US2929441A - Liquid fuel burner feed control system - Google Patents

Description

March 22, 1960 P. s. DICKEY LIQUID FUEL BURNER FEED CONTROL SYSTEM Original Filed Aug. 5, 1950 2 Sheets-Sheet l R Y m m m m V D W. %o:\ wm BEBE o S O L m m w m m o m 4 w p h 0 5 f o O o 4 OIL RETURNED I000 2000 3000 LBS. OF OIL BURNED/ BURNER/HOUR FIG. I

A RNEY March 22, 1960 P. s. DICKEY 2, 29,441

LIQUID FUEL BURNER FEED CONTROL SYSTEM Original Filed Aug. 5, 1950 2 Sheets-Sheet 2 INVENTOR.

PAUL S. DICKEY Paul S. Dickey, East Cleveland, Ohio, assignor to Bailey Meter Company, a corporation of Delaware Original application August 5, 1950, Serial No. 177,819, now Patent No. 2,702,591, dated February 22, 1955.

Divided and this application November 29, 1954, erial No. 471,763

7 Claims. (Cl. 158-36) My invention relates to fuel burning systems and apparatus and particularly to the control of wide-range return-flow mechanical fuel oil burner atomizers.

A further object of my present invention is to provide a system and apparatus maintaining a differential between the oil supply pressure and the oil return pressure to a mechanical atomizer, which differential is varied in predetermined relation with rating or demand.

Another object is to provide such a system and apparatus capable of varying the ratio of supply pressure to return pressure in accordance with variations in the oil supply pressure or rate.

These and further objects will be apparent from the description of the drawing.

In the drawings:

Fig. 1 is a graph of operating conditions illustrative of the invention.

Fig. 2 is a schematic showing of a vapor generator fired by wide-range return-low oil burners to which the in vention has been applied.

Referring now in particular to Fig. 2, my invention is illustrated as applied to wide-range return-flow mechanical oil burner atomizers generally indicated at 10. The particular construction of the atomizer head and burner box assembly may be of the type described and claimed in the copending application of L. W. Heller, SN 115,013, filed September 10, 1949, which is now Patent 2,715,546 patented August 16, 1955. In Fig. 2 I show two groups of burner assemblies 19 representative of a single or plurality of burners which may be used for heating any space such as a furnace.

Liquid fuel, preferably oil under a substantial pressure, is delivered to the burners through a supply pipe 11. in return-flow atomizer constructions, a portion of the fuel is by-passed and returned to the reservoir or fuel pump inlet to vary the capacity of the burner. In Fig. 2 such return oil enters the header 12.

The conduit 11 has fuel, such as oil, supplied thereto at a constant pressure, and it as well as the return conduit 12 are adapted to be connected in communication with the various burners by means forming no part of the present invention. Air is supplied from a fan or blower 30 through a passage 31 to the furnace for supporting combustion of fuel discharged from the burners 1G, and a boiler 32 is heated by the combustion of the fuel for generating steam which is delivered through a conduit 33 to a point of use. The pressure of the steam discharged from the boiler 32 may be employed in this case as an indication of demand on the furnace, a drop in pressure indicating an increase in demand, and an increase in pressure indicating a decrease in demand. It will be appreciated that the furnace may be employed for heating something other than the boiler, and that the demand may be indicated by changes in temperature of some object or material being heated. Connected in the fuel supply conduit 11 and the return conduit 12, as shown in Fig. 2, are valves 35 and 36 which are controlled by pressure actuated diaphragms 37 and 38 respectively. The

Patented Mar. 22 1960 c TQ valve 35 is so designed that it is moved towards its open position as the pressure supplied to the diaphragm 37 is increased and the valve 36 is designed to close on an increase in the pressure supplied to the diaphragm 38.

The fan or blower 30 is driven by a power unit 46, such as a turbine, and a conduit 41 delivers operating fluid to the power unit under the control of a valve 42 which is adapted to be moved towards its open position by a diaphragm 43 when the pressure supplied thereto is increased. Arranged in the air passage 31 is a damper 44 connected by a link 45 to a control mechanism 46 which operates when pressure supplied thereto is increased to move the damper toward its open position.

For controlling the supply of fuel and air to the burners 10, in response to changes in demand on the furnace, there are provided means operating in response to changes in steam discharge pressure for regulating the pressure supplied to the diaphragms 37, 38, 43 and the damper control mechanism 46. This means comprises a pressure responsive device 50, such as a Bourdon tube, subjected to the steam pressure in the conduit 33 through a pipe 51. A pilot valve 52 is connected to the Bourdon tube and controls the supply of pressure fluid to a chamber 53 of a relay 54 for moving a member 55 against the action of a spring 56 to position a pivoted beam 57 which regulates fluid supply and discharge valves 58 and 59. The positions of these valves determines the pressure in a chamber 60 which communicates through a restricted connection 61 with an opposing chamber 62. When the pressure supplied to the chamber 53 balances the tension of the spring 56, the beam 57 assumes a position to close the supply and discharge valves, and the pressure in the chamber 60 is held at the value existing when the balance was reached. An increase in the pressure supplied to the chamber 53 results in an operation of the beam 57 to open the supply valve 58 and effect a continuing increase in the pressure in the chamber 60. If the pressure in the chamber 53 drops below the value balancing the'spring 56, the discharge valve 59 is open to etfect a continuing decrease in the pressure in the chamber 60. The relay 54 is disclosed in the Gorrie Patent Re. 21,804 and need not be described further herein.

The pilot valve 52 is connected so as to increase the pressure in the chamber 53 when the Bourdon tube operates on a drop in the steam pressure in the conduit 33. An increase in the steam pressure causes the Bourdon tube to position the pilot valve so as to reduce the pressure in the chamber 53. This p lot valve is like that described in the Johnson Patent 2,054,464.

The pressure in the chamber 60 of the relay 54 is delivered through conduits 65 and 66 to the diaphragm 43, and is delivered through a branch conduit 67 to the control mechanism 46 for the damper 44. The pressure is also delivered from the conduit 65 to a chamber 68 in a relay 69 which operates to supply a pressure to a conduit 70 communicating with a branch conduit 71 leading to the diaphragm 38, and communicating with another branch conduit 72 leading to a chamber'73 in a relay 74 which controls the flow of pressure fluid through aconduit 75 to the diaphragm 37. An operation of the relay 54 to increase the pressure supplied to the conduit 65 results in an opening of the valve 42 to increase the speed of the turbine for driving the blower 30 to supply more air to the passage 31, an operation of the control mechanism 46 to open the damper 44, and an operation of the relay 69 to increase the pressure in the conduit 70 for effecting a closing movement of the valve 36 in the fuel return line 12. The pressure increase in the conduit 70 is also delivered through the conduit 72 to the relay 74 and causes the latter to operapse-441 ate so as to increase the pressure in the conduit 75 for opening the valve 35 in the fuel supply line.

As the valve 36 is closed and the valve 35 is opened, the pressures at the burner sides of these valves are increased so that more oil is forced through the burners to satisfy the demand on the furnace. It is desirable that the valves 35 and 36 be operated so that the difierential in pressure between the supply and discharge sides of the burners is varied in desirable manner with rating or demand. For maintaining the desired interrelation there is provided arelay 80 having bellows 81 and 82 subjected through conduits 83 and 84 to the pressures at the supply and discharge sides, respectively, of the burners. The bellows operate against spring loaded fulcrumed levers 85 and 36 respectively. An adjustable roller fulcrum $7 for the levers 85, 86 compares the pressure effects of the bellows 81, 82 and the system controls the position of a linkage'88 arranged to position the movable element of the pilot valve 89, for establishing in a conduit 90 a. fluid pressure representative of the desired differential in pressure between the supply oil and the return oil, or departure therefrom.

The size and location of the bellows 81, 82, as well as the length and pivoting of the linkage 85, 86, 88, is determined by the expected range in pressures of the supply 'oil and of the return oil. The spring adjustments 91 and 92, as well as the movable fulcrum 87, may be manually manipulated during operation to establish the desired difierential in pressure which may be arranged to have des red functional relation with rating or demand on the unit as a whole. 7

The pressure result of the relay 80, applied within the pipe 90, is effective within a chamber 93 of the relay 74 to aid the pressure in the chamber 73 in operating the relay 74 to determine the pressure supplied to the diaphragm 37.

If the pressure at the discharge side of the burners should increase for some reason, more than the res sure desirably increases at the supply side, the bellows 82 would operate to lower the movable element of the pilot 89 to increase the pressure supplied to the chamber 93 of relay 74. The relay 74 would be operated by this increased pressure to increase the pressure supplied through the conduit 75 to the diaphragm 37 for opening the valve 35 and increasing the pressure at the supply side of the burners. if the pressure at the discharge side does not increase as much as it did on. the supply side, then the bellows 82 would operate the linkage 38 to reduce the pressure supplied to the chamber 93 and the relay '74 would o erate to redu e the Dressure on the diaphragm 37 tending to close the valve 35 so as to reduce the pressure at the supplyside of the burners. It will be appreciated that the bellows 81, 82 may be positioned to maintain any desired functional relation between the pressure of the oil in the supply conduit 11 and that of the oil in the return conduit 12. Thus I may match the curves A, B, C of Fig. 1 or other desired plotted conditions.

In the installation from which the teristics of Fig. 1 were obtained, the desired relation of supply pressure 'to'whirl chamber pressure, as determined by the relative indications of pressure gages in the supply conduit 11 and return conduit 12, is obtained in the fuel burning range from 4500 lb. per hour down to approximately 500 lb. per hour by the throttling'of valves 35 and 36. When the pounds per hour of oil burned are increased above approximately 2500, the latter valve is opened to such a slight degree and the amount of return oil flow is so small that it is not possible to determine its rate by the customary orifice meter and so the curve D is not extended to show return oil flow for the higher output range.

However, below a 2500 lb. per hour rate, and in order to avoid undue reduction in the velocity of oil introduction through the tangential slots into the whirl operating characchamber while reducing the rate of delivery to the furnace, control of the pressure differential is further effected by simultaneous manipulation of valves 35 and 36, through progressive throttling of the supply by control valve 35, while'progressively manipulating valve 36 to permit a progressive increase in return oil flow. The rate of return oil flowfor the lower range of burner output, below 2500 lb. per hour, is shown by curve D of Fig. 1. This correlated regulation of valves 35 and 36 results in a relationship as shown by curve A for supply pressure and curve B for the return or relative whirl chamber pressure. Curve C depicts the relative differential between these two pressures.

Thus the invention provides a method of straight mechanical atomizer operation at maximum burner output, and return flow operation from the maximum rate down to the minimum. As before stated. the rate of return oil flow at a burner rate above 2000 lb, per hour, for example, is negligible and the rate of return oil how at the minimum burner rate does not rise to a troublesome quantity, as will be clear from curve D. On the other hand, the reduced pressure differential, occurring through the lower rate burner output range, avoids a wide spray angle from the atomizer.

The amount of oil returned to the conduit 12 is substantially less at any atomizer delivery rate than with any prior art methods of return flow atomizer control. This is graphically demonstrated in Fig. 1 wherein the curves A and B represent the supply pressure and return pressure, respectively, of an actual operating installation using the same atomizer controlled to maint in a substantially constant differential pressure (curve C) from 2300 lb. of oil per burner per hour to 250 lb. of oil per burner per hour, the supply pressure at the top rating being 1000 p.s.i. and the return pressure 870 p.s.i. It will be noted that the recirculated or return oil rate, shown by curve D. is much greater, at all ratings, than that for the invention system, as shown by curve D.

For obtaining a high operating efficiency of the furnace. there is provided control means for additionally regulating the valves 35 and 36 in the fuel line so as to maintain a predetermined ratio'between the total air flow and thetotal fuel supplied to the burners. This control means includes a relay having diaphragms 101 and 102 acting in opposition upon a lever system 103 for positioning the movable element of the pilot valve 104. Arranged in the fuel conduits l1 and 12 are devices 105 and 106 for measuring the flow rate of fuel oil through the conduits. Each of these devices may be like that disclosed in my Patent No. 2,459 089 and need not be described herein as it forms no part of the present invention. the devices 105, 106 and operates to supply to a conduit 108 a pressure which is proportional to the diiference between the measurements of fuel flow. It will be appreciated then that the pressure in the conduit 108 is di rectly proportional to the total fuel consumption at the burners 10. Pressure in the conduit 108 is subjected on the diaphragm 101'so as to urge the linkage 103 in a counterclockwise direction. Arranged in the air passage 31 is an orifice 109 and pressures at opposite sides of the orifice are subjected through pipes 110. 111 on a device 112 which operates in response to differential pressures for supplying a pressure to a co1duit'113 directly proportional to the total air flow to the furnace. The pressure in the conduit 113 is delivered to the diaphragm 102 for opposing the action of the diaphragm 101.

The pilot valve 104 is positioned by the linkage 103 for controlling the pressure in a conduit 115 to a chamber 116 of the relay 69. The pressure supplied to the chamber 116 aids the pressure in the chamber 68 for determining the pressure supplied through the conduit 70 to the diaphragm 38 and to the chamber 73 of the relay 74. As long as the ratio of the total fuel supply as the total airsup ty remains constant, the pressure A device 107 is connected to supplied from the relay 100 to the chamber 116 will be held at some predetermined value and the supply of fuel and air to the furnace will be varied only with changes in steam pressure. If the supply of fuel becomes too great for the amount of air supply the pressures delivered to the diaphragms 101 and 102 will effect a positioning of the pilot valve 104 to decrease the pressure supplied to the chamber 116 of the relay 69. This relay then cperates to decrease the pressure supplied through the conduit 70 so as to effect a closing of the valve 55 and an opening of the valve 36 for reducing the total fuel discharged from the burners until the ratio of total fuel to total air reaches the value at which the relay 100 is balanced. If the quantity of fuel discharged to the burners is insufficient relative to the air supply, the relay 100 is unbala .ced in the opposite direction to increase the pressure delivered to the relay 69 and effect an increase in the pressure supplied to the diaphragms 37 and 38. The valve 35 is then opened and the valve 36 is closed to increase the discharge of fuel from the burners.

It will be seen that the control system of Fig. 2 operates to automatically control the supply of fuel and air to the burners responsive to a demand factor such as steam pressure developed by the vapor generator which is heated by the burners. If the rate of total fuel supply is not in desired proportion to the rate of total air supply the ratio relay 1% effects a modification of the steam pressure control in the positioning of the fuel control Valves 35 and 36. Each and all of the atomizers 10 are subjected to a differential pressure between the pressure of the oil supply and the pressure of the oil return which follows a predetermined relation with rating. If the instantaneous pressure differential between the oil supply and oil return is not in accordance with the adjustment of the relay 80 then the control of the supply oil valve 35 which is basically from steam pressure as a demand index and further responsive to total air fiow-total fuel flow relation, is further modified by departure of fuel oil differential pressure from the desired value for that operating level.

While I have illustrated and described a certain preferred embodiment of my invention it will be understood that this is by way of example only, and that I do not expect to be limited except as to the claims appended hereto.

This application is a division of my copending applica tion Serial No. 177,810 filed August 5, 1950, now Patent 2,702,591.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a liquid fuel circulating system including at least one mechanically atomizing liquid fuel burner, a fuel supply conduit'connected to the burner, and a fuel return conduit leading from the burner; the combination of means supplying liquid fuel under pressure to the supply conduit, a first fuel flow regulating valve in the fuel supply conduit, a second fuel fiow regulating valve in the fuel return conduit, means responsive to a decrease in demand upon the system positioning said first valve in a closing direction and simultaneously positioning said second valve in an opening direction in amounts proportional to the decrease in demand and vice versa, and means responsive to the difference in pressure between the liquid fuel in the supply and return conduits positioning one of said valves to vary said difference in pressure in predetermined relation to variations in demand upon the system.

2. In a liquid fuel circulating system including at least one mechanically atomizing liquid fuel burner, a fuel supply conduit connected to the burner, and a fuel return conduit leading from the burner; the combination of means supplying liquid fuel under pressure to the supply conduit, a first fuel flow regulating valve in the fuel supply conduit, a second fuel flow regulating valve in the fuel return conduit, means responsive to a decrease in demand upon the system for relatively positioning said valves to decrease the fuel discharge from the burner and vice versa, and means responsive to the difference in pressure between the liquid fuel in the supply and return conduits relatively positioning said valves to vary the difference in pressure in correspondence with variations in demand upon the system.

3. In a liquid fuel circulating system including at least one mechanically atomizing liquid fuel burner, a fuel supply conduit connected to the burner, and a fuel return conduit leading from the burner; the combination of means supplying liquid fuel under pressure to the supply conduit, a first fuel flow regulating valve in the fuel supply conduit, a second fuel flow regulating valve in the fuel return conduit, means responsive to changes in demand upon the system positioning said first valve in amounts directly proportional to such changes and simultaneously positioning said second valve in amounts inversely proportional to such changes; and means responsive to the difference in pressure between the liquid fuel in the supply and return conduits readjusting the position of the first regulating valve to vary said difference in pressure in predetermined relation to variations in demand upon the system.

4. In a liquid fuel circulating system including at least one mechanically atomizing liquid fuel burner, a fuel supply conduit connected to the burner, and a fuel return conduit leading from the burner; the combination of means supplying liquid fuel under pressure to the supply conduit, a first-fuel flow regulating valve in the fuel supply conduit, a second fuel flow regulating valve in the fuel return conduit, means responsive to changes in demand upon the system positioning said first valve in amounts directly proportional to such changes and simultaneously positioning said second valve in amounts inversely proportional to such changes; and means responsive to the difference in pressure between the liquid fuel in the supply and return conduits readjusting' the position of the first regulating valve to maintain the difference in pressure between the liquid fuel in the supply and re turn conduits increasing as the demand upon the system increases and vice versa.

5. In a liquid fuel circulating system including at least one mechanically atomizing liquid fuel burner, a fuel supply conduit connected to the burner, and a fuel return conduit leading from the burner; the combination of means supplying liquid fuel under pressure to the supply conduit, a first fuel flow regulating valve in the fuel supply conduit, a second fuel fiow regulating valve in the fuel return conduit, means responsive to an increase in demand upon the system positioning said second valve in a closing direction in amount corresponding to the increase in demand and vice versa, means determining the difference between the flow rates in the supply and return conduits; and means responsive to the last named means for simultaneously positioning the first and second valves in accordance with changes in the difference between the fiow rates.

6. In a liquid fuel circulating system including at least one mechanically atomizing liquid fuel burner, a fuel supply conduit connected to the burner and a fuel return conduit leading from the burner; the combination of means supplying liquid fuel under pressure to the supply conduit, a first direct acting flow regulating valve 111 the fuel supply conduit, a second reverse acting regulating valve in the fuel return conduit, means for generating a control signal corresponding to the demand upon the system for simultaneously positioning said first and second valves, means determining the difference be tween the flow rates in the supply and return conduits, and means responsive to said last named means for adusting the control signal in accordance with changes in the difference between said flow rates.

7. In a liquid fuel circulating system including at least one mechanically atomizing liquid fuel burner, a fuel,

supply conduit connected to the burner and a fuelv return conduit leading from the burner, the combination of means supplying liquid fuel under pressure to the Supply conduit, a first valve in the supply conduit anda sec ond valve in the return conduit, means for generating a first control signal corresponding to the desired rate of oil discharge from the burner, means under the control of said first signal adiusting the relative positions of the first and second valves in accordance with changes in the first signal, means generating a second control signal in accordance with the difference between the flow rates in the supply and return conduits; and means responsive to said second control signal adjusting the relative positiofis oi the first and second valves to maintain a pre determined relationship between the first and second control signals. 1 v

References Cited in the file of this patent UNITED STATES PATENTS 2,536,158

Chamherlin et a1, Jan. 2, 1951 2,536,556 Lawrence a Jan. 2, 1951 2,540,778 Dickey Feb. 6, 1951 2,604,149 Wynne July 22, 1952 2,702,590 Stillman Feb. 22, 1955 2,702,591 7 Dickey Feb. 22, 1955 UNITED siATEs PATENT orriclE CERTIFICATE @F CQRREC'HQN Patent No. 2,929,441 March 22 1969 Paul S. Dickey It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected belo Column l between lines 17 and 18 insert the following paragraph:

The main object of my present invention is the provision of apparatus for operating a wide. range return==flow mechanical liquid fuel atomizer whereby the angle of spray or atomization may be controlled with variable rates of fuel atomization so that carbon deposition may be avoided without modifying the axial position of the atomizer relative to the furnace or burner throat,

Signed and sealed this 6th day of September 1960,

(SEAL) Attest:

ERNEST W. SWIDER ROBERT C(; WATSON Attesting Officer Commissioner of Patents

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