Патент USA US2412739код для вставки
Dec. 17, 1946. ‘ ~ I ' J, D. MCCRACKEN APPARATUS FOR STEAM GENERATOR CONTROL Filed May 7, 1943 2,412,739 Patented Dec. 17,1946 2,412,739 UNITED STATES PATENT OFFICE 2,412,739 APPARATUS FOR STEAM GENERATOR ' CONTROL James D. McCracken, Chicago, 111., assignor to Askania Regulator Company, Chicago, 111., a corporation of Illinois Application May 7, 1943', Serial No. 486,050 1 4 Claims. The invention relates generally to apparatus for steam generator control, and more particu larly to the control of combustible material flow to the steam generator. Modern, high pressure, steam generators or boilers are designed to generate steam at very high rates and to have relatively small capacity for (Cl. 236-14) 2 in supplying means. Next there is the time lag in the controls which are responsive to the supply of combustion air and which govern the means supplying the fuel. Inasmuch as these time lags are all additive, a very substantial time lag exists, resulting in numerous undesirable conditions, in-. cluding hunting and initial, considerable excess storing heat energy. As a result, such generators supply of combustion air with an- increase in or boilers are highly responsive to the energy load and, conversely, an initial excess fuel supply input, that is, the supply of fuel and combustion 10 for a large decrease in load. ' air and are, therefore, capable of following rel~ It is an object of this invention, therefore, to atively rapid changes in load or steam demand. provide a new and improved apparatus for steam An ideal method of controlling such a steam gen generator control. ‘ 7 erator would be to change the supply of fuel and Another object of the invention is to obtain of combustion air concurrently with load. Such increased stability of control and to obtain such an ideal control might be approximated by having increa'sedstability by a simple method and appa the means for supplying fuel and the means for ratus. supplying combustion air both directly respon A further object is to provide a method of sive to or controlled by the load. Such a method controlwhereby a condition to be satis?ed by of control will hereinafter be referred to as the adjustment of two variables calls for or governs “parallel” method or system. This method of directly all of a ?rst variable and simultaneously control, however, has one particular disadvantage, part only of a second variable, the remainder of namely, the possibilityof feeding straight fuel the second variable being‘ called for or governed to the boiler in the absence of combustion air by the ?rst variable. . . 7 should there be a failure of the combustion air * Another object is to provide a new apparatus supply equipment or its control. The results of for steam generator control which attains to a such feeding of fuel without combustion air are degree the simultaneity of response of the “par su?iciently disastrous in these modern steam gen erators that a second type or method of control has heretofore been employed. This second method or type of control will here inafter be referred to as the “series” method and consists in having the load call for the required combustion air and the air flow in turn call for the corresponding fuel. In this way, no fuel is supplied to the boiler without the required amount of combustion air being available. This method, therefore, eliminates the particularly serious disadvantage of the “parallel” method, but allel” system without, however, incurring the risk of disastrously excessive fuel supply over com—_ 30 bustion air supply, an inherent disadvantage of the “parallel” system. , Still another object is to provide a new appa.— ratus for steam generator control which assures operation of the combustion air control and supply means before the fuel supply means can respond in full to an increase in load, but at the same time attains a moreprompt response of the fuel supply than can be obtained by the “series” system. ‘ has its own disadvantages, some of which will 40 Other objects and advantages will become ap parent from the following detailed description presently be mentioned. ‘ taken in connection with the accompanying Though controls have been perfected until, in some instances, they operate substantially simul taneously with the change in load or demand, there is inherently in such control devices some element of time lag, and as one control device acts on another, and that one in turn on still another, this time lag accumulates and builds up until it is substantial. There is even a greater time lag in the devices that are governed by the con trols as, for example, the combustion air supply ing means in a boiler. Thus in the case of the "series” method, there is, ?rst, the time lag in the controls responsive to the change in load. There is next the time lag in the combustion air drawing, composed of a single, diagrammatic ?g ure. . The method of this invention has a great ' ‘variety of applications andmay be practicedby different types of apparatus. It is, however, par ticularly well adapted for the control of a steam generator and will, for purposes of disclosure, be described hereinafter as adapted to such control of a steam generator and as practiced by a pre _ ferred apparatus. It is not intended, however, .that the invention is to be limited to the particu lar disclosure. On the contrary, it is intended to cover all adaptations of the method and all modi ?cations or alternative constructions of therap 2,412,739 3 paratus falling within the scope and spirit of the invention as de?ned by the appended claims. In its broad aspects, the invention provides a method of control whereby a condition to be sat is?ed by the adjustment of two variables calls for or governs directly all of a ?rst variable and 4 times, and translates that demand into an ap propriate and proportional supply of fuel and of combustion air. To that end, there is provided a ?rst or master regulator 8 which translates the steam header pressure into a measure of steam demand, a second regulator 9 which will herein after be referred to as the load regulator or the combustion air controller regulator, and a third simultaneously part only of a second variable, the remainder of the second variable being called for regulator II] which will hereinafter be known and or governed by the ?rst variable. In a steam referred to as a combustion or fuel regulator. 10 generator the condition to be satis?ed is, of course, . The regulators are each “Askania” regulators the steam demand or the load on the generator. embodying the well known “Askania” jet pipe The two variables are fuel and combustion air principle. which must be supplied in such quantities as to More particularly, the master regulator 8 com ?ll the demand for steam and also, of course, in prises a weight ll selected to maintain a desired such ratio as to insure proper combustion of the pressure in the drum of the steam generator or fuel. . boiler. Opposing the action of this weight is a In a modern steam generator, the supply of pressure responsive device I2 connected by a con combustion air for any considerable length of duit 13 to the steam header 2. The weight H time without a supply, or at least an adequate and the pressure responsive device l2, through supply, of fuel is, undesirable and harmful but not an appropriate lever system It, act on an disastrous. However, the feeding of fuel in the “Askania” jet pipe l5 through which air‘ under absence of combustion air produces results which pressure is ?owing. Disposed opposite the nozzle not only are undesirable and harmful but which of the jet pipe I5 is an ori?ce l6 forming one may be classed as disastrous. Accordingly, in the terminus of a conduit H which is connected to a method of this invention as applied to the control . . pressure responsive device [8' arranged to act on of a steam generator, the combustion air is the the jet pipe [5 in opposition to the weight II. It variable which is governed directly and com~ will be seen from the foregoing that the primary pletely by the condition to be satis?ed and the impulse for the masterregulator is the pressure in fuel is made the variable which is partially gov erned directly by the condition to be satis?ed and 30 the steam header 2 as modi?ed by the weight H, while the secondary impulse is the ‘pressure partially governed by or made responsive to the supply of combustion air, so as to assure that an excessive supply of fuel in the absence of com bustion air does not occur. In‘ the drawing, there is shown diagrammat ically a preferred apparatus for practicing the method of this invention. As shown, I represents a boiler or steam generator having a steam head created in the pressure responsive device IS, the regulator reaching a state of balance when’ the two impulses equally affect the jet pipe 15. The regulator 8' may thus be said to be an equilibrium device. . , , The second or load regulator 9 comprises an “Askania” jet pipe 20 through which a fluid under pressure, preferably oil, is flowing. Disposed op er 2, a combustion air intake or supply conduit 3, a fuel supply conduit 4, here shown as project 40 posite the nozzle of the jet pipe 20 are a pair of ori?ces 2|. The right hand one of these is by ing‘ into and discharging in the direction of the a conduit 22 connected to one port of a hydraulic combustion air supply conduit, and an up-stack motor 23, whilethe other of the, ori?ces is by or exhaust conduit 5- for the products of com a. conduit 24 connected to the other port of the bustion. Thecontroller for the combustion air hydraulic motor. The motor 23 is here shown supply is herein shown diagrammatically as a as a piston and cylinder device and is operatively damper 6 located in the up-stack 5. It is to be connected to govern the combustion air supply understood that this is a purely symbolic show controller represented by the damper 5. The ing intended to represent any type of controller regulator 9 receives its primary impulse from the for the combustion air, supply. In actual prac tice, such controllers take a variety of forms, in-' 50 master regulator 8, and to that end is provided with a ?rst pressure responsive device ‘25 which is cluding exhaust fans, blowers or other devices by a conduit 28 connected to the conduit ll to which may be driven by electric motors or by be subjected to the pressure in that conduit, steam turbines, directly or through hydraulic which is a measure of the steam demand or load couplings or various other media in an attempt on the boiler. The pressure responsive device 25 to attain regulation without hunting. All of is, of course, so arranged as to tend to move the such controllers, whether complicated or simple, jet pipe 23 in such direction ‘as to cause an in director indirect, have some time lag in their op crease of ?ow through the up-stack 5, that is, eration. The fuel supply, likewise, is diagram an increase in the quantity of combustion air sup. matically shown as controlled by a damper ‘I located in the fuel supply conduit 4. This again (ii) plied. 'In order to maintain a metered relation ship between the steam demand and the com is intended purely as a symbolic showing, repre bustion air flow which in turn, under proper oper sentative of any type of controller for the fuel ation and after initial adjustments made, is pro supply, whether that be one adapted for the con portional to the energy supplied to the boiler, the trol ofgas, liquid fuel, powdered coal, or a stoker. These control means, likewise, have an inherent time lag. It is known that the vpressure in the header 2 is a measure of the load or the steam demand on _ or steam generator I and when prop boiler ‘the erly utilized and interpreted may be employed to ‘control the supply of fuel and combustion air to. the steamgenerator. Herein the control appa ' secondary impulse on the load regulator 9 is the combustion air flow. To that end the reguluator has a second pressure responsive device 21 acting in opposition to the ?rst device 25; Herein the' combustion air flow is. measured by the pressure drop across the boiler and, accordingly, ‘the pressure responsive device 27 has opposite sides thereof connected by conduits 2'8 and 29‘; ‘re spectively, to appropriate points- of‘ the boiler. The combustion or fuel regulator llli comprises indication of the load or steam demand, that is, an “Askania” jet pipe 30 through which, as in'the ofthe changing condition to bev satis?ed at all 75 ratus utilizes this steam header pressure as an 2,412,739 case of the regulator 9, a ?uid under pressure, preferably oil, is flowing. Disposed opposite the nozzle of the jet pipe are a pair of ori?ces 3|, the right hand one of which is by a conduit 32 connected to one port of a hydraulic motor 33, while the other ori?ce is, through a conduit 34, connected to the opposite port of the motor 33. Herein the motor 33 is shown as a piston and cylinder device operatively' associated to govern tions, the pressure in the header 2 will drop and this pressure change will, through the conduit I3, be [transmitted ‘to the pressure responsive de vice l2. As a consequence, weight I I will over~ come the pressure responsive device l2 and, through the lever system M, will pivot the jet pipe H3 in such direction that the jet of air dis charged therefrom will strike more directly upon the fuel supply controller, herein symbolically 10' the ori?ce l6. This movement of the jet pipe I5 continues until the pressure in the conduit l'l, illustrated as the damper 1. acting through the pressure responsive device ‘ In order to obtain a more immediate response I3, is su?cient ,to equalize the force exerted by than is obtainable by the “series” method of regu the lever system I 4 thereby bringing ‘the jet pipe lation and yet eliminate the hazards and dis astrous results of the “parallel” system of regula 15 It? to rest in this new equalized position. The pressure in the conduits 26 and 36 is thus pro tion, the'fuel supply in this invention is, as above portional ‘to the steam demand and through the stated, governed partially directly by the steam pressure responsive device 25 acts as the primary demand and partially by the ?ow of combustion impulse on the regulator ,9 and causes thev jet air. To that end the regulator In is supplied with pipe 20 thereof to be pivoted in a direction to two primary impulses; one the steam demand, the cause movement of the controller 6 in such direc other the combustion air flow. Accordingly, the regulator is provided with a ?rst pressure re sponsive device 35 which is by a conduit 35 con nected to the conduit 23 and hence is subjected to the air pressure generated in the conduit I‘! of the . master regulator, which air pressure is propor tional to the steam demand or load. The device 35 is, of course, arranged to urge the jet pipe 30 in such direction as to cause an increase in the supply of fuel. A second pressure responsive de vice 3‘! has its opposite sides connected by conduits 38 and 39 to the conduits 28 and 25, respectively, so as to be responsive to the combustion air flow through the boiler I. The second pressure re sponsive device 37 is connected to act in the same direction as the pressure responsive device 35 and the two are so adjusted that an appropriate variation in the fuel supply is obtained for each variation in the steam demand. It will also be understood that the percentage of control which each of the devices 35 and 3'! exercises may be varied so that the fuel supply may be made ten per cent directly responsive to the steam demand and ninety per cent responsive to the combus tion air ?ow, or the fuel supply may be made twenty per cent, thirty per cent, and so forth, directly responsive to steam demand, and cor respondingly less responsive to combustion air ?ow to ?t any desired condition. ‘ The secondary impulse of the combustion regu tion as to increase the flow of combustion air. The movement of the jet pipe 20 under this pri mary impulse is arrested and eventually stabi lized by the pressure responsive device 21 which receives [the secondary impulse to which the reg ulator is subjected, namely, a measure of the combustion air flow through the boiler. . Simultaneously with this increase in steam de mand, or at least as nearly so as sensitive con 30 trols can make it, and without waiting for the increased combustion air flow to take place, which is delayed not only by the ‘time lag in the controls but also in the means for producing the increased supply of combustion air, a partial in ;-= crease in [the supply of fuel is obtained. This results because of the partially direct control of the fuel regulator Ill by the steam demand. This steam demand is directly re?ected on the regu lator ll) through the conduit 36 and the pressure 40 responsive device 35, and functions to pivot the jet pipe 30 in a direction to bring about an in creased fuel supply. The regulator I ii in response to [this impulse directly from the master regula tor 8 is, of course, adjusted to bring about a por tion only of the total increase in fueLnecessary to satisfy the increase in steam demand. While the percentage of the increased fuel supply thus obtained in direct response to the increase in steam demand may be varied to satisfy different conditions, this percentage in steam generators is preferably something less than ?fty per cent. Large steam generators are, for economic reasons, usually not; operated onlow loads. Furthermore, at the loads at which large steam generators are operated a partial increase in fuel supply without a corresponding increase in the combustion air supply can take place without disastrous results. lator ii! is, of course, the actual fuel supply, and to that end the regulator ID has a third pressure responsive device 43 intended to receive an im pulse proportional to the actual fuel supply. The manner in which this actual fuel supply is measured may take a variety of forms depending upon the character of the fuel. Therefore, the measuring means illustrated in the drawing is As a. consequence, a portion of the fuel supply again but symbolic of any suitable measuring means; Herein a restriction 4| in the fuel supply 60 may be under the direct control of the steam demand to gain the advantage of more prompt conduit 4 is shown with conduits t2 and 43 con response without the possibilities of disastrous nected at one of their ends to the conduit ll on results should the controls not function to bring opposite sides of the restriction and at their re “about an increased combustion air supply. maining ends to opposite sides of the pressure responsive ‘device so to indicate, by the pressure -' differential on opposite sides of the restriction, ‘the quantity of fuel supplied. The regulators 9 and it, like the regulator 8, may appropriately be described as, equilibrium devices. As an aid [to a better understanding of the method andof the. function of the apparatus, the operation thereof for a typical example will be described brie?y. Let it be assumed, therefore, that there has been an increase in the steam de mand or load on the boiler. Under those condi ‘ The balance of the fuel supply is under the control of combustion air ?ow, and to, that end receives its impulse from the difference in air pressure on the opposite sides of the boiler. The pressure responsive device 37 which receive this second primary impulse aids the device 35‘ and between the two a full increase in the fuel supply commensurate with the increased steam‘ demand is obtained. The actual fuel supply createsthe secondary impulse imparted to the regulator Hi and, through the pressure responsive device 40, arrests the movement of the jet pipe 30 when the 2,412,739 full increase in fuel supply called for has been met. ‘ It is believed apparent from the foregoing that I have provided a vastly improved method of and 8 ond device; means for measuring thecombus- ' tion air flow through the steam generator; 9. sec ond signal generator connected to control the power means for said ?rst device including a?rst means connected and responsive to said master signal generator to receive the signal generated thereby and a second means acting in opposition apparatus for the control of two variables, and particularly a method of and apparatus for con trolling the supply of fuel and combustion air in to said ?rst means and connected to said com a steam generator. My invention, among other bustion air ?ow measuring means; and a third things, decreases hunting and it does so not by 10 signal generator connected to control the power a suppression of the oscillations, but by elimina ‘means for said second device including a ?rst tion of ‘the cause for'such oscillations. It is the ' means connected and responsive to said master time lag between a change in demand and the signal generator to receive the signal generated ful?llment of the conditions ‘satisfying that thereby and partially to regulate the fuel supply changed demand which causes hunting, and this directly in accordance with the load on the steam time leg'is reduced by at least partially increas generator, and a second means connected di ing or decreasing the energy input to the, steam rectly and only to said combustion air flow meas generator substantially concurrently with the uring means partially to regulate the fuel supply change in demand. This, moreover, is accom in accordance with combustion air flow. plished without the possibility of disastrous re 3. Control apparatus for a steam generator or sults in the event of combustion air supply failure. the like having a header comprising, in combina I claim as my invention: tion, a master signal generator responsive to the 1. Control apparatus for a steam generator or pressure in the header and operable to generate the like comprising, in combination, a master a signal representative of the load on the steam regulator responsive to the pressure of the steam generator; a ?rst device for controlling the com of the steam generator and operable to generate bustion air supply to the steam generator; power a fluid pressure signal proportional to the steam means for adjusting said ?rst device; a second pressure; a ?rst device for controlling the com device for controlling the fuel supply to the steam bustion air supply to the steam generator; a ?rst generator; a power means for adjusting said sec fluid actuated power means for adjusting said ond device; means for measuring the combustion ?rst device; a, second device for controlling the 30 air ?ow through the steam generator; a'seoond fuel supply to the steam generator; 2. second ?uid signal generator including an equilibrium device actuated power means for adjusting said second device; combustion air flow measuring means; a second regulator for translating the signal of said master regulator into a fluid pressure signal ap plied to said ?rst power means, said second reg ulator being connected to said ?rst power means to permit of the supply of fluid pressure thereto and including a ?rst pressure responsive means connected to said master regulator to receive the signal generated thereby and a second pressure responsive means acting in opposition to said ?rst means and connected to said combustion air flow measuring means; and a third regulator operable to translate the signal of said master regulator and a signal generated entirely by combustion air flow through the steam generator into a ?uid pressure signal governing a portion of the fuel supply in direct response to the master signal and the balance of the fuel supply in response to the combustion air flow only, said third regulator being connected to said second power means to supply fluid thereto and including a ?rst pressure responsive means connected to said master regu lator to receive the signal generated thereby, a second means connected directly and only to said combustion air flow measuring means, and a third means connected to be responsive to the rate of fuel supply adapted to balance said last named ?rst and second means when the fuel supply equals the combined demand of the mas ter regulator and the combustion air ?ow. 2. Control apparatus for a steam generator or the like having a header comprising, in combina tion, a master signal generator responsive to the pressure in the header and operable to generate a signal representative of the load on the steam generator; a ?rst device for controlling the com bustion air supply to the steam generator; power 7 means for adjusting said ?rst device; a second device for controlling the fuel supply to the steam generator; a power means for adjusting said sec connected to control the power means for said ?rst device and connected to be responsive to said master regulator to adjust the air supply entirely and proportionally in response to the load; and a third signal generator connected to control the power means for said second device and con nected to said master regulator and to said com bustion air flow measuring means to regulate the fuel supply partially directly in accordance with the load on the steam generator and partially directly in accordance with the combustion air flow only. a 4. In a control apparatus for a steam genera terror the like, a master regulator connected to be responsive to a primary impulse indicative of the load on the steam generator and to a sec ondary impulse generated by the regulator in re sponse and proportional to the primary impulse to which it is subjected; a combustion air sup ply controller; a second regulator connected to govern said combustion air supply controller and connected to be responsive to the secondary im pulse of said master regulator actingv as a pri4 mary impulse and to an impulse proportional to the ?ow of combustion air through the steam generator acting as a secondary impulse whereby the supply of air is varied in direct proportion to the load; a fuel supply controller; and a regula tor connect-ed to govern said fuel supply con troller, said last named regulator being connected tosaid master regulator to be responsive to the secondary impulse or? said master regulator to control a portion or the fuel supply directly and immediately in response to the load on the steam 7 ‘generator and also connected to‘be responsive directly to an impulse constituting a measure of ' the combustion air supply exclusively, to govern the balance of the fuel supply in accordance with the combustion air supply only. JAMES D. MCCRACKEN.