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The prospects of 2-methylfuran (2MF) as a biofuel and gasoline blend stock are quite high. Therefore, a skeletal chemical kinetic mechanism – containing 238 species and 1156 reactions – for the simulation of premixed flames involving isooctane (representing gasoline)/2MF blends is proposed in the present work. The proposed model has been validated against a wide range of experimental data at various pressures, temperatures and compositions. It is demonstrated in the present work that the proposed mechanism can predict the concentrations of gaseous soot precursors as well. Moreover, the compatibility of the NOx sub-mechanism in the present model has been assured through validations against a wide range of recent experimental data. The results obtained in this work suggest that there are little chances of co-oxidation reactions among the species generated from the initial decomposition of both isooctane and 2MF. Furthermore, there is around 26% variation in the peak laminar burning velocity when the mole fraction of 2MF is increased from 10% to 90% in isooctane/2MF blend. [ABSTRACT FROM AUTHOR]

The prospects of 2,5-dimethylfuran (DMF) as a bio-derived fuel that can be blended with gasoline are believed to be impressive. However, the effects of blending DMF on the key combustion parameters like the laminar burning velocity and ignition delay time of gasoline/air mixture need to be studied extensively for the successful implementation of the fuel mixture in spark ignition engines. Therefore, a skeletal chemical kinetic mechanism, comprising of 999 reactions among 218 species, has been developed in the present work for this purpose. The proposed chemical kinetic model has been validated against a wide range of experimental data for the laminar burning velocity and ignition delay time of isooctane (representing gasoline), DMF and their blends. It has been found from the present study that the thermal diffusivity of the unburnt gas mixture changes by a very small amount from the corresponding value for the pure isooctane/air mixture when DMF is added. Unlike isooctane, the DMF molecule does not consume H radicals during its primary breakup. Therefore, the maximum laminar burning velocity increases marginally when 50% DMF is blended with isooctane due to the increased presence of H radicals in the flame. The negative temperature coefficient behaviour in the ignition delay time of the isooctane fuel vanishes when 30% DMF (v/v) is blended to it. [ABSTRACT FROM AUTHOR]

In this work, a two-dimensional computational fluid dynamics study is reported of ann-heptane combustion event and the associated soot formation process in a constant volume combustion chamber. The key interest here is to evaluate the sensitivity of the chemical kinetics and submodels of a semi-empirical soot model in predicting the associated events. Numerical computation is performed using an open-source code and a chemistry coordinate mapping approach is used to expedite the calculation. A library consisting of various phenomenological multi-step soot models is constructed and integrated with the spray combustion solver. Prior to the soot modelling, combustion simulations are carried out. Numerical results show that the ignition delay times and lift-off lengths exhibit good agreement with the experimental measurements across a wide range of operating conditions, apart from those in the cases with ambient temperature lower than 850 K. The variation of the soot precursor production with respect to the change of ambient oxygen levels qualitatively agrees with that of the conceptual models when the skeletaln-heptane mechanism is integrated with a reduced pyrene chemistry. Subsequently, a comprehensive sensitivity analysis is carried out to appraise the existing soot formation and oxidation submodels. It is revealed that the soot formation is captured when the surface growth rate is calculated using a square root function of the soot specific surface area and when a pressure-dependent model constant is considered. An optimised soot model is then proposed based on the knowledge gained through this exercise. With the implementation of optimised model, the simulated soot onset and transport phenomena before reaching quasi-steady state agree reasonably well with the experimental observation. Also, variation of spatial soot distribution and soot mass produced at oxygen molar fractions ranging from 10.0 to 21.0% for both low and high density conditions are reproduced. [ABSTRACT FROM PUBLISHER]

A new thermo-diffusive analysis of one-dimensional laminar lean or rich off-stoichiometric premixed spray flames has been performed using a chain branching/chain breaking chemical kinetic scheme and under the assumption that the fuel droplets evaporate in a sharp front. The sensitivity of the flame structure, speed and the location of the evaporation front to the initial droplet load have been demonstrated. A linear stability analysis reveals the way in which the spray's presence modifies the neutral stability curves. [ABSTRACT FROM AUTHOR]

The combustion characteristics for the turbulent diffusion flames using the unsteady flamelet concept have been numerically investigated. The Favre-averaged Navier-Stokes equations are solved by a finite volume method of SIMPLE type that incorporates the laminar flamelet concept with a modified k - ε turbulence model. The NO formation is estimated by solving the Eulerian particle transport equations in a postprocessing mode. Two test problems are considered: CH4/H2/N2 jet flame and CH4/H2 stabilised bluff body flame. The temperature and species profiles are well captured by the flamelet model. Two different chemical mechanisms (GRI 2.11 and 3.0) give nearly identical results for temperature and species except NO. The GRI 3.0 gives significantly higher NO levels compared to the GRI 2.11. This is mainly attributed to the difference in NO formation by the prompt mechanism. The NO formation is sensitive to the number of flamelet particles. The NO levels for two test flames do not change when the flamelet particle number exceeds six. [ABSTRACT FROM AUTHOR]