Patent ID: 12228068

V. DETAILED DESCRIPTION

In certain embodiments, the spark current profile (i.e., spark power) may be tailored to the flow velocity in the electrode gap and to the location of spark occurrence. This can permit a less variable SOC and, thus, enable meeting the above engine performance targets with ultra-lean Hydrogen fuel mixtures.

In certain embodiments, the above deficiencies may be mitigated by a method to a) detect the location of the spark and associated flow velocity based on spark voltage trends after voltage breakdown, b) predict the SOC based on simulations correlating spark location, flow velocity, spark power and SOC, and c) adjust the spark waveform/power, during the same spark event, to minimize the variations in SOC.

In certain embodiments, enhanced accuracy of the Predictive Model-Based Spark Control may be achieved to maintain the start of combustion (SOC) within a much tighter variation resulting in improved engine performance in terms of fuel efficiency, power density, transient response, and emissions.

In certain embodiments, a method of controlling the start of combustion in an internal combustion engine is disclosed, comprising: providing a prechamber comprising: an external surface and an internal surface enclosing a prechamber volume; one or more ejection ports communicating between the external surface and the internal surface for introducing a fuel-air mixture into the prechamber volume; a spark-gap electrode assembly, comprising: 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 electrodes gaps to ignite the fuel-air mixture; measuring the initial trend of spark voltage or spark current of the spark; determining whether the spark was initiated at the leading edge or trailing edge of the electrode gap; determining whether the flow at the location of the spark is fast or slow; and adjusting a power of the spark based on whether the spark was initiated at the leading edge or 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 surface-to-volume ratio between about 2 mm−1and about 4 mm−1. The surface-to-volume ratio of the one or more electrode gaps may vary proportionally with BMEP from about 2 mm−1for engine power density of about 10 bar BMEP to about 4 mm−1for engine power density of about 20 bar BMEP. The fuel-air mixture may have uniform flow velocity distributions in the prechamber volume and electrode gap that vary by less than 50% from cycle to cycle.

The power of the spark may be adjusted by predetermined amounts determined using combustion simulations and stored in one or more ignition control module lookup tables to achieve a target start of combustion value and to achieve stable engine operation. The power to the spark may be increased if the spark was initiated at the leading edge. The power of the spark may be increased inversely proportional to the flow velocity at the location of the spark. The power to the spark may be decreased if the spark was initiated at the trailing edge. The power of the spark may be decreased inversely proportional to the flow velocity at the location of the spark.

The determining steps may comprise comparing the initial trend of spark voltage or spark current of the spark with predetermined spark waveforms. The predetermined spark waveforms may be determined by considering at least one of whether the spark initially is located between the leading edge and 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 in which the spark was introduced to achieve a target start of combustion.

The method may further comprise determining an arc blowout condition exists when a steep, short increase of the spark voltage is detected to be exponential or a sinusoidal ringing. The method may further comprise determining that a stable flame condition exists when either of the following is detected: (1) a flat trend of the spark voltage after a voltage breakdown event followed by a later rate of increase that is above a predetermined value; or (2) an immediate increase in spark voltage after a voltage breakdown event that is not exponential or a sinusoidal ringing and that has a rate of increase below a predetermined value. The method may further comprise determining that a flame quenching or slow combustion condition exists when either of the following is detected: (1) decreasing spark voltage after a voltage breakdown event indicating insufficient arc travel and stretching from the leading edge of the electrodes; or (2) increasing spark voltage at a rate above a predetermined value after a voltage breakdown event indicating an arc blowout is predicted from the trailing edge or leading edge of the electrodes. The method may further comprise determining that a fast combustion or knock condition exists when an increasing spark voltage within a predeterminate range is detected after a voltage breakdown event. The method may further comprise predicting 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 the spark voltage or the spark current trends after a voltage breakdown event.

In certain embodiments, a high energy programmable ignition system for internal combustion engines is disclosed comprising: at least one of a spark voltage sensor for sensing a spark voltage from one or more spark gap electrodes in a prechamber and a spark current sensor for sensing a spark current from one or more spark gap electrodes in a prechamber; 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 the initial trend of spark voltage or spark current of the one or more spark gap electrodes; determine whether the spark was initiated at the leading edge or trailing edge of the one or more spark gap electrodes; determine whether the flow at the location of the spark is fast or slow; adjust a power to the spark based on whether the spark was initiated at the leading edge or trailing edge and whether the flow of the spark is fast or slow to control the initial rate of flame growth by adjusting the ignition delay to maintain a substantially constant start of combustion.

The ignition control module may be configured to adjust the power of the spark by predetermined amounts determined using combustion simulations and stored in one or more ignition control module lookup tables to achieve a target start of combustion value and to achieve stable engine operation. The ignition control module may be configured to increase the power to the spark if the spark was initiated at the leading edge. The ignition control module may be configured to increase the power of the spark inversely proportional to the flow velocity at the location of the spark. The ignition control module may be configured to decrease the power to the spark if the spark was initiated at the trailing edge. The ignition control module may be configured to decrease the power of the spark inversely proportional to the flow velocity at the location of the spark.

The ignition control module may be configured to compare the initial trend of spark voltage or spark current of the spark with predetermined spark waveforms. The predetermined spark waveforms may be determined by considering at least one of whether the spark initially is located between the leading edge and 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 power of the spark in the same cycle in which the spark was introduced to achieve a target start of combustion. The ignition control module may be configured to determine an arc blowout condition exists when a steep, short increase of the spark voltage is detected to be exponential or a sinusoidal ringing.

The ignition control module further may be configured to determine that a stable flame condition exists when either of the following is detected: (1) a flat trend of the spark voltage after a voltage breakdown event followed by a later rate of increase that is above a predetermined value; or (2) an immediate increase in spark voltage after a voltage breakdown event that is not exponential or a sinusoidal ringing and that has a rate of increase below a predetermined value. The ignition control module further may be configured to determine that a flame quenching or slow combustion condition exists when either of the following is detected: (1) decreasing spark voltage after a voltage breakdown event indicating insufficient arc travel and stretching from the leading edge of the electrodes; or (2) increasing spark voltage at a rate above a predeterminate value after a voltage breakdown event indicating an arc blowout is predicted from the trailing edge or leading edge of the electrodes. The ignition control module further may be configured to determine that a fast combustion or knock condition exists when an increasing spark voltage within a predetermined range is detected after a voltage breakdown event. The ignition control module further may be 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 the spark voltage or the spark current trends after a voltage breakdown event.

In certain embodiments, a method of controlling the start of combustion in an internal combustion engine is disclosed, comprising: providing a prechamber comprising: an external surface and an internal surface enclosing a prechamber volume; one or more electrode gaps between a corresponding one or more pairs of electrodes; one or more rotational ports communicating between the external surface and the internal surface for introducing a fuel-air mixture into the prechamber volume and including a port axis that defines an index angle, a rotational offset and a penetration angle for creating a spiral flow in the prechamber volume; one or more scavenging ports communicating between a main combustion chamber and the prechamber volume and located between the one or more rotational ports and the one or more electrode gaps to generate a radial flow in the prechamber; wherein the combination of the spiral flow and the radial flow generates a flow substantially orthogonal to the one or more electrode gaps to achieve a consistent laminar flow in the electrode gaps; introducing a spark across at least one of the one or more electrodes gaps to ignite the fuel-air mixture; measuring the initial trend of spark voltage or spark current of the spark; determining whether the spark was initiated at the leading edge or trailing edge of the electrode gap; determining whether the flow at the location of the spark is fast or slow; and adjusting a power of the spark based on whether the spark was initiated at the leading edge or 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.

Each of the one or more scavenging ports may be located upstream of a corresponding one of the one or more electrode gaps by a predeterminate angle (α) and may be located a predeterminate distance (δ) from the corresponding one of the one or more electrode gaps. The predeterminate angle (α) may be defined by the following equation:
α≤[360−90(number of electrode gaps)] degrees.
The radial flow may have a radial velocity (vrad), the spiral flow may have a rotational velocity (vrot), the one or more rotational ports may be located a distance (h) from the one or more electrode gaps, and the predeterminate distance (δ) may be defined by the following equation:
δ<(vrot/vrad)h.
The predeterminate angle (α) and the predeterminate distance (δ) depend on the average velocity of the spiral flow and the average velocity of the radial flow throughout the ranges of engine speeds and loads.

The power of the spark may be adjusted by predetermined amounts determined using combustion simulations and stored in one or more ignition control module lookup tables to achieve a target start of combustion value and to achieve stable engine operation. The power to the spark may be increased if the spark was initiated at the leading edge. The power of the spark may be increased inversely proportional to the flow velocity at the location of the spark. The power to the spark may be decreased if the spark was initiated at the trailing edge. The power of the spark may be decreased inversely proportional to the flow velocity at the location of the spark. The step of adjusting the power of the spark may be performed in the same cycle in which the spark was introduced to achieve a target start of combustion. The method may further comprise determining an arc blowout condition exists when a steep, short increase of the spark voltage is detected to be exponential or a sinusoidal ringing. The method may further comprise determining that a stable flame condition exists when either of the following is detected: (1) a flat trend of the spark voltage after a voltage breakdown event followed by a later rate of increase that is above a predetermined value; or (2) an immediate increase in spark voltage after a voltage breakdown event that is not exponential or a sinusoidal ringing and that has a rate of increase below a predetermined value. The method may further comprise determining that a flame quenching or slow combustion condition exists when either of the following is detected: (1) decreasing spark voltage after a voltage breakdown event indicating insufficient arc travel and stretching from the leading edge of the electrodes; or (2) increasing spark voltage at a rate above a predetermined value after a voltage breakdown event indicating an arc blowout is predicted from the trailing edge or leading edge of the electrodes. The method may further comprise predicting 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 the spark voltage or the spark current trends after a voltage breakdown event.

In certain embodiments, a prechamber for use in generating laminar flow in one or more electrode gaps is disclosed, comprising: an external surface and an internal surface enclosing a prechamber volume; a spark-gap electrode assembly, comprising: 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; one or more rotational ports communicating between the external surface and the internal surface for introducing a fuel-air mixture into the prechamber volume and including a port axis that defines an index angle and a rotational offset and a penetration angle for creating a spiral flow in the prechamber volume; one or more scavenging ports communicating between a main combustion chamber and the prechamber volume and located between the one or more rotational ports and the spark-gap electrode assembly to generate a radial flow in the prechamber; wherein the combination of the spiral flow and the radial flow generates a flow substantially orthogonal to the one or more electrode gaps to achieve a consistent laminar flow in the electrode gaps.

Each of the one or more scavenging ports may be located upstream of a corresponding one of the one or more electrode gaps by a predeterminate angle (α) and may be located a predeterminate distance (δ) from the corresponding one of the one or more electrode gaps. The predeterminate angle (α) may be defined by the following equation:
α≤[360−90(number of electrode gaps)] degrees.
The radial flow may have a radial velocity (vrad), the spiral flow may have a rotational velocity (vrot), the one or more rotational ports may be located a distance (h) from the one or more electrode gaps, and the predeterminate distance (δ) may be defined by the following equation:
δ<(vrot/vrad)h.
The predeterminate angle (α) and the predeterminate distance (δ) depend on the average velocity of the spiral flow and the average velocity of the radial flow throughout the ranges of engine speeds and loads.

In certain embodiments, a prechamber for use in generating laminar flow in one or more electrode gaps, comprising: an external surface and an internal surface enclosing a prechamber volume; a first spark-gap electrode assembly, comprising: a first primary electrode disposed within the prechamber volume; and a first ground electrode disposed within the prechamber volume and offset from the first primary electrode to form a first electrode gap; one or more rotational ports communicating between the external surface and the internal surface for introducing a fuel-air mixture into the prechamber volume and including a port axis that defines an index angle and a rotational offset and a penetration angle for creating a spiral flow in the prechamber volume; a first scavenging port communicating between a main combustion chamber and the prechamber volume and located between the one or more rotational ports and the first electrode gap to generate a first radial flow in the prechamber; wherein the combination of the spiral flow and the first radial flow generates a first combined flow substantially orthogonal to the first electrode gap to achieve a consistent laminar flow in the first electrode gap.

The first scavenging port may be located upstream of the first electrode gap by a predeterminate angle (α) and may be located a predeterminate distance (δ) from the first electrode gap. The predeterminate angle (α) may be less than 270 degrees. The radial flow may have a radial velocity (vrad), the spiral flow may have a rotational velocity (vrot), the one or more rotational ports may be located a distance (h) from the one or more electrode gaps, and the predeterminate distance (δ) may be defined by the following equation:
δ<(vrot/vrad)h.

The predeterminate angle (α) and the predeterminate distance (δ) may depend on the average velocity of the spiral flow and the average velocity of the radial flow throughout the ranges of engine speeds and loads.

The prechamber may further comprise: a second spark-gap electrode assembly, comprising: a second primary electrode disposed within the prechamber volume; and a second ground electrode disposed within the prechamber volume and offset from the second primary electrode to form a second electrode gap; a second scavenging port communicating between the main combustion chamber and the prechamber volume and located between the one or more rotational ports and the second spark-gap electrode assembly to generate a second radial flow in the prechamber; wherein the combination of the spiral flow and the second radial flow generates a second combined flow substantially orthogonal to the second electrode gap to achieve a consistent laminar flow in the second electrode gap. The second scavenging port may be located upstream of the second electrode gap by the predeterminate angle (α) and may be located the predeterminate distance (δ) from the second electrode gap. The predeterminate angle (α) may be less than 180 degrees.

In certain embodiments, advanced 3D combustion CFD (Computational Fluid Dynamic) and 1D modeling and simulations of the ignition kernel dynamic, defined as arc travel and arc stretching occurring at the spark gap electrodes, may be used to create the correlations between the arc voltage and current waveforms, the ignition kernel dynamic and the predicted SOC and flame characteristics. Then, such correlations may be used to derive spark control methods for each engine and spark plug design. This may be used to create a Predictive Model-Based Spark Control having the following functionality:

In certain embodiments as shown inFIG.3, when a sufficient arc travel and arc stretching310is predicted from the spark gap electrodes leading edge to achieve the correct SOC and stable flame, the spark may be ended to avoid electrode hotspots causing early SOC and high rates of electrode wear. In those embodiments, the spark current320may be as shown inFIG.3.

In certain embodiments as shown inFIG.4, when an insufficient arc travel and stretching410is predicted from the leading edge of the electrodes to result in flame quenching or hotspots, an enhancement of the spark waveform or a subsequent spark with enhanced waveform, predicted to achieve the correct SOC and stable flame, may be triggered within the same cycle. In those embodiments, the spark current420may be as shown inFIG.4.

In certain embodiments as shown inFIG.5, when a sufficient arc stretching510is predicted from the trailing edge of the electrodes to achieve the correct SOC and stable flame, the spark may be ended to avoid electrode hotspots causing early SOC and high rates of electrode wear. In those embodiments, the spark current520may be as shown inFIG.5.

In certain embodiments as shown inFIG.6, when an arc blowout610is predicted from the trailing edge or leading edge of the electrodes to result in flame quenching, an enhancement of the spark or a subsequent spark with enhanced waveform, predicted to achieve the correct SOC and stable flame, may be triggered within the same cycle. In those embodiments, the spark current620may be as shown inFIG.6.

In certain embodiments as shown inFIG.7, an Active Scavenge Prechamber700may have electrodes710arranged radially, having a large surface and a small gap designed for achieving high durability, and one or more scavenging ports720. In certain embodiments, having engine power densities equal or greater than 20 bar BMEP, the typical electrode surface may be equal or greater than 9 mm2and the gap size may be equal or smaller than 0.25 mm. Thus, the resulting gap surface to volume ratio may be equal or greater than 9 mm2/(9 mm2×0.25 mm)=4 mm−1. In certain embodiments having engine power densities smaller than 20 bar BMEP, the electrode gap surface to volume ratio may be smaller than 4 mm−1. In certain embodiments, in applications having power density of approximately 10 bar BMEP, the electrode surface may be approximately 1 mm2and the gap size may be approximately 0.5 mm. In these embodiments, the resulting gap surface to volume ratio may be approximately 1 mm2/(1 mm2×0.5 mm)=2 mm−1. In certain embodiments, applications having power densities between 10 bar BMEP and 20 bar BMEP, may use electrode surface to volume ratios that are approximately proportional to the power density ratio. For example, an application with power density of 15 bar BMEP may use an electrode surface to volume ratio of approximately 3 mm−1(15/10×2=15/20×4=3).

In certain embodiments, the flow velocity in the gap between the electrodes and four typical spark locations, on the edge of the electrode, of an Active Scavenge prechamber plug800with radial gap may be as shown inFIG.8. In these embodiments, the fuel-air mixture flow velocity distribution in the prechamber volume and the direction of the flow and its magnitude within the electrode gap may be fairly uniform and repeatable with a cycle-to-cycle variation that is less than 50%.

In certain embodiments, four locations may be characterized as follows:Location (810): Leading edge/Slow VelocityLocation (820): Leading edge/Fast VelocityLocation (830): Trailing edge/Slow VelocityLocation (840): Trailing edge/Fast Velocity

Depending on the location where the spark initially takes place and the local flow velocity, the arc travel and the flame kernel development may result in significant variability of the SOC, causing large combustion instability preventing operation at high engine power density (BMEP) and efficiency (BTE), especially with H2-ICE operating with ultra-lean fuel mixture conditions.

In certain embodiments, a range of spark voltage and current variabilities obtained during engine operation with an Active Scavenge Prechamber and a high-energy programmable open-loop ignition system may be as shown inFIG.9. Analysis of these waveforms may permit determination of the extent of arc stretching variability910and the occurrence of arc blowout920identified when a steep, short increase of the spark voltage is detected to be exponential or a sinusoidal ringing.

In certain embodiments, by properly analyzing the spark voltage and current waveforms, it may be possible to determine the general location where the spark first occurred, for example location (810): leading edge/slow velocity or location (840): trailing edge/fast velocity.

In certain embodiments, the general location where the spark first occurred may be used to generate a prediction of the rate of flame growth and resulting SOC using validated combustion CFD. The values of the spark locations and corresponding SOC predictions may be compiled in a lookup table.

In certain embodiments as shown inFIG.10, a Predictive Model-Based Spark Control may include a programmable high-energy, closed-loop ignition system1000with added spark voltage sensor1010and current sensor1020of spark plug1030to the ignition coil secondary windings constituting the ignition coil1040. These sensors may provide the spark waveform feedback signal1050to the Smart Spark Control Module1060(otherwise known as Ignition Control Module) that generates a spark waveform control signal1070and a spark trigger control signal1080to the Ignition Driver1090which in turn may adjust the ongoing (a.k.a., nominal) spark current waveform, during the same spark event, to a predeterminate current waveform stored in an Ignition Control Module lookup table, as necessary to achieve a SOC that is sufficiently close to the target value, thus reducing the combustion cycle-to-cycle variabilities and the occurrence of combustion anomalies like backfire, knock and preignition.

In certain embodiments, the spark voltage sensor1010, the spark current sensors1020and the Smart Spark Control Module1060may be incorporated in a high-energy programmable spark ignition system. In certain embodiments, the high-energy programmable spark ignition system may be as described in reference [4] above.

In certain embodiments, the overall functionality of the Predictive Model-Based Spark Control System (a.k.a., Adaptive Control Prechamber Ignition System) may be as depicted inFIG.11.

In certain embodiments, the spark waveform feedback signal from the ignition coil may be used by the Smart Spark Control Module to predict the SOC based on combustion simulation results stored in lookup tables and to issue three primary commands to the Ignition Driver as follows:a. No adjustment of the ongoing spark if the predicted SOC is on target1110.b. Enhance the ongoing spark energy/power to a predeterminate spark waveform stored in lookup tables if the predicted SOC occurs later than target1120.c. Reduce the ongoing spark energy/power to a predeterminate spark waveform stored in lookup tables if the predicted SOC occurs earlier than target1130.

In certain embodiments, based on the above input commands the Ignition Driver1090may generate the primary pulses to the ignition coil required to obtain the predetermined spark waveform stored in lookup tables which is necessary to achieve an SOC close to the target value and, hence, reduce the cycle-to-cycle variations in the SOC.

In certain embodiments as shown inFIG.12, a Predictive Model-Based Spark Control Method may include the following steps: In step1210, the raw voltage and/or current feedback signal from the ignition coil secondary side may be fed to the Smart Spark Control Module signal conditioning and processing circuit. In step1220, the spark waveform feedback signal may be converted into signal data by the signal conditioning and processing circuit.

In certain embodiments as shown in step1230, the signal data from the conditioning and processing circuit may have specific trends which provide the basis for determining the general initial spark location and associated flow velocity. Exemplary trends are shown inFIGS.13-16.FIG.13shows an example of a steep arc voltage increase1310that is equal or greater than approximately 20 Volts/μs following the spark breakdown.FIG.14shows an example of gradual arc voltage increase1410that is in the range of approximately 10 Volts/μs, following the spark breakdown.FIG.15shows an example of flat arc voltage1510following the spark breakdown with steep rise1520at a later time.FIG.16shows an example of arc voltage decrease1610following the spark breakdown.

In certain embodiments as shown in step1240, the signal data may be derived from the spark voltage after the voltage breakdown event and may be used with a method that predicts the general initial spark location and associated flow velocity based on the specific trend of the signal. Following are some exemplary predictions: The trend shown inFIG.13may be indicative of a trailing edge spark occurring at a fast location (for example location840, having a velocity of approximately 20 m/s) and can result in a fast combustion or knock condition. The trend shown inFIG.14may be indicative of a trailing edge spark occurring at a slow location (for example location830, having a velocity of approximately 10 m/s) and can result in a stable flame producing a normal combustion having a SOC close to target. The trend shown inFIG.15may be indicative of a leading-edge spark occurring at a fast location (for example location820, having a velocity of approximately 15 m/s) and can result in a stable flame producing a normal combustion having a SOC close to target. The trend shown inFIG.16may be indicative of a leading-edge spark occurring at a slow location (for example location810, having a velocity of approximately 10 m/s) and can result in slow combustion or quenching condition.

In certain embodiments as shown in Step1250, the general initial spark location and associated flow velocity information may be used in a look-up table where the correlation between general initial spark locations and associated flow velocity, spark waveforms and target SOC value are provided based on combustion CFD simulation predictions. In certain embodiments, a combustion CFD simulation for a leading-edge spark occurring at a slow location (for example location810) may be as shown inFIG.17. In the case of location810, an initial flame front may be achieved after about 4.8 crank angle degrees (CAD) (11.70−6.90=4.8). This initial flame front, for example, may be used to define the SOC. In certain embodiments, the CFD images depicted inFIG.17show the flow velocity field within the spark gap being uniform and having a magnitude of approximately 10 m/s. Image1710shows the initial spark1720taking place at the leading edge at −11.70 CAD timing. Image1730shows that at −10.09 CAD timing the arc has travelled1740within the gap by approximately 0.6 mm due to the force acting onto the arc by the flow field. Image1750shows at −8.50 CAD a flame kernel1760has developed within the electrode gap. Image1770shows that at −6.90 CAD an initial flame1780front is formed outside the gap. This condition 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 given engine operating conditions, maintaining a consistent ignition delay (or SOC) may be achieved by the predictive model-based spark control, which may prevent the occurrence of abnormal combustion limiting the attainment of higher engine power density and efficiency.

Other examples of combustion simulations for different sparks occurring at different locations are provided in reference [1] above. In certain embodiments as shown inFIG.18, an example lookup table may correlate the spark general initial locations to the spark waveforms required to achieve the target SOC value. In certain embodiments, the spark current profile1810may correlate to location810slow leading edge, the spark current profile1820may correlate to location820fast leading edge, the spark current profile1830may correlate to location830slow trailing edge, and the spark current profile1840may correlate to location840fast trailing edge.

In certain embodiments, for any given target SOC, higher energy/power sparks may be required when the general initial spark location is the leading edge, and the spark energy/power may be inversely proportional to the flow velocity at the location of spark. Conversely, lower energy/power sparks may be required when the general initial spark location is the trailing edge. The target SOC may be dependent on the ignition timing (IT) and may be defined to be approximately in the middle of the range of the SOC variations.

In certain embodiments as shown in Step1260, same-cycle adjustment of the ongoing spark waveform may be made to match the predetermined spark waveform from the lookup table1250that corresponds to the predicted general initial spark location and may be required to achieve the target SOC. For example, if the previous cycle had spark location810(slow leading edge) and the prediction for the present cycle is location830(slow trailing edge), then the spark waveform should be adjusted from waveform1810to waveform1830.

In certain embodiments as shown in Step1270, continuous loop control may be performed for each combustion cycle by the Smart Spark Control Module to make same-cycle adjustment to the ongoing spark waveform as necessary to match the predetermined spark waveform from the lookup table that corresponds to the predicted general initial spark location and may be required to achieve the target SOC.

The Predictive Model-Based Spark Control of certain embodiments improves upon the state of the art. The combustion instabilities (backfire, knock and preignition shown inFIG.2), primarily experienced with but not limited to Hydrogen engines, may be mitigated by improving the air-fuel mixture homogeneity and by reducing the engine power output which in turn reduces the engine efficiency. There are no known ignition systems featuring adaptive spark control that can mitigate the extent of combustion instabilities as defined in this disclosure. Neither high nor low energy/power ignition systems may be able to mitigate combustion instability especially with Hydrogen engines to any meaningful extent.

In certain embodiments, a conventional spark ignition system may include an ignition driver1910, an ignition coil1920and a spark plug1930as shown inFIG.19. Compared to the conventional system (FIG.19), the Predictive Model-Based Spark Control system (otherwise known as Adaptive Control Prechamber Ignition system1000as shown for example inFIGS.10and11) may feature: voltage sensors1010and/or current sensors1020on the secondary side of the coil windings1040as shown inFIG.10; a Smart Spark Control Module1060as shown inFIGS.10and11; and a communication path to feed the Spark Waveform Control Signal1070and the Spark Trigger Control Signal1080from the Smart Spark Control Module to the Ignition Driver1090as shown inFIG.10.

In certain embodiments, remarkable improvements in H2-ICE performance may be achieved with the combination of Active Scavenge Prechamber technology and Predictive Model-Based Spark Control.

In certain embodiments, advanced combustion modeling and simulations of the ignition process including the spark event, the arc-travel and stretching, and resulting flame propagation may be used to predict the relationship between the spark energy/power, the flow within the electrode gap, and the initial flame development defining the SOC for different engines and at various conditions. This information may be used to adjust the spark energy/power characteristic during the same cycle spark event, to minimize the SOC variations and to significantly reduce the propensity to combustion anomalies, such as backfire, knock and preignition, that prevent achieving high engine power densities and efficiencies.

In certain embodiments, spark voltage and/or current from the secondary side of the coil windings may be used as feedback signal/s1050by the Smart Spark Control Module1060(FIG.11) which controls the Ignition Driver1090(FIG.10) and allows the necessary adjustment in the spark current waveform to minimize the SOC variations.

In certain embodiments, the initial trend of the spark voltage signal after the voltage breakdown event may be used to determine the location where the spark first occurs and the flow velocity at that location. This information may be used to predict the time of the SOC occurrence. Then correlations between spark power and SOC, which may be stored in lookup tables, may be used to adjust the ongoing spark power to match the target SOC. This method of controlling the spark power during the same cycle spark event may be necessary to reduce the variations in SOC which may result in improved engine combustion performance and emissions. Moreover, controlling the spark power during the same cycle spark event may minimize the rate of electrode erosion with high-energy ignition systems and thus may enable remarkable improvements in the spark plug electrode durability.

Accordingly, certain embodiments offer the unique advantage of enabling engines fueled with Hydrogen mixtures to operate at higher power densities, with higher efficiency and lower emissions. This means that, as a result of this invention, Hydrogen engines can compete with fuel cells and thus provide a viable alternative to accelerate the global decarbonization.

In certain embodiments, the flow dynamic of the active scavenge prechamber spark plug may be such that the flow regime in the gap varies from laminar to turbulent for various regions within the electrode gap. With reference toFIGS.7,8,17and18, in certain embodiments the velocity of the flow in the gap may not be uniform. As a result, the Reynolds number (Re=ρgv/μ; where ρ represents the gas density, g represents the gap size, v represents the flow velocity and μ represents the viscosity) may range from ˜1100 to ˜3100. This means that the flow regime may vary from laminar (Re<2000) to turbulent (Re>2000). While in the laminar flow regime the trajectories of the flow particles2010in electrode gap2020may be substantially parallel to each other as depicted inFIG.20. While in the turbulent flow regime the trajectories of the flow particles2110in electrode gap2020may be characterized by the occurrence of localized small-scale vorticity (a.k.a., eddies) as depicted inFIG.21. The presence of localized eddies may interfere with the arc travel during spark discharge preventing a predictable arc movement which results in erroneous estimations of the start of combustion (SOC). Moreover, when the arc enters a turbulent region during its travel within the gap, it is likely to slow down and form hot spots on the surface of the electrodes which cause combustion instabilities. In certain embodiments, it is therefore desirable to avoid any region having turbulent flow regime within the gap.

In certain embodiments, the direction of the flow entering the gap substantially orthogonal to the gap may maintain a consistent laminar flow within the gap between the electrodes, which may have a Re of for example approximately 1200. This condition may ensure that the flow will enter the gap smoothly, maintaining the direction of the velocity vectors substantially parallel and preventing the formation of eddies. Moreover, in certain embodiments computational fluid dynamic (CFD) simulations indicate that a laminar flow having Re in the gap of approximately 1200 can be achieved with a density of approximately 17.3 kg/m3, with a viscosity of approximately 38.96 e−6Pa, with an electrode gap size of approximately 0.3 mm, and with the velocity of the flow in the gap of approximately 9 m/s.

In certain embodiments,FIG.22depicts CFD simulation results representing flow velocity vectors2210in an electrode gap having Re of approximately 1500 and a uniform velocity of approximately 14 m/s. In these embodiments, the laminar regime is maintained throughout the electrode gap surface to maximize the predictability of arc travel, initial flame development and SOC and, hence, improve the accuracy of the Predictive Model-Based Spark Control.

In certain embodiments, a scavenging port may be positioned upstream of the electrode gap to achieve a laminar flow regime throughout the electrode gap. In certain embodiments,FIG.23shows a CFD simulation of the interaction between the rotational flow component2310of the spiral flow created in the prechamber with the radial flow2320ensuing from the scavenging port. In these embodiments, the interaction between these two flows results in a combined flow2330having a direction that is substantially orthogonal to the gap between the two electrodes that may be conducive to a laminar flow regime.

In certain embodiments,FIG.24shows a prechamber with a scavenging port2410located upstream of electrode gap2420to generate laminar flow in electrode gap2420. In certain embodiments, one or more rotational ports2430may be oriented to create a rotational flow having a clockwise direction, and scavenging port2410may be located upstream of electrode gap2420at a predeterminate angle (α)2440which depends on the average velocity of the rotational flow and the average velocity of the radial flow throughout the range of engine speeds. In certain embodiments, the predeterminate angle alpha (α)2440may be may be defined by the following equation:
α≤[360−90(number of electrode gaps)] degrees
for example, 1 electrode gap→α may be within 270 degrees; 2 electrode gaps→α may be within 180 degrees; 3 electrode gaps→α may be within 90 degrees; 4 electrode gaps→α may be within 0 degrees, which means that each scavenging port may be approximately aligned with each electrode gap.

In certain embodiments,FIG.25depicts a cross section of a prechamber in which the scavenging port2410is located in between electrode gap2420and rotational ports2430at a predeterminate distance (δ)2510from electrode gap2420. In certain embodiments, predeterminate distance (δ)2510which may depend on the average velocity of the rotational flow and the average velocity of the radial flow throughout the range of engine speeds. In certain embodiments, predeterminate distance (δ)2510may be defined by the following equation:
δ<(vrot/vrad)h
wherein the radial flow has a radial velocity (vrad), the spiral flow has a rotational velocity (vrot) component, and the one or more rotational ports are located a distance (h)2520from the one or more electrode gaps2420.

In certain embodiments shown inFIGS.26A and26B, a prechamber may include multiple scavenging ports2410may be used with multiple electrode gaps2420. In certain embodiments, each scavenging port2410may be may be located upstream of a corresponding electrode gap2420at a predeterminate angle (α)2440.

In certain embodiments as shown inFIG.27, a prechamber spark plug may provide a prechamber2700having a prechamber wall2710of generally cylindrical form having a plurality of holes2720disposed in circumferentially spaced relation about the external surface2730of the prechamber wall2710through which a corresponding plurality of fuel-air mixture streams enter a plurality of holes2720through which the fuel-air mixture stream exits into the prechamber volume. One center hole2750can be disposed between the external surface2730and the internal surface2740proximate to the top of the prechamber2700. Each of the plurality of holes2720and center hole2750can correspondingly direct a plurality of the fuel-air mixture streams into the prechamber volume to achieve a spiral flow pattern inside the prechamber volume characterized by radial, axial and rotational flow components, as further described herein.

In certain embodiments, the number of holes2720may be from about 1 to about 12. The diameter of holes2720may be from about 0.5 mm to about 4.0 mm. The diameter of center hole2750may be from about 0.5 mm to about 4.0 mm. Each of holes2720may define a pattern radius2760, an index angle2770which is measured from a reference2790, and a rotational offset2780. In certain embodiments, the pattern radius2760may be from about 2 mm and about 10 mm. In certain embodiments, the index angle2770for the first hole may be about 0 degrees to about 120 degrees. In certain embodiments, the rotational offset2780may be about 0 mm to about 10 mm.

In certain embodiments as shown inFIG.28, each of holes2720may define a penetration angle2810. In certain embodiments, penetration angle2810may be about 10 degrees to about 75 degrees.

As will be understood by one of ordinary skill in the art, the pre-determined configuration of the prechamber2700and plurality of holes2720can achieve a spiral flow pattern velocity characterized by radial, axial and rotational velocity components and having a velocity of the fuel-air mixture in-filling streams in the spiral flow pattern greater proximate the periphery of spiral flow pattern and lesser proximate the center of the spiral flow pattern; however, the invention is not so limited and the velocity of the fuel-air mixture in-filling streams in the spiral flow pattern can be adjusted by altering the configuration and the angle of one or more of the plurality of holes2720disposed in the prechamber wall2710to achieve other spiral flows having, for example, greater velocity at the center of the spiral flow pattern and lesser at the periphery, or permutations and combinations thereof.

While the invention has been described with reference to the specific embodiments thereof, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the true spirit and scope of the invention as defined by the appended claims. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, method, operation, or operations, to the objective, spirit, and scope of the invention. All such modifications are intended to be within the scope of the claims appended hereto. While the methods disclosed herein have been described with reference to particular operations performed in a particular order, it will be understood that these operations may be combined, sub-divided, or re-ordered to form an equivalent method without departing from the teachings of the invention. Accordingly, unless specifically indicated herein, the order and grouping of the operations are not a limitation of the invention.