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The cellular instabilities of premixed C1–C3 alkane–air mixtures were investigated at an initial temperature of 400 K and different initial pressures (0.25–1.5 MPa). Flame propagation images were recorded using high-speed Schlieren photography techniques. Cellular instabilities were analyzed using both qualitative and quantitative methods. The results showed that with an increase in the initial pressure, the flame instabilities of these three alkane–air mixtures increased as a result of the enhanced hydrodynamic instability. For a given initial pressure and with an increasing equivalence ratio, the thermal-diffusive instability was the main influencing factor on the flame instability of methane when Φ ≤ 1.0, whereas it was the result of hydrodynamic and thermal-diffusive instability when Φ > 1.0. The flame instability of ethane and propane was caused by the enhanced hydrodynamic and thermal-diffusive instability when Φ ≤ 1.0, whereas it was determined by diffusion-thermal instability when Φ > 1.0. Under the conditions with the strongest cellular instability, the cellular instability of these three alkane–air mixtures tended to increase with an increasing number of carbon atoms in the fuel. • Constant volume combustion vessel and schlieren photography techniques were used. • Flame instabilities of C1–C3 alkane–air premixed flames were investigated. • Critical Peclet number of the unstable flame was evaluated. • Cellular instabilities were analyzed using both qualitative and quantitative methods. [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]

The influence of dissociated methanol (DM) and diluent (CO 2 and N 2) addition on methane was investigated in a constant volume chamber under initial conditions of 3 bar and 343 K. CO was also added in separate proportions instead of DM under the same conditions to assess its effect. The laminar burning velocity, Markstein length and flame instability were analyzed systematically under various equivalence ratios (0.8–1.4), dissociated methanol gas ratios (40 and 80%), CO ratios (40 and 80%) and dilution ratios (0–15%). Furthermore, the flame speed of the fuel mixture and the production rate of key reactants were analyzed based on the calculation results of the Aramco Mech 2.0 mechanism to determine the influence principles of dilution. The results show that dissociated methanol gas increases the flame speed of the mixtures and promotes instability of the flame, and H 2 is the dominant component in enhancing the combustion process. Within the dilution ratio range of this study, the diluents decrease the laminar burning velocity of the mixtures since the addition of diluent gas decreases the concentration of key reactants, such as H and OH. The addition of diluent gas can inhibit the flame instability, but the effect is not clear. Compared with N 2 , the effect of CO 2 is more significant. • Methane/dissociated methanol/diluent fuel mixture was investigated. • The laminar burning velocity, Markstein length and flame instability were analyzed. • Laminar burning velocity was investigated both experimentally and numerically. [ABSTRACT FROM AUTHOR]

• K-Ce catalysts promote the low temperature combustion of soot by enhancing contact with soot particles and increasing oxygen vacancies. • Catalytic activity is optimal when the molar ratio of K/(K+Ce) is 0.2 and soot/KC-0.2 mixture weight ratios is feasible below 1:10. • K-Ce catalysts and K-Ce based mixed catalysts have good stability at temperatures lower than 600 °C. • Mixed catalysts with commercial catalysts participation are synthetized to further study the catalytic effect of KC-0.2 based mixed catalyst on soot combustion. A series of K-Ce catalysts with different K/(K+Ce) molar ratios are successfully prepared by hydrothermal method, to optimize catalyst diesel particlate filter (CDPF) regeneration efficiency of soot elimination. The K-Ce catalyst is an excellent promoter for soot combustion by thermogravimetric analysis (TGA), and the KC-0.2 catalyst has the best catalytic activity because proper K ions lead to more oxygen vacancies and improve contact efficiency with soot. This result corresponds well to characterization analysis, such as XRD, SEM and XPS. In a 10%O 2 /90%N 2 atmosphere, the KC-0.2 has the highest average mass loss rate (W mean), maximum mass loss rate (W max) and combustion stability index (R w). The weight ratios of the soot/KC-0.2 mixture are less than 1:10, making catalytic oxidation easier for the soot. Thermal aging in static air at 600 °C is used to investigate the catalytic stability of KC-0.2, and the TGA results show that KC-0.2 has good stability at temperatures lower than 600 °C. Compare to KC-0.2, the KC-0.2 based mixed catalyst with ZrO 2 participation is further prepared by mechanical method and has better catalytic activity because the presence of Zr enhances redox surface sites of catalyst. This facilitates the exploration of novel catalysts through combinatorial catalysis. [Display omitted] [ABSTRACT FROM AUTHOR]