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Патент USA US3056270

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Oct. 2, 1962
Filed Jan. 24, 1958
55 29 26a 50
: 2a zwzlawqraz
, L,
United States Patent O?ice
Patented Oct. 2, 1962
Albert .luhh, Alvaston, and Christopher Linley Johnson,
Allestree, England, assignors to Rolls-Royce Limited,
Derby, England, a British company
Filed Jan. 24, USS, Ser. No. 711,036
Claims priority, application Great Britain Jan. 28, 1957
4 Claims. (Cl. oil-39.28)
ing arrangement, a valve in the by-pass, and pressure-re
sponsive means operating the valve, the pressure-re
sponsive means being responsive to the pressure in the
combustion chamber and to the pressure at the inlet to
the pump and being arranged to open the valve When the
combustion chamber pressure differs from the pump inlet
pressure by a selected amount.
One form of fuel system of this invention will now
be described with reference to the accompanying diagram
10 matic drawing.
gine, such for instance as a gas-turbine engine, having a
The fuel system illustrated is suitable for an aircraft
combustion chamber into which a continuous flow of fuel
gas-turbine jet propulsion engine.
This invention relates to a liquid fuel system for an en
is delivered in operation of the engine.
The engine illustrated comprises a compressor 40 which
In such an engine, there is usually provided primary
draws in air from atmosphere and delivers the compressed
(or pilot) fuel injector means and secondary (or main) 15 air to combustion equipment 4-1 wherein fuel is burnt
fuel injector means, and the maximum quantity of fuel
with the air and from which the combustion gases are
delivered through the primary fuel injector means is a
small proportion of the total fuel delivered to the com
bustion chamber under maximum fuel ?ow operating con
delivered to a turbine 42‘. The exhaust gases from the
turbine 42 pass into a jet pipe 43 and ?ow to atmosphere
through a propelling nozzle 44 which is shown as a vari
20 able area nozzle.
This invention has for an object to provide a simple
The fuel system for delivering fuel to the combustion
fuel system which caters for a wide range of fuel flows
equipment 41 comprises a fuel tank 9, a main fuel pump
whilst obtaining good atomization of the fuel in the com
10, shown as a centrifugal pump, having a suction pipe
bustion chamber. ‘It will be appreciated that good atom
111 leading from the fuel tank and a main delivery pipe
ization is desirable in order to maintain combustion, and
12 having connected in it a fuel-cooled oil cooler 13
difficulties have been experienced with known fuel sys
through which the fuel from the pump it) is passed, a
tems in maintaining combustion at relatively low fuel
control mechanism ‘14 of any known or convenient kind
?ows such as are necessary under some operating condi
by which the delivery of fuel from pump it} into the
tions, for instance such as are necessary to satisfy engine
main fuel line 12 is metered to suit the total engine fuel
requirements when a gas-turbine engine is operating at
requirements, which vary according to the desired engine
high altitudes.
rotational speed, the altitude of operation and other fac
According to the present invention, a fuel system for
tors, primary (or pilot) fuel injector means 15, secondary
an engine having a combustion chamber to which fuel is
fuel injector means 16 and a system by which the total
delivered continuously in operation, comprises primary
fuel flow to the injector means ‘15, 16, is divided between
and secondary fuel injectors, a main pump with control 35 them. The fuel pump 10 may be driven by the engine,
means metering the total fuel delivery to the fuel injec
or may be driven as indicated by an air turbine 8 which
tors by the main pump, a main fuel line receiving the total
is supplied with operating air from the engine compressor
fuel delivery, branch fuel lines leading from the main fuel
4-6 through conduit 45 or by any other convenient drive
line to the primary and secondary fuel injectors respec
tively, and a pressurizing arrangement, including a pump 40
The fuel dividing system comprises branch lines 17a,
mechanically driven from the engine, in the branch line
1712 leading respectively to a manifold 46 for the pri
leading to the primary injector or injectors whereby a
mary fuel injector means 15 and to a manifold 47 for
supply of fuel at adequate pressure for atomization is
the secondary injector means 16.
maintained to the primary injector or injectors at all total
The branch line 17a has ?tted in it an auxiliary pump
fuel ?owsv Said pressurizing arrangement may also in 45 18 and a shut-off cock 19. The pump 18 is shown as
clude means to limit the maximum delivery pressure to
a gear-type positive-displacement pump and it is driven
the primary injectors.
from the engine through a mechanical drive indicated
The pressurizing arrangement may comprise a posi~
at 20. The pump 18 has associated with it means to
?ve-displacement pump driven mechanically from the en
limit to a selected maximum value the pressure rise
gine and having a by-pass ?tted with a relief valve to open 50 across the pump and this means is shown as a by-pass
when the delivery pressure reaches a selected value, or a
conduit 21 containing a spring-loaded pressure relief valve
pump of the pressure compensated kind driven mechan
ically from the engine.
According to a preferred feature of the invention a non—
return valve is incorporated in the branch fuel line lead
ing to the secondary fuel injectors.
The provision of
22 which opens when the delivery pressure reaches the
desired value above‘the pressure at the inlet of the pump
18. The pump 18 also has associated with it a fuel re-.
55 circulating by-pass conduit 23, the purpose of which will
be described below.
The branch line 17b has ?tted in it a spring-loaded
taminated with carbon being drawn in from the combus
non-return valve 24 which permits fuel to flow towards
tion chamber when the pressure on the inlet side of the
the secondary fuel injector means 16, and a shut-01f cock
pressurizing pump is less than the pressure within the 60 25 which may be operatively coupled with shut-off cock
combustion chamber.
19 as indicated at 26.
' ,.
According to another preferred feature of the inven
The recirculating by-pass 23 has connected in it "a
tion, there is provided means whereby, when the metered
valve comprising a valve body 27, and a piston valve
total fuel delivery into the main fuel line is less than the
element 28 having two lands 28a, 28b dividing the body
rate of delivery of the pump of the pressurizing arrange 65 into three chambers 29, 3t}, 31, of which chamber 31
ment in the branch line to the primary injector or injec
contains a spring 32 urging the piston valve to a posi
tors, a quantity of fuel is circulated in the pump of the
tion in which flow through the portion of conduit 23
pressurizing arrangement, thereby to avoid cavitation.
leading from the outlet of pump 18 into the valve body
One fuel system according to this feature of the invention
27 is cut off. Chamber 29 is sealed off from chambers
comprises a non~return valve in the branch line to the 70 30, 31 by the land 28a and is connected by conduit 33 to
secondary fuel injector or injectors, a recirculating by-pass
the branch line 17b at a point downstream of the non
between the inlet and outlet of the pump of the pressuriz
return valve 24. The chamber 34) is connected by a drill
such a non-return valve prevents air which may be con
3,0 56,259
ing 34 to chamber 31. It will be clear that when the
piston valve moves su?‘iciently far to the right the two
portions of conduit 23 are joined through chamber
30 so connecting the inlet and outlet of pump 18.
The spring 32 may alternatively be housed in the cham~
delivered to the combustion chamber through the nozzle
trifugal pump is thus incapable of supplying the mini
ber 29.
Pump 13 operates as an auxiliary ?ow assisting means
In operation of the fuel system, fuel metering is ef
fected prior to division of the fuel between the injector
which is capable of supplying the minimum ?ow to the
nozzles at low engine speeds and high altitude. Since
means 15' and 16, and an adequate pressure of the fuel
entering the combustion chamber through the primary
The low pressure head available from the cen
mum fuel flow through the specially designed burner noz
zle. To overcome this difficulty pump 18 is provided.
pump 18 is capable of supplying the required flow, the
10 required pressure must be maintained.
It will be clear that with the fuel system of this in
injector means 15 to ensure good atomization is main
vention adequate atomization pressure is maintained at
tained under all operating conditions by the pump 18 .
the primary injector means 15 under all operating con
At low fuel flows, the suction elfect of pump 18 pre
vents the pressure in the main pipe line 12 from eXceed~
If desired, a ?lter may be incorporated in the line 17a
ing that necessary to open non-return valve 24 and so 15
so as to ?lter the fuel passing to the primary fuel in
the whole of the fuel is delivered to the primary in
jector means. This filter can be small in relation to
jector means 15. As the fuel ?ow increases so that pres
the total contamination in the fuel, since the quantity
sure on the delivery side of the pump 18 increases until
of fuel which is handled by the pump 18 will be of the
at a preselected value of the pressure, the relief valve
order of 5 to 10% of the main engine fuel requirements.
22 opens so preventing any further increase of this pres
sure and thus of the rate of fuel delivery through the
We claim:
1. A fuel system for an engine having a combustion
primary injector means 15‘ (which in eifect is a restric
tion). Any further increase in the total fuel flow is ac
companied by an increase in pressure in the main fuel line
12 so that non-return valve 24 opens permitting the ad
ditional fuel to flow to the secondary injector means 16.
Under some conditions of operation, for example at
high altitude, the total engine fuel requirements may be
chamber to which fuel is delivered continuously in opera
tion of the engine comprising primary and secondary fuel
injectors delivering liquid fuel in the combustion chamber,
a main pump, control means metering the total fuel
delivery of said main pump to said fuel injectors, a
main fuel line receiving said total fuel delivery, ?rst
so low that the pump 18 tends to deliver more fuel than
and second branch fuel lines leading from said main
is delivered into the main delivery pipe 12 so that there
fuel line to said primary fuel injectors and said second
ary fuel injectors respectively, pressurizing means includ
ing a constant displacement pump mechanically driven
from the engine connected in said ?rst branch fuel line,
is a tendency for cavitation to occur in the pump 18.
Such cavitation is avoided by permitting recirculation of
a quantity of fuel in a path including the pump 18 and
the recirculation by-pass 23.
Opening of the valve 27, 28 to permit said recircula
a non-return valve connected in said second branch fuel
35 line and permitting flow towards said secondary fuel in
tion is effected automatically as follows. When cavita
tion is likely to occur, there is no ?ow in branch line
jectors, and means connected between the inlet and outlet
17b, and the combustion chamber pressure acts on the
of fuel from the outlet to the inlet of said constant dis
of the constant displacement pump permitting delivery
piston valve through the column of liquid fuel in branch
placement pump when said rate of delivery of said con
line 17b and displaces the piston valve 28 to the right 40 stant displacement pump exceeds said rate of delivery
against the action of the inlet pressure of pump 18 plus
to said main fuel line by the main pump, said means
the load of spring 32‘ in the arrangement shown (or less
permitting delivery of fuel from the outlet to the inlet
the spring load when the spring is in chamber 29) until
of the constant displacement pump comprising a recir
the portions of the conduit 23 are joined through cham
culating by-pass connecting the inlet and outlet of the
ber 30, when recirculation occurs.
Since, when the spring 32 is in chamber 29‘, the inlet
pressure of pump 18 necessary to close valve 28 will
be higher than the combustion chamber pressure, it will
be necessary to employ a higher spring loading of the
non-return valve 24, than when the spring 32 is in cham
ber 31.
The operation of the device may be summed up as
The fuel system includes primary burners 15 which are
constant displacement pump, a valve in the by-pass, and
pressure-responsive means operating the valve, the pres
sure-responsive means being responsive to the pressure
of the fuel in said second branch line downstream of said
non-return valve which pressure is proportional to the
pressure in the combustion chamber when the pressure
of the fuel in the main line is insul?cient to open the
non-return valve and to the pressure at the inlet to the
constant displacement pump and being arranged to open
the valve when the combustion chamber pressure diifers
operative at all times and secondary burners 16 which 55 from the pump inlet pressure by selected amount.
are operative at high fuel flows only.
2. A fuel system according to claim 1, wherein said
valve in the recirculating by-pass comprises a casing, a
The primary burner nozzle 15 includes an ori?ce that
is designed to require a high fuel pressure to pass the
valve element movable in the casing and having a pair
minimum operating fuel ?ow in order that good atomiza
of spaced lands dividing the casing into two end cham
tion is obtained. The fuel system relies primarily on
bers and a center chamber between the lands, a drilling
centrifugal pump 10 which is designed for proper opera
in one land connecting one end chamber and the center
tion at high fuel ?ows when both the primary and sec
chamber, a connection from the other end chamber to
ondary burners are in operation and thus when control
the branch fuel line which leads to the secondary fuel
14 operates to vary fuel ?ow in the secondary burner.
injector at a point in the branch fuel line downstream of
The centrifugal pump 10‘ is driven by air turbine 8 to 65 the non-return valve, a pair of connections respectively
provide the fuel with su?icient head for delivery into the
from the inlet and outlet of the pump of the pressurizing
combustion chamber 41. Under conditions at which all
arrangement to the center chamber, and a spring urging
the fuel ?ow is going through the primary burners 15,
the valve element towards one end of the casing, the
the engine will normally be operating at idling speed and
probably at a substantial altitude. Under these condi 70 valve element having a position in which the connection
from the outlet of the pump is covered and being urged
tions a centrifugal pump driven by a compressor pres
towards this position by the pressure in the center cham
sure driven air turbine, will be running at a low speed
ber and being urged to uncover this connection by the
and consequently be giving a very small pressure rise.
pressure in said other end chamber.
However, under these conditions a sufficient pressure head
3. A fuel system according to claim 2, wherein the
is required in order that a least
fuel ?ow be 75
spring urges the valve element to the position in which
the connection from the pump outlet is covered.
4. A fuel system according to claim 2, wherein the
spring urges the valve element away from the position in
which the connection from the pump outlet is covered. 5
References Cited in the ?le of this patent
Vogt ________________ __ Sept. 9, 1952
Jubb ________________ __ June 30, 1953 1°
Lee _________________ __ Feb. 23, 1954
Schaffer ______________ __ May 18, 1954
Smith ________________ __ July 13, 1954
Torell _______________ .... May 24, 1955
Australia ____________ __ Feb. 10, 1955
Ballantyne et a1 ________ __ Dec. 6, 1955
Nims ________________ __ Aug. 7,
Redding _____________ __ Nov. 12,
Ballantyne ___________ .. Nov. 19,
Cruckshank __________ __ May 27,
Great Britain _________ .._ J an. 25, 1956
Great Britain ___________ __ J an. 9, 1957
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