US2277493A - Draft producing and regulating means - Google Patents

Description

DRAFT. PRODUCING AND REGULA'IING MEANS Filed Nov. 20, 1939 INVENTOR.

NEWTON FQANK" LANE ATTO EY.

Patented Mar. 24, 1942 UNITE STATES PATENT OFFICE 2,277,493 DRAFT PRODUCING AND REGULATING MEANS Newton Frank Lane, Decatur, Ill. Application November 20, 1939, Serial No. 305,323

5 Claims.

This invention relates to improvements in draft-producing and regulating means, and more particularly to such means a utilized for producing a controlled and balanced drafting effect in locomotive type boilers, through the use of auparticularly to the features of the invention relating to the control of quantity of drafting air as well as control of draft balance, in accordance with boiler steaming requirements and a furnace condition, such as a variable draft pressure in a predetermined zone of the boiler assembly.

It is a maJor object of the present invention to provide a fully automatic draft arrangement and draft control system, which operate responsively to boiler steam pressure or boiler steaming requirements, and also responsively to draft conditions to influence the draft-producing means utilized in connection with locomotive type boilers.

A number of attempts, have been made in the past, but with no degree of success, to draft locomotive type boilers mechanically through the use of an induced draft fan or blower, generally located in or adjacent to the smoke box. It has also been attempted to augment the volume of air utilized for combustion, by the installation of forced draft fans or blowers of various types,

serving to introduce the combustion air under a positive pressure, through or beneath the grate bars. Neither of these devices or methods is, considered alone, fully satisfactory for the purpose of drafting locomotive type boilers, largely because of the widely varying pressure conditions existing between the zones in and adjacent'to the l fire box, and those zones in which the air, charged with solid particles resulting from combustion, exists at a high temperature, as in the smoke box. With the use of a forced draft system alone, the zones of combustion are put under a substantial positive pressureycreating a tendency at times for the gases and flames to be driven out through the fire door. On the other hand, utilizing only an induced draft blower, there results a partial vacuum in the zone of combustion. Thus at the numerous times of opening the fire door, there results a detrimental inrush of cold air which reduces the temperature of the gases of combustion and reduce the heat otherwise available to generate steam. It is accordingly an additional object of the present invention so to regulate the speeds, and hence the displacements of the fore and aft blowers, that there is maintained a volume and flow of air through the combustion zone which consists of only a desirable excess over combustion requirements, the displacement capacities of the two blowers being so proportioned that although combustion chamber pressures fluctuate within small limits, there is never any subatmospheric condition at the fire door. This arrangement results in what may, for convenience, be termed a balanced draft system.

It is a still further important object of the invention to provide, as a part of or adjunctively to a balanced draft system of the type described, a fullautomatic control arrangement therefor, whereby the speeds and displacements of the forced draft and induced draft blowers may be not only proportioned correctly, but may be varied directly and automatically in keeping with steaming requirements, as well as in keeping with a furnace condition, such as draft requirements or draft pressure.

Still further objects of the invention will be noted from the following detailed description of a preferred embodiment of the draft-regulating and'balancing agencies, as well as from the accompanying drawing, which consists of a single figure, showing in the upper portion, a diagrammatic view of a locomotive boiler and cab structure in which is indicated a preferred physical disposition of certain of the control instruments as well as the induced-draft blower and turbine and forced-draft blower and turbine, the remainder of the figure consisting of a partly diagrammatic and partly physical representation of the electropneumatic control features characterizing the selected embodiment of the invention.

Referring now by characters of reference to the drawing, the boiler shellis indicated generally at' I0, and the fire box at l I. Below the grate bars (not shown), is a substantially air-tight ash pan l2 into which is directed the discharge pipe H of a forced draft blower I 4, impelled by a highspeed steam turbine l5. Two or more of the turbine-blower assemblies l4--I5 may, if desired, be employed.

In the front end of the locomotive boiler assembly, specifically in the smoke box It of the example shown, is a housing I! for a high speed steam turbine. For purposes of the present schematic representation the housing I! may be taken as representing the turbine itself, and

which is operatively connected to an induced draft blower 20. This is shown as consisting of a, propeller type fan located just inwardly of the lower end of an elbow-shaped fitting 2| directed to the boiler stack 22. The fitting H is provided with an extension 23 connecting into the exhaust saddle of the locomotive, and in operation, the blast of air and gases emitted from the induced draft blower 29 through the stack, exhibits a substantial eductive effect on the connection 23, thus serving markedly and in an improved manner to reduce back pressure in the exhaust passages.

Disposed in an overfire zone adjacent the fire arch, is a hollow stay-bolt connection 24. The tubular element 24 communicates with a line of piping I 48 and I M connecting to the apparatus for automatic control of the drafting system in accordance with draft pressures in this zone, all as hereinafter more fully described.

In the present example, the cab of the locomotive, indicated generally at 26, is shown in longitudinal section in order better to reveal the physical location of certain of the control instruments and agencies hereinafter more particularly described.

It will .be understood that the forced draft blower turbine I5 and the induced draft blower turbine I! are supplied with suitable steam supply and exhaust lines which, for clearness of illustration, have been omitted from the diagrammatic figure of the locomotive in the upper part of the drawing, although certain of the piping elements are hereinafter referred to in connection with the control apparatus.

Referring now to the preferred form of the control elements and their assembly, the system in the selected example being of electro-magnetic and pneumatic type, the system will be described by utilization'of the same reference characters employed in the parent application, Serial No. 143,463, now Patent No. 2,184,647, in order to facilitate cross reference between that application and the present.

Proceeding now to a description of the means by which is effected an automatic control of the blowers in keeping with the steam pressure or steaming requirements of the boiler, it is seen that this type of control involves, at least in part, an influence of the main steam supply, a conduit for this purpose being indicated at 90, which is connected into the dry pipe or steam fountain (not shown), the pipe 96 serving directly to affect a control unit designated generally as 9!. This unit is conveniently of a type involving a metal bellows indicated at 92, connected to the boiler as through the pipe 90, and through a lever connection 83, serves to actuate a pendulum-type control lever S4, pivotally mounted on a control panel 95. The lever 94 includes a pair of horizontal arms provided at their extremities with contacts 93 and 8|. The length of the aligned horizontal arms of this lever is so selected, relative to the distance between,

a pairof fixed contacts IIJE! and IilI, that when the lever is in its mid-position, neither of the switches 98-IQI! or 8I-I9I is closed. When, however, the lever is moved to the right or the left, the contact 93 or 8| as it approaches the adjacent stationary contact, serves to close the circuit. Each of the switches is illustrated only diagrammatically, any one of a number of suitable types of switches now available being suitable for this purpose.

The electrical circuit may be considered as having its origin in either of a pair of supply leads IE5 and IE6 taken with a ground leg of the circuit. The leads are conveniently connected to the usual 32 volt supply system of the locomotive, and accordingly may be energized through the generator or storage batteries, or both.

The circuits originating in the control leads I85 and I I36, are continued beyond the control panel designated generally at I I0, through a pair of conductors III and H2, a ground wire H3 being provided in the circuit relation indicated, and electrically connected to the lever 94 in the example disclosed.

The leads III and H2 are continued into a control panel II5, the latter being provided with a pivotally mounted, pendulum-type switch lever I Iii, provided similarly to the lever 94, with horizontal arms, the extremities of which carry contacts II! and II 8, serving after the manner of the elements 98, 8| to control the circuits through a pair of switch contacts indicated at MS and I20, respectively arranged in the lines H2 and III. Theswitches IIIII9 and II8I20 may be similar in design and capacity to the switches associated with the panel 95. Beyond the switches on the panel II5, the circuits are continued through leads I22 and I 23, a ground wire I28 being provided for return purposes, and a ground connection efiected as at I25. It will have appeared that the control circuit is of the type known as a single wire system, in which one side of each circuit is completed through a grounded leg which may conveniently consist, in part, of the metal portions of the locomotive structure and associated parts.

There is by preference mounted on the control panel I45, and operatively connected to the pendulum lever H6, a variable volume control chamber indicated-at I39, and provided, for example, with a movable diaphragm I3I, or in lieu thereof a piston (not shown), or some equivalent of the diaphragm or piston. To the diaphragm, for example, is conducted a control rod I32 pivotally connected to the lever I I6, the movement of this lever under the influence of the diaphragm, being opposed by a variably-loaded compression spring I35, the loading of which is subject to adjustment as through threaded elements and lock nuts, the assembly of which is indicated at I36. The variable volume control chamber I38 is supplied internally with air under pressure through a conduit I-'iIJ, which has its origin or entrance end, in the boiler structure at such location as to maintain the conduit under a pressure which varies directly with the variation in overfire draft supply, the entrance end of pipe I40 being, in the disclosed example, in the hollow stay-bolt 24. For convenience of providing a visual indication of the pressure in the zones over or beyond the fire, the conduit I 45 may be branched and continued as at MI, to a pressure gauge I42, preferably located in the cab as shown, or at some other point for convenient visual indication to the engineer or fireman.

The control circuits are each completed beyond the panel H5, through the control wires 422 and I23, the former being connected to a pair of similarly disposed solenoid windings I 45 and I 35, for the energization thereof, the return circuit from each such winding being completed through the leads I 41 and I48 connected to the ground lead I24, grounded at I25. In similar manner, the lead I23 is connected to a pair of similarly disposed electromagnets or solenoids I49 and I50, the return connections from which are completed through the conductors I41 and I48 to the ground at I25. It will have appeared that the solenoids or electromagnets are related in pairs, one pair comprising the magnets I45 and I49, and the other comprised of solenoids I46 and I50. Each of the pairs of magnets is provided with a common, double-end armature structure indicated generally at II and I52, and the armatures of each such structure connected through plungers I53 and I54 to an adjacent air control valve of piston and cylinder type. These air control valves include a piston I55 operating in a cylinder I56 on the one side, and a piston I51 operating in a cylinder I58, on the other side. The cylinders I56 and. I58 are of doubleend type, the cylinders being provided with air under pressure, as from the brake system of the locomotive, through air inlet pipes I60 supplying the cylinder I56, and I6I supplying cylinder I58, the pipes I60 and IBI being, for example, connected into the air reservoir (not shown) of the locomotive. Each cylinder is provided with a pair of outlets respectively near the upper and lower ends of the valve, these outlets being indicated in the control for the forced draft turbines, at I10 and HI, and in connection with the cylinder I58 serving to control the induced draft blower turbine, at I12 and I13.

The paired air discharge tubes or conduits from each valve cylinder, are connected respectively to the upper and lower ends of a doubleended cylinder-and-piston control unit, or air servo-motor, the motor cylinders being indicated at I16, for the forced draft turbine control, and I11 for the induced draft turbine control. These cylinders are each provided with a power piston, the pistons being designated respectively at I18 and I19.

Each power piston is connected through a rod, such as I85 or I86, thence through a pivotal connection I81 and I88, to a steam valve. The two steam valves illustrated are preferably of socalled chronometer type, providing a plurality of steam-admission passages through the body of the valve, which are graduated and so arranged that the first position of each valve provides an idling regulation of the associated turbine or turbines, while the remainder of the positions provide, in sequence, for augmenting the steam supply to, and hence serve to enhance the air displacement by the turbines controlled therethrough. Through the provision oflinks such as I90 and I9I, the movements of the servo-motor pistons are translated to the valve actuating arms I95 and I96, operatively associated, respectively, with the valve bodies I91 and I98. The former of these serves to control the flow of steam through a boiler-connected steam supply pipe I99 and a forced-draft turbine supply pipe 200, and the latter valve controls the flow of steam through a boiler-connected steam supply pipe 2!, thence to the supply line to the induced draft turbine, indicated at 202.

It has been found convenient in practice to provide the steam supply pipe 200 under the control of the Valve I91, with at least a pair of branches, one thereof such as 265 leading to the steam supply for the stoker drive, and another shown at 206 being directed to the forced-draft turbines. If desired, hand valves 201 and 208 may be utilized for manual regulation or proportioning of the flow of steam through the respective branches 205 and 206.

The operation of the control system may be briefly reviewed by noting that, as the steam pressure increases in the boiler and hence in the conduit 90, and hence that, as the steaming requirements of the boiler decrease, the increased pressure will influence the unit 9I in a manner to swing the lever 94 to the left, thus serving to bring the contact 98 into engagement with the stationary contact I00, thus completing the circuit through the ground and through the control legs I06 and H2, thence, assuming the switch II1-I I9 to be closed, through the lead I22 so as to energize the upper coils I45 and I46 of the solenoid valve-operating assembly. This will cause the armature assemblies I5I and I52 to be actuated upwardly, into the positions shown by the drawing, raising the pistons I55 and I51, closing the inlets I16 and I12 to the servo-motors, but opening the inlets Ill and I13. This actuation will have the effect of putting the air pressure from the air supply system against the lower faces of pistons I18 and I19 of the servo-motors, with the effect of raising, in the positions shown, the valve-actuating levers I95 and I96. If the circuit remains closed as indicated, for an appreciable time, the valves will thus be actuated toward steam-restricting positions, and will be brought to positions in which the steam supply is only sufficient to cause the turbines and blowers to operate at idling speed.

It will have been noted that this actuation is dependent upon the closed position of switch Il6-II1, this switch being closed only in response to a predetermined but substantial air pressure in the overfire zone. It is accordingly seen that the controls are responsive primarily to the steam supply and boiler steaming requirements, and also secondarily subjected to the in fluence of the overfire draft pressure. This is true since the one of the switches carried by panel II 5, which is closed, the switches being operable only one at a time or selectively, is determined by draft conditions.

Assuming now an opposite set of conditions to prevail, namely a relatively reduced steam pressure and a relatively reduced draft pressure, the influence of the bellows unit 9| will operate to close the switch 8IIOI' and permit the switch 98I00 to open. Assuming the switch 8I-IOI to be closed, and assuming a low draft condition to prevail in the overfire zone, so that switch IIB-IZiI is closed, a different control circuit will now be completed, one side through the ground, and the other side through the leads I05, I I I and I29, so that the coils I49 and I50 become energized, at the same time coils I 45 and I46 being deenergized. This will result in a movement of the armatures I5! and I52 to their lowermost positions in the figure, in a manner to move the valve pistons I55 and I51 in a direction toward the opposite ends of the valve cylinders. Under this condition, air is excluded from the lower end of the motor cylinders and admitted to the upper ends thereof, assuming them to be mounted in the positions shown. Thus the valve levers I95 and I96 will be actuated to a steam-admitting position, the extent of their opening depending upon the amount and duration of air admission to the servo-motor, as influenced by the controls described. This set of conditions serves to increase the speed of the forced draft turbines as well as the speed of the induced draft turbine in a manner to increase the draft supply, and similarly the steaming rate. It is to be observed that the increase or decrease of turbine and blower speeds, is always such as to keep the induceddraft and forced-draft units correctly proportioned in output.

It is preferred to provide for an adjustment of the extent of actuation and proportionate movement of the valve-operating levers I95 and I96, as through the provision of a number of openings I95A and IQBA, selectively utilized for the connection of a pivot pin on each of the links I99 or IEI to the associated valve lever. It will clearly appear from the drawing that as the links I90 or I9I are set farther inwardly, or more closely to the pivots of the associated valve levers I95 or it, a given movement of the associated air piston will serve to effect a greater angular movement of the throttle valve element controlled thereby. This facility for adjusting the relative range of movements of the chronometer valves, is of importance in the present assembly in that it enables a given installation to be adjusted to proportion the speeds and hence the displacements of the induced and forced draft blowers to each other, throughout the range of their throttling control. This feature enables the maintenance with considerable accuracy of a substantially balanced draft condition, irrespective of whether the drafting requirement be great or small. This feature also enables a compensating adjustment of the controls to care for differences in the different blower assemblies, as well as certain inherent differences necessary to be adjusted for in different types of locomotives, as well as individual differences found in different locomotives of any given type.

It is preferred so to set the control instruments such as the steam-pressure responsive unit SI, and the draft-responsive unit carried by panel II 5, that an appreciable range of pressure occurs between opening and closing valve move ments. This is preferably at least a five pound pressure differential, and in many cases it is advisable to provide for a ten pound difference in setting, so as to prevent unnecessary hunting of the controls in response to minor variations in steam pressure. Similarly, the setting of the draft responsive control avoids excessive changes in the control circuits and avoids needless control actuation in response to minor variations in draft pressures.

It is desirable in most installations, to provide for a manual control of the steam supply through the turbines, in case of failure of any part of the control system, or so as to enable the operator, as in an emergency, to meet extreme conditions by manually controlling the amount of draft. Among the instruments preferably so provided, is a, master steam pressure control indicated at 289, a draft control for the forced draft fans shown at 2I0, and a chronometer type, hand throttle valve designated as 2| I. These are preferably disposed at a convenient point of access to the fireman, as on the left side of the cab 26, their positions as shown having been found convenient in practice.

While the exact physical location of many of the items of control apparatus heretofore described, is not material to the invention, it may for completeness be pointed out as advantageous and practical to locate the two master control units such as SI and H in the cab for example in the side-by-side arrangement suggested by the upper figure of the drawing showing these units located over the window on the firemans side of the cab. It has been found advantageous prior to installation, to assemble the chronometer valve, solenoid assembly and servo-motor for each of the blower systems, as a unit, each such unit, such as indicated at 220, preferably including, for example, the forced draft control elements comprising solenoids I45 and I49, together with valve I56 and air motor "6, lever I t5 and chronometer valve I91, together with immediate piping and appurtenances. Similarly, the induced draft control agencies are assembled as a unit shown as to location at 22I, and including the solenoids I 46 and I50; the air valve I58, air motor I", valve lever I96 and chronometer valve I98. A suggested and practical location of th units 220 and 22! is in the cab, under the firemans seat in about the location shown in the upper portion of the drawing. Optionally, these units may be located elsewhere as desired, say under the engineers seat in the cab.

-It will have appeared that the system described serves to compensate for differences in fuel bed according to type of fuel being burned, and to compensate for other variations in specific operating conditions, so that the speeds of the fans are correctly proportioned, through an automatic control, at all times. Concurrently both fans are subject to control under the influence of steam pressure, and hence of steaming rate, as Well as draft pressure. The ideal operating condition is, of course, to maintain the optimum steam and draft pressure to meet a given set of working conditions of the locomotive, and when desired, to maintain as high a pressure as possible without loss of steam through popping of the safety valve, which obviously results in inefficiency and loss of thermal values.

While the invention has been described by making specific reference to a presently preferred embodiment of the invention, the description is not to be understood in a limiting sense, since obviously many changes may be made within the intended scope of the invention as defined by the claims hereunto appended.

I claim as my invention:

1. In combination in a steam locomotive, a balanced draft producing and control system including a steam turbine-driven blower of forceddraft type, having its outlet ahead of the grates and adapted to force a supply of combustion air therethrough, a steam turbine-driven induceddraft blower located in the smoke box of the locomotive boiler, a fitting forming a discharge passage from the induced draft blower and so directioned as to impart a steam eductive effect to the engine exhaust passages into the stack, and such that exhaust impulses coact in the draft-inducing action of the last said blower, the two blowers being so proportioned with respect to each other as to maintain in the drafting system between the blowers, a pressure substantially of the order of atmospheric; a control system for the blowers including an energized control circuit, a first pressure-responsive switch in said circuit having a loaded pressure-movable element subjected to draft pressure in an overfire zone, and hence influenced by effect on draft pressure, of exhaust and steam demand, a second, similar pressureresponsive switch subjected to boiler steam pressure, electromagnetic means in said control circuit, and a steam throttle valve for each of the steam turbines, and functional connections between said electromagnetic means and throttle valves.

2. In combination in a steam locomotive, a balanced draft producing and control system ineluding a turbine-driven blower of forced-draft type, having its outlet ahead of the grates and adapted to force a supply of combustion air therethrough, a turbine-driven induced-draft blower of substantially greater volume displacement capacity than the forced draft blower, and located in the smoke box of the locomotive boiler, a fitting forming a discharge passage from the induced draft blower, and so directioned as to impart a steam eductive effect to the engine exhaust passages into the stack, and so connected to the exhaust passages that the exhaust impulses coact with the induced draft blower in its draft inducing effect, and further coact with the induced draft blower in affecting the blower control system, the two blowers being so proportioned with respect to each other as to displacement capacity, as to maintain at all times during blower operation, a substantially balanced draft pressure condition between the grates and the induced-draft blower, and to maintain in the drafting system betweenthe blowers, a pressure substantially of the order of atmospheric; a control system for the blowers including a first pressure-responsive apparatus having a loaded pressure-movable element subjected to draft pressure in an overflre zone and above the fire arch, and hence affected by fluctuations of draft pressure by reason of exhaust fluctuations and varying steam demand, a second pressure-responsive apparatus subjected to boiler steam pressure, electromagnetic means influenced by said pressure-responsive apparatus, separate fluid pressure control devices, each in individual throttling relation to the steam supply to one vof the blowers, both said devices being subject to control of said electromagnetic means, and arranged to effect concurrent throttling actuation in the same direction, means for varying the proportionate throttling effect of said devices on the two blowers, as influenced by said electromagnetic means, and means for varying the loading and response of each said pressure-movable element, whereby to provide for variation in range of pressure influence on the blower turbines.

3. In a draft-producing and controlling system for locomotive boilers, an air displacement device or blower of forced-draft type arranged to supply air to the grates, a blower in the smoke box, and arranged to coact in the draft-inducing effect of the engine exhaust, a steam turbine in driving relation to each of said blowers, a throttle valve in the steam supply line of each turbine, directly controlling the admission of steam thereto, an air motor connected to each of said throttle valves, an electromagnetic controldevice connected with each air motor, an energized control circuit for said electromagnetic control devices, a pressure switch in said circuit, provided with fluid connections for response of the switch to changes in boiler steam pressure, and a second pressure switch in said control circuit, provided with fluid connections to effect its response tochanges in draft pressure in an overfire zone, the exhaust connection into the smoke box, together with the smoke box blower and draft zone to which said second pressure switch is responin the steam supply line of each turbine, directly I controlling the admission of steam thereto, an air motor connected to each of said throttle valves, an electromagnetic control device connected with each air motor, an energized control circuit for said electromagnetic control devices, a pressure switch in said circuit, provided with fluid connections for response of the switch directly to changes in boiler steam pressure, and

a second pressure switch in said control circuit, provided with fluid connections to effect its response to changes in draft pressure, the pressure switches being arranged in series in the control circuit, and the second pressure switch being connected for pressure response, to a zone in the draft system to render this switch responsive in part to changes in exhaust rate, and hence responsive also to variations in steam demand. 5. In a draft-producing and controlling system for locomotive boilers, an air blower of forceddraft type arranged to supply air to the grates, a blower in the smoke box arranged to coact with the engine exhaust in draft-inducing effect, a separate steam turbine in driving relation to each of said blowers, a throttle valve of modulating type in the steam supply line of each turbine directly controlling the admission of steam thereto, an air motor of double-end cylinder type, connected to each of said throttle valves, an electromagnetic control device of double-coil type connected with each air motor, a bloweraccelerating circuit arranged to energize like coils of the electromagnetic control devices, a blowerretarding circuit connected to the remaining coils of the electromagnetic control devices, a pressure switch having a movable contact element provided with fluid connections for response of the switch directly to changes in boiler steam pressure and having separately engageable contacts respectively arranged in the accelerating circuit and the retarding circuit, a second pressure switch having a movable element and fluid connections thereto to effect its response to changes in draft pressure, and stationary contacts respectively arranged in the accelerating circuit and retarding circuit, with corresponding terminals of the first said switch and second said switch related in series, the movable element of said second pressure switch being connected for its pressure response, to a zone in the draft system to render said second switch responsive in part to changes in exhaust rate, and hence responsive also to variations in steam demand as reflected in changes in exhaust volume.

NEWTON FRANK LANE.

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