US2982346A - High efficiency portable heater - Google Patents

Description

May 2, 1961 R. A. ANDERSEN HIGH EFFICIENCY PORTABLE HEATER Filed Nov, I 16, 1958 ATTORNEY INVENTOR RIALPH A. ANDERSEN Kaat-T gbr/Ele Illll IIIIIIIII May 2, 1961 R. A. IANDERsr-:N

HIGH EFFICIENCY PORTABLE HEATER 2 Sheets-Sheet 2 Filed Nov. 6, 1958 INVENTOR. RALPH A. ANDERSENl ATTORNEY 2,932,346 j HIGH ErrlcmNcY PORTABLE rmArE Ralph A. Andersen, Moline, Ill., assignor to American Air Filter` Company, Inc., Louisville, Ky., a corporation of Delaware `Filed Nov. 6, 1958, Ser. No. 772,378

9 Claims. (Cl. 158-4) The present invention relates to improvements in portable air heaters, particularly, of the type illustrated in the specification and drawings ofthe application for uatent of Arthur F. Hubbard,.Serial Number 251,215, filed October 13, 1951 for Portable Heater, now Patent No. 2,744,516 grantedMay 8, 1956, and is a continuation in part of'my application Serial No, 514,578 iiled June 10, 1955 now United States Patent 2,897,814, granted Aug. 4, 1959. l- Heaters of this type employ gasoline as fuel and are intended for use in Arctic climates where air temperatures as low as -65 are encountered. One difficulty encountered is that when ice crystal suspensions are present in the air at lowatmospheric temperatures, ice builds up around the burner nozzle in the combustion chamber and interferes with the flow of the `fuel sprayed into the chamber. Another difficulty encountered is that because the combustion chamber is short, combustion may extend into the Aheat exchanger so `that the heat exchanger is subject to excessively high temperatures in spotsand to the eroding action of the llame, which reduces itseffective life, and also, carbon is deposited on the walls of the exchanger and'reduces heat transfer. An object of the present invention is to preventV heating the metal of the heat exchanger to excessive temperatures. i

. Another object is to confine combustion substantially to the combustion` chamber so as to prevent or reduce erosionv of the heat exchanger surfaces.

.In`accordanceiwith one feature of the invention,.com bustion is improved and conlned to the combustion charnber by a seriesk of` bafes. The preferredy arrangement comprises an annular baie ring spaced fromV the wall of the Acombustion chamber so as to`allow flow of heated air around the exterior edge of the ring; in conjunction with a target `baille in alignment with thecentral `opening ofi the annularbale, to spreadthefflamqand a throttling baffle at the end of the combustion chamber. By continng 'combustion tofthe. combustion chamber, erosionbf the heat exchangerwalls is greatly reduced or eliminated. 1 f 'f 1. The Vinvention `will be described in greater detail in 551911681 Patent 2,982,346 Patented May 2, 1.961

to by U-shaped braces 3 so as to provide an air passage-A way 4 between the outer jacket and the outer wall of the heat exchanger. The heat exchanger has a cylindrical peripheral wall with an opening therein where the stack 5 is attached, and has `end walls 6 and 7, the latter providing an opening 8 where the combustion chamber 9 is attached in any suitable manner. The heat exchanger is made up of tubes 11 extending longitudinally and lune-shaped in cross section, the tubes being arranged spirally and providing passageways 12 for 110W of air to be heated through the heat exchanger. Between the tubes are spaces 13 extending spirally to the periphery so as to carry the products of combustion to the stack.

The combustion chamber'9 carries a detachable cover plate or cap 14 in which is secured a suitable burner nozzle 15, and varying sized apertures 16, and relatively small aperture 17 (Figs.V 2 and 4) are provided in the cylindrical wall and 'cover respectively of the combustion chamber foradmission of air to support combustion. The air is supplied by a fan or blower 18 (Fig. l) driven by a suitable motor 19, the fan and motor being detachably mounted as described and claimed in the first application above identified.

The fan directs air past the straightening vanes 21 into a plenum chamber 22. From this chamber air ows into the air passages 4, 12, of the heat exchanger, and through the varyingsized apertures 16, in the wall and the relatively small apertures 17 in the cover 14 of the combustion'chamber. A suitable duct, not shown, may be connected `to the end 23 of the heater to conduct heated air where desired.

Heaters of this typeV are designed to be operated vin arcticregions, where atmospheric temperatures as low as -65 are encountered, and employ gasoline as the fuel. Notwithstanding the-high temperature attained in the cornbustion chamber, the cold gasoline sprayed under preslsure from the nozzle cools the nozzle so that-moisture freezes thereon and builds up a cylinder of ice that interferes with the proper ow of fuel spray Vfrom the nozzle, The feature of the invention directed to preventing icegformation-about the nozzle now will be described. Y

the following specication taken in connectionwith the accompanying .drawing illustrating preferred embodiments of lthe invention'by Wayoffexamplegand wherein;y

Figure l lis` a fragmentary view, partly in section, of a heaterto which the. invention pertains;Y I

a FiguresZ is an enlarged plan view, partly in section, ,V

Referring to Figurep4, Athe dished cover 14 of thecombustion chamber has a casting 25 riveted thereto which provides a middle opening 26. to receive the burner nozzle15, and has an upper threaded opening 27 to receive aV spark Vplug not shown. An electrode 28 is carried by the casting forVV cooperation with the spar-k plug. Sloping bafes 29 are Weldedto theinside surface of the cover eoV Y trallytowardjthe nozzle. Theopening 26` has a-tapered seat 31 (Figure 3) at its ends against which the nozzle to deflect air entering the relatively rsmall, holes 17, cenabuts, and the nozzle passes through opening 32 and l extends partly into `chamber 33;. The nozzle 1S termi,

. Figure 4is atrend elevation of the combustion" chamber cover, as seen from the'left of Figure 2; ,K A ,Figure Sis ia side elevation' =of `Figure, 4, viewed; from theleft; v l .i g if.

, `Figure 6 ,is a frontl elevational view-with parts A brolzen wanatthe eombustsachembeu Y' nates'fin a face34 (Fig. 9) surrounding an orilice whichY directs-fa line spray through the opening 35 in the cover 'into the combustionchamber. Chamber 33:` has` recesses 36, 37 which merge tangentially with the chamber.` n, .1' I`he cover has an openingA 38, and a generally U- shaped tube 39 has onefendin thisopening, secured ,thereto'as by.weldingthe ohernd `of the tube passing throughj an wins in thaw inte met 36.. 0f the @einen aasaaw 33. A similar U-tube 41 extends from opening 42 into chamber 33. It will be seen that the tubes 39, 41 extend into the combustion chamber so that, air supplied by blower 18 enters the tubes by' openings 38, 42 and is heated as it passes through the tubes. The air' thus heated is discharged into chamber 33 to heat the fuel nozzle tip enough to prevent ice build up on the nozzle. By having the heated air enter chamber 33 more or less tangentially, the interference with the spray issuing from the nozzle is minimized, and the heated air has a better and more extensive wiping action.

Adjacent the nozzle end of the combustion chamber is mounted an annular plate 45 extending diametrically across the chamber, and having its flanged outer edge 46 spaced from the chamber wall as indicated at 47.

This plate is constructed of a heat resistant alloy, such as, for example, Hasteloy X, which is an alloy of chromium, nickel and silicon. It is supported from the wall of the combustion chamber by a series of angular rods 48 riveted at one end to the plate and at the other end to the wall of the combustion chamber 9. The plate 45 is so located, and the opening 49 in the plate is of such size as to allow part of the fuel spray to pass through, and part to impinge against the plate, so the part of the chamber between this plate and the cover provides a forward combustion zone 50 in which air entering of the relatively small holes 17 in the cover and the relatively small holes 16a in the forward combustion zone is mixed with the fuel.

Beyond plate 45 in alignment with the opening 49 is located a second imperforate flanged plate 51 supported from the wall of the combustion chamber by rods 52 which extend through openings in the chamber wall. The plate 51 is also constructed of a heat resistant alloy, such as, for example, the Hasteloy X referred to above. Certain of the rods 52 are grooved as indicated at 53, and receive a spring clip 54 to hold the rods in place. The third rod floats free to allow for temperature contraction or expansion changes.

The imperforate baflle plate 51 should preferably be of a peripheral configuration that corresponds with that of the aperture 49 in the annular balle plate 46. Moreover, it is desirable that the extent or size of said plate 51 in dimension transverse to the longitudinal axis of the combustion chamber 9 approximate that of the aperture 49 and preferably, as illustrated in the drawings, be of a transverse dimension that is somewhat less than that of the aperture 49.

The openings 16a in thewall of the combustion charnber disposed intermediate the annular baille plate 45 and the cover plate 14 are made relatively small. In

contradistinction therewith, at least a plurality of the apertures disposed in the portion of the combustion chamber wall disposed on the downstream side of the baille plate 45 are made appreciably larger, such as the illustrated (Figure 2) openings 16b located in the combustion chamber wall intermediate the annular bale -plate 45 and the imperforate baille plate 51 and the openings 16e` located in the combustion chamber wall intermediate the imperforate baffle plate 51 and the orifice plate 56 that is disposed at the junction of the combustion chamber 9 and the heat exchanger 2. The large apertures 16b and 16e thus permit the major portion of combustion air to be introduced downstream of the annular bafile plate 45.

The above described sizing and spacing of the baille members 45 and 51 together with the number and locat r3. is utilized for temperature control purposes. In a unit of the character described, fuel turndown ratios in the order of about to l or greater are obtainable, thus providing a degree of control that has not been heretofore obtainable in combustion structures constructed in accordance with the teachings of the art.

In order to obtain the turndown ratios of the order specified above it is necessary to permit the introduction of sufllcient air to burn the minimal amounts of fuel introduced and to introduce said air in such manner as not to snuff out a small flame, Also, since at very low temperatures gasoline will not vaporize, it is necessary to start combustion by the amount of heat produced at tion of the varying sized apertures 16a, 16b and 16e cooperate to contribute materially to the advantages and results that flow from practice of the herein described invention. Y

One of the advantages obtained through utilization of the above described structure and structural interrelationships is a combustion'unit employing a constant llame `andin which modulation of the volume of vfuel the spark electrode gap. If excess quantities of air are introduced adjacent the spark gap enough heat will not be generated there in opposition to the low air temperatures to vaporize the fuel as well as to ignite the same. Consequently it is also necessary to introduce the air in such manner as to permit vaporization and ignition when extremely small quantitles of fuel are being introduced.

These desirable objectives are readily achieved in the disclosed structure and structural interrelationships. Inherent in the above described construction is the provision of the forward combustion zone 50 which includes that portion of the combustion chamber 9 disposed intermediate the annular baille plate 45 and the cover plate 14. This structure serves as a means to effectively contain an extremely small flame when the amount of fuel introduction is reduced and the volume of spray emerging from the nozzle is at minimal value. Cooperating to produce the above described novel results is the selective provision of only relatively small air intake openings 16a in the walls of the combustion chamber 9 in said zone 50 and the provision of only relatively small air intake openings 17 in the cover plate 14 with their associated dellecting plates 29 which are positioned to direct the intake air flowing through said aperture 17 away from nozzle 15 and the conically shaped spray emerging therefrom.

The number and sizing of the apertures 16a and'17 serve to limit the amount of low temperature intake air selectively introduced into the zone 50 to that sufficient to support combustion of minimal amounts of fuel and additionally prevents the spark gap ignition and vaporization problems mentioned above. .The deflecting plates 29 serve to direct the incoming air away from the spray cone and away from the envelope of flame produced at low firing rates thus preventing snuff out thereof and still permit introduction of sufficient air into the zone 50 to mix'with the fuel during periods of maximum fuel introduction. Without the above described structure forming the forward combustion zone 50 and the selective air intake means therefore the entire unit would run cold at low rates of fuel introduction and the 'cover plate 14 would, in turn, also become cold and the preheating of the nozzle would be defeated with resultant -ice formation thereon and consequent inop erability of the unit.

- YAnother advantage attendant the herein described structure is the minimization of the throwing of portions of the ambient or partially burnt gases to the outside shell ofthe combustion chamber wherein they are subjected to cooling the thereby cause deposits of partially combusted material as a result of arrested combustion. In combustion units of the confined combustion shell type such as herein conceived, the described baffle system contributes materially to the prevention of the flame from assuming a long, tongue-like configuration or torch shape, which producesso-called wet combustion wherein actual wet particles of unburned fuel plus fly ash particles emerge fromV the flame at high lvelocity and impinge upon the heat exchanger surfaces with a resulting deleterious and destructive acid corrosion effect. The disposition of the baille 51 serves to prevent the flame from spiraling into a long narrow torch axially to the combustion chamber.

spray and deflect the same back into the forward com-l bustion zone 150 to increase the rate of heatjtransfer to the conduits 39 and141 and thereby provide additional quantities of heat to prevent the icing effects on the nozzle occasioned by theincreased passage of low temperature fuel therethrough.; The batlie 51 will intercept the inner perip'aheral.portions of ,the conically shaped sprayv passing through the aparture 49 anddeect the sam'e outwardly into intimate engagement withthe combustion air entering through the apertures 1Gb. The air entering lthrough the apertures 16b in the form of jets aids vin the complete combustion of `therdetlected spray and also contributes toithe'combustion thereof at a'location spaced inwardly from the shell surface. u l t n Y- "Theaboveidescribed sizingY and spacing of the baies 45,'and151 permitsthemaior portion Qf the ccnical. Spray to pass the baffle 51 without impingement thereon and to come into proximity with the combustion air entering through the relatively large apertures 16h and 16a to effect complete combustion thereof. The orifice plate 56 cooperates with a nal row of apertures 16d, which serve to furnish a curtain of combustion air through which the flame must pass before emerging from the combustion chamber 9. The plate 56 serves to prevent the ame from hugging the wall of the chamber 9 by forcing it inf wardly wherein the above mentioned air curtain can mix therewith for nal combustion before emergence from the combustion chamber. apertures'lb, the relatively large apertures 16e on the downstream side of the baille 51 serve to permit the introduction of relatively large quantities of air which in turn aids in minimizing flame impingement upon the inner surface of the combustion chamber 9.

The annular baiiie 45, in addition to dening the above Also as was the caserwith the.

Y plate-so as to be struckby a portion of the tlamepassing through said aperture therein; and means forforcing air through said perforate outer wall into said combustion chamber 'to support combustion of the fuel introduced therein., j 1

. 2. In a heater, they combination comprising an elongated hollow casing defining a combustion chamber provided with an end wall at one end, a nozzle centrally mounted on said `end wall to introduce a conicallyv shaped spray of fuel into said casing, an annularly shaped flame baie plate disposed substantially perpendicular to the longi-v tudinal axis of said chamber and spaced from said nozzle a distance permitting its aperture defining innerpedge to intercept and deflect the outer peripheral portion of said conical spray and a ame bale disc disposed substantially perpendicular to the longitudinal axis of said chamberland spaced from said annular baffle plate a distance permitting the same VVto intercept and deflect-the inner portion of said spraypassing through said annular baffle plate.

(3. The combination as set forth in claim 2 including orifice defining means disposed at the end of said chamber'remote from said end wall and adjacent air' curtain forming means to yinsure complete fuel combustion ad' jacent thereto at a location removed from said combustion chamber surface.

4. In an air heater the combination comprising an elongate cylindrical combustion chamber having a perforate circumferential wall for admission of air thereinto, a cover plate closing one end of said chamber having a fuel spray burner mounted thereon for introducing a conically shaped spray of fuel into said chamber, an

described forward combustion zone 50, serves also to dene a path for counter current air flow from the zone 55 to the zone 50 in the annular space 47 intermediate the anged edge 46 thereof and the wall of the combustion chamber 9. Although the underlying reasons are not clearly understood, the provision of this counter current flow path and the induced flow of air therethrough from the zone 55 to the zone 50, appears to inhibit the tendency of the ame to assume an undesired torch pattern during relatively high rates of fuel introduction.

Having thus describedk my invention, I claim:

1. In an air heater, the combination vcomprising an elongate cylindrical combustion chamber having a perforatev circumferentialfouter wall for admission of air thereinto, and open at one end to provide communicationy `with an adjacent heat exchanger, a spray burner centrally disposed at the opposite end of said chamber in substantial axial alignment with the longitudinal axis thereof for introducing a conically shaped spray of vfuel into said chamber, an` annular ame Vbaffle plate disposed substantially perpendicular to the longitudinal axis of said chamber and intermediate said nozzle and the center of said chamber, said annular baflie plate shaped to provide a peripheral space intermediate its outer edge and the is positioned to intercept and deect the peripheral portion of said conically shaped spray of fuel and flame to maintain the same within the portion of the chamberv proximate the size -of the aperture in said annular plate 65. chamber' wall and ay central aperture whose defining edge disposed substantially"perpendicular to the longitudinal axis of said Achamber and spaced from said annular bathe annular baie plate disposed substantially perpendicular to the longitudinal axis of said chamber and in spaced relation intermediate said cover plate and the center of said chamber to define a'forward combustion zone disposed therebetween, said annular baflie plate having a centrally disposed aperture therein with its aperture dening inner edge positioned to intercept and deflect the outerV peripheral portion of said conical spray to maintain the same within said forward combustion zone and to permit the central portion thereof to pass therethrough, the circumferential wall of said combustion chamber having relatively small perforations therein in the portion thereof included in said forward combustion zone and relatively large perforations therein downstream of said annular plate for limiting the amount of Y combustion air introduceable into said zone to support selective combustion therein at relatively low rates'of fuel introduction to said burner.

5. The combination as set forth in claim 4 wherein said cover plate includes a plurality of relatively small perforations therein disposed remote from said burner and means adjacent said apertures to deflect the air introduced therethrough toward the circumferential wall of said combustion chamber.

6. In an air heater-the combination comprising an elongate cylindrical combustion chamber having a c ircumferential Vwall with a'plurality of aperturestherein for admission of air thereinto, and open at one end to provide communication with an adjacent heat exchanger, A

positioned intermediate said lcover plate and the center of said chamber and defining,` with said adjacent por- .tions of said chamber, a forward combustion zone disposed'therebetween, said annularly shaped baffle platetde-V finng a central aperture sized to intercept and deflect the peripheral portion of said conical spray and permit Y the central portion thereof to pass therethrough, a second flame baliie plate sized to approximate thesiz'e of the aperture in said annulaibale'plate and of a similar shape therewith disposed vsubstantially perpendicular to the longitudinal axis of said chamber and spaced from said annular baille plate so as to be struck `by the inner `peripheral portion of the llame passing through said aperture therein, said combustion chamber having a plurality of relatively small apertures therein the portion thereof defining said forward combustion zone and a plurality of relatively large apertures therein in the portion thereof disposed intermediate said annular baille plate and said open end for effecting the majority of air introduction into said chamber through said relatively large apertures and means for forcing air through said apertures to support combustion of fuel introduced into said combustion chamber.

7. The combination as set forth in claim 6` wherein said cover plate includes a plurality of relatively small perforations therein disposed remote from said burner and means adjacent said apertures to deect the air introduced therethrough circumierentially adjacent the inner surface of said cover plate.

8. The combination as set forth in claim 6 including orifice defining means disposed at the open end of said chamber and adjacent vto a plurality `of apertures to insure mixture of said .fuel with air introduced through said apertures `and complete'combustion of fuel at a .location removed from said combustion chamber surface.

9. The -combination as set forth in claim 2 wherein said casing is provided with a plurality of relatively small perforations in the portion thereof disposed intermediate said annularly shaped baille plate and said end wall to admit relatively small -amounts of combustion air to the portion of .said chamber deiined thereby and a plurality of relatively larger perforations in the portion thereof disposed intermediate said annular baille plate and said baille disc -to admit relatively larger amounts of combustion air to the portion of said chamber defined thereby.

rReferences Cited in the file of this patent UNITED STATES PATENTS 1,322,999 Bester Nov. 25, 1919 V1,515,295 Bogre Nov. 11, 1924 2,287,057 Page June 23, 1942 42,368,179 Turpin Jan. 30, 1945 2,518,364 Owen Aug. 8, 1950 UNITED STATES PATENT OFFICE CERTIFICATE 0F `CORRECTION Patent No. 2,982,346 May 2, 1961 Ralph A, Andersen It is hereby certified that'error appears in the shove numbered patent requiring correction and that the said Letters Patent4 should read as corrected below. Y,

Column l, line 18, for "uatent" read patent l line 30, before "flow," insert proper column 2, line 7l, for "oher" read other column 4, line 63, for "the" read and column 5, line l5, for "aperture" read aperture column 7, line 7, after "therein" insert in f Signed and sealed this 17th day of Octoberl 1961,

(SEAL) Attest:

ERNEST W. SWIDEE DAVID L. LADD Attesting Officer Commissioner of Patents USCOMMDC-

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