Reduce Soot Emissions Research Articles

Numerical Study of Combustion and Emission Characteristics of a Diesel/Methanol Dual Fuel (DMDF) Engine

In comparison to the extensive experimental studies, numerical studies of a diesel/methanol dual fuel (DMDF) engine are very limited. In this work, an improved KIVA-3V code was coupled with the CHEMKIN solver to model combustion and emission of a DMDF engine. First, a chemical reaction mechanism including 65 reactions and 43 species was developed and validated with premixed flame species profiles. Second, new engine experiments at varied loads in both diesel and DMDF modes were performed to further validate the present model. Results show that the model predicts the engine combustion and emission in two modes well. At last, parameter studies on diesel injection timings and exhaust gas recirculation (EGR) rates were performed. Results show that the ignition delay time in DMDF mode is longer than that in diesel mode. Methanol supplied through the intake port significantly reduces soot emissions and slightly increases NOx emissions at different injection timings. In two modes, soot emissions are both formed ...

EXPERIMENTAL STUDY OF THE EFFECTS OF AIR-INJECTION, INJECTION TIMING AND COOLED EGR ON THE COMBUSTION, EMISSIONS AND PERFORMANCE OF A NATURE ASPIRATED DIRECT INJECTION DIESEL ENGINE

In this literature, a combined method has been employed to simultaneously reducesmoke (Soot) and oxide of nitrogen (Nox) and maintain the performance parameters of dieselengine. This includes creating an air jet by designing an air-cell inside the piston body, advancedinjection timing and using cold exhaust gas recirculation. The tested engine was an MT4.244engine that worked as natural aspiration. The air-cell causes reduction in both Soot and NOxemissions. Furthermore, applying cold EGR had a noticeable effect on NOx emission reduction.Advancing injection timing, the performance parameters of the engine could be improved. Thetests were done in 25%, 50%, 75% and 100% load conditions, for the engine speed of 2000 rpm.The results showed that by simultaneous reduction of Soot and NOx emissions, performanceparameters can be kept in a suitable range. The greatest reductions in NOx and Soot emissionshave been observed in 100% load. There have been no considerable changes in BSFC (BrakeSpecific Fuel Consumption and power) while injection timing advances have been applied for5° CA and 5% EGR.

Oxygenate screening on a heavy-duty diesel engine and emission characteristics of highly oxygenated oxymethylene ether fuelOME1

Oxygenated fuel components are known to reduce soot emissions in diesel engines significantly while having little effect on NOx emissions. Several compounds were mixed with diesel fuel and tested for their emission characteristics on a 1.8 l heavy duty diesel engine. The C1-oxygenate dimethoxy methane (OME1) which contains no C–C bonds in its molecular structure was found to have the best effect on the reduction of soot and particle number emissions. OME1 belongs to the group of oxymethylene ethers (OMEn) and has the molecular structure CH3–O–(CH2–O)n–CH3 while n=1. For further investigations, a pure OME1-fuel with cetane number 48 was used which contained OME1 and additives to enhance viscosity, lubricity and cetane number. Engine testing including aftertreatment with a Pt coated oxidation catalyst (DOC) proved the soot-NOx trade-off to vanish completely even at stoichiometric operation. CO and most unburned fuel emissions were efficiently reduced by the DOC. The emission of formaldehyde and methane was measured using FTIR spectrometry. No CH2O emissions could be detected. Near stoichiometric conditions, a growing output of methane was observed, which was not converted in the DOC. This can be explained with the high share of methyl groups, which react to methane with other radicals. As OME1 shows low cetane number (CN), high volatility and weak viscosity and lubricity, the characterization of the less volatile OMEn with n=3…5 and CN > 90 is recommended. These are expected to show similar emission characteristics and might have a smaller potential of methane formation.

Injection strategy for simultaneous reduction of NOx and soot emissions using two-stage injection in DME fueled engine

The ultimate purpose of this study is the reduction of exhaust emissions from a dimethyl ether (DME) fueled diesel engine without deterioration of engine performance, such as indicated mean effective pressure (IMEP) and indicated specific fuel consumption (ISFC). In this study, we applied multiple injection strategies to achieve the research goal. In a comparison between diesel and DME single injection combustion, the IMEP in both fuels was similar around the top dead center (TDC) injection condition (this is the typical injection timing). However, the nitrogen oxide (NOx) emission in DME was higher than that in diesel. The single injection combustion in DME and diesel was compared on the basis of the same energy input condition. When the injection timing was advanced in order to reduce the DME NOx emission, the IMEP in DME decreased below the diesel level. Therefore, multiple injection strategies, including pilot injection, split injection, and advanced+post injection, were applied in this study. In the experimental results, the pilot injection strategy with advanced main injection (2nd injection) resulted in the lowest NOx, HC, and CO emissions. In the case of soot emission, DME itself has soot free combustion, and emitted an ignorable amount of soot. Moreover, the pilot injection strategy showed the highest IMEP level and the lowest ISFC level in the test conditions.

Reducing Soot Emissions in a Diesel Series Hybrid Electric Vehicle Using a Power Rate Constraint Map

This paper considers a diesel series hybrid electric vehicle (SHEV) and proposes the utilization of an engine-generator power rate constraint map to reduce soot emissions without a significant compromise in fuel economy. Specifically, model predictive control (MPC) is used to split the vehicle power demand between the engine-generator unit and the battery. To achieve a reduction in soot, the engine-generator power rate is constrained. Unlike existing strategies, the power rate limit is not a fixed value but varies, depending on the power level, resulting in a map. This constraint map is designed by formulating the soot emission reduction problem as an optimization problem, which is solved through a three-step offline discrete optimization process. The optimization relies on a quasi-static soot emissions map that captures the trends, even during transients, but underestimates the magnitudes. Therefore, to evaluate the performance of the MPC-based power management with the power rate constraint map, experiments are conducted through an engine-in-the-loop simulation framework. Experimental results show that compared with a constant power rate constraint, soot emissions can be reduced by 44.5% while compromising fuel economy by only 0.3% through the proposed approach. As a tradeoff, the ampere-hour (Ah) processed in the battery, which is a variable that has been shown to correlate with battery capacity loss, increases by 5.5%.

Characterization of Exhaust Gas Recirculation for Diesel Low Temperature Combustion

Exhaust Gas Recirculation (EGR) is common on most modern diesel engines resulting in significant reduction of NOx emissions. Heavy EGR application is an enabling technique for the advanced combustion modes operating in the low temperature combustion (LTC) regime, wherein simultaneous NOx and soot emission reduction can be attained. The primary effect of EGR is the dilution of the intake charge following the displacement of fresh air by the combustion products. However, the correlation between EGR and its effectiveness is non-linear due to the lean burn nature of boosted diesel engines. This correlation is further complicated when oxygenated fuels are used for combustion in the LTC mode. In this work, the intake oxygen concentration [O2]int is selected as a representative of EGR and its effectiveness in emission abatement is shown using an array of experimental results. An EGR characterization model is developed to quantify the dynamic interaction between [O2]int and engine operating variables, namely the intake boost, exhaust gas recirculation (EGR) amount, the fueling quantity and the fuel type. The model is validated on the research engine platform in steady state and transient tests. Finally, the control of EGR effectiveness is experimentally demonstrated to achieve ultra-low NOx emissions at different engine operating points.

A numerical study on RCCI engine fueled by biodiesel/methanol

A 3-D numerical simulation platform based on the KIVA4-CHEMKIN code was constructed by incorporating a newly developed skeletal chemical kinetics mechanism to study the reactivity controlled compression ignition (RCCI) engine performance, combustion and emission characteristics. In the present study, methanol is assumed to be induced into the engine through the intake port, while biodiesel is directly injected into the engine by the end of the compression stroke. The skeletal biodiesel and methanol dual fuel chemical reaction mechanism coupled with CO, NOx and soot formation mechanisms was developed and validated by comparing the ignition delay predicted by the developed mechanism with that of the detailed biodiesel and methanol mechanisms, and also by comparing the simulation results of KIVA-CHEMKIN with the experimental results under different engine operating conditions. A good agreement has been achieved in terms of ignition delay, in-cylinder pressure and heat release rate (HRR). The methanol mass fraction was varied from 0% to 80% at an interval of 20% to form different reactivity stratification. Simulation results revealed that under 10% load conditions, the increasing methanol reduced the peak pressure and heat release rate, whereas under 50% and 100% loads, the peak pressure both appeared at 60% methanol induction. Also, the reactivity distribution and ringing intensity were discussed, aiming at investigating the fuel gradient effects and knocking level, respectively. For the emissions, a general decreasing trend on CO emission was observed at both 50% and 100% loads while at 10% load, a slight increasing trend was shown. In respect of NOx, it appeared that the emission under medium and high loads showed no tangible change with port methanol increase. However, a remarkable drop was observed at 10% load. Besides, the RCCI with more port-injection methanol showed a good ability to reduce soot emission.

Experimental study on diesel conventional and low temperature combustion by fueling four isomers of butanol

Effects of butanol on conventional and low temperature combustion were investigated on a single-cylinder diesel engine. Four butanol isomers, n-butanol, sec-butanol, iso-butanol and tert-butanol were added into diesel by volume ratios of 20% and 40%, referred to as N20/N40, S20/S40, I20/I40 and T20/T40, respectively. Experiments were conducted over a wide range of EGR from 0% to ∼65%. Results indicate that butanol/diesel blends show the retarded combustion phasing and higher premixed heat release compared with pure diesel. Differences in cylinder pressures and heat release rates among different butanol/diesel blends get larger as EGR rate and blending ratio increases. Ignition delays from the longest to shortest are in the sequence of iso-butanol/diesel, sec-butanol/diesel, n-butanol/diesel and tert-butanol/diesel. Butanol/diesel blends exhibit higher thermal efficiencies compared with diesel in a certain EGR region. The addition of butanol isomers can significantly reduce soot emission and a higher blending ratio results in greater soot reduction. And the soot emissions, from the highest to lowest, are in the order of tert-butanol/diesel, n-butanol/diesel, sec-butanol/diesel, and iso-butanol/diesel, which is consistent with the commonly recognized view that a lower soot emission accompanies with a longer ignition delay. The difference in soot emission among different butanol/diesel blends is predominantly determined by fuel’s cetane number, meanwhile physical properties such as volatility can also influence soot emissions to some extent. Regulated gaseous emissions are not significantly affected by addition of butanol isomers.

Spray and Combustion Characteristics of Neat Acetone-Butanol-Ethanol, n-Butanol, and Diesel in a Constant Volume Chamber

Intermediate product of biobutanol production, acetone-butanol-ethanol (ABE) as an alternative fuel has drawn increasing attention in recent years due to its potential to eliminate various production costs. In this work, neat acetone-butanol-ethanol (ABE) with a component volumetric ratio of 3:6:1, n-butanol, and neat diesel were studied in a preburn type constant volume chamber with optical access. The ambient temperature and oxygen ranged from 800 to 1200 K and 21% to 11%, respectively, covering both conventional and low temperature combustion (LTC) regimes. Time resolved images of the spray and natural flame luminosity (indicator of soot) were captured by a high speed camera coupled with a copper vapor laser beam. The images show that the flame lift-off length and liquid penetration of n-butanol and ABE are much longer and shorter, respectively, than that of diesel under all tested conditions. This results in a longer “gap” between the liquid spray and the flame in ABE and n-butanol combustion that provides more space and time for the droplets to evaporate and mix with the ambient air, which is expected to decrease the local equivalence ratio at the combustion region. Indeed, the natural flame luminosity of ABE and n-butanol is reduced significantly under all tested conditions compared to that of diesel. For all the tested fuels, especially ABE, the combustion duration decreases with the reduction of ambient temperature due to a stronger premixed combustion, while it increases with the reduction of oxygen concentration due to the dilution effect. Therefore, ABE has a high potential to reduce soot emissions when used in diesel engines, but it would also suffer from combustion phasing retardation like butanol under LTC conditions with high EGR.

The multi-objective optimization of combustion chamber of DI diesel engine by NLPQL algorithm

The optimization procedure used in the present investigation is based on NLPQL algorithms and focused on the reduction of soot and NOx simultaneously while maintaining a reasonable power performance. The parameters to be optimized are related to the injection and geometric features of the combustion chambers, which greatly influences the process of air/fuel mixing, combustion and emissions formation.By utilizing ESE Module of AVL FIRE software, a model of combustion system which can simulate the compression and expansion process of engine working cycle is established. From the perspective of reducing soot emissions, using orthogonal design method, we can achieve a set of optimizing parameters of combustion chamber quickly. Basing on the best design of the DOE, optimization with NLPQL method was done applying different variable range and objective definitions (weighing factors Soot/NOx/IMEP = 5/3/1).Comparing the transient flow field contours before and after optimization, the formation of emissions can be described accurately and comprehensively. Furthermore, the numerical results from simulations are compared with testing carried out on an 8.9 L Cummins Diesel engine. For most investigated operating conditions and Europe Steady Cycle, simulated results of emissions show a good consistency with testing data.

Study of the control strategies on soot reduction under early-injection conditions on a diesel engine

To explore the more effective method to fulfill soot reduction challenges of early-injection conditions, different engine operating parameters such as intake pressure, exhaust gas recirculation (EGR), equivalence ratio, intake temperature, coolant temperature, injection pressure and fuel properties such as using the blends of diesel/gasoline, diesel/n-butanol and dual-fuel were investigated on a diesel engine. A wide range of injection timing from 5°CA to −70°CA ATDC were tested, which covered both conventional diesel injection and early-injection conditions. Results showed that the soot emission increased as the injection timing was advanced from −35°CA to −55°CA ATDC, which was attributed to that more spray liquid was out of the piston bowl and impinged on the piston top and cylinder liner. The soot emission decreased as the injection timing further advanced from −55° to −70°CA ATDC, which was attributed to the suppressed soot formation. Although more advanced injection (−55° to −70°CA ATDC) decreased soot emissions, the combustion efficiency was deteriorated. EGR combined with higher intake pressure resulted in lower soot emissions than that of sole EGR control under the same equivalence ratio. Increasing intake temperature and coolant temperature reduced soot emissions at the injection timing later than −55°CA ATDC but barely affected the soot peak-value. Increasing injection pressure had little impact on soot emissions at early-injection conditions. Regarding to fuel properties, employing the diesel/gasoline and diesel/n-butanol blends dramatically reduced soot emissions and the smokeless combustion was achieved by using pure gasoline or n-heptane. Soot peak-value of diesel/gasoline combustion was higher than that of diesel/n-butanol at low diesel replacement ratio (30%), while for high replacement ratio (70%) the opposite trend was presented. The dual-fuel injection composed by port-injection of gasoline and direct-injection of diesel was more effective in reducing soot emissions than that of single direct-injection under the same gasoline/diesel ratio.

Effects of gasoline research octane number on premixed low-temperature combustion of wide distillation fuel by gasoline/diesel blend

Wide Distillation Fuel (WDF) refers to the fuels with a distillation range from initial boiling point (IBP) of gasoline to final boiling point (FBP) of diesel. In this paper, the WDF was prepared by blending diesel fuel and different gasoline fuels with various RONs (90#, 97# and 100#). Experiments were conducted on a direct injection diesel engine with these fuels to investigate the sensitivity of gasoline RON on combustion and emission characteristics in premixed LTC mode from medium load (6bar IMEP) to high load (10bar IMEP). The results indicate that WDF90 has slightly higher combustion efficiency at medium load with a slight increase in NOx emissions. At high load, no significant difference in combustion and emission characteristics was observed WDFs with different RONs from 90# to 100#. All of the three WDFs can significantly reduce soot emissions at both medium load and high load in LTC combustion compared with diesel fuel. Premixed low-temperature combustion of WDF is a promising approach to increase gasoline thermal efficiency compared to SI mode, whereas thermal efficiency is insensitive to gasoline RONs.

Attaining Soot Oxidation Temperature by Inductive Coils Exposed to Electromagnetic Waves

This paper presents the findings in attaining soot oxidation temperature by using carbon steel coils exposed to electromagnetic waves. Soot are unburned carbon product in the exhaust gases during the combustion of diesel fuel, which are subjected to stringent emission regulations due to its harmful properties. The unburned carbon can be oxidised by heating as after-treatment strategy but in order for the oxidation to occur, it would require a temperature of not less than 600°C. In the present work, eight heating elements made from various carbon steel coil sizes were exposed to electromagnetic waves in the microwave oven cavity which heats up the coils to the oxidation temperature. Electromagnetic waves heating utilises electromagnetic radiation to induce electric field in a conductive material that causes the material to be heated. The microwave oven used has a power rating of 1000 W, with a microwave range of 2450 Mhz. Measurement of coils temperature and exposure time to electromagnetic waves were recorded and analysed. The results showed that only the coils with bigger coil loop size, i.e. 20 mm and lowest number of turns, i.e. 10 turns attained the threshold temperature of 600°C, while smaller diameter coil would accelerate the rate of heating. The findings from the research work are significant facts in the future development of in-situ exhaust gas after treatment system in reducing soot emissions.

Effects of injection timing on performance and emissions of a HD diesel engine with DMCC

Experiments were conducted on a 6-cylinder turbocharged intercooled heavy duty (HD) diesel engine with diesel/methanol compound combustion (DMCC) mode. The baseline engine was equipped with a common rail fuel injection system and had been modified to run under DMCC mode. In DMCC mode, methanol is fumigated into the intake manifold to form lean air/methanol homogeneous mixture, and then ignited by the direct-injected diesel fuel in cylinder. This study is aimed to investigate the effects of injection timing on performance and exhaust emissions of the engine with DMCC mode. Experimental results showed that under DMCC mode both increasing methanol substitution ratio and advancing injection timing could increase the peak cylinder pressure and the maximum heat release rate. The brake specific energy consumption (BSEC) and exhaust temperature of DMCC engine decreased with advancing injection timing. NOX was increased and soot was decreased as the diesel injection timing was advanced. Compared with the diesel fuel mode, the DMCC mode had benefits in reduction of intake air temperature, NOX and soot emissions, while there was an obvious increase in NO2, HC and CO emissions. In addition, the HC and CO emissions of DMCC mode exhibited a decreasing trend according to an advance in the injection timing.

Effect of injection timing on particle size distribution from a diesel engine

The present work focused on the effect of injection timing, which changed from 23°CA before top dead center (−23°CA ATDC) to 8°CA after top dead center (8°CA ATDC), on particle size distribution (PSD) from a diesel engine operated under 0% and 40% EGR rates. The results show that PSDs under 0% EGR is dominated by the nucleation mode (NM), and injection timing shows no significant effect on NM on a log plot, while the early and late injections produce the low AM. Under 40% EGR, PSD is dominated by NM with very early and late injections, while it is dominated by the accumulation mode (AM) for −20 to −5°CA ATDC, and an apparent “AM bump” occurs at round −10°CA ATDC. The phenomenon of “AM bump” indicates that the coupling early or late injection and EGR favors low temperature combustion (LTC), and which results in a simultaneous reduction in soot (AM) and NOx emissions. A negative relationship between Nnuc and Nacc with the change in injection timing suggests that LTC potentially promotes the formation of NM. A more evident trade-off relationship between Ntot and Mtot is presented under 40% EGR than that under 0% EGR, which indicates that in-cylinder PM formation and oxidation is more dependent on injection timing under 40% EGR.

Effects of Diluents on Soot Surface Temperature and Volume Fraction in Diluted Ethylene Diffusion Flames at Pressure

Soot surface temperature and volume fraction are measured in ethylene/air coflowing laminar diffusion flames at high pressures, diluted with one of four diluents (argon, helium, nitrogen, and carbon dioxide) using a two-color technique. Both temperature and soot measurements presented are line-of-sight averages. The results aid in understanding the kinetic and thermodynamic behavior of the soot formation and oxidation chemistry with changes in diluents, ultimately leading to possible methods of reducing soot emission from practical combustion hardware. The diluted fuel and coflow exit velocities (top-hat profiles) were matched at all pressures to minimize shear effects. In addition to the velocity-matched flow rates, the mass fluxes were held constant for all pressures. Addition of a diluent has a pronounced effect on both the soot surface temperature and volume fraction, with the helium diluted flame yielding the maximum and carbon dioxide diluted flame yielding minimum soot surface temperature and volume fraction. At low pressures, peak soot volume fraction exists at the tip of the flame, and with an increase in pressure, the location shifts lower to the wings of the flame. Due to the very high diffusivity of helium, significantly higher temperature and volume fraction are measured and explained. Carbon dioxide has the most dramatic soot suppression effect. By comparing the soot yield with previously measured soot precursor concentrations in the same flame, it is clear that the lower soot yield is a result of enhanced oxidation rates rather than a reduction in precursor formation.

Experimental and numerical study on soot formation and oxidation by using diesel fuel in constant volume chamber with various ambient oxygen concentrations

The study on effects of exhaust gas recirculation (EGR) on soot behavior is very important to reduce soot emissions and control the low temperature combustion process in diesel engines. In this work, high time-resolved quantitative soot measurements were experimented on a constant volume chamber by using European low-sulfur diesel fuel at three ambient oxygen concentrations (21%, 18%, 15%). Meanwhile, an improved semi-empirical soot model was coupled into computational fluid dynamics (KIVA-3V Release 2) code for in-depth understanding the soot formation and oxidation processes. Results demonstrated that numerical results of the improved semi-empirical soot model showed good agreement with experimental data in the whole processes of soot formation/oxidation and soot distribution under different oxygen concentrations. The mass concentration of acetylene, soot precursor species and soot mass initially increased with decreasing ambient oxygen concentrations from 21% to 15% and then began to decrease at 12% oxygen, while OH radicals reduced monotonically from 21% oxygen to 12%. At 12% oxygen, the concentrations of local rich sooty zone, acetylene and soot precursor species were as high as those under higher oxygen concentrations, but the total area of soot zone shrank remarkably at 12% oxygen. Compared to 21% ambient oxygen concentration, both soot formation and oxidation rates were increased under 18% oxygen, while the higher soot mass under 18% oxygen was the result of stronger soot formation mechanism. At 15% oxygen, both soot formation and oxidation rates were reduced and the maximum peak of soot mass concentration was caused by the suppressed oxidation mechanism. At 12% oxygen, reaction rates of soot formation and oxidation dropped to the very low level and the reduction in soot mass concentration and number density were achieved. Finally, it could be concluded that the retarded and reduced soot mass concentration at low ambient oxygen was the result of suppressed soot inception reaction from precursor species.

ECU 커먼레일 디젤기관에 있어서 매연 및 NOX배출물 동시 저감용 일체형 요소-SCR 촉매필터 시스템의 특성에 관한 연구

The aim of this study is to develop an integrated urea-SCR catalytic filter system for reducing soot and NOX emissions simultaneously in diesel engines. In this study, the characteristics of exhaust emissions relative to reactive activation temperature under four kinds of engine loads are experimentally investigated by using a four-cycle, four- cylinder, direct injection type, water-cooled turbo intercooler ECU common-rail diesel engine with the integrated urea- SCR MnO 2-V2O5-WO3/TiO2/SiC catalytic filter system operating at three kinds of engine speeds. The urea-SCR reactor is used to reduce NOX emissions, and the catalytic filter system is used to reduce soot emissions. The reactive activation temperature is very important for reacting a reducing agent with exhaust emissions. The reactive activation temperatures in this experiment is applied to 523, 573 and 623 K. The fuel is sprayed by the pilot and main injections at the variable injection timing between BTDC 15° and ATDC 1° according to experimental conditions. It is found that the NO X conversion rate is the highest as 83.9% at the reactive activation temperature of 523 K in all experimental conditions of engine speed and load, and the soot emissions shown by the average reduction rate of approximately 93.3% are almost decreased below 0.6% in all experimental conditions regardless of reactive activation temperatures. Also, the THC and CO emissions by oxidation reaction of Mn, V and Ti are shown in the average reduction rates of 70.3% and 38% regardless of all experimental conditions.

디젤엔진에서 바이오디젤의 배기가스 특성 평가

본 연구에서는 바이오디젤연료 혼합비변화에 대한 디젤엔진의 배기특성에 대해 조사하였다. 실험에 사용된 연료는 경유와 바이오디젤(폐식용유) 혼합연료 BD3, BD5, BD20, BD50 및 BD100을 사용하였으며, 실험변수로서 분사압력(Δ<SUB>Pinj</SUB>)을 400bar, 600bar, 800bar, 1000bar 및 1200bar로 설정하였다. 분사압력과 바이오디젤 혼합연료 혼합비에 따른 정량적인 NOx와 Soot의 배기특성 해석을 위하여 통계학에 기초한 피어슨 상관계수와 스피어만 상관계수의 개념을 도입하였다. 본 연구의 결과로서 실험 조건 전체에 대한 피어슨 상관계수는 -0.732, 스피어만 상관계수는 -0.724로 NOx와 Soot 발생의 상관관계가 선형적이다. 특히 분사압력 800bar 조건에서 피어슨 상관계수가 -0.089으로 NOx와 Soot 배출량 상관관계가 0에 가깝기 때문에, 바이오디젤 연료 혼합비 제어를 통한 NOx와 Soot의 동시저감이 가능하다고 판단된다.

Reductions in aircraft particulate emissions due to the use of Fischer–Tropsch fuels

Abstract. The use of alternative fuels for aviation is likely to increase due to concerns over fuel security, price stability, and the sustainability of fuel sources. Concurrent reductions in particulate emissions from these alternative fuels are expected because of changes in fuel composition including reduced sulfur and aromatic content. The NASA Alternative Aviation Fuel Experiment (AAFEX) was conducted in January–February 2009 to investigate the effects of synthetic fuels on gas-phase and particulate emissions. Standard petroleum JP-8 fuel, pure synthetic fuels produced from natural gas and coal feedstocks using the Fischer–Tropsch (FT) process, and 50% blends of both fuels were tested in the CFM-56 engines on a DC-8 aircraft. To examine plume chemistry and particle evolution with time, samples were drawn from inlet probes positioned 1, 30, and 145 m downstream of the aircraft engines. No significant alteration to engine performance was measured when burning the alternative fuels. However, leaks in the aircraft fuel system were detected when operated with the pure FT fuels as a result of the absence of aromatic compounds in the fuel. Dramatic reductions in soot emissions were measured for both the pure FT fuels (reductions in mass of 86% averaged over all powers) and blended fuels (66%) relative to the JP-8 baseline with the largest reductions at idle conditions. At 7% power, this corresponds to a reduction from 7.6 mg kg−1 for JP-8 to 1.2 mg kg−1 for the natural gas FT fuel. At full power, soot emissions were reduced from 103 to 24 mg kg−1 (JP-8 and natural gas FT, respectively). The alternative fuels also produced smaller soot (e.g., at 85% power, volume mean diameters were reduced from 78 nm for JP-8 to 51 nm for the natural gas FT fuel), which may reduce their ability to act as cloud condensation nuclei (CCN). The reductions in particulate emissions are expected for all alternative fuels with similar reductions in fuel sulfur and aromatic content regardless of the feedstock. As the plume cools downwind of the engine, nucleation-mode aerosols form. For the pure FT fuels, reductions (94% averaged over all powers) in downwind particle number emissions were similar to those measured at the exhaust plane (84%). However, the blended fuels had less of a reduction (reductions of 30–44%) than initially measured (64%). The likely explanation is that the reduced soot emissions in the blended fuel exhaust plume results in promotion of new particle formation microphysics, rather than coating on pre-existing soot particles, which is dominant in the JP-8 exhaust plume. Downwind particle volume emissions were reduced for both the pure (79 and 86% reductions) and blended FT fuels (36 and 46%) due to the large reductions in soot emissions. In addition, the alternative fuels had reduced particulate sulfate production (near zero for FT fuels) due to decreased fuel sulfur content. To study the formation of volatile aerosols (defined as any aerosol formed as the plume ages) in more detail, tests were performed at varying ambient temperatures (−4 to 20 °C). At idle, particle number and volume emissions were reduced linearly with increasing ambient temperature, with best fit slopes corresponding to −8 × 1014 particles (kg fuel)−1 °C−1 for particle number emissions and −10 mm3 (kg fuel)−1 °C−1 for particle volume emissions. The temperature dependency of aerosol formation can have large effects on local air quality surrounding airports in cold regions. Aircraft-produced aerosols in these regions will be much larger than levels expected based solely on measurements made directly at the engine exit plane. The majority (90% at idle) of the volatile aerosol mass formed as nucleation-mode aerosols, with a smaller fraction as a soot coating. Conversion efficiencies of up to 2.8% were measured for the partitioning of gas-phase precursors (unburned hydrocarbons and SO2) to form volatile aerosols. Highest conversion efficiencies were measured at 45% power.