US2897814A - High efficiency portable heater - Google Patents

Description

2 Sheets-Sheet 1 R. A. ANDERSEN HIGH EFFICIENCY PORTABLE HEATER ziw M h V.

Aug. 4, 1959 Filed June 10, 1955 INVENTOR. RALPH A. ANDERSEN ATTORNEY Aug. 4, 1959 R. A. ANDERSEN 2,897,814

HIGH EFFICIENCY PORTABLE HEATER 2 Sheets-Sheet 2 Filed June 10, 1955 INVENTOR.

Fig.8 I 0 2 ATTORNEY RALPH A. ANDERSEN United States Patent 2,897,814 v rnon EFFICIENCY PORTABLE HEATER Ralph A. Andersen, Moline, Ill., assignor to American Air Filter Company, Inc., Louisville, Ky., a corporation of Delaware Application June 10, 1955, Serial No. 514,578

2 Claims. (Cl. 126-110) The present invention relates to improvements in portableair heaters, particularly, of the type illustrated in the specification and drawings of the application for patent of Arthur F. Hubbard, Serial Number 251,215, filed October 13, 1951 for Portable Fluid Fuel Burning Air Heater, now Patent No. 2,744,516 granted May 8,

heat exchanger is subject to excessively high temperatures in spots, and to the eroding action of the flame, which reduces its effective life, and also, carbon is deposited on the walls of the exchanger and reduces heat transfer.

It is an object of the present invention to prevent the formation of ice around the burner nozzle in the combustion chamber at low atmospheric temperature.

Another object is to prevent heating the metal of the heat exchanger to excessive temperatures.

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

In accordance with one feature of the present invention, provision is made for directing a flow of hot air around the tip of the fuel nozzle of the burner, so as to maintain a temperature at the tip to prevent ice build up. In the preferred construction, there is provided an air chamber adjacent the nozzle tip discharginginto the combustion chamber, and air is conducted to this chamber through a tube or tubes that pass through the combustion zone, so the air flowing through the tube is heated. As the nozzle is designed to produce a whirling spray, it is preferred-to have this heated air enter the air chamber about the nozzle tangently, so as not to interfere with the spray, and to produce a better wiping effect and better penetration across the nozzle face.

In accordance with another feature of the invention, combustion is improved and confined to the combustion chamber by a series of baflles. The preferred arrangement comprises an annular bafile ring spaced from the wall of the combustion chamber so as to allow flow of heated air around the exterior edge of the ring; in conjunction with a target baflle in alignment with the central opening of the annular baflle, to spread the flame, and a throttling bafile at the end of the combustion chamber. By confining combustion to the combustion chamber, erosion of the heat exchanger walls is greatly reduced or eliminated.

The invention Will be described in greater detail in the following specification taken in connection with the 2,897,814 Patented Aug. 4, 1959 ICC accompanying drawing illustrating preferred embodiments of the invention by way of example, and wherein:

Figure 1 is a fragmentary view, partly in section, of a heater to which the invention pertains;

- Figure 2 is an enlarged plan view, partly in section, of the combustion chamber showing the invention applied thereto;

Figure 3 is a sectional view taken on line IIIIII of Figure 4;

Figure 4 is an end elevation of the combustion chamber cover, as seen from the left of Figure' 2;

Figure 5 is a side elevation of Figure 4, viewed from the left;

Figure 6 is a front elevational view with parts broken away, of the combustion chamber;

Figure 7 is a detail of the annular plate;

Figure 8 is a front elevation of the bafile plate;

Figure 9 is a front elevation of the nozzle mounting casting; and

Figure 10 is an enlarged fragmentary section taken along line 10-10 of Figure 2.

Referring to the drawing, in Figure 1 there is partly diagrammatically illustrated a type of heating apparatus to which the invention relates. The heater comprises an outer cylindrical jacket 1 having a cylindrical heat exchanger 2 within the jacket held in spaced relation thereto'by U-shaped braces 3 so as to provide an air passageway 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 flow 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 apertures 16, 17 (Figs. 2 and 4) are provided in the cylindrical wall and cover respectively of the combustion chamber for admission 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 application above identified. The fan directs air past the straightening vanes 21 into a plenum chamber 22. From this chamber air flows into the air passages 4, 12, of the heat exchanger, and through the apertures 16, 17 in the wall and cover 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 type are designed to be operated in arctic regions, where atmospheric temperatures as low as -65 F. are encountered, and employ gasoline as the fuel. Notwithstanding the high temperature attained in the combustion chamber, the cold gasoline sprayed under pressure from the nozzle cools the nozzle so that 'rnoisture freezes thereon and builds up a cylinder of ice that interferes with the proper flow of fuelspray from the nozzle. The feature of the invention directed to preventing ice formation about the nozzle now will be described.

Referring to Figure 4, the dished cover 14 of the combustion chamber has a casting 25 riveted thereto which provides a middle opening 26 to receive the burner nozzle 15, and has an upper threaded opening 27 to receive a spark plug not shown. An electrode 28 is carried by the casting for cooperation with the spark plug,

Sloping' baffles 29 are welded to the inside surface of the cover to deflect air entering holes 17, centrally toward the nozzle. The opening 26 has a tapered seat 31 (Figure 3) atits ends against which the nozzle abuts, and the nozzle passes through opening 32 and extends partly into chamber 33. The nozzle 15 terminates in aJface 34 (Fig. 9) surrounding an orifice which ;directs a fuel spray through the opening 35 in the cover into the combustion chamber. Chamber 33 has'recesses 36, 37 which merge tangentially with the chamber.

The cover has an opening 38,.and a generally U-shaped tube 39 has one end in this opening, secured thereto as by welding, the other end of the tube passing through an opening in the cover into recess 36 of chamber 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. Theplate 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 turbulent preheating zone 50 in which air entering holes 17 in the cover and 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. 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.

This plate 51, which is made of a heat resisting substance or alloy such as Hasteloy X, deflects the flame radially outwardly. Flame flows through annular space 47 and into zone 55, where it impinges on and breaks up the flame moving radially from plate 51. Also, air

' enters through holes 16 opposite to the radial movement of the flame to add to the turbulence. A choke plate 56 is provided at the open end of the combustion chamber, where it joins the heat exchanger. As the baffle plate 51 spreads the flame its velocity is diminished so-that combustion is eifectively completed in the combustion chamber and only the hot products of combustion enter the heat exchanger. This eliminates or reduces carbon deposits on the walls of the heat exchanger, thus maintaining efiicient heat transfer and increasing the efiective life of the heat exchanger.

I claim as my invention:

1. An improved construction for air heaters of the type having outer casing means defining a substantially enclosed space, a combustion chamber casing disposed within said outer casing means and partially occupying said space, a cover plate for said combustion chamber casing with a nozzle receiving opening therein surrounded by an annular recess thereabout, a fuel nozzle having a surface containing a fuel spray discharging orifice mounted in said nozzle receiving opening axially of said annular recess for introducing a fuel spray into said combustion chamber casing, and air impelling means for directing a flow of unheated air within said space and against the front side of said cover plate, said construction comprising a plurality of generally U-shapedconduit members disposed entirely within said combustion chamber and exposed to flame impingement therein, each of said conduit members having inlet means extending through said cover plate and exposed to the space on the front side thereof to receive a portion of saidflow of incoming unheated air externally of said combustion chamber casing and outlet means positioned to discharge said incoming air through said plate in heated condition into said annular recess and in substantially tangential relation to said orifice containing surface of said fuel nozzle to prevent ice formation thereon when said units are used in severe cold weather operations without substantial interference with said fuel spray discharge therefrom.

2. In a heater, the combination comprising an elongated hollow casing defining a combustion chamber provided with an end wall at one end having a nozzle receiving opening therein surrounded by an annular recess thereabout, a nozzle centrally mounted in said opening axially of said annular recess having a surface containing a fuel spray discharging orifice therein to introduce a conically shaped spray of fuel into said casing, an annularly shaped flame baffle plate having a centrally disposed aperture therein disposed substantially perpendicular to the longitudinal axis of said chamber and spaced from said nozzle a distance permitting its aperture defining inner edge to intercept and deflect the peripheral portion of said conical spray to maintain the same within the portion of said chamber disposed intermediate said end wall and said baffle plate, and an air heating conduit disposed within said portion of said combustion chamber intermediate said end wall and said annular baflie plate, said air heating conduit having inlet means extending through said end wall positioned to receive incoming air externally of said combustion chamber and outlet means positioned to discharge said incoming air in heated condition into said annular recess and in substantially tangential relationship to said orifice containing surface of said nozzle to prevent ice formation thereon when said units are used in severe cold weather operations.

References Cited in the file of this patent UNITED STATES PATENTS

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