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PurposeThe purpose of this computational fluid dynamics (CFD) study is to give insight about the influence of the piston bowl geometry and the fuel ignition features on the resonance of direct injection diesel engines combustion chambers in order to provide support to the experimental findings on combustion noise.Design/methodology/approachThe resonance due to the burned gases oscillations in a diesel combustion chamber is caused by the sudden rise in pressure due to the initial ignition of the air‐fuel mixture, and leads to the resonance noise. In the CFD study presented here the excitation source is represented by imposing locally in a small area (excitation zone) the pressure and temperature gradients of the start of combustion. The CFD approach is first validated against the acoustic modal theory. A parametric study representing different ignition conditions is then performed with a real bowl geometry.FindingsThe solutions obtained are analysed in terms of the energy of resonance (ER) and the response in the frequency domain. It was found that the response in frequency only varies with the diameter of the bowl, while the ER varies significantly in function of the injection conditions.Research limitations/implicationsThese first conclusions need to be verified on the one hand by taking into account the piston motion, and, on the other hand, by modelling in a more realistic way the combustion excitation.Practical implicationsThis CFD study has brought some insight into the flow phenomena that affect the resonance modes of a combustion chamber.Originality/valueThis CFD study uses a novel methodology to model the effect of the combustion excitation on the resonance modes of a combustion chamber.

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The preparation, characterization, and application in oxidation reactions of new biomimetic catalysts are reported. Brazilian Sao Simao kaolinite clay has been functionalized with [meso-tetrakis(pentafluorophenyl)porphinato]iron(III), Fe(TPFPP). To obtain the functionalized clay, the natural clay was purified by dispersion-sedimentation, expanded by insertion of dimethyl sulfoxide (DMSO), and functionalized with amino groups by substitution of DMSO with ethanolamine. These previous steps allowed clay functionalization with Fe(TPFPP), leading to a layered material with a basal spacing of 10.73 A. Clay functionalization with the porphyrin was confirmed by formation of the secondary amine, as demonstrated by FTIR bands at 3500-3700 cm(-1). UV-vis spectroscopy revealed a red shift in the Soret band of the iron porphyrin in the functionalized material as compared to the parent iron porphyrin catalyst in solution, indicating Fe(III)P --> Fe(II)P reduction. The catalytic performance of the functionalized clay was evaluated in the epoxidation of cyclooctene, with complete selectivity for the epoxide (100% epoxide yield), and ketonization of cyclohexane, cyclohexanone being the major product. The novel catalyst was also evaluated in the Baeyer-Villiger (BV) oxidation of cyclohexanone, with 85% conversion of cyclohexanone in epsilon-caprolactone, with total selectivity to epsilon-caprolactone.