US1951350A

US1951350A - Flash boiler control

Info

Publication number: US1951350A
Application number: US524668A
Authority: US
Inventors: Doble Warren
Original assignee: Individual
Current assignee: Individual
Priority date: 1931-03-23
Filing date: 1931-03-23
Publication date: 1934-03-20
Anticipated expiration: 1951-03-20

Description

March 20, 1934. w. DOBLE' 1,951,350

- FLASH BOILER CONTROL 7 Film} March 23. 1931 2 Sheets-Sheet 1 INVENTOR. [Var/"er; Dob/z ATTOR March .20, 1934. w. DOBLE FLASH BOILER CONTROL Filed March 25, 1931 2 Sheets-Sheet 2 INVENTOR.

I War/e77 006/2 ATTORNEYS.

Patented Mar. 20, 1934 FLASH BOILER CONTROL Warren Doble, Emeryville, Calif.

Application March 23, 1931, Serial No. 524,668

11 Claims.

This invention relates to the control of a boiler of the type which has been characterized as a flash boiler but which can be also classified, and possibly more accurately, as a forced circulation boiler. Such a boiler comprises a relatively long tube. In one size the tube is about six hundred feet in length and is wound into a series of coils,

water being forced into one end of this coiled tube to supply a working fluid. Steam issues from the other end when the tube is heated, generally by passing the products of combustion from a suitably maintained fire over the tube.

This invention is particularly concerned with the regulation and control of the water admitted to the tube to maintain the steam issuing from the boiler substantially at a predetermined temperature and pressure at all times during operation of the boiler.

As is disclosed in the co-pending application of Warren Doble, Serial No. 221,262, filed September 22, 1927, and entitled Normalizer, the introduction of a small amount of water into the tube at a considerable distance from the main water inlet or foot has been found to be effective in maintaining the steam delivered very close to a predetermined temperature, the injection of the water being controlled by a thermostat responsive to a condition within the boiler, such as the temperature of the boiler tube or the steam within the tube. However, the functioning of this structure, while very successful, nevertheless includes the difficulty that the primary water introduced into thefoot or inlet end of the tube is apt to be in excess of, or less than, the amount of water actually required, due to widely fluctuating loads upon the boiler. Since such boilers are most advantageously used in automotive practice for vehicles such as automobiles and rail cars where the load varies rapidly, the boiler may be either flooded or locally over heated in the primary portion, that is the portion of the tube between the foot and the normalizer inlet. While the normalizer regulates the temperature of the steam being emitted from the boiler, the normalizer does not prevent the Overheating of sections of the boiler in advance of the normalizer inlet nor can it increase the temperature of the steam passing the thermostat should the steam be below the critical temperature at which the thermostat is set.

Since such boilers are ordinarily operated under pressures between 500 and 2500 pounds per square inch and since the span of operating pressure can vary more than 2000 pounds per square inch, the overheating or flooding is a material factor in securing efiicient operation while the overheating of localized sections aifects the safety of the boiler tube.

The control of the boiler must also take into account the desirability of having the heat supply for the boiler an intermittent one. In one successful form of boiler, the heat is furnished by blowing an air stream through a carburetion which is subsequently ignited and blown into the boiler to pass over the coiled tube. The blower for supplying the air operates intermittently an the fire accordingly is periodic.

It is therefore the general, broad object of the present invention to provide for the control of a forced circulation boiler so that localized overheating or flooding of the boiler are prevented, while steam of the proper temperature and pressure is produced.

The foregoing and other objects are attained in the embodiment of the invention shown in the drawings, in which Figure 1 is a schematic view illustrating a forced circulation boiler and a feed control embodying gny invention.

Figure 2 is a schematic view illustrating a forced circulation boiler and a modified form of control of my invention.

My invention includes the provision of a device for controlling the'introduction of water into a boiler by means of which steam is furnished by the boiler at a substantially uniform temperature without having either overheatingor flooding of the boiler occur. Particularly, my invention contemplates the utilization of the normalizer principle previously disclosed and a primary or main feed water control of such a nature that overheating and flooding are obviated.

The form of the invention shown diagrammatically in Figure 1 provides a relatively'long tube 6, in one instance approximately six hundred feet in length, which is wound into a plurality of coils and is disposed within a suitable outer casing 7 to absorb heat. The heat is conveniently secured from products of combustion formed upon ignition of a fuel-air mixture directed into the boiler casing through a venturi 8 by a blower 9 which forces air over a carburetion device 10. The fuel-air mixture is ignited by a suitably energized spark plug l1,'the products of combustion passing counter-current to the fluid in the tube 6. Water is injected into the foot or inlet 12 of the boiler and is withdrawn as steam through outlet 13 under-control of a throttle valve 4. The products of combustion able automatic devices responsive to boiler conditions and, preferably, the blower 9 and the ignition of the fuel-air mixture are controlled in accordance with the temperature and pressure in the boiler. To this. end a temperature device, such-as a thermostat 21, is provided which is responsive to a condition within the boiler, for instance, the temperature of the boiler tube. A pressure device 22 is also provided to be responsive to steam pressure in the boiler. The temperature device 21 includes a rod 23 adapted to bear upon and position a spring biased rocker 24. Spring biased contact arms 26 and 27 depend upon the movement of the rod 23 and the rocker 24 to open or close certain electrical circuits. I

The contact arm 26 is included in an electrical circuit with a battery 28, one side of which is grounded, a master switch 29, contacts 31 and 32 controlled by the pressure device 22, contacts 33 and 34 controlled by the contact arm 26, a spark plug 11, and an electric motor .35 for the blower 9, one side of the spark plug and of the blower motor being grounded.

The other contact arm 27 carries a contact 36 cooperatively positioned with a contact 37. These contacts control a circuit including in series the contacts 31 and 32, the master switch 29, the battery 28, and a grounded solenoid 38 for operating the normaliz'er valve 39.

The temperature device 21 is so constructed that when the boiler tube is at a low temperature the contacts 33 and 34 are in abutment. When the master switch 29 is closed and the pressure in the boiler is low so that the contacts 31 and 32 on the pressure device are in abutment, cur rent flows through the contacts 31 and 32, and contacts 33 and 34 to the blower motor 35 to inject a fuel-air mixture which is subsequently ignited by the simultaneously energized spark plug 11, whereupon heat is available" in the boiler to generate steam.

When the temperature rises above a predetermined or desired value, the rod 23 forces the rocker arm 24 to permit contacts 36 and 3'? to abut so that the solenoid 33 is energized to open the normalizer valve 39 and admit a stream or slug of water through a pipe 21 into the boiler tube just in advance of the thermostat 21. This water tends to reduce the temperature of thermostat 21 below the predetermined value, and concurrently reduces the excessive temperature of the passing steam. Such reduction affects the thermostat 21 and causes the rocker 24 again to open contacts 36 and 37. Since the'movement required for this purpose is small, contacts 33and 34 are not disturbed. With the opening of contacts 36 and 37, the solenoid 38 is deenergized,- the valve 39 is closed and thefiow of normalizer water is stopped, whereupon'the temperature of the" thermostat again begins to rise above the predetermined value. The opening and closing of the contacts 36 and 3'? can repeat an indefinite number of times until the temperature of the thermostat drops materially below the predetermined value, during which time the boiler is said to be flooded or until the temperature rises materially above the predetermined value at which time the thermostat 21, opens the contacts 33 and 34 and interrupts the supply of heat, after which the temperature drops and the cycle repeats. The temperature of the outgoing steam is thus kept substantially uniform, in practice being maintained within one 7 or two degrees Fahrenheit of the desired value. If at any time during the operation of the boiler, the pressure exceeds the value for which the device 22 is adjusted, the contacts 31 and 32 are opened and the circuit to the blower motor 35 and the spark plug 11 is broken thus stopping the supply of heat and preventing further pressure rise. While the above described control system is effective to maintain the temperature of'the outgoing steam approximately at a desired value, it is not effective if the steam arriving at the thermostat is very low in temperature nor to prevent overheating of the primary portion of the boiler tube especially just in'advance of the I operation is erratic, particularly wherethe load I on the boiler fluctuates. The boiler .tube may be alternately overheated with a liability of failure of the tube or a considerable length of the tube may be filled with water, with the result that the temperature of the steam issuing from 1 the tube subsequently falls far below the desired value.

Since in one design the boiler tube is about six hundred feet in length and the temperature responsive device is positioned about thirty feet from the outlet end, water injected into. the inlet end or foot must pass through about five hundred seventy feet of tubing before coming to the temperature responsive device. A period of time of the order of at least six seconds usually elapses before this distance is traversed. This time lag is too great for satisfactory andprecise control under adverse or unusual conditions.

In accordance with my invention I provide a boiler control system for securing steam substantially at the desired temperature under all conditions. In the system as shown in Figure 1, I position a second temperature device 46 in the primary portion of the .boiler tube, preferably immediately in advance of the normalizer inlet 41, so that the thermostat 46- is responsive to a condition within the boiler, for instance either the boiler tube temperature or the steam temperature within the tube. This thermostat 46 acts so that upon an extraordinary temperature being present at this point, the water admitted to the tube at the foot is controlled. The temperature device 46 includes a rod 47 which acts upon a bell crank 48 for moving a valve rod 49 relative to a valve seat provided in the water inlet control valve 51.

When the temperature of the thermostat 46 is relatively low, the flow of water to the boiler is shut down or throttled to the rate correspond ing to that temperature. When the temperature responsive device 46 responds .to -a higher temperature, the valve is opened-to admit more der being in communication with one side of the valve 51 through a pipe 58 and the conduit 19. The opposite end of the cylinder is connected to the other side of the valve 51 and with the inlet of the boiler tube through a pipe 59. The piston 56 preferably carries a piston rod 61 which is joined to a lever 62 for actuating a control valve 63. This control valve regulates operation of the water pump 1'7 by controlling the fluid operating the pump, in this instance steam drawn from the outlet 13 of the boiler through a conduit 64.

The pressure drop established across the valve 51 is that maintained by the spring bias placed upon the piston 56 so that the flow of water through the valve is proportional to the opening therethrough, which inturn is proportional to the temperature to which the temperature responsive means 46 is accommodated.

In Figure 2 there is shown an arrangement in every'respect identical to the arrangement shown in Figure 1 with the exception that the

conduits

58 and 59 are joined by a conduit 76 which is in parallel with the conduit 19. Controlling flow through the conduit '76 is a valve 77 which is actuated through a crank 78 by a rod 79 extending to a similar crank 81 on the throttle valve 4. The arrangement of the valves 4 and '77 and of the cranks 81 and 78 is such that when the valve 4 is closed the valve '77 likewise is closed and that increments of opening of the valve 4 pro-- '76 as controlled by the valve '77. The water now into the primary portion of the boiler, that is, the

portion between the letters A and B in Figure 2,

is entirely controlled by the two

valves

51 and 77 while water fiow into the secondary portion of the boiler, that is, between B and C in Figure 2,

. is entirely controlled by the fiow through the normalizer inlet 41.

In considering a control system for aboiler of this type it is advisable to consider the primary portion and the secondary portion of the .boiler separately. The primary portion is filled mainly with water and saturated steam while the secondary portion is filled mainly with superheatedv steam. The control-merely of the primary portion of the boiler is insufiicient properly to control the temperature of the delivered steam since any variation in the flow of primary water is long delayed in changing the temperature of the delivered steam. Further, when such a change has once been initiated it causes a large change in temperature of delivered steam dueto the long delay. For instance, if it is assumed thatthe boiler is producing steam at a relatively constant rate and with a slight deficiency of primary flow then the temperature of the delivered steam gradually would rise. Should this cause an increase in the primary flow of water then a great deal of primary water would be introduced into portant reason is that as the point in the boiler the boiler before the temperature of the issuing steam would be effected. The principal reason for this is that the increase of flow of primary water causes a slight increase of pressure within the boiler and, because the large or primary portion of the boiler is filled with an elastic mixture of steam and water,.the compression of this mixture provides ample space for the addition of considerable extra primary water. A second im- 85 at which the last drop of water is converted into steam advances toward the delivery end of the boiler due to the introduction of additional primary water, the thermostat located in the boiler vis not promptly responsive to. such action and before the thermostat reduces the flow of primary water a considerable delay has occurred and the boiler then contains more water than it is able to generate into superheated steam at the proper temperature with the result that the temperature of the delivered steam drops sud-. denly and flooding occurs. This cycle may repeat so that the delivered steam fiuctuates widely in temperature.

For example, taking a practical instance I have found that the temperature at the point B can vary between wide limits, namely, between about 600 degrees Fahrenheit and 900 degrees Fahrenheit, while during such variation the temperature of the delivered steam from the boiler remains exactly at 900 degrees Fahrenheit. This result is accomplished by injection of the normalizer water through the normalizer inlet 41. The temperature of steam passing point B controls the amount of time that secondary or normalizer water is entering at point B. If-the steam coming to this point is relatively hot it requires a greater total of secondary or normalizer water to lower it to the desired temperature at the outlet of the boiler. If the steam at point -B is relatively cooler it requires relatively less such a change in the primary water flow that considerable time elapses {before the effect is had on the primary thermostat 46. g

In some installations of boilers of this type there mustbe delivered widely varying quantities of steam and consequently Widely varying quantities of heat are released to the boiler tube 6. In some installations exhaust steam from the main engine operates a steam turbine for driving the blower 9 in addition to the electric motor 35 so that as the quantity of steam being exhausted through the outlet 13 is increased the fire is likewise and .correspondingly increased. It is therefore necessary to increase the flow of primary water into the inlet12 largely in accordance with the increased heat of the fire- For this reason the valve 51 is incorporated in the water inlet line to the foot of the boiler. As particularly indicated in Figure 2 bothnvalve 51 and valve 77 are included in the system. Valve '77 is disclosed as operated by the throttle which controls the fiow of steam issuing from the boiler. 150

I With this mechanical connection between the such as the thermostat actuated valve 51 for slowly accommodating any accumulated inaccuracy or disparity between the flow of primary water and the heat of the fire.

If it be assumed that the vehicle being propelled with the described power plant is an automobile and if it be further assumed that the throttle valve 4 controls the flow of steam to the main engine then a series of rapid accelerations might result in an accumulated insufliciency of primary water flowing through the foot 12 of the boiler. Such accumulated insufliciency would cause a gradual heating of the thermostat 46 which, then, would gradually open the valve 51 to supply a greater amount of primary water. If, however, an excessive amount of primary water were forced into the boiler such excess would result in a drop in temperature of the thermostat 46 which would then diminish the flow through the valve 51. Although such fluctuations in temperature of the thermostat 46 are relatively slow and are much too slow to be entirely relied upon for the complete control of the boiler, they nevertheless maintain the temperaturein advance of the normalizer inlet 41 within the correcting range of the thermostat 21. As a further example, if it is assumed that the cleanliness of the heating surface is influenced by a deposit of soot making the boiler less efficient then the temperature at the thermostat 46 would be somewhat lower and would correspondingly diminish the quantity of primary water to meet this contingency.

If, for any reason, the temperature at the point 46 becomes unduly high the movement of thermostat 46 opens the contacts 82 and 83 thereby breaking the circuit to the blower 35 and interrupting the supply of heat.

In both forms of the flash boiler control system of my invention there is provided means for regulating accurately the temperature of the superheated steam issuing from the boiler outlet despite wide fluctuations and great variations in the operating conditions of the boiler.

It is to be understood that I do not limit myself to the form of the flash boiler control shown and described herein, as the invention, as setforth in the following claims may be embodied in a plurality of forms.

I claim:

1. A flash boiler control comprising a tube, means for heating said tube, a first means for injecting water into one end of said tube whereby said water flows through said tube and is converted into steam, a second means for injecting water into said tube to mix with the steam there in, a thermostat controlling said second means, and a thermosat responsive to the temperature of said steam prior to the mixture of water therewith for controlling said first injecting means.

2. A flash boiler control comprising a tube,

means for heating said tube, a thermostat re-v sponsive to temperature within said tube, means of said tube.

4. A flash boiler control comprising means for defining a course for fluid, means for introducing fluid to 'said course at the initial point thereof,

means'for introducing fluid to said course at an intermediate point thereof and means responsive to a thermal condition between said initial point and said intermediate point for controlling the introduction of fluid at said initial point.

5. A flash boiler control comprising a tube,

1 means for heating the tube, means for supplying primary water to an inlet" in the tube, means for controlling the primary water supplied to the tube in accordance with a temperature within the tube, means for injecting a slug of water into the tube at a point remote from said inlet, and means for controlling the injection of the slug of water in accordance with steam temperature in the tube.

6. A control for a flash boiler including a long tube adapted (to be heated, the control comprising means for injecting water into the tube at one point to supply primary feed water and into the tube at another point to supply secondary feed water, and means for controlling the primary water injection in accordance with a thermal condition within the tube between said points.

7. A control for a flash boiler having a long tube adapted to be heated by a fire, the control comprising means for injecting primary feed water into one end of the tube, means for injecting secondary water into the tube at a point adjacent the other end of the tube, thermally responsive means for roughly coordinating the injection of the primary water with the fire, and

means for coordinating the injection of secondlot that steam within a portion of the tube adjacent v to an outlet therefrom roughly approximates a desired temperature, means for injecting secondary water into said portion, and means for controlling the injection of said secondary water so that steam closely approximating a desired temperature is supplied.

9. The methodof operating a flash boiler having a long tube adapted to be heated by a flre comprising introducing feed water into the tube automatically in variable quantities always substantially less than the equivalent steam demand and heat available so that steam within a portion of the boiler is at a higher temperature than a desired temperature, and introducing additional water into said portion in response to said higher temperature so that the steam tempera- 11. A flash boiler control comprising a tube, means for heating said tube, means for introducing fluid into said tube between the ends thereof; means for introducing fluid into said tube at an end thereof, thermostatic means in said tube between the points of introduction of fluid for controlling the introduction of fluid into said end of said tube, and means responsive to the quantity of vapor discharging from said tube for controlling the introduction of fluid into said end of said tube WARREN DOBLE.