.
• Par définition également, les sections de passage du secteur sont d'une part, lorsque le secteur comporte plus d'une aube, la ou les sections de passage du flux entre la ou les paires d'aubes adjacentes du secteur (ce sont les sections de passage internes du secteur) ; et d'autre part, la moitié des section de passage du flux entre une aube d'extrémité du secteur et l'aube du secteur adjacent en vis-à-vis de celle-ci (ce sont les sections de passage externes du secteur).
• Suivant un mode de calcul de section de passage, une section de passage du flux entre deux aubes adjacentes est déterminée sur la base de la plus petite distance entre celles-ci. Les plus petites distances entre aubes adjacentes, dans les trois canaux inter-aubes 101, 102, 103 représentés sur la figure 2, sont les distances D1, D2, D3.
• Notons tout d'abord que par extension du concept de section de passage, une section de passage peut être définie non pas par une aire de passage, mais par une largeur de passage pour le flux.
• Dans ce dernier cas, la distance D2 (pour une section de passage interne du secteur), les moitiés des distances D1 et D3 (pour les sections de passage externes du secteur) peuvent être considérées comme les sections de passage du secteur de distributeur.
• Nous revenons maintenant à la définition première des sections de passage, dans laquelle la détermination des sections de passage est sous forme d'aires.
• Ainsi, une section de passage du flux entre deux aubes adjacentes est égale à l'aire de la section d'espace libre entre les deux aubes, dans le plan sensiblement parallèle à l'axe des aubes et dans lequel la distance entre les aubes est la plus faible.
• Cette section est illustrée sur la figure 3, pour le canal inter-aubes 101. La figure 3 représente en effet une coupe des secteurs de distributeurs 100 et 200, en position relative de montage. Cette coupe est faite dans le plan P1 de moindre distance entre les aubes adjacentes 220 et 110, et qui apparaît en figure 2. On notera que la digitalisation des aubes des secteurs 100 et 200, permet d'obtenir la section réelle du passage 101 et de connaître les positions réelles des quatre parois 111, 222, 135-235, 145-245, délimitant le secteur, représentées sur la figure 3.

The figure 3 shows the section of the distributor sector following the plane P1. It shows the geometry of the passage in the inter-blade channel 101.
On the basis of the information provided on the section of the figure 3 , the value of the passage section of interaubes channel 101 can be determined as follows:

• Firstly, a flow passage section between two adjacent blades is defined as being substantially equal to the minimum flow passage area between them.
• By definition, also, the passage sections of the sector are, on the one hand, when the sector comprises more than one blade, the flow passage section or sections between the pair or pairs of adjacent blades of the sector (these are the sections). internal passage of the sector); and on the other hand, half of the flow passage sections between an end blade of the sector and the blade of the adjacent sector opposite it (these are the outer passage sections of the sector) .
• According to a passage section calculation mode, a passage section of the flow between two adjacent blades is determined based on the smallest distance between them. The smaller distances between adjacent vanes, in the three inter-vane channels 101, 102, 103 shown in FIG. figure 2 , are the distances D1, D2, D3.
• Let us first note that by extension of the concept of passage section, a passage section can be defined not by a passage area, but by a passage width for the flow.
• In the latter case, the distance D2 (for an internal section of the sector), the halves of the distances D1 and D3 (for the external sector passage sections) can be considered as the passage sections of the distributor sector.
• We now return to the first definition of passage sections, in which the determination of the passage sections is in the form of areas.
• Thus, a passage section of the flow between two adjacent blades is equal to the area of the free space section between the two blades, in the plane substantially parallel to the axis of the blades and in which the distance between the blades is the weakest.
• This section is illustrated on the figure 3 , for the inter-blade channel 101. The figure 3 represents in fact a section of the distributor sectors 100 and 200, in relative mounting position. This cut is made in the plane P1 of lesser distance between the adjacent blades 220 and 110, and which appears in figure 2 . It will be noted that the digitalisation of the blades of the sectors 100 and 200 makes it possible to obtain the real cross-section of the passage 101 and to know the real positions of the four walls 111, 222, 135-235, 145-245 delimiting the sector, represented on the figure 3 .

Knowing these positions, the area of the part of the plane P1 located between these four walls can be calculated or determined. This determination can be done in several ways, more or less approximate.

The distance between the platforms 130-230 and 140-240 being in first approximation constant (these platforms being substantially of cylindrical and coaxial shapes), the value of the passage section S ₁₀₁ in the inter-blade channel 101 between the two adjacent blades 220 and 110, is the product of the smallest distance between the blades, D1, by the distance H between the platforms.

Therefore, at the ends of the sector, the passage section relative to the considered sector (or measured), called 'external', is worth half of this product: It is therefore S _100/1 = ½ x S ₁₀₁ = ½ x D1 x H in the case of the section relating to the inter-vane channel 101 of the figure 4 .

For the channels 102 and 103, the passage sections relative to the sector 100 are respectively: S _100/2 = S ₁₀₂ = D2 × H (internal passage section); and finally S _100/3 = ½ x S ₁₀₃ = ½ x D3 x H (outer passage section).

The passage section attributable to the distributor 100 is: $${\mathrm{<figure-callout\; id="100"\; label="S"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">S</figure-callout>}}_{\mathrm{100}}\mathrm{=}{\mathrm{<figure-callout\; id="100"\; label="S"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">S</figure-callout>}}_{\mathrm{100}\mathrm{/}\mathrm{1}}\mathrm{+}{\mathrm{<figure-callout\; id="100"\; label="S"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">S</figure-callout>}}_{\mathrm{100}\mathrm{/}\mathrm{2}}\mathrm{+}{\mathrm{<figure-callout\; id="100"\; label="S"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">S</figure-callout>}}_{\mathrm{100}\mathrm{/}\mathrm{3}}\mathrm{=}\mathrm{½}{\mathrm{S}}_{\mathrm{101}}\mathrm{+}{\mathrm{<figure-callout\; id="102"\; label="S"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">S</figure-callout>}}_{\mathrm{102}}\mathrm{+}\mathrm{½}<figure-callout\; id="103"\; label="\; S"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\; </figure-callout>{\mathrm{S}}_{}{\mathrm{}}_{\mathrm{103}}\mathrm{.}$$

The method previously indicated is to measure the actual distance H between the two walls 135-235 and 145-245 of the platforms 130 and 140, and to multiply it by the distance D1 between the walls 111 and 222 of the adjacent blades 110 and 220.

One can alternatively exploit more finely the information available in the numerical models of the sectors to more accurately determine the area of passage between the adjacent blades; for example, note that the portion of the plane P1 located between the four aforementioned walls substantially forms a trapezium (the walls of the blades are parallel), and determine the area of this part of the plane P1 accordingly.

In the end, we obtain for the sector, the values of its various sections of passage, the sum of which constitutes the section of passage attributable to the sector or sector.

• on identifie les différentes sections de passage, internes et externes, qui sont à déterminer ;
• on coupe les modèles numériques du secteur et des secteurs adjacents par le plan, parallèle à l'axe des aubes, et dans lequel la distance entre les aubes est la plus faible ;
• on détermine l'aire de la partie du plan située dans le passage inter-aubes considéré ;
  la section de passage valant cette aire pour les sections internes, et la moitié de cette aire pour les sections externes.

In summary, to determine the passage sections of a dispenser sector as the sector 100 shown in the figures:

• we identify the different sections of passage, internal and external, which are to be determined;
• cutting the numerical models of the sector and adjacent sectors by the plane, parallel to the axis of the blades, and in which the distance between the vanes is the lowest;
• the area of the part of the plane located in the inter-blade passage considered is determined;
  the passage section equaling this area for internal sections, and half that area for external sections.

The method of choosing a sector arrangement for turbomachine distributor according to the invention will now be detailed.

In the example considered, it is only sought to optimize the choice of eleven sectors to occupy positions I to XI of a distributor, presented on the figure 4 .

In a first step, the database of three-dimensional digital models of a number of sectors is digitized.

In general, each of the distributor sectors is digitized alone (or at least, without specifically being in relative mounting position relative to the reference vanes). Its digitalization makes it possible to obtain its three-dimensional numerical model. As the dispenser sector is digitized alone, it is easier to obtain a complete model of the sector, that is to say including all of its external surfaces.

The digital model obtained by digitization involves digitizing the contact surfaces of the distributor sector. These contact surfaces are the surfaces 131,132,141,142 which serve to maintain the sector relative to the adjacent sectors in relative mounting position.

The numerical models of the reference vanes are also obtained. For each reference blade, its model contains the mounting surfaces of the sector that includes the dawn. These models can for example be an extract from the three-dimensional digital model of the distributor (or only the sector).

The database of the different sectors is then created, including the reference vanes.

For example, we can assume that we produce the hundred digital models of one hundred sectors for distributors, numbered from 1 to 100. Each three-dimensional model includes the representation of its contact surfaces, thus allowing the registration of the sector relative to to adjacent areas.

dans lequel S_i est la section de passage du secteur i et S₀ la section de passage nominale d'un secteur, et la somme porte sur tous les secteurs de l'arrangement considéré. (D'autres choix pour le critère sont bien entendu possibles).In a second step, a selection criterion is set to evaluate the quality of a given sector arrangement, and a preferred value is chosen for this criterion. This criterion is a function of the passage sections of the sectors in relative position of assembly in the arrangement. We choose here the following criterion: $$\mathrm{Criterion}\mathrm{=}\underset{\mathrm{arrangement}}{\mathrm{\Sigma }}\mathrm{(}{\mathrm{S}}_{\mathrm{i}}\mathrm{-}{\mathrm{S}}_{\mathrm{0}}{\mathrm{)}}^{\mathrm{2}}$$

where S _i is the passage section of the sector i and S ₀ the nominal passage section of a sector, and the sum relates to all sectors of the arrangement considered. (Other choices for the criterion are of course possible).

The preferred value for this criterion is zero.

• On réalise le montage virtuel en position relative de montage des onze secteurs. Cette opération est faite en mettant en correspondance les surfaces de contact de chaque secteur avec celles des secteurs adjacents. Naturellement, pour la détermination des sections de passage externes des aubes situées aux positions d'extrémité dans un arrangement (s'il y a lieu), on prend en compte comme aube de référence le modèle numérique d'une aube aux cotes nominales, recalée par rapport au secteur d'extrémité.
• Les modèles numériques des secteurs étant dans cette position relative de montage, on détermine les sections de passage des différents secteurs, et à partir de celles-ci on détermine la valeur du critère cité précédemment, pour l'arrangement évalué.

During the third stage (C.), sectors 1 to 100, all the sectoral arrangements making it possible to constitute a distributor part are envisaged. Each arrangement is presented as following individual references of the sectors of the arrangement, ordered according to the positions 1 to XI and for example one of the arrangements is the following: (28-4-90-80-54-43-91-3 -11-35-66), in which for example sector No. 28 occupies position I and sector No. 66 position XI.
For each of the possible arrangements of the hundred sectors in the eleven positions, one operates in the following way:

• The virtual assembly is carried out in the relative mounting position of the eleven sectors. This operation is done by matching the contact surfaces of each sector with those of adjacent sectors. Naturally, for the determination of the external passage sections of the vanes located at the end positions in an arrangement (if any), the reference numerical model of a dawn with nominal dimensions is taken into account as a reference blade. compared to the end sector.
• The numerical models of the sectors being in this relative mounting position, the cross sections of the different sectors are determined, and from these the value of the criterion mentioned above is determined for the evaluated arrangement.

Having calculated all these values of the choice criterion, we can proceed to the last step. In the course of this one, one selects the arrangement which gives to the criterion its value closest to zero.

Claims (10)

Method for selecting a sector arrangement (100,200,300) for a turbomachine distributor, characterized in that it comprises the following steps: A. digitalization is created of a database of three-dimensional numerical models of sectors; B. a criterion for choosing an arrangement of sectors and a desired value for this criterion is fixed, the criterion being a function of the geometry and the relative position of the sectors; C. for different evaluated arrangements, the relative positions of the sectors assembled together are determined by virtual editing, and according to these, the value of the criterion of choice for the evaluated arrangement; D. the arrangement for which the selection criterion has the value closest to the desired value is retained. The method of selecting a sector arrangement according to claim 1, wherein in step C, at least one evaluated arrangement is the combination of an arrangement selected by the method and another sector or another chosen arrangement using the method. A method of selecting a sector arrangement according to claim 1 or 2, wherein in step A. the database used for the method contains sectors (100,200,300) from a single distributor. A method of selecting a sector arrangement according to claim 1 or 2, wherein in step A. the database used for the method contains sectors from at least two different distributors. A method of selecting a sector arrangement according to any one of claims 1 to 4, the distributor areas having contact surfaces (131,132,141,142), and being placed in relative position with respect to adjacent distributor sectors by abutting these contact surfaces, in which in the database created in step A), the numerical models of the sectors of the arrangement comprise a modeling of the contact surfaces involved in their relative mounting position, and in step C) the virtual editing of the numerical models of the sectors in an evaluated arrangement is made by matching the contact surfaces of the adjacent sectors of said arrangement. A method of selecting a sector arrangement according to any one of claims 1 to 5, wherein the step A) of creating a database of digital models by digitization is carried out using a means non-contact optical measurement. A method of selecting a sector arrangement according to any one of claims 1 to 6, wherein the selection criterion is a function of the respective passage sections (S _i ) of the distributor sectors. A method of selecting a sector arrangement according to claim 7, wherein for determining the cross section (S _i ) of a sector disposed at one end of the arrangement, a theoretical numerical model of a reference dawn (220,310). A method of selecting a sector arrangement according to claim 7 or 8, wherein a flow section (S101, S102, S103) of the flow between two adjacent blades is substantially the minimum flow passage area therebetween , and the passage sections (S100 / 1, S100 / 2, S100 / 3) of the distributor being on the one hand, half of the flow passage sections (S101, S103) between an end blade of the sector and the reference blade set back in relation thereto, and secondly, when the sector comprises more than one blade, the flow passage section or sections (S102) between the pair or pairs of adjacent blades of the area; a passage section of the flow between two adjacent blades is equal to the area of the free space section between the two blades, in the plane substantially parallel to the axis of the blades and in which the distance (D1, D2, D3 ) between the blades is the weakest. A method of selecting a sector arrangement according to any one of claims 7 to 9, wherein, a flow passage section (S ₁₀₁ , S ₁₀₂ , S ₁₀₃ ) between two adjacent vanes being substantially the minimum area of passage of the flow between them, and the passage sections (S _100/1 , S _100/2 , S _100/3 ) of the distributor being on the one hand, half of flow passage section (S ₁₀₁ , S ₁₀₃ ) between an end blade of the sector and the reference blade set back in relation thereto, and secondly, when the sector comprises more than a blade, the flow passage section or sections (S ₁₀₂ ) between the one or more pairs of adjacent blades of the sector; a flow passage section between two adjacent blades is determined based on the smallest distance (D1, D2, D3) therebetween.

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