Title:
APPARATUS AND METHOD FOR BURNING CONTAMINATED FUEL
United States Patent 3658249


Abstract:
A fuel system for a gas turbine engine adapted to handle dirty fuel includes a separating device of a centrifuge-filter type through which fuel is supplied from a fuel pump to a fuel control which controls the operation of the engine. The centrifuge-filter has a swirl chamber with a tangential inlet, a central annular filter, and outlets both outside and inside of the filter. It discharges a large portion of the fuel substantially clean and a small portion bearing the dirt. The clean fuel flows through the fuel control to small diameter ports of fuel nozzles and, at higher fuel flow rates, through a resistance valve or valves to large area ports of the fuel nozzles. The dirty fuel flows to the large flow ports of the nozzles, by-passing the fuel control. Alternatively, the centrifuge-filter may be downstream of the fuel control. In either case, a line from adjacent the outer surface of the filter to the pump inlet or to the large area ports acts to clean the filter by recirculating or discharging the finer dirt which tends to accumulate on the filter at low fuel flow rates.



Inventors:
SHARPE CECIL H
Application Number:
05/082573
Publication Date:
04/25/1972
Filing Date:
10/21/1970
Assignee:
GENERAL MOTORS CORP.
Primary Class:
Other Classes:
60/39.24, 239/127, 239/533.2, 239/549
International Classes:
F02C7/22; F02C7/224; (IPC1-7): B05B9/00
Field of Search:
239/125,127,533,547 60
View Patent Images:
US Patent References:
3402891Furnace pump and oil burner circuit1968-09-24Clark et al.
3034570Fluid centrifuge1962-05-15Carmon et al.
2753927Fuel flow control1956-07-10Garraway et al.
2747555Fuel supply system for internal combustion engines1956-05-29Brunner
2740469Flow control apparatus1956-04-03Colestock
2439257Fuel atomizing nozzle1948-04-06Lum



Primary Examiner:
King, Lloyd L.
Parent Case Data:


This application is a continuation-in-part of my U.S. Pat. application, Ser. No. 752,820 now abandoned, for Fuel System for Contaminated Fuel filed Aug. 15, 1968.
Claims:
I claim

1. A system for supplying fuel to a combustion engine including fuel spraying means having small and large fuel flow ports, the system being adapted to minimize the effect of contaminants in the fuel upon the performance of the engine; the system comprising, in combination, means for supplying fuel under pressure, dirt separating means supplied thereby having a first outlet for a major portion of relatively clean fuel and a second outlet for a minor portion of relatively dirty fuel, fuel control means for controlling the rate of clean fuel flow to the engine connected to the first outlet, means connecting the fuel controlling means to the small fuel ports for discharge of a minor portion of maximum fuel flow, valve means connecting the fuel control means to the large fuel ports for discharge of clean fuel at higher fuel flow rates, and means connecting the second outlet to the large fuel ports by-passing the fuel control means.

2. A system for supplying fuel to a combustion apparatus including fuel injection means having small and large fuel flow ports, the system being adapted to minimize the effect of contaminants in the fuel upon the performance of the apparatus, the system comprising, in combination, means for supplying fuel under pressure, fuel control means for controlling the rate of fuel flow to the apparatus supplied by the supplying means, dirt separating means supplied by the supplying means having a first outlet for a major portion of relatively clean fuel and a second outlet for a minor portion of relatively dirty fuel, means connecting the first outlet of the separating device to the small fuel flow ports for discharge of a minor portion of maximum fuel flow, valve means connecting the first outlet of the separating device to the large fuel flow ports for discharge of clean fuel at higher fuel flow rates, and means connecting the second outlet of the separating device to the large fuel flow ports for discharge of the said relatively dirty fuel.

3. A system as recited in claim 2 in which the fuel controlling means is supplied with fuel from the supplying means through the separating means.

4. A system as recited in claim 2 in which the separating means is supplied with fuel from the supplying means through the fuel controlling means.

5. A system for supplying fuel to a combustion apparatus including fuel injection means having small and large fuel flow ports, the system being adapted to minimize the effect of contaminants in the fuel upon the performance of the apparatus, the system comprising, in combination, means for supplying fuel under pressure, fuel control means for controlling the rate of fuel flow to the apparatus supplied by the supplying means, dirt separating means supplied by the supplying means having a first outlet for a major portion of relatively clean fuel and a second outlet for a minor portion of relatively dirty fuel, means connecting the first outlet of the separating device to the small fuel flow ports for discharge of a minor portion of maximum fuel flow, means connecting the first outlet of the separating device to the large fuel flow ports for discharge of clean fuel at higher fuel flow rates, means connecting the second outlet of the separating device to the large fuel flow ports for discharge of the said relatively dirty fuel, and means for diverting a controlled amount of the relatively clean fuel into the means connecting the second outlet to the large fuel flow ports to aid flow of the dirty fuel through the connecting means and large flow ports.

6. A system for supplying fuel to a combustion engine including fuel injection means having small and large fuel flow ports, the system being adapted to minimize the effect of contaminants in the fuel upon the performance of the engine, the system comprising, in combination, means for supplying fuel under pressure, fuel control means for controlling the rate of fuel flow to the engine supplied by the supplying means, dirt separating means supplied by the supplying means having a first outlet for a major portion of relatively clean fuel and a second outlet for a minor portion of relatively dirty fuel, means connecting the first outlet of the separating device to the small fuel flow ports for discharge of a minor portion of maximum fuel flow, means connecting the first outlet of the separating device to the large fuel flow ports for discharge of clean fuel at higher fuel flow rates, and means connecting the second outlet of the separating device to the large fuel flow ports for discharge of the said relatively dirty fuel, the separating means comprising two centrifuge-filters connected in series, the first centrifuge-filter in series being smaller than the second and having its clean fuel outlet connected to the inlet of the second centrifuge-filter, the dirty fuel outlets of the two centrifuge-filters being connected in parallel, and comprising means for diverting fuel around the first centrifuge-filter at higher fuel flow rates.

7. A system for burning fuel containing a significant amount of particulate contaminants comprising, in combination, means for supplying such fuel under pressure, a combustion apparatus fed by the supplying means for burning the fuel, fuel nebulizing means in the combustion apparatus including first nebulizing means of relatively low fuel flow capacity and relatively low tolerance for particulate contaminants and second nebulizing means of relatively high fuel flow capacity and relatively high tolerance for particulate contaminants, means for controlling the rate of flow from the supplying means to the nebulizing means, and separating means connected between the supplying means and the nebulizing means, the separating means being effective to separate the fuel into a first portion consisting of a major portion of the fuel and an insubstantial portion of the said particulate contaminants and a second portion consisting of the remainder of the fuel and particulate contaminants, the separating device having a first outlet for the first portion and a second outlet for the second portion, means connecting the first outlet to the first nebulizing means, and means connecting the second outlet to the second nebulizing means.

8. A system for burning fuel containing a significant amount of particulate contaminants comprising, in combination, means for supplying such fuel under pressure, a combustion apparatus fed by the supplying means for burning the fuel, fuel nebulizing means in the combustion apparatus including first nebulizing means of relatively low fuel flow capacity and relatively low tolerance for particulate contaminants and second nebulizing means of relatively high fuel flow capacity and relatively high tolerance for particulate contaminants, means for controlling the rate of flow from the supplying means to the nebulizing means, and separating means connected between the supplying means and the nebulizing means, the separating means being effective to separate the fuel into a first portion consisting of a major portion of the fuel and an insubstantial portion of the said particulate contaminants and a second portion consisting of the remainder of the fuel and particulate contaminants, the separating device having a first outlet for the first portion and a second outlet for the second portion, means connecting the first outlet to the first nebulizing means and means connecting the second outlet to the second nebulizing means, the system also including means for diverting a fraction of the first portion from the first connecting means into the second connecting means at low fuel flow rates to flush the second portion through the nebulizing means.

9. A system for burning fuel containing a significant amount of particulate contaminants comprising, in combination, means for supplying such fuel under pressure, a combustion apparatus fed by the supplying means for burning the fuel, fuel nebulizing means in the combustion apparatus including first nebulizing means of relatively low fuel flow capacity and relatively low tolerance for particulate contaminants and second nebulizing means of relatively high fuel flow capacity and relatively high tolerance for particulate contaminants, means for controlling the rate of flow from the supplying means to the nebulizing means, and separating means connected between the supplying means and the nebulizing means, the separating means being effective to separate the fuel into a first portion consisting of a major portion of the fuel and an insubstantial portion of the said particulate contaminants and a second portion consisting of the remainder of the fuel and particulate contaminants, the separating device having a first outlet for the first portion and a second outlet for the second portion, means connecting the first outlet to the first nebulizing means and means connecting the second outlet to the second nebulizing means, the system also including means for diverting a fraction of the first portion from the first connecting means into the second connecting means at low fuel flow rates to flush the second portion through the nebulizing means, the system also including means for diverting fuel from the first connecting means into the second connecting means at high fuel flow rates to accommodate fuel flow to the first nebulizing means to the capacity of the first nebulizing means.

Description:
The invention herein described was made in the course of work under a contract or subcontract thereunder with the Department of Defense."

My invention is directed primarily to a fuel system adapted to cope with contaminated or dirty fuel and to render combustion engines capable of operating for substantial periods of time on badly contaminated fuel.

The problem arises with engines such, for example, as gas turbine engines in which the fuel is mixed with air by spraying through a nozzle or nozzles which have ports of small diameter which are easily clogged by particles of foreign matter, which may be called dirt.

The obvious mode of attack upon this problem is to provide large filtering systems of very fine pores to intercept and separate the dirt from the fuel before it passes to the engine. This is not feasible because filters clog, thus preventing flow of fuel. There are, of course, systems involving backwashed filters, but these are heavy and the problem of disposing of the dirt-laden fuel remains.

Prior patent applications of Richard G. Grundman and me, for Fuel Nozzle Contaminant Trap, abandoned Ser. No. 617,164 filed Feb. 20, 1967 and Ser. No. 778,002 filed Nov. 14, 1968, of common ownership with this application, are directed to a device for intercepting the larger solid particles in the fuel. Our U.S. Pat. No. 3,477,647 for Fuel Spray Nozzle, Nov. 11, 1969, discloses a fuel nozzle which is more tolerant of contaminants than those generally known.

It still is desirable, however, to provide other means to reduce the amount of contaminants which pass to the fuel nozzle ports of small diameter. If the amount of contaminant passing to the nozzle is sufficiently small, it may be intercepted by a filter in the nozzle or the supply line to the nozzle. It is also, of course, desirable to minimize the amount of dirt passing through the fuel control of the engine, although the fuel control may be more tolerant of dirt than the small ports of the fuel nozzle.

In aircraft gas turbines, it has been common practice to use fuel nozzles in which atomization is effected by swirling the fuel in a chamber from which it flows over the lip of an opening at one end of the chamber. Because of the wide range of flow, it is usual in aircraft gas turbines to have nozzles of the duplex type with a primary set of fuel swirl ports of small size and a secondary set of swirl ports of relatively large size. The result is that high swirl velocities can be obtained with the small ports at low flow rates, and adequate capacity is provided by use of both sets of ports at high flow rates. Fuel nozzles of this general character are shown, for example, in U.S. Pat. Nos. to Wortman, 2,893,647 and to Grundman, 2,954,172. Fuel flow to the secondary ports may be shut off when the flow rate is small by valve mechanism in the nozzle or by separate control means.

According to the preferred embodiment of my invention, the contaminated fuel supplied by a suitable pump is passed through any suitable device or system which acts to separate the fuel into a relatively large flow of substantially clean fuel and a relatively small flow of fuel bearing the larger particles of dirt and, as far as feasible, the smaller contaminant particles also. The clean fuel is supplied through the engine fuel control to the small port or ports of the fuel nozzle or nozzles, which are thus isolated from the dirt. The relatively small portion of dirty fuel, which preferably is controlled by a valve or orifice, flows directly to the large flow ports of the nozzles, by-passing the fuel control and being isolated from the small ports. As a result, the dirty fuel is burned in the combustion chamber of the engine and there is no problem of safety involved in storing or disposing of the contaminated fuel. Also, there is no problem of filter loading.

The separating device preferably is a centrifuge-filter with an annular chamber in which the fuel is swirled from a tangential inlet. A cylindrical filter near the axis of the device encloses the clean fuel outlet. The dirty fuel is discharged at the periphery of the chamber, bearing with it the larger or heavier contaminant particles and most of the finer dirt. Preferably, a further outlet adjacent the outer surface of the filter discharges some fuel bearing finer dirt to clean the filter. This fuel is recirculated through the pump to the separator or is discharged with the dirty fuel from the peripheral outlet.

Principal objects of my invention are to provide means to make fuel control systems and fuel spray systems of usual satisfactory types tolerant of dirty fuel; to provide a fuel system for an engine having large and small fuel nozzle ports in which the dirt is routed to the large ports of the nozzle; to provide a system in which the fuel control of the engine is isolated from the contaminated fuel; and to provide a system in which the major portion of the fuel is metered and a small portion of fuel bearing the contaminant by-passes the metering device, wherein the by-passed portion of the fuel is small enough not to prejudice undesirably the control of the engine by the fuel control.

A further object of the invention is to provide a method of burning dirt-contaminated fuel capable of satisfactorily using known and preferred fuel handling and spraying apparatus. A still further object of the invention is to provide a process for burning dirt-contaminated fuel involving separating out a minor portion of the fuel bearing the more troublesome contaminants from the remainder, routing the two portions through at least partially separate courses to combustion apparatus, and burning the fuel therein.

A still further object is to provide a system in which a portion of the metered fuel is sent along with the contaminated fuel to flush the contaminated fuel line.

The nature of my invention and its advantages will be clear to those skilled in the art from the succeeding detailed description of presently preferred embodiments of the invention and the accompanying drawings thereof.

FIG. 1 is a schematic diagram of a fuel supply system for a gas turbine engine.

FIG. 2 is a sectional view of a dirt separating device taken on planes parallel to the axis of a swirl chamber.

FIG. 3 is a schematic diagram illustrating a modified system.

FIGS. 4, 5, and 6 are schematic representations of various known configurations of combustion apparatus.

FIG. 7 is a schematic diagram of a gas turbine fuel system illustrating various modifications to the system of FIG. 1.

Referring first to FIG. 1, a fuel system according to my invention may include a fuel inlet line 5 to which fuel is fed from any suitable source such as an aircraft boost pump (not illustrated), a fuel pump 6 which may be driven by the engine, a dirt separating device 7 of a type which may be referred to as a centrifuge-filter, but which will be called herein a "separator" for convenience, and a fuel control 9 which may be of any suitable type adapted to control the engine.

Such fuel controls ordinarily include a manual input to determine engine power level and devices responsive to such factors as engine speed, compressor discharge temperature, turbine inlet temperature, and the like, with means to meter fuel to achieve smooth acceleration and deceleration of the engine and avoid overspeed or over-temperature. Essentially, a typical fuel control may include a fuel metering valve and means responsive to the manual input and suitable parameters to control the metering valve and, in most cases, a by-pass valve to return excess pumped fuel to the pump inlet. It will be clear that the details of the fuel control are entirely immaterial to my invention. The engine to which fuel is supplied ordinarily includes one or more fuel spray nozzles 10, the flow to which is normally controlled by the fuel control. As previously mentioned, in my preferred system a minor part of the fuel by-passes the control 9.

The pump 6 discharges through a line 11 into the separator 7. This device, which will be described in more detail later, includes a casing 13 defining an annular chamber 14 concentrically within which is mounted an annular filter or screen 15. Line 11 enters the separator tangentially so that the fuel flowing from the pump into the separator swirls around the axis of the separator as indicated by the arrow 17. The fuel control is supplied from the separator through an axial filtered or clean fuel discharge port 18 within the filter and a clean fuel line 19. Excess fuel supplied to the control over what is metered to the engine is returned to the pump inlet through a line 21. The fuel control may be regulated manually through a suitable control lever 22. This control lever 22 also controls a shutoff valve 23 in the line 25 by which metered fuel is delivered from the fuel control. The shutoff valve may be incorporated in the fuel control but is shown separately in this schematic; its purpose is simply to shut off all fuel when the engine is shut down, and it is not a metering device.

From the line 25, the major part of the metered fuel flows through an engine supply line 26 to a heat exchanger 27 which is an optional part of the system. It is customary to provide oil to fuel heat exchangers in gas turbine fuel systems for the purpose of cooling the engine lubricant. The lubricating oil may be circulated through a coil 29 in heat exchange relation to the metered fuel. From the heat exchanger, the clean metered fuel is delivered to a clean fuel manifold 30 from which it is supplied through branch lines 31 to the fuel nozzles 10. Each fuel nozzle branch line 31 is connected directly to the portion 33 of the fuel spraying device including the small area, small flow, or primary fuel ports. The nozzle also includes resistance valve means 34 by which the line 31 is connected to the large area, large flow, or secondary fuel port means 35 of the nozzle.

Such a nozzle may be of the character of those shown in U.S. Pat. Nos. to Wortman 2,893,647 and to Grundman, 2,954,172. If the engine has one nozzle, it may incorporate the valve 34 as in those patents. If it has a number of nozzles, each may incorporate such a valve; or, if desired, a single resistance valve means 34 may control flow from the manifold 30 to the secondary ports of all the nozzles. U.S. Pat. Nos. 2,701,164 and 3,477,647 show duplex fuel nozzles having separate fuel lines for connection to an external common fuel routing valve.

As is well known by those skilled in the art, and as explained in the Wortman and Grundman patents, the valve 34 is held closed by a spring but opens when the pressure in line 31 reaches a value indicative of the fact that the large fuel ports should receive some of the fuel so as not to overload the small fuel ports. It may be added that the portions of the fuel system so far described, apart from the separator, are conventional and, also, that the presence of an ordinary filter ahead of the fuel control is conventional.

Proceeding now to the improvements which involve my invention, it will be noted that the separator 7 has a dirty fuel outlet 37 which is a tangential discharge port extending from the perphery of chamber 14 in the direction of swirl of the fuel. The swirling motion of the fuel tends to concentrate the contaminants at the periphery of chamber 14 and thus direct them into the port 37, and a relatively small portion of the fuel entering the separator is discharged through this port into a dirty fuel line 38. From this line the fuel proceeds through instrumentalities to be described to a dirty fuel manifold 39 which is directly connected through branch lines 41 to the, or all of the, large nozzle ports 35 or, in other words, to the outlet end of resistance valve means 34. The resistance valve means serves as a check valve to prevent passage of the dirty fuel to the small flow ports 33. If a single resistance valve 34 is used, it may connect manifold 30 to manifold 39.

The dirty fuel line 38 is preferably connected to manifold 39 through a dirt trap 42 and a shutoff valve 43. The shutoff valve 43, as indicated schematically, is connected to the fuel control lever 22, as is shutoff valve 23. These valves preferably open concurrently when the fuel control is moved from the "Off" position to bring the engine into operation.

The dirt trap 42 may be provided to trap and hold larger and more troublesome particles of contaminants which are separated from the fuel by the separator 14 and discharged into line 38. Such a trap may be of the type described in the aforementioned patent applications. As illustrated schematically herein, the trap has a generally cylindrical housing or body 45 with an inlet 46 on the axis at one end and an outlet through an orifice 47 on the axis at the other end or head of the cylinder. The orifice 47 is provided to control or regulate the dirty fuel flow and might be located at some other point in the dirty fuel line. It may, if desired, be adjustable. Such adjustability is not ordinarily considered to be needed, however. Orifice 47 connects through a line 49 with the shutoff valve 43 which discharges into manifold 39.

The dirt trap includes an annular barrier 50, the margins of which are slightly spaced from the cylindrical walls of the body 45 and which has radial holes 51 for fuel to flow through the barrier. The size of the holes and the width of the radial gap between the barrier and the housing are preferably such as to trap large particles of contaminants in the radial gap between the barrier and housing while allowing free flow of fuel through the radial holes 51. It is to be understood that the trap 42 is primarily for the purpose of catching large contaminant particles which are too large to pass through the large flow ports 35 of the fuel nozzles. While this explanation of the operation of the dirt trap is sufficient for an understanding of the present invention, in which it is an optional feature, reference may be made to the aforementioned application, Ser. No. 778,002 for further explanation of the principles and structure of such traps if such reference is needed.

Another feature of the invention which may be quite desirable in some installations is means for diverting some of the clean fuel into the dirty fuel line 49 to insure enough flow that contaminants may not deposit out or cake in the line 49 and manifold 39. To accomplish this in the system of FIG. 1, the clean metered fuel line 25 is provided with a branch 53 which connects through a check valve 54, line 55, and an orifice 56 with the dirty fuel line 49. The orifice limits the flow from the clean fuel line going directly to the large ports 35 so that an undue amount of fuel is not diverted from the small ports 33. The diversion of this fuel does not affect the total fuel flow to the engine, since it has been metered by the fuel control 9. The check valve 54 prevents any back flow from the dirty fuel line into the clean fuel line.

In connection with the metering of fuel, it will be understood that the relatively small amount of fuel which flows from the separator through the dirty fuel lines 38, 49 and which is not metered, can be compensated for by the calibration of the fuel control or may be insufficient to affect materially the operation of the fuel control. In this connection, the fuel by-passing the fuel control through line 49 may be compensated for much the same as flow through an idle orifice which exists in some fuel controls.

As previously stated, so far as the system is concerned, the means for separating the clean from the dirty fuel may be of any character adapted to use in the system; a filter or a centrifuge, for example; but the presently preferred separator is a centrifuge-filter of the type illustrated in FIG. 2.

My copending application, Ser. No. 82,574, filed Oct. 21, 1970 , a continuation-in-part of Ser. No. 752,820, is directed to preferred dirt separator structure of the type shown in FIG. 2. In FIG. 2, it will be seen that the separator 7 includes a case 13 made up of a main body 57 and a cover 58, the cover being retained on the body by a ring of bolts 59. The case and cover define between them the annular chamber 14 which is sealed by an O-ring 61. The separator inlet is shown at 11 and the clean fuel outlet 18 is in the body.

The preferred filter is a cylindrical screen 15 of fine-mesh wire cloth, the ends of which are seated in a recess 62 in the cover and a recess 63 in the body, the screen and the recesses being coaxial with chamber 14. The screen 15 is sealingly seated against the body and cover so that fuel can enter outlet 18 only through the screen.

The tangential outlet 37 may be similar to the inlet 11, although preferably of smaller diameter. In operation, the fuel which enters tangentially swirls around in the chamber 14 outside the screen 15, most of it passing through the screen and out through the outlet 18. A small part of the fuel, controlled by orifice 47, flows out the tangential outlet 37, bearing with it the dirt which is centrifuged toward the outer boundary of the chamber 14. The swirling flow of fluid also acts to sweep or wash the outer surfaces of the filter elements to minimize accumulation of dirt or sludge on these surfaces.

It has been found that there is a tendency for a small part of the finer or lighter dirt and lint to miss the outlet 37 and accumulate slowly on the screen, particularly at low flow rates, as when starting the engine. In most cases, therefore, it is deemed desirable to include a preferably tangential outlet adjacent the screen and at a point of high flow velocity to discharge a small quantity of fuel and thus remove such fine or light particles from the screen.

As shown in FIGS. 1 and 2, a tangential outlet 65 is provided from recess 62 adjacent the base of the screen to recirculate a small amount of fuel and fine contaminants through a line 66 and a check valve 67 to the pump inlet line 5. This outflow removes dirt from screen 15 which would otherwise accumulate. Flow through line 66 should be controlled at an appropriate value by the capacity of the line or valve 67, or by other means such as a suitable orifice 68.

Experience so far with the separator indicates that improved results are achieved if the diameter of the screen is small relative to that of the chamber 14. This provides better separation and better cleaning of the screen. Very good results have been obtained with a screen of diameter about one-quarter the diameter of the chamber.

Referring again to FIG. 1, an additional feature of the separating system, which is optional, depending upon the nature of the installation, is shown. This involves the provision of a second tangential inlet 73 to the separator chamber 14. This inlet is supplied by a branch from the pump outlet line 11 through a resistance valve 74 which opens when the pressure across it rises to a value which indicates that flow into the separator is at a particular substantial level. This feature permits a high injection speed of the fuel into the separator at low rates of flow without creating unduly high resistance to flow as the flow rate increases. In this respect, of course, the operation is similar to that of the resistance valves in fuel nozzles which open a second set of ports as flow rate increases.

In its preferred configuration, the separator 7 relies principally on the centrifugal effect in normal operation rather than straining or filtering, but the filter 15 is a desirable part of the device, particularly in case of very low flows which may occur when starting or stopping the power plant or when idling at high altitudes; also to assist in eliminating that portion of fine dirt that misses outlet 37 in a given pass through the separator.

FIG. 3 illustrates schematically a second embodiment of the invention in which the separator 7 is disposed downstream of the fuel control 9. Reference numerals on FIG. 3 correspond to those on FIG. 1, and since the only necessary change is the reversal of the sequence of the fuel control and separator, no explanation of this system is deemed necessary. With such a system, there is the disadvantage that all of the dirt goes through the fuel control. There is the advantage that all of the fuel is metered except any returned from adjacent the screen through line 66. This line may be omitted or it may have a fixed resistance to flow, or include means for holding the flow constant or otherwise controlling the flow so that the amount of fuel returned may be compensated for by the fuel control. There may, of course, be some installations in which this arrangement of parts would be preferred. It is to be understood that a system according to FIG. 3 may include such accessory devices as the dirt trap 42, the flushing line 53, 54, 55, 56, the shutoff valves 23 and 43, and the heat exchanger 27 as shown on FIG. 1 if desired.

If the fuel control 9 in either FIG. 1 or FIG. 3 is of a type which responds directly to a limiting parameter of turbine operation such as temperature or speed, the operation is not affected by flow to the engine by-passing the control, as through line 38 in FIG. 1 and line 66 in FIG. 3. Otherwise, some control of such by-passing flow so it may be compensated for is needed.

It may be noted that FIGS. 1, 2, and 3 described above were included in my parent application, Ser. No. 778,002. FIG. 7 is directed to changes in the system which may render it more suitable for some installations.

FIG. 7 illustrates schematically a fuel system and combustion apparatus involving a number of departures from that shown in FIG. 1. The combustion apparatus may be the same as that referred to with respect to FIG. 1, but is illustrated differently. Considering first the elements in FIG. 7 which are common to FIG. 1, the fuel inlet line 5, pump 6, separator 7, fuel control 9, and fuel spray nozzle 10 may be as previously described except that the resistance or fuel dividing valve 34 is shown as separate from the fuel nozzle.

The first difference from the prior system which may be mentioned lies in the addition of a second separator 8 which is connected between the pump discharge line 11 and separator 7. Separator 8 may be identical to separator 7 except dimensionally and, therefore, need not be described in detail. Separator 8 is substantially smaller than separator 7, the exact size being a matter of variation depending upon the parameters of the system such as range of fuel flow.

Each separator includes a casing 13 defining an annular chamber 14 with the screen 15, central clean fuel outlet 18, on the axis of the device, peripheral tangential outlet 37 to discharge a small amount of dirt-laden fuel, and tangential outlet 65 adjacent the screen to discharge contaminants. The peripheral outlets discharge into dirty fuel lines 38 and 38', respectively, and the outlets adjacent the screen into lines 66 and 66', respectively. Lines 66 and 66' are shown connected to the inlet 46 of the dirt trap rather than the pump inlet, as will be further described.

The additional separator 8 is to improve performance at low fuel flows, this being the reason for the smaller size of the separator 8. Low fuel flow discharged from pump 6 flows through line 11 into the small separator 8 and the separated clean fuel is discharged through a line 20 into the inlet of the larger separator 7 from which it is discharged through the line 19 into the fuel control as previously described. In this case, the separation takes place in the smaller and therefore more strongly swirling separator 8 and the separator 7 is essentially idle.

A by-pass line including a resistance valve 12 connects the inlet line 11 and outlet line 20 of the separator 8. As flow increases, the pressure drop through the separator increases, and at some suitable value of pressure drop the resistance valve 12 begins to open to direct a substantial part of the discharge from pump 6 directly into the main or larger separator 7. This takes place at a level of flow at which the separator 7 maintains a swirl rate sufficient for proper separation of the contaminant brought in through the by-passing valve 12. At maximum flows, it is contemplated that much the greater portion of the fuel is fed directly to the separator 7. It would be possible to shut off the separator 8 under these circumstances, but it is not necessary, and the additional complication is not considered desirable. When the second separator is provided, it is considered that the second inlet to the separator as shown at 73 in FIG. 1 is not needed.

FIG. 7 shows another feature which is added to the system of FIG. 1, this being a resistance valve 16 connected to by-pass the separator 7. This is considered to be a safety feature in the unlikely event that the screen 15 should be blocked by an extremely heavy inflow of contaminants. Such a valve could, of course, be added to the system of FIG. 1 to connect lines 11 and 19 of that figure. Obviously, valve 12 will by-pass the smaller separator 8 in the event it should become blocked.

The outlet 65 adjacent the screen in the separator of FIG. 1 is connected through a check valve and controlling orifice 68 to the fuel inlet line 5. A further difference in the system of FIG. 7 lies in the fact that this outlet 65 is connected to the main dirty fuel line and thus directly to the fuel consuming device, omitting the recirculation through the pump. This is considered to be desirable as reducing the load on the separator from recirculating any part of the separated out contaminants through them.

Thus, as illustrated in FIG. 7, all of the lines 38, 66, 38', and 66' are connected to a dirty fuel conduit 40 which enters the dirt trap 42. Flow from the lines into the conduit 40 may be controlled by suitable orifices as indicated at 70, 71, and 72. These orifices may act to apportion the flow as desired between the various discharge lines to maximize the scouring of fine contaminants from the screens 15 while avoiding excessive discharge of fuel into the dirty fuel conduit 40 and ultimately into the dirty fuel manifold 39.

The dirt trap 42 is connected in the system in the same way as in FIG. 1 and performs the same function of intercepting large pieces of dirt which might plug even the large flow fuel nozzle, and therefore need not be further described.

A further new feature of the system of FIG. 7 lies in a control valve 78 which serves to control the flow of the dirty fuel to the engine and to control addition of clean fuel to the dirty fuel line to wash the contaminated fuel along the way if needed. This apparatus thus is substituted for the check valve 54 and orifice 56 in line 53 of the device of FIG. 1.

The control valve 78 includes a body defined by two parts 79 and 80 between which is mounted a flexible diaphragm 82. The body part 79 includes a partition 83 within which is slidably mounted a valve plug 84 which is fixed to the center of diaphragm 82 and is biased by a compression spring 86. The valve plug 84 includes a conical nose 87 which cooperates with an annular seat 88 to provide a valve 90 to control flow of the dirty fuel. As shown, a line 91 connects the outlet of the dirt trap 42 to an inlet through the valve seat 88. When the valve 90 opens, line 91 is connected with the chamber 92 in the control valve 78 which in turn is connected through a line 94 and shuttle valve 43 with the dirty fuel manifold 39 and thus to the fuel nozzle or nozzles 10.

The branch 53 of the clean fuel line enters the valve 78 through part 79 into a space 95 to the right of the diaphragm as illustrated so that pressure in this line tends to open the valve 90. A passage 96 through the valve plug 84 connects the chamber 92 with the space 98 on the opposite side of diaphragm 82. Thus, the pressure in line 53 tends to open valve 90 and pressure in line 94 and the force of spring 86 tend to close the valve. A slot 99 in valve plug 84 serves as a secondary valve which connects space 95 with chamber 92 when the valve 90 opens so that, when dirty fuel is allowed to flow from line 91 to the fuel nozzle, some clean fuel is also discharged into the line to dilute the fuel and help to move it along.

Thus, when the engine is brought into operation, the supply of fuel to dirty fuel manifold 39 is not opened until there is pressure downstream of the clean fuel shutoff valve 23 in manifold 30 and line 53. This pressure acts to open valve 92 and also the slot 99 so that the fuel separated out by the separators 7 and 8 is allowed to flow to the large flow ports of the fuel nozzle 10. When the control valve 78 is provided, the manually operated shutoff valve in the dirty fuel line, indicated at 43 in the system of FIG. 1, is no longer needed.

The clean fuel from manifold 30 flows through branch line 31 into the small flow port or ports 100 of the fuel nozzle 10 and the manifold 39 is connected to the large flow port or ports 102 of the nozzle. Fuel discharged from ports 100 swirls within the structure 33 of the small flow portion of the nozzle, which is illustrated as a swirl chamber similar to those illustrated in the fuel nozzle patents referred to above, and discharges as a conical spray. The dirty fuel is discharged through ports 102 into the outer swirl chamber 35 from which it is discharged. If the flow of the dirty fuel is not sufficient for good atomization, the atomization is assisted by the small flow nozzle 33. When the total fuel flow becomes too great for the small fuel ports, the resistance valve 34 begins to open, diverting a portion of the clean flow into the large flow ports 102 as is well understood. In FIG. 7, the fuel nozzle 10 is illustrated as discharging into a combustion liner 104 of conventional structure within which the fuel is mixed with air and burned. Manifolds 30 and 39 are shown as extending for connection to additional fuel nozzles, if present.

In connection with the discussion of the combustion chamber, reference may be made briefly to FIGS. 4, 5, and 6. FIG. 4 illustrates combustion apparatus of the can-annular type, FIG. 5 apparatus of the full annular type, and FIG. 6 a single liner cylindrical combustion apparatus. In both FIG. 4 and FIG. 5, a combustion apparatus is defined between outer and inner walls 106 and 107, respectively. In FIG. 4, combustion takes place within a number of combustion liners 104 each of which mounts a fuel nozzle 10. In FIG. 5, combustion takes place between the outer and inner walls 110 and 111 of an annular combustion liner within which a number of fuel nozzles 10 are mounted. In both FIG. 4 and FIG. 5, each of the nozzles 10 is connected through branch lines to the fuel manifolds 30 and 39 which correspond to those illustrated in FIGS. 1 and 7.

In FIG. 6, a combustion apparatus comprises a casing or wall 112 within which is suitably supported a combustion liner 104 within which is mounted the nozzle 10 connected to the fuel manifolds or lines 30 and 39. In all these cases, the clean and dirty fuel manifolds 30 and 39 are connected to a nozzle or nozzles within a combustion apparatus. Thus, the contaminated fuel is sprayed or nebulized and burned along with the clean fuel in a single combustion apparatus and in a single combustion step.

It should be apparent that the various features in which FIG. 7 differs from the system of FIG. 1 may be employed individually. Thus, various combinations of the arrangements of these figures are possible. The second separator 8 may be provided or omitted, the additional inlet 73 to the separator may be provided or eliminated, the fuel discharged from the outlet 65 adjacent the screen may be returned to the pump inlet or may be directed into the dirty fuel line, the flow of the fuel into line 39 may be controlled by the shutoff valve 43 and orifice 56 of FIG. 1, or by the control valve arrangement 78 of FIG. 7. As stated above, the valve 34 which controls flow from the clean fuel line into the large flow ports as flow increases may be included as part of each nozzle or may be a separate valve distinct from the nozzle.

The discussion so far has been directed primarily to the description of preferred apparatus, but the method of burning fuel, or the method of introducing fuel into the combustion apparatus which has been implicitly described, may now be taken up briefly. To put it briefly, the method which is described in this application comprises in its preferred embodiment supplying fuel containing particulate contaminants, separating the fuel into a major portion which is relatively free of particulate contaminants, and especially of particulate contaminants of larger dimensions, and into a minor portion in which the contaminants are substantially entirely carried, conducting the two fuel flows to suitable combustion apparatus which includes means for spraying or otherwise nebulizing the clean fuel and additional means for handling the contaminated minor portion of the fuel, delivering the two portions of the fuel as a spray into the combustion apparatus, and burning them jointly in the combustion apparatus.

It will be clear to those skilled in the art that my invention provides a superior system for improving the ability of an engine to operate for substantial periods of time on badly contaminated fuel without significant compromise of the fuel metering and fuel injection components of the engine fuel system. Also, since the dirt-laden fuel is diverted to the fuel nozzle large flow ports and is burned in the normal engine combustion chamber or chambers, there is neither a storage problem nor a hazard from venting the fuel. The centrifuge action relieves the filters of a great part of the burden of separating contaminants, and the swirling of the fuel over the screens provides a filter washing action. Such washing or recirculation of fuel from adjacent the screens prevents clogging of the screens.

The detailed description of preferred embodiments of the invention for the purpose of explaining the principles thereof is not to be considered as limiting or restricting the invention, since many modifications may be made by the exercise of skill in the art without departing from the scope of the invention.