Emission Characteristics of Particulate and Gaseous Pollutants from a Light-Duty Diesel Engine with SDPF.

Due to the inherent combustion characteristics of diesel engines, particulate matter (PM) and nitrogen oxides (NOx) are the main pollutants of diesel engines. NOx emissions under low load and low temperature are the focus of future regulation. Selective catalytic reduction coated on diesel particulate filter (SDPF) can reduce NOx and PM emissions of diesel engines at the same time, especially improving the emission characteristics of NOx under low load and low temperature. In this paper, a light-duty diesel engine with diesel oxidation catalyst (DOC) and SDPF was studied, and emission of particulate and gaseous pollutants of the engine before DOC, after DOC, and after SDPF was measured under 10 steady-state operating conditions. The effects of SDPF on particulate size distribution, the filtration efficiency of particulate, and the conversion efficiency of gaseous pollutants were analyzed. The results show that DOC + SDPF can trap PM with particle sizes between 10 and 23 nm by 1-2 orders of magnitude, and the conversion and filtration efficiency of DOC + SDPF for both gaseous pollutants and PM exceeds 90% under low-temperature and low-load conditions. The filtration efficiency of SDPF is 94.37% for PM and 90.36% for PN, and the conversion efficiency is 91.43% for NOx.

Interactions between Used Cooking Oil Biodiesel Blends and Elastomer Materials in the Diesel Engine.

Used cooking oil (UCO) biodiesel may be one of the most potential alternative fuels in China to lower the dependency on crude oil for transportation. An experimental study has been conducted to assess the interactions between biodiesel produced from UCO in Shanghai and elastomer materials on high-speed marine diesel engines by immersing elastomer materials into conventional fossil diesel, 5, 10, and 20%, of a volumetric blending ratio of UCO biodiesel and pure UCO biodiesel. The test duration is 168 h at different temperatures of 25, 50, and 70 °C. Meanwhile, the effects of the mixing ratio of UCO biodiesel and the immersion temperature on the compatibility of elastomer materials with UCO biodiesel were analyzed. The results revealed that elastomer materials such as nitrile butadiene rubber (NBR), ethylene propylene diene monomer (EPDM), fluororubber (FKM), and silicone rubber (SR) exposed to biodiesel blends would reveal worse but acceptable changes than those exposed to petroleum diesel, including the slight increase of mass and volume and decline of tensile strength and hardness. FKM, NBR, and SR represented better compatibility with pure UCO biodiesel than diesel, and EPDM showed worse compatibility with UCO biodiesel as the blend ratio rises. In general, the recommended volumetric mixing ratio of UCO biodiesel should be no larger than 20%. The present study could be helpful for the investigation of UCO biodiesel blends as a potential fuel to satisfy the energy demand.

Study of spatial and temporal aging characteristic of catalyzed diesel particulate filter catalytic performance used for diesel vehicle.

Catalyzed diesel particulate filters (CDPFs) have been widespread used as a technically and economically feasible mean for meeting increasingly stringent emissions limits. An important issue affecting the performance of a CDPF is its aging with using time. In this paper, the effects of noble metal loadings, regions and using mileage on the aging performance of a CDPF were investigated by methods of X-ray diffraction (XRD), X-ray photoelectron spectroscopy and catalytic activity evaluation. Results showed that aging of the CDPF shifted the XRD characteristic diffraction peaks towards larger angles and increased the crystallinity, showing a slowing downward trend with the increase of the noble metal loadings. In addition, the increase of the noble metal loading would slow down the decline of Pt and Pt4+ concentration caused by aging. The characteristic temperatures of CO, C3H8 conversion and NO2 production increased after aging, and the more the noble metal loadings, the higher the range of the increase. But noticeably, excessive amounts of noble metals would not present the corresponding anti-aging properties. Specifically, the degree of aging in the inlet region was the deepest, the following is the outlet region, and the middle region was the smallest, which were also reflected in the increase range of crystallinity, characteristic temperatures of CO, C3H8 conversion and NO2 production, as well as the decrease range of Pt and Pt4+ concentrations. The increase of aging mileage reduced the size of the aggregates of the soot and ash in CDPFs, however, improved the degree of tightness between particles. Meanwhile Carbon (C) concentration in the soot and ash increased with the aging mileage.

A phenomenological model for particle number and size distributions of a diesel engine with a diesel oxidation catalyst.

Particle number is a key index for evaluating particulate emissions, and diesel oxidation catalysts (DOCs) are one of the most important technologies for controlling the particulate emissions of a diesel engine. In this paper, a novel phenomenological one-dimensional model was established to predict particle number and size distributions at a DOC outlet with the aim of investigating the effects of DOC on particle number emissions. The phenomenological model consisted of two submodels: submodel-1, a global kinetic model for calculating particle size in particle number and size distributions after particles had passed through the DOC, and submodel-2, an original global parametric model for calculating the particle number at the DOC outlet. The effects of the sampling process, fuel properties, and the engine operating condition were considered in submodel-2. An 8.8 L, direct-injection, heavy-duty diesel engine was tested. The particle number and size distributions at the DOC inlet and outlet were determined using an engine exhaust particle sizer. The test data, coupled with literature results, were used to calibrate and validate the phenomenological model. This model was then applied to investigate the influence of various factors on particle number and size distributions at the DOC outlet. It was found that dilution temperature, fuel sulfur content, exhaust gas temperature, and gas hourly space velocity (GHSV) played a key role in the particle number after DOC oxidation. The particle number concentration at the DOC outlet increased as fuel sulfur content and exhaust gas temperature increased and decreased as GHSV and dilution temperature increased. In general, results proved that this phenomenological model was accurate enough to predict particle number and size distributions at a DOC outlet under most operating conditions. It may serve as a useful tool for research and development focusing on PM reduction of diesel engines and air pollution control.

[Particulate Component Emission Characteristic from a Diesel Bus with DOC and CDPF].

A diesel bus was tested with a China City Bus Cycle (CCBC) on a heavy chassis dynamometer, and the components of the particulate emissions with different after-treatment equipment were investigated. Results showed that OC was less than EC in the particulates of the bus emissions without the use of after-treatment equipment. The organic components were mainly fatty acids (60.9%) and n-alkanes (32.4%), with a few hopanes and PAHs. Fatty acid components were mainly C16:0, C18, C14, and C18:1. The n-alkanes were mainly C18-C24, with C21H44 and C22H46 accounting for the greatest portion. PAH mass was concentrated in medium and small molecular weight components, such as Pyr, FL, and PA. While PAH toxicity was dominated by medium and high molecular weight components, BaP was the most toxic, followed by B(b+k)F, BaA, and IcdP. The total toxicity of the PAHs decreased by 2.7% after DOC treatment and continued to decrease by 89.6%-93.8% after CDPF treatment. After-treatment equipment significantly reduced the OC+EC emissions by 18.9% (DOC) and 70.5%-72.5% (CDPF), but the reduction rate varied from one component to another. The different precious metal loadings of the CDPF did not obviously affect the reduction rate.

[Effects of Different Precious Metal Loads of CDPF on Characteristics of VOCs Emissions from a Diesel Bus].

Based on heavy chassis dynamometers, an experimental study was conducted in a diesel bus with proton transfer reaction mass spectrometry (PTR-MS). It investigated the effects of volatile organic compound (VOC) emission characteristics with three different diesel oxidation catalyst (DOC)+catalyzed diesel particulate filter (CDPF) after-treatments for a typical Chinese city bus driving cycle (CCBC). The results reveal that the major compounds from the diesel bus are OVOCs, aromatic hydrocarbons, alkenes, alkanes, nitrogenous organic compounds, and polycyclic aromatic hydrocarbons (PAH), and that the OVOCs account for more than 50%of the total VOCs. With the same precious metal composition and ratio of the proportion in the CDPF catalyst, the emissions of VOCs decrease with an increase in precious metal load. The emission reduction rates of the VOCs are 36.2%, 40.1%, and 41.4%, respectively, when the precious metal loads are 15 g·ft-3 (type A after-treatment device), 25 g·ft-3 (type B), and 35 g·ft-3 (type C). The average emission rates of alkanes for the three kinds of DOC+CDPF after-treatments are all over 59% for the entire CCBC cycle. The type C after-treatment device can reduce the alkane emissions by 70.2%, with a slight advantage for the OVOC reduction compared with type A and type B devices. For unsaturated hydrocarbons, including aromatic hydrocarbons, alkenes, and PAHs, the after-treatment devices have a catalytic effect, but there is no significant difference between them. The emissions of nitrogenous organic compounds are greatly decreased, by 50.5%, with the type A after-treatment, but the reduction rate decreases with an increase in precious metal load. In addition, OVOCs, aromatic hydrocarbons, and alkenes are the most important contributors to ozone formation. The adoption of DOC+CDPF reduces the emissions of VOCs and, therefore, the ozone formation potential. Taking into account the emission reduction rates and costs of the three different after-treatments and for weighting coefficients of 0.8 and 0.2, respectively, the type B after-treatment is the optimal solution.

[Effects of DOC+CDPF on Emission Characteristics of Heavy-duty Diesel Vehicle].

Based on the revolving drum test bench, an experimental study was conducted in heavy-duty diesel vehicle at China Stage Ⅲ with and without DOC+CDPF to investigate the effects of DOC+CDPF on the gaseous and particle emission characteristics under C-WTVC driving cycle. The results showed that from city circulation conditions to high way circulation conditions to high-speed circulation conditions, the CO, THC, CO2 and PM emission factors of the test vehicle without DOC+CDPF decreased while NOx and PN emission factors increased, the particle number concentration showed two peaks versus the size of the particles and accumulated particles predominated. After the test vehicle was equipped with DOC+CDPF, the emissions factors decreased and the faster the circulation speed, the greater the decreasing amplitudes of the emissions factors. Throughout the C-WTVC, the decreasing amplitudes of CO, THC, CO2, and NOx emission factors were 70.36%, 72.73%, 17.00% and 7.76%, the PM and PN emission factors decreased by 93.77% and 98.91% respectively. The particle number concentration still had two peaks versus the size of the particles and the nuclear mode particles predominated. Besides, the size of the accumulated particles peak diminished.

[Influence of Noble Metal and Promoter Capacity in CDPF on Particulate Matter Emissions of Diesel Bus].

This study investigates the influence of noble metal capacity and promoter capacity in diesel oxidation catalysts (DOC) and catalyzed diesel particulate filters (CDPF) on particulate matter (PM) emissions. Four types of exhaust aftertreatments were applied to a diesel bus engine that meets the national Ⅲ emissions regulations. On-board tests were conducted respectively. PM emissions from the engine were strongly influenced by noble metal capacity in DOC and CDPF, especially at high speeds (the total number of particles increased by 70.8% when the noble metal capacity decreased by 5 g·ft-3 at 60 km·h-1). The higher the noble metal capacity was, the lower the PM emissions became, especially for PM in nuclei mode. The lanthanide material contributed to reducing PM emissions significantly. The content of precious metals could be reduced by 25% with proper lanthanide material, while the treatment effect of exhaust particles was guaranteed. In summary, aftertreatments are not sensitive to accelerating conditions, but the purification efficiency is obviously different under decontamination conditions.

[Emission Characteristics of Particulate Matter from Diesel Buses Meeting Different China Emission Standards Fueled with Biodiesel].

Based on heavy chassis dynamometer, an experimental study was conducted in diesel buses compliant with China Ⅲ,Ⅳ,Ⅴ emissions standards respectively, fueled with three different blends of petroleum diesel/biodiesel (0%,5%and 10%, V/V biodiesel blends), which investigated the characteristics of particulate matter (PM) emission under CCBC driving cycle. Results of study showed that the total PM number and mass emission from China Ⅴ bus respectively decreased by 68.1%,56.2%,57.5% and 52.7%,64.8%, 88.5% compared to China Ⅲ bus. When compared to China Ⅳ bus, the PM mass emission decreased by 43.0%, 47.3% and 42.1%, while the number increased by 4.0%,7.6% and 14.7%. The nucleation mode PM emission of China Ⅲ bus was mainly from high-speed driving condition, while China Ⅳ and Ⅴ buses were from middle-low speed. The accumulation mode PM emissions of China Ⅲ, Ⅳ and V buses were all mainly from middle-low speed driving conditions. In relatively lower speed conditions, compared to China Ⅲ bus, the nucleation mode PM emissions of China Ⅳ and Ⅴ buses obviously decreased, so was accumulation mode PM. Compared to China Ⅳ bus, emission of China Ⅴ bus did not improve obviously and the nucleation mode PM emission even increased. In high-speed driving condition, the nucleation mode PM emission from China Ⅲ bus increased dramatically, while those from China Ⅴ and Ⅳ buses slightly increased. Meanwhile, the accumulation PM number and mass emission of China Ⅳ bus was obviously higher than those of China Ⅴ and Ⅲ buses. When fueled with B10, the relatively bigger sizes PM emission of China Ⅲ bus deteriorated rapidly, indicating that China Ⅲ bus was not suitable for fuel with high blending ratio of biodiesel.

[Effect of DOC/CCRT Aging on Gaseous Emission Characteristics of an In-used Diesel Engine Bus].

Based on heavy chassis dynamometer, an experimental study was conducted in diesel bus with China Stage Ⅲ, which investigated the effects of gaseous emission characteristics under CCBC driving cycle, such as carbon monoxide (CO), total hydrocarbons (THC), nitric oxide (NO), nitrogen dioxide (NO2), nitrogen oxides (NOx) and carbon dioxide (CO2) with the fresh/aged oxidized catalyst (DOC) and oxidation catalysts coupled catalyzed particulate trap (DOC+CDPF, referred CCRT). The results showed that using fresh and aged DOC/CCRT, the diesel bus could reduce CO, THC and NO emissions, meanwhile increase NO2 emissions, but NOx and CO2 emissions remained basically unchanged. In idle speed, acceleration, deceleration and constant speed of working conditions, the diesel bus using the fresh DOC had better oxidation efficiency of the CO and THC emissions than the bus using the aged DOC. The diesel bus using the fresh CCRT had higher oxidation efficiency of THC emissions, but lower oxidation efficiency of CO emissions than the bus using the aged CCRT. The diesel bus using the fresh DOC/CCRT had a higher rate of NO emissions reductions and NO2 emissions increments than the bus using the aged DOC/CCRT, but it did not basically affect the NOx emissions.

[Emission Characteristics of Gaseous Pollutants from City Bus Fueled with Biodiesel Based on DOC+CDPF Technology in Real Road Conditions].

The gaseous emissions of stage Ⅲ standard City bus with and without DOC+CDPF after-treatment fueled with biodiesel blends on real road in steady-state and transient conditions were studied using OBS-2200 gaseous portable emission measurement. The results showed that B20 led to a decrease of CO and THC emission rates compared with those of B0. In steady-state condition, CO and THC average mass emission rates of B20 decreased by 26.43% and 10.44% respectively and in transient condition the decrease rates were 22.78% and 4.95%. Meanwhile, B20 eventuated in higher CO2 and NOx emission rates. In steady-state condition, CO2 and NOx average mass emission rates of B20 increased by 8.41% and 8.26% respectively and in transient condition the increase rates were 7.15% and 9.13%. DOC+CDPF caused a more obvious reduction of CO and THC emission rates of B20 compared with B0. In steady-state condition, CO and THC average emission rates decreased by 60.58% and 79.92%, while in transient condition they decreased by 63.67% and 82.57%. The influence of DOC+CDPF on emission reduction of CO2 and NOx was not obvious.

[Particle emission characteristics of diesel bus fueled with bio-diesel].

With the use of the Engine Exhaust Particle Sizer (EEPS), a study on the characteristics of particle emissions was carried out on a China-IV diesel bus fueled with blends of 5% , 10% , 20% , 50% bio-diesel transformed from restaurant waste oil and China-IV diesel (marked separately by BD5, BD10, BD20, BD50), pure bio-diesel (BD100) and pure diesel (BD0). The results indicated that particulate number (PN) and mass (PM) emissions of bio-diesel blends increased with the increase in bus speed and acceleration; with increasing bio-diesel content, particulate emissions displayed a relevant declining trend. In different speed ranges, the size distribution of particulate number emissions (PNSD) was bimodal; in different acceleration ranges, PNSD showed a gradual transition from bimodal shape to unimodal when bus operation was switched from decelerating to accelerating status. Bio-diesel blends with higher mixture ratios showed significant reduction in PN emissions for accumulated modes, and the particulate number emission peaks moved towards smaller sizes; but little change was obtained in PN emissions for nuclei modes; reduction also occurred in particle geometric diameter (Dg).

[Emission characteristics of polycyclic aromatic hydrocarbons in exhaust particles from a diesel car].

The emission characteristics of polycyclic aromatic hydrocarbons (PAHs) in exhaust particles from a diesel car were studied. In the experiment, pure diesel fuel and B10 fuel with a biodiesel blend ratio of 10% were chosen. The gaseous emissions of HC, CO and NO(x) under New European Driving Cycle (NEDC) were measured, and exhaust particulate matter (PM) samples were analyzed by gas chromatography-mass spectrometry. The emission characteristics of PAHs in exhaust particles were highlighted. The results show that the emission concentrations of HC, CO, NO(x), and PM decreased when the diesel car used B10 fuel. Fluoranthene and pyrene were dominant in PAHs of PM emissions when the diesel car used pure diesel or B10 fuel. Compared to pure diesel, there was a slight increase in low-ring PAHs emissions when the diesel car used B10 fuel. On the contrary, PAHs emissions in middle and high-ring declined significantly. Besides, Benzo [ a] pyrene equivalent toxicity analysis results show that the BEQs of B10 fuel decreased by 21.6% compared to pure diesel. That means the toxicity of PAHs in exhaust particles declined when the diesel car used biodiesel fuel.

[FTIR detection of unregulated emissions from a diesel engine with biodiesel fuel].

Biodiesel, as one of the most promising alternative fuels, has received more attention because of limited fossil fuels. A comparison of biodiesel and petroleum diesel fuel is discussed as regards engine unregulated exhaust emissions. A diesel fuel, a pure biodiesel fuel, and fuel with 20% V/V biodiesel blend ratio were tested without engine modification The present study examines six typical unregulated emissions by Fourier transform infrared spectroscopy (FTIR) method: formaldehyde (HCHO), acetaldehyde (C2 H4 O), acetone (C3 H6 O), toluene (C7 H8), sulfur dioxide (SO2), and carbon dioxide (CO2). The results show addition of biodiesel fuel increases the formaldehyde emission, and B20 fuel has little change, but the formaldehyde emission of pure biodiesel shows a clear trend of addition. Compared with the pure diesel fuel, the acetaldehyde of B20 fuel has a distinct decrease, and the acetaldehyde emission of pure biodiesel is lower than that of the pure diesel fuel at low and middle engine loads, but higher at high engine load. The acetone emission is very low, and increases for B20 and pure biodiesel fuels as compared to diesel fuel. Compared with the diesel fuel, the toluene and sulfur dioxide values of the engine show a distinct decrease with biodiesel blend ratio increasing. It is clear that the biodiesel could reduce aromatic compounds and emissions of diesel engines. The carbon dioxide emission of pure biodiesel has a little lower value than diesel, showing that the biodiesel benefits control of greenhouse gas.

[Emission characteristics of a diesel car fueled with coal based Fischer-Tropsch (F-T) diesel and fossil diesel blends].

According to the first type test cycle of China national standard GB 18352.3-2005, the CO, NO(x), HC, PM and CO2 emission characteristics of a PASSAT diesel car fueled with Shanghai local IV diesel, coal based Fischer-Tropsch (F-T) diesel, and the blends of coal based F-T diesel and Shanghai local IV diesel up to 10% and 50% by volume were analyzed respectively. And the environmental impacts such as decreased air quality, health impact, photochemical ozone, global warming, and acidification that could be caused by CO, NO(x), HC, PM and CO2 emission of the diesel car were also assessed. The results showed that under GB 18352.3-2005 No. 1 test driving cycle, which consisted of four urban driving cycles and one extra urban driving cycle, the CO, HC, PM and CO2 emissions were released mainly in the urban driving cycles whereas the NO(x) emissions occurred mainly in the extra urban driving cycle. Compared with Shanghai local IV diesel, all of the CO, NO(x), HC, PM and CO2 emissions of the diesel car decreased to different extents when fueled with coal based F-T diesel blends. Moreover, the aerosol generation potential, global warming potential and acidification potential of F-T diesel fueled diesel car were also reduced. To sum up, coal based F-T diesel would be one of the alternative fuels to diesel in China.

[Research on NEDC ultrafine particle emission characters of a port fuel injection gasoline car].

A Santana gasoline car with multi-port fuel injection (PFI) system was used as the research prototype and an engine exhaust particle sizer (EEPS) was employed to investigate the exhaust ultrafine particle number and size distribution characters of the tested vehicle in new European driving cycle (NEDC). The tested results showed that the vehicle's nuclear particle number, accumulation particle number, as well as the total particle number emission increased when the car drove in accelerated passage, and the vehicle's particle number emission was high during the first 40 seconds after test started and when the speed was over 90 km x h(-1) in extra urban driving cycle (EUDC) in NEDC. The ultrafine particle distribution of the whole NEDC showed a single peak logarithmic distribution, with diameters of the peak particle number emission ranging from 10 nm to 30 nm, and the geometric mean diameter was 24 nm. The ultrafine particle distribution of the urban driving cycle named by the economic commission for Europe (ECE) e. g. ECE I, ECE II - IV, the extra urban driving cycle e. g. EUDC, and the idling, constant speed, acceleration, deceleration operation conditions of NEDC all showed a single peak logarithmic distribution, also with particle diameters of the peak particle number emission ranging from 10 nm to 30 nm, and the geometric mean diameters of different driving cycle and different driving mode were from 14 nm to 42 nm. Therefore, the ultrafine particle emissions of the tested PFI gasoline car were mainly consisted of nuclear mode particles with a diameter of less than 50 nm.