NOx Values Research Articles

Air Pollutant Emission Factors of Inland River Ships under Compliance

Inland river ships (IRSs) use diesel with a lower sulfur content and emit relatively low emissions, making it challenging to monitor their emissions. Sniffer monitoring equipment was installed from August 2020 to June 2022 at the Gezhou Dam of the Yangtze River and monitored emissions from 8,238 IRSs passing through the lock. We partnered with the maritime department to select 100 ships passing through the lock to extract fuel oil samples for direct fuel sulfur content (FSC) detection, which determined the actual FSC of the passing ships. The monitoring data from these 100 ships indicated that the relative error of the SO2 emission factors (EFs) and FSC results is significant at the 10-parts-per-million level. The monitoring data from the remaining 8,138 ships showed that the EFs of NO, NO2, PM2.5, and PM10 were 24.02 ± 16.92 g kg−1, 10.30 ± 18.08 g kg−1, 0.72 ± 0.60 g kg−1, and 0.92 ± 0.70 g kg−1, respectively. The NOx EFs of container ships are higher than those of other ship types, while the PM EFs for different ship types do not significantly differ. Based on these EFs, we calculated the average emission rates for different types of ships passing through locks, which is a real-time measurement method for estimating ship emissions. In addition, a comparison of ship EF measurements over the past 20 years revealed that EF values for SO2, NOx, and PM exhibited a downward trend, with the calculated results of the current study determined to be the lowest numerical level.

A full-scale CFD model of scavenge air inlet temperature on two-stroke marine diesel engine combustion and exhaust emission characteristics

Most ships in the maritime transport sector are equipped with large two-stroke marine diesel engines in their propulsion systems. Therefore, ensuring stable and long-term operation of these engines is crucial to maintaining freight transportation. The design of the ship's machinery, particularly the diesel engine, is a crucial step in achieving this goal. Computational Fluid Dynamics (CFD) tools can be used to achieve this goal. This article presents a full-scale CFD study on the effect of different scavenge air inlet temperatures (300, 312, 330 and 340 K) on the combustion process and generation of exhaust emissions in a two-stroke marine diesel engine using ANSYS Forte software. Regarding the cylinder pressure, the presented model agrees well with experimental data. The maximum cylinder pressure decreases as the scavenge air inlet temperature increases, whereas the maximum cylinder temperature increases as the scavenge air inlet temperature increases. The maximum NOX, CO and UHC emission values are calculated to be 2256.5, 20375.8 and 3743.9 ppm, respectively, at a scavenge air inlet temperature of 340 K. Due to the higher combustion temperature caused by the increasing scavenge air inlet temperature, it is observed that the exhaust emission levels increase.

Experimental investigation of the effects of aqueous ammonia and water mixtures on the efficiency and emissions of a compression ignition engine

In this study, different concentrations of aqueous ammonia and pure water were fumigated and aspirated into the cylinder from the engine intake manifold. Aqueous ammonia (NH4OH) with 5 %, 10 % and 15 % ammonia (NH3) concentration was used in the experiments. Both aqueous ammonia and pure water were converted into cold vapor using an ultrasonic evaporator and conveyed to the combustion chamber as fume. Experiments were carried out at a constant engine speed of 660 rpm. Torque values of 25 %, 50 %, and 100 % (386 Nm) were used in the experiments, respectively. As a result of the experiments, it was seen that as the ammonia percentage increased, the engine efficiency was negatively affected. At 100 % torque, when comparing the BTE value of pure diesel fuel with the BTE values of experiments with 5 %, 10 %, and 15 % ammonia addition, decreases of 0.09 %, 2.27 %, and 3.57 % were observed, respectively. In experiments conducted with pure water, although the thermal efficiency increased significantly as the torque ratio increased, it still could not reach the thermal efficiency of pure diesel fuel. On the other hand, it has been observed that water vapor improves NO and HC emissions. While the NOx value tends to increase with the increase in ammonia concentration at low and medium load values, the NOx value tends to decrease relatively as the ammonia concentration increases at 100 % torque value. The highest NOx emission value, 534 ppmvol, occurred in the experiments with 15 % NH4OH addition. It was observed that the NOx emission value of all experiments conducted with aqueous ammonia additive at 100 % torque was lower than pure diesel. In this study, the effects of NH4OH and H2O on engine performance and emissions were investigated.

Analysis of carbon and nitrogen from atmospheric sources by bulk deposition sampling at various locations in Germany

Atmospheric deposition of particulate matter is an important indicator of air pollution and a significant factor in material surface fouling. The elemental composition of this nutrient-containing dust depends largely on the exposure region and time as well as on climate. Therefore, in this paper we report an analysis of atmospheric pollutions with a self-made low-cost bulk deposition sampler directed at sampling deposition via air transport and rainfall. We used the device in diverse environments - thus comparing an urban region, an area surrounded by forest and an area mainly dominated by agriculture. The total organic carbon (TOC) and total nitrogen (TN) amounts were selected as indicator parameters and analyzed in a biweekly rhythm for three and a half and two years, respectively. The TOC value responded to particulate matter in the urban area, especially significant were the influences of the New Year's firework in urban and pollen in the rural forest area. In contrast, the TN value was more under the influence of the nitrogen emissions in the agriculture-dominated area. However, the TN value did not correlate with the NOx values in the urban area because the atmospheric nitrogen emissions in the city might originate from various emission sources. Summarizing, the TOC and TN values of the self-made low-cost bulk deposition sampler were in good agreement with environmental events of their immediate surrounding. Moreover, the selected containers and sampling procedures are universally applicable to monitor and analyze organic as well as inorganic parameters (e.g. metal ions) of atmospheric deposition.

Grey-Taguchi and ANN optimization in CI Engines using acetylene & biodiesel blends for Low Emissions and Better Performance

This study aimed to reduce smoke and NOx emissions in a diesel engine fuelled with a 20% blend of Calophyllum inophyllum and Prosopis juliflora biodiesel (B20) with neat diesel, supplemented with acetylene at flow rates of 1, 2, and 3 liters per minute (lpm) in dual-fuel mode. Using the Grey-Taguchi method and an L9 (3^3) orthogonal array, the effects of compression ratio, fuel type, and acetylene flow rate were examined. Regression models were developed to predict brake thermal efficiency, smoke, and NOx emissions based on these controllable factors. The study found that the optimal individual values for NOx, brake thermal efficiency, and smoke were 2353 ppm, 31.52%, and 48.7 ppm, respectively. The best-combined results were achieved with a compression ratio of 17.5 and an acetylene flow rate of 3 lpm using the CI20 blend. The findings demonstrated significant improvements in output response factors when the optimal combination was applied, as validated by experimental and artificial neural network (ANN) simulations. The Grey-Taguchi approach proved effective in reducing emissions while enhancing engine performance.

Experimental and Numerical Simulation Research on Different Shapes of Flame-Stabilizing Baffles in the Furnace

The use of fully premixed combustion in small gas boilers can improve denitrification efficiency. On the basis of fully premixed combustion, adding flame stabilizers inside the boiler can further reduce production of oxides of nitrogen. Four types of flame-stabilizing baffles were added at a certain position inside the furnace after the fully premixed burner. Experiments were conducted separately on the Noporous baffle, and numerical calculations were performed for 36 operating conditions of the four baffles. The experimental results and numerical calculations indicate that under experimental conditions, NOx emissions were all below 40 mg/m3, and the net heat efficiency of the boiler was above 80%. Under a maximum firing rate, CO emissions are below 20 ppm, and the minimum error between the calculated and experimental values is 2.2%. The calculation error of CO emissions under various working conditions does not exceed 6.8%, indicating that the impact of different-shaped baffles on CO emissions is relatively small. When installing a Nonporous baffle, the error between the experimental and calculated exhaust temperature values under minimum firing rates is 6.6%, the error between the calculated and measured values under middle firing conditions is 2.9%, and the error between the calculated and measured values under maximum firing rate conditions is 3.0%. Among the four different partition conditions, the exhaust temperature of the Nonporous baffle is the lowest. Under the same excess air coefficient, the pressure in the furnace for the middle and maximum firing rate is higher than that of the minimum firing rate, and the experimental values are in good agreement with the calculated values. When installing the Strip baffle, the calculated CO2 emission is the lowest. The experimental results show that the NOx in the flue gas inside the furnace is mainly NO, and the NO content exceeds 75%, reaching a maximum of 85%. The experimental results show that the minimum NOx emission value is 26.9 mg/m3. The error between the measured and calculated NOx values when installing a Nonporous baffle is 20.4%. All of the above indicate that installing a flame-stabilizing baffle at an appropriate position in the furnace can further reduce NOx emissions, and the optimization amplitude is related to the shape of the baffle.

Stallion Sperm Freezing with Different Extenders: Role of Antioxidant Activity and Nitric Oxide Production.

Sensitivity to freezing remains a critical issue in stallion semen cryopreservation procedures. To explore this topic in-depth, semen was collected from ten stallions, diluted with three different extenders, transported to the laboratory, and then centrifuged and frozen with four different extenders. We conducted analyses of sperm kinetics, mitochondrial membrane potential (MMP), and hydrogen peroxide content both before and after freezing. Additionally, we assessed antioxidant activity using the ABTS and FRAP methods and measured nitric oxide stable metabolites (NOx) in the blank extenders, seminal plasma, and extenders conditioned by spermatozoa before and after freezing. We found significant variability in the antioxidant activity and NOx content of the blank extenders and the seminal plasma. In the seminal plasma, ABTS-based antioxidant activity and NOx values were correlated with some sperm kinematic parameters and MMP in refrigerated semen, while no correlation was observed in frozen sperm parameters. Sperm function varied significantly between stallions but not between extenders, either before or after freezing. However, significant differences in antioxidant activities and NOx values were found among extenders conditioned following freezing. These results provide new insights into the factors contributing to the variability in individual stallions' tolerance to sperm freezing.

Optimization of performance and emission parameters of hydrogen enriched dual fuel diesel engine using response surface methodology

The global need for petroleum and its dwindling availability throughout the world demand an alternative fuel. Hydrogen-enriched algal biodiesel (ABD) is a potential option against conventional fuels due to its availability and positive effects on performance and emissions. Azolla pinnata algae is a high-yield fuel with reduced adverse impacts on the environment, requiring 2–5 days to double its biomass. This research work involves post-experimentation modeling to assess the performance and emissions of a CRDI diesel engine using a hydrogen-enriched blended fuel of Azolla pinnata ABD. Response surface methodology has been applied to optimize the load, fuel blend, and hydrogen gas substitution for performance and emissions characteristics. The ABD and hydrogen gas are varied between 0 and 40% in the pilot fuel for loads between 0 and 80%. The model indicates that the optimized load, blend, and hydrogen fuel substitution for this research are, respectively, 80%, 40%, and 40%. At the above-mentioned optimized parameters, the optimized values of BTE, CO, CO2, HC, and NOx are found to be 30.90%, 19.99 g/kWh, 288.89 g/kWh, 0.21 g/kWh, and 1.57 g/kWh, respectively. Adequacy precision greater than 4 and a percentage error between predicted and experimental values less than 5% indicate the model's ability to predict performance and emissions characteristics eventually.

Investigation effects of different calorific values and operating conditions on biogas flame: a CFD study

ABSTRACT This study investigates different biogas fuels’ and operating conditions’ effects on flame temperatures and emissions (CO, CO2, NOx, and soot). Different calorific values (15.580, 17.880, 20.430, 23.080, and 26.230 MJ/kg) were obtained by changing methane content. Furthermore, various gas pressure (0.5, 1, 2, and 3 atm), excess air coefficient (1.4, 1.8, 2.5, and 4), and oxygen values (21, 23, 25, and 27%) were simulated for 8.6 kW thermal capacity furnace. Increasing the calorific value of biogas fuels, CO, NOx, and soot emissions and flame length tend to increase, while CO2 decreases. Increasing gas pressure, flame temperature, and CO2, CO, and NOx decrease, while soot emissions tend to increase. As a result of the decrease in the air excess coefficient from 4.0 to 1.4, there is a increase in the flame temperature, flame length, and soot, CO, CO2, and NOx emissions. On the other hand, oxygen content from 21% to 27% oppositely affected these parameters, excluding flame length.

Harnessing NOx emission management: A virtual sensor model for natural gas power generation engines with active pre-chamber

This paper presents a NOx Sensor machine learning model for a highly efficient 2MW power generation lean burn gas engine with an active pre-chamber. As gas power generation continues to evolve, engine efficiency and the accurate measurement of NOx emissions has taken on greater importance. However, the working life of existing NOx sensors pales in comparison to the lifecycle of an engine. This paper studies a series of machine learning NOx sensor models and carries out a comparative analysis. We introduce a predictive analytics model used for monitoring the emissions of active pre-chamber gas engines. This real deployment aims to detect the deviations in emissions across an entire fleet of gas engines, even when no physical sensors are installed in the engines. Finally, a model has been implemented that allows the prediction of NOx values, in engines that did not have them initially, with a 5–10 % precision. For example, with NOx at 120 ppm, the virtual sensor provides values close to +-10 ppm. It has been observed that such features as the setpoint value of the active pre-chamber gas pressure, in a lean burn gas engine with active pre-chamber, are among those parameters that have the greatest impact on the model estimation.

Effect of Porosity on Combustion Performance in Packed Bed Porous Media

This study investigates the effect of packed bed material porosity and air-to-fuel ratio on the combustion stabilization of a premixed gaseous mixture. An experimental work was carried out in a single-layer concept of a packed bed on a constant cross-sectional area tubular burner. Two types of materials, Alumina (Al2O3) and Zirconia (ZrO2), with different porosities, namely 0.36, 0.4, 0.44, and 0.46, were tested. The results showed that porosity has a significant effect on the position of the reaction zones. As porosity decreases, the reaction zone moves downstream of the packed bed. The excess air ratio does not affect the position of the reaction zone but has an impact on the temperature distribution inside the porous medium. The packed bed material affects the volume of the reaction zone and the temperature distribution inside the porous media, where Zirconia has a reaction zone volume higher than Alumina. The concentration of NOx was reduced with increasing porosity. Zirconia media exhibits a lower level of NOx emission compared to Alumina. For an excess air ratio of 1.6, the maximum NOx values were 22.5 and 17.5 ppm for Alumina and Zirconia, respectively.

Comparison of microwave assisted foam drying processes to improve the physicochemical properties and to reduce GHG values of the melon powder processes

AbstractIn this study, in the process of valorizing melon biomass into food powder at 360, 540, 720 and.900 W power values; Drying rate, moisture rate, effective moisture diffusion, SMER-SEC energy consumption and greenhouse gas emission (GHG) values of production processes were investigated. It was determined that the average drying rates of the samples varied between 0.2393–0.9376 g moisture/g dry matter.minute. According to microwave power values, the effective moisture diffusion values of the products were found to vary between 5.47 × 10–7-2.27 × 10–6 m2/s. It was determined that the average SMER values of the drying processes varied between 0.024–0.047 kg/kWh and SEC values varied between 21.12–40.93 kWh/kg. According to the drying processes, NOX, SO2 and CO2 values were calculated to vary between 0.210–1.106, 0.00–2.919 and 49.50–200.168 g, respectively. It was found that the most suitable microwave power in terms of drying kinetics, energy consumption and greenhouse gas values was 900 W.

Endotoxin-Induced Sepsis on Ceftriaxone-Treated Rats' Ventilatory Mechanics and Pharmacokinetics.

Sepsis can trigger acute respiratory distress syndrome (ARDS), which can lead to a series of physiological changes, modifying the effectiveness of therapy and culminating in death. For all experiments, male Wistar rats (200-250 g) were split into the following groups: control and sepsis-induced by endotoxin lipopolysaccharide (LPS); the control group received only intraperitoneal saline or saline + CEF while the treated groups received ceftriaxone (CEF) (100 mg/kg) IP; previously or not with sepsis induction by LPS (1 mg/kg) IP. We evaluated respiratory mechanics, and alveolar bronchial lavage was collected for nitrite and vascular endothelial growth factor (VEGF) quantification and cell evaluation. For pharmacokinetic evaluation, two groups received ceftriaxone, one already exposed to LPS. Respiratory mechanics shows a decrease in total airway resistance, dissipation of viscous energy, and elastance of lung tissues in all sepsis-induced groups compared to the control group. VEGF and NOx values were higher in sepsis animals compared to the control group, and ceftriaxone was able to reduce both parameters. The pharmacokinetic parameters for ceftriaxone, such as bioavailability, absorption, and terminal half-life, were smaller in the sepsis-induced group than in the control group since clearance was higher in septic animals. Despite the pharmacokinetic changes, ceftriaxone showed a reduction in resistance in the airways. In addition, CEF lowers nitrite levels in the lungs and acts on their adverse effects, reflecting pharmacological therapy of the disease.

Integrated optimization of dedicated engine and energy management strategy for the plug-in hybrid commercial vehicle at high altitude

To improve fuel efficiency and reduce pollutant emissions of plug-in hybrid commercial vehicles (PHCVs) at high altitude, an integrated optimization of dedicated engine of PHCV (DEP) and energy management strategy (EMS) is performed. Firstly, the physical model of DEP is established using experimental data. Its empirical model is developed through machine learning with samples generated by the physical model. Subsequently, a hybrid model-based successive approximation method is proposed to optimize various combinations of control parameters including fuel injection timing, rail pressure, VGT opening and EGR rate, aiming at reducing brake specific fuel consumption (BSFC) and NOx within the major working zone of DEP. This optimized DEP is then integrated into the PHCV model to collectively optimize EMS at this challenging altitude. Results demonstrate that this method considerably reduces optimization time without compromising model accuracy. Notably, at 4000 m altitude and under the CHTC-C driving cycle, overall BSFC reduces with a minimum of 194.27 g/(kW·h), most brake specific NOx values remain under 7.5 g/(kW·h), and optimal working range broadens. With integrated optimization, the DEP predominantly works in low-fuel consumption and low-emission zone. Consequently, the fuel economy of PHCV improves by 30.03 %, while NOx and CO2 emissions decrease by 35.88 % and 18.05 %, respectively.

Comparative study of combustion and thermal performance of a meso-scale combustor under co- and counter-rotating fuel and oxidizer swirling flows for micro power generators

Direct energy conversion systems, such as thermophotovoltaic and thermoelectric generators, have received increasing attention in micro power generation. Micro and meso-scale combustors are one of the most core components in these systems. So, developing combustion stabilization technologies for micro or meso-scale combustors is of great importance. In these systems, a hydrocarbon fuel with high energy density is burned in a micro or meso-scale combustor. Many studies have been conducted to explore various combustion stabilization techniques, but as a novelty, in this work, we study the combustion and thermal performance of a meso-scale micro power generator powered by a swirling fuel jet discharging into a co- or counter-rotating air coflow. To do so, we used 3D-printed axial swirlers with double annulus to form the swirling co- and counter-rotating fuel (methane) jet-air coflow configurations at various air and fuel flow rates. Blow-out limit, flame characteristics, combustor mean outer wall temperature, pollutant emissions, emitter efficiency, and normalized temperature standard deviation are investigated in this study. The results show that swirl addition enhances the blow-out limit significantly and co-rotating swirling flows generally enhances the flame blow-out limit when compared with the counter-rotating swirling flows mode at high fuel flow rates. Moreover, the combustor with co-rotating swirling flows has shorter lift-off height and longer flame length. The sensitivity of the flame lift-off height to an increment of the fuel mass flow rate is smaller in co-rotating than in counter-rotating swirling flows (more than 40%). Furthermore, it is observed that under the same operating conditions, co-rotating swirling flows exhibit lower values of CO and NOx in the flue gas and higher values of mean outer wall temperature, combustion efficiency, emitter efficiency, and normalized temperature standard deviation. The enhancement of the emitter efficiency by implementing co-swirl configuration is about 35%, 26%, and 8% for the methane flow rates of 0.050, 0.100, and 0.150slpm, respectively when compared with the counter-swirl mode. The results of this work can provide useful information to choose between co- and counter-rotating flows for combustors of combustion-based micro power generators.

Production of green hydrogen from sewage sludge / algae in agriculture diesel engine: Performance Evaluation

Alternative fuel opportunities can satisfy energy security and reduce carbon emissions. In this regard, the hydrogen fuel is derived from the source of environmental pollutants like sewage and algae wastewater through hydrothermal gasification technique using a KOH catalyst with varied gasification process parameters of duration and temperature of 6–30 min and 500-800 °C. The novelty of the work is to identify the optimum gasification process parameter for obtaining the maximum hydrogen yield using a KOH catalyst as an alternative fuel for agricultural engine applications. Influences of gasification processing time and temperature on H2 selectivity, Carbon gasification efficiency (CE), Lower heating value (LHV), Hydrogen yield potential (HYP), and gasification efficiency (GE) were studied. Its results showed that the gasifier operated at 800 °C for 30 min, offering maximum hydrogen yield (26 mol/kg) and gasification efficiency (58 %). The synthesized H2 was an alternative fuel blended with diesel fuel/TiO2 nanoparticles. It was experimentally studied using an internal combustion engine. Influences of H2 on engine performance, like brake-specific fuel consumption, brake thermal efficiency and emission performances, were measured and compared with diesel fuel. The results showed that DH20T has the least (420g/kWh) brake-specific fuel consumption (BSFC) and superior brake thermal efficiency of about 25.2 %. The emission results revealed that the DH20T blend showed the NOX value increased by almost 10.97 % compared to diesel fuel, whereas the CO, UHC, and smoke values reduced by roughly 31.25, 28.34, and 42.35 %. The optimum fuel blend (DH20T) result is recommended for agricultural engine applications.

What controls ozone sensitivity in the upper tropical troposphere?

Abstract. Ozone is an important contributor to the radiative energy budget of the upper troposphere (UT). Therefore, observing and understanding the processes contributing to ozone production are important for monitoring the progression of climate change. Nitrogen oxides (NOx ≡ NO + NO2) and volatile organic compounds (VOCs) are two main tropospheric precursors to ozone formation. Depending on their abundances, ozone production can be sensitive to changes in either of these two precursors. Here, we focus on processes contributing to ozone chemistry in the upper tropical troposphere between 30∘ S and 30∘ N latitude, where changes in ozone have a relatively large impact on anthropogenic radiative forcing. Based on modeled trace gas mixing ratios and meteorological parameters simulated by the ECHAM5/MESSy2 Atmospheric Chemistry (EMAC) general circulation model, we analyze a variety of commonly applied metrics including ozone production rates (P(O3)), the formaldehyde (HCHO) to NO2 ratio and the share of methyl peroxy radicals (CH3O2) forming HCHO (α(CH3O2)) for their ability to describe the chemical regime. We show that the distribution of trace gases in the tropical UT is strongly influenced by the varying locations of deep convection throughout the year, and we observe peak values for NOx and P(O3) over the continental areas of South America and Africa where lightning is frequent. We find that P(O3) and its response to NO is unsuitable for determining the dominant regime in the upper troposphere. Instead, α(CH3O2) and the HCHO/NO2 ratio in combination with ambient NO levels perform well as metrics to indicate whether NOx or VOC sensitivity is prevalent. We show that effectively only the knowledge of the availability of NO and HO2 is required to adequately represent O3 precursors and its sensitivity towards them. A sensitivity study with halving, doubling and excluding lightning NOx demonstrates that lightning and its distribution in the tropics are the major determinants of the chemical regimes and ozone formation in the upper tropical troposphere.

Summer Ozone Mechanism and Control Strategy in Beijing-Tianjin-Hebei Region Using Brute-Force Method

In recent years, the ozone (O3) volume fraction in the Beijing-Tianjin-Hebei Region in summer have remained high, light to moderate pollution occurs frequently, and research on related response mechanisms is urgently needed. This study applied the WRF-Chem model to simulate the change in ozone volume fraction in this region by setting 13 precursor emission scenarios in a representative month in the summer of 2018. The results revealed that VOC-sensitivity and no-sensitivity regimes commonly occurred in the Beijing-Tianjin-Hebei Region in July, and the VOC-sensitivity regimes were mainly accumulated in the central Beijing-Tianjin-Hebei Region, with a north-to-south zonal distribution and an area share of 15.60%-26.59%. The relative response intensity (RRI) of O3 volume fraction to precursor emissions in urban areas had large spatial variability, with RRI_VOC and RRI_NOx in the ranges of 0.03-0.16 and -0.40-0.03, respectively. The higher the latitude of urban areas, the more dramatic were the RRI values, indicating a more significant regional transport influence. The lower RRI_NOx values in urban areas with high intensity of precursor emissions implied a negative dependence of RRI_NOx on local NO2 concentrations; however, RRI_VOC was not significantly correlated with NO2levels and was more dependent on the relative abundance of precursors (VOCs:NOx). The ratio of RRI_VOC to RRI_NOx showed negative values in majority of the cities; therefore, collaborative VOCs emission reduction is necessary to suppress the deterioration of O3 volume fraction. The absolute value of this ratio was much lower in cities with high industrialization and urbanization than in ordinary small and medium-sized cities, implying that the demand for collaborative VOCs emission reduction in these cities will be higher. However, even under 50% reduction of precursors, the improvement in O3 volume fraction was limited in regional cities, and the combined prevention in neighboring cities remains important.

Investigation and impact assessment of soybean biodiesel, methyl oleate, and diesel blends on CRDI performance and emissions

In the present study, a binary biofuel blend was prepared by blending soy methyl ester (SME100) and methyl oleate (MO) SME50-M50 with diesel. The physiochemical properties of blended fuels were also investigated. The performance and emissions characteristics of all fuel blends were estimated using a common-rail direct injection (CRDI) engine. The outcomes demonstrate a reduction in brake-specific fuel consumption (BSFC) when enriched biodiesel is used in comparison to SME100, nonetheless by the virtue of viscosity and heating value there is an increase in the BSFC value when compared to diesel. The average BSFC values were obtained as 5.3% (E25), 10.6% (E50), 17.5% (E75), 30% (SME100) and 14.9% (SME50-M50) higher than that of diesel. BTE was found to be highest for E25 and lowest for SME100 among all the blends. NOx emissions with blended biodiesel were slightly higher than diesel on account of MO being unsaturated, resulting in shorter ignition delay. The average NOx values obtained were higher than that of diesel and the corresponding values are 2.91% (E25), 4.1% (E50), 5.8% (E75), 8.3% (SME100) and 15.8% (SME50-M50). As a result of the increased oxygen content of the fuel, the concentrations of UHC and CO depreciated with the rise in concentration of soy methyl ester and MO (SME50-M50). Currently, Euro 6.2, which is the most recent emission regulation, uses 10% biofuel (B10); however, the results of this study establishes that E25, as an alternate fuel, complies with the contemporary engines without requiring any engine modifications.

Pollution characteristics, sources, and photochemical roles of ambient carbonyl compounds in summer of Beijing, China

Ambient carbonyls are important precursors of radicals and ground-level ozone (O3). In this study, sources, precursors, and impacts on radicals and O3 of carbonyls were investigated based on online observations of volatile organic compounds (VOCs) at an urban site in Beijing during June 2021. Carbonyls accounted for 36% and 42% of mixing ratios and OH reactivity for total measured VOCs, respectively. Formaldehyde was the most abundant carbonyl, with the mean level of 4.13 ± 2.28 ppb. Source apportionment results based on the multi linear regression (MLR) method suggested that secondary production contributed 41%, 25%, 36%, and 30% of formaldehyde, acetaldehyde, propanal, and acetone, respectively. Key precursors of carbonyls were then identified based on the calculation of their production rates. It was found that alkenes contributed 59%–80% of aldehydes production. Impacts of carbonyls on HOx radicals (OH and HO2) and O3 production were explored using a box model based on observations (OBM). Photolysis of HONO, formaldehyde, and O3 were the dominant primary sources of HOx radicals during daytime of O3 pollution days, with average relative contributions of 52%, 28%, and 19% to the total primary production rate of HOx, respectively. Aldehydes accounted for 32% (20% from formaldehyde) of average HOx removal rates. The relative incremental reactivity (RIR) values of NOx determined by the OBM were negative, suggesting that the O3–VOCs-NOx sensitivity was in the VOCs-limited regime. Using the observed concentrations of carbonyls as constraints of OBM, the absolute values of RIR for NOx tended to increase but those for anthropogenic VOCs tended to decrease. Formaldehyde showed the largest RIR value for anthropogenic VOCs during O3 pollution days. These findings indicated the important impacts of carbonyls on O3 production and O3–VOCs-NOx sensitivity.