U.S. patent application number 15/600221 was filed with the patent office on 2017-11-23 for spark exciter variable control unit.
This patent application is currently assigned to Alphaport, Inc.. The applicant listed for this patent is Alphaport, Inc.. Invention is credited to John Heese, Anthony J. Miranda.
Application Number | 20170335801 15/600221 |
Document ID | / |
Family ID | 60329958 |
Filed Date | 2017-11-23 |
United States Patent
Application |
20170335801 |
Kind Code |
A1 |
Miranda; Anthony J. ; et
al. |
November 23, 2017 |
Spark Exciter Variable Control Unit
Abstract
A hardware configuration and related variable control strategy
is disclosed that accepts an electric power input typical of space
flight systems and converts that energy into a spark pulse train
with variable performance metrics for the following system
parameters: time to first spark, peak breakdown voltage amplitude,
spark repetition rate and energy delivered per spark, which have
all been optimally chosen to reliably ignite certain fuel mixtures
and which have been proven to be beneficial for use in aerospace
applications.
Inventors: |
Miranda; Anthony J.;
(Hinckley, OH) ; Heese; John; (Akron, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Alphaport, Inc. |
Cleveland |
OH |
US |
|
|
Assignee: |
Alphaport, Inc.
Cleveland
OH
|
Family ID: |
60329958 |
Appl. No.: |
15/600221 |
Filed: |
May 19, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62339538 |
May 20, 2016 |
|
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|
62339521 |
May 20, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F02K 9/95 20130101; H01T
14/00 20130101; F05D 2220/80 20130101; H01T 4/10 20130101; H01T
15/00 20130101 |
International
Class: |
F02K 9/95 20060101
F02K009/95; H01T 15/00 20060101 H01T015/00 |
Claims
1) A spark exciter variable control unit comprising an exciter
assembly, an ignitor and a means for adjusting and setting
parameters required for reliably initiating ignition and combustion
of non-hypergolic green, wherein the means for adjusting and
setting parameters required for reliably initiating ignition and
combustion of non-hypergolic green fuels comprises at least one of
1) adjusting the exciter assembly and/or ignitor with at least one
remote variable potentiometer; 2) adjusting the exciter assembly
and/or ignitor through a digital communication from a remote device
which employs an embedded microcontroller, and 3) adjusting the
exciter assembly and/or ignitor utilizing a Field Programmable Gate
Array (FPGA), wherein the means for adjusting and setting of
parameters is employed to determine optimal combustion
performance.
2) The spark exciter variable control unit of claim 1, wherein the
spark exciter variable control unit comprises: (1) an input
connector for receiving an electrical current; and a (2) a DC-DC
electrical current converter; wherein the exciter assembly and
ignitor generates sparks having a voltage, energy and frequency to
reliably ignite non-hypergolic fuels.
3) The spark exciter variable control unit of claim 2, wherein the
power inputs to and outputs from the spark exciter variable control
unit are in a range which is suitable for space flight.
4) The spark exciter variable control unit of claim 3, wherein the
input connector function supplies an input voltage ranging from
about 9 V to about 120 V and wherein the output current may be
adjusted within the range of from about 6 kV to about 25 kV. 5) The
spark exciter variable control unit of claim 4, wherein the output
breakdown current supplied to a spark gap within an igniter
assembly may be adjusted to about 15 kV, wherein the spark rate may
be adjusted within the range from about 1 to about 300 sparks per
second and wherein the spark energy may be adjusted between about 1
mJ to about 115 mJ.
6) The spark exciter variable control unit of claim 5, wherein the
exciter assembly comprises a circuit board that receives input
power from a power source, a filter to reduce conducted
disturbances, a timing circuit, a power converter and a driver,
wherein ignitor comprises a capacitor, a spark plug and a spark
gap, wherein a flyback transformer is positioned between the
exciter assembly and the ignitor, wherein the flyback transformer
comprises a primary end and a secondary end, wherein the secondary
end of the transformer is connected in series with the capacitor
and the spark gap and is used to generate a breakdown voltage
across the spark gap to ignite the spark plug.
7) The spark exciter variable control unit of claim 6, wherein the
timing circuit controls the operation and function of the power
converter which charges the capacitor within the ignitor and
wherein the timing circuit controls the operation and function of
the driver which provides an electrical power pulse to the
transformer.
8) A method of converting an electrical input within a spark
exciter variable control unit having an input ranging from about 9V
to about 120V to an output comprising: adjusting and setting the
output to be in the range of about 6 kV to about 25 kV, wherein
spark exciter variable control unit comprises an exciter assembly,
an ignitor and a means for adjusting and setting parameters
required for reliably initiating ignition and combustion of
non-hypergolic green fuels, wherein the means for adjusting and
setting of parameters is employed to determine optimal combustion
performance, wherein the exciter assembly comprises a circuit board
that receives input power from a power source, at least one filter
to reduce conducted disturbances, a timing circuit, a power
converter and a driver, wherein ignitor comprises a capacitor, a
spark plug and a spark gap, wherein a flyback transformer is
positioned between the exciter assembly and the ignitor, wherein
the flyback transformer comprises a primary end and a secondary end
which is used to generate a breakdown voltage across a spark gap,
wherein the secondary end of the transformer is connected in series
with the capacitor and the spark gap, wherein the timing circuit
controls the operation and function of the power converter which
charges the capacitor within the ignitor and wherein the timing
circuit controls the operation and function of the driver which
provides an electrical power pulse to the transformer, and wherein
the step of adjusting and setting parameters required for reliably
initiating ignition and combustion of non-hypergolic green fuels
includes at least one of 1) adjusting and setting the exciter
assembly and/or ignitor with at least one remote variable
potentiometer; 2) adjusting and setting the exciter assembly and/or
ignitor through a digital communication from a remote device which
employs an embedded microcontroller, and 3) adjusting and setting
the exciter assembly and/or ignitor utilizing a Field Programmable
Gate Array (FPGA), wherein the step of adjusting and setting of
parameters is employed to determine optimal combustion
performance.
9) The method of claim 8, wherein the electrical input received
from the power source is passed through a filter.
10) The method of claim 9, wherein the electrical input is passed
through the timing circuit.
11) The method of claim 10, wherein the timing circuit turns on a
power converter which charges the capacitor within the ignitor.
12) The method of claim 11, wherein after the capacitor is charged
by the power converter, the timing circuit initiates controlled
operation of a driver.
13) The method of claim 12, wherein the driver sends an electrical
input to the transformer which outputs an electrical current within
the ignitor, wherein the transformer and capacitor are discharged
in conjunction to generate the breakdown voltage across the spark
gap.
14) The method of claim 13, wherein the timing circuit is
adjustable through use of at least one associated dial.
15) The method of claim 14, wherein operation of the power
converter is adjustable through use of a dial connected to the
timing circuit, optionally, wherein the capacitor comprises a
storage capacity which is adjustable through use of an associated
dial.
16) The method of claim 14, wherein operation of the driver is
adjustable through use of a dial connected to the timing circuit,
optionally, wherein operation of the driver is also adjustable
through use of a dial directly connected to the driver.
17) The method of claim 13, wherein the electrical input passed
through the timing circuit is adjustable through use of at least
one associated microcontroller.
18) The method of claim 17, wherein operation of the power
converter is adjustable through use of the microcontroller
associated with the timing circuit, optionally, wherein the
capacitor comprises a storage capacity which is adjustable through
use of an associated microcontroller.
19) The method of claim 17, wherein operation of the driver is
adjustable through use of the microcontroller associated with the
timing circuit.
20) The method of claim 19, wherein operation of the driver is
further adjustable by a microcontroller associated with the driver.
Description
I. CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims the benefit under 25 U.S.C.
.sctn.119(e) of U.S. Provisional Application No. 62/339,538 filed
on May 20, 2016 and of U.S. Provisional Application No. 62/339,521
filed on May 20, 2016, both of which are incorporated by reference
in their entireties.
II. TECHNICAL FIELD
[0002] Provided is a spark exciter variable control unit used to
determine optimal and threshold performance values required to
reliably initiate combustion of flammable substances and mixtures
for uses including but not limited to propulsion systems for
aerospace and other applications.
III. BACKGROUND
[0003] Use of hypergolic propellants to power rockets and other
space and/or aircraft is relatively common within the industry.
Such propellants typically consist of a fuel (e.g., hydrazine) and
an oxidizer which spontaneously ignite when they come into contact
with each other. One advantage of hypergolic fuel systems are that
ignition systems are not required or used for ignition and
combustion of hypergolic propellants. Hypergolic fuel systems,
however, can be extremely toxic and corrosive both to the
propulsion system and to the environment. For this reason, the
space industry is moving towards use of "green" propellants that
will enable safer, more cost-effective space flight. "Green
propellants" or "green fuels" are not hypergolic or toxic and offer
a higher return on investment in not requiring ground support
equipment and significant time for delivery and filling of fuel
within the propulsion system.
[0004] The benefits of using "green" fuels within propulsion and
other mechanical systems are significant in that they offer higher
energy output per weight and improved ignition reliability when
paired with a compatible spark exciter unit. Consequently, "green"
fuels also require less storage space than that which is required
for other conventional fuels.
[0005] Relative to the standard hypergolic fuels such as hydrazine,
these "green" fuel mixtures are more difficult to ignite reliably
and require much more energy to ignite and to burn. What is
therefore needed within the industry is an improved spark exciter
system which is capable of consistently initiating combustion of
various types of "green" fuels.
[0006] NASA Glenn Research Center has published the results of a
test of several potential spark exciter systems, and established
that a spark exciter system that is capable of reliably igniting
and sustaining combustion of a "green" fuel mixture of liquid
oxygen and liquid methane (LO.sub.2/LCH.sub.4) requires
approximately 200-300 sparks per second, each with 55-75 mJ of
energy delivered per spark, a breakdown voltage on the order of
9-10 kV, and a deterministic and repeatable time to first spark.
However, current commercially available spark exciters have not
been able to consistently achieve ignition with sufficient
reliability for aerospace applications.
[0007] As different "green" fuels are considered for selection as
aerospace propellants, it is extremely useful to be able to test
and characterize the combinations of conditions and spark exciter
performance parameters that lead to reliable ignition of that
specific fuel mixture. The present disclosure provides an
electronic device that is capable of varying spark exciter
operational parameters, including but not limited to the amount of
energy delivered per spark, the spark repetition rate, and peak
breakdown voltage. In an ideal test setup, the spark exciter
variable control unit allows users to find the optimal spark
exciter performance parameters required for reliable ignition and
combustion of their system as environmental and system parameters
are varied, including but not limited to fuel mixtures, fuel types,
fuel flow rates, combustion chamber geometries, spark
gaps/igniters, and many other factors that affect ignition and
combustion in aerospace applications. The environmental parameters
can be adjusted to reflect actual mission profiles and the related
ignition challenges that will be faced in the end application. This
can be done manually with control switches or via command control
using an embedded microcontroller. The spark exciter variable
control unit allows the combustion system designer/operator to
quickly test their system to determine the optimal spark exciter
performance parameters needed to reliably ignite their specific
application across the range of environmental conditions that they
expect their system to operate in. This lowers the risk of failures
associated with selecting a fixed spark exciter unit that has fixed
performance parameters but offers no margin information for the
application that it will be operating in. That is, the unit may
successfully ignite a ground test rig under certain operating
conditions, but the system designer/operator would not know how
close to the failure point or failure threshold level the system is
operating at. For example, if 55 mJ is approximately the minimum
threshold energy per spark required for reliable ignition and
combustion of a propulsion system test rig at specific operating
conditions, selecting a 60 mJ per spark exciter might not be
sufficient to allow enough margin for other conditions that can't
be tested on the ground test rig. Since the present variable
control unit that can assist in determining the threshold value,
one of skill in the art can proceed with additional confidence in
the spark exciter performance parameters selected for the
particular mission or end application. Such end applications
include but are not limited to rocket propulsion systems, aircraft
engines, race cars, land vehicles, systems used within the gas and
oil industry, power turbines, watercraft, etc.
IV. SUMMARY
[0008] Provided is a spark exciter variable control unit and a
related method implemented for reliably initiating non-hypergolic
combustion of green fuels for use in space flight and other
applications.
[0009] According to one aspect of the present disclosure, a spark
exciter variable control unit is provided which includes an exciter
assembly, an ignitor and a means for adjusting and setting
parameters required for reliably initiating ignition and combustion
of non-hypergolic green, wherein the means for adjusting and
setting parameters required for reliably initiating ignition and
combustion of non-hypergolic green fuels includes at least one of
1) adjusting the exciter assembly and/or ignitor with at least one
remote variable potentiometer; 2) adjusting the exciter assembly
and/or ignitor through a digital communication from a remote device
which employs an embedded microcontroller, and 3) adjusting the
exciter assembly and/or ignitor utilizing a Field Programmable Gate
Array (FPGA), wherein the means for adjusting and setting of
parameters is employed to determine optimal combustion
performance.
[0010] According to another aspect of the present disclosure, the
spark exciter variable control unit includes: (1) an input
connector for receiving an electrical current; and (2) a DC-DC
electrical current converter, wherein the exciter assembly and
ignitor generates sparks having a voltage, energy and frequency to
reliably ignite non-hypergolic fuels.
[0011] According to a further aspect of the present disclosure, the
power inputs to and outputs from the spark exciter variable control
unit are in a range which is suitable for space flight.
[0012] According to a further aspect of the present disclosure, the
input connector function supplies an input voltage ranging from
about 9 V to about 120 V and the output current may be adjusted
within the range of from about 6 kV to about 25 kV.
[0013] According to a further aspect of the present disclosure, the
output breakdown current supplied to a spark gap within an igniter
assembly may be adjusted to about 15 kV, the spark rate may be
adjusted within the range from about 1 to about 300 sparks per
second and the spark energy may be adjusted between about 1 mJ to
about 115 mJ.
[0014] According to a further aspect of the present disclosure, the
exciter assembly includes a circuit board that receives input power
from a power source, a filter to reduce conducted disturbances, a
timing circuit, a power converter and a driver; the ignitor
includes a capacitor, a spark plug and a spark gap; a flyback
transformer is positioned between the exciter assembly and the
ignitor; the flyback transformer includes a primary end and a
secondary end, wherein the secondary end of the transformer is
connected in series with the capacitor and the spark gap and is
used to generate a breakdown voltage across the spark gap to ignite
the spark plug.
[0015] According to a further aspect of the present disclosure, the
timing circuit controls the operation and function of the power
converter which charges the capacitor within the ignitor and the
timing circuit controls the operation and function of the driver
which provides an electrical power pulse to the transformer.
[0016] Also provided is a method of converting an electrical input
within a spark exciter variable control unit having an input
ranging from about 9V to about 120V to an output including:
adjusting and setting the output to be in the range of about 6 kV
to about 25 kV, wherein spark exciter variable control unit
includes an exciter assembly, an ignitor and a means for adjusting
and setting parameters required for reliably initiating ignition
and combustion of non-hypergolic green fuels, wherein the means for
adjusting and setting of parameters is employed to determine
optimal combustion performance, wherein the exciter assembly
includes a circuit board that receives input power from a power
source, at least one filter to reduce conducted disturbances, a
timing circuit, a power converter and a driver, wherein ignitor
includes a capacitor, a spark plug and a spark gap, wherein a
flyback transformer is positioned between the exciter assembly and
the ignitor, wherein the flyback transformer includes a primary end
and a secondary end which is used to generate a breakdown voltage
across a spark gap, wherein the secondary end of the transformer is
connected in series with the capacitor and the spark gap wherein
the timing circuit controls the operation and function of the power
converter which charges the capacitor within the ignitor and
wherein the timing circuit controls the operation and function of
the driver which provides an electrical power pulse to the
transformer, and wherein the step of adjusting and setting
parameters required for reliably initiating ignition and combustion
of non-hypergolic green fuels includes at least one of 1) adjusting
and setting the exciter assembly and/or ignitor with at least one
remote variable potentiometer; 2) adjusting and setting the exciter
assembly and/or ignitor through a digital communication from a
remote device which employs an embedded microcontroller, and 3)
adjusting and setting the exciter assembly and/or ignitor utilizing
a Field Programmable Gate Array (FPGA), wherein the step of
adjusting and setting of parameters is employed to determine
optimal combustion performance.
[0017] According to a further aspect of the present disclosure, the
electrical input received from the power source is passed through a
filter.
[0018] According to a further aspect of the present disclosure, the
electrical input is passed through the timing circuit.
[0019] According to a further aspect of the present disclosure, the
timing circuit turns on a power converter which charges the
capacitor within the ignitor.
[0020] According to a further aspect of the present disclosure,
after the capacitor is charged by the power converter, the timing
circuit initiates controlled operation of a driver.
[0021] According to a further aspect of the present disclosure, the
driver sends an electrical input to the transformer which outputs
an electrical current within the ignitor, wherein the transformer
and capacitor are discharged in conjunction to generate the
breakdown voltage across the spark gap.
[0022] According to a further aspect of the present disclosure, the
timing circuit is adjustable through use of at least one associated
dial.
[0023] According to a further aspect of the present disclosure,
operation of the power converter is adjustable through use of a
dial connected to the timing circuit, optionally, wherein the
capacitor includes a storage capacity which is adjustable through
use of an associated dial.
[0024] According to a further aspect of the present disclosure,
operation of the driver is adjustable through use of a dial
connected to the timing circuit, optionally, wherein operation of
the driver is also adjustable through use of a dial directly
connected to the driver.
[0025] According to a further aspect of the present disclosure, the
electrical input passed through the timing circuit is adjustable
through use of at least one associated microcontroller.
[0026] According to a further aspect of the present disclosure,
operation of the power converter is adjustable through use of the
microcontroller associated with the timing circuit, optionally,
wherein the capacitor includes a storage capacity which is
adjustable through use of an associated microcontroller.
[0027] According to a further aspect of the present disclosure,
operation of the driver is adjustable through use of the
microcontroller associated with the timing circuit.
[0028] According to a further aspect of the present disclosure,
operation of the driver is further adjustable by a microcontroller
associated with the driver.
V. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a block diagram showing several input and output
capabilities/ranges of an exemplary spark exciter variable control
unit, which can be utilized to determine the optimal spark exciter
performance specification for specific fuels and end
applications.
[0030] FIG. 2 is a system diagram showing the hardware
configuration and circuit topology of an exemplary spark exciter
variable control unit for igniting green propellants for space
flight.
[0031] FIG. 3 is an assembly drawing of an exemplary spark exciter
variable control unit.
[0032] FIGS. 4 and 5 are detailed views of the top and bottom
covers of an exemplary cylindrical spark exciter variable control
unit.
[0033] FIG. 6 is a detailed view of a typical cylindrical housing
of an exemplary spark exciter variable control unit.
VI. DETAILED DESCRIPTION
[0034] Provided herein is a spark exciter variable control unit
capable of igniting non-hypergolic fuel mixtures. The spark exciter
variable control unit disclosed herein incorporates the electrical
components of the exciter near the assembly which houses the
igniter.
[0035] The spark exciter variable control unit disclosed herein may
be used with "green" fuels. Non-limiting examples of "green" fuels
which may be used within the present spark exciter system include
liquid oxygen-hydrogen (LO.sub.2/LH.sub.2), liquid oxygen-methane
(LO.sub.2/LCH.sub.4), nitrous oxide propane
(N.sub.2O/C.sub.3H.sub.8), and other liquid hydrocarbons
(LO.sub.2/hydrocarbon).
[0036] As mentioned above, these "green" fuels are more difficult
to ignite and burn in a consistent manner since higher energies are
required to produce higher heat for ignition and combustion. The
higher energies input (including higher spark energy) establishes
the reliability necessary for igniting and combusting "green"
fuels. As such, an improved ignition/igniter system is needed which
is capable of providing improved time to first spark repeatability,
variable spark repetition rate, variable energy delivered per spark
and variable maximum applied breakdown voltage. The present spark
exciter variable control unit is capable of providing these
functions for reliable combustion of "green" fuels in a consistent
and continuous manner for the increased ignition temperatures
required for initiating combustion of "green" fuels as compared to
the ignition temperature of conventional fuels. The present spark
exciter variable control unit accomplishes this by producing a
higher energy output which is capable of not only igniting "green"
fuels, but also, different combinations of "green fuels". Also, as
mentioned above, the advantage of using the present spark exciter
system for combusting "green" fuels is that "green" fuels are more
dense and energy potent. Thus, less space is needed to store
"green" fuels within the vehicle or other mechanical device for
operation than that which would be needed to store conventional
fuels which would provide an equivalent amount of power.
[0037] The present spark exciter variable control unit achieves
this objective through the use of a control strategy (also referred
to herein as a "control system") integrated within the spark
exciter electronics design. An example of a previous spark exciter
electronics design is disclosed within U.S. Pat. No. 8,653,693
which is herein incorporated by reference in its entirety. The
components of the present spark exciter which allow for the
implementation of the control strategy include a power source, an
electronic filter, a driver (also referred to herein as a "driver
circuit", a timing sequence (also referred to herein as a "timing
circuit"), a power converter, a flyback transformer, an energy
storage capacitor, and an igniter (for example, a spark plug). The
electrical components may be integrated within a single or multiple
electrical boards. In certain embodiments, the electronic
components are integrated within a single electrical board. To
allow for the variable control of the parameters listed previously,
additional inputs/interfaces are available at the timing circuit
that allow remote control of the spark exciter performance
parameters. In certain embodiments, the electronic components are
integrated into a stainless steel hermetic enclosure which is
operated within a vacuum environment. The unit is compact in nature
and efficiently transfers energy to a given spark gap. The unit is
designed to provide a fixed frequency spark rate with controlled
spark energies and is designed to NASA supplied specifications for
space operation of flight systems.
[0038] Referring to FIG. 2, the spark exciter variable control unit
embodiment (10) includes an exciter assembly (12) and an igniter
(14). An example of an igniter may be a spark plug although it
should be understood that any type of igniter or spark plug may be
used with the unit. The embodiment of the exciter assembly (12)
shown (also referred to herein as the "electronic assembly")
includes a circuit board that first receives input power from a
power source (16), filters the power which is received to reduce
conducted disturbances, and powers several downstream circuits. The
exciter (12) also includes a timing circuit (20). The timing
circuit (20) runs a power converter (22). The timing circuit (20)
also controls the operation of a driver (26) which is used to
provide an electrical power pulse to a transformer (28). The timing
circuit allows for the variable spark exciter performance
parameters to be selected by the user. One embodiment utilizes
remote variable potentiometers to adjust the performance parameters
mentioned earlier. Other methods for variation of these spark
exciter performance parameters include but are not limited to
digital communications with remote devices using an embedded
microcontroller, Field Programmable Gate Array (FPGA), or similar
hardware. Parameters can be adjusted one at a time, several at a
time, or via a small script that could be performed by the spark
exciter variable control unit. That is, each spark could be defined
individually, meaning that each subsequent spark energy could be
increased by 1 mJ, etc. In certain cases, ignition reliability can
be improved by initially generating high spark energies, high spark
rates and high peak breakdown voltages. However, these operating
metrics do not need to be sustained shortly after ignition as
combustion continues. Consequently, there can be a dynamic
reduction of spark exciter performance specifications after
ignition.
[0039] The transformer includes a primary and a secondary winding
which is used to generate the breakdown voltage across the spark
gap. The secondary end of the transformer (28) is connected in
series with the energy storage capacitor (24) and the spark gap.
The energy storage capacitor (24) is connected across and charged
by the power converter (22). Varying the power converter output
voltage, which is equal to the voltage across the capacitor, sets
the stored energy value that will ultimately be delivered to the
spark gap over the duration of the spark event. The greater the
capacitor voltage, the greater the amount of stored spark energy.
During operation, the exciter driver circuit (26) sends a voltage
pulse to the primary of the flyback transformer (28). When the
driver pulse is terminated, the magnetic field in the transformer
core rapidly decreases and voltages related to the turns number are
generated across the primary and secondary windings. By varying the
duration of the primary pulse, the amount of energy stored in the
transformer core gap is varied. This energy is related to the
flyback energy available and the related peak flyback voltages,
which in this case is the peak breakdown voltage level. The series
connection of the capacitor (24) and transformer (28) secondary
causes the sum of the voltages to appear across the gap. This
generates a high voltage pulse that is sufficient to cause
breakdown to occur across the gap and an arc or plasma to be
generated. The low impedance plasma effectively closes the gap and
creates a current loop path that allows the energy storage
capacitor to discharge through the secondary of the transformer,
transferring the capacitor energy to the spark gap and initiating
the ignition process. Repeated spark generation and ignition of the
air/fuel mixture ensures that combustion is maintained throughout
the engines operation. Varying the spark rate ensures a greater
probability of ignition success due to the fact that one failed
ignition event will be followed up shortly after by another
attempt. Most systems typically don't want to wait too long before
the next spark because unburned fuels could be building up and
creating a potentially hazardous situation. This is the reason why
high spark rates can be beneficial to ignition reliability and also
the same reason why a deterministic and relatively quick time to
first spark may be advantageous.
[0040] The spark exciter assembly may be integrated with the
igniter within a single assembly or enclosure or alternatively, the
exciter assembly and the igniter may consist of two separate
electrically connected components. The exciter assembly may be
designed in any shape required for a particular application. In
certain embodiments, the exciter assembly may be designed to be
rectangular in shape. Although the positioning and design of the
various components of the exciter assembly as well as the igniter
have been described above, it is understood that a person of
ordinary skill in the art may develop alternative designs of the
exciter and igniter units and may position the various components
described above anywhere with respect to the circuit board
depending upon any specifications that may be required for a
particular application.
[0041] In the end application, the power input for the spark
exciter originates from a power source from a vehicle or other
electrical equipment. The power source may stem from a battery, an
alternator, a generator or any other power source suitable for use
within the art. In certain embodiments, the power input may be a
direct current (DC) input originating from a DC power source. The
power source may be run at any voltage suitable for use within the
art. In certain embodiments, the power source may be run between
about 9 to about 50 volts. In further embodiments, the power source
may be run between about 24 and about 32 volts (28 Vdc
nominal).
[0042] The present exciter system shown in FIG. 2 is run from a DC
power source. However, the exciter system of the present disclosure
also encompasses designs capable of accepting an alternating
current (AC) power input which originates from an AC power source.
Thus, in certain embodiments, the power source may also be
generated from an AC power source.
[0043] After electrical power is received from a source within the
exciter assembly (12), it is passed through a filter (18) to reduce
conducted disturbances. The filter may encompass any component
suitable for use within the art as a filter. Examples of component
devices which may be used as filters include but are not limited to
inductors, capacitors, diodes, current limiters, inrush current
limiters, resistors and combinations thereof.
[0044] After current passes through the filter it is run to the
driver circuit (26), the timing circuit (20) and the power
converter (22). The timing sequence circuit controls the
operation/function of the transformer driver and the power
converter circuits. The power converter is first turned on to
charge the capacitor, then the power converter is shut down. The
driver circuit then sends a pulse to the transformer to initiate
the fly-back voltage that causes a high voltage pulse and breakdown
at the spark gap location. The stored capacitor energy is then
dissipated at the spark gap until it is depleted. The process
includes some additional delays as needed, but this pattern will
repeat as long as power is applied to the spark exciter unit.
[0045] As shown in the block diagram of FIG. 1, the spark exciter
variable control unit of the present disclosure may have an input
of about 9V to about 120V and an output breakdown voltage of about
6 kV to about 25 kV. Spark rate may range from about 1 to about 300
sparks per second and spark energy may range from about 1
millijoule (mJ) to about 115 mJ.
[0046] The present exciter assembly may be used to break down the
gap of any igniter (e.g., any spark plug). It also provides a
control strategy which is reliable in that it works repeatedly to
produce relatively hot plasma compared to conventional igniter
systems and sustains ignition rates of a specific number of sparks
per second. In certain embodiments, the spark exciter is
specifically designed for incorporation and operation of flight
systems. In certain embodiments, the spark exciter is designed for
use in propulsion systems for space craft. In such embodiments, the
spark exciter may encompass an exciter electronic assembly which is
directly mounted on a flight-qualified igniter. The spark exciter
may therefore comprise a compact single unit to reduce ignition
system complexity. As a single unit, the spark exciter eliminates
the use of a corona-prone ignition cable to produce reliable sparks
for ignition of "green" fuels such as liquid oxygen, liquid methane
fuels (LO.sub.2/LCH.sub.4) or other LO.sub.2/hydrocarbons. The
spark exciter is capable of producing 50 to 120 millijoule of
energy per spark at a rate of about 100 to about 300 sparks per
second through the generation of a spark gap breakdown of up to
about 18 kilovolts. In certain embodiments, the spark exciter may
have the following parameter values or equivalents thereof--spark
rate: 100 Hz; voltage input 24-32 VDC; peak spark potential 15 kV;
and delivered energy 70 mJ.
[0047] The present exciter assembly may be set to accommodate the
continuous ignition and combustion any type of "green" fuel that is
being used within the system. This is accomplished by setting the
energy level per spark and the spark rate generated by the exciter
assembly. By setting these parameters within the exciter assembly,
the exciter assembly can generate the peak voltage for breaking
down the spark gap which is required to ignite the particular
"green" fuel that is to be burned. In one embodiment of the present
disclosure, the output voltage is about 15 kV, the spark rate is
about 100 Hz, and the delivered energy is about 70 mJ. In another
embodiment of the present disclosure, the output voltage is about
15 kV, the spark rate is about 260 Hz, and the spark energy is
about 50 mJ. In another embodiment of the present disclosure, the
output voltage is about 15 kV, the spark rate is about 110 Hz, and
the spark energy is about 105 mJ. In another embodiment of the
present disclosure, the output voltage is about 15 kV, the spark
rate is in the range of about 11 to about 100 Hz, and the spark
energy is in the range of about 12 to about 100 mJ. In another
embodiment of the present disclosure, the output voltage is in the
range of 0.1 kV to 18 kV, the spark rate is in the range about 11
to about 100 Hz, and the spark energy is in the range about 12 to
about 100 mJ.
[0048] FIGS. 3 through 6 are technical drawings of an exemplary
spark exciter variable control unit which illustrates a typical
cylindrical unit assembly with associated detail drawings showing
how a typical housing unit could fit together.
[0049] In certain embodiments, the capacitor is capable of storing
about 300V although the storage capacity of the capacitor may vary
depending on the type of capacitor used within the spark exciter
system and the ignition and combustion requirements for the
particular fuel that is being used. Once the electrical current is
discharged from the transformer, it is combined with the current
discharged from the capacitor to bridge the spark gap. Thus, in one
embodiment described herein, about 15,000V originating from the
transformer is combined with about 300V originating from the
capacitor to fill the spark gap (30). This current will cause the
spark gap (30) to arc and break down plasma to generate. The plasma
will function as a conductor, closing the loop within the circuit.
As current flows through the spark gap (30), the plasma and high
temperature is maintained across the gap causing combustion of the
air/fuel mixture. After the spark is generated, there is a delay.
In certain embodiments, the timing circuit may wait beyond the
amount of time for the spark to end before it starts the process of
respectively powering the capacitor and transformer again through
the power converter and the driver. This process is repeated to
provide continuous reliable ignition and combustion of the air/fuel
mixture.
[0050] Through the timing circuit, the exciter assembly is able to
provide variable spark rate capable of igniting and combusting
"green" fuels. Typically the timing circuit allows the spark rate
to be set anywhere from between about 1 to about 300 sparks per
second. In certain embodiments, spark rate may be set to about 200
sparks per second while in other embodiments spark rate may range
from about 1 to 110 sparks per second. The timing circuit and
overall exciter system, however, may be set to generate any spark
rate which is required for ignition and combustion of the specific
"green" fuel being utilized within the system.
[0051] Thus, the timing of the spark rate is driven by the hardware
of the exciter assembly (12) which includes the timing circuit, the
driver, the power converter, the transformer and the capacitor. In
general, these components within exciter assembly (12) include
numerous resistors and capacitors which run the timing of the spark
or ignition within the igniter. In particular, the timing circuit
(20) includes various resistors and capacitors which first powers
the power converter (22) to initiate the filling of an electrical
potential within the capacitor (24), turns the power converter (22)
off, initiates a brief delay and subsequently powers the driver
(26) which in turn powers the transformer. A brief delay is
introduced into the system as the capacitor (24) is discharged and
the spark gap is broken down. The timing circuit (20) then
reinitiates current flow to the power converter (22) to recharge
the capacitor (24) and repeat the process over again. Thus, the
system may be described as an analog electronic system which
incorporates the use of a resistor-capacitor circuit. Time delays
and constellations between the different components within the
system are based on an RC time constant between the different
components within the system. Briefly, the operation of components
of the exciter assembly (12) as well as the timing circuit (20) can
be described as follows. A first component within the exciter
assembly (12) or timing circuit (20) will run for certain period of
time and will initiate operation of the next component downstream
from the first component. Once operation of the first component is
complete, the second component will run for a certain period of
time and initiate operation of the next component downstream from
the first component. This process continues until operation of all
the components within the cycle are completed. Once the cycle is
complete, the circuit resets to begin the process over again.
[0052] The present exciter assembly may be adjusted and set to
accommodate the continuous ignition and combustion any type of
"green" fuel that is being used within the system. This is
accomplished by adjusting the energy level per spark and the spark
rate generated by the exciter assembly to determine the ignition
and combustion settings for the particular fuel being utilized and
by setting the ground test unit according. By determining,
adjusting and setting these parameters within the exciter assembly,
the exciter assembly can generate the peak voltage for breaking
down the spark gap which is required to ignite the particular
"green" fuel that is to be burned. In one embodiment of the present
disclosure, the output voltage may be adjusted to about 15 kV, the
spark rate to about 100 Hz, and the delivered energy to about 70
mJ. In another embodiment of the present disclosure, the output
voltage may be adjusted to about 15 kV, the spark rate to about 260
Hz, and the spark energy to about 50 mJ. In another embodiment of
the present disclosure, the output voltage may be adjusted to about
15 kV, the spark rate to about 110 Hz, and the spark energy to
about 105 mJ. In another embodiment of the present disclosure, the
output voltage may be adjusted to about 15 kV, the spark rate may
be adjusted to be in the range of about 11 to about 100 Hz, and the
spark energy may be adjusted to be in the range of about 12 to
about 100 mJ. In another preferred embodiment of the present
disclosure, the output voltage may be adjusted to be in the range
of 0.1 kV to 18 kV, the spark rate may be adjusted to be in the
range about 11 to about 100 Hz, and the spark energy may be
adjusted to be in the range about 12 to about 100 mJ.
[0053] Accordingly, the ground test unit may be described as a
variable system wherein the energy level per spark, the spark rate
and the peak voltage that is used to break down the spark gap can
be adjusted and changed to meet the ignition and combustion
requirements of the fuel being utilized. In certain embodiments,
the spark exciter ground test unit is an analog system wherein
dials are used to control the spark rate, output voltage and
delivered energy. In certain embodiments, the spark exciter ground
test unit includes at least three dials to control spark rate,
output voltage and delivered energy. In operation, turning the dial
adjusts a resistor or potentiometer that adjusts the spark rate and
spark energy through a dial. With respect to the capacitor, a dial
may be used to change the output voltage of the power converter to
change the energy stored in the capacitor to a higher or lower
voltage within the spark loop. In summary, the spark exciter ground
test unit may be adjusted with a potentiometer or resistor through
the use of a dial which may be connected to various components
within the exciter system including the timing circuit, power
converter, capacitor, driver and transformer. In other embodiments,
the spark exciter ground test unit may include a microcontroller or
computer system which is used to adjust the various ignition and
combustion parameters or variables described above. In such
embodiments, one or more microcontrollers may be connected to
various components within the exciter system including the timing
circuit, power converter, capacitor, driver and transformer. In
further embodiments, the spark exciter ground test unit also
includes an interface which is used to adjust or change the
ignition and combustion parameters or variables described above.
Thus, the spark exciter ground test unit may change the ignition
and combustion parameters mechanically, manually or
electronically.
[0054] While the spark exciter variable control unit and
corresponding methods have been described above in connection with
various illustrative embodiments, it is to be understood that other
similar embodiments may be used or modifications and additions may
be made to the described embodiments for performing the same
function disclosed herein without deviating therefrom. Further, all
embodiments disclosed are not necessarily in the alternative, as
various embodiments may be combined or subtracted to provide the
desired characteristics. Variations can be made by one having
ordinary skill in the art without departing from the spirit and
scope hereof. Therefore, the spark exciter variable control unit
should not be limited to any single embodiment, but rather
construed in breadth and scope in accordance with the recitations
of the appended claims.
* * * * *