Methanol is a promising fuel for As the initial pressure increases-efficiency, low-emission combustion, but its behavior in pre-chamber direct-injection turbulent jet ignition (TJI) under different initial pressures remains unclear. This study combines experiments and CFD simulations to investigate methanol jet flame development at initial pressures of 2-10 bar. Schlieren and direct flame imaging, synchronized with pressure measurements, show that increasing pressure shortens ignition delay, raises jet velocity from about 60 to 300 m/s, and increases pre-chamber peak overpressure from below 0.3 to above 2.5 bar. The flame evolves from a diffuse, unstable structure into a slender blue jet with stronger penetration and a larger reaction area. At higher pressures, however, the flame front lags behind the jet tip, suggesting weaker flame anchoring due to enhanced strain and quenching near the leading edge. Regime analysis further indicates that elevated pressure intensifies turbulence and flow acceleration, shifting the methanol jet flame from reaction-controlled to turbulence-dominated combustion, as reflected by a lower Damkohler number and earlier transition to thin and broken reaction zones. These results clarify pressure-dependent turbulence-chemistry interactions and provide guidance for optimizing methanol pre-chamber ignition systems.

In-cylinder flow dynamics plays a decisive role in balancing combustion stability and NOx emissions in direct-injection hydrogen engines. This study numerically investigates the coupled effects of intake-port architecture and piston-crown geometry on mixture formation and combustion behavior in a large-bore hydrogen engine for stationary power-generation applications. Three intake-port configurations (Helical, Hybrid, and Tangential) and four piston geometries (Bowl, Flat, Omega, and Lens) were systematically evaluated. The overall performance of each configuration was assessed based on mixture homogeneity near ignition, turbulence distribution before ignition, combustion development, peak in-cylinder temperature, and NOx formation tendency. Among the investigated intake ports, the Tangential design provided the most favorable flow organization for hydrogen direct injection, characterized by weaker swirl-dominated confinement, more effective tumble-related charge motion, stronger retention of injection-induced turbulence, and improved global mixture homogenization, with the homogeneity index exceeding 75 % near ignition. Under the Tangential-port condition, the Lens piston showed the most favorable overall balance by promoting late-stage tumble breakdown near top dead center and converting bulk organized motion into effective small-scale turbulence for mixing preparation and flame development. By contrast, the Bowl piston accelerated combustion through locally richer stratification near the spark region, whereas the Omega piston showed a pronounced tendency toward incomplete flame development under the present simulation conditions. Overall, the Tangential-port/Lens-piston combination offered the best compromise among mixture homogeneity, combustion robustness, and low-NOx operation, indicating that tumble-oriented charge motion coupled with controlled turbulence amplification near ignition is a promising design strategy for large-bore hydrogen engines for stationary power generation.

Concerns about mitigation deterrence have prompted calls for pathways that avoid multigigatonne reliance on carbon dioxide removal (CDR), yet such pathways can also discourage near-term investment in CDR, leaving the technologies technically and economically underprepared if large-scale deployment becomes necessary due to unfulfilled emission reduction pledges. Here we model a new pathway in which CDR and decarbonization "Co-Scale" aggressively in parallel without one undermining the other, with the intention that we can readily course-correct if effort in one domain does not materialize. We treat this scenario as a stylized upper bound of what is climatically achievable under ideal enabling conditions, rather than what is immediately feasible under current technical, economic, and environmental constraints. We compare this pathway with two conventional designs, i.e., CDR-Led and Decarb-Led. In CDR-Led, large-scale CDR can substitute for deep decarbonization, while in Decarb-Led, rapid emissions reductions are prioritized and CDR plays a limited complementary role. We find that compared to these two conventional scenarios, Co-Scale reaches net zero CO2 seven years earlier, accumulates 4 times more net negative CO2 by 2100, cuts the 1.5 degrees C overshoot duration by roughly half, and limits end-of-century warming to 1 degrees C rather than 1.37-1.39 degrees C. Relative to the recent focus on Decarb-Led pathways, Co-Scale's main constraints is the feasibility of geological carbon storage, while food, water, and cost pressures are comparatively less restrictive.

The Wiebe combustion model that describes the multistage propagation process in turbulent jet ignition systems has not yet been established. This study developed a method for multiple Wiebe combustion modeling that integrates raw experimental data, algebraic analysis, and the least squares algorithm. The results show that the three standard Wiebe functions failed to accurately match the experimental data due to the asymmetric characteristics of the experimental mass fraction burned profiles. The smooth curvature filters out the combustion characteristics of the flame multi-stage propagation, and the reconstruction heat release rate and characteristic time deviate from the actual situation. In contrast, the multiple Wiebe function format herein achieved calculation accuracy for mass fraction burned exceeding 99 % and precisely captured the heat release rate and combustion phasing at each stage. Specifically, experimental heat release rate data combined with sensitivity analyses of parameters a and m determined the appropriate number of Wiebe functions and characteristic times. Then algebraic analysis subsequently provided form factor values endowed with staged propagation reflecting the heat release behaviour of the flame type. Finally, the least squares algorithm was applied to obtain the unique value of combustion efficiency parameters. The Levenberg-Marquardt algorithm demonstrated markedly superior fitting performance compared to both gradient descent and Gauss-Newton algorithms. The four-stage combustion dynamics was revealed by the phenomenological combustion model. This research provides a key basic module for the 0-dimensional modeling of ammonia engine with jet-ignition system.

Gasoline compression ignition (GCI) engines face significant challenges at medium-to-high loads, including excessive maximum pressure rise rate (MPRR), strong pressure oscillations (MAPO), combustion roughness, and increased soot emissions. In this study, a six-cylinder high-compression-ratio GCI engine was employed to systematically evaluate injection control strategies for mitigating MPRR and MAPO under medium-to-high load conditions (BMEP of 1.1-1.8 MPa), while also examining the influence of fuel properties on combustion behavior and thermal efficiency. Results show that single injection leads to severe combustion intensity and elevated MPRR and MAPO. In contrast, a double-injection strategy significantly improves combustion stability. With a 3 mg pilot mass and a 10 degrees CA pre-main interval, MPRR is reduced from 14.75 bar/deg to 5.15 bar/deg (-64.4%) and MAPO from 6.75 bar to 1.3 bar (-80.7%). Furthermore, the G80D20 fuel enhances combustion phasing and thermal efficiency, achieving a peak effective thermal efficiency of 48.4%. These findings demonstrate that coordinated optimization of compression ratio, injection strategy, and fuel properties provides an effective pathway for achieving stable, low-oscillation, and high-efficiency operation in high-load GCI engines.

Hydrogen internal combustion engines (HICEs) represent a promising solution for enhancing the stability of renewable energy systems by enabling long-term energy storage and power generation. However, the elevated thermal load encountered under high-altitude operating conditions poses a significant technical challenge. This study systematically investigates the influence of intake port configurations and combustion chamber geometries on the thermal load of HICEs operating at an altitude of 2500 m, employing three-dimensional numerical simulations. The results indicate that, in comparison with helical intake ports, tumble intake port designs mitigate in-cylinder flow intensity, enhance indicated thermal efficiency, and reduce thermal load. Likewise, a straight combustion chamber configuration leads to lower turbulent kinetic energy and reduced combustion intensity when compared to re-entrant combustion chamber or open combustion chamber. The optimal combination of a tumble intake port and a straight combustion chamber achieves an indicated thermal efficiency of 45.89 % and reduces the thermal load to levels comparable to those observed under plain (sea-level) conditions. Consequently, moderating in-cylinder turbulence is essential for thermal load mitigation in high-altitude HICEs.

The narrow-throat pre-chamber (PC) possesses characteristics such as high pressure buildup and high jet velocity, resulting in superior ignition performance for lean combustion engines. Nevertheless, tilted PC configurations produce varied jet dynamics, which are poorly understood compared to vertical PC configurations. It necessitates reevaluating the corresponding design guidelines, especially for nozzle orientation. This study numerically explores how the nozzle tilt angle in the vertical orientation and the PC deflection angle in the horizontal orientation affect the performance of a methane-fueled PC engine. A three-dimensional numerical model of the PC engine was developed and extensively validated against cylinder pressure and heat release rate. The study reveals the velocity order of the non-uniformity of the jet and inflow and its impact for the first time. It concludes that the jet velocities of the orifices become non-uniform and follow some rules as the nozzle tilt angle deviates from 0 degrees: orifices near the reference plane exhibit the lowest jet velocity; the velocities of the orifices on both sides of the normal plane are symmetrically distributed; the side closer to the PC top have higher velocities than the other side. As the absolute value of the nozzle tilt angle increases, the average jet velocity decreases. Although the nozzle tilt angle of 0 degrees achieves the highest average jet velocity and the most efficient combustion, the flame non-uniformity becomes evident with tilt angles greater than or equal to 0 degrees. In contrast, negative tilt angles enhance flame uniformity, with the tilt angle of-13 degrees achieving up to a 38% improvement in flame uniformity. Overall, the tilt angle of-6 degrees provides the best balance between efficient combustion and uniform flame distribution, making it most suitable for use in the tilted PC. It is further concluded that the higher inflow velocity on the acute-angled side of the PC enhances pressure buildup across the tilted PC through varying PC deflection angles.

Passive pre-chambers (PPC) feature a simple structure and hold significant application potential in internal combustion engines. However, their scavenging process presents challenges, making structural optimization crucial. This paper quantitatively evaluates flame propagation, turbulent kinetic energy, indicated thermal efficiency (ITE), and net emissions under stoichiometric conditions in a 16.8 L 6-cylinder heavy-duty natural gas engine with PPC combing both experimental and numerical approaches. It also investigates the effects of volume ratio, orifice diameter, asymmetry, and installation azimuth on combustion, scavenging, flow patterns, and ITE, aiming to elucidate intrinsic structure-flow-combustion relationships. Results show that turbulent jet ignition (TJI) increases ITE by 1.5% and shortens combustion duration. Scavenging primarily depends on the total orifice area to PPC volume ratio and installation azimuth. The PPC volume ratio of 2.9% achieves the optimal balance between scavenging and ignition energy. Reducing orifice diameter enhances jet momentum and turbulence; the asymmetric design (three 1.5 mm orifices + one 1.8 mm orifice) achieves synergistic flame development in radial and axial directions. At an installation angle of gamma = 23 degrees , the jet and in-cylinder swirls achieve optimal coupling, compensating for flow field inhomogeneities and yielding the fastest combustion. Although scavenging is not optimal at this angle, combustion benefits outweigh scavenging benefits. Regarding emissions, TJI increases CO and NOx due to higher temperatures and advanced phasing, but reduces HC and CH4 via enhanced oxidation in crevice and wall regions. In summary, optimal coordination of PPC structural parameters improved ITE to 47.83%, representing a 2.3% increase over the original.

This study investigates the impact of 2-ethylhexyl nitrate (EHN) addition on fuel efficiency and emissions in a 6cylinder, turbocharged heavy-duty diesel engine using multi-injection strategies. Four fuels were tested: E1500, E2000, E3000 (with 1500, 2000, and 3000 ppm EHN, respectively), and commercial diesel. The experimental results indicated that cylinder pressure, heat release rate profiles, and calculated combustion phase exhibited minimal variations across different fuels under varying load conditions. Increasing EHN concentration reduced fuel consumption and improved thermal efficiency but raised nitrogen oxides (NOx) emissions, particularly from E2000 to E3000. Soot and carbon monoxide (CO) emissions decreased with higher EHN levels, while hydrocarbons (HC) emissions remained largely unaffected. Performance and emissions were evaluated using the World Harmonized Stationary Cycle (WHSC) and off-road cycle tests. E3000 demonstrated the best Brake Specific Fuel Consumption (BSFC), Brake Thermal Efficiency (BTE), and soot emissions, but NOx emissions increased significantly. In addition E1500 broke the trade-off relation between NOx and soot under two cycles due to EHN addition and high 90 % recovery temperature (T90). Considering fuel economy and environmental protection E1500 showed better performance under WHSC, while E3000 was more suitable for off-road applications. These findings highlight EHN's potential for optimizing diesel engine performance and emissions in heavy-duty applications.

This study provides insights into the dynamic behavior of a microwave resonant plasma system for hydrogen production via ammonia cracking, supporting its potential for hydrogen supply. Specifically, ammonia is a promising zero-carbon fuel for heat engines (e.g., internal combustion engines and gas turbines), but problems of instability and high emissions during combustion limit its application. To overcome these limitations, a compact, catalyst-free ammonia cracking system is needed. Plasma offers a novel approach to hydrogen production via ammonia cracking and holds potential to address bottlenecks in hydrogen applications. Although plasma-based methods have been studied, the dynamic response of ammonia cracking systems to varying operating conditions remains poorly understood. This study presents the first quantitative investigation of the dynamic response of an ammonia cracking system for hydrogen production using microwave resonant plasma. Stable plasma is formed in a compact quarter-wavelength coaxial cavity resonator. Under steady-state conditions at 200 W, 1 bar, and 1 SLPM ammonia flow, an ammonia cracking ratio (ACR) of 40.95% and a hydrogen production energy yield of 11.71 g/kWh are achieved. Spectroscopy confirms key intermediates (NH2*, NH*, H-alpha) and products (N-2, N-2(+)), with spectral intensity increasing monotonically with input power. A linear correlation (R-2 > 0.99) between ACR and overall, H-alpha, and NH2* emission intensities is established at 1.0 bar, enabling real-time ACR monitoring via high-speed imaging of the plasma light emissions. Response time increases with power variation and is longer for power increases than decreases for the same power variation. At atmospheric pressure, the response time is 1.31 ms for a power increase from 160 W to 180 W and 1.10 ms for a power decrease from 180 W to 160 W, demonstrating the millisecond-level dynamic response of the proposed microwave plasma ammonia cracking system.

Ammonia is a promising carbon-free fuel for internal combustion engines; however, its low flame speed and poor ignition stability limit the engine combustion performance. Passive pre-chamber ignition (PCI) can enhance ignition through multiple reactive jet flames, but the effects of pre-chamber throat and orifice geometries on jet flame stability and quenching under ammonia-fueled conditions remain unclear. In this study, a numerical model of passive pre-chamber engine fueled by pure ammonia was established and experimentally validated against cylinder pressure, heat release rate (HRR), and natural flame luminosity (NFL) of ammonia flames. Three throat/ orifice geometries were studied. The impacts of pre-chamber throat and orifice diameters on jet flame temperature, OH radical distribution, flow characteristics, and wall heat transfer within the throat-orifice region were analyzed. Results show that a high pre-chamber to main-chamber pressure difference (Delta P) and jet velocity do not necessarily accelerate ammonia combustion. Compared to the baseline engine with a throat diameter of 5 mm and orifice diameter of 2 mm, reducing the orifice diameter to 1.4 mm or reducing the throat diameter of 3 mm decreases the indicated thermal efficiency (ITE) from about 36% to 34% and 33%, and increases unburned NH3 from 33 to 36 and 38 g/kW & sdot;h, respectively. The ammonia combustion rate and stability are significantly affected by flame quenching. Reducing throat or orifice diameter enhances jet momentum but increases wall heat transfer significantly, leading to lower temperature and OH levels at the orifice exit and thereby reducing the jet flame stability. A quenching tendency index (QTI) is proposed to quantify the local competition between chemical heat release and wall heat loss, classifying orifice flames into robust, weakened, and near-extinction regimes. Pre-chambers with lower heat-transfer losses sustain unquenched orifice flames with higher temperatures and OH levels, enabling faster main-chamber combustion. Overall, high pre-chamber jet velocity must be accompanied by unquenched flames at the orifice to achieve high ammonia engine combustion efficiency.

To meet the demand for high-efficiency and clean combustion in advanced power systems, Pre-chamber Jet Ignition (PJI) has garnered widespread attention as a highly promising strategy for intensifying ignition. However, for heavy hydrocarbon fuels such as aviation kerosene, the fundamental physical principles governing the PJI process remain to be fully elucidated. In this study, we conducted an experimental investigation into the dynamic characteristics of turbulent jets generated from an aviation kerosene pre-chamber within a constant-volume combustion bomb. The investigation first reveals the system’s inherent robustness to the initial injection pressure. The physical origin of this robustness is attributed to a decoupling between the mixture preparation process and the initial spray momentum. Secondly, through a quantitative analysis of jet velocity fluctuations, a direct correlation is established between the macroscopic behavior of the jet and the evolution of its underlying vortex dynamics. Finally, this study establishes a universal non-dimensional correlation that unifies all experimental conditions. This result reveals a new and complex jet phenomenon governed by the synergistic effect of a dynamic pressure source and secondary combustion. This research not only deepens the understanding of the physical mechanisms governing the PJI process for heavy fuels but also provides a theoretical foundation for the design and optimization of related advanced power systems.

To address the ignition challenges of aviation kerosene under extreme conditions for power systems in the lowaltitude economy, this research introduces an "electrically heated pre-chamber" technology that uses active thermal management. Using a visualized constant volume combustion bomb in combination with CFD simulations, this study investigates the effects of preheating temperature and equivalence ratio on the ignition success rate, jet characteristics, and combustion-related physicochemical processes of aviation kerosene within the prechamber. The research found that ignition success is co-determined by preheating temperature and equivalence ratio, with preheating temperature being the primary controlling factor. Preheating temperature dictates an intensity-duration trade-off. At higher temperatures, strong but short-lived jets facilitate rapid ignition under severe conditions, while at lower temperatures, weaker yet longer-lasting jets contribute to combustion stability. The influence of the equivalence ratio on jet performance was found to be non-monotonic. Under fuel-rich conditions (an equivalence ratio of 1.6), a significant "chemical supercharging" effect was observed. Finally, the study identified that the pressure dynamics within the pre-chamber serve as the intrinsic physical link between the initial ignition conditions and subsequent jet behavior. The macroscopic characteristics of the jet are ultimately determined by the dynamic competition between pressure buildup from combustion heat release and pressure relief through the nozzle orifices. These findings provide a theoretical basis and data support for designing novel power systems geared towards the low-altitude economy.

Three representative combustion models, SAGE, G-equation, and ECFM, were systematically assessed and corrected for ultra-lean heavy-duty port fuel injection hydrogen spark-ignition engine conditions at 1000, 1400, and 1800 rpm. SAGE underestimated heat release because turbulent hydrogen mass diffusion was insufficient. The G-equation model underpredicted combustion intensity because its turbulent flame speed closure was inadequate. ECFM overpredicted the burning rate because flame-surface generation and the stretch response were excessive. Model-specific corrections substantially improved the predictions at 1000 rpm. The corrections comprised a lower turbulent Schmidt number for SAGE, a Damköhler-type turbulent flame speed formulation for G-equation, and a lower flame stretch constant for ECFM. With a consistent turbulent Schmidt number, G-equation calibration was less sensitive to species transport than ECFM calibration. However, all corrected models underestimated CA10-90 at higher speeds, identifying late-stage near-wall burnout as a key limitation of predictive CFD for ultra-lean hydrogen engines.

The ignition of ammonia fuel by hydrogen pre-chamber jet flame is an important strategy for achieving high-efficiency and low-emission combustion in ammonia engines. Although turbulence dominates the jet ignition process and the H2 content in the pre-chamber is relatively low compared to the entire system, differential diffusion induced by H2 can still influence flame development. In this study, a large-eddy simulation (LES) model was established based on the experimental data of H2 jet ignition in NH3/air premixed mixtures under constant-volume combustion vessel conditions. Comparative simulations were performed using the mixture-averaged diffusion model and the unity Lewis number model to elucidate the effects of differential diffusion. The results show that, within the pre-chamber, differential diffusion accelerates the transport of preferentially diffusing species, especially H and H2, enhancing OH formation and local heat release in the early flame region and establishing initial differences in the flame front. These early differences modulate flame-vortex interactions and influence flame propagation in the main chamber, affecting the spatial organization of reaction zones, temperature fields, and flame morphology. As a result, local reaction activity and the spatial distribution of pollutants, such as NO, are altered, even though turbulence eventually dominates flame development in the main chamber. These findings demonstrate the importance of accounting for differential diffusion to accurately predict flame development and pollutant distribution.Novelty and significance statementThis study reveals the critical role of differential diffusion (DD) in hydrogen pre-chamber jet ignition of ammonia/air mixtures. The LES results show that, in the pre-chamber, DD enhances preferentially diffusing species transport and OH formation, thereby accelerating flame propagation. These differences are subsequently transmitted to the main chamber, where they modulate early flame-vortex interactions and influence flame morphology and propagation. Although turbulence dominates later stages, the induced variations are preserved and amplified. The findings provide new insight into flame development and highlight the importance of accounting for DD effects in simulations of hydrogen pre-chamber jet ignition.

High NOx emissions pose a critical challenge for ammonia engines. This study proposes ammonia post-injection as a strategy to achieve in-cylinder NOx active reduction in ammonia direct-injection engines, offering an innovative approach for NOx emission control. Computational fluid dynamics (CFD) simulation results elucidate the characteristics of ammonia combustion and NOx evolution under ammonia post-injection conditions. The post-injected ammonia can efficiently reduce the in-cylinder NOx it encounters, leading to a significant decrease in NOx concentration. Chemical kinetics analysis was conducted to reveal the underlying mechanisms and reaction pathways of the SNCR effect on NOx. The reduction of NOx primarily proceeds through the reactions between NO/NO2 and NH/NH2. NO is reduced via three pathways, yielding NNH (by NH2), N2O (by NH), and N2 (by NH and NH2), respectively. In contrast, NO2 is reduced via a single pathway that yields N2O under the action of NH and NH2. NH2 plays the overwhelmingly dominant role in reducing both NO and NO2. The effectiveness and feasibility of ammonia postinjection in reducing NOx emissions were evaluated through engine experiments. The experimental results demonstrate that the ammonia post-injection strategy enables significant NOx reduction for ammonia direct-injection engines. In the current work, a 14.4

In recent years, the application of long-endurance unmanned aerial vehicles (UAVs) has significantly expanded across various sectors, owing to their enhanced ability to maintain prolonged operational periods. Piston engines, regarded as the quintessential propulsion system for UAVs, face significant challenges related to fuel safety and combustion efficiency, especially when operated using conventional gasoline as the energy source. In the pursuit of enhanced safety measures, aviation kerosene has emerged as a preferred alternative to traditional fuels, providing improved safety profiles for UAV propulsion systems. Nevertheless, its high kinematic viscosity may result in diminished combustion efficiency and stability, potentially giving rise to issues with knocking. By utilizing the unique advantages of the pre-chamber jet, this technology enhances spray diffusion and improves combustion characteristics. Through numerical simulations, this research provides a detailed analysis of the impact of the main combustion chamber injection timing, pre-chamber ignition timing, and their synergistic control strategies on combustion and engine performance. The results demonstrate that by precisely controlling the fuel injection timing and ignition timing, the combustion process can be significantly optimized, reducing the occurrence of knocking and thereby enhancing the overall performance of the engine. The engine equipped with the JESD system shows a notable improvement in both combustion efficiency and power output compared to the original spark-ignition engine. The indicated fuel consumption (IFC) is reduced by 5.5%, the combustion efficiency is increased from 83.87% to 92.94%, and the ITE is improved from 27.2% to 31.72%. These improvements not only enhance the engine's fuel economy but also bolster its reliability and performance in long-endurance UAV applications.

Methanol compression ignition serves as a cornerstone of decarbonization in heavy-duty transportation, yet combustion instability remains a critical bottleneck restricting its development. This study fundamentally clarifies the mechanism underlying methanol combustion instability through optical diagnostics combined with chemical reaction kinetics analysis, and addresses this issue via molecular fuel design by adding cetane improvers, namely 2-ethylhexyl nitrate (EHN) and di-tert-butyl peroxide (DTBP). Detailed analysis shows that methanol combustion instability arises from the combined effects of poor fuel-air mixture homogeneity, high turbulence intensity, and the absence of a low-temperature exothermic stage. In the specific spray configuration and conditions of this experiment (ambient temperature: 950 K; ambient pressure: 4 MPa), the equivalence ratio of methanol spray is approximately twice that of n-heptane, while its temperature is about 17 % lower, leading to around 47 % of the methanol fuel-air mixture being in a misfiring state. At the same time, mixing in the central region of the methanol spray is highly non-uniform, with a scalar dissipation rate 2.4 times that of n-heptane. The methanol spray flame exhibits almost no low-temperature combustion process. The addition of cetane improvers mitigates these issues. In particular, EHN prolongs the duration of low-temperature chemistry and advances high-temperature combustion significantly, resulting in a more regular flame structure and suppressing flame-edge wrinkling. EHN outperforms DTBP in improvement efficacy because its regenerative NO2 cycle (NO2 -> HONO -> NO -> NO2) catalytically accelerates methanol dehydrogenation, whereas DTBP's chain-terminating methyl radicals limit its effectiveness. These results demonstrate that suitably designed cetane improvers can act as molecular catalysts, enabling methanol to achieve diesel-like stability while maintaining near-zero soot emissions, and providing a pathway toward scalable carbon-neutral heavy-duty transportation and marine power.

Understanding the staged energy release mechanism in jet ignition is crucial for mitigating explosion hazard of battery thermal runaway and optimizing combustion powertrains. Yet current Wiebe combustion models poorly predict its staged processes, leaving the link between energy release and ignition/emission performance unclear. In this work, a 0-D combustion model using the triple-Wiebe function to predict multi-stage propagation was developed for flame ignition with single/double-peak heat release rate (HRR) profiles. Meanwhile, the ignition/NOx emission performance was revealed by integrating pressure-driven Wiebe combustion model with staged thermodynamic sub-model. The results show that the standard format fails to predict jet ignition processes. The triple-Wiebe function from conventional time division approximates the experimental mass fraction burned (MFB) and pressure trends, but overestimates the HRR peak at jet ignition and underestimates it at early auto-ignition stage. The modified triple-Wiebe function, which adjusts the algebraic solution time range for form factor m, can accurately predict MFB, HRR, and pressure, with only a slight lag in predicting the combustion phase during the auto-ignition combustion stage. Moreover, by reducing the overall HRR of the single-peak mode, particularly during the early jet ignition stage, it can be transformed into a double-peak mode. This achieves comprehensive performance regulation, including weakened jet ignition capability, enhanced local auto-ignition capability, reduced N2O emissions, and increased NO emissions. The present study provides a key zero-D modeling module for ammonia jet-ignition engines and theoretical guidance for reducing gas explosion hazards and optimizing powertrains.