Spark control based on predictive model

Abstract

In certain embodiments, significant improvements in H2-ICE performance can be achieved by combining active pre-chamber scavenging techniques with predictive model-based spark control to overcome the shortcomings of existing combustion technologies. In certain embodiments, advanced combustion modeling and simulation of the ignition process, including the spark event, arc travel and stretch, and the resulting flame propagation, can be used to predict the relationship between spark energy / power, flow within the electrode gap, and flame development (SOC) for different engines, different spark plugs, and under different conditions. This information can be used to adjust the spark energy / power characteristics during the same-cycle spark event to minimize SOC variation and significantly reduce the propensity for combustion anomalies (e.g., flashback, knock, and pre-ignition) that hinder the achievement of high engine power density and efficiency. Corresponding methods and systems are provided.

Description

[0001] This application is a divisional application of the Chinese national phase application (application number 202380015226.6) of the PCT international application (titled “Predictive Model-Based Spark Control”) with an application date of July 9, 2023 and application number PCT / US2023 / 027192.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to U.S. Patent Application No. 63 / 388,359, entitled “Predictive Model-Based SparkControl,” filed on July 12, 2022. The entire contents of the foregoing patent application are incorporated herein by reference to the extent consistent with the present disclosure. Technical Field

[0004] The present disclosure relates generally to systems and methods for predictive model-based spark control, and more particularly to methods and systems for adjusting spark energy / power characteristics during same-cycle spark events to minimize start-of-combustion (SOC) variations and significantly reduce the propensity for combustion anomalies (e.g., backfire, knock, and pre-ignition) that prevent the achievement of high engine power density and efficiency. Background Art

[0005] The following references describe problems in the prior art, which are described in more detail below. To the extent consistent with the present disclosure, these references are incorporated herein by reference:

[0006] [1] “Prechamber Combustion: Enabling the Competitive Carbon-NeutralICE”, Emmanuella Sotiropoulou, Prometheus Applied Technologies, et al., 23rd CIMAC Congress, June 12–16, 2023.

[0007] [2] “Ignition Energy and Ignition Probability of Methane-Hydrogen-Air Mixtures”, Hankinson G, Mathurkar H, Lowesmith BJ, Loughborough University, Leicestershire, UK, September 2009, h2knowledgecentre.com.

[0008] [3] "Arc Travel Ignition Technology", Tozzi L, Sotiropoulou E, Zhu S, Prometheus Applied Technologies, LLC, Lepley D.T, Altronic, LLC, Hoerbiger Engine Solutions, Yasueda S, GDEC, Inc. 15. Tagung "DER ARBEIT SPROZESS DES VERBRENNUNGSMOTORS", September 24 - 25, 2015.

[0009] [4] "Optimizing High-Energy Tunable Ignition Technology: Preventing Electrode Damage while Extending the Lean Flammability Limit of Gas Engines", Lepley, D.T etc., GMRC, October 2014.

[0010] [5] Tozzi L, Sotiropoulou E, 2017, "Active Scavenge Prechamber", U.S. Patent No. 9,850,806.

[0011] [6] Sotiropoulou etc., 2020, "Prechamber Spark Plugs: The Evolution from Low Emission Natural Gas to Zero Emission H2 Operation", MTZ Worldwide, 6:46 - 50.

[0012] Natural gas (NG) internal combustion engines (designated NG-ICE) and hydrogen (H2) internal combustion engines (designated H2-ICE and defined as engines using any fuel mixture that includes at least 10% hydrogen in addition to NG, ammonia (NH3), and other fuels) are typically subject to large variations in the coefficient of variation of indicated mean effective pressure (COV-IMEP), a high tendency to lubricating oil autoignition (LOA), engine misfires, backfire, knock, and pre-ignition, defined as extreme combustion instabilities. Due to these constraints, H2-ICEs are particularly limited to relatively low levels of engine power density (IMEP) and indicated thermal efficiency (ITE), and to relatively high nitrous oxide (NOx) emissions. The best performance currently achieved by state-of-the-art H2-ICEs is limited to the following:

[0013] -COV-IMEP>2%

[0014] -IMEP≤16 bar

[0015] -ITE≤41%

[0016] -NOx≥100mg / Nm 3

[0017] On the other hand, the performance level required to consider H2-ICE as a competitive and sustainable energy conversion solution suitable to compete with hydrogen fuel cells (H2-FC) requires the following parameters:

[0018] -COV-IMEP≤1%

[0019] -IMEP≥20 bar

[0020] -ITE ≥ 49%

[0021] -NOx≤25mg / Nm 3

[0022] This level of performance requires an ultra-lean hydrogen mixture with high Lambda (λ) values ​​greater than λ = 3 (and in some cases greater than λ = 4). These levels of fuel mixture dilution require a high energy / power spark ignition system to reliably ignite the hydrogen mixture at ultra-lean Lambda, thereby reducing variations in the state of combustion (SOC) that can lead to combustion anomalies such as backfire, knock, and pre-ignition that significantly reduce the maximum achievable engine power density and efficiency.

[0023] An advanced SOC can result in rapid combustion, which can lead to knock and pre-ignition. Conversely, a retarded SOC can result in slow combustion, which can lead to backfire, flame failure, and engine misfire.

[0024] Figure 1 A graph 100 is shown, which indicates that the minimum ignition energy required for H2 at λ = 4 (ϕ = 0.25) 110 is 50 times higher than at stoichiometric (λ = ϕ = 1.0) 120.

[0025] However, proper operation using adjustable / programmable high power spark requires the correct flow rate between the electrodes, which is high enough to prevent high electrode wear rates and hot spots that can cause backfire, detonation and pre-ignition, but low enough to avoid flame kernel extinguishment, causing the engine to misfire.

[0026] The mechanism of this combustion anomaly is as follows:

[0027] Insufficient arc travel of high-power sparks can lead to hot spots on the spark plug electrodes, which lead to an advance in the SOC, resulting in high cylinder combustion pressures and temperatures. This creates hot areas on the valves, spark plugs, cylinder heads, and piston crowns. These hot areas will then ignite the incoming flow of the H2-rich mixture during intake, leading to combustion anomalies such as backfire, knock, and pre-ignition.

[0028] Figure 2 A series of phenomena leading to combustion anomalies originating from hot spots on the electrodes due to incorrect arc travel of high-power sparks is described.

[0029] The formation of hot spots on the electrodes can lead to an advance in SOC, which in turn causes higher cylinder pressures and combustion chamber temperatures (see Figure 2 These conditions will increase the combustion heat release rate (HRR) in the next cycle, resulting in higher cylinder pressure and combustion chamber temperature (see Figure 2 Therefore, detonation may occur in subsequent cycles (see Figure 2 230) and intake flashback (also known as frontfire) / pre-ignition (see Figure 2 Cycle #86 240 in ).

[0030] The occurrence of these combustion anomalies prevents Fb-ICE from achieving power density (IMEP) levels above approximately 16 bar and therefore limits the achievement of the engine efficiency (ITE) and emissions (NOx) levels required to consider Hi-ICE as a sustainable energy conversion solution and thereby compete with H2-FC.

[0031] There is a need to address the aforementioned deficiencies in the art. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1A graph depicts minimum ignition energy required for CH4 and H2 according to certain embodiments.

[0033] Figure 2 Depicted is a sequence of events leading to combustion anomalies in an H2-ICE, according to certain embodiments.

[0034] Figure 3 Depicted is a spark gap of an electrode 310 and a corresponding spark current curve 320 , according to certain embodiments.

[0035] Figure 4 Depicted is a spark gap of an electrode 410 and a corresponding spark current curve 420 , according to certain embodiments.

[0036] Figure 5 Depicted is a spark gap of an electrode 510 and a corresponding spark current curve 520 , in accordance with certain embodiments.

[0037] Figure 6 Depicted is a spark gap of an electrode 610 and a corresponding spark current curve 620 , in accordance with certain embodiments.

[0038] Figure 7 An active scavenging pre-chamber design for operation with an H2-ICE is depicted, according to certain embodiments.

[0039] Figure 8 Depicted are the electrode gap and four typical spark locations according to certain embodiments.

[0040] Figure 9 Depicted are typical ranges of spark voltage and current variations achieved during engine operation using an actively scavenged pre-chamber and a high energy programmable open-loop ignition system, according to certain embodiments.

[0041] Figure 10 An ignition system with the addition of spark voltage and current sensors and an intelligent spark control module is described according to certain embodiments.

[0042] Figure 11 A flow chart of a predictive model-based spark control system according to certain embodiments is depicted.

[0043] Figure 12 A flow chart of a predictive model-based spark control method according to certain embodiments is depicted.

[0044] Figure 13 Depicted is a sharp increase in arc voltage after spark breakdown, according to certain embodiments.

[0045] Figure 14 Depicted is a gradual increase in arc voltage after spark breakdown, according to certain embodiments.

[0046] Figure 15 It is depicted that the arc voltage flattens out after spark breakdown and increases sharply later, according to certain embodiments.

[0047] Figure 16 Depicted is the arc voltage reduction after spark breakdown according to certain embodiments.

[0048] Figure 17 Depicted is a combustion CFD simulation for a leading edge spark occurring at a slow position, according to certain embodiments.

[0049] Figure 18 A lookup table is depicted that relates the initial position of the spark to the spark waveform required to achieve a target SOC value, according to certain embodiments.

[0050] Figure 19 A conventional spark ignition system is depicted in accordance with certain embodiments. DETAILED DESCRIPTION

[0051] In certain embodiments, the spark current profile (i.e., spark power) can be tailored based on the flow rate in the electrode gap and the location where the spark occurs. This can result in minimal SOC variation, thereby enabling the aforementioned engine performance targets to be met with ultra-lean hydrogen fuel mixtures.

[0052] In certain embodiments, the above drawbacks may be mitigated by a) detecting the location of the spark and associated flow rate based on spark voltage trends following voltage breakdown, b) predicting SOC based on simulations that relate spark location, flow rate, spark power, and SOC, and c) adjusting the spark waveform / power during the same spark event to minimize variations in SOC.

[0053] In certain embodiments, a method for controlling the start of combustion in an internal combustion engine is disclosed, comprising: providing a prechamber, the prechamber comprising: an outer surface and an inner surface, the outer surface and the inner surface enclosing a prechamber volume; one or more injection ports communicating with the outer surface and the inner surface for introducing a fuel-air mixture into the prechamber volume; a spark gap electrode assembly comprising: a main electrode disposed within the prechamber volume; and one or more ground electrodes disposed within the prechamber volume and offset from the main electrode to form one or more electrode gaps; introducing a spark across at least one of the one or more electrode gaps to ignite the fuel-air mixture; measuring an initial trend of a spark voltage or spark current of the spark; determining whether the spark is initiated at a leading edge or a trailing edge of the electrode gap and determining whether the flow at the location of the spark is fast or slow; and adjusting the power of the spark based on whether the spark is initiated at a leading edge or a trailing edge and whether the flow of the spark is fast or slow to control the initial rate of flame propagation by adjusting the ignition delay to maintain a substantially constant start of combustion. The one or more electrode gaps may have a maximum value of about 2 mm. -1 to about 4mm -1 From about 2mm for an engine power density of about 10 bar BMEP -1 To about 4mm for engine power density of about 20 bar BMEP -1 The surface to volume ratio of the one or more electrode gaps can vary in proportion to the BMEP. The fuel-air mixture can have a uniform velocity profile in the pre-chamber space and the electrode gaps that varies by less than 50% between cycles.

[0054] The power of the spark can be adjusted by a predetermined amount, determined using combustion simulations and stored in one or more ignition control module lookup tables, to achieve a target combustion initiation value and stable engine operation. If the spark is initiated at the leading edge, the power of the spark can be increased. The power of the spark can be increased inversely proportional to the flow rate at the location of the spark. If the spark is initiated at the trailing edge, the power of the spark can be decreased. The power of the spark can be decreased inversely proportional to the flow rate at the location of the spark.

[0055] The determining step may include comparing an initial trend of a spark voltage or spark current of the spark to a predetermined spark waveform. The predetermined spark waveform may be determined by considering at least one of: whether the spark is initially positioned between a leading edge and a trailing edge, and whether the spark initially has a flow velocity between an average leading edge velocity and an average trailing edge velocity. The step of adjusting the power of the spark may be performed in the same cycle as the spark introduction to achieve a target combustion initiation.

[0056] The method may also include determining that an arc extinction condition exists when a sharp, short-term increase in the spark voltage is detected that oscillates exponentially or sinusoidally. The method may also include determining that a stable flame condition exists when any of the following conditions are detected: (1) the spark voltage flattens after a voltage breakdown event that subsequently increases at a rate exceeding a predetermined value; or (2) the spark voltage increases immediately after a voltage breakdown event that does not oscillate exponentially or sinusoidally and increases at a rate less than a predetermined value. The method may also include determining that a flame extinction or slow burn condition exists when any of the following conditions are detected: (1) the spark voltage decreases after a voltage breakdown event that indicates insufficient arc travel and stretch from the leading edge of the electrode; or (2) the spark voltage increases at a rate greater than a predetermined value after a voltage breakdown event that indicates arc extinction is predicted from the trailing or leading edge of the electrode. The method may also include determining that a fast burn or detonation condition exists when an increasing spark voltage within a predetermined range is detected after the voltage breakdown event. The method may further include using at least one of a spark voltage trend or a spark current trend following the voltage breakdown event to predict combustion initiation based on one or more of: engine design, fuel characteristics, and one or more operating conditions.

[0057] In certain embodiments, a high energy programmable ignition system for an internal combustion engine is disclosed, comprising: at least one of a spark voltage sensor and a spark current sensor, the spark voltage sensor being used to sense a spark voltage from one or more spark gap electrodes in a pre-combustion chamber, the spark current sensor being used to sense a spark current from one or more spark gap electrodes in the pre-combustion chamber; and an ignition control module configured to: receive at least one of the spark voltage and spark current from the one or more spark gap electrodes, measure an initial trend of the spark voltage or spark current of the one or more spark gap electrodes; determine whether a spark is initiated at a leading edge or a trailing edge of the one or more spark gap electrodes; determine whether a flow at the location of the spark is fast or slow; and adjust the power of the spark based on whether the spark is initiated at a leading edge or a trailing edge and whether the flow of the spark is fast or slow to control an initial rate of flame growth by adjusting an ignition delay so as to maintain a substantially constant start of combustion.

[0058] The ignition control module can be configured to adjust the power of the spark by a predetermined amount to achieve a target combustion initiation value and achieve stable engine operation, the predetermined amount being determined using a combustion simulation and stored in one or more ignition control module lookup tables. The ignition control module can be configured to increase the power of the spark if the spark is initiated at the leading edge. The ignition control module can be configured to increase the power of the spark inversely proportional to the flow rate at the location of the spark. The ignition control module can be configured to decrease the power of the spark if the spark is initiated at the trailing edge. The ignition control module can be configured to decrease the power of the spark inversely proportional to the flow rate at the location of the spark.

[0059] The ignition control module can be configured to compare an initial trend in the spark voltage or spark current of the spark to a predetermined spark waveform. The predetermined spark waveform can be determined by considering at least one of whether the spark is initially positioned between the leading edge and the trailing edge, and whether the spark initially has a velocity between an average leading edge velocity and an average trailing edge velocity. The ignition control module can be configured to adjust the power of the spark during the same period as the spark is introduced to achieve a target combustion initiation. The ignition control module can be configured to determine that an arc extinction condition exists when a sharp, brief increase in the spark voltage is detected that exhibits exponential or sinusoidal oscillations.

[0060] The ignition control module can also be configured to determine that a stable flame condition exists when any of the following conditions are detected: (1) a spark voltage flattening trend after a subsequent voltage breakdown event with a rate of increase exceeding a predetermined value; or (2) an increase in spark voltage immediately following a voltage breakdown event that does not oscillate exponentially or sinusoidally and has a rate of increase less than a predetermined value. The ignition control module can also be configured to determine that a flame extinction or slow burn condition exists when any of the following conditions are detected: (1) a decrease in spark voltage after a voltage breakdown event indicating insufficient arc travel and stretch from the leading edge of the electrode; or (2) an increase in spark voltage at a rate greater than a predetermined value after a voltage breakdown event indicating that arc extinction is predicted from the trailing edge or leading edge of the electrode. The ignition control module can also be configured to determine that a fast burn or knock condition exists when an increase in spark voltage within a predetermined range is detected after a voltage breakdown event. The ignition control module may be further configured to use at least one of a spark voltage trend or a spark current trend following the voltage breakdown event to predict combustion initiation based on one or more of: engine design, fuel characteristics, and one or more operating conditions.

[0061] In certain embodiments, advanced 3D combustion CFD (computational fluid dynamics) and 1D modeling and simulation of ignition core dynamics (defined as arc travel and arc stretch occurring at the spark gap electrodes) can be used to create a correlation between arc voltage and current waveforms, ignition core dynamics, and predicted SOC and flame characteristics. This correlation can then be used to derive a spark control method specific to each engine and spark plug design. This can be used to create a predictive model-based spark control with the following capabilities:

[0062] In certain embodiments, as Figure 3 As shown, when the arc travel and arc stretch 310 from the leading edge of the spark gap electrode are predicted to be sufficient to achieve the correct SOC and a stable flame, the spark can be terminated to avoid electrode hot spots leading to early SOC and higher electrode wear rates.

[0063] In certain embodiments, as Figure 4 As shown, when the arc travel and stretch 410 from the leading edge of the electrode is predicted to be insufficient, resulting in flame extinction or hot spots, an enhancement to the spark waveform or a subsequent spark with an enhanced waveform can be triggered within the same cycle, which is predicted to achieve the correct SOC and a stable flame.

[0064] In certain embodiments, as Figure 5 As shown, when the arc stretch 510 from the trailing edge of the electrode is predicted to be sufficient to achieve the correct SOC and a stable flame, the spark can be terminated to avoid electrode hot spots leading to early SOC and higher electrode wear rates.

[0065] In certain embodiments, as Figure 6 As shown, when arc extinction 610 is predicted from the trailing or leading edge of the electrode resulting in flame extinction, an enhancement to the spark or a subsequent spark with an enhancement waveform (which is predicted to achieve the correct SOC and stable flame) may be triggered within the same cycle.

[0066] In certain embodiments, as Figure 7 As shown, the active scavenging pre-combustion chamber design 700 may have an electrode 710 and one or more scavenging ports 720, with the electrode 710 being radially arranged with a large surface and small gap designed to achieve high durability. In certain embodiments where the engine power density is equal to or greater than 20 bar BMEP, a typical electrode surface may be equal to or greater than 9 mm 2 , and the gap size can be equal to or less than 0.25 mm. Therefore, the resulting gap surface to volume ratio can be equal to or greater than 9 mm 2 / (9mm 2 x 0.25mm) = 4mm -1In certain embodiments where the engine power density is less than 20 bar BMEP, the electrode gap surface to volume ratio may be less than 4 mm -1 In certain embodiments, in applications where the power density is about 10 bar BMEP, the electrode surface may be about 1 mm 2 And the gap size can be about 0.5 mm. In these embodiments, the resulting gap surface to volume ratio can be about 1 mm 2 / (1mm 2 x 0.5mm) = 2mm -1 In certain embodiments, applications with power densities between 10 bar BMEP and 20 bar BMEP may use an electrode surface to volume ratio that is roughly proportional to the power density ratio. For example, an application with a power density of 15 bar BMEP may use an electrode surface to volume ratio of approximately 3 mm. -1 The electrode surface to volume ratio is (15 / 10x2=15 / 20x4=3).

[0067] In some embodiments, the flow rate in the gap between the electrode of the active scavenging pre-chamber plug 800 with radial gap and four typical spark locations (located on the edge of the electrode) can be as follows: Figure 8 In these embodiments, the fuel-air mixture flow velocity distribution within the pre-combustion chamber space, as well as the direction of the flow within the electrode gap and its magnitude, can be fairly uniform and repeatable, with cycle-to-cycle variations of less than 50%.

[0068] In some embodiments, the four locations may be characterized as follows:

[0069] ■ Position (810): Leading edge / slow

[0070] ■ Position (820): Leading edge / Fast

[0071] ■ Position (830): Trailing edge / slow speed

[0072] ■ Position (840): Trailing Edge / Fast

[0073] Depending on the location of the initial spark occurrence and the local flow velocity, arc travel and flame kernel development can lead to significant variations in SOC, resulting in severe combustion instabilities, which hinder engine operation at high power density (BMEP) and efficiency (BTE), especially using H2-TCE operating at ultra-lean fuel mixture conditions.

[0074] In certain embodiments, the range of spark voltage and current variations achieved during engine operation using an actively scavenged pre-chamber and a high energy programmable open loop ignition system may be as follows: Figure 9Analysis of these waveforms can allow the extent of arc stretch variation 910 to be determined, and the occurrence of arc extinction 920 can be identified when a sharp, brief increase in spark voltage is detected that oscillates exponentially or sinusoidally.

[0075] In some embodiments, by properly analyzing the spark voltage and current waveforms, the approximate location where the spark first occurs can be determined, such as location (810): leading edge / slow, or location (840): trailing edge / fast.

[0076] In certain embodiments, the approximate location where the spark first occurs can be used to generate predictions of the flame growth rate and resulting SOC using validated combustion CFD. The values ​​of the spark location and corresponding SOC predictions can be compiled in a lookup table.

[0077] In certain embodiments, as Figure 10 As shown, predictive model-based spark control can include a programmable high-energy closed-loop ignition system 1000, in which a spark voltage sensor 1010 and a current sensor 1020 of a spark plug 1030 are added to the secondary winding of an ignition coil 1040. These sensors can provide a spark waveform feedback signal 1050 to an intelligent spark control module 1060 (also referred to as an ignition control module). The intelligent spark control module 1060 generates a spark waveform control signal 1070 and a spark trigger control signal 1080 to an ignition driver 1090. The ignition driver 1090 can then adjust the ongoing (also referred to as the nominal) spark current waveform to a predetermined current waveform stored in the ignition control module lookup table as needed during the same spark event to achieve an SOC sufficiently close to the target value, thereby reducing combustion cycle-to-cycle variations and the occurrence of combustion anomalies such as backfire, knock, and pre-ignition.

[0078] In some embodiments, the spark voltage sensor 1010, the spark current sensor 1020, and the intelligent spark control module 1060 can be incorporated into a high energy programmable spark ignition system. In some embodiments, the high energy programmable spark ignition system can be as described in reference [4] above.

[0079] In certain embodiments, the overall functionality of the predictive model-based spark control system (also known as an adaptive control pre-chamber ignition system) can be as follows: Figure 11 shown.

[0080] In certain embodiments, the spark waveform feedback signal from the ignition coil can be used by the intelligent spark control module to predict the SOC based on the combustion simulation results stored in the lookup table and issue the following three main commands to the ignition driver:

[0081] a. If the predicted SOC occurs at the target 1110, no adjustment is made to the ongoing spark.

[0082] b. If the predicted SOC occurs later than the target 1120, then the ongoing spark energy / power is boosted to a predetermined spark waveform stored in the lookup table.

[0083] c. If the predicted SOC occurs earlier than the target 1130, then reduce the ongoing spark energy / power to a predetermined spark waveform stored in the lookup table.

[0084] In certain embodiments, based on the input commands, the ignition driver 1090 may generate a main pulse to the ignition coil required to obtain a predetermined spark waveform stored in a lookup table (the predetermined spark waveform is necessary to achieve an SOC close to the target value), thereby reducing cycle-to-cycle variation in the SOC.

[0085] In certain embodiments, as Figure 12 As shown, the predictive model-based spark control method may include the following steps: In step 1210, the raw voltage and / or current feedback signal from the secondary side of the ignition coil may be fed to the signal conditioning and processing circuit of the intelligent spark control module. In step 1220, the spark waveform feedback signal may be converted into signal data by the signal conditioning and processing circuit.

[0086] In certain embodiments, as shown in step 1230 , the signal data from the conditioning and processing circuitry may have certain trends that provide a basis for determining an approximate initial spark location and associated flow rate. Figures 13 to 16 Exemplary trends are shown. Figure 13 An example is shown where the sharp arc voltage increase 1310 after spark breakdown is equal to or greater than about 20 volts / μs. Figure 14 An example of a gradual arc voltage increase 1410 in the range of about 10 volts / μs after spark breakdown is shown. Figure 15 An example of a flat arc voltage 1510 after spark breakdown and a sharp rise 1520 that occurs shortly thereafter is shown. Figure 16 An example of an arc voltage drop 1610 after spark breakdown is shown.

[0087] In certain embodiments, as shown in step 1240, signal data can be derived from the spark voltage following the voltage breakdown event and used in conjunction with a method to predict the approximate initial spark location and associated flow rate based on specific trends in the signal. The following are some example predictions: Figure 13 The trends shown may indicate that a trailing edge spark occurs at a fast location (eg, location 840 , having a velocity of approximately 20 m / s) and may result in a fast combustion or knock condition. Figure 14The trends shown may indicate that a trailing edge spark occurs at a slow location (eg, location 830 , with a velocity of approximately 10 m / s) and may result in a stable flame that produces normal combustion with an SOC close to the target. Figure 15 The trends shown may indicate that a leading spark occurs at a fast location (eg, location 820 , with a velocity of approximately 15 m / s) and may result in a stable flame that produces normal combustion with an SOC close to the target. Figure 16 The trends shown may indicate that a leading edge spark occurs at a slow location (eg, location 810 , having a speed of approximately 10 m / s) and may result in a slow burn or flameout condition.

[0088] In some embodiments, as shown in step 1250, the approximate initial spark position and associated flow rate information may be used in a lookup table that provides a correlation between the approximate initial spark position and the associated flow rate, spark waveform, and target SOC value based on combustion CFD simulation predictions. In some embodiments, a combustion CFD simulation of a leading edge spark occurring at a slow position (e.g., position 810) may be performed as follows: Figure 17 As shown. It can be seen that in the case of position 810, an initial flame front can be obtained after about 4.8 crank angle degrees (CAD) (11.70-6.90=4.8). For example, this initial flame front can be used to define the SOC. In some embodiments, Figure 17 The CFD images shown show that the flow velocity field within the spark gap is uniform and has an amplitude of approximately 10 m / s. Image 1710 shows that at a timing of -11.70 CAD, the initial spark 1720 appears at the leading edge. Image 1730 shows that at a timing of -10.09 CAD, due to the force of the flow field on the arc, the arc has advanced 1740 approximately 0.6 mm within the gap. Image 1750 shows that at -8.50 CAD, a flame kernel 1760 has developed within the electrode gap. Image 1770 shows that at -6.90 CAD, the leading edge of the initial flame 1780 forms outside the gap. This condition is defined as the start of combustion (SOC). The total time from the appearance of the spark (-11.70 CAD) to the SOC (-6.90 CAD) defines an ignition delay of 4.8 CAD. Maintaining consistent ignition retard (or SOC) for given engine operating conditions can be achieved through predictive model-based spark control, which prevents abnormal combustion that limits achieving higher engine power density and efficiency.

[0089] Other examples of combustion simulations for different sparks occurring at different locations are provided in the aforementioned reference [1]. In some embodiments, Figure 18As shown, an example lookup table can correlate the approximate spark initiation location to the spark waveform required to achieve a target SOC value. In certain embodiments, spark current curve 1810 can be correlated to the slow leading edge at location 810, spark current curve 1820 can be correlated to the fast leading edge at location 820, spark current curve 1830 can be correlated to the slow trailing edge at location 830, and spark current curve 1840 can be correlated to the fast trailing edge at location 840.

[0090] In certain embodiments, for any given target SOC, a higher energy / power spark may be desired when the approximate initial spark location is at the leading edge, and the spark energy / power may be inversely proportional to the flow rate at the spark location. Conversely, a lower energy / power spark may be desired when the approximate initial spark location is at the trailing edge. The target SOC may depend on ignition timing (IT) and may be defined approximately in the middle of the SOC range.

[0091] In certain embodiments, as shown in step 1260, the ongoing spark waveform may be adjusted on a cycle-by-cycle basis to match a predetermined spark waveform from the lookup table 1250 that corresponds to the predicted approximate initial spark position and may be required to achieve the target SOC. For example, if the previous cycle had spark position 810 (slow leading edge) and the current cycle is predicted to be position 830 (slow trailing edge), the spark waveform should be adjusted from waveform 1810 to waveform 1830.

[0092] In certain embodiments, as shown in step 1270, the intelligent spark control module may perform continuous loop control for each combustion cycle to make cycle-by-cycle adjustments to the ongoing spark waveform as needed to match a predetermined spark waveform from a lookup table that corresponds to a predicted approximate initial spark position and may be required to achieve the target SOC.

[0093] The predictive model-based spark control of certain embodiments improves upon the prior art. Combustion instabilities, which primarily occur in, but are not limited to, hydrogen engines, can be mitigated by improving the homogeneity of the air-fuel mixture and by reducing engine power output (which in turn reduces engine efficiency). Figure 2 ). Currently, there are no known ignition systems featuring adaptive spark control that can mitigate the degree of combustion instability defined in this disclosure. Neither high energy / power ignition systems nor low energy / power ignition systems can mitigate combustion instabilities, particularly in hydrogen engines, to any meaningful degree.

[0094] In certain embodiments, as Figure 19As shown, a conventional spark ignition system may include an ignition driver 1910, an ignition coil 1920, and a spark plug 1930. Figure 1 ) compared to the spark control system based on predictive model (also known as e.g. Figure 10 and Figure 11 The adaptive control pre-chamber ignition system 1000 shown may have the following features: a voltage sensor 1010 and / or a current sensor 1020 on the secondary side of the coil winding 1040, such as Figure 10 As shown; intelligent spark control module 1060, such as Figure 10 and Figure 11 and a communication path for feeding the spark waveform control signal 1070 and the spark trigger control signal 1080 from the intelligent spark control module to the ignition driver 1090, as shown Figure 10 shown.

[0095] In certain embodiments, significant improvements in H2-TCE performance can be achieved through a combination of active pre-chamber scavenging techniques and predictive model-based spark control.

[0096] In certain embodiments, advanced combustion modeling and simulation of the ignition process, including the spark event, arc travel and stretch, and the resulting flame propagation, can be used to predict the relationship between spark energy / power, flow within the electrode gap, and initial flame development, which defines the SOC for different engines and under different conditions. This information can be used to adjust the spark energy / power characteristics during the same-cycle spark event to minimize SOC variations and significantly reduce the propensity for combustion anomalies (e.g., flashback, knock, and pre-ignition) that prevent the achievement of high engine power density and efficiency.

[0097] In some embodiments, the spark voltage and / or current from the secondary side of the coil winding may be controlled by the intelligent spark control module 1060 ( Figure 11 ) is used as feedback signal 1050, the intelligent spark control module 1060 controls the ignition driver 1090 ( Figure 10 ) and allows necessary adjustments in the spark current waveform to minimize SOC variations.

[0098] In certain embodiments, the initial trend of the spark voltage signal after a voltage breakdown event can be used to determine the location where the spark first occurs and the flow rate at that location. This information can be used to predict when SOC will occur. The correlation between spark power and SOC (which can be stored in a lookup table) can then be used to adjust the ongoing spark power to match the target SOC. This method of controlling spark power during same-cycle spark events may be necessary to reduce SOC variations, which can lead to improved engine combustion performance and emissions. Furthermore, controlling spark power during same-cycle spark events can minimize electrode erosion rates in high-energy ignition systems, thereby significantly improving spark plug electrode durability.

[0099] Thus, certain embodiments provide the distinct advantage of enabling engines fueled by hydrogen mixtures to operate at higher power densities, with higher efficiency and lower emissions. This means that, thanks to the present invention, hydrogen engines can compete with fuel cells, providing a viable alternative for accelerating global decarbonization.

[0100] Although the present invention has been described with reference to its specific embodiments, it will be understood by those skilled in the art that various changes can be made and equivalents can be substituted without departing from the true spirit and scope of the present invention as defined by the appended claims. In addition, many modifications can be made to adapt specific circumstances, materials, compositions of matter, methods, one or more operations to the purpose, spirit and scope of the present invention. All such modifications fall within the scope of the appended claims. Specifically, although the method disclosed herein has been described with reference to specific operations performed in a particular order, it will be understood that these operations can be combined, subdivided or reordered to form equivalent methods without departing from the teachings of the present invention. Therefore, unless specifically indicated herein, the order and grouping of operations are not limitations of the present invention.

Claims

1. A method for controlling the start of combustion in an internal combustion engine, comprising: A pre-combustion chamber is provided, comprising: an outer surface and an inner surface, said outer surface and said inner surface enclosing a pre-chamber space; one or more injection ports communicating with the outer surface and the inner surface for introducing a fuel-air mixture into the pre-combustion chamber space; Spark gap electrode assembly, comprising: a main electrode disposed in the pre-combustion chamber space; and one or more ground electrodes disposed in the pre-chamber space and offset from the main electrode to form one or more electrode gaps; introducing a spark across at least one of the one or more electrode gaps to ignite the fuel-air mixture; measuring an initial trend of a spark voltage or a spark current of the spark; determining whether the spark is initiated at a leading edge or a trailing edge of the electrode gap; determining whether the flow at the location of the spark is fast or slow; and The power of the spark is adjusted based on whether the spark is initiated at the leading edge or the trailing edge and whether the spark flow is fast or slow to control the rate of flame propagation in order to maintain a substantially constant initiation of combustion.

2. The method according to claim 1, wherein The power of the spark is adjusted by a predetermined amount determined using a combustion simulation and stored in one or more ignition control module lookup tables to achieve a target combustion initiation value and achieve stable engine operation.

3. The method according to claim 1, wherein If the spark is initiated at the leading edge, the power of the spark is increased.

4. The method according to claim 3, wherein: The power of the spark increases inversely proportional to the flow rate at the location of the spark.

5. The method according to claim 1, wherein If the spark is initiated at the trailing edge, the power of the spark is reduced.

6. The method according to claim 5, wherein: The power of the spark decreases inversely proportional to the flow rate at the location of the spark.

7. The method according to claim 1, wherein The determining step includes comparing an initial trend of a spark voltage or spark current of the spark with a predetermined spark waveform.

8. The method according to claim 7, wherein: The predetermined spark waveform is determined by considering at least one of whether the spark is initially located between the leading edge and the trailing edge, and whether the spark initially has a flow velocity between an average leading edge velocity and an average trailing edge velocity.

9. The method according to claim 1, further comprising: When a sharp, brief increase in the spark voltage is detected that oscillates exponentially or sinusoidally, an arc extinction condition is determined to exist.

10. The method according to claim 9, further comprising: When arc extinction is predicted, the spark is intensified or a subsequent spark with an intensified waveform is generated within the same cycle to achieve the desired combustion initiation.

11. The method according to claim 1 , further comprising: A stable flame condition is determined to exist when either of the following conditions is detected: (1) the spark voltage flattens out after a subsequent voltage breakdown event with a rate of increase exceeding a predetermined value; or (2) the spark voltage increases immediately after a voltage breakdown event that does not oscillate exponentially or sinusoidally and has a rate of increase less than a predetermined value.

12. The method according to claim 1, further comprising: A flame extinction or slow burn condition is determined to exist when either of the following is detected: (1) a decrease in spark voltage following a voltage breakdown event indicating insufficient arc travel and stretch from the leading edge of the electrode; or (2) an increase in spark voltage at a rate greater than a predetermined value following a voltage breakdown event indicating that arc extinction is predicted from the trailing edge or leading edge of the electrode.

13. The method according to claim 1, further comprising: When an increased spark voltage within a predetermined range is detected after a voltage breakdown event, a fast combustion or knock condition is determined to exist.

14. The method according to claim 1, further comprising: The combustion initiation is predicted based on one or more of: engine design, fuel characteristics, and one or more operating conditions using at least one of a spark voltage trend or a spark current trend following a voltage breakdown event.

15. The method according to claim 1, further comprising: When insufficient arc travel and stretch is predicted, the spark is intensified or a subsequent spark with an intensified waveform is generated within the same cycle to achieve the desired combustion initiation.

16. The method according to claim 1, further comprising: When sufficient arc travel and arc stretch are predicted, the spark is terminated.

17. An ignition system for an internal combustion engine, comprising: at least one of a spark voltage sensor for sensing a spark voltage from one or more spark gap electrodes in the pre-chamber and a spark current sensor for sensing a spark current from the one or more spark gap electrodes; as well as The ignition control module is configured to: receiving at least one of a spark voltage and a spark current from the one or more spark gap electrodes, measuring an initial trend of a spark voltage or spark current of the one or more spark gap electrodes; determining whether the spark is initiated at a leading edge or a trailing edge of the one or more spark gap electrodes; determining whether the flow at the location of the spark is fast or slow; The power of the spark is adjusted based on whether the spark is initiated at the leading edge or the trailing edge and whether the spark flow is fast or slow to control the rate of flame growth in order to maintain a substantially constant initiation of combustion.

18. The system according to claim 17, wherein: The spark control module is configured to adjust the power of the spark by a predetermined amount determined using a combustion simulation and stored in one or more spark control module lookup tables to achieve a target combustion initiation value and achieve stable engine operation.

19. The system of claim 17, wherein: The spark control module is configured to increase power of the spark if the spark is initiated at the leading edge.

20. The system of claim 19, wherein: The spark control module is configured to increase the power of the spark inversely proportional to the flow rate at the location of the spark.

21. The system of claim 17, wherein: The spark control module is configured to reduce power of the spark if the spark is initiated at the trailing edge.

22. The system of claim 21, wherein: The spark control module is configured to reduce the power of the spark inversely proportional to the flow rate at the location of the spark.

23. The system of claim 17, wherein: The ignition control module is configured to compare an initial trend of a spark voltage or spark current of the spark to a predetermined spark waveform.

24. The system of claim 23, wherein: The predetermined spark waveform is determined by considering at least one of whether the spark is initially located between the leading edge and the trailing edge, and whether the spark initially has a flow velocity between an average leading edge velocity and an average trailing edge velocity.

25. The system of claim 17, wherein: The ignition control module is configured to determine that an arc extinction condition exists when a sharp, brief increase in the spark voltage is detected that oscillates exponentially or sinusoidally.

26. The system of claim 25, wherein: The ignition control module is configured to, when arc extinction is predicted, enhance the spark or generate a subsequent spark with an enhanced waveform within the same cycle to achieve a desired initiation of combustion.

27. The system of claim 17, wherein: The ignition control module is further configured to determine that a stable flame condition exists when either of the following conditions is detected: (1) the spark voltage flattens out after a subsequent voltage breakdown event with a rate of increase exceeding a predetermined value; or (2) the spark voltage increases immediately after a voltage breakdown event that does not oscillate exponentially or sinusoidally and has a rate of increase less than a predetermined value.

28. The system of claim 17, wherein: The ignition control module is further configured to determine that a flame extinction or slow burn condition exists when either of the following is detected: (1) decreasing the spark voltage after a voltage breakdown event indicating insufficient arc travel and stretch from the leading edge of the electrode; or (2) increasing the spark voltage at a rate greater than a predetermined value after a voltage breakdown event indicating that arc extinction is predicted from the trailing edge or leading edge of the electrode.

29. The system of claim 17, wherein: The ignition control module is further configured to determine that a fast combustion or knock condition exists when an increased spark voltage within a predetermined range is detected after a voltage breakdown event.

30. The system of claim 17, wherein: The ignition control module is further configured to predict the start of combustion based on one or more of engine design, fuel characteristics, and one or more operating conditions using at least one of a spark voltage trend or a spark current trend following a voltage breakdown event.

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