Search Results (174)

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

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

Pulse detonation engines (PDEs) have become a transformative technology in the field of aerospace propulsion due to the high thermal efficiency of detonation combustion. However, initiating detonation waves within a limited space and time is key to their engineering application. Direct initiation, though theoretically feasible, requires very high critical energy, making it almost impossible to achieve in engineering applications. Therefore, indirect initiation methods are more practical for triggering detonation waves that produce a deflagration wave through a low-energy ignition source and realizing deflagration to detonation transition (DDT) through flame acceleration and the interaction between flames and shock waves. This review systematically summarizes recent advancements in DDT methods in pulse detonation engines, focusing on the basic principles, influencing factors, technical bottlenecks, and optimization paths of the following: hot jet ignition initiation, obstacle-induced detonation, shock wave focusing initiation, and plasma ignition initiation. The results indicate that hot jet ignition enhances turbulent mixing and energy deposition by injecting energy through high-energy jets using high temperature and high pressure; this can reduce the DDT distance of hydrocarbon fuels by 30–50%. However, this approach faces challenges such as significant jet energy dissipation, flow field instability, and the complexity of the energy supply system. Solid obstacle-induced detonation passively generates turbulence and shock wave reflection through geometric structures to accelerate flame propagation, which has the advantages of having a simple structure and high reliability. However, the problem of large pressure loss and thermal fatigue restricts its long-term application. Fluidic obstacle-induced detonation enhances mixing uniformity through dynamic disturbance to reduce pressure loss. However, its engineering application is constrained by high energy consumption requirements and jet–mainstream coupling instability. Shock wave focusing utilizes concave cavities or annular structures to concentrate shock wave energy, which directly triggers detonation under high ignition efficiency and controllability. However, it is extremely sensitive to geometric parameters and incident shock wave conditions, and the structural thermal load issue is prominent. Plasma ignition generates active particles and instantaneous high temperatures through high-energy discharge, which chemically activates fuel and precisely controls the initiation sequence, especially for low-reactivity fuels. However, critical challenges, such as high energy consumption, electrode ablation, and decreased discharge efficiency under high-pressure environments, need to be addressed urgently. In order to overcome the bottlenecks in energy efficiency, thermal management, and dynamic stability, future research should focus on multi-modal synergistic initiation strategies, the development of high-temperature-resistant materials, and intelligent dynamic control technologies. Additionally, establishing a standardized testing system to quantify DDT distance, energy thresholds, and dynamic stability indicators is essential to promote its transition to engineering applications. Furthermore, exploring the DDT mechanisms of low-carbon fuels is imperative to advance carbon neutrality goals. By summarizing the existing DDT methods and technical bottlenecks, this paper provides theoretical support for the engineering design and application of PDEs, contributing to breakthroughs in the fields of hypersonic propulsion, airspace shuttle systems, and other fields. 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

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

Reducing CO₂ emissions in general aviation is a critical challenge, where battery electric and fuel cell technologies face limitations in energy density, cost, and robustness. As a result, hydrogen (H₂) dual-fuel combustion is a promising alternative, but its practical implementation is constrained by abnormal combustion phenomena such as knocking and pre-ignition, which limit the achievable H₂ energy share. In response to these challenges, this paper focuses on strategies to mitigate these irregular combustion phenomena while effectively increasing the H₂ energy share. Experimental evaluations were conducted on an engine test bench using a one-cylinder dual-fuel H₂ kerosene (Jet A-1) engine, utilizing two strategies, including water injection (WI) and rising the air–fuel ratio (AFR) by increasing the boost pressure. Additionally, crucial combustion characteristics and emissions are examined and discussed in detail, contributing to a comprehensive understanding of the outcomes. The results indicate that these strategies notably increase the maximal possible hydrogen energy share, with potential benefits for emissions reduction and efficiency improvement. Finally, through the use of 0D/1D simulations, this paper offers critical thermodynamic and efficiency loss analyses of the strategies, enhancing the understanding of their overall impact. Full article

This study focused on evaluating the combustion ignition, burnout, stability, and intensity of Hwange coal and Pinus sawdust blends within a drop tube furnace (DTF) through modelling. The cocombustion of coal with biomass is gaining attention as a strategy to improve fuel efficiency and reduce emissions. Hwange coal, a key energy source in Zimbabwe, produces significant emissions, while Pinus sawdust offers a renewable alternative with favourable combustion properties. Optimising cocombustion performance is highly dependent on understanding various mass- and energy-conservation-related parameters in detail, hence the motivation of this study. The fuels of interest were blended through increasing the Pinus sawdust mass percentages up to 30%. A DTF that is 2 m long and 0.07 m in diameter was modelled and validated successfully using particle residence time and temperature profiles. An increase in blending resulted in an increase in combustion intensity, as made apparent by the heat of reaction profiles, which were also shown to be dependent on the kinetic rate of the reaction between CO and O₂ to form CO₂. The burnout rate profiles demonstrated that as blending increased, heat was released more abruptly over a short distance; hence, combustion became less stable. The burnout rate profiles were shown to be dependent on the kinetic rate of reaction between char and O₂ to form CO. The effect of DTF wall temperatures (1273, 1473, and 1673 K) was also studied, with the results showing that at a low temperature, the reaction zone was delayed to a distance of 0.8 m from the injection point, as compared to 0.4 m at 1673 K. In summary, this study demonstrated that combustion ignition, burnout, and intensity increased with the blending ratio of Pinus sawdust, whilst combustion stability decreased. 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

Aviation is one of the most important industries in the current global scenario, but it has a significant impact on climate change due to the large quantities of carbon dioxide emitted daily from the use of fossil kerosene-based fuels (jet fuels). Although technological advancements in aircraft design have enhanced efficiency and reduced emissions over the years, the rapid growth of the aviation industry presents challenges in meeting the environmental targets outlined in the “Flightpath 2050” report. This highlights the urgent need for effective decarbonisation strategies. Hydrogen propulsion, via fuel cells or combustion, offers a promising solution, with the combustion route currently being more practical for a wider range of aircraft due to the limited power density of fuel cells. In this context, this paper designs and models a nitrogen–hydrogen heat exchanger architecture for use in an innovative hydrogen-propelled aircraft fuel system, where the layout was recently proposed by the same authors to advance sustainable aviation. This system stores hydrogen in liquid form and injects it into the combustion chamber as a gas, making the cryogenic heat exchanger essential for its operation. In particular, the heat exchanger enables the vaporisation and superheating of liquid hydrogen by recovering heat from turbine exhaust gases and utilising nitrogen as a carrier fluid. A pipe-in-pipe design is employed for this purpose, which, to the authors’ knowledge, is not yet available on the market. Specifically, the paper first introduces the proposed heat exchanger architecture, then evaluates its feasibility with a detailed thermodynamic model, and finally presents the calculation results. By addressing challenges in hydrogen storage and usage, this work contributes to advancing sustainable aviation technologies and reducing the environmental footprint of air travel. 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

The integration of solar Photovoltaic (PV) systems into the AC grid poses stability challenges, especially with increasing inverter-based resources. For an efficient operation of the system, smart grid-forming inverters need to communicate with the Supervisory Control and Data Acquisition (SCADA) system. However, Internet-of-Things devices that communicate with SCADA make these systems vulnerable. Though many researchers proposed Artificial-Intelligence-based detection strategies, identification of the location of the attack is not considered by these strategies. To overcome this drawback, this paper proposes a novel Convolution extreme gradient boosting (ConvXGBoost) method for not only detecting Denial of Service (DoS) and False Data Injection (FDI) attacks but also identifying the location and component of the system that was compromised. The proposed model is compared with the existing Convolution Neural Network (CNN) and decision tree (DT) strategies. Simulation results demonstrate the effectiveness of the proposed method for both the smart PV and PV fuel cell (PV-FC) systems. For example, the proposed model is efficient with an accuracy of 99.25% compared to the 97.76% of CNN and 99.12% of DT during a DoS attack on a smart PV system. Moreover, the proposed method can detect and identify the attack location faster than other models. 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