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This paper reports the effect of post-injection on pollutant emissions from a four-cylinder, direct-injection diesel engine fueled with biodiesel. Characteristics of exhaust pollutants were measured and evaluated for different main-post intervals (MPIs) and post-injection rates (PIRs). Measurements included emissions of carbon monoxide (CO), total hydrocarbons (THC), nitrogen oxides (NO x ) and particulate matter (PM), the particle number concentration distribution, and the reactivity and graphitization degree of the soot particles. Increasing the MPI or PIR increased the emissions of CO and THC but decreased those of NO x . At both low and high MPI values, higher PM emissions and particle number concentrations were observed for the 12 and 20% PIRs. At a PIR of 4%, PM emissions and particle number concentration increased with the increase in MPI. The size distributions of exhaust particulates exhibited a trimodal character under the applied operating conditions. The particle geometric mean diameter decreased with the increase in MPI, probably as a result of an increased yield of soluble organic compounds. Post-injection significantly impacted the reactivity of emitted soot particles, as evidenced by changes in the graphitization degree of soot. [ABSTRACT FROM AUTHOR]

We investigate effects of post injection strategies on regular exhaust emissions and soot particulate matters on in-cylinder emission control. A trade-off relation indicates that CO and THC emissions increase as post injection timing delays, but NOx emission significantly decreases when crank angle intervals increase because of cylinder volume expansion and heat transfer. In PM emission, total particle concentration and particle size distributions indicate that, at early post injection timing, SOF emission is relatively low but soot emission is relatively large caused by high temperature and local lean oxygen conditions. As crank angle intervals increasing, soot emission decreases quickly and becomes insensitive to the post injection timing. When SOF emission has an obvious increasing trend, there is a lowest level for the PM emission at intermediate post injection timing. Moreover, variations for total particle concentration are similar with soot emission at different post injection strategies. Particle size distribution result illustrates that PS is insensitive to post injection timing at different post injection strategies. [ABSTRACT FROM AUTHOR]

Highlights: [•] Zirconia introduction favors copper dispersion and inhibits copper crystallization. [•] Zirconia addition is beneficial to enriching copper species on the ZSM-5 surface. [•] The interaction between copper and zirconium enhances the lattice oxygen and site reducibility. [•] The Cu-Zr/ZSM-5 presents a wide activity window within the range of diesel exhaust temperatures. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an investigation of the carbonyl emissions from a direct injection heavy-duty diesel engine fueled with pure diesel fuel (DF) and blended fuel containing 15% by volume of ethanol (E/DF). The tests have been conducted under steady-state operating conditions at 1200, 1800, 2600rpm and idle speed. The experimental results show that acetaldehyde is the most predominant carbonyl, followed by formaldehyde, acrolein, acetone, propionaldehyde and crotonaldehyde, produced from both fuels. The emission factors of total carbonyls vary in the range 13.8–295.9mg(kWh)−1 for DF and 17.8–380.2mg(kWh)−1 for E/DF, respectively. The introduction of ethanol into diesel fuel results in a decrease in acrolein emissions, while the other carbonyls show general increases: at low engine speed (1200rpm), 0–55% for formaldehyde, 4–44% for acetaldehyde, 38–224% for acetone, and 5–52% for crotonaldehyde; at medium engine speed (1800rpm), 106–413% for formaldehyde, 4–143% for acetaldehyde, 74–113% for acetone, 114–1216% for propionaldehyde, and 15–163% for crotonaldehyde; at high engine speed (2600rpm), 36–431% for formaldehyde, 18–61% for acetaldehyde, 22–241% for acetone, and 6–61% for propionaldehyde. A gradual reduction in the brake specific emissions of each carbonyl compound from both fuels is observed with increase in engine load. Among three levels of engine speed employed, both DF and E/DF emit most CBC emissions at high engine speed. On the whole, the presence of ethanol in diesel fuel leads to an increase in aldehyde emissions. [Copyright &y& Elsevier]

Copper–cerium–zirconium catalysts loaded on TiO 2 prepared by a wet impregnation method were investigated for NH 3 -selective catalytic reduction of NO x , aiming to study the effects of the Ce/Zr molar ratio on the performance of Cu–Ce–Zr/TiO 2 catalysts. The Cu–Ce 0.25 –Zr 0.75 /TiO 2 sample exhibited nearly 100% NO x conversion over a wide temperature range (165–450 °C), which is strikingly superior to that of Cu/TiO 2 (210–389 °C) within the range of exhaust temperatures of diesel engines. The factors that govern the activity enhancement were extensively investigated by using a series of characterization techniques, namely X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction by hydrogen (H 2 -TPR). The results showed that the addition of zirconium and/or cerium refined the copper dispersion, prevented copper crystallization and partially incorporated the copper ions into the zirconia (ceira) lattice, which led to enhance the redox abilities of Cu–Ce–Zr/TiO 2 catalysts. [ABSTRACT FROM AUTHOR]