Search Results (52)

As fossil fuels are being replaced by lower-carbon alternatives, the EU renewable energy directives RED II/III mandate increases in the proportion of advanced biofuels within liquid fuels, aiming to reduce greenhouse gas emissions over first-generation biofuels. It is crucial to study how these fuels affect engine performance to ensure they also meet emissions standards of relevance to air quality. Advanced biofuels, mainly from lignocellulosic feedstocks, are promising options. This work tested model butanolysis-derived blends using hydrotreated vegetable oil (HVO) as the base fuel, due to its lower carbon footprint, favourable combustion properties, and potential to replace diesel without engine modifications, along with ultra-low sulphur diesel (ULSD). Physical properties such as density and flash point were tested on the butyl-based biofuel blends. The measured densities fell between those of pure HVO and ULSD, while the measured flash points exceeded the minimum standards required for fuels. This study examines the use of such blends with a EU Stage V emission compliant Yanmar L100V compression ignition (CI) engine as part of a generator set, using model butanolysis biofuel mixtures blended with HVO at various ratios. A CI engine was chosen because generators, off-road machinery, heavy-duty vehicles, and marine vessels will continue to rely on CI engines for the foreseeable future. Ignition delays (IDs), brake-specific fuel consumption (BSFC), gaseous and particulate matter (PM_2.5) emissions were determined. Gaseous emissions were measured with a Horiba MEXA7100D, and PM_2.5 was collected on filters for gravimetric analysis. All blends, including pure HVO, had shorter IDs than diesel. Emissions of nitrogen oxides (NOx = NO + NO₂), carbon monoxide (CO), and total hydrocarbons (THC) decreased compared to diesel. PM_2.5 levels dropped with the additions of advanced biofuels relative to pure HVO and ULSD. CO emission factors were below EU Stage V limits, but slight exceedances occurred for THC and NOx. Full article

In the context of the new power system, coal-fired units are transitioning into peaking units. This study investigates the combustion characteristics and NO_X emissions of a 600 MW opposed wall-fired boiler within a load range of 50% to 20%, and further analyzes the impact of burner operation modes on boiler performance at the 20% ultra-low load. The results indicate that as the boiler load decreases from 50% to 20%, the average temperature in the primary combustion zone drops from 1634.3 K to 1457.0 K, and the ignition distance extends from 0.228 m to 0.260 m, leading to a significant decline in combustion stability. Notably, at the 20% ultra-low load, although the drop in temperature suppresses the formation of thermal NO_X, the flow short-circuiting caused by the shrinking of the recirculation zone results in pulverized coal particles missing the optimal reduction window; the formation pathway dominated by fuel NO_X causes the NO_X concentration at the furnace outlet to surge to 670.6 mg/m³. Furthermore, the burner operation modes significantly influence boiler performance at the 20% ultra-low load. While ensuring combustion stability, operating the lower-tier burners effectively reduces NO_X emissions by up to 21.6%. Considering both combustion stability and NO_X emissions, prioritizing the operation of lower-tier burners is recommended. This study reveals the underlying mechanisms behind the surge in NO_X concentrations at ultra-low loads of 20% and proposes optimal burner operation strategies, providing a theoretical foundation for the clean and stable operation of boilers during deep peak shaving. Full article

Among pathways toward carbon neutrality, substituting hydrocarbons with hydrogen-carrier fuels such as ammonia presents significant potential for carbon emission reduction. This study examines the combustion characteristics of ammonia (NH₃) and simulated LPG consisting of 70% propane (C₃H₈) and 30% butane (C₄H₁₀) by volume blends under non-premixed conditions using a crossflow slot burner. Flame appearance, OH* chemiluminescence, flame temperature, and CO and NO_x emissions were evaluated at equivalence ratios (Φ) of 0.4, 0.7, and 1.0, with ammonia fractions ranging from 0% to 70%. Increasing ammonia content decreased OH* chemiluminescence intensity, indicating a reduced radical pool and lower reaction intensity, particularly under lean conditions. Nevertheless, stable combustion was achieved at Φ = 1.0 due to improved mixing and heat recirculation. Flame temperature declined by only 9.3%, even at 70% ammonia, confirming good thermal stability. NO_x emissions exhibited non-monotonic behavior, increasing at moderate ammonia fractions due to fuel-bound nitrogen and thermal mechanisms, and then decreasing at higher ammonia levels as flame temperature and radical activity diminished, while CO emissions remained low up to 50% ammonia near stoichiometric conditions but increased under ultra-lean operation because of limited oxidation kinetics. These results highlight the feasibility of simulated LPG–NH₃ blends as transitional low-carbon fuels in practical combustion systems. Full article

Urban air quality management has been playing a significant role due to its effects on public health and pollution characteristics of countries with constantly changing policies. Traditional approaches capture how much pollution is present but are unable to detect changes in the chemical character of the atmosphere, the relationships between co-emitted species, the balance of photochemical processing, and the combustion fingerprint of emission sources. This study introduces a framework that identifies and diagnoses such evolutions within the pollutants of the atmosphere. A chemistry-aware Variational Autoencoder is trained on 19 multivariate pollution features (7 raw concentrations, 5 chemical ratios, 7 temporal gradients) at London Marylebone Road (urban roadside) and North Kensington (urban background) from 2015 to 2019, and tested on 2022–2025. A four-method ensemble framework (VAE reconstruction error, reconstruction probability, Isolation Forest, and statistical Z-score) requires ≥3 agreement to identify high-confidence departed pollution states. Per-feature decomposition of the reconstruction probability diagnoses the chemical character of each departure. At the roadside site, 14.5% of post-COVID hours fall within departed states, dominated by the CO/NO_x combustion ratio (513.2) and the photostationary state proxy (391.4), chemical relationships rather than individual concentrations. This indicates that at the point of emission, London’s fleet modernisation and Ultra Low Emission Zone (ULEZ) have changed the combustion fingerprint and photochemical equilibrium. The same structural indicators are carried over during the COVID-19 lockdown; however, O₃ rises 3.2× during the pandemic period, reflecting suppressed NO titration. Conversely, at the urban background site, where the departures are driven by concentrations and boundary-layer trapping ($r=-0.659$), the combustion fingerprint of the atmosphere is invisible to detect (CO/NO_x$=-45.0$). These findings indicate that London’s emission landscape has undergone fundamental transformations over the past decade, and the consequences of ULEZ and similar interventions or greater impacts of pandemic-related events are non-homogeneously distributed across the relevant region. Full article

Homogeneous Charge Compression Ignition (HCCI) combustion has been widely reported to offer high efficiency and ultra-low nitrogen oxide emissions compared to conventional spark-ignited (SI) combustion. However, reported efficiency benefits strongly depend on boundary conditions, engine hardware, and the chosen reference concept. This study presents a systematic experimental comparison between HCCI and SI combustion using gasoline and ethanol on the same single-cylinder research engine under unthrottled and otherwise identical operating conditions. Combustion stability, indicated efficiency, combustion phasing, and gaseous emissions are evaluated. The results show that HCCI combustion provides substantially reduced CO (ethanol: −61.1%; gasoline: −80.6%) and NO_x (ethanol: −96.1%; gasoline: −86.3%) emissions and superior combustion stability for both fuels. Ethanol further improves efficiency and emissions compared to gasoline. Contrary to common expectations reported in the literature, no universal efficiency advantage of HCCI combustion over SI operation is observed under the specific boundary conditions and with the investigated engine configuration of this study. A detailed loss analysis shows that, for the present setup, increased gas exchange and heat transfer losses offset the higher working cycle efficiency (without gas exchange) of HCCI combustion. Full article

The increasing need to reduce reliance on fossil-derived aviation fuels and mitigate environmental impacts has intensified research into renewable alternatives for aviation energy systems. The growing interest in ethanol-based fuels is primarily driven by their simple oxygen-rich molecular structure and advantageous physicochemical characteristics, yet experimental studies examining their application in hybrid power architectures, including micro-turboprop engine-based power sources, are still limited. This study presents an experimental investigation of ethanol–Jet A1 fuel blends used in a micro-turboprop engine operating as a power generation unit for unmanned aerial vehicle applications. Ethanol was blended with Jet A1 at volumetric fractions of 10%, 20% and 30% and the engine was tested under multiple operating regimes corresponding to different electrical power outputs. Exhaust gas temperature, electrical power output and gaseous emissions (CO and NO_x) were measured for each operating condition. The results indicate that low ethanol fractions (E10) provide performance comparable to neat kerosene, while higher ethanol fractions lead to a reduction in exhaust gas temperature at low-power regimes due to the lower heating value and high latent heat of vaporization of ethanol. Emission measurements showed a decrease in NO_x emissions with increasing ethanol content, associated with lower combustion temperatures, while CO emissions increased at low-power regimes due to incomplete combustion under lean conditions. Additionally, combustion instability was observed during rapid transitions from maximum to idle regime operation for higher ethanol blends, attributed to transient ultra-lean mixtures, evaporative cooling, and reduced reaction rates. The results demonstrate that ethanol–kerosene blends can be used in micro-turboprop systems at low blend ratios without major performance penalties, but transient operating conditions impose stability limits that must be considered in practical UAV power system applications. Full article

Non-thermal plasma is a promising technology for odor abatement from agricultural and domestic waste. However, its widespread application is often limited by the inherent trade-off between energy efficiency and processing capacity in conventional reactors. To address this challenge, we propose a novel multi-needle-to-cylinder dielectric barrier discharge reactor integrated with a deflector ring. By synergistically optimizing the electrode topology and modulating the flow field, this reactor achieves enhanced removal of complex ammonia–sulfur odor mixtures. The underlying mechanisms were elucidated through computational fluid dynamics (CFD) simulations coupled with systematic performance evaluation. Experimental results demonstrate that an 8-needle electrode configuration provides the optimal balance between discharge density and energy efficiency. CFD simulations further reveal that the deflector ring effectively suppresses gas bypass and promotes recirculation vortices downstream, thereby extending the residence time significantly. Mechanistic studies indicate that the removal of recalcitrant inorganic sulfides (e.g., CS₂ and H₂S) follows a synergistic mass-transfer–reaction controlled process, which is markedly improved by flow field optimization. In contrast, organic sulfides are governed primarily by chemical kinetics and show little dependence on flow variations. Under an extremely short residence time of 0.57 s (corresponding to a flow rate of 2.0 m³/h) and an ultra-low specific energy input of 6.26 J/L, the system achieved nearly complete removal of organic sulfides. Even for challenging inorganic sulfides, removal efficiencies reached 80.9% for H₂S and 45.3% for CS₂, while O₃/NO_x/SO₂ byproducts were quantified. For industrial deployment, these byproducts can be managed by standard downstream polishing. By effectively coordinating discharge characteristics with flow dynamics, this study provides both theoretical insight and technical support for the development of next-generation, energy-efficient, high-throughput industrial odor control systems. Full article

Growing renewable penetration increases deep peak-shaving demands, making stable wide-load operation of coal-fired boilers essential. A full-process CFD model of a 660 MW ultra-supercritical boiler was established, covering the furnace, heat-transfer surfaces, rear-pass duct, and selective catalytic reduction (SCR) system. Simulations at 25–100% boiler maximum continuous rating (BMCR) quantified load effects on combustion and emissions. Predicted furnace outlet temperature and major flue-gas species matched field data with deviations within ±6%. Lowering the load from 100% to 25% BMCR contracted the high-temperature core in the furnace and reduced mean temperature and mixing. Furnace nitrogen oxides (NO_x) formation decreased as the load decreased. However, NO_x at 25% BMCR increased because separated over-fire air (SOFA) was not applied. Reduced combustion intensity increased the level of unburned carbon in fly ash, which rose by approximately 3.5% at 25% BMCR, relative to the rated condition. Pronounced flow maldistribution also appeared at 25% BMCR. The SCR-inlet flow analysis indicated that the original guide vane design was not suitable for wide-load operation and that inlet-velocity uniformity deteriorated, especially at low loads. An optimized guide vane scheme is proposed, improving SCR-inlet uniformity over the full load range while mitigating ash deposition and erosion risks. Full article

As an energy-intensive sector, China’s iron and steel industry is crucial for achieving “Dual Carbon” goals. This study fills the research gap in systematically comparing the synergistic effects of multiple policies by evaluating five key measures (2020–2023) in ultra-low-emission retrofits and clean energy alternatives. Using public macro-data at the national level, this study quantified cumulative reductions in air pollutants (SO₂, NOx, PM, VOCs) and CO₂. A synergistic control effect coordinate system and a normalized synergistic emission reduction equivalent (AP_eq) model were employed. The results reveal significant differences: Sintering machine desulfurization and denitrification (SDD) showed the highest AP_eq but increased CO₂ emissions in 2023. Dust removal equipment upgrades (DRE) and unorganized emission control (UEC) demonstrated stable co-reduction effects. While electric furnace short-process steelmaking (ES) and hydrogen metallurgy (HM) showed limited current benefits, they represent crucial deep decarbonization pathways. The framework provides multi-dimensional policy insights beyond simple ranking, suggesting balancing short-term pollution control with long-term transition by prioritizing clean alternatives. Full article

Coal-fired power plants exacerbate hazy weather under low winter temperatures, while sulphate ions (SO₄²⁻) in condensable particulate matter (CPM) emitted from ultra-low emission coal-fired power plants accelerate sulphate formation. The transformation of gaseous precursors (SO₂, NOx, NH₃) is the main pathway for sulphate formation by homogeneous or non-homogeneous reactions. For the sustainability of the world, in this paper, the effects of condensation temperature, H₂O, NO_X and NH₃ on the SO₄²⁻ generation characteristics under low-temperature rapid condensation conditions are investigated. With lower temperatures, especially from 0 °C cooling to −20 °C, the concentration of SO₄²⁻ was as high as 26.79 mg/m³. With a greater proportion of H₂SO₄ in the aerosol state, and a faster rate of sulphate formation, H₂O vapour condensation can provide a reaction site for sulphuric acid aerosol generation. SO₄²⁻ in CPM is mainly derived from the non-homogeneous reaction of SO₂. SO₃ is an important component of CPM and provides a reaction site for the formation of SO₄²⁻. SO₂ and SO₃, in combination with Stefan flow, jointly play a synergistic role in the generation of SO₄²⁻. The content of SO₄²⁻ was as high as 36.18 mg/m³. While NO_X sometimes inhibits the formation of SO₄²⁻, NH₃ has a key role in the nucleation process of CPM. NH₃, SO₂ and NO_X have been found to rapidly form sulphate with particle sizes up to 5 µm at sub-zero temperatures and promote the formation of sulphuric acid aerosols. Full article

To develop eco-friendly low-temperature NH₃-SCR catalysts for the non-electric industry, a series of CeMn-modified Ba₂Ti₅O₁₂ catalysts were synthesized using the sol-gel method to achieve denitrification. Activity tests revealed that Ce-Mn-modified Ba₂Ti₅O₁₂ catalysts exhibit excellent low-temperature denitrification performance with a broad operational temperature window. Characterization through XRD, XPS, BET, NH₃-TPD, and EPR indicated that Ce-Mn modification enhances surface oxygen chemisorption and increases acidity, significantly improving NO_x reduction. Notably, the optimal catalyst achieved NO_x conversion rates exceeding 90% within the temperature range of 90 to 240 °C under a gas hourly space velocity (GHSV) of 28,000 h⁻¹. In particular, the coexistence of Ce and Mn species promotes the oxidation of NO to NO₂, facilitating the “fast SCR” reaction. The abundance of valence states further enhances the catalyst’s ultra-low-temperature NH₃-SCR denitration performance. Full article

Enhancing the operational flexibility and environmental performance of coal-fired boilers under wide-load conditions presents a critical challenge in China’s low-carbon transition, particularly for low-quality coals (LQCs) with abundant reserves, poor combustibility, and high NO_x emissions. To overcome the intrinsically low reactivity of LQC, peak-shaving performance and combustion behavior were systematically investigated on an MW-grade pilot-scale test platform employing the fuel modification strategy in this study. Stable fuel modification was achieved without any auxiliary energy for LQCs and Shenmu bituminous coal (SBC) across a load range of 20~83% and 26~88%, respectively, demonstrating the excellent fuel reactivity and strengthened release control of volatile and nitrogenous species. The modified LQC exhibited ignition, combustion, and burnout characteristics comparable to Shouyang lean coal (SLC), enabling a “dimensionality-reduction utilization” strategy. The double-side fuel modification device (FMD) operation maintained axially symmetric temperatures (<1250 °C) in horizontal combustion chambers, while single-side operation caused thermal asymmetry, with peak temperatures skewed toward the FMD side (<1200 °C). Original NO_x emissions were effectively suppressed, remaining below 106.89 mg/m³ (@6%O₂) for LQC and 122.76 mg/m³ (@6%O₂) for SBC over broad load ranges, and even achieved ultra-low original NO_x emissions (<50 mg/m³). Distinct load-dependent advantages were observed for each coal type: SBC favored high-load thermal uniformity and low-load NO_x abatement, whereas LQC exhibited the inverse trend. These findings underscore the importance of a load-adaptive coal selection and FMD operation mode. This study provides both theoretical insights and engineering guidance for retrofitting coal-fired power units toward flexible, low-emission operation under deep peak-shaving scenarios. Full article

SO₂ and NO_x emissions from iron and steel production pollute the atmosphere. With the implementation of ultra-low emission standards, the requirements for flue gas purification have become more stringent. Activated carbon, due to its rich surface chemistry, stable physical structure, and excellent adsorption and renewability, has a significant effect on the synergistic removal of multiple pollutants from industrial flue gas, and its industrial application has achieved a SO₂ removal rate of ≥98% and a NO_x removal rate of ≥83%. Firstly, we analyze the structure of activated carbon and the adsorption principle, discuss the mechanism of desulfurization and denitrification, and explore the shortcomings of the technology; then, we summarize the modification methods of activated carbon, determine the impregnation method of loading non-precious metal oxides as the optimal solution, and elucidate the loading conditions, process, and reaction mechanism; finally, we discuss the current status of the research, analyze the process deficiencies and the direction of optimization, and look forward to the prospect of development. Full article

The automotive industry faces increasing challenges due to fuel scarcity and pollutant emissions, necessitating the implementation of strategies that optimize engine performance while minimizing the environmental impact. This study aimed to analyze the influence of oil viscosity and fuel quality on the engine performance and pollutant emissions in an internal combustion engine. A Response Surface Methodology (RSM)-based experimental design was employed. Three oil viscosity levels (SAE 5W-30, 10W-30, and 20W-50) and three fuel quality levels (87, 92, and 95 octane) were evaluated using a Chevrolet Grand Vitara 2.0L (General Motors, Quito, Ecuador) tested on a dynamometer. The oil grades were selected to represent a practical range of viscosities commonly used in commercial vehicles operating under local conditions. The results indicate that using lower-viscosity oil (SAE 5W-30) increased the engine power by up to 6.25% compared to when using SAE 20W-50. Additionally, using higher-octane fuel led to an average power increase of 1.49%, attributed to improved combustion stability and the ability to operate at a more advanced ignition timing without knocking. The emissions analysis revealed that high-viscosity oil at high RPMs increased CO₂ emissions to 14.4% vol, whereas low-viscosity oil at low RPMs reduced CO₂ emissions to 13.4% vol. Statistical analysis confirmed that the engine speed (RPM) was the most influential factor in emissions (F = 163.11 and p < 0.0001 for CO₂; F = 247.02 and p < 0.0001 for NOx), while fuel quality also played a significant role. These findings suggest that optimizing the oil viscosity and selecting the appropriate fuel can enhance engine efficiency and reduce emissions, thereby contributing to the development of more sustainable automotive technologies. Future research should explore the use of ultra-low-viscosity lubricants (SAE 0W-20) and assess their long-term effects on engine wear. Full article

Many cities are still struggling to comply with current air quality regulations. Road transport is usually a significant source of NOx emissions, especially in urban areas. Therefore, NOx from road vehicles needs to be further reduced below current standards to ultra-low or even zero-impact levels. In a novel, holistic powertrain design approach, this paper presents powertrain solutions to achieve zero-impact NOx emissions with an N1 class III diesel light commercial vehicle. The design is based on a compliance test matrix consisting of six real-world scenarios that are critical for emissions and air quality. As a design baseline, a vehicle concept meeting the emission requirements as set out in the European Commission’s 2022 Euro 7 regulation proposal is used. The baseline vehicle concept can achieve zero-impact NOx emissions in 67% of these scenarios. To achieve zero-impact NOx emissions in all scenarios, further advanced emission solutions are mandatory. In congested urban areas, the use of an exhaust gas aftertreatment system preheating device with at least 20 kW of power for 1 min is required. In high-traffic highway situations, an underfloor SCR unit with a minimum volume of 12 l or the restriction of the maximum vehicle speed at 130 km/h is required. Full article