Increase In Chemical Reaction Rate Research Articles

Comparison of the effect of heat release and products from heterogeneous reaction on homogeneous combustion of H2/O2 mixture in the catalytic micro combustor

Numerical simulation was carried out to investigate the hetero-/homogeneous combustion of stoichiometric H2/O2 premixed flames in a platinum-coated planar micro channel. Three-dimensional Computational Fluid Dynamics (CFD) models with detailed reaction mechanisms for homogeneous (gas phase, G) and heterogeneous (catalytic, C) reactions were adopted. The effects of the heat released and products from heterogeneous reaction (CR) on the homogeneous reaction (GR) were analyzed and compared systematically. In the presence of additional released heat, the flame temperature, intermediate concentrations and product yield increased, especially near the inner wall. The promotion effect of heat released from the CR on the GR was indicated, and it mainly reflected in the increase of chemical reaction rate and fuel consumption. When the heat released and the products from the CR were added simultaneously, the flame temperature and species (OH) concentration were still low as compared with the model without addition. The inhibition effect of the product on the GR was larger than the promotion effect of the additional heat on the GR. The increase in the chemical reaction rate and fuel conversion rate demonstrated that, the heat released from the CR could improve the combustion efficiency of the micro combustor.

Super-equilibrium increase of chemical reaction rate in the detonation front and other effects in the detonation wave initiated by a shock wave

In the present work the problem of detonation wave formation in a shock tube was considered in one-dimensional formulation. The Monte Carlo non-stationary method of statistical simulation (MCNMSS), also known as DSMC, was used for simulation. The method automatically takes into account all details of mass and heat transfer. At an initial moment, the low-pressure channel (LPC) of the shock tube was filled with gas A while the high-pressure chamber (HPC) was filled with gas C. The cross-sections of the HPC and LPC, as well as the temperatures of gases A and C were equal to each other. At the beginning of the simulation the ratio of pressures in the HPC and LPC was equal to 100. It was assumed that chemical reactions $$\mathrm{{A}}+\mathrm{{M}} \rightarrow \mathrm{{B}}+\mathrm{{M}}$$ ( $$\mathrm{{M}}=\mathrm{{A}},\, \mathrm{{B}}$$ and $$\mathrm{{C}}$$ ) took place. The ratio of molecular masses of gases $$\mathrm{{A}},\, \mathrm{{B}}$$ and $$\mathrm{{C}}$$ was taken as 20:20:1. Different reaction thresholds were considered. For the case of a low reaction threshold, the velocity of the resulting detonation wave was found to be higher than the Chapman–Jouguet velocity. A region with constant values of flow parameters inside product was observed. An increase of the reaction threshold led to disappearance of this region and gave rise to something similar to an expansion wave, with peaks of flow parameters at the leading part of the detonation wave. The values of these peaks were found to be constant in time. The velocity of the detonation wave became appreciably lower than the Chapman–Jouguet velocity. Further increase of the reaction threshold led to disappearance of detonation. The reactions $$\mathrm{{A}}+\mathrm{{B}} \rightarrow \mathrm{{B}}+\mathrm{{B}}$$ and $$\mathrm{{A}}+\mathrm{{C}}\rightarrow \mathrm{{B}}+\mathrm{{C}}$$ turned out to be very important for initiation of detonation.

연소공기의 산소부화농도에 따른 난류확산 평면화염의 연소특성

Combustion using oxygen enriched air is an energy saving technology that can increase thermal efficiency by improving the burning rate and by increasing the flame temperature. Flame figures, OH radical intensities, temperature distributions and emissions concentration were examined according to oxygen enriched concentration(OEC) in a turbulent diffusion flat flame. As long as the oxygen enriched concentration was increased, the length and volume of the flat flame was decreased while OH radical intensity was raised and the flame temperature was increased. However, RMS of the fluctuating temperature was decreased, and more homogeneous temperature field was formed. Thermal NO also was increased with increase of oxygen enriched concentration, but CO was decreased due to the increase of chemical reaction rate.