Search Results (155)

Biogas from palm oil mill effluent (POME) is a promising fuel that has many advantages as an alternative fuel. The methane content in biogas derived from POME is up to 75% and can be used as an alternative fuel in an internal combustion engine. One of the technologies for utilizing biogas in compression ignition engines is the Diesel Dual-Fuel (DDF) technique due to the different characteristics of fuel and the impact on the environment due to significantly reducing emissions. This study aims to find the effect of biogas POME composition and energy ratio on the DDF engine’s performance and emissions. The simulations using AVL BOOST software were confirmed by experimental engine parameters. The modeling was conducted on the biogas energy ratio (20%, 40%, 60%, and 75% POME) and biogas POME composition (55% and 75% methane). The results showed that the fuel consumption of diesel fuel was reduced by up to 69%, and NO_x and soot emissions were reduced by up to 92% and 80%, respectively, with dual-fuel mode operation. Meanwhile, the value of brake mean effective pressure (BMEP) and efficiency was reduced by up to 18%, volumetric efficiency decreased by up to 4%, the increase in brake specific energy consumption (BSEC) was up to 23%, and brake specific fuel consumption (BSFC) was up to 155%. The optimum of the engine’s performance and emission was 40% biogas ratio with 75% methane content. Full article

The escalating global demand for primary energy—still predominantly met by conventional carbon-based fuels—has led to increased atmospheric pollution. This underscores the urgent need for alternative energy strategies capable of reducing carbon emissions while meeting global energy requirements. Hydrogen, as a clean combustible fuel, offers a promising alternative to hydrocarbons, producing neither soot, CO₂, nor unburned hydrocarbons. Although nitrogen oxides (NO_x) are the primary combustion by-products, their formation can be mitigated by controlling flame temperature. This study investigates the viability of hydrogen as a clean energy vector by simulating an unsteady, turbulent, non-premixed hydrogen jet flame interacting with an air co-flow. The numerical simulations employ the Unsteady Reynolds-Averaged Navier–Stokes (URANS) framework for efficient and accurate prediction of transient flow behavior. Turbulence is modeled using the Shear Stress Transport (SST k-ω) model, which enhances accuracy in high Reynolds number reactive flows. The combustion process is described using a presumed Probability Density Function (PDF) model, allowing for a statistical representation of turbulent mixing and chemical reaction. The simulation results are validated by comparison with experimental temperature and mixture fraction data, demonstrating the reliability and predictive capability of the proposed numerical approach. Full article

This study aimed to investigate the effects of diesel/ethanol/n-butanol mixed fuel on the marine diesel engine combustion and emissions at different ethanol blending ratios, different single injection times, and pre-injection times. In addition, this study takes the injector fault phenomenon as an example, simulates the three fault phenomena of the injector, and uses a variety of algorithms to optimize the probabilistic neural network model to achieve the fault state identification and diagnosis of the injector. The results of research showed that, with the increase in the ethanol blending ratio, the peak cylinder pressure shows a decreasing trend. The ignition delay period is extended, and the peak instantaneous heat release rate increases. Compared with D100, the nitrogen oxide (NO_x) emissions of D50E40B10 mixed fuel are reduced by 12.3%, soot emissions are reduced by 29.18%, and carbon monoxide (CO) emissions are increased by 5.7 times. With the injection time advances, the peak values of cylinder pressure and heat release rate show an increasing trend, soot emissions gradually decrease, and NO_x and CO emissions gradually increase. The peaks of the cylinder pressure and heat release rate in the pilot injection stage gradually decrease as the pilot injection time advances, while the peak heat release rate in the main injection stage increases. In terms of emissions, NO_x emissions first decrease and then increase as the pilot injection time advances, while soot emissions gradually increase. The average accuracy of the PSO-PNN neural network model reaches 90%, and the average accuracy of the WOA-PNN neural network model reaches 95%. Therefore, the WOA-PNN neural network model is determined to be the optimal injector fault diagnosis model, which can be applied to the identification and diagnosis of injector fault states of diesel engines. Full article

This study investigates the impact of circumferential angle (φ) and interaction angle (θ) between hydrogen jets and diesel sprays in a co-axial hydrogen–diesel injector on combustion and emissions in a hydrogen–diesel dual-fuel engine using 3D CFD simulations. The results demonstrate that a co-axial dual-layer nozzle design significantly enhances combustion performance by leveraging hydrogen jet kinetic energy to accelerate fuel–air mixing. Specifically, a co-axial alignment (φ = 0°) between hydrogen and diesel sprays achieves optimal combustion characteristics, including the highest in-cylinder pressure (20.92 MPa), the earliest ignition timing (−0.3° CA ATDC), and the maximum indicated power of the high-pressure cycle (47.26 kW). However, this configuration also results in elevated emissions, with 29.6% higher NOx and 34.5% higher soot levels compared to a φ = 15° arrangement. To balance efficiency and emissions, an interaction angle of θ = 7.5° proves most effective, further improving combustion efficiency and increasing indicated power to 47.69 kW while reducing residual fuel mass. For applications prioritizing power output, the φ = 0° and θ = 7.5° configuration is recommended, whereas a φ = 15° alignment with a moderate θ (5–7.5°) offers a viable compromise, maintaining over 90% of peak power while substantially lowering NOx and soot emissions. Full article

Ammonia is a carbon-free fuel with strong potential for emission reduction. However, its high auto-ignition temperature and low reactivity lead to poor ignitability and unstable combustion. In contrast, coal-to-liquid (CTL) fuel offers high cetane number, low sulfur content, and low aromaticity, making it a clean fuel with excellent ignition performance. Blending CTL with ammonia can effectively compensate for ammonia’s combustion limitations, offering a promising pathway toward low-carbon clean combustion. This study explores the effects of post-injection strategies on combustion and emission characteristics of a CTL–ammonia dual-fuel engine under different levels of ammonia energy fractions (AEFs). Results show that post-injection significantly improves combustion and emission performance by expanding ammonia’s the favorable reactivity range of ammonia and enhancing NH₃ oxidation, particularly under moderate AEF conditions (5–10%) where ammonia and CTL demonstrate strong synergy. For emissions, moderate post-injection notably reduces CO at low AEFs, while NO_X emissions consistently decrease with increasing post-injection quantity, with greater suppression observed at higher AEFs. Soot emissions are also effectively reduced under post-injection conditions. Although total hydrocarbon (THC) emissions increase due to ammonia’s low reactivity, post-injection mitigates this accumulation trend to some extent, demonstrating overall co-benefits for emission control. Comprehensive evaluation indicates that the combination of 5–10% AEF, 8–12 mg post-injection quantity, and post-injection timing of 10–15 °CA achieves the most favorable balance of combustion efficiency, emissions reduction, and reaction stability, confirming the potential of the CTL–ammonia dual-fuel system for clean and efficient combustion. Full article

This study aims to investigate the impact of combustion chamber geometry and biodiesel on the performance of diesel engines under various load conditions. Simulations were conducted using AVL FIRE software, followed by experimental validation to compare the performance of the prototype Omega combustion chamber with the optimized TCD combustion chamber (T for turbocharger, C for charger air cooling, and D for diesel particle filter). This study utilized four types of fuels: D100, B10, B20, and B50, and was conducted under different load conditions at a rated speed of 1800 revolutions per minute (rpm). The results demonstrate that the TCD combustion chamber outperforms the Omega chamber in terms of indicated thermal efficiency (ITE), in-cylinder pressure, and temperature, and also exhibits a lower indicated specific fuel consumption (ISFC). Additionally, the TCD chamber shows lower soot and carbon monoxide (CO) emissions compared to the Omega chamber, with further reductions as the load increases and the biodiesel blend ratio is raised. The high oxygen content in biodiesel helps to reduce soot and CO formation, while its lower sulfur content and heating value contribute to a decrease in combustion temperature and a reduction in nitrogen oxide (NOx) production. However, the NOx emissions from the TCD chamber are still higher than those from the Omega chamber, possibly due to the increased in-cylinder temperature resulting from its combustion chamber structure. The findings provide valuable insights into diesel engine system design and the application of oxygenated fuels, promoting the development of clean combustion technologies. Full article

A wide experimental campaign was developed on an automotive turbocharged diesel engine, using two blends between diesel oil and waste cooking oil methyl esters (WCOME) and neat biodiesel. A conventional B7 diesel oil was considered as a reference fuel. The two blends, respectively, included 40 and 70% of WCOME, on a volumetric basis. The influence of biodiesel was analyzed by testing the engine in two part-load operating conditions, applying proper control strategies to the exhaust gas recirculation (EGR) circuit and rail pressure, to assess the interactions between the engine management and the tested fuels. The variable nozzle turbine (VNT) was controlled to obtain a constant level of intake pressure in the two experimental points. Referring to biodiesel effects at constant operating mode, higher WCOME content generally resulted in better efficiency and soot emission, while NO_X emission was negatively affected. EGR activation allowed for limited NO formation but with penalties in soot emission. Furthermore, interactions between the EGR circuit and turbocharger operations and control led to higher fuel consumption and lower efficiency. Finally, the increase in rail pressure corresponded to better soot emission and penalties in NO_X emission. Combining all these effects, the selection of EGR rate and rail pressure values higher than the standard levels resulted in better efficiency, NO_X, and soot emissions when comparing blends and neat biodiesel to conventional B7, granting advantages not only with regard to greenhouse gas emissions. Combustion parameters were also assessed, showing that combustion stability and combustion noise were not negatively affected by biodiesel use. Combustion duration was reduced when using WCOME and its blend, even if the center of combustion was slightly shifted along the expansion stroke. The main contribution of this investigation to the scientific and technical knowledge on biodiesel application to internal combustion engines is related to the development of tests on diesel–biodiesel blends with high WCOME content or neat WCOME, identifying their effects on NO_X emissions, the definition of integrated strategies of HP EGR system, fuel rail pressure, and VNT for the simultaneous reduction in NO_X and soot emissions, and the detailed assessment of the influence of biodiesel on a wide range of combustion parameters. Full article

Biodiesel and 2-methylfuran (MF) exhibit significant potential as alternative fuels due to advancements in their production techniques. Despite this potential, the low cetane number (CN) of biodiesel–MF (BMF) blends limits their practical use in diesel engines due to poor auto-ignition characteristics and extended ignition delays. This study addresses this issue by investigating the impact of the cetane improver 2-ethylhexyl nitrate (2-EHN) on the performance and emissions of a BMF30 blend. The blend consists of 70% biodiesel and 30% MF, with 2-EHN added at concentrations of 1% and 1.5% to enhance ignition properties. The experiments were conducted on a four-cylinder, four-stroke, direct-injection compression ignition (DICI) engine at a constant speed of 1800 rpm with brake mean effective pressures (BMEP) ranging from 0.13 to 1.13 MPa. The results showed that 2-EHN improved the CN of the BMF30 blend, leading to earlier combustion initiation and longer combustion duration. At low BMEP (0.13 MPa), 2-EHN increased the peak rate of heat release and in-cylinder pressure, whereas at higher BMEP (0.88 MPa), these parameters decreased. The key findings include a reduction in brake-specific fuel consumption (BSFC) by 5.49–7.33% and an increase in brake thermal efficiency (BTE) by 3.30–4.69%. Additionally, NOx emissions decreased by 9.4–17.48%, with the highest reduction observed at 1.5% 2-EHN. CO emissions were reduced by 45.1–85.5% and soot emissions also declined. Hydrocarbon (HC) emissions decreased by 14.56–24.90%. These findings demonstrate that adding 2-EHN to BMF30 blends enhances engine performance, reduces key emissions, and offers a promising alternative fuel for diesel engines. Full article

Methanol is a promising low-carbon fuel that can effectively reduce environmental pollution from ships compared to traditional fuels. The timing of methanol injection is a major factor affecting the performance of internal combustion engines, and either too late or too early injection can severely impact the combustion efficiency of an engine. This paper focused on a 4135Aca marine diesel engine produced by the Shanghai Diesel Engine Factory in China. Using CONVERGE/3.0 software for numerical simulation, the study analyzed the impact of methanol injection timing on the combustion and emission characteristics of marine diesel engines. It was found that the determination of methanol injection timing should comprehensively consider the effects of the combustion start point, mixture quality, flame front propagation speed, and evaporation heat absorption. Appropriate methanol injection timing can improve the combustion duration, cylinder pressure, and heat release rate, enhancing the power performance of marine diesel engines. This study shows that methanol injection at −30 °CA can effectively control the in-cylinder combustion process, improve combustion efficiency, and significantly reduce the emissions of pollutants such as soot (by 60.5%), HC (by 3.6%), CO (by 95.3%), etc. However, it can lead to an increase in NOx (by 3.7%) generation under high-temperature conditions. This research can provide a certain reference for the engineering application of methanol direct injection engines for ships. Full article

The growth of global trade has fueled a booming shipping industry, but high pollutant emissions from low-speed marine diesel engines have become a global concern. In this study, it is hypothesized that the combustion efficiency of biodiesel B10 in low-speed two-stroke diesel engines can be improved and pollutant emissions can be reduced by optimizing the exhaust gas recirculation (EGR) rate and injection time. This study systematically analyzed the effects of EGR rate (5%, 10%, and 20%) and injection time (0 °CA to 6 °CA delay) on combustion and emission characteristics using numerical simulation combined with experimental validation. The results showed that the in-cylinder combustion temperature and NOx emission decreased significantly with the increase in EGR rate, but the soot emission increased. Specifically, NOx emissions decreased by 35.13%, 59.95%, and 85.21% at EGR rates of 5%, 10%, and 15%, respectively, while soot emissions increased by 12.25%, 26.75%, and 58.18%, respectively. Delaying the injection time decreases the in-cylinder pressure and temperature peaks, decreasing NOx emissions but increasing soot emissions. Delaying the injection time from 2 °CA to 4 °CA and 6 °CA decreased NOx emission by 16.01% and 25.44%, while increasing soot emission by 4.98% and 11.64%, respectively. By combining numerical simulation and experimental validation, this study provides theoretical support for the combustion optimization of a low-speed two-stroke diesel engine when using biodiesel, and is of great significance for the green development of the shipping industry. Full article

The physical and chemical properties of methanol differ significantly from those of conventional diesel, and its injection strategy plays a critical role in engine performance. In this study, a three-dimensional simulation model of a methanol–diesel dual-fuel engine integrated with chemical reaction kinetics was developed using CONVERGE software. The effects of methanol injection position and angle on combustion characteristics, emission performance, and engine economy were systematically investigated through numerical simulation and theoretical analysis, leading to the optimization of the methanol injection strategy. By varying the distance between the methanol nozzle and the cylinder head as well as the methanol injection angle, changes in temperature, pressure, heat release rate (HRR), and other engine parameters were analyzed. Additionally, the impact on emissions, including soot, HC, CO, and NOx, was evaluated, providing a theoretical foundation for optimizing dual-fuel engine performance and enhancing methanol utilization efficiency. The results indicate that the methanol injection position minimally affects engine performance. When the methanol spray is positioned 3 mm from the cylinder head, it facilitates the formation of a homogeneous mixture, resulting in optimal power output and enhanced environmental performance. In contrast, the injection angle has a more pronounced effect on combustion and emission characteristics. At a methanol injection angle of 65°, the mixture homogeneity reaches its optimal level, leading to a significant enhancement in combustion efficiency and engine power performance. Excessive injection angles may lead to combustion deterioration and reduced engine performance. The primary reason is that an excessive spray angle may cause methanol spray to impinge on the cylinder wall. This leads to wall wetting, which adversely affects mixture formation and combustion. Full article

Diesel–methanol dual-fuel (DMDF) mode holds significant potential for achieving highly efficient and clean combustion in modern marine engines. However, issues such as low methanol substitution rate and high pollutant emissions persist, and the underlying mechanisms are not fully understood. This study numerically investigated the combustion and emissions of a heavy-duty marine engine operating in DMDF mode. Multi-cycle simulations, incorporating diesel and methanol dual-fuel chemical mechanisms, were carried out to explore engine performance across various key parameters, including valve phasing, injection pressure, injection phasing, and nozzle diameter. The results indicate that valve phasing can greatly affect the indicated thermal efficiency, particularly at large valve overlap angles. This is primarily attributed to the variations of methanol film mass and thereby overall combustion efficiency. The optimized valve phasing increases the indicated thermal efficiency by 2.4%. By optimizing injection parameters, the formation of methanol film is effectively reduced, facilitating the improvement in the indicated thermal efficiency. The optimal injection pressure and nozzle diameter are 20 bar and 0.3 mm, respectively, resulting in increases in indicated thermal efficiency of 1.28% and 1.07%, compared to the values before optimization. Advancing injection timing and increasing nozzle diameter markedly decrease methanol film mass because some methanol remains undisturbed by the intake flow, while large droplet sizes tend to enhance the resistance to airflow. As injection pressure rises from 20 bar to 50 bar, the spray–wall interaction region expands, droplet size diminishes, and methanol film formation increases. Consequently, the combustible methanol in the cylinder is reduced, undermining the indicated thermal efficiency. Additionally, there exists a trade-off relationship between NO_x and soot emissions, and the high heat release rate results in increased NO_x but decreased soot emissions for diesel–methanol dual-fuel engines. Full article

In the present work, the combustion process of a retrofitted high-speed marine Diesel Methanol Dual Fuel (DMDF) engine is numerically evaluated. This study examines the effects of two important operational parameters, the methanol energy substitution ratio (MESR) and diesel injection timing, with a focus on engine performance and emissions. To perform the analysis, a CFD numerical combustion model was developed, and a mean value model, along with other data-driven models, were employed to estimate the intake cylinder conditions. The numerical models were calibrated and validated using experimental data measured at the DMDF experimental testbed at the Laboratory of Marine Engineering (LME). The models were utilized to conduct a parametric study considering various engine speeds and loads, diesel injection timings, and MESRs up to 75%. The impact of these parameters was quantified with respect to in-cylinder pressure, ignition timing, combustion efficiency, NO_x, soot, and HC emissions. The results revealed that an increased methanol ratio leads to delayed ignition timing, shorter combustion duration, and reduced in-cylinder peak pressure and combustion efficiency. NO_x and soot emissions are also reduced, whereas the concentrations of unburned hydrocarbons in the exhaust gas increase significantly and mainly consist of Volatile Organic Compounds (VOCs). Although advancing injection timing in dual-fuel mode improves combustion efficiency, it increases the maximum in-cylinder pressure and NO_x emissions. The other emissions are either reduced or maintained at the same levels. Moreover, the results suggest that there is a trade-off between NO_x emissions and combustion performance, which must be taken into account when the operational parameters are adjusted for these engines. Finally, the maximum MESRs are estimated to ensure safe combustion within acceptable peak pressure limits and adequate combustion performance. Full article

For computational fluid dynamic (CFD) modeling of advanced combustion engines, the cylinder is usually considered a closed system in which the initial conditions are estimated based on the experimental data. Most of these approximations hinder observing the effect of design parameters on engine performance and emissions accurately, and most studies are limited to a few design parameters. An approach is proposed based on the combination of a 1D gas dynamic and a 3D CFD model to simulate the whole engine with as few simplifications as possible. The impact of changing the in-cylinder initial conditions, injection strategy (dual direct injection or multiple pulse injections), and piston bowl geometry on a reactivity controlled compression ignition (RCCI) engine’s performance, emissions, and fuel stratification levels was investigated. It was found that applying the dual direct injection (DDI) strategy to the engine can be promising to reach higher load operations by reducing the pressure rise rate and causing stronger stratification levels. Increasing the number of injection pulses leads to lower Soot/NOx emissions. The best reduction in the pressure rise rate was found by the dual direct strategy (38.36% compared to the base experimental case) and higher exhaust gas recirculation (EGR) levels (41.83% reduction in comparison with the base experimental case). With the help of a novel piston bowl design, HC and CO emissions were reduced significantly. This resulted in a reduction of 54.58% in HC emissions and 80.22% in CO emissions. Full article

Aviation’s non-CO₂ effects account for approximately 66% of the sector’s Effective Radiative Forcing (ERF). However, non-CO₂ emissions and their climate effects are particularly challenging to assess due to the number of variables involved. This research provides a framework for characterizing the full climate impact of individual real-world flights in terms of global surface temperature change (ΔT) with the aid of a validated CFM56-7B26/3 engine model and spatially and temporally resolved meteorological data. Different modelling methods were used to evaluate NO_x and soot emissions and the relative differences between them were quantified, while a contrail formation model was implemented to quantify the distances travelled where persistent contrails were formed. The ΔT was evaluated over 77 years using a Linear Temperature Response Model (LTR). The results show that NO_x-induced effects such as the increase in short-term ozone had the highest impact on ΔT in the first year of emissions, while CO₂ was more detrimental to ΔT in the long term. Unlike the mid and long-range flights examined, the climb segment of the short-range flight had a more significant impact on ΔT than the cruise segment. ΔT sensitivity studies for different emission modelling methods showed differences up to 13% for NO_x and 14% for soot. Full article