A comparative investigation between particle oxidation catalyst (POC) and diesel particulate filter (DPF) coupling aftertreatment system on emission reduction of a non-road diesel engine.

Non-road emission regulations are becoming increasingly rigorous, which makes it necessary for non-road engines to adopt aftertreatment systems. The commonly used aftertreatments mainly include diesel oxidation catalytic (DOC), diesel particulate filter (DPF), particle oxidation catalyst (POC), selective catalytic reduction (SCR) and ammonia purification catalyst (ASC). The purpose of this study is to investigate the effects of using an integrated system (DOC + DPF/POC + SCR + ASC) on non-road diesel engine emissions under steady-state and transient operating conditions, respectively. The major works are the comparison between POC and DPF from the viewpoint of emission reduction. The results show that both POC and DPF can effectively reduce particulate matter (PM) and nitrogen oxide (NOX) emissions under steady-state conditions, and DPF has better purification effect than POC, especially for PM. The PM conversion rate of DPF is up to 87%, while that of POC is only 60% under the non-road steady-state test cycle (NRSC). Both NOX and hydrocarbon (HC) conversion rates are high, exceeding 95%. The conversions of PM, NOX, HC, and carbon monoxide (CO) of DPF in the non-road transient test cycle (NRTC) are 92.83%, 96.99%, 96.86% and 81.45%, respectively, while those of POC are 60.12%, 95.45%, 92.82% and 79.51%, respectively. Both the POC and DPF systems can meet the emission regulation limits. As a result, POC has the potential to substitute DPF in non-road engines due to its lower product and maintenance costs. We hope that the comparison study will provide useful guidance for improving the emissions performance of non-road diesel engines.

Effects of inhalation frequency on inhalation/exposure dose of hazardous nanoparticles and toxic gases during cigarette smoking.

In this study, we measured the pollutants generations during cigarette smoking under various inhalation frequency experiment scenarios by a self-developed smoking machine. Some concepts, the effective inhaled amount and exposure amount were proposed to quantitatively estimate emission rates. Important findings include: For interval 1 s, 2 s, 3 s, 4 s and 9 s (called from 1 s to 9 s herein), effective inhaled nano-scale PN (particle number) per cigarette was 8.43E+09 #, 7.24E+09 #, 5.74E+ 09 #, 3.82E+09 # and 1.15E+09 #, it decreased linearly with interval time; exposure amount of PN in side stream smoke was 1.06E+10 #, 1.2E+10 #, 1.48E+10 #, 1.84E+10 # and 8.74E+10 #, it increased with interval time. For toxic gases, all pollutants decreased with interval time in main stream smoke. In side stream smoke, NOx and CO firstly increased with interval time and then decreased (with the highest value at 3 s interval time), while HC always increased with interval time. So, this study is useful to understand the relationship between pollution and smoking habit.

Measurement of harmful nanoparticle distribution among filters, smokers' respiratory systems, and surrounding air during cigarette smoking.

This study was undertaken to investigate the filtration effect of filter on nanoparticle and the deposition behavior of nanoparticle in the human respiratory system from the aspect of nanoparticle number during cigarette smoking. For that, two kinds of experiments were designed. One is machine experiment, a well-controlled simulated respiratory system was designed to measure the raw emission and filter effect. Another is human experiment, volunteers were asked to inhale smoke into the oral cavity only and lungs, respectively, to distinguish smoke path. Results revealed that effective inhaled nanoparticle amount of a Taishan and a Hongtaishan cigarette were 5.8E + 9 (#) and 9.4E + 7 (#), respectively. The filter's integrated reduction rate was 41.65% for nanoparticle. For Taishan cigarette, 35.4% and 41.7% of raw emitted nanoparticles were deposited in the oral cavity and lungs, respectively, the rest of 22.9% was exhaled to surrounding air. The corresponding values were 25.6%, 41.5% and 32.9%, respectively, for Hongtaishan. The current findings are expected to provide basic assessments of filter effect and harm to human and to be a warning for smokers.

Quantitative detection, sources exploration and reduction of in-cabin benzene series hazards of electric buses through climate chamber experiments.

In this study, a large-scale in-cabin benzene series hazard detection is firstly performed on 20 electric buses by a full-scale climate chamber. The sources of BTEX are analyzed deeply by parts detection, and a series of effective measures are performed to reduce BTEX. Firstly, the in-cabin BTEX pollution with considerations of a series of parameters, such as interior configuration, environment temperature, vehicle age, and ventilation mode, is analyzed. The result shows that: 1) The VOCs concentrations decrease with vehicle age, higher configuration level and better ventilation system (particularly, fresh wind mode reduce VOCs fastly), while increases with environment temperature; 2) BTEX in bus cabins occupy approximatively 70.1% of TVOC, thus the BTEX overproof is the main culprit which causes VOCs to exceed standard. Then, measurements on components/materials VOCs releases were performed in a small climate chamber to discriminate key species and their sources. Xylene released from glues materials is found as a key species that causes BTEX/VOC to exceed limitation. Lastly, some measures, such as optimizations of materials selection and manufacturing crafts, are adopted to improve in-cabin pollution, and positive effects are obtained. For example, ethylbenzene and xylene released from HL 125 (a polyurethane adhesive) decrease by 2456% and 1930% respectively after improvement. And in-cabin xylene and TVOC decrease by 2274% and 222%, respectively, and all of them are lower than limitation value.

The study of laser cooling of TeH- anion in theoretical approach.

The probabilities of laser cooling of TeH- anion via a spin-forbidden transition and a three-electronic-level transition are proposed. The potential energy curves of the X1Σ+, a3∏, A1∏, and b3Σ+ electronic states of tellurium monohydride anion (TeH-) are calculated using multi-reference configuration interaction method. Davidson corrections, core-valence correlations and spin-orbit coupling effects are also considered. The AWCV5Z-PP pseudopotential basis set of Te atom is used. Spectroscopic parameters of the Λ-S and Ω states are obtained by solving radial Schrodinger equation. These results are reported at the first time. Permanent dipole moments of the Ω states and transition dipole moments of the a21↔X0+ and A1↔X0+ transitions are also calculated. Highly diagonally distributed Franck-Condon factors of the a21↔X0+ and A1↔X0+ transitions are obtained, the value of f00 is 0.9970 and 0.9980, respectively. Spontaneous radiative lifetimes of the a21 and A1 excited states are predicted. i.e. τ(a21) = 200.3 ns and τ(A1) = 84.3 ns. Only the main pump laser is required to driving a21↔X0+ and A1↔X0+ transitions. The laser wavelengths both are in the visible region. Doppler temperatures and recoil temperatures of laser cooling TeH- anion are also predicted.

Dispersion behaviors of exhaust gases and nanoparticle of a passenger vehicle under simulated traffic light driving pattern.

In the present study, the flow structure and pollutants dispersions were investigated by experiment and simulation on a typical passenger vehicle under simulated traffic light driving pattern. Some important findings were achieved: 1) gaseous pollutants diffuse drastically during first 0.3-0.6 m distance depending on wind velocity, at 1.25 m/s wind speed which is the similar level of exhaust gas, the pollutant concentration rises suddenly at ~0.6 m because exhaust plume is twisted by bottom gas flow, and a low velocity zone is produced; 2) as wind speed increases, the vehicle-induced turbulence is more and more important on pollutant dispersion pattern than exhaust plume dynamics. For instance, at 1.25 m/s and 4.17 m/s wind speeds, pollutants decrease to zero at ~1.6 m behind tail pipe, but at 0 m/s condition, pollutant relative fraction is still at ~0.12 level even at very long distance; 3) solid particle has larger attenuation rate than gaseous pollutants, only after ~0.6 m the particle number (PN) and diameter are very close to background values. Solid particle can diffuse to farther distance in vehicle transverse direction, when a car passes through the pedestrians with a 3 m distance, pedestrians expose to 2.6-3 times higher PN relative to atmosphere with diameters of 28-33 nm, this is very hazardous for human health; 4) exhaust pollutants disperse difficultly when followed by a car with a commonly waiting distance. At free dispersion scenario only behind ~0.6 m, PN decreases to 5800 #/cm3 (background value), but in-cabin PN of the following car (behind 0.8 m) rises to 3.5 × 104 #/cm3 (even after 2-3 times decay through ventilation system). This study provides implications for future studies on transport planning.