Pulsing Combustion

1. Field of the Invention

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.

2. Description of the Prior Art

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. Perhaps one of the first pulsing combustors was the pulse-jet engine utilized in the German V-1 rocket or buzz bomb which is described on pages 2 and 3 of the book Rocket Propulsion Elements by George P. Sutton (John Wiley & Sons, 1949.).

Another known pulsing combustor is disclosed in U.S. Pat. No. 2,857,332 to Tenney et al and is utilized in a machine for producing dispersions of liquid in air or other gases. In the Tenney et al device, a fuel-air mixture is supplied through an inlet portion of a combustor with combustion air passing sequentially through a throat of an air inlet passage and over a sloping step in a fuel injection tube. Fuel is discharged as a spray and is metered in proportion to the incoming air. The fuel-air mixture is forced through a plurality of diverging passages into a combustion zone of the combustor. The passages each have a port at the combustion chamber end of each passage. Each port is covered by a finger-like portion of a metal valve preferably made of a flexible steel. The finger-like portions of the valve are sufficiently flexible to be deflected against a backing plate by the inrush of the air-fuel mixture when the burner is operating.

Initially, the starting air-fuel mixture is introduced into the burner chamber and is ignited by a spark plug. The resulting explosion causes the finger-like portions of the valve to close against the intake ports leaving an exhaust tube as the only path of exit for the combustion zone gases. The mass of gases in the exhaust tube is then driven forceably at extremely high velocity outwardly of an open end of the exhaust tube by the expanding combustion gases produced by the explosion in the combustion zone. The rush of gases out of the exhaust tube causes a low pressure area in the combustion zone. The low pressure area induces a fresh charge of combustible air-fuel mixture through the ports and into the combustion zone. Fuel is fed to the combustion zone through a plurality of fuel ports and the air used is atmospheric air. The burner depends on the low pressure zone existing in the combustion chamber after exhaustion of the hot combustion products to induce a further flow of the air-fuel mixture into the combustion zone.

A resonant intermittent combustion heater system using a pulsing combustion arrangement similar to the pulsing combustor disclosed in U.S. Pat. No. 2,857,332 is also known in the prior art and is disclosed in U.S. Pat. No. 2,715,390, issued to Tenney et al.

A different pulsing combustion arrangement having a burner is disclosed in U.S. Pat. No. 2,959,214 issued to Durr et al. During ignition of the burner in the Durr et al device, a spark plug is activated along with a pump to supply air through a conduit under pressure to a tightly closed fuel tank. The air streaming through the tube vaporizes an amount of fuel at a diaphragm and this mixture flows into a mixing tube. The mixing tube mixes the fuel-air mixture with a further supply of air and the resulting mixture then is ignited by the spark. The burning does not provide a complete combustion of the fuel-air mixture and therefore unburned combustible components circulate within a cyclone-form combustion tube before reaching an exhaust tube. As the burner continues to operate, a part of the cyclone-form combustion tube becomes hot and the unburned combustible components which enter the cyclone combustion tube are ignited. An explosion takes place within the combustion tube and the explosion provides a sudden blast of exhaust gases through the exhaust tube. These explosions follow each other uniformly and a resonant intermittent combustion takes place providing an automatic suction of fuel and air

A spraying device having a different pulsing combustor with an oscillating burner resonator fed by a carburetor is disclosed in U.S. Pat. No. 3,758,036 issued to Bauder et al. A blower is set into operation so that a fuel whirling chamber is pressurized via a starting air pipe and fuel is supplied to the fuel whirling chamber by a tank through a nozzle. The fuel-air mixture is then supplied through a tube to the burner and an ignition device in the burner ignites the fuel-air mixture. During subsequent operation, air is drawn into a valve chamber through a suction valve provided on a front side of the carburetor and is mixed with fuel from the fuel nozzle. On a side wall of the carburetor is a lid which carries an adjusting device for the oscillating burner resonator. The adjusting device includes an air evacuating valve associated with the fuel whirling chamber and a pressure space enclosed by the lid. A diaphragm is sealed at its edges to an outside of the lid with a middle area of the diaphragm being connected to a valve closing part of the air evacuating valve.

The Bauder et al patent also discloses a portable spraying apparatus having a hand held gun. The burner in the Bauder et al patent is cooled by air in a surrounding cooling cover which obtains the air from a blower through a pipe. An oscillating tube, also surrounded by the cooling cover, conducts the hot combustion products away from the burner toward a front section of the cooling cover. A liquid agent is introduced by the nozzle into the oscillating pipe so that the hot combustion products of the burner will turn the liquid into a steam or mist which will be expelled through a widened end section of the gun.

A known recirculating burner is disclosed in U.S. Pat. No. 3,366,154 issued to Walsh et al which shows a compact portable burner useful in flame cultivation of crops. Some of the products of combustion are recirculated from a discharge end of the burner to a position between the discharge end and a venturi throat and just forward of an oil nozzle for the purpose of providing a clean flame and more efficient burning of the fuel. A recirculation jacket surrounds a central portion of the burner and has a top wall, a bottom wall and a pair of similar symmetrically disposed side walls in a predetermined outwardly spaced relation to top, bottom and side walls of the burner. The front ends of the jacket wall and the burner wall are joined together by a front shoulder. Similarly, the rear end of the jacket wall and the burner wall are joined together by a rear shoulder. A plurality of openings is provided in the burner walls adjacent and slightly rearwardly of the front shoulder and a similar plurality of openings is provided adjacent and slightly forwardly of the rear shoulder. Hot combustion gas enters the plurality of front shoulder openings and is recirculated to the rear and reenters the burner by venturi action at the rear shoulder openings to provide a more efficient burning of the fuel as well as improved vaporization of the fuel which is preferably fuel oil.

Other patents and publications which disclose combustor arrangements of interest to the present invention include: U.S. Pat. Nos. 2,634,804 of Erickson; 2,589,566 of Neth et al; 2,077,323 of Hendrix; 2,411,675 of Alexander; 1,719,015 of Lewis; 1,885,040 of Arnold; 4,259,928 of Huber; British Pat. No. 166,455; French Pat. No. 1,366,565; and, "Pulsating Combustion: An Old Idea May Give Tomorrow's Boiler's a New Look", Power, pp. 88-91, Aug. 1954.

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.

It is therefore an object of the present invention to provide an improved combustion device having a floating valve member mounted in the wall of a combustion chamber of the combustion device which reciprocates in a floating manner to regulate a supply of a combustible mixture to the combustion chamber.

It is therefore another object of the present invention to provide a pulsing combustion device which provides an efficient and economical use of fuel and which overcomes the disadvantages of known combustion devices.

Yet another object of the present invention is to 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.

The combustor of the present invention is 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.

It is therefore still another object of the present invention to 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.

It is therefore yet still another object of the present invention to provide a heating system in which the spent gases of combustion are utilized to improve the efficiency of the system.

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.

My U.S. Pat. Nos. 4,488,865 and 4,480,985, teach and claim specific embodiments of my pulsing combustion device and process. My U.S. Pat. No. 4,479,484 teaches and claims specific embodiments of a fluid heating device incorporating my pulsing combustion device.

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 with reference to the accompanying drawings wherein like members bear like reference numerals and wherein:

FIG. 1 is a cross-sectional view of one embodiment of a pulsing combustion device according the present invention;

FIG. 2 is a view through the line 2--2 of FIG. 1;

FIG. 3 is a cross-sectional view of another preferred embodiment of a heating device according the the present invention;

FIG. 4 is a view through the line 12--12 of FIG. 3;

FIG. 5 is an enlarged view of a portion of the heating device of FIG. 3;

FIG. 6 is a cross-sectional side view of another embodiment of a pulsing combustion device utilized as a fluid heating device;

FIG. 7 is an enlarged top view of a floating valve shown in the pulsing combustion device shown in FIG. 6;

FIG. 8 is a top view of another embodiment of a floating valve suitable for use in the pulsing combustion device of this invention;

FIG. 9 is a side view of another embodiment of a pulsing combustion device according to this invention;

FIG. 10 is a cross section of one embodiment of a hot water heater utilizing a pulsing combustion device according to this invention;

FIG. 11 is a perspective view of a hot air heater utilizing a pulsing combustion device according to this invention;

FIG. 12 is a perspective view of another embodiment of a hot air heater utilizing a pulsing combustion device according to this invention;

FIG. 13 is a sectional view of the combustible gas mixing and feeding portion of the apparatus; and

FIG. 14 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, one embodiment of a 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 (see FIG. 3). 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. 6.

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 floatihg 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 of 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 centimeters (ten inches) long with a diameter of about 2.5 centimeters (one inch) (i.e., a 10:1 ratio). The floating valve is about 1 centimeter (three-eighths of an inch) in length and reciprocates through a length of approximately 0.5 centimeter (three-sixteenths of an inch). The combustible mixture is pressurized to approximately 2.5-3.5 kg/cm.sup.2 (40-50 psi) with an air to propane mixture ratio of about 25 to 1. An interior temperature of approximately 925.degree. C. was very quickly developed in the combustion chamber 15 after ignition of the combustible mixture.

With reference now to FIGS. 3, 4 and 5, another preferred embodiment of a heating device according to the present invention includes the pulsing combustion device 510 generally as described in connection with FIG. 1 but with some modifications. An elongate, cylindrical combustion chamber shell or burner shell 514 defines a combustion chamber 515 with the combustion chamber shell 514 generally tubular with a length that is considerably greater than its width. An end cap 576 is disposed at an inlet end of the combustor shell 514 with the end cap 576 together with the combustor shell 514 defining a path of reciprocation in the space 517 for the floating valve 520. After combustion, the combustion gases exit through an exhaust tube 550 disposed at an exhaust end 518 of the combustor shell 514. The combustion chamber 515 is closed except for the outlet for combustion gases and the inlet for admitting the combustible mixture.

The combustible mixture is formed in a mixing chamber means 505 which is supplied with air through conduit 508 and gas through conduit 509. The combustible mixture is then supplied to a pumping mechanism 506 which pressurizes the combustible mixture. Since the mixture is, of course, highly flammable, the pumping mechanism 506 must be appropriately protected against electrical discharges and other disturbances which might ignite the mixture.

The pumping mechanism 506 may discharge the combustible mixture as a series of discrete pulses at a desirable rate. A typical rate of discharge is about 3000 pulses per minute. An automobile emission system pollution control pump ("smog" pump) has been successfully utilized experimentally to pressurize the combustible mixture in discrete pulses. Such a pump generally has two vanes and rotates at 1500 rpm.

The pulsed supply of the combustible mixture is then passed through a suitable, conventional check valve 507 and then immediately into a supply line 540. The distance between the pumping mechanism 506 and the pulsing combustion device 510 is appropriately short and is preferably not provided with baffles or large chambers so as to maintain the "pulsed" nature of the supply to the extent possible.

In other words, the supply line 540 is arranged so as to convey the combustible mixture to the poppet valve 520 as a series of discrete pulses to the extent readily possible.

The combustible mixture is supplied by the line 540 through a passageway 534 to the lower surface of the reciprocating floating valve 520. The passageway 534 communicates with a chamber 532 having a spring 530 which assists in the upward movement of the floating valve 520 thereby providing operation at lower combustible gas pressures.

The inner face of the end cap 576 includes an annular channel which communicates with the chamber 532 by way of four radial slots 517. The radial slots 517 are arranged in the shape of a cross with the remainder of the inner face of the end cap 576 forming a valve seat for a bottom surface 521 of the floating valve. The outer periphery of the surface 521 sealingly abuts the inner surface of the end cap when the floating valve is in its rearwardmost position.

A flange is secured, for example, by welding, to the end cap 576 to facilitate the assembly of the end cap 576 with the shell 514. A plurality of bolts 574 extend through openings in the flange and are threadably received by corresponding nuts 572 which are secured, as by welding, to the shell 514. A sealing gasket, not shown, preferably of neoprene or another gasket material suitable for high temperature use may be preferably disposed between the end cap 576 and the lower end wall of the burner shell 514.

The end cap preferably has four holes for receiving the bolts 574. In this way, two of the bolts may be used to join the end cap and the burner shell together and the remaining two bolts may be used to mount the combustion device in the furnace or other location of operation.

As discussed more fully below, the combustion device according to the present invention need not be arranged vertically, but instead can be mounted horizontally or inverted or in any suitable configuration.

The floating valve 520 disposed for reciprocal movement in the burner or combustor shell 514 is generally mushroom-shaped with an open interior or bore 526, see also FIG. 5. The floating valve 520 is preferably of integral construction and includes a base having a first diameter and a tube 523 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 of the base of the floating valve and a side wall 519 of the end cap 576 to allow the free reciprocal movement of the valve.

The floating valve 520 is disposed beneath the combustor shell 514 for reciprocation, as in the embodiment of FIG. 1. A plurality of ports 524, sixteen in number as shown in FIG. 4, is disposed about the floating valve 520 beneath the shoulder 522 of the valve 520 and provides communication between the bore of the floating valve and the small clearance between the side wall of the valve and the side wall 519. Preferably, the floating valve is recessed immediately beneath the outer end of the ports 524 around the entire periphery of the valve. In this way, communication with the ports is more easily obtained.

A diffuser ring 529 extends upwardly from the base of the poppet valve to define a cup 528. The diffuser ring 529 is generally shaped as an inverted "L" in cross section, see FIG. 13, and defines an annular chamber which forms an extension of the ports 524. The annular chamber directs the combustible mixture upwardly along the inner wall 526 of the poppet valve to assist in the rapid ignition of the heating device.

The use of the diffuser ring 529 has resulted in a nearly instantaneous ignition upon firing of the spark plug 560 and is believed to result in an increased thermal efficiency for the device.

The floating valve includes an annular wall 523 which extends along the burner shell 514. The annular wall 523 preferably fits smoothly within the burner shell 514 so as to securely guide the floating valve during its reciprocal movement without binding or otherwise inhibiting the free movement of the valve 520.

Care must be taken that the annular wall 523 is not too loose to permit the valve 520 to become "cocked" in the burner shell 514. Likewise, the annular wall must not be so tight as to inhibit or restrict movement of the valve. In this regard, the thermal expansion of the valve and the burner shell must be taken into consideration when selecting the various materials of construction and when sizing the components.

As in the embodiment of FIG. 1, a spark plug 560 extends into the combustion chamber through a threaded bore in the combustor chamber shell 514 and is provided to initially ignite the combustion gases within the shell 514.

The check valve 507 is provided in the line 540 to prevent backfire through the supply line 540 by preventing a flame in the combustion chamber 515 from spreading backwardly into the combustible mixture supply line 540. If desired, additional or different backfire prevention devices could be provided.

The exhaust tube 550 at the exhaust end 518 of the burner shell 514 has a first end 551 disposed at the exhaust end surface 512 of the burner shell 514 and a second end 552 disposed outside the burner shell 514. The exhaust tube 550 is relatively small in cross-sectional diameter with respect to the burner shell 514.

The outer surface of the burner shell 514 is preferably provided with a plurality of suitable, conventional vanes which facilitate a heat exchange with the surrounding air. In addition, the exhaust pipe 550 communicates with an inner heat exchange coil and an outer heat exchange coil by way of a T-fitting 552. The inner and outer heat exchange coils each encircle the burner shell 514 to provide an efficient and compact configuration and so as to effectively transfer heat to the surrounding air. The inner and outer heat exchange coils are themselves conventional and preferably include heat exchange vanes, not shown, on an outer surface of the coils to facilitate a transfer of heat to the surrbunding medium. The heat exchange vanes may be of aluminum or copper or any other suitable material which readily conducts heat.

The exhaust gases from the inner and outer coils may then be recombined and are supplied to a suitable conventional exhaust.

The pulsing combustion device 510 of FIG. 3 is preferably provided in a gas heat exchange configuration such as a conventional forced air furnace housing, not shown. The pulsing combustion device 510 may be mounted for updraft, downdraft or crossdraft air flow with the air to be heated being flowed over the coils and over the burner shell 514. In this way, the air to be heated cools the burner shell to prevent overheating.

The air to be heated is preferably driven over the coils and the burner shell by a suitable conventional blower, not shown, with the pulsing combustion device being mounted in a closed housing, not shown, to direct the forced air over the coils and the burner shell.

FIG. 6 shows, in simplified somewhat schematic form, another 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. 7 or in the form of open slots as shown in FIG. 8. Use of the flat plate floating valve 620 avoids problems of the valve binding as may occur with the floating valve configuration shown in FIGS. 1 and 3. 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 spring assistance as shown in FIG. 3.

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. 14 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. 6 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. 6 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. 9. As shown in FIG. 9, 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. 6 and 9, and heat exchanger walls 710, as shown in FIG. 9, may be effected by any suitable means, including those described above. Heat exchange liquid coil 630 is shown in FIG. 6 as exemplary of a suitable heat exchanger means.

FIG. 10 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. 10, 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. 11 schematically shows one embodiment of a pulse combustor of this invention used in an air heating system. FIG. 11, 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 931 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.degree. 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. 11, combustion air is provided through air intake 941 of combustion air blower 940 where it is pressurized to about 31/2 to about 7 inches of water, preferably about 4 to about 6 inches of water. The combustion air pressure and flow rate is maintained and regulated by combustion air flow regulator shown generally as 924 in FIG. 11. Referring also to FIG. 13, 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 about 2 inches to 31/2 inches of water and preferably about 3 inches to 31/2 inches of water. 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. 13, 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 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. 11 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. 12 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. 12 operates in the same fashion as the embodiment shown in FIG. 11 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, 2000.degree. to over 2500.degree. F. 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 8 inches in diameter and 48 inches in length with combustible gas inputs of up to 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.

While in the foregoing specification this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details disclosed herein can be varied considerably without departing from the basic principles of the invention.