US2579215A - Wide range liquid fuel burner and method for increasing adjustability r ge of whirl-type atomizing burners - Google Patents

Description

2,579,215 wIDE RANGE LIQUID FUEL BURNER AND METHOD FOR INCREASING Dec. 18, 1951 J. A. TE NUYL ADJUSTABILITY RANGE OF WHIRLTYPE ATOMIZING BURNERS med oct. 4, 1948 4 Sheets-Sheet l Dec. 18, 1951 1. A, TE NUYL 2,579,215

WIDE RANGE LIQUID FUEL BURNER AND METHOD FOR INCREASING ADJUSTABILITY RANGE 0F' WHIRL-TYPE ATOMIZING BURNERS Filed Oct. 4, 1948 4 Sheets-Sheet 2 JZ 25 i 55 2f 2f 7 u n A" V' T 5/ RW a Hy. z

Dec. 18, 195] J, A, TE NUYL 2,579,215

WIDE RANGE LIQUID FUEL BURNER AND METHOD FOR INCREASING ADJUSTABILITY RANGE OF' WHIRL-TYPE ATOMIZING BURNERS Filed Oct. 4, 1948 4 Sheets-Sheet 5 /Wfw/of.- .bbs/mus Angl/'s172705 fe /Vay/ Dec. 18, 1951 J A. TE NUYL.

WIDE RANGE LIQUID FUEL BURNER AND METHOD FOR INCREASING ADJUSTABILITY RANGE OF' WHIRL-TYPE ATOMIZING BURNERS Filed Oct. 4, 1948 n 4 Sheets-Sheet 4 Patented Dec.j 18, 1951 WIDE RANGE LIQUID FUEL BURNER AND METHOD FOR INCREASING ADJUSTABIL- ITY R! BURNERS GE F WHIRL-TYPE ATOMIZING Johannus Augustinus te Nuyl, Delft, Netherlands, assignor to Shell Development Company, San Francisco, Calif., a corporation of Delaware Application October 4, 1948, Serial No. 52,732 In the Netherlands October 27, 1947 18 Claims. (CL 158-36) This invention lrelates to burners for liquid fuel provided with whirl or vortex chambers for atomizing liquid fuel under pressure by discharge through an orice while rotating. In such burners the fuel is conducted through one or more whirling ports or channels, directed tangentially to the circular whirl chamber, into the Whirl chamber near an outer wall thereof and moves in a more or less spiral path toward the center line of the chamber with a progressively increasing angular velocity; the rotating fuel finally leaves the chamber through the spray nozzle oriice in the form of a hollow or annular jet, which is subsequently converted into a conical spray of fuel the apex angle of which is called the angle of atomization.

In such atomizers the quantity of liquid atomized in unit time is proportional to the square root of the supply pressure, i.v e., the pressure of the fuel supplied to the whirl chamber. However, unless special precautions are taken, the adJustability range of these burners is small, as the ratio between the largest and smallest quantity of atomized fuel is only proportional to the square root of the ratio between the maximum and minimum supply pressures.

It is an object of the invention to improve the adjustability range of' such whirl-type atomizing liquid fuel burners.

- such a way that the angle of atomization is maintained substantially constant over considerable variations in the viscosityv of the fuel fed to the burner.

With these and other objects in view, which will become apparent from the following description, reference is made to the accompanying drawings forming a part of this specification and illustrating three preferred embodiments of the invention by way of illustration, and not by way of limitation, wherein:

'Fig. 1 is a viscosity-flow rate diagram illustratlng the relationship between viscosity, flow rate and supply pressure;

Fig. 2 is a diagrammatic flow diagram showing an installation according to the invention wherein variations in viscosity are caused by means of variations in temperature;

Fig. 3 is an enlarged, longitudinal sectional view of a whirl-type atomizing nozzle;

Fig. 4 is a diagrammatic flow diagram of a umodied installation wherein two liquid fuels of different viscosities are used; and

Fig. 5 is a diagrammatic flow diagram of another modii'ied installation wherein gas is admixed to the liquid fuel.

The invention is based upon the phenomenon of pressure atomizers of the whirl-type that, for

a given fuel pressure, the rate of flow of atomf ized fuel through the outlet orifice increases with increasing viscosities up to a certain maximum, after which, if the viscosity is further increased, the rate of flow decreases. This relationship is shown for two widely diverging values of thel supply pressure; the curve at the left, marked Pmln is for a low supply pressure, and the curve at the right, marked Pmax is for a high lsupply pressure. In this diagram fuelviscosities, V, are plotted as ordinates and rates of flow or rates of fuel consumption, Q, are plotted as abscissae. The influence of viscosity on the delivery or flow rate of atomizer nozzles has heretofore been discussed; see Transactions, A. S. M. E., July 1939, pp. 373-381.

Without limiting the invention to any theory, and merely for the purpose of facilitating comprehension of the relationship shown in Fig. l, reference is made to Fig. 3, wherein a whirl-type atomizer is shown, having a swirl plug 6 fitted to the end of a fuel supply pipe 1 by a cap 8, and closed at the rear by a screw plug 9. 'I'he swirl plug forms a vortex chamber having a plurality of swirling ports I0 disposed tangentially to the circular peripheral Wall of the vortex chamber, and an axial, constricted outlet orifice Il. Fuel supplied through the pipe 'l enters the vortex chamber tangentially at the periphery and liquid spins or swirls about the axis, its angular velocity tending to vary inversely as the radius of swirl. This implies an infinite, angular velocity at the axis of the vortex chamber; this being impossible, an air core, indicated at I2, is formed.

The outlet orifice I l from the vortex chamber is relatively small compared to the diameter of the vortex chamber, and the rotating mass of liquid is forced forwardly by the pressure head towards this orifice. It is thus under the iniiuence of two main forces, one, the translational force which urges the fuel axially forward, and the other, the centrifugal or spinning component, which tends to make it ily outwards radially directly as it emerges from the restricting boundary wall of the orifice. As a result the fuel actually emerges from the orifice as atube of liquid which is divergently conical and forms a rapidly thinning film, indicated at I3. This film ruptures or breaks up into fine droplets, indicated at I4, due to the instability of the thin film.

It is the formation of the air core I2 which is believed to account for the extremely low coeiiicients of discharge obtained with nozzles of this type. Measurements shown that the air core tends to increase in diameter as the supply pressure increases, and that it is substantially cylindrical, i. e., of uniform diameter throughout its length within the vortex chamber. A limit to the increase in the diameter of the air core with pressure is imposed by the fact that ultimately, with further increase of supply pressure and, hence, output, the friction losses due to viscosity tend to restrict the angular velocity around the axis to some maximum limit, thus inhibiting further increase in the diameter, and tending to lead to av slight diminution of the angle of atomization as more fuel is forced through the orifice due to the increasing pressure.

The less viscous the liquid, the less is the internal friction, and the greater the swirl velocity of the liquid toward the axis of the vortex chamber. Hence, for a given pressure, low viscosity fuel results in an increase in the diameter of the air core l2, resulting in the eiiiux through the orice H of a thinner tube of fuel and in a smaller ow rate. With a more viscous liquid the liquid near the axis is retarded to a greater degree by viscous friction with respect to the more slowly rotating liquid, near the periphery; this causes the liquid, in flowing toward the vortex axis. to accelerate angularly at a lower rate than in the case of less viscous liquid. This results in a damped swirl with a lesser centrifugal effect, and smaller air-core diameter,l and, hence, a greater rate of ilow through the orifice. It should be understood that these eifects apply only when the fuel pressure is great enough to impart effective swirl, and at lower pressures the nozzle behaves like a plain orifice and produces less output at increased viscosity.

Reverting to Fig. l, this effect is illustrated, for example, by points b and c on curve Pm. If the pressure is maintained constant, the rate of flow can be increased from b' to c' by increasing the viscosity from Vr to V2.

Fig. 1 further illustrates that only a limited range of discharge flow rates can be achieved at a constant viscosity. Thus, at the constant viscosity V1, an increase in the supply pressure from Pmm to Pm results in an increase in the flow rate from a to b'. It was, according to this invention. found that the adlustability range of such burners can be extended by causing an increase in viscosity simultaneously with an increase in the supply pressure. For example, if the viscosity is 'Vr when the supply pressure is Pmm. the viscosity may be increased along any desired linear or nonlinear curve, such as the dotted line a to c, until the viscosity is V2 at the higher pressure Pm. The rate of oil consumption is thereby increased to c', and the resulting adjustability ranges from a' to c', which is considerably larger than the range a' to b.

Another important feature of the invention is concerned withrthe angle of atomization, It 1S generally observed that increases in the viscosity at a given pressure produce large decreases in the angle of atomization. It is, however, desirable to maintain the angle of atomization substantially 5 constant toI prevent impingement of drops of liquid against the walls of the combustion chamber incident to an increase of the angle, and/or to avoid flow of combustion air around the fuel cone with resultant poor mixing incident to a decrease in the angle. In accordance with the invention it was found to be possible to select a higher viscosity V2 for the higher pressure Pm such that the angle of atomization is the same or substantially the same as that obtained at the lower viscosity V1 at the lower pressure Pmi, e. g., differing only a few degrees. Moreover, the curve a to c is preferably selected such as to maintain a constant or substantially constant angle of atomization at intermediate pressures and viscosities; adjustment along a straight line as indicated may, for example, be used. By way of illustration, it is. possible to select V1 and Va at 5 and 80 centistokes, respectively, while maintaining the angle of atomization constant within a few degrees, e. g., less than 4, that is, permitting a change in the angle of atomization, measured in degrees of arc, of less than 1A times the ratio of the highest to the lowest kinematic viscosity of the fuel. This is remarkable, since the angle of atomization is reduced as much as when the viscosity is increased from 5 to 80 centistokes and the supply pressure is maintained at a Pmm of 5 kg. per sq. cm.

It is possible, of course, to effect a still greater adjustability range from a' to d by adjusting the viscosity along the curve a-d; but this would entail a considerable variation in the angle of atomization and is not, for this reason, preferred. It is therefore, desirable to adjust the fuel pressure and the viscosity in mutual dependence, in order to obtain the desired eifect: a wide ad- Justing range with a constant angle of atomization.

The viscosity can be varied in any suitable manner, for instance, by supplying different fuels of different viscosities from different sources when the supply pressure is changed; by varying the temperature; by mixing two or more liquids of different viscosities in varying proportions; and by adding to the fuel various combustible or non-combustible gases soluble therein. Methods and apparatus for regulating viscosity are known, per se, and the invention is not limited to the specic arrangements herein disclosed. It may be noted, however, that whereas the prior viscosity regulating devices sought to maintain a constant viscosity, according to the instant invention the viscosity is increased with increasing pressure.

Referring to Figs. 2 and 3 of the drawing, the installation comprises the atomizing nozzle of Fig. 3 previously described, it being understood that V the invention is applicable to burners equipped with any type of whirl-type atomizer, wherein the fuel is fed into a vortex chamber through swirling ports, i. e., tangentially disposed ducts.

slots, or channels, formed in the side or end wall or the vortex chamber of swirl discs, vanes, inserts, etc. essentially nearthe periphery thereof,

7o and discharged from the vortex chamber after angular acceleration through an axial orifice.

The invention is likewise applicable to the Well known spill return burners,.wherein a portion of the fuel fed into the vortex chamber is returned through a spill return line. Fuel is supplied to the supply pipe 1 ki'roin any source, not shown, through a pipe I5 by a steam-powered feed pump Il and flowed through a heat exchanger or oil heater I1. The fuel oil pressure may be adjusted manually or automatically in response to a thermoetat or boiler pressure responsive element (not shown) by means o f the steam valve I8. 4The heater I1 is heated by steam supplied through line I3 provided with control valve 26 which is operated manually or automatically dependent upon the pressure and the temperature of the oil leaving the heater. Automatic operation of the valve 28 may be effected through a. pressure responsive element, e. g., a bellows 21| connected by a capillary tube 22 to a pressure vessel 23 with expansible liquid such as alcohol and having a thermostatic well 24 projecting into the supply line 1. Increases in the temperature of the oil in line 1 above an equilibrium temperature cause a rise in the pressure of the liquid within the vessel 23, tending to close the valve to reduce the admission of steam` to the heater I1. This lowers the fuel oil temperature, tending to reestablish the equilibrium temperature.

The pressure within vessel 23 is further controlled by a plunger 25 operating an expansible bellows 26 and actuated through a linkage from a spring-biased piston 21 in cylinder 28, exposed to pressure in the line 1 through a capillary tube 29. The linkage includes a slide 38 with a fixed upper pivot 38a and an adjustable lower pivot on a link 3I at the end of a screw 3Ia, and providing a track for roller 32. Rods 33 and 34 connect the roller axle to pivotal connections on the rod 25 and the piston rod 35. Pressure applied through n tube 29 depresses the piston 21 and the rods 35 and 34, thereby urging. roller 32 downward along its track; this places rods 33 and 25 under compression distending bellows 26 and increasing the pressure within the vessel 23, and permitting the valve 28 to close to admit less steam to the heater and increasing the oil viscosity. The resulting lower temperature will act on well 24 to decrease the pressure and again open valve 2 0: but the response is made such that the system comes to an equilibrium at a lower temperature following a rise in the pressure in line 1. The fuel system described is such that vthe heating decreases according as the supply pressure in the line 1 rises, thereby causing the viscosity of the oil to increase; conversely, the heating increases and the viscosity is lowered as the supply pressure falls. By adjusting the screw 3Ia the response ofthe bellows 26 to pressure changes can be adjusted, thereby permitting the control `to be adapted to different kinds of oil.

The pressure in line 1 may also be controlled by a by-pass line 38 having a control valve 31 actuated by bellows 38, this line being preferably connected between the pressure line downstream from the heater and the suction side cf the pump, as shown. It is then possible to operate the pump I6 at a constant speed and to vary the supply pressure in line 1 b /control of the valve 31. Such an arrangement/ advantageous particularly in the case of low oil pressures. it being then easier for the oil heater to maintain the speed of circulation; the response of the installation is thereby increased. The by-pass line 36 may, of course, be omitted.

The heating may, of course, be effected by other means than steam, and the heater I1, heat supply line I9 andcontrol valve 20 may be regarded as typifying a viscosity regulator of any other character in which viscosity is regulated by means of he ting agents other than steam, suchas a flame, an lectric heat generator, hot gases. etc., controlled by a valve or a switch; it may also be regarded as typifying a viscosity regulator having a mixing chamber in\to\`which lighter fluid may be delivered by pipe I9 under control of the valve 28. Moreover, it is possible to provide other forms of viscosity regulating devices and control systems therefor. Thus, the viscosity regulator may admit a cooling fluid to increase the viscosity as the pressure rises.

The control by means of heating, specically described in connection with Fig. 2, is particularly suitable in cases where heat is readily available, as in factories and on ships.

In the installation shown in.Fig. 4, `the atomizer can be supplied ,from two reservoirs 48 and 4I containing different fuels of lower and higher viscosities, respectively. by means of separate feed pumps 42 and 43, driven by a common motor 44. The reservoirs may, if desired, be provided with heating coils 45 and '46 for controlling viscosity, e. g., for maintaining a uniform viscosity. If desired, the fuels in reservoirs 40 and 4I may be the same, but maintained at different temperatures to have different viscosities. The proportion of the two fuels in the mixture supplied to the atomizer is controlled by means of a mixture control apparatus comprising a cylinder 41 containing a reciprocable piston 48 which functions as a control valve to cover or uncover ports at the ends of the cylinder. The piston 48 is actuated by a linkage, indicated collectively at 49, constructed like that described for Fig. 2, in response to movement of a springbiased piston 50 acted on by pressure of fuel in line 1 via capillary tube 5I. The piston differs from that according to Fig. 2 in that a rise in pressure in the line 1 raises it, moving the piston 48 to the left.

Low and high viscosity fuels are fed to the cylinder through lines 52 and 53. respectively, provided with check valves 54 and 55, and communicating with the cylinder space through axially, displaced inlet ports. 'Ihe length of the piston 48 is equal to the distance, center to center, between the inlet ports. Outlet ports, located diametrically opposite the inlet ports, are in communication with discharge lines 56 and 51, connected to the supply line 1. It is evident that, with the piston 48 in its intermediate position shown, approximately equal quantities of fuels from the reservoirs 40 and 4I will ow transversely through the cylinder 41 and into supply line 1. To increase the fuel consumption of the burner the motor 44 can be speeded up (as by a rheostat controlling the field coil, not shown), resulting in a higher pressure in the line 1; this causes piston 50 to rise and piston 48 to move toward the left, thereby throttling the flow of low viscosity oil through lines 52 and 56 and increasing the flow of higher viscosity oil through lines 53 and 51. Conversely, slowing down the motor 44 lowers the pressure, moving piston 48 to the right and increasing the proportion of low viscosity oil supplied to the burner.

By adjusting the pivot point of the slide in the linkage the system can be adapted to different kinds of oil of divergent viscosities.

The pressure can also be varied without changing the motor speed by providing by-pass lines 58 and 59 around the pumps, provided with adiustable, bellows-actuated control valves and 6I. These valves may be cotrolled by a common capillary tube 62 to eifect simultaneous asuma adjustment of both valves and avoid upsetting the ratio-control action of the piston. These valves are, preferably, of the type having a spring-retained valve head urged to closed or controlled position by springs 6l and B4. The valves serve also as safety by-pass or check valves, to permit return of oil in the event that Lathe piston 48 completely closes of! the port at 'fi-. r-Ithe end of one of the lines 52 or 5I.

The modified system according to Fig. 4, involving mixing of different fuels instead of varying the temperature may, for instance, be applied i n domestic heating installations.

According to the embodiment shown in Fig. 5, the viscosity of the normally liquid fuel is varied by mixing it with a gas, e. g., liquefied hydrocarbon gas such as propane, which will dissolve in or be dispersed in the liquid fuel, this arrangement being particularly suitable in cases where such gas is available in suilicient quantities, as for instance, in petroleum refineries. The normally liquid fuel is fed from a reservoir l via a pump 66, powered by electric motor 51, and flowed through line 68 having a check valve 59 into a mixing chamber 10. The gas is supplied from a gas tank 1I in which it is compressed with the aid of a compressor 12 and liquefied. Gas line 13, fitted with check valve 1| and flow control valve 15, ends in a nozzle 16 within the mixing chamber 10. The resulting mixture is discharged from the top of the mixing chamber to the supply line 1 leading to the atomizer. The valve 15 is controlled by a spring-biased piston `11 acted on'. by the pressure in the line 1 via 80, permitting use of a constant speed motor.

In this embodiment it is also possible to provide a linkage between the piston 11 and valve 15. as was described for Fig. 2, to vary the response and adapt the system for fuels of different viscosities. It is also possible to vary the relation between the gas supply and the fuel supply by varying the spring load acting on the piston.

I claim as my invention:

' 1. Method of operating a whirl-type pressureatomizing liquid fuel burner having a. vortex chamber for increasing the adjustability range thereof comprising the steps of supplying liquid fuel to the vortex chamber of said burner in a direction to cause the fuel to swirl about the axis of the vortex chamber, discharging the resulting swirling fuel through a constricted outlet orifice substantially at the .axis of rotation of the swirling fuel, regulating the rate of flow through said orifice by varying the pressure of the fuel in said vortex chamber in the same sense as the desired change in rate of flow, and

varying the viscosityof the fuel simultaneously` the change in composition is effected by admixing.

to a normally liquid fuel, gas which is dispersible in the said normally liquid fuel to produce the said liquid fuel supplied to the vortex chamber, and changing the proportion of said gas and normally liquid fuel to vary the viscosity of the said liquid fuel supplied to the vortex chamber.

6. The method according to claim 5 wherein the gas is a normally gaseous, liquefied hydrocarbon gas.

7. Method of operating a whirl-type pressureatomizing liquid fuel burner having a vortex chamber for increasing the adjustability range thereof comprising the steps of supplying liquid fuel to the vortex chamber of said burner near .the periphery of said vortex chamber and in a direction to cause the fuel to swirl with an angular velocity about the axis of the vortex chamber, discharging the resulting swirling fuel through a constricted outlet orifice substantially at the said axis with an increased angular velocity, regulating the rate of ilow through said orifice by varying the pressure of the fuel in said vortex chamber in the same sense as the desired change in rate of flow, and varying the viscosity of the fuel simultaneously with and in the same sense as the pressure.

8. Method of operating a whirl-type pressureatomizing liquid fuel burner having a vortex chamber for increasing the adjustability range thereof and maintaining a substantially constant angle' of atomization comprising the steps of supplying liquid fuel to the vortex chamber of said burner in a direction to cause the fuel to swirl about the axis of the vortex chamber, discharging the resulting swirling fuel through a constricted outlet orifice substantially at the axis of rotation of the swirling fuel, regulating the rate of flow through said orifice by varying the pressure of the fuel in said vortex chamber inA the same sense as thedesired change in rate of flow, and varying the viscosity of the fuel simultaneously with and in the same sense as the pressure to an extent to maintain the angle of atomization substantially constant at different pressures.

9. The method according to claim 8 wherein the change in the angle of atomization, measured in degrees of arc, is less than about 0./25 times the ratio of the highest to the lowest kinematic viscosity of the fuel.

10. Method of operating a whirl-type pressureatomizing liquid fuel burner having a vortex chamber for increasing the adjustability range thereof and maintaining a substantially constant angle of atomization comprising the steps of supplying liquid fuel to the vortex chamber of said burner near the periphery of said vortex chamber in a direction to cause the fuel to swirl with an angular velocity about the laxis of the vortex chamber, discharging the resulting swirling fuel through a constricted outlet orifice substantially at the said axis with an increased angular veloc- 12. The method according to claim 10 wherein the variation in viscosity is effected by changing the composition of the fuel.

13. A pressure-atomizing liquid fuel burner installation comprising: a whirl-type atomizing burner having a vortex chamber, swirling ports for admitting liquid fuel into the vortex chamber in a direction to swirl therein, and a oonstricted outlet orifice; a conduit for supplying liquid fuel under pressure to said swirling ports; a viscosity regulator for varying the viscosity of fuel in said conduit; means for varying the pressure of liquid supplied through said conduit; and control means responsive to the pressure of fuel supplied through said conduit for controlling the operation of said viscosity regulator, said control vmeans being arranged to increase the viscosity of the fuel as said pressure is increased.

14. The burner installation according to claim 13 wherein the viscosity regulator comprises means for regulating the temperature of the fuel, and the control means is arranged to increase the temperature of the fuel as the said pressure falls and to decrease the temperature as the said pressure rises.

15. The burner installation according to claim 13 wherein the viscosity regulator comprises a fuel heater, and the control means is arranged to increase the supply of heat to the heater as the said pressure falls and to decrease the supply of heat as the said pressure rises.

16. In combination with the burner installation according to claim 13, a plurality of sources of fuels of different-viscosties; and means for mixing fuel from each of said sources and supplying the resulting mixture under pressure to said conduit, the viscosity regulator comprising means for varying the proportion in which said fuels are mixed, and the control means being arranged to increase the proportion of less viscous fuel as the said pressure falls.

17. In combination with the burner installation according to claim 13, a source of normally liquid fuel; a source of normally gaseous fluid; means for mixing said gaseous fluid with said normally liquid fuel and supplying the resulting mixture to said conduit, the viscosity regulator comprising means for varying the proportion in which said normally liquid fuel and normally gaseous fluid are mixed, and the control means being arrangedl to increase the proportion of the normally gaseous fluid as the said pressure falls.

18. A pressure-atomizing liquid fuel burner installation comprising: a whirl-type atomizing burner having a vortex chamber, swirling ports for admitting liquid fuel into the vortex chamber near the periphery thereof in a direction to swirl therein about the axis of the chamber, and a constricted outlet orifice substantially at said axis; a conduit for supplying liquid fuel under pressure to said swirling ports; a viscosity regulator interposed in said conduit; means forwarying the pressure of liquid supplied through said conduit; and control means responsive to the pressure of fuel supplied through said conduit for controlling the operation of said viscosity regulator, said control means being arranged to increase the viscosity of the fuel as said pressure is increased.

JOHANNUS AUGUSTINUS 'rE NUYL.

` REFERENCES CITED The following references are of record in the vfile of this patent:

UNITED STATES PATENTS Number Name Date 1,534,091 Sxnoct Apr. 21, 1925 1,975,937 Graham Oct. 9, 1934 2,079,430 Bargeboer May 4, 1937 2,374,041 Saha Apr. 17. 1945

Images