Emissions Of Internal Combustion Engines Research Articles

Numerical study of NOx formation mechanism in ammonia-hydrogen compound fuel marine engines under varying conditions

Ammonia and hydrogen are considered promising fuels for achieving zero carbon emissions in internal combustion engines. However, the mechanism of NOx formation in ammonia–hydrogen combustion remains insufficiently studied owing to the complex interaction between thermal NOx and fuel NOx. This study investigates the effects of varying equivalence ratios, N2/NH3 ratios, and initial temperatures on NOx formation using a decoupling method. Results show that thermal NOx dominates under all conditions, contributing approximately 64%–75% of total NOx. As the equivalence ratio increases from 0.6 to 1.0, the proportion of thermal NOx decreases by 7.2%. Conversely, increasing the N2/NH3 ratio from 0.8 to 1.2 leads to a reduction in both fuel and thermal NOx, while the relative proportion of thermal NOx increases. The trends in thermal NOx proportion exhibit opposite behavior with respect to equivalence ratio and N2/NH3 ratio. When the inlet temperature rises from 400 K to 480 K, thermal NOx emissions increase by 54.2%. Of the factors studied, temperature has the greatest impact on both thermal and fuel NOx formation. These findings offer valuable insights into NOx emission characteristics for researchers working on ammonia-fueled engines.

Effects of Water Injection in Diesel Engine Emission Treatment System—A Review in the Light of EURO 7

Water in the engine/combustion chamber is not a novel phenomenon. Even humidity has a major effect on internal combustion engine emissions and can thus be considered the first invisibly present emission technology. With modern techniques, the problematic aspects of water, such as corrosion and lubrication issues, seem to disappear, and the benefits of water’s effect in combustion may also be enhanced in the context of EURO 7. The current study examines the literature on the effects of water on diesel combustion in chronological sequence, focusing on changes over the last three decades. Then it analyzes and re-evaluates the water effect in the current technology and the forthcoming Euro 7 regulatory context, comparing the conclusions with current automotive applications and mobility trends, in order to show the possible benefits and prospective research avenues in this sector. Techniques introducing water to combustion could be a major approach in terms of the EURO 7 retrofit mandate, as well as a feasible technique for concurrent nitrogen oxides and particulate reduction.

Innovative Metal Coating Strategies for Enhanced Engine Performance and Emission Mitigation in Internal Combustion Engines: A Comprehensive Review

This comprehensive work addresses the pressing environmental concerns associated with the automotive industry`s expansion and its reliance on fossil fuels. Focusing on the pivotal role of energy in vehicle propulsion, the paper explores diverse energy utilization methods and their conversion into mechanical energy for mobility. While chemical energy currently powers most vehicles, it contributes to detrimental emissions, necessitating innovations to enhance fuel quality, engine design, and materials. The research emphasizes refining the performance, and life cycle, and minimizing exhaust emissions of internal combustion engines. A key focus of this paper is the proposal of a novel approach that advocates the application of coatings to the combustion surface and catalytic converter to bolster engine performance and curtail emissions. The researchers highlight the efficacy of metal coatings, including thermal barrier coatings and catalytic coatings, presenting a comprehensive overview of experimental research articles endorsing the positive impact of metal coating strategies. These coatings aim to enhance combustion dynamics, manage thermal stresses, and optimize catalytic converter efficiency. In this technical paper offers valuable insights for researchers and engineers committed to mitigating the environmental impact of the automotive industry. It underscores the critical need for optimizing engine performance and minimizing emissions, with a specific emphasis on the promising potential of metal coating technologies to significantly contribute to these overarching objectives.

Pengaruh Modifikasi Permukaan Piston terhadap Emisi Gas Buang Motor Bakar Kapasitas 100 cc

Technological advances in motorized transportation are progressing rapidly, making motorized vehicles the main mode of transportation. The increasing number of motorized vehicles in society results in a significant increase in exhaust emissions. Combustion in vehicle engines is not always perfect, producing exhaust gases containing compounds harmful to human health, such as carbon monoxide (CO), hydrocarbons (HC), carbon dioxide (CO2), and nitrogen oxides (NOx). This study investigates the effect of variations in piston dome shape on exhaust emissions in a 100cc internal combustion engine using RON 90 fuel. The goal is to find the optimal compression ratio to produce cleaner exhaust emissions. The research data are presented in tabular form and analyzed using one-way ANOVA and graphs. The results showed a significant reduction in CO and HC emissions at all engine speeds (1000, 2000, 4000, and 5000 rpm) with variations in piston dome shape. The reduction in CO emissions ranged from 55.07% to 85.73%, while the reduction in HC emissions ranged from 54.14% to 86.10%. These results suggest that variations in piston dome shape can be an effective solution to minimize harmful exhaust emissions in internal combustion engines.

A pathway for implementing ammonia solutions as fuel blends for achieving low-emission combustion in diesel engines

The intriguing exploration of ammonia fuel has captured the spotlight of researchers, heralded for its status as a zero-carbon fuel and acclaimed as a potent inhibitor of NOx emissions in internal combustion engines. Ammonia solution, one of the forms of ammonia fuel, demonstrates its ability to blend seamlessly with conventional fuel. However, the slower combustion reaction of ammonia is a significant challenge to overcome. One of the effective approaches to improve the combustibility of ammonia fuel in diesel engines is to blend ammonia solution with diesel emulsion fuel. So, the focus of this study was to comprehensively analyze the effects of blending ammonia solution at various concentrations with diesel emulsion fuel and to closely examine their effects on combustion sustainability and emission profiles in diesel engines. The ammonia solution used is an aqueous solution containing 28 wt% of ammonia. Herein, five different fuel samples were examined: diesel, water/diesel (W/D), and W/D containing 1, 3, and 5 wt% ammonia solution (A1%-W/D, A3%-W/D, and A5%-W/D, respectively). The tests were carried out with a conventional diesel engine running at a fixed engine speed of 2400 rpm, while the loads were adjusted to a variety of levels. Interestingly, we found that the diesel emulsion containing a 5 wt% ammonia solution is ineffective in diesel engines, leading to performance degradation and unstable combustion. Compared with diesel, the rate of heat release was increased by 17.6 %, 15.3 %, 10.9 % for W/D, A1%-W/D, and A3%-W/D, respectively. Furthermore, the presence of ammonia solution prolonged the ignition delay period and facilitated the reduction of NO emissions. Compared with diesel fuel, the W/D, A1%-W/D, and A3%-W/D fuels reduced NO emissions by 39.3 %, 29.5 %, and 25 %, respectively. The results of this study demonstrated that the introduction of ammonia solution at concentrations up to 3 % by weight blended with diesel emulsion fuel can be effectively combusted in a diesel engine, promoting sustained combustion stability while contributing to a significant reduction in exhaust emissions.

Comparative Analysis Of Cycle-To-Cycle Variabilities And Combustion Development In An Optical Spark-Ignition Engine Fueled By Pure Hydrogen And Propane: Insights From Chemiluminescence and PI

Hydrogen, derived from renewable sources and devoid of carbon emissions, is a pivotal energy carrier for the future. Representing a viable substitute for fossil fuels in internal combustion engines (ICEs), contemporary studies advocate using very-lean and ultra-lean hydrogen-air mixtures, with a fuel-air equivalence ratio below 0.5, as a potent strategy to reduce NOx emissions in hydrogen-fueled ICEs. An experimental setup with an optical spark-ignition engine was devised to investigate the primary factors influencing cycle-to-cycle variations in H2ICEs by optimizing mixture homogeneity and focusing the study on flame interaction with in-cylinder aerodynamics. Simultaneous in-cylinder pressure, chemiluminescence, and PIV analyses were performed to characterize and compare the behaviors of ultra-lean hydrogen-air and propane-air flames, assessing flame development and cyclic variation features. Results indicate that the flame development of hydrogen and propane is significantly different. Propane exhibited increased in-cylinder pressure trace variability at lean and rich flammability limits with a high flame development difference between fast and slow cycles. In contrast, hydrogen-air mixtures under various equivalence ratios (from very-lean to ultra-lean) presented much more stable in-cylinder pressures. Furthermore, fast propane flames were mainly advected to the cylinder's symmetrical axes, while fast hydrogen flames started further away from the spark plug. Horizontal and vertical PIV measurements showed a single structure flow field over the studied conditions with mainly intensity variations over the measured cycles. Fast flames were associated with more intense tumble motion. The differences between fast and slow flames for hydrogen are attributed to the early flame development. However, after initial differences in flame development over several crank angles, there are similarities in all cycles, suggesting that the low variability in in-cylinder pressures is mostly due to the robustness of hydrogen flame ignition and its independence from in-cylinder flow small variations at the early development phase.

Shape/penetration analysis and comparisons of isolated spray plumes in a multi-hole Diesel spray

Fuel injection systems significantly impact the combustion process and play a key role in reducing harmful exhaust emissions in internal combustion engines. For dual-fuel (DF) engines operating in gas mode, ignition of the main fuel is typically controlled by directly injected liquid pilot fuel. Liquid pilot fuel’s initial penetration and total mass considerably impact exhaust emissions and combustion stability. We investigated the spray morphology of a multi-hole diesel fuel injector within a constant-volume spray chamber using high-speed shadowgraphy and Mie-scattering measurements. Two methodologies were employed. The first one utilized a nozzle equipped with a thimble structure to isolate a single plume. The second methodology known as plume-blocking, involved sealing the orifices of the multi-hole nozzle to generate a single-spray plume. Our findings revealed that the plume-blocking approach demonstrated greater penetration than the thimble-equipped nozzle. The rapid penetration of this method may restrict its applicability to single-spray studies. Sprays generated from this partially sealed nozzle exhibited noticeable disparities compared to an unblocked nozzle, whereas a nozzle equipped with a thimble produced similar outcomes to the standard nozzle. The orifices when sealed, modify the flow distribution within the sac volume, which consequently affects the spray characteristics. In summary, this research provides insights into the impacts of various plume isolation methods on spray morphology, thereby enhancing the understanding of spray behaviour in transient conditions by comparing plume variations and disturbances under various fuel pressure and ambient conditions.

Novel virtual sensors development based on machine learning combined with convolutional neural-network image processing-translation for feedback control systems of internal combustion engines

Physical sensors are commonly used to record performance data of internal combustion engines (ICEs) for online feedback control and calibration, but they are prone to diagnostic and increased development costs. Lookup tables are commonly used in conventional calibration and feedback control; however, the table parameters increase with the advancement of ICE technologies under transient operations. Consequently, the calibration and control systems are time-consuming. This work proposes novel virtual sensors to address these issues by predicting the combustion, performance, and emission of ICEs using neural networks and image processing/translation. The novel sensors are targeted for onboard feedback control systems under transient driving. Firstly, a virtual diesel engine (VDE) was developed and calibrated against experimental data taken from a production 2.2 L turbocharged diesel engine. The VDE was calibrated under WLTC, JC08, and NEDC transient operations and was used to generate teaching data. Next, the virtual sensors are developed using five machine learning (ML) regressors. The result shows that the coefficient of determination R2 from all ML regressors exceeded 0.94, and the XG-Boost outperforms other ML techniques with R2 > 0.977. XG-Boost parameter estimations were 8 times faster than that on a desktop simulation. Then, an image classification model using a deep convolutional neural network (D-CNN) is constructed, and the dependency of performance parameters and exhaust emissions with the rate of heat release (R.H.R) and in-cylinder pressure profile is confirmed. The performance parameters and emissions dependency was compared individually with R.H.R. and the in-cylinder pressure profile. As a result, a strong correlation between the performance and R.H.R. was observed. Finally, a generative adversarial network (GAN) model was constructed to translate the in-cylinder pressure profile to R.H.R. profile. A novel method to develop virtual sensors for advanced feedback control of any type of ICEs is proposed for the first time.

Study on exhaust gas recirculation diesel engine using karanja oil methyl ester with low heat rejection in direct injection

Energy is a fundamental necessity for man›s life in the digital world today. The rapid depletion of fossil fuel resources forces rigorous alternative fuel analysis. Petroleum diesel can better replace vegetable oils, edible or motored today. The rapid depletion of fossil fuel resources forces rigorous alternative fuel analysis. Petroleum diesel can better replace vegetable oils, edible or not. Karanja may be a possible supplier of diesel fuel for non-edible oil substitution. Current combustion surfaces for pistons, valves, and cylinders have been filled with ceramic materials, which make the engine totally adiabatic (LHR). The performance of a biodiesel-powered compressing ignition (CI) engine may be further boosted by utilising the engine›s heat effectively and increasing thermal efficiency. Exhaust Gas Recirculation (EGR) is actually one of the most important methods of limiting NOx emissions in internal combustion engines. Explore the output with and without exhaust gas recirculation on a retarded timing engine with diesel and karanja oil methyl ester (KOME). The LHR with a retarded timing engine yielded improved thermal brake efficiency (TBE), decreased HC, smoke, and CO emissions, while increasing KOME›s NOx in comparison with an uncoated engine. As the EGR rate grew, NOx and BTE were reduced marginally with increased HC, CO, and smoke. 24.1 g/kw-hour CO, 10.1 g/kw-hour NOx, and 0.55 g/kW-hour HC were registered at 20 percent of EGR.

Study of the effect of cavitation flow patterns in diesel injector nozzles on near-field spray atomization characteristics using a LES-VOF method

The spray atomization process plays a critical role in achieving high efficiency and reducing emissions in internal combustion engines. The fuel injection atomization process, especially the spray primary atomization process, is significantly influenced by turbulent flow and cavitation phenomena within the nozzle. In this study, based on the coupled large eddy simulation(LES) and a volume-of-fluid (VOF)method, the effects of four typical nozzle internal flow patterns on the spray primary breakup in the near-nozzle region were investigated. To realize this objective, the generation of four distinct flow patterns was accomplished through the design and construction of corresponding nozzle structures: (1) nearly single-phase flow in a tapered-orifice nozzle with low orifice location, (2) strong geometry-induced sheet cavitation flow with sheet region extending to the nozzle orifice exit in a normal cylindrical orifice, (3) vortex-induced string cavitation flow in a tapered-orifice nozzle with relative high orifice location, and (4) geometry-induced sheet cavitation is partially suppressed while it is enhanced in the orifice region close to exit in a convergent-divergent orifice. The numerical results unequivocally reveal that the initial atomization of the spray exhibits remarkable efficacy in the case of the conventional cylindrical nozzle, characterized by internal regions of substantial sheet cavitation, despite a relatively minimal flow discharge coefficient. Conversely, the normal tapered-orifice nozzle, lacking significant cavitation, demonstrates a larger flow discharge coefficient, yet its initial atomization performance is notably suboptimal.It is worth noting that the appropriate vortex-induced cavitation in the nozzle can correspond a higher flow rate with a thin string-type cavitation and simultaneously a better spray atomization quality with a strong vortex flow. Also it is concluded that a convergent-divergent nozzle with appropriate transition location can achieve strong atomization .

Investigation on formaldehyde generation characteristics and influencing factors of PODE/methanol dual-fuel combustion mode.

Polyoxymethylene dimethyl ether (PODE) and methanol are important low-carbon substitutable fuels for reducing carbon emissions in internal combustion engines. In the research, the impacts of methanol ratio, injection timing, and intake temperature on HCHO generation and emission were investigated using both engine tests and numerical simulations. Results suggest that an increase in methanol ratio suppresses auto-ignition tendency of PODE, leading to the increase of ignition delay period, pressure peak, and heat release rate peak inside the cylinder. The decrease in in-cylinder combustion temperature contributes to an increase in HCHO emission due to partial oxidation of methanol in the cylinder and exhaust pipe. While the injection timing is gradually postponed from -10 °CA ATDC to 2 °CA ATDC, in-cylinder high-temperature area decreases, the quantity of unburned methanol increases, but part of HCHO is converted to HCO due to H radical influence, resulting in 72% increased HCHO emission. With the increment of intake temperature, the oxidation and decomposition of in-cylinder methanol accelerate, leading to an improvement in combustion stability, more uniform temperature distribution, and a decrease in unburned methanol, which results in lower HCHO emission. When the intake temperature is rose from 30 to 60 °C, HCHO emission decreases by 11.2%.

Theoretical and experimental evaluation of electric coolant pump benefits in real driving cycles

Engine thermal management is a promising option to reduce fuel consumption and harmful emissions of Internal Combustion Engines. This is particularly suitable to support the transition towards a carbon-neutral transportation sector, considering that the role of combustion engines is expected to persist in the near and medium future. In this study, a prototype pump electrically actuated was compared to a mechanical pump of a downsized gasoline engine that propels a real vehicle. In the first phase of the analysis, the cooling circuit was tested from a hydraulic point of view on all its branches using an engine mounted on a bench equal to that working on the vehicle. The hydraulic circuit was fully characterized via pressure transducers and flow meters in all branches for different thermostat lifts, representing different coolant temperatures. On the same bench, the OEM pump and an electrically actuated one, suitably redesigned on an operating point more representative of the real operating conditions, were tested. A vehicle propelled with the same tested engine (having a conventional mechanically actuated pump) was run on the road following three different driving cycles. The engine revolution speeds were registered, as well as the temperature of the cooling fluid. The electric and mechanical pumps were compared using the performance maps previously obtained. The electric pump speed was set to deliver the same coolant flow rate as the OEM pump, following the same sequence of thermostat lifts. The results show that a 60 % average reduction of the pump energy consumption is possible, leading to an average specific CO2 emission reduction of 1 g/km. This result is even more relevant during urban driving, with emission savings hitting 2.5 g/km.

A skeletal chemical reaction mechanism for gasoline-ABE blends combustion in internal combustion engine

Acetone-butanol-ethanol (ABE), serving as the intermediate product in the biobutanol production process, has garnered significant attention as a promising alternative fuel, thanks to its ability to avoid the costs and energy consumption associated with biobutanol purification, as well as its potential to improve thermal efficiency and reduce pollutant emissions of internal combustion engine. However, to date, there has been limited in-depth research into the chemical reaction mechanism for the combustion of gasoline-ABE blends and its application in engine simulations. In this study, a skeletal chemical reaction mechanism of gasoline-ABE blends was constructed, which consists of 87 components and 387 reactions, using a manifold trajectory-based dimension reduction algorithm developed by our research group. The findings illustrate that the skeletal mechanism can accurately predict ignition delay, laminar flame speed, and premixed flame species profiles for each component within gasoline-ABE blends, including isooctane, n-heptane, toluene, acetone, butanol, and ethanol. The skeletal mechanism was subsequently coupled with a CFD model to further validate its efficacy in engine combustion simulation. The results indicate that the combustion characteristics of gasoline-ABE blends in the engine can be reliably reproduced. After conducting a comprehensive simulation analysis, it is revealed that gasoline blended with 30 vol% ABE361(A:B:E = 3:6:1) exhibits a shorter initial combustion duration, an extended main combustion duration, reduced CO emissions, but also increased NOx emissions.

Numerical Prediction on In-Cylinder Mixture Formation and Combustion Characteristics for SIDI Engine Fueled with Hydrogen: Effect of Injection Angle and Equivalence Ratio

Although their ease of transport, storage, and use makes hydrocarbon fuels dominant in commercial energy systems, the emission of harmful gases, including greenhouse gases, is a fatal disadvantage. Despite ongoing research to improve thermal efficiency and reduce the emissions of internal combustion engines using conventional hydrocarbon fuels, achieving net-zero carbon requires decarbonizing fuels rather than reducing the use of internal combustion engines. Hence, transitioning away from hydrocarbon fuels and evolving internal combustion engines into clean engines using carbon-free fuels, such as hydrogen, is necessary. This study designs a 2.0 L research engine and numerically analyzes its combustion characteristics and spray behavior by varying the spray angle and equivalence ratio. When comparing the turbulence kinetic energy at a 45-degree spray angle with that at 30 degrees and 60 degrees, on average, there was a difference of approximately 37.54 m2/s2 and 26.21 m2/s2, respectively. However, misfires occur in the lean condition. Although hydrogen has a wide flammability range, poor mixture formation under lean conditions can result in misfires. The 60-degree spray angle resulted in the highest combustion temperatures and pressures for all equivalence ratio conditions, consequently leading to the highest emissions of nitrogen oxides. Specifically, at a lambda value of 2.5, the 60-degree spray angle emitted approximately 29 ppm, 0 ppm, and 161 ppm of nitrogen oxides for each respective spray angle.

Numerical Analysis to Investigate the Impact of Skirt Geometric Parameters on Secondary Piston Movement in a Single-cylinder Diesel Engine

Currently, modern internal combustion engines are receiving great attention due to their efficiency, particularly in response to the increasing limits imposed by environmental and emission legislation. Sound emissions of internal combustion engines are mainly caused by three sources of noise: combustion, mechanical and aerodynamic flow. The secondary motion of the piston plays a crucial role in the analysis of performance, noise, vibration and reliability of internal combustion engine (ICE). In the presented article, a mathematical simulation model has been developed by using of the GT-Suite software to study the rotational and lateral motion of the piston (called secondary motion) as well as the piston slap in ICE. This model takes into account the effect of variation in the major geometric parameters of the skirt design, such as the piston pin offset (P.P.O) and the length of the skirt. Furthermore, a combined model that accounts for the interplay between the secondary dynamics of the piston and the dynamic fluid lubrication has been developed. This model utilizes a mixed lubrication approach for the purpose of simulation. The results of this simulation have demonstrated that the variations in length of the skirt and the P.P.O have a considerable effect on piston secondary motion and tribological performances, and that the lateral motion of the piston is significantly influenced by the piston side force, which plays a crucial role in this behavior.

Sophisticated strategies for designing fast-charging lithium-ion batteries without sacrificing the energy density

The use of electric vehicles (EVs) is a green approach to mitigating climate change and pollution associated with the emissions of internal combustion engines. Therefore, research on lithium-ion batteries (LIBs), which are major EV components, has become vital. LIBs in EVs should be characterised by high energy and power densities for long-term use. In this study, the electrochemical performance during fast charging was examined with the active material (AM) content kept constant at 94 wt% so as not to sacrifice energy density, and the ratio of conducting agent (CA) to binder altered to account for the remaining 6 wt% of the composition. We evaluated the charging properties of Ni-rich cathodes and carried out cyclic voltammetry, electrochemical impedance spectroscopy, cross-sectional field-emission scanning electron microscopy and pore size distribution analyses. Evidence reveals that when the CA:binder ratio is 4:6, AM is hampered by the binder, which inhibits electronic conduction and hence increases its resistance to electrochemical reactions. On the other hand, at 7:3 CA:binder ratio, the void spaces in the cathode are filled by CA, decreasing porosity and hindering Li+ transfer through the electrolyte. As a result, a 6:4 CA:binder ratio is optimal for fast-charging in terms of electronic and ionic conduction. The results of this study indicate that electrochemical performance can be controlled by the inactive components' ratio, and our research proposes the best electrode composition with respect to the CA:binder ratio for fast-charging.

Effect of hydrogen incorporation on the mechanical properties of DLC films deposited by HiPIMS in DOMS mode

The automobile industry has increased its efforts in reducing the emissions of internal combustion engines by improving their efficiency. Decreasing the energy losses by friction in the engines parts is at the core of this attempt. One of the technologies that have been applied in achieving this is the application of carbon coating in engine parts surfaces because of their low friction coefficient characteristics. In this study, DLC films, a specific type of carbon coatings, were deposited using the Deep oscillation magnetron sputtering (DOMS) method, which is a variation of the high-power impulse magnetron sputtering (HiPIMS) method. Those films were deposited with an increasingly higher hydrogen content, and then their mechanical, morphological, and tribological properties were studied. All of this was carried out to verify if the higher hydrogen content is beneficial to use as piston ring coatings in order to decrease friction losses. The variation in the hydrogen content was achieved by increasing the partial pressure of methane inside the deposition chamber during the deposition, which allowed the deposition of films with up to 30 at. % of hydrogen. The variation allowed the depositions of films with a hardness above 10 GPa, a friction coefficient lower than 0.16 (30 % lower when compared to hydrogen-free DLCs), and with specific wear rates in the order of 10−16 mm3/Nm. The hydrogen content also changed the morphology of the films' surface, as well as increasing its deposition rates by 27 %.

Theoretical and experimental research on the use of hydrogen in the automotive spark ignition engine

Reducing the level of pollutant emissions of internal combustion engines requires the adaptation of solutions that improve the combustion process in the cylinder but those solutions may increase their constructive complexity. For this reason, the use of hydrogen is an effective solution, both for replacing fossil fuels and for reducing the concentration of pollutant emissions. The use of hydrogen as an additional fuel for the automotive spark ignition engines offers the possibility of obtaining increased energy performance, decreased pollutant emissions level and decreased concentration of greenhouse gas emissions. The paper presents the results of the some theoretical and experimental investigations carried on an automotive spark ignition engine, analysing the influence of the hydrogen on combustion and implicitly on energy performance and pollution. The simulation of thermo-gas-dynamic processes in the cylinder of the engine fed successively with gasoline/gasoline and hydrogen, allowed the authors to develop a specific and efficient procedure for conducting experimental investigations. The results of the theoretical and experimental research obtained and presented in the paper highlight the advantages of using hydrogen as an additive to gasoline fuelling in the automobile spark ignition engine: the improvement of combustion (reduction of combustion duration, increase of indicated thermal efficiency, reduction of specific energy consumption) and reduction of the level of polluting emissions and of the emission of greenhouse gases. An engine adjustment strategy for the sharp reduction of the concentration of nitrogen oxides is also presented.

A 3D computational study of the formation, growth and oxidation of soot particles in an optically accessible direct-injection spark-ignition engine using quadrature-based methods of moments

The accurate prediction and assessment of soot emissions in internal combustion engines play a central role in the development of modern, sustainable powertrains. The modeling of soot requires high-fidelity models capturing both the gaseous soot precursors with suitable mechanisms and an accurate description of all physico-chemical processes related to the solid particulate. Semi-empirical models based on acetylene are frequently used but are limited in covering complex fuel compositions.For this reason, we present the coupling of a detailed quadrature-based method of moments (QMOM) soot model to a state-of-the-art flow solver for the simulation of gasoline engines. A close coupling with the underlying gas phase and the additional consideration of polycyclic aromatic hydrocarbons (PAHs) as precursors allow an accurate description of the entire cause-and-effect chain. The fully coupled model is then applied in a 3D-CFD simulation of an optically accessible research engine to investigate the formation, growth and oxidation of soot particles. Experimental high-speed measurements of soot- luminescence and extinction were used for validation purposes. Together with all preceding models along the engine cycle, the newly implemented model is used to identify the root cause of the observed soot formation hotspots. Particular emphasis is placed on the effects of soot oxidation.

Experimental and numerical study of Cu-SSZ-13 SCR system for NOx reduction and hydrothermal aging under diesel exhaust conditions

Selective catalytic reduction (SCR) is a crucial technique for mitigating nitrogen oxides emission of internal combustion engines. Compared with vanadium-based catalysts, copper-based molecular sieve catalysts exhibit superior low-temperature catalytic performance and anti-aging properties. The catalytic characteristics of Cu-SSZ-13 catalyst in both fresh and aged states are investigated through experimental and numerical simulations. The catalytic performance of Cu-SSZ-13 catalyst with 200 g/L coating is investigated under wide inlet temperatures (180 °C–450 °C) and ANR (ammonia to nitrogen ratio) (1–1.4) conditions via an engine emission test device. Further, the apparatus is adopted to evaluate performance at various aging temperatures (600 °C, 700 °C, and 800 °C). The aging factor is introduced based on experimental results to establish and correct the kinetic model for SCR aging state. The results illuminate that the increase of ANR fails to compensate for decline of catalytic efficiency under low-temperature conditions (150 °C).The generated quantity of isocyanate acid through the side reaction of urea hydrolysis increases proportionally with ANR. And it increased supply only resulted in a marginal 1 %–3 % improvement of catalytic efficiency. As SV decreases from 60,000 h−1 to 35,000 h−1, the catalyst efficiency increases from 22 % to 45 %, resulting in an elevation of reactant concentration and its gradient on the catalyst surface. This leads to accelerated reaction rates and enhanced diffusion effects. The catalytic efficiency can be significantly enhanced at low temperatures when NO2 fraction in NOx falls within the range of 10 %–25 %. The sensitivity of SCR reactions to aging varies at low temperatures (<250 °C) due to the distinct reaction sites on catalyst for different types of SCR reactions. The NO2 SCR reactions exhibit minimal susceptibility, while the rapid SCR reactions are significantly impeded. Moreover, it has been observed that the catalyst microstructure was completely deteriorated under hydrothermal aging test at 900 °C operating condition. In general, the low-temperature catalytic performance of Cu-SSZ-13 catalyst can be further optimized by pretreating inlet gas components and optimizing the catalyst structure.