Dynamoelectric machine coil spaceblock having flow deflecting structure in coil facing surface thereof

A dynamoelectric machine includes a rotor having a plurality of adjacent coils; a spaceblock disposed between adjacent coils to define at least one cavity adjacent the spaceblock and between mutually adjacent coils; and the spaceblock including a body having one of: a substantially T-shaped cross-section, a substantially hexagonal cross-section and a substantially truncated arrow cross-section, the cross-section providing at least one flow deflector structure on at least one cavity facing surface of the spaceblock for intercepting and redirecting circulating coolant flow in the cavity towards a central region of the at least one cavity.

BACKGROUND OF THE INVENTION

The present invention relates to a structure for enhanced cooling of a dynamoelectric machine rotor by intercepting and redirecting a circulating coolant flow in a cavity.

In large dynamoelectric machines, such as a turbo-generator, the rotor consists of machined slots along its length in which copper coils are placed. The portions of these coils which extend outside the rotor body are called endwindings. In the endwinding region of a rotor, coils are held tightly by spaceblocks, which are further classified as space, spacer and wedge blocks, depending on their location.

The power output rating of dynamoelectric machines is often limited by the ability to provide additional current through the rotor field winding because of temperature limitations imposed on the electrical conductor insulation. Therefore, effective cooling of the rotor winding contributes directly to the output capability of the machine. This is especially true of the rotor endwindings, where direct, forced cooling is difficult and expensive due to the typical construction of these machines. As prevailing market trends require higher efficiency and higher reliability in lower cost, higher-power density generators, cooling the rotor endwindings becomes a limiting factor. In order to cool the endwindings and coils, a circulating coolant flow is passed through the cavities between spaceblocks and coils, and enters the grooves in coils, which start from these cavities and discharge into a chimney.

U.S. Pat. No. 6,465,917 describes a method for augmenting heat transfer by providing a spaceblock having at least one flow deflector structure provided on a cavity facing surface for intercepting and redirecting circulating coolant flow towards a central region of the respective cavity deflector structure increasing the flow velocity of the large single flow circulation cell by introducing additional cooling flow directly into, and in the same direction as, the naturally occurring flow cell. This approach is shown inFIGS. 4 and 5of the present application. While this method increases the heat transfer in the cavity by augmenting the strength of the circulation cell, the center region of the cavity may still be left with low velocity and therefore low heat transfer.

BRIEF DESCRIPTION OF THE INVENTION

A first aspect of the disclosure provides a dynamoelectric machine, comprising: a rotor having a plurality of adjacent coils; a spaceblock disposed between adjacent coils to define at least one cavity adjacent the spaceblock and between mutually adjacent coils; and the spaceblock including a flow deflector structure on a cavity facing surface of the spaceblock for intercepting and redirecting circulating coolant flow in the cavity towards a central region of the at least one cavity.

A second aspect of the disclosure provides a spaceblock for a gas-cooled dynamoelectric machine, the spaceblock comprising: a body having one of: a substantially T-shaped cross-section, a substantially hexagonal cross-section and a substantially truncated arrow cross-section, the cross-section providing at least one flow deflector structure on at least one cavity facing surface of the spaceblock for intercepting and redirecting circulating coolant flow in the cavity towards a central region of the at least one cavity.

A third aspect is directed to a dynamoelectric machine, comprising: a rotor having a plurality of adjacent coils; a spaceblock disposed between adjacent coils to define at least one cavity adjacent the spaceblock and between mutually adjacent coils; and the spaceblock including a body having one of: a substantially T-shaped cross-section, a substantially hexagonal cross-section and a substantially truncated arrow cross-section, the cross-section providing at least one flow deflector structure on at least one cavity facing surface of the spaceblock for intercepting and redirecting circulating coolant flow in the cavity towards a central region of the at least one cavity.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings wherein identical reference numerals denote the same elements throughout the various views,FIGS. 1 and 2show a rotor10for a gas-cooled dynamoelectric machine, which also includes a stator12surrounding the rotor. The rotor includes a generally cylindrical body portion14centrally disposed on a rotor spindle16and having axially opposing end faces, of which a portion18of one end face is shown inFIG. 1. The body portion is provided with a plurality of circumferentially-spaced, axially extending slots20for receiving concentrically arranged coils22, which make up the rotor winding. For clarity, only five rotor coils are shown, although several more are commonly used in practice.

Specifically, a number of conductor bars24constituting a portion of the rotor winding are stacked in each one of the slots. Adjacent conductor bars24are separated by layers of electrical insulation25. The stacked conductor bars are typically maintained in the slots by wedges26(FIG. 1) and are made of a conductive material such as copper. Conductor bars24are interconnected at each opposing end of the body portion by end turns27of the coils, in an area which may be referred to as the end strap region. Coils22include a coil side section including axially extending coils23and extend axially beyond the end faces to the end strap region. Collectively, axially extending coils23and end turns27are referred to as endwindings28. The end turns27are also separated by layers of electrical insulation.

Referring specifically toFIG. 1, a retaining ring30is disposed around the end turns at each end of the body portion to hold endwindings28in place against centrifugal forces. Retaining ring30is fixed at one end to the body portion and extends out over rotor spindle16. A centering ring32is attached to the distal end of retaining ring30. It should be noted that retaining ring30and centering ring32can be mounted in other ways, as is known in the art. The inner peripheral edge of centering ring32is radially spaced from rotor spindle16so as to form a gas inlet passage34, and endwindings28are spaced from rotor spindle16so as to define an annular region36. A number of axial cooling channels formed along slots20(FIG. 2) are provided in fluid communication with the gas inlet passage34via the annular region36to deliver cooling gas to the coils22(FIG. 2).

Turning toFIG. 2, end turns27at each end of rotor10(FIG. 1) may be circumferentially and axially separated by a number of spacers or spaceblocks40. (For clarity of illustration, the spaceblocks are not shown inFIG. 1). Where spaceblocks40are disposed between end turns27, they may be referred to as an end strap block48. Furthermore, axially extending coils23may be circumferentially separated by a number of spaceblocks40. In this location, spaceblocks40may be referred to as coil side blocks50or body wedge blocks52. The term “wedge” may be applied to these blocks because they may be provided with a wedge shape to accommodate the arcuate shape required to mate with coils23in this location. In any event, spaceblocks40are elongated block members of an insulating material located in the spaces between adjacent coils whether at the axially extending coil side section or end strap region. Spaceblocks40may extend beyond the full radial depth of the endstrap section or the coil side section into annular gap36.

As shown best inFIG. 3, in most cases, a spaceblock40disposed between adjacent coils (whether axially extending coils23or end straps27) defines first and second cavities42, adjacent to spaceblock40and between mutually adjacent coils. The spaces between the concentric stacks of endwindings28(FIG. 3) are divided into cavities42. These cavities are bounded on the top by retaining ring30and on four sides by adjacent end straps27and adjacent spaceblocks48, as shown inFIG. 2. Similarly, as shown best inFIG. 2, spaceblocks40between radial stacks of axially extending coils23may be divided into cavities54,56. Typically, as shown for the outermost coils inFIG. 2, spaceblock40(body wedge blocks52) disposed between adjacent coils23define only one cavity54adjacent thereto because the spaceblock is disposed directly against an end of a rotor tooth29. Cavities54are bounded on the top by retaining ring30and on four sides by adjacent coils23and adjacent spaceblocks40(coil side block50and body wedge block52). In accordance with embodiments of the invention, however, as shown for the innermost coils inFIG. 2, cavities56may also be present where spaceblock40(body wedge block52) is not against an end of rotor tooth29. Cavities56may be bounded on the top by retaining ring30(or wedges26(FIG. 1)) and on four sides by adjacent coils23, adjacent spaceblocks40(coil space blocks50) and an end of rotor tooth29.FIG. 1shows this latter situation.

As best seen inFIG. 1, each of the above-described cavities is in fluid communication with gas inlet passage34via annular region36. A portion of the cooling gas entering annular region36between endwindings28and rotor spindle16through gas inlet passage34thus enters the cavities42,54,56, circulates therein, and then returns to annular region36between the endwinding and the rotor spindle. Gas flow is shown by the arrows inFIGS. 1 and 3.

The inherent pumping action and rotational forces acting in a rotating generator cavity typically produce a large single flow circulation cell, as schematically shown inFIG. 3. This flow circulation cell exhibits its highest velocity near the peripheral edges of the cavity, leaving the center region inadequately cooled due to the inherently low velocity in the center region of the cavity. As can be seen fromFIG. 3, large areas of the corner regions are also inadequately cooled because the circular motion of the flow cell does not carry cooling flow into the corners.

Referring now toFIGS. 4-5, there is illustrated a partial section of the rotor endwinding assembly showing some of the cavities142with the direction of rotation indicated by arrow X according to U.S. Pat. No. 6,465,917. At least one and preferably each spaceblock140is provided with a flow deflector structure144on the surface146thereof disposed on the downstream side of the respective cavity (hereinafter downstream surface) for redistributing coolant flow to the center of the respective cavity142to increase the heat transfer coefficient there. Each deflector structure144has a lower generally curved surface148for intercepting and redirecting flow as shown by arrow A. The upper surface150is generally planer so that the deflector defines a generally thin flow facing edge152so as to effectively intercept flow without unnecessary pressure loss.

In operation, rotor rotation in direction X will cause cooling gas to be drawn through gas inlet34(FIG. 1) into annular region36between end winding28and rotor spindle16. A kinetic pressure head is present which drives the cooling gas toward the downstream side146of cavity142in a generally circular flow. At least a portion of the coolant flow is intercepted by deflector144and redirected as shown by arrow A to the central region of the cooling cavity142, which would otherwise be generally starved of coolant flow. Coolant flow that is not intercepted by the deflector continues in its generally circulatory flow as shown by arrow B. The intercepted flow and the non-intercepted flow are rejoined on the upstream side of the cavity and continue in a clockwise direction, in the illustrated configuration, under the spaceblock140and into the next sequential cavity. A single flow deflector is provided that spans a substantial portion of the depth or axial dimension of the cavity, for example, at least about 75% and more preferably on the order of 100% of the depth of the cavity.

Turning now toFIG. 5, a partial section is shown of the rotor endwinding showing cavities242defined between spaceblocks240and with the direction with rotation indicated by arrow X according to U.S. Pat. No. 6,465,917. As illustrated, at least one deflector structure244is provided to deflect coolant flow to the central region of the adjacent cavity. As in the embodiment ofFIG. 4, in the illustrated assembly, the defector structure(s)244are provided on the downstream surface246of at least one spaceblock240. However, in this case, each deflector244extends only a part depth or part axially of the spaceblock so as to leave at least one vertical flow region for some high momentum circulating coolant flow to reach the outer radial corner of the cavity while the remainder of the coolant is deflected towards the center of the cavity.

A partial depth deflector may be disposed to span the part depth of the cavity from adjacent one endwinding wall of the cavity, adjacent the other endwinding wall of the cavity, or generally centrally of its associated spaceblock. In one case, single deflector244may be provided to span about one half of the depth of the associated spaceblock.

Thus, as illustrated, the coolant flow into the respective cavity242will flow to and begin its flow radially outwardly along the spaceblock surface246. A portion of that flow is intercepted and deflected by the deflector structure(s)244toward the central region of the respective cavity as shown by arrow A. The remainder of the coolant flow bypasses the deflector structure because of the gaps defined by its truncated axial length and continues up and radially outwardly along the spaceblock, as shown by arrow C, for continuing as circulating flow, as shown by arrow B. The deflected flow and the non-deflected flow are rejoined at the upstream side of the cavity to continue in a clockwise direction, below and around the spaceblock240to the next sequential cavity242.

Deflector144,244may extend at least about 20% and more preferably at least about 25% of the circumferential dimension of the cooling cavity so as to effectively intercept and redirect the flow towards the central region of the cavity, rather than merely causing surface turbulation. The curved configuration of the lower surface148,248of the deflector enhances the deflector function.

Referring now toFIGS. 6-15, according to embodiments of the invention, at least one and preferably each spaceblock340includes a shape configured to aid in intercepting and redirecting a circulating coolant flow within a cavity342. Each of theFIGS. 6-15work substantially similar to the above-describedFIGS. 4 and 5embodiments.

InFIG. 6, each spaceblock340has a substantially T-shaped cross-section, providing at least one flow deflector structure on at least one cavity facing surface360(FIG. 7only for clarity) of the spaceblock for intercepting and redirecting circulating coolant flow in the cavity towards a central region of the at least one cavity. In this case, spaceblocks340are illustrated in a partial section of the rotor endwinding assembly in the setting of cavities342, i.e., end straps27. Similarly, spaceblock340according to any of theFIGS. 6-15embodiments may be disposed within axially extending coils23as shown inFIG. 2. Thus, spaceblock340may be disposed within axially extending coils23and/or end straps27, as shown best inFIGS. 1-2. Consequently, as used herein, “coil facing” may mean facing axially extending coils23or end straps27, collectively coils22of endwindings28.

FIGS. 7-15show enlarged perspective views of different embodiments of spaceblock340, and in particular, different cross-sectional shapes for spaceblock340resulting in differently shaped flow deflector structures344. In each of the herein-described embodiments, except perhapsFIG. 14, flow deflector structure344extends from a radially extending surface360(FIG. 7only for clarity) of spaceblock340.

FIGS. 7 and 8show embodiments (andFIG. 6) of spaceblock340including a substantially T-shaped cross-section that provide a flow deflector structure344to each of the pair of cavities342on either side of spaceblock340(FIG. 6).FIG. 7shows an embodiment in which each flow deflector structure344spans only a portion of a depth of a respective cavity, i.e., it is not as thick as the rest of spaceblock340, similar to theFIG. 5embodiment.FIG. 8shows an embodiment in which each elbow portion346of the substantially T-shaped cross-section includes a curved surface348.

FIGS. 9 and 10show embodiments of a spaceblock having a substantially L-shaped cross-section. In this case, only a single flow deflector structure344is provided. InFIG. 10, an elbow portion350of the substantially L-shaped cross-section includes a curved surface352.

InFIG. 11, flow deflector structure344includes a substantially right angle triangular section354having a rotor facing ledge structure356. In addition, as in other embodiments, flow deflector structure344may span only a portion of a depth of the at least one cavity.FIGS. 12 and 13show embodiments in which spaceblock340has a substantially truncated arrow shaped cross-section. That is, spaceblock340has an arrow head cross section except a tip of the arrow has been eliminated. This structure provides a flow deflector structure for each adjacent cavity. InFIG. 12, as in other embodiments, the flow deflector structure may span only a portion of a depth of the at least one cavity.

FIG. 14shows an embodiment in which spaceblock340has a substantially hexagonally-shaped cross-section providing a flow deflector structure to each of the pair of adjacent cavities.FIG. 15shows an embodiment in which each flow deflector structure344includes a substantially peaked edge structure358, which would extend into each of the pair of adjacent cavities.

In any of the herein described embodiment, in which flow deflector structure344spans only a portion of the depth of the cavity(ies), it may extend about one half of a depth of the cavity. In other embodiments, flow deflector structure344spans a substantial portion of a depth of the at least one cavity.

The terms “first,” “second,” and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another, and the terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context, (e.g., includes the degree of error associated with measurement of the particular quantity). The suffix “(s)” as used herein is intended to include both the singular and the plural of the term that it modifies, thereby including one or more of that term (e.g., the metal(s) includes one or more metals). Ranges disclosed herein are inclusive and independently combinable (e.g., ranges of “up to about 25 wt %, or, more specifically, about 5 wt % to about 20 wt %”, is inclusive of the endpoints and all intermediate values of the ranges of “about 5 wt % to about 25 wt %,” etc).

While various embodiments are described herein, it will be appreciated from the specification that various combinations of elements, variations or improvements therein may be made by those skilled in the art, and are within the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.