GB2149491A - Heat storage regenerator for gas turbines etc. - Google Patents

Abstract

A rotating (or reciprocating), porous ceramic burner regenerator 3 for aero-engines, gas turbines, furnaces, gasifiers, boilers, etc, consists of a ceramic, porous regenerator drum, with lateral ducts conveying the compressor air through the drum walls to the annular walls of a burner. A proportion of the air is distributed into the combustion chamber by an apertured inner wall. The remainder flows and enters the top of the burner to entrain the fuel into the top of the combustion chamber. The flame jet then flows through an adjacent wall section of the regenerator and stores heat in it. Thus the regenerator wall sections under the burners act as storage heaters while the adjacent sections preheat the burner airflow by flowing counterflow to the flame jet as they both flow through the rotating regenerator. The burner may incorporate automatic back flush rejection of fuel ash and refiring of the unburnt carbon; a bypass system for startup, and multiple regenerators for high capacity systems. The invention can be used with oil, gas or coal or any hot fluid. Several burners may be arranged around an engine casing. <IMAGE>

Description

SPECIFICATION Drum/Reciprocating Blade Heat Storage Regenerator for Aero-Engines, Gas Turbines Furnaces, Boilers, Burners etc.

This invention relates to a rotating/reciprocating heat storage unit designed for applications for all forms of gas turbines, aero-engines, boiler and furnaces, burners, gas duct applications and to general plant applications where improvement in heat and power generation efficiency are of primary importance.

Hitherto heat recovery systems fitted to heat generation or power production plant, suffer from a number of disadvantages. These are (i) they are usually installed in low temperature exhaust duct systems and, therefore, heat transfer rates are low requiring large heat storage mass or large heat transfer surfaces to recoverthe heat (ii) on line cleaning is difficult if not impossible to achieve (iii) heat recovery efficiences are relatively poor, and (iv) response to turndown and to load change in the primary plant is usually sluggish in view of the large inertia of the system.

The objective of the present invention is to overcome the above disadvantages of conventional heat recovery systems by providing a range of drum/reciprocating heat storage regenerators, which, for general application the unit will be located, not in the low temperature combustion exhaust gases but in the high temperature flame gases in the combustor before they leave the latter and enter the heat consuming plant or power production plant such as a gas turbine.

According to the invention there are three basic embodiments. These are the rotating type and the reciprocating type for use with high pressure burners or combustors, such as in gas or aeroengine turbines and a third embodiment similar two the first two, but for low pressure burners or combustors such as used in industrial boilers.

The first embodiment, the drum type consists of an enclosed large diameter, horizontal, porous, heat storage drum rotating slowly around an horizontal axis with the burners or combustors located round the outer drum casing and the combustors firing through the porous wall of the drum. Separate ducts are provided disposed at right angles to the vertical plane of the outer case perimeter to interconnect with the outlet duct of the compressor and the drum casing between each burner. By this means the compressor pressurised air flows through these ducts and vertically up through the porous wall of the drum thus extracting heat stored in each of the wall sections between the burners thus preheating the combustion air supply to each burner in this manner.The burner inner annular walls are provided with rows of different size holes in such a manner that the pressure drop distributes the air flow into the combustion chamber to give the correct flame pattern and sufficient dilution air is introduced at the outlet end to cool the flame prior to it impinging on the outer surface of the rotating ceramic drum. In addition some of the preheated pressurised air flows within the combustor annular wall to the top of the burner to entrain the fuel supply entering the combustion chamber. Thus the porous ceramic matrix drum rotates at a speed slow enough to store sufficient heat in each burner impingement section such that when this section passes through the air supply duct its heat is imparted to preheat the air to a given design temperature.The preheated air then enters the burner combustion chambers and reduces the fuel supply requirements for each burner for a given duty as a result of the heat which is recovered and the increase in flame temperature which results.

A further feature of the design is that as each storage section rotates through the air duct the upward flow of air carries with it the carbon-ash particles collected on the surface during the passage of the drum through the burner impingement section. In this manner any collected unburned carbon is directly refired into the burner combustion chamber thus raising the combustion efficiency.

However ash particles will collect over a period of time and to get rid of these two back flushing ducts are incorporated, diametrically opposite each other.

These interconnect with the compressor outlet and allow pressurised air to flow up through the rotating drum wall taking with it the ash particles residing on the outer surface and discharging these with the gas flow into the gas turbine inlet, alternatively bypassing the ash gas flow through a bypass duct to gas cleaning equipment. A further objective of this arrangement is to size the in let duct such that a final flow of relatively cool dilution air flows from the compressor along with the ash particles into the gas turbine inlet blading. Thus this cools and reduces the temperature of the burner hot gases nearer to the gas turbine inlet temperature and, incidentally, cools off the ash particles. Other variants are described in the claims.

In the second embodiment of the invention the burner is arranged on the casing housing and this encloses a reciprocating, rectangular porous ceramic blade which is fitted with a drive motor to oscillate the ceramic blade back and forth by a rack and pinion gear unit. Thus depending on the rate of oscillations the burner flame impinges on the heat storage section of the ceramic blade and when moved forward by the gear drive unit into the air duct section the heat is transmitted to the air thus preheating it to a given design temperature.

Provision is made for dilution air to flow into an annular section of the unit, the inner wall with rows of holes to cause the air to mix with the flame gas flow from the burner to give any design temperature.

The third embodiment of the invention incorporates either of the two previous embodiments, that is the rotating or reciprocating type but with the use of low pressure burners, the primary air being supplied by a fan, turbo-blower or low pressure compressor, through ducting connecting these units with the inlets to the burner annular air jackets. In such applications the burners are located on the drum outer casing as previously described for the first embodiment and the burners will fire through the drum wall onto an inner core section forming an annular space between it and the duct casing, thence the burner flame gases flow horizontally along this space to the outlet duct opening into the boiler or furnace unit depending on the application.In the case of the second embodiment the burners may be located on a common casing housing a common reciprocating blade to cater for the number of burners required with a common compressor unit providing the primary and dilution air supply. Alternatively the burners can be located on individual reciprocating housings with separate compressor or fan units.

Other variants of the above embodiments are described in the claims.

Further features of the invention appear from the following description given with reference to the drawings, in which: Fig. 1 is a cross-section of the first embodiment of the invention through a rotating drum type as applied to the high pressure burners in axial flow aero-engines, compressor/gas turbine arrangements.

Fig. 2 Ditto but showing the cross-section through the high pressure burner.

Fig. 3 Ditto but showing the cross-section through the rotating drum and the back flushing cleaning arrangement.

Fig. 4 Cross-section of the second embodiment of the invention, the reciprocating type.

Referring to Figs. 1 and 2 the first embodiment of the invention, assuming a liquid fuel is used, air enters the compressor inlet at 17 and is compressed in passing through the compressor stages, whence leaving the outlet it flows through a series of ducts 11 fitted between the burners at 5 Fig. 2, the latter located equally around the outer compressor-gas turbine casings 1 and 2. The compressed air then flows upwards through the inter-burner, heat storage sections of the rotating porous ceramic drum 3 located between the burners and as a result heat is extracted to preheat the airflow.The latter then enters the annular circular ducts 12 Fig. 1, superimposed around the drum 3, whence it flows into the adjacent burner inlet ducts 4; thence up through the burner air jackets 5, whence it flows into the burner combustion chambers 13 in varying proportions depending on the pressure drop through the various sized rows of holes 7 arranged round the inner wall of the combustion chambers.

The pattern of airflow into the combustion chambers when combined with the liquid fuel flow entrained from pipe 6 by the combustion airflow entering the axial guide vanes 8, determines the flame pattern in the combustion chamber 13 and the degree of flame cooling required to ensure a period of long life for the rotating drum. The pressurised flame then flows through the walls of the porous drum and is deflected, horizontally, into the gas turbine outlet duct 19. Thus heat is stored in the inter-burner sections of the porous drum as the latter slowly rotates through the width of the burner flame jets. On further rotation these sections enter the preheat air ducts 11, where, as described previously, the upflow of pressurised air flowing through ducts 11 extracts the storage heat to preheat the air to a given design temperature.By this means fuel is saved by preheating the combustion air to each burner to a high degree of temperature.

The rotating drum is supported on a twin-annular frame 22 housing a number of smail roller bearings located at either end of the drum with a worm drive gear box and pinion/gear units 9 and 10 to slowly rotate the drum at a controlled speed by a speed controller operated through a thermacouple located in the outlet air duct 12.

Reverse flush cleaning of the ash particles collected on the outer surface 18 of the rotating drum is carried out by the arrangement shown in Fig. 3. This consists of two diametrically opposed inlet ducts 15 through which pressurised airfrom the compressor 17 flows up through the inner surface of the rotating drum as it rotates past these ducts and this lifts the collected ash dust off the outer drum surface 18 and both dust and airthen flow through the outlet ducts 14 into the inlet section of the gas turbine 16, or, alternatively, through the bypass duct 42 to gas cleaning plant (not shown). These designs have the dual effect of attemperating the temperature of the inlet flame gases to the gas turbine to any desired design temperature and, incidentally, also cooling the ash dust temperature.

Referring to the second embodiment of the invention, the reciprocating blade type, for use with low or high pressure burners, this comprises an annular casing burner 25 and 28 fitted with an inlet port 23. Primary and cooling air from a fan or compressor (not shown) flows through this port and 33 the annular rectangular section of a porous ceramic reciprocating blade and stored heat is extracted and imparted to the airthus preheating it depending on the degree of heat stored in the blade section 33.The preheated air now flows through the annular space 36 and a proportion of it through the inner wall holes 27 to cool the flame gases to a temperature tolerable for the inner surface of the reciprocating blade section 35 while the remaining airflows a coaxial annularswirlervanes 26, thus entraining the liquid fuel from the pipe 32, into the combustion chamber 37. The flame is thus formed in the combustion chamber 37 and flows as a jet to impinge and flow through the impingement section of the blade 35. Thus heat is stored in 35 during the forward stroke of the blade. On the reverse stroke the blade sections 34 and 35 respectively move up into the positions indicated by 29 and 34, thus the air flowthrough port 23 is now preheated by flowing through the new heat storage annular section 34 while the flame jet is storing fresh heat into the storage section of the blade 35. Thus as the blade reciprocates back and forth with time delays during each stroke heat is respectively stored into the flame impingement section of the blade and extracted simultaneously from the other section to preheat the combustion incoming air. When the flame leaves the blade impingement section 35 itflows into the air dilution section 38 where air from an inlet port 31 and annular space 30 flows through distribution holes 32 to mix with the flame in 38 to give any pre-mix design temperature.

To remove ash particles collected on the surfaces of the regenerator at 33,34 and 35 valve 39 is opened and the fan or compressor is started up to "blow blast" the said ash particles off surfaces 33 and 34 and through the exhaust pipe 40. The regenerator blade is now moved one position to repeat the process to clean the remaining surface 35. The valve 39 is now closed and the regenerator and the burner operate in cyclic operation as before.

Claims (16)

1. A porous ceramic heat storage regenerator of rotating circular drum or reciprocating rectangular blade design and associated equipment, wherein, large improvements in energy savings characterize the designs; such improvements, by way of example, in the drum type, result from the combustion and dilution air being highly preheated by passing it, radially, counterflowto the burner flame jets as they flow through adjacent rotating regenerator wall sections associated with each burner; with means for conveying the airflow from a fan or compressor to the underside and through the rotating regenerator wall thus recovering the heat energy stored in the wail, thence, means to convey the preheated air to the burners, equally spaced round an external casing supporting the regenerator, the said burners in a canted or perpendicular attitude (5 - Fig. 2) and of the "can" type with annular walls, the inner one having rows of holes to distribute the dilution airto partially cool the flame to an acceptable temperature to avoid damage to the regenerator, the said burners also fitted with coaxial fuel supply pipes surrounded by air guidance swirler vanes through which the theoretical air for combustion flows from the top of the burner annular walls, entraining the fuel as it enters the combustion chambers, thus producing a highly efficient flame jet; means being provided to guide the said flame counterflow through the rotating drum walls of the regenerator thus storing heat energy in the said drum walls ready for recovery by subsequent counterflow airflow through the same drum wall sections, thence the flame jets of all the burners join in a common duct, means being provided to convey the total gas flow to the exhaust duct of the plant; means being provided to support, rotate and seal the drum wall sections between the flame jets and the air flow; means also to refire the carbon particles into the burners and dispose of the ash particles to the exhaust duct or to a bypass duct to divert part of the gas flow with the ash to gas cleaning plant; provision also being made for the flame jets to bypass the regenerator during light-up of the burners.

2. A heat storage regenerator according to Claim 1 wherein the means for conveying the airflow from the fan or compressor to the underside section of the rotating regenerator consist of peripherally canted ducts extending between the outlet duct of the compressor and into a circumferential duct between the burners, forming part of the support casing for the regenerator.

3. A heat storage regenerator according to Claim 1 wherein the means to support and rotate the regenerator consists of a circular external casing with flanged connections for the burners and interconnecting ducts extending circumferentially between the burners such ducts flanged to take the airflow ducts as in Claim 2 the means of rotation consisting of a large diameter internal double frame, coaxial with the internal diameter of the regenerator drum and fitted with housings to take small roller bearings on each of the frames, thus by this means providing a support for the porous ceramic regenerator, a drive mechanism provided on one side of the frame consisting of pinion and large gear attached to the frame, a circumferential drive shaft extending through the support casing and attached to it a worm and gear box unit to give a suitably low speed range to rotate the regenerator.

4. A heat storage regenerator according to Claim 1 wherein a rotating seal of suitable design fitted to a coaxial rotating member in the case of a compressor/gas turbine assembly and forming a seal with the internal diameter of the underside of the canted air ducts as in Claim 2 and the flame jet outlet ducts as in Claim 5, there being no seal in certain applications, it being replaced by a vertical circular division plate; longitudinal seals also fitted across the width of the internal diameter of the regenerator to preclude mixing of the air and flame gas streams.

5. A heat storage regenerator according to Claim 1 wherein the means of conveying the flame jets from the underside of the regenerator surface into the common outflow duct consists of individual ducts fitted to each burner outlet, open at the top end to accept the jet flame as it issues from the regenerator and open on one side to allow the flame jet to be deflected into the path of the common outflow duct but enclosed on all other sides.

6. A heat storage regenerator according to Claim 1 wherein carbon particles collected on the outer surface of the rotating regenerator during combustion are refired into the combustion chambers of the burners by the preheated airflow passing upwards through the regenerator walls thence carrying the particles back into the combustion chamber of each burner.

7. A heat storage regenerator according to Claim 1 wherein two diametrically opposite ducts fitted as an integral part of the external casing and extending between the compressor outlet duct and the underside of the regenerator, cause air from the said compressor to flow up through the rotating regenerator walls into the outer circumferential casing duct, thence deflected down into the common outfiow duct carrying with it any ash particles rejected by the burners, alternatively, if heavy ash fuels are used provision of an ash bypass duct to divert part of the gas flow, along with the ash, to gas cleaning plant, the clean gas merging with the main gas flow, or, alternatively, exhausted to atmosphere; such systems of back flushing to clean the regenerator drum also used as a method of further dilution of the outflow flame gases to any required design temperature.

8. A heat storage regenerator according to Claim 1 in which the regenerator is of the reciprocating rectangular blade type (Fig. 4) or rotating drum type (Figs. 1 and 2) whereby the blade or drum are driven by reverse motors to oscillate them back and forth, dwelling at each stroke or cycle, to allow sufficient time for the airflow to be preheated to the design temperature by flowing counterflow to the flame jet through the blade or drum sections previously stored with heat energy during the previous stroke or cycle when the flame jet flowed through it, the reverse action taking place during the subsequent reverse stroke or cycle.

9. A heat regenerator according to Claim 1 and Claim 8 of the reciprocating type whereby the ash particles collected on the inner blade are removed by opening an exhaust valve and blowing the dust through an exhaust duct by operating the fan or compressor.

10. A heat regenerator according to Claim 1 and Claim 8 of the reciprocating type whereby the flame jet outlet duct is fitted and of annular wall construction with inner wall holes designed to distribute cold dilution airto mix and cool the jet flame to any required design temperature as the said flame issues from the regenerator; such dilution air, alternatively, conveyed from the main preheated burner airflow outlet duct by a suitable interconnecting duct and valve system.

11. A heat storage regenerator and associated equipment according to Claim 1 wherein more than one assembly of rotating regenerator and associated air supply ducts, flame ducts and burners are fitted in parallel or series to increase the overall capacity of the unit.

12. A multiple heat storage generator assembly according to Claim 1 and Claim 8 wherein multiple units of the reciprocating type (Fig. 4) are installed in parallel or series to increase the overall capacity.

13. A heat storage regenerator according to Claim 1 wherein provided a proportion of the circumferential outer casing perimeter is occupied by burner locations the opposite remaining perimeter of the porous ceramic drum regenerator is installed with a rectangular circumferential slot to allow the said slot to be rotated round in line with the burners during the light-up period thus bypassing the air and flame flows of the need to flow through the regenerator porous wall during this period, switching the regenerator to its normal position when the burner flames are fully established.

14. A heat storage regenerator according to Claims 1 to 13 wherein the latter apply to the reciprocating rectangular blade type of regenerator.

15. A heat storage regenerator and associated equipment according to all the preceding claims wherein such equipment is used in conjunction with compressor/gas turbines assemblies; boilers; furnace plant or any type of heat and power generation plant where the object is to considerably reduce the specific fuel consumption of such plant.

16. Aero-engines, gas turbines, furnaces, industrial and commercial boilers, gasifiers, or, heat or power production units, using any type of fuel, all incorporating a heat storage generator according to the preceding claims and as shown in the drawings Figs. 1,2,3,and4.