US2201616A - High speed steam generators, especially supercharged steam generators burning fluid fuels - Google Patents

Description

May 21, 1940.]

W. D. LA MONT HIGH SPEED STEAM GENERATORS, ESPECIALLY SUPERCHARGED STEAM GENERATORS BURNING FLUID FUELS Filed Aug. 22, 1933 45 22 INVEN TOR MaZZerZbu MIa/YonZ X14 ATTORNEY.

Patented May 21, 1940 PATENT orrica HIGH SPEED STEAM GENER ATORS, ESPE- CIALLY SUPERCHARGED STEAM GEN- ERATORS BURNING FLUID FUELS Walter Douglas La Mont, North Colebrook, Comm, assignor to W. D. La Mont Inc., Wilmington, Del., a corporation of Delaware Application August 22, 1933, Serial No. 686,268

6 Claims.

This invention relates to high speed steam pro ducing apparatus.

It has particular reference to supercharged steam generators, especially those burning fluid fuels, wherein all fluids, namely, the fuel, the air (for supporting combustion) and the main working fluid in the tubes of the steam generator each flow at extremely high velocities in the performance of their several duties.

It further concerns the coordination at all speeds, of the velocities of all flowing fluids to insure the maximum and constant evaporation of the main working fluid in a minimum period of time.

It makes possible the definite uni-directional flow of all fluids, especially the main working fluid under all conditions of high temperature radiant heat transfer at high rates of heat release.

The main object of my invention is to reduce the size, weight and cost of high speed steam generators. By my improved methods of operating said generators, I insure their continued performance under long sustained overload conditions, through many years of life without any danger at any time of destroying the steam generator, regardless of how high combustion temperatures may climb, how rapidly heats from the fire may be released or how fast fluids in all my high speed generator fluid streams may flow with my improved methods of supercharging and coordinating their various velocities.

It is vital that the main working fluid espec- "ially, flow unidirectionally at all times, under all steam making loads and speeds, regardless of 0 firebox temperatures or rates of heat release.

Old fashioned boilers, using solid lump fuels lying on grates or moving along on stokers released their heats mainly by heat conduction or convection up through the flrebed. Radiation was a minor factor as a method of heat release, because the surfaces of the fuel lumps were meager compared with the volume of material to be gasified and burned in each lump. This condition was improved greatly by pulverizing and making fluid this solid fuel. As is well known. heat has three methods of travel, conduction and radiation. Since radiations of heat and light travel with the speed (186,000 miles per second) of electricity, (as compared with the snail like pace of heat transfer by either convection or conduction) and since vast fuel-surface areas in the fire box are essential in order to utilize radiant heat transfer efiectively as a method of flame propagation and heat release from fuels, only highly fluid fuels either finely divided, such as fuel gases, or susceptible to extreme fine subdivision, such as liquid fuels into almost invisible and in some cases invisible particles, can actually be rated as high speed fluid fuels capable of extremely rapid combustion, mainly through the agency of heat and light radiations during the reception and release of their own heats, practically instantaneously, and while they are in fluid suspension in their oxidizing medium.

High speeds of combustion through large surface areas of fuels in suspension, travelling at extremely high velocities through radiant combustion zones produce high temperatures in boiler fireboxes.

These'same high temperatures make radiation increasingly important as a means and method of transferring heat from an intensely hot fluid fuel fire to the tube surfaces, behind which the main working fluid of the steam generator is flowing at high velocities.

Any slight increase in fire temperature produces a marked favorable difference in stepping up the rate of heat transfer to the tube walls, this rate increasing approximately as the fourth power of the added temperature increase.

If the speeds of combustion supporting air and fuel are properly related at all times, so the fluid fuel will be thoroughly mixed with the fluid air at all times in their correct proportion for economical and thermally eflicient combustion, and if, as the temperature of combustion in the boiler firebox increases, the velocity of the water or other main working fluid is stepped up accordingly, the problem then becomes one of definitely insuring unidirectional flow of the main working fluid, into and throughout the length of each individual steam generating tube exposed to radiant heat, or each square foot of radiant heat receiving surface (and fraction thereof) exposed to the action of radiant heat, namely, the tube surface in the high speed steam generator wall.

Before my invention as described in this present patent application, I endeavored to secure unidirectional fiow of my main working fluid flowing through radiant heat receiving water wall tubes, each tube of considerable length and of small size (and preferably substantially uniform diameter) to insure rapid radiant heat pick-up.

When fire-box, or so called combustion chamber pressures on unburned and burned fuel gases remained down around a few inches of water, and I employed forced circulation with orifices or restrictions, for pressure drop delivery and water distribution purposes at or near the inlet for working fluid entering each long, small diameter boiler tube in my boilers having constant circulation of water through a steam and water separating device; I found, in the case of fluid fuel fires, a tendency for these fires to rove back and forth or here and there in the combustion chamber, momentarily mtensifying locally certain heat receiving areas in the tubular water wall while these tubes carried rapidly flowing water in their interiors.

With stoker fires it was possible, in each individual installation of a water wall in the firebox, when said water wall comprised long, small diameter tubes, in accordance with my previous water wall inventions, to experimentally determine where local hotter areas were, and to provide larger orifices in the water wall tubes passin through these areas and/or accomplish larger pressure drops through the orifices. This preliminary experimental work of determining exactly where local hotter areas were and provide larger orifices in the water-wall tubes passing through these areas and/or larger pressure drops through the orifices, was no matter for a novice to undertake, because often in boilers of the same identical design, the intensely hot areas would be found in different places in the walls of the combustion chamber and further would wander as firebox temperatures changed, not similarly, for some unaccountable reason, even though all factors may have appeared identical.

With hotter, higher speed, fluid fuel fires, this wandering action becomes a roving action, of great intensity and suddenness, abruptly delivering, or failing to deliver, heats rapidly to certain sections of waterwall tubes at various localized areas, always impossible to determine in advance and constantly changing position.

These abrupt changes in the heat supplied at localized and constantly varying water wall heat reception areas are due to combustion conditions in the firebox changing constantly.

When rates of heat release or the temperatures in the combustion chamber are raised to a high point, steam and water delivery from the outlets of the tubular water wall members develop a rhythm, the wall pants, (with a noise somewhat like a fatigued animal), the tubes rhythmically belching steam and water, pausing, or gulping in their steam and water delivery, then belching more steam and water. The water wall tubes as a whole when acting in the above manner, positively deliver water and steam in a one path fiow to their outlets, but this delivery at the outlets and throughout the length of the tube is intermittent. It is not continuously uniform nor is it uni-directional.

There is a distinct difl'erence in the operating characteristics of a so called full tube generating steam, compared to a tube in which steam is being generated with less than sufficient water to fill the tube; especially when tubes of both types are subjected to exceptionally high rates of heat release, and the condition of uni-directional fiow of working fiuidsis considered.

A full tube is a. tube having at least that proportion of water and steam by volume, which it would have if it were possible to operate the tube under the same heat conditions with natural circulation.

Such a tube is distinctly difierent in its steam generating action from tubes operating under the preferred methods of steam generation in my previous inventions, in that such so called full tubes would not have a water restricting means, or pressure drop device, or water metering member; at or near their tube inlets for the purpose of operating such steam generating tubes with less water than they would normally operate with, if such water metering or water restricting means or pressure drop devices were not used.

In my co-pendlng patent applications #530,228,

.filed April 15, 1931, and #556,183, filed August 1'7, 1931, I refer to the operation of full tubes with the art as disclosed in said patent applications.

I have now found that since there is a distinct difference in the operating characteristics of so called full tubes and tubes with less water than sufiicient to fill said tubes, the art in these previous applications of mine does not disclose how full tubes can be employed in water walls exposed directly to radiant heat, to give them improved steam generating characteristics obtaining with tubes having less than suflicient water to fill; when both types are exposed to exceptionally high rates of heat release.

Other objects of my present invention include: a positive and controlled supply of water to each of the steam generating tubes or elements conveying working fluid through the water wall surrounding the combustion zone; to provide steady and continuous circulation of the water through the water passages or tubes of the water wall, or water wall boiler; to provide for the proper and adequate flow of water through the different parts of the steam generating apparatus and in such relation to the steam generated in said parts, or to the condition of the steam generated therein, that an adequate flow of water may be maintained through each part and in suitable relation in one part relative to the other. It is a still further object of the invention to provide for the positive control of the amount of water delivered to or flowing through the different parts and to control the conditions under which it flows so as to accomplish the proper delivery to, and flow through, the different parts of the steam generating apparatus to suit conditions of steam generation in said parts.

A still further object is to increase the amount of water circulated and therefore the speed of the circulation of steam and water in the tube with the increase in the rate of heat release, in

order to increase the rate of heat transfer from the metal of the tubes to the water and steam and move the forming bubbles of steam away from their point of formation faster, thus protecting the water wall tube from the increasing heat to which it is exposed with every increase in the rate of heat release in the combustion chamber.

An important object of this invention is to disclose how so called full water wall tubes can be operated with positive input of water into each tube in sufficient quantity to protect each tube regardless of how high rates of heat release are obtained in the combustion chamber, and to show and describe how uni-directional flow of steam and water within and throughout the length of the tube can also always be uniformly obtained under the same combustion chamber heat releasing conditions.

The placing of pressure drop devices at or near the discharge end of the tubes or at or near the end of the main part of the tube exposed mainly to radiant heat is a preferred position for these pressure drop devices or orifices, if orifices are to be used.

In practical application of my previous invenfit) tions using orifices at or near the entrance to the tube and passing only water through it, I have found, especially in waste heat work and with waterwall tubes of very short length exposed to moderate rates of heat release: that a very small diameter hole for the orifice in each tube was required to pass the proper amount of water into the tube for protection of the tube without circulating an unnecessarily large amount of water and to still have-a pressure drop of sufficient amount to insure one path fiow into the tube.

Without use of distilled water, or in cases where water containing large amounts of carbonates is used, this small orifice presented a serious problem to prevent clogging which screening of the circulating water line and of the orifices does not entirely eliminate.

I have found that if the orifice is put at a point in the steam generating element where both steam and water is passed through it, a much larger hole can be used, or with'other forms of resistors or pressure drop devices, much larger areas-can be used. This is due to the great increase in volume of steam compared to water per lb.

If the orifice is placed beyond the point in the tube where steam begins to form there is a marked increase in the size of the hole which can be used to pass a given amount of water with a given pressure drop.

As the orifice is moved forward in the tube toward the exit end, the size of the hole used can be increased reaching a maximum of course at the outlet end where it will be passing a maximum of steam with the excess water.

A prime object of the present invention is to increase the speed of steam generation thus making my steam generating apparatus, smaller, lighter weight, and less expensive. My invention is a high speed steam generator whose water walls in the radiant heat releasing and receiving area, namely, the combustion zone, will not "pant or belch their steam and water at the water wall tube outlets, but will have positive uni-directional flow of water in each wall tube, at all times, regardless of combustion conditions in the firebox or the size or movement of large steam bubbles shifting from side to side in individual water wall tubes, or group of water wall tubes.

The way these results are obtained, or these objects carried out, together with the mechanical arrangement of parts and the relation of these features to each other, is more particularly brought out in the drawing, the description and the claims forming parts of this present patent application.

Since my present invention is directly concerned with a high speed steam generator and high speed methods of steam generation I show in the drawing in:

Fig. l a complete power plant manufactured and arranged in accordance with my invention and utilizing my high speed steam generator;

Fig. 2 is a section taken along the lines A-A in Fig. 1;

Fig. 3 is an enlarged detail drawing of my pressure drop device as used in Figs. 1 and 2 and shown on a smaller scale in these two previous figures;

Fig. 4 is an enlarged detail drawing of another form of pressure drop device which is shown even more in detail in Fig. 4-A;

Fig. 5 is a diagrammatic view of a down-flow tubular water wall in a radiant heat releasing firebox or combustion zone made in accordance with my invention and wherein the fuel air mixture and the burned gases travel practically parallel to the water fiowing in the water wall tubes:

Fig. 6 is similar to Fig. 5, the difference between the two figures being that here the fuel gases,

unburned and burned, travel in general in counterecurrent relation to the high velocity flow gfbthe main working fluid in the water wall u es;

Fig. 7 illustrates a coil type of water wall diagrammatically, the coils leading the water upward, the fiow of unburned and burned gases also being upward; the circulating pump preferably has a separate wheel for each steam generating tube to discharge water directly and only to the tube connected to it.

Fig. 8 is a similar diagrammatic view to that in Fig. 7 wherein coils forming a water wall or a liquid wall of working fiuid around the firebox or combusition chamber lead the water upward while the unburned and burned gases flow counter-current or downwardly; the circulating pump preferably here again having a separate wheel (or plunger if a reciprocating pump is used) for each tube to discharge water directly into and maintain hydraulic pressure inside of each water tube as shown in Fig. 7.

Fig. 9 is an enlarged view of pressure drop device used in thediagrammatic drawing Figs. 5, 6, '7 and 8.

The figures shown diagrammatically may be individually used as apparatus arrangements in place of the form of vertical or substantially vertical tubular water wall shown in my high speed steam generator illustrated in Fig. 1.

I have found that with tubes having an opened unrestricted end at their exit, it becomes more dlfiicult to maintain uni-directional flow of the working fluid throughout the length of the steam generating tubes in the combustion zone, exposed to radiant heat, as the rates of heat release are increased due to the making of the fire hotter.

With present rates of heat release, such as are used in U. S. Navy full power practice, positive and controlled supply of water delivered tothe entrance of the tube will protect the tubes from burning, but with very high temperatures in the combustion chamber, obtained in test work, a surging and panting occurs within the tubes at intervals.

With increase in the length of the tubes and use of the unusually high rates of heat release obtainable with a supercharger fan, oil preheating and fine atomization, etc., this "panting condition is still more aggravated.

Therefore it becomes very important to find a means to insure uni-directional flow to give proper operation to steam generator tubes exposed to extremely high temperatures which it is now possible to obtain in the combustion chambers of boilers.

With high rates of evaporation, the volume of steamin a tube is large, and with the open or unrestricted end at exit, together with the rapidly forming and moving steam volume it is evident that the column of steam and water in the tube is not by any means stable and is quite elastic in character.

Steam forming very quickly and in large quantity in local sections in the tube, from time to time, builds up a local pressure condition in the tube above that caused by the general steam and water flow from the tubes; due to the fact that the path of the steam from the tube outlet to the water level cylinder and turbine is not free, being already crowded with steam flow from all tubes and a pressure above the pressure already in this path is required to drive the extra volume of steam through to the turbine.

The main force for flow in the tube itself, with present methods, is the increasing steam volume trying to leave the tube and carrying the water with it.

with natural circulation, the steam going out the exit end of the tube has to overcome a real hydraulic head of water and steam to reach the steam drum. The only force for circulation upward is that of convection circulation which is of very small degree and the rapidly expanding steam, which has real power, quickly expands in two directions, especially when the formation is rapid and local and in large volume which often occurs.

When it expands away from the tube exit as well as toward it, back flow of steam and water occurs reversing the circulation to a considerable extent. This leaves the tube, at the local section, with steam expanded to a high heat and with considerably lesswater, which aggravates the condition. Since the column of steam and water in the tube is very elastic in character, the back fiow of the steam quickly compresses the medium opposing it, thereby increasing the portion lacking sufficient water with further aggravation of the steam locking condition.

The combined results of the forces acting may, with natural circulation, stop all water flowing in the tube and if the back flow increases it may even drive water and steam from the tube at the inlet end into tubes adjacent to it.

With the forced circulation and pressure drop distributed to each tube as set forth in my copending applications #556,183 filed August 17. 1931, and 530,228 filed April 15, 1931, water will be forced into each tube and inter-communication between tubes at the inlet ends is stopped regardless of the forces acting in the generating tubes.

This insures the inflow of water during steam locking conditions as well as at all other times, but the volume of the incoming water entering into the tube through the pressure drop device or small orifice per pound, compared to the volume of steam leaving per pound, is about 1 to 20 even at high pressures; and the effect of this incoming water as a force to create flow in the tube is small.

The main factor causing flow of steam and water in the tube is still the increasing volume of steam trying to leave the tube in two directions.

The exit end is open, the steam is forming rapidly, the column of water and steam in the tube is very elastic and far from stable.

When a local section receives high heat effects especially when this occurs near the end of a long tube the steam in this section rapidly increases in pressure against that of the pressure zone leading to the water level cylinder and against the pressure in the elastic column of steam and water toward the inlet end.

This immediately results in the compression of the elastic column of steam and water toward the inlet end with back flow of steam and water destroying uni-directional flow in the tube. When the compressed steam and water column becomes solid enough, the back flow is stopped and then reversed and this reversal movement is augmented by the steam forming toward the inlet end of the tube during this period of reverse flow. The result is a sudden increase in the reversed flow like a spring action and surging or panting of steam and water occurs in the tube. If this becomes too pronounced it will produce similar results in other parts of the tube, the power delivery becomes uneven and unsatisfactory and the lack of uni-directional flow with increased surging may finally result in injury to the tube.

To provide for uni-directional flow in a steam generating tube more must be accomplished than to merely provide positive water input and stopping of flow of water out of the tube at the tube inlet.

tube must be made more compact and nearer in nature to a hydraulic column, or a long slim plunger of water.

The path of the steam from the outlet to the' water level cylinder must be cleared and a force or pressure condition created acting on the steam and water within the tube substantially throughout the entire length.

I have found that by using forced circulation in the system and combining this force with a pressure drop delivery at or near the outlet of each tube, a pressure zone can be created within the tube above that on the other side of the discharge ends of the tubes leading to the water" level cylinder, and the difference in pressure between the two pressure zones can be made of any degree desired.

This mechanically created head of pressure within the tube makes a more compact column increases the speed of steam and water travellingin the tube, which in turn moves the steam away from its point of formation on the tube more quickly, increasing the rate of heat transfer to the steam and water and thereby assisting in protecting the tube at the increased rate of heat release.

The artificial pressure zone within the tube above that at the discharge end leading to the turbine, in effect clears a path from the tube to the turbine removing the main interference from steam and water issuing from adjacent tubes.

The difference in pressure between the pressure within the tube at the discharge end and the pressure at the other side of the discharge end leading to the water level cylinder and turbine should be at least equal the sum of the following three conditions.

1. Assuming the steam and water were flowing through the tube without creating an artificial zone of lower pressure from the discharge end to the water level cylinder; there would result a certain pressure drop from this flow.

2. Additional steam forming rapidly in any section of the tube requires a certain pressure drop to deliver it from the outlet end of the tube without the steam being required to develop a back flow force sufllcient to compress the steam and water column in the direction of the inlet end.

a 3. Water entering the tube requires a certain The elastic column of steam and water in the pressure drop condition at the entrance of the tube to cause it to flow into the tube in sufflcient quantity to protect the tube and to assist in making uni-directional fiow of the working fiuid possible.

There is a maximum degree of pressure drop for each of the above conditions at each rate of heat release.

If these maximums at each rate of the heat release are added together and the resulting pressure drop applied to all tubes at each rate of heat release then uni-directional fiow will be obtained in all the tubes. The pressure drop artificially arranged at the outlet of the tube, not only provides for normal flow throughout the length of the tube and all tendencies to back fiow, but also provides for a pressure drop sufiicient to cause water to flow into the tube and protect the tube and make the column of steam and water in the tube compact. In addition the amount of water circulated is increased with increase in heat release to insure the creation of a compact water and steam column, an increase in the speed of steam and water fiow and the supply of sufiicient water to protect the tube. As a result of the co-ordination of pressure drop with amount of water from the forced circulation a positive controlled supply of water into each steam generating tube is provided.

In the preferred embodiment of my invention I use mechanical means for forced circulation such as a pump with positive characteristics as to water discharge against varying pressures and which may or may not have a separate wheel or other means of separate water delivery into each tube. This pump is combined with the use of restrictors or pressure drop devices such as an orifice at or near the discharge end of each steam generating tube to create a pressure zone within the tube above that of the pressure zone from the discharge end of the tube leading to the water level cylinder, to the extent that the difference in pressure between these two zones at least equals the pressure drop required to insure uni-directional flow into and throughout the length of all tubes at all times.

The additional water circulated to meet the additional requirements from increase in heat release is obtained nct only from co-ordinating the speed of the circulating pump with the speed of the fuel and air pump but also by varying the opening in a by pass of the circulating pump co-ordinated with the change in fuel and air used, the action of an automaticjcombustion control and/or the working of the throttle or boiler stop valve.

The word co-ordinate means to adjust the feeding to and circulation of water in the steam generator in relation to the steam making requirements regardless as to whether the change is in proportion, progressive or otherwise as called for by the requirements for additional water to be circulated.

It is to be understood that my invention is not limited to a particular type of tube or its method of operation, or to a particular type of restrictor or pressure drop device or orifice, or to means with forced circulation to create a zone of higher pressure within the main part of the steam generating section of the tube as compared to the pressure zone past the main part of the steam generating section toward the outlet and leading to the water level cylinder and turbine; nor is it confined to a particular type of force circulation means such as a pump; nor is it confined to a particular means for co-ordinating the amount of water circulated with the rate of heat release such as with the speed of the drive for the fuel and/or the air; nor is such coordination of the amount of water circulated with the heat released confined to the use of a by pass on the circulating pump; nor is the pressure drop device confined to at or near the outlet of the tube. In all cases, however, a proper pressure drop is provided between the pressure within the main part of the steam generating tube and the outlet part leading to the water level cylinder, which when combined with the amount of water circulated will insure unidirectional fiow of water and steam throughout the length of the tube and give positive delivery of water into and through the tube in quantity sumcient to protect the tube and give sufficient speed of water and steam travel in the tube to carry away all heat sent into the metal of the tube.

And in all cases proper provisions are made at each rate of heat release, to meet with a fully adequate supply of working fiuid all changes in heat distribution, heat intensity and heat location; acting on all tubes at all times to that extent which is the maximum necessary in any one tube at any time.

In Fig. 1, the numbered parts on the drawing are as follows: firebox I, fuel oil burner 2, air venturi 3, air pipe 4, air supercharger 5, auxiliary turbine 6, inlet steam for auxiliary turbine I, water level cylinder 8, high pressure steam pipe 9 to main turbine I0, condenser II, inlet circulating cooling water for condenser I2, outlet for circulating cooling water for condenser I3, condenser discharge pipe I4 to feed water tank I5, condensate pump I6, feed pump I'I, feed pump discharge pipe I8, water level regulator valve I9, feed pipe by-pass I9a, feed stop and check valve 20, safety valve 2 I, bottom blowoif valve 22, gauge glass 23, water level regulator device 24, water level device control pipe 25, boiler circulating pump 26, fuel oil pump 21, auxiliary turbine discharge pipe 28, condensate pump suction pipe 29, condensate pump discharge pipe 30, boiler circulating suction pipe 3I, boiler circulating pump discharge pipe 32, boiler inlet header or manifold 33, steam generating water wall tubes 34, steam generating water wall tubes discharge pressure drop devices 35 and/or figure 92 steam generating water wall tubes collecting header 36, steam generating water wall tubes collecting leads 31, fuel tank 38, fuel oil suction pump pipe 39, fuel oil pump discharge pipe 48, supercharger air for suction inlet 4I, boiler 42, makeup feed inlet pipe 43, boiler circulating pump by pass 44 and boiler circulating pump with separate wheel for water discharge to each steam generating tube 260 of Figs. 7 and 8.

The operation of my improved power unit is as follows:

Make-up feed water is put into feed water tank I5 by water inlet lead 43. This water with condensate water from the condenser is picked up by the condensate pump suction pipe 29 of condensate pump I6 and delivered to the boiler feed pump [1 by a condensate discharge pipe 30. Boiler feed pump II discharges boiler feed water through feed pump discharge I8 past water level regulator valve I9 operating on feed pipe bypass I90. and past feed stop on check valve 20 into water level cylinder 8. The feed water in the water level cylinder 8 is mixed with excess unevaporated water, if any, discharged from the boiler and the mixture is picked up by the boiler circulating pump 26 through its suction pipe 3i and discharged positively against any back pressure in the system; through boiler circulating discharge pipe 32 into boiler inlet manifold 33 and into steam generator water wall tubes 34 or direct from the pump to the tubes, Fig. 7 and Fig. 8. The water in the water wall steam generating tubes, and the steam generated by the tubes passes by the pressure drop device or restricting means 35 and/or 92 at or near the outlet of each tube into a zone of lower pressure in the water and steam collector header 36 of the water wall steam generator tubes. From this point water and steam passes through the steam generator water wall tubes collecting leads 31, still of a distinctly lower pressure zone than that in the water wall steam generating tubes, and enters through water level cylinder 8 also in a lower pressure zone. Separation of steam from water occurs and steam and water enters through water level cylinder in the boiler and the excess water, if any, falls to the water level where it mixes with the incoming make-up feed and is then circulated by the boiler circulating pump as previously described. By pass 45 with the automatic by pass valve 44 on the boiler circulating pump is used in coordinating the amount of water circulated with the air and fuel required at different rates. The automatic valve may be operated by an automatic combustion control device, by the speed of the auxiliary turbines or by other means. The steam discharge is separated in the water level cylinder, while of high pressure, the steam at this point is of distinctly lower pressure than the steam and water in the steam generating water wall tubes. This is due to the combined use of a forced circulating means from the water level cylinder such as by a circulation pump and the use of a restricting or pressure drop device at or near the outlet of each steam generating water wall tube. This high pressure steam discharges from the water level cylinder 8 through main steam pipe 9 to the turbine I0, a branch lead pipe I also takes steam from the water level cylinder 8 to the auxiliary turbine 'I which discharges through the turbine discharge pipe 28 to condenser. II. The steam from the main turbine I discharges directly into condenser II. Circulating water keeps the condenser cool by condenser inlet pipe I2 and condenser outlet pipe I3. The condensate from the condenser flows through condenser discharge pipe I4 to feed water tank I5. The condensate mixes with the make-up feed in the feed water tank and is picked up by the condensate pump I6 to be sent through the system as previously described. Fuel in fuel tank 38 is picked up by the fuel oil pump 21 through its suction pipe 39 and is discharged through a discharge pipe 40 to the fuel oil burner 2. Air is picked up by the supercharger fan at its suction M and discharged by it into the firebox I, of boiler 42 through air venturi lead 3. The restrictors or pressure drop devices 35 and/or 92 at or near the outlet of each steam generating water wall tube 34 are used in combinations with forced circulation such as a boiler circulating pump 26 placed before the inlet of all steam generating water wall tubes 34 to create a pressure zone above the pressure zone on the discharge side of the steam generating water wall tubes 34. The high pressure zone in the steam generating system extends from the discharge side of the forced circulating means to the restrictors or pressure drop devices at or near the outlet of the steam generating water wall tubes. The lower pressure zone in the steam generating system extends from the discharge side of the restricting or pressure drop devices at or near the outlet of the steam generating water wall tubes to the suction of the force circulation means. The diiference in pressure between the high and low pressure zones and the steam generating system is arranged to act on all tubes in which unidirectional flow is required. This difference in pressure is arranged to equal at least the following maximum pressure drop requirement of any tube at any time. (1) The pressure drop required between the inlet header and the inlet of a steam generator tube to insure positive flow of water into the tube in suflicient quantity to protect the tube and assist in making unidirectional fiow plus, (2) the back flow force or tendency of the steam to back flow when formed and trying to flow in two directions plus, (3) the pressure drop which would be produced in the tube caused by the steam and water flow in the tube with its resultin volume and velocity, and resistance to flow; assuming the tube is operating without delivering water and steam to an artificially created lower pressure zone.

My purpose in including the diagrammatic figures on the side of my sheet of drawings is to show some, other forms of apparatus arrangement which may be equally applicable to my power plant as a whole in carrying out my present invention.

It is to be understood that the power plant shown in its entirety in Fig. 1 is merely one way of accomplishing my invention and that instead of the generating unit for the creation of steam at high speeds indicated as numeral I I may use either the generator indicated as numeral I in Fig. 5 or indicated as numeral I in Fig. 6 or indicated as numeral I in Fig. '7 or indicated as numeral I in Fig. 8 or as some other modification or type as comes within the claims or the scope of the invention as outlined herein. The water may run opposite the force of gravity or in the same direction as gravity or in combinations. It is further to be understood that the pumps 260 are three separate pumps on the same shaft to be driven by steam turbine 6 in the same way that it drives pump 26 in Fig. 1, thereby delivering water directly from each pump to each generator tube. This or any other method of directly driving water into each tube may be used in place of the arrangement shown in Fig. 1 or Figs. 5, 6, 7, 8.

Various arrangements and modifications may be made within the spirit of the invention and those shown in the drawing and a more detailed description are merely typical. They illustrate some of the many possible combinations included within the scope of the invention and those shown in the drawing. They illustrate the scope of the invention and in no sense are to be taken as limiting the invention.

I claim:

1. In a steam generator, a circuit for water and steam generated therefrom comprising a vessel in which a water level is maintained, positive water circulating means connected in circuit with said vessel, a steam generating tube connected in circuit with said positive circulating means and to said vessel in a space therein unoccupied by water, said positive circulating means circulating water from said vessel through said steam generating tube independently of the feed input thereto, and fluid flow controlling means at the outlet of said steam generating tube to of said steam generating tubes to control the control the flow of water and steam within said tube, said steam generating tube receiving water in quantity greater than is evaporated.

2. In a steam generator, a circuit for water and steam generated therefrom comprising a vessel in which a water level is maintained, positive water circulating means connected in circuit with said vessel, steam generating tubes connected in circuit with said positive circulating means and to said vessel in a space therein unoccupied by water, said positive circulating means circulating water from said vessel through said steam generating tubes independently of the feed input thereto, and fluid flow controlling means near the outlets of said steam generating tubes to control the flow of water and steam within said tubes, said steam generating tubes receiving in quantity greater than is evaporated.

3. In a steam generator, a circuit for water and steam generated therefrom comprising a vessel in which a water level is maintained, positive water circulating means connected in circuit with said vessel, a steam generating tube connected in circuit with said positive circulating means and to said vessel in a space therein unoccupied by water, said positive circulating means circulating water from said vessel through said steam generating tube independently of the feed input thereto, and a pressure drop device near the outlet of said steam generating tube to control the flow of water and steam within said tube, said steam generating tube receiving water in quantity greater than is evaporated.

4. In a steam generator, a circuit for water and steam generated therefrom comprising a vessel in which a water level is maintained, positive water circulating means connected in circuit with said vessel, steam generating tubes connected in circuit with said positive circulating means and to said vessel in a space therein unoccupied by water, said positive circulating means circulating water from said vessel through said steam generating tubes independently of the feed input thereto, and restricting orifices at the outlets space therein unoccupied by water, said positive circulating means circulating water from said vessel through said steam generating tubes 'independently of the feed input thereto and in a direction opposite to the travel of the heating gases through said combustion chamber, and pressure drop devices near the outlets of said steam generating tubes to control the flow of water and steam within said tubes, said steam generating tubes receiving water in quantity greater than is evaporated.

6. In a steam generator, a combustion chamber adapted to have heating gases travelling therethrough, a circuit for water and steam generated therefrom by said heating gases comprising a vessel in which a water level is maintained, positive water circulating means connected in circuit with said vessel, steam generating tubes connected in circuit with said positive circulating means and to said vessel in a space therein unoccupied by water, said positive circulating means circulating water from said vessel through said steam generating tubes independently of the feed input thereto and in the same direction as the travel of the heating gases through said combustion chamber and in a quantity greater than is evaporated, and a restricting orifice at the outlet of each steam generating tube to contrc. the flow of water and steam within said tube, said steam generating tubes receiving water in quantity greater than is evaporated.

WALTER DOUGLAS LA MONT.

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