US3088518A

US3088518A - Differential temperature compensator for radial seals

Info

Publication number: US3088518A
Application number: US64793A
Authority: US
Inventors: Walker H Rayburn
Original assignee: Combustion Engineering Inc
Current assignee: Combustion Engineering Inc
Priority date: 1960-10-25
Filing date: 1960-10-25
Publication date: 1963-05-07
Anticipated expiration: 1980-05-07

Description

y 7, 1963 w. H. RAYBURN 3,088,518

. DIFFERENTIAL TEMPERATURE COMPENSATOR FOR RADIAL SEALS Filed Oct. 25, 1960 H07 END COLD 5N0 5:6 ,52 izflmfl'l g,

7 AW! P 3 99 a6 2 a i; \o !"l"!" 30 M a T.

3,088,518 Patented May 7, 1963 The present invention relates generally to heat exchange apparatus, and particularly it relates to an improved radial sealing arrangement for use between a rotor and adjacent end plates of a housing enclosing the rotor of a rotary regenerative heat exchanger.

In rotary regenerative heat exchange apparatus of the type herein defined, a cylindrical rotor has compartments carrying heat transfer material which are first exposed to heating gases and then as the rotor turns about its axis, the compartments of heat transfer material are exposed to air or other fluid to be heated passing through an air passage where the heated heat transfer material imparts absorbed heat to the air. The rotor is surrounded by a housing having end or sector plates formed with openings that provide for the flow of heating gases and air therethrough. To prevent mingling of the two fluids, radial partitions that form the rotor compartments are provided with radial sealing members that wipe against imperforate portions of the sector plate.

Radial sealing members are usually secured to the end edges of the radial partitions in such a manner that they twist and bend in accordance with the temperature gradient of the radial partitions to which they are attached. Various arrangements for mounting the radial sealing members independent from the radial partitions and actuating them into a sealing relationship with the adjacent face of an end plate have been tried and in many instances found to be satisfactory under certain conditions. Among such arrangements that have been tried are thermal actuating means that move the sealing means in re sponse to an increase or decrease in the average temperature of a thermally responsive element. A serious objection to the use of such an arrangement relates to the fact that such means is not dependent on the degree of distortion but only on the intensity of the temperature. Thus such an actuating means would provide a continuous and sometimes excessive actuation so long as the temperature would continue to lie or rise above a given reference point.

Under certain conditions of operation as during a start up or during a cleaning operation when the flow of air or other cool fluid through the heat exchanger has been substantially curtailed, the temperature of a heat exchanger will rise substantially and assume a nearly constant tmperature throughout such that thermal actuating means of the usual type will continue to expand and force the sealing means against the end plate to provide excessive wear and possible binding of the relatively moving members.

Such wear or binding of the sealing members may necessitate their repair or replacement even before they have been placed in active service. The present invention therefore has as one of its principal objects the thermal actuation of a sealing unit only when subjected to normal operating conditions that impress a temperature differential across the rotor of a heat exchanger.

A further object of this invention is to provide a device for maintaining a fixed position at the outboard end of a radial seal in a rotary regenerative heat exchanger where a diaphragm thereof is turned down as a result of a temperature gradient caused by the passage of a heating fluid and a fluid to be heated therethrough.

When fluid flow is directed through a heat exchanger the diaphragms deflect in accordance with the formula:

ocATX where:

a=coeflicient of expansion of the metal,

AT=temperature differential across the heat exchanger in F.

X :radial length of diahpragm in inches, and

Y=axial depth of diaphragm in inches.

Thus any system designed to compensate precisely for normal thermal deflection of a rotor must be actuated by a differential of temperature across such structure rather than merely by a variation in temperature at a particular point.

Therefore, the present invention is directed to an improved sealing arrangement that compensates directly for a differential in temperature across the rotor of a rotary regenerative heat exchange apparatus.

The invention will be more clearly understood upon consideration of the following detailed description of an illustrative embodiment thereof when read in conjunction with the accompanying drawings in which:

FIGURE 1 is a sectional elevation in diagrammatic form showing a rotary regenerative heat exchanger involving the invention.

FIGURE 2 is an enlarged fragmentary view in section showing the relationship of the various elements that comprise the invention.

In the drawings, the numeral 10 designates a cylindrical shell of a rotor divided into a series of sector shaped compartments by radial partitions or diaphragms 11 connecting it with a rotor post '12 which is turned slowly about its axis by a motor and. reducing gear arrangement illustrated at 13. The rotor compartments are packed with regenerative heat exchange material in the form of perforate material or spaced metallic plates which first absorb heat from hot gases entering the heat exchanger through a duct 15 from a boiler furnace to be discharged after passing over the heat exchange material through an outlet duct 16 to which an induced draft fan (not illustrated) is usually connected. As the rotor turns slowly about its axis the heated plates are moved into the stream of air admitted through duct 17. After passing over plates and absorbing heat therefrom, the stream of heated air is conveyed to a boiler furnace or other place of use through a duct 18.

A housing 20 enclosing the rotor Ill is provided at either end opposite the rotor with end or sector plates 21 which are apertured at 22 and 23 to admit and discharge streams of hot gas and cool air flowing through the rotor. In order that streams of gas and air do not bypass the rotor by flowing through the annular clearance space 24 between the rotor shell 10 and rotor housing 20, it is customary to provide circumferential seals indicated at 25 on the end edge of rotor shell 10 to bear against confronting parts of sector plates 21 and seal oif space 24 from each end of the rotor. Radial sealing means 30 are also provided at the end edges of the radial partitions to bridge the space between the partitions and the confronting imperforate face of the adjacent end plate.

The radial sealing means at one or both ends of the rotor are supported independent of the radial partitions in order that thermal deformation or turn down of the partitions due to a temperature gradient across the heat absorbent element and adjacent partitions will not be transmitted to the sealing members to alter their predetermined sealing relationship.

In this invention, radial sealing means of this general type are pivoted at 32, preferably adjacent the rotor post, while the remote end thereof is axially movable toward or away from the confronting face of the adjacent end plate 21. Pivoted sealing means of this type are necessarily provided only at What is commonly termed the hot end of the rotor inasmuch as during operation uneven thermal expansion of the rotor forces the rotor to turn-down or move away from the end plate at the hot end of the rotor while at the opposite or cold end of the rotor the reverse is true and the rotor including sealing means attached thereto is moved toward the confronting face of the end plate.

Accordingly, the seal actuating means comprises essentially two radially extending

expansion bars

34 and 35 that are securely attached at their inner ends to axially remote parts of the diaphragm 11 in order that their outboard ends may be entirely free to move radially relative to the adjacent diaphragm. A slot 36 in one or both expansion bars embracing a pin 39 on the diaphragm adjacent thereto permits unencumbered radial expansion of the expansion bar while it simultaneously provides an axial support for their outboard ends. Since thermal distortion or turn-down of a diaphragm occurs primarily at its distal end, the slot 36 and supporting pin 39 are preferably positioned substantially midway between inner and outer extremities of the diaphragm to provide a substantial support for the sealing means that is subject only to a fractional amount of turn-down evident at its outer end. The expansion bars are preferably comprised of a material such as stainless steel having a high coefiicient of expansion in order that a small change in temperature will provide substantial radial movement at their outboard ends. Both expansion members are however formed of the same material and of the same length to provide equal expansion when subjected to a common temperature and different degrees of expansion when subjected to different temperatures.

The outboard ends of the expansion bars 34- and 35 are pivotally attached at 42 and 44 to an axial connecting bar 46 and includes a cantilever portion 48 extending axially to a point laterally adjacent the outboard end of the pivoted radial seal. The connecting bar 46 is formed from the same material as the diaphragm adjacent thereto in order that the connecting bar and a laterally adjacent segment of the diaphragm will expand or contract in unison when subjected to the prevailing temperature.

A driver cam 52 having a radial slot 54 formed therein is secured to the cantilever end 48 of the connecting bar 46 and arranged to slidably embrace a pin 56 protruding from the side of the radial seal. The length of the driver cam 52 and its slot 54 is determined by the size, material and operating temperatures of the heat exchanger whose radial seal it is designed to actuate, since rotation of the driver cam 52 about pivot 42 should provide a vertical component of force to pin 56 that neutralizes the turn-down of the rotor occurring at pin 39.

Under conditions that obtain a constant temperature at both ends of the rotor the

radial expansion bars

34 and 35 will be of equal length and the connecting bar 46 linked normal thereto will lie in a substantially vertical position. With the expansion bars thus positioned the driver cam 52 will lie in its original horizontal position 4 and the pivoted radial seal 30 will continue to lie in its original non-actuated or neutral position.

When normal flow of a heating fluid and a fluid to be heated through the heat exchanger is initiated, the temperature gradient across the rotor will increase with the greatest increase of temperature occurring at the hot end adjacent expansion bar 34. This varying increase of temperature effects substantially greater thermal expansion of bar 34 than of bar 35 thereby forcing the upper end of connecting bar 46 to slope outward and incline the driver cam 52 upward such that it raises the pin 56 and the pivoted sealing member 30 to which it is attached towards the adjacent end plate to neutralize the downward movement of the diaphragm 11 that occurs between the pin 39 and the rotor post as caused by rotor turndown.

Thus operating conditions which normally effect distortion or rotor turn-down and result in excessive leakage of fluid through the clearance space between the sealing means and the adjacent end plate are utilized to actuate the sealing means into a preferred sealing relationship with the adjacent face of the end plate. Moreover, under certain conditions where there exists no temperature differential across the rotor there can be no actuation of the sealing means, and such sealing means are not forced unnecessarily into contact with the adjacent housing members.

While this invention has been described with reference to the embodiment illustrated in the drawing it is evident that numerous changes may be made in the several elements to provide the desired degree of seal actuation without departing from the spirit of the invention, and it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What I claim is:

1. A regenerative heat exchanger having a rotor including a cylindrical rotor shell joined to a rotor post by radial partitions to form sectorial compartments that carry a mass of heat transfer material, and a cylindrical housing surrounding the rotor provided at opposite ends thereof with end plates including imperforate portions located between circumferentially spaced apertures that direct the flow of heating fluid and fluid to be heated through the regenerative heat transfer material carried by the rotor, radial sealing means bridging the space between an end edge of each radial partition and the adjacent end plate to preclude fluid flow therebetween, said sealing means including radially extending leaf members pivotally attached at one end thereof to an axial end edge of said radial partition, and actuating means at the distal end of said leaf members lying adjacent the inlet aperture for the heating fluid arranged to move them toward the adjacent end plate in response to the differential of temperature that distorts the radial partitions in the opposite direction.

2. Regenerative heat exchange apparatus having a rotor including a cylindrical rotor shell joined to a rotor post by radial partitions to form sectorial compartments that carry a mass of heat transfer material, and a cylindrical housing surrounding the rotor and provided at opposite ends thereof with end plates including irnperforate portions located between circumferentially spaced apertures that direct the flow of heating fluid and a fluid to be heated through the regenerative heat exchange material carried by the rotor, radial sealing means bridging the space between an end edge of each radial partition and the adjacent end plate to preclude fluid flow therebetween, said sealing means including a radially extending leaf member lying adjacent and pivotally attached at one end to the radial partition, actuating means linked to the opposite end of said leaf member to bias it toward the end plate inversely as the radial partition moves away therefrom, said actuating means comprising radial expansion bars at axially spaced ends of each diaphragm having one end fixed thereto while the distal ends thereof 5 6 are free to expand radially in response to a change of having a linkage means including a radial slot in the temperature, a linking bar pivotally attached to the disdriver cam slidably embracing a pin aflixed to the side of tal ends of said expansion bars, and means responsive to said pivoted sealing means. an inclination of said linking bar adapted to provide a component of force moving the sealing means into seal- 5 References C d 1 1 the fil 0f thIS patent ing relationship with the adjacent end plate.

3. A regenerative heat exchanger as defined in claim UNITED STATES PATENTS 2 wherein the means responsive to the inclination of said 2,681,203 Boestad et June 15, 1954 l'ki b i d a flixdth toand in ng ar compr ses a river c m a e ere FOREIGN PATENTS lying adjacent the pivoted sealing means.

4. A regenerative heat exhanger as defined in claim 3 10 1,144,668 France Oct. 16, 1957

Claims

1. A REGENERATIVE HEAT EXCHANGER HAVING A ROTOR INCLUDING A CYLINDRICAL ROTOR SHELL JOINED TO A ROTOR POST BY RADIAL PARTITIONS TO FORM SECTORIAL COMPARTMENTS THAT CARRY A MASS OF HEAT TRANSFER MATERIAL, AND A CYLINDRICAL HOUSING SURROUNDING THE ROTOR PORVIDED AT OPPOSITE ENDS THEREOF WITH END PLATES INCLUDING IMPERFORATE PORTIONS LOCATED BETWEEN CIRCUMFERENTIALLY SPACED APERTURES THAT DIRECT THE FLOW OF HEATING FLUID AND FLUID TO BE HEATED THROUGH THE REGENERATIVE HEAT TRANSFER MATERIAL CARRIED BY THE ROTOR, RADIAL SEALING MEANS BRIDGING THE SPACE BETWEEN AN END EDGE OF EACH RADIAL PARTITION AND THE ADJACENT END PLATE TO PRECLUDE FLUID FLOW THEREBETWEEN, SAID SEALING MEANS INCLUDING RADIALLY EXTENDING LEAF MEMBERS PIVOTALLY ATTACHED