Prediction Model-Based Spark Control

Abstract

In certain embodiments, a significant improvement in H2-ICE performance can be achieved by a combination of active scavenging pre-combustion chamber technology and predictive model-based spark control to overcome the drawbacks of known combustion technologies. In certain embodiments, advanced combustion modeling and simulation of the ignition process, including spark events, arc movement and elongation, and resulting flame propagation, can be used to predict the relationship between spark energy / output, flow within the electrode gap, and flame growth (SOC) for different engines, different spark plugs, and various conditions. This information can be used to adjust the spark energy / output characteristics during the spark event of the same cycle in order to minimize SOC variations and significantly reduce the tendency of combustion anomalies such as backfire, knocking, and pre-ignition that prevent the achievement of high engine output density and efficiency.

Description

Technical Field

[0001] I. Cross - Reference to Related Applications This application claims priority to U.S. Patent Application No. 63 / 388,359, filed on July 12, 2022, entitled "Predictive Model - Based Spark Control". The entire disclosure of the above - mentioned patent application is incorporated herein by reference to the extent consistent with the present disclosure.

[0002] II. Field of the Invention The present disclosure generally relates to systems and methods for predictive - model - based spark control, and more particularly, to methods and systems for adjusting spark energy / output characteristics during spark events of the same cycle to minimize combustion - start - of - combustion (SOC) variations and significantly reduce the tendency of combustion anomalies such as backfire, knocking, and pre - ignition, which impede the achievement of high engine output density and efficiency.

Background Art

[0003] III. Background of the Invention The following references describe problems of the prior art, which will be explained in more detail later. These references are incorporated herein by reference to the extent consistent with the present disclosure. [1] “Prechamber Combustion: Enabling the Competitive Carbon - Neutral ICE”, Emmanuella Sotiropoulou, Prometheus Applied Technologies, et al, 23rd CIMAC Congress, June 12 - 16, 2023. [2] "Ignition Energy and Ignition Probability of Methane-Hydrogen-Air Mixtures", Hankinson G., Mathurkar H., Lowesmith B.J., Loughborough University, Leicestershire, UK - September 2009 - h2knowledgecentre.com。 [3] "Arc Travel Ignition Technology", TozziL., Sotiropoulou E., Zhu S., Prometheus Applied Technologies, LLC. Lepley D.T., Altronic, LLC, Hoerbiger Engine Solutions. Yasueda S., GDEC, Inc. 15. Tagung "DER ARBEITSPROZESS DES VERBRENNUNGSMOTORS" September 24-25, 2015。 [4] "Optimizing High-Energy Tunable Ignition Technology: Preventing Electrode Damage while Extending the Lean Flammability Limit of Gas Engines," Lepley, D.T., et al, GMRC, October 2014。 [5] Tozzi L., Sotiropoulou E. 2017. Active Scavenge Prechamber. U.S. Patent No. 9,850,806。 [6] Sotiropoulou, et al, 2020. Prechamber Spark Plugs: The Evolution from Low Emission Natural Gas to Zero Emission H2 Operation, MTZ Worldwide, 6:46-50。

[0004] A natural gas (NG) internal combustion engine represented as NG-ICE and an engine defined as a hydrogen (H2) internal combustion engine represented as H2-ICE that uses any fuel mixture containing at least 10% H2 in addition to NG, ammonia (NH3), and other fuels are generally affected by large variations in the coefficient of variation of the indicated mean effective pressure (COV-IMEP), lubricating oil autoignition (LOA) defined as extreme combustion instability, misfires, backfires, knocking, and preignition tendencies. Due to these constraints, in particular, H2-ICEs are limited to relatively low levels of engine output density (IMEP) and indicated thermal efficiency (ITE) as well as relatively high levels of nitrogen oxide (NOx) emissions. Currently, the best performance achieved by conventional H2-ICEs is limited as follows. - COV-IMEP > 2% - IMEP ≤ 16 bar - ITE ≤ 41% - NOx ≥ 100 mg / Nm 3

[0005] On the other hand, the performance levels required for H2-ICEs to be considered a competitive and sustainable energy conversion solution suitable for competing with hydrogen fuel cells (H2-FCs) would need to achieve the following parameters. - COV-IMEP ≤ 1% - IMEP ≥ 20 bar - ITE ≥ 49% - NOx ≤ 25 mg / Nm 3

[0006] Such performance levels require ultra-lean hydrogen mixtures with high lambda (λ) values exceeding λ = 3 and, in some cases, exceeding λ = 4. Dilution of these levels of fuel mixtures requires a high-energy / high-output spark ignition system that reduces variations in the start of combustion (SOC) that can cause combustion anomalies such as backfires, knocking, and preignition, which reliably ignite the hydrogen mixture at ultra-lean lambda and thus significantly reduce the achievable maximum engine output density and efficiency.

[0007] Advanced SOC can cause high-speed combustion, and as a result, knocking and pre-ignition may occur. In contrast, retarded SOC can cause low-speed combustion, and as a result, backfire, flameout, and misfire may occur.

[0008] Figure 1 shows a chart 100 indicating that the minimum ignition energy required for H2 at λ = 4 (φ = 0.25) 110 is 50 times higher than that at stoichiometry (λ = φ = 1.0) 120.

[0009] However, for proper operation with adjustable / programmable high-output sparks, an appropriate flow velocity between the electrodes is required that is high enough to prevent high rates of electrode consumption and hot spots leading to backfire, knocking, and pre-ignition, but low enough to avoid the quenching of the flame kernel leading to engine misfire.

[0010] The mechanisms of these combustion abnormalities are as follows.

[0011] When the arc movement of the high-output spark is insufficient, hot spots occur on the spark plug electrodes, as a result, the SOC advances, and thus the cylinder combustion pressure and temperature increase, and high-temperature regions occur in the valves, spark plugs, cylinder head, and piston crown. Therefore, these high-temperature regions ignite the flow of the high-concentration H2 mixture flowing into the intake air, causing combustion abnormalities such as backfire, knocking, and pre-ignition.

[0012] Figure 2 shows a series of phenomena leading to combustion abnormalities due to inappropriate arc movement of the high-output spark following hot spots on the electrodes.

[0013] When a hot spot is formed on the electrode, the SOC advances, and the cylinder pressure and combustion chamber temperature may increase (see the 83rd cycle 210 in FIG. 2). These conditions increase the combustion rate of heat release (HRR) in the next cycle and further increase the cylinder pressure and combustion chamber temperature (see the 84th cycle 220 in FIG. 2). As a result, in subsequent cycles, knocking (see the 85th cycle 230 in FIG. 2) and intake backfire (also known as front fire) / pre-ignition (see the 86th cycle 240 in FIG. 2) may occur.

[0014] Due to the occurrence of these abnormal combustions, the H2-ICE is prevented from reaching an output density (IMEP) exceeding approximately 16 bar, and the H2-ICE is regarded as a sustainable energy conversion solution. Therefore, achieving the required levels of engine efficiency (ITE) and exhaust gas (NOx) to compete with H2-FC is limited. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0015] It is necessary to address the aforementioned drawbacks in the art. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] IV. BRIEF DESCRIPTION OF THE DRAWINGS

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DETAILED DESCRIPTION OF THE INVENTION

[0017] V. DETAILED DESCRIPTION In certain embodiments, the spark current profile (i.e., spark output) can be adjusted according to the flow velocity at the electrode gap and the spark generation position. This can make the variation of SOC smaller, and thus may enable achieving the above engine performance goals with an ultra-lean hydrogen fuel mixture.

[0018] In certain embodiments, the above drawbacks can be alleviated by a method of: a) detecting the spark position and the associated flow velocity based on the trend of the spark voltage after voltage breakdown; b) predicting the SOC based on a simulation that correlates the spark position, flow velocity, spark output, and SOC; and c) adjusting the spark waveform / output during the same spark event to minimize the variation of the SOC.

[0019] In certain embodiments, a method for controlling combustion initiation in an internal combustion engine, comprising providing a prechamber, the prechamber including an outer surface and an inner surface enclosing a prechamber volume, one or more discharge ports communicating between the outer surface and the inner surface for introducing a fuel-air mixture into the prechamber volume, a spark gap electrode assembly including a primary electrode disposed within the prechamber volume and one or more ground electrodes disposed within the prechamber volume and offset from the primary 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 the spark voltage or spark current of the spark, determining whether the spark starts at the leading edge or the trailing edge of the electrode gap, determining whether the flow at the spark position is high or low, and adjusting the output of the spark based on whether the spark starts at the leading edge or the trailing edge and whether the flow of the spark is high or low, and adjusting the ignition delay to maintain substantially constant combustion initiation, thereby controlling the initial flame propagation speed. One or more of the electrode gaps are about 2 mm-1 ~ about 4 mm -1 and may have a surface area to volume ratio. The surface area to volume ratio of one or more electrode gaps is about 2 mm for an engine output density of about 10 bar BMEP -1 ~ about 4 mm for an engine output density of about 20 bar BMEP -1 and may vary proportionally to the BMEP. The fuel-air mixture may have a uniform flow velocity distribution that varies by less than 50% per cycle in the pre-combustion chamber volume and the electrode gap.

[0020] The output of the spark is determined using combustion simulations and adjusted by a predetermined amount stored in one or more ignition control module look-up tables to achieve a target combustion start value and achieve stable engine operation. The output to the spark can be increased if the spark is initiated at the leading edge. The output of the spark can be increased inversely proportional to the flow velocity at the position of the spark. The output to the spark can be reduced if the spark is initiated at the trailing edge. The output of the spark can be reduced inversely proportional to the flow velocity at the position of the spark.

[0021] The determining step may include comparing an initial trend of 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 located between the leading edge and the trailing edge and whether the spark initially has a flow velocity between the average leading edge velocity and the average trailing edge velocity. The step of adjusting the output of the spark can be performed in the same cycle in which the spark is introduced to achieve target combustion start.

[0022] This method may further include determining that an arc extinction state exists when a steep and short rise of the spark voltage is detected to be exponential or sinusoidal ringing. This method may further include determining that a stable flame state exists when any of the following is detected: (1) a flat trend of the spark voltage after a voltage breakdown event, followed by a subsequent rate of rise exceeding a predetermined value, or (2) an immediate rise of the spark voltage after a voltage breakdown event that is not exponential or sinusoidal ringing and has a rate of rise less than a predetermined value. This method may further include determining that an extinguishing or slow combustion state exists when any of the following is detected: (1) a decrease in the spark voltage after a voltage breakdown event indicating insufficient arc movement and elongation from the leading edge of the electrode, or (2) a rise in the spark voltage at a rate exceeding a predetermined value after a voltage breakdown event indicating that arc extinction from the trailing edge or leading edge of the electrode is predicted. This method may further include determining that a high-speed combustion or knocking state exists when a rise in the spark voltage within a predetermined range is detected after a voltage breakdown event. This method may further include predicting combustion initiation based on at least one of the trend of the spark voltage or the trend of the spark current after a voltage breakdown event, based on one or more of engine design, fuel characteristics, and one or more of one or more operating conditions.

[0023] In certain embodiments, a high energy programmable ignition system for an internal combustion engine includes at least one of a spark voltage sensor for detecting a spark voltage from one or more spark gap electrodes in a pre - combustion chamber and a spark current sensor for detecting 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 the spark current from the one or more spark gap electrodes, measure an initial trend of the spark voltage or the spark current of the one or more spark gap electrodes, determine whether the spark starts at the leading edge or the trailing edge of the one or more spark gap electrodes, determine whether the flow at the position of the spark is fast or slow, and adjust the output to the spark based on whether the spark starts at the leading edge or the trailing edge and whether the flow of the spark is fast or slow, and control the initial rate of flame growth by adjusting the ignition delay to maintain substantially constant combustion initiation. A high energy programmable ignition system is disclosed.

[0024] The ignition control module may be configured to adjust the output of the spark by a predetermined amount determined using combustion simulation and stored in one or more ignition control module look - up tables to achieve a target combustion initiation value and achieve stable engine operation. The ignition control module may be configured to increase the output to the spark if the spark starts at the leading edge. The ignition control module may be configured to increase the output of the spark inversely proportional to the flow velocity at the position of the spark. The ignition control module may be configured to reduce the output to the spark if the spark starts at the trailing edge. The ignition control module may be configured to reduce the output of the spark inversely proportional to the flow velocity at the position of the spark.

[0025] The ignition control module may be configured to compare an initial trend of a spark voltage or a spark current of a spark with a predetermined spark waveform. The predetermined spark waveform may be determined by considering at least one of whether the spark is initially located 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 ignition control module may be configured to adjust the output of the spark in the same cycle in which the spark is introduced in order to achieve a target combustion start. The ignition control module may be configured to determine that an arc extinction state exists when it is detected that a steep and short rise of the spark voltage is exponential or sinusoidal ringing.

[0026] The ignition control module may be further configured to determine that a stable flame state exists when any of (1) a flat trend of the spark voltage after a voltage breakdown event, a subsequent rate of rise exceeding a predetermined value thereafter, or (2) an immediate rise of the spark voltage after a voltage breakdown event that is not exponential or sinusoidal ringing and has a rate of rise less than a predetermined value is detected. The ignition control module may be further configured to determine that an extinguished or low-speed combustion state exists when any of (1) a decrease in the spark voltage after a voltage breakdown event indicating insufficient arc movement and elongation from the leading edge of the electrode, or (2) a rise in the spark voltage at a rate exceeding a predetermined value after a voltage breakdown event indicating that arc extinction from the trailing edge or leading edge of the electrode is predicted is detected. The ignition control module may be further configured to determine that a high-speed combustion or knocking state exists when an increase in the spark voltage within a predetermined range is detected after a voltage breakdown event. The ignition control module may be further configured to predict combustion start based on at least one of a trend of the spark voltage or a trend of the spark current after a voltage breakdown event, based on one or more of engine design, fuel characteristics, and one or more of one or more operating conditions.

[0027] In certain embodiments, advanced 3D combustion CFD (Computational Fluid Dynamics) of ignition kernel dynamics defined as arc movement and arc elongation occurring at the spark gap electrodes, as well as ID modeling and simulation, can be used to create correlations between arc voltage and current waveforms, ignition kernel dynamics, predicted SOC (Start of Combustion), and flame characteristics. Next, such correlations can be used to derive a spark control method for each engine and spark plug design. Using this, a prediction model-based spark control with the following functions can be achieved.

[0028] In certain embodiments such as shown in Figure 3, if sufficient arc movement and arc elongation 310 are predicted from the leading edge of the spark gap electrode to achieve proper SOC and a stable flame, the spark can be terminated to avoid electrode hot spots that cause early SOC and high electrode wear rates.

[0029] In certain embodiments such as shown in Figure 4, if insufficient arc movement and elongation 410 that result in flame extinction or hot spots are predicted from the leading edge of the electrode, a subsequent spark with an enhanced spark waveform or an enhanced waveform that is predicted to achieve proper SOC and a stable flame can be triggered within the same cycle.

[0030] In certain embodiments such as shown in Figure 5, if sufficient arc elongation 510 is predicted from the trailing edge of the electrode to achieve proper SOC and a stable flame, the spark can be terminated to avoid electrode hot spots that cause early SOC and high electrode wear rates.

[0031] In certain embodiments such as shown in Figure 6, if arc blowout 610 that results in flame extinction is predicted from the trailing or leading edge of the electrode, a subsequent spark with an enhanced spark or an enhanced waveform that is predicted to achieve proper SOC and a stable flame can be triggered within the same cycle.

[0032] In certain embodiments, such as those shown in FIG. 7, the active scavenging pre - combustion chamber design 700 can have electrodes 710 that are radially arranged and have a large surface area and a small gap designed to achieve high durability, and one or more scavenging ports 720. In certain embodiments having an engine output density of 20 bar BMEP or more, a typical electrode surface area can be 9 mm 2 or more, and the gap size can be 0.25 mm or less. Thus, the resulting gap surface area to volume ratio can be 9 mm 2 / (9 mm 2 ×0.25 mm)=4 mm -1 or more. In certain embodiments having an engine output density less than 20 bar BMEP, the electrode gap surface area to volume ratio can be less than 4 mm -1 . In certain embodiments, for applications having an output density of about 10 bar BMEP, the electrode surface area can be about 1 mm 2 , and the gap size can be about 0.5 mm. In these embodiments, the resulting gap surface area to volume ratio can be about 1 mm 2 / (1 mm 2 ×0.5 mm)=2 mm -1 . In certain embodiments, for applications having an output density between 10 bar BMEP and 20 bar BMEP, an electrode surface area to volume ratio approximately proportional to the output density ratio can be used. For example, an application having an output density of 15 bar BMEP can use an electrode surface area to volume ratio of about 3 mm -1 (15 / 10×2 = 15 / 20×4 = 3).

[0033] In certain embodiments, the flow velocity in the gap between the electrodes and four typical spark positions at the edges of the electrodes of the active scavenging pre - combustion chamber plug 800 having a radial gap can be as shown in FIG. 8. In these embodiments, the flow velocity distribution of the fuel - air mixture within the pre - combustion chamber volume portion and the direction and magnitude of the flow within the electrode gap are extremely uniform and reproducible with less than 50% cycle - to - cycle variation.

[0034] In certain embodiments, four positions can be characterized as follows. · Position (810): Leading edge / Low speed · Position (820): Leading edge / High speed · Position (830): Trailing edge / Low speed · Position (840): Trailing edge / High speed

[0035] Depending on the location where the spark first occurs and the local flow velocity, the SOC can vary significantly due to arc movement and flame kernel formation, especially in H2-TCE operating in an ultra-lean fuel mixture state, causing large combustion instabilities that prevent operation at high engine output density (BMEP) and efficiency (BTE).

[0036] In certain embodiments, the range of spark voltage and current fluctuations obtained during engine operation using an active scavenging pre-chamber and a high-energy programmable open-loop ignition system can be as shown in FIG. 9. Analysis of these waveforms can enable determination of the degree of arc elongation variation 910 and the occurrence of arc extinction 920, which is identified when the steep and short rise of the spark voltage is detected as being exponential or sinusoidal ringing.

[0037] In certain embodiments, by appropriately analyzing the spark voltage and current waveforms, it may be possible to determine the approximate location where the spark first occurred, such as position (810): leading edge / low speed or position (840): trailing edge / high speed.

[0038] In certain embodiments, using the approximate location where the spark first occurred, it is possible to generate a prediction of the flame growth rate and the resulting SOC using validated combustion CFD. The values of the spark position and the corresponding SOC predictions can be compiled in a lookup table.

[0039] In certain embodiments, such as those shown in FIG. 10, the prediction model-based spark control may include a programmable high energy closed-loop ignition system 1000 with a spark voltage sensor 1010 and a current sensor 1020 added to the secondary winding of the ignition coil that makes up the ignition coil 1040. These sensors can provide a spark waveform feedback signal 1050 to a smart spark control module 1060 (also known as an ignition control module), and the smart spark control module 1060 generates a spark waveform control signal 1070 and a spark trigger control signal 1080 to the ignition driver 1090. The ignition driver 1090 thereby adjusts the ongoing (i.e., nominal) spark current waveform to a predetermined current waveform stored in the ignition control module look-up table as needed to achieve a SOC that is close enough to the target value during the same ignition event, thus reducing variations between combustion cycles and the occurrence of combustion anomalies such as backfire, knocking, and pre-ignition.

[0040] In certain embodiments, the spark voltage sensor 1010, the spark current sensor 1020, and the smart spark control module 1060 can be incorporated into a high energy programmable spark ignition system. In certain embodiments, the high energy programmable spark ignition system can be as described in reference [4] above.

[0041] In certain embodiments, the overall function of the prediction model-based spark control system (also known as an adaptive control pre-chamber ignition system) can be as shown in FIG. 11.

[0042] In certain embodiments, the smart spark control module can use the spark waveform feedback signal from the ignition coil to predict the SOC based on the combustion simulation results stored in the look-up table and issue the following three main commands to the ignition driver. a. If the predicted SOC is as desired, no adjustment of the ongoing spark 1110. b. If the predicted SOC occurs after the target, increase the in - progress spark energy / output to a predetermined spark waveform stored in the look - up table 1120. c. If the predicted SOC occurs earlier than the target, reduce the in - progress spark energy / output to a predetermined spark waveform stored in the look - up table 1130.

[0043] In a particular embodiment, based on the above input command, the ignition driver 1090 can generate a primary pulse to the ignition coil required to obtain a predetermined spark waveform stored in the look - up table to achieve an SOC close to the target value, and thus can reduce the inter - cycle variation of the SOC.

[0044] In a particular embodiment as shown in FIG. 12, the prediction - 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 can be supplied to the signal conditioning and processing circuit of the smart spark control module. In step 1220, the spark waveform feedback signal can be converted into signal data by the signal conditioning and processing circuit.

[0045] In a particular embodiment as shown in step 1230, the signal data from the conditioning and processing circuit may have a predetermined trend that provides a basis for determining the approximate initial spark position and the associated flow rate. Exemplary trends are shown in FIGS. 13 - 16. FIG. 13 shows an example of a steep arc voltage rise 1310 of more than about 20 volts / μs following spark breakdown. FIG. 14 shows an example of a gentle arc voltage rise 1410 in the range of about 10 volts / μs following spark breakdown. FIG. 15 shows an example of a flat arc voltage 1510 following spark breakdown, including a steep rise 1520 at a later time. FIG. 16 shows an example of an arc voltage drop 1610 following spark breakdown.

[0046] In certain embodiments, such as those shown in step 1240, signal data can be derived from the spark voltage after a voltage breakdown event and used with a method for predicting a general initial spark position and associated flow rate based on a predetermined trend of the signal. The following are some exemplary predictions. The trend shown in FIG. 13 may indicate that a trailing edge spark occurs at a high speed position (e.g., position 840 having a speed of about 20 m / s), which may result in high speed combustion or a knocking condition. The trend shown in FIG. 14 may indicate that a trailing edge spark occurs at a low speed position (e.g., position 830 having a speed of about 10 m / s), which may result in a stable flame producing normal combustion with an SOC close to the target. The trend shown in FIG. 15 may indicate that a leading edge spark occurs at a high speed position (e.g., position 820 having a speed of about 15 m / s), which may result in a stable flame producing normal combustion with an SOC close to the target. The trend shown in FIG. 16 may indicate that a leading edge spark occurs at a low speed position (e.g., position 810 having a speed of about 10 m / s), which may result in low speed combustion or an extinguished condition.

[0047] In certain embodiments, such as those shown in step 1250, a lookup table can be used for the approximate initial spark position and associated flow velocity information, where a correlation between the approximate initial spark position and associated flow velocity, the spark waveform, and the target SOC value is provided based on combustion CFD simulation predictions. In certain embodiments, the combustion CFD simulation for a leading edge spark occurring at a low speed position (e.g., position 810) can be as shown in FIG. 17. In the case of position 810, it can be seen that the initial flame front can be achieved approximately 4.8 crank angle degrees (CAD) (11.70 - 6.90 = 4.8) later. This initial flame front can be used, for example, to define the SOC. In certain embodiments, the CFD image shown in FIG. 17 shows that the flow velocity field within the spark gap is uniform and has a magnitude of approximately 10 m / s. Image 1710 shows that the initial spark 1720 occurs at the leading edge at a timing of -11.70 CAD. Image 1730 shows that at a timing of -10.09 CAD, the arc has moved approximately 0.6 mm within the gap due to the force acting on the arc by the flow field 1740. Image 1750 shows that a flame kernel 1760 has occurred within the electrode gap at -8.50 CAD. Image 1770 shows that the front of the initial flame 1780 is formed outside the gap at -6.90 CAD. This state is defined as the start of combustion (SOC). The total time from the occurrence of the spark (-11.70 CAD) to the SOC (-6.90 CAD) defines an ignition delay of 4.8 CAD. For a given engine operating state, predictive model-based spark control can achieve the maintenance of a consistent ignition delay (or SOC), thereby preventing the occurrence of abnormal combustion that limits the achievement of higher engine output density and efficiency.

[0048] Other examples of combustion simulations for different sparks occurring at different positions are provided in the above reference [1]. In a particular embodiment as shown in FIG. 18, a look-up table example can correlate a schematic initial position of a spark to a spark waveform necessary to achieve a target SOC value. In a particular embodiment, the spark current profile 1810 can be correlated to the low-speed leading edge at position 810, the spark current profile 1820 can be correlated to the high-speed leading edge at position 820, the spark current profile 1830 can be correlated to the low-speed trailing edge at position 830, and the spark current profile 1840 can be correlated to the high-speed trailing edge at position 840.

[0049] In a particular embodiment, if the schematic initial spark position is the leading edge for any given target SOC, a higher energy / output spark may be required, and the energy / output of the spark may be inversely proportional to the flow velocity at the position of the spark. Conversely, if the position of the schematic initial spark is the trailing edge, a lower energy / output spark may be required. The target SOC may be determined by the ignition timing (IT) and may be defined to be approximately in the middle of the range of SOC variations.

[0050] In a particular embodiment as shown in step 1260, an in-cycle adjustment of the ongoing spark waveform can be made to match a predetermined spark waveform from the look-up table 1250 that corresponds to the predicted schematic initial spark position and may be required to achieve the target SOC. For example, if the previous cycle has a spark position 810 (low-speed leading edge) and the prediction for the current cycle is at position 830 (low-speed trailing edge), the spark waveform should be adjusted from waveform 1810 to waveform 1830.

[0051] In a particular embodiment as shown in step 1270, continuous loop control can be performed for each combustion cycle by the smart spark control module as needed to match a predetermined spark waveform from the look-up table that corresponds to the predicted schematic initial spark position and may be required to achieve the target SOC, to make an in-cycle adjustment to the ongoing spark waveform.

[0052] The prediction model-based spark control of certain embodiments is an improvement over the prior art. Primarily, but not limited to, the combustion instabilities (backfire, knocking, and pre-ignition shown in FIG. 2) that occur in hydrogen engines can be mitigated by improving the homogeneity of the air-fuel mixture and reducing the engine output that reduces engine efficiency. There is no known ignition system characterized by adaptive spark control that can mitigate the degree of combustion instability as defined in the present disclosure. Neither high-energy / output ignition systems nor low-energy / output ignition systems can mitigate combustion instabilities in hydrogen engines to any significant degree.

[0053] In certain embodiments, a conventional spark ignition system may include an ignition driver 1910, an ignition coil 1920, and a spark plug 1930, as shown in FIG. 19. Compared to a conventional system (FIG. 19), a prediction model-based spark control system (also known as an adaptive control pre-chamber ignition system 1000 as shown in FIGS. 10 and 11) may be characterized by a voltage sensor 1010 and / or a current sensor 1020 on the secondary side of the coil winding 1040 as shown in FIG. 10, a smart spark control module 1060 as shown in FIGS. 10 and 11, and a communication path for supplying a spark waveform control signal 1070 and a spark trigger control signal 1080 from the smart spark control module to the ignition driver 1090 as shown in FIG. 10.

[0054] In certain embodiments, a significant improvement in H2-ICE performance can be achieved by a combination of active scavenging pre-chamber technology and prediction model-based spark control.

[0055] In certain embodiments, advanced combustion modeling and simulation of the ignition process, including spark events, arc movement and elongation, and resulting flame propagation, can be used to predict the relationship between spark energy / output, flow within the electrode gap, and initial flame growth that defines the SOC, for different engines and under various conditions. This information can be used to adjust the spark energy / output characteristics during the spark event of the same cycle to minimize SOC variations and significantly reduce the tendency of combustion anomalies such as backfire, knocking, and pre-ignition that impede the achievement of high engine output density and efficiency.

[0056] In certain embodiments, the spark voltage and / or current from the secondary side of the coil winding can be used as a feedback signal 1050 by a smart spark control module 1060 (FIG. 11) that controls the ignition driver 1090 (FIG. 10) and enables the necessary adjustments to the spark current waveform to minimize SOC variations.

[0057] In certain embodiments, the initial tendency 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 velocity at that location. This information can be used to predict the time of SOC occurrence. Then, using the correlation between the spark output and the SOC that can be stored in a look-up table, the ongoing spark output can be adjusted to match the target SOC. This method of controlling the spark output during the spark event of the same cycle may be necessary to reduce variations in the SOC, and as a result, improve the combustion performance and exhaust gases of the engine. Further, by controlling the spark output during the spark event of the same cycle, the rate of electrode corrosion by a high energy ignition system can be minimized, and thus the durability of the spark plug electrodes can be significantly improved.

[0058] Accordingly, certain embodiments provide the unique advantage that an engine fueled by a hydrogen mixture can operate with higher efficiency and lower exhaust gases at a higher power density. This means that, as a result of the present invention, hydrogen engines can compete with fuel cells and thus provide a viable option for accelerating global decarbonization.

[0059] Although the present invention has been described with respect to its specific embodiments, it should be understood by those skilled in the art that various modifications can be made and equivalents can be substituted without departing from the true spirit and scope of the invention as defined by the appended claims. Additionally, many modifications can be made to adapt a particular situation, material, composition, method, or one or more operations to the objectives, spirit, and scope of the invention. Such modifications are all intended to be within the scope of the appended claims. In particular, the methods disclosed herein are described with respect to specific operations performed in a particular order, but it will be understood that these operations can be combined, subdivided, or reordered to form equivalent methods without departing from the teachings of the invention. Accordingly, unless otherwise indicated herein, the order and grouping of operations are not intended to limit the invention.

Claims

1. A method for controlling combustion initiation in an internal combustion engine, comprising providing a pre - combustion chamber, wherein the pre - combustion chamber has an outer surface and an inner surface enclosing a pre - combustion chamber volume portion, one or more discharge ports communicating between the outer surface and the inner surface for introducing a fuel - air mixture into the pre - combustion chamber volume portion, a spark - gap electrode assembly comprising a primary electrode disposed within the pre - combustion chamber volume portion, one or more ground electrodes disposed within the pre - combustion chamber volume portion and offset from the primary electrode so as to form one or more electrode gaps, and the spark - gap electrode assembly including 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 the spark voltage or spark current of the spark, determining whether the spark is initiated at the leading edge or the trailing edge of the electrode gap, determining whether the flow at the position of the spark is high - speed or low - speed, adjusting the output of the spark based on whether the spark is initiated at the leading edge or the trailing edge and whether the flow of the spark is high - speed or low - speed, and adjusting the ignition delay to maintain substantially constant combustion initiation so as to control the initial speed of flame propagation, and a method comprising.

2. The one or more electrode gaps have a surface - area - to - volume ratio of about 2 mm －１ to about 4 mm －１ The method according to claim 1.

3. The surface - area - to - volume ratio of the one or more electrode gaps is about 2 mm for an engine output density of about 10 bar BMEP －１~about 4 mm for engine output density of about 20 bar BMEP －１ The method according to claim 2, which changes in proportion to the BMEP at －１ . **Claim 4** The method according to claim 1, wherein the fuel-air mixture has a uniform flow velocity distribution that changes by less than 50% per cycle in the pre-combustion chamber volume portion and the electrode gap. **Claim 5** The output of the spark is determined using combustion simulation and adjusted by a predetermined amount stored in one or more ignition control module look-up tables to achieve a target combustion start value and achieve stable engine operation, according to the method of claim 1. **Claim 6** The output to the spark is increased when the spark is started at the leading edge, according to the method of claim 1. **Claim 7** The output of the spark is increased in inverse proportion to the flow velocity at the position of the spark, according to the method of claim 6. **Claim 8** The output to the spark is reduced when the spark is started at the trailing edge, according to the method of claim 1. **Claim 9** The output of the spark is reduced in inverse proportion to the flow velocity at the position of the spark, according to the method of claim 8. **Claim 10** The step of determining includes comparing the initial trend of the spark voltage or spark current of the spark with a predetermined spark waveform, according to the method of claim 1. **Claim 11** 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 the average leading edge velocity and the average trailing edge velocity, according to the method of claim 10. **Claim 12** The step of adjusting the output of the spark is performed in the same cycle in which the spark is introduced, to achieve a target combustion start, the method according to claim 1.

13. The method according to claim 1, further comprising determining that an arc extinction state exists when a steep and short rise of the spark voltage is detected to be exponential or sinusoidal ringing.

14. The method according to claim 1, further comprising determining that a stable flame state exists when any of (1) a flat trend of the spark voltage after a voltage breakdown event, a subsequent rate of rise exceeding a predetermined value, or (2) an immediate rise of the spark voltage after a voltage breakdown event having a rate of rise that is not exponential or sinusoidal ringing and is less than a predetermined value is detected.

15. The method according to claim 1, further comprising determining that an extinguished or low-speed combustion state exists when any of (1) a decrease in the spark voltage after a voltage breakdown event indicating insufficient arc movement and elongation from the leading edge of the electrode, or (2) a rise in the spark voltage at a rate exceeding a predetermined value after a voltage breakdown event indicating that arc extinction from the trailing edge or leading edge of the electrode is predicted is detected.

16. The method according to claim 1, further comprising determining that a high-speed combustion or knocking state exists when an increase in the spark voltage within a predetermined range is detected after a voltage breakdown event.

17. The method according to claim 1, further comprising predicting the combustion start based on at least one of the trend of the spark voltage or the trend of the spark current after a voltage breakdown event, based on one or more of engine design, fuel characteristics, and one or more of one or more operating conditions.

18. A high-energy programmable ignition system for an internal combustion engine, At least one of a spark voltage sensor for detecting a spark voltage from one or more spark gap electrodes in a pre-combustion chamber and a spark current sensor for detecting a spark current from one or more spark gap electrodes in the pre-combustion chamber, An ignition control module, Receiving at least one of the spark voltage and the spark current from the one or more spark gap electrodes, Measuring an initial trend of the spark voltage or the spark current of the one or more spark gap electrodes, Determining whether the spark is initiated at the leading edge or the trailing edge of the one or more spark gap electrodes, Determining whether the flow at the position of the spark is high speed or low speed, Based on whether the spark is initiated at the leading edge or the trailing edge and whether the flow of the spark is high speed or low speed, adjusting the output to the spark and adjusting the ignition delay to maintain substantially constant combustion initiation, thereby controlling the initial speed of flame growth An ignition control module configured to perform the above, A high energy programmable ignition system including the above.

19. The ignition control module is configured to adjust the output of the spark by a predetermined amount determined using combustion simulation and stored in one or more ignition control module look-up tables to achieve a target combustion start value and achieve stable engine operation. The system according to claim 18.

20. The ignition control module is configured to increase the output to the spark when the spark is initiated at the leading edge. The system according to claim 18.

21. The ignition control module is configured to increase the output of the spark in inverse proportion to the flow velocity at the position of the spark. The system according to claim 20.

22. The system according to claim 18, wherein the ignition control module is configured to reduce the output to the spark when the spark is initiated at the trailing edge.

23. The system according to claim 22, wherein the ignition control module is configured to reduce the output of the spark in inverse proportion to the flow velocity at the position of the spark.

24. The system according to claim 18, wherein the ignition control module is configured to compare the initial trend of the spark voltage or spark current of the spark with a predetermined spark waveform.

25. The system according to claim 24, 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 the average leading edge velocity and the average trailing edge velocity.

26. The system according to claim 18, wherein the ignition control module is configured to adjust the output of the spark in the same cycle in which the spark is introduced in order to achieve a target combustion start.

27. The system according to claim 18, wherein the ignition control module is configured to determine that an arc extinction state exists when a steep and short rise of the spark voltage is detected to be exponential or sinusoidal ringing.

28. The system according to claim 18, further configured to determine that a stable flame state exists when any of (1) a flat trend of the spark voltage after a voltage breakdown event, a subsequent rate of rise exceeding a predetermined value, or (2) an immediate rise of the spark voltage after a voltage breakdown event having a rate of rise that is not exponential or sinusoidal ringing and is less than a predetermined value is detected.

29. The ignition control module is further configured to determine that an extinguishing or low-speed combustion state exists if either (1) a decrease in spark voltage after a voltage breakdown event indicating insufficient arc movement and elongation from the leading edge of the electrode, or (2) an increase in spark voltage at a rate exceeding a predetermined value after a voltage breakdown event indicating that arc extinction from the trailing edge or the leading edge of the electrode is predicted, is detected, for the system according to claim 18.

30. The ignition control module is further configured to determine that a high-speed combustion or knocking state exists if an increase in spark voltage within a predetermined range is detected after a voltage breakdown event, for the system according to claim 18.

31. The ignition control module is further configured to predict the combustion start using at least one of the tendency of the spark voltage or the tendency of the spark current after a voltage breakdown event, based on one or more of engine design, fuel characteristics, and one or more of one or more operating conditions, for the system according to claim 18.

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