Search Results (5)

In response to increasingly stringent emission regulations, low-carbon fuels have received significant attention as sustainable energy sources for internal combustion engines. This study investigates four representative low-carbon fuels, methane, methanol, hydrogen, and ammonia, by systematically summarizing their combustion characteristics and emission profiles, along with a review of existing after-treatment technologies tailored to each fuel type. For methane engines, unburned hydrocarbon (UHC) produced during low-temperature combustion exhibits poor oxidation reactivity, necessitating integration of oxidation strategies such as diesel oxidation catalyst (DOC), particulate oxidation catalyst (POC), ozone-assisted oxidation, and zoned catalyst coatings to improve purification efficiency. Methanol combustion under low-temperature conditions tends to produce formaldehyde and other UHCs. Due to the lack of dedicated after-treatment systems, pollutant control currently relies on general-purpose catalysts such as three-way catalyst (TWC), DOC, and POC. Although hydrogen combustion is carbon-free, its high combustion temperature often leads to elevated nitrogen oxide (NO_x) emissions, requiring a combination of optimized hydrogen supply strategies and selective catalytic reduction (SCR)-based denitrification systems. Similarly, while ammonia offers carbon-free combustion and benefits from easier storage and transportation, its practical application is hindered by several challenges, including low ignitability, high toxicity, and notable NO_x emissions compared to conventional fuels. Current exhaust treatment for ammonia-fueled engines primarily depends on SCR, selective catalytic reduction-coated diesel particulate filter (SDPF). Emerging NO_x purification technologies, such as integrated NO_x reduction via hydrogen or ammonia fuel utilization, still face challenges of stability and narrow effective temperatures. Full article

Selective catalytic reduction filter (SDPF) technology constitutes a critical methodology for controlling nitrogen oxide (NOx) and particulate matter emissions from light-duty diesel vehicles. A series of SDPFs with different sulfur poisoning times and concentrations were prepared using the worldwide harmonized light vehicles test cycle (WLTC). Bench testing revealed that sulfur poisoning diminished the catalyst’s NH₃ storage capacity, impaired the transient NOx reduction efficiency, and induced premature ammonia leakage. After multiple sulfur poisoning incidents, the NOx reduction performance stabilized. Higher SO₂ concentrations accelerated catalyst deactivation and hastened the attainment of this equilibrium state. The characterization results for the catalyst indicate that the catalyst accumulated the same sulfur content after tail gas poisoning with different sulfur concentrations and that sulfur existed in the form of SO₄²⁻. The sulfur species in low-sulfur-poisoning-concentration catalysts mainly included sulfur ammonia and sulfur copper species, while high-sulfur-poisoning-concentration catalysts contained a higher proportion of sulfur copper species. Neither species type significantly altered the zeolite coating’s crystalline structure. Sulfur ammonia species could easily lead to a significant decrease in the specific surface area of the catalyst, which could be decomposed at 500 °C to achieve NOx reduction performance regeneration. In contrast, sulfur copper species required higher decomposition temperatures (600 °C), achieving only partial regeneration. Full article

Previous studies of transients in existing water distribution networks (WDNs) accounted for only single worst cases in optimizing surge protection measures, considered only pressure at pipe end nodes, and did not examine the effect of regulating the duration of demand increase. This study presents a comprehensive model for identifying the minimal set of worst transient cases for which optimized surge protection achieves zero Surge Damage Potential Factor (SDPF) for all transient loading cases. The model introduces $SDP{F}_P$ to account for pressure at all computational nodes along pipes, as opposed to relying on $SDP{F}_N$, which considers pressure at pipe end nodes only. The existing New York Tunnel network was used for model validation and for determining the optimal diameters for additional duplicate pipes to achieve higher pressure under steady-state conditions and protect the network from transients due to demand increase. Compared to previous studies, the model achieved $SDP{F}_N=0$ with a lower cost for sudden demand increase at a single predefined node. For concurrent sudden demand increase at two nodes, the model identified a total of 8 critical transient cases and corresponding optimum duplicate pipe diameters that achieved $SDP{F}_N=0$ and $SDP{F}_P=0$ with 46% and 74% higher costs than previous studies, respectively. The higher costs are necessary; previous studies did not achieve zero $SDP{F}_N$ and $SDP{F}_P$ in 39% and 91% of transient cases, respectively. To reduce duplicate pipe costs, the model was used to examine the effect of regulating the duration for a gradual demand increase. Using only the pipes optimized for steady-state service, the minimum duration for satisfying the transient pressure constraints was identified as ~260 s for the concurrent demand increase scenario. Slight relaxation of the minimum allowable pressure constraint allows a reduction in the duration to 150 s. For applying a demand increase over a smaller duration, duplicate pipes would be needed and can be optimized using the model. These results indicate the advantage of the proposed model in achieving full protection of existing WDNs while maintaining computational efficiency and cost-effectiveness. Full article

Environmental effects can be reduced by using renewable resources in various applications. The date palm fibers (DPF) used in this study were extracted from waste date ranches of the Najran region by retting and manual peeling processes. The biocomposites were developed by reinforcing the silane-treated DPF (SDPF) at different wt.% in eugenol phthalonitrile (EPN) and difunctional benzoxazine (BA-a) copolymer. The impact strength, tensile, flexural, and dynamic mechanical properties and thermogravimetric analysis were evaluated to understand the mechanical, thermomechanical, and thermal properties. Results confirmed that 30 wt.% SDPF-reinforced poly (EPN/BA-a) composites produced the highest mechanical and thermomechanical properties, and were considered optimized SDPF reinforcement. Furthermore, hybrid composites with 30 wt.% SDPF and 15 wt.% silane-treated glass fibers (SGF) reinforcement having different lamination sequences were also studied. The lamination sequences showed a significant impact on the mechanical and thermomechanical properties, as properties were further enhanced by adding a core layer of SGF in hybrid composites. However, the thermal properties of SDPF/SGF laminates were higher than SDPF biocomposites, but the SGF lamination sequence did not produce any impact. According to the limiting oxygen and heat resistance indexes, the developed SDPF/SGF laminates are self-extinguishing materials and can be used in temperature-tolerant applications up to 230 °C. Full article

In this paper, the validity of the shell-evolution picture is investigated on the basis of shell-model calculations for the atomic mass number $25\lesssim A\lesssim 55$ neutron-rich nuclei. For this purpose, the so-called SDPF-MU interaction is used. Its central, two-body spin–orbit, and tensor forces are taken from a simple Gaussian force, the M3Y (Michigan 3-range Yukawa) interaction, and a $\pi +\rho$ meson exchange force, respectively. Carrying out almost a complete survey of the predicted effective single-particle energies, it is confirmed here that the present scheme is quite effective for describing shell evolution in exotic nuclei. Full article