EP2202385A1 - Treatment of the compressor housing of a turbomachine consisting of a circular groove describing a ripple intended to control vane head vortices - Google Patents

Abstract

The housing has an internal surface rotationally symmetrical around an axis of a turbomachine, where the surface has a circular groove (6) that is arranged opposite to a front part of a head of row of vanes (3). The groove reduces or controls a vortex of the head, where the groove defines an undulation along its circular direction and wireless loop. The undulation is in a plane of the internal face. A width (I) and a depth of the groove are constant. Independent claims are also included for the following: (1) a compressor of a turbomachine comprising a housing (2) a method for reducing or controlling a vortex of vanes of a mobile wheel of a compressor of a turbomachine.

Description

Technical area

The invention relates to a turbomachine stator casing treatment for reducing and / or controlling vane head vortices of a moving wheel. More particularly, the invention relates to a turbomachine compressor stator casing, to a turbomachine compressor and to a method for reducing and / or controlling the blade head vortex of a turbomachine compressor impeller.

State of the art

When operating a turbomachine, typically a compressor comprising at least one mobile wheel provided with vanes and rotating in a casing forming the outer casing of the fluid duct (liquid or gaseous) to be displaced and compressed, a vortex at the head dawn starts and can negatively influence the flow of fluid along the blades. This phenomenon is illustrated in figure 1 . The head vortex 4 'is originated in the pressure difference between the intrados and extrados of the blade 3' in motion. The general direction of the flow is indicated by the arrow 1 'and the direction of movement of the blades is indicated by the arrow 2'. Due to the necessary mechanical clearance between the dawn head and the casing, this pressure difference gives rise to a vortex 4 'whose main axis 5' is essentially parallel to the casing surface and oriented substantially along the tangent to the casing. profile of the dawn 3 'at the place of the profile where it is born. This vortex propagates on the upper side of the blade 3 'where it has originated and creates a dead zone blocking part of the flow between the two neighboring blades. This blocking is likely to generate a return flow from the compressor downstream upstream of it. The flow can become pulsed and vibrate the blades. This is a phenomenon called pumping where the blades are subjected to significant vibrational stresses.

It is known from the state of the art to provide different types of compressor case treatments for controlling the influence of the head vortex on fluid flow and compressor performance.

The document US 6,582,189 B2 discloses various crankcase treatments consisting essentially of making grooves either parallel to the axis of rotation of the movable wheel, or perpendicular to the axis in question, or a combination of both. Typically, this document provides for the presence of a circular groove section intersecting a series of grooves parallel to the axis of the machine and extending from an area upstream of the blades to a zone facing the portion before blade heads, the circular groove section being opposite the front part of the blade heads of the moving wheel. Alternatively, this document provides the presence of identical grooves parallel to the axis of the machine and whose downstream ends are curved in the direction of movement of the blades relative to the surface of the housing. These different designs are supposed to reduce the importance of such a vortex and its impact on the efficiency of the machine.

It is also known from the document EP 1 961 920 A1 to provide a casing treatment where grooves forming closed contours are made opposite the blade heads of a moving wheel. These closed contours typically cover two to three vanes, that is to say that the width of the contour in the direction of rotation corresponds to 1.5 to 2.5 no vanes of the moving wheel.

It is also known from the document JP 58-113504 to provide in the surface of the housing opposite the blade heads of a turbine a series of parallel straight or curved grooves.

In these teachings, the groove networks practiced are intended to form a volume where the nascent vortex can circulate and dissipate at least partially. The presence of a series of grooves distributed evenly around the periphery of the inner surface of the housing according to these various teachings certainly allows a non-stationary action on vortex phenomena at the head of dawn but these different treatments involve a rather heavy implementation from a machining point of view.

Presentation of the invention

The object of the invention is to improve the reduction and / or the control of the blade head vortices of a turbomachine wheel and to simplify the implementation of the corresponding treatment.

The invention consists of a turbomachine stator casing, comprising an inner surface substantially symmetrical in revolution about the axis of the machine, the casing being intended to receive a rotor provided with at least one row of blades whose ends describe a circular motion near the inner surface of the housing during the rotation of the rotor, the inner surface of the housing having at least one circular groove facing the front portion of the head of the row of blades, the groove being intended reducing and / or controlling the vane head vortex; where the groove describes a ripple along its circular direction.

This groove profile provides the advantage of creating a continuous leak between the blade head and the housing and an intermittent leak at a specific position of the blade head. These two types of leakage allow a single casing treatment very simple to implement to control vortex eddies by the combination of a recirculation volume and the generation of pulsed jets.

Preferably the groove describes an endless loop.

Preferentially, the corrugation of the groove is in the plane of the internal surface.

Preferably the center line of the groove describes a sinusoid.

où
x_m(Θ) est l'amplitude de la ligne médiane,
x_m0 est une constante,
Θ est la position angulaire dans un plan perpendiculaire à l'axe de la machine,
ω _¡ est la fréquence de la composante du signal par tour de carter,
A_i est le coefficient d'amplitude de la composante du signal,
et n est un entier ≥1.Preferably the amplitude of the center line of the groove along the axis of the machine or an axis contained in the plane of the inner surface at the groove and oriented according to the flow of the fluid is governed by the law $$x_m\left(\mathrm{\theta }\right)=x_{m0}+{\displaystyle \underset{i=1}{\overset{\mathrm{not}}{\Sigma }}}{\mathrm{AT}}_i\cdot \sin \left({\mathrm{\omega }}_i\cdot \mathrm{\theta }\right)$$

or
x _m (Θ) is the amplitude of the median line,
x _m0 is a constant,
Θ is the angular position in a plane perpendicular to the axis of the machine,
ω _¡ is the frequency of the signal component per crankcase revolution,
A _i is the amplitude coefficient of the component of the signal,
and n is an integer ≥1.

Preferentially n> 1.

Preferably, the width of the groove is constant.

Preferably, the depth of the groove is constant.

Preferably the housing comprises a single groove per stator blade row and the width of the corrugation of the groove measured in a direction parallel to the axis of the machine is equal to or less than one third of the corresponding blade width measured according to the same direction.

Preferably the groove is made by machining, preferably by means of a milling tool.

The invention also consists of a turbomachine compressor comprising a casing and a rotor such as the invention, where the corrugation of the groove is opposite a part of the blade head not exceeding the front half, preferentially the first third of the length of the blades measured along the axis of the machine or an axis contained in the plane of the inner surface at the groove and oriented according to the flow of the fluid.

The invention also consists in a method for reducing and / or controlling the vane head vortex of a turbomachine compressor moving wheel rotating in a stator forming a casing of the fluid stream, consisting in producing a circular groove on the inner surface of the casing facing the front part of the blade heads of the moving wheel; where the groove is made so that it describes a ripple along its circular path.

Preferably the groove describes an endless loop.

Preferably the groove is made by machining where the machining tool moves relative to the housing along the axis of the machine along the path of the groove during machining.

Brief description of the figures

• The figure 1 is a schematic view corresponding to the folding in the plane of the blade sheet of a mobile wheel of a turbomachine according to the state of the art.
• The figure 2 is a schematic view corresponding to the folding in the plane of the blade sheet of a mobile wheel of a turbomachine and illustrating the crankcase treatment according to the invention.

Best way to realize the invention

The figure 2 illustrates an elevational view of the blades of a moving wheel, the outer surface of the wheel being folded in the plane of the sheet. The general direction of the flow is indicated by the arrow 1. The direction of displacement of the blades 3 is illustrated by the arrow 2. The crankcase treatment consists of a groove 6 continuous around the periphery of the internal surface of the casing of the turbomachine . This groove forms an endless loop and describes undulations along its profile. The center line of the groove describes undulations along the inner surface of the housing so that the groove evolves opposite the front part of the blade heads 3. The groove is of approximately constant width and depth. The undulation described is a sinusoid whose period corresponds to twice the pitch of blade, that is to say the distance between two neighboring blades. The center line 7 of the groove 6 and its edges upstream and downstream describe along the inner surface of the casing a sinusoidal trajectory. The median plane of the profile is perpendicular to the axis of rotation of the moving wheel. The profile of the groove evolves in an annular band whose upstream edge 8 is at a distance from the leading edge of the blades 3 and the downstream edge 9 is at a distance from the leading edge corresponding to about a third of the length of the blade. 'dawn.

The trajectory or the corrugated profile of the center line of the groove has the advantage of generating in addition to its stationary effect a non-stationary effect similar to that of the repeated grooves of the state of the art while being much simpler to put implemented. Indeed, the continuous volume formed by the groove creates a permanent leak between the intrados and the extrados of the blade head and thus allows stabilization of the head vortex in a stationary manner, that is to say so constant along the periphery of the inner surface of the housing. In addition, the fact that the groove covers several axial positions makes it possible to create an intermittent leak between the lower surface and the upper surface of the blade head for a given position of the head. This intermittent leakage induces a pulsed jet that reduces the incidence of flow on the blade head. Depending on the period of the undulation and depending on the speed of rotation of the moving wheel, the pulsed jets generated can induce non-stationary phenomena.

• sa profondeur p ;
• sa largeur I ; et
• la position de sa ligne médiane x_m selon un axe parallèle à l'axe de la machine.

The groove can be characterized by the following parameters:

• its depth p;
• its width I; and
• the position of its median line x _m along an axis parallel to the axis of the machine.

The depth p and the width I are generally constant, but it would be possible to vary them. The depth is typically of the order of the clearance between the blade heads and the inner surface of the housing. In practice, the depth is slightly greater in order to compensate for possible wear resulting from friction between the blade heads and the casing. This game usually corresponds to about 1 to 2% of the blade height.

où x_m est exprimé en fonction de l'angle Θ de la position angulaire de la rainure dans un plan perpendiculaire à l'axe de la machine, x_m0 est une constante, ω_¡ est un paramètre correspondant à la fréquence du signal par tour de carter, A_i est un coefficient d'amplitude et n est un entier ≥1.The position x _m of the center line is governed by the following law: $$x_m\left(\mathrm{\theta }\right)=x_{m0}+{\displaystyle \underset{i=1}{\overset{\mathrm{not}}{\Sigma }}}{\mathrm{AT}}_i\cdot \sin \left({\mathrm{\omega }}_i\cdot \mathrm{\theta }\right)$$

where x _m is expressed as a function of the angle Θ of the angular position of the groove in a plane perpendicular to the axis of the machine, x _m0 is a constant, ω _¡ is a parameter corresponding to the frequency of the signal per revolution of casing, A _i is an amplitude coefficient and n is an integer ≥1.

When n is 1, the law defines a pure sine whose shape is defined by the following two parameters: amplitude A and frequency ω.

When n is greater than 1, we obtain a more complex form with this time 2n parameters. This increases the frequency content, which makes it possible to interact on several fundamental frequencies of the flow (for example the Crow and Widnall frequencies of vorticity stability) or of the dawn (for example, the bending modes of the head of dawn). In practice n is equal to 2 or 3 but higher values are possible.

By adapting these parameters, in particular the frequency of the sinusoid (s), it is also possible to induce a non-stationary force on the blade head to damp the oscillations of certain modes of the blades. The oscillations to which the vanes are subjected are, for example, of the "bending" type corresponding to a bending deformation of the blade and also of the "Stripe" type, which is a so-called deformation of the blade. The frequency content of the groove can therefore be selected so as to generate forces countering certain oscillations inherent in certain operating modes of the machine and particularly harmful for the lifetime of the blade.

The realization of the crankcase treatment is particularly easy. It requires the machining of the groove by means of a machining machine where the cutting tool is moved relative to the housing or vice versa, according to the desired profile. In practice, the housing is moved in rotation relative to the cutting tool which is moved only according to the axis of the turbomachine. It is the axial displacement of the synchronized cutting tool with the rotational displacement of the housing which defines the corrugations of the groove.

Although only one groove is shown in the figure 2 it is quite possible to provide two grooves or more.

Claims (14)

Turbomachine stator casing, comprising an inner surface substantially symmetrical in revolution about the axis of the machine, the casing being intended to receive a rotor provided with at least one row of blades (3) whose ends describe a movement circular around the inner surface of the casing during the rotation of the rotor, the inner surface of the housing having at least one groove (6) circular facing the front portion of the head of the blade row (3), the groove (6) being intended to reduce and / or control the blade vortex;
characterized in that
the groove (6) describes a corrugation along its circular direction. Housing according to the preceding claim, characterized in that the groove (6) describes an endless loop. Housing according to the preceding claim, characterized in that the corrugation of the groove (6) is in the plane of the inner surface. Housing according to the preceding claim, characterized in that the center line (7) of the groove (6) describes a sinusoid. Housing according to the preceding claim, characterized in that the amplitude of the center line (7) of the groove (6) along the axis of the machine or an axis contained in the plane of the inner surface at the groove and oriented according to fluid flow is governed by law $$x_m\left(\mathrm{\theta }\right)=x_{m0}+{\displaystyle \underset{i=1}{\overset{\mathrm{not}}{\Sigma }}}{\mathrm{AT}}_i\cdot \sin \left({\mathrm{\omega }}_i\cdot \mathrm{\theta }\right)$$

or
x _m (Θ) is the amplitude of the median line,
x _m0 is a constant,
Θ is the angular position in a plane perpendicular to the axis of the machine,
ω _¡ is the frequency of the signal component per crankcase revolution,
A _i is the amplitude coefficient of the component of the signal,
and n is an integer ≥1. Housing according to the preceding claim, characterized in that n> 1. Housing according to the preceding claim, characterized in that the width I of the groove (6) is constant. Housing according to the preceding claim, characterized in that the depth p of the groove (6) is constant. Housing according to the preceding claim, characterized in that it comprises a single groove (6) per stator blade row and the width of the corrugation of the groove measured in a direction parallel to the axis of the machine is equal or less than one third of the width of the blades (3) corresponding measured in the same direction. Housing according to the preceding claim, characterized in that the groove (6) is made by machining, preferably by means of a milling tool. Turbomachine compressor comprising a housing and a rotor according to one of the preceding claims, characterized in that the corrugation of the groove (6) is opposite a part of the blade head not exceeding the front half, preferably the first third of the length of the blades measured along the axis of the machine or an axis contained in the plane of the inner surface at the groove and oriented according to the flow of the fluid (1). A method of reducing and / or controlling the vane head vortex of a turbomachine compressor moving wheel rotating in a stator forming a casing of the fluid duct, comprising forming a circular groove (6) on the inner surface of the casing opposite the front part of the blade heads (3) of the moving wheel,
characterized in that
the groove (6) is made so that it describes a ripple along its circular path. Method according to the preceding claim, characterized in that the groove describes an endless loop. Method according to the preceding claim, characterized in that the groove is made by machining where the machining tool moves relative to the housing along the axis of the machine along the path of the groove during machining.

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