US2000580A - Art of combustion of liquid fuels - Google Patents

Description

May 7, 1935.- E. H.' cARRu'rHERs y 2,000,530

` I ART OF COMBUSTION OF LIQUID FUELS Fi1ed lay 19, 1931 3 sheets-sheet 1 iINVENToR. BY l/ ATTORNEY.

May 7, 1935-v E. H. cARRuTHl-:Rs 2,000,580

ART OF COMBUSTION 0F LIQUID FUELS Filed May 19, 1931 '5 Sheets-Sheet 2 Cowrv/vr Volcans PUMP A TTORNE Y.

May 7, 1935. E. H, cz/luaRLrHERsn 2,000,580

.ART 0F COMBUSTION OF LIQUID FUELS Filegi hay 19. 1931 s sheets-sheet 3 Figa co was ,al ffl/Y I' BY ATTORNEY.

Patented May 7, 1935 2,000,580 A Aar or commsfnon oF maum Fons Y Eben H. Carruthers, Ithaca, N. Y., assignor to United Furnace Engineering Company, Inc., New York, N. Y., a corporation of Delaware Application May 19, 1931, Serial No. 538,453

This invention relates to the art of combustion of liquid fuels, particularly oil, especially for use in the burners of furnaces in whichlclose control'of the` combustion and resulting 8856s is 5 desirable.

In all prior liquid fuel combustion systems of i which I am aware, the regulation of the flow of liquid fuel is by the employment ofa valve which is designed to control the pressure back of the 0 burner orifice, or by an automatic pressure re- -ducing valve to maintain a constant pressure \back of the orifice, or combinations of both. Under the old systems, it has been practically impossibleto maintain the flow rate of the oil constant with xed settings of the pressure ulators and valves. A

For example, changes in temperature of the-oil, in the viscosity of the oil, or the building up of reg- ` .said material in the valve or orifice, may cause wide variations in flow. These variations must -be counteracted by constant manipulation of the valve or regulator, if conditions are to be kept at all constant. \The' result of the uctuations is a flame of uneven character, and thegases of combustion may become very detrimental to the articles in the furnace to which the heat -is applied.

v In.me1ting metals metals, it is very desirable to maintain a Ycertain selected' furnace atmosphere or composition of gases of combustion, to avoid certain detrimental eects on the materials subjected to heat. For example, in melting copper, a highly oxidizing atmosphere will cause oxidization of the copper; on the other hand, a highly reducing flame will allow the copper to absorb carbon monoxide, which is known to be detrimental to the metal. In-the case of heat treatment or annealing of ferrous metal, an oxidizing ame is injurious to the surface of the metal, causing scaling; and therefore control of this atmosphere is desirable again.

A neutral atmosphere which is the dividing line or small range between the oxidizing and the reducing atmosphereis usually the most desirable to maintain, but in apparatus` novvI in use the setting of the valves or other parts is done by purely human observation of the operator, which cannot be relied on at all times.

I Since it is desirable to maintain some particular atmosphere. it is necessary to have a constant liiow rate 4of liquid fuel to the burnengin order to avoid theuctuations in thepratio of the fuel to air mixture, which in turn causes fluctuations in the resulting furnace atmosphere, and

or in heat treatmentA of passage of the liquid fuel from the pump to lthelv burner.'

be high,` running, for example,"from 1000 pounds it is necessary to maintain a constant liquid fuel ilcw rate along with the flow rate of air that is I se An object of the present invention is to .provide a new and improved method of and apparatus for producing a constant selected or predetermined furnace atmosphere or composition of gases of l combustion within a furnace.

Other objects are, to provide means for effecting a Iconstant flow rate of liquid fuel and vmixing said fuel with the desired proportions of y airto maintain combustion, said liquid fuel being preferably atomized prior to its mixture with the air, whereby air may be supplied at low pressures; to provide a. system of burning liquid fuel which allows the selection of a certain furnace atmosphere, and which includes means for` indicating the said `furnace atmosphere .and means fou` maintaining the selected atmosphere without variations; and' a method and appara- 20 tus for high combustion eiiiciency, applicable for utilizing fuel oils of high, low and intermediate gravities. l

Inv the accompanying drawings, which illustrate various types of apparatus embodying my invention and capable .of use in the practice of my method:

Figs. 1, 2 and 3 are diagrammatic views of several forms of apparatus embodying my invention. I 30 Referring first to the form of Fig. 1, 5 designates preferably a volumetric flow displacement pump designed to be driven by va suitable prime mover or motor 6 at a constant speed. This pump is coupled to a liquid fuel storage tank 'I by a suitable pipe connection 8, and is designed to deliver the .liquid fuel, preferably oil,v to a burner designated generally. by the numeral 9. I8 designates a connecting pipe line for the The burner \9 has a discharge orifice I I; the area of this orifice should be of a size so that, for a set deliveryrate, the pressure behind it will to 10,000 pounds per` square inch.

' The pressures now known :to the art for spraying liquid fuels cannot be accurately called high pressures since they are but a small fraction of the high pressures employed present invention.' At the novel pressures of 1000 to 10,000 pounds per square inch, the strain energy supplied in such. quantities that when the pressure is released, this energy is absorbed as surface tension in the particles which at the according to the 50 pressures mentiond are necessarily of such proportions as to present the requisite surface for the absorption, which' energy is sumcient to cause vaporization or volatilization of the oil when the pressure is released, it thus being impossible for the oil 4particles to remain as -drop- A lets and condense or coalesce of themselves as in existing methods since the entire quantity of liberated oil heretofore was not completely blown into -a gas but the divisionH ofthe oil under the action of pressure was 4flnal at a stage where the maior portion of the oil consisted of droplets of considerable size; hence by means of my invention, in combination with a ame, upon liberation of the oil, I efiect complete atomizatiomg,

vaporization and combustion directly at the orifice. This action occurs immediately, simultaneously land instantaneously, all of the oil being blown directly and completely into a vaporous or volatile state solely through pressure. Accordingly the specific pressures are not limitar-y but include all equivalent lowerand higher pressures which produce the same results within the spirit and scope of the invention.

It is an important and characteristic feature of my invention that the liquid fuel is passed to the burner at a constant flow rate, and this I accomplish without the employment of valves or regulating means interposed vbetween the pump and the burner, as has heretofore been necessary.

In practice, the pump should displace, in a unit of time, a definite amount of liquid fuel regardless f the pressure it must discharge this fuel against. so that the volume of liquid delivered to the burnerl through the connecting line I will be at a constant rate, regardless of the pressure in said line or back of the discharge orifice Il. c

Due to the presence of relatively high pressure backfof the discharge oritlce, it will be apparent that the liquid fuel passing from the pump to the burner will be broken up into fine particles and, as it i8 discharged through the orifice, the drop in pressure from y the high values to the low pressure values will cause intense .atomization of the liquid fuel, rendering it suitable for complete combustion when mixed with air. c

As illustrated in each of 'the forms of apparatus shown, air is delivered to a furnace mixing chamber l2 of a furnace I3 from a fan or blower 20, and from thence the mixture of air and atomized liquid is passed `to thecombustion chamber I4. of the furnace through an opening i5. Since the liquid fuel has been highly atomized upon leaving the oriiice Il, the air is not.

relied on totake any part in breaking up the liquid fuel; it is needed only to mix with the atomized liquidy to support combustion, Consequently, the air employed may be low pressure air supplied from low pressure fans, etc., at a considerable saving over present methods. The employment of low pressure air also has the effect of decreasing noise inthe operation of the burner.

The rate at which the air is supplied to the combustion chamber, whenapparatus of the form of Fig. 1 is employed, may be controlled by a vvalve or damper4 I6. disposed in the air line I1 connecting the blower 20 and the chamber lz. rnaddmon to uns vave ls, and at som convenient location in line I1, I providel a. Venturi meter I8, or a thin plate orifice or its equivalent, communicating with a manometer or other suitable indicator device I9. The function of4 this indicator device is to show relatively the weight-time rate of air passing through the line to vthe combustion space of the furnace, by indicating the pressure drop' through the meter.

The indicator device may be calibrated in terms of percentage of gas composition of thel furmoe gases, thereby having the advantage of giving the operator a definite scale by which he can regulate the atmosphere to suit the requirements of the material being heated.

The furnace atmosphere, or the composition and relative proportions or the gases resulting from this combustion, depend upon the relative proportions or rates at which the fuel and air are being delivered. Since the fuel rate is definitely fixed at a certain value, changes in the resulting gases will be effected by changes in the air rate only, which changes will be lindicated on the air flow indicator I9. For, every position of this indicator, then, there will be a corresponding analysis of the gases resulting from combustion. These may be determined by taking samples directly from the furnace and analyzing them by any of the generally known methods, and the resulting figures placed on the indicator. c

After analyses are made for a sufilcient number of. points to form the scales of the indicator, the sampling and analysis apparatus may be discarded. From then on, the readings of the scales will indicate the composition of the gases, and the operator, by adjustment of theair valve or gate, may bring the indicator to any particular scale reading and thus establish the corresponding furnace atmosphere.

In the operation of the form of Fig. 2, it is contemplated that the air flow is kept constant by a suitable automatic air dow regulator 2| and thepump 5 for the liquid fuel, regulated so that the rate of flow of fluid 'may be varied to any selected krate, but after the selection the rate of flow of the liquid will be constant. In this manner, the ratio of fuel to air may be selected and controlled so as to give the desired resulting furnace atmosphere as described in connection with the form of Fig. l. apparatus, I employ, in place of the venturi meter I8, the regulator 2| of well known construction.v 'Ihis regulator may be set .to allow .varied by the employment of a variable speed motor; and the percentages' of gases calibrated in terms of said speed.

The operation of the form-of Fig. 2 is substantially the same asdescribed for the form of In this form of- Fig. 1, with the exception that the changes in the composition and relative` proportionsof the products of combustion is eifected by manipulation of the' mechanical volumetric adjusting means of the pump, or alternatively, by regulacal adjustment of the pumpis displacement, or to the indicator of the pumps speed of rotation in the case of the speed adjustment.

Fig. 3 illustrates apparatus comprising a -combination of the forms of Figs. l and` 2. In this ease, the positive blower or'fan .20 and the constant volume displacement pump 5 are driven by the same power means 6, through connecting shafts or suitable gearing. 'I'he pump 5 is provided, as in Fig. 2, with the adjustable velumetric control means l22 and the'dial or indicator 23, indicating the percentages of the gases of combustion as a function of the flow rate of liquid fuel therethrough. While the power means E is rotating at any desired constant speed, the operation and control will be identicalwiththat oftheform ofFig.2,theratecf speed of the blower 2li.v

Since the rate at which the blower delivers air and the flow rate of the pump 5 are proporsupplv of air being constant, due to the`constant tional to the speed at which said units aredriven.

'highly desirable in providing an accurate heat control for the vfurnace to which the system is applied, and permits the furnace to be banked or maintained at a minimum temperature when not in actual use. i

In priorliquid fuel combustion systems, the supplies of liquid fuel and air 'must be entirely shut olf when the furnace is not in actual use. Due to this fact, the furnaces, ovens. etc. cool ofi between heats and result in considerable waste of fuel in bringing the apparatus to working temperature forA the next heat.

I claim: v

l. The herein described method of effecting combustion of a liquid fuel which consists in prducing a fiow'of the liquid at a constant ow rate while subjected to high pressure at or above substantially 1000 pounds per square inch, atomizing said liquid by said pressure prior to itsy mixture with air, and then mixing air and they atomized liquid in predetermined proportions and igniting'the mixture.

2. The method according to claim l in which the air mixed within the atomized liquid is ata ,pressure relatively low with respect to the said uid in the furnace and ignitlng the mixture.

4. The herein described method of effecting combustion of liquid fuel in a furnace, which' consists in producing a flow of the liquid by pres- Sure above substantially 1000 pounds per square inch at a constant flow rate. atomizing said liquid prior to its admixture with air, and then 6 mixing ai' ln controlled and measured quantities with the atomized liquid and igniting the mixture.

5. The herein described method of effecting combustion of liquid fuel in a furnace which consists in producing a ow of the liquid "at a constant flow rate, atomizing said liquid by pressure above or at substantially 1000 pounds per square inch prior to its admixture with air, then mixing air in controlled quantities with the atl5 omized liquid and ienitlng the mixture.

y 6. The herein described method of effecting combustion of a liquid fuel which consists in producing a flow of the liquid while subjected to high pressure at or above substantially 1000 pounds per square inch, atomizing said liquid by said'pressure prior to its admixture with air, mixing air and the atomized liquid, and igniting the said mixture. Y

7. 'I'he herein described method of effecting 25 combustion of a liquid fuel which consists in producing a flow of the liquid while subjected to high pressure at or above substantially 1000 pounds per square inch, atomizing said liquid by said pressure prior to its admixture with air, mixing low pressure air and the atomized liquid, and igniting the said mixture.

8. The herein described method of effecting combustion of a liquid fuel which consists in producing a flow of the liquid while subjected to high pressure at or vabove substantially 1000 pounds per square inch, atomizing said liquid by said pressure prior to its admixture with air, mixing low pressure air and the atomized liquid in predetermined proportions, and igniting the 40 said mixture.

9. The herein described method of eiecting combustion of a liquid fuel in a furnace to produce a selected constant furnace atmosphere within the furnace, which consists in supplying d5 a mixture vof air and liquid fuel to the furnace in constant quantities, the liquid fuel being atomized at a.pressure at or above substantially v1000 pounds per square inch, varying the quani tity of one ofthe fluids of the mixture whilemaintaining the other constant, and igniting the mixture.

l0. The herein described method pf effecting combustion of liquid fuel in a furnace, which consists in producing a flow of the liquid at a constant flow rate while subjected to a pressure at or above substantially one thousand pounds per square inch to atomize the liquid, then mixf ing air in controlled and measured-quantities with the atomizea nquiasnd in simultaneouslyeffecting -equal changes in both air'.and liquid flow for the purpose of changing'the rate of heat liberation in the furnace without. changing the Y vatmospheric condition, andthenv igniting the

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