Improvements in Air Heaters and in the Apparatus and Appliances for Facilitating and Accelerating Combustion in the Furnaces of Steam Generators.
Year: 1897

page_text: Date of Application, 7th Apr., 1897
Complete Specification Left, 7th Feb., 1898-Accepted, 7th Apr., 1898
PROVISIONAL SPECIFICATION.
Improvements in Air Heaters and in the Apparatus and Appliances
for Facilitating and Accelerating Combustion in the Furnaces of
Steam Generators.
I, WILLIAM HENRY WATKINSON, of "The Pines," Crookston, near Glasgow,
Professor of Prime Movers, in the Glasgow & West of Scotland Technical College,
Glasgow, do hereby declare the nature of this invention to be as follows:-
The objects of my invention are, firstly, to reduce the cost and increase the
efficiency of air heaters; secondly, to increase the temperature of the air supplied
to boiler furnaces beyond that to which it is raised in the air heater, and to reduce
the amount of air required for combustion; thirdly, to an improved combination
for the supply of heated air to boiler furnaces.
My improved air heater consists of a number of sheets of metal or other suitable
substance, arranged parallel to each other at short distances apart in such a way
that they together with the casing containing them form a series of parallel passages
or flues, through every alternate one of which the products of combustion pass and
through the others the air passes on its way to the furnace. At or near each end
of the heater suitable distributing and collecting boxes, or branches, are fixed for
distributing separately the furnace gases and air into their respective passages
and collecting them after they have passed through the heater. The products of
combustion from the boiler enter one of these boxes, and after passing through
the heater and giving up part of their heat to it they enter their collecting box at
the other end, and from this box they are led to the chimney. Similarly the air
enters one of the boxes, passes through the heater and into the collecting box at
the other end and thence to the furnace. The heated air may be supplied to the
furnace either above or below the grate, or partly above and partly below, suitable
valves being provided so as to vary the amount supplied both above and below the
grate.
The parallel sheets of the air heater may be either plane or corrugated. When
they are plane, special transverse rods, or projections, are placed in the various
passages, at suitable distances apart for the purpose of causing more rapid and
thorough mixing of the parts of each stream, with the object of increasing the
These
rapidity of the transference of heat to and from the walls of the passages.
transverse projections, or rods also give increased stiffness to the walls.
Suitable doors are provided for enabling the flues of the air heater to be cleaned
and examined.
In order to still further increase the temperature of the air after it has passed
through the heater I arrange to mix with it a portion of the products of com-
bustion in their hot state, as they leave the boiler and before they have been cooled
by the air heater. This may be accomplished by placing the fan, or steam blower,
between the air heater and the furnace and letting it draw the air through the
heater and some of the hot products of combustion as they leave the boiler to mix
with the air.

page_text: In another modification the stream of air after passing through the heater may
be utilized, as in a jet pump, to induce a flow of some of the hot products from the
boiler, and in this way the air will be raised to a higher temperature by the mixing
with these hot products. When this latter method is adopted the fan or blower
may be placed in any convenient position, either forcing the air into the air heater
directly, or into a closed stokehold, or it may draw the products from the heater.
When the chimney draught is sufficient the fan or blower may, of course, be dis-
pensed with. A suitable valve is provided for the regulation of the amount of
hot products mixed with the air. As with the above described arrangements the
temperature of the air supply is very much higher than usual I prefer to use water-
tube fire bars in the boiler.
When a fan is used its shaft bearings may be kept cool by sending some of the
feed or circulating water through them. Wherever high pressure water is avail-
able I arrange to drive the fan by means of a Pelton water wheel or other suitable
hydraulic motor and in these cases part of this water is used for cooling the fan
shaft bearings. This method of driving the fan by means of a hydraulic motor
will be especially advantageous on board large warships and in all other cases
where power is distributed hydraulically.
Improvements in Air Heaters and in the Apparatus and Appliances
for Facilitating and Accelerating Combustion in the Furnaces of
Steam Generators.
I, WILLIAM HENRY WATKINSON, of The Pines, Crookston, near Glasgow,
Professor of Engineering, in the Glasgow and West of Scotland Technical College,
Glasgow, do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by
the following statement:-
The objects of my invention are:-Firstly, to reduce the cost and increase the
efficiency of air heaters; secondly, to increase the temperature of the air supplied
te boiler furnaces beyond that to which it is raised in the air-heater, and to reduce
the amount of air required for combustion; thirdly, to obtain an improved com-
bination for the supply of heated air to boiler furnaces.
My improved air heater consists of a number of sheets of metal, or other suitable
substance, arranged parallel to each other at short distances apart, in such a way
that they, together with the casing containing them, form a series of parallel
passages or flues through every alternate one of which the products of combustion
pass and through the others the air passes on its way to the furnace. At or near
each end of the heater suitable distributing and collecting boxes, or branches are
fixed for distributing separately the furnace gases and air into their respective
passages and collecting them after they have passed through the heater. The pro-
ducts of combustion from the boiler enter one of these boxes and after passing
through the heater and giving up part of their heat to it they enter their collecting
box at the other end, and from this box they are led to the chimney. Similarly
the air enters one of the boxes, passes through the heater and into the collecting
box at the other end and thence to the furnace. The heated air may be supplied
to the furnace either above or below the grate, or partly above and partly below,
suitable valves being provided so as to vary the amount supplied both above an

page_text: below the grate. The parallel sheets of the air heater may be either plane
or corrugated. When they are plane special transverse rods or projections are
placed in the various passages, at suitable distances apart for the purpose of causing
more rapid and thorough mixing of the parts of each stream, with the object of
increasing the rapidity of the transference of heat to and from the walls of the
passages. These transverse projections, or rods also give increased stiffness to the
walls.
Suitable doors are provided for enabling the flues of the air heater to be cleaned
and examined.
In order to still further increase the temperature of the air after it has passed
through the heater I arrange to mix with it a portion of the products of combustion
in their hot state as they leave the boiler and before they have been cooled by the
air heater.
This may be accomplished by placing the fan, or steam blower, between the air
heater and the furnace and letting it draw the air through the heater and some of
the hot products of combustion as they leave the boiler to mix with the air.
In another modification the stream of air after passing through the heater may
be utilized, as in a jet pump, to induce a flow of some of the hot products from the
boiler, and in this way the air will be raised to a higher temperature by mixing
with these hot products. When this latter method is adopted the fan or blower
may be placed in any convenient position, either forcing the air into the air heater
directly, or into a closed stokehold, or it may draw the products from the heater.
When the chimney draught is sufficient the fan or blower may, of course, be dis-
pensed with. A suitable valve is provided for the regulation of the amount of hot
products mixed with the air. As with the above described arrangement the tem-
perature of the air supply is very much higher than usual, I prefer to use water-tube
firebars in the boiler.
When a fan is used its shaft bearings may be kept cool by sending some of the
feed or circulating water through them. Wherever high pressure water is avail-
le I arrange to drive the fan by means of a Pelton water wheel or other suitable
hydraulic motor, and in these cases part of this water is used for cooling the fan
shaft bearings. This method of driving the fan by means of a hydraulic motor
will be especially advantageous on board large warships and in all other cases where
power is distributed hydraulically.
The nature of my invention will be better understood by reference to the accom-
panying three sheets of drawings, in which the same letters refer to similar parts
throughout the several views.
On Sheet I Figs. 1, 2, and 3 illustrate one form of my improved air-heater.
Fig. 1 is a front elevation.
Fig. 2 is an end elevation.
Fig. 3 is a plan shewing part of the casing cut away at "
"
The products of combustion after leaving the boiler enter the air-heater by the
distributing box or chamber at a, flow through the passages shewn in black and
leave by the collecting box or chamber at b.
The air to be heated enters by the distributing boxes at "c" and "c" flows
through the passages shewn in white, and leaves by the collecting boxes at "d"
and "d."
The air thus heated is then led by suitable conduits to the boiler furnaces.
Figs. 6 and 6, Sheet I, shew one method of connecting the sheets of metal so as
to form the flattened tubes or flues of which the heater is built up.
Fig. 6 is a plan of one of these flattened tubes and Fig. 6 is a transverse section
on the line M N Fig. 6. In this case the sheets are kept at the proper distance

page_text: form an air heater as shown, for a modified form of tube, in Figs. 9 and 10
Sheet II, also in Figs. 13, 14 and 15 Sheet III. The products of combustion flow
through the spaces between the tubes thus built up and encased.
Doors are provided in the casing to facilitate the removal of soot and ash.
Suitable boxes or chambers are fitted at each end of the air heater for distribut-
ing the air and products of combustion to their respective passages in the heater
and similar chambers are provided for collecting them after they have flowed
through these passages. These chambers are shown at a, b, c, d, Fig. 1, Sheet I;
Fig. 9, Sheet II., and Figs. 13 and 14, Sheet III.
Fig. 4, Sheet I, shows another method of preparing the sheets of which the
tubes are built up. In this case each tube is made out of one sheet of embossed
metal. This sheet is then bent about the line s t, and formed into a tube, as
illustrated in Figs. 7 and 8, Sheet I, which show two such tubes in transverse
section. The longitudinal joint may be made by rivetting, as shown in Fig. 7;
by means of set-screws, as shown in Fig. 8, or by welding. Fig. 5 is a longitudinal
section of one of these tubes. The embossed parts of the sheets may be cup-shaped
instead of being as in Fig. 4.
A. modified form of the heater is shown by Figures 9 and 10, Sheet II. Fig. 9
is an elevation and Fig. 10 is a plan with part of the casing cut away at e.
Figs. 11 and 12, Sheet II show the form of the flattened tubes used in this
modification. The part of the sheets J J¹ M M is corrugated, but the parts J K L M
and J K L M¹ are left plane for convenience in fitting the parts together.
The dotted lines in Fig. 11 indicate the positions of the distance strips in every
alternate flue. These distance strips are for the same purpose as the distance strips
already described and illustrated by Figs. 6 and 6*, Sheet I, and the joints may be
made by any of the means described in connection with those figures. Instead of
using strips, as and for the purpose just described, the edges of the sheets may be
flanged and these flanged sheets may be connected together either by rivetting or
welding the flanges. A number of tubes thus formed are placed, at suitable
distances apart, within a casing, as shown in Figs. 9 and 10, the air flowing through
the tubes and the products of combustion flowing through the spaces between the
tubes, as indicated by the arrows.
When it is desirable to fix the flattened tubes, constructed in any of the ways
herein described, into tube-plates I prefer to do so by casting the tube plates on to
the tubes, the latter being supported at suitable distances apart during the process.
In another modification the tube plates may have flanged holes formed in them
for the reception of the tubes.
Figs. 13, 14, and 15, Sheet III, show both these methods of fixing the tubes into
tube plates. The tube-plate P P¹ is cast on to the tubes T, and the tube plate P₂ P3
has flanged holes formed in it for the reception of the ends of the tubes.
The transverse section of the heater Fig. 15, Sheet III, shows tubes of the three
types illustrated by Figs. 64, 7 and 8 Sheet I, placed within the same casing. In
this case the tubes are held at the proper distances apart by corrugations in the
sheets M, M, and N2 N3 of the casing, Fig. 15, Sheet III.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is:
1. An air-heater consisting of a number of parallel corrugated sheets of metal
and a suitable casing constructed in the manner and for the purposes substantially
as herein described and illustrated by the figures in the accompanying two sheets
of drawings.
2. An air-heater consisting of a number of plane parallel sheets of metal and a
suitable casing in combination with transverse rods or projections placed in the
various passages, in the manner and for the purposes substantially as herein
described.

page_text: 3. The arrangement and combination of parts for the mixing of a portion of the
hot products of combustion with the heated air supplied to the boiler furnaces, in
the manner and for the purposes substantially as herein described.
4. The combination, in connection with steam boilers, of a fan driven by a
Pelton wheel, or other suitable hydraulic motor, in the manner and for the purposes
substantially as herein described.
3. The arrangement and combination of parts for the cooling of the bearings of
the fan shaft in the manner and for the purposes substantially as herein described.
Dated this Fifth day of February 1898.
CRUIKSHANK & FAIRWEATHER,
Chartered Patent Agents,
62, St. Vincent Street, Glasgow, Agents.