US3261331A

US3261331A - Steam generator system

Info

Publication number: US3261331A
Application number: US315587A
Authority: US
Inventors: George M Egart
Original assignee: Individual
Current assignee: Individual
Priority date: 1963-10-11
Filing date: 1963-10-11
Publication date: 1966-07-19
Anticipated expiration: 1983-07-19

Description

July 19, 1966 G. M. EGART 3,261,331

STEAM GENERATOR SYSTEM Filed Oct. 11, 1963 5 Sheets-Sheet 1 Passxwrz 4/4: 53mm:

.fZa,

INVENTOR 56627? 11.52747 5;.

@dnwu, 734011271) 9 July 19, 1966 G. M. EGART 3,

STEAM GENERATOR SYSTEM Filed Oct. 11, 1963 5 Sheets-Sheet 4 gym/ 3W0 Y- We 27?! July 19, 1966 e. M. EGART 3,261,331

STEAM GENERATOR SYSTEM I5 20 CA R5 United States Patent 3,261,331 STEAM GENERATOR SYSTEM George M. Egart, 202 N. Merrill, Park Ridge, Ill. Filed Oct. 11, 1963, Ser. No. 315,587 16 Claims. (Cl. 122448) This invention relates to a steam generator system and particularly to such a system wherein the boiler or steam generator is of the rapid response type.

Steam generators of the aforesaid character are widely used in the heating of railway passenger trains and the generator system is carried on the diesel locomotive and in its operation is intended to generate steam in a control-led manner such as to maintain the output pressure within a predetermined range at the output end of the generator where the output is connected to the train steam line. The upper limit of this predetermined output pres sure range is established in every instance substantially below the setting of the safety valve of the system, and may be adjustably varied according to the number of cars on the particular train with which a locomotive is associated. Since such steam generator systems are designed for a particular maximum capacity, it is customary to provide from one to three such steam generators on those locomotives that are intended to haul relatively long trains, and for extreme situations a fourth generator is used.

Such a steam generator system has been made by and sold by Vapor Heating Corporation of Chicago, Illinois, under the name of Vapor-Clarkson steam generator, and such steam generator system as made and sold by Vapor Heating Corporation, over the last few years at least, have been substantially identical in most respects with the steam generator system shown in C-larkson et a1. Patent No. 2,751,894, patented June 26, 1956.

The Vapor-Clarkson steam generator system is almost universally used on diesel passenger locomotives in the United States, and while the system functions reasonably well under ideal conditions and when the steam load or the train length are not excessive, many situations have developed where proper heating of the associated train can not be attained even though enough steam generator capacity is provided. The difiiculty in heating long trains has caused at least one railway to resort to installation of one or more steam generators in a rear car of long trains.

While the maximum steam output of such a conventional system serves as a basic and limit on its train heating capacity, further limiting factors are imposed, first, by the necessity to maintain, for any particular train length, a minimum head end steam pressure which, despite progressive line losses and car-by-car steam consumption along the train line, will assure a rear car line pressure sufficient to heat the rear car of the train, and second, by related limiting characteristics of such conventional systems which produce an extremely wide variation between maximum and minimum steam pressures, that render it impossible for the desired maximum steam pressure to be attained when the load exceeds the low fire output capacity of the boiler.

In other words, the droop in pressure between low fire and high fire is such that high output cannot be obtained except with low pressures.

The net result of the foregoing limiting characteristics has been that when the load approaches the maximum boiler output, the Vapor-Clarkson system tends to operate at an output steam pressure that is near the lower limit of the relatively large basic pressure range required by the ice system. Keeping in mind that the upper limit of the basic pressure range must be set substantially below the setting of the safety valve, such inherent tendency under high load, to operate at a greatly reduced output steam pressure, often renders such a conventional generator incapable of heating the rear cars of a train even though the total heating load is less than the rated maximum capacity of the generator or group of generators.

Thus, the total heating load, and the train length constitute variables that may render such a conventional steam generator, or a group of such generators, incapable of heating the rear cars of a train, and a related variable factor that is encountered is the effective area of the train steam line. Standard passenger cars in the United States are now being equipped with 2 /2 inch steam lines, but many passenger cars are still in use having 2 inch steam lines. Thus for a particular train the effective or average area of the train steam line may vary, the most favorable condition so far as car heating is concerned being provided by a train made up entirely of cars having 2% inch steam lines, and this variable has further complicated the problem of attaining satisfactory heating of passenger trains.

It is the primary object therefore of the present invention to enable the steamgenerat-ing systems, including those now installed and in use on passenger locomotives and the like, to be operated in a more satisfactory and a more efficient manner, to the end that the usefulness of such equipment may be greatly increased, and more satisfactory heating of passenger trains may be attained.

Other important objects of the invention are to enable the maximum output steam pressure in such systems to be readily varied or set, to control the output steam pressure within a relatively narrow and accurately determined range, to enable this accurately determined steam pressure range to be attained in such :a way that-it is not disturbed or appreciably changed when the maximum steam output pressure is adjusted to a different value, and to enable the maximum output steam pressure to be governed in such a Way and with such certainty as to permit operation of the system at steam pressures relatively close to the setting of the safety valve of the system.

More specifically it is an object of the invention to enable the generator or boiler of such systems to be more fully utilized, and an object related to the foregoing is to enable the firing of the boiler of such a system to be accomplished more efficiently.- Other objects related to the foregoing are to minimize the periods of low fire operation of the boiler so as to thereby produce increased efliciency and more effective utilization of boiler capacity, and to initiate each burner operation at high fire so as to assure quick response to an indicated demand for steam.

Other and further objects of the present invention will be apparent from the following description and claims, and are illustrated in the accompanying drawings, which, by Way of illustration, show preferred embodiments of the present invention and the principles thereof, and what is now considered to be the best mode in which to apply these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the invention.

In the drawings: 1

FIG. 1 is a schematic view illustrating a steam generator system embodying the invention;

FIG. 2 is a vertical central sectional view of a control valve that is embodied in the system, the valve being shown in its fully closed position;

FIG. 3 is a fragmental portion of FIG. 2 showing the valve member in a partially opened position;

FIG. 4 is a view similar to FIG. 3 and showing valve member in its fully open position;

FIG. 5 is graph showing a typical pressure drop curve that may be encountered in the steam line of a railway train;

FIG. 6 is a view showing the pressure characteristics of a steam generator system embodying the present invention;

FIG. 7 is a graph showing the required head end pressure for trains of different length and showing the performance characteristics of the present generator system as compared with the prior art system; the graph being based on the use of a 2 /2 inch diameter train line; and

FIG. 7A is a graph similar to FIG. 7 but based on the use of a 2 inch diameter train line.

For purposes of disclosure the invention is herein illustrated as embodied in a steam generating unit or system 10 which in most of its details is constructed and arraged as shown and described in Clarkson et a1. Patent No. 2,751,894, patented Tune 26, 1956, and in the drawings of this application, those elements of the Clarkson et a1. patent that are employed without material change have been shown exactly as they were shown in the aforesaid prior patent. With respect to such elements of the system which may be identical with the Clarkson et al. disclosure, and with respect to the general theory of operation thereof, reference is made to the Clarkson et a1. patent, and such disclosure is incorporated by reference herein as a part of the present disclosure.

Thus, FIG. 1 of the drawings corresponds almost exactly with FIG. 1 of the Clarkson et al. patent with the exception that the valve 41 of such patent has been replaced by a control valve V which is utilized to control the basic Clarkson et al. system to produce a different and more efiicient functioning thereof. In FIG. 1 it will be apparent that the system of the present invention em- .tbodies a rapid response boiler B having coils 16 defining a path along which boiler feed water is advanced so as to be heated by the flue gases from a combustion chamber 17. The output from the coils 16 of the boiler B is in the form of wet steam that is fed through an output line 30 to a steam separator 31 and the separated liquid in the form of warm water is returned through a return line 32 and associated connections to the water supply source, as will be described. The steam output of the steam separator 31 passes through a shut-oft" valve 39 to an output line 38 which, in the use of the system, is connected to the head end of the main steam line of an associated train.

The boiler or generator B is supplied with gaseous or liquid fuel through a nozzle 18, and air for supporting combustion is supplied from a blower structure 52 under the control of a butterfly valve 52A. The rate of supply of fuel and air to the combustion chamber 17 is controlled by a servo unit 24, that is in turn governed by the rate of flow of feed water that is being supplied to the boiler B. The rate of supply of feed water is, in turn, governed by the steam pressure at the steam separator 31, this general governing action having been obtained in the Clarkson et a1. system by a steam pressure responsive valve 41, while in the present instance such control is obtained by the valve V as will be described in detail hereinafter. Fuel is supplied to the servo unit 24 from a tank 107, and under control of the servo unit 24, is fed through a line 59 to the fuel nozzle 18 of the boiler B.

The rate of supply of feed water through the line is controlled, as noted above, by the valve V and this is accomplished by bypassing varying proportions of water the the

2- supplied by the feed pump 21, the bypass Water being returned to the supply tank from the valve V to a return line 43.

In order that the operation of the steam connector system 10 of this invention may be better described, FIGS. 5 to 7A have been included in the drawings to bring out the limiting conditions that must be met by a train heating system in order to attain proper and satisfactory heating of a train.

Thus FIG. 5 of the drawings constitutes a graph showing typical train line pressure drop curves that are representative of the pressure drop that is encountered in a long train between the lea-ding car and the rear car. The curves included in FIG. 5 are calculated rather than being based upon test data, and these curves take into account an assumed steam consumption or load per car as well as the car lengths and the line losses introduced by line size, fittings and the like. As will be apparent, the progressive pressure drop assumes a parabolic form and the line losses for any particular train length become particularly rapid where the head end pressure is relatively low. As to curve 50, where the head end pressure is indicated at 210 lbs. per square inch, the pressure drop is quite rapid so that at the ninth car in a train, the pressure would have dropped to 100 lbs. per square inch which is usually considered to be the minimum pressure that is required for proper heating of a car.

Curve 51, as shown in FIG. 5, starts with a head end pressure of 240 lbs. per square inch and it is to be noted particularly that the curve 51 diverges upwardly with respect to the curve so that throughout a complete twenty-four car train the steam pressure in the line remains above lbs. per square inch. Such a pressure of 100 lbs. per square inch is necessary to provide a margin of safety in case of a sudden pressure drop in some part of the system.

Even greater improvement is shown by curves 52 of FIG. 5 where the head end pressure is indicated as 290 lbs. per square inch, and in this instance through the entire train of twenty-four cars the steam pressure is maintained above 193 lbs. per square inch.

Keeping in mind that the curves are based on an assumed load of 300 lbs. of steam per hour per car, it will be clear that the employment of a 290 lb. head end steam pressure would provide a great margin of safety so far as heating is concerned in the event that weather conditions increase the heating load above that assumed in calculating curve 52. Particularly, it is noted that a relatively small increase in head end pressure produces a very marked increase in the available pressure at the rear end or rear car of a train, and hence it should be observed broadly that so far as train heating is concerned, operation at a high head end pressure is particularly desirable.

The data used in plotting the pressure drop curves of FIG. 5 has been employed in FIGS. 7 and 7A to plot steam demand and head end

pressure demand curves

53 and 53A which are generally similar, but differ in that demand curve 53 is based on a 2 /2 inch diameter train line, while demand curve 53A is based on the use of a 2 inch diameter train line. In both instances, curves 53 and 53A are based on the assumption that a steam pressure of 100 lbs. per square inch is required at the rear car of a train in order to properly heat the rear car.

it may be noted here that FIGS. 7 and 7A contain further plotted data showing a performance characteristic of the unit 10 of this invention and of the prior art Vapor- Clarkson generator unit that is currently used as standard equipment on railway passenger locomotives.

As a basis for further discussion of FIGS. 7 and 7A, the graph of FIG. 6 requires explanation. FIG. 6 constitutes a comparative graph showing the operating and pressure characteristics of the pressure unit it? and of the prior Vapor-Clarkson steam generator system, the graph being based on test data obtained by operation of a par- 'cular steam unit in its original form on a diesel locomotive unit. In numerical and tabulated form, this test data was as follows:

TABLE I.TEST OF NO. 4740 VAPOR-CLARKSON GENERA- TOR 0N AT & SF LOCOMOTIVE UNIT #542 [Using standard Vapor-Clarkson controls] Pin Plate Burner Low Fire High Fire High Fire Setting Marking Off at Off at On at- *Safety valve setting at 285#.

The pressure readings of Table I are of course based on the particular steam unit tested, so that different test readings must be expected with other steam units.

TABLE II.TES1 OF NO. 4740 GENERATOR ON AT & SF UNIT #542 [Using by-pass regulator valve V and making no change in servo or other adjustments] Steam Air Burner High Pressure Pres- 01f Fire On Setting sure 275 107 275 260 235# Safety Valves at 285# 250 91 250 230 200# Maxhnum setting lim- 200 67 200 180 155# ited by safety valve 160 50 165 135 115# setting.

Cycling operation under low load conditions The data shown in Tables I and II illustrates the recurrent onoff cycling that takes place under conditions where there is no load, or where the load is substantially less than the full maximum output of the generating system, and it should be observed that where such a system is operating fairly close to its full output, it does not cycle through on and off cycles, but modulates its output as will be described in some detail hereinafter.

The test data shown in Table I has been utilized in the graph of FIG. 6 to plot steam generator output pressure against the steam generator output, it being noted that the generator on which the test data of Table I was obtained had a low fire steam output of 1600 lbs. per hour and a steam output of 4800 lbs. per hour at high fire setting. Thus with respect to the original Vapor-Clarkson unit the lowest steam output pressure of 165 lbs. per square inch represents the level at which steam output pressure must fall on the tested unit in order to establish high fire operation of the boiler, and this point has been plotted in FIG. 6 at 55A and shows that at this point in the cycle of test operation of the Vapor-Clarkson generator, the steam output rate first reaches its maximum. In the Vap'or-Clarkson data of Table I, the high fire opertion continues until the steam pressure reaches 195 lbs. and this value has been plotted in 5513. At this point in the operating cycle the adjustment of the burner toward low fire operation is started and this adjustment continues until the output pressure reaches 230 lbs. per square inch, this point being plotted at 55C.

At this point in the cycle, the firing adjustment is held at low fire by what is termed the delay adapter that is shown in FIG. 73 of the 1950 Vapor Corporation Bulletin No. 2203 Rev. A, this figure being shown on page 67 of such bulletin. Fundamentally, this delay adapter is in the form of an adjustable friction detent of the over-center type, and in the unit that was tested, a further increase in output steam pressure of 35 lbs. per

square inch was required to move the delay adapter burner has been turned off as indicated at 55D the steam pressure in every instance starts to drop, and the delay adapter then iseiTectiVe to prevent turning on of the burner until the head pressure has reduced to 230 lbs. per square inch. This relation has been plotted at 55E. When the burner has been turned on, as indicated at 55E in FIG. 6, the burner will start to adjust gradually toward its high fire position, it being assumed that the load in this instance is greater than the output capacity at low fire, and such adjustment continue and is caused by a further substantial reduction in output steam pressure, and when the output or head pressure has fallen to lbs. the burner goes into its high fire operation as indicated at point 55A, heretofore described. The several points 55A to 55E have been connected by lines to form an operating characteristic curve or loop 55 that Was attained with the conventional Vapor-Clarkson generator above discussed.

The lowest output steam pressure of 165 lbs. plotted at 55A in FIG. 6, constitutes an important limiting characteristic of the conventional Vapor-Clarkson steam generator, and it might be pointed out that where the load exceeds the low fire output of 1600 lbs. per hour, the conventional Vapor-Clarkson unit never reaches its shutoff point 55D, but on the contrary modulates between high fire and low fire operation with a substantial proportion of such operation in the low and intermediate firing ranges.

The operating test data set forth in Table II are based on the tests of the unit 10 of the present invention, including the control valve V. This data shows that the burner was turned on at 235 lbs. head pressure, since the burner starts at low fire, this has been plotted at point 56E, in FIG. 6. As will be hereinafter described in some detail, the unit 10 almost immediately assumes its high fire setting so that as plotted in 56A in FIG. 6, the high fire operation starts while the head pressure is still at approximately 235 lbs. This high fire operation continues until a head pressure of 260 lbs. has been reached, and this value has been plotted in 5613 in FIG. 6. The firing rate is then gradually decreased in response to increase in head pressure up to 285 lbs. where the burner reaches low fire and is then shut off as plotted at 56D in FIG. 6. The points 56A to 56E have been connected in series in FIG. 6 to provide a characteristicpressure-output curve or loop 56 for the unit 10 of this invention.

It will be noted in the test data included in Tables I and II that the safety valve setting was 285 lbs. during both tests, and it will be further noted that the burner-off setting of the valve V was somewhat higher than the shut-off setting of the control valve of the Vapor-Clarkson unit. This was deliberate in that the valve V that is employed under this invention has characteristics of reliability which enable such a lower safety margin to be adopted. This is primarily due to the expected and rather uncontrollable variations that occur in the use of the delay adapter with the bypass control valve of the Vapor-Clarkson equipment.

It may be pointed out that most railways now prefer to use an even higher safety valve setting of 295 so that the on and off pressures for the steam generators may be correspondingly increased.

The radically different operation of the unit 10 as thus described, results in an unexpected improvement over the train-heating capabilities of the basic Vapor-Clarkson system, and as a basis for description of this improved operation, the features of the control valve V and the manner of its association in the basic system will now be described. Thus, as shown in FIGS. 2, 3, and 4, the valve V has a sectional, upright housing 60 comprising a base plate 61, relatively tall main body 62, and an upper body 63 that are secured together by means such as cap screws 64. Aligned

central bores

62B and 63B are formed re spectively in the main body 62 and the upper body 63 to slidably receive an elongated valve stem 65 which at its upper end projects slidably through and beyond an upstanding sleeve 163 formed at and integrally on the upper body 63, and which at its lower end projects into a stepped cylinder formed by a pair of

enlarged counterbores

166 and 266.

From the horizontal meeting plane of the

body members

62 and 63, the upper body member 63 has an upward counterbore to form an enlarged Water inlet chamber 163, and the main body 26 has a similar downward counterbore defining an enlarged water outlet chamber 162. Radial bores 263 and 262 extend from the respective inlet and

outlet chambers

163 and 162 for connection in the feed Water bypass circuit as will be described.

The adjacent ends of the

chambers

162 and 163 have shallow and relatively

large counterbores

362 and 363 which define a mounting pocket for an annular valve seat member 69 which will be described in further detail hereinafter and which is arranged to receive and cooperate as will be described, with an enlarged valve head 71 formed integrally with the valve stem 65. The valve head '76 is urged upwardly toward its closed position by an expansive coil spring 71 mounted on the top of the upper body 63 and surrounding and associated with the upper end of the valve stem 65, as will be described, and at its lower end the valve stem 65 has a stepped piston 72 fixed thereto for cooperation with the valve spring 71 in moving the valve head 7 1 between its open and closed positions. The form and relationship of the valve seat 69 and the valve head 71) will be described in detail hereinafter.

The stepped piston 72 has its smaller upper end 172 slidable in the cylinder 166 and it has its lower and larger end 272 slidable in the lower cylinder 266. A central bore 72B is extended through the piston 72 and is counterbored and threaded at 72T at its lower end. The lower end of the piston extends downwardly through the bore 72B and a locking ring 72R recessed into the piston rod 65 is seated in the enlarged counterbore 723T and is held in place by a plug 7 4 which, in addition to its holding function, also serves a controlling purpose as will be hereinafter described.

The smaller upper end 172 of the piston is adapted to A be subjected to steam pressure, as will be described, and a steam inlet port 75 from the upper end of the cylinder 166 opens laterally through the body 63.

For purposes that will hereinafter be described, in detail, the larger piston 272 is subjected to a constant but variably adjustable fluid pressure, and this pressure may be supplied through an inlet opening '76 that is provided in the base plate 61 so as to open into the lower end of the cylinder 266 near the outer edge of the cylinder. It will be noted that the upper end of the cylinder 266 has a lateral vent opening 77 to prevent pressure build up within this space.

According to the present invention, the air or other pres sure fluid that is furnished to the cylinder 266 is continuously bled off at a relatively low rate, and for accomplishing this, the base plate 61 has a plug 78 threaded therethrough in a central relation, and held in position by a lock nut 78N. The plug 78 has a hardened steel bolt 80 extended through a central passage in the plug, and a nut SUN on the lower end of the bolt holds the bolt 80 in position. It may also be noted that the head of the bolt 80 engages a resilient ring 81 to hold the same in position in a recess 78R in the plug 78. The bolt 86 has a central passage 82 extended therethrough which may be reduced at its upper end as at 82R, and this passage constitutes the bleed passage from the cylinder 266.

The bleed passage 82 is open or effective at all times except when the piston 272 is at the lower end of its stroke and when this condition prevails, an annular sealing ring 85 formed centrally and in a downwardly facing relationship on the nut 74, engages the resilient ring 81 so as to close the vent or bleed passage 82 and thus isolate a predetermined central area of the lower face on the piston 272 from the upward force of the pressure fluid in the cylinder 266. The functioning of the piston 272 and its 8 related parts in the operation of the steam generator 10 will be described in detail hereinafter.

The spring 71, at its lower end, surrounds the threaded sleeve 163 and bears downwardly against a suitable screw threaded collar 86, this collar having a lock screw 86L associated therewith for locking the collar 86 in adjusted position. The upper end of the piston rod 65 has a universal coupling 87 associated therewith at one end by means including a screw threaded connection and a lock nut 87, and the upper or other end of the universal coupling is similarly associated with an upper bolt 88. The bolt 88 has a collar 89 thereon which engages the upper end of the spring 71, and a ball thrust bearing 90 rests in place on the top of the washer 89 and is secured in this position by a nut and washer arrangement 91.

The valve spring 71 acts to urge the valve head 70 toward its valve-closing position, and the line 40 from the steam separator is connected to the steam inlet passage 75 for applying the output steam pressure to the piston 172. It is this steam pressure that urges the valve head 70 in a valve opening direction. Such movement of the valve head 70 controls the bypass flow of said water from the line 25 and to this end, the water inlet passage 263 is connected to the line 23 by a line 42 and the water outlet passage 262 is connected by a line 43 to direct the bypass water back to the supply tank 20.

The valve stroke in the present valve V is limited in extent by engagement of the annular flange or ring 85 with the resilient ring 31 at the bottom of the pressure air cylinder 266, and in the present instance adjustment of the plug 78 may be employed to vary this maximum stroke of the valve head within a small range of adjustment.

In the embodiment shown herein and as used in the tests described hereinabove, the valve head 70 moves through a downward opening stroke that includes a first and major portion of its stroke wherein the effective valve opening is increased very gradually, this portion of the stroke being in the present instance. Further downward movement of substantially produces a rapid increase in the effective valve opening, and thereafter in any further movement up to about /2", the downward movement of the valve head 70 may be considered as an idle movement in that no further increase in the effective valve opening is caused.

As above pointed out, the steam pressure from the steam separator acts on the upper end of the piston 172 so as to tend to compress the spring 71 and open the valve V, and under the present invention, as will be described in further detail hereinafter, this valve opening force applied by the steam pressure is opposed by the resilient action of pressure air in the cylinder 266 which acts upwardly on the piston 272. Thus, the valve closing forces in this instance are provided by the substantially constant force of the spring 71 coupled with the force provided by the pressure air which of course may be adjusted or varied to thus provide for adjustment of the operating points of the valve V. Thus the air pressure within the cylinder 266 is provided from a source 94 and connecting

pipes

95 and 95A, a pressure regulating valve 96 being provided between the

lines

95 and 95A for adjustably varying the air pressure that is supplied to the cylinder 266. The regulating valve 26 may of course be located remotely with respect to the unit 10, and hence the heater operation may be controlled from the locomotive cab. It should be noted that selecting a specific air pressure reading on regulating valve 96 will effectively establish the operating steam pressure of the steam generator. Thus the air pressure regulator 96 is calibrated to read steam pressure directly.

With the arrangement thus provided the spring 71 operates at all times within a limited range of compression and this range of compression is the same regardless of the value of the air pressure established in the cylinder 266. Basically, the spring 71 is relatively long and relatively soft and in a valve V of the dimensions and stroke above specified, a two inch spring about seven inches long and having a spring rate of about 119 lbs. per inch may be employed to produce the desired operation. With such an arrangement and with the piston 172 having a diameter of about 2 /2, the valve head 70 may be moved throughout its entire range in response to a steam pressure variation of about lbs. and the operation of the spring 71 is the same, no matter what the adjustment of the air pressure may be. In this connection it is pointed out that the area of the piston 272 that is subjected to air pressure in' the present instance is twice the area of the piston 172 that is subjected to steam pressure, and hence a lower air pressure may be employed.

In the particular valve that was used in obtaining the test data upon which FIG. 6 of the drawings is based, the air pressure in the cylinder 266 was adjusted so that the valve head 70 would be moved to its fully open position when the steam pressure reached a value of 275 lbs., and at this steam pressure value, the valve head 70 was moved to its fully open position wherein the bypass was completely open so that all of the boiler feed water was bypassed, and the burner was consequently shut off.

When the valve head 70 is in its fully open position, the downwardly projecting ring 85 on the piston 272 closes the bleed passage 82, and this has an important controlling action on the operation of the system. When the bleed passage 82 is closed, the area of the piston 272 that is enclosed within the downwardly projecting ring 85 'is no longer subjected to pressure air that is supplied by the line 95A and the upward resilient forces applied by a piston 272 to the valve member are correspondingly reduced in accordance with the area of the piston 272 that has thus been described. In the present instance the proportioning of the diameters of the ring 85 and the piston 272 are such that a substantial further drop in the steam pressure in the cylinder 166 is required before the combined action of air pressure and spring pressure causes the valve head 70 to return to its fully closed position wherein the burner of the boiler is turned on at high fire. Such closure of the valve takes place almost instantaneously because as soon as the ring 85 is lifted off of its resilient seat 81, the entire lower face of the piston 272 is again rendered effective so that there is a sudden increase in the total force tending to close the valve. In the valve V that was used in the tests above described, the proportioning of the two different areas of the piston 272 was such that the steam pressure was required to drop to about 235 lbs. per square inch.

The valve head and valve seat In a broad sense, the operation of the valve head 70 through its downward stroke from the closed position of FIG. 2 and through the position shown in FIG. 3, and finally to the fully open position of FIG. 4, is such that throughout the movement from the FIG. 2 position to the position of FIG. 3, the effective valve opening gradually is increased, and soon after thevalve head 70 passes downwardly beyond the position shown in FIG. 3, there is a sudden increase in the effective valve area so that in this situation, the valve V acts as a complete dump valve to re turn all of the boiler feed water and thus stop operation of the burner.

As will be evident particularly in FIGS. 3 and 4 of the drawings the valve seat member 69 has a central cylindrical opening or bore 169 through which the valve stem extends, and at its lower end, the bore 169 is counterbored to provide a tapered downwardly facing seat 269 that is annular in character. The seat 269 meets the bore 169 in an annular edge 369 which becomes important in consideration of the functioning of the valve as will hereinafter appear. Just above the head 70, the valve stem 65 has a reduced diameter portion 165 that is defined by shoulders at its upper and lower ends, and the lowermost of these shoulders defines the upper end of the valve head 70 in a manner that will be described in detail hereinafter.

The head 70 comprises an enlarged integral portion of the valve stem 65, and the lower portion of the head being the largest, and this lower portion has its upper edge defined by an annular upwardly facing tapered seat 270 that is complemental to the downwardly facing tapered seat 269. Above the tapered seat 270, the valve head 70 has an upwardly extended tapered section 170 that meets the inner upper edge of the seat 270 along an annular line 270L. The upper end of the section 170 terminates in an annular corner 370 that is defined by the intersection of the surface of the section 170 with the shoulder that defines the lower end of the reduced section of the valve stem.

At its lower end, as defined by the annular line 270L, the tapered section has a diameter that is precisely equal to the diameter of :the bore 169 of the valve seat member 69, and the section 170 tapers gradually toward a smaller diameter at the upper end thereof as defined by the annular edge 370.

Thus when the valve member 70 is in its upper position of FIG. 2, the seats 269 and 270 are engaged and the valve is fully closed, and as the valve stem 65 is moved downwardly, an annular space is formed between the tapered surface of the section 170 and the annular line 369 of the valve seat 69. This annular space thus constitutes the effective valve opening, and as the valve stem 65 is moved progressively downwardly, this annular space is gradually increased, as will be evident by a comparison of FIGS. 2 and 3. When the annular upper edge 370 of the valve head 70 passes the horizontal plane of the annular line 369, continued downward movement causes the effective area of the valve opening to be rapidly increased, and this increase takes place at a rate that greatly exceeds the rate of increase in the earlier portions of the valve opening movement. Hence, in the final downward movements of the valve head 70, as for example from the position of FIG. 3 to the position of FIG. 4, the effective area between the annular edge 370 and the annular edge 360 soon exceeds the area between the reduced portion 165 of the valve stem and the bore 169. In other words, the ratio of area increase with respect to the valve stem movement suddenly increases, so that a well defined cut-off point is provided where the sudden dumping of all of the flow from the feed water line causes the burner to be quickly shut off. The point of sudden enlargement of the bypass line effectively establishes the minimum firing rate and prevents fire at a rate below that required for stable combustion.

The movement of the valve member 70, downwardly beyond its fully open position of FIG. 4 brings the annular member 85 into engagement with the resilient annular member 81, and this immediately reduces the effective area of the lower or larger piston 272. The net result of this is that a differential is established for the valve V so that the steam pressure must drop a considerable amount before the valve spring 71 will again be able to move the valve head 70 to its closed position. In the present instance this differential has been established as requiring a 40 lb. per square inch further decrease in the head'end steam pressure. Thus when the pressure has dropped off in the required amount, the spring 71 starts gradually to lift the valve stem 65. As soon as the members 85 and 81 have been separated to a slight extent, the air pressure in the lower cylinder 266 again becomes effective through out the entire lower area of the piston 272 so that additional pressure equal to the 40 lb. differential above-mentioned is immediately applied to the valve stem, and this results in almost immediate upward movement of the valve head 70 from its fully open position to its fully closed position. This of course results in a full volume flow of feed water through the servo unit so that the burner is quickly adjusted to its high fire position and the generator starts production of steam at its maximum output rate.

Operation close to maximum output capacity In FIG. 6 of course the full cycling operation of both the prior system and the system of the present invention have been illustrated, and it has been pointed out that basically FIG. 6 shows such cycling as it occurs when the systems are working under no load, or relatively light load. However, when such a system is working at a load which exceeds or closely approximates the maximum steam output of the system, the operation is quite different in that the boiler does not go through its off-on cycles, but in contrast, operates close to the maximum output capacity with the flame modulating between high fire and an intermediate fire. This is because under such conditions, the increase in head steam pressure will cause a gradual reduction in the firing rate, and when the rate of steam production falls below the rate of steam consumption, the pressure in the output line of the system falls so as to tend to increase the firing rate in the boiler. Thus, with respect to the Vapor-Clarkson system, operation at a level closely approximating the high fire maximum output causes the boiler to modulate within a range such as the range indicated by the shaded area M in FIG. 6. Under such circumstances the boiler will not go off and on, nor will the output pressure fall below the level 55B to any appreciable degree.

As applied to the steam generator of this invent-ion, a similar situation prevails as will be evident in FIG. 6 of the drawings wherein the modulating area within which the generator operates when the load closely approximates the maximum output is indicated by a shaded area N that lies immediately below the line 56B56D of FIG. 6.

A comparison of the Vapor-Clarkson operation and the operation of the generator 10 of this invention shows that under such modulating ope-ration of the Vapor-Clarkson unit may have its output pressure reduced to something below 200 lbs. per square inch, while in the unit of this invention the modulating operation of the unit maintains a much higher minimum output steam pressure that, in the selected example, is above 260 lbs. per square inch.

The improved heating of long trains In FIGS. 7 and 7A such operation of the Vapor-Clarkson unit and the ope-ration of the steam generator of this invention have been plotted against the steam demand curve presented in trains of ditferent lengths, FIG. 7, showing this relationship where a 2 /2" train line is used while FIG. 7A shows this relationship where a 2" train line is employed.

Thus, in FIG. 7, the output of a single Vapor-Clarkson unit has been illustrated by the line 1-55 which at its opposite ends is determined by plotting the

points

55E and 55B of the Vapor-Clarkson operation as illustrated in FIG. 6. Similarly, a line 2 55, and a line 3-55 have been illustrated in FIG. 7 showing the output capacity of two Vapor-Clarkson units and three Vapor-Clarkson units, respectively, and these merely serve to add the output of the indicated number of individual steam generating units.

Similarly, the line 156 and the line 2-56 have been plotted on FIG. 7 to show the output capacity of one unit 10 of this invention, and two units 10 of this invention.

FIG. 7A has the output capacity of the steam generating units plotted thereon in the same general manner as in FIG. 7.

Thus, it will be clear for example in FIG. 7 that with the steam demand curve 53 as plotted therein, the maximum number of cars that can be heated by a single Vapor- Clarkson unit is but 16 cars, and this same limitation is resent with respect to the steam generating units 10 of the present invention, it being noted that in both instances the limitation is produced by the maximum capacity of the steam generators rather than by the steam line. When more than one generator is employed, however, the situation is radically different. Thus, when two Vapor-Clarkson units are employed, the output capacity is such that I2 the two uni-ts will heat more than 16 cars, but because of the relatively low pressure that is attainable with the Vapor-Clarkson units, the maximum capacity is 21 cars.

Even where a third Vapor-Clarkson steam generator is added, there is but a slight increase in the steam pressure so that three such Vapor-Clarkson generators will have no greater heating capacity on the train than the two Vapor-Clarkson units. In other words, even with three Vapor-Clarkson units, only 21 cars can be heated.

In contrast to this then it should be noted that where two units It]! of this invention are employed, the output capacity and the output pressure characteristics are such that 26 cars may be effectively heated.

Similarly, as shown in FIG. 7A, the unit 10 of this invention enables greater efficiency to be attained even when a 2" trainline is used.

Thus, the low output pressure of a single Vapor-Clarkson unit will heat but 13 cars, while a single unit It) of this invention will heat 16 cars and is limited only by the maximum output of the unit.

Where two steam generators are used, the units 10 will heat 18 cars, while two Vapor-Clarkson units will heat but 15 units; the limitation in each instance being imposed by pressure drop in the trainline.

Conclusion From the foregoing description it will be apparent that the present invention enables steam generating systems of the kind now used in passenger locomotives and the like to be operated in a more satisfactory and efiicient manner so that the usefulness of such generating systems is increased and passenger trains may be heated with greater effectiveness. It will also be apparent that the present invention enables the maximum steam output pressure in such systems to be readily varied or set, and it also enables the output steam pressure to be controlled within relatively narrow and accurately determined limits.

It will also be evident that the present invention enables the maximum steam output pressure to be governed in such a way in railway steam generating units that the maximum output pressure of such systems may be set relatively close to the setting of the safety valves in the systems. It will further be evident that the present invention enables the generator or boiler of such steam generating systems to be utilized with greater etficiency than has been possible heretofore, and as a further point, the firing of the boiler is accomplished under the present invention with greater efiiciency.

It will also be apparent that the present invention makes it possible to minimize the periods of low fire operation in steam generators of the kind used in railway work for heating purposes and because low fire operation is minimized, the boiler capacity is utilized more effectively and more effioiently.

It will also be apparent that under the present invention the burner is immediately adjusted to its high flame operation when the burner is started, and therefore, steam production is attained relatively early in the cycle at the maximum output rate of the unit.

Thus while a preferred embodiment of the invention has been illustrated herein, it is to be understood that changes and variations may be made by those skilled in the art without departing from the spirit and scope of the appended claims.

I claim:

1. In a steam generating system having a boiler with a fluid fuel burner and a feed water line for the boiler having a constant rate feed water pump discharging to said feed water line, burner control means including a fuel valve for turning the burner on or off and varying the firing rate thereof between low fire and high fire operation, servocontrol mechanism through which said feed water line is connected and responsive to the fiow rate of feed water through said servo mechanism to said boiler to govern said burner control means to turn the burner oif in response to feed water flow rates below a predetermined minimum feed water flow rate and to turn the burner on in response to a feed water flow greater than said predetermined minimum feed water flow rate and While the burner is on to vary the firing rate of the burner in substantially direct proportion to the feed water flow rate, a bypass line connected to said feed Water line between said feed pump and said servo mechanism and through which varying proportions of the feed water may be bypassed, and control valve means variably governing said bypass line and responsive in recurrent variations in the steam output pressure of said boiler, said control valve means including means responsive to a predetermined maximum steam output pressure to fully open said bypass line to thereby reduce the feed water flow rate to a value below said minimum flow rate to thereby shut off said burner, means for gradually opening said control valve means in responsive to increases in said output steam pressure until said maximum output steam pressure is reached, and means for maintaining said bypass line fully open when said maximum steam output pressure is reached and until said output steam pressure falls to a predetermined minimum output pressure while thereafter immediately fully closing said control valve to thereby cause maximum flow of feed water to the servo unit and immediate operation at high fire.

2. In a steam generating system having a boiler with a burner for burning fluid fuel and a liquid supply line for supplying water to the boiler, means for pumping said water at a constant rate through said supply line, a servo unit actuated by the flow rate of the feed water at a particular point in said supply line to vary the supply of fuel in direct proportion to the variations in the flow rate of the feed water at said point in said supply line, and means responsive to the output steam pressure of the boiler to bypass said water from said supply line before it reaches said point for varying the flow rate of feed water at said point, said last-mentioned means comprising a valve member having a spring normally urging said valve member toward said closed position and means associated with the valve member and responsive to steam pressure for imparting movement to the valve member in an opening direction, piston and cylinder means associated with said valve member for applying resilient force to the valve member in the same direction as said spring, a source of air under pressure, means including a variably settable pressure reducing valve for applying pressure airto said piston and cylinder means, said valve member being formed to gradually increase the effective area of the valve opening as the valve member is moved in an opening direction, and in the final portion of the opening stroke of the valve member, being arranged to rapidly increase the effective valve opening.

3. A steam generating system according to claim 2 in which said piston and cylinder device has a bleed opening for gradual bleeding pressure air from the cylinder and said piston having means thereon effective when the valve member is in its fully open position to close said bleed opening and isolate a substantial area of the piston from the air pressure within said cylinder.

4. In a steam generating system having a boiler with a burner for burning fluid fuel and a liquid supply line for supplying said water to the boiler, means for pumping said water at a constant rate to said supply line, a servo unit actuated by the flow rate of the feed water at a particular point in said supply line to vary the supply of fuel in direct proportion to the variations in the flow rate of the feed water at said point in said supply line, and means responsive to the output steam pressure of the boiler to bypass said water from said supply line before it reaches said point for varying the flow rate of feed water at said point, said last-mentioned means comprising a control valve having a valve body having inlet and outlet chambers with an intermediate valve port, a valve member cooperating with said port and movable in one of said chambers between open and closed positions, said valve member being formed to gradually increase the effective area of the valve opening as the valve member is moved in an opening direction, and in the final portion of the opening stroke of the valve member, being arranged to rapidly increase the effective valve opening; resilient means urging said valve member toward closed position, steam pressure responsive means for moving said valve member from closed position toward open position in amounts substantially proportional to the increase of such steam pressure between a predetermined intermediate level and a predetermined maximum level, and differential producing means modifying the action of said resilient means for maintaining the valve member in its fully open position until the steam pressure has decreased to a predetermined minimum level substantially below said intermediate level and to thereupon immediately close said valves.

5. In a steam generating system having a boiler with a burner for burning fluid fuel and a liquid supply line for supplying said Water to the boiler, means for pumping said water at a constant rate to said supply line, a servo unit actuated by the flow rate of the feed Water at a particular point in said supply line to vary the supply of fuel in direct proportion to the variations in the flow rate of the feed water at said point in said supply line, and means responsive to the output steam pressure of the boiler to bypass said water from said supply line before it reaches said point for varying the flow rate of feed water at said point, said last-mentioned means comprising a control valve having a valve body having inlet and outlet chambers with an intermediate valve port, a valve member cooperating with said port and movable in one of said chambers between open and closed positions, said valve member being formed to gradually increase the effective area of the valve opening as the valve member is moved in an opening direction, and in the final portion of the opening stroke of the valve member, being arranged to rapidly increase the effective valve opening; resilient means urging said valve member toward closed position, steam pressure responsive means opposing said resilient means for adjusting said valve member from closed position toward said open position by valve movements that vary directly with increase of the steam pressure from a predetermined intermediate level to a predetermined maximum level, and means for maintaining the valve member in its open position until the steam pressure falls below said intermediate level to a predetermined minimum level and to thereupon immediately close said valve.

6. In combination with a steam generating system of the kind in which the fuel and air supply is governed in response to the rate of feed water flow to the boiler, and in which the rate of feed water flow to the boiler is varied by variably by-passing all or part of a constant feed water flow in a feed Water supply circuit, a bypass control valve having a valve member movable between open and closed positions and a spring urging the valve member to closed position, said valve member being formed to gradually increase the effective area of the valve opening as the valve member is moved in an opening direction, and in the final portion of the opening stroke of the valve member, being arranged to rapidly increase the effective valve opening, piston and cylinder means connected to the output steam pressure of the boiler for applying opening force to the valve member, piston and cylinder means for applying closing force to said valve member, and means including a variably settable pressure reducing valve for applying pressure aid to said last-mentioned piston and cylinder means.

7. The combination defined in claim 6 wherein means are provided for reducing the force applying effectiveness of said last-mentioned piston and cylinder means while said valve member is in its fully open position.

8. The combination defined in claim 6 wherein movement of said valve member to its open position partially disables said last-mentioned piston and cylinder means.

9. In a bypass control valve for use in the bypass of the feed Water supply line of a steam generator, a valve body having a valve chamber with inlet and outlet passages and a valve port within the chamber between said passages, a valve member in said chamber movable between open and closed positions with respect to said valve port, said valve member being formed to provide a gradual increase in the effective valve opening as the valve member moves from closed position to substantially its open position and then to rapidly increase such effective area as the valve member completes its movement to said open position, steam pressure responsive means for urging said valve member toward open position, a valve spring urging said valve member to closed position and air pressure responsive means for supplementing the force of the spring in urging said valve member toward closed position.

10. A control valve according to claim 9 wherein means are provided for reducing the efiectiveness of the air pressure responsive means while the valve member is in its open position.

11. In a bypass control valve for use in the bypass of the feed water supply line of a steam generator, a valve body having a valve chamber with inlet and outlet passages and a valve port within the chamber between said passages, a valve member in said chamber movable between open and closed positions with respect to said valve port, said valve member being formed to provide a gradual increase in the effective valve opening as the valve member moves from closed position to substantially its open position and then to rapidly increase such effective area as the valve member completes its movement to said open position, double acting piston and cylinder means connected to said valve member and having a small piston and a large piston respectively subjectable to different pressure sources thereby to be subjected to steam pressure for urging the valve member to ope-n position and to air pressure for urging the valve member to closed position.

12. In a steam-pressure actuated bypass control valve for the feed water supply system of a steam generator, a valve body having inlet and outlet chambers with an intermediate valve port, a valve member cooperating with said port and movable in one of said chambers between open and closed positions, said valve member being formed to gradually increase the effective area of the valve opening as the valve member is moved in an opening direction, and in the final portion of the opening stroke of the valve member, being arranged to rapidly increase the effective valve opening, resilient means urging said valve member toward closed position, steam pressure responsive means for moving said valve member from closed position toward open position in amounts substantially proportional to the increase of such steam pressure between a predetermined intermediate level and a predetermined maximum level, and differential producing means reducing the force of said resilient means for holding the valve member in fully open position until the steam pressure has decreased to a predetermined minimum level substantially below said intermediate level and for then immediately moving said valve member to fully closed position.

13. In a bypass control valve for use in the bypass of the feed water supply line of a steam generator, a valve body having a valve chamber with inlet and outlet passages and a valve port within the chamber between said passages, a valve member in said chamber movable between open and closed positions with respect to said valve port, said valve member being formed to provide a gradual increase in the effective valve opening as the valve member moves from closed position to substantially its open position and then to rapidly increase such effective area as the-valve member completes its movement to said open position, resilient means including a valve spring for yieldingly urging the valve member to closed position, steam pressure responsive means opposing said resilient means for adjusting said valve member from closed position toward said open position by valve movements that vary directly with increase of the steam pressure from a predetermined intermediate level to a predetermined maximum level, and means for maintaining the valve member in its open position until the steam pressure falls below said intermediate level to a predetermined minimum level, and for then applying a substantial resilient valve closing force to immediately move the valve member to closed position.

14. In a control valve, a valve body having a valve chamber with inlet and outlet passages and a valve port within the chamber between said passages, a valve member in said chamber movable between open and closed positions with respect to said valve port, said valve member being formed to provide a gradual increase in the elfective valve opening as the valve member moves from closed position to fully open position, pressure means for biasing said valve member toward its open position, and two-stage biasing means for opposing the action of said pressure means, said biasing means being formed to apply a predetermined amount of biasing force in a first stage of operation when said valve member is in said fully open position and to apply an increased amount of biasing force in all other positions of said valve member, thereby allowing a holding action of said valve member in said open position until said pressure means falls to a predetermined level.

15. A valve as set forth in claim 14 wherein said twostage biasing means includes a spring interconnected with said valve member to move it towards closed position, and air pressure means for biasing said valve member toward closed position, and means for reducing the effectiveness of said air pressure means when said valve member is in its fully opened position.

167 The valve as set forth in claim 14 wherein said two-stage biasing means includes a regulated source of air pressure.

References Cited by the Examiner UNITED STATES PATENTS 2,834,569 5/1958 Nickerson 25 l62 3,029,060 4/ 1962 Anderson 25 l-62 3,105,468 10/1963 Gardham l2245l FREDERICK L. MATTESON, 111., Primary Examiner.

C. R. REMKE, Assistant Examiner.

Claims

2. IN A STEAM GENERATING SYSTEM HAVING A BOILER WITH A BURNER FOR BURNING FLUID FUEL AND A LIQUID SUPPLY LINE FOR SUPPLYING WATER TO THE BOILER, MEANS FOR PUMPING SAID WATER AT A CONSTANT RATE THROUGH SAID SUPPLY LINE, A SERVO UNIT ACTUATED BY THE FLOW RATE OF THE FEED WATER AT A PARTICULAR POINT IN SAID SUPPLY LINE TO VARY THE SUPPLY OF FUEL IN DIRECT PROPORTION TO THE VARIATIONS IN THE FLOW RATE OF THE FEED WATER AT SAID POINT IN SAID SUPPLY LINE, AND MEANS RESPONSIVE TO THE OUTPUT STEAM PRESSURE OF THE BOILER TO BYPASS SAID WATER FROM SAID SUPPLY LINE BEFORE IT REACHES SAID POINT FOR VARYING THE FLOW RATE OF FEED WATER AT SAID POINT, SAID LAST-MENTIONED MEANS COMPRISING A VALVE MEMBER HAVING A SPRING NORMALLY URGING SAID VALVE MEMBER TOWARD SAID CLOSED POSITION AND MEANS ASSOCIATED WITH THE VALVE MEMBER AND RESPONSIVE TO STEAM PRESSURE FOR IMPARTING MOVEMENT TO THE VALVE MEMBER IN AN OPENING DIRECTION, PISTON AND CYLINDER MEANS ASSOCIATED WITH SAID VALVE MEMBER FOR APPLYING RESILIENT FORCE TO THE VALVE MEMBER IN THE SAME DIRECTION AS SAID SPRING, A SOURCE OF AIR UNDER PRESSURE, MEANS INCLUDING A VARIABLY SETTABLE PRESSURE REDUCING VALVE FOR APPLYING PRESSURE AIR TO SAID PISTON CYLINDER MEANS, SAID VALVE MEMBER BEING FORMED TO GRADUALLY INCREASE THE EFFECTIVE AREA OF THE VALVE OPENING AS THE VALVE MEMBER IS MOVED IN AN OPENING DIRECTION, AND IN THE FINAL PORTION OF THE OPENING STROKE OF THE VALVE MEMBER, BEING ARRANGED TO RAPIDLY INCREASE THE EFFECTIVE VALVE OPENING.