Search Results (150)

Currently, the general focus of engine-produced pollution reduction lies in exhaust gas aftertreatment methods. This paper attempts a paradigm shift in the field by applying the pre-combustion treatment technologies by fumigation method, which consists of introducing an aqueous solution into the engine intake, which could lead to a significant reduction in polluting emissions. Common and inexpensive substances used (sodium borate, citric acid, podium carbonate, hydrogen peroxide, potassium permanganate, and ammonium nitrate) in tests are not ordinarily known to be combustible. The key to the research is understanding the thermochemical phenomena during combustion. The method used was to formulate hypotheses regarding thermochemical reactions and validate them by measuring parameters and pollutant emissions (CO, CO₂, NO, NO₂, NO_x, and smoke) of a single-cylinder engine mounted on the test stand. The results indicate that chemical fumigation leads to a significant reduction, specifically a decrease in CO by 145 ppm and NO_x (NO₂ and NO) by 55 ppm at an engine speed of 1500 rpm. All substances fumigated into the engine intake increased the exhaust gas temperature. The highest increase is nearly 150 °C at 1500 rpm, while the least pronounced rise is 50 °C at 3500 rpm. Additionally, a decarbonization process of a passenger car engine is presented, carried out by applying the fumigation method simultaneously with potassium permanganate and ammonium nitrate. In this case, the results showed that the opacity index decreased to 0.01 m⁻¹. Full article

High-efficiency diesel and lean-burn engines produce lower exhaust temperatures, which can delay the activation of after-treatment catalysts such as Diesel Oxidation Catalysts (DOCs). This study explores ion beam sputtering as a post-synthesis strategy to enhance the low-temperature activity of commercial Pt/CeO₂–ZrO₂ catalysts. Low-energy ions (0.5–1.5 keV) were applied with controlled variations in treatment number, beam current, and exposure time to selectively generate oxygen vacancies and improve Pt dispersion. Structural and chemical effects were characterized using X-ray diffraction (XRD), BET surface area measurements, X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS). Catalytic performance was evaluated through CO and C₃H₆ oxidation under conditions mimicking lean-burn engine exhaust. Increasing the number of ion treatments progressively lowered light-off temperatures, correlating with enhanced Pt–Ce³⁺ interactions and improved surface reducibility. Variations in beam current and exposure time further modulated these surface effects, confirming the tunable nature of the approach. The results demonstrate that ion beam sputtering selectively modifies the catalyst surface without altering the bulk structure, directly linking atomic-scale modifications to improved low-temperature activity. This strategy offers a promising route to overcome delayed light-off issues in modern high-efficiency engines, providing a precise, controllable method to optimize emission control catalysts. Full article

Improving the efficiency of spark-ignited (SI) engines while simultaneously reducing emissions remains a critical challenge in meeting global energy demands and increasingly stringent environmental regulations. Lean burn combustion is a proven strategy for increasing efficiency in SI engines. However, the air dilution level is limited by the mixture’s ignition ability and poor combustion efficiency and stability. A promising method to extend the dilution limit and ensure stable combustion is the implementation of an active pre-chamber combustion system. The pre-chamber spark-ignited (PCSI) engine facilitates stable and rapid combustion of very lean mixtures in the main chamber by utilizing high ignition energy from multiple flame jets penetrating from the pre-chamber (PC) to the main chamber (MC). Together with the increase in efficiency by dilution of the mixture, nitrogen oxide (NO_X) emissions are lowered. However, at peak efficiencies, the NO_X emissions are still too high and require aftertreatment. The use of exhaust gas recirculation (EGR) as a dilutant might enable simple aftertreatment by using a three-way catalyst. This study experimentally investigates the use of EGR as a dilution method in a PCSI engine fueled by methane and analyzes the benefits and drawbacks compared to the use of air as a dilution method. The experimental results are categorized into three sets: measurements at wide open throttle (WOT) conditions, at a constant engine load of indicated mean effective pressure (IMEP) of 5 bar, and at IMEP = 7 bar, all at a fixed engine speed of 1600 rpm. The experimental results were further enhanced with numerical 1D/0D simulations to obtain parameters such as the residual combustion products and excess air ratio in the pre-chamber, which could not be directly measured during the experimental testing. The findings indicate that air dilution achieves higher indicated efficiency than EGR, at all operating conditions. However, EGR shows an increasing trend in indicated efficiency with the increase in EGR rates but is limited due to misfires. In both dilution approaches, at peak efficiencies, aftertreatment is required for exhaust gases because they are above the legal limit, but a significant decrease in NO_X emissions can be observed. Full article

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

In recent decades, environmental requirements for reducing the toxic components emitted from vehicle exhausts have decreased drastically. Technologies for after-treatment of diesel vehicle emissions are being improved continuously in order to meet increasingly stringent regulations. Passenger cars are a significant source of air pollution, especially in urban areas. The EU has decided to phase out internal combustion engines. Stricter Real Driving Emissions (RDE) testing procedures have also been introduced, aiming to assess the emissions of nitrogen oxides (NO_x) and particle number (PN). The present work investigates the interaction between performance and smoke emissions of a diesel vehicle on a pre-established route in an urban environment with an everyday (normal) driving style. The results showed that when the vehicle is technically sound and meets its technical specifications, smoke emissions are within normal limits. Full article

Combustion processes in compression ignition engines lead to the inevitable generation of nitrogen oxides, which cannot be limited to the currently desired levels just by optimising the in-cylinder processes. Therefore, simulation-based engine development needs to include all engine-related aspects which contribute to tailpipe emissions. Among them, the SCR (selective catalytic reduction) aftertreatment-related processes, such as urea–water solution injection, urea decomposition, mixing, NOx catalytic reduction, and deposits’ formation, are the most challenging, and require as much attention as the processes taking place inside the cylinder. Over the last decade, the urea-SCR aftertreatment systems have evolved from underfloor designs to close-coupled (to the engine) architecture, characterised by the short mixing length. Therefore, they need to be tailor-made for each application. This study presents the CFD-based development of a multi-platform SCR system with a short mixing length for mobile non-road applications, compliant with Stage V NRE-v/c-5 emission standard. It combines multiphase dispersed flow, including wall wetting and urea decomposition kinetic reaction modelling to account for the critical aspects of the SCR system operation. The baseline system’s design was characterised by the severe deposit formation near the mixer’s outlet, which was attributed to the intensive cooling in the mounting area. Moreover, as the simulations suggested, the spray was not appropriately mixed with the surrounding gas in its primary zone. The proposed measures to reduce the wall film formation needed to account for the multi-platform application (ranging from 56 to 130 kW) and large-scale production capability. The performed simulations led to the system design, providing excellent UWS–exhaust gas mixing without a solid deposit formation. The developed system was designed to be manufactured and implemented in large-scale series production. Full article

Exhaust emissions from ships are significant threats to the environment and human health, necessitating effective control measures and treatment technologies. In response to the increasing stringency of emission regulations set by the International Maritime Organization (IMO) and national governments, the shipping industry must adopt advanced techniques to mitigate these emissions. The study focuses on the current status of exhaust pollution prevention and control on the Lijiang River and describes the latest progress in ship emission management. It summarizes the sources and hazards of nitrogen oxides (NO_X), sulfur oxides (SO_X), and particulate matter (PM) emitted from ships. The study introduces and compares several exhaust treatment key technologies for desulfurization, denitrification, and integrated desulfurization and denitrification to emphasize their principles, processes, and characteristics. It also demonstrates the future prospects for controlling exhaust gas pollution on inland ships and advocates for the development of integrated technologies that are efficient, space-saving, and cost-effective. The research aims to provide a valuable reference for inland ship exhaust pollution prevention and control. Full article

Compressed natural gas (CNG) in dual-fuel diesel engines offers environmental benefits but significantly increases unburned methane (CH₄) emissions, especially at low engine loads. This study investigates the effectiveness of different catalytic converters in methane oxidation under transient test conditions (WHTC). Three types of catalysts (Pt-, Rh-, and Pd-based) were evaluated using a combined approach of empirical engine bench tests and mathematical modelling. The results showed that, under actual exhaust gas temperature conditions, the average methane conversion efficiencies were 3.7% for Pt, 17.7% for Rh, and 31.3% for Pd catalysts. Increasing the exhaust gas temperature by 50% improved the conversion efficiencies to 7.3%, 51.8%, and 69.2%, respectively. Despite this enhancement, none of the catalysts reached the 90% efficiency threshold required to increase the CNG content of the fuel beyond 6% without exceeding emission limits. The results highlight the need for high-activity Pd-based catalysts and optimised thermal management strategies to enable the broader adoption of dual-fuel engines, while complying with Euro VI standards. 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

To address the current issues with diesel vehicle exhaust after-treatment system particulate sensors—such as low accuracy and inability to perform continuous measurements of particulate mass concentration—a new sensor based on the light scattering method is proposed. During the research, it was found that the light scattering method can be affected by soot particles in the exhaust, which contaminate the optical components and reduces measurement accuracy. To solve this issue, a structure with alumina ceramic embedded lenses and optical fibers was designed, effectively improving the sensor’s resistance to contamination. The detection device is based on the principle of light scattering, and a particulate concentration measurement system with a 90° scattering angle was built. Calibration experiments were conducted using the dust particles generated by the device. The experimental results show that this sensor can measure particulate concentrations accurately, in real time, and with good stability, achieving a calibration error of less than ±5%. Full article

Strict gaseous emission standards are applied globally to regulate the maximum amounts of pollutant emissions that can be produced from all vehicles. The exhaust aftertreatment systems used by automotive manufacturers rely on the utilization of precious metals (Pt, Pd, Rh). However, much effort has been devoted on the reduction or the replacement of the amount of Platinum Group Metals (PGMs) in three-way catalysts (TWC), both from a cost-effectiveness as well as an environmental point of view. PROMETHEUS catalyst, which was recently homologated for Euro 6 applications, is a low-cost, Cu-based TWC, which consists of a significantly lower quantity of PGMs compared to conventional state-of-the-art catalysts and achieves similar or even better catalytic efficiencies. In this review paper, a complex reaction scheme is proposed for the first time for a catalytic converter utilizing Cu and PGMs, following an extensive literature investigation of the available models. The scheme also accounts for the surface reaction mechanisms of the main processes and the side reactions potentially taking place during the TWC operation in the presence of Cu and at least one of the following PGMs: Pt, Pd or Rh. At a next step, the proposed reaction scheme will be validated based on experimental data, using mathematical modelling of a PROMETHEUS catalytic converter incorporating Cu and PGM nanoparticles. Full article

Diesel engines employed in non-road machinery are significant contributors to nanoparticulate matters. This paper presents a novel device based on the principle of split-stream rushing to mitigate particulate matter emissions from these engines. By organizing and intensifying the airflow movement of the jet in the rushing region, the probability of collisions between nanoparticles is enhanced. This accelerates the growth and coagulation of nanoparticles, reducing the number density of fine particulate matter. This, in turn, facilitates the capture or sedimentation of particulate matter in the diesel engine exhaust aftertreatment system. The coagulation kernel function tailored for diesel engine exhaust nanoparticles is developed. Then, the particle balance equation is solved to investigate the evolution and coagulation characteristics. Afterwards, three-dimensional numerical simulations are performed to study the flow field characteristics of the split-stream rushing device and the particle evolution within it. The results show that the device achieves a maximum coagulation efficiency of 59.73%, increasing the average particle diameter from 96 nm to 121 nm. The particle number density uniformity index exceeded 0.93 in most flow regions, highlighting the effectiveness of the device in ensuring consistent particle distribution. Full article

The even more restrictive regulations imposed on chemical and acoustic emissions of ships necessitate the installation of after-treatment systems onboard. The spaces onboard are limited, and the Exhaust Gas Cleaning Systems (EGCSs) have big dimensions, so an appropriate integration and optimization of EGCSs allows to save space and comply with international regulations. Moreover, in the available literature, there is a lack of guidelines about the design of integrated EGCSs. This study aims to develop an ad hoc optimization methodology that uses combined Computational Fluid Dynamics (CFD)–Finite Element Method (FEM) simulations, surrogate models, and Genetic Algorithms to optimize the acoustic properties of EGCSs while considering the limits imposed by the efficiency of chemical reactions for the abatement of NO_x and SO_x. The developed methodology is applied to a Diesel Oxidation Catalyst (DOC), and the obtained results lead to a system that integrates the silencing effect into the DOC. Full article

The Pt/CeO₂ catalyst has attracted significant attention due to its exceptional performance in NO oxidation. This study comprehensively examines the effects of calcination temperature and H₂ pretreatment on the structure and activity of the Pt/CeO₂ catalyst. Experimental findings indicate that the calcination temperature significantly affects the catalyst’s redox performance, thereby modulating its efficacy in NO oxidation reactions. H₂ pretreatment facilitates the creation of oxygen vacancies on the catalyst, assisted by the reduction in PtO_x to Pt, enhancing the formation of activated oxygen and thereby improving NO oxidation. This study offers valuable insights into the design and optimization of Pt/CeO₂ catalysts for environmental applications, particularly in the development of exhaust gas after-treatment technologies. Full article

Heavy-duty diesel vehicles are a significant source of nitrogen oxides (NOx) in the atmosphere. The Selective Catalytic Reduction (SCR) system is a primary aftertreatment device for reducing NOx emissions from heavy-duty diesel vehicles. With increasingly stringent NOx emission regulations for heavy-duty vehicles in major countries, there is a growing focus on reducing NOx emissions under low exhaust temperature conditions, as well as monitoring the conversion efficiency of the SCR system over its entire lifecycle. By reviewing relevant literature mainly from the past five years, this paper reviews the development trends and related research results of SCR technology, focusing on two main aspects: low-temperature NOx reduction technology and the combination of SCR systems with remote On-Board Diagnostics (OBD). Regarding low-temperature NOx reduction technology, the results of the review indicate that the combination of multiple catalytic shows potential for achieving high conversion efficiency across a wide temperature range; advanced SCR system arrangement can accelerate the increase in exhaust temperature within the SCR system; solid ammonium and gaseous reductants can effectively address the issue of urea not being able to be injected under low-temperature exhaust conditions. As for the combination of SCR systems with remote OBD, remote OBD can accurately assess NOx emissions from heavy-duty vehicles, but it needs algorithms to correct data and match the emission testing process required by regulations. Remote OBD systems are crucial for detecting SCR tampering, but algorithms must be developed to balance accuracy with computational efficiency. This review provides updated information on the current research status and development directions in SCR technologies, offering valuable insights for future research into advanced SCR systems. Full article