U.S. patent number 3,650,317 [Application Number 05/044,259] was granted by the patent office on 1972-03-21 for rotary regenerative heat exchanger.
Invention is credited to Mark Carey Sedgwick Barnard, Hugh Christopher Bramley, Peter Jacobus Collet.
United States Patent |
3,650,317 |
Barnard , et al. |
March 21, 1972 |
ROTARY REGENERATIVE HEAT EXCHANGER
Abstract
A rotary regenerative heat exchanger in which inlet and outlet
seals defining a path for one or other of the fluids between which
heat is to be exchanged enclose respective areas of inlet and
outlet end faces of the matrix of the heat exchanger of different
magnitude, thereby to reduce the magnitude of the resultant axial
force on the matrix. In this way forces due to fluid pressure
acting on opposed end faces of the matrix can be balanced thereby
to reduce stress within the matrix and also to avoid wear on the
seals due to an unresolved end thrust on the matrix. Additionally,
the areas of the seals can be adjusted to avoid tipping of the
matrix about its axis of rotation.
Inventors: |
Barnard; Mark Carey Sedgwick
(Solihull, Warwickshire, EN), Bramley; Hugh
Christopher (Solihull, Warwickshire, EN), Collet;
Peter Jacobus (Solihull, Warwickshire, EN) |
Family
ID: |
10292326 |
Appl.
No.: |
05/044,259 |
Filed: |
June 8, 1970 |
Foreign Application Priority Data
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Jun 11, 1969 [GB] |
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29,487/69 |
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Current U.S.
Class: |
165/9;
165/DIG.22; 60/39.512 |
Current CPC
Class: |
F28D
19/047 (20130101); Y10S 165/022 (20130101) |
Current International
Class: |
F28D
19/04 (20060101); F28D 19/00 (20060101); F28d
019/04 () |
Field of
Search: |
;165/9 ;60/39.51H |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Davis, Jr.; Albert W.
Claims
What we claim as our invention and desire to secure by Letters
Patent of the United States is:
1. An axial flow rotary regenerative heat exchanger comprising a
rotary matrix in which heat exchange is effected between two fluids
passed in counterflow between spaced end faces of the matrix, a
spindle by which the matrix is supported and on which it is
rotatable, means for rotating the matrix about said spindle, a pair
of seals respectively engaging said spaced faces and respectively
enclosing areas of said spaced faces and defining a flow path
through the matrix for one of said fluids, a further seal engaging
one of said faces and enclosing an outlet area for the other of
said fluids, said other fluids being admitted to the matrix through
the other of said spaced faces externally of the seal of said pair
of seals engaging said other face and a housing containing said
matrix and said seals and supporting said spindle, the housing
having ports communicating directly with the seals and also having
an inlet port therein for the other of said fluids and
communicating through the interior of said housing with both said
spaced faces of the matrix externally of said seals, the matrix
surface area enclosed within the outlet seal of said pair being
smaller than that enclosed within the inlet seal of said pair and
the matrix surface area surrounding the area enclosed by said
outlet seal plus the matrix surface area enclosed within said
further seal being greater than that surrounding the area enclosed
by said inlet seal, whereby the resultant thrust on the matrix due
to the inlet and outlet pressures of said one fluid and the
difference in areas enclosed by said inlet and outlet seals is
substantially balanced by an opposite resultant thrust on the
matrix due to said other fluid pressure and said difference in
areas surrounding the areas enclosed by said inlet and outlet
seals.
2. A heat exchanger as claimed in claim 1 in which the seals are of
sector shape and the inlet seal for said one fluid encloses a
larger area than the outlet seal for said one fluid by said inlet
sealing having its circumferential portion of larger radius than
the circumferential portion of said outlet seal.
3. A heat exchanger as claimed in claim 1 in which said other fluid
is the cooler fluid and said one fluid is the hotter fluid.
Description
The invention relates to a rotary regenerative heat exchanger for
effecting exchange of heat between two fluids. The invention is
particularly, but not exclusively, concerned with a rotary
regenerative heat exchanger of the kind employed in a gas turbine
engine for exchanging heat between hot gases which have been
expanded through a turbine of the engine and air which has been
compressed by a compressor of the engine.
One type of rotary heat exchanger that has been used in association
with a gas turbine engine includes a rotary disclike matrix having
seals engaging the end faces of the matrix and defining paths
through the matrix for the air and hot gases. Due to fluid friction
in the air and hot gases passing through the heat exchange passages
or pores in the matrix, pressure drops are produced in the
respective streams. Hitherto the inlet and outlet areas defining
the paths through the matrix for the hot gases have been
substantially equal and therefore there has been unequal fluid
loading on the end faces due to the difference between the inlet
and outlet gas pressures. Unequal fluid loading on the end faces of
the matrix imparts an axial thrust on the matrix and could tend to
tip it about its axis, thereby imparting undesirable stresses in
the matrix. Where the matrix is made of a brittle material such as
a ceramic or like material, such as silicon nitride, these stresses
could cause damage to the matrix. Also resistance to the axial
thrust on the matrix would create a wear problem due to the
tendency for relative movement to occur between the matrix and its
housing.
According to the invention, a rotary regenerative heat exchanger
comprising a rotary matrix and seals engaging inlet and outlet
faces of the matrix and defining areas of said faces through which
fluids between which heat is to be exchanged are to be passed is
characterized in that the inlet and outlet seals defining a path
for one or other of the fluids enclose respective areas of the
inlet and outlet faces of the matrix of different magnitude,
thereby to reduce the magnitude of the resultant axial force on the
matrix.
Preferably, the matrix is enclosed within a housing having an inlet
for one of the fluids between which heat is to be exchanged,
whereby the whole of the inlet and outlet faces of the matrix,
except those portions thereof enclosed within fluid inlet and
outlet seals, is subjected to the inlet pressure of said one fluid
and the matrix is engaged by a pair of seals enclosing respectively
areas of the inlet and outlet faces of the matrix and defining a
flow path through the housing and the matrix for said other fluid,
the matrix surface area enclosed within the outlet seal being
smaller than that enclosed within the inlet seal and the surface
area surrounding the area enclosed by the outlet seal being greater
than that surrounding the area enclosed by the inlet seal, whereby
the resultant thrust on the matrix due to the inlet and outlet
pressures of said other fluid and the difference in the areas
enclosed by said seals is substantially balanced by an opposite
resultant thrust on the matrix due to said one fluid pressure and
said difference in the areas surrounding the areas enclosed by said
seals.
There may be an additional seal to define the outlet area and the
path through the housing of said one fluid after it has been passed
through the matrix.
The said one fluid may be the cooler fluid and said other fluid the
hotter fluid.
By way of example, a rotary regenerative heat exchanger, in
accordance with the invention, for a gas turbine engine is now
described with reference to the accompanying drawings, in
which:
FIG. 1 is a diagrammatic axial section through the matrix of the
heat exchanger and its associated seals and indicating pressures
acting on different portions of the end faces of the matrix;
FIG. 2 is a plan view of the matrix in the direction of arrow II in
FIG. 1;
FIG. 3 is an underplan view of the matrix in the direction of arrow
III in FIG. 1, and
FIGS. 4 and 5 are respectively axial sections through the matrix
and its associated seals and housing to the left and to the right
of the axis of rotation of the matrix, these figures being drawn to
a considerably larger scale than in FIG. 1.
Referring to the drawings and particularly to FIGS. 4 and 5, the
heat exchanger comprises a housing 1 of generally circular shape in
plan supporting a spindle 2 on which the matrix 3 is rotatable. The
matrix is in the shape of a flat disc and is preferably made of a
ceramic or like material, such as silicon nitride. The matrix 3 has
inner and outer peripheral portions 4, 5 which are non-porous and
an intermediate annular portion 6 formed with heat exchange
passages or pores extending substantially parallel with the axis of
the matrix. The matrix is rotated by means of a pinion not shown
engaging a toothed annulus 7 through a radially resilient driving
member 8 permitting relative radial expansion and contraction
between the annulus 7 and the matrix 3. The annulus 7 may be
constructed in accordance with copending patent application No.
851,704, now abandoned and the driving member 8 may be of any
convenient form, for example, it may be a spirally wound spring
strip or a corrugated spring strip.
The housing supports three generally sector-shaped bellows seals 9,
10, 11 (see FIGS. 2 and 3) which carry flat sealing strips 12, 13,
14 of similar shape. The sealing strips make sliding sealing
engagement with end faces 15 and 18 of the matrix. The seal 9
encloses a region 16 within the housing and a corresponding area of
the end face 15 communicating with atmosphere. The seal 10 encloses
a region 17 within the housing and a corresponding area of the end
face 18 of the matrix. The region 17 communicates with the outlet
end of a turbine of the gas turbine engine. The seal 11 encloses a
region 19 within the housing and a corresponding area of the end
face 18 of the matrix. The region 19 leads to a combustion chamber
of the engine. The remaining portions of the end faces 15 and 18 of
the matrix communicate with an internal region 20 of the housing
which receives compressed air delivered by a compressor of the
engine. Compressed air is therefore delivered into region 20 and
hot gases from the turbine are delivered into the region 17. As the
matrix rotates, air passes through heat-exchange passages or pores
in the part of the matrix portion 6 shown in FIG. 5 and enters the
region 19. Simultaneously hot gases pass through heat-exchange
passages or pores in the part of the matrix portion 6 shown in FIG.
4 and enter the region 16. In this way, the matrix is heated by the
hot gases and imparts heat to the compressed air.
Referring to FIG. 1, at the left-hand side of the housing, the
pressure of gases P17 delivered by the turbine, i.e., the pressure
at the region 17 embraced by the seal 10, will be greater than
atmospheric pressure P16 at the region 16 embraced by the seal 9.
Therefore where the seals 9 and 10 and their sealing strips 12, 13
are of equal shape and size as in known rotary regenerative heat
exchangers, there would be a downward thrust on the matrix.
Furthermore the compressor delivery pressure P20 in the region 20
acting upwardly from underneath the right-hand side of the matrix
being higher than the pressure P19 in the region 19 enclosed by the
seal 11 would tend to cause tipping of the matrix about the spindle
2. The dominant loading is the former and the purpose of this
invention is to minimize the risk of wear or damage to the matrix.
Where the matrix is made of a ceramic or like material such as
silicon nitride this is of significant importance.
In accordance with the invention, the area enclosed by the sealing
strip 13 of the seal 10 and subjected to the pressure P17 of gas
delivered by the turbine is made larger than that enclosed by the
sealing strip 12 of the seal 9. Also, the effective area of the
upper end face 18 of the matrix outside the seal 13 subjected to
the compressed air inlet pressure P20 within the interior of the
housing 1 is made smaller than that of the corresponding part of
the lower end face 15. This is accomplished by making the sector
radius of the seal 10 longer than that of the seal 9 and thereby
moving the peripheral portions of the bellows of the seal 10 and
the sealing strip 13 closer to the outside diameter of the matrix
disc. This is shown by comparing FIGS. 2 and 3 in which the sector
radius of the seal 10 is "R + X" and the sector radius of the seal
9 is R. A value for "X" is calculated hereinafter. The pressure P17
of the hot gases in the region 17 is greater than the pressure P16
in the region 16 and as the area enclosed by the seal 10 is greater
than that enclosed by the seal 9, there is a resultant downward
force due to the hot gases in the regions 17 and 16 acting on the
matrix. There is also a resultant upward force acting on the matrix
due to the compressed air pressure P20 within the housing acting on
the whole of the matrix end faces except those within the sealing
strips 12, 13 and 14. By selecting appropriate dimensions of the
sealing strips 12 and 13, the resultant upward force due to the
compressed air can be made to substantially balance the resultant
downward force due to the hot gases in the regions 17 and 16,
thereby reducing stress within the matrix and also avoiding wear on
the seals due to an unresolved end thrust on the matrix.
Furthermore by selecting appropriate dimensions for the sealing
strips, tipping of the matrix about the shaft 2 can be avoided.
A numerical example giving the difference in radius "X" between the
seals 10 and 9 for vertical equilibrium of the left-hand side of
the axis of rotation now follows. The pressure difference between
the regions 17 and 16 is 0.4 lb. per square inch and the
appropriate area of seal 10 is 2 square feet. Therefore the
downward thrust acting on the matrix = 2X 144X .sup.. 4 = 115 lb.
The peripheral length of the seal 10 is 52 inches and the pressure
in the region 20 is 45 lb. per square inch. Therefore for vertical
equilibrium the downward resultant force derived from the different
pressures P17 and P16 and the difference in areas of seals 10 and 9
must be equal to the resultant upward force due to the pressure P20
acting outside the seals 10 and 9 and thus the area difference
between the seals 9 and 10 is 115/45 = 2.6 square inches. Therefore
the radius difference, X = 2.6/52 = 0.05 inches.
The foregoing description refers to a matrix having a non-porous
rim portion 4 and a non-porous hub portion 5. Where the porous
portion of the matrix extends to the periphery of the matrix,
passages or pores of the matrix that are not open at both ends to
the gas path, open at both ends to the air path or sealed at both
ends by the sealing strips 12 and 13 must be blocked to prevent
leakage of gas through the matrix. Alternatively, the passages
could be inclined to the axial direction in such a way that they
will be open at both ends to the gas path, open at both ends to the
air path or sealed at both ends by the sealing strips 12 and
13.
* * * * *