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Oct. ‘8; 1946.
2,408,879
c. A. PUGH
CARBURATION APPARATUS FOR INTERNAL-COMBUSTION EKGINES END ‘THE LIKE
Filed April 21, 1943‘
3
SheetYs-Sheet 1
Iwvgural?
2,408,879
C. A. P U G7H
CARBURATION i'Z’PARATUSV FOR INTERNAL-COMBUSTION ENGINES AND THE LiKE
Filed April 21. 1943
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INVENTOR
Cyril A. Pugh
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Oct. 8, 1946.
.
c. A. PUGH
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2,408,879
TION APPARATUS F0 RI INTERNAL-COMBUSTION ENGINES
CARBURA
Filed April 21, 1943
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Patented Oct. 8, 1946
ATENT OFFICE
UNITED STATES
2,408,879
CARBURATION APPARATUS FOR INTERNAL
COP/BUSTION ENGINES AND THE LIKE
Cyril Alphonso Fugh, Ilford, England, assignor to
The Plessey Company Limited, Ilford, England,
a British company
Application April 21, 1943, Serial No. 483,876
In ‘Great Britain September 8, 1941
7 ‘Claims.
1
This invention consists in improvements in or
relating to carburation apparatus for internal
combustion engines and the like and has for its
object to provide means whereby the fuel supply
to the engine ‘can be so controlled that any pre
determined miXture strength can be maintained
overth'e whole speed range of the engine.
(Cl. 123—119)
2
system having the various parts arranged in ac
cordance with the present invention;
Figure 2 is another schematic illustration of a
modi?ed form of the invention,
‘
Figure 3 illustrates a detail of ‘the adjustment
for the outlet of the centrifugal pump;
7 Figure 4 shows a modi?cation of the invention
in a form similar to that illustrated in Figure 1;
This invention comprises a carburation system
and
having vin combination 'a fuel jet, a fuel conduit
Figure 5 is a schematic view showing the car
through which fuel is supplied under pressure to
buration system in its relation to the engine with
the jet, a centrifugally controlled pressure, relief
\vhichit is associated.
valve opening from the fuel conduit, and a meter
Like reference numerals indicatelike parts in
ing ori?ce in the fuel conduit situated at a posi
the
several figures of the drawings.
tion therein between the jet and the connection
In
the schematic arrangement illustrated in
15
of the conduit with the pressure relief valve.
Figure 1 it is to be understood that a positive dis
Conveniently, the system compriseswalso a cen
placement fuel delivery pump, not illustrated, is
trifugal pump geared or otherwise connected to
provided for supplying fuel in eXcess of require
the engine to which fuel is to be supplied so as
ments through a fuel line Hi to a fuel jet ‘H, or
to run at engine speed or at a constant multiple
20 its equivalent through which fuel is supplied ‘to
of the engine -speed,>a pressure relief valve regu
the engine or the like. 'In the fuel line ii! is a
lating chamber, a piston ‘or diaphragm situated
metering ori?ce I2 controlled by a metering valve
withinthe chamber and dividing it into two parts,
l3 which‘is adjustable in relation to the orifice in
an operative connection between ‘the piston or
order to set the effective area of the ‘ori?ce as re
diaphragm and the pressure relief valve, and 25 quired. Prior to reaching the ‘metering ori?ce,
conduits connecting the two parts ‘of the cham
considered in the direction of fuel flow from the
ber respectively with the inlet and outlet of the
pump. indicated by the arrow I6, is a branch con
centrifugal pump.
duit l 5 leading to a pressure relief valve It.
In one form of the invention that part of 7the
This valve as illustrated is in the form of a
regulating chamber adjacent the relief valve is piston valve having a valve stem l-l connected
connected to the inlet to the centrifugal pump
to the valve iii of say area a and a larger piston
and also to the jet conduit or line, whereas the
face l8 of 'say area b. It is obvious that the
opposite ‘part 'of the regulating chamber is con
valve it instead of beingin the form of a piston
nected to the fuel feed line and also to or near
valve could be in the form of a diaphragm-oper
the periphery of the impeller of the centrifugal
ated valve as shown in Figure 4 in which the
pump.
larger area it? is represented by the diaphragm t8
.Thus, the centrifugal pump is connectedacross
and is connected, for instance by a pin, being the _
the 'two parts of the regulating chamber and
equivalent of stem H. to a valve such as 56.
tends to ‘develop its pressure in opposition to'that
Whether valve 15 is a piston valve or a diaphragm
to which it is normally subjected by its ‘connec
operated valve the following considerations ap
tion to the pump feed line and to :the jet linere
ply equally in both cases. On that side of the
spectively.
Where it is necessary ‘or desirable ‘to ‘introduce
a correction to the jet pressure {depending upon
air
someentering
variable‘the
factorsuch
engine, this
as the ‘density
be obtained
of
piston IE3 from which the valve l5 extends, the
valve chamber I8 is provided with an outlet 25}
leading to the suction side of the main pump or to
a return line to the fuel tank past one surfacelof
balanced valve 2!. The other surface of the
valve 2i is in connection with the jet supply line
through a conduit 23 and the connection of
by varying the radial position of the outlet from
the pressure regulating centrifugal pump radially
the conduit 23 with line 22 is between the jet
with respect to the aXis or centre of the impeller.
The foregoing and other features of the inven 50 l l and the metering ori?ce l2. The object of the
tion will now be described in connection with some
'balancedlvalve 2! is to cause the pressure in the
preferred examples of the invention read'in con
junction with the accompanying drawings, in
relief valve chamber is that communicates with
the low pressure side of the fuel supply system ‘to
which
Figure 1 illustrates schematically a carburation
between the metering ori?ce l2 and the ‘jet ‘H.
be the same vas that which exists in the passage
2,408,879
3
4
Leading from the valve chamber I9 also on that
may be considered as the high pressure part.
side of the piston I8 from which the valve pin
I‘I extends is another conduit 24 leading to the
taining an adjustable restriction 35 to the fuel
The latter part is connected by a duct 34 con
suction side of a centrifugal pump 25. The out~
let conduit 28 from the pump 25, that is to say.
from the pressure side thereof, passes into cham
ber IS on the other side of piston I8. Still an
line ID by way of a duct 36, and also by another
duct 31 to a position at or near the periphery of
the impeller of the centrifugal loading pump 25.
With this arrangement, assuming the delivery
through adjustable restrictions 40 and III and
The latter as before is mounted on or is geared to
the engine shaft so as to rotate at engine speed
other conduit 21 entering on the same side of the
or at a speed close to a constant multiple of en
valve I8 as conduit 26, leads through a ?xed or
regulatable restriction 28 to the suction side of 10 gine speed. The low pressure part of the regu
lating chamber is connected by ducts 38, 39
the pump.
duct 42 to the jet line 22. A further branch con
duit 43 connects the low pressure part of the reg
pressure from the main pump to be represented
by P2, the pressure on the inlet side of the main
control valve I6 to be P1 and on the opposite side
ulating chamber to the inlet to the centrifugal
thereof to be Pl-I-P it will follow that
pump 25.
_
The metering ori?ce I2, the area of which is
controlled by the needle valve I3, may be made
to have a de?nite relation to the induction pres
where P=pressure rise across centrifugal pump. 20 sure, temperature, exhaust back pressure, throt
The arrangement ensures that whatever
tle opening, or any other engine variable or var
change of pressure may occur either inside or
iables, Thus any adjustment which is the equiv
outside the system the rate of delivery of fuel to
alent of that obtainable by means of the screw of
the jet II will remain directly proportional to
valve I3 may be used to adjust the system for
the engine speed, as the pressure difference
any of the engine variables speci?ed. For in
across the ori?ce I2 is maintained by the cen
stance, the valve I3 may be adjusted in accord
trifugal pump proportional to the square of the
ance with the variables above-mentioned by a
engine speed, and the ?ow through the ori?ce
mechanism such as is described in United States
varies as the square root of the pressure differ
Patent No, 2,383,563 and, in order to avoid un
ence across it.
30 necessary illustration this valve may therefore be
It will be observed that pressure P1 will exist in
considered as one which is automatically adjust
the connection between the metering ori?ce I2
able by the mechanism referred to.
and the jet I I and that this pressure, which may
In order to provide for adequate fuel pressure
be considered a datum pressure, is controlled by
on starting, the pressure relief valve I6 is con
the jet II and the surrounding conditions.
The metering ori?ce I2 can be controlled by
veniently urged towards its closed position by
the needle Valve I3 in order to adjust the size of
this ori?ce for variation of mixture control to the
high pressure part of the regulating chamber 32
means of a rod 44, one end of which enters the
and communicates with and presses on the pis
ton I8 or its diaphragm equivalent. The other
haust back pressure, that is to say, to alter the 40 end of rod 44 is formed as a piston 45 working
rate of ?ow or delivery of fuel to the jet II,
within a starting pressure chamber 46 and that
Whatever adjustment may be made, however, the
part of the latter which is nearer the regulating
result of that adjustment will remain as before
chamber is connected through a duct 41 with the
constant and unaltered by changes of pressure
pressure fuel feed line III by way of duct 35. The
inside or outside the system.
45 other part of the starting pressure chamber to
If desired, a light spring maybe employed to
the right of piston 45 is connected through a duct
assist in moving the relief valve I6 towards its
48 with the fuel return line 29 and also contains
engine or to correct for inlet air pressure or ex
closed position and thus to assist in starting the
the spring 49 normally urging piston 45 and rod
engine or in running at low speeds, Also a bleed
44 into engagement with piston I8 or its equiva
may be provided near the eye of the impeller of 50 lent.
the centrifugal pump in order to remove gas or
In operation, when the engine is not running,
vapour that may collect in this position and that
the pressure relief valve I6 will be held on its seat
would otherwise tend to impede the regular ac
by the rod 44 under pressure of spring 49, the rod
tion of the centrifugal pump.
44 and piston 45 being in the dotted-line positions
In the modi?ed arrangement illustrated in
illustrated. When, after starting, the pump de
Figure 2, the positive displacement fuel pump is
livery pressure reaches a predetermined mini
indicated at 30 and the supply and return lines
mum value, pressure of the fuel forces piston 45
I0 and 29 respectively are shown in their connec
to move against the action of its spring, thereby
tion to the pump. As in the previous example a
disengaging rod 44 from piston I8, thus freeing
metering ori?ce I 2 and its associated needle valve
valve It‘.
I3 is arranged in line I!) between the branch con
In order to explain more clearly the operation
duit I5 leading to the pressure relief valve I6
of the regulating arrangement above described
and the jet line 22, In this case, however, the
the following analysis is given,
chamber I9 is substituted by two chambers SI
It is desired that for any given setting of the
and 32 separated by a guide 33 which constitutes
metering ori?ce I2, that is for given values of
a seal in which valve. stem II has a sliding ?t.
induction pressure, exhaust back pressure, etc.,
Within the chamber 32 the piston I8 (or its
the delivery of fuel to a jet such as II shall be
very nearly proportional or as nearly propor
equivalent in the form of a diaphragm) is sit
tional as possible to the engine speed. This will
uated and divides the chamber 32 into two parts
sealed off from one another and is capable of 70 be so if the pressure difference across the meter
ing ori?ce I2 is proportional to the square of the
sliding to and fro within the chamber in accord
engine speed and the amount of flow through the
ance with movements of valve I6. That part of
centrifugal pump is either so small as to be negli
chamber 32 lying to the left of piston I8 may be
gible compared with the ?ow through the meter
considered as the low pressure part of the cham
ing ori?ce or is itself proportional to the square
ber, whereas that on the opposite side of piston I8
12,408,879
6
‘5
andso, adding (3) to (2),
root or the (pressure ‘difference across the meter
ing ori?ce. The second condition, in one form 'or
P1-pzitKz'l"K1‘(K2—1)'}’(Pi‘-Pi)
the other, is ‘easily/satis?ed ‘by suitable design.
As to the first, since the centrifugal "pump 25 is
geared to the engine, the pressure difference
(4) ,
‘so that the pressure drop across the metering ori
?ce is proportional to the pressure drop across
the centrifugal pump, ‘which ‘establishes ‘the de
across‘it will be proportionalto the square of the
engine speed and ‘so the requirements are re
duced to the condition that the pressure differ
ence across the metering ori?ce l2 shall be pro
portional to the pressure difference across the
sired relationship.
Since K234 and K1>0, it is
clear that
(P1“-Pz)>(Pi'-P§)
i. e.
centrifugal pump. Now‘let
(Pz'_'Pi)'>I(P2"—P§)
P1=Pressure i'n'fe‘ed line.
and since
Pz=Pressure in jet line.
P}‘=P‘ressure'in high'pre'ssure part of 'the regulating ‘1.5
chamber.
‘
;‘=‘Pressure in low pressure 'part of the "regulating
(P1'—P%) and (P2'—'Pi)
must have di?erent signs it follows that
chamber.
P1~ P}
Then ‘(P1—P2) is the pressure drop across the me
is positive, as I indicated above. This means that
tering ori?ce, and
'
20 the ?ow in the centrifugal pump will be inwards,
towards-the centre of the impeller.
Y<Pl—P%)
It will be seen from (4) above that the factor
is the pressure drop across the centrifugal pump,
of proportionality depends on the relative adjust
while
ment of the restrictions in the lines, through the
constant K1, so that either one or both of them
'(P1—' P1)
is the pressure drop across the restriction 35 in
the duct from the feed line to the regulating
chamber 32, and
(Pi-P2)
is the pressure drop across the restrictions 4?! in
the duct leading from the regulating chamber 32
to the jetline.
It will appear that both
may be used for tuning.
Furthermore, one or
both of them‘may consist‘of two adjustable leaks
in series. In the example just described, adjust
able leaks £5] and ‘M are shown to be in series
30 and a valve 553 is provided to icy-pass one of these
two, namely, the leak 4!. The by-pass valve 59
may be connected to the throttle as, for example,
through the medium of cam 5i or it may be other_
wise so controlled as to provide enrichment or
35 weakening of the engine mixtureduring acceler
(P: — P i)
ation or during cruising or during any other de
and
sired operation.
(Pi; Pé)
The spindle l5i on which cam 5| turns may be
are positive, though at present it is only obvious
considered as an element mechanically coupled
that they must have the same sign, and that, for 40 to and consequently movable as an operative part
given settings of the restrictions 35 and 46 in
of the throttle.
these lines, they must be proportional, since both
In addition to adjustment for tuning, the leaks
are caused by the same flow, i. e.
may be so adjusted that their actual sizes will
the ?ow through the centrifugal pump
P%—P2=K1(P1—P1‘)
(1) 45 determine
25 and this may be adjusted to eliminate the
where K1 is a positive constant, depending on
production of vapour which might otherwise oc
the relative settings of the two restrictions.
cur at the eye of the impeller.
Now if
'
For the purpose of tuning, it is desirable to be
able to vary the radial position of the outer con
A=the area of the pressure relief valve face
50 nection to the centrifugal pump 25. One such
:the area of the relief valve pin, and
means for effecting this adjustment is illustrated
B=the area of the piston or diaphragm in the
in Figure 3 in which in the casing of the cen
regulating chamber
trifugal pump near its periphery is formed a re
Then for the equilibrium of the pressure relief
cess or pocket 52 and the upper surface or" this
valve,
55 pocket is closed by a disc 53 forming a contin
P1A+ P§(B-— A) = PjB
uation with the wall of the impeller chamber.
In the disc 53 there is an outlet 54 communicat
i. e.
ing with the pocket beneath the disc 53 and any
P1— Pi = K2(Pl — Pt)
(2)
preferred mechanism illustrated by a rack and
pinion linkage 55 may be utilised to rotate disc
Where
K2=g and K2> 1. since B> A
Now from (2), subtracting
(P%~ P5)
from each side,
P1— Pi: (K2— 1) (Pl— Pi)
and multiplying by K1,
K1(P1— P%):K1(K2—1)(Pi— Pi)
i. e.
53 about the axis of a central spindle 5t in order
to vary the radial distance of the port 54. The
chamber 52 communicates with lines 26 or 31 of
the previously described examples.
Figure 5 shows schematically the relative dis
position of the various parts of the carburation
system in their relation to an engine shown in
outline at 200. The principal portions of the
carburation system are referred to by refer
ence numerals corresponding to those employed
above in connection particularly with Figure 2.
I claim:
-
1. A carburation system for supplying liquid
fuel to an engine comprising in combination a
75 fuel jet, a fuel conduit through which fuel is
2,408,879
7
supplied under pressure to the jet, a pressure re
lief valve opening from the fuel conduit, a meter
ing ori?ce in the fuel conduit situated at a position
therein between the jet and the connection of
the conduit with the pressure relief valve, a cen
trifugal pump to which fuel is supplied, means
to drive the pump at a speed which maintains
5. A carburation system according to claim 1,
in which the part of the regulating chamber
Which is nearer to the relief valve is connected
to the inlet to the centrifugal loading pump and
also to the low pressure side of the metering ori
?ce, and the opposite part of the regulating
chamber is connected in the region of the pe
riphery of the impeller of the centrifugal load
a constant relation to engine speed, a regulat
ing pump and also to the high pressure side of
ing chamber for the pressure relief valve, a trans
versely disposed movable element situated within 10 the metering ori?ce, and in which the connec
tions to the two parts of the regulating cham
the chamber and dividing it into two parts, an
ber from the two sides of the metering ori?ce
operative comiection between the movable ele
contain adjustable leaks, one at least of the ad
ment and the pressure relief valve, and conduits
connecting the two parts of the chamber respec
justable leaks comprising two leaks in series in
tively with the inlet and outlet of the centrifu 15 combination with a valve for by-passing one of
gal pump.
the leaks together with an engine speed control
2. A carburation system according to claim 1
element and means operatively connecting the
in which the transversely disposed movable ele
last-mentioned valve to the said speed control
ment in the regulating chamber comprises a pis
element.
6. A carburation system according to claim 1,
20
ton.
in which that part of the piston chamber which
3. A carburation system according to claim 1
in which the transversely disposed movable ele
is connected to the inlet of the centrifugal pump
ment in the regulating chamber comprises a dia
is in connection with the return side of the relief
phragm,
valve and is combined with a further balanced
4. A carburation system according to claim 1, 25 relief valve situated on the return side of the
main relief valve and chamber for the said fur
in which the part of the regulating chamber
ther balanced relief valve, one end of which
which is nearer to the relief valve is connected
chamber is connected to the low pressure side of
to the inlet to the centrifugal loading pump and
the metering ori?ce so as to equalize the pres
also to the low pressure side of the metering ori
fice, and the opposite part of the regulating 30 sure on the low pressure sides of the relief valve
and the metering ori?ce.
chamber is connected in the region of the pe
7. A carburation system according to claim 1
riphery of the impeller of the centrifugal loading
in which said pump has an impeller, character
pump and also to the high pressure side of the
ized by means for varying the effective radius of
metering ori?ce, and in which the connections
to the two parts of the regulating chamber from 35 the impeller for the purpose of tuning.
the two sides of the metering ori?ce contain ad
justable leaks.
'
CYRIL ALPHONSO PUGH.
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