US3154095A

US3154095A - Flow divider for dual-orifice fuel injection nozzle

Info

Publication number: US3154095A
Authority: US
Inventors: William T Cleminshaw; William G Webster
Original assignee: Parker Hannifin Corp
Current assignee: Parker Hannifin Corp
Priority date: 1962-09-28
Filing date: 1962-09-28
Publication date: 1964-10-27
Anticipated expiration: 1981-10-27

Description

1964 w. T. CLEMINSHAW ETAL 3,154,095

FLOW DIVIDER FOR DUAL-ORIFICE FUEL INJECTION NOZZLE Original Filed Oct. 24, 1958 2 Sheets-Sheet 1 INVENTORS WILLIAM T CLEMINSHAW WILLIAM G. WEBSTER 1 1M, 77M? f DmmW ATTORNEYS 1964 w. 'r. CLEMINSHAW ETAL 3,154,095

FLOW DIVIDER FOR DUAL-ORIFICE FUEL INJECTION NOZZLE Original Filed Oct. 24, 1958 2 Sheets-Sheet 2 com com 09 COM COM

5.: uzE 5 INVENTORS WILLIAM T CLEMINSHAW WILLIAM G. WEBSTER BY I' 0m, waly, 0m

T m mu uaamwwE hjz AT TORNEYS United States Patent 3,154,08 FLQW DIVKDER FUR DUAL-GRHFIGE FUEL ENJECTEON NOZZLE William T. Cleminshaw, Shaker Heights, and Wiliiam G.

Webster, Chagrin Falls, Ghio, assignors to Parker- Hannifin Corporation, Cleveland, Ohio, a corporation of Ohio Continuation of abandoned appiication Ser. No. 769,483, Oct. 24, 1958. This application Sept. 28, 1962, Sci. No. 230,924

3 Claims. (Cl. 137469) The present invention relates generally as indicated to a dual-orifice fuel injection nozzle and flow divider therefor for use with a gas turbine power plant. This application is a continuation of applicants prior copending application Ser. No. 769,483, filed October 24, 1958, now abandoned.

In order that the needs of the flow divider may be more readily comprehended it has been deemed well first to review some of the basic fundamentals of fuel injection nozzle design. First of all, the single orifice nozzle, commonly referred to as a simplex nozzle, must necessarily have a relatively narrow range of useful fuel flow (maximum to minimum) at which the mean droplet size is in the fine mist classification (less than about 150 microns) for efiicient combustion. Following is a table of typical simplex nozzles and their characteristics assuming 500 psi. as the maximum fuel pressure:

The limitations of the simplex nozzle are at once evident from the foregoing table. To make the useful flow range wider or to provide for better fuel atomization various nozzles have been developed such as the duplex, spill, and dual orifice types.

Inasmuch as the flow divider herein has particular utility in combination with a dual orifice nozzle, only that type of nozzle will be discussed further herein. Essentially, the dual orifice nozzle comprises two concentrically arranged simplex nozzles, one being the primary nozzle with a primary discharge orifice which produces the desired quality spray of fuel into the combustion chamber of a gas turbine at low flow rates and low fuel pressures, and the other being the secondary nozzle with a secondary discharge orifice which produces the desired quality spray of fuel at high flow rates and high fuel pressures. Such dual orifice nozzles may be designed for useful flow ranges of 100:1 or greater and usually fuel is discharged solely through the primary orifice up to a prescribed fuel pressure and at fuel pressures exceeding such prescribed value the secondary orifice is cut in as by a fluid pressure actuated flow divider valve, the energy of the primary discharge assisting in the atomization of initial low flow secondary discharge as occurs just after the valve opens communication of the secondary orifice with the fuel supply line. It is in connection with the flow divider that difficulties have been encountered heretofore because of the necessity or desirability of pro viding for metering of the secondary flow during the cutin period thereof, i.e. making the pressure-flow curve of moderate slope so that an increase in fuel pressure will result in a proportionate increase in secondary flow. It is easy enough to produce the desired sensitivity of secondary flow to fuel pressure but, Without more, the pressure drop of the how divider continues to rise disproportionately to the rise in secondary flow. For instance at 500 psi. fuel pressure, such flow divider may have a pressure drop of 300-400 p.s.i., thereby making available at the secondary orifice a fuel pressure of only -200 p.s.i. (or less if line losses between the flow divider and nozzle are considered) and consequent reduced maximum fiow.

On the other hand, it is a simple matter to design a flow divider which has a quick opening valve characterized by its flat or only slight slope pressure-flow curve and low pressure drop; but, with such flow divider there is no or poor control of secondary flow at the critical secondary cut-in period.

Hitherto, in such a flow divider for a dual orifice fuel injection nozzle it has been proposed to provide a spring actuated dual valve assembly in which the valve casing is formed with a constantly open primary passage for flow of fuel from the inlet port to the primary orifice of the nozzle, and with a secondary passage which communicates with the secondary orifice of the nozzle, the flow of fuel from the inlet port to the secondary passage being under the control of the dual valve assembly and of the pressure in the combustion chamber of the gas turbine.

In a known dual valve type flow divider there are provided concentric inner and outer valve members of which the inner valve member opens first whenever the fuel pressure in the inlet port exceeds a predetermined value sufiicient to overcome the spring pressure and the back pressure acting thereon. When the inner valve member has been thus moved away from its seat, a larger area of the outer valve member is exposed to the fuel pressure, whereupon said outer valve member is actuated against spring pressure and back pressure to open position thereby permitting flow of fuel from the inlet port and through the secondary passage to the secondary orifice of the nozzle.

A disadvantage of this known type of flow divider is that when the first valve member is unseated, no further rise in fuel pressure is required to establish flow of fuel through the secondary orifice of the dual orifice nozzle and thus the fuel flow to the secondary orifice is insensitive to pressure, especially during the critical period of secondary cut-in.

Another disadvantage of this known type of flow divider is that it is quite complex and costly in structure requiring a close sliding fit between the outer valve member and the valve casing, a similar sliding fit between the inner and outer valve members, and separate springs for actuating the respective valve members.

With the foregoing in mind, it is one principal object of this invention to provide a flow divider for a dual orifice fuel injection nozzle which is characterized by its simplicity, namely, the provision of a single valve member capable of accurately regulating or metering the flow of fuel to the secondary orifice of the nozzle under stated conditions of operation of the gas turbine.

It is another object of this invention to provide a flowdivider for a dual orifice fuel injection nozzle which is characterized in that its pressure versus flow curve during initial opening has sufficient slope to procure a good, quality fuel spray from the secondary orifice for efficient combustion and to procure fl-ow regulation in accordance with the fuel pressure at the inlet port.

It is another object of this invention to provide a flow divider for a dual orifice fuel injection nozzle which is characterized in that after the initial opening movement of the spring-actuated valve member thereof and after the secondary orifice discharge has reached a prescribed value, a secondary restriction in the flow divider automatically becomes effective to create a pressure differential on a larger area of the valve member such that the valve member is moved at a more rapid rate to flatten and then reverse the slope of the pressure versus flow curve of the flow divider so that an increasing proportion of the inlet pressure will be available in the secondary nozzle beyond the flow divider for forcing fluid through such secondary nozzle.

It is another object of this invention to provide a flow divider of the character indicated which embodies a dash pot effective to smooth out the movements of the valve member and either to prevent or minimize chatter.

It is another object of the invention to provide a method of varying the fixed restriction in the valve member of the flow divider for facilitating the matching of flow characteristics of two or more nozzles.

It is another object of this invention to provide a flow divider of the character indicated which is of simple, compact form essentially comprising a valve casing; a unitary double area valve member movably supported in the casing and providing an initial throttling restriction for procuring secondary orifice flow that is sensitive to fuel pressure acting on one exposed area and a secondary restriction for modifying the initial restriction through the effects of the fuel pressure acting on a larger exposed area; and a spring that holds the valve member in seated position until the fuel pressure in the inlet port of the casing exceeds a predetermined value.

It is another object of this invention to provide a novel combination of a flow divider and a fuel injection nozzle which are joined together in operative relation by a pair of tubes, the tubes being secured together in side by side relation and communicating at their ends respectively with the primary and secondary passages of the fiow divider casing and with the primary and secondary orifice passages of the nozzle casing.

Other objects and advantages of the present invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawings:

FIGURE 1 is a side elevation view, partly in cross section, showing one form of flow divider operatively connected by a pair of tubes to a dual orifice fuel in jection nozzle;

FIGURE 2 is an end elevation view of the flow divider and fuel injection nozzle assembly as viewed from the righthand side of FIGURE 1;

FIGURE 3 is a cross-section view of another form of flow divider for use with a dual orifice fuel injection nozzle; and,

FIGURE 4 is a pressure versus flow graph showing typical curves for dual orifice nozzles with flow dividers of both conventional form and of a form in accordance with the present invention.

Referring now in detail to the drawings and first to FIGURES 1 and 2, the reference numeral 1 denotes a dual orifice fuel injection nozzle formed with a primary passage 2 which leads to the primary orifice or nozzle and with a secondary passage 3 which leads to the secondary orifice or nozzle.

As is well-known in the art, the dual orifice nozzle l is basically two single orifice nozzles built concentrically one within the other. The primary or small nozzle, is so made as to produce the desired quality of spray at the minimum flow rates of fuel while the secondary or main nozzle has sufficient capacity to supply the maximum required flow at the available fuel pressure. Utilization 4 of the primary nozzle energy to accelerate secondary nozzle flow occurs at the orifices where the primary spray cone accelerates the low energy secondary cone and assists in its atomization.

Referring to FIGURE 4, curve A, labeled Primary Nozzle, shows the pressure versus flow characteristics of a typical 50 lbs/hr. at p.s.i. primary nozzle, considering the inlet pressures shown on the ordinate axis to be the pressures at the primary nozzle inlet. The curve follows the usual pattern for a fixed orifice with the pressure having a squared relation to the flow so that the slope of the curve is quite steep. Thus, the flow increases from 0 to 50 lbs/hr. when the pressure rises from 0 to 100 p.s.i., but only from 50 to 100 lbs/hr. when the pressure is increased from 100 to 400 p.s.i.

Curve B, labeled Secondary Nozzle, shows the pressure vs. flow characteristics of a typical 600 lbs/hr. at 400 p.s.i. secondary nozzle, considering the inlet pressures shown on the ordinate axis to be the pressures in the secondary nozzle circuit beyond the flow divider valve. This nozzle is designed to give large flows with moderate pressure and hence isrelatively insensitive at low pressures, that is, flow increases are large in relation to pressure increases.

Curve C, labeled Total Flow With Conventional Flow Divider represents the total discharge of fuel from the primary and secondary nozzles when a conventional flow divider, whose individual pressure versus flow characteristics are shown by curve C, is used. The pressures for curve C are the pressures at the inlet port leading to the primary nozzle and the flow divider. The corresponding pressures in the secondary nozzle, beyond the flow divider valve, are of lesser values due to the pressure drop across the flow divider valve.

As will be seen from the chart, curve C for the conventional flow divider is very flat and of substantially uniform slope in the useful flow range, which extends to about 600 lbs/hr. As a result, curve C for the total flow is quite flat at the cut-in region for the secondary nozzle, i.e., 100 to about p.s.i., and therefore the complete nozzle is relatively insensitive in this region in that relatively large increases of total flow are obtained with small increases in inlet pressure.

Curve D, labeled Total Flow With Novel Flow Divider, represents the combined flow from the primary and secondary nozzles when a flow divider in accordance with the present invention, and having flow characteristics in acordance with D, is used. (The opening pressure for both the conventional and novel flow dividers considered is 100 p.s.i. meaning that a spring to give this opening pressure is used. It is understood that these values, as well as other values shown on the chart, are given by Way of example and that other desired slopes and flow divider opening pressures may be provided with the use of the present invention.)

With reference again to curve D concerning the flow divider according to the present invention, it will be noted that it has a steeper slope in the low flow range than does curve C. This results in curve D for total flow with the fiow divider of the present invention having a steeper slope in the cu=t-in range than curve C for total flow with a conventional flow divider, and therefore the complete nozzle will be more sensitive to pressure variations in this range in that greater variations in inlet pressure are required for given variations in the total flow.

As will be more fully explained later, the slope of curve D for the flow divider valve in accordance with the present invention levels off at about 300 lbs/hr. fuel fiow, which corresponds to about 195 p.s.i. at the inlet port of the flow divider, and thereafter the pressure drop across the flow divider decreases with further increase in flow and inlet pressure. This results in a humpback curve which is important for obtaining optimum characteristics for the complete nozzle. Curve D continues downward through the remainder of the useful flow range and, in

the illustration shown, reaches its low point at about 700 lbs./hr. flow, which is beyond the useful range for the nozzle being considered. it is at this point, i.e., 700 lbs./hr., that a fixed restriction in the flow divider becomes substantially the sole controlling factor for the flow through the flow divider valve so that fiow will again become directly sensitive to inlet pressure and thereafter flow through the flow divider will increase at a rapidly decreasing rate as the pressure is increased. As hereinafter explained, the fixed restriction in the flow divider of the present invention is not so small as to cause an unduly large pressure drop through the flow divider in the useful large pressure drop through the flow divider in the useful fiow range, and thus a major proportion of the pressure supplied at the inlet port becomes available for procuring a high rate of flow through the secondary nozzle after the cut-in range has been passed.

The areas in FIGURE 4 which are labeled rain, coarse mist, etc., represent the quality of atomization obtained with total flows from the primary and secondary nozzles. Thus it is seen that curve D falls Within the fine mist category at fiow divider inlet pressures of zero to 60 p.s.i. and from 110 to 430 p.s.i. and falls within the very fine mist category in the small intermediate range of 60 to 110 p.s.i. On the other hand, the use of the conventional flow divider results in curve C, which curve falls in the fine mist category at zero .to 60 p.s.i., the very fine mist category from 60 to 102 p.s.i., back to the fine mist category from 102 to 115 p.s.i., the coarse mist category from 1 15 to 175 p.s.i., and back to the fine mist category from 175 to 405 p.s.i. From this it is further evident that nozzles equipped with a flow divider in accordance with the present invention have the additional advantage that more uniform atomization is obtained than with conventional flow dividers.

With these points in mind the flow divider 4 as shown in FIGURES 1 and 2, comprises an outer flanged casing 5 which is adapted to be mounted in fixed position with respect to the gas turbine. Brazed or otherwise secured at one end of the outer casing 5 is the adapter 6 having a fuel filtering screen 7 in the fuel inlet passage 8. Also brazed or otherwise secured in the outer casing 5 is a tubular inner casing 9' which has a passage 10 at one end providing a seat for a reciprocable valve member 11. Said inner casing 9 is formed with a plurality of radial passages 12 through the wall thereof which lead to a secondary chamber 14 defined between the outer and inner casings. The conical end of the valve member 11 is held against its seat in casing 9 as by means of the coil spring 15-which bears at one end on the valve member 11 and at the other end against a spring abutment cup 16 which is held in place by the thimble 17 screwed into the end of the outer casing 5. The thimble 17 and outer casing 5 may be wire locked together as shown to prevent inadvertent loosening, and the joint between the spring abutment cup 16 and the end of the inner casing 9 may be sealed as by means of an O-ring l8 Ofrubberlike material which is squeezed axially in a chamber defined between-the abutment cup and the inner casing.

The innerend of the inner casing 9 defines with the port adaptor 6 and with the outer casing 5 a primary chamber 19 into which fuel freely flows from the inlet passage 8. The outer casing 5 is formed with a primary outlet passage 20 which communicates with the primary passage 2 of the nozzle by way of the tube 21 which has its opposite ends fitted into and brazed or otherwise secured to the outer casing 5 and to the nozzle casing 22, respectively.

The secondary chamber 14 (including also the space above valve member 11) communicates with the secondary outlet passage 23 in the outer casing 5 and said secondary outlet passage 23 communicates. with the secondary orifice passage 3of the nozzle 1 by way of the tube 24 which, like tube 21, has its ends fitted into and brazed respectively to the outer casing 5 and to the nozzle casing 6 22. Preferably, the primary and

secondary tubes

21 and 24 extend'alongside one another and are brazed together to form a strong and rigid divider-nozzle assembly.

The valve member 11 preferably has a conical tip as shown which engages the seat formed at the inner end of the passage 1'1 Adjacent the tip the valve member 11 has a stepped skirt which is sliclably fitted in the complementary bore and counterbore in the inner casing 9 and which defines an intermediate chamber 25 into which fuel flows from passage 10 when the valve is open. An orifice plate 28 having an orifice 29 is press fitted within the valve skirt. Plate 28 with slightly different orifices 29 may be readily removed and replaced to facilitate matching one nozzle with another. The fuel flows to the secondary passage 3 via the series of openings 26 in valve member 11, the orifice 29, secondary chamber 14, passage 23, and secondary tube 24. The stepped formation of the valve member 11 forms with the inner oasing 9 a dash pot 27 to cushion the movements of the valve member 11 and to prevent chattering thereof.

The abutment cup 16 previously referred to constitutes a stop for the opening movement of the valve member 11 away from its seat and in order to prevent overlap of the skirt of the valve member with radial passages 12, the end of the cup is notched as shown.

Operation of the nozzle, when designed with the flow characteristics indicated by curves A, B, D and D of FIG- URE 4, is as follows:

Spring 15 is set to open at p.s.i., hence at pressures of 0 to 100 p.s.i. in passage 8 and primary chamber 1), fuel will flow only through the primary outlet passage 20, through the primary tube 21, the primary orifice passage 2, and through the primary orifice of nozzle 1 into the combustion chamber of the gas turbine. The fuel delivery at this time is in accordance with the lower portion of curve A, FIGURE 4.

When the fuel pressure in chamber 19 exceeds 100 p.s.i., it will, in acting on the small exposed area of the tip of the valve member 11, open the valve-by overcoming the opposing force exerted by the spring 15 and-by any back pressure in the secondary chamber behind the valve member 111, the latter at this time being negligible. With the opening of the flow divider valve, flow of fuel is established through the secondary nozzle via chamber 25, openings 26, orifice 29, slots 12, chamber 14, passage 23, tube 24, passage 3, and the secondary discharge orifice, not shown, of the nozzle 1.

During the initial opening movement, or cut-in'period of the flow divider valve member 11, the flow characteristic through the flow divider alone is in accordance with the first portion of curve D, which is rather steep, that is, the flow increases in small amounts as the pressure increases. Meanwhile, the flow through the primary nozzle, curve A, is increasing in smaller and smaller increments as the pressure increases. During this period the orifice 29 has a negligible elfect upon the flow through the flow divider and the combined or total flow, curve D, through both primary and secondary nozzles-is increasing at a moderate rate with pressure increases so as to afford good sensitivity and control during the cut-in period and still fall within the fine mist area to give good atomization.

As the inlet pressurein chamber 19 is increased further and the valve member 11 moves further awayfrom its seat, the rate of pressure drop between the valve member and its seat decreases while the rate of pressure drop through orifice 29 increases, and the pressure in chamber 25 begins to approach the pressure in inlet port 19. The increasing pressure in chamber 25, acting on the larger area of valve member 11 gradually becomes the dominating opening force on the valve member 11 and a point is reached at which the pressure drop through the flow divider starts to decrease even though the inlet pressure and flow continues to increase. This results in the down- '7 ward dip of curve D beyond inlet pressures of about 195 p.s.i.

The downward dip of curve D is preferably so determined in relation to the flow characteristics of the primary and secondary nozzles that the total flow curve D continues upward in substantially a straight line, and well within the fine mist region, throughout the useful flow range, which i this example extends to approximately 600 lbs/hr. Also, as evidenced by the downward dip of curve D, as pressure at the inlet port 19 is increased over 195 p.s.i., a decreasing amount of this pressure is lost by way of pressure drop through the fiow divider and hence an increasing proportion of the inlet port pressure is available beyond the flow divider for forcing fluid through the secondary nozzle. This is an important aspect of this invention since it permits adjustment of the total flow, curve D, to a slope in the higher flow ranges which is flatter than that obtainable with a conventional flow divider. Thus the fiow divider of the present invention, with its humpback flow curve, affords both sensitivity at the cut-in range plus substantial flow with moderate pressure at the higher flow ranges.

Once the valve member 11 is fully open so that the throttling or needle valve effect is substantially eliminated and the pressure drop through the seat is less than the pressure drop through the orifice 29, the pressure in chamber 25 will be substantially the same as the pressure in chamber 19 and flow through the flow divider will be largely determined by the orifice 29 so that the pressure vs. flow curve, curve D, of the flow divider alone will again turn upwardly. However, this is preferably de signed to occur beyond the useful flow range so that it is not a factor during normal operation.

By way of further review, it is clear that the provision of a primary orifice alone in the nozzle 1 would not do, since the flow range would be insufiicient. In other words, the flow versus pressure curve labeled Primary has much too steep a slope. On the other hand, if the nozzle had only a secondary or main orifice, the fuel would be injected into the combustion chamber of the gas turbine in the form of Rain, or Coarse Mist at low fuel pressures, up to say, about 125 p.s.i. in the example given. One may ask what if both primary and secondary orifices were provided and controlled as by a simple on-off rotary plug valve or the like to open and close the secondary orifice line. This expedient may suffice insofar as producing the proper spray from the secondary orifice because the time of cut-in could be at a fuel pressure sufficiently high to achieve good atomization. However, such on-oif valve would not provide for any secondary flow control at the critical time. On the other hand, if both primary and secondary orifices were provided with just a throttling type valve used as a flow divider to control the secondary flow (an ordinary spring actuated needle type check valve, for example) there would be an excessively large pressure drop through the valve itself, thereby sacrificing in flow capacity at the expanse of pressure.

From the foregoing, it is at once evident that one of the principal advantages of the present flow divider is that the valve herein is a double-area spring-loaded valve member which, during the initial stages of the opening or secondary cut-in movement, functions as a springloaded throttling or metering needle valve to provide a secondary flow which is sensitive to pressure. That would be the portion of the Flow Divider curve from about 100 p.s.i. to about 195 p.s.i. in which interval the secondary flow increases from zero to about 120 lbs./hr., i.e., total flow less primary flow. Thereafter, the fixed restriction (the orifice 29) of the valve member 11 comes into play to modify the effects of the variable restriction of the valve seat and to cause a dip in the Flow Divider curve, whereupon as the pressure continues to rise, so does the secondary nozzle flow, but with a decreasing impediment from the flow divider valve.

Basically, the form of the flow divider shown in FIG- URE 3 is the same as that shown in FIGURES 1 and 2 in that there is an outer casing 30 formed in two

parts

31 and 32 clamped together as by screws 34 and sealed as by means of the O-ring 35. The one part 31 is provided with a fuel inlet port adaptor 36 wherefrom the fuel passes through a cylindrical screen assembly 3'7. In this case, the inner casing 38 is clamped to the central threaded boss portion 39 of the part 32 as by means of the nut 40 which bears on a shoulder of said inner casing 38.

Here again, as in FIGURES 1 and 2, the valve member 41 is provided with a conical tip 42 which engages a seat 43 formed in the inner casing 38 and is formed with a stepped skirt which defines the intermediate chamber 45 between the primary chamber 46 and the secondary chamber 47, the latter being communicated with the secondary tube 48 which at one end is brazed or otherwise secured in place to the outer casing part 32 and which at its other end is connected to the secondary passage of the nozzle casing as shown in FIGURE 1. The primary chamber 46 is communicated by way of the primary tube 4? which at one end also is brazed or otherwise secured to the outer casing part 32 and which at its other end communicates with the primary passage of the nozzle as shown in FIGURE 1. The inner casing 38 and valve member 41 also form between them the dashpot 50.

In this case the openings 51 constitute the fixed restriction equivalent to orifice 29 of FIGURE 1. A spring 54 is compressed between the valve member 41 and the boss member 39 to normally tend to keep the tip 42 against seat 43. A desired number of shims 53 may be employed as shown to vary the spring pressure.

Inasmuch as the flow divider shown in FIGURE 3 has substantially the same characteristics as that shown in FIGURE 1, it is not deeemed necessary to repeat the details of operation thereof.

A characterizing feature of this invention is that the conical tip of valve member 11 and the conical tip 42 of valve member 41 has a relatively short metering section of, say, 30 included angle that engages seat 10 (FIGURE 1) or seat 43 (FIGURE 3) and provides, in conjunction with spring 15 (FIGURE 1) or with spring 54 (FIGURE 3) for fine metering of the secondary flow. Forward of the metering section, the conical tip has a taper of 60 or included angle so as to provide a more rapid change in the metering action so as to make the reverse slope of the flow divider curve dip more rapidly.

It has been found that with flow dividers in accordance with the present invention to achieve satisfactory secondary flow regulation during the critical cut-in period and to achieve a substantially linear Nozzle +Flow Divider flow curve, the area relationship of the intermediate chamber to the inlet seat should be from about 4:1 to about 611, preferably 5:1 with the spring rate and the fixed restriction selected to provide a moderate upward and downward slope on the flow divider flow curve. A wide departure from this range of relationship of valve areas results in a flow divider curve which in the case of, say, a 2:1 ratio continues to slope upwardly, first under the sole control of the spring and metering section and then more steeply as the fixed restriction, comes into play, and which in .the case of, say, 1021 ratio has an insignificant metering portion from which the curve slopes steeply downward and then slopes upwardly at a quite steep angle as the function of the fixed restriction.

It is to be understood that, although reference hereinbefore has been made specifically to dual orifice fuel injection nozzles, the present invention has utility with other so-called dual circuit systems. Similarly, in multinozzle systems, flow dividers as herein disclosed may be associated with the respective nozzles or a single flow divider can be used to control the flow of fuel to a secondary manifold for all the nozzles.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims, or the equivalent of such, be employed.

We therefore particularly point out and distinctly claim as our invention:

1. A flow divider for a dual orifice fuel injection nozzle comprising a casing having an inlet port for fuel under pressure, a primary chamber and outlet passage constantly open to said inlet port and adapted to be communicated with a primary orifice of such nozzle, and a secondary chamber and outlet passage adapted to be communicated with a secondary orifice of such nozzle, said chambers being arranged coaxially, and said passages being arranged in side by side parallel relation; and a unitary spring closed valve member movable in said casing and forming therewith an intermediate chamber also coaxial with said primary and secondary chambers, said casing having a connecting passage leading from said primary chamber to said intermediate chamber and terminating in a valve seat against which said valve member is spring seated; said valve member having a first area exposed to fuel pressure in said primary chamber and said connecting passage and having a second larger area about four to six times that of said first area exposed to fuel pressure in said intermediate chamber when said valve member has been moved away from said seat under the influence of fuel pressure in said primary chamber and said connecting passage acting on said first area and overcoming the spring pressure acting on said valve member; said valve member defining with said seat a variable, increasing area orifice during such movement of said valve member away from said seat; said flow divider being provided with a restricted passage communicating said intermediate chamber with said secondary chamber which effects a buildup of fuel pressure in said intermediate chamber to act on said second area and thereby move said valve member for providing progressively increasing flow to said secondary outlet passage at successively increasing and decreasing fuel pressure acting on said second area.

2. A flow control valve assembly comprising a body formed with a passage for flow of fluid therethrough; and a spring-seated, fluid pressure actuated valve axially reciprocable in said body to open and close said passage; said valve and body defining coaxial inlet and outlet chambers With relatively axially movable walls of substantially greater projected area from about four to six times that of said valve which is exposed to fluid under pressure when in passage closing position; said valve member defining with said seat a variable, increasing area orifice during movement of said valve member away from said seat; said chambers having fluid communication with each other via a control orifice of flow capacity such that during initial opening movement of said valve under the influence of fluid pressure acting on the aforesaid area thereof, the flow of fluid through said passage increases in substantially direct proportion to increase in fluid pressure and the pressures in said chambers are substantially equalized by said orifice as fluid flows therethrough and through said chambers, the flow capacity of said orifice further being such that as the fluid flow therethrough increases, with consequent increased pres sure drop, the then predominant fluid pressure in said inlet chamber acting on the aforesaid projected area of the movable wall thereof effects continued opening movement of said valve and hence increased flow through said passage while such predominant fluid pressure is decreasing; said valve having a radially enlarged skirt portion which is axially slidable in a counterbore in said body to form a dashpot therebetween to cushion the movements of said valve.

3. A flow control valve for a fuel injection nozzle and the like comprising a casing having an inlet port for fuel under pressure, a primary chamber constantly open to said inlet port, and a secondary chamber and outlet port adapted to be communicated with an orifice of such nozzle, said chambers being arranged coaxially; and a unitary spring closed valve member movable in said casing and forming therewith an intermediate chamber also coaxial with said primary and secondary chambers; said casing having a connecting passage leading from said primary chamber to said intermediate chamber and terminating in a valve seat against which said valve member is spring seated; said valve member having a first area exposed to fuel pressure in said primary chamber and said connecting passage and having a second larger area about four to six times that of said first area exposed to fuel pressure in said intermediate chamber when said valve has been moved away from said seat under the influence of fuel pressure in said primary chamber and said connecting passage acting on said first area and overcoming the spring pressure acting on said valve member; said valve member defining with said seat a variable, increasing area orifice during such movement of said valve member away from said seat; said valve member having a restricted passage therethrough communicating said intermediate chamber with said secondary chamber which effects a build-up of pressure in said intermediate chamber to act on said second area and thereby move said valve member for providing progressively increasing flow to said outlet port at successively increasing and decreasing fuel pressure acting on said second area.

References Cited in the file of this patent UNITED STATES PATENTS 2,593,884 Ifield Apr. 22, 1952 2,836,193 Giuliano et al. May 27, 195? 2,917,072 Saville Dec. 15, 1959