US2038813A - Air preheating system - Google Patents

Description

April 1936- I F. F. TOWNSEND 2,038,813

AIR PREHEATING SYSTEM Filed July 28, 1932 lNVEN TOR FT w/zsend Patented Apr. 28, 1936 UNITED STATES PATENT OFFICE 5 Claims.

The objects of this invention are to provide a practical and efiicient system for preheating the air for combustion in furnaces, particularly in marine installations; to utilize the waste heat of 5 the stack in the preheating operation; to combine the ventilation of the fireroom with the preheating action; to control the stack for effecting better combustion, even burning fire, and the like.

These objects are attained by the novel features of construction, combinations and relations of parts hereinafter described and broadly claimed.

The drawing accompanying and forming part 15 of the specification illustrates certain practical embodiments of the invention, but it is to be understood that the structure may be modified as regards such disclosure within the true spirit of the invention and broad scope of the claims.

Fig. 1 is a broken transverse cross-section and Fig. 2 is a broken longitudinal section illustrating the invention incorporated in a marine installation, Fig. 2 appearing as on line 2-2 of Fig. 1.

Fig. 3 is a horizontal sectional view as on substantially the plane of line 33 of Fig. 2.

Fig. 4 is a top plan and Fig. 5 a broken vertical section illustrating details of the adjustable choke mechanism in the top of the stack.

In Figs. 1 and 2, the stack 6 is shown as jacketed at l to form an annular preheating chamber, which may be of downwardly increasing crosssection, as indicated, to properly allow for expansion of the air as it picks up heat in its down- 35 ward flow.

Air is forced into the preheating chamber in the present illustration by a ventilator 8, which is shown as connected by a transverse box or flue 9, with the lower end of a portion of the preheat- 40 ing chamber which is partitioned off from the balance of the chamber by a bottom wall I and upwardly flaring side walls ll, these forming in eifect an upwardly opening segmental funnel for admitting the cold air into the chamber. Up-

45 wardly inclined bafiles I2 prevent reverse flow downthrough this air funnel.

The volume of air admitted for preheating purposes may be suitably controlled as by means of a damper or valve I3, shown at the entrance of the 50 passage 9, connecting the ventilator to the preheating chamber.

The air admitted through the segmental funnel Ill-ll takes up heat from the stack in its upward travel, such transfer of heat being facili- 55 tated by the baffles. This inlet funnel is shown as flaring upwardly to allow for expansion in the air and to compensate for the upwardly decreasing cross-section of the preheater chamber. From the upper end of the funnel, the air passes downwardly through the gradually enlarging portion of the preheater chamber and at the bottom of the stack the heated air passes out through an opening l4, into a chamber or passage l5, extending over the top of the boiler l6, down across the back of the'boiler at I l and then forwardly beneath the firebox at I 8 and into the combustion chamber at the front of the furnace at l9. To accomplish this circulation, it will be seen that the space over the top, down across the back and forwardly beneath the boiler is closed in by suitable bulkheads, partitions or covering walls 20. In this particular disclosure, the boilers are indicated as oil-fired, the burners being indicated at 2|, closed in at the front by the cover wall 20, so that all the air for combustion is supplied by the preheater. This air takes up heat which otherwise would be lost up the stack and carries it back to the furnace, enveloping the boiler in its flow to the combustion space to form an insulating mantle about the boiler, tending to equalize boiler temperatures. This produces a smooth burning fire and eliminates pulsing of the furnace.

The ventilator is shown as opening at the lower end down into the boiler room at- 22. Above this fresh air discharge, a nozzle 23 is shown projecting from the side of the ventilator into the mouth of an injector funnel 24, which delivers injected air taken from the fireroom into the lower portion of the preheater chamber at 25. In addition to gaining air for preheating purposes, this construction aids in the ventilation of the stoke hole by circulating cooling air in front of the boiler.

To increase the draft of the stack and to check the entrance of air when in port, the stack may 40 be closed in more or less at the top by the adjustable choke construction shown in detail in Figs.

4 and 5 and consisting of the leaves or segments 26, confined to sliding radial movement by pins 21, working in slots 28 and shiftable radially by reason of engagement of said pins in the cam slots 29 of cam rings 30. Thelatter are shifted by suitable means, such as pinions 3|, carried by shaft 32, extended up the stack, said pinions engaging gear teeth 33 in the edges of the cam rings. These sliding segments serve as adjustable shutters for keeping air from entering the stack when the ship is in port and they may be closed up more or less when at sea to increase the draft, particularly if the stack be of over size. These shutters also aid in preventing eddies in the stack. The construction may vary within wide limits to suit different conditions and requirements. The draft provided by the ventilator may be sufiiient for ordinary purposes, but it is possible for some installations a blower or blowers may be used for forcing the air through the preheater. The

choke in the stack may be adjusted conjointly with the control of air to, the preheater, so as to hold' or release the heat in the stack more or less in accordance with the volume of air admitted for preheating.

What is claimed is:

1. In apparatus of the character disclosed, the combination of a boiler furnace and a stack, an air preheater jacket about the stack, means for forcing air for combustion into said preheater jacket, means for carrying air from said'preheating jacket across the top of the boiler, down across the back of the boiler, forwardly beneath the furnace and into the combustion chamber of the latter, said air forcing means including.

a ventilator and arpassage extendingirtherefrom into the jacket of the stack, said ventilator being arranged to deliver fresh air in front of the boiler and an air injector above the point of delivery of such fresh air extending from the veni 3. In combination with a boiler furnace and a stack, an air preheating jacket about said stack,

an upwardly opening segmental air delivery funnel in said jacket, means for introducing air for preheating purposes into the lower portion of said funnel, means for carrying preheated air from the lower portion of the jacket tothe furnace including a passage extending downwardly about and beneath the boiler to the combustion space of the furnace.

4'. In combination with a boiler and a stack, an air preheating jacket about said stack, an upwardly opening segmental air delivery funnel in said jacket, means for introducing air for preheating purposes into the lower portioriof said funnel, means for carrying preheated air from the lower portion of the jacket to the furnace and upwardly inclined baflles in the 'air inlet funnel.

5. The herein disclosed combination of a marine boiler having a stack, an air preheating jacket about said stack and internally partitioned into an entrance passage extending from a lower portion of the jacket to an upper portion of the same and expanding upwardly and a discharge passage communicating with said entrance passage and extending from the upper portion of the jacket downwardly and expanding downwardly to the foot of the jacket, enclosing means form- ,ing an air passage from the foot of said preheating jacket back over the top of the boiler, downwardly across the back of the boiler and forwardly beneath the boiler to the combustion V chamber atthe front of the boiler and .a ships ventilator connected with the, lower end of said upwardly expanding inlet passage for supplying the air for preheating purposes.

FRANK F. TOWNSEND. V

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