Reduction Of Nitrogen Oxide Emissions Research Articles

Elevated Formation of Particulate Nitrate From N2O5 Hydrolysis in the Yangtze River Delta Region From 2011 to 2019

AbstractAerosol nitrate has become the most abundant compound during aerosol pollution in eastern China. The Chinese government implemented a stringent policy during 2013–2017 to tackle aerosol pollution. However, the response of nitrate to nitrogen oxides (NOx) reduction is unclear owing to the limitation of long‐term measurement. Here, we performed a 9‐year continuous measurement of aerosol compositions in Shanghai and confirmed a decrease in most species except nitrate. The contribution of nitrate to fine particulate matter (PM2.5) increased significantly, reaching up to 35% in pollution episodes after 2017. This is in contrast to the evident reduction in NOx emissions. We found that the elevated dinitrogen pentoxide (N2O5) hydrolysis is responsible for the observed nitrate trend. Increased ozone and decreased nitrogen dioxide (NO) facilitated the formation of N2O5, and increased nitrate proportion promoted the uptake of N2O5 and eventually enhanced the conversion efficiency of NO2 to nitrate. Our results highlight the importance of synergic control of aerosol and ozone pollution.

SST-Based Grid Reinforcement for Electromobility Integration in Distribution Grids

Electric Vehicles (EVs) are gaining acceptance due to the advantages they offer in the reduction of nitrogen oxide and carbon dioxide emissions. The need for emission reduction and the potential of EVs for these reductions is reflected in the current sustainable mobility policies of the EU as well as the German government. Increasing the penetration of EVs in the grid requires an expansion of EV charging infrastructure, which in turn requires either grid reinforcement or solutions for more efficient use of existing infrastructure to avoid or postpone grid reinforcement. Distribution transformers face increased loading due to EV charging and need to be protected from overloading during peak load periods to ensure continuity of service. Therefore, transformers are one of the components that are upgraded or replaced as a part of grid reinforcement. In this paper, we propose the connection of a Solid-State Transformers (SST) between two buses operating at the same-voltage level as an alternative to replacement or upgrading of conventional transformer as well as to prevent their overloading. We analyse how the proposed topology can be useful to reduce the impact of EV integration on the overloading of distribution transformers and node voltage violations in the distribution grid.

Investigation on a high gravity device for reduction of NOx emission from marine diesel engines.

High gravity technology, as a process intensification technology, has demonstrated thegreat advantages in the field of gas purification on account of its excellent mass transfer efficiency and energy-efficient, but it is rarely applied in the field of nitrogen oxides (NOx) purification of marine diesel engine exhaust. In this paper, a high-gravity bowl-shaped-disk rotating bed (HBRB) without catalytic was designed for diesel exhaust after-treatment. A diesel oxidation catalyst (DOC) was installed in the front of the HBRBto regenerate more nitrogen dioxide (NO2) easily reduced by urea. A bench test of a 6-cylinder marine diesel engine with the HBRB was carried out. The effects of the HBRB speeds, urea concentrations, and engine operating conditions on NOx purification efficiency in engine exhaust were experimentally investigated. The experimental result indicates that the maximum NOx removal efficiency of the HBRB can reach 69.1%. The improvement of the NOx removal efficiency is not obvious at the HBRB speed of over 1500 r/min. The pre-oxidation degree of nitric oxide (NO) and urea concentration largely affect the NOx removal efficiency. The HBRB has great potential in marine diesel engine exhaust denitration.

Numerical Study on the Effects of Pilot Diesel Quantity Coupling EGR in a High Pressure Direct Injected Natural Gas Engine

ABSTRACT The natural gas high pressure direct injection (HPDI) engines have attracted attention due to their high combustion stability and thermal efficiency comparable to diesel. However, the nitrogen oxides (NOx) emissions from HPDI engines remain high. In this study, the coupling effects of the exhaust gas recirculation (EGR) and pilot diesel quantity were investigated on a four stroke HPDI engine by simulation. Three pilot diesel quantities and four EGR rates were involved, and the combustion and emission characteristics of the engine were compared and discussed. The results show that with increasing EGR rate, the maximum combustion pressure (Pmax) decreases with different pilot diesel quantity, and the crank angle corresponding to the maximum combustion pressure (CPmax), the crank angle corresponding to the maximum heat release rate (CHRRmax) and the crank angle corresponding to the 50% cumulative heat release (CA50) are all pushed back. NOx emissions decrease gradually with the increase of EGR rate, but soot, unburned hydrocarbon (HC) and carbon monoxide (CO) emissions and methane escape all increase and the indicated thermal efficiency (ITE) decreases. The traditional “trade-off” relationship between NOx and soot emissions still exists on HPDI engine and becomes more obvious as the quantity of pilot diesel increases. NOx and soot emissions can be well balanced at moderate EGR rate. Increasing the quantity of pilot diesel can partially offset the hysteresis effect of EGR on the combustion process. And when the EGR rate is controlled within 30%, increasing the quantity of pilot diesel is beneficial to reduce HC and CO emissions and methane escape. By increasing the quantity of pilot diesel coupled with a moderate level of EGR rate, it is possible to significantly reduce NOx emissions while maintaining the ITE, methane escape and unburned diesel, HC and CO emissions at the same level as without EGR. But soot emissions will increase substantially.

An experimental study on biodiesel production and impact of EGR in a CRDI diesel engine propelled with leather industry waste fat biodiesel

The purpose of the predominant endeavor is the way of through an experiment aspect for the reticular effect of exhaust gas recirculation (EGR) on combustion, performance, emissions besides energy characteristic of common rail direct injection (CRDI) engine fuelled with leather industry waste fat biodiesel and diesel blends. Biodiesel was converted by the transesterification process from the raw fat oil extracted with leather waste fat feedstock. This work takes advantage of blends of both like B10, B20, B30 along with engines that were run with various EGR rates (5%, 10%, and 15%) to evaluate engine outcome parameters. The maximum in-cylinder pressure was examined with the blend B20 with EGR 5% rate about 6.65% higher than pure diesel fuel. The high heat release rate (HRR) was ascertained with the blend B30 with EGR 10% rate about 23.81% higher than neat diesel fuel. The brake thermal efficiency (BTE) for the blend B10 with EGR 5% rate is higher than other test conditions but 4.2% let down associated with simple diesel fuel. The nitrogen oxides (NOx) were lesser than the clean diesel fuel at all test fuels, the highest NOx emission reduction was achieved in blend B30 with EGR 15% rate of about 87.59% than neat diesel fuel operation. The smoke opacity increased by raising the EGR level, the combination B30 with EGR 5% rate displayed low smoke opacity about 64.5% lower than neat diesel fuel. The hydrocarbon (HC) emission was lower than neat diesel at a low EGR rate, the blend B10 with EGR 5% rate displayed the lowest HC emission about 85.71% decreased then neat diesel operation. The carbon monoxide (CO) emission displayed lower than neat diesel at low EGR rate, the blend B10 with EGR 5% rate displayed the lowest CO emission about 50% than neat diesel. As of energy analysis, it was noted that the heat equivalent to brake power and heat lost to engine cooling water is higher in diesel fuel than biodiesel blends and the heat lost to exhaust gases and heat unaccounted loss were lower in diesel than biodiesel blend. Finally, the TOPSIS optimization study was carried out for finding the optimum input conditions which could result in improved combustion, performance, and reduced emissions. The B30% blend with EGR 15% at full load achieved 1st rank with 0.849 relative closeness value. So, this operating condition was projected as the best prospect for the application of a CRDI diesel engine.

Response of Summer Ozone to Precursor Emission Controls in the Yangtze River Delta Region

Surface ozone concentrations in the Yangtze River Delta (YRD) region in China have shown a significant increase with the dramatic reduction of anthropogenic nitrogen oxide (NOx) emissions since 2013. As the nonlinearity between ozone and its precursors (i.e., NOx and volatile organic compounds (VOCs)) varies greatly in time and space, we quantify the monthly changes of surface ozone with the co-control of NOx and VOCs anthropogenic emissions in the YRD region from May to October 2017 by using the GEOS-Chem model. Model evaluations show that the GEOS-Chem model exhibits good performance to simulate ozone concentrations in the region. For May–September 2017, most areas in the YRD region are under a transitional regime, but the regions with high anthropogenic emissions including Shanghai and southern Jiangsu are under a VOCs-limited regime. In October, basically, the entire YRD region is under a VOCs-limited regime. Generally, reducing VOCs emissions only is the most effective method for ozone control in the YRD. Nanjing is under a VOCs-limited regime in May, June, September, and October, and under a transition regime from July to August. The VOCs/NOx emission reduction ratio of 1:1 is effective for ozone mitigation in Nanjing (Shanghai) in May, June, and September (for May–September); the corresponding ratio is 2:1 in October. Hangzhou belongs to a transitional regime from May to September and is under a VOCs-limited regime in October. Reducing NOx emissions only would control ozone in Hangzhou from May to September, while the VOCs/NOx emission reduction ratio of 1:1 is favorable to reduce ozone concentrations in October. During high pollution days on July 22–27, 2017, the three cities belong to a transitional regime and reducing NOx emissions only is generally the most effective way to control high ozone pollution. GEOS-Chem tagged ozone simulation shows that ozone problem in the region is caused by the joint effect of local generation and regional and long-distance transport. Local generation (19.0–50.7%) is generally the largest contributor to monthly mean ozone concentrations in Jiangsu and Shanghai, Zhejiang, and central eastern China; the contribution of ozone from regions outside the YRD is larger in spring and autumn (42–76.0%) than in summer (23.3–51.8%). Since the annual VOCs (NOx) anthropogenic emissions in the region have shown a decline by 8% (11%) from 2017 to 2020 and would continue to reduce by 10% (10%) by 2025 according to the Chinese government requirement, the growth of ozone would be stopped in the YRD for May–September but likely to continue in October. Our study thus would provide a scientific base for guiding the effective emission reduction strategies to control ozone pollution in the YRD region.

Coupling effect of Fe-based catalyst on Nitrogen oxides control in the process of nitrogen reduction and combustion denitration of long flame coal pyrolysis

ABSTRACT Civil dispersed coal combustion has become an important source of Nitrogen oxides (NOx), which has caused serious pollution to the ecological environment. In order to control NOx emission in the combustion process of civil coal, coal-based solid clean fuel should be used instead of dispersed combustion of coal, so as to achieve the purpose of reducing NOx emission. The pyrolysis and combustion tests of different iron additives loaded coals were performed. The raw and pyrolytic chars were prepared and characterized by X-ray photoelectron spectroscopy (XPS), nitrogen adsorption, scanning electron microscope (SEM) and X-ray diffraction (XRD). The results indicate that iron additives introduced into raw coal in one step have coupling effect on NOx emission control during pyrolysis and combustion. The addition of iron can lead to more Fe2O3, Fe3O4 and α-Fe in coke and promote coke cracking. Supporting iron catalysts could make coke structure more porous, which increases the contact area of gas. These all make the conversion of N2 increase from 16.71% to 29.64% during pyrolysis. The existence of iron catalyst can also promote the proportion of pyridinic N (N-6) and quaternary nitrogen (N-Q) relatively increase. At the same time, the existence of iron catalyst is beneficial to catalytic reduction of NOx by C and CO. The emissions of NOx during combustion can be reduced by 34.01%. The iron catalyst introduced in one step has a coupling effect on NOx control in coal pyrolysis-combustion process, which realizes a two-step nitrogen reduction effect in combustion. It provides theoretical basis for ultra-low NOx emission in clean fuel combustion.

Seasonality and reduced nitric oxide titration dominated ozone increase during COVID-19 lockdown in eastern China

With improving PM2.5 air quality, the tropospheric ozone (O3) has become the top issue of China’s air pollution control. Here, we combine comprehensive observational data analysis with models to unveil the contributions of different processes and precursors to the change of O3 during COVID-19 lockdown in the Yangtze River Delta (YRD), one of the most urbanized megacity regions of eastern China. Despite a 44 to 47% reduction in volatile organic compounds (VOCs) and nitrogen oxides (NOx) emissions, maximum daily 8-h average (MDA8) ozone concentrations increase from 28 ppbv in pre-lockdown to 43 ppbv in lockdown period. We reproduce this transition with the WRF-Chem model, which shows that ~80% of the increase in MDA8 is due to meteorological factors (seasonal variation and radiation), and ~20% is due to emission reduction. We find that daytime photochemistry does not lead to an increase but rather a decrease of daytime O3 production during the lockdown. However, the reduced O3 production is overwhelmed by the weakened nitric oxide (NO) titration resulting in a net increase of O3 concentration. Although the emission reduction increases O3 concentration, it leads to a decrease in the Ox (O3 + NO2) concentration, suggesting reduced atmospheric oxidation capacity on a regional scale. The dominant effect of NO titration demonstrates the importance of prioritizing VOCs reduction, especially from solvent usage and the petrochemical industry with high emission ratios of VOCs/NOx.

Effects of diesel–Calophylluminophyllum biodiesel–propyl alcohol blends on performance, emissions, and combustion of diesel engine

AbstractThe present experimental work aims to study the effects of higher alcohol with diesel–Calophyllum inophyllum biodiesel on diesel engine characteristics. The higher alcohol used for the investigation was propyl alcohol. Three samples were prepared with a diesel–biodiesel blend (B20) at 6%, 12%, and 18% concentration by volume of propyl alcohol (B20P6, B20P12, and B20P18). Tests were carried out on a single‐cylinder, four‐stroke diesel engine with varying loads and compression ratio. At higher compression ratios, the modified blends of propyl alcohol reported better efficiencies compared to diesel. Blend B20P12 has a 1.6% higher average brake thermal efficiency than diesel. For all blends, the brake specific fuel consumptions (BSFCs) were found to be increased in comparison to diesel. The blends B20P6 and B20P12 reported 12.8% and 13.8% higher average BSFCs than those of diesel. The blends B20P6 and B20P12 reported 15.7% and 29.5% less carbon monoxide emissions than diesel, respectively. A decrease of up to 4.6% in hydrocarbon emissions was also reported with propyl alcohol blends. Along with a reduction in nitrogen oxide emissions, propyl alcohol blends also reported lower peak cylinder pressure and a lower heat release rate compared to diesel. At a higher compression ratio, increased engine knock was observed with a higher amount of propyl alcohol. The experimental evaluation concluded that a 12% concentration by volume of propyl alcohol is the optimum value of the additive in the diesel–C. inophyllum biodiesel blend.

Emissions of nitrogen dioxide in the northeast U.S. during the 2020 COVID-19 lockdown

We have quantified the emissions of Nitrogen dioxide (NO2) in the Northeast megalopolis of the United States during the COVID-19 lockdown. The measurement of NO2 emission serves as the indicator for the emission of the group of nitrogen oxides (NOx). Approximately 56% of NO2 emissions in the US are from mobile sources, and the remainder is from stationary sources. Since 2002, clean air regulations have resulted in approximately 5% compound annual reduction of NOx emissions in the US (8.2% in the study area). Therefore, when studying the impact of sporadic events like an epidemic on emissions, it is necessary to account for the persistent reduction of emissions due to policy driven emission reduction measures. Using spaceborne sensors, ground monitors, National Emission Inventory data, and the US Motor Vehicle Emission Simulator, we quantified the reduction of total NOx emissions, distinguishing stationary sources from on-road mobile sources (trucks and automobiles). When considering total NOx emissions (stationary and mobile combined), we find that the pandemic restrictions resulted in 3.4% reduction of total NOx emissions in the study area in 2020. This is compared to (and in addition to) the expected 8.2% policy driven reduction of NOx emissions in 2020. This somewhat low reduction of emissions is because most stationary sources (factories, power plants, etc.) were operational during the pandemic. Truck traffic, a significant source of mobile emissions, also did not decline significantly (average 4.8% monthly truck traffic reduction in the study area between March and August 2020), as they were delivering goods during the lockdown. On the other hand, automobile traffic, responsible for 24% of total NOx emissions, dropped significantly, 52% in April, returning to near normal after 5 months. While the reduction of automobile traffic was significant, especially in the early months of the pandemic, its effect on emissions was relatively insignificant.

Experimental investigation of the achieving methods and the working characteristics of a near-zero NOx emission turbocharged direct-injection hydrogen engine

Hydrogen, as clean and renewable energy, is regarded as a promising fuel applied to internal combustion engines. The relatively high level of Nitrogen oxides (NOx) emissions is an important limiting factor to realize the application of hydrogen engine. Previous researches on the NOx emissions reduction were based on the naturally-aspired or supercharger hydrogen engine with medium load and efficiency. In this study, a 2.0 L turbocharged direct-injection engine is used to find the methods of achieving near-zero NOx emission (without any posttreatment equipment) with large power and high thermal efficiency. The effects of the coefficient of excess air (λ), the timing of the start of injection (SOI), and injection pressure on NOx emissions are investigated detailly with the engine speed range of 1000 rpm to 4000 rpm. The target of the NOx emission is set below 20 ppm according to the emission standards. A leaner combustion (λ = 3.29@ 3000 rpm) compared to λ = 2.62@ 2000 rpm is required to achieve near-zero emission. The utilization of the turbocharger and improved injection pressure increase the power and efficiency simultaneously. The maximum brake mean effective pressure (BMEP) can reach 13.3 bar@3000 rpm, and the maximum brake thermal efficiency (BTE) reaches 40.4% @2000 rpm with near-zero NOx emission. Various techniques, such as turbocharging, exhaust gas recirculation, and increased compression ratios, are also compared to qualify the trade-off relationships among the power, efficiency, and emission of the direct-injection hydrogen engine. These conclusions can be used to broaden the working boundary and optimize the fuel economy of turbocharged direct-injection hydrogen engines with near-zero NOx emission.

Influence of Exhaust Gas Recirculation on Performance, Combustion, and Emission Characteristics of a Common Rail Direct Injection Diesel Engine Fueled by Diesel/Higher Alcohol Blends

Abstract Emission and combustion parameters of common rail direct injection combustion engine with different proportions of exhaust gas recirculation (EGR) rate and long-carbon-chain alcohol blends on performance are the main motive of this research. To lessen the dependency on diesel fuel and reduce harmful emissions, 1-hexanol is used, as it has better fuel properties than small-carbon-chain alcohol, and it can be blended with diesel. In common rail direct injection combustion engine, research was conducted, in which fuel blends (1-hexanol-diesel) were variant, i.e., (10%, 20%, 30%) by volume whereas engine speed was fixed at 1500 rpm by varying the load at 25% step from 25 to 100%. Blends were examined with various exhaust gas recirculation rates (10 and 20%) to see what impact they have on engine properties. It was observed that the higher the proportion of 1-Hexanol, the lower the engine performance. The research revealed that for the blend D70H30, around 8.24% rise in brake specific fuel consumption, slight rise in hydrocarbon, 2.80% reduction in brake thermal efficiency (BTE), and 16.70% reduction in nitrogen oxides (NOx) emission. With 1-hexanol-diesel blends, the engine is noted to function effortlessly, so as a substitute to the diesel upto 30% of the 1-hexanol can be used while increasing the total cost of implementation. Increase in hexanol and EGR percentage shown negative impact on the brake thermal efficiency, HC and CO emission however, NOx and CO2 emissions were found to be decreased.

Wintertime haze and ozone at Dinosaur National Monument

ABSTRACT Dinosaur National Monument (DINO) is located near the northeastern edge of the Uinta Basin and often experiences elevated levels of wintertime ground-level ozone. Previous studies have shown that high ozone mixing ratios in the Uinta Basin are driven by elevated levels of volatile organic compounds (VOCs) and nitrogen oxides (NOx) from regional oil and gas development coupled with temperature inversions and enhanced photochemistry from persistent snow cover. Here, we show that persistent snow cover and temperature inversions, along with abundant ammonia, also lead to wintertime haze in this region. A study was conducted at DINO from November 2018 through May 2020 where ozone, speciated fine and coarse aerosols, inorganic gases, and VOCs were measured. Three National Ambient Air Quality Standards (NAAQS) ozone exceedances were observed in the first winter, and no exceedances were observed in the second winter. In contrast, elevated levels of particulate matter were observed both winters, with 24-h averaged particle light extinction exceeding 100 Mm−1. These haze events were dominated by ammonium nitrate, and particulate organics were highly correlated with ammonium nitrate. Ammonium nitrate formation was limited by nitric acid in winter. As such, reductions in regional NOx emissions should reduce haze levels and improve visibility at DINO in winter. Long-term measurements of particulate matter from nearby Vernal, Utah, suggest that visibility impairment is a persistent issue in the Uinta Basin in winter. From April through October 2019, relatively clean conditions occurred, with average particle extinction of ~10 Mm−1. During this period, ammonium nitrate concentrations were lower by more than an order of magnitude, and contributions from coarse mass and soil to haze levels increased. VOC markers indicated that the high levels of observed pollutants in winter were likely from local sources related to oil and gas extraction activities. Implications: Elevated ground-level ozone and haze levels were observed at Dinosaur National Monument in winter. Haze episodes were dominated by ammonium nitrate, with 24-h averaged particle light extinction exceeding 100 Mm−1, reducing visual range near the surface to ~35 km. Despite elevated ammonium nitrate concentrations, additional gas-phase ammonia was available, such that any increase in NOx emissions in the region is likely to lead to even greater haze levels.

Selective non-catalytic reduction of nitrogen oxides in the production of iron ore pellets

Purpose. Using mathematical modeling, to assess the feasibility of introducing a Selective Non-Catalytic Reduction (SNCR) system as a measure to reduce nitrogen oxide emissions from the production of iron ore pellets. To determine the peculiarities of using ammonia solution and urea solution as reagents for the SNCR process, the influence of the injection of these reagents on the temperature regime during iron pellet production, as well as assess the expected efficiency of the SNCR method for purification of exhaust gases from nitrogen oxides. Methodology. The research results have been obtained using CFD-modeling in the ANSYS Fluent software package. To model this process, a computational domain is constructed, which corresponds in size to the preheating zone (PRE zone) of the actual iron pellet production plant. Two series of calculations are performed for this domain: the first, without adding a reagent, and the second, with a urea solution as a reagent for the SNCR system. Findings. For the first series of calculations, the temperature field and the pressure field in the computational domain is obtained. Experimental research makes it possible to assert that the physical conditions of the mathematical model are close to those at a real plant for the production of pellets. In the second series of calculations, the temperature field in the computational domain is obtained and the influence of the reagent injection of the SNCR system is determined, namely, the temperature decrease in the PRE zone of the pellet production plant by 1025 . The expected efficiency of reduction of nitrogen oxides using a 50% urea solution is about 60%. Originality. It has been revealed that the process of urea solution evaporation is intense, which accelerates the beginning of urea decomposition and, accordingly, the reduction reaction of nitrogen oxides. The temperature drop in the zone of moisture evaporation does not exceed 1025 C. The reagent injection (50% urea solution) with a consumption of 219 kg/h does not significantly affect the temperature regime in the PRE zone. Modeling the chemical reactions of the SNCR process with the injection of 50% urea solution droplets through lances into the PRE zone chamber indicates a 60% reduction in nitrogen oxide emissions. Practical value. The introduction of the SNCR system at pellet production plant can reduce nitrogen oxide emissions, which will have a positive impact on the environmental situation in metallurgical regions.

Comparison of emissions and engine performance of safflower and commercial biodiesels

Safflower oilseed needs to be studied in detail in relation to the production of biodiesel and its application in engines to be an alternative to commercial biodiesel used around the world. The aim of this study is to compare safflower biodiesel with commercial biodiesel in terms of emissions and performance of an engine using blends biodiesel (B11, B15, B30, and B100). Commercial biodiesel consists of soybean oil and fat. The tests were performed on a single-cylinder, four-stroke, naturally aspirated, and direct-injection diesel engine at four engine loads with a constant engine speed of 3000 rpm. The comparison shows that safflower biodiesel has relatively closer fuel properties to commercial biodiesel than those of diesel oil. The engine power was less affected by increasing engine loads and increasing safflower biodiesel blends compared to commercial biodiesel. Safflower B11 reduced the specific consumption by 2% in relation to diesel (D100) at a load of 3000 W. Safflower biodiesel B11 showed lower carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxide (NOx), and exhaust gas temperature (EGT) compared to commercial biodiesel at high engine loads. The use of safflower biodiesel and commercial biodiesel blend B11 reduced NOx emissions by 15% at a high load of 3000 W. Therefore, safflower biodiesel is a promising alternative to diesel, although it has a higher production cost.

Coupling control of superheat and nitrogen oxides for gas engine heat pump

Gas engine heat pump (GEHP) is gradually developing due to the high energy efficiency. However, the gas engine is easily disturbed by load fluctuation, which affects the stability of GEHP operation and causes higher nitrogen oxides (NOx) emission concentrations. Therefore, an efficient control method is necessary to ensure system stability, improve energy efficiency and reduce NOx emissions. In this paper, a coupling control strategy of superheat and NOx is proposed. The results show that the superheat can maintain stability with the small overshoot and adjustment time of less than 400 s when the engine speed changes. When the superheat setting value changed continuously, the superheat overshoot and error are less than 0.5 °C and the adjustment time is about 100 s. Meanwhile, the system outlet temperature is stable, the overshoot is less than 1 °C. The amplitude variation of the refrigerating capacity is similar to the amplitude variation of the superheat. The variation range of total heat capacity is greater than that of refrigerating capacity. In addition, the performance and emission of the GEHP are respectively studied when the superheat is 4 °C and 7 °C, at the optimum excess air coefficient. The NOx emissions are always below 100 ppm, but the primary energy ratio (PER) is higher under the superheat of 4 °C. Therefore, the proposed coupling control strategy can achieve good stability, excellent performance and emission characteristics.

Influence of hexanol/hydrogen additives with diesel fuel from CRDI diesel engine with exhaust gas recirculation technique: A special focus on performance, combustion, gaseous and emission species

Emission and combustion parameters of common rail direct injection combustion engine with different proportions of exhaust gas recirculation rate and 1-hexanol blends with hydrogen on performance are the main motive of this research. To lessen the dependency on diesel fuel and reduce harmful emissions, 1-hexanol is used, as it has better fuel properties than small-carbon-chain alcohol, and it can be blended with diesel. In common rail direct injection combustion engine, a research was conducted, in which fuel blends (1-hexanol-diesel) were variant, i.e., (10%, 20%, 30%) by volume whereas engine speed was fixed at 1500 rpm by varying the load at 25% step from 25 to 100%. Blends were examined with various exhaust gas recirculation rates (10% and 20%) to see what impact they have on engine properties. It was observed that the higher the proportion of 1-Hexanol, the lower the engine performance. The research revealed that for the blend D70H30/H2, around 8.24% rise in brake specific fuel consumption, slight rise in hydrocarbon, 2.80% reduction in brake thermal efficiency, and 16.70% reduction in nitrogen oxides (NOx) emission. With 1-hexanol-diesel-hydrogen blends, the engine is noted to function effortlessly, so as a substitute to the diesel up to 30% of the 1-hexanol can be used while increasing the total cost of implementation.

Assessment of Sectoral NO x Emission Reductions During COVID‐19 Lockdown Using Combined Satellite and Surface Observations and Source‐Oriented Model Simulations

Large emission reductions of anthropogenic nitrogen oxides (NOx) due to the coronavirus disease 2019 (COVID-19) lockdown policies in China have been extensively reported since the outbreak, while assessments of sectoral emission changes during that period are still limited. In this study, a source-oriented community multiscale air quality (CMAQ) model was applied to quantify NO2 concentrations from major emission sectors. A new optimization approach was employed to obtain the sectorial emission reductions using satellite and ground-level observations as constraints. The optimized emissions significantly improved the model performance of NO2 during the lockdown period. February NOx emission changes varied with regions and sectors, with relatively larger reductions in transportation (286.6 kt) and industrial sources (260.1 kt). The maximum amount of NOx emission reduction occurred in the North China Plain (230.6 kt). Our work presents a quick and reliable technique for assessing sector-specific emission changes due to short-term emission control policies.

Spectral project - application of FAST-OAD code to the conceptual design of a hydrogen fuelled commercial aircraft

With the increase in the air traffic, reducing the aviation environmental impact is the key challenge of the community. This has called for more research in the area of using alternative fuels which will reduce the greenhouse gas emissions and which can provide similar or better environmental performance. This work presents a preliminary design methodology of a mid-range single aisle commercial aircraft using Hydrogen as fuel which is stored in an integrated tank in the fuselage. The iterative design process was achieved by using overall aircraft design approach through the FAST-OAD open-source software.This study describes the models used for a first approximation of structural and insulation weight of liquid Hydrogen (LH2) tank and fuel boil off computations. It then presents the impacts of an LH2 storage system on the overall aircraft design with an emphasis on the centre of gravity (CG) travel and the additional fuselage length necessary to accommodate the LH2 tank. An additional parametric study has also been carried out to understand the effect of some design parameters on overall design. Finally, an environmental study has been conducted to evaluate the direct emissions of this aircraft in operation. The only emissions that result from the combustion of hydrogen are nitrogen oxides (NOx) which were evaluated using the Boeing Fuel Flow Method (BFFM2) and water vapor (H2O) which was evaluated based on the fuel burned. As a result of this study significant reduction in NOx and CO2 emissions as compared to existing design are envisaged, thus showing the promising potential of Hydrogen fuelled aircraft.

Detailed Analysis of the Effects of Biodiesel Fraction Increase on the Combustion Stability and Characteristics of a Reactivity-Controlled Compression Ignition Diesel-Biodiesel/Natural Gas Engine

A single-cylinder marine diesel engine was modified to be operated in reactivity controlled compression ignition (RCCI) combustion mode. The engine fueling system was upgraded to a common rail fuel injection system. Natural gas (NG) was used as port fuel injection, and a diesel/sunflower methyl ester biodiesel mixture was used for direct fuel injection. The fraction of biodiesel in the direct fuel injection was changed from 0% (B0; 0% biodiesel and 100% diesel) to 5% (B5) and 20% (B20) while keeping the total energy input into the engine constant. The objective was to understand the impacts of the increased biodiesel fraction on the combustion characteristics and stability, emissions, and knocking/misfiring behavior, keeping all other influential parameters constant. The results showed that nitrogen oxides (NOx) emissions of B5 and B20 without the need for any after-treatment devices were lower than the NOx emission limit of the Euro VI stationary engine regulation. B5 and B20 NOx emissions decreased by more than 70% compared to the baseline. Significantly more unburned hydrocarbons (UHCs) and carbon monoxide (CO) emissions were produced when biodiesel was used in the direct fuel injection (DFI). The results also showed that using B5 and B20 instead of B0 led to an increase of 18% and 13.5% in UHCs and an increase of 88.5% and 97% in CO emissions, respectively. Increasing the biodiesel fraction to B5 and B20 reduced the maximum in-cylinder pressure by 3% and 10.2%, respectively, compared to B0. Combustion instability is characterized by the coefficient of variation (COV) of the indicated mean effective pressure (IMEP), which was measured as 4.2% for B5 and 4.8% for B20 compared to 1.8% for B0. Therefore, using B20 and B5 resulted in up to 34.9% combustion instabilities, and 18.5% compared to the baseline case. The tendency for knocking decreased from 13.7% for B0 to 4.3% for B20. The baseline case (B0) had no misfiring cycle. The B5 case had some misfiring cycles, but no knocking cycle was observed. Moreover, the historical cyclic analysis showed more data dispersions when the biodiesel fraction increased in DFI. This study shows the potential of biodiesel replacement in NG/diesel RCCI combustion engines. This study shows that biodiesel can be used to effectively reduce NOx emissions and the knocking intensity of RCCI combustion. However, combustion instability needs to be monitored.