Title: System and method of optimizing fuel injection timing in a locomotive engine
Abstract: Systems and methods for reducing engine emissions in a locomotive are presented. In an embodiment, a fuel injector or a fuel injection pump of a fuel injection mechanism includes a plunger with an upper helix whose angle changes between points on the plunger that correspond to an idle throttle position and a full throttle position. As such, injection timing is optimized, and engine emissions are reduced.
Patent Number: 6,945,233 Issued on 09/20/2005 to Stewart, et al.
| Inventors:
|
Stewart; Ted E. (Jacksonville, FL);
Miller; David P. (Ponte Vedra Beach, FL)
|
| Assignee:
|
CSXT Intellectual Properties Corporation (Jacksonville, FL)
|
| Appl. No.:
|
702050 |
| Filed:
|
November 6, 2003 |
| Current U.S. Class: |
123/500; 123/478 |
| Intern'l Class: |
F02M 037/04 |
| Field of Search: |
123/500,501,503,504,495,478
417/494,499,289
|
References Cited [Referenced By]
U.S. Patent Documents
| 3566849 | Mar., 1971 | Frick.
| |
| 3567346 | Mar., 1971 | Mekkes et al.
| |
| 4327694 | May., 1982 | Henson et al.
| |
| 4838232 | Jun., 1989 | Wich.
| |
| 4881506 | Nov., 1989 | Hoecker.
| |
| 4886640 | Dec., 1989 | Garner, Jr. et al.
| |
| 5033442 | Jul., 1991 | Perr et al.
| |
| 5048480 | Sep., 1991 | Price.
| |
| 5097812 | Mar., 1992 | Augustin.
| |
| 5409165 | Apr., 1995 | Carroll, III et al.
| |
| 5685273 | Nov., 1997 | Johnson et al.
| |
| 6009850 | Jan., 2000 | DeLuca.
| |
| 6305358 | Oct., 2001 | Lukich.
| |
| 6321723 | Nov., 2001 | Merkle et al.
| |
| Foreign Patent Documents |
| 723982 | Feb., 1955 | GB.
| |
| 1 431 747 | Apr., 1976 | GB.
| |
| 62-17364 | Jan., 1987 | JP.
| |
Other References
International Search Report for Application No. PCT/US03/40690, dated Jun. 14, 2004.
Engine Maintenance Manuel, Fuel System, Section 11, pp. 11-1-11.11.
GE Instructions on Large Bendix Fuel-Oil Injection Pump GE Parts 132X1254-1,
132X1535 and 132X1715, pp. 1-16 (Feb. 1991).
Paul G. Burman and Frank Deluca, "Fuel Injection and Controls for Internal Combustion
Engines," Simmons-Boardman Publishing Corporation, pp. 69 and 165, (1962).
Exhibit #1 as Described in Attached IDS.
|
Primary Examiner: Gimie; Mahmoud
Attorney, Agent or Firm: McGuireWoods LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. patent application Ser. No.
10/325,852, filed on Dec. 23, 2002, now issued as U.S. Pat. No. 6,799,561, the
entire contents of which are incorporated by reference.
Claims
1. A method for manufacturing an emissions-efficient plunger for a fuel injection
mechanism for a combustion engine, comprising:
obtaining emissions data for said combustion engine at different throttle positions
while using an injection mechanism with a reference plunger having a reference
helix, said reference helix having a reference helix angle, said reference helix
angle defining an injection timing;
determining, based on said emissions data, optimal helix angles at least at a
first and a second throttle position within said throttle positions, said optimal
helix angle at said first throttle position being different from said optimal helix
angle at said second throttle position; and
forming an optimal plunger that includes said optimal helix angles.
2. A method according to claim 1, wherein said first throttle position is at
a lower throttle position than said second throttle position, and wherein said
forming comprises altering the optimal helix angle at said lower throttle position
so that the injection timing is retarded in comparison with that for said reference helix.
3. A fuel injector for an engine fuel system, said engine fuel system having
a plurality of throttle positions, each of said throttle positions having corresponding
emissions characteristics, said fuel injector comprising:
an injector body;
a plunger within said body, said plunger having an upper helix ridge and a lower
helix ridge, the helix ridges defining a channel and determining opening and closing
of fuel ports of the injector;
the upper helix ridge having a ridge portion sloping from a first point on the
plunger surface towards a second point on the plunger surface, the first point
being associated with an idle throttle position, the second point being associated
with a full throttle position,
said ridge portion including at least two segmented portions between the first
and second points, the at least two segmented portions corresponding to associated
throttle positions between said idle and full throttle positions, said at least
two segmented portions having unequal associated helix angles, said unequal helix
angles of the at least two segmented portions being angled in accordance with emissions
characteristics of the engine at the associated throttle positions.
4. A fuel injector for an internal combustion engine, comprising:
a housing defining a cylindrical chamber having a longitudinal axis and axially-spaced
first and second fuel ports communicating therewith each of which is communicated
with a source of fuel under low pressure;
a plunger mounted in said chamber for reciprocating axial movement through successive
operative cycles, each including a pump stroke and a return stroke in timed relation
to the repetitive cycles of said engine,
a fuel injection nozzle constructed and arranged to inject a fuel charge into
an engine cylinder during each pump stroke of said plunger;
said fuel injection nozzle being communicated with a pump portion of said cylindrical
chamber defined by a free end of said plunger,
said plunger having an annular axially extending peripheral chamber defined by
first and second annular ridges and openings communicating said peripheral chamber
with the pump portion of said cylindrical chamber, the arrangement being such that
fuel within the pump portion of said cylindrical chamber communicating with said
nozzle will be pressurized to effect injection only during each reciprocating cycle
of said plunger when said first and second fuel ports are closed by said plunger
and the end portion of said plunger is moving through the pump stroke thereof,
said plunger being mounted for controlled rotational movement within said cylindrical
chamber in accordance with a desired operating energy level of said engine between
a notched range from idle to full throttle,
the axial position of said second ridge spaced apart from said second fuel port
progressively increasing for each notch position from idle to full throttle at
the time of the closing of said first fuel port thereby increasing the amount of
fuel injected and energy level of the engine;
the axial position of said first ridge on said plunger when moved into closed
relation to said first fuel port during each pump stroke at any particular notch
determining the commencement of fuel injection in relation to the top dead center
position of a piston of the engine cylinder within which injection occurs,
the axial position of said first ridge through the notched range being divided
into a plurality of sections including a low section relating to the lower branches
having a configuration which balances fuel efficiency and NO
x emissions
in favor of low NO
x emissions and a high section relating to the higher
notches having a configuration which balances fuel efficiency and NO
x emissions
in favor of high fuel efficiency.
Description
BACKGROUND
1. Field
Embodiments of the present invention relate to systems and methods for
reducing engine emissions in a diesel engine, such as a locomotive diesel engine.
2. Description of Related Art
Locomotive manufacturers and remanufacturers supply locomotive diesel
engines to the rail transportation industry, which includes establishments furnishing
transportation by line-haul railroad, as well as switching and terminal establishments.
In recent years, Environmental Protection Agency (EPA) emissions standards for
locomotive diesel engines have become increasingly demanding. In particular, standards
enacted under the Federal Clean Air Act of 1998 require significant reductions
of individual emission compounds, including oxides of nitrogen (NO
x)
NO
x gases, which include the compounds nitrogen oxide (NO) and nitrogen
dioxide (NO
2), are a major component of smog and acid rain.
Exhaust from a locomotive diesel engine includes various gaseous-constituents,
such as NO
x, carbon monoxide (CO), carbon dioxide (CO
2),
and hydrocarbons (HC), as well as particulate matter. Severe environmental and
economic consequences may ensue if locomotive engine emissions do not comply with
applicable EPA standards.
U.S. Pat. No. 6,470,844 to Biess et al. discloses a system and method that automatically
shuts down a primary engine of a locomotive after the primary engine has been idling
for a predetermined period of time. A small secondary engine is started to perform
useful functions on behalf of the shut-down primary engine. Because it reduces
locomotive idle time, this approach reduces engine emissions. However, engine emissions
remain a cause for concern when the primary engine is running.
Therefore, what is needed is a system and method for reducing engine emissions
in a locomotive.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partially broken away cross-sectional view of a fuel injector according
to an embodiment of the present invention.
FIGS. 1B, 1C, 1D, 1E, and 1F illustrate a complete
stroke of a fuel injector plunger for a switcher-type engine.
FIGS. 1G, 1H, and 1I illustrate plunger rotation at an idle throttle
position, a half throttle position, and a full throttle position for a switcher-type engine.
FIGS. 2A, 2B, and 2C illustrate a fuel injector plunger in various
exemplary degrees of rotation according to an embodiment of the present invention.
FIGS. 3A, 3B, and 3C illustrate exemplary planar views of an
axial portion of a plunger according to embodiments of the present invention.
FIG. 4 illustrates a selected portion of a plunger according to an embodiment
of the present invention.
FIG. 5 illustrates a selected portion of a plunger according to an embodiment
of the present invention.
FIGS. 6A and 6B illustrate exemplary plungers according to embodiments of the
present invention.
FIG. 7 illustrates a process according to an embodiment of the present invention.
FIG. 8 is a graph illustrating NOx emissions profile in gms/hr for a switcher-type
locomotive engine employing a prior art unit injector.
FIG. 9 is another representation of the graph shown in FIG. 8.
FIG. 10 is a graph illustrating an experiment that compares a switcher helix
(switcher helix 1) and a standard helix for a switcher engine that had the
timing thereof retarded for notches N5 down through the idle positions.
FIG. 11 is a graph illustrating NOx emissions profile for the experiment shown
in FIG. 10.
FIG. 12 is a graph illustrating an experiment that compares another switcher
helix (switcher helix 2) and a standard helix for a switcher engine that
had the timing thereof retarded for notches N6 down through the idle positions.
FIG. 13 is a graph illustrating NOx emissions profile for the experiment shown
in FIG. 12.
FIG. 14 is a graph illustrating an experiment in which a switcher helix (switcher
helix 2) was uniformly retarded by changing the fly-wheel pointer position.
FIG. 15 is a graph illustrating NOx emissions profile for the experiment shown
in FIG. 14.
FIG. 16 is a graph illustrating NOx emissions profile in gms/hr for a line-haul
locomotive engine employing a prior art unit injector.
FIG. 17 is a graph illustrating helix performance for a line-haul locomotive engine.
FIG. 18 is a graph illustrating NOx emissions profile in gms/hr for a line-haul
locomotive engine.
DETAILED DESCRIPTION
Systems and methods for an engine, such as a diesel engine in a locomotive,
are presented. In various embodiments, a fuel injection mechanism includes a fuel
injector (unit injector) or fuel injection pump. The fuel injector or fuel injection
pump includes a plunger with an upper helix whose angle changes between points
on the plunger that correspond to an idle throttle position and a full throttle
position. As such, injection timing is optimized, and engine emissions are reduced.
In other embodiments, the fuel injection mechanism employs a nozzle tip formed
of a chromium hot-work steel. Accordingly, reductions in engine emissions may be
sustained over long periods of time.
FIG. 1 is a partially broken away cross-sectional view of a fuel injector
100
according to an embodiment of the present invention. In various embodiments, injector
100 may be a unit injector for a fuel system of an engine, such as a diesel
engine manufactured by GM EMD (General Motors Electro-motive Division). EMD-type
engines employ mechanical control of injection timing and may be implemented effectively
in various settings, such as, for example, locomotive (line-haul, switcher, passenger,
or road), marine propulsion, offshore- and land-based oil well drilling rigs, stationary
electric power generation, nuclear power generating plants, and pipeline and dredge
pump applications. In one embodiment, injector
100 is implemented in an
EMD 567, 645, or 710 series engine.
For exemplary purposes, drawings herein depict a unit injector and associated
plungers for EMD-type engines. However, it is to be understood that teachings herein
may be similarly applied to engines that employ fuel injection pumps, such as diesel
engines manufactured by GE Transportation Systems, including the GE
7FDL
and
7HDL engines, and diesel engines manufactured by ALCO. In such engines,
each fuel injection pump includes a plunger that supplies fuel to an injector via
a high pressure fuel line. Helices of such plungers may be modified consistent
with principles presented herein. A nozzle tip as described herein also may be utilized.
Fuel injector
100 includes a body
150, a plunger
110, a
housing nut
115, a bushing
120, a nozzle tip
130, and spray
holes
140. Other components of injector
100 are not shown in FIG.
1 and are known in the art. Injector
100 is located and seated in
a hole of a cylinder head of an engine fuel system.
In an embodiment, nozzle tip
130 of injector
100 may be formed
of
a chromium hot-work steel. The steel may be substantially through-hardened, and
may conform, for example, to the H11 specification of the American Iron and Steel
Institute (AISI) or the T20811 specification of the Unified Numbering System (UNS).
As such, nozzle tip
130 may create effective atomization for longer periods
of time, without deterioration of spray holes
140. Accordingly, injector
100 may have an extended life of use in an injection system.
Plunger
110 slidably fits within bushing
120. Bushing
120
includes an upper port
160 and a lower port
170. Upper port
160
and lower port
170 are pathways for fuel. The amount of fuel injected into
a cylinder depends on the extent to which the ports are closed, as described below.
The specific form of plunger
110, including diameter, roundness, and straightness
thereof, may vary depending on the implementation. Diameters of plungers may vary
depending on the amount of fuel that is needed for injection. In an exemplary implementation,
plunger
110 may have a diameter of between about 8 and 22 mm. Materials
for plunger
110 may be chosen to prevent plunger
110 from substantially
wearing down over time, and thus to prevent performance of plunger
110 from
being degraded. Plunger
110 may be formed, for example, of bearing quality
or high alloy steel, such as a chromium/nickel alloy. For example, the steel may
conform to the 51501 or 52100 specifications of the Society of Automotive Engineers
(SAE). Use of appropriate metals may ensure that helices described below maintain
their shape for longer periods of time.
Plunger
110 includes an upper helix
180 and a lower helix
190.
Upper helix
180 and lower helix
190 determine the opening and closing
of upper port
160 and lower port
170 of bushing
120. Upper
helix
180 determines when injection starts, and; lower helix
190
determines when injection ends. As such, the helices determine the volume of fuel
that is injected.
For example, FIGS. 1B-1F illustrate a complete stroke of the plunger
110
with respect to bushing
120 for a switcher-type engine. At the top of the
stroke, the upper and lower ports
160,
170 open to admit fuel as
shown in FIG.
1B. As plunger stroke begins, fuel escapes through the upper
port
160 as shown in FIG.
1C. As shown in FIG. 1D, as both the upper
and lower ports
160,
170 are closed by the plunger
110, the
high pressure created forces fuel into the cylinder. Injection ends as the lower
port
170 opens to allow fuel below the plunger
110 to escape, as
shown in FIG.
1E. FIG. 1F illustrates the bottom of the stroke at which
the lower port
170 is fully open.
Upper helix
180 and lower helix
190 include ridges that define
a shallow fuel channel
195 encircling an axial portion of plunger
110.
Upper helix
180 and lower helix
190 may be formed in various ways.
In some embodiments, upper helix
180 and/or lower helix
190 are formed
as a part of a machining operation that produces plunger
110. In other embodiments,
an existing plunger is modified by a selective machining operation to produce upper
helix
180 and/or lower helix
190.
In particular, upper helix
180 includes a ridge portion that slopes from
a first point on the plunger surface towards a second point on the plunger surface.
Sloping may involve one or more instances of ascending, descending, or neither
ascending nor descending, between the first and second points. In some embodiments,
the first point may be associated with an idle throttle position of injector
100,
and the second point may be associated with a full throttle position of injector
100. Changes in slope of the ridge portion imply that the ridge portion
may include multiple segments of predetermined length and/or height. In some embodiments,
changes in slope may occur gradually such that one or more portions of the ridge
portion are curved in perspective; for such embodiments, segments of the ridge
portion may be extremely short. In other embodiments, changes in slope may be abrupt
such that the ridge portion appears to have one or more clearly distinct portions.
Plunger
110 may be given a constant stroke reciprocating motion by
an injector cam acting through a rocker arm and plunger follower (not shown). Timing
of the injection period during the plunger stroke may be set by an adjusting screw
at the end of the rocker arm.
Plunger
110 may be rotated via a rack and gear (not shown), as known
in the art. Rotation of plunger
110 regulates the time that upper port
160
and lower port
170 may open and close during the downward stroke, thus determining
the quantity of fuel injected into the cylinder. As plunger
110 is rotated
from idle throttle position to full throttle position, the pumping part of the
stroke is lengthened, injection is started earlier, and more fuel is injected.
For example, FIGS. 1G-1I illustrate plunger rotation at an idle position, a half
throttle position (half load), and a full throttle position (full load) for a switcher-type
engine. As illustrated, the effective stroke of the plunger is lengthened from
idle to full load.
Proper atomization of fuel is accomplished by the high pressure created during
the downward stroke of plunger
110, which forces fuel past a needle valve
(not shown), causing the needle valve to lift, thus forcing fuel out through spray
holes
140 in nozzle tip
130 of injector
100.
A "helix angle" of a helix is the angle between a tangent to the helix and a
line
perpendicular to the internal axis of the helix and intersecting the tangent point.
Changes in helix angle generally correspond to changes in the observed slope of
a helix of a plunger. That is, when the helix angle changes, one may observe a
change in slope (also called "lead") of the helix. For embodiments herein, for
ease of explanation, a plunger is described as having one helix with multiple helix
angles (i.e., multiple slopes or leads). However, it is to be understood that the
upper helix of a plunger herein actually has one or more portions of respective
helices that have associated helix angles.
According to various embodiments of the present invention, plunger
110
has an upper helix whose helix angle changes at least once from a first point on
plunger
110 which corresponds to an idle throttle position to a second point
on plunger
110 which corresponds to a full throttle position. As such, injection
timing of injector
100 may be optimized as plunger
110 is rotated
within bushing
120.
In some embodiments, the helix angle changes such as to advance injection timing.
Alternatively or additionally, the helix angle changes such as to retard, or neither
advance nor retard, injection timing. By optimizing injection timing, emissions
and combustion efficiency may be improved for an engine.
In an EMD-type unit injector, degrees of rotation of plunger
110 within
bushing
120 may be associated with predetermined discrete throttle positions.
Table 1 list exemplary associations that be implemented in a diesel-electric locomotive.
Plunger
110 in Table 1 diameter ranging from about 0.420 to 0.422 inches,
for example.
| TABLE 1 |
| |
| Degrees of Rotation and Throttle Positions |
| Degree of Rotation of |
|
| Plunger 110 |
Throttle Position |
| |
| 0° |
Idle |
| 25° |
Notch 1 |
| 50° |
Notch 2 |
| 75° |
Notch 3 |
| 100° |
Notch 4 |
| 125° |
Notch 5 |
| 150° |
Notch 6 |
| 175° |
Notch 7 |
| 200° |
Notch 8 |
| |
As Table 1 illustrates, adjacent throttle positions are uniformly separated by
25°. For instance, when a locomotive engineer moves a throttle selector from
notch
4 to notch
5, the plunger
110 is rotated 25° within
bushing
120. Similarly, when the throttle selector is moved from notch
5
to notch
6, plunger
110 is rotated another 25°.
It is to be appreciated that Table 1 represents an exemplary division into discrete
throttle position, and that 25° is an exemplary division. In other engine
implementations, there may be more or fewer discrete throttle positions, and/or
the division between discrete throttle positions need not be uniform. Moreover,
in some embodiments, such as, for example, marine and stationary power embodiments,
there may not be discrete throttle positions. For example, the operating of a lever
may gradually and continuously increase or decrease the throttle, i.e., rotate
a plunger within a bushing.
According to some embodiments of the present invention, helix angles on
a plunger, and point(s) on the plunger at which transitions in helix angle occur
are selected based on emissions data and/or empirical engine performance testing.
For example, weighted emissions duty cycles or other relevant data may be studied.
If, for example, it is demonstrated that emission levels are problematic for an
engine running in idle, notch
1, and notch
2, then the upper helix
of a plunger may have different helix angles at points on the plunger, such as
points corresponding to those throttle settings, in order to retard or advance
injection timing. The form of lower helix
190 also may be varied, which
may impact upon the injection process.
Moreover, the effects of varying helix angles, which may be engine-and
implementation-specific, may be studied to determine optimal helix angles and transition
points on a plunger for throttle settings ranging from full to idle. Exemplary
criteria for evaluating implementations may include emissions levels and combustion
efficiency. In various embodiments, helix angles and transition points may be chosen
to ensure compliance with regulatory emissions limits, while minimizing fuel penalties
associated with compliance.
FIGS. 2A,
2B, and
2C illustrate plunger
110 in various
degrees of rotation according to an embodiment of the present invention. Upper
helix
180 generally slopes from a point
210 corresponding to an idle
throttle position (FIG. 2A) to a point
240 corresponding to a notch
8
throttle position (FIG.
2C).
More particularly, FIG. 2A shows that upper helix
180 generally slopes
downward from point
210. FIG. 2B shows a change in slope (helix angle) of
upper helix
180 at a point
220 corresponding to a notch
5
throttle position, and another change in slope (helix angle) at a point
230
corresponding to a notch
6 throttle position. Finally, FIG. 2C shows upper
helix
180 slope to a point
240 corresponding to a notch
8
throttle position.
It is to be appreciated that FIGS. 2A,
2B, and
2C are merely illustrative
of an exemplary plunger
110 according to an embodiment of the present invention.
The precise form of upper helix
180, including the number of transitions
in slope (helix angle), and the points on plunger
110 at which transitions
occur, as well as the angular measurements of each helix angle, may vary depending
on the implementation.
FIGS. 3A,
3B, and
3C illustrate planar views of an axial portion
of plunger
110 between lines B and B′ of FIG. 2A according to embodiments
of the present invention. Upper and lower helices are shown in each figure. Parallel
lines identify points along the upper helix that correspond to particular throttle settings.
FIG. 3A shows a reference upper helix
310 and a reference lower helix
320. Reference upper helix
310 has a helix angle that does not substantially
change from idle (0°) to notch
8 (200°). As seen in FIG. 3A, the
slope of reference upper helix
310 is substantially constant from idle to
notch
8.
FIG. 3B shows an exemplary upper helix
330 and lower helix
340
according to an embodiment of the present invention. For purposes of comparison,
reference upper helix
310 and reference lower helix
320 of FIG. 3A
are shown in dashed lines in FIG.
3B. Portions of upper helix
330
that coincide with reference upper helix
310 are indicated with x's. Coinciding
portions of lower helix
340 and reference lower helix
320 are similarly indicated.
Upper helix
330 has associated helix angles that change from idle to
notch
8. Specifically, from idle to notch
6, upper helix
330
has an associated slope (helix angle). From notch
6 to notch
8, upper
helix
330 has a different slope (helix angle).
More particularly, from idle to notch
6, the helix angle of upper helix
330 is greater than that of reference upper helix
310. That is, between
the parallel lines corresponding to idle and notch
6 in FIG. 3B, the slope
of upper helix
330 (with respect to a line perpendicular to the internal
axis of the helix) is greater than the slope of reference upper helix
310.
At idle, upper helix
330 is displaced towards a top of plunger
110
(away from reference lower helix
320) as compared with reference upper helix
310. From notches
6 to
8, the helix angle of upper helix
330
is substantially the same as that of reference upper helix
310. That is,
between the parallel lines corresponding to notch
6 and notch
8,
the slope of upper helix
330 and that of reference upper helix
310
are substantially the same, and the respective helices are coincident.
Accordingly, the exemplary design of upper helix
330 of FIG.
3B retards injection timing for idle to notch
6 relative to a design incorporating
reference upper helix
310. Such retarding may improve emissions for an engine
whose fuel injection system includes plunger
110.
FIG. 3C shows an exemplary upper helix
350 and lower helix
360
according to an embodiment of the present invention. For purposes of comparison,
reference upper helix
310 and reference lower helix
320 of FIG. 3A
are shown in dashed lines in FIG.
3C. Portions of upper helix
350
that coincide with reference upper helix
310 are indicated with x's. Coinciding
portions of lower helix
360 and reference lower helix
320 are similarly indicated.
Upper helix
350 has associated helix angles that change from idle to
notch
8. Specifically, from idle to notch
5, upper helix
350
has an associated slope (helix angle). From notch
5 to notch
7, upper
helix
350 has a different slope (helix angle). From notch
7 to notch
8, upper helix
350 has yet a different slope (helix angle).
More particularly, from idle to notch
5, upper helix
350 is displaced
towards a top of plunger
110 (away from reference lower helix
320)
as compared with reference upper helix
310. Between the parallel lines corresponding
to idle and notch
5 in FIG. 3C, the slope of upper helix
350 is substantially
the same as the slope of reference upper helix
310. From notches
5
to
7, the helix angle of upper helix
330 is greater than that of
reference upper helix
310. That is, between the parallel lines corresponding
to notch
5 and notch
7, the slope of upper helix
350 is greater
than that of reference upper helix
310.
From notches
7 to
8, the helix angle of upper helix
330
is substantially the same as that of reference upper helix
310. That is,
between the parallel lines corresponding to notch
7 and notch
8,
the slope of upper helix
350 and that of reference upper helix
310
are substantially the same, and the respective helices are coincident.
Accordingly, the exemplary design of upper helix
350 of FIG.
3C retards injection timing for idle to notch
7 relative to a design incorporating
reference upper helix
310. Such retarding may improve emissions for an engine
whose fuel injection system includes plunger
110.
FIG. 4 illustrates a selected portion of plunger
110 according to another
embodiment of the present invention. The portion shown corresponds to portion A
identified in FIG.
1. Upper helix
480 is generally shown in FIG.
4. Parallel lines identify points a long upper helix
480 that correspond
to particular throttle settings. Although only portions of upper helix
480
corresponding to idle, notch
1, notch
2, and notch
3 throttle
settings are shown, teachings herein may be applied for other throttle settings.
A reference helix
401 is shown for purposes of comparison. Reference helix
401 has an associated helix angle (slope) that does not change between an
idle and notch
3 throttle setting.
Exemplary helices
420 and
410 are also shown in FIG.
4.
Helix
420 has a helix angle less than that of reference helix
401.
As such, helix
420 may retard injection timing for idle, notch
1,
notch
2, and notch
3 settings as compared to a plunger that includes
reference helix
401. Alternatively, helix
410 has a helix angle greater
than that of reference helix
401. As such, helix
410 may advance
injection timing for idle, notch
1, notch
2, and notch
3 settings
as compared to a plunger that includes reference helix
401.
FIG. 5 illustrates a selected portion of plunger
110 according to another
embodiment of the present invention. The portion shown corresponds to portion A
identified in FIG.
1. Upper helix
580 is shown in FIG.
5.
Parallel lines identify points along upper helix
580 that correspond to
particular throttle settings. Although only portions of upper helix
580
corresponding to idle, notch
1, notch
2, and notch
3 throttle
settings are shown, teachings herein may be applied for other throttle settings.
Upper helix
580 has three associated helix angles (slopes) between idle
and notch
3 settings. In particular, upper helix
580 has a first
helix angle (slope) between the idle and notch
1 positions. At notch
1,
the helix angle increases—the illustrated slope becomes steeper—and
injection timing is thus advanced. At notch
2, the helix angle decreases—the
illustrated slope becomes less steep—and injection timing is thus retarded.
At notch
3, the helix angle conforms to a helix angle of a reference helix
(not shown), and timing is neither advanced nor retarded relative to the reference helix.
In various engines, helix timing changes may be complementary to flywheel timing
changes. Accordingly, in some embodiments, both the design of an upper helix and
flywheel timing adjustments may be employed to optimize injection timing. In an
exemplary embodiment, helix angles for upper helix
580 of FIG. 5 may be
chosen such that, exclusive of flywheel timing adjustments, injection timing is
altered by about -2° relative to a reference helix (not shown) at notch
1;
+2° at notch
2; and 0° at notch
3. Further optimization
of injection timing may be achieved by adjusting flywheel timing.
In an embodiment similar to FIG. 3B above, upper helix
330 may be modified
such that, (1) from idle to notch
5, the helix angle of upper helix
330
is greater than that of reference upper helix
310, and at idle, upper helix
330 is displaced towards a top of plunger
110; and (2) from notches
5 to
8, the helix angle of upper helix
330 is substantially
the same as that of reference upper helix
310, and those helices are coincident.
Exemplary injection timing for such a modified injector is shown in Table 2. For
purposes of comparison, timing values for an injector with reference upper helix
310 are also shown.
| TABLE 2 |
| |
| Exemplary Injection Timings |
| |
|
Injection |
|
|
| |
|
Timing of |
| |
|
Reference |
Injection |
| |
|
Injector |
Timing of |
| |
|
with |
Injector with |
| |
|
Reference |
Upper Helix |
| |
Throttle |
Upper Helix |
330 (as |
| |
Position |
310 |
modified) |
Difference |
| |
|
| |
Notch 8 |
19° BTDC |
19° BTDC |
0° |
| |
|
(Before Top |
| |
|
Dead |
| |
|
Center) |
| |
Notch 7 |
17° BTDC |
17° BTDC |
0° |
| |
Notch 6 |
15° BTDC |
15° BTDC |
0° |
| |
Notch 5 |
14° BTDC |
13° BTDC |
-1° |
| |
Notch 4 |
13° BTDC |
11° BTDC |
-2° |
| |
Notch 3 |
9° BTDC |
6.5° BTDC |
-2.5° |
| |
Notch 2 |
7° BTDC |
4.5° BTDC |
-2.5° |
| |
Notch 1 |
5° BTDC |
1.5° BTDC |
-3.5° |
| |
Idle |
4° BTDC |
0.5° ATDC |
-4.5° |
| |
|
|
(After Top |
| |
|
|
Dead Center) |
| |
|
FIG. 6A illustrates a plunger
110 with an upper helix
610 according
to an embodiment of the present invention. Upper helix
610 may optimize
injection timing for an engine that includes plunger
110. As shown, upper
helix
610 somewhat resembles a staircase. The specific form of upper helix
610 may depend on emissions data and/or empirical engine performance testing,
as described above. In some embodiments, transitions in steps may be related to
transitions in discrete throttle settings. For instance, for certain embodiments,
the width of certain steps may span about 25° of the circumference of plunger
110. Height of the various steps may vary.
In other embodiments, it may be desirable to optimize injection timing at higher
throttle settings. For example, in a line-haul locomotive, which travels at high
speeds much of the time, much of the EPA weighted emissions duty cycle is associated
with high notches. Accordingly, for engines in such locomotives and engines in
other analogous contexts, the upper helix of a plunger may be modified, for example,
such that injection timing is optimized for high notches. FIG. 6B illustrates an
exemplary embodiment of a plunger
110 that includes an upper helix
650
and a reference helix
670. Upper helix
650 may reduce emissions for
higher notches as compared with reference helix
670. In another exemplary
embodiment (not shown), the helix angle of an upper helix may not substantially
change or may change only slightly (resembling a straight line, for example) at
lower notches, and then may change more substantially at higher notches to optimize
injection timing at those notches.
FIG. 7 illustrates a manufacturing process
700 according to an embodiment
of the present invention. In task
701, an engine throttle setting in need
of optimized injection timing is identified. In task
710, a helix angle
capable of optimizing injection timing for the identified engine throttle setting
is determined. The determined helix angle may advance, retard, or not alter injection
timing. In task
720, a plunger for a fuel injector is formed. An upper helix
of the plunger may include at least two segmented portions between points on the
plunger respectively corresponding to a first and second throttle position. The
segmented portions have unequal associated helix angles. One of the segmented portions
may correspond to the throttle setting identified in task
701 and may have
an associated helix angle substantially equal to the helix angle determined in
task
710. In task
730, a fuel injector that includes the plunger
is assembled. The fuel injector may include a through-hardened chromium hot-work
steel nozzle tip such as that described above.
In some embodiments, a machining device, such as a programmable device, may be
employed to manufacture the plunger. For instance, a plunger with an upper helix
having multiple unequal helix angles may be formed from scratch. Alternatively,
an existing plunger, such as a plunger whose upper helix has substantially one
helix angle, may be modified, such that the modified plunger has an upper helix
having multiple unequal helix angles at desired positions of the plunger.
It should be appreciated that when configuring the slope of the upper helix (the
timing helix), this may affect the total volume of the fuel chamber defined between
the upper helix and the lower helix. Because it may be desirable to maintain the
same amount of fuel injected per stroke, it may thus also be desirable to alter
the position or configuration of the lower helix in order to maintain the same
volume of fuel injected per stroke for such plunger with the modified upper helix.
In other words, when manufacturing a plunger for a particular engine that utilizes
a preexisting or reference plunger having a reference upper helix and a reference
lower helix which define the volume of fuel to be injected at each notch, when
replacing such plunger with a plunger manufactured in accordance with the present
invention in order to improve on emission characteristics of the engine by modifying
the slope of the upper or injection timing helix, it may also be desirable to alter
the lower helix to ensure that the total volume of fuel injected per stroke is
not changed in comparison with the original plunger having the original reference
helices. This may be accomplished, for example, by adding or subtracting material
in the region of the lower helix, preferably without changing the slope of the
lower helix, (i.e., either moving the lower helix towards or away from the upper
helix without changing the slope of the lower helix).
It should also be appreciated that the timing, as determined by the configuration
of the upper helix, can be customized in accordance with the present invention
to address difference types of emissions or contaminates. For example, as the present
invention may relate to the railroad industry, there is a particular desire to
reduce the amount of NOx emissions (nitrogen oxide and nitrogen dioxide emissions).
It is known that for NOx, the emissions thereof is directly related to combustion
temperature. Specifically, as combustion temperature goes down, NOx emissions goes
down. As combustion temperature goes up, NOx emissions goes up. By retarding the
timing or onset of combustion by changing the configuration of the upper helix
at a particular notch in relation to a reference or prior art plunger, this will
reduce the combustion temperature and hence reduce NOx emissions. Specifically,
changing the upper helix slope to retard the timing of combustion will cause the
combustion to be delayed, resulting in an insufficient amount of combustion time
for the fuel to bum completely and hence reducing the temperature that is reached.
It should be appreciated, however, that because the fuel does not bum completely,
combustion efficiency and fuel efficiency will go down in comparison with the reference
plunger for those notches in which the timing has been retarded in comparison with
the reference plunger. It has been found, however, that the fuel penalty (i.e.,
the increase in inefficiency of fuel bum) can be engineered to be sufficiently
low such that the benefit or degree of reduction in NOx emissions far out weighs
any percentage increase in fuel bum. In one embodiment of the present invention,
a desired weighted NOx emissions is predetermined, and the upper or timing helix
is cut or angled in a manner that achieves that desired level of emissions while
simultaneously obtaining the best fuel efficiency for that emissions level. For
example, in the event that a particular maximum emissions level is desired (e.g.,
as a maximum threshold that might be set by the Environmental Protection Agency
for a particular type of engine) as measured in grams/BHP-HR.
In accordance with one aspect of the present invention, the emissions at each
throttle position is measured to determine the throttle position or range of positions
that are most detrimental to emissions. By retarding the timing to reduce NOx emissions,
for example, at the most critical throttle positions (or notches in the case of
a locomotive engine) a significant benefit to the total weighted emissions can
be achieved with a relatively insignificant impact on fuel efficiency. Specifically,
by retarding the timing at the throttle position(s) that have the greatest impact
on emissions output, a significant reduction in emissions can be achieved with
the least fuel penalty. It should be appreciated that in the case of NOx emissions,
as the emissions are decreased, fuel efficiency is likewise decreased. However,
it is one aspect of the invention to achieve a desired weighted NOx emissions output
while minimizing the fuel penalty, and achieving this by retarding the timing of
fuel injection at the more critical throttle position or positions.
It should also be appreciated that while increasing combustion temperature may
increase NOx emissions, it may also reduce other types of emissions such as hydrocarbons
and particulates. Therefore, in some applications, it may be desirable to focus
efforts on other types of emissions such that the timing might be advanced in respect
to a prior art or reference plunger to reduce emissions of such type. In that case,
rather than balancing emissions against fuel efficiency, it may instead be desirable
to balance one type of emissions versus another type of emissions. For example,
it may be desirable to reduce hydrocarbon and particulate emissions and setting
a desired maximum threshold for such emissions, and then customizing or altering
the timing angle to achieve a minimalized increase in any NOx emissions that may
be associated with the improvement of the particulate or hydrocarbon emissions
resulting from the advanced timing.
FIG. 8 illustrates the NOx emissions profile in grams per hour plotted against
notch position for a switcher-type locomotive engine. The locomotive used was GP38-2
and the engine used was General Motors EMD (Model 16-645E). The engine utilizes
a conventional prior art unit fuel injector having a standard, single slope timing
helix. As shown towards the top of the graph, the EPA has conducted tests to determine
the duty cycle of operation for a standard switcher-type locomotive at each notch
position. For example, the EPA has determined that an engine of this type runs
59.8% of the time in the idle position, 12.4% of the time at notch
1, 12.3%
of the time at notch
2, 5.8% of the time at notch
3, 3.6% of the
time in notch
4, 3.6% of the time at notch
5, 1.5% of the time at
notch
6, 0.2% of the time at notch
7, and 0.8% of the time at notch
8. The cumulative duty cycle numbers are illustrated in the chart. Also,
illustrated towards the bottom of the chart is the cumulative weighted NOx in grams
per hour, taken as a percentage. For example, as illustrated, 81.10% of the cumulated
weighted NOx emissions takes place at notches N
5 and below. As illustrated
in FIG. 9, which is another representation of FIG. 8, 72.2% of the EPA weighted
duty cycle resides in the idle and N
1 notches, although this constitutes
only 22.1% of the weighted NOx emissions. Notches N
2-N
5 represent
25.3% of the EPA weighted engine duty cycle, and constitute 59.0% of weighted NOx
emissions. Finally, notches N
6-N
8 represent only 2.5% of the weighted
duty cycle as determined by the EPA, and 18.9% of the weighted NOx emissions. As
can be appreciated, the NOx emissions associated with notch
5 at 523.9 grams
per hour as a weighted number is the highest on a chart. The inventors have determined
that because 81.1% of accumulative weighted NOx emissions and grams per hour reside
in notches N
5 and below, it would be advantageous to reduce NOx emissions
at those levels by retarding the timing at notches N
5 and below to achieve
the desired net total NOx emissions in grams per BHP-hour of 14.0.
In accordance with the method contemplated herein, the timing may be retarded
at at least one notch level (if not more) to achieve the reduction in NOx emissions
as desired, while minimizing the fuel penalty associated with achieving that level
of NOx emissions. In one aspect of the invention, the degree of retardation at
the one or more throttle or notch positions may be established by trial and error
after determining which notch positions are most critical in relation to NOx emissions.
For example, once the data of FIG. 9 is established, it becomes readily apparent
that retarding the timing at notch
5 and perhaps notches below that level
is particularly desirable. The extent to which each of the notches has its timing
retarded in relation to the original reference plunger is one that may be established
experimentally through trial and error. Alternatively complex algorithmic formula
and software may be developed to derive the optimal level of retardation or advancement
(if any) to achieve a desired emissions output with a minimized fuel penalty.
FIG. 10 illustrates a comparison of a plunger employing a standard or reference
helix (prior art) for a switcher engine versus a plunger sample ("Switcher Helix
#1") having a modified slope in comparison with a standard helix for that engine
such that the timing thereof was retarded for notches N
5 down through the
idle positions. The amount of retardation at each notch is compared to the standard
timing and is illustrated by reference to the timing in degrees relative to top
dead center. As illustrated in FIG. 11, this retardation in the timing illustrated
in FIG. 10 resulted in a total reduction of 1.8 grams/BHP-HR in comparison with
the standard or reference helix. That is, the weighted NOx emissions was reduced
from 13.7 grams/bhp-hour to 11.9 grams of NOx/bhp-hour. In addition, this was achieved
with only a 0.75% fuel penalty (i.e., a 0.75% decrease in combustion efficiency.)
FIG. 12 illustrates the test results using the same engine, but with another
plunger (Switcher Helix
2) in which the timing was retarded for notches
N
6 and below, and a comparison with the standard or reference helix. As
illustrated in FIG. 13, this resulted in a reduction of weighted NOx from 13.7
grams/BHP-hour to 9.3 grams/BHP-hour, for a reduction of 4.4 grams/BHP-hour. However,
this was achieved at a 1.9% fuel penalty.
FIG. 14 illustrates an experiment that was conducted in order to determine what
would happen if the timing for switcher helix
2 was uniformly retarded by
changing the fly-wheel pointer position. This was conducted at four degrees after
top dead center. As illustrated in FIG. 15, this resulted in an undesirable fuel
penalty of 12.8%.
FIGS. 16-18 illustrate data derived for a different type of engine than the
switcher engine discussed above with respect to FIGS. 8-15. Specifically, FIGS.
16-18 relate to a line-haul type engine (General Motors EMD 16-645E3B) used in
locomotive model SD40-2. As illustrated in FIG. 16, notch
8 represents a
significantly high percentage of the total weighted NOx emissions when using the
reference prior art plunger. Accordingly, it would be desirable to significantly
retard the timing at notch
8 to improve NOx efficiency. As illustrated in
FIG. 17, in one embodiment the line hall helix at 4 degrees after top dead center
had its slope modified relative to the standard helix for that engine by having
the slope altered so that the timing is substantially retarded at notches N
8-N
3
in comparison with the standard helix. However, at notches N
2, N
1
and idle, the timing was advanced in order to improve upon fuel efficiency at these
lower notch levels since the retarded timing at the higher notches, e.g. notch
8 significantly improves upon the emissions characteristics at the higher
level, thus enabling some room for improved fuel efficiencies at the lower notch
levels to improve upon fuel economies in those lower notches so that the resulting
weighted NOx level resulted in 6.7 grams/BHP-HR, with a 4% fuel penalty. Results
are also shown where at 6 degrees after top dead center the timing was modified,
and resulted in NOx level of 6.0 grams/BHP-HR, with an 8% fuel penalty. FIG. 18
illustrates NOx emissions with line-haul helixes at 4 and 6 degrees after top dead
center in comparison with the standard helix. As illustrated, the total weighted
NOx emissions at the higher notches (N
6, N
7, N
8) was substantially
reduced, especially N
8, when line-haul helixes were used.
It will be appreciated by those skilled in the art that the term "helix" or "helices"
do not necessarily refer to a timing ridge of what is in fact a helix or of a helical
shape. Specifically, heretofore the upper timing line or ridge that has been formed
in injector plungers have been helical in shape and have thus been referred to
as the "upper timing helix" or the like. It can be appreciated, however, that in
accordance with the present invention, the upper timing structure formed in the
plunger need not at all be shaped as a helix, as can be appreciated, for example,
from the shape of the timing structures or helixes
330,
610,
650,
etc. Thus, the term "helix" should refer broadly to the upper timing structure
formed on the plunger.
The foregoing description of embodiments is provided to enable any person skilled
in the art to make or use embodiments of the present invention. Various modifications
to these embodiments are possible, and the generic principles presented herein
may be applied to other embodiments as well. For instance, embodiments herein may
be applied in conjunction with other apparatus and methods, such as other technologies
for reducing engine emissions and/or improving engine performance.
It is to be appreciated that the specific form of the upper and lower helices
of a plunger may be varied in any of a multitude of ways consistent with the teachings
of the present application. Helix angles may be varied to achieve desired performance
criteria for particular implementations.
As such, the present invention is not intended to be limited to the embodiments
shown above but rather is to be accorded the widest scope consistent with the principles
and novel features disclosed in any fashion herein.
*
