Search Results (112)

This study investigates the impact of different combustion control strategies on marine engine combustion and emission characteristics at a high ammonia energy ratio. Compared to the strategy of maintaining a constant fuel injection duration, the strategy of keeping the fuel injection pressure constant allows the kinetic energy of diesel to remain at a higher level. This results in an increase in combustion efficiency and indicated the thermal efficiency of the engine, while also reducing CO₂ and soot emissions. However, when the ammonia energy ratio increases to more than 50%, the indicated thermal efficiency starts to decrease along with the increase in the emissions of N₂O and unburned ammonia. To address these issues, one of the potential means is to improve the in-cylinder combustion environment by increasing the in-cylinder gas temperature. This can enhance combustion efficiency and ultimately optimize the performance and emission characteristics of dual-fuel engines, which results in an increase in the combustion efficiency to 98% and indicated thermal efficiency to 54.47% at a relatively high ammonia energy ratio of 60%. Emission results indicate that N₂O emissions decrease from 1099 ppm to 25 ppm, while unburned ammonia emissions drop from 16016 ppm to 100 ppm. Eventually, the greenhouse gas emissions were reduced by about 85.3% in comparison with the baseline case. Full article

This study proposes a data-driven optimization framework to enhance emission control performance in diesel engine selective catalytic reduction (SCR) systems under transient operating conditions. A one-dimensional SCR model was constructed in GT-Power, and simulation datasets were generated using experimentally measured inputs from the World Harmonized Transient Cycle (WHTC), with representative emission responses obtained by varying fixed ammonia-to-NOx (A/N) ratios. Building on these datasets, a hybrid prediction model combining Long Short-Term Memory (LSTM) networks and multi-head attention mechanisms was developed to accurately forecast SCR outlet NH₃ leakage and NOx emissions. The model exhibited high predictive accuracy, achieving R² values exceeding 0.977 and low RMSE across training, validation, and test sets. Based on the model predictions, a constrained dynamic multi-objective optimization strategy was implemented to adaptively adjust ammonia dosing, aiming to simultaneously minimize NH₃ leakage and NOx emissions. The optimized NH₃ injection profiles were validated through reapplication in the GT-Power simulation environment. Compared to the baseline fixed-ratio control strategy, the proposed approach reduced NH₃ leakage and NOx emissions by 34.40% and 11.15%, respectively, as determined for the transient segment of the WHTC cycle. These results demonstrate the effectiveness of integrating physics-based simulation, deep learning prediction, and dynamic optimization for improving aftertreatment adaptability and emission compliance in real-world diesel engine applications. All reported values are based on a single simulated WHTC cycle without statistical uncertainty analysis. Full article

Piston engines used for powering automobiles as well as machinery and equipment have traditionally relied on petroleum-derived fuels. Subsequently, renewable fuels began to be used in an effort to reduce the combustion of hydrocarbon-based fuels and the associated greenhouse effect. Researchers are currently developing technologies aimed at eliminating fuels containing carbon in their molecular structure, which would effectively minimize the emission of carbon oxides into the atmosphere. Ammonia is considered a highly promising carbon-free fuel with broad applicability in energy systems. It serves as an excellent hydrogen carrier (NH₃), free from many of the storage and transportation limitations associated with pure hydrogen. Safety concerns regarding the storage and transport of hydrogen make ammonia an increasingly important fuel also due to its larger hydrogen storage capacity. This manuscript investigates the use of ammonia for powering a dual-fuel engine. The results indicate that the addition of ammonia improves engine performance; however, it may also lead to an increase in NO_x emissions. Due to the limitations of ammonia as a fuel, approximately 40% of the energy input must still be provided by diesel fuel to achieve optimal engine performance and acceptable NO_x emission levels. The presented research findings highlight the significant potential of NH₃ as an alternative fuel for compression-ignition engines. Proper control of the injection strategy or the adoption of alternative combustion systems may offer a promising approach to reducing greenhouse gas emissions while maintaining satisfactory engine performance parameters. 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

As a major emission pollutant from diesel engines, NOx is extremely harmful to the environment and human health. In order to reduce NOx emissions, countries around the world have been implementing increasingly stringent emissions regulations. The urea injection strategies of the Selective Catalytic Reduction (SCR) system are the main factors affecting NOx emissions and NH₃ slips of diesel engines. In this study, test data were obtained from an engine test stand and a Support Vector Machine (SVM) was developed using the test data to predict NOx conversion efficiency and NH₃ slip. The SVM model was optimized using the Crested Porcupine Optimizer (CPO) to improve its prediction accuracy and was made to replace the mathematical model to save computational time. Finally, the Nondominated Sorting Genetic Algorithm II (NSGA-II) was used to optimize the urea injection volume for all conditions. The optimized urea injection volume maximizes the NOx conversion efficiency of the SCR system while controlling the NH₃ slip within 10 ppm. In addition, based on this method, the urea injection pulse spectrum under full operating conditions was obtained, and the optimized urea injection amount can effectively reduce the NOx accumulation of the WHTC cycle by about 7.5%, as shown through bench testing. Full article

The aim of this study was to assess the impact of adding ethanol to diesel fuel on particulate matter (PM) and nitrogen oxides (NOx) emissions in the Perkins 854E compression-ignition engine. Tests were carried out under European Stationary Cycle (ESC) conditions using the Horiba Mexa 1230 PM analyzer (HORIBA, Ltd., Kyoto, Japan) for particulate measurement and the AVL CEB II analyzer (AVL, Graz, Austria) for NO_x concentration. The engine under investigation featured direct injection, turbocharging, a common-rail fuel supply system, and complied with the Stage IIIB/Tier 4 emission standard. Two types of fuel were used: conventional diesel fuel (DF) and diesel with a 10% ethanol additive by volume (DFE10). In addition to emissions measurements, key engine performance parameters, such as torque, effective power, and fuel consumption, were analyzed. The ESC test was specifically chosen to isolate the influence of the fuel’s properties by avoiding the effects of changes in combustion control strategies. Due to the lower calorific value of DFE10 compared to DF, a slight increase in fuel consumption was observed under certain operating conditions. Nevertheless, overall engine performance remained largely unchanged. The test results showed that the use of DFE10 led to a significant 44% reduction in particulate matter emissions and a moderate 2.2% decrease in NO_x emissions compared to conventional diesel fuel. These findings highlight the potential of ethanol as a diesel fuel additive to reduce harmful exhaust emissions without negatively affecting the performance of modern diesel engines. Full article

Dual-fuel combustion technology allows for lower emissions of particulate matter (PM) and nitrogen oxide (NOx). However, under low load conditions, this mode of combustion has large amounts of emissions of carbon monoxide (CO) and unburned hydrocarbons (HCs) and low thermal efficiency. Several solutions have been presented to solve the issues associated with this operating mode. Optimizing the injection strategy is a potential method to enhance engine performance and reduce emissions, given that the injection parameters have significant effects on the combustion process. The present investigation optimized a methane/diesel dual-fuel engine’s emissions and performance using response surface methodology (RSM). Three parameters were investigated as input variables: dwell time (DT), diesel pre-injection timing (IT), and engine load (EL). RSM was used to optimize brake thermal efficiency (BTE), NOx emissions, and HC emissions, aiming to identify the best combination of these input factors. The RSM analysis revealed that the optimal combination of input parameters for achieving maximum BTE and minimum NOx and HC emissions is an 87% engine load, an 8° crank angle (CA) dwell time, and a 11° bTDC pre-injection timing. The RSM model demonstrated high accuracy with a prediction error less than 4%. 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

In this paper, a novel technical route, namely combining the low-pressure exhaust gas recirculation (LP-EGR) and variable compression ratio (VCR), is proposed to address the inferior fuel economy for marine dual-fuel engines of low-pressure gas injection in diesel mode. To validate the applicability of the proposed technical route, firstly, a zero-dimensional/one-dimensional (0-D/1-D) engine simulation model with a predictive combustion model DI-Pulse is established using GT-Power. Then, parametric investigations on two LP-EGR schemes, which is implemented with either a back-pressure valve (LP-EGR-BV) or a blower (LP-EGR-BL), are performed to qualitatively identify the combined impacts of exhaust gas recirculation (EGR) and compression ratio (CR) on the combustion process, turbocharging system, and nitrogen oxides (NOx)-brake specific fuel consumption (BSFC) trade-offs. Finally, an optimization strategy is formulated, and an optimization program based on response surface methodology (RSM)–particle swarm optimization (PSO) is designed with the aim of improving fuel economy while meeting Tier III and various constraint conditions. The results of the parametric investigations reveal that the two LP-EGR schemes exhibit opposite impacts on the turbocharging system. Compared with the LP-EGR-BV, the LP-EGR-BL can achieve a higher in-cylinder pressure level. NOx-BSFC trade-offs are observed for both LP-EGR schemes, and the VCR is confirmed to be a viable approach for mitigating the penalty on BSFC caused by EGR. The optimization results reveal that for LP-EGR-BV, compared with the baseline engine, the optimized BSFC decreases by 10.16%, 11.95%, 10.32%, and 9.68% at 25%, 50%, 75%, and 100% maximum continuous rating (MCR), respectively, whereas, for the LP-EGR-BL scheme, the optimized BSFC decreases by 10.11%, 11.93%, 9.93%, and 9.58%, respectively. Furthermore, the corresponding NOx emissions level improves from meeting Tier II regulations (14.4 g/kW·h) to meeting Tier III regulations (3.4 g/kW·h). It is roughly estimated that compared to the original engine, both LP-EGR schemes achieve an approximate reduction of 240 tons in annual fuel consumption and save annual fuel costs by over USD 100,000. Although similar fuel economy is obtained for both LP-EGR schemes, LP-EGR-BV is superior to LP-EGR-BL in terms of structure complexity, initial cost, maintenance cost, installation space requirement, and power consumption. The findings of this study provide meaningful theoretical supports for the implementation of the proposed technical route in real-world engines. Full article

Nowadays, the use of ammonia as a green fuel for internal combustion engines has attracted wide attention. The diesel/ammonia dual direct injection mode has shown great potential, but there is still a lack of basic research on injection strategies for this mode. In this study, the combustion and emission characteristics of diesel/ammonia dual direct injection mode were investigated using a rapid compression and expansion machine (RCEM) combined with CONVERGE software_v3.0. The research focuses on the effects of two injection strategies, including ammonia injection pressure, the ammonia injector nozzle hole diameter, and the compression ratio. The results indicate that minor increases in ammonia injection pressure have negligible impacts on emissions with the same nozzle hole diameter. Increasing the nozzle hole diameter significantly reduces unburned ammonia emissions while increasing HC and N₂O emissions. Increasing the compression ratio enhances diesel combustion but does not significantly affect ammonia combustion. Considering the ammonia energy substitution rate and the combustion performance of the actual engine, a high ammonia injection pressure and compression ratio are necessary for engine applications, while an appropriate ammonia orifice diameter is required to meet the emission performance. Full article

This study compares the technological routes of concrete production in Panama from an environmental perspective, focusing on water, energy, and CO₂ flows per process to identify opportunities for improvement. It addresses a critical gap found in the literature where flow diagrams and production processes are presented as being standardized across concrete plants, offering an in-depth qualitative analysis of resource flows. Data from 20 concrete plants revealed significant variability in resource use and potential environmental impacts due to differences in technology, location, and resource availability. Flow diagrams and similarity dendrograms highlight the similarities and differences in the technological routes. The key findings include variability in water sources and energy consumption patterns, with some utilizing rainwater harvesting and water recycling and most plants relying on grid electricity and diesel. The best practices include the implementation of environmental indicators and water recycling systems. CO₂ injection, already adopted by two plants, shows promise; however, its potential additional energy demands should be assessed. Covering aggregate storage areas for temperature control reduces water spraying needs and could support rainwater harvesting, with opportunities to integrate solar panels. Regular maintenance of concrete trucks also enhances efficiency and reduces environmental impact due to diesel consumption. The study underscores the importance of tailored strategies to improve water and energy efficiency, aligning with national and international initiatives such as “Reduce tu Huella” (Reduce your Footprint) and the 2030 Agenda. These findings provide actionable insights to support the development of a more sustainable concrete industry in Panama and beyond. Full article

Compression ignition engines are widely recognized for their reliability and efficiency, remaining essential for transportation and power generation despite the transition toward sustainable energy solutions. This study employs ANSYS Forte to analyze the combustion and performance characteristics of a direct-injection, single-cylinder, four-stroke engine fueled with an n-heptane-based diesel surrogate. The investigation considers varying SOI timings (−32.5°, −27.5°, −22.5°, and −17.5° BTDC) and EGR rates (0%, 15%, 30%, 45%, and 60%). The simulation incorporates the RNG k-ε turbulence model, the power-law combustion model, and the KH-RT spray breakup model. The results indicate that the optimal peak pressure and temperature occur at an SOI of −22.5° BTDC with 0% EGR. Advancing SOI enhances oxidation, reducing NOx and CO emissions but increasing UHC due to delayed fuel–air mixing. Higher EGR rates lower in-cylinder pressure, temperature, HRR, and NOx emissions while elevating CO and UHC levels due to oxygen depletion and incomplete combustion. These findings highlight the trade-offs between combustion efficiency and emissions, emphasizing the need for optimized SOI and EGR strategies to achieve balanced engine performance. Full article

Given the intricate combustion process and the multitude of control parameters inherent to the high-pressure direct injection (HPDI) diesel/natural gas dual-fuel engine, achieving precise combustion control represents a significant challenge. It is imperative to develop a high-precision engine model and integrate it with advanced control algorithms to achieve an optimal combustion strategy. In this study, a system-level engine plant model with high accuracy and real-time performance was developed using a modular modeling method through the calibration of experimental data and the simplification of model calculations. In this model, the relative error of the model simulation is controlled to be less than 5%, and the real-time factor (RTF) is less than 1. The multi-stage combustion process was parameterized by performing piecewise linear fitting of the heat release rate curve, and the relationship between injection parameters and combustion parameters was established using multiple regression analysis. On this basis, a model predictive control (MPC) algorithm was designed and verified in the constructed model-in-the-loop (MiL) platform. The results demonstrate that the designed MPC algorithm can accurately track the combustion phasing CA50 and the indicated mean effective pressure (IMEP) targets with a maximum error of 0.0624° and 0.046% within 6 and 8 cycles while ensuring the stability of the control process. The MiL platform not only meets the current combustion control requirements but also provides a general basis for the development of subsequent engine multi-control strategies and cooperative control optimization. Full article

Ammonia, as a hydrogen carrier and an ideal zero-carbon fuel, can be liquefied and stored under ambient temperature and pressure. Its application in internal combustion engines holds significant potential for promoting low-carbon emissions. However, due to its unique physicochemical properties, ammonia faces challenges in achieving ignition and combustion when used as a single fuel. Additionally, the presence of nitrogen atoms in ammonia results in increased NOx emissions in the exhaust. High-temperature selective non-catalytic reduction (SNCR) is an effective method for controlling flue gas emissions in engineering applications. By injecting ammonia as a NOx-reducing agent into exhaust gases at specific temperatures, NOx can be reduced to N₂, thereby directly lowering NOx concentrations within the cylinder. Based on this principle, a numerical simulation study was conducted to investigate two high-pressure injection strategies for sequential diesel/ammonia dual-fuel injection. By varying fuel spray orientations and injection durations, and adjusting the energy ratio between diesel and ammonia under different operating conditions, the combustion and emission characteristics of the engine were numerically analyzed. The results indicate that using in-cylinder high-pressure direct injection can maintain a constant total energy output while significantly reducing NOx emissions under high ammonia substitution ratios. This reduction is primarily attributed to the role of ammonia in forming NH₂, NH, and N radicals, which effectively reduce the dominant NO species in NOx. As the ammonia substitution ratio increases, CO₂ emissions are further reduced due to the absence of carbon atoms in ammonia. By adjusting the timing and duration of diesel and ammonia injection, tailpipe emissions can be effectively controlled, providing valuable insights into the development of diesel substitution fuels and exhaust emission control strategies. Full article

With the increasingly prominent environmental and energy issues, emission regulations are becoming more stringent. Ammonia diesel dual fuel (ADDF) engine is one of the effective ways to reduce carbon emissions. This study investigated the effect of multiple injection strategy on the combustion and emission characteristics of liquid ammonia/diesel dual direct injection (DI) engines through numerical simulation. The results showed that under the condition of maintaining the same pre injection diesel fuel and high ammonia energy ratio (80%), with the introduction of multiple injection, the peak cylinder pressure decreased and the peak phase advanced, the combustion start angle (CA10) advanced, the heat release showed a multi-stage pattern. The times of injection (TSOI) has a significant effect on combustion and emissions. As TSOI increased, ignition delay decreased, the combustion duration is shortened, and the combustion is accelerated. Notably, overall emissions of NOx and N₂O have decreased, but the emissions of unburned NH₃ have increased. Optimized the state of ammonia injection (SOAI) timing and ammonia injection pressure (AIP), showed that advancing SOAI timing and increasing AIP improved combustion. Advanced the SOAI timing to −8 °CA ATDC, resulted in a significant NOx emissions decrease with an increase in TSOI, reaching over 50%. Although increasing injection pressure can improve combustion, it also results in higher N₂O emissions. Full article