Decrease In NOx Research Articles

Experimental Study on Treating Waste Printed Circuit Boards by Molten Salt Oxidation

The waste management of e-wastes is a significant challenge, especially for the disposal of waste printed circuit boards (WPCBs). An effective, economic and environmental-kind recycling technology is in great demand. Molten salt oxidation (MSO) is a robust thermal process, has the inherent capability of destroying organic constituents of wastes while retaining the inorganic constituents in the molten salt. In the present study MSO is employed for the disposal of waste printed circuit boards aimed at describing the treating method of WPCBs using MSO, and evaluating the efficiency of this alternative. Molten salt oxidation experiments of WPCBs have been conducted in a lab-scale molten salt reactor using a ternary carbonate salt (Li, Na, K)2CO3. The operation parameters investigated are the temperature of molten salts, the excess air factor and the residence time of the reactants in the salt bath. Results show that the retention efficiency of bromine is higher than 99.9%, irrespective of the operating conditions. The emissions of CO and SO2 decrease with temperature increasing, while the emission of NOx first decreases and later increases. And when the residence time is lengthened, the emissions of CO, NOx and SO2 decrease. Compared to the temperature and the residence time’s role, the effect of excess air factor on the emissions of CO, NOx and SO2 is relatively small. Over 95% of the copper in WPCBs are recycled. The fibreglass that is the main component of the ash content is dissolved by the molten carbonates and retains in the salt bath. The results of the present study show molten salt oxidation is an environmentally friendly and effective alternative technology for the disposal of WPCBs.

Impacts on air pollution and health by changing commuting from car to bicycle.

Our study is based on individual data on people's home and work addresses, as well as their age, sex and physical capacity, in order to establish realistic bicycle-travel distances. A transport model is used to single out data on commuting preferences in the County Stockholm. Our analysis shows there is a very large potential for reducing emissions and exposure if all car drivers living within a distance corresponding to a maximum of a 30min bicycle ride to work would change to commuting by bicycle. It would result in >111,000 new cyclists, corresponding to an increase of 209% compared to the current situation. Mean population exposure would be reduced by about 7% for both NOx and black carbon (BC) in the most densely populated area of the inner city of Stockholm. Applying a relative risk for NOx of 8% decrease in all-cause mortality associated with a 10μgm-3 decrease in NOx, this corresponds to >449 (95% CI: 340-558) years of life saved annually for the Stockholm county area with 2.1 million inhabitants. This is more than double the effect of the reduced mortality estimated for the introduction of congestion charge in Stockholm in 2006. Using NO2 or BC as indicator of health impacts, we obtain 395 (95% CI: 172-617) and 185 (95% CI: 158-209) years of life saved for the population, respectively. The calculated exposure of BC and its corresponding impacts on mortality are likely underestimated. With this in mind the estimates using NOx, NO2 and BC show quite similar health impacts considering the 95% confidence intervals.

Effect of varying 9-Octadecenoic acid (oleic fatty acid) content in biofuel on the performance and emission of a compression ignition engine at varying compression ratio

ABSTRACTThe 9-Octadecenoic acid (oleic fatty acid) content of vegetable oil seeds can be altered by mutagenesis, thereby increasing its content in the oil, for the purpose of increasing shelf life. In this work, the effect of varying the oleic acid content in ester on the performance and emission of a CI engine was examined. For this purpose, the situation was simulated by adding commercially available 9-Octadecenoic acid to pongamia ester; in terms of different percentages, the experiments were conducted with 10% and 20% extra oleic acid, at 16, 17, 17.5 and 18 compression ratio (CR). The results indicate that the smoke emission and BSEC increase with increase in oleic acid content, whereas the BTE and NOx decrease with increased proportions of oleic acid for all CRs. Pongamia methyl ester with 10% extra oleic acid at 17 CR results in lower NOx when compared to neat pongamia methyl ester at a normal CR of 17.5. Smoke emission increases with extra oleic acid content for all CRs; however, it is minimum at 17 CR for 10% extra oleic acid. From the research it is concluded that pongamia methyl ester with 10% extra oleic acid at 17 CR results in better performance and emission.

An experimental investigation on the performance, combustion and emission characteristics of a variable compression ratio diesel engine using diesel and palm stearin methyl ester

An attempt has been made to use biodiesel prepared from non-edible portion of palm oil as fuel of a conventional mono-cylinder compression ignition engine. The present experimental investigation takes into account the combined effect of using blends of diesel–palm stearin biodiesel as fuels and the compression ratio on different performance, combustion and emission characteristics of the said engine. The experiments have been carried out on a single-cylinder, direct injection diesel engine at varying compression ratio of 16:1–18:1 in four steps. It is observed that the brake thermal efficiency reduces by 7.9% when neat biodiesel is used instead of diesel. But, it increases with the increase in compression ratio for all the blends. Brake specific fuel consumption and exhaust gas temperature increase with the addition of biodiesel to diesel and also with the increase in compression ratio. Heat release rate decreases with biodiesel, and it is minimum at the rated compression ratio of 17.5:1 for all the fuels considered here. On the other hand, ignition delay is found to be more with neat diesel, and it increases with the decrease in compression ratio. Significant reductions in emissions of carbon monoxide (CO), hydrocarbon (HC) and smoke are observed with biodiesel, while the emissions of oxides of nitrogen (NOx) and carbon dioxide (CO2) increase. The decrease in compression ratio increases the emissions of CO, HC and smoke, but the emissions of NOx and CO2 decrease with the decrease in compression ratio.

Optimization of the piston bowl geometry and the operating conditions of a gasoline-diesel dual-fuel engine based on a compression ignition engine

This paper describes the optimization of the piston bowl geometry and the operating conditions of a dual-fuel engine based on a compression ignition engine using gasoline port fuel injection and diesel direct injection. KIVA-3V code coupled with a CHEMKIN chemistry solver was used for simulation and a micro-genetic algorithm was used as the optimization algorithm. The micro-genetic algorithm has a smaller population than a conventional genetic algorithm. And in the optimization, the proposed algorithm has six populations for each generation, sixteen variables composed of seven geometry variables and nine operating condition variables. As a result of optimization, a 9% improvement in the gross indicated specific fuel consumption and a simultaneous decrease of the overall NOx and soot emissions were achieved. Also, the amounts of carbon monoxide and unburned hydrocarbons were decreased. The baseline case has a re-entrant shape, while the optimized case has a shallow shape and a narrower spray angle. Furthermore, under operating conditions, the gasoline/total fuel ratio was increased to 90% (similar to a gasoline HCCI (Homogenous charge compression ignition) engine), the EGR (Exhaust gas recirculation) rate was increased to 40% for dilution, and both the boost pressure and initial temperature were decreased.

Elevation of Oxidative Stress and Decline in Endogenous Antioxidant Defense in Elderly Individuals with Hypertension.

Hypertension is becoming an important medical and public health problem all over the world and is the most common disorder of ageing. There is a growing evidence of involvement of vascular oxidative stress in the development of hypertension from animal studies. However, studies on humans with hypertension, particularly in elderly are least and data remained controversial. Moreover, studies in elderly people with hypertension are scarce. To investigate the possible role of oxidative stress and antioxidant defense in the pathogenesis of hypertension in elderly. A cross-sectional study was conducted on elderly males (n=60) with newly diagnosed hypertension and with normal blood pressure. Oxidative stress and antioxidant status were evaluated by assessing the following parameters: plasma Malondialdehyde (MDA), and antioxidants: Superoxide Dismutase (SOD) activity, reduced Glutathione (GSH), and vitamin C levels; and total Nitric Oxide concentration in plasma (NOx). Difference between groups was determined by using unpaired t-test/Mann-Whitney U test. Bivariate correlation and multiple regression analysis were used to determine the relationship between variables. A significant rise in plasma MDA (p-value=0.013) and lower levels of endogenous antioxidants: SOD (p-value≤0.001) and GSH (p-value≤0.001) were observed in elderly individuals with hypertension when compared to healthy controls. Though not significant, there was a mean decrease in plasma NOx in hypertensive subjects than normotensive ones. While vitamin C showed no significant difference between two groups. Decrease in GSH (β=-0.398; p-value=0.001) and SOD (β=-0.423; p-value≤0.001) were the significant determinants of hypertension in elderly individuals. Above findings indicate that elevation in oxidative stress and decrease in endogenous antioxidant level may be involved in the pathogenesis of hypertension. However, it remains unclear whether oxidative stress causes or augments hypertension.

Experimental investigations on combustion, performance and emissions characteristics of compression ignition engine powered by B100/ethanol blend

In the study are presented the results of co-combustion of biodiesel B100 with ethanol fuel as blend. The 1-cylinder direct injection compression ignition engine was used during the study. Tests were conducted at a constant angle of fuel injection and constant rotational speed equal to 1500 rpm. Results of thermal cycle parameters and emission characteristics are presented. On the basis of results stated that ethanol fuel fraction in blend causes the increase in peak heat release rate. With the increase in ethanol fuel fraction the ignition delay increased but combustion duration decreased. With the increase in ethanol fuel fraction in blend thermal efficiency increased as well. It also noticed almost constant emission of THC, the increase in NOx emissions and decrease emissions in CO and CO2 .

Effects of novel microemulsion fuel additive Ce–Ru–O catalysts on diesel engine emissions

ABSTRACTThis paper investigated the role of microemission characteristics of a diesel engine when CeRuO2 blended with diesel is used as a fuel. The major problem areas for combustion ignition (CI) engines are emissions. A novel microemulsion-based protocol was utilized to disperse the catalysts in the diesel fuel. The fuel was prepared comprising CeO2, Ce0.95Ru0.05O2, Ce0.9Ru0.1O2, and Ce0.8Ru0.2O2 by volume (0, 5, 10, and 20 mole%) was used in a CI engine. The catalyst microemulsion system remains stable upon its addition to the diesel fuel. The results show that the CI engine works well and the power outputs are steady running with the biodiesel blends at different loads. The acquired information were studied and found a decrease in HC, CO, NOx, and soot.

The influence of fuel injection pump malfunctions of a marine 4-stroke Diesel engine on composition of exhaust gases

The article presents results of a laboratory study on exhaust gas emission level from a marine diesel engine. The object of the laboratory study was a four-stroke marine diesel engine type Al 25/30 Sulzer, operated at a constant speed. The examination on the engine was carried out according to regulations of the Annex VI to MARPOL 73/78 Convention. The laboratory study consisted of 3 observations: the engine assumed to be operating without malfunctions, delay of the fuel injection by 5° of crankshaft angle in the second engine cylinder, and the leakage of the fuel pump on the second engine cylinder. Additionally, parameters of fuel consumption and thermodynamic parameters of the marine engine were measured during the research. Simulated malfunctions caused changes in total weighed NOx, CO, and CO2 emissions for all considered engine loads. All simulated malfunctions caused a small change in measured thermodynamic parameters of the engine. The engine operation with the delayed fuel injection and the fuel leakage in the fuel pump in one cylinder caused a decrease of NOx and CO emission level. Fuel leakage in the fuel pump causes the CO2 emission to decrease only at low engine load. Calculations of the weighed specific fuel consumption present a 1-2% change in the engine efficiency.

Experimental investigation into effects of addition of zinc oxide on performance, combustion and emission characteristics of diesel-biodiesel-ethanol blends in CI engine

This study is to investigate the effect of zinc oxide nano particle addition to diesel-biodiesel-ethanol blends. Solubility tests were done for the fuels at three different temperatures. Out of eighteen blends, six blends were stable at 5°C, 15°C and above 25°C. Out of the six blends, two blends were checked for properties as per ASTM standards. One of them was chosen for testing the performance, combustion and emission characteristics in a diesel engine. In the same blend, zinc oxide was added in the amount of 250ppm. Property testing of the blended fuel indicated that there was an increase in calorific value due to addition of nano particle. The performance tests were conducted on a single cylinder four stroke direct injection diesel engine at a constant speed of 1500 rpm. For the blend containing zinc oxide, there was an increase in BSFC, HRR and cylinder pressure. Also, there was a decrease in BTE, NOx and smoke, as compared to diesel. The addition of zinc oxide nano particles increased the BTE and decreased the BSFC as compared with the biodiesel diesel ethanol blend at full load. This study gives a direction to utilize the renewable fuel to reduce the consumption of fossil fuel.

Modeling of specific fuel consumption and emission parameters of compression ignition engine using nanofluid combustion experimental data

This paper investigated the use of mathematical models in predicting the brake specific fuel consumption, and exhaust emissions of a diesel engine in terms of parameters such as load and volume fractions of Fe3O4 magnetic nanoparticles. Regression analysis was performed using the experimental data. The experiments were carried out by dispersing the Fe3O4 nanoparticles in the diesel fuel with the nanoparticle concentrations of 0.4 and 0.8vol.%. Moreover, the experiments were performed under variable load conditions, for which a direct-injection diesel engine was employed. The predicted values obtained by the regression equations were compared with the values obtained from the experimental measurements. Analysis of variance (ANOVA) of the results at 95% confidence level showed significance in the developed mathematical models. Furthermore, the regression fitted models were able to predict the brake specific fuel consumption and emission characteristics with a correlation coefficient (R2) in the range of 94%–98% within the domain of experimental variables. In addition, the nanofluid fuel with the nanoparticle concentration of 0.4vol.% had an optimal value. The results also revealed a dramatic decrease in NOx and SO2 emissions, while a significant increase was observed in the CO emission and smoke opacity by adding magnetic nanoparticles in diesel fuel.

H2-rich syngas strategy to reduce NOx and CO emissions and improve stability limits under premixed swirl combustion mode

The combustion performance of H2-rich model syngas was investigated by using a premixed swirl flame combustor. Syngas consisting mainly of H2 and CO was blended with components such as CH4 and CO2 in a mixing chamber prior to combustion at atmospheric condition. The global flame appearance and emissions performance were examined for high (H2/CO = 3) and moderate (H2/CO = 1.2) H2-rich syngases. Results showed that higher H2 fractions in the syngases produce lower NOx emissions per kWh basis across all equivalence ratios tested. CO emissions are equivalence ratio dependent and are less affected by the H2 fraction in the syngas. Increasing CO2 diluent ratios result in the decrease of NOx, particularly for moderate H2-rich syngases. In contrast, syngas without CO shows an increase of NOx with increasing CO2 for fuel-lean mixtures. Addition of CO2 increases the lean blowout limit of all syngases. Higher fraction of H2 produces lower lean blowout limits due to the characteristics of high diffusivity of hydrogen molecules and high flame speed that assist in the stabilisation of the flame under flame-lean conditions. The range of blowout limits for moderate and high H2-rich and pure hydrogen syngases under diluent ratios up to 25% were within the range of ϕ = 0.12–0.15.

The performance analysis and design optimization of fuel temperature control for the injection combustion engine

The purpose of the paper is to analyze the performance and design optimization of fuel temperature control in the injection combustion engine. There is a fuel temperature control device designed between the injection and fuel pump to cool down or warm up the fuel. Thermoelectric module (TEC) chips are applied in the device to absorb or dissipate heat from the fuel. There are several results relating exhaust emission and engine output performance to fuel temperature in this paper to display the optimization of fuel temperature for the injection engine. The experimental results indicate that increasing fuel temperature will result in an increase in CO, HC, and in a decrease in NOx. Increasing the fuel temperature may affect the fuel consumption and engine output for a gasoline engine at different A/F (air to fuel) ratios. With enhanced understanding and analyses, the effects of fuel temperature on engine performance, fuel consumption and emissions can be taken into account in engine design and evaluation.

Application of Nagchampa biodiesel and rice husk gas as fuel

ABSTRACTThis paper elaborates the application of Nagchampa biodiesel and rice husk producer gas in dual mode using rice husk producer gas. Nagchampa biodiesel was examined under both single and dual fuel mode having a persistent gas flow rate of 21.69 kg/h at discrete loads. The test results disclosed that the engine shows improved performance and emission characteristics at optimum load of 8 kW. There is a decrease in NOx, smoke opacity, and performance, while HC, CO, and CO2 increase moderately with respect to gas flow rate. It can finally be concluded that biodiesel exhibits lower performance and improved emission than that of neat diesel.

An experimental study on the effect of using gas-to-liquid (GTL) fuel on diesel engine performance and emissions

Gas to Liquid (GTL) fuel is considered one of the most propitious clean alternative fuels for the diesel engines. The aim of this study was to experimentally compare the performance and emissions of a diesel engine fueled by GTL fuel, diesel, and a blend of GTL and diesel fuels with a mixing ratio of 1:1 by volume (G50) at various engine load and speed conditions. Although using the GTL and G50 fuels decreased slightly the engine maximum power compared to the diesel fuel, both the engine brake thermal efficiency and engine brake specific fuel consumption were improved. In addition, using the GTL and G50 fuels as alternatives to the diesel resulted in a significant decrease in engine CO, NOx, and SO2 emissions.

Investigating the influence of water injection on the emissions of a diesel engine

There are many methods to decrease the nitrogen oxide emissions of a diesel engine. One promising measure is water injection into the engine’sintake manifold. As emission limits become more and more stringent, the diesel engine NOx–particulate trade-off is a challenge for engine developers. To overcome this challenge, a single-point water injection system has been developed to investigate the influence of different amounts of injected water on the behaviour of a 4-cylinder diesel engine. The amount of injected water was varied from 0 to 100% water-to-fuel ratio in part-load operation (BMEP = 2, 3.5 and 5 bar). The influence on the intake air cooling effect, exhaust emissions, combustion and engine parameters was evaluated. The combustion temperature and the NOx emissions decreased drastically (63% NOx decrease for a BMEP of 5 bar and a waterto-fuel ratio of 100%). This benefit had the drawback of an increase of the particle matter emission at high water-to-fuel ratio. The combustion process and performance parameters regarding efficiency, torque and fuel consumption were marginally influenced by the water injection. This work has achieved a major reduction of NOx raw emissions of a diesel engine. Further research lines could include research on water injection at high load operation points in the engine map.

Sulfate Aerosols from Non-Explosive Volcanoes: Chemical-Radiative Effects in the Troposphere and Lower Stratosphere

SO2 and H2S are the two most important gas-phase sulfur species emitted by volcanoes, with a global amount from non-explosive emissions of the order 10 Tg-S/yr. These gases are readily oxidized forming SO42− aerosols, which effectively scatter the incoming solar radiation and cool the surface. They also perturb atmospheric chemistry by enhancing the NOx to HNO3 heterogeneous conversion via hydrolysis on the aerosol surface of N2O5 and Br-Cl nitrates. This reduces formation of tropospheric O3 and the OH to HO2 ratio, thus limiting the oxidation of CH4 and increasing its lifetime. In addition to this tropospheric chemistry perturbation, there is also an impact on the NOx heterogeneous chemistry in the lower stratosphere, due to vertical transport of volcanic SO2 up to the tropical tropopause layer. Furthermore, the stratospheric O3 formation and loss, as well as the NOx budget, may be slightly affected by the additional amount of upward diffused solar radiation and consequent increase of photolysis rates. Two multi-decadal time-slice runs of a climate-chemistry-aerosol model have been designed for studying these chemical-radiative effects. A tropopause mean global net radiative flux change (RF) of −0.23 W·m−2 is calculated (including direct and indirect aerosol effects) with a 14% increase of the global mean sulfate aerosol optical depth. A 5–15 ppt NOx decrease is found in the mid-troposphere subtropics and mid-latitudes and also from pole to pole in the lower stratosphere. The tropospheric NOx perturbation triggers a column O3 decrease of 0.5–1.5 DU and a 1.1% increase of the CH4 lifetime. The surface cooling induced by solar radiation scattering by the volcanic aerosols induces a tropospheric stabilization with reduced updraft velocities that produce ice supersaturation conditions in the upper troposphere. A global mean 0.9% decrease of the cirrus ice optical depth is calculated with an indirect RF of −0.08 W·m−2.

Modeling of the anthropogenic heat flux and its effect on regional meteorology and air quality over the Yangtze River Delta region, China

Abstract. Anthropogenic heat (AH) emissions from human activities caused by urbanization can affect the city environment. Based on the energy consumption and the gridded demographic data, the spatial distribution of AH emission over the Yangtze River Delta (YRD) region is estimated. Meanwhile, a new method for the AH parameterization is developed in the WRF/Chem model, which incorporates the gridded AH emission data with the seasonal and diurnal variations into the simulations. By running this upgraded WRF/Chem for 2 typical months in 2010, the impacts of AH on the meteorology and air quality over the YRD region are studied. The results show that the AH fluxes over the YRD have been growing in recent decades. In 2010, the annual-mean values of AH over Shanghai, Jiangsu and Zhejiang are 14.46, 2.61 and 1.63 W m−2, respectively, with the high value of 113.5 W m−2 occurring in the urban areas of Shanghai. These AH emissions can significantly change the urban heat island and urban-breeze circulations in the cities of the YRD region. In Shanghai, 2 m air temperature increases by 1.6 °C in January and 1.4 °C in July, the PBLH (planetary boundary layer height) rises up by 140 m in January and 160 m in July, and 10 m wind speed is enhanced by 0.7 m s−1 in January and 0.5 m s−1 in July, with a higher increment at night. The enhanced vertical movement can transport more moisture to higher levels, which causes the decrease in water vapor at ground level and the increase in the upper PBL (planetary boundary layer), and thereby induces the accumulative precipitation to increase by 15–30 % over the megacities in July. The adding of AH can impact the spatial and vertical distributions of the simulated pollutants as well. The concentrations of primary air pollutants decrease near the surface and increase at the upper levels, due mainly to the increases in PBLH, surface wind speed and upward air vertical movement. But surface O3 concentrations increase in the urban areas, with maximum changes of 2.5 ppb in January and 4 ppb in July. Chemical direct (the rising up of air temperature directly accelerates surface O3 formation) and indirect (the decrease in NOx at the ground results in the increase in surface O3) effects can play a significant role in O3 changes over this region. The meteorology and air pollution predictions in and around large urban areas are highly sensitive to the anthropogenic heat inputs, suggesting that AH should be considered in the climate and air quality assessments.

Modeling lightning-NO<sub><i>x</i></sub> chemistry on a sub-grid scale in a global chemical transport model

Abstract. For the first time, a plume-in-grid approach is implemented in a chemical transport model (CTM) to parameterize the effects of the nonlinear reactions occurring within high concentrated NOx plumes from lightning NOx emissions (LNOx) in the upper troposphere. It is characterized by a set of parameters including the plume lifetime, the effective reaction rate constant related to NOx–O3 chemical interactions, and the fractions of NOx conversion into HNO3 within the plume. Parameter estimates were made using the Dynamical Simple Model of Atmospheric Chemical Complexity (DSMACC) box model, simple plume dispersion simulations, and the 3-D Meso-NH (non-hydrostatic mesoscale atmospheric model). In order to assess the impact of the LNOx plume approach on the NOx and O3 distributions on a large scale, simulations for the year 2006 were performed using the GEOS-Chem global model with a horizontal resolution of 2° × 2.5°. The implementation of the LNOx parameterization implies an NOx and O3 decrease on a large scale over the region characterized by a strong lightning activity (up to 25 and 8 %, respectively, over central Africa in July) and a relative increase downwind of LNOx emissions (up to 18 and 2 % for NOx and O3, respectively, in July). The calculated variability in NOx and O3 mixing ratios around the mean value according to the known uncertainties in the parameter estimates is at a maximum over continental tropical regions with ΔNOx [−33.1, +29.7] ppt and ΔO3 [−1.56, +2.16] ppb, in January, and ΔNOx [−14.3, +21] ppt and ΔO3 [−1.18, +1.93] ppb, in July, mainly depending on the determination of the diffusion properties of the atmosphere and the initial NO mixing ratio injected by lightning. This approach allows us (i) to reproduce a more realistic lightning NOx chemistry leading to better NOx and O3 distributions on the large scale and (ii) to focus on other improvements to reduce remaining uncertainties from processes related to NOx chemistry in CTM.

Decreasing NOx of a Low-Speed Two-Stroke Marine Diesel Engine by Using In-Cylinder Emission Control Measures

The authors applied one-dimensional (1-D) simulation and 3-D Computational Fluid Dynamics (CFD) simulation to evaluate the potential of in-cylinder control methods on a low-speed 2-stroke marine engine to reach the International Maritime Organization (IMO) Tier 3 NOx emissions standards. Reducing the combustion temperature is an important in-cylinder measure to decrease NOx emissions of marine diesel engines. Miller-cycle and Exhaust Gas Recirculation (EGR) are effective methods to reduce the maximum combustion temperature and accordingly decrease NOx emissions. The authors’ calculation results indicate that with a combination of 2-stage turbocharging, a mild Miller-cycle and 10% EGR rate, the NOx emissions can be decreased by 48% without the increased Specific Fuel Oil Consumption (SFOC) penalties; with a medium Miller-cycle and 10% EGR, NOx can be decreased by 56% with a slight increase of SFOC; with a medium Miller-cycle and 20% EGR, NOx can be decreased by 77% and meet IMO Tier 3 standards, but with the high price of a considerable increase of SFOC. The first two schemes are promising to meet IMO Tier 3 standards with good fuel economy if other techniques are combined.