A PULSING COMBUSTION DEVICE

Abstract: A pulsing combustion device includes a combustion cham­ ber (906) having an inlet (920) for combustible mixture and an unvalved outlet (905), and a floating valve member (915) con­ trolling the supply of combustible mixture. The floating valve may be annular shaped with an ignition means extending through a central portion of the end of the combustion cham­ ber. The pulsing combustion device may be used as a water heater by immersion in a water tank, or as an air heater by pass­ ing the combustion gases through a closed heat exchanger over which treatment air is passed. The device may have a pressurized combustion air flow regulator (924) providing higher pressure combustion air to a lower pressure combusti­ ble mixing chamber to which fuel gas is added.

Description: The invention disclosed herein pertains generally to improvements in combustors or burners and more particularly relates to gas and fuel mixing for such combustors and hot air furnaces having an improved pulsing combustor. A vast number of burner arrangements are known for a virtually limitless number of specific uses. Typically, combustion takes place in an open combustion zone with the combustion gases then passed through a heat exchanger to heat a fluid such as air or water. Conventional combustion devices are unsatisfactory since oftentimes combustion is incomplete producing various pollutants and furthermore because the efficiency obtainable from such combustion devices is relatively poor. The known burners or combustors used for heating liquids such as water are generally quite massive and consume large amounts of fuel (usually oil or gas). Most presently used burners rely on a continuous flow of the fuel, thus perhaps wasting some of the fuel due to incomplete combustion. Combustion devices having an intermittent flow of fuel are known, for example, as in a conventional piston engine or in a pulsing combustor. WO-A-82/02242 discloses a pulsing combustion device having the features defined in the pre-characterising part of claim 1. Accordingly, the need exists for an improved burner which provides an efficient and economical use of fuel. Such an improved burner would have particular utility in steam generation devices and in home heating equipment especially where a fluid is to be heated by the combustion. The present invention provides a pulsing combustion device comprising: means for defining an elongate combustion chamber having an inlet at one end for a combustible mixture of fuel and combustion air and an unvalved outlet at the opposite end open to the atmosphere for combustion gases: a floating valve member mounted in reciprocation relation within a limiting chamber adjacent said one end of said combustion chamber, said valve member having a first side in communication with said combustion chamber and a second side in communication with a supply of a pressurized combustible mixture and having a plurality of evenly arcuately spaced ports in said valve member said reciprocation of said valve member in said limiting chamber closing and opening communication through said ports between said supply of combustible mixture and said combustion chamber; means for supplying a pressurized combustible mixture of fuel and combustion air to said second side of said floating valve member; means for igniting and combusting said combustible mixture in said combustion chamber to produce pressurized combustion gases, said floating valve member being reciprocated by said pressurized combustible mixture in communication with said second side of said pressurized combustion gases in commmunication with said first side to regulate the flow of said combustible mixture of fuel and combustion air into said combustion chamber, characterised in that said valve member is a flat plate valve member, and in that said ports are peripheral ports through the flat plate valve member adapted to direct said combustible mixture axially along the periphery of said combustion chamber. A pulsing combustion device according to the present invention comprises a combustion chamber with an inlet for a combustible mixture and an unvalved outlet to the atmosphere for combustion gases. A pressurized combustible mixture is supplied to a floating valve with through ports providing controlled communication between the supply of the combustible mixture and the combustion chamber. Reciprocation of the floating valve member increases and decreases the flow of combustible mixture into the combustion chamber. The combustible mixture is ignited and burned in the combustion chamber. The floating valve is reciprocated in its mounting in the wall of the combustion chamber by the pressure of the pressurized combustible mixture and the pressure of the combustion gases to regulate the flow of the combustible mixture into the combustion chamber. EP-A-67223 teaches and claims specific embodiments of my pulsing combustion device and process and specific embodiments of a fluid heating device incorporating my pulsing combustion device. This application teaches and claims further improvements to my pulsing combustion device and its use in water heating and hot air heating applications. Heating devices for a wide variety of purposes according to the present invention may use a pulsing combustion device as described either submerged in a fluid or having a flow of fluid, either liquid or gas, encircling the combustion chamber so that the fluid is heated. Heat exchange may be enhanced by placement of baffles in and/or downstream of the combustion zone and combustion products may be passed through a wide variety of coil and/or finned heat exchangers. Likewise, the fluid to be heated may be passed through coil and/or finned heat exchangers. A particularly suitable combustible mixture supply means and system is described. Preferred embodiments of a pulsing combustion device and preferred embodiments of heating devices including the pulsing combustion device, according to the present invention are described by way of example only with reference to the accompanying drawings wherein like members bear like reference numerals and wherein: Fig. 1 is a cross-sectional view of a known pulsing combustion device; Fig. 2 is a view through the line 2-2 of Fig. 1; Fig. 3 is a cross-sectional side view of an embodiment of a pulsing combustion device of the invention utilised as a fluid heating device; Fig. 4 is an enlarged top view of a floating valve shown in the pulsing combustion device shown in Fig. 3; Fig. 5 is a top view of another embodiment of a floating valve suitable for use in the pulsing combustion device of this invention; Fig. 6 is a side view of another embodiment of a pulsing combustion device according to this invention; Fig. 7 is a cross section of one embodiment of a hot water heater utilizing a pulsing combustion device according to this invention; Fig. 8 is a perspective view of a hot air heater utilizing a pulsing combustion device according to this invention; Fig. 9 is a perspective view of another embodiment of a hot air heater utilizing a pulsing combustion device according to this invention; Fig. 10 is a sectional view of the combustible gas mixing and feeding portion of the apparatus; and Fig. 11 is a sectional side view of another embodiment of the floating valve of a pulsing combustion device of this invention. With reference to Fig. 1, a known pulsing combustion device 10, includes an elongate combustion chamber shell or burner shell 14 which defines a combustion chamber 15. The combustion chamber shell 14 is generally tubular with a length that is considerably greater than its width. The combustion chamber shell is preferably circular in cross section, but may of course be square, rectangular or of any other suitable configuration. The combustion chamber 15 is closed except for the outlet for combustion gases and the inlet for admitting the combustible mixture. The combustible mixture may be supplied by a line 40 through a ball valve chamber 34 by way of a reciprocating floating valve 20. The ball valve chamber 34 is provided within an end cap 17 disposed at an inlet end of the combustor shell 14. The end cap 17 together with the combustor shell 14 define a path of reciprocation for the floating valve 20. After combustion, the combustion gases exit through an open exhaust tube 50 disposed at an exhaust end 18 of the combustor shell 14. If desired, the ball valve chamber may be deleted or replaced by a suitable conventional check valve. The ball valve chamber 34 or the check valve 507 may serve to prevent a flashback of the combustible mixture. Any suitable flame arrestor may be used, such as flame arrestor 601 as shown in Fig. 3. As shown in Fig. 1, ball valve chamber 34 and unvalved exhaust tube 50 have diameters which are considerably smaller than the cross-sectional diameter of the burner shell 14. Thus, the burner shell 14 is substantially closed on each end and has two restricted passageways: the ball valve chamber 34 at the inlet to the combustion chamber 15 and the exhaust tube 50 disposed at the exhaust end 18 of the burner shell 14. The burner shell 14, the ball valve chamber 34 and the exhaust tube 50 are all preferably made of a temperature resistant steel or other material which can tolerate the high temperatures generated in the combustion chamber while the combustible mixture is burning. A flange 76 is secured, for example, by welding, to the end cap 17 to facilitate the assembly of the end cap 17 with the shell 14. A plurality of bolts 74 extend through openings in the flange and are threadably received by corresponding nuts 72 which are secured, as by welding, to the shell 14. The end cap 17 is thereby detachably secured to the shell 14 by the nuts 72 and the bolts 74. A sealing gasket 78, preferably of neoprene or another gasket material suitable for high temperature use may be preferably disposed between the end cap 17 and a lower end wall of the burner shell 14. The floating poppet valve 20 disposed for reciprocal movement in the burner or combustor shell 14 may be generally mushroom-shaped with an open interior or bore 26, as shown in Figs. 1 and 2. The floating valve 20 is of integral construction and includes a base 27 having a first diameter and a tube 23 having a reduced diameter with the bore extending through the tube and through a portion of the base. A small clearance is provided between a side wall 25 of the base of the floating valve and a side wall 19 of a base portion of the burner shell 14 to allow the combustible mixture to flow therethrough. The side wall 19 of the burner shell 14 is disposed between an annular shoulder portion 16 and the end cap 17 of the burner shell 14. The floating valve 20 is preferably made of a temperature resistant metal or other suitable material for high temperature use. The floating valve 20 is disposed within the combustor shell 14 for reciprocation between the annular shoulder 16 provided on a lower portion of the combustor shell 14 and the cap 17 of the combustor shell 14. A corresponding annular shoulder 22 on the base portion of the poppet valve 20 limits movement of the floating valve 20 toward the combustion chamber when the shoulder 22 of the poppet valve contacts the shoulder 16 of the burner shell 14. Movement of the valve 20 away from the combustion chamber is limited by contact of a rear surface 21 of the floating valve 20 with an inside surface 11 of the cap 17 of the combustor shell 14. A plurality of ports 24 are disposed around the floating valve 20 beneath the shoulder 22 of the floating valve 20 and provides communication between the bore of the valve and the small clearance between the valve side wall 25 and the side wall 19. The ports 24 are preferably arranged substantially parallel to the rear surface 21 of the valve 20 and extend radially from the bore. A spark plug 60 extends into the combustion chamber through a threaded bore in the combustor chamber shell 14. The spark plug 60 is provided to initially ignite the combustion gases in the shell 14. The spark plug 60 is preferably threaded into the combustion chamber shell 14 so as to provide a seal between the spark plug 60 and the combustor shell 14. The spark plug 60 is disposed near the floating valve 20 but far enough from the inlet end of the combustion chamber 25 to not interfere with the reciprocation of the floating valve 20. The ball check valve provided in the combustible mixture supply line 40, as shown in Fig. 1, includes a smooth ball 30 arranged to reciprocate toward and away from a rear seat 32 of the ball valve chamber 34. The ball 30 is preferably maintained in contact with the rear surface 21 of the floating valve 20. Furthermore, the extent of reciprocation of the valve 20 is preferably small with respect to the diameter of the ball 30, so that the ball 30 is held within the chamber 34 by the floating valve 20 during reciprocation. Still further, it is preferred that the valve seat snugly against the ball 30 when the ball is received on the rear seat 32 so that the valve 20 may maintain a sealing relationship for the ball and seat 32 when the valve is in contact with the end cap 17. Alternatively, various arrangements may be provided at a front end of the ball valve 34 such as fingers or a lattice to retain the ball 30 in the ball valve chamber 34. The ball check valve during reciprocation assists in the regulation of the flow of combustible mixture into the combustion chamber 15 along with the floating valve 20. The ball valve 30 also prevents backfire through the supply line 40 by preventing a flame in the combustion chamber 15 from spreading backwardly into the combustible mixture supply line 40. If desired, additional or different backfire prevention devices, such as a suitable conventional check valve or other type of flame arrestor, could be provided in supply line 40 upstream of the ball valve 34 or instead of the ball valve 34. The exhaust tube 50 at the exhaust end 18 of the burner shell 14 has a first end 51 disposed inside the burner shell 14 and a second end 52 disposed outside the burner shell 14. The exhaust tube 50 is relatively small in cross-sectional diameter with respect to the burner shell 14. The burner shell 14 preferably has a sloping or curving exhaust end surface 12 which slopes inwardly toward the exhaust tube 50 and with the tube 50 preferably ending at, or perhaps extending only slightly through, a central portion of the end surface 12. If the inner end of the exhaust tube 50 protrudes too far into the combustion chamber 15, the efficient operation of the chamber may be interrupted. It is preferable, however, to have the end surface 12 curved or sloping to provide a tornadic action which is believed to cause intense heat and complete combustion of the combustible mixture and therefore a more efficient use of the fuel within the pulsing combustor. It is to be noted that the exhaust tube 50 may have to be adjusted in size and location to "tune" the exhaust flow from the combustion chamber shell or burner shell 14. By "tuning" the exhaust tube 50, the desired operating characteristics of the burner namely, the number of pulses per minute, the pressure in the combustion chamber 15, the velocity of the gas exhausted and other such factors may be optimized. For example, if the tube diameter is too large, the combustion of the gases may not produce a sufficient pressure to reciprocate the floating valve 20. Generally it can be stated that the burner shell 14 is considerably larger in diameter than the exhaust tube 50. The appropriately sized exhaust tube 50 is rigidly secured to the combustion chamber 14, preferably by welding. The appropriate relative dimensions for the shell 14, the exhaust tube 50 and the floating valve 20 will be readily determined experimentally by one skilled in the art upon reading the present specification. Specifically, in each embodiment, it is recommended that values for all but one of the variables be preselected with the remaining variable sized according to the preferred operation of the device. During operation, a pressurized combustible mixture is supplied to the bottom of the floating valve through the combustible mixture supply line 40 by way of the ball valve chamber 34. The combustible mixture is preferably an air and gas combination with the gas preferably being either natural gas or propane although pure ethane, pure methane or other combustible gases would also suffice. Gas and air are mixed through a suitable conventional valving system, from an air compressor, and a source of fuel gas, not illustrated, in a suitable, conventional manner to form the combustible mixture which is supplied to the combustible mixture supply line 40. The pressurized combustible mixture initially lifts the ball valve 30 from its seat 32 in the ball valve chamber and since the ball is in contact with the rear surface 21 of the floating valve 20, the floating valve 20 is also lifted so that the combustible mixture can flow around the ball valve 30 into the small clearance between the valve side wall 25 and the side wall 19 of the shell 14. The combustible mixture may then flow through the ports 24 into the combustion chamber by way of the bore 26 of the floating valve. The combustible mixture exerts a force against the entire rear surface 21 of the floating valve 20 as soon as it is lifted and thereby lifts the floating valve 20 quickly away from the end cap 17 of the burner shell 14. With continued force against the rear surface 21, floating valve 20 continues upwardly being restricted by the shoulder 22 of the floating valve 20 contacting the shoulder 16 of the burner shell 14. Since the valve 20 floats on a cushion of the combustible mixture, no lubrication of the floating valve is needed and the valve is cooled by the incoming combustible mixture. Note also that unlike the normal poppet valve which is either cam operated or spring loaded, the valve of the present invention is reciprocated by the pressure differential between a pressure in the combustion chamber 15 and a pressure in the combustible mixture supply line 40 and may have the assistance of a spring in some embodiments. The combustible mixture then flows between the side wall 19 of the burner shell 14 and the side wall 25 of the floating valve 20. The mixture flows around and through the ports 24 in the floating valve 20 and into the open interior 26 thereof. Note that because the shoulder 22 of the valve 20 is close to or in contact with the shoulder 16 of the burner 14, the combustible mixture is constrained to flow through the ports 24 in the valve 20. The combustible mixture then flows out a front bore 26 in the floating valve 20 and flows into a main portion of the burner shell 14. After the combustible mixture has first entered the combustion chamber 15, the spark plug 60 is fired to initially ignite the mixture. Once the spark plug 60 has initially ignited the combustible mixture the spark plug 60 is no longer utilized. Instead, further ignition of the combustion mixture occurs due to the continuing flame or heat still retained in the combustion chamber 15. When a new charge of combustible mixture is admitted into the combustion chamber 15, the continuing flame ignite the fresh combustion mixture. Thus the combustion, charging and ignition process continues automatically. Combustion thereupon takes place of the combustible mixture which increases the pressure within the combustion chamber and thereby forces the floating valve 20 toward the inner surface 11 of the cap 17 of the burner shell 14. At the same time, the ball valve 30 is forced to seat itself on the ball valve seat 32 of the ball valve chamber 34. With the ball 30 seated and the floating valve 20 also seated, a double seal is provided to prevent the combustible mixture from backfiring by flowing into the combustion mixture supply line 40. As the burned combustible mixture is exhausted from the combustion chamber 15 through the exhaust tube 50, the pressure in the combustion chamber 15 decreases. When the pressure in the combustion chamber 15 has decreased sufficiently, for example, to an effective pressure below the effective pressure of the combustible mixture in the combustible mixture supply line 40, the pressure of the combustible mixture forces the floating valve 20 upwardly from the cap 17 of the burner shell 14 to repeat the process. With the pressurized mixture pushing against the rear surface 21 of the floating valve 20 and the hot exhaust products pushing on an inside rear surface 28 of the floating valve 20, the valve acts like a differential piston. When the floating valve is in its lowermost position, the cross-sectional area of the floating valve 27 upon which the exhaust products force acts, is significantly larger than the area upon which the combustible mixture force acts, only the cross-sectional area, of the supply line 40. Thus a lower pressure than the pressure in the combustible mixture supply line 40 is required in the combustion chamber 15 before the floating valve 20 is lifted from engagement with the end cap 17 of the burner shell 14. The length of reciprocation of the floating valve 20 is desirably smaller than the diameter of the ball valve 30 to ensure that the ball valve 30 stays in the ball valve chamber 34. In this way, it should be noted that the pressure of the mixture in the line 40 acts on the exposed lower surface of the ball 30 when the ball is seated in the chamber 34 whereas the pressure of the combustion gases effectively acts on the entire cross-sectional area of the floating valve. Thus a significantly lower pressure in the combustion chamber than in the supply line will keep the ball seated in the ball check valve. Once the pressure within the combustion chamber 15 has dropped sufficiently, the ball is unseated, the pressurized combustion gases rapidly begin to act on the entire lower surface of the floating valve 20 with the result that the valve is quickly driven upwardly toward the shoulder 16. As soon as contact is made between the valve shoulder 22 and the shoulder 16 of the burner shell 14, the effective area of the floating valve on which the combustion gases act is reduced to the cross-sectional area of the combustion chamber. After the combustion gases have expanded sufficiently, the force on the floating valve upper surface will be sufficient to urge the floating valve downwardly away from the surface 16. At that point, the effective surface area of the floating valve, as seen by the combustion gases, increases with the result that the floating valve is more easily urged downwardly. Furthermore, once the ball 30 seats in the ball check valve, the effective surface area of the floating valve as seen by the combustion mixture is significantly reduced to the cross-sectional area of the supply line 40. Thus the combustion gases may now more easily keep the valve 20 and the ball 30 seated in the lowermost position. Because the effective areas of the floating valve upon which the combustible mixture and combustion gases act are quickly changing during the reciprocation of the floating valve, the speed at which the valve travels is increased significantly. That is, the valve moves quickly between its uppermost and lowermost positions because a slight movement of the valve immediately results in a significant increase in the effective area of the dominant force. Thus, the varying surface area helps maintain the floating valve in the uppermost and lowermost positions and helps to quickly move the floating valve between the positions. The valve 20, as shown in Figs. 1 and 2, has a passageway provided in the front face whereas the rear surface 21 is completely closed. An upper section of the valve 20 including the bore 26 is defined by an annular portion or tube 23 which is reduced in size with respect to the base portion 27 of the valve. The valve is preferably machined from a solid piece of metal. The bore 26 extends completely through the upper section and only partially through the base portion 27 of the valve 20. The plurality of ports 24, which are arranged radially communicate with the bore 26. The ports 24 extend into the bore 26 to provide a path of flow for the combustible mixture. The size and the number of the ports 24 in the poppet valve 20 depends upon the type of fuel used and the pressure at which the combustible mixture is supplied. The combustible mixture preferably enters the combustion chamber only through the ports 24 and thus, the valve 20 may serve as a flame holder or flame tube to contain the flame generated by the burning of the combustible mixture. Floating valve 20 may suitably reciprocate at up to about 3500 times per minute in the pulse combustion device. The frequency of reciprocation may vary and depends upon the relative size of the combustor shell and the exhaust tube 50, the rate of flow of the fuel and air mixture through the floating valve, and the pressure at which the combustible gases are supplied. While variation of physical characteristics and conditions may vary the pulsing rate, generally, for most purposes the frequency of reciprocation of the floating valve will be about 3200 to about 3400 cycles per minute. However, for some purposes it may be desired to have the frequency reciprocation as low as 800 to 900 cycles per minute. One preferred embodiment of the present invention has a burner shell which is about 25 cm long with a diameter of about 2.5 cm (i.e., a 10:1 ratio). The floating valve is about 1 cm in length and reciprocates through a length of approximately 5 mm. The combustible mixture is pressurized to approximately 2.5-3.5 kg/cm² with an air to propane mixture ratio of about 25 to 1. An interior temperature of approximately 925 o C was very quickly developed in the combustion chamber 15 after ignition of the combustible mixture. As taught in my earlier filed application, a pumping mechanism may provide the combustible mixture as a series of discrete pressurized pulses at the desired rate of cycling of the floating valve. To facilitate use of lower pressure combustible mixture a spring may be provided in a chamber beneath the floating valve to urge the floating valve toward the open position. Fig. 3 shows, in simplified somewhat schematic form, an embodiment of a pulse combustion burner according to this invention. Combustion chamber, shell 614 defines combustion chamber 615 with end cap 676 at the inlet end. Floating valve 620 is a flat plate with peripheral through openings 624 which may be in the form of holes as shown in Fig. 4 or in the form of open slots as shown in Fig. 5. Use of the flat plate floating valve 620 avoids problems of the valve binding as may occur with the floating valve configuration shown in Fig. 1. Use of the flat plate floating valve also permits operation with less space between the edges of the valve and the inner walls of the chamber in which it reciprocates. Preferably, the through openings 624 direct the combustible gases along the walls of combustion chamber 615 to provide a hollow, high combustion efficiency blue flame. This configuration also provides exceptionally high heat transfer through combustion chamber walls 614 due to the proximity of the flame to the heat exchange surface and due to scrubbing action by the combustible gases and flame action along the interior of walls 614 to reduce film heat transfer coefficients. To achieve high peripheral activity in combustion chamber 615, through openings may be at right angles to the plane of flat plate 620 or may be angled to direct the gaseous flow therethrough along combustion chamber walls 614. It is readily apparent that flat plate floating valve 620 may be used in any of the embodiments described utilizing ball valve 30 as shown in Fig. 1 or with spring assistance. Likewise suitable for use in all embodiments previously described in my patents and in this disclosure are advantageous embodiments wherein the floating valve, preferably the flat plate floating valve, as shown in Fig. 11 is in the form of annular floating valve 628 having through holes 624 and the combustible gas inlet is in the form of a plurality of inlets 641 supplied by gas manifold 642 around a corresponding annular area in the end cap 676. The annular structure of the end cap may have a hollow cylindrical portion 677 extending into the combustion chamber with a solid end a short distance into the combustion chamber from the limit of travel of the floating valve and having the ignition means 660 extending therethrough. For example, a spark plug or other ignitor may be placed through the solid end of the cylindrical portion of the end cap extending into the combustion chamber. This location for the ignitor provides ignition more evenly to the hollow flame. Another feature shown in Fig. 3 is that combustion chamber shell 614 has open end 618 open to the atmosphere instead of closed end 18 with small unvalved exhaust tube 50 as shown Fig. 1. The embodiment shown in Fig. 3 has constriction baffles 670, 671 and 672 with exhaust ports 680, 681 and 682, respectively. The constriction baffles are preferably of conical shape as shown. I have found that two or three constriction baffles within combustion chamber 615 results in cleaner combustion in a smaller combustion chamber with increased heat transfer through combustion chamber shell 614. The exhaust ports in the constriction baffles must be tuned for the system geometry in the same manner as described above with respect to exhaust tube 50. The constriction baffles may be advantageously used with any of the embodiments described, regardless of configuration of the floating valve and with or without restricted exhaust tube 50, as shown in Fig. 1. Generally, 2 to about 6 constriction baffles may be used to achieve improved heat exchange with a more compact burner-heat transfer unit. To provide a shorter burner-heat transfer unit, the heat transfer portion may be folded as shown schematically in Fig. 6. As shown in Fig. 6, combustible gas input 740 provides combustible gas to a floating valve assembly, as described, which provides pulsed combustible gas to the combustion chamber 715 where it is combusted. The combustion products pass upwardly against constriction baffles 770 and 771 and through exhaust ports 780 and 781, respectively, through exhaust tube 750 to heat exchanger 710 with constriction baffles 772 and 773, and exits by exhaust tube 750. Instead of constricted exhaust tube 750, any larger diameter tube may be used to convey combustion product gas to heat exchanger 710. Heat removal from combustion chamber walls 614 as shown in Figs. 3 and 6, and heat exchanger walls 710, as shown in Fig. 6, may be effected by any suitable means, including those described above. Heat exchange liquid coil 630 is shown in Fig. 3 as exemplary of a suitable heat exchanger means. Fig. 7 shows one embodiment of a hot water heater of this invention utilizing a pulse combustor of this invention. Water tank 810 has water inlet 811 and hot water outlet 812. The water tank top 813 may be depressed to provide mounting bracket 814 and outlet water jacket 815. Air bleed and safety means 816 is provided in an upper portion of the tank. Water drain means 817 may be provided as desired. A pulsed combustor of this invention 880 is mounted with its combustion zone 881 in the region of outlet water jacket 815 to provide direct heat transfer through the combustion chamber walls to water being withdrawn through hot water outlet 812. Heat transfer zone 882 of combustor 880 extends downwardly into the volume of water and combustion products exhaust tube 850 conveys combustion products for further heat transfer in finned heat transfer means 851 and the exhaust exits from the water heater through exhaust conduit 852 at relatively cool temperatures. Control components of the pulsed combustor 880 are schematically shown: spark plug 860 and suitable ignition power supply 861; air supply line 862 and compressor and metering means 863; gas supply line 864 and pressure and metering means 865; mixing means 866 for mixing air and gas and flashback arrestor 867 preventing ignition prior to combustion chamber 881. Any of the floating valve configurations and heat exchanger configurations described may be used in this embodiment. I have found that the operation of the combustor by introduction of the combustible gas mixture downwardly from the top, as shown in the water heater in Fig. 7, provides easier ignition starting of the combustor. Additionally, this configuration allows rapid heating of the water as it is being withdrawn permitting smaller volume and lower temperature water storage. This configuration also provides operation at lower combustible gas pressures of less than about 4 inches water column and down to as low as 2 inches water column and less. The pulse combustor may be in a vertical position extending either downwardly or upwardly in the water tank, or may be in a horizontal position in the water tank. The pulse combustor of this invention is particularly well suited for use in air heating systems. Fig. 8 schematically shows one embodiment of a pulse combustor of this invention used in an air heating system. Fig. 8, in simplified schematic form, shows air heater 900 wherein an air treatment passage is defined by air treatment duct 930 with cold air entering as shown by arrows 901 and leaving as heated air shown by arrows 902. The air to be heated, usually return air from an enclosed volume, such as a room, is driven through treatment duct 930 by an upstream blower, not shown, and first passed over heat exchanger 903 and then passed in direct contact with pulse combustor chamber 906 and pulse combustor exhaust manifold 904 and through treatment unit comprising any desired humidification means and filtering means. The treatment air blower means, filtering means and humidification means are not shown, but are any such suitable means as conventionally used in warm air furnaces as known to the art. Although shown in a horizontal air passage configuration, the entire assembly may be rotated 90° and operated in either a down-pass or up-pass mode. The pulse combustor will operate in any of these positions. As shown in Fig. 8, combustion air is provided through air intake 941 of combustion air blower 940 where it is pressurized to a pressure in the range 0.875 to 1.75 kPa, preferably in the range 1 to 1.5 kPa . The combustion air pressure and flow rate is maintained and regulated by combustion air flow regulator shown generally as 924 in Fig. 8. Referring also to Fig. 10, combustion air flow regulator 924 has rod 925 with tapered head 927 which fittingly engages tapered inlet 928. Combustion air flow regulator rod 925 is preferably threaded and is readily adjustable through a threaded bore in the T-shaped end of combustion air pressurized conduit 942. Suitably, lock nut 926 is provided to lock combustion air flow regulator rod 925 in desired position and if desired, bearing means may be provided within combustion air pressurized conduit 942 to assure centering of tapered head 927 within tapered inlet 928. It is readily seen that as tapered head 927 is advanced into tapered inlet 928 the flow of pressurized combustion air is decreased and its pressure, assuming a constant speed combustion air blower 940, is increased. Combustible fuel gas, such as natural gas, is introduced through gas supply line 921 into a mixing chamber downstream from combustion air flow regulator 924. Not shown in the drawing in gas supply line 921 is a suitable gas pressure controller, as is well known to the art, to provide fuel gas at a pressure of 0.5 to 0.875 kPa and preferably 0.75 to 0.875 kPa. High pressure air gas tap 923 is provided to monitor the pressure of combustion air prior to passage through tapered inlet 928 and may be provided with a safety switch which allows a gas valve in gas supply line 921 to open only after desired pressure is reached in combustion air pressurized conduit 942. Low pressure combustible mixture tap 922 is provided in combustible gaseous mixture supply line 920 for control purposes. I have found that using the high pressure combustion air supply as described in conjunction with pulse combustor that there has been no tendency for flashback, however, safety codes may require that a spark arrestor be placed in combustible gaseous mixture supply line 920. Due to the low pressure combustible gaseous mixture supplied to floating valve 915, I have found it desirable to provide an enlarged combustible gas inlet chamber 912 to provide a greater force upon the combustible gas supply line side of floating valve 915. As shown in Fig. 10, floating valve 915 has combustible gas feed bores 916 in communication from valve chamber 913 to pulse combustor chamber 906 wherein combustible gas feed director flange 917 directs the combustible gas along the periphery of pulse combustor chamber 906. Valve chamber 913 is defined by pulse combustor removable end piece 907 which is provided with holding flange 908 for secure fastening to pulse combustor chamber 906 by assembly bolts 910 passing through pulse combustor holding flange 909 and tightened with assembly nuts 911. Provision of the removable combustor end piece 907 facilitates changing of dimensions of combustible gas inlet chamber 912 and valve chamber 913 to accommodate different types of floating valves 915 as have been described herein before. The pulse combustor operates in the same fashion as previously described herein. The pulse combustion is initiated by ignitor 960 and takes place within pulse combustor chamber 906 with combustion gases passing through pulse combustor exhaust 905 and into exhaust manifold 904 feeding tubes passing through heat exchanger 903 and through an unvalved opening (not shown) to the atmosphere. The air heater as shown in Fig. 8 incorporating the pulse combustor and passing the air stream being treated in sequence over the finned heat exchanger through which combustion exhaust gases are passed in closed relationship and over the pulse combustion chamber 906 and pulse combustion exhaust manifold 904 provides high efficiency heating of the air stream to be treated. Fig. 9 schematically shows another embodiment of an air heater according to the present invention, wherein the cold air to be treated 901 is passed downwardly in sequence through heat exchanger 903 and finned pulse combustion chamber 950 and finned exhaust manifold 951 to exit as heated air shown by arrows 902. The embodiment shown in Fig. 9 operates in the same fashion as the embodiment shown in Fig. 8 except that the pulse combustor chamber and the combustion exhaust manifold is provided with expanded heat exchange surfaces. In all of the pulse combustors of this invention, while reference has been made to pulsed combustion it should be understood that the flame is a continual flame generally attached to the upper side of the floating valve which serves as a flame holder limiting combustion to a combustion zone adjacent the floating valve. Likewise, the action of the floating valve during combustion is generally a modulating action of increasing and decreasing the flow of combustible gas by movement of the floating valve. The combustion obtained by the pulsed combustor of this invention results in a high temperature, 1090 o C to over 1370 o C clean burn blue flame. The fuel efficiency in the combustor of this invention may be in excess of 95 percent and preferably in excess of 96.5 percent. The small size and geometry of the combustor unit and the hollow flame together with the scrubbing action of the flame and gases along heat transfer surfaces provides exceptionally high heat transfer through the combustor walls. The pulsed combustor of this invention provides a clean, cool combustion product stream which may be vented through a small tube without the need for a conventional chimney. During experimental operation of various models of the present invention, noise levels observed were from blowers and accessory equipment, the combustor itself contributed very little to the overall noise level. Condensation formed in the exhaust was only slightly acidic and the device could readily be adjusted so as to provide no unburned hydrocarbons in the exhaust. While some specific dimensions have been set forth, a wide variety of sizes of combustors according to this invention for various applications have been operated, for example, having combustion chambers up to 20 cm in diameter and 122 cm in length with combustible gas inputs of up to 120kW (412,000 Btu per hour). Higher gas inputs are feasible in larger units. The pulse combustor of this invention may be used to provide the advantages of high efficiency energy utilization, both in increased fuel efficiency in combustion and in thermal transfer of heat from the combustion products. These high efficiencies result in small physical size combustors suitable for a wide variety of heating applications, such as for heating gases, liquids or solids such as industrial or home space heating, industrial or home hot water boilers and hot water heaters, chemical process heating, deep fat fryers, cooking griddles and other heating appliances and processes. Preferred embodiments of the present invention can further provide a heating device having a pulsing combustion device wherein the combustion gases heat either a liquid or a gas, which liquid or gas cools the shell of the burner. Preferred embodiments of the present invention are especially useful in any type of a fluid heating system, such as a home heating or hot water heating system. Present home heating systems are often large and expensive as well as being energy-inefficient because much of the heating value of the fuel is wasted. It would be advantageous to provide a building heating system in which a simple and compact pulsing combustion device is used to heat the fluid medium by which the home is heated. This would provide a more efficient use of heating fuels, since in many of today's home heating systems a large percentage of the heat generated is lost through the chimney. The need therefore remains for a building heating system which efficiently utilizes heat energy contained in the combustion gases produced by the burner. Preferred embodiments of the present invention can provide an efficient and low cost heating system for a building wherein the fluid medium which heats the home is itself heated by a compact pulsing combustion device. Preferred embodiments of the present invention can also provide a heating system in which the spent gases of combustion are utilized to improve the efficiency of the system.

Claims: A pulsing combustion device comprising: means (614) for defining an elongate combustion chamber (615) having an inlet at one end for a combustible mixture of fuel and combustion air and an unvalved outlet at the opposite end open to the atmosphere for combustion gases: a floating valve member (620) mounted in reciprocation relation within a limiting chamber adjacent said one end of said combustion chamber, said valve member having a first side in communication with said combustion chamber (615) and a second side in communication with a supply (640) of a pressurized combustible mixture and having a plurality of evenly arcuately spaced ports (624) in said valve member (620), said reciprocation of said valve member (620) in said limiting chamber closing and opening communication through said ports (624) between said supply (640) of combustible mixture and said combustion chamber (615); means (640) for supplying a pressurized combustible mixture of fuel and combustion air to said second side of said floating valve member (620); means (660) for igniting and combusting said combustible mixture in said combustion chamber (615) to produce pressurized combustion gases, said floating valve member (620) being reciprocated by said pressurized combustible mixture in communication with said second side and said pressurized combustion gases in communication with said first side to regulate the flow of said combustible mixture of fuel and combustion air into said combustion chamber (615), characterised in that said valve member (620) is a flat plate valve member, and in that said ports (624) are peripheral ports through the flat plate valve member adapted to direct said combustible mixture axially along the periphery of said combustion chamber (615). A pulsing combustion device as claimed in Claim 1, wherein the floating valve member (628) is annular-shaped and the ignition means (660) extends through the centre opening of the floating valve member. A pulsing combustion device as claimed in Claim 1, mounted within an air treatment duct (930) and having said unvalved outlet (905) leading into an exhaust manifold means (904) in gas flow communication with one end of a closed heat exchanger means (903), the other end of said closed heat exchanger means open to said atmosphere, all situated within said air treatment duct (930); blower means for passage of cold air to be heated in sequence through said air treatment duct (930) and in thermal exchange with said heat exchange means (903) and said combustion chamber (906) and exhaust manifold (904), providing heated air. A pulsing combustion device as claimed in Claim 3, wherein said combustion chamber (950) and said exhaust manifold (951) have extending fins providing higher heat exchange. A pulsing combustion device as claimed in Claim 1 or Claim 3, further comprising combustion air blower means (940) to a pressurized combustion air conduit (942) at 0.875 to 1.75 kPa, a combustion air flow regulator means (924) at one end of said pressurized conbustion air conduit (942) controlling combustion air flow to a combustible mixture mixing chamber, means (921) for supplying fuel gas at a pressure of 0.5 to 0.875 kPa to said mixing chamber, and combustible gaseous mixture supply line means (920) for supplying pressurized combustible mixture from said mixing chamber to said second side of said floating valve member (915). A pulsing combustion device as claimed in Claim 5, having a higher pressure tap (923) in said pressurized combustion air conduit (942), a low pressure tan (922) in said combustible mixture supply line (920), and control means opening said means for supplying fuel gas only after said pressure is reached in said pressurized combustion air conduit. A pulsing combustion device as claimed in Claim 5, wherein said combustion air flow regulator (924) is adjustable. A pulsing combustion device as claimed in Claim 3, further comprising combustion air blower means (940) to a pressurized combustion air conduit (942) at 1 to 1.5 kPa, a combustion air flow regulator means (924) at one end of said pressurized combustion air conduit (942) controlling combustion air flow to a combustible mixture mixing chamber, means (921) for supplying fuel gas at a pressure of 0.75 to 0.875 kPa to said mixing chamber, and combustible gaseous mixture supply line means (920) for supplying pressurized combustible mixture from said mixing chamber to said second side of said floating valve member (915). A pulsing combustion device as claimed in Claim 3, wherein an end (907) of said combustion chamber comprising said inlet for a combustible mixture is removably attached to said elongate combustion chamber (906). A pulsing combustion device as claimed in Claim 9, wherein said end (907) and said combustor chamber (906) are provided with holding flanges (908, 909) extending radially therebeyond with through bores which may be aligned providing passage and securement for assembly bolts (910). A pulsing combustion device as claimed in Claim 9, wherein the inner side of said combustion chamber end (907) defines an enlarged combustible gas inlet chamber (913). A pulsing combustion device as claimed in Claim 1, additionally comprising at least one constrictor plate (670) having an exhaust port (680) with a cross section relatively small with respect to the cross section of said combustion chamber (615) located across said combustion chamber above the zone of combustion. A pulsing combustion device as claimed in Claim 12, having 2 to 6 constrictor plates (670, 671...) in series. A pulsing combustion device as claimed in Claim 13, wherein the portion of said combustion chamber toward said outlet and including at least one of said constrictor plates is folded over and arranged adjacent to the portion of said combustion chamber toward said inlet end. A pulsing combustion device as claimed in Claim 1, having said combustion chamber (880) mounted within a tank (810) for containment of water and in heat transfer relation thereto, said tank provided with a cold water inlet (811) and a hot water outlet (812). A pulsing combustion device as claimed in Claim 15, wherein the unvalved outlet (850) is in gas flow communication with one end of a closed heat exchanger means (851), the other end (852) of which closed heat exchanger means (851) is open to said atmosphere, all situated within the tank (810). A pulsing combustion device as claimed in Claim 16, wherein the combustion chamber (880) extends downwardly into the water providing direct heat transfer therewith. A pulsing combustion device as claimed in Claim 17, wherein a water withdrawal chamber (815) in the upper portion of said tank surrounds the portion of said combustion chamber (880) toward said combustible mixture inlet (867) A pulsing combustion device as claimed in Claim 17, wherein said combustion chamber extends upwardly or horizontally into said water providing direct heat transfer therewith. A pulsing combustion device as claimed in any one of Claims 1 to 19, wherein the flat plate floating valve member (620) reciprocates at about 3000 to about 3400 cycles per minute.

Inventors: DAVIS, ROBERT E.
Applicants: ARKANSAS PATENTS, INC.
Application year: 1985
Main classification: F23C11
IPC codes: B08B3, F24H1, F23C15, F22B1