U.S. patent number 3,793,825 [Application Number 05/221,325] was granted by the patent office on 1974-02-26 for time delay gas turbine starting system with fuel pressure and flame sensing circuitry.
This patent grant is currently assigned to Ford Motor Company. Invention is credited to Irwin C. Dickhart, James E. Fenton.
United States Patent |
3,793,825 |
Dickhart , et al. |
February 26, 1974 |
TIME DELAY GAS TURBINE STARTING SYSTEM WITH FUEL PRESSURE AND FLAME
SENSING CIRCUITRY
Abstract
A fuel pressure sensing switch prevents actuation of a starter
motor until after fuel pressure at the nozzle reaches a
predetermined level. This arrangement prevents air flow from
reaching a velocity at which ignition is difficult before adequate
fuel is present. The electrical system also includes a control
battery and a supplemental battery that are connected in parallel
for normal system operation and recharging and are connected in
series across the starter motor during starter motor operation.
Inventors: |
Dickhart; Irwin C. (Westland,
MI), Fenton; James E. (Ann Arbor, MI) |
Assignee: |
Ford Motor Company (Dearborn,
MI)
|
Family
ID: |
22827342 |
Appl.
No.: |
05/221,325 |
Filed: |
January 27, 1972 |
Current U.S.
Class: |
60/790;
60/223 |
Current CPC
Class: |
F02C
7/262 (20130101); F02C 7/26 (20130101) |
Current International
Class: |
F02C
7/26 (20060101); F02C 7/262 (20060101); F02c
007/26 () |
Field of
Search: |
;60/39.14,223 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Croyle; Carlton R.
Assistant Examiner: Olsen; Warren
Attorney, Agent or Firm: Harrington; Donald J. Zerschling;
Keith L.
Claims
We claim:
1. In a gas turbine engine having a starter motor, an ignition
system and a fuel supply system, said fuel supply system including
a fuel pump means for supplying pressurized fuel to a combustion
chamber of the engine, a starting control system comprising an
electrical energy source, a manual switching means for initiating
engine starting, said manual switching means connecting said energy
source to said fuel pump means to initiate operation of said fuel
pump means, fuel pressure sensing means for sensing when fuel
pressure reaches a predetermined value, and a switch means
connected to said fuel pressure sensing means for actuating said
starter motor when fuel pressure reaches said predetermined value,
said electrical energy source comprising a first battery and a
second battery, switching mechanism normally connecting said first
battery in parallel relationship with respect to said second
battery, and switching mechanism connecting said batteries in
series across said starter motor during actuation of said starter
motor.
2. The engine of claim 1 in which the starting control system
comprises ignition circuit means for actuating the ignition system
both from the parallel connection of said first battery and said
second battery and from the series connection of said
batteries.
3. The engine of claim 2 in which the ignition circuit means
connects the ignition system in series with said batteries during
actuation of said starter motor.
4. The engine of claim 3 in which the starting control system
comprises a flame sensing means for sensing the presence of a flame
in the engine, and a time delay means for deactuating the starter
motor if a flame is not sensed with a predetermined time after a
starting cycle is initiated.
5. The engine of claim 4 in which the fuel supply system comprises
a solenoid valve connected between said fuel pump means and the
engine combustion chamber, said time delay means closing said
solenoid valve if a flame is not sensed within a predetermined time
after a starting cycle is initiated.
6. The engine of claim 5 in which the fuel supply system comprises
an engine driven fuel pump in series with said fuel pump means and
a fuel nozzle, said fuel nozzle being located in the engine
combustion chamber.
7. The engine of claim 6 comprising an air pump for urging a
fuel-air mixture toward an ignitor of the ignition system, said air
pump being actuated by a series connection of said batteries during
actuation of said starter motor.
8. The engine of claim 1 comprising an air pump for urging a
fuel-air mixture toward an ignitor of the ignition system, said air
pump being actuated by a series connection of said batteries during
actuation of said starter motor.
Description
SUMMARY OF THE INVENTION
This invention relates to and is assigned to the assignee of U. S.
Pat. No. 3,600,887 to Gault et al.
Prior art starting systems for gas turbine engines actuate a
starter motor immediately upon initiation of the starting cycle. In
most cases this conventional approach functions satisfactorily, but
under certain conditions such as cold weather starting, high fuel
viscosity can delay fuel flow to the combustion chamber until after
air flow produced by engine rotation exceeds the relatively low
levels conducive to ignition. Additionally, most prior art starting
systems rely upon a single battery to power the appropriate relays
in the starting and operating circuit and power the starter
motor.
In the starting system of this invention, a fuel pressure sensing
device prevents starter actuation until after fuel pump operation
produces a predetermined fuel pressure at the fuel nozzle. The
system also reduces battery size and increases overall electrical
efficiency by using two batteries that are connected in parallel to
provide power to the circuit components but are connected in series
across the starter motor for starter motor actuation. In a gas
turbine engine having a starter motor and a fuel supply system that
includes an electrical fuel pump for supplying pressurized fuel to
the engine, the starting control system comprises an electrical
energy source, a manually actuated switch for connecting the energy
source to the fuel pump to initiate operation of the fuel pump, a
fuel pressure sensing device for sensing when the fuel pressure
reaches a predetermined value, and a switch connected to the fuel
pressure sensing device for actuating the starter motor only after
fuel pressure reaches the predetermined value. A switch mechanism
normally connects two batteries making up the electrical energy
source in parallel with each other for supplying power to the
relays and other components of the system and to a charging
mechanism. During starter motor actuation, the switch mechanism
connects the two batteries in series across the starter motor and
thereby greatly reduces the current required by the starter motor.
During starting, the switch mechanism also can connect the two
batteries in series across the ignition system and a supplemental
air pump that urges a fuel air mixture toward an ignitor of the
ignition system.
If a flame is not sensed within a predetermined time limit, usually
about 4 seconds, after initiation of the starting cycle, the
starting cycle is aborted and the engine is allowed to coast to a
halt before another starting cycle is attempted. If a flame is
sensed within the predetermined time limit, the starter motor,
ignition system, and supplemental air pump remain actuated until
gas generator speed reaches a self sustaining level. A flameout
during this period does not abort the starting cycle unless a flame
is not reestablished within the predetermined time limit. A starter
lockout relay prevents manual reactuation of the starter motor
whenever engine speed exceeds a predetermined value, typically
about 10 percent of design speed.
The fuel supply system preferably includes an engine driven fuel
pump in series with the electrical fuel pump and a fuel nozzle
located in the engine combustion chamber. A fuel pressure boosting
function then is provided by the electrical fuel pump, which is
particularly useful during engine starting. The ignition system
preferably is actuated by both a series connection and a parallel
connection of the batteries. During starter motor actuation, the
ignition system is connected to a series connection of the
batteries to insure strong ignition system operation despite the
large voltage drop caused by the current drain of the starter motor
under low temperature starting conditions.
BRIEF DESCRIPTION OF THE DRAWINGS
In FIGS. 1 - 7 of the drawings, the windings of relays are
represented by circles. Switches actuated by each relay are
connected to the relay by dashed lines and are designated by the
relay number with a letter suffix.
FIG. 1 is a schematic circuit diagram of a control system of this
invention showing the relays and switches in unactuated conditions.
In FIGS. 2 - 7, actuates switches, relays, lights and connecting
leads are designated by heavy lines.
FIG. 2 shows the condition of the circuit after the manual switch
has been moved to the on position in preparation for a starting
cycle.
FIG. 3 shows the circuit condition after the manual switch has been
moved momentarily to the start position. The manual switch is
spring loaded to return to the on position as indicated by the
arrow associated therewith in FIG. 3.
FIG. 4 shows the circuit configuration after a flame has been
sensed in the engine combustion chamber and engine speed has
exceeded the point at which reactuation of the starter motor would
be detrimental to starter and engine components.
FIG. 5 shows the circuit after engine speed has reached a self
sustaining value and operation of the starter motor, air pump and
ignition system has been discontinued. The circuit arrangement of
FIG. 5 remains in effect during normal engine operation.
FIG. 6 shows the circuit when a flameout is sensed at an engine
speed exceeding the self sustaining value. The control circuit does
not attempt an immediate relighting but waits until engine speed
declines approximately to idling speed at which time the circuit
makes one relighting attempt by switching to the configuration
shown in FIG. 7.
FIG. 8 is a schematic of a fuel flow system useful with the
electrical circuitry of FIGS. 1 - 7.
DETAILED DESCRIPTION
Referring to FIG. 1 of the drawings, the control system of this
invention comprises a main bus lead 10 and a ground lead 12. A
manually actuable switch 14 similar to the conventional automotive
ignition switch is connected to main lead 10 and is movable to an
operating position where it connects main lead 10 to an operating
contact 16 and to a starting position where it connects main lead
10 to both operating contact 16 and a starting contact 18. The
switch pole is spring loaded so that releasing the switch while in
the starting position returns the pole to the operating contact. A
relay 20 connects operating contact 16 to ground lead 12.
A normally open switch 56a connects starting contact 18 with a
junction 22. A time delay relay 24 in series with a normally closed
switch 68a connects junction 22 to ground lead 12. A normally open
switch 62a in series with a relay 26 connects junction 22 to ground
lead 12. A relay 28 connects junction 22 to ground lead 12. A
normally open switch 26a connections junction 22 to a junction 30.
Junction 30 is connected by a normally closed switch 40a to a
junction 32 and a relay 34 connects junction 32 to a junction 36. A
normally open switch 34a connects junction to ground lead 12.
Junction 32 is connected by a normally open switch 62b to a
junction 38. A normally closed switch 52a in series with a time
delay relay 40 and a normally closed switch 26b connects junction
38 to junction 36. Junction 36 is connected by a normally open
switch 26c to ground lead 12.
A normally open switch 20a connects main lead 10 to a junction 42
that is connected by a normally closed switch 24a to junction 30
and by a normally open switch 52b to junction 38. A normally open
switch 34b connects junction 38 to a junction 44. Junction 44 is
connected by a normally open switch 72a in series with a normally
open switch 84a and a fuel solenoid 46 to ground lead 12. Switch
84a is in parallel with a normally closed switch 78a. Junction 44
also is connected to ground lead 12 by a normally closed switch 72b
in series with a combined overspeed-overtemperature warning light
48.
Fuel boost pump 50 connects junction 42 with ground lead 12.
Junction 42 also is connected to ground lead 12 by a relay 52 in
series with a normally open switch 68b and by a normally closed
switch 52c in series with a flameout light 54. A starter lockout
relay 56 in series with a speed sensing switch 58 connects junction
42 to ground lead 12. Speed sensing switch 58 typically opens when
engine rotational speed rises above about 12 percent of design
speed and closes when engine rotational speed falls below about 10
percent of design speed. A normally open switch 64a connects
junction 42 to a junction 60. Junction 60 is connected by a relay
62 to ground lead 12. A relay 64 in series with a speed sensing
switch 66 connects junction 42 to ground lead 12. Speed sensing
switch 66 typically is open at engine speeds exceeding about 42
percent of design speed.
Relay 68 in series with a flame sensing device 70 connects junction
42 to ground lead 12. Flame sensing device 70 can be an ultraviolet
light sensor assembly that changes from a high impedance to a low
impedance when a flame appears in the engine combustion chamber. A
relay 72 in series with an overtemperature sensing switch 74 and an
overspeed sensing switch 76 connect junction 42 to ground lead 12.
Temperature sensing switch 74 is closed normally but opens when
engine temperature exceeds a predetermined maximum. Speed sensing
switch 76 is closed normally but opens when engine speed exceeds a
predetermined maximum. A relay 78 in series with an oil pressure
sensing switch 80 connect junction 42 to ground lead 12. Oil
pressure switch 80 is closed normally but opens when engine oil
pressure exceeds some predetermined minimum.
A normally open switch 28a connects main lead 10 to a junction 82.
A relay 84 connects junction 82 to ground lead 12. Junction 82 also
is connected to ground lead 12 by a relay 86 in series with a
normally open fuel pressure sensing switch 88. Fuel pressure
sensing switch 88 closes when fuel pressure at the injection nozzle
exceeds a predetermined value, typically about 2-4 psi. A starter
relay 92 in series with a normally open switch 86a connect main
lead 10 to ground lead 12.
An electrical storage battery 94 has its positive terminal
connected to main lead 10 and its negative terminal connected to
ground lead 12. Relay 92 operates a starter switch 96 that
comprises two switch poles 98 and 100 connected to each other by an
insulating bar 102. Pole 98 normally connects the negative terminal
of battery 94 to the negative terminal of a second battery 104.
Both batteries 94 and 104 typically are 12 volts. Pole 100 normally
connects the positive terminal of battery 94 to the positive
terminal of battery 104. When switch 96 is actuated, pole 98
connects the positive terminal of battery 94 to the negative
terminal of battery 104 and pole 100 connects the positive terminal
of battery 104 through a starter motor 106 to ground lead 12. The
cathode of a diode 108 is connected to the positive terminal of
battery 104 and its anode is connected to main lead 10.
The positive terminal of battery 104 is connected to one terminal
of a switch 84b. Another terminal in switch 84b is connected
through an air pump 110 to ground lead 12. Air pump 110 provides
supplemental air flow within the engine combustion chamber that
urges air and fuel toward the ignitor of the ignition system. A
diode 112 connects terminal 60 to the pole of switch 84 and through
the ignition system 114 to ground lead 12. Actuation of switch 84b
moves its pole into contact with both of the terminals in the
switch.
Turning for a moment to FIG. 8, the inlet of fuel pump 50 is
connected to a fuel tank 120 and its outlet is connected to an
engine driven fuel pump 122. The outlet of pump 122 is connected to
fuel solenoid 46. Fuel pressure sensor 88 is connected between the
outlet of solenoid 46 and a fuel nozzle 124 located in the engine
combustion chamber. Fuel pressure produced by operation of fuel
boost pump 50 is transmitted through the engine driven fuel pump
even though the latter is not operating. Fuel nozzle 124 imposes a
sufficient flow restriction on the fuel to produce a pressure
signal at sensor 88.
OPERATION
Operation of the system is illustrated in FIGS. 2 - 7 of the
drawings. A starting cycle begins by moving manual switch 14 to
contact 16 as shown in FIG. 2. Energized relay 20 closes switch 20a
and thereby applies the potential of the parallel connection of
batteries 94 and 104 to junction 42. Fuel pump 50 and flameout
light 54 are energized and energized relay 56 closes switch 56a.
Energized relay 64 closes switch 64a and thereby energizes relay 62
which closes switch 62a and 62b. Energized relay 72 closes switch
72a and opens switch 72b. Relay 78 opens switch 78a.
Switch 64a also connects the voltage in bus lead 10 across ignition
system 114. The ignition system is energized by a minimum of about
8 volts so such connection energizes the ignition system.
The starting cycle continues with manual movement of switch 14 into
contact with terminal 18 as well as terminal 16 as shown in FIG. 3.
Contact with terminal 18 needs to be only momentary and the spring
mechanism associated with switch 14 returns the pole of switch 14
to terminal 16 after the switch is released by the vehicle
operator. The momentary contact energizes relay 26 which closes
switch 26a and thereby connects junction 42 through switches 24a
and 26a to junction 22. Energized relay 26 also opens switch 26b
and closes switch 26c. The time delay period of relay 24 begins
running. Relay 28 is energized to close switch 28a and relay 34 is
energized to close switches 34a and 34b. Switches 62b, 34b, 72a and
84a apply electrical potential across fuel solenoid 46 and thereby
open the solenoid.
When fuel pressure at the fuel nozzle reaches the preset actuation
point of fuel pressure sensing switch 88, switch 88 closes and
thereby energizes relay 86 which closes switch 86a. Energized relay
92 moves poles 98 and 100 of switch 96 to a lower position where
pole 98 connects the positive terminal of battery 94 to the
negative terminal of battery 104 and pole 100 connects the positive
terminal of battery 104 through starter motor 106 to ground lead
12. The starter motor thus is connected across batteries 94 and 104
in series. Switch 84b connects the positive terminal of battery 104
through air pump 110 to ground lead 12 and also connects the
positive terminal of battery 104 through ignition system 114 to
ground lead 12. At this point, the starter motor is cranking the
engine which is receiving supplemental air from air pump 110,
ignition energy from ignition system 114, and pressurized fuel
having at least a predetermined pressure level from fuel pump 50
via open fuel solenoid 46.
Assuming that the starting cycle proceeds properly, the next event
is the occurrence of a flame within the combustion chamber. Flame
sensor 70 energizes relay 68 which opens switch 68a and closes
switch 68b (see FIG. 4). Switch 68a deenergizes time delay relay
24. Switch 68b energizes relay 52 which opens switch 52a, closes
switch 52b and opens switch 52c. Switch 52b connects junction 42
directly to fuel solenoid 46. Switch 52c extinguishes the flameout
light 54 and thereby indicates to the vehicle operator that a flame
exists within the combustion chamber. As engine rotational speed
increases through the predetermined setting of speed sensing switch
58, switch 58 opens and thereby deenergizes relay 56 which opens
switch 56a. Opening switch 56a serves a starter lockout function by
preventing subsequent manual reactuation of the starter motor until
engine speed has declined below the setting of switch 58.
Turning now to FIG. 5, continued acceleration of the engine
produces sufficient oil pressure to open switch 80 and eventually
reaches the preset point of speed sensing switch 66. Switch 80
deenergizes relay 78 to close switch 78a. Switch 66 opens to
deenergize relay 64 which in turn opens switch 64a to deenergize
relay 62. Switch 62a opens to deenergize relay 26 which opens
switch 26a and thereby deenergizes relay 28. Relay 28 opens switch
28a to deenergize both relays 84 and 86.
Relay 84 opens switch 84a and 84b. Note that if oil pressure
sensing switch 80 has not opened previously to deenergize relay 78
and thereby close switch 78a, fuel solenoid 46 will close and
thereby halt engine operation. Relay 86 deenergizes relay 92 which
returns starter switch 96 to its original position where it
disconnects starter motor 106, air pump 110, and ignition system
114 from the series connection of batteries 94 and 104. The circuit
retains the FIG. 5 configuration for all subsequent normal
operation.
FIG. 6 shows the circuit configuration immediately after a flameout
has occurred at an engine speed exceeding the normal idling speed.
Flame sensor 70 has deenergized relay 68, thereby closing switch
68a and opening switch 68b. Switch 68b deenergizes relay 52 which
closes switch 52a and 52c and opens switch 52b. Switch 52c
illuminates light 54 to indicate to the vehicle operator that a
flameout has occurred. Switch 52b disconnects the fuel solenoid 46
and thereby cuts off fuel flow to the engine.
The system of the invention provides for one relighting attempt at
a speed approximating the idling speed. FIG. 7 shows the circuit
configuration when engine speed has declined to the desired value,
which is the speed at which speed sensing switch 66 closes. Relay
64 closes switch 64a and thereby energizes relay 62 which closes
switches 62a and 62b. Switch 62b connects junction 42 through
switches 34b, 72a and 78a to fuel solenoid 42. Solenoid 42 opens
and reestablishes the supply of fuel to the combustion chamber.
Switch 64a also activates the ignition system 114. Switch 52a
begins the time delay of relay 40.
If reignition occurs before the time delay period of relay 40
expires, relay 68 energizes relay 52 to stop the time delay period
and reestablish the position shown in FIG. 5 of switches 52a, 52b
and 52c. When engine speed exceeds the preset speed of switch 66,
relay 64 is deenergized.
Turning back to FIG. 3, if during cranking a flame does not appear
before the time delay of relay 24 expires, relay 24 is energized to
open switch 24a. Since the pole of switch 14 no longer touches
contact 18, opening switch 24a deenergizes relays 26, 28 and 34 and
also deenergizes fuel solenoid 46. Deenergized relay 28 opens
switch 28a which deenergizes relays 84 and 86. Relay 86 in turn
deenergizes starter relay 92 and thereby terminates the starting
cycle. Another starting cycle can be initiated after relay 24
resets.
Flame sensing assemblies other than the ultraviolet type can be
used as flame sensor 70. It is interesting to note that the system
of the invention energizes the ignition system under a variety of
circumstances. Note, for example, that the ignition system remains
energized even after the delays of either time delay relay expire
to ignite if possible whatever excess fuel remains in the
combustion chamber and remains energized during cranking under cold
weather conditions where the voltage of each battery can decline as
low as 4 volts.
A light can be included in series with relay 92 to indicate to the
engine operator that the starter motor is being energized. Reverse
biased diodes can be connected in parallel with one or more relays
to prevent physical shock and vibration from momentarily
deenergizing the relay. An alternator can be connected across leads
10 and 12 to recharge batteries 94 and 104.
Thus this invention provides a starting and operating control
system for a gas turbine engine that greatly improves the
probability of a successful start by insuring the presence of fuel
in the combustion chamber before engine cranking begins. The system
also connects at least two batteries in series across the starter
motor during starter motor operation while operating normally on a
parallel connection of the batteries.
* * * * *