Diesel Engine Exhaust Gas Research Articles

Catalytic hydrolysis of HCN on the coupled sites of Lewis acid and surface hydroxyl of Fe-BEA catalyst leading to the presence of HCHO positively affects NH3-SCR activity

Formaldehyde (HCHO) in the exhaust gas of diesel or natural gas engines is usually considered to be a serious hindrance to the NH3-SCR process. However, the promotion effects of HCHO on the NH3-SCR activity and its temperature dependence were discovered in this work for the first time. For the Fe-BEA catalysts, below 300 °C, a notable decrease in activity observed, up to 40 % at 300 °C, and HCN selectivity reached 35 %. However, with the increase in temperature, a significant promotion effect was produced. Not only for the increase of NOx conversion, but also the diminish of the by-product HCN. The disparity in the number and activity of Lewis acid sites (Fe3+) and surface hydroxyls was the primary reason why Fe-BEA catalysts with varying Fe contents exhibited different influence. The presence of HCHO resulted in a modification of the oxidation pathway of NH3 at high temperatures. Surface hydroxyls facilitated the hydrolysis reaction of the as-formed HCN to produce NH3, with NH3 on Lewis acid sites subsequently re-participating in the SCR process. This enhanced the NOx conversion and the selectivity of carbon-containing products. Furthermore, it was demonstrated that HCHO completely converted to hexamethylenetetramine (HMTA) by reacting with NH3 prior to passing through the SCR catalyst. The thermal decomposition of HMTA on the catalyst was identified as a crucial step for the subsequent generation of HCN, and the detailed mechanism of how to effectively inhibit the decrease of de-NOx activity and the formation of HCN in the HCHO-containing NH3-SCR conditions was elucidated. This study paves the way for the development of effective SCR catalysts for the synergistic control of HCN from mobile and stationary sources.

Waste to hydrogen: Investigation of different loads of diesel engine exhaust gas

In this study, green hydrogen production by utilizing diesel engine exhaust gas waste heat in steam and organic Rankine with internal heat exchanger with two thermoelectric generators and proton exchange membrane electrolyzer combined system under different load conditions is investigated. Thermo-economic, enviro-economic and exergo-environmental analyses of the maximum hydrogen production point determined for different waste heat conditions are carried out. Total and specific investment cost and levelized cost of hydrogen determined under different loads are compared. Simple and dynamic payback period, profit ratio of investment and net present value of the combined system at different selling prices of hydrogen are determined and their feasibility is analyzed. Carbon reduction and carbon credit gain amount due to green hydrogen produced in line with zero emission targets are compared under different waste heat conditions. Exergetic sustainability index of the system were determined within the scope of exergo-environmental analysis. In terms of economic and environmental performance, a hydrogen cost of 2.04 $/kg was obtained under 100% load and a carbon saving of 7211 $ was achieved depending on the hydrogen produced. Dynamic payback period and net present value were found to be 4.467 years and 404,696 $, respectively, if the hydrogen selling price was 5 $/kg under 100% load. It is found that a 50% load reduction leads to an increase in dynamic payback period and levelized cost of hydrogen by 18.6% and 13.72%, respectively, and a decrease in net present value and profit ratio of investment by 54.39% and 12.39%, respectively. On the other hand, since the exergy destruction decreases with the decrease in the load, exergo-environmental index is found to decrease by 2.03%.

An experimental investigation of the impacts of titanium dioxide (TiO2) and ethanol on performance and emission characteristics on diesel engines run with castor Biodiesel ethanol blended fuel

Investigating the impact of ethanol and TiO2 on the performance and emission characteristics of diesel engines running on a blend of ethanol and castor biodiesel is the primary goal of this study. The nanoparticles of ethanol, biodiesel, and TiO2 diesel fuel were combined at several concentrations. Diesel, B10, B20, B30, B10E10T, B20E10T, B30E10T, B10E20T, B20E20T, and B30E20T were among the various fuels that were investigated. The physiochemical properties of all the sample fuels were assessed, including density, pour point, cloud point, fire point, flash point, and kinematic viscosity. Following this, other engine performance indicators, such as torque, power, and fuel-consumption, were examined. Studies were also carried out on the properties of emissions, including CO, CO2, HC, and NO. Peak braking power and engine torque were found for each fuel under investigation at around 2750 and 2500 rpm, respectively. The addition reduced the brake-specific fuel consumption for B10E20T by 7.41 % while increasing the braking engine's torque and power by 8.64 and 3.86 %, respectively, in compared to blends without the TiO2 additions. When compared to diesel, the exhaust emission data without the addition of TiO2 revealed a decrease in CO and HC emissions but an increase in CO2 and NO emissions. On the other hand, using ethanol blend reduced NO emissions. According to the overall findings, diesel engine performance, combustion characteristics, and exhaust gas emissions were enhanced averagely by 7.43 % when a certain ratio of ethanol, biodiesel, and TiO2 additives (B10E20 + 50 ppm) was used.

Experiments on thermal neutralization of marine oily waters

During the operation of the ship's power plant, the formation of oily waters is inevitable. Numerous methods and technologies used on ships do not always ensure the purification of oily waters to the amount of oil content regulated by national and international standards and requirements. In this regard, the development of a new type of installations that allow for the complete purification of oily waters from petroleum products, as well as to reduce their energy and weight and size indicators is relevant. The article presents the first results of experimental studies of the method of thermal neutralization of oily waters, consisting in their spraying in the gas outlet tract of a marine diesel engine, followed by evaporation of water and afterburning of petroleum products from the composition of oily waters with exhaust diesel gases. The research was carried out on a specially designed laboratory stand. The burner of the stand allows to obtain exhaust gases identical in composition and temperature to the exhaust gases in the flue of a marine diesel engine. A gas or liquid medium can be supplied to the flue through the nozzle. Within the framework of the described research period, the influence of the flow rate and composition of the medium supplied to the flue on the temperature at various points of the flue and the resulting composition of the exhaust gases were evaluated. The main task of this stage of the study is to determine the effect of the flow rate and composition of the medium supplied to the flue on the compliance of the gas parameters at the outlet of the installation with the standards for the content of harmful substances in the exhaust gases of marine diesel engines.

Non-PGM hollow fibre-based after-treatment for emission control under real diesel engine exhaust gas conditions

Hollow fibre (HF)-based technologies for emission control, as an alternative to the traditional monolithic technology, offers a promising route to the uptake of non-PGM catalytic systems. In this work, a series of Cu-doped LaCoO3 perovskites were investigated as potential non-PGM Diesel Oxidation Catalysts (DOC). Two HF-based modules, comprising single-channel (i.e., 1CM) and four-channel (i.e., 4CM) HFs respectively, were impregnated with the best catalyst candidate, and their performance was tested under real exhaust gas conditions, using a single-cylinder diesel engine. Compared to the 1CM, the 4CM demonstrated enhanced CO conversion, and reduced performance towards Total Hydrocarbon (THC) conversion. Overall, these findings reveal the influence of HF morphology on catalytic performance, and in turn, will contribute towards the refinement of HF-based technology for emission control, as well as enabling the transition towards non-PGM catalytic systems.

Utilization of hydrogen and methane as energy carriers with exhaust gas recirculation for sustainable diesel engines

Hydrogen and methane as secondary fuels in diesel engines can be promising solutions to meet energy demand. The current study investigated the effect of the specialty gases of different compositions on diesel engine performance and exhaust gases. Four gases with various compositions of exhaust gas recirculation (Carbon monoxide, Carbon dioxide, and Nitrogen) and fuels (Hydrogen and Methane) were used at various mass flow rates of 10, 20, and 25 LPM (liter per minute), and various engine speeds of 2000, 2500, 3000, and 3500 rpm (revolutions per minute). The procured results revealed that adding specialty gases improved brake thermal efficiency and power. Similarly, the brake-specific fuel consumption was also massively retarded compared to diesel due to the influence of the hydrogen and methane composition. However, the fuel with the higher nitrogen reported less BTE (brake thermal efficiency) and comparatively higher exhaust gas temperature owing to the higher presence of nitrogen in their composition. Regarding emissions, including exhaust gas recirculation dropped the formation of pollutants efficiently compared to diesel. Among various fuels, Case 1 (30 % H2, 5 % CH4, 5 CO2, and 60 % CO) reported the lowest emission of NOx, and Case 2 (25 % H2, 5 % CH4, 5 CO2, 30 % CO, and 35 % N2) of CO and CO2 emissions. Generally, specialty gases with a variable composition of exhaust gas recirculation gases can be a promising sustainable replacement for existing fossil fuels.

Experimental evaluation of the significance of scheduled turbocharger reconditioning on marine diesel engine efficiency and exhaust gas emissions

Poor clearances, misalignments, and carbon deposits in a turbocharger due to high running hours can decrease engine efficiency. This study analyzes the effects of turbocharger reconditioning on the performance and emissions formation of a marine diesel generator engine. The engine test experiments were performed on a university training ship's auxiliary diesel engine with 4309 running hours before and after the TC overhaul. As a result, cylinder peak pressure was increased by a maximum of 3.57 % while fuel saving of 5–8 g/kWh was realized. Lower exhaust gas temperatures and improved charge air pressure by up to 7.7 % were recorded. A significant CO emission reduction of 21.6 % was recorded at idle load whereas NOx and CO2 emissions were reduced to a maximum of 4.86 % and 7.30 % at 50 % engine load. The results indicate that scheduled TC overhaul and maintenance are very useful to improve the engine’s fuel economy, and performance and reduce exhaust emissions.

Pengaruh Campuran Minyak Jarak Pagar dengan Dexlite Terhadap Performa Mesin Diesel

One of the alternative energy fuels in the transportation sector is biodiesel. Biodiesel made from a mixture of vegetable materials has great potential as an environmentally friendly fuel for diesel engines. This experimental research aims to analyze the effect of using Jatropha curcas (Jatropha curcas Linn) oil on diesel engines. The experiment was carried out using a mixture of Dexlite and pure castor oil (JCO) with varying compositions of JCO 0%, JCO 20%, and JCO 30%. Torque test results against load show an insignificant comparison between Dexlite without mixture and Dexlite with 20% and 30% JCO mixture, especially when loading high using Prony Brake. Although the effective engine power of the three fuel variations does not show significant differences at the same engine speed and load, the use of a mixture of Dexlite and 20% castor oil at an engine speed of 1700 rpm is more effective in improving diesel engine performance and saving fuel. Additionally, fuel consumption decreases as load increases, indicating high efficiency potential. In the context of exhaust gases, the mixture also has the potential to reduce the opacity of diesel engine exhaust gases.

The marine diesel engine exhaust gas temperature baseline model based on particle swarm optimised generalised regression neural network

ABSTRACT This study addresses limitations in traditional condition monitoring for marine diesel engine (MDE) reliability and stability by proposing a hybrid machine learning and deep learning (DL) model called Particle Swarm Optimization-Generalized Regression Neural Network (PSO-GRNN) for real-time exhaust gas temperature (EGT) monitoring. The model integrates Mahalanobis distance (MD) calibration, wavelet packet denoising, and Pearson correlation analysis for comprehensive data preprocessing. Validation is conducted using historical '6L34DF' diesel engine data. Particle Swarm Optimization (PSO) optimizes the spread value (σ) of the Generalized Regression Neural Network (GRNN) to establish an optimal baseline model for EGT prediction. Experimental results show that PSO-GRNN outperforms Backpropagation Neural Network (BPNN), GRNN, Bidirectional Gated Recurrent Unit (BiGRU), Genetic Algorithm- Generalized Regression Neural Network (GA-GRNN), and Deep Belief Network-Support Vector Regression (DBN-SVR) in terms of training time and accuracy, demonstrating its suitability for MDE baseline modeling.

Design and assessment of a novel mobile carbon capture system: Energy and exergy analyses

In this work, we designed a mobile carbon capture (MCC) system that can effectively capture CO2 from the exhaust gas of diesel engines for applications in commercial vehicles. We present the results of energy and exergy analyses conducted on this system, which includes an energy recovery unit, a cooling unit, CO2 adsorption and desorption units, and a CO2 liquefaction unit. Three processes were considered to capture CO2: temperature vacuum swing adsorption (TVSA), vacuum pressure swing adsorption (VPSA), and vacuum swing adsorption (VSA). Energy is produced using turbines and generators, which supply the necessary power to run the MCC system, thus overcoming the limitation of mobile devices, i.e., lack of energy source. The energy requirement for each process was found to be in the order of VPSA > TVSA > VSA. In terms of specific energy consumption (SEC) and exergy efficiency, VSA was the most suitable process. As an MCC system, the VSA process consumes a small amount of energy in the designed system, and CO2 can be captured, liquefied, and stored by utilizing the energy contained in the exhaust gas. Because the TVSA process is expected to operate with less additional energy input, it can be used as an MCC system to improve the efficiency of each process unit. Our study can serve as a basis for advancing carbon capture technologies that can be implemented in commercial vehicles to reduce the greenhouse effect and help control global warming.

Potential of Variable Geometry Radial Inflow Turbines as Expansion Machines in Organic Rankine Cycles Integrated with Heavy-Duty Diesel Engines

This work evaluates the feasibility of utilizing an organic Rankine cycle (ORC) for waste heat recovery in internal combustion engines to meet the stringent regulations for reducing emissions resulting from the combustion of fossil fuels. The turbine is the most crucial component of the ORC cycle since it is responsible for power production. In this study, a variable geometry radial inflow turbine is designed to cope with variable exhaust conditions. A variable geometry turbine is simply a radial turbine with different throat openings: 30, 60, and 100%. The exhaust gases of a heavy-duty diesel engine are utilized as a heat source for the ORC system. Different engine operating points are explored, in which each point has a different exhaust temperature and mass flow rate. The results showed that the maximum improvements in engine power and brake specific fuel consumption (BSFC) were 5.5% and 5.3% when coupled to the ORC system with a variable geometry turbine. Moreover, the variable geometry turbine increased the thermal efficiency of the cycle by at least 20% compared to the system with a fixed geometry turbine. Therefore, variable geometry turbines are considered a promising technology in the field and should be further investigated by scholars.

Abatement of photochemical smog precursors through complete hydrocarbon oxidation over commercial Pd catalysts under fuel-lean conditions with NO promoting effect

Currently, severe environmental issues have led to a great transition in the automotive industry from internal combustion engine vehicles to electric vehicles, but this transition will take time more than 10 years, which still requires the use of internal combustion engine vehicles. However, these vehicles emit a significant amount of hydrocarbons, in addition to nitrogen oxides (NOx), due to incomplete fuel combustion. They contribute to the formation of photochemical smog when they react with NOx in the presence of sunlight. To effectively remove these hydrocarbons from the exhaust gas of turbo-gasoline engines or diesel engines, we investigated the abatement of propane and iso-pentane, two typical hydrocarbons. In particular, we studied commercial Pd catalysts and revealed how the Pd loading and aging process simulating 4k and 100k mileage affected hydrocarbon abatement abilities, and their phases were identified using characterization technique, including CO chemisorption, X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HR-TEM). We also suggested the reaction pathway for the complete oxidation of propane over Pd catalyst based on the reaction orders of propane and oxygen: Propane adsorbs on O atoms of PdO, and the kinetically relevant C–H bond cleavage step occurs by the interaction with abundant neighboring O atoms of PdO. Finally, the propane and iso-pentane abatement ability of the Pd catalyst aged for 100k mileage were evaluated under realistic exhaust gas conditions, and the effect of each gas component in the realistic exhaust gas was identified; water inhibits the catalytic reaction of hydrocarbons by occupying the active sites, whereas NO catalyzes the hydrocarbon oxidation reaction by either changing the reaction pathway or active sites under fuel-lean conditions. These findings enable us to effectively reduce environmental pollution and facilitate a smoother transition from internal combustion engine vehicles to electric vehicles.

Enhancing the Fuel Efficiency of Cogeneration Plants by Fuel Oil Afterburning in Exhaust Gas before Boilers

Cogeneration or combined heat and power (CHP) has found wide application in various industries because it very effectively meets the growing demand for electricity, steam, hot water, and also has a number of operational, environmental, economic advantages over traditional electrical and thermal systems. Experimental and theoretical investigations of the afterburning of fuel oil in the combustion engine exhaust gas at the boiler inlet were carried out in order to enhance the efficiency of cogeneration power plants; this was achieved by increasing the boiler steam capacity, resulting in reduced production of waste heat and exhaust emissions. The afterburning of fuel oil in the exhaust gas of diesel engines is possible due to a high the excess air ratio (three to four). Based on the experimental data of the low-temperature corrosion of the gas boiler condensing heat exchange surfaces, the admissible values of corrosion rate and the lowest exhaust gas temperature which provide deep exhaust gas heat utilization and high efficiency of the exhaust gas boiler were obtained. The use of WFE and afterburning fuel oil provides an increase in efficiency and power of the CPPs based on diesel engines of up to 5% due to a decrease in the exhaust gas temperature at the outlet of the EGB from 150 °C to 90 °C and waste heat, accordingly. The application of efficient environmentally friendly exhaust gas boilers with low-temperature condensing surfaces can be considered a new and prosperous trend in diesel engine exhaust gas heat utilization through the afterburning of fuel oil and in CPPs as a whole.

Performance assessment of hybrid recuperative heat exchanger for diesel engine generated exhaust gas

In this study, the use of supplemental heat energy from exhaust gas of a stationary diesel engine was assessed to explore a new method of drying black nightshade seeds in a solar-exhaust gas greenhouse dryer. The energy recovery potential of a hybrid recuperative heat exchanger (HRHE) was demonstrated with the objective of utilizing the recovered energy from an engine on milling operations to heat a fluid stream of drying air. The results show that 4.45 kW of thermal energy was available in exhaust gas of a diesel engine operated at 2500 rpm when mass flow rate was 45.07 kg/h at a temperature of 357.36 °C. The rate of heat utilized for solar-exhaust gas mode ranged from 40.49 to 685.94 J/m2.s and from 21.69 to 668.11 J/m2.s in exhaust gas mode of drying. The heat exchanger raised the dryer temperature by an average of 11.78 °C when temperature differences between inside and outside were compared in solar-exhaust gas mode of drying. The average hourly rise in temperature inside the dryer was 8.04 °C with a minimum rise of 3.7 °C and a maximum of 9.41 °C when exhaust gas was utilized to provide heat energy. The performance of the solar-exhaust gas greenhouse dryer improved when thermal energy was used as a supplement in drying and as a result the drying time for black nightshade seeds was significantly reduced from 11 h in solar mode to 10 h in solar-exhaust gas mode of drying. Moreover, the seeds were dried for 14 h when exhaust gas mode of drying was performed without utilizing solar energy. The percent internal uncertainty for experimental measurements of relative humidity (γ) was 4.1% and 17.5% for temperature (T) observations. The three proposed thermal models for temperatures and moisture evaporation performed better with low RMSEs in exhaust gas mode compared to the other modes of drying.

Role of oxidation catalysis in after-treatment of exhaust gases of diesel engines

Introduction (problem statement and relevance). The oxidation catalysis provides the necessary efficiency and performance of diesel filters for trapping dispersed particles and systems for selective treatment of nitrogen oxides. In addition, oxidation catalysts can be a tool for neutralizing emissions of methane and some non-regulated but very hazardous polycyclic and partially oxidized hydrocarbons. There are also poorly studied theoretical issues of oxidation catalysis associated with mutual influence of toxic components contained in exhaust gases of diesel engines.The purpose of the study is to clarify the oxidation catalysis role in the general problem of after-treatment of toxic emissions of diesel engines, development and testing of catalysts and converters for neutralization of toxic combustion products of engines powered by natural gas.Methodology and research methods. Research into the catalysts under flow conditions using modern methods of gas analysis, IR spectroscopy, engine tests of the developed catalytic converters.Scientific novelty and results. The paper shows the role of oxidation catalysis in solving the common problems of after-treatment of hazardous emissions of diesel engines including both direct after-treatment of toxic compounds and supporting functions. Catalysts of higher efficiency and a series of converters for gas engines have been developed. Innovative methods to increase the resistance of oxidation catalysts to sulfur oxides have been proposed.Practical significance. The developed catalysts and converter designs are recommended for implementation in KAMAZ-820.52-260 and Cummins 250 and 280 gas engines.

Advancements in low-temperature NH3-SCR of NOx using Ba-based catalysts: a critical review of preparation, mechanisms, and challenges.

Presently, selective catalytic reduction (SCR), with either carbon monoxide, urea, hydrocarbons, hydrogen, or ammonia as a reductant, has become a nitrogen oxide (NOx) removal technology (NOx conversion) of many catalytic companies and diesel engine exhaust gas. Although, there exists a serious threat of low-temperature limitations. So far, certain scientists have shown that barium-based (Ba-based) catalysts have the potential to be highly effective at SCR of NOx at low temperatures when ammonia is used as the reducing agent. The process of NOx storage and reduction which alternate SCR is known as the Lean NOx trap. Herein, we give the condensed advancements and production of the catalysts that involve BaO in low-temperature NH3-SCR of NOx, the advantages of BaO catalysts compared to the recently hot electrocatalysis, the stability of BaO catalyst materials, and the condensed advancements and production of the catalysts that involve BaO in low-temperature NH3-SCR of NOx. These catalysts are viewed in the light of their preparation method, particulate, and posture in mixed oxides. Also, the characteristic features of Ba-based catalysts are carefully considered and briefed under the following areas: preparation method and precursor, crystallinity, calcination temperature, morphology, acid sites, the specific surface area for reaction, redox property, and activation energy of catalysts. More to these are the discussions on Eley-Rideal [E-R] and Langmuir-Hinshelwood [L-H] mechanisms, the H2O/SO2 and O2 permissiveness, and the NH3-SCR reaction mechanism over Ba-based catalysts highlighting their possible effects. Finally, we proposed the prospect and the likely future research plan for the low-temperature NH3-SCR of NOx.

Tribological performance of nanopowder blended bio-diesel

Biodiesel is renewable, sustainable, and an alternative fuel for compression ignition engines, and often recognized as a comparable fuel to diesel in diesel engines. This is due to a variety of factors, including less dependency on imported petroleum, less global warming, and lower diesel engine exhaust gas emissions. Cottonseed oil is converted into biodiesel by the well-known transesterification method. The ultrasonication approach is used to evaluate the bio - diesel B20 (0.8 %diesel + 0.2 %biodiesel) as well as B50 (0.5 % diesel + 0.5 %biodiesel) with Aluminum oxide nanoparticles in concentration of 50 and 100 ppm. The tribological properties of these blended samples are investigated at varied speeds and loads considering AISI 1040 steel disc with aluminium pins. The addition of Al2O3Nanoparticles helps in further enhancing the tribological properties of the biodiesel made of cotton seed oil. The results reveal that a properly concentrated Al2O3 nanofluid has strong tribological characteristics and has the capability to substitute conventional lubrication. The nanofluid has higher tribological qualities over pure cottonseed oil as well as boosts its performance substantially.

Combustion and emissions characteristics of a diesel engine fuelled with diesel fuel and different concentrations of amino-functionalized multi-walled carbon nanotube

Nanoparticles have recently been used as fuel additives to enhance diesel engine performance and exhaust gas emissions. Amino-functionalized multiwalled carbon nannotubes (NH2-MWCNTs) are catalysts that can be applied in diesel engines because of their promising properties. This study conducted an experimental investigation to determine the impacts of adding NH2-MWCNTs to diesel fuel using a single-cylinder CI engine running at a constant speed (1500 rpm) and various loads. The NH2-MWCNTs were added to diesel fuel at four concentrations of 25, 50, 75, and 100 ppm. Also, the same doses of pristine multiwalled carbon nanotubes (MWCNTs) were added to diesel to be used as a reference for NH2-MWCNTs. Most NH2-MWCNTs blends were preferred in combustion characteristics, engine performance, and exhaust emissions compared to diesel and MWCNTs blends. Thus, there was a considerable increase in cylinder pressure and heat release rate compared to pure diesel. Also, the brake thermal efficiency was increased, and the brake-specific fuel consumption was decreased compared to diesel. Most NH2-MWCNTs combinations appeared to decrease NOx, soot, and CO levels significantly. The NH2-MWCNTs blends are generally favored over the pristine MWCNTs blends in reducing exhaust emissions.

Essential Features of Gliding Arc Plasma for High-Performance Hydrocarbon Selective Catalytic Reduction of NOxat Low Temperatures

The high removal efficiency of NOx from diesel engine exhaust gas at low temperatures remains challenging due to the poor activity of catalysts under this condition. This work investigated the effectiveness of gliding arc plasma in the NOx removal over the Ag/γ-Al2O3 catalyst with n-heptane as a reducing agent source for NOx reduction. The plasma conjugated with the catalyst was performed like an injection method, i.e., a small part flow (1/26) that consisted of n-heptane was reformed to H2 and oxygenated hydrocarbons (OHCs) by gliding arc plasma before mixing it with the gas containing NOx. Then, the overall gas was passed through the catalyst stage at various temperatures from 127 to 253 °C. The experimental data revealed that NOx removal efficiency significantly increased with plasma treatment. The enhancement by plasma treatment increased with temperature from 127 to 226 °C, but the enhancement reduced at a temperature of 253 °C. The result came from formation of H2 and OHCs in the treated plasma gas, which reactivated NOx removal over the catalyst at low temperatures. Moreover, the enhanced NOx removal efficiency in a wide low-temperature range is obtained due to considerable hydrogen formation by the gliding arc plasma. To sum up, the highest NOx removal efficiency was 68.5% under a temperature of 226 °C and specific energy input of 34.6 J/L, while it was 20.3% for the catalyst alone; in other words, the removal efficiency increased by 48.1% with using plasma under these conditions. Owing to its low energy consumption, high-throughput gas treatment, and effectiveness at low temperatures, the technology is promising in practical applications for refining diesel exhaust gases.

Study on the restructuring of soot particles from diesel engine exhaust gas discharged into a simulated atmospheric environment

This paper investigates the restructuring of soot particles from a diesel engine (operated at low and high (30% and 90%) loads of 1200 rpm) exhaust gas discharged into a simulated atmospheric environment. The morphological characteristics of soot particles during the aging times of 0 min, 30 min, 60 min, 120 min, and 180 min were observed by transmission electron microscopy (TEM) to analyze the changes of primary particle diameter (dp), the radius of gyration (Rg), aggregation parameters (aspect ratio, roundness, and root form factor) and fractal dimension (Df) of soot. The results indicate that the dp of the low-load soot tends to increase in the 0–30 min aging period and then it behaves smoothly till to 180 min, while the dp of the high-load soot tends to decrease and then increase, with the minimum value of dp occurring at 60 min of aging. In terms of Rg, the low-load soot appears to age more quickly than the high-load soot, owing to the shorter branch chains for the low-load soot than that for the high-load soot. The trends in the aspect ratio (AR), roundness (RN), and root form factor (RFF), of soot during aging indicate that soot is developing towards a more compact aggregation, especially for the low-load soot. In addition, the Df value tends to increase during the aging process for the low- and high-load soot, but compared to the high-load soot, the low-load soot shows a higher aging degree and faster aging speed during the aging process.