Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
IMPROVED SYSTEM FOR CONTROL OF COMPRESSORS AND AIR DRYERS IN
TUNNELS
BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
[0001] The present invention relates to locomotive air supply systems
and, more
particularly, to an air supply control system for optimizing operation of the
air supply system
when a locomotive is about to enter into a tunnel.
2. DESCRIPTION OF THE RELATED ART
[0002] Heavy haul freight trains such as those operated in North America
typically
have four to seven 4500 horse power diesel locomotives in a consist at the
head end of the
train to provide the required tractive effort. The first locomotive in the
consist is typically
called the lead locomotive and the remaining locomotives in the consist are
generally referred
to as the trailing locomotives. The tractive effort (propulsion) and brakes on
the trailing
locomotives are controlled by the driver in the lead locomotive.
[0003] When the locomotive consist travels through a tunnel, the multiple
high-horse
power locomotives can produce ambient temperatures in the tunnel as high as
140 C (284
F) at the location of the trailing locomotives. This very high ambient
temperature is the
result of both the accumulated waste heat from the locomotives and inefficient
combustion at
the trailing locomotives due to the oxygen depletion that results from the
operation of the
lead locomotive.
[0004] Traditionally, the air compressors on the locomotives are operated
based on
local pressure governor controls. The air compressors are turned on when the
pressure in the
first main reservoir drops to about 120 psi and turned off when the pressure
in first main
reservoir increases to 140 psi. Desiccant-type air dryers used to dry the
compressed air
produced by the air compressors regenerate the material in the desiccant bed
by purging the
desiccant bed with dry air from the main reservoir system on an independent
cycle as
determined by the air dryer or on an independent cycle determined by the air
dryer only when
the compressor is operating.
[0005] A typical two-stage locomotive compressor generally includes a
first
pressurization stage, an intercooler, a second pressurization stage, and an
aftercooler. The
internal air temperature in the second stage may be as high as 300 F above
ambient
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temperature due to the heat of compression. This air is cooled to 20 F to 40
F above
ambient by the aftercooler before it is supplied to the main reservoir system.
[0006] In a tunnel, where the ambient temperature can reach 140 C (284
F) at the
trailing locomotives, the internal temperature in the second stage of the air
compressor can
reach up to 600 F due to the high initial ambient temperature and the heat of
compression.
Operating temperatures in this range can result in high rates of wear and
degradation of the
air compressor. Furthermore, the outlet temperature of 324 F resulting from
the high
ambient temperature plus the 20 to 40 F cooling delta of the aftercooler can
degrade the air
dryer as its treats the overly hot air discharged from the compressor. Thus,
there is a need in
the art to protect the air supply system from the overly hot air in a tunnel.
BRIEF SUMMARY OF THE INVENTION
[0007] The present invention comprises a system for controlling an air
supply system
of a train. The system includes a locomotive control system programmed to
determine the
location of a locomotive consist having a first locomotive and at least one
trailing
locomotive, where each locomotive in the consist has an air compressor and a
main reservoir
system. The air supply system may comprise an air dryer that is additionally
controlled for
tunnel operation. An air supply controller is interconnected to the air
compressor and,
optionally, the air dryer of each locomotive in the consist and programmed to
command each
air dryer to perform a regeneration cycle if the locomotive consist is
approaching a tunnel.
The air supply controller also commands each compressor to operate until a
predetermined
pressure in the air supply system is achieved if the locomotive consist is
approaching a
tunnel. In one embodiment, the air supply controller is also programmed to
allow the
compressor of the first locomotive to operate and to inhibit the compressors
of all trailing
locomotives from operating while the locomotive consist is in a tunnel. The
air supply
controller is further programmed to sequentially operate the compressor of
each trailing
locomotive if the air supply system has a pressure below a predetermined
threshold while the
locomotive consist is in a tunnel. In another embodiment, the air supply
controller is
programmed to reset the first compressor to operate when the air supply system
has a
pressure below a predetermined threshold that is above a pressure that will
cause the
compressor of each trailing locomotive to operate while the locomotive consist
is in a tunnel.
The air supply controller is further programmed to allow the compressor of
each trailing
locomotive to operate if air supply system has a pressure that is below the
pressure that will
cause the compressor of each trailing locomotive to operate while the
locomotive consist is in
a tunnel. In either embodiment, the air supply controller is further
programmed to reset the
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compressors in the consist for normal operation after the locomotive consist
has exited a
tunnel.
[0008] In use, the control system involves determining the location of a
locomotive
consist having a first locomotive and at least one trailing locomotive, where
each locomotive
in the consist has an air compressor and a main reservoir system with an
optional air dryer,
and then conditioning the air dryer, if the locomotive is so equipped, for an
upcoming tunnel
by one of several means based on the air compressor and air dryer
configuration. For
example, in some locomotive configurations having an independently
controllable air dryer,
the control system may command each air dryer to perform a regeneration cycle
if the
locomotive consist is approaching a tunnel to minimize the likelihood of the
air dryer on a
trailing locomotive to regenerate while in the tunnel. If the regeneration of
the air dryers is
interlocked with the compressor "on" signal, however, compressor operation may
be
inhibited on trailing locomotives to prohibit regeneration of the trailing air
dryers while in a
tunnel. Lastly, the control system may simply suppress the regeneration of air
dryers on the
trailing locomotives during tunnel operation. Each compressor is then
commanded to operate
until a predetermined pressure in the air supply system is achieved if the
locomotive consist
is approaching a tunnel. In one embodiment, the compressor of the first
locomotive is
operated and the compressors of all trailing locomotives are inhibited from
operating while
the locomotive consist is in a tunnel. If the air supply system has a pressure
below a
predetermined threshold while the locomotive consist is in a tunnel, the
compressor of each
trailing locomotive is sequentially operated. In another embodiment, the first
compressor is
reset to operate when the air supply system has a pressure below a
predetermined threshold
that is above a pressure that will cause the compressor of each trailing
locomotive to operate
while the locomotive consist is in a tunnel. The compressor of each trailing
locomotive is
then operated normally if air supply system has a pressure that is below the
pressure that will
cause the compressor of each trailing locomotive to operate while the
locomotive consist is in
a tunnel. In either embodiment, the default operational state of the air
supply system is
restored after the locomotive consist has exited a tunnel.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0009] The present invention will be more fully understood and
appreciated by
reading the following Detailed Description in conjunction with the
accompanying drawings,
in which:
[0010] FIG. 1 is a schematic of an air supply system with an air supply
controller
according to the present invention;
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[0011] FIG. 2 is a schematic of a locomotive control system used with air
supply
controller according to the present invention;
[0012] FIG. 3 is a flowchart of one embodiment of an air supply control
process
according to the present invention; and
[0013] FIG. 4 is a flowchart of another embodiment of an air supply
control process
according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0014] Referring now to the drawings, wherein like reference numerals
refer to like
parts throughout, there is seen in Fig. 1 an air supply controller 10 for
optimizing operation of
the air supply system 12 as a train approaches and passes through a tunnel.
Air supply
system 12 provides the compressed air for operating the braking system of the
train. Air
supply controller 10 is interconnected to a locomotive control system 14 as
well as the air
supply system 12 formed by the locomotives 16 in a consist, depicted in FIG. 1
as a lead
locomotive 16a along with trailing locomotives 16b through 16n. Each
locomotive 16 in the
consist is interconnected to air supply system 12 and includes at least one
air compressor 20
that provides compressed air to a main reservoir system 22 having a first main
reservoir 24, a
check valve 26, an optional air dryer 28, and a second main reservoir 30. Main
reservoir
system 22 of each locomotive is interconnected by a pipe 32 to a main
reservoir line 34 that
interconnects the main reservoir system 22 of all locomotives 16a through 16n
in a consist so
that any locomotive 16 in a consist can recharge the main reservoir system 22
of other
locomotives 16 and maintain the appropriate amount of pressure in air supply
system 12 so
that the braking system remains operational.
[0015] Controller 10 is preferably interconnected to air supply system 12
of each
locomotive 16 by using individually addressable air compressors 20 and,
optionally, air
dryers 28 that can be electronically signaled and thus individually controlled
by controller 10.
For example, controller 10 may be interconnected to each air compressors 20
and air dryers
28 via a wired network 36 or a wireless network, such as IEEE 802.11. For a
wired network
36, a spare wire in the existing 27 pin train lines used for intra-train
communications may be
used, such as by including a carrier network signal overlaid on the existing
27 pin train line
compressor control wire, which is typically wire number 22. Compressors 20
normally will
be put into an "on" state when the pressure in main reservoir system 22 falls
below a certain
lower threshold, such as 120 psi, and turned "off" when pressure in main
reservoir system 22
a certain upper threshold, such as 140 psi. Controller 10 is configured to
change this default
or normal operation of compressors 20 as explained in more detail below.
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[0016] Locomotive control system 14, such as the LEADER system available
from
New York Air Brake of Watertown, New York, is installed in or operated from
lead
locomotive 16a. Locomotive control system 14 may be present in more than one
locomotive
16, but typical practice to have locomotive control system 14 of lead
locomotive 16a in
control of the rest of the train. Referring to Fig. 2, locomotive control
system 14 includes a
track database 40 having geographic location data for track features and, more
specifically,
the location of each tunnel along a particular route. Locomotive control
system 14 further
includes a global positioning system (GPS) 42 and a processor 44 for
determining the current
location of lead locomotive 16a in the track database 40. Locomotive control
system 14 can
thus determine when the train is about to enter or has exited a tunnel in
track database 40 by
comparing the GPS location of the train to the location data in track database
40. As an
alternative or supplement to GPS location services, locomotive control system
14 can receive
and identify signals sent by wayside signaling devices that are placed along a
route and used
to, among other things, notify a passing locomotive control system 14 when the
train is
approaching or exiting a tunnel. It should be recognized by those of skill in
the art that
controller 10 may be implemented in a device that is separate from locomotive
control system
14, or may be incorporated into locomotive control system 14 as an additional
module,
provided that the appropriate control can be maintained over compressors 20
and air dryers
28 as explained below.
[0017] Air supply controller 10 is programmed to control compressor 20
and air dryer
28 on lead locomotive 16a as well as on each of the trailing locomotives 16b
through 16n in a
consist to minimize operation of compressors 20 and air dryers 28 in the high
ambient
temperatures in a tunnel. Controller 10 minimizes unnecessary air regeneration
in a tunnel by
pre-charging the air supply system 12 prior to entering the tunnel, and then
preferentially
only allowing compressor 20 and air dryer 28 of lead locomotive 16a to operate
while in the
tunnel as the ambient air temperature at lead locomotive is much lower than
the ambient
temperatures at trailing locomotives 16b through 16n.
[0018] More particularly, as seen in Fig. 3, air supply controller 10 may
be
programmed to implement a control process 50 that begins with a determination
of the
location of a train 52. As explained above, controller 10 may determine the
location of the
train by communicating with locomotive control system 14 to glean the location
of the train
on the track database relative to a tunnel or to determine whether a wayside
track signal
indicating an upcoming tunnel has been received and processed. If a check
determines that
the train is approaching a tunnel 54, controller 10 commands all air dryers 28
to complete a
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regeneration cycle 56 so that the desiccant bed of each air dryer 28 is fully
regenerated prior
to entering the tunnel and preferentially avoiding the need for a regeneration
cycle to be
performed until all locomotives 16 exits the tunnel. As a regeneration cycle
uses
approximately fifteen to twenty percent of dry product air, performing the
regeneration cycle
in advance minimizes air consumption in the tunnel. This step 56 may be
omitted if the
consist does not include air dryer 28. Once the regeneration cycle is
complete, controller 10
commands the compressors to turn "on" 58 even if the main reservoir pressure
is greater than
120 psi to charge air supply system 22 to about 140 psi prior to entering the
tunnel. Once a
check 60 determines that air supply system 22 has achieved 140 psi, controller
10 inhibits the
operation of compressors 20 of trailing locomotives 16b through 16n while the
train is in the
tunnel. As air dryer 28 typically monitors the on/off state of its associated
compressor 20 and
only initiates a regeneration cycle when compressor 20 is in an "on" state,
the regeneration
cycle of air dryers 28 of locomotives 16b through 16n will also be inhibited.
Controller 10
next enables compressor 20 of lead locomotive 16a to operate in a normal
fashion 64, thereby
maintaining the pressure in main reservoir system 22 between the typical
limits, e.g., between
120 psi and 140 psi. Controller 10 may also be configured to provide a fault
tolerance by
monitoring the pressure in main reservoir system 22. If a check 66 determines
that fault
tolerance is enabled, a check 68 is performed to determine whether the air
pressure in main
reservoir system 22 has dropped below a minimum threshold, such as 118 psi. If
so,
controller 10 sequentially enables compressors 20 of trailing locomotives 16b
through 16n to
operate 70 until the pressure in main reservoir system 22 is restored to
within an acceptable
tolerance. For example, if compressor 20 of lead locomotive 16a is unable to
maintain the
pressure in main reservoir system 22 within minimum tolerance, then compressor
of second
locomotive 16b is operated to pressurize main reservoir system 22. If two
compressors are
unable to maintain adequate pressure in main reservoir system 22, controller
10 can then
operate compressor of locomotive 16n, etc., thereby sequentially adding air
supply restoration
capacity from the front of the locomotive consist toward the end of the
consist until the
demand is satisfied. Controller 10 can determine whether pressurization is
sufficient using
on-board diagnostics, such as those available from locomotive control system
14, or through
dedicated sensors. If fault tolerance was not enabled, or if fault tolerance
was enabled and
main reservoir system 22 pressure has been restored, controller 10 again
determines the
location of the train 72 and checks 74 whether the train has exited the
tunnel. If so, all
compressors and air dryers in the consist are reset to operate in their
default or normal mode
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76, and process 50 concludes until controller 10 determines that the next
tunnel is
approaching.
[0019] In another embodiment of the invention, controller 10 can
implement a control
process that only requires connection to compressor 20 and air dryer 28 (if
applicable) of lead
locomotive 16a. As with the embodiment of FIG. 1, controller 10 is
interconnected to
locomotive control system 14 to determine when the consist is approaching a
tunnel. When a
tunnel is imminent, controller 10 resets compressor 20 so that the "on" lower
pressure
governor setting of lead locomotive is slightly above the upper "on" tolerance
for the
remaining locomotives. For example, lead locomotive 16a can be reset to 125
psi and will
thus turn on if the pressure drops below 125 psi, while the other compressors
in the consist
will not turn on until the main reservoir pressure drops to below 120 psi.
Provided that
compressor 20 of lead locomotive 16a is operational and has sufficient
capacity to satisfy
demand, pressure in main reservoir system 22 will not drop below 125 psi and
thus
compressors 20 of the trailing locomotives 16b through 16n will not operate.
More
specifically, as seen in Fig. 4, air supply control controller 10 may be
programmed to
implement a control process 80 that begins with a determination of the
location of a train 82.
As explained above, controller 10 may determine the location of the train by
communicating
with locomotive control system 14 to glean the location of the train on the
track database
relative to a tunnel or to determine whether a wayside track signal indicating
an upcoming
tunnel has been received and processed. If a check determines that the train
is approaching a
tunnel 84, controller 10 commands air dryer 28 on the lead locomotive to
complete a
regeneration cycle 86 so that the desiccant bed of air dryer 28 is fully
regenerated prior to
entering the tunnel and preferentially avoiding the need for a regeneration
cycle to be
performed until locomotive 16 exits the tunnel. As a regeneration cycle uses
approximately
fifteen to twenty percent of dry product air, performing the regeneration
cycle in advance
minimizes air consumption in the tunnel. This step may be omitted if lead
locomotive does
not have an air dryer 28. Once the regeneration cycle is complete, controller
10 commands
compressor 20 to turn "on" 88 even if the main reservoir pressure is greater
than 120 psi to
charge air supply system 22 to about 140 psi prior to entering the tunnel.
Once a check 90
determines that air supply system 22 has achieved 140 psi, the lower governor
"on" setting
for compressor 20 of lead locomotive 16a is then reset 92 to a higher
threshold pressure for
turning "on," such as 125 psi, to maintain the pressure in the main reservoir
system between
the limits of 120 psi and 140 psi throughout the time the train is in the
tunnel. Provided
compressor 20 of lead locomotive 16a is operational and has capacity to
satisfy demand, the
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pressure in main reservoir system 22 should not drop below 125 psi and
compressors of
trailing compressors 16b through 16n will not need to operate. To provide a
fault tolerance,
compressors 20 of all other locomotives 16b through 16n operate normally so
that if lead
locomotive 16a is unable to maintain the pressure in main reservoir system 22
above the
standard lower threshold of 120 psi, compressors 20 of locomotives 16b through
16n in the
consist will operate in the usual way and turn "on" when main reservoir system
22 pressure
drops below 120 psi. Finally, controller 10 determines the location of the
train 96 and if a
check 98 determines that the locomotive consist has exited the tunnel, such as
by
communicating with locomotive control system 14 that uses GPS and or track
wayside
signals, compressor 20 is restored to its default or normal operational mode
100 and process
80 concludes until the train approaches the next tunnel.
[0020] Thus, in any embodiment of the invention, air supply controller 10
changes the
default operation of at least one compressor 20 and its associated air dryer
28 to minimize the
amount of time the compressors 20 and associated air dryers 28 of trailing
locomotives 16b
through 16n will be operated while the train in in a tunnel. When the
locomotive consist exits
a tunnel, the conventional operation of compressors 20 and air dryers 28 can
be restored so
that air supply system 12 functional in the default or normal mode.
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