US2865611A - Rotary regenerative heat exchanger - Google Patents

Description

Dec. 23, 1958 M. BENTELE ROTARY REGENERATIVE HEAT EXCHANGER Filed March 13, 1953 2 Sheets-Sheet l DC. 23, 1958 M- BENTELE 2,855,611

ROTARY REIGEINERATIVE HEAT EXCHANGER Filed March 13, 1953 2 Sheets sheet 2 2,865,611 ROTARY REGENERATIYE FEAT EXCHANGER Max Bentele, Newcastle-upon-Tyne, England, assignor to Q. A. Parsons & Company Limited, Newcastle-upon- Tyne, England Application March 13, 1953, Serial No. 342,231

4 Claims. (Cl. 257-6) This invention relates to rotary regenerative co-unterow heat exchangers of the type used with combustion turbines and which consist of a rotating drum or disc accommodating a matrix, passing alternately through high pressure and low pressure sides of the cycle.

In the drum type of regenerator as applied to a conventional open-cycle gas turbine, high pressure air from a compressor, enters the high pressure side of the regenerator, passes through openings on the inside of the rotating drum, is heated by the matrix and then leaves through openings on the outside surface of the drum and thence to the high pressure side outlet of the regenerator. Ho-t gas from the turbine enters the low pressure side inlet ofthe regenerator, passes in counterow through the drum and matrix where it is cooled and then leaves through the low pressure side outlet into the atmosphere.

The matrix is arranged in chambers, the radial walls of which, in conjunction with seals, prevent leakage flow from the high pressure to the low pressure side.

In the disc type regenerator the matrix is of a type which prevents ilow of gas or air perpendicular to the main air or gas flow and does not need to be accommodated in chambers. It is usually of the flame trap type with triangular straight passages. The passages are normally greater than those of wire mesh matrices, but they are still liable to clogging.

Dust or other particles may enter the heat exchanger with the cold air from the compressor, or with the hot gas from the turbine.

The rst case namely that of dust entering the heat exchanger with the -cold air, applies where the compressor is insensitive to dust and the air is therefore filtered insufficiently, if at all, before the compressor. This is possible with centrifugal compressors for example.

The second case namely that of particles entering the heat exchanger with the hot gas coming from the turbine, applies where the combustion products contain contaminants and solids such as soot and y ash and these are not fully precipitated before the turbine or regenerator.

In both drum and disc type regenerators particles which are small enough to be entrained by the air and gas irrespective of changes of velocity and direction pass through the matrix and thus do not cause a problem. Other rates arent O particles either creep slowly through the matrix inthe same direction as the gas flow, but at a slower speed than the gas, or are trapped in the rst layers of the matrix. Fo-r these particles creeping slowly through the matrix, the longer the time they are in the matrix thev greater is the tendency for them to adhere to the matrix and thus clog it. Clogging of the matrix adversely affects the pressure drop and heat transfer.

The object of the invention is to provide a method and means for the continuous and eiective cleaning of the narrow passages of the matrix of rotary regenerative counterow heat exchangers of the type used with combustion turbines and which consist of a rotating drum CCV or disc accommodating a matrix, passing alternately through high pressure and low pressure sides of the cycle, free of the above disadvantages.

The invention consists in a method for the continuous and effective cleaning of narrow passages in the matrix 0f rotary regenerative counterflow heat exchangers of the type suitable for use with combustion turbines and consisting of a rotating drum or disc accommodating the matrix and passing alternately through high pressure and low pressure sides of the cycle in which use is made of the dilerence in pressure between the high pressure and low pressure sides during the transition period in which the rotor of the regenerator is passing between the high pressure and low pressure sides and vice versa, to cause dust and other particles suspended in and adhering to the matrix to travel in a certain direction depending upon the source of the particles and the position of their deposition in the matrix with sealing shoes so constructed and arranged as to provide towards the end of this transition period a sudden connection of one side only of the part of the matrix passing between the sealing shoes, to the regenerator housing thus making available a strong current of air through the matrix so as to sweep away adhering particles and increase the speed through the matrix of the creeping particles.

In other terms the invention consists in a method with means for the continuous and effective cleaning of narrow passages in the matrix of rotary regenerative counterow heat exchangers of a ty'pe suitable for use with combustion turbines and which consist of a rotating drum or disc accommodating the matrix, with a pressure difference between hot gas and cold gas sides, the matrixy passing alternately through the high pressure and low pressure sides of the cycle in which use is made of the difference in pressure between the high pressure and low pressure sides during the transition period in which the rotor of the regenerator is passing between sealing shoes separating the high pressure and low pressure sides and vice versa, to cause dust and other particles suspended in and adhering to the matrix to travel in a certain direction depending on the source of the particles and the position of their depo-sition in the matrix yby so constructing and arranging the sealing shoes so as to provide t0- wards the end of this transition period a sudden connection of one of the faces either inlet o-r outlet of the matrix to a region of low pressure enabling a strong current of air from the high pressure side of the regenerator to blow through the matrix sweeping away adhering p particles and increasing the speed through the matrix of those dust and other particles suspended therein or thereon.

Referring to the accompanying diagrammatic drawings:

Figure 1 shows an arrangement for a drum type ofV Figures 3a and 3b illustrate the application of thek invention to a disc type of regenerator.

Referring to Figure 1 ambient air 1 enters a compressor 2 and is compressed. On leaving the compressor it enters the high pressure side, designated by the letters H. P., inlet I of a regenerator 3, passes through openings 4 on the inside surface of drum 5, is heated byv a matrix 6 contained in chambers formed within the; drum and leaves through openings 7 on the outside sur- I face of the drum, and thence to the high pressure side oulet II.

The preheated air leaving the outlet II is further heated in a combustion chamber 8 and expanded in a turbine 9, the exhaust of which is connected to the low pressure side, designated by the letters L. P., inlet HI of the regenerator, passes,Y in counterflow through the drum and matrix where it is cooled, and then leaves through the low pressure side outlet into atmosphere.

The drum rotates in a clockwise direction. Sfealings 10 and 11, 12 and 13 prevent leakage flow from high Y pressure to low pressure sides of the regenerator.

Dust and other particles entering the heat exchanger with the air from the compressor are shown by chain dotted lines 14, the use of the dotted line being to indicate dust particles in the air stream. They enter with the air'through the inlet I and then through holes 4 of the drum and some tend to adhere to the inner part of the matrix whilst some percolate slowly. As each chamber passes 'between the seals 12 and 13 its inner side is connected to the low pressure side of the regenerator first by` overlapping the sealing shoe 13 with respect to the opposed sealing shoe 12. The high pressure air trapped lin said chamber provides a strong current of air which Viiows radially inwards towards the outlet IV, sweeping away all the particlesl suspended in the matrix with it.f

Gas from the turbine exhaust containing dust and other particles such as soot or fly ash indicated by dotted lines, entersV the regenerator at III, enters the drum through holes 7, and the said particles tend to adhere to the outside'of the drum. When the chambers reach sealing shoes 10 and 11 they are connected to the inner side of the drum first and by virtue of the fact that outer shoe 11 overlaps inner shoe 10 the particles are blown outward and into compartment 16 of shoe 11 and are carried from there by a stream of air indicated by the chain dotted line 17, the use of the chain dotted line being to express dust particles in the air stream. The dustby this air stream is carried into a precipitator 18. The clean air leaves the precipitator and is reunited with the main stream in or after the combustion chamber. The dotted line shown leaving the precipitator is intended to indicate a stream of dust leaving the precipitator.

Referring to Figures 2a, 2b and 2c, these represent the drum chambers moving from the low pressure side to the high pressure side. Figure 2a represents theY blast period. The inner sealing shoe 1t) provides a sudden connection to the high pressure inlet l, and the resulting air blast blows the particles oating in or adhering to the matrix into space 20 between the matrix and the outer shoe 11. Y

Soon after, as shown in Figure 2b, which represents the beginning of the cleaning period, this space 20 is connected to the compartment 16 and thence to the precipitator' 18. The pressure diterence between high pressure air inletI and duct i6l provides a small airflow 1 7 in the direction shown. Figure 2c represents the end oi the cleaning period. In order to prevent` any particles from escaping into the outlet II, an overlap 21 of the sealing shoe 11 covers the chamber during the cleaning period.

` Referring now to Figure 3u, this illustrates an example of sealing shoes for use with a disc type of regenerator.

The general principle of action is similar to that explained with reference to Figures 2a, 2b and 2c.

Figure 3b shows a modified type of shoe for removing dust particles and the like adhering to the cold gas side of the disc. The sealing shoe 13Y is made broader and contains a groove Z2 opposite the trailing edge of the shoe 12.` The groove is connected tothe high pressure" sidel by holes 23 which permit air to ow from the high pressuref side and sweep the particles and contaminants intoE thel exhaust IV.l

In most cases the method and meansvI have described 4 above are sufficient for eiective action, but should cases occur where for instance the plant has to run for long periods on low lo-ads and an external source of compressed air is available this external source may be used to supplement the supply of cleaning air. For this purpose an arrangement as shown in Figure 3b may 'oe used to replace shoes 10 and 13 shown in Figure l, the groove being opposite the compartment 16 in the first case. The compressed air supply is connected to the groove 22.

General The percentage of particles trapped in the first layers of the matrix may be increased by arranging a wire cloth or the like on one or both sides of the matrix.

In the drum type of regenerator where the matrix is accommodated in chambers, where the air from the cornpressor is dust laden but the gas from the turbine is clean or its dust concentration is no higher than that of the preheated air after the heat exchanger, the chambers should preferably be made to empty inwards by constructing the inner and outer sealing shoes in such a way that the chambers passing through the seals from the high pressure to the low pressure side are suddenly connected to the inside of the drum lirst and then after the pressure in each chamber has reached the low pressure value it is opened to the outside of the drum.

The only chambers which need cleaning are those leaving the high pressure side where dust and other particles Will be deposited mainly in that part of the matrix nearest the inner periphery. For cleaning purposes therefore it is only necessary to arrange for the sealing shoes at the point where the chambers pass from the high pressure side to the low pressure side to be constructed and arranged so that the chamber is connected to the inside of the drum first and the dust particles are blown inwards into the exhaust duct on the low pressure side.

For the disc type of regenerator, a modified system is preferred whereby the sealing shoe on the side where the gas or air enters the matrix, is made broader as exemplified above and contains a groove opposite to the trailing edge of the opposite shoe, which is connected to the high pressure side by holes, these holes being disposed to permit enough air ow to the groove as is necessary for sweeping away particles and contaminants in the passages into the exhaust of the hot gas side of the disc.

In the case Where the air from the compressor is clean, while the gas from the turbine is dust laden, the chambers, in the case of the drum type regenerator, are preferably connected to the inner side of the drum lirst, thus ejecting the dust and other particles outwards into a compartment in the outer shoe at the side where the drum is passing from the low pressure to the high pressure side, this compartment being connected to a precipitator where the particles are precipitated, the clean air from the precipitator being reunited with the main` mass iiow in or after the combustion chamber, or any component downstream of the high pressure side of the regenerator.

For a disc type of regenerator similar means are applied.

In the case where both the air from the compressor and that from the turbine contain dust'and other particles, then both methods are preferably applied and particles are removed' by the shortest route continuously and effectively.

In turbine plants which run for long periods on low load, the pressure difference between the high pressure side and the low pressure side may not be suicient to ensure satisfactory cleaning of the matrix. To combat this it is preferred to supplement the supply of cleaning air fromv or by means of an external source of compressed air in conjunction with sealing shoes containing grooves and connected to the compressed air supply by holes.

I claim:

l. In a rotaryV regenerative counter iiow heat exchanger, and: in combination, va rotor having a plurality on partitions symmetrically disposed about4 itsV axis. and: dening compartments, a heat exchange matrix contained in the said compartments, stationary casing and partition means comprising sealing shoes cooperating with the said rotor partitions to divide the heat exchanger into a low pressure hot gas side and a high pressure cold gas side, conduit means for conducting hot and cold gases to and from the heat exchanger in the said respective sides thereof and arranged for owing the cold gas through the said compartments in one direction and the hot gas through the said compartments in the opposite direction, the said sealing shoes comprising a pair of shoes on opposite faces of the rotor, and arranged to cooperate with a pair of adjacent rotor partitions to form therewith an enclosed space, one of said shoes continuing beyond the other in the direction of rotation ofthe rotor to maintain a closure with a said partition after it has passed the cooperating shoe, whereby as a partition passes the second said shoe, a pressure difference is created across the matrix in the rotor compartment following the said partition causing gas ow to remove particles suspended in and adhering to the matrix.

2. The combination according to claim 1, in which the matrix only partially lls the said compartments leaving a space adjacent the first said shoe of the pair.

3. The combination according to claim 2, in which the shoe of the pair which continues beyond the .other shoe of the said pair is a shoe on the up stream face of the rotor as it enters the high pressure side of the heat exchanger, and the said shoe comprises an exhaust duct for receiving the air blown through a said compartment toetlier with particles discharged therewith.

4. The combination according to claim 3, comprising a conduit for conducting gas from the said exhaust duct back into the cycle with gas discharged fro-m the high pressure side of the heat exchanger, the said conduit including a precipitator for removing suspended particles.

References Cited in the tile of this patent UNITED STATES PATENTS 1,315,822 Doran Sept. 9, 1919 1,970,127 Colby et a1. Aug. 14, 1934 2,347,829 Karlsson et al. May 2, 1944 2,537,558 Tigges Jan. 9, 1951 2,583,671 Schmitter Jan. 29, 1952 2,667,034 Alcock Jan-26, 1954 FOREIGN PATENTS 545,523 Germany Feb. 11, 1932 543,093 Great Britain Feb, 10, 1942

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