GB2311363A - A combustion chamber baffle for a boiler - Google Patents

Abstract

A combustion chamber baffle 60 for use in a boiler 64 has at one end a raised lip protruding from the plane of the baffle 60. The lip is provided with a turbulator comprising a single row of tabs. The tabs are located at the top edge of the raised lip. The height of the raised lip is adjustable. The tabs increase the surface area and may initiate turbulence. As the combustion gases pass through/over the turbulator, the gases are subject to an area of low pressure which occurs immediately above each tab resulting in expansion and elevated heat release. The underside of the combustion chamber baffle 60 does not include any form of insulating panel. In an alternative embodiment (not shown) the single row of tabs could be found anywhere in the plane of the raised lip.

Description

IMPROVEMENT IN AND RELATING TO BOTLERS BACKGROUND TO THE INVENTION The invention relates to an improved baffle fitted inside a@ heat exchanger of a boiler and to an improved boiler incorporating such a baffle.

the The boiler which is to heat water incorporates / heat exchanger having a flow passage for a first fluid and a flow passage for a second fluid separated by a thermally conductive wall structure which is tubular. The water to be beated is contained in a jackat surrounding the thermally conductive tubulr structure and is provided with later inlet and ontle: connections.

The inside of one end of the heat exchanger is utilized as a combustion chamber for liquid, gaseous or solid fuel and/provided with a suitable opening. Heat is exchanged in this space by radiation and convection and additionally, if solid feel is burned, by conduction. An outlet for gaseous products of combustion is provided at or near the opposite and of the exchanger.

The combustion chamber is defined and separated from the remainder of the tubular exchanger by z baffle which is supported inside the heat exchanger towards the outlet for combustion products. on on. side of the baffle a gap or slot is provided bet"een the edge of the baffle and the thermally conductive wall through which the hot gases of combustion pass towards the outlet froa the exchanger. The baffle can be constructad of suitable heat resisting metal or refractory material or may be achieved by deformation and extansion of the thermally conductive heat exchanger wall. The extansion of the heat exchanger wall forming the baffle is disposed at an angle of substantially 90 degree. to the thermally conductive itll and may be hollow so that it contains utter.

Conventional methods utilized to improve heat exchanger efficiency in boilers include extending the heat exchanger surface by corrugating.

dimling, finning or incorporating protrubences such as tabs of varicus shape, angle or round profile which are integral to the gas side surface of the heat exchanger. Such measures, as well as extending the surface area, may initiate turbulence which with reduction of pressure enhances heat release froa the gases of combustion and may be utilised in combination with plate type baffles.

Various type. of plate type baffles are employed to increase length of travel of the gases of combustion through a heat exchanger and elevate beat release by introducing turbulance and reduction of pressure of the gases.

As this invention is an improved baffle, 3 types of typical plate type baffles are now described.

The invention can be applied equally to r heat exchanger with the tubular thermally conductive wall substantially in the vertical plane with a substantially horizontal baffle and to a heat exchanger with the conductive wall in substantially the horizontal plane with the baffle in substantially the vertical plane.

In the interest of clarity these will be described as Sn example with the conductive wall only in substantially the vertical plane.

Type A A flat type baffle in sche horizontal plane situated and suitably supported above and defining the combustion chamber which is below the baffle. The baffle covers the whole of the inner cross sectional area of the heat exchanger and is perforated with a seri@s of holes or slots through which the hot gases of combustion pass. The combustion chamber pressure is increased and the gases passing upwards at relatively high velocity through the holes or slots to the area of lover pressure above the baffle become turbulent, expand and release beat. A plurality of such baffles, suitably supported and spaced one above the other, Say be employed and the velocity of the gases id progressively decreased.

Limitations are imposed by this type of baffle system which may cause such high combustion chamber pressure that any decrease in draught, (negative pressure), at the combustion gas outlet from the heat exchanger can cause the static pressure against which the combustion air fan can operate efficiently to be exceeded. This may result in noisy and u=eUable operation.

Type B A flat plate type baffle in the horizontal plans suitably supported above and defining the combustion chamber which is below tbe baffle.

The baffle does not cover the whole cross sectional area of the gas side of the heat exchanger. A gap, substantially the width of the baffle, is provided between the edge of the baffle and the heat exchanger wall through which the gases of combustion from the combustion chamber pass in a vertical direction. A plurality of such baffles suitably supported and spaced may be fitted one above the other with the gaps at opposing ends.

The gases of combustion passing through the gaps have to reverse direction to pass through each successive gap and length of travel and time in the exchanger is increased. The increase in combustion chamber pressure is not as great and the heat release due to decrease in pressure and expansion is not as high as for the Type A baffle system.

Tvpe C The effectiveness of the flat baffle system cited as type B has been improved by forming a raised lip protruding upwards across the whole width at the gap end. This forces the gases of combustion passing upwards through the gap to contact or scrub the heat exchanger wall over an increased area. In addition the raised lip induces increased turbulence and heat release as the gases abruptly change direction over the top of the raised lip.

The baffles described above as Type C are as utilised in Camray 2 boilers manufactured by Boulter Boilers Ltd of Magnet Works, Whitehouse Road, Ipswich. The Camray 2 boiler is illustrated in Figures 1 and 2 and these will now be described in more detail.

Both Figures 1 and 2 illustrate a heat exchanger reference 1. The boiler has a metal outcasting 2. Contained within the casing is a heat exchanger 3.

Heat exchanger 3 is fixed vertically being a square or rectangular tube in horizontal cross section. The heat exchanger 3 is hollow inside with angle section baffle supports 4 continuous welded to vertical thermally conductive walls. The heat exchanger 3 is provided with a water jacket 5 with inlet water connection 6 to the waterway 7 and outlet water connection 8 near the top.

The bottom of the heat exchanger is fitted with ceramic fibre refractory slab 9 and sealed with a ceramic or metal bottom closure 10. The heat exchanger 3 is secured to bottom support 11 to which the outer casing 2 is secured.

The exterior of the water jacket 5 is enclosed on its four vertical sides with fibreglass insulation 12. A fuel burner 13 with fan and sequence controller is fitted to fire horizontally having a blast tube 14 passing through a cylindrical aperture through the water jacket 5 and heat exchanger wall into the combustion chamber which is defined by bottom baffle 19.

The gases of combustion produced by the substantially horizontal flame reverse direction in the combustion chamber to pass upwards through gas flow passages 16, 17 and 18 which are defined by baffles 19, 20 and 21. The gases of combustion change direction substantially 180 degrees to pass through the gas flow passage defined by each baffle successively. Baffles 19 and 20 are provided with a vertical lip la or upstand defining the gas flow passaged 16 and 17.

The top of the heat exchanger is provided with a sealing cover which has a connection 23 for the exhaust flue pipe. The exhaust flue pipe passes upward through a hole in the tope of the boiler casing. A removable cover 25 is provided at the top of the heat exchanger, in front of cover 22 to enable the baffles 19, 20 and 21 to be removed for inspection and cleaning of the exchanger. Front top panel 26 and front panel 27 are removable to provide access to cover 25 and fuel burner 13.

Figure 2 shows the heat exchanger 3 with the water jacket 5, waterway 7 and water inlet connection 6 surrounded by fibreglass insulation 12 fixed to bottom support 11. Fuel burner 13 is fixed to the front of the water jacket with blast tube 14 protruding into the combustion chamber 15 below bottom baffle 19 defining the combustion chamber and gas flow passage 16.

A further improvement to the Type C boiler is provided by the Camray 3 boilers manufactured by Boulter Boilers Ltd of Magnet Works, Whitehouse Road, Ipswich. This improvement is illustrated in Figures 3-6 inclusive and will now be described.

Figure 3 is as Figure 1 except for bottom baffle 19 and middle baffle 20.

Figure 3 shows baffles 19 and 20 replaced by new baffles 28 and 30 respectively. The raised lips or upstands 2a on baffles 28 and 30 are increased in height to lengthen gas flow passages 16 and 17.

The baffle as illustrated in both Figures 3 and 4 is a metal plate with channels formed on the under side to retain a flat channel fibre refractory tile. The metal channels rest on angle side and rear supports 4 welded to make them integral to the inside wall of the heat exchanger 3.

The improvement to the baffle comprises a turbulator section which occupies gas flow passages 16 and 17. The gases passing upwards from the combustion chamber through the gas flow passages 16 and 17 pass through the turbulator section The turbulator section comprises a series of (plurality of) tabs 29 which project from the vertical face of the raised lips or upstands 2a on the baffle towards to the substantially vertical heat exchanger wall at an angle of substantially 90 degrees. The tabs 29 are punched out from the raised lip 2a which has a back plate attached to cover the holes so formed. The projecting tabs are formed with gaps between them in rows and so arranged that the tabs in one row do not align with the tabs in the next row. This can be more clearly illustrated in both Figures 5 and 6. The tabs 29 are substantially square and flat. The dimension and spacing of the series of insulated tabs 29 is such that the increase in combustion chamber pressure is minimal and within the capacity of fans fitted as standard and readily available to supply air for efficient combustion of the fuel.

In this piece of prior art, the hot gases of combustion pass over the edges of the tabs 29 comprising the turbulator and as they do they become turbulent and are subject to an area of low pressure which occurs immediately above each tab resulting in expansion and elevated heat release.

The free projecting ends of the turbulator tabs 29 are in close proximity to the vertical thermally conducted wall of the heat exchanger but do not contact it when the heat exchanger is in use.

In fact, this improvement is more particularly described in UK patent number 2 248 918 and the person skilled in the art is directed to this particular patent as it is believed to be the closest prior art to the current invention.

The arrangement and configuration of the tabs 29 on the raised lip 31 of the bottom baffle plate 28 of the Camray 3 boiler still however tends to create a significantly high combustion chamber pressure (although much less than much of the prior art) which can still result in noisy and unreliable operation of the boiler.

It is an object of the present invention to provide a baffle system that is cheaper to engineer, reduces the combustion chamber pressure that it presently associated with the Camray 3 boiler system and also reduces the carbon monoxide and "NOx" emissions associated with all gas fired boilers.

Summarv of the Invention According to the invention in its broadest sense, there is provided a combustion chamber baffle for use in a boiler having at one end a raised lip protruding from the plain of the baffle, the lip being provided with a turbulator and characterised in that the turbulator comprises a single row of tabs.

Preferably, the tabs are located at the top edge of the raised lip in its normal attitude of operation.

More preferably still, the baffle is designed not to accommodate any insulating panel when normally in use.

Optionally, the row of tabs which constitute the turbulator is formed integrally with the rest of the baffle.

Arguably, the raised lip is provided with means to make it adjustable in height.

The invention includes within its scope, a combustion chamber baffle substantially as herein described.

The invention also inciudes within its scope, a multiple baffle system incorporating at least one baffle in accordance with any of the arrangements specified above.

The invention further includes within its scope a boiler incorporating a baffle or baffle system according to any of the arrangements specified above.

Brief Description of the Drawings Figure 1 is a vertical sectional view of a water boiler showing the baffle plate system as employed in the Camray 2 range of boilers manufactured by Boulter Boilers Ltd, White house Road, Ipswich.

Figure 2 is a horizontal sectional view of the boiler as described in Figure 1.

Figure 3 is a vertical sectional view of a water boiler showing the improved plate baffle system as employed in the Camray 3 range of boilers manufactured by Boulter Boilers Ltd, Whitehouse Road, Ipswich.

Figure 4 is a horizontal sectional view of the boiler in Figure 3 showing the turbulator tabs.

Figure 5 is a perspective view of the improved bottom baffle associated with the Camray 3 boiler.

Figure 6 is an exploded view of the Camray 3 boiler illustrated in Figure 3.

Figure 7 is a perspective view of the proposed improvement to the Camray 3 boiler system.

Description of the Preferred Embodiments Figures 7 illustrates a boiler generally referenced 64, incorporating a multiple baffle system, the baffle system comprising a combustion chamber baffle 60 and two other baffles referenced 61 and 62. Figure 7 also illustrates thermostat pockets 63 for control and limit thermostat phials. The internal base of the boiler 64 is provided with an insulating panel 65 that covers substantially the entire internal base area of the boiler 64.

In this particular embodiment, the combustion chamber baffle has at one end, a raised lip with an integral turbulator in the form of the single row of tabs located at the "top" edge of the raised lip in the combustion chamber baffles normal attitude of operation, The raised lip is substantially parallel to the internal opposing wall of the boiler. Each respective tab that forms the turbulator is substantially oblique to the raised lip and each respective free edge of each respective tab that is substantially parallel to and equally spaced from the internal opposing wall of the boiler, in use, (even allowing for the expansion of the metal due to the heat of the boiler) does not come into contact with the internal wall of the boiler.

The underside of the combustion chamber baffle is designed not to accommodate any form of insulating panel when it is normally in use. This has the effect of increasing the available combustion chamber area itself which, in turn, reduces the combustion chamber pressure and leads to a quieter "startup" for the boiler.

The absence of the insulating panel that is normally associated with the underside of the combustion chamber baffle has also allowed the positioning of the burner 13 in this new boiler to be raised vertically (in the boilers normal attitude of operation) by an amount normally associated with the depth of an insulating panel. This new positioning of the burner 13 has enabled the burner to be supplied with a burner guard (not illustrated) that surrounds the burner when in use to comply with new European legislation.

The combustion chamber baffle is formed from one sheet of metal, the appropriate shape being first punched out of the sheet of metal and then bent into shape. The other baffles 61 and 62 in this embodiment, are also punched out of a single sheet of metal but because they are substantially flat, they do not require subsequent bending into shape although, handles as can be clearly seen in Figure 7 are welded or otherwise secured to these other two baffles.

The flow of the hot combustion gases passing over the edges of the tabs comprising the turbulator of each respective baffle is shown. As the gases pass through/over the turbulator, the gases are subject to an area of low pressure which occurs immediately above each tab resulting in expansion and elevated heat release.

In alternative embodiments not illustrated, the turbulator on the combustion chamber baffle need not necessarily be found on the top edge of the raised lip. The single row of tabs could be found anywhere in the plain of the raised lip. Furthermore, in alternative embodiments not illustrated, the single row of tabs need not necessarily be parallel with the top edge of the raised lip.

For the avoidance of doubt, a single row is intended to have a broad meaning whereby both a substantially straight single row and a substantially curved single row are intended to be covered by this specification.

In alternative embodiments not illustrated, both the raised lip and the tabs forming the turbulator need not necessarily be respectively, parallel to or/to the internal opposing wall of the boiler. Furthermore, the tabs forming the turbulator need not necessarily be tessellated square cut outs, the tabs could conceivably be a "sore tooth" arrangement.

Furthermore, in yet another preferred embodiment not illustrated, the height of the raised lip could be adjusted by providing the raised lip with adjusting means.

Claims (8)

Claims

1. A combustion chamber baffle for use in a boiler having at one end a raised lip protruding from the plain of the baffle, the lip being provided with a turbulator and characterised in that the turbulator comprises a single row of tabs.

2. A combustion chamber baffle as claimed in Claim 1 characterised in that the tabs are located at the top edge of the raised lip in its normal attitude of operation.

3. A combustion chamber baffle as claimed in either Claim 1 or Claim 2 characterised in that the baffle is designed not to accommodate any insulating panel when normally in use.

4. A combustion chamber baffle as claimed in any of the preceding Claims characterised in that the row of tabs which constitute the turbulator is formed integrally with the rest of the baffle.

5. A combustion chamber baffle as claimed in any of the preceding Claims characterised in that the raised lip is provided with means to make it adjustable in height.

6. A combustion chamber baffle substantially as herein described with reference to and as illustrated in Figure 7 of the accompanying drawings.

7. A multiple baffle system incorporating at least one baffle as claimed in any of the preceding Claims.

8. A boiler incorporating a baffle or baffle system as claimed in any of the preceding Claims.