Labyrinth seal with tunable flow splitter

A flow splitter includes a stepped ring and a flow restriction. The stepped ring includes a first inner wall having a first diameter, a second inner wall having a second diameter less than the first diameter, a radial step that transitions from the first to the second inner wall, and a plurality of apertures circumferentially located along the first inner wall and partially through the radial step. The first flow restriction has at least a portion thereof at a position between the first diameter and the second diameter. Further, the first flow restriction directs a flow of at least one of a gas and a fluid towards the first inner wall, and is configured to split the flow into an exit flow and a secondary flow. The exit flow exits the stepped ring via the plurality of apertures and the secondary flow proceeds downstream directed by the second inner walls.

FIELD OF TECHNOLOGY

The present disclosure relates to flow splitters and more particularly, but not exclusively, to a flow splitter method, system, and/or apparatus that may be employed in a turbine engine. Further, this present disclosure relates to enhancement of engine seal systems. The improvements are applicable to a variety of engine types such as turbine engines. Although the improvements are applicable to turbine engines used for propulsive power in air, the improvements are also applicable to turbine engines employed in marine, underwater, and land applications.

BACKGROUND

Flow splitters are generally employed to split an incoming flow (e.g., a gas flow or liquid flow) into two or more flows. Aircraft and other machinery employ flow splitters to, for example, direct fluids to various components, create core flow and bypass flows, and/or simply direct cooling airflows. Seals are also employed to control air flow and liquid flow in static and moving parts within machinery. For example, turbine engine seals are located in numerous locations such as on rotors, turbines, and etc., so as to provide cavities for transitioning gases (e.g., air) and fluids to pass therethrough. A labyrinth seal is a type of seal often found in turbines and compressors thereof. These seals are often employed to control air or liquid leakage from high pressure regions to low pressure regions. For example, a labyrinth seal may be employed to seal two components together in such a manner to permit a controlled flow (e.g., airflow) from a high pressure region through a sealed boundary to a low pressure region. At times, it may be beneficial to redirect some of the flow between the high and low pressure regions. Accordingly, it may be beneficial to employ a flow splitter with, for example, a labyrinth seal to split incoming flow between high and low pressure regions to create two or more distinct flows. Such a task, however, can be problematic and, if not executed properly, can cause damage to downstream components and/or engine inefficiencies.

Accordingly there is room for improvement in this area.

DETAILED DESCRIPTION

FIG. 1Aillustrates an exploded view of an exemplary flow splitter100according to an embodiment. The flow splitter100, depicted along a center-line axis102, includes a stepped ring104and an upstream restriction106. The stepped ring104includes a first inner wall108having a first inner diameter110and a second inner wall112having a second inner diameter114that is less than the first inner diameter110.

A transition or radial step116transitions between the first and second inner walls108,112, respectively. A first end118of the radial step116is adjacent to (or transitions to) the first inner wall108. A second end120of the radial step116, which is opposite the first end118, is adjacent to (or transitions to) the second inner wall112. Though not shown, it will be appreciated that more than one radial step may be employed to transition between the first and second inner walls,108,112, respectively. Further, though the radial step116illustrated is substantially perpendicular to the first and second inner walls108,112, one or more steps (not shown) at an angle other than 90 degrees may instead be employed.

The stepped ring104of the flow splitter100also includes a plurality of apertures122,124,126,128,130,132,134136circumferentially positioned around and through the first inner wall108and a portion of the radial step116. Though the present embodiment illustrates eight apertures122-136, other embodiments may employ more or less than eight apertures. It is noted that the apertures122-136pass through the stepped ring104by passing through both the first inner wall108and a portion of the step116.

According to the illustrated embodiment, the upstream restriction106of the flow splitter100has a diameter138(a.k.a. a restriction diameter) that is greater than the second inner diameter114of the second inner wall112, but less than the first inner diameter110of the first inner wall108. As will be described below with respect toFIG. 1B, when the upstream restriction106is positioned within the stepped ring104, the upstream restriction106diverts a flow140(e.g., a flow of gas or liquid) towards the first inner wall108to create a restricted flow142. At least some of this flow is diverted into an exit flow144that passes through each of the plurality of apertures122-136. Any remaining restricted flow142passes as a secondary flow146that is directed by the second inner wall112.

The volume or rate of exit flow144that exits the stepped ring104can be manipulated or tuned by varying the quantity and/or circumferential extent of the apertures (e.g., apertures122-136). For example, if the circumferential extent of one or more of the apertures122-136were increased, the rate or volume of the exit flow144would also increase, and accordingly the rate or volume of the secondary flow146would decrease. Conversely, if the circumferential extent of one or more of the apertures122-136were decreased, the rate of the exit flow144would decrease, and accordingly the rate of the secondary flow146would increase. Alternatively, the quantity of apertures could be increased to increase the rate of exit flow144or decreased to decrease the rate of exit flow144.

It is noted that the quantity and/or sum circumference of the apertures may be increased to the point where the secondary flow146reduces to substantially zero. If increased even further, the secondary flow146may be caused to reverse direction and aspirate out the apertures (e.g., apertures122-136).

If adjustable aperture size is desired, it is contemplated that the flow splitter100may include an aperture adjustment structure such as ring148(a.k.a. an exemplary adjustable flow control structure), as shown in phantom. The aperture adjustment ring148is configured to modify the rate of the exit flow144. According to an embodiment, the aperture adjustment ring148may be caused to move in a first direction150to at least partially cover one or more of the apertures122-136and therefore decrease the effective size of the one or more apertures122-136. It will be appreciated that decreasing the effective size of the one or more apertures122-136will decrease the rate of the exit flow144while also causing the secondary flow146rate to increase. At a later time, the aperture adjustment ring148may be moved in a second direction152to increase the effective aperture sizes back to the original state. It is noted that the circumferential extent of the apertures122-136could be of such a magnitude that moving the aperture adjustment ring148through the second direction152causes an aspirated flow154within the second inner wall112(i.e., creates a negative pressure to cause the secondary flow146to reverse direction).

It will be appreciated that an aperture adjustment ring (e.g., aperture adjustment ring148) could be placed in locations (e.g., outside or within the first inner wall108) other than that shown. Further, it will also be appreciated that other types of aperture adjustment structures may be employed to the same or similar effect.

Referring now toFIG. 1B, a cross-sectional view of the flow splitter100along1B-1B ofFIG. 1Ais illustrated, with the upstream restriction106placed within the stepped ring104. As set forth above with respect toFIG. 1A, the restriction diameter138(FIG. 1B) of the upstream restriction106is greater than the second inner diameter114but less than the first inner diameter110. As such, there is a gap156between the first inner wall108and the upstream restriction106. When in operation, the upstream flow140comes into contact with the upstream restriction106and creates an obstructed flow158. Due to the gap156, a portion of the obstructed flow158passes through the gap156as a restricted flow142. At least some of the restricted flow142is concentrated along the first inner wall108and is conveyed out of the stepped ring104via the apertures122-126(seeFIGS. 1A and 1B) as exit flow144. The remainder of the flow (i.e., the secondary flow146) is conveyed downstream through the second inner wall112.

With reference to bothFIGS. 1A and 1B, by varying the quantity and/or size of the apertures (e.g., apertures122-136), the rate of exit flow144that passes out through the apertures122-136can be adjusted or tuned. For example, if the circumferential extent of the apertures122-136were increased, the rate of the exit flow144would also increase. Similarly, if the circumferential extent of the apertures122-136were decreased, the rate of exit flow144leaving the stepped ring104via the apertures122-136would also decrease. If desired, the quantity and/or sum circumferential size of the apertures could be increased to decrease the rate of secondary flow146to substantially zero. If increased further, an effective negative pressure can be created within the second inner wall112, causing the secondary flow to reverse direction (see reversed flow154) and aspirate out of the stepped ring104via the apertures122-136.

The flow splitters described herein may be employed in a variety of environments where the splitting of a gas (e.g., air) or liquid flow is desired. For example,FIG. 2Aillustrates an exploded view of an exemplary flow splitter200in a labyrinth seal system202. Labyrinth seal systems such as labyrinth seal system202may, for example, be part of a turbine engine environment.

The flow splitter200includes a stepped ring204(a.k.a. stator) along with an upstream restriction206(a.k.a. a first set of labyrinth knives) that is positioned on a rotor208. As illustrated, the flow splitter200is shown along a center-line axis210. According to the present embodiment, a downstream restriction212(a.k.a. a second set of labyrinth knives) is also employed. Though the present embodiment depicts two knives in the first set of labyrinth knives206and three knives in the second set of labyrinth knives212, embodiments are envisioned where the quantity of labyrinth seal knives employed in either or both sets206,212differ than those illustrated.

The stator204includes a first inner wall214having a first inner diameter216and a second inner wall218having a second inner diameter220, which is less than the first inner diameter216. As will be appreciated, the first and/or second walls214,218may include an abradable material to protect the labyrinths knives206and/or212during operation.

With continued reference toFIG. 2A, a transition or radial step222serves as a flow blocker and a transition between the first and second inner walls214,218, respectively. Positioned along the circumference of the first inner wall214is a plurality of holes or apertures224,226,228,230,232,234,236,238that pass through the first inner wall214and a portion of the radial step222before exiting the stator204. Though the present embodiment depicts the apertures224-238as slots with the slot widths being greater than the slot heights, spherical-like holes or other geometries may be employed.

The first set of labyrinth knives206is at a first height240and the second set of labyrinth knives212is at a second height242, while the rotor208has a rotor diameter244. The height240of the first set of labyrinth knives206is selected such that the at least a portion246of the labyrinth knives206is positioned between the first inner diameter216and the second inner diameter220of the stator204. Effectively, the sum of the rotor diameter244and twice the first height240creates an upstream restriction diameter (see e.g., restriction diameter138ofFIG. 1A).

The height242of the second set of labyrinth knives212, as illustrated in2B, is selected such that no portion of the second set of labyrinth knives212extends to or past the second inner diameter220when mounted to the rotor208and positioned within the stator204.

It is noted that according to an alternate embodiment, the first set of labyrinth knives206may be allowed to pass through grooves (not shown) in or on the first inner wall214. Similarly, according to an alternative embodiment, the second set of labyrinth knives212may be allowed to pass through grooves (not shown) in or on the second inner wall218.

When the rotor208is positioned within the stator204and put into operation, as shown inFIG. 2B, airflow248that passes along the rotor208is obstructed by the first set of labyrinth knives206creating an obstructed flow250. However, due to a gap252between the first set of labyrinth knives206and the first inner wall214, a leakage flow254will pass downstream from the first set of labyrinth knives206. At least some of the leakage flow254is concentrated along the first inner wall214and will be conveyed out of the stator204via the plurality of apertures224-238as exit flow256. It is noted that the more closely aligned the passage of each aperture224-238is with the leakage flow254, the greater the rate of exit flow256leaving via the apertures224-238will be. Any remaining flow that does not leave as exit flow256will pass downstream within the second inner wall218as a secondary flow258. In other words, the labyrinth seal system (i.e., the stator204along with the first set of labyrinth knives206coupled to the rotor208) is configured to split the air leakage flow256from the first set of labyrinth knives206into the exit flow256that passes out of the stator204via the apertures224-238and into the secondary flow258that passes over the second inner wall218.

It is contemplated that the exit flow256may be simply exhausted or employed to work somewhere else. For example, as shown in phantom, at least a portion of the exit flow256may be employed to prime (i.e., pressurize) another labyrinth seal or other component260(represented as a simple block).

With regard to the second set of labyrinth knives212, there is a gap262between the second set of labyrinth knives212and the second inner wall218. In addition to manipulating the exit flow256by manipulating the apertures224-238(e.g., quantity and/or sum circumferential size), varying the first knife gap262and/or the second knife gap252can also effect the volume of exit flow256, and therefore secondary flow258.

If the embodiment depicted inFIG. 2Bis employed in a gas turbine setting, it is beneficial that the gap262of the downstream flow restriction (i.e., second set of labyrinth knives212) does not have a direct line of sight with the concentrated leakage flow (i.e., leakage flow254).

Referring now toFIG. 3an exemplary turbine engine300that may employ one or more flow splitters (e.g., flow splitter100ofFIGS. 1A and 1Band flow splitter200ofFIGS. 2A and 2B) described herein is illustrated. The turbine engine300includes a fan302, a low pressure compressor304(“LP compressor”), an intermediate pressure compressor306(“IP compressor”), a high pressure compressor308(“HP compressor”), a combustor310, a high pressure turbine312(“HP turbine”), an intermediate pressure turbine314(“IP turbine”) and a low pressure turbine316(“LP turbine”). The HP compressor308, the IP compressor306and the LP compressor304are connected to a respective one of an HP shaft318, an IP shaft320and an LP shaft322, which in turn are connected to a respective one of the HP turbine312, the IP turbine314and the LP turbine316. The shafts extend axially and are parallel to a longitudinal center-line axis324. WhileFIG. 3illustrates a three-shaft engine, it will be appreciated that other embodiments can have configurations including more or less than three shafts.

During general operation of the engine300, ambient air326enters the fan302and proceeds as a bypass airflow328and a primary air stream330. The primary air stream330is created as the ambient air326is directed across a fan rotor332into an annular duct334(in part circumscribed by a fan case336) and into the combustor310. The bypass airflow328provides a fraction of engine thrust while the primary air stream330is directed to the combustor310(i.e., turbine combustion zone). The primary air stream330mixes with fuel in combustor310where ignition occurs. As a result of the ignition, expanding gas passes over the turbines312,314,316and is exhausted through a nozzle338generating thrust.

As will be appreciated, turbine engines such as turbine engine300often employ a variety of flow splitters and/or labyrinth seals. It is contemplated that variations of the flow splitters and labyrinth seals (e.g., flow splitters100,200ofFIGS. 1A-1B, 2A-2B, respectively, and labyrinth seal system202ofFIGS. 2A-2B) described herein may be employed in a turbine engine such as exemplary turbine engine300ofFIG. 3. For example, flow splitter and/or labyrinth seal embodiments or variations thereof may be employed in a region340next to HP turbine312near HP shaft318when it is desired to split an airflow. It will be appreciated that flow splitters or labyrinth seal systems employing a flow splitter described herein may also be coupled to other shafts such as IP shaft320and LP shaft322, or other regions of the turbine engine300to control airflow(s).

It is noted that other machinery besides turbine engine300may benefit from the flow splitters and labyrinth seals described herein.

With reference now toFIG. 4, a flowchart depicts a technique400or method for manufacturing a labyrinth seal according to an embodiment. Technique400begins at block402with assembling a rotor having at least one upstream labyrinth knife and at least one downstream labyrinth knife protruding from the rotor. It is contemplated that the labyrinth knives may be coupled to the rotor in such a manner that allows for replacement if desired. That is, one or more of the labyrinth knives may be removable.

After assembling the rotor, process control proceeds to block404, where creating a stator having a first inner wall at a first diameter and a second inner wall at a second diameter less than the first diameter occurs. The stator is configured such that at least a portion of the first labyrinth knife is positionable between the first and the second inner diameters. It is contemplated that the stator may be created from multiple modular components or simply machine, cast, and/or etc. as a single unit. If desired, abradable material may be added to the first and/or inner wall to protect the labyrinths knives during a transient operation.

Upon creating the stator, machining of a plurality of holes through the first inner wall of the stator and partially though a transition from the first inner wall to the second inner wall occurs at block406. The apertures or hole pass through the stator and may take on a variety of forms. For example, one or more holes may be machined as slots such that the circumferential dimensions of the one or more holes has a width different than its height. Alternatively, the holes may be machined to have a spherical opening or other geometry.

It is noted that the assembling at block402, the creating at block404, and the machining at block406need not occur in the order set forth. Rather, according to alternate embodiments, the actions or processes set forth in blocks402-406may occur in any order or one more processes may occur simultaneously.

Referencing back to the sequence set forth inFIG. 4, after machining the apertures or holes through the stator, process control proceeds to block408and positioning the rotor within the stator occurs such that the at least one upstream labyrinth knife is at least partially surrounded by the first inner wall and the at least one downstream knife is at least partially surround by the second inner wall. When in operation, the labyrinth seal with its flow splitter (i.e., stator and at least one upstream knife) is configured to split an upstream flow into an exit flow and a secondary flow. The exit flow exits the stator via the plurality of holes and the secondary flow passes downstream within the second inner wall.

It is contemplated, as shown at block410, that technique400may include adding an adjustable flow control structure to at least one hole of the plurality of holes. The flow control structure is configured to manipulate or tune the effective size of the apertures and, as such, control the rate of exit flow through the apertures. In turn, the rate of secondary flow past the second inner wall is also controlled. According to some embodiments, the flow control structure may be able to manipulate the rate of exit flow to such an extent that the secondary flow within the second inner wall reverses direction.

All terms used in the claims are intended to be given their broadest reasonable constructions and their ordinary meanings as understood by those knowledgeable in the technologies described herein unless an explicit indication to the contrary is made herein. In particular, use of the singular articles such as “a,” “the,” “said,” etc. should be read to recite one or more of the indicated elements unless a claim recites an explicit limitation to the to the contrary. Likewise, the use of the words “first”, “second”, and etc. may be interchangeable and need not necessarily indicate a sequence or a quantitative limit.