US2025629A - Method of and apparatus for controlling marine boilers - Google Patents

Description

Dec. 24, 1935. s. wUNscH 2,025,629 METHOD OF AND APPARATUS FOR CONTROLLING MARINE BOILERS Filed July 29, 1935 Patented Dec. 24, 1935 METHOD OF AND APPARATUS FOR CON- TROLLING MARINE BOILERS Guido Wiinsch, Berlin-Steglitz, Germany, assignor to Askania-Werke A. G. vormals Central Werkstatt Dessau und Carl Bamberg- Friedenau, a German company Application July 29,1935, Serial No. 33,789 In Germany January 25, 1934 6 Claims. (Cl. 23614) This invention relates to a method of and apparatus for controlling the operation of marine boilers or other steam power plants wherein separate boilers or groups of boilers are employed and, among other objects, aims to provide a novel mode of controlling the combustion on separate groups of boilers or boiler units by supplying combustion supporting air under positive pressure from a common source and regulating m. the pressure thereof in accordance with the greatest demand on any of the individual boilers or boiler groups. Also, the invention provides a method of and novel means for regulating the supply of such air ,to each boiler group according to its individual demand. Furthermore, the invention aims to provide novel, highly efilcient and dependable apparatus for practicing the method.

,Other aims and advantages of the invention 20. will appear in the specification, when considered in connection with the accompanying drawing,

wherein:

Fig. 1 is a diagrammatic view of one embodiment of the invention; and

Fig, 2 is a sectional view taken through a portion of the mechanism as indicated by the line 22 in Fig. 1.

In the majority of marine boilers, the combustion air is supplied to the different boiler groups simultaneously from a common source under a positive pressure which is higher than the pressure in the combustion chamber or chambers. This type of boiler installation is usually built in two different forms. In one form, the 35- air for all boiler groups is supplied through a common duct. In the other form, especially aboard ships, all of the boiler groups are located in a common boiler room which is supplied Y with air under positive pressure by a common forced draft fan. So long as the boiler groups in either form operate at identical loads, the automatic control of air for combustion can easily be accomplished. It is only necessary to r proportion the correct amount of air to the individual combustion chambers in proportion to the load of all the boilers. However, greater difliculties arise if the different boiler groups have to operate under different loads as is usually the case aboard ships and, especially, aboard torpedo boats. The present invention embodies a simple method whereby it is possible to provide each individual boiler-group with the correct amount of air in spite of the fact that the different boiler groups may be running on different loads and regardless of which type of boiler plant, above described, is employed.

As stated, the present -method controls the positive air pressure in accordance with the load of that boiler group which is carrying the maximum load, regardless of which boiler group happens to carry the maximum load at any given time. If the method provided only means to admit the correct amount of air to the boiler group which carries the maximum load, all boilers running at lower loads would operate with excess air. The invention, therefore, provides in addition means for controlling the air to the boiler groups operated on lower loads so that each individual boiler group will operate under the maximum efficiency. This is accomplished by providing means to control dampers which regulate the amount of air supplied for combustion from .a common header or out of the common boiler room in proportion to the load which each individual boiler group is carrying.

Referring particularly to the drawing, two groups of boilers l0 and H, such as are used for the port and starboard engines on a torpedo boat, are shown as being located in .a common boiler room l2. For the purposes of this description, each group of boilers may be treated as having a single combustion chamber to which the combustion supporting air is admitted. The air is supplied to the boiler room through a conduit [3 and is maintained under positive pressure,

conveniently, by a series of centrifugal or forced draft fans I, which are shown as being driven by steam turbines l5 supplied with steam through valved branch lines l6 between the steam mains I1 and I8 leading from the two groups of boilers. These turbines are controlled by an automatic throttle valve l9, which is operated in response to the demand of the boiler group working under the greatest load, as will presently be described. The air, under pressure, is supplied to the boiler furnaces through conduits 20 and 2 I, respectively, which have adjustable louvre dampers 22 and 23, respectively, controlled automatically in accordance with the load demand on each boiler, as will presently be explained.

In accordance with the invention, the air pressure in the boiler room is controlled by varying the setting of the throttle valve l9. While this may be accomplished in various ways, the valve is herein shown as being operated by hydraulic mechanism having a piston 24 connected to it and operating in a cylinder 25. The piston is controlled by an automatic jet pipe regulator of the Askania type such as is shown in U. S. Patent No. 1,959,889. In this case, the differential pressure between the boiler room and the combustion chambers, for example, between point a which may be anywhere in the boiler room and point b within the combustion chamber of either boiler group, herein group I0, is applied through pipes 26 and 21 to the opposite sides of a diaphragm 28 which is connected to actuate the pivoted jet pipe 29. The action of the diaphragm on the jet pipe is opposed by a spring 30 connected at its lower end to a cylindrical roller which rides on two cams 32 and 33 (Fig. 2). These cams are adjusted automatically in accordance with the load variations of the respective boiler groups I and II, whereby a higher load on either boiler group will modify the action of the jet pipes. The cams are so arranged that the adjustment of the compression of the spring 30, which is dependent upon its point of contact with either cam, represents the load of the boiler group which happens to be operating at the greater load. The regulator has a compensating cylinder 34, the jet pipe and cylinder being connected by conduits 35 and 36 to the cylinder 25 on opposite sides of the piston 24, thereby operating the control valve l9 in accordance with the compression of the spring 30 which is proportional to the greater boiler load. Since the two combustion chambers of the boiler groups are supposed to be connected to a common stack, the draft in them is expected to be the same. Therefore, the differential pressure between the points a and b will be nearly the same as the differential pressure between the points a and I).

Now, the difi'erential pressure between the points a and b or b changes according to the second powerof the flow of air through the louvres 22 and 23. It is necessary to control the louvre dampers for each individual boiler group to obtain the maximum efliciency. Otherwise, the boiler group or groups operating at the lower load would be supplied, with excess air. In this example, the louvre dampers are operated by separate cylinders 31 and 38 having pistons 39 and 40 and piston rods 4| and 42 mechanically connected to the respective groups of louvres. The pistons are shown as being actuated by jet pipe regulators or relays 43 and .44 of the well known Askania type. These relays have diaphragms 45 and 46 which are operated by the difierential in pressurebetween points b and c and b and 0', respectively, the points 0 and 0' being in the respective air conduits. The diaphragms act on one side of the respective jet pipes against the action of adjustment springs 41 and 48 and the tension of these is automatically varied according to the loads on the respective boiler groups, herein, by means of cams 49 and 50 acting on rollers i and 52. These cams are shown as being operated simultaneously with the respective cams 32 and 33 in accordance with changes in individual boiler loads.

While the boilers may use any fuel, they are herein shown as being oil fired, burners 53 and 55, only one for each boiler group being shown. However, provision is made for a plurality of such burners, as indicated. Oil is supplied to the respective burners from conduits or headers 55 and Fit-through control valves 51 and 58. These control valves are actuated automatically by cams 53 and 5d contacting with rollers 6i and 62 connected to the valve stems. These cams are also operated simultaneously with the respective cams 32 and 33 in accordance with the separate boiler loads. The proportion of air and fuel is coordinated by the valve settings or adjustment of the jet pipe regulators 43 and 44.

The cams 32, 49 and 59 for the boiler group Ill are shown as being mounted on a single piston rod 63 actuated by a piston 64 in a cylinder 6 65; while the cams 33, 50 and 60 for boiler group II are similarly mounted on a piston rod 66 actuated by a piston 61 in a cylinder 68. These groups of cams operate in much the same manner as that disclosed in the copending application of Wunsch et al., Ser. No. 4,204, filed January 30, 1935. In this instance, the pistons 64 and 51- are operated hydraulically in response to the respective boiler loads as measured by the pressure or drop in pressure in the two steam mains i1 and I8. They are shown as being actuated by fluid jet regulators 69 and 10 which are controlled by bellows diaphragms H and 12 connected to the respective steam mains by branch lines 13 and 14. The action of the diaphragms on the jet pipes is controlled by springs 15 and 16, the tension of which may be adjusted by thumb nuts I1 and I8 and the diaphragms act upon the jet pipes through a system' of links and levers, as shown, against the tension of springs I9 and 80 having rollers 8| and 82 riding on cams 83 and 84, preferably secured to the piston rods 63 and 66, respectively. A pressure drop in either of the lines will indicate an increase in the boiler load or demand upon the boiler. A decrease in steam pressure on one of the bellows diaphragms, say diaphragm II, will cause the jet pipe 69 to rotate or move in a clockwise direction and thereby move the piston 64 and the associated cams 49, 59 and 32 to the right. This movement of the piston rod and the associated cam 83 will increase the tension on spring 19 acting against the jet pipe and tend to restore it to its neutral position. Thus, the movement of the piston rods and the cams represents the respective loads on the boiler groups "I and II.

In this instance the pressure of the oil delivered to .the respective burners 53 and 54 is employed to control the admission of air from the air conduits 20 and 2| into the combustion chambers. For this purpose, the burners have associated cylinders 85 and 86 carrying spring urged pistons 81 and 88 respectively which are mechanically connected to air dampers 89 and 90 in the form of valves (not shown in detail). The arrangement is such that the moment the oil valves are opened by their respective cams-the respective air dampers for the burners will be simultaneously opened to insure adequate supply 01' air for each burner.

The operation of the control mechanism is as 'follows: The two master controls 69 and i0 deally to the respective loads measured by the steam e0 pressures in mains l1 and I8. The pressure differential between one of the combustion chambers and the boiler room is determined and'controlled by means of regulator 29, piston 24 and cylinder 25 in accordance with the load of the 5 boiler which carries the higher load.

The individual air supply to each boiler or boiler group is then modified by regulators 43 and 44 which operate the louvre dampers 22 and 23. In special applications it may be so ar- 7 ranged that the louvres of the boiler which carries the higher load are all the way open and its air supply is directly controlled by the regulator 29. It has been found practically sumcient in many cases to control only the boiler group group with the lower load. Such a simplification is only possible if the two loads do not vary to a great extent relatively to each other. This simplified form of the invention could also be regarded as covered by this application.

The number of burners in operation is varied in accordance with and directly proportional to the respective loads. As'th'e individual burnersare either fully open or closed, the dampers attached to them will also be either opened or closed. It is emphasized, however, that other means of oil flow control could also be used, as,

for instance, as described in the aforesaid co-' pending application without restricting the scope of the invention.

With this arrangement, therefore, it is possible to control the boilers which have a common air supply independently at various loads.

Having thus described the novel method and illustrative apparatus for practicing the same, it will be understood that theinvention is by no means restricted to the particular application thereof herein shown and described. The same method may be practiced on any number of boiler groupsand the apparatus may be modified accordingly. Moreover, the invention is not l mited to the use of the particular types of jet pipe regulators or other hydraulic controls, but it is contemplated that electrical, pneumatic or mechanical control mechanism may be employed. Also, the method is applicable to groups of boilers using any kind of fuel. All such modifications should be considered as being covered by this disclosure.

Obviously, the present invention, insofar as the method is involved, is not limited to the specific steps herein shown and described. Moreover, the

.invention, insofar as the apparatus is involved,

is not limited to the particular embodiment herein shown and described. Furthermore, it is not indispensable that all the features of the invention be used conjointly, since they may be employed advantageously in various combinations and sub-combinations.

What is claimed is:

1. That method of controlling the main supply of air through a common chamber to the furnaces of a plurality of separate boilers supplying steam to independent mains, which is characterized by supplying said chamber with air under pressure; obtaining separate governing impulses which represent the loads on the respective boilers; producing pressure impulses representing the pressure difference between the chamber and the furnace of one of the boilers; and regulating the supply of air in accordance with said pressure impulses acting inopposition to the governing impulses which represent the load on the boiler which is operating at the highest load, irrespective of the load on the other boilers.

2. That method of controlling the main supply of air through a common source to the combustion chambers of a plurality of separate boilers supplying steam to independent mains, whichiis characterized by supplying the air under pressure to said source; obtaining separate governing impulses representing the loads on the respective boilers; applying the governing impulses which represent the highest load on any boiler to operate a regulator which controls the supply of air, irrespective of the load on the other boilers; and modifying the action of said regulator in response 5 to diiferential pressure impulses representing the pressure difference between the air in said source and the combustion chamber of one of the boilers.

3. In combination with a plurality of separate boilers supplying steam to independent mains, a closed boiler room in which said boilers are located; fans for delivering air into said boiler room to maintain a positive pressure therein; a main regulator connected to control the operation of said fans; and means for controlling the operation of said main regulator including indi-* vidual regulators connected to the respective boiler mains; independent cams actuated by each of said individual regulators and so connected to the main regulator that the cam which is operated by the individual regulator responding to the highest boiler load always acts upon said main regulator; and means to modify the action of said main regulator in response to pressure impulses representing the pressure diiference between the boiler room and one of the boiler furnaces.

4. In apparatus for controlling the supply of air to the furnaces of a plurality of separate boilers supplying steam to independent mains and having separate furnaces, a closed boiler room in which said boilers are located; means for delivering air to said boiler room to maintain a positive pressure therein; a. main regulator for controlling the supply of air delivered by said means; a plurality of cams connected to operate said regulator; individual pressure responsive means connected to the steam mains of the respective boilers for actuating the respective cams, the operative connections between said cams and the main regulator being such that the cam which is operated in response to a pressure representing the load of that boiler carrying the highest load always controls the action of the main regulator.

5. In combination with a plurality of separate boilers supplying steam to independent mains and having separate furnaces, a common closed boiler room in which said boilers are located; an air pump for delivering air into the room to maintain a positive pressure therein; a main regulator connected to control the supply of air delivered by said air pump; a pressure diaphragm connected to said main regulator and operated by pressure impulses representing the pressure difference between the air in the boiler room and the combustion chamber of one of the boilers;

a seriesof. separate cams, one for each boiler, also connected to operate the main regulator in opposition to said diaphragm; individual regulators responding to pressures which represent the loads on the respective boilers connected to act'uate said separate cams independently of each other, the actuating mechanism between said cams and said main regulator being so constructed and arranged that only the cam which is actuated in response to pressures representing the highest load on any boiler will function to operate the main regulator at any one time; and separate regulators for controlling the supply of combustion constituents to each of the boiler furnaces in accordance with their respective loads.

6. In apparatus for controlling the supply of air to the furnaces of a plurality of boilers supplying steam to independent mains and operating at varying loads, a common air chamber for supplying air to the boiler furnaces; means for delivering air under positive pressure to said chainher; a main regulator connected to control the supply of air to the chamber; separate governing devices, one for each boiler, connected to respond to steam pressure impulses representing the loads on the respective boilers; and means so cOiinecting said governing devices to operate the main regulator that the one responding to the highest boiler load always acts on said regulator independently of the others.

GUIDO wfiNscH.

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