US2110334A - Superheater - Google Patents

Description

March 8, 1938. w KNlGHT 2,110,334

' SUPERHEATER Filed Jan. 27,1937 2 Sheets-Sheet 2 Eiga 63 I nveW/Zo r.-

mzwam alrnzg m Patented Mar. 8, 1938 UNITED STATES PATENT OFFICE 1 Claim.

This invention relates to superheaters more particularly for use in connection with locomotive boilers of the type wherein the superheater tubes project rearwardly from the smoke box 'into fire tubes of the boiler, and the object is to provide an improved construction of superheater, among other things applicable to existing locomotives, giving adequate superheat while at the same time providing for the delivery to the cylinders of steam at a pressure greaterthan is effected by superheaters as hitherto known.

My'invention will be well understood by reference to the following description of the illustrative embodiment thereof shown by way of example in the accompanying drawings, wherein:

Fig. 1 is a transverse section on two planes through the smoke box of a locomotive having my superheater applied thereto looking rear- Wardly toward the front flue sheet of the boiler;

Fig. 2 is a part section, part plan, of the header shown in Fig. 1;

Fig. 3 is a longitudinal section on the line 3-3 of Fig. 2;

Fig. 4 is a plan view of one of the superheater units;

Fig. 5 is an enlarged vertical section of a part of one of the superheater units; and

Fig. 6 is a fragmentary plan thereof on the same scale.

Locomotive superheaters of the type comprising a header across the top of the smoke box providing a chamber for the reception of saturated steam from the dry pipe and of superheated steam for discharge to the cylinders and superheater tubes connecting the same and extending into the flues of the boiler are well known. As at present constructed they have been de veloped on the theory that it is necessary to pass the steam through the heated zone in small columns to effect the necessary heat exchange. Hence superheater tubes of relatively small diameter have been disposed either with multiple loops in a single flue or with successive loops disposedserially in a number of adjacent fiues. The resulting great friction causes a marked loss of pressure in the steam as delivered to the cylinders, hitherto accepted as inevitable. In accordance with my invention by a proper balance of constructional features I provide for the passage of steam in larger columns through shorter paths and under much lower velocity. While thus departing from conventional methods of construction, I have demonstrated by actual dynamometer car tests that, while obtaining an equal degree of superheat, the cylinder horse power available when using a superheater designed as described indetail hereinafter,. is throughout a wide range of piston speeds as greatly in excess of that ordinarily afforded by the conventional type of commercial superheater now in use as is thehorse power resulting from that type of superheater, in excess of the horse power developed by use of saturated steam alone without any superheat.

Referring now to the drawings, I have there shown partially the smoke box of a locomotive boiler to which open through the front flue sheet I fire tubes or flues 9, at least certain of which, arranged generally in vertical and horizontal ranks, are of such diameter as to be adapted to receive therein superheater tubes. In the upper portion of the smoke box parallel to the flue sheet is disposed a. cast steel header ll, best shown in Fig. 2, divided by the serpentine partition l3into a saturated steam chamber having an intake port l5 communicating with the dry pipe from the steam dome and a saturated steam chamber having oiftak'e ports I! by which the superheated steam is led to the cylinders. Steam from the former compartment is delivered to the latter through superheater tubes l9 disposed in the flues and each comprising a single U-shaped loop extending'into the flue, the path of the steam being, in contrast with the conventional practice, from the saturated steam chamber through the single loop in a single flue and hence directly to the superheated steam chamber.

The tubes I9 are of substantially the maximum size which can thus be accommodated in the flue, and this may be expressed by saying that the combined width of the two legs of the loop (see Fig. 4) is substantially equal to the internal diameter of the flue 9 which receives them.

For constructional reasons it is desirable to gang up or manifold together certain of the superheater tubes, but only under conditions providing for substantially uniform distribution of steam through the various loops and free flow of the same. I have found it possible tocombine the loop tubes in units of which there is one corresponding to every flue of a rank extending in one direction, herein the horizontal rank, and corresponding tonot more than two of the other rank, herein two of the vertical rank. In the construction shown the connections whereby the superheater tubes proper are connected to the header comprise sections of tube 2! of suitable length and of a cross sectional area equivalent to that of two superheater tubes. Thus by way of example and without limitation, where the tubes I!) are of two-inch external diameter and with a wall of nine-gauge metal on the Birmingham wire gauge, the tube 2| may be of two and seveneighths inch external diameter and of the same wall thickness. The tubes 2| pass vertically through the staggered openings 23 in the lower wall of the header H (Fig. 2) and are expanded therein. To permit this the upper wall of the header opposite the openings 23 has aligned openings closed by the plugs 25 and access may be had to these by means of a removable section 21 (Fig. 1) of the boiler shell. The lower ends of the tubes 2| are connected by welding to cast steel fittings 29 which are extended downwardly and sweep forwardly in an easy curve with a gradual taper to substantially the diameter of the superheater tube. The end of the tube l9 may have, immediately outward of the flue sheet, as best seen in Figs. 3 and 4, an easy curve through a vertical angle complementary to the angle formed by the curve of the lower portion of the fitting 29, with which may be combined a curve in a horizontal plane, as seen in Fig. 4, providing for proper spacing of the fitting at the ends of the loop, and then be continued for a short distance in a right line to align with the reduced end of the fitting to which it is welded. The tube l9, fitting 29. and tube 2| are thus autogenously united in an integral whole free of mechanical joints and 'a smooth and uninterrupted passage from the header to the tube is provided through which the steam can flow with minimum friction. The other leg of the tube is connected to a similar fitting connected by a similar length of tube 2| with the superheated steam chamber of the header.

To provide for the accommodation of two superheater tubes in each set of the tubular connections, the larger upper portion of the fitting 29 is formed laterally thereof and at an angle parallel to the tapered, forwardly curved, lower end thereof with an extension 3| which tapers toward the forward end thereof substantially to the size of the superheater tube l9, and the end of the superheater tube in the immediately overlyingflue 9 is welded to this extension. It will thus be seen that in the example of the invention illustrated there is a pair of. steam connections, a saturated steam connection and a superheated steam connection, for each two flues of a vertical row, and such a set of two pairs for each flue of the horizontal row as will be apparent by a comparison of Figs. 1 and 2. Since there is a natural tendency for the steam to flow in a straight line, causing unequal distribution of the steam passing through the lower unit as compared with the upper evenwhen only two tubes are compounded, I provide for equalizing the flow of steam through the lower and upper superheating loops. As best shown in Figs. 5 and 6, such means may comprise an interior flange for directing a flow of steam into the upper loop, herein organized as a transverse partition 33 at the enlarged upper end of the fitting which merges with the lowermost part of the wall of the extension 3i.

Referring to Fig. 2, it will be noted that on the removal of any of the tubes for inspection or repair where the units which supply the lower pair of tubes are removed by cutting the pipes 2|, usually near their upper ends where they are most subject to erosion or the tubes 19 near where the ends enter the fittings 29, the tubes, suitably cut to length, and the fittings may be moved; up to form a unit serving the upper set of two flues, thus providing a considerable economy in use.

By means of the construction shown I provide an inexpensive and light construction with a minimum number of joints to cause trouble either by loosening under vibration or by burning under the temperatures involved and provide for the substantially even flow of steam in relatively large columns subject to a minimum amount of friction and corresponding maintenance of pressure at a sufliciently low velocity to provide for the heating thereof to the desired degree of superheat. The construction of the down-comer connections shown does not mask the forward end of theflues and they can be positioned sufllciently close thereto without interfering with the draft through the flues so that the portions of the tubes exposed to the cooler gases which are found in the smoke box are so short that there is'no objectionable loss of superheat.

I am aware that the invention may be embodied in other specific'forms without departing from the spirit or essential attributes thereof, and I therefore desire the present embodiment to be considered in all respects as illustrative and not restrictive; reference being had to the appended claim rather than to the foregoing description to indicate the scope of the invention.

I claim:

In combination with a boiler having a fire tube barrel provided with superheater flues arranged in vertical and transverse ranks and opening to a smoke box, a header in the smoke box across the top of the barrel and divided into chambers for saturated and superheated steam, the lower wall of said chambers having openings, tubular steam connections secured in said openings, superheater tubes each comprising a single U- shaped loop disposed in a flue, the tubes being of such cross section. that the combined width of the two legs thereof corresponds substantially to the internal diameter of the flue, the legs of the tube being connected respectively to connections communicating respectively with the saturated and superheated steam chambers, there being a pair of connections corresponding to each flue of a horizontal rank and each pair of connections accommodating tubes from a plurality of fiues of a vertical rank and means for equalizing the flow of steam from each saturated steam connection into the tubesappurtenant. thereto comprising internal guiding flanges within the down-comers.

WILLIAM G. KNIGHT.

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