US 3232335 A
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Description (OCR text may contain errors)
Feb. 1, 1966 G. KALBFLEISCH 3,232,335
ROTARY REGENERATIVE PREHEATER Filed March 21, 1962 2 Sheets-Sheet l Feb. 1, 1966 G. KALBFLEISCH 3,232,335
ROTARY REGENERATIVE PREHEATER Filed March 21, 1962 2 Sheets-Sheet 2 Fig.2
United States Patent Ofilice 3,232,335 Patented Feb. 1, 1966 3,232,335 ROTARY REGENERATIVE PREHEATER Georg Kalbfleisch, Eppelheim, near Heidelberg, Germany,
assignor to Svenslra Rotor Maskincr Aktiebolag, Stockhoim, Sweden, a company Filed Mar. 21, 1962, Scr. No. 181,398 Claims. (Cl. 165-9) The invention relates to rotary regenerative preheaters in which the inactive sectors of the heat retaining mass are covered by means of movable sector plates. Such preheaters, for example, are utilized in large size boiler plants for preheating the combustion air by means of the hot flue gases. In such applications, the distortions which the heat retaining mass undergoes under the influence of the temperature fluctuations are of considerable importance. If the sector plates, which separate the flue gas channel from the air channel, are adjusted when the filling mass is cooled down so that the smallest possible clearance is provided in order to minimize air leakage, the adjustment must be changed when the filling mass has become heated. Previously, this subsequent adjustment was manually performed by trained personnel, and the aim has been to adjust the sector plates automatically so that they swing in accordance with the distortion of the filling mass body and readjust themselves to the correct clearance. In one prior art type of preheatcr, the movable sector plates are urged separately and independently of each other against the rotor and are supported thereon by means of roller elements producing rolling friction. By means of this direct support on the rotor, the desired clearance may be secured. The prerequisite is, of course, that the urging force be sufficiently large to prevent an inadvertant uncovering of the sector plate from the heat retaining mass. Obviously this urging force which supports the sector plates results in a corresponding intensive and permanent load on the supporting element; for example, the supporting wheel resting on the flange of the heat retaining mass. Such a permanent intensive mechanical strain involves a corresponding wearing out and consequent shortening of the life of the parts, since the supporting element operates at high temperatures in air preheaters heated by flue gases and is subjected to the mechanical and chemical attacks caused by the impurities contained in the flue gas.
In rotary regenerative preheaters of smaller and medium sizes, the forgoing problems are not of major significance. In very large preheaters, however, the strains and the corresponding wearing of the parts assume such a magnitude that it is advisable to improve the device.
According to the present invention the rotary regenerative preheater, which is of known construction, is provided with movable sector plates covering the inactive sectors of the heat retaining mass. The presently disclosed preheater eliminates the disadvantages of the known prcheaters of the type above described by providing a device which senses the actual level of the front face of the heat mass of the inactive zone and by means of a servo motor readjusts the sector plate to the correct clearance by swinging in accordance with the distortion of the filling mass. In this arrangement, the swinging force acting upon the sector plate is not directly created by any structure resting on the heat retaining mass and following the movement of this heat retaining mass. To create this force for shifting the sector plate, which force may assume considerable proportions in large preheaters, a servo motor is provided so that a very slight force is suiiicient for the sensing. The force for the sensing need only be relatively slight to follow the variations of the level of the front faces of the heat retaining mass caused by the distortion and on the other hand he sufiicient to control the servo motor. Such slight sensor forces, therefore, will mean a corresponding slight wear.
For the sensing of the heat retaining mass, many possibilities are available; for example, a mechanical method may be employed by means of a sensor, a pneumatic method may follow the impingement plate principle, magnetic methods, etc., may be used.
According to this invention, three embodiments are illustrated. An air preheater with rotating heat retaining mass is illustrated as the preferred embodiment, the heat retaining mass being carried by the axis of rotation with the result that the distortions are strongly predominant at the circumference of the heat retaining mass. In addition, the embodiments of this invention disclose a rim flange on the circumference of the heat exchanging mass suitable as a guiding member. The principles of construction are in no way bound to the specific embodiments disclosed herein. The methods of sensing may, for example, be applied similarly to other embodiments, particularly with regard to simple cinematographic reversion of rotary preheaters having a stationary heat retaining mass and consequently revolving ducts.
The invention will he understood more clearly from this following discussion with relation to the accompanying drawings of which:
FIG. 1 illustrates a preferred embodiment of my invention,
FIG. 2 shows another embodiment thereof, and
FIG. 3 shows a third embodiment.
The illustration of a rim edge and an end portion of a sector plate is sufiicient to describe the manner of operation of this invention. Accordingly, FIG. 1 shows the shell ll of a rotor having a rim flange 2 attached thereto. Above flange 2, described hereafter as the front face of the rotor, a sector plate 3 is located. In order to prevent premature Wear and disturbing noises during operation, sector plate 3 does not touch the front face of the rotor or slide thereon. The clearance between the sector plate 3 and the front face of the rotor, however, remains very small in order to keep leakage losses to a minimum.
The sector plate 3 is supported at its right hand end, not shown in the drawings, in such a manner as to allow it to be swung up and down, thereby adapting itself to the position of the rotor filled with heat retaining mass. This adaptation is effected by the schematically shown pneumatic servo motor control of FIG. 1.
A pressure medium controlled by the pneumatic servo motor control is delivered by a conduit 4 via throttle 5, and via a succeeding conduit 4 to a nozzle 6 provided at the end of the sector plate 3 and directed towards the rotor flange 2, the rotor flange 2 thereby serving as an impingement plate. The pressure in the conduit 4 is dependent on the distance of flange 2 from the orifice of nozzle 6. It is thereby possible for control cylinder 7 to operate in dependence upon the clearance between flange 2 and sector plate 3. The medium acting on pressure piston 8 is taken from the conduit 4 of, for example, pressurized air. The control of the pressure piston 8 is carried out by means of control device 9, which in accord ance with the position of the control piston 7 is effective by means of conduits 10 to supply the required proportion of pressure air to opposite sides of piston S. The control device 9, therefore, represents a power amplifier. The pressure piston 8, by means of its piston rod 11, is directly in engagement with the sector plate 3. Piston rod 11 may be passed through cover 12 attached to shell 30 of the preheater housing and may be sealed with respect to cover 12 by means of yielding sleeve 13.
Adjustment means 14 is provided to adjust the length Of the piston rod 7, thereby providing adjustable con- 3. trol. A similar turn-buckle 15 is provided in the piston i'od 11 of the pressure rod 8 for the same purpose.
It is evident from the previous discussion that an increase in the clearance between flange 2 and plate 3 is followed by a decrease of pressure in conduit portion 4' and accordingly in the control device 7. This decrease in pressure is reflected to pressure piston 8 which will act to decrease the clearance and cause the control pressure to return to its normal value. Each deviation of the control pressure from its normal value responding to an increase or decrease of clearance due to a distortion or" the rotor results in a swinging of the sector plate and restoration of the clearance between plate 3 and flange 2.
Obviously, the air nozzles may be placed within the circumferential segments of rotor shell 1 as well as within flange 2. In this manner, all of the required sealings could be adjusted to the desirable clearance, a clearance of about 3 mm. proving by experience to be quite satisfactory. The pneumatic control of FIG. 1 is suitable for such modifications. Pressure air of the order of 4 to atmospheres above atmospheric pressure may be utilized, while the guide pressure after throttling may be in the order of about 1.5 atmospheres above atmospheric pressure.
The described servo control of FIG. 1 is illustrative only as an example of one of many possibilities. Similarly, hydraulic, electric and other servos are usable. It is also noted that means external of the servo system may be employed for emergency reasons to act on piston 8. An electric motor may be provided to coordinate the power amplifier by action of the attendant. Such an action may become necessary, for example, when it is observed that the pressure has increased sufliciently high that a strong rubbing and even a jamming of the sector plates may be concluded. correspondingly, it is possible to permit the pressure medium in the main line to directly influence pressure piston 8, so that the sector plates are automatically moved apart. Furthermore, it is possible to operate the pressure piston with oil instead of air.
FIG. 2 shows a mechanical sensor device. Many of the same structural details are present in that embodiment as are disclosed in the embodiment of FIG. 1 and are denoted with the same reference numerals.
In this mechanical sensor device, a hinged sensor lever 24) is attached to the sector plate 3 and is slideable on flange 2 of the rotor. To the sector plate 3 the power amplifier 9 is attached by means of a stationary support member 21. A change in the clearance between the flange 2 and sector plate 3 causes a swinging of the sensor lever 20 and a consequential movement of the control rod '7". Power amplifier 9 is therefore acted upon to actuate the servo motor, or piston 8. Again, the rods passing through cover 12 of the housing may be sealed off by means of folded bellows 13, i3 and 13".
Use of the sliding sensor has the disadvantage of wear to flange 2 and lever 20, but the wear remains within acceptable limits due to the slight forces involved. A high grade special material may be utilized to reduce the wear and achieve a satisfactory life. Furthermore, the sensor 20 may be constructed to make roller contact with flange 20.
In FIG. 3 a magnetic system 34 is provided and attached to that portion of sector plate 3 which is adjacent edge flange 2. Portion 31 is of non-magnetic material having heat insulating properties. Ceramic, asbestos, etc. may be utilized. The magnetic resistance of the magnetic circuit comprising elcctromagnet 34 and flange 2 is determined by the distance between the sector plate 3 and flange 2 of the rotor. By using as a source, a constant amplitude alternating voltage from current generator 32, the magnitude of current in the circuit is accordingly changed, as the clearance varies. The change in current is coupled through transformer 33 to affect control of the position of plate 3. As an alternative to the use of transformer 33, sensing coils may he transformer coupled to the coils of system 34 to detect changes in current.
In connection with the embodiment of FIG. 3, control current coupled from the circuit including system 34 may be utilized to control an electric servo motor which readjusts sector plate 3.
The basic principle of operation of the embodiments herein described consists of sensing distortion of the filling mass body which may result in the transmission of relatively slight forces, and of utilizing the sensed forces to create substantially greater forces necessary for the proper adjustment of the sector plates. It is therefore advantageous to locate the sensing members at the points of greatest disortion. If an air preheater with rotary heat exchanging mass is considered, in which the heat exchanging mass is carried by a shaft, the sensing is carried out along the circumference of the rotor; for example, on the edge flange. This type of air preheater is the most common and was used in the explanation of all three examples of embodiments. In air preheaters in which the rotary heat exchanging mass is carried along the circumference, however, the distortions are greatest in the central portion, and the sensing is performed at the inner bordering shell of the heat retaining mass. The sensor members therefore sweep over the heat retaining mass along circular paths of the greatest possible spacial disortion. By reversal of the process, the same results are obtained in air preheaters having stationary heat retaining masses and rotary connection ducts.
In all these examples, use of a servo motor may result' in the derivation of very great adjustment forces so that even with the largest air preheaters a readjustment may The forces of the sensing" be effected without difficulties. devices result, on the other hand, in only slight wear and a correspondingly long life. Very large air preheaters are constructed with capped dishing of the front faces, and a sufliciently narrow air clearance can not be achieved by surface plane sector plates. The plates may, therefore, be divided up so that the separate surface plane portions may adapt themselves to the dished front face. Individual distance adjustments are accordingly effected on each of the separate portions.
It will be apparent to one skilled in the art that many modifications of the disclosed embodiments of this invention may be made without departing from the spirit and scope of the appended claims.
What is claimed is:
1. In a rotary regenerative heat exchanger of the type having a heat retaining mass traversed in counter-flow by heat emitting and heat absorbing media, said mass being supported by a cylindrical member separated into sector. compartments, and spaced inlet and outlet means for said media, said cylindrical member and said inlet and outlet means being provided for a relative rotation therebetween, the inlet and outlet means being separated by sector shaped plates located in sealing relation with respect to the respective axial ends of said cylindrical member and each covering a certain number of said sector compartments, said sector plates being movable in spaced relation to cooperating portions of said cylindrical member, means for sensing the gap between each of said sector plates and the cooperating member of said cylindrical portion, power amplifying means operatively associated with said sensing means, and means connected to said power amplifying means and respectively to said sector plates for adjusting said gap to a predetermined size in response to said sensing means.
2. In a rotary regenerative heat exchanger according to claim 1 wherein said sensing means comprises a magnetic system.
3. In a rotary regenerative heat exchanger according to claim 1 wherein said sensing means comprises magnetic means, a current source operatively connected in an electrical circuit to said magnetic eans and a transformer connected in the circuit with said current source and magnetic means, current changes caused by variation in the gap between each sector plate and the cooperating portion of said cylindrical portion being transmitted by said transformer to the power amplifying means.
4. In a rotary regenerative heat exchanger according to claim 1 wherein said sensing means comprises at least one nozzle on one of the members forming the gap and an impingement plate on the other of the members forming the gap, air pressure means supplying air pressure to said nozzle, variation in the air pressure caused by variation in the gap size producing an impulse transmitted to said power amplifying means.
5. In a rotary regenerative heat exchanger according to claim 1 wherein said sensing means comprises a lever pivoted on said sector plate and engaging the cooperating portion of said cylindrical portion, and means connecting said pivoted lever with said power amplifying means.
References Cited by the Examiner UNITED STATES PATENTS 2,503,720 4/1950 Gieseke 33-147 X 2,557,075 6/1951 Caputo 308-10 X 2,579,211 12/1951 Stevens et al. 165-9 2,678,193 5/1954 Stevens 165-9 2,747,843 5/1956 Cox et a1. 165-9 2,856,238 10/1958 Dacus 317-12330 X 2,945,681 7/1960 Burchfield 165-9 3,122,200 2/1964 Koch 165-9 15 ROBERT A. OLEARY, Primary Examiner.
CHARLES SUKALO, Examiner.