Turbulent Jet Ignition (TJI) engines show promising potential for enhancing engine efficiency. However, they differ significantly from conventional spark ignition engines in terms of in-cylinder combustion modes, rendering traditional detonation evaluation methods inadequate for accurately assessing TJI engine detonation states. This study introduces two new metrics: Before θPmax (the crank angle corresponding to peak cylinder pressure) Detonation Energy (BPDE) and After θPmax Detonation Energy (APDE) to characterize the knock behavior of TJI engines. Through analyzing the knock characteristics of the TJI engine under different compression ratio (CR), the author found that when the CR increased from 13 to 17 and the ignition angle was set to 12°CA bTDC, the engine's AMAPO increased by 0.55 MPa, and TDE increased by 0.8 MPa·°CA. However, when the CR reached 19, although TDE increased by 0.192 MPa·°CA, AMAPO decreased by 0.145 MPa. Two newly introduced metrics explain this phenomenon: when the CR increased from 17 to 19, ABPDE rose by 62.3% while AAPDE decreased by 15.5%. Knock energy primarily shifted to ABPDE, causing AAPDE to decline and resulting in the decrease of AMAPO. Additionally, no super-knock phenomena were observed at a CR of 19 and 70% load. The knock frequency distribution of TJI engines at different CRs was analyzed using Fast Fourier Transform (FFT). Statistical probability distribution (PD) and cumulative distribution (CD) were employed to estimate changes in Maximum Amplitude Pressure Oscillation (MAPO) across varying CRs. The knock characteristics of TJI engines were further detailed.

Addressing the critical role of spray characteristics in mixture formation and combustion characteristics, this study investigates methanol-blended, ethanol-blended, and five pure alcohol fuels (methanol, ethanol, isopropanol, *n*-butanol, isobutanol). Spray dynamics were captured via high-speed photography and Schlieren imaging in a constant-volume chamber. Computational simulations isolated the effects of fuel properties (density, viscosity, surface tension) and ambient conditions (pressure, temperature) on spray morphology. A Random Forest (RF) model leveraging out-of-bag (OOB) error estimation quantified parameter importance and predicted spray characteristics (penetration, cone angle, area). After hyperparameter tuning, the optimized RF model achieved high-fidelity predictions (e.g., spray area: R2 = 0.98, RMSE = 118). Key findings reveal ambient pressure as the dominant factor influencing spray characteristics, followed by ambient temperature, while fuel properties exhibit operating-condition-dependent effects. This integrated experimental-computational-ML framework enables rapid spray parameter optimization and facilitates inverse design of alcohol-fuel nozzles and combustion chambers, advancing cleaner and more efficient combustion technologies.

Owing to its superior combustion performance, abundant reserves and clean combustion products, hydrogen has been regarded as a promising alternative fuel for internal combustion engines (ICEs). The direct injection hydrogen internal combustion engines can offer larger power without the risk of backfires, compared to port fuel injection. To avoid the NOx emission and improve the power output, lean boosting is adopted to reduce the pressure-increase rate and combustion temperature. As well as the low exhaust temperature of hydrogen engine, which pose significant challenges for the turbocharger system. Against this background, an experimental study was carried out on an 8.2 L DI hydrogen engine. Three types of turbochargers were compared: wastegate turbocharger (WG), variable geometry turbocharger (VGT), and two-stage turbocharger (TS). All tests were performed under operating conditions constrained by pre-ignition and super-knock, aiming to maximize thermal efficiency. The brake thermal efficiency (BTE) varied from 31.1% to 34.4% across the tested engine speeds. The TS turbocharger yielded the maximum BTE of 34.4% at 1300 rpm. This work further investigated the effects of different turbochargers on the energy and exergy distributions of the engine. Energy analysis results reveal that the two-stage turbocharge exhibits the lowest exhaust energy loss, the variable geometry turbocharger demonstrates the lowest coolant energy loss, and the wastegate turbocharger achieves the lowest intercooler loss. Exergy analysis results indicated that the TS system achieved the maximum total available exergy efficiency of 67.9% at 1600 rpm, accompanied by the minimum exergy destruction.

To investigate the influences of direct injection strategies on the combustion and emission performances of hydrogen/gasoline dual-fuel engines, a turbocharged direct-injection gasoline engine was modified into a dualfuel engine for hydrogen and gasoline, which was equipped with HDI) Experiments were conducted under stoichiometric and lean-burn conditions to investigate the influence of hydrogen direct injection timing, hydrogen ESR, and 2 on in-cylinder pressure, HRR, combustion phase, cycle variation, BTE, and exhaust emissions. The results show that hydrogen addition most significantly shortens the early flame development, thereby accelerating flame propagation, advancing combustion phase, enhancing Pmax and BTE, reducing HC and CO emissions due to more complete combustion, while increasing NOX emissions caused by elevated in-cylinder temperature. EOI remarkably affects mixture formation and combustion performance, and - 180 degrees CA ATDC is verified as the optimal injection timing, which provides sufficient mixing time and favorable combustion phasing. Under lean-burn conditions, the coupling control of ESR and 2 achieves a balanced trade-off between efficiency and emissions. Excessively lean mixture or overly retarded injection timing would prolong combustion duration, increase cycle variation and incomplete combustion products.

Knock severely restricts the development of downsized and turbocharged gasoline engines, and fuel formulation optimization is a cost-effective knock suppression strategy. This study combines experimental tests, CFD simulations and reactive force field molecular dynamics (ReaxFF-MD) simulations to investigate the knock suppression mechanism of methanol blending in RON92 gasoline for a 2.0 L turbocharged spark-ignition engine, with methanol mass blending ratios (MR) controlled at 0%, 5%, 10% and 15%. Experimental results show that methanol blending significantly smooths in-cylinder pressure traces and reduces knock intensity (KI) without obvious impact on combustion speed, and the in-cylinder thermal environment and flame propagation characteristics show negligible differences under different MR, indicating fuel intrinsic properties dominate knock suppression. ReaxFF-MD simulations at 1800-2400 K reveal methanol has little effect on gasoline's thermal pyrolysis and initial fragmentation, but effectively inhibits the formation of key intermediates (CH2O and CO) associated with low-temperature oxidation and chain reactions. This work verifies the excellent knock suppression performance of low-proportion methanol blending, and clarifies its atomic-scale mechanism from intermediate evolution and product formation, providing a theoretical basis for high-performance anti-knock fuel design and engine knock control.

To enhance fuel-air mixing in compression ignition engines, the Lateral swirl combustion system (LSCS) was proposed and demonstrated excellent performance in diesel engines. However, no studies have yet applied LSCS to the increasingly popular diesel/ammonia dual-fuel engines. This study investigates the role of LSCS in diesel/ ammonia Reactivity Controlled Compression Ignition (RCCI) combustion and its potential to enhance zerocarbon fuel utilization. By introducing an LSCS chamber with a rim structure and developing a 3D computational model based on nitrogen tracking method, we examined the impact of Start of injection (SOI) and Swirl Ratio (SR) on in-cylinder combustion and emission characteristics. Results show that the LSCS rim structure enhances wall jet and improves air utilization. Across all SOI conditions, LSCS achieved higher Indicated mean thermal efficiency (ITE) than non-convex combustion system (NCCS), with a maximum improvement of 1.9%. The greenhouse gas (GHG) emissions were slightly reduced, while emission of unburned ammonia was reduced by approximately 13%. At SR = 1.25, the interaction between wall jet and swirl motion created optimal local equivalence ratio distribution, resulting in maximum ITE, an increase of 1.34% compared to the original LSCS case, as well as the minimum GHG and ammonia emissions. Therefore, LSCS demonstrates potential to further enhance diesel/ammonia RCCI engine performance while reducing GHG and unburned ammonia emissions.

The diesel/ammonia combustion mode can significantly cut down carbon emissions, while the growth in fuel NOx due to the introduction of ammonia poses a potential emission problem. To explore the generation and reduction mechanisms for different sources of NO (oxidant-source NO and fuel N*O), an ammonia/n-heptane chemical kinetic mechanism was constructed. With the N element tracking method, the different sources NO emission characteristics of a diesel/ammonia reactivity-controlled compression-ignition (RCCI) engine were probed through varying diesel start of injection (SOI), injection pressure, nozzle hole number, and spray angle. The results indicated that in a diesel/ammonia RCCI engine, the production of fuel-source N*O occurred earlier than that of oxidant-source NO. During the NO reduction process, thermal DeNOx mainly occurred at the center of the combustion chamber and near the edge oxidant-source NO, and fuel-source NO emissions initially increased and then decreased. The area of unburned ammonia distribution is most enriched near the cylinder wall. As the SOI increased, at higher injection pressures, fuel-source NO was generally higher, while at medium injection pressures, oxidant-source NO emissions were higher. The trends of oxidant-source NO and fuel-source N*O with an increasing nozzle hole number were opposite, while the change in total NO emissions was not significant. When the spray angle was reduced to 122 degrees, the total NO emissions decreased by 49% compared to the original 162 degrees. This suggests that adjusting the spray angle can significantly lower NO emissions without reducing engine efficiency.

This study experimentally and numerically evaluates the impact of ammonia-water direct injection (DI) nozzle configurations on knock suppression in gasoline spark-ignition (SI) engines under high-load conditions. The original six-hole injector was modified into two single-hole variants: DI-1 (nozzle holes oriented toward the piston) and DI-2 (holes directed toward the cylinder head). Experiments analyzed 12 end-of-injection (EOI) timings (-330 degrees CA to 0 degrees CA ATDC) and varying direct injection ratios (DIr) to assess knock suppression, combustion stability, and temperature distribution. Numerical simulations using CONVERGE software validated experimental results and provided insights into in-cylinder spray dynamics and flame propagation. Findings revealed that DI-1 significantly outperformed DI-2, achieving a broader effective knock suppression range (KI reduction up to 42 %) at minimal pulse widths (DIr = 3.5 %) due to enhanced cooling of the end-gas mixture via piston-directed spray alignment with tumble flow. Early-phase injection near bottom dead center (BDC, -180 degrees CA ATDC) optimized cooling efficiency by maximizing spray dispersion during compression, whereas delayed injection post-BDC diminished suppression due to altered spray-wall interactions. The original six-hole injector, despite requiring higher DIr (9.5 %), demonstrated robust cooling performance but faced challenges in precise low-flow control. Combustion analysis highlighted that ammonia-water injection reduced peak cylinder pressure (by 8-12 %) and delayed combustion phasing (CA50 by 4-6 degrees CA), necessitating a balance between DIr and ignition timing to avoid excessive retardation. Temperature field simulations confirmed DI-1's superior peripheral cooling, reducing high-temperature regions (>730 K) by 18 % compared to DI-2. This work underscores the viability of ammonia-water as a knock inhibitor and proposes nozzle orientation optimization as a critical pathway for minimizing inhibitor consumption while maintaining thermal efficiency. The results provide actionable insights for designing high-performance DI systems in downsized, high-efficiency SI engines.

The use of alcohol fuels in automotive engines holds significant potential for reducing reliance on fossil fuels and mitigating greenhouse gas emissions. This study investigated the macroscopic spray characteristics of methanol, ethanol, isopropanol, n-butanol, and isobutanol using a constant volume chamber and the schlieren method. The effects of varying ambient temperatures, ambient pressures, injection pressures, and fuel temperatures on the spray characteristics of these alcohol fuels were systematically analyzed. An artificial neural network (ANN) was employed to predict spray characteristic parameters, with Bayesian optimization applied for hyperparameter tuning, leading to the development of an optimal ANN model utilizing fuel properties as input. The results revealed that although the overall trends in spray characteristics were consistent among different alcohol fuels under varying conditions, the magnitude of changes differed significantly due to variations in their physicochemical properties. The developed ANN model demonstrated high predictive accuracy (R-2 > 0.98), closely matching experimental data. This study highlights the potential of ANN-based models to reduce experimental workload in the development of carbon-neutral fuels and advanced fuel injection systems, contributing to cleaner and more efficient combustion technologies.

Knock detection is crucial for ensuring engine reliability and performance. Conventional approaches, such as the maximum amplitude of pressure oscillations (MAPO), face limitations including poor noise robustness, low sensitivity to incipient knock, and reliance on empirically defined thresholds. This study proposes a knock detection and diagnosis framework WPKNN based on weighted PCA and k-nearest neighbors. By constructing a time-sensitive weighted principal component score sequence, the method effectively captures weak incipient knock features, significantly enhancing detection sensitivity and accuracy. Furthermore, a novel statistic KNNp is introduced that integrates local neighborhood variations and global principal component information, enabling precise identification of knock. It overcomes the limitations of the MAPO method, which relies solely on a single-peak indicator. In addition, kernel density estimation (KDE) is employed to adaptively determine dual thresholds for slight and severe knock, thereby improving the knock risk management. To support knock tracing, an advanced contribution-based diagnostic mechanism is established. It combines enhanced complete decomposition contribution (ECDC) and enhanced partial decomposition contribution (EPDC) methods, which accurately identify the key parameters most responsible for knock evolution. Experiments on a turbocharged gasoline engine under various knock conditions confirm that the WPKNN framework improves detection reliability, and provides robust support for intelligent combustion control and active knock suppression strategies.

The injection behavior of fuel is intimately linked with the engine's combustion process and emissions. Accurate modeling and predicting the spray characteristics of these fuels are essential to the effective large-scale deployment of alternative fuels and the development of corresponding fuel supply systems. Spray test data for methanol, ethanol, isopropanol, n-butanol, isobutanol, and gasoline under various operating conditions were collected through schlieren imaging in a constant volume chamber. This study addresses two primary objectives: first, to predict the spray tip penetration (STP) for each tested fuel using both response surface methodology (RSM) and artificial neural networks (ANN), and to compare the predictive performance of these two methods. Second, to fill the gap in the absence of a universal model for the spray characteristics of alcohol fuels, multiple topological indices, which are tools for converting molecular structure information into numerical descriptors, were utilized to describe the alcohol fuels and to develop an ANN model. The findings revealed that both the RSM and ANN models exhibited high accuracy and reliability in predicting the STP for individual fuel datasets, with the RSM model marginally outperforming the ANN model in terms of fit quality. The ANN model, developed using topological indices to describe alcohol fuels, achieved R2 of 0.9939, 0.9936, and 0.9949 on the training set for predicting three spray characteristic parameters, demonstrating high precision, robustness, and reliability. The ANN model developed in this study, based on topological indices, shows significant potential to serve as a universal model for predicting the spray characteristics of alcohol fuels across a range of operating conditions. Expanding the database to incorporate additional fuels and spray conditions would allow the universal model to be used for promoting the efficient and clean use of alcohol fuels and advancing the development of highefficiency, low-carbon internal combustion engines.

The real driving emissions of gasoline and diesel vehicles are significantly influenced by altitude, temperature, and starting conditions. In this study, the real driving emissions (RDEs) of gasoline and diesel vehicles compliant with China V standards were investigated under various conditions. The adaptability of RDE testing in China was evaluated by analyzing vehicle emissions at different altitudes, ambient temperatures, and starting conditions. The results show that, with increasing altitude, CO, NOx, and PN emissions generally exhibit a downward trend, particularly for gasoline vehicles, whose conformity factors remain well below the China VI limit. However, for China V diesel vehicles relying solely on EGR technology, NOx emissions significantly exceed China VI standards, indicating that EGR alone is insufficient to meet regulatory requirements. Temperature variations have little effect on the emissions of China V PFI gasoline vehicles, while diesel vehicles continue to exhibit excessive NOx emissions under varying temperatures. Although the cold-start phase generates substantial pollutant emissions, the EMROAD evaluation method excludes this phase, resulting in limited differences between cold- and hot-start emission results. Nevertheless, the inclusion of cold-start emissions should be considered in future RDE assessments.

With the ongoing downsizing of engines and the increasing adoption of direct injection systems, flash boiling and spray-wall impingement have become inevitable phenomena, particularly for methanol and ethanol, which are promising alternatives to gasoline. This study experimentally investigated the wall-film characteristics after spray impingement under varying flash-boiling intensities in a constant-volume chamber using high-speed imaging combined with the Refractive Index Matching (RIM) technique. Key parameters-the ambient-tosaturation pressure ratio (Pa/Ps), fuel temperature, and ambient pressure-were systematically varied. The results show that as Pa/Ps decreased from 1.0 to 0.15, sprays transitioned from non-flash to flare flash-boiling regimes, accompanied by spray collapse and droplet coalescence, leading to a morphological change in the wall film from uniform to converging curved structures. Increasing flash-boiling intensity markedly reduced the overall film area but caused localized thickening, which was more evident for methanol than for ethanol. Fuel temperature exhibited nonlinear effects: maintaining moderate superheating (approximately 313-343 K for methanol and ethanol) effectively reduced wall wetting, whereas excessive heating intensified spray collapse and film thickening. At low ambient pressures (0.03-0.01 MPa), flash boiling further accelerated film evaporation, leaving only minimal residues for alcohol fuels. These findings provide guidance for optimizing fuel temperature and injection strategies to minimize wall wetting and improve mixture formation in gasoline direct injection (GDI) engines.

Internal combustion engines are evolving to attain advanced combustion modes with higher percentage of compression ignition combustion. Homogeneous charge compression ignition is limited by load range and combustion stability, so hybrid combustion modes have emerged as a key research hotspot. In order to optimize hybrid combustion modes, combustion modes should be accurately identified. Therefore, this study introduces new criterion and method to identify combustion modes. The results show that high compression ratio spark ignition engines are prone to autoignition, however, a trade-off relationship exists between high percentage of compression ignition combustion and the optimal combustion phase. As low percentage of compression ignition is favorable for engine efficiency, reduction of the combustion intensity should be considered. Under spark ignition assistance, both single-fuel and dual-fuel combustion exhibit a combustion mode where spark ignition and compression ignition occur simultaneously, which is defined as spark-assisted compression ignition combustion mode. The peak value (HP) for the second derivative of heat release rate at the onset of a combustion mode is strongly correlated with burning intensity and can be used to identify different combustion modes. The HP of spark ignition combustion is less than 1.5 J/deg3. Spark-assisted compression ignition combustion has an HP between 1.5 J/deg3 and 5.0 J/deg3, while the HP of premixed compression ignition combustion is at least 5.0 J/deg3.

The potential use of hydrogen in automotive internal combustion engines could aid in the energy transition and contribute to achieving carbon neutrality. This paper has investigated the impact of operating parameters boundary for a novel preignition event on a 2.0L hydrogen direct injection (HDI) engine to address the challenge of abnormal combustion limiting the application of HDI engines. The identified characteristics of the event and its potential harm to the engine has been summarized. Experiments have shown that the novel preignition event predominantly occurred mainly during 170- 80 degrees CA BTDC, hence the name PEMC (preignition in the early/mid compression stroke) event, and caused a surge in cylinder pressure. In 77.2 % of the selected cases, the PEMC events resulted in increased NOx emissions. In 93.1 % and 91.5 % of the cases, there was a decrease in brake power and brake thermal efficiency, respectively. Unlike the low speed, high load preignition of gasoline engines, PEMC events were more likely to occur in the torque range of 70-100 Nm and could be monitored in a lean mixture environment with lambda = 1.5-3.3. PEMC events were found in the interval of 180- 320 degrees CA BTDC at injection timing and were most intense at 240- 250 degrees CA BTDC. To prevent PEMC events completely, it is recommended to delay the injection timing beyond 180 degrees CA BTDC. The paper has employed a model based on experimental data and Random Forest algorithms to predict PEMC events. The model demonstrated an accuracy of 98.76 % and 97.69 % for the training and test data, respectively. It has been effective in predicting the occurrence of PEMC events under various operating conditions. The paper has offered an alternative solution for the novel preignition in HDI engines.

Diesel/ammonia operation is one of the ways to efficiently utilize ammonia and reduce carbon emissions, however, the increase in fuel NO introduces serious emission problems. To explore the generation mechanisms of fuel NO and oxidant source NO, a multi-component diesel/ammonia chemical reaction mechanism was constructed in this study, and based on 3D CFD simulation and N-element tracking method, the combustion and different source NO emission characteristics of diesel/ammonia reactivity controlled compression ignition (RCCI) engine at low loads were investigated by pilot injection timing (SOI1) and pilot injection ratio (PIR). In addition, the effect of different first injection spray angle (SA1) and double injection spray angle (SA(total)) on the engine operation was investigated. The results showed that high PIR and delayed SOI1 enhanced the engine IMEP but led to high PRRmax. At a PIR of 15 %, total NO emissions increased as SOI1 advanced, and the trend was reversed when the PIR was higher than 15 %. Fuel NO was produced earlier than the oxidant source N & lowast;O. In terms of 1 spatial distribution, high concentrations of both NO and N & lowast;O were distributed in and around the secondary diesel fuel ignition location, and fuel NO began to be reduced where the oxidant source N & lowast;O was rapidly formed. The reduction mechanism of NO in the cylinder was a multi-path reduction mechanism incorporating Thermal DeNOx, NO Reburning, and inverse reaction pathways for NO formation from the oxidant source. Appropriate reduction of the SA(total) can significantly reduce the total NO emission while maintaining no significant reduction in IMEP. When SA(total) was 82 degrees, the total NO emission was only 16.3 % of the original spray angle and PRRmax was further reduced. After optimization, when a narrow SA(total) of 82 degrees, SOI1 of -15 degrees CA, and PIR of 35 % were used, the IMEP of the engine increased by 5.9 %, and the total NO emission was reduced by 86 %, while PRRmax did not exceed the PRR upper limit.

Under the appropriate injection strategies, both direct water injection and direct ammonia-water injection can effectively suppress the knock, but the effect of the knock suppression is slightly different. In this paper, water and ammonia-water were respectively injected directly into the cylinder of a high performance port gasoline injection engine by modified low-flow direct injectors. The effects of direct injection timing and injection ratio on knock, combustion and emission were investigated. Both water and ammonia-water can effectively suppress knock in SI mode. Compared to water, ammonia-water exhibits a more prominent inhibitory effect on knock at lower DI ratios. However, when the ratio was further increased, the difference between the effects of ammonia-water and water on the inhibition of knockdown became less pronounced. Water and ammonia-water DI affect the knock through different mechanisms due to their unique chemical properties. While water predominantly influences the later combustion phases due to its rapid vaporization and high specific heat capacity. Ammonia-water primarily impacts the early combustion phase because of its complex combustion process and lower laminar flame speed.

Auto-ignition triggering plays an important role in the study of knock, accurate and generalized calculation methods are of great significance. In this study, a brand new calculation method of end-mixture auto-ignition timing based on heat release rate (HRR) is proposed based on several sets of data with different knock intensities of a small turbocharged gasoline engine. The calculation method effectively eliminates the effect of fluctuations in the actual HRR data by setting the search range and the auto-ignition threshold, and also eliminates the calculation delay caused by the second-order derivatives of HRR in the regular calculation method. Under this calculation method, the auto-ignition and knock characteristics present a good fit. The effects of combustion parameters on auto-ignition are significantly different. The changes in engine coolant and inlet air temperature as well as the over-rich mixture significantly affected the auto-ignition trigger pressure, while the ignition timing and the over-lean mixture had no effect on it. The effects of methanol on auto-ignition trigger pressure were also significantly different under various injection timings. The calculation of auto-ignition timing provides a vital prerequisite for the study of auto-ignition triggering, which is of obvious significance for the study of knock.

Under appropriate strategies, direct methanol injection can suppress the knock effectively. In this paper, methanol was injected as an anti-knock agent by modified low-flow direct injectors into the cylinder of a high-load port injection gasoline engine. The effects of methanol injection timing and methanol ratio on knock suppression were investigated. The knock intensity (KI), knock probability, and auto-ignition timing were used as the primary basis for quantifying the knock. The results show that methanol injection timing has a significant impact on combustion. Maximum knock suppression can be achieved when methanol is injected near the bottom dead center. The too-early and too-late injections will affect the knock suppression. There was an apparent knock phenomenon when methanol was injected near the end of the compression stroke. When the ratio of methanol is meager, methanol will instead increase the intensity of the knock. As the methanol ratio rises, the knock is gradually and effectively suppressed. There is a specific methanol ratio beyond which higher methanol ratios do not significantly increase the knock suppression effect. When methanol was injected late in the compression stroke, low methanol ratios did not seriously increase the knock intensity, but high methanol ratios did not eliminate the knock either.

This study aims to investigate the impact of methanol direct injection strategy on the combustion and emission characteristics of a dual-fuel turbocharged engine running under high load of 1500 rpm. Five methanol injection timings ranging from 330 degrees CA (crank angle) to - 60 degrees CA ATDC (after top dead center) were tested under four different methanol energy substation ratios. Based on the experimental results, a suitable injection timing was selected to study the effect of methanol energy substation ratio. The results showed that different injection timings had varying effects on engine combustion and emission characteristics. End of injection timing of methanol (EOI) at - 180 degrees CA ATDC resulted in fuller atomization of methanol, which delayed combustion and reduced the combustion rate, with the lowest knock intensity and highest indicated mean effective pressure. However, this timing also had the highest emissions of NOx. Further experiments were conducted at EOI = - 180 degrees CA ATDC under eight different energy substation ratios. The results demonstrated that adjusting the injection strategy of methanol can effectively change the engine's performance. The optimal injection strategy was found to be EOI = - 180 degrees CA ATDC and an energy substation ratio range of 4.6%-8.9%. This research provides valuable insights into the use of methanol as a fuel and its impact on engine characteristics.