US2037994A - Apparatus for metering fluids - Google Patents

Description

April 1936. w. NEUBAUER 2,037,994

APPARATUS FOR METERING F LUIDS 4 Filed July 9, 1932 4 Sheets-Sheet 1 INVENTOR. faw/lv W Nzuanuae ATTORNEY April 21, 1936. E. w. NEUBAUER 2,037,994

APPARATUS FOR METERING FLUIDS Filed July 9, 1932 4 Sheets-Sheet -2 INVENT OR. 1T0 Wl/V W hrozm 'urkz.

ATTORNEY April 21, '1936. E. w. NEUBAUER APPARATUS FOR METERING FLUIDS 4 Sheets-Sheet 3 I Filed July 9, 1932 I INVENTOR.

, EDWIN W Nruaguzn.

Mfl

ATTORNEY Patented -Apr. 21, 1936 APPARATUS FOR IVIETEBING FLUIDS I Edwin W. Neuhauer, Portland, Oreg., assignor to Ray Burner Company, San Francisco, Call! a corporation of Delaware Application July 9,1932, Serial No. 621,677

4 Claims.

My invention relates to a method and apps;- ratus for metering fluids in such manner as to prevent change in rate of flow of a fluid caused by change in viscosity thereof. More particularly, the method and apparatus of my invention are especially adapted in oil burner systems where it is extremely desirable to maintain a uniform flow of oil to the burner, unaiiected by variations in viscosity of the oil. This application is a continuation in part of my copending application, Serial No. 533,169, filed April 27, 1931.

. Introduction In oil burner systems, the control of rate of flow of oil to the burner has heretofore been quite a.- problem, particularly in such systems which function automatically to shut ofl and turn on the oil. With a system set for a predetermined flow or rate of oil to the burner, changes in oil viscosity have heretofore affected the rate of flow, thus rendering unstable the size of the. burner flame. In the automatic systems referred to, the

oil decreases in viscosity after its flow to the burner is shut off, because the remainder of 1 in the system warms, under actual boiler-room conditions, when the burner is on. Consequently, if the oil is turned on again, the burner flame size will be diiferent from that prior to the shutextremely difficulty. Upon burning of the oildn the burner the oil flowing in the system becomes heated and its viscosity decreases. Obviously,

I with the conventional type of system, the burner flame size will be affected by such changes in visccsity. If an attendant is constantly present to take care of an oil burner system, he can regulate.

the size of the burner flame to maintain it substantially constant, by opening or closing a man-' ually operable valve for controlling the rate of flow. The added expense of an attendantmakes his presence undesirable.

Oba'ccts of invention Various systems have been heretofore employed in an effort to overcome'the foregoing described difliculty. However, none of these systems has been able to maintain constant rate of flow regardless of changes in viscosity of the oil.

- It is therefore one of ihe objects of my invention to pro-slide an apparatus and method which will meter a fluid, such as oil to an oil burner,

at a substantially flxed predetermined rate regardless of viscosity changes in the fluid.

Another object of the invention is the provision of an apparatus, of the character described, which can be economically manufactured. An additional object of my invention is the provision of an apparatus, the mode of operation of which is simple and which, therefore, requires little or no attention.

A further object is the provision of a method and apparatus, of the character described, which will permit the utilization of heavier and cheaper oils than heretofore possible in previous automatic systems, thus materially reducing the cost of operation.

Other objects of my invention will become apparent from a perusali of the following description of my invention. 7

Although the apparatus and method of my invention are of general application and therefore can be employed for any purpose where it is desired to render inefiective change in viscosity of a liquid upon rate of flow thereof, the apparatus and method are particularly adapted for a fuel oil burner system, where the use of the system of my invention has solved the heretofore bothersome problem. I have therefore chosen for the purpose of illustrating the principle of my invention, the application thereof in an oil burner system.

General description In general terms, the apparatws of my inven-. tion employed with an oil burner, comprises a conduit system for distributing oil from a given source. The system includes a plurality of conduits or fluid conducting means, through which the oil has a divided flow. One conduit or fluid conducting means is connected to the oil burner to provide for delivery of oil to the burner, while another forms a branch conduit or fluid conducting means connected with the delivery conduit to by-pass the surplus oil back to the given source. The oil is distributed throu the system from the source, by a substantially constant volumetric pump (i. e., a pump which is capable of feeding an approximately fixed volume of oil per unit of time). In each of the plurality of conduits or fluid'conducting means b yond the point of division of fluid flow, are formed restricted 1 yrs of materially less cross-sectional area than that of the conduits connected to the ends of the eways, so as to offer considerable resistance to the flow of oil and thereby convert the head on the oil into streamline viscous friction. Each restricted passageway is of such length and cross-sectional area as to create a substantial pressure drop across the passageway (i. e., difference in pressure between the pressure of the oil entering the passageway and its pressure leaving the passageway) greater than the back pressure created by the oil in the portion of the conduit bra'nch be-' yond the discharge end of the passageway.

Passageways of the character described will cause flow of oil therethrough in compliance with Poiseuilles law, which is, briefly, that for tubes or passageways of properly selected diameter and length, the rate of flow of a fluid therethrough is directly proportional to'the pressure and to the fourth power of the tube radius (the square of the cross-sectional area) and inversely proportional to the length of the tube and to the viscosity of the fluid. Tubes in which the flow of fluids obeys Poiseuille's law are called Poiseuilie tubes; the restricted passageways in the system of my invention are, therefore, of the character of Poiseuilie tubes.

Mathematically, Poiseuilles law may be expressed as follows:

2 17 T "E1? where,

V=volume of oil T=time 1'=tube radius =pressure of oil across tube l=length of tube u=absolute viscosity of oil The ratio of volume to time is the same as oil rate which may be designated as O. For a given tube, a, r, 8 and l are constants. Therefore, for a. given tube the formula may be expressed as follows:

Oil rate=(a constant) stant. Therefore, if the viscosity of the oil increases or decreases due to change in temperature, the pressure across these Poiseuilie restricted passageways must increase or decrease proportionately. Thus, because of the Poiseuille fluid flow eifect,changes in viscosity of the'oil which might occur, are automatically compensated by a proportional change of a factor occurring in the Poiseuille formula; and the same quantity of oil will, consequently, flow from each restricted passageway regardless of changes in viscosity of the oil.

Description of figures my invention in which one number of Poiseuille tubes. or restricted passageways is employed in one branch and a different number of tubes in' another branch.

Figure 3 illustrates in vertical section a Poiseuilie tube or passageway constructed in the form of a valve, to allow flexibility of adjustment in controlling the quantity of oil to the burner. and also to allow adjustment of across the passageway.

Figure 4 is a diagrammatic view of a typical fuel burner installation, in which a high low flame control is utilized.

pressure drop.

Figure 5 is a vertical sectional view of a type of valve diflerent from that shown in Figure 3.

Figure 6 is a horizontal sectional view of a preferred Poiseuilie valve unit employed in the system of my invention. The section is taken in planes indicated by line 6-6 in Figure 9.

Figure 7 is a longitudinal sectional view taken in a plane indicated by line 1-1 in Figure 6.

Figure 8 is a transverse sectional view taken in planes indicated by line 8-8 in Figure 6.

Figure 9 is an end elevation of the unit, looking in the direction of arrow 9 in Figure 6.

Figure 10 is a horizontal sectional elevation taken in a plane indicated by line lO-ill in Figure 8.

Description of Figure 1 modification With reference to Figure 1, which is for the purpose of illustrating the principle of the in-- vention, the system in its simplest form may comprise a tank or reservoir 2 for holding the oil, in which is located a constant volumetric discharge pump 3 of any suitable construction, A main supply line 4, connected to the discharge end of pump 3, leads to the burner 6 anda branch line I by-passes oil from the main supply line back to tank 2. It is to be observed that the conduit portion 9 of the main supply line between branch 1 and burner 6 provides for delivery of voil to the burner, and that the oil has a divided flow through conduit portions 9 and I. A Poiseuille tube 9 is interposed in .burner delivery line 8 and another Poiseuilie tube H of larger size is connected in by-pass branch I. i

The division of flow of oil through the two conduits or fluid conducting means I and 9 will be proportional to the size of tubes ii and 9, respectively. For example, if the constant volumetric dischargepump' 3 has a displacement of .50

20 gallons of oil per hour and the two tubes are it be desired to feed, for example, only five gallons of oil mr hour to the burner 9, the size of tube 9 may be so selected with respect to the size of tube II as to cause three times as much oil to flow through the by-pass branch I as through the delivery conduit 9. Because of the character of the restricted passageways formed by Poiseuilie tubes 9 and II, the flow of oil to the burner will be substantially constant regardless of changes in viscosity of the oil. The latter would not be the case if ordinary valves or tubes were employed in place of the Poiseuille'restricted passageways, it being a phenomenon in the flow of liquids that for a. given branch system the quantities of fluid flowing through the various branches will ordinarily change upon change in viscosity of the fluid. From a' purely academic point of view, the phenomenon of the peculiar action of the Poiseuilie tubes may be explained as follows. Due to the restricted passageways which the tubes provide, a damming efl'ect obtains at the points A and B,

- pressure drop or the proportionate the branches tend to vary so as to cause more than the proportionate share of oil to flow through, for example, branch I, the damming effect at B will hold the oil back and allow only share of through .tubev I I. This same effect obtains at A in case more oil tends to flow through'branch 8. The mutual damming effects at both A and B, therefore, compel a constant distribution of oil through the branches. Because Poiseuille tubes 9 and H are of such character and of such dimensions that the internal friction developed therein during the flow of oil therethrough produces a pressure drop or difference in pressure between the ends of each tube greater than the back pressure (at A and B developed in the system beyond the-discharge ends of the tubes, the tubes render negligible the unbalancing eifect of such back pessure upon flow of oil through the tubes. This, coupled with the proportionate damming effect, results in a constant division of flow in the two branches for all viscosities of the oil. In actual practice, it is preferable to select the length and diameter of each tube, so that the difference in pressure between the ends of the tube is from 10 to 15 times the back pressure. v

As long as the restricted passageways or tubes 9 and II form Poiseuille tubes or substantially Poiseuille tubes (i. e., passageways which will have the precedingly pointed out characteristics and in which the flow of fluids will obey Poiscuilles law) change in viscosity of the oil will have no material effect on distribution of flow. By selecting the size of burner branch tube 9 with respect to the size of by-pass branch tube H, the quantity of oil to the burner may be fixedly predetermined in accordance with the capacity of pump 3, the quantities of oil flowing through the two branches being proportional to the sizes of the tubes, as previously explained. For any particular metering system, the actual dimensions of a set of tubes when properly selected may vary .within wide limits, depending upon the normal viscosity variation of the fuel oil at the temperature employed,- the capacity of the constant volumetric discharge pump, and the practical pressure range which can be safely developed in the system and still effect feeding of oil through the system. g

With respect to the practical pressure, it has been previously explained that, for agiven tube,

to preclude unsafe pressures developing in the high viscosity of the oil, to the system. The actual system for relatively preclude bursting of dimensions of the tubes, to form Poiseuille tubes,

' practical pressure range; 8;

may be readily calculated from Poiseuilles formula. by those skilled in the art pertaining to the flow of liquids. In making such calculations, the known factors are: the oil rate (determined by the constant volumetric discharge pump) P (the ''u (the viscosity range of the oil being employed); and, finally,

the division of flow desired in the two branches oil to flow namely, the delivery and by-pass' fluid conducting means or conduits. The length for a preselected cross-sectional area of each tube, or vice versa, may therefore be calculated from the formula,

The following examples will illustrate some of the many wide ranges which the various factors in the system of my invention (employing two Poiseuille tubes through which the fluid has divided flow) may have, depending upon operating conditions desired, and for systems in which the friction developed outside the Poiseuille tubes is negligible compared to that in tubes.

Example I Constant volumetric dis- 40 gals. per hr.

charge pump capacity.

m Desired feed to the burner 10'gals. per hr.

By-pass feed 30 gals. per hr.

Viscosity range of oil to be 600-2400 seconds burned. Saybolt furol Pressure developed 'l7%lbs.-7llbs.per

sq. in.

6 ins. long and .19

in. diameter 6 ins. long and .25

in. diameter Poiseuille :tube 9 to burner may be.

Poiseuille tube II in by-pass branch may be.

Example II Poiseuille tube 9 to burner 10 ins. long and may be. Poiseuille tube in by-pass '10 ins. long and branch may be. .270 in. diameter I I Example III Constant volumetric dls- -40 gals. per hr.

charge pump capacity.

. Desired feed to the burner-.. 15 gals. per hr.

By-pass feed 25 gals. per hr. Viscosity range of oil to be 2014-5350 seconds burned. Saybolt furol 'Premure developed. ..s 25% lbs-67 A lbs.

' persq. in.

.167 in. diameter v Poiseuille-tube 9 to burner 10 ins. long and .3

may be. in. diameter Poiseuille tube II in by'-pass l0 ins. long and .3 4

branch may be. in. diameter Example IV Constant volumetric dis- 40 gals. per hr.

charge pinnp capacity. .Desired feed'to the burner-.. 8 gals. per hr. ,By-pass feed"; 32 gals. per hr.

Viscosity range of oil to be 116-580 seconds Saybolt furol 18 lbs'.-90 lbs. per

sq. in.

12 ins. long and burned. Pressure developed Poiseuille tube 9 to burner may be. Poiseuille tube H in by-pass branch may be.

12 ins. long and .203' in. diameter .143 in. diameter Example V Constant volumetric dis- 25 gals. per hr.

charge pump capacity. Desired feed to the burner 10 gals. per hr. By-poss teed 15 gals. per hr. Viscosity range of 'oil to be 583-2330 seconds burned. Saybolt iurol Pressure developed... 20 lbs.- lbs. per sq. in. Poiseuille tube 9 to burner 6 ins. long and .186

may be. in. diameter Poiseuille tube I i in by-pass 6 ins. long and .206

branch may be. in. diameter Example VI Constant volumetric dis- 25 gals. per hr.

charge pump capacity. Desired feed to the burner 5 gals. per hr. By-pass feed 20 gals. per hr. Viscosity rangeof oil to be 1110-2775 seconds burned. Saybolt iurol Pressure developed 40 lbs.-l00 lbs. per

Sq. in.

Poiseuille tube 8 to burner 10 ins. long and may be. .176 in. diameter Poiseuille tube II in by-pass 10 ins. long and branch may be. .249 in. diameter Example VII Constant volumetric dis- 55 gals. perhr.

charge pump capacity. Desired feed to the burner.. 10 gals. per hr.

By-pass teed 45 gals. per hr. Viscosity range of oil to be 566-2265 seconds burned. Saybolt iurol Pressure developed. 20 lbs.-80 lbs. per

sq. in. Poiseuille tube 9 to burner 6ins. long and .185

may be. in. diameter Poiseuille tube II in by-pass 6 ins. long and .269

Poiseuille tube 9 to burner 10 ins. long and may be. .176 in. diameter Poiseuille tube II in by-pass 10 ins. long and branch may be. .313 in. diameter In the examples set forth, either one or both of the tubes, 8 and I I may be made longer or shorter, by correspondingly increasing or decreasing, respectively, the diameter or cross-sectional area,

provided that no values are selected that will introduce errors in the Poiseuille equation.

Description of Figure 2 modification Instead of employing two single Poiseuille tubes of diflferent size, with one connected in the delivery conduit and the other in the by-pass conduit, to efiect the predetermined division in flow oi fluid through the two conduits or branches, I may employ all tubes of the same size with a given number in the by-pass branch and a different number in the burner or delivery branch The quantities of oil which will. flow through the two branches per unit of time will be directly proportional to the number or Poiseuille tubes in each branch.

Figure 2 illustrates diagrammatically a system in which Poiseuille tubes, all of the same size, are employed with diii'erent numbers in each branch or conduit. I The oil is pumped from tank or reservoir 2' by constant volumetric discharge pump 3', through main supply line l, connected to the burner 0'; and a'branch line 1' by-passes oil back to tank 2'. Die portion oi. main supply line 4' connected to the burner forms a branch 8' the oil having a division of flow betwwn this branch and branch 1". Three Poiseuille tubes 8'. all of the same size, may be interposed in burner branch 8' and seven Poiseuille tubes ll, of the same size as tubes 8', maybe interposed in bypass branch 'I'. With such connection, the division 01' flow in burner branch 8' with respect to by-pass branch 1' will be as 3 is to "I.

For example, assuming that the capacity of constant volumetric discharge pump 3' is 10 gallons per hour; in an hour's time 3 gallons will flow to the burner and 7 gallons will be by-passed. Thus, as with respect to the Figure 1 embodiment, the provision of the means for producing the eflect of a Poiseuille type of fluid flow in each of the fluid conducting means beyond the point of division of fluid flow,'enables the rate of flow to ,be unaffected by viscosity changes. The following examples illustrate some of the many ranges possible for a lo-gallon-per-hour constant volumetric discharge pump and with tubes connected as in Figure 2.

' Example IX With tubes each 6 inches long and .1 inch in diameter, the system will meter oils ranging in viscosity from seconds Saybolt universal to 5000 seconds Saybolt iurol, with a pressure range of .34 pounds to 204 pounds per square inch.

Example X If the tubes 01' Figure 2 are each twenty inches long and .08 inch in diameter, the system will meter the same range or oil viscosity as in Example Ix, but with a pressure range of .28 pounds to 1688 pounds per square inch.

Example XI Tubes, each 4 inches long and .12 inch in diameter will also meter the same range of oil viscosity as in Example IX, but with a pressure range of .011 pound to 66 ppunds per square inch.

"nimble valve (m. a) The preferred type or system is, due to its simplicity, that illustrated in Figure 1, where only two Poiseuille tubes are employed. However, in such system where the tubes are fixed in size, variable-flow to the burner cannot be obtained. For fixed sizes of the tubes, only a constant quantity of oil will be fed to the burner per unit of time. In order that this quantity may be variably controlled, I have devised an adjustable valve which has a restricted passageway, forming a Poiseuille tube the effective cross-sectional area of which may be changed to vary the size of the passageway. Figure 3 illustrates one form of valve, which may be substituted for either one of the tubes in Figure l, or two of the valves may be employed in place of both of the tubes. By varying the ratio of the Poiseuille restricted passageway sizes, it is apparent that different quantitles of oil per unit of time may be caused to flow to the burner.- Hence, the size of the burner time may be regulated when desired.

iii

With reference to Figure 3, the valve comprises an elbow 2|, having a hub 22, adapted to be connected to a conduit in the system by threads 23, and also having a hub 24 threaded onto sleeve 26. Sleeve 26 is threaded in connecting member 21, in turn threaded onto the tube 28 which is formed with a frusto-conical or tapered passageway 29. In the passageway is mounted for movement a complementary tapered valve element or plug 3| having a stem 32 provided with threads 33, threaded in plug 34 sealing elbow 2|. The

end of stem 32 projects beyond plug 34 and is pro- A vided with flats 36, whereby the stem 32 may be gripped by a suitable tool to eiiect turning thereof and consequent movement of plug 3| longitudinally of passageway 29. It is to be noted that the circumferential space 31 between the inner surface of tube 23 and the surface of plug 3i is restricted, thus providing a restricted passageway having the characteristics'of a Poiseuille tube. Movement of plug 3| will vary the effective diameter or cross-sectional area of the passageway 3?. To center plug 3| in its movement, the end thereof is provided with a pin 38 connected to radially projecting pins 39 adapted to contact with the lower enlarged cylindrical portion of tube 28. This portion is threaded at 4| to provide means for connection of the discharge end of the tube.

From Figure 3 it can be seen that the portion of the conduit system outside of restricted passageway 3,1 is of large bore, so as to offer negligible resistance to the flow of fluid through such portion, thereby eliminating outside turbulence which might otherwise afiect the flow of fluid through, restricted passageway 31. Also, it is to be observed that the length of passagewayi31 is not materiallyincreased or decreased by movement of plug 3|; compared. to change in crosssectional area of said passageway 31 caused by such movement. As the valve element or plug 3| is moved upwardly, the'cross-sectional area of passageway 31 is diminished and the flow of fluid is consequently retarded. Downward movement of the plug 3| increases the cross-sectionalv area of the restricted passageway to produce increased flow. The variations in cross-sectional area of passageway 31, to form various sized restricted passageways having the characteristics of Poiseuille tubes, may be readily predetermined from the factors entering Poiseuilles formula as previously pointed out.

System: employing adjustable valve (Fig. 4)

supply of oil is held in tank or reservoir to.

which is connected a main supply line 52, having connected therein a strainer 53 at the intake side of a constant volumetric displacement pump 54., Pressure gauge 56, preferably locatedadjacent the discharge side of the pump 5|, gives a visual indication of the pressure built up in the system. The supply line branches at 51, one portion, preferably the major portion, of the oil being returned to the tank 5| through by-pass branch 58; In

the by-pass branch 58, I provide a valve 59 of the construction disclosed in Figure 3. In another branch Gl, leading to the burner 62, a similar valve 53 is provided. A third branch 64 is preferably provided with a high-low flre valve 66 which is adjustable to open or close branch at the point 51, portions ball valve or a gate valve.

tions. It is unnecessary be employed in the system of 64. Another branch 61 of the system includes a standard safety valve 68, which safety valve is set to open at a predetermined pressure, i. e., the maximum pressure that can be safely developed in the system without causing rupturing thereof. In operation, 011 normally flows through the by-pass branch 53 and through the burner branch. 6 i. Thus. the oil passing through line 52 diverges being fed through the branches 59 and SI. The proportionate flow between such branches depends entirely upon the adjustment of the valves 59 and 63 relative to each other; and the rate of feed to theburner may be varied atwill by adjusting either of valves 59 or 63 to change the ratio between-the crosssectional areas of restricted passageways 31 in the valves. With one style of apparatus the pump 54, which is preferably a rotary gear constant volumetric displacement pump, discharges sixty gallons of oil per hour uniformly and constantly into the main supply line 52-. Depending upon operating conditions, the burner 32 utilizes from five to ten gallons of oil per hour, and the valves may be so adjusted that the remaining fifty to fifty-five gallons is fed back through the return or by-pass line 58 to the intake side of the pump or to the tank.

To maintain valves 59 and 63 at substantially the same temperature so that the viscosity of the oil in both valves may be substantially the same, I preferably connect the bodies of valves 59 and 63 by a heat-conducting strip 69 of metal or any other suitable heat-conducting material. With this arrangement, accurate metering of the oil to the burner, which might not otherwise occur if the oil viscosity were diflerent in the two valves,

is insured.

It may sometimes be desirable to diminish the flame size of burner 62 without relatively adjusting valves 59 and 63. This can be done by opening high-low flame valve 66. Valve 66 may be any suitable manually-operable valve, such as a In normal operation of the system, valve 66 is closed, but when it is desired to produce a low flame the valve may be opened any predetermined amount depending upon the flame size desired; Upon opening of valve 66 a relatively iarge portion of the oil will be subtracted from the burner branch line SI, and the oil supplied to the burner willbe correspondingly diminished to produce low fire condito have a valve similar to valves 59 and 63 in branch line 64, because generally, when valve 68 is operated, the oil in the system is ata viscosity equilibrium (that is, the system has been operating a substantial period and consequently all the oil is at substantially the same temperature and viscosity). Regardless of whether valve 68 is open or closed, valves 59 and 63 will meter the oil to the burner at a constant rate for any fixed position of the high-low flame valve.

' It is to be observed with respect to the high-low flame valve 66, that the flame size of-the burner diminishes upon opening of the valve. ,Thus,. clogging of the system by foreign matter which might pass through strainer 53 is precluded. With respect-to burner valves heretofore employed for diminishing the flame size and which depend upon closing of the valve to effect such diminishment, clogging is quite apt to occur.

As previously explained, only one valve, 59 or 63, having a Poiseuille restricted passageway, need as Y Figure the other Poiseuille restricted passageway may be formed by an ordinary fixed Poiseuille tube of the character disclosed in Figure 1. It is desirable, however, to employ the two valves 68 and 88 because then, if the pressure in the system builds up to dangerous limits because of the oil being of high viscosity, both .valves may be adjusted together to increase the cross-sectional areas of both re- Modified form of valve (Fig. 5)

In Figure 5 is illustrated-a type of valve having a Poiseuille restricted passageway, which valve is automatically adjustable to maintain substantially constant the pressure in the system. A pair of such valves may be substituted for valves 58 and 68 in Figure 4.

The valve comprises a cylindrical tube 8| having an enlarged chamber 82 at one end and a second enlarged chamber 88 at the opposite end. Nipples 84 and 85 are connected to the chambers 82 and 83, to provide means for attachment of the valve in the conduit system. A plug 86 is movably mounted in the cylindrical portion of tube 8 I, the plug 86 being provided with a helical passage way 81. One end of passageway 81 communicates with chamber 82 and the other end of passageway 81 communicates with chamber 83. The sides of passageway 81 are preferably curved so that the passageway is, in section, a portion of a circle; and the passageway 81 is gradually tapered from the chamber 82, through which oil enters the valve, to the chamber 83, which is the discharge chamber for the valve. It is to be observed thatpassageway 81 forms with the inner surface of tube 8| a restricted passageway. The -size of such restricted passageway may be predetermined from Poiseuilles formula, by those skilled in the art, in the manner previously pointed out.

The under side of plug 88 is recessed at 88 to provide a seat for spring 88 which is connected to adjustable screw 8|, threaded in the bottom of chamber 88, to provide means for placing a predetermined tension on spring 89, thus normally maintaining plug 88 co-extensive with tube 8|. As the pressure in the system tends to increase or decrease, plug 86, because of its floating mounting on spring 88, will move downwardly or up-- wardly, respectively, to vary the effective length of passageway 81 in tube 8|. During such movement the effective cross-sectional area of the passageway 81 is not materially changed compared to the change in-length. Consequently, with increase or decrease in length of passageway 81, the resistance which is developed in the passageway is respectively increased or decreased to maintain substantially constant pressure. For example, if plug 88 is in a fixed position and the pressure rises due to increase in oil viscosity, theplug or'valve element will move downwardly against the action of spring 89. Such movement shortens the length of restricted passageway 81 decrease the resistance to flow. With such thereof, communicating with tank I 84 decrease in resistance to flow, the pressure will drop. It is thus seen that with the valv of Figure 5-instead of variations in viscosity being automatically compensated by changes in pressure as with respect to the previous described modifications-increase or decrease in viscosity which would normally alter rate of flow, is automatically compensated by a proportional decrease or increase, respectively, of the length of re.- stricted passage 81. In this connection, it will be recalled from the Poiseuille formula previously discussed, that rate of flow is directly proportional to the pressure and to the square of the "cross sectional area, and inversely proportional to the length of the passage and to the viscosity of the fluid. As a result, if the pressure and area are maintained substantially constant as in the Figure 5 valve, and since the rate of flow is maintained substantially constant, the length of passage 81 will vary inversely with changes in viscosity. Consequently, because of the Poiseuille fluid flow effect, the Figure 5 modification compensates automatically for changes in viscosity of the fluid, by inverse changes of the length (Z) factor occurring in the Poiseuille formula, instead of the pressure (P) factor. By the use of the valve of Figure 5, the necessity of a safety valve in the system is obviated, and substantially constant pressure conditions will obtain regardless of change in oil viscosity.

' Preferred construction (Figs. 6 through 10) The valve system of my invention is especially adapted for use with oil burners in all places where it is desirable to burn cheap, thick oils,

by means of a system the functioning of which is automatic to preclude the expense of an at tendant. For example, the system finds particular applicability in apartment houses, hotels, and small industrial jobs.-

For such uses the practical range of fuel rate to the burner is 1 gallon per hour to 34 gallons per hour, or 3 horse-power to horse-power burner capacity. This calls for an oil pumping capacity of not less than 35 gallons per hour. The fuel oils available on the market for such heating purposes range in viscosity, at normal temperature, from 40 seconds Saybolt universal to 3200 seconds Saybolt furol. I have, therefore, constructed a. unit containing two valves, connected so that the oil has divided flow therethrough and capable of forming Poiseuille restricted passageways, to meet the practical re quirements in the uses pointed out. Such unit is shown in Figures .6 through 10.

The unit comprises a casing IIiI terior chamber I02, and provided with a flanged bottom I03 adapted to be secured over a reservoir or tank I 84 in which is located a constant volumetric discharge pump I06. To meet the requirements of the practical system, a constant volumetric discharge pump of 35 gallons per hour capacity will sumce. Preferably a slow, constant speed, medium pressure, tight, induction motor actuated, and rotary gear pump is employed. Tank Ill-is not the main supply tank, which latter tank is generally located outside of the burner room. Casing IUI is therefore formed with a passageway I88, in a vertical end wall and into which oil may be fed from a main supply tank (not shown). Pump I 86 is connected to conduit I08, communicating with chamber I 82 which is kept full of oil fed by the pump. The conduit lil8is secured to the bottom of casing having an inmeans of apertured cap I II threaded into the bottom wall and against packing ring II2 rounding conduit I09.

Adjacent the side walls H3 and H4 of casing IN and at the top thereof are formed a pair of tapered tubes H6, one end II1 of each of which communicates with the chamber I02. The shape and arrangement of each of tubes II6 are the same; therefore only one will be described- In each of tubes H6 is mounted for movement a complementary tapered valve element or plug I I8 adapted to form with the inner surface of the tube a restricted Poiseuille passageway H9. The large end of plug H8 is recessed at I20 to allow sliding over guide stem I2I integral with plug I22, threaded into casing wall I23. Into the small end of valve plug I I8 is threaded a stem I24, extending through wall I128 of the casing and journaled in any suitable gland and seal structure I3I. By turning outer end l32 of stem I 24 with any suitable tool or key, longitudinal movement of valve element I I3 is effected to vary the crosssectional area of restricted passageway H0. Due to the fact that tube IIS is considerably longer than valve element M8, the effective length of restricted passageway I 59 is not changed by such movement of the valve element.

Wall I26 of the casing is formed with an enlarged discharge passageway I33, communicating with aperture I34 in which may be connected a conduit leadirm to the burner. Passageway I33 also communicates with the restricted passageway II9 in one of the valves formed by tube H6 and plug H8. The discharge end of the other valve (by-pass valve) communicates with vertical passageway I36, open at the bottom and leading to tank I04. One of the core holes I31 in the top of casing IOI is threaded to receive a pressure gauge, while the other core hole I38 is plugged.

It is thus seen that fluid from the fluid source or feeding means divides, after leaving conduit member I09, and flows through the two Poiseuille passages II9.- One of such passages 9 forms part of the delivery line to the burner together with passageway I33 and aperture I34; and the other forms part of a branch together with vertical passageway I36, for by-passing'the fluid.

back to the source. Therefore, as with respect to the previously described systems, there are provided both a, delivery conduit or fluid conducting means to the burner, and a branch conduit or fluid conducting means connected or communicating with the delivery conduit; and in each of such conduits is provided, beyond the point of division of fluid flow, the Poiseuille fluid flow efiectuating means.

In the side wall (Figure 8) H3 of the casing and below the valve adjacent said wall isformed a passage I39, the inner end of which communicates with chamber I02. The outer end of passage I39 is closed by a cap I4I, threaded into the casing and in which is seated one end of spring I42. Spring I42 bears against valve member I43 which normally closes the inner end of passage I39. Should the pressure in the system exceed a safe amount, valve member I43 will yield against the compression of spring I42; and the oil will pass through passage I39 and through aperture I44 communicating with the passage.

Aperture I44 is formed in the bottom of the casing and the oil will therefore lead back into tank I04. Thus a safety valve is provided for the system, it being apparent that the size of spring.

I diameter.

I42 may be so selected as to cause the spring to I yield only when the maximum safe pressure in the system obtains. a

I preferably employ a high-low flame control valve in the unit of the preferred construction. Such valve (Figure 6) comprises a stem I41 journaled in the boss I48, formed in side wall II4 of the casing IOI and below the valve adjacent said wall. The stem I41 is also journaled in a suitable gland and seal structure I49 secured to boss I48. Inner end of stem I41 is provided with a recess I5I which communicates with the chamber I02;and the wall of the stem adjacent the recess is formed with an aperture I52 adapted to communicate with a passage H53, communicating with the bore of boss I48 and leading to tank I04. Normally, stem I 41 is in such position that aperture I52 is not in communication with passage I53; therefore no oil will flow therethrough.

When it is desired to reduce the size of the burner flame, stem I41 may be turned to effect registry of aperture I52 with passage I53; the oil will thus by-pass from chamber I32 into tank I04 and will .be subtracted from the system to reduce the size of the burner flame.

The mode of operation of the unit described is the same as that explained in connection with Figure 4. However, with the unit of the preferred construction it is not necessary to employ the heat conducting strip connected to the valves,

because all the valves are part of the same integral casting, in which the oil will necessarily be of the same temperature and viscosity.

I shall now give the actual dimensions of the valve elements in the preferred unit device of my invention, which makes the device suitable for the range of fuel oil feed to the burner and for the oil viscosity range usually encountered in the previously described systems where the unit finds general applicability. Valve element or plug I I8 is preferably 4% inches long, is circular in cross-section and tapers uniformly and graduaily from the large end, which is 78 of an inch in diameter, to the small end which is inch in The taper of tube H6 is of the same degree or complemental to the taper of plug II8. With such dimensions the restricted'passageways .I I3 will provide Poiseuille tubes in the described systems.

The relative clearance between said passageways and the clearances of each of said passageways may beflxed so as to cause feeding of the desiredquantity of oil to the burner at the desired pressure range. When the valve elements I I8 have been once fixed to obtain the desired clearance relationship, the functioning of the unit device is entirely automatic (1. e., a constant rate of discharge will be fed to the burner unafiected' by change in viscosity of the oil).

Example XII pressure will range from 6 pounds to 1'70 pounds 7 upon the viscosityper square inch, depending range of the oil.

Example XIII With a clearance of .030 inch in the by-pas's valve and .024 inch in the burner valve, the feed rate to the burner will be 10.4 gallons per hour.

Example XIV If the clearance is .045 inch in'the by-pass valve and .024 inch in the burner valve. the feed rate to the burner will be 5.17 gallons per hour,

- with a, by-pass rate of 29.83 gallons'pe'r hour, for

oils ranging from 30 seconds Saybolt furol to 600 seconds Saybolt furol in viscosity. The pressure will range from 8 pounds to 165 pounds per square inch.

In the operation of the preferredunit device when connected to piping, back pressure is 'de- -veloped on both the burner valve and the bypass ,valve. Therefore care should be taken in setting the system for operation with any given oil rate to the burner and with any given oil visco'sity,that the back pressure is not great enough to unbalance the system. The pressure drop across the valves should consequently be made many' times the back pressure, as has been previously explained. To further minimize the effect of back pressure -I prefer to employ onehalf inch piping connected to the burner valve and inch piping as the burner tailpiece. Such piping is sufliciently large to oflernegligible resistance to the flow ofoil in the burner branch compared to the high viscous resistance developed in the restricted passageways of the valves.

It is to be understood that the preferred unit and dimensions thereof are given for the purpose 'of describing a, device which will be satisfactory for most practical purposes. Such dimensions may be varied in a manner which will be apparent to those skilled in the art, from the teachings of my invention. Also, although a constant volumetric pump and true Poiseuille restricted passageways or tubes are preferred to obtain the best results, the system of my invention will operate and still give far superior results than systems heretofore employed, even if there is slight slippage of the pump and even if the restricted passageways donot form true Poiseuille tubes but approximate the characteristics of such tubes or passageways.

Conclusion viscosity of such fluids.

From the preceding description it is seen that I have provided a system and a device of simple construction, which are therefore economical to build. Since the apparatus compels accurate metering of oil to the burner, regardless of change in viscosity of the oil, it makes possible the use ,ofcheaper and heavier grades of oil, the

- employment of which have been heretofore preeluded because such ois fluctuate widely in viscosity.

I claim: 1. A system for delivering liquid at a constant rate irrespective of changes in viscosity of the liquid, comprising a source, means for feeding liquid from said source at a. substantially con- 1 stant volume rate, a delivery conduit extending Poiseuilles law.

2. The combination with a fuel oil burner and a source of fuel oil, of means for delivering fuel oil from said source to said burner and for maintaining the rate of volume delivery to said burner substantially constant irrespective of changes in the viscosity of the oil, comprising means for feeding oil from said source. at a substantially constant volume rate, a delivery conduit extending from said feeding means to said burner, a branch conduit connected to-said delivery conduit between said feeding means and said burner, whereby the fluid flow from said feeding means will divide and flow through said delivery and branch conduits, and means in said branch conduit and in said delivery conduit intermediate said burner and said branch conduit eflectuating flow in each of said conduits substantially in compliance with Poiseuilles law.

3. The combination with a liquid fuel burner or the like; of a liquid feedingsystem for feeding and metering liquid to said burner'comprising means for supplying to said system a substantially constant volume of liquid per unit of time, liquid conducting means communicating with said liquid supplying means and connected to said burner, and branch liquid conducting means communicating with said first mentioned conducting means whereby the liquid from said liquid supplying means will divide and flow through said first mentioned liquid conducting means and said branch liquid conducting means; and means for preventing changes in viscosity of the liquid from altering rate of flow of said liquid through said liquid-conducting means comprising liquid flow control, means in each of said ccnductingmeans located beyond the point of division of liquid flow, each of said liquid control means being of such character as to produce the effect of 'a Poiseuille type. of liquid flo w 4. -In' a system for delivering liquid to an oil burner or the like at a substantially constant rate irrespective of changes in viscosity of the liquid; a plurality of'liquid-conducting means through which the liquid has a divided flow; means connected with said liquid conducting means for supplying to said system a substantially constant volume of liquid per unit of time; and means for preventing changes in viscosity of the liquid from atering rate of flow of said liquid through said liquid-conducting means comprising liquid flow control means in each of said liquidconducting means located beyond the point of division of liquid flow, each of said liquid control means being of such character as to cause changes in viscosity of the liquid to be compensated for by proportionally changing a factor in v the Poiseuille liquid flow formula.

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