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Ignition electrodes have an immense impact on the accurate measurement of the flame propagation spherical radius. In this study, a flame-radius calculation method is designed. The method is able to eliminate effects due to the ignition electrodes. The adaptability and optimization effects of the proposed method are analyzed. The results show that the ratio of the angle is affected by the ignition electrodes under the Han II method. There are three obvious divisions include a high-value area, a sharp-variation area, and a mild-variation area. The ratio of the angle affected by the ignition electrodes is only applicable to the mild-variation region when the flame presents respective convex and concave distributions. For these distributions, the increment rate of the mean radius is 0.4–0.85% and 0.42–3.19%. The reduced rate of the standard deviation of the radius extraction value is 11.91–22.1% and 5.13–17.99%, and the reduced rate of the radius extraction value range is 20.32–39.51% and 0.32–8.09%. [ABSTRACT FROM AUTHOR]

The effect of dissociated methanol (H2:CO = 2:1 by volume) on laminar burning velocity of natural gas (methane as the main component) was studied by using a constant volume bomb (CVB). Nitrogen, as diluent gas, was added into the natural gas (CH4) - dissociated methanol (DM) mixtures to investigate the dilution effect. Experiments were conducted at initial temperature of 343 K and initial pressure of 0.3 MPa with equivalence ratios from 0.8 to 1.4. Laminar burning velocities were calculated through Schlieren photographs, correlation of in-cylinder pressure data and Chemkin-Pro. Results show an increase in laminar burning velocity with initial temperature and proportion of dissociated methanol but a decrease with initial pressure and proportion of nitrogen. The laminar burning velocities were 25.1 cm/s, 38.7 cm/s and 83.2 cm/s respectively at stoichiometric ratio when the proportions of the dissociated methanol were 0%, 40% and 80%. Adding more dissociated methanol tends to shift the peak burning velocity towards the richer side while adding nitrogen has the opposite effect. More dissociated methanol will lead to earlier cellularity. • The influence of dissociated methanol on laminar flame of natural gas was studied. • Laminar burning velocities were calculated through Schlieren, correlation and Chemkin Pro. • Burning velocity increases with fraction of methanol but decreases with fraction of nitrogen. • Adding more dissociated methanol shifts the peak burning velocity towards richer mixtures. • Lewis number and cellularity were both analysed to show instability of combustion. [ABSTRACT FROM AUTHOR]

This paper studies the effects of ash species and ash aging deposition on the physical and chemical properties of KC catalysts. By thermogravimetric analysis (TGA), the pure KC catalyst has good stability and catalytic activity at 600 °C. In the loosely contacting soot particles (PU)/ash/KC mixtures, the negative effect of ash on KC catalytic soot oxidation is relatively weak. The addition of ash makes the active site areas between PU and KC catalyst lose contact without changing the physicochemical properties of the catalyst. By contrast, the ash aging deposition on KC at 400 °C has an obviously negative effect on the soot combustion catalyzed by KC, because ash aging deposition leads to enormous changes in the chemical properties and catalytic activity of KC. This finding is consistent with characterization analyses such as XRD, SEM, XPS and Raman. Ash aging deposition destroys the KC structure and reduces the activity of KC to catalyze soot oxidation, and CaSO 4 has the greatest effect on the oxidation activity. Consequently, ash aging deposition causes structural property damage of as-prepared catalysts, leading to the failure of CDPF catalytic layer. This study provides a new idea for the selection and optimization strategy of catalysts in CDPF. • In loosely contact PU/ash/KC mixtures, the negative effect of ash on KC catalytic soot oxidation is relatively weak. • At 400 °C, ash aging deposition will lead to destruction of physicochemical properties of KC, and CaSO 4 has the greatest negative effect on the catalytic activity of catalyst. • The ash aging deposition can destroy the catalytic activity of KC to the greatest extent within 20 h at 400 °C aging temperature. [ABSTRACT FROM AUTHOR]

The initial conditions such as temperature, pressure and dilution rate can have an effect on the laminar burning velocity of natural gas. It is acknowledged that there is an equivalent effect on the laminar burning velocity between any two initial conditions. The effects of initial temperatures (323 K–423 K), initial pressures (0.1 MPa–0.3 MPa) and dilution rate (0–16%, CO2 as diluent gas) on the laminar burning velocity and the flame instability were investigated at a series of equivalence ratios (0.7–1.2) in a constant volume chamber. A chemical kinetic simulation was also conducted to calculate the laminar burning velocity and essential radicals' concentrations under the same initial conditions. The results show that the laminar burning velocity of natural gas increases with initial temperature but decreases with initial pressure and dilution rate. The maximum concentrations of H, O and OH increase with initial temperature but decrease with initial pressure and dilution rate. Laminar burning velocity is highly correlated with the sum of the maximum concentration of H and OH. [ABSTRACT FROM AUTHOR]