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Effect of dimethyl ether (DME) addition on PAH and soot formation mechanisms as well as particle-size distribution function (PSDF) behavior of C2H4 premixed burner-stabilized stagnation (BSS) flame was studied. A wide range of DME addition from pure C2H4 to pure DME was considered. The sectional aerosol dynamics model with detailed gas- and particle-phase kinetic mechanism was employed for the simulations. The results indicate that soot growth rate by nucleation, and especially the H-abstraction C2H2 addition (HACA) mechanism and polycyclic aromatic hydrocarbons (PAH) condensation increased significantly inside the stagnation boundary layer, due to strong flame-wall interaction. The PSDF curve in the post-flame region was unimodal, while that in the stagnation boundary layer was bimodal. The first peak of the PSDF curve in the stagnation boundary was resulted from the enhanced nucleation rate, and the second peak was due to the intensified soot surface growth by HACA reaction and PAH condensation. The rich premixed C2H4 BSS flame did not exhibit the synergistic effect of DME addition on PAH and soot formations. Soot formation rate decreased monotonously with DME addition for the C2H4 premixed BSS flame. Topology of soot PSDF behavior of the C2H4 premixed BSS flame changed significantly when DME addition exceeded above 20%.

In this paper, the moderate or intense low-oxygen dilution (MILD) technology was employed to reduce NOx emission index of the DME flame, whose NOx emission was expected high due to its higher adiabatic flame temperature. Experiments and modeling were conducted to study NOx emission mechanism of the DME-MILD jet diffusion flame. Various co-flow temperatures ( T c o ∗ ) and oxygen concentrations ( X O 2 ∗ ) were involved to investigate dependence of NOx emission mechanism on hot dilution level. NOx formation pathway in all subzones was clarified, employing the reaction path and sensitivity analyses. The results showed that for the DME-MILD jet flame, NOx was generated mainly through the NNH and N2O pathways, which was rather different from the traditional DME jet diffusion flame. EINOx increased gradually with the increment in X O 2 ∗ or T c o ∗ . A strong NO NO2 conversion process and ultra-clean performance were verified for the DME-MILD jet flame.

Thermoelectric devices can provide clean energy conversion and are environmentally friendly. However, few studies have been conducted to understand the dynamic characteristics of (thermoelectric generators) TEGs. The stability of output performance plays a very important role in TEG. Based on the thermoelectric effect and heat transfer theory, a dynamic model for waste heat recovery in a general TEG was developed to asses the influence of heat reservoir and heat sink. The validity of the theoretical model was demonstrated by experiments and it was found that the model prediction agrees well with the experimental results. The dynamic response characteristics, such as hot and cold semiconductor surface temperatures, maximum output power and system efficiency, were studied using this dynamic model. The results showed that enhancing heat dissipation on cold side is the crucial to improve the output performance of TEG, and that the fluctuation of hot reservoir leads to rapid change of output power generated by TEG, which is dangerous to electric devices. The dynamic model proposed in the present study can be used in the design and operation analysis of TEGs.