US3837329A

US3837329A - Liquid fuel-fired grille

Info

Publication number: US3837329A
Application number: US00376662A
Authority: US
Inventors: P Mutchler
Original assignee: US Department of Army
Current assignee: MILL AND MINE SERVICES Inc A CORP OF; US Department of Army
Priority date: 1973-07-05
Filing date: 1973-07-05
Publication date: 1974-09-24
Anticipated expiration: 1991-09-24

Abstract

A cooking surface or grille heated uniformly by the products of combustion from a liquid fuel-fired burner, wherein the products of combustion are caused to flow beneath the cooking surface of the grille through inverted V-shaped channels which define gastight passageways that extend from the back to the front of the grille and in the opposite direction through adjacent V-shaped gas-tight channels alternating with the inverted V-shaped channels to provide an efficient and uniform transfer of heat energy from the combustion gases to the cooking surface of the grille.

Description

0 United States Patent 1191 1111 3,837,329

Mutchler Sept. 24, 1974 [5 LIQUID FUEL-FIRED GRILLE 3,525,325 8/1970 Perl 126/39 J [75] Inventor: [131:] A. Mutchler, University City, Primary Examiner wimam F. O,Dea

' Assistant Examiner-Harold Joyce [73] Assignee: The United States of America as Attorney, Agent, or Firm-Eugene E. Stevens, III;

represented by the Secretary of the Herbert Berl; Lawrence E. Labadini Army, Washington, DC. 22 Filed: July 5,1973 L k ff Z d I b h coo mg su ace or gn e eate um ormy y t e [2]] Appl- 376,662 products of combustion from a liquid fuel-fired burner, wherein the products of combustion are [52] U.S. Cl. 126/44, 126/39 J caused to flow at t ooking surface of the [51] Int. Cl. F24c 3/06 grille through inverted P Channels which [58] Field of Search 126/44, 19.5, 39 J, 39 H, fine g g p g y that extend from the back 12 39 N, 39 K, 391 to the front of the grille and in the opposite direction through adjacent V-shaped gas-tight channels alternat- 5 R m- Cited ing with the inverted V-shaped channels to provide an UNITED STATES PATENTS efficient and uniform transfer of heat energy from the combustion gases to the cooking surface of the grille. 252,307 l/1882 Fagan 126/44 I 1 3,408,999 ll/1968 Mutchler 126/44 7 Claims, 3 Drawing Figures fl o 2 I '1' 11 g 1 37 1 III/HI 1 [4 20 l I J I 1 I I 1 1 *1 /L: I I I II I I I i] I9 I II I I0 I; .H I ily l lil 7 3' I I 23 /;L/\ 1 1 11 I I8 il- I7 I I, l- I 1] l/ 1'1 i x: 71 14 I "/i l I 1 I I I I t l I I 1 I) i ii. I i l I, l2

PAYENTEUSEPZMSH smut III III FIG.

PAIENIEU 2 74 SHEET 2!! 2 LIQUID FUEL-FIRED GRILLE The invention described herein may be manufac tured, used and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION This invention relates to cooking equipment and, more particularly, to a cooking surface or grille heated by the combustion gases from a liquid fuel-fired burner.

Many different types of heating arrangements for cooking surfaces or grilles are known in the art wherein either a portion of the surface or substantially all of the surface is exposed to a source of thermal energy, as for example, by the direct application of flames from gas burners or the conduction of heat from electrical resistance coils. Even with cooking surfaces constructed of highly conductive materials, localized hot spots and uneven heating over the surface is a common problem in the art. It is recognized that the maintenance of an evenly heated cooking surface is highly desirable insofar as this will facilitate the production of uniformly cooked food items. A cooking surface having a uniform temperature throughout is difficult to achieve especially when the source of thermal energy is combustion gas from a liquid fuel-fired source since it has proven to be virtually impossible to effect an efficient and uniform heat exchange from the hot gas to the cooking surface. One such attempt to uniformly heat'a cooking surface using a special combustion gas distribution arrangement is described in US. Pat. No. 3,408,999 which issued to Paul A. Mutchler on Nov. 5, 1968 wherein the combustion gases are first caused to flow around and beneath the peripheral edges of the cooking surface so that the heat will flow from the peripheral edge toward the center of the surface. It is obvious that even with such an arrangement, the temperature at the periphery of the cooking surface will tend to be higher than at the center and that the heat exchange occurring within the relatively large chambers beneath the cooking surface will be somewhat inefficient due to the inability to precisely control the turbulence and flow of gases therein. The invention described herein provides a more precise control on both the direction or location and the quantum of the gas streams and produces a highly turbulent stream which more efficiently gives up heat to the heat exchange surface than does a less turbulent gas stream.

SUMMARY OF THE INVENTION The present invention is concerned with a cooking surface or grille heated by the flow of hot combustion gases which employs a novel arrangement for transferring the thermal energy within the hot gases to the cooking surface. The hot gases are caused to flow in one direction lengthwise of the cooking surface through a series of adjacent inverted V-shaped gastight channels and then enter into connecting adjacent V-shaped channels which alternate with said inverted V-shaped channels and conduct the gases in the opposite direction. Said channels are composed of heatconductive materials. The passage through the channels promotes a turbulent flow of the hot gases which increases the efficiency of heat transfer and the flow of hot gases in opposite directions results in a balancing of the heat output across the surface of the grille by balancing the high temperature at the input end with the relatively low temperature gas at the output end.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view, partially broken away, of a liquid fuel-fired cooking apparatus according to the present invention; FIG. 2 is a sectional view in elevation taken in a plane passing through line 22 of FIG. 1; FIG. 3 is a sectional view in elevation taken in a plane passing through line 33 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 of the drawing, there is illustrated a cooking apparatus according to the present invention comprising a liquid fuel-fired burner in combination with a grille housing.

The liquid fuel burner shown and designated generally as 10 contains a liquid fuel combustor ll of the same type as that described in US Pat. No. 3,408,999. Combustor 11 is centered on a rigid perforated plate 12 located at the upstream end of a rectangular combustion chamber 13 and is connected to an external source of liquid fuel and combustion air under pressure, neither of which are shown in the drawing. Sprayed liquid fuel and air, in addition to excess combustion air passing through the perforated plate 12, are blended and caused to burn within the combustion chamber 13 and the combustion gases are caused to flow, at the downstream end of the combustion chamber, into a combustion products pipe 14. Combustion chamber shroud l5 incloses the combustion chamber and creates an annular space 16 therebetween. A portion of the air supply is forced through annular space 16 cooling the walls of the combustion chamber to prevent overheating. A cylindrical shroud 17 spaced from and inclosing the combustion products pipe 14 allows the flow of cooling air to pass from the annular space 16 through the annular space 19 around pipe 14. At the downstream end of the combustion products pipe 14, the combustion gases and cooling air streams come together to produce a mixture of blended gases having a temperature significantly lower than that of the combustion gases. The blended gases pass through a cylindrical inlet connector 19 into the grille housing 20.

There is disclosed in FIGS. 1 and 2, a grille housing designated generally as 20, rectangular in outline, having a top wall 21 or cooking surface of a heatconductive material, an opposed bottom wall 22 spaced from said top wall and a peripheral side wall 23 between said top and bottom walls defining a hollow chamber 24. A layer of insulation 25 covers the base of the chamber and a metal spacer plate 26 rigidly secured to said peripheral side walls divides the chamber into a lower portion which contains the layer of insulation and a top portion, the hot gas chamber designated generally as 35, which contains the hot gas distribution system. A row of similarly positioned angle irons within hot gas chamber 35 welded to the underside of top wall 21 and the top side of the spacer plate 26 divide the top portion of the chamber 24 in a series of alternating V- shaped 27 and inverted V-shaped 28 gas-tight channels that alternate across the width of the chamber with each channel extending lengthwise of the chamber. The angle irons employed for this purpose have side walls equal in size and have an included angle between said side wall of approximately It is preferred that the base of each channel be not more than 2 inches in width.

The hot gas blend from the burner passes through the cylindrical inlet connector 19 into a rectangular inlet manifold 29 which extends transversely of the chamber 24 at the rear of the cooking apparatus 20. Apertures 30 located in the inlet manifold 29 provide an opening into each of the inverted V-shaped channels 28 allowing the hot gas to flow into and pass as separate streams along each channel 28 toward the front of the grille housing. At this point, each hot gas stream flows from the downstream end of each channel 28 into the next adjacent V-shaped channel 27 through openings 31 in their respective common walls and then flows in the opposite direction down each channel 27 toward the back of the grille housing. The combustion gas streams exit from each channel 27 into a common exhaust manifold 32 located above the inlet manifold and then pass out as waste gas through an exhaust pipe 34. Undersized exit ports 33 in the wall of the exhaust manifold communicate with each of the channels 27 allowing the gas to exit while maintaining a slight back pressure within the channels which aids in promoting turbulence within each gas stream.

In operation, liquid fuel, such as kerosene or gasoline, and combustion air, are delivered to the combuster 11 under pressure and caused to burn within the combustion chamber 13. The temperature of the combustion gases as they exit from the combustion chamber are of the order of 900F. to l,800F. Excess air is caused to flow through the

annular spaces

16 and 18 cooling the walls of the combustion chamber 13 and the walls of the pipe 14, respectively. At the downstream end of the combustion products pipe 14, the combustion gases join and blend with the cooling gases producing a gas mixture that passes through the cylindrical inlet connector 18 at temperatures of about 300F. to l,000F. The hot gas mixture from the inlet connector 19 flows into the inlet manifold 29 and, in turn, via apertures 30 into each of the inverted V- shaped channels 28. The hot gas streams proceed down each channel 28 and at the downstream end pass through openings 31 into the connecting and adjoining V-shaped channel 27. The gas streams exit from each channel 27 via exit ports 33 into the exhaust manifold and then flow to the atmosphere via exhaust pipe 34. The temperature of the gases leaving the exhaust pipe range from 200F to 400F.

It is to be noted that the hot gas circulation beneath the top wall 21 (cooking plate) is such that the gases do not contact the top wall when at their highest temperature but flow through the inverted V-shaped channels 28 isolated from the underside of the top wall. Some of the heat energy from the gas is transferred to the conductive side walls of

channels

27 and 28 so that the temperature of the gas streams declines as each stream continues down its respective channel 28. On their return path through channels 27, the hot gas streams, now reduced in temperature, are now in direct contact with the underside of the top wall and transfer a substantial portion of their thermal energy to said wall. The net result ofthe gas flow, first in one direction and a separate flow in the opposite direction, both flows being in heat conductive relationship, is to balance the heat energy transmitted or applied to the top wall on the cooking surface. The relatively narrow size of the channels in combination with the undersized exit ports 33 entering the exhaust manifold contribute to a slight back pressure within each of the channels which promotes turbulence within each of the gas streams. A turbulent gas stream results in a highly efficient transfer of thermal energy from the hot gas medium to the conductive top wall 21. A system, as described herein, permits the use of liquid-fuel burners which heretofore had been considered to produce temperatures too high for conventional cooking and which are notoriously inefficient both in terms of heat exchange and ability to provide a uniformly heated surface.

I claim: 1. A cooking apparatus comprising a housing having spaced opposed top and bottom walls and an encompassing peripheral side wall extending therebetween to define a hot gas chamber with the surface of the top wall serving as a cooking surface to transfer heat from said hot gas chamber to an article of food to be cooked; gas inlet means in said housing to permit introduction of hot gases into said hot gas chamber;

combustor means cooperating with said gas inlet means generating hot gases which enter said hot gas chamber via said gas inlet means to provide heat for cooking;

gas distribution means. within said hot gas chamber communicating with said gas inlet means to conduct said hot gases in a plurality of separate, parallel and substantially equal streams in a first direction longitudinally within said chamber and continuing in a second direction opposite to said first direction, said streams in said first direction being in heat conducting relationship with said streams in said second direction and said streams in said second direction being in heat conducting relationship with said top wall, said streams being sufficient in number to provide even heat distribution in the transverse direction;

gas outlet means in said housing to receive said gases after completion of travel in said second direction beneath said top wall to discharge said gas from said chamber.

2. A cooking apparatus according to claim 1 wherein said gas distribution means comprises a plurality of alternating V-shaped and inverted V-shaped gas-tight channels which extend lengthwise of said chamber, each of said inverted V-shaped channels connecting with said gas inlet means at one end and connecting with said V-shaped channels at the opposite end whereby the hot gases pass from said inlet means into each of the inverted V-shaped channels through which they flow in one direction and pass into the V-shaped channel flowing in the opposite direction and finally leaving the cooking apparatus through said gas outlet means.

3. A cooking apparatus according to claim 2 wherein said side walls of said channels are heat conductive.

4. A cooking apparatus according to claim 3 wherein the apex of the angle formed by the side walls of said triangular channel is approximately 5. A cooking apparatus according to claim 4 wherein said combustor means is a liquid fuel burning combustor.

6. A cooking apparatus according to claim 5 wherein said housing is of generally rectangular shape.

7. A cooking apparatus according to claim 6 wherein the connection between said V-shaped channel and said gas outlet means is undersized to produce back pressure and promote turbulence in said hot gas streams.

Claims

1. A Cooking apparatus comprising a housing having spaced opposed top and bottom walls and an encompassing peripheral side wall extending therebetween to define a hot gas chamber with the surface of the top wall serving as a cooking surface to transfer heat from said hot gas chamber to an article of food to be cooked; gas inlet means in said housing to permit introduction of hot gases into said hot gas chamber; combustor means cooperating with said gas inlet means generating hot gases which enter said hot gas chamber via said gas inlet means to provide heat for cooking; gas distribution means within said hot gas chamber communicating with said gas inlet means to conduct said hot gases in a plurality of separate, parallel and substantially equal streams in a first direction longitudinally within said chamber and continuing in a second direction opposite to said first direction, said streams in said first direction being in heat conducting relationship with said streams in said second direction and said streams in said second direction being in heat conducting relationship with said top wall, said streams being sufficient in number to provide even heat distribution in the transverse direction; gas outlet means in said housing to receive said gases after completion of travel in said second direction beneath said top wall to discharge said gas from said chamber.

4. A cooking apparatus according to claim 3 wherein the apex of the angle formed by the side walls of said triangular channel is approximately 90*.

5. A cooking apparatus according to claim 4 wherein said combustor means is a liquid fuel burning combustor.