US3073684A

US3073684A - Gas purifying muffler

Info

Publication number: US3073684A
Application number: US817236A
Authority: US
Inventors: Sr David P Williams
Original assignee: Individual
Current assignee: Individual
Priority date: 1959-06-01
Filing date: 1959-06-01
Publication date: 1963-01-15
Anticipated expiration: 1980-01-15

Description

15, 1963 D. P. WILLIAMS, SR 3,

GAS PURIFYING MUFFLER Filed June 1, 1959 INVENTOR. 5,4 V/D P W/LL/AMJ, 5/2

QZiLVW A T TORNE Y5 United States Patent Calif.

Filed June 1, 1959, Ser. No. 817,236 7 Claims. (Cl. 23-477) The present invention relates generally to the cleaning of exhaust gases from automotive combustion engines and the like, and is particularly directed to improvements in exhaust gas purifying mufiier elements as disclosed in my copending applications Serial Numbers 691,369; 712,962, now US. Patent No. 2,956,865; and 763,940, now U.S. Patent No. 3,042,499.

With the recent emphasis placed upon the correction of health endangering air pollution, particularly in highly populated areas, many devices have been developed for cleaning the exhaust gases of the ever increasing multitude of automobiles and other motor vehicles in concentrated operation in such areas. It has long been hoped that a relatively economical device could be developed for universal employment upon these automobiles, trucks, buses, and the like to the ends of effectively removing noxious fumes and smoke and other objectionable substances from the gases exhausted from the engines thereof, as well as the usual accomplishment of noise mufiling. With such a device in universal automotive employment, one of the foremost, if not the principal source of present day air pollution would be eliminated.

Unfortunately known exhaust gas purification devices have suffered from various shortcomings in design which render the devices insufficiently efficient and reliable in operation to reduce air pollution to the desired extent.

More particularly, the basic operating principle of most gas purification devices is to fully eliminate the normal air polluting constituents such as carbon monoxide, hydrocarbons, aldehydes and the like of the incompletely burned fuel exhausted from internal combustion engines by further burning or reacting of the exhaust gases to completion. In the accomplishment of the foregoing, known gas purifiers have utilized a burning chamber or after-burner in conjunction with an ignition flame at high temperature to ignite exhaust gases introduced to the chamber and maintain the chamber at a high temperature conducive to substantial further burning of the gases. The burned gases are then exhausted from the burning chamber through the exhaust or tail pipe of the automotive vehicle and usually provision is additionally made to muffle the attendant exhaust noise. In prior gas purification devices it has not been possible to reliably sustain the flame and chamber at a sufficiently high minimum temperature, e.g., of the order of 2000 degrees Fahrenheit, to insure complete burning or reacting of exhaust gases during all stages of engine operation whether steady state or changing. In addition, the ignition flame has been subject to quenching by the exhaust gases entering the chamber at extremely high velocity during various stages of engine operation. These deficiencies seriously detract from the efliciency and reliability of the device for exhaust gas cleansing, a substantial portion of unburned air polluting exhaust gas being able to issue from such a device because of incomplete, or at times the flame is quenched, no after burning of the exhaust gas. Aside from the difficulty heretofore encountered in establishing the requisite minimum high temperature at the burning chamber it has been difiicult to provide burning The present invention overcomes these previously encountered inadequacies and disadvantages by the provision of an improved exhaust gas purifying muffler which insures the complete combustion of exhaust gas Without regard to engine operating conditions and for practicable periods of use without replacement. Particular advantage herein lies in the provision of structure which is capable of withstanding, and provides for the continued maintenance of extremely high temperatures in a combustion chamber and the continuous burning of an ignition flame under all operating conditions.

it is an object of the present invention to provide means for preventing the escape of exhaust gases from an internal combustion engine without their complete combustion whereby the removal of air polluting constituenrs is insured.

Another object of the present invention is to provide an economical exhaust gas purifying muffler which will satisfactorily function under all conditions of engine op eration and for extended periods of use without requiring maintenance or replacement.

A very important object of this invention is the provision of superheating means in exhaust gas purification apparatus for concentrating heat in the burning chamber thereof and thereby establishing an extremely high minimum temperature therein at which complete combustion of exhaust gases is assured.

Another extremely important object of the present invention is the provision of an exhaust gas purifying muffier including means for decreasing the momentum of entering exhaust gases in the region of the ignition flame thereof to prevent quenching of the flame by the gas.

It is a further object of this invention to provide an exhaust gas purifying mutller which is relatively cool at its exhaust end and from which the complete combustion products are exhausted at relatively low temperatures.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of the preferred form of the invention which is illustrated in the drawing accompanying and forming part of the specification. It is to be understood, however, that variations in. the showing made by the said drawing and description may be adopted within the scope of the invention as set forth in the claims.

Referring to said drawing:

FIGURE 1 is a cross sectional view in a median plane along the axis of an improved exhaust gas purifying muffler in accordance with the present invention;

FIGURE 2 is a transverse sectional view taken on the plane 2-2 of FIGURE 1, and

FIGURE 3 is a transverse sectional view taken on the plane 33 of FIGURE 1.

Considering now the invention in some detail and referring to the illustrated form thereof in the drawing, there is generally provided an improved gas purifying mufller 11 including an exhaust gas receiving chamber 12 of novel construction adapted to decrease the momentum of exhaust gases as received from an automotive internal combustion engine or the like for introduction to a firing chamber 13. A burner 14 is disposed at one end of the firing chamber to establish an ignition flame of extremely high temperature therethrough for igniting the exhaust gases of decreased momentum entering thereinto. By virtue of the decreased momentum of the gas entering the fin'ng chamber, quenching of the ignition flame by the gases, as would occur at the full velocity and quantity flow of exhaust gases at entry into the receiving chamber 12 under various stages of operation of the engine, is prevented. The ignition flame extends also into a burning chamber 16 which adjoins the firing chamber 13 and into which the ignited exhaust gases flow for completion of combustion. In order to insure that the combustion ofthe exhaust gases be conducted to full completion in the burning chamber 16, it is necessary for the temperature therein to be maintained at an extremely high minimum, of the order of 2009 degrees Fahrenheit, for all conditions of operation. Such a high minimum temperature has been heretofore entremely difficult if not impossible to establish and maintain in previous exhaust gas cleansing devices. However, in the improved muflier 11 of the present invention the attainment of such a high minimum temperature is ft.- cilitated by means of an exhaust chamber 17 which is arranged to convey the gaseous combustion products from the burning chamber to an outlet such as the tail pipe 18 of the motor vehicle and at the same time superheat the combustion products to the ends of concentrating heat in the burning chamber. More particularly, the combustion products are directed from the burning chamber 16 through a circuitous passage 19 in the exhaust chamber 17 which extends into heat exchange relation with the firing chamber 13 and then into heat exchange relation with the burning chamber 16. The combustion products are hence superheated by a surplus of heat in the firing chamber and the superheated combustion products deliver their heat to the burning chamber in transit to the tail pipe 13 to hence concentrate heat in the burning chamber and maintain a high temperature thereat. Such structural arrangement of the exhaust chamber 17, moreover, facilitates discharge of the combustion products to the tail pipe 18 at relatively low temperature and maintains the exterior portions of the muflier relatively cool.

With regard to the details of preferred structure of the improved exhaust gas purifying mufller 11, same is preferably enclosed by an outer cylindrical shell 21 closed at one end by a transverse closure face 22 centrally apertured as shown generally at 23 to receive the tail pipe 18 of previous mention. 'The walls of the shell 21 are best, double and constructed of spaced inner and outer thermally conducting

jacket members

24, 26 of. for example thin stainless steel sheet, with a layer 27 of high temperature withstanding refractory material interposed therebetween. A particularly suitable layer material which is able to withstand temperafares to 4200 degrees Fahrenheit has been found to be a ceramic known commercially as Purolay and manufactured by Mexico Refractories of Emeryville, Calif. The other end of the outer shell 21 is best outwardly flanged as at 28 to facilitate attachment of a front closure plate 29, of for example stainless steel, thereto as by means of bolts .31. The front plate 29 is hence detachable from the shell 21 and serves to mount various elements'of the mufiler as subsequently described for disposal interiorly of the shell.

The exhaust gas receiving chamber 12 of previous mention which very advantageously serves to decrease the momentum of entering exhaust gases to the end of eliminating quenching of the ignition flame is outwardly defined by an elongated hollow cylinder 32 of heat conducting structural material such as stainless steel. The cylinder is closed at both ends and has diametrically opposed

central apertures

33, 34 in its respective end faces. The cylinder 32 extends coaxially through the front end plate 29 of outer shell 21 from an external position forwardly of the plate to an internal position at substantially the transverse median plane of the shell. The cylinder 32 is firmly secured to the plate 29, as by welding, so as to be concentrically enclosed by outer shell 21 when the plate 29 is secured thereto. The receiving chamber 12 is inwardly defined by an elongated tube 36 extending coaxially through the aperture 33 in the rear end face of cylinder 32 and terminating at the front end face thereof. Tube 36 includes an enlarged stepped portion 37 at its' terminating intersection with the front end face for purposes subsequently described.

4 The tube also inwardly defines the firing chamber 13 of previous mention and it is thus to be noted that the receiving chamber 12 is annular and concentrically surrounds the firing chamber.

Considering now the manner in which the above described structural arrangement of receiving chamber 12 and tiring chamber 13 is employed to decrease the momentum of exhaust gases prior to introduction to the firing chamber, an exhaust gas inlet pipe 33 communicates radially with the receiving chamber 12 through the periphery of cylinder 32 at a point opposite stepped portion 37 of tube 36. Exhaust gases from an engine are thus discharged through the pipe 38 radially into the receiving chamber 12. The portion of the tube 3 rearwardly from the stepped portion 37 is provided with a large number of closely spaced perforations 39 such that radial communication is thereby provided between the receiving chamber 12 and firing chamber 13. The exhaust gases discharged from the inlet pipe 33 radially into the front end of the receiving chamber 12 are hence deflected and turned at right angles by the stepped portion 37 and again turned at right angles in discharging from the receiving chamber 12 through the perforations 39 radially into the firing chamber 13 as depicted by the arrows in FIGURE 1. A portion of the energy of the exhaust gases is expended in changing flow direction in this manner during passage through the receiving chamber into the firing chamber and the velocity of the exhaust gases is hence materially reduced. In addition, the gases are broken up into many small streams in passing through the perforations 39 such that the mass of the gases is distributed over a large volume of the firing chamber. The reduction in velocity and distribution of mass of the exhaust gases hence results in a material decrease in the momentum of same at entry into the firing chamber 13.

Combustion of the exhaust gases entering the firing chamber 13 is initiated and maintained by means of the burner 14 hereinbefore mentioned. The burner includes a burner nozzle'41 which communicates with the firing chamber 13 at the front end thereof through a tube 42 coaxially engaging the aperture 34 in the front end face of cylinder 32. A fuel line 43 connects a fuel supply 44 to the nozzle and an air line 46 connects the nozzle to a source of pressurized air (not shown). The air and fuel are intimatelymixed in the nozzle 41 and ejected therefrom into the firing chamber as a highly combustible mixture. The burner 14 further includes a spark plug 47 or equivalent means for igniting the fuel mixture upon entering the front end of the firing chamber to establish" an intense steady high temperature flame extending therethrough. By virtue of the extremely high temperature of the flame, particularly at its point of origin, the tube 36 is fabricated from extremely high temperature withstanding metal, preferably Inconel, and an annular ceramic block 48, preferably of Purolay ceramic, is disposed concentrically within stepped portion 37. Radially aligned bores are provided through the peripheral walls of cylinder 32, tube 36, and ceramic block 48 for receiving the spark plug 47 such that the electrodes 49 thereof extend into the front end of the firing chamber 13 proximate the burner nozzle 41. Suitable electrical power supply means (not shown) provides spark plug energization through leads 51 to cause the ignition spark between the electrodes 49 which ignites the combustible mixture from the nozzle to establish the flame longitudinally rearward through the firing chamber 13. The exhaust gases entering the firing chamber rearwardly of the burner 14 are in turn ignited by the flame with quenching of the flame by the entering gases being prevented due to the reduc-- tion in their momentum effected in passing through the receiving chamber 12.

The ignited exhaust gases flow from the firing chamber 13 into the adjoining burning chamber 16 for completion of combustion, and the ignition flame extends therea into to support such complete burning. In the preferred structural embodiment, the burning chamber 16 is disposed within the outer shell 21 coaxially rearward of the firing chamber 12. By virtue of the extremely high temperatures concentrated at the burning chamber in accordance with various of the salient aspects of the present invention, the chamber is defined by a hollow cylindrical block 52 of high temperature withstanding refractory material, preferably the Purolay ceramic material of previous mention. Tube block 52 is closed at its rearward end and has inner and outer diameters substantially equal to the outer diameters of the tube 36 and cylinder 32 respectively. The inner cylindrical wall of the forward end of the block concentrically engages the periphery of tube 36 which projects axially for a short distance beyond the rear end face of cylinder 32. The block and cylinder faces are thus placed in abutting engagement such that the block in effect forms a coaxial extension of the cylinder and the burning chamber 16 interiorly defined thereby is in axially aligned communication with the firing chamber 13 interiorly defined by the tube 36. The ignition flame produced by burner 14 thus extends axially into the burning chamber 16 to heat same to high temperatures and support burning to completion of the ignited exhaust gases entering from the firing chamber 13.

The resulting combustion products of the burned exhaust gases are discharged from the burning chamber 16 for exhaust through the tail pipe 18. As hereinbefore mentioned, the combustion products are not discharged directly to the tail pipe, but rather are advantageously employed in conjunction with the novel exhaust chamber 17 as a superheated heat exchange medium to concentrate heat in the burning chamber whereby temperatures are attained therein at which complete combustion of exhaust gases are insured. The foregoing is preferably accomplished by the provision of a plurality of axially elongated circumferentially spaced slots 53 extending radially through the block 52 to provide communication between the burning chamber 16 and exhaust chamber 17 which is defined by the annulus existing between the block 52, and cylinder 32, and the outer shell 21. In addition an intermediate cylindrical shell 54, closed at its rearward end, is disposed within exhaust chamber 17 concentrically between the block 52, cylinder 32, and outer shell 21 with the inner face of the rear end thereof in abutment with the outer rear end face of the block. The intermediate shell 54 extends longitudinally forward to a position proximate the front closure plate 19 and is rigidly secured in spaced relation thereto by means of a plurality of standoff legs 56 projecting from this plate. The intermediate shell 54 hence partitions the exhaust chamber in such a manner as to form the circuitous passage 19 of previous mention therethrough for conveying the combustion products into heat exchange relation with the firing chamber 13 and then into heat exchange relation with the burning chamber. More particularly, the combustion products discharged radially through the slots 53 enter the inner portion of the passage 19 annularly defined between the block 52, cylinder 32 and intermediate shell 54 and are hence directed in an axially forward direction as indicated by the arrows in FIGURE 1. In passing over the surface of cylinder 32 the combustion products are superheated by virtue of the substantial amount of heat transmitted thereto from the firing chamber 13 by radiation as well as direct metallic conduction. The super-heated combustion products in turn pass through the end portion of passage 19 transversely defined between the front rim of intermediate shell 54 and front closure plate 29 to then enter the outer portion of the passage annularly defined between the intermediate shell and outer shell 21. The superheated combustion products are directed rearwardly through the outer portion of passage 19 and through the transverse end portion between the closed ends of intermediate and

outer shells

54, 21 respectively to the tail pipe 18. In passing over the intermediate shell 54, the superheated combustion products deliver their heat thereto and a large portion of this heat is transmitted by direct conduction to the burning chamber defining block 52 and concentrated thereat. The temperature in the burning chamber 16 is thereby maintained at an extremely high minimum tem perature heretofore unrealizable which supports complete burning of the exhaust gases with absolutely reliability. Moreover, inasmuch as a substantial amount of heat is conducted from the combustion products during their passage through the exhaust chamber, the temperature of the products at discharge through the tail pipe 18 is relatively cool.

In order that the intermediate shell 54 withstand the extremely high temperatures of the combustion products constantly passing over its surfaces, it is to be noted that such shell 54 is best constructed similarly to outer shell 21. More specifically, the intermediate shell is preferably of double wall construction comprising spaced inner and outer thermally conducting

jacket members

57, 58, of for example thin stainless steel sheet, with a layer 59 of high temperature withstanding refractory material, preferably Purolay ceramic, interposed therebetween. The refractory material of the intermediate and

outer shells

54, 21 respectively, moreover, provides a very strong noise-mufiling action to the exhaust from the engine of the automotive vehicle with which employed.

There is thus provided by the present invention an im proved exhaust gas purifying muffler for automotive em ployment in which the exhaust gases are reliably burned to absolute completion. The partially burned exhaust gases discharged from an internal combustion engine into the inlet pipe 38 to the mufiler for ignition in the firing chamber 13 by the flame issuing from burner 14, are first passed through the novel momentum reducing receiving chamber 12 wherein the exhaust gas momentum is diminished to the extent that all likelihood of quenching of the burner fiame by the gas entering the firing chamber is eliminated. The ignited exhaust gases enter the burning chamber 16 into which the burner flame also extends and are therein combusted to completion. An extremely high temperature in excess of 2000 degrees Fahrenheit is maintained in the burning chamber by virtue of the unique exhaust chamber 17 surrounding same which provides superheating of combustion products discharged from the burning chamber and transfer of the heat back to the burning chamber during passage of the combustion products to the tail pipe 18. With this high temperature, not only is poisonous carbon monoxide burned to harmless carbon dioxide, but aldehydes and other undesirable exhaust gas constituents are substantially entirely eliminated. The combustion products are discharged in an extremely purified non air polluting relatively low temperature condition from the tail pipe 18. The refractory and high temperature withstanding metal construction of the muffler 11, moreover, facilitates long periods of service without maintenance or requiring replacement.

What is claimed is:

l. Exhaust gas cleansing muffler means comprising a closed outer cylindrical shell, an elongated closed hollow cylinder extending coaxially through 'a first end of said shell a substantial distance into the interior thereof, an elongated open ended tube concentrically disposed within said cylinder and defining therewith an inner cylindrical firing chamber concentrically enclosed by an outer annular receiving chamber, said tube having a plurality of perforations distributed over a substantial internal end portion of the periphery thereof, an exhaust gas inlet communicating with said cylinder at a point radially opposite the unperforated end portion of said tube, a burner disposed at the unperforated end portion of said tube for generating an ignition flame axially through the firing chamber defined by the tube, a hollow cylindrical block amnes a end of the block and spaced longitudinally inward from said second end of said outer shell while having an open end spaced longitudinally inward from said first end of said outer shell to define a superheating exhaust chamher, and an exhaust outlet communicating with said exhaust chamber through the second end of said outer shell.

2. Exhaust gas cleansing muffier means as defined by claim 1, further defined by said tube being of Inconel and said block being of ceramic material capable of withstanding temperatures of the order of 4200 degrees Fahrenheit. v

3. Exhaust gas cleansing mufiier means as defined by claim 1, further defined by said outer and intermediate shells each com-prising spaced inner and outer thin metallic jackets with a layer of high temperature withstanding ceramic material interposed therebetween.

exhaustgas purifying mufiier comprising a closed outer cylindrical shell having spaced double metal lie walls with alayer of high temperature withstanding ceramic material interposedtherebetween, an elongated hollow metallic cylinder closed at both ends and extending coaxially through the front end of said shell a substantial distance into the interior thereof, an elongated open-ended tube of Inconel concentrically disposed within said cylinder and having an enlarged stepped portion at the fron-t end thereof, said tube having a plurality of perforations distributed over the reduced diameter peripheral portion thereof, an exhaust gas inlet pipe adapted for connection to the exhaust system of an internal combustion engine and extending radially through the peripheral wall of said cylinder at a point opposite the enlarged stepped portion of said tube, an annular block of extremely high temperature withstanding ceramic mater'ial concentrically recessed within the enlarged stepped portion of said tube at the inner periphery thereof, burner means disposed within the front end of said tube proximate said annular block for directing a high temperature self-supporting flame longitudinally rearward through said tube, a hollow cylindrical block of high temperature withstanding ceramic material concentrically dis posed within said outer shell, said block having an open front end connected in coaxial communication with the rear end of said tube and a closed rear end spaced longitudinally inward from the rear end of said shell, said block having a plurality of axially elongated circumferentially spaced slots extending radially through the periphery thereof, a hollow cylindrical intermediate shell having a spaced double metallic Walls with a layer of high temperature withstanding ceramic material interposed therebetween and disposed concentrically about said cylindr ical block in radially spaced relation therewith, said intermediate shell having a closed rear end in abutment with the rear end of the cylindrical block and spaced longitudinally inward from the rear end of said outer shell while having an open front end spaced longitudinally inward from the front end of said outer shell, and an exhaust pipe communicably connected atv the center of the rear end of said outer shell. I

5. An exhaust gas purifying muffier as defined by claim 4, further defined by said burner means comprising a nozzle disposed coaxially at the front end of said tube for spraying a combustible fuel-air mixture axially rearward theret'nrough, anda spark plug extending through said annular block with the spark plug electrodes communicating with the interior of the tube to ignite said combustible mixture and establish said high temperature flame.

6. An exhaust gas purifier comprising a cylindrical tube defining a firing chamber, a hollow cylindrical block having a closed end and an open end secured in coaxial communication to one end of said tube to define a burning chamber extension of said firing chamber, said block of refractory material and having radial passages through the periphery thereof, a burner coaxially secured to the distal end of said tube relative to said block for generating and projecting a flame coaxially through said firing chamber and into said burning chamber extension, exhaust gas inlet means communicating with said firing chamber through said tube intermediate said burner and burning chamber extension, means defining an annular passage concentrically about said block and tube and in heat exchange relation therewith, said annular passage "communicating with said radial passages and extending longitudinally therefrom to a position adjacent said burner, and means defining a second annular passage concentrically about said first annular passage and in heat exchange relation therewith, said second passage radially communicating atone end with said first passage at said position adjacent said burner, said second passage extending longitudinally along the entire length of said first passage to terminate in an exhaust outlet adjacent said block.

7. An exhaust gas purifier according to claim 6, further defined by said exhaust gas inlet means comprising means defining an annular receiving chamber concentrically interposed between said tube and first annular passage and in heat exchange relation therewith, said receiving chamber in radial communication with said firing chamber through a plurality of radial gas flow passages through said tube, and an exhaust gas inlet radially communicating with said receiving chamber at a position longitudinally displaced from said gas flow passages whereby exhaust gas entering the receiving chamber through the inlet means is twice turned at right angles and bro-ken up into plurality of separate distributed streams in passing through the passages into the firing chamber.

References Cited in the file of this patent UNITED STATES PATENTS 1,605,484 Thompson et al. Nov. 2, 1926 1,839,880 Hyatt Jan. 5, 1932 2,203,554 Uhri et al June 4, 1940 2,492,947 Bellstedt Jan. 3, 1950 2,753,925 Campbell et a1. July 10, 1956

Claims

1. EXHAUST GAS CLEANSING MUFFLER MEANS COMPRISING A CLOSED OUTER CYLINDERICAL SHELL, AN ELONGATED CLOSED HOLLOW CYLINDER EXTENDING COAXIALLY THROUGH A FIRST END OF SAID SHELL A SUBSTANTIAL DISTANCE INTO THE INTERIOR THEREOF, AN ELONGATED OPEN ENDED TUBE CONCENTRICALLY DISPOSED WITHIN SAID CYLINDER AND DEFINING THEREWITH AN INNER CYLINDRICAL FIRING CHAMBER CONCENTRICALLY ENCLOSED BY AN OUTER ANNULAR RECEIVING CHAMBER, SAID TUBE HAVING A PLURALITY OF PERFORATIONS DISTRIBUTED OVER A SUBSTANTIAL INTERNAL END PORTION OF THE PERIPHERY THEREOF, AN EXHAUST GAS INLET COMMUNICATING WITH SAID CYLINDER AT A POINT RADIALLY OPPOSITE THE UNPERFORMATED END PORTION OF SAID TUBE, A BURNER DISPOSED AT THE UNPERFORATED END PORTION OF SAID TUBE FOR GENERATING AN IGNITION FLAME AXIALLY THROUGH THE FIRING CHAMBER DEFINED BY THE TUBE, A HOLLOW CYLINDRICAL BLOCK HAVING ONE CLOSED END AND DISPOSED CONCENTRICALLY WITHIN SAID OUTER CYLINDERICAL SHELL WITH THE OPEN END OF THE BLOCK IN COAXIAL COMMUNICATION WITH THE INTERNAL END PORTION OF SAID TUBE AND THE CLOSED END INWARDLY LONGITUDINALLY SPACED FROM THE SECOND END OF THE SHELL, SAID BLOCK DEFINING A BURNING CHAMBER AND HAVING A PLURALITY OF AXIALLY ELONGATED CIRCUMFERENTIALLY SPACED SLOTS EXTENDING RADIALLY THROUGH THE PERIPHERY THEREOF, A HOLLOW CYLINDRICAL INTERMEDIATE SHELL DISPOSED CONCENTRICALLY ABOUT SAID BLOCK AND RADIALLY SPACED THEREFORM, SAID INTERMEDIATE SHELL HAVING A CLOSED END IN ABUTMENT WITH THE CLOSED END OF THE BLOCK AND SPACED LONGITUDINALLY INWARD FROM SAID SECOND END OF SAID OUTLER SHELL WHILE HAVING AN OPEN END SPACED LONGITUDINALLY INWARD FROM SAID FIRST END OF SAID OUTER SHELL TO DEFINE A SUPERHEATING EXHAUST CHAMBER, AND AN EXHAUST OUTLET COMMUNICATING WITH SAID EXHAUST CHAMBER THROUGH THE SECOND END OF SAID OUTER SHELL.