Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
20349~
SECONDARY FUEL MODULATING VALVE
Field of the Invention
This application pertains to a valve for modulating the
flow of a secondary fuel, such as propane, to a diesel engine in
response to changing engine loads.
Background of the Invention
Diesel engine fuel systems which utilize diesel fuel
as the primary fuel and a secondary fuel such as propane are
well known. Conventionally, dual fuel systems of this sort are
employed to increase the horsepower output by the diesel engine.
As a general rule, it is undesirable to operate a diesel engine
in excess of the maximum rated horsepower specified by the engine
manufacturer, since this may cause damage to the engine and/or
void the manufacturer's warranty coverage for the engine. Dual
fuel systems are nevertheless desirable in that the price of the
secondary fuel is typically less than the price of the primary
diesel fuel. If a diesel engine can be operated efficiently and
within the manufacturer's specifications with a dual fuel system,
then significant cost savings may be realized over extended
operating cycles when the combined cost of the primary and
secondary fuels are taken into account.
United States Patent No. 4,953,515 issued 4 Septe~ber,
1990 for an invention of William Albert Fehr and Brian George
Buck entitled "Diesel Engine Secondary Fuel Injection System",
discloses a method of economically operating a dual fuel diesel
engine in a manner which optimizes the engine's performance by
continually varying the relative amounts of primary and secondary
~uel in~ected into the engine, as a function of one or more
engine performance parameters such as turbo-charger boost
pressure, whilst adhering to the manufacturer's specifications
~or operating the engine.
More particulary, the Patent a~oresaid discloses an
apparatus ~or supplying a secondary fuel to a turbo-charged
diesel engine. The apparatus incorporates a plurality of
:'~ , , .: . .
. ', r
'' .~ ~ :': .
203492g
adjustable pressure sensors which are coupled to the engine's
turbo-charger. The sensors detect the boost pressure output by
the turbo-charger and produce output signals representative
thereof. An equal plurality of normally closed valves are
coupled between the engine and a secondary fuel reservoir. The
valves are electrically connected to corresponding ones of the
pressure sensors, such that the valves open in response to the
corresponding pressure sensor output signals, allowing the
secondary fuel to flow to the engine. The sensors are adjusted
to detect selected turbo-charger boost pressures distributed
within a pre-defined boost pressure range. The plurality of
sensors thus produces a corresponding range of output signals as
the engine turbo-charger boost pressure increases, thereby
sequentially opening or closing the valves to supply more or less
secondary fuel to the engine as the turbo-charger boost pressure
increases or decreases.
A disadvantage of the prior art apparatus described
above is that premature detonation of the secondary fuel may
occur if the engine is operated under high load at low R.P.M.
Secondary fuels such as propane are typically admitted into the
engine's combustion chambers with air. Such admission occurs
before the primary diesel fuel is injected into the combustion
cham~er. If the engine is operated under high load at low
R.P.M., its operating temperature may exceed the temperature
required to ignite the secondary fuel. That is, the secondary
fuel may be ignited before the primary diesel fuel is injected
into the combu6tion chamber, adversely effecting engine perform-
ance. The present invention overcomes the foregoing disadvan-
tage.
Summarv of the Invention
In acc~rdance with the preferred embodiment, theinvention provides a valve for controlling the flow of secondary
fuel to a turbo-charged dieeel engine. The valve incorporates
a cylinder, a fir~t inlet port which couples the cylinder to a
secondary fuel reservoir, a second inlet port which couples the
2~34928
cylinder to the engine's turbo-charger, a discharge port which
couples the cylinder to a secondary fuel inlet of the engine, and
a piston which is slidably displaceable within the cylinder to
controllably open and close the discharge port in response to
changes in the turbo-charger's boost pressure.
The piston moves between a closed position in which the
piston blocks secondary fuel flow from the first inlet port to
the discharge port, a first range of open positions in which the
piston allows progressively increasing amounts of secondary fuel
to flow from the first inlet port to the discharge port, and a
second range of open positions in which the piston allows
progressively decreasing amounts of secondary fuel to flow from
the first inlet port to the discharge port.
A conduit in the piston conveys secondary fuel through
the piston, between an inlet and an outlet of the conduit. The
conduit inlet overlaps the first inlet port during displacement
of the piston between the closed position and the first and
second ranges of open positions, thereby facilitating secondary
fuel flow from the first inlet port into the conduit during the
displacement of the piston. The conduit outlet is displaced away
from the discharge port when the piston is in the closed
position, thereby preventing secondary fuel flow from the conduit
to the discharge port when the piston is in the closed position.
The conduit outlet overlaps the discharge port during displace-
ment of the piston in the first and second ranges of open
positions, thereby facilitating secondary fuel flow from the
conduit to the discharge port during displacement of the piston
in the ~irst and second ranges of open positions.
During slidable displacement of the piston through the
~irst range o~ open positions, the conduit outlet moves across
the discharge port to progressively increase the overlap between
the conduit outlet and the discharge port. During slidable
displacement of the piston through the second range of open
positions, the conduit outlet moves ~urther across the discharge
,,
. - , -
,
: -: : ; , .......... .
., , . : : -
2034928
port to progressively decrease the overlap between the conduit
outlet and the discharge port.
Advantageously, biasing means are provided, to bias
the piston towards the closed position. Preferably, the bias
means is a spring having a spring tension selected to maximize
the overlap between the conduit outlet and the discharge port
upon application of a preselected turbo-charger boost pressure
to the piston.
Limit means are advantageously provided to limit
displacement of the piston in the second range of open positions,
thereby limiting the minimum overlap between the conduit outlet
and the discharge port in the second range of open positions.
The limit means may comprise a member threadably fastened through
the cylinder to stop displacement of the piston at a pre-
selected point.
Control means are preferably provided to control
secondary fuel flow from the secondary fuel reservoir through the
fir~t inlet port. The control means may comprise a second
cylinder coupled to the second inlet port, a second piston
elidably displaceable within the second cylinder, in response to
changes in the turbo-charger boost pressure, controllable closure
means for controllably closing the first inlet port, and coupling
means for coupling the second piston to the closure means. An
increase in the turbo-charger boost pressure causes a correspon-
dlng displacement of the second piston, which in turn causes the
coupling means to correspondingly displace the closure means
relative to the first inlet port to increase the open cross-
sectional area of the first inlet port. Similarly, a decrease
in the turbo-charger boost pressure causes a corresponding
displacement of the second piston, which in turn causes the
coupling means to correspondingly displace the closure means
relative to the first inlet port to decrease the open cross-
sectlonal area o~ the ~irst inlet port.
203~2~
Alternatively, the control means may comprise a lever
pivotally coupled between the second piston and the first inlet
port, one end of the lever carrying a seal for sealingly engaging
the first inlet port. In this case, an increase in the turbo-
charger boost pressure causes a corresponding displacement of thesecond piston and the lever, which moves the seal away from the
first inlet port to increase the open cross-sectional area of the
first inlet port. Similarly, a decrease in the turbo-charger
boost pressure causes a corresponding displacement of the second
piston and the lever, which moves the seal toward the first inlet
port to decrease the open cross-sectional area of the first inlet
port.
Brief Description of the Drawinas
Figure 1 is a block diagram of the basic components of
a diesel engine propane injection system incorporating the
invention.
Figures 2a through 2d are cross-sectional illustra-
tions of a secondary fuel modulating valve constructed inaccordance with the preferred embodiment of the invention.
Figure 2a shows the modulating valve's piston in the
closed position, blocking secondary fuel flow through the valve's
~uel discharge port.
Figure 2b shows the modulating valve's piston at the
lower limit of its first range of open positions. Secondary fuel
has just begun to flow through the valve's discharge port at this
point.
Figure 2c shows the modulating valve's piston at the
upper limit of its first range of open positions, which coincides
with the lower limit of its second range of open positions.
Secondary fuel flow through the valve's discharge port is
maximized at this point.
- 5 -
.. . . .
- .
,
.
.. . . .
-` 203~92~
Figure 2d shows the modulating valve's piston at the
upper limit of its second range of open positions. Secondary
fuel flow through the valve's discharge port is reduced at this
point to avoid premature detonation of the secondary fuel.
Detailed Description of the Preferred Embodiment
Figure 1 is a block diagram which illustrates the basic
components of a diesel engine propane injection system incorpor-
ating a secondary fuel modulating valve constructed in accordance
with the preferred embodiment of the invention. A suitable
secondary fuel such as liquid propane is stored in tank l and is
supplied, through electric lock-off device 2, vaporizer/regulator
valve 3 and fuel line 4 to secondary fuel modulating valve 5 in
the form of vapour at a pressure of about .5 to about 3 pounds
per square inch. Diesel engine 10 is equipped with a turbo-
charger 12. Conduit 8 couples turbo-charger 12 to modulating
valve 5, which controllably discharges secondary fuel through
conduit 6 and orifice 7 into air intake pipe ll. Air intake pipe
11 delivers air from the engine's air cleaner (not shown), mixed
with secondary fuel, to turbo-charger 12.
As shown in Figure 2, modulating valve 5 incorporates
a cylinder 20 which contains a piston 22. Vaporized propane is
supplied to cylinder 20 through first inlet port 24. More
particularly, secondary fuel line 4 is threadably coupled to
aperture 26. Vaporized propane flows through fuel line 4 into
region 28, and i8 then controllably admitted into cylinder 20
through first inlet port 24, as hereinafter explained. Conduit
8 is threadably coupled to second inlet port 30 to supply
pressurized air from turbo charger 12 to cylinder 20, against the
base of piston 22. The turbo-charger boost air slidably
displa¢es piston 22 within cylinder 20, controllably opening and
closing discharge port 32 in response to changes in the turbo-
charger boost pressure, as hereinafter explained in greater
detail. Conduit 6 i8 threadably coupled to discharge port 32,
thus coupling cylinder 20 to the secondary fuel inlet of engine
10 ~i.e. orifice 7 and air intake pipe 11).
2034928
As will now be explained, a progressive increase in the
turbo-charger boost pressure slidably displaces piston 22 within
cylinder 20 from a closed position (Figure 2a) in which piston
22 blocks secondary fuel flow from first inlet port 24 to
discharge port 32, through a first range of open positions
(Figures 2b & 2c) in which piston 22 allows progressively
increasing amounts of secondary fuel to flow from first inlet
port 24 to discharge port 32, and through a second range of open
positions (Figures 2c & 2d) in which piston 22 allows progres-
sively decreasing amounts of secondary fuel to flow from first
inlet port 24 to discharge port 32.
A conduit 34 is machined in piston 22 to convey
secondary fuel through piston 22, between inlet 36 and outlet 38
of conduit 34. A recess 40 is cut in piston 22, around conduit
inlet 36. Recess 40 effectively enlarges conduit inlet 36, thus
ensuring that the enlarged conduit inlet overlaps first inlet
port 24 throughout the range of displacement of piston 22 between
its closed position and its first and second ranges of open posi-
tions, thereby facilitating secondary fuel flow from first inlet
port 24 into conduit 34 regardless of the position of piston 22.
An annular recess 42 is cut around the circumference
of piston 22, intersecting conduit outlet 38. Recess 42 remains
beneath discharge port 32 when piston 22 is in its closed
position, thus ensuring that conduit outlet 38 is displaced away
from discharge port 32 when piston 22 is in its closed position,
preventing secondary fuel flow from conduit 34 to discharge port
32 when piston 22 is in its closed position. However, recess 42
effectively enlarges conduit outlet 38, thus ensuring that,
throughout the range of displacement of piston 22 in either of
its firet or second ranges of open positions, the enlarged
conduit outlet overlaps discharge port 32, thereby facilitating
secondary fuel flow through conduit 36 to discharge port 32
throughout displacement o~ piston 22 in its first or second
ranges of open positions.
. .
.
,.~
2~34~
During slidable displacement of piston 22 through its
first range of open positions, conduit outlet 38 moves across
discharge port 32 from the lower limit depicted in Figure 2b to
5the upper limit depicted in Figure 2c, progressively increasing
the overlap between conduit outlet 38 and discharge port 32, thus
progressively increasing the quantity of secondary fuel passed
through discharge port 32 to engine 10. During slidable
displacement of piston 22 through its second range of open posi-
10tions, conduit outlet 38 moves further across discharge port 32,
from the lower limit depicted in Figure 2c to the upper limit
depicted in Figure 2d, progressively decreasing the overlap
between conduit outlet 38 and discharge port 32, thus progress-
ively decreasing the quantity of secondary fuel passed through
15discharge port 32 to engine 10.
A "biasing means" namely, spring 44, is provided for
biasing piston 22 towards the closed position. A vent hole 45
is drilled through the upper end of the casing enclosing cylinder
2020 to allow piston 22 to move without regard to air or gases
trapped between the top of piston 22 and the inner walls of
cylinder 20 above piston 22. The tension of spring 44 is
selected to maximize the overlap between conduit outlet 38 and
discharge port 32 upon application of a preselected turbo-
25charger boost pressure to piston 22. That is, the spring tension
i5 adjusted to maximize secondary fuel flow to engine 10 when
turbo-charger 12 is generating a particular boost pressure.
Typically, maximum secondary fuel flow will be desired when
engine 10 is operating in its mid horsepower or cruise range.
A "limit means", namely threaded member 46, is provided
for setting the upper displacement limit of piston 22 in its
second range of open positions. Member 46 is threadably fastened
through the top o~ cylinder 20 to bear against the top of piston
3522 when piston 22 i5 at the upper limit o~ its second range of
open positions. Member 46 thus stops upward displacement of
piston 22 at a selected point which may be defined by threadably
: - ': ' .
2~3~92~
advancing or retracting member 46 within cylinder 20. Member 46
accordingly prevents upward displacement of piston 22 from
cutting off secondary fuel flow entirely, which would occur if
piston 22 were displaced upwardly to the point that conduit
outlet ~8 no longer overlapped discharge port 32. More particu-
larly, member 46 limits the minimum overlap between conduit
outlet 38 and discharge port 32 at the upper and of the second
range of open positions. Lock nut 48 holds member 46 in place
once it has been adjusted.
A suitable "control means" is provided for controlling
secondary fuel flow from region 28 through first inlet port 24.
In the preferred embodiment, the control means incorporates a
second cylinder 50 which is coupled to second inlet port 30 via
passage 52. A second piston 54 is mounted for slidable displace-
ment within second cylinder 50, in response to changes in the
turbo-charger boost pressure. A "controllable closure means",
namely seal 56 mounted on the end of lever 58, is provided for
controllably closing first inlet port 24 as hereinafter de-
scribed. Lever 58, which is pivotally connected to the body of
valve 5 and to the rod of second piston 54, serves as a "coupling
means" for coupling second piston 54 to seal 56.
If no pressurized turbo-charger boost air is supplied
through passage 52, spring 60 biases second piston 54 toward the
left, as viewed in Figure 2, which in turn forces the seal-
carrying portion of lever 58 to the right, thus sealing first
inlet port 24 and preventing secondary fuel flow from region 28
into conduit 34. An increase in the turbo-charger boost pressure
causes corresponding displacement of second piston 54 (to the
right, as viewed in Figure 2), overcoming the biasing action of
spring 60, and causing lever 58 to correspondingly displace seal
56 away from ~irst inlet port 24 (to the left, as viewed in
Figure 2), increasing the open cross-sectional area of first
inlet port 24 and thus increasing the quantity of secondary fuel
passing from region 28 into conduit 34. A decrease in the turbo-
charger boost pressure allows spring 60 to corresponding
. -.
. .
- '~ . . .
~'' ' ~ .' .
- 203~92~
displace second piston 54 to the left, causing lever 58 to
correspondingly displace seal 56 towards first inlet port 24,
decreasing the open cross-sectional area of first inlet port 24
and thus decreasing the quantity of secondary fuel passing from
region 28 into conduit 34.
In operation, when turbo charger 12 is not supplying
pressurized boost air to engine 10 or to modulating valve 5,
spring 44 holds piston 22 in its closed position and spring 60
biases second piston 54 and lever 58 to force seal 56 against
first inlet aperture 24 (Figure 2a). Secondary fuel is thus
prevented from entering conduit 34 and no secondary fuel flows
to engine 10 through discharge port 32.
When turbo charger 12 begins to supply pressurized
boost air to engine 10 and to modulating valve 5, piston 22 is
displaced upwardly, overcoming the biasing action of spring 44
and moving piston 22 into the lower portion of its first range
of operating positions (Figure 2b). At the same time, second
piston 54 overcomes the biasing action of spring 60, pivoting
lever 58 to move seal 56 slightly away from first inlet aperture
24. A small amount of secondary fuel is thus allowed to enter
conduit 34 and flow to engine 10 through discharge port 32. As
the turbo-charger boost pressure increases, piston 22 moves
upwardly through its first range of operating positions; second
piston 54 and lever 58 move seal 56 further away from first inlet
port 24; and progressively larger amounts of secondary fuel enter
conduit 34 and flow to engine 10 through discharge port 32.
When engine 10 reaches its mid horsepower or cruise
operating range, turbo charger 12 supplies sufficient pressurized
boost air to engine 10 and to modulating valve 5, to displace
piston 22 upwardly into the upper portion of its first range of
operating positions (Figure 2c). Second piston 54 concurrently
moves to pivot lever 58 and move seal 56 still further away from
first inlet aperture 24. A still larger amount of secondary fuel
is thus allowed to enter conduit 34 and flow to engine 10 through
-- 10 --
,
.
203~928
discharge port 32. It will be noted that the maximum amount of
secondary fuel is supplied to engine 10 through discharge port
32 at this point, because outlet 38 entirely overlaps discharge
outlet 38 and because second piston 54 has pivoted lever 58 to
the maximum possible extent, thus moving seal 56 into its
furthest position away from first inlet aperture 24 to maximize
secondary fuel flow from region 28 into conduit 34.
When engine 10 operates above its mid horsepower or
cruise range, turbo charger 12 supplies sufficient pressurized
boost air to engine 10 and to modulating valve 5, to displace
piston 22 upwardly into its second range of operating positions.
As described above, second piston 54 has already displaced lever
58 and seal 56 to the maximum possible extent, thus maximizing
secondary fuel flow from region 28 into conduit 34. However,
when piston 22 is in its second range of operating positions, the
decreased overlap between outlet 38 and discharge outlet 32
reduces the flow of secondary fuel to engine 10 through discharge
port 32, thus preventing premature detonation of the secondary
fuel.
If engine 10 is operated to cause turbo-charger 12 to
supply sufficient pressurized boost air to engine 10 and to
modulating valve 5, to displace piston 22 upwardly to contact
member 46 (Figure 2d), then the overlap between outlet 38 and
discharge outlet 32 is held to a selected minimum (as opposed to
having no overlap) thus allowing a further reduced amount of
secondary fuel (as opposed to no secondary fuel) to flow to
engine 10 through discharge port 32.
As will be apparent to those skilled in the art in the
light of the ~oregoing disclosure, many alterations and modifica-
tlons are possible in the practice o~ this invention without
departing ~rom the spirit or scope thereof. For example, the
invention may be adapted for use with engines having different
horespower ratings by inserting orifices of varying diameters
into aperture 26. Accordingly, the scope of the invention is to
-- 11 --
- 2034928
be construed in accordance with the substance defined by the
following claims.
- 12 -
,
,
. . .
,......
