This study proposes an idea of NOx reduction and high efficiency combustion by combination of burner and furnace. This is basically attributed to the use of entrainment of burnt gases to flame in furnace. The entrainment of burnt gases leads the dilution of flame and the recovery of heat to be exhausted. The phenomena are strongly related to the geometry of burner and furnace. The temperature, concentration, and flow field characteristics were investigated for piloted propane non-premixed flames in the cylindrical furnaces in terms of NOx emission. The effects of the furnace inner diameter, D1, air inlet velocity difference, ΔUa, and global equivalence ratio,φ, on NOx emission were investigated. Moreover, two kinds of materials: Pyrex glass and stainless steel were used as the furnace wall to evaluate the radiation effect through the comparison of the flame characteristics. The emission index of NOx, EINOx, decreases roughly with the increase of above parameters. This decrease is observed to be a consequence of dilution by the burnt gases and flame stretch. The dilution is attributed to the recirculation structure, which is formed at the bottom of the furnace. The flame stretch is related to the velocity difference, which is introduced by multiple air inlets. The EINOx of confined non-premixed flame is scaled by the parameter D1UFΔUa, which is proportional to Re,cDa-1. Here, UF is the fuel velocity, Re,c is the furnace Reynolds number reflecting the turbulence in the furnace, and Da is the Damköhler number reflecting the flame stretch. The parameter D1UFΔUa is related linearly to the volume flow rate entrained in to the flame. Thus, this study verified that the EINOx of confined non-premixed flame is dominated primarily from the entrainment of burnt gases by the recirculation vortex and secondarily by the turbulence at the flame boundary, which is generated by the air velocity difference. In addition, it is found that under present experimental conditions, the radiation effect on the EINOx is small and constant with respect to the parameters. Thus, this idea has a potential for practical applications.
The control of nitrogen oxides (NOx) is currently a major issue in designing an effective combustion system because NOx has several detrimental effects on the environment and human health. However, it is difficult to understand NOx formation processes in flames because of complicated interactions between the flow and chemistry. In this study, a partially-stirred-reactor combustion model is implemented in the OpenFOAM CFD tool to model confined turbulent non-premixed propane jet flames, and the NOx emission is evaluated in terms of the global equivalence ratio. The code solves Reynolds-Averaged Navier Stokes equations on an unstructured mesh in a cylindrical coordinate system. The computational predictions of scalar and flow fields in the combustion chamber are extensively compared to experimental measurements, and they show a good agreement. The oxidation and heat-release rates of propane are computationally evaluated, and they are used to verify the scalar fields such as temperature and mole fractions of species. The increase in the global equivalence ratio increases the maximum temperature of the furnace because of the enhancement of reaction rate, and thereby, leads to the enrichment of the NOx emission.
We produced porous glass fiber reinforced ceramic by mixing clay and crushed waste glass fiber reinforced plastic (GFRP) before firing the mixture. Sprues and runners, which are by-products from the manufacture of plastic merchandise by injection molding, were used as waste GFRP. By observing the ceramic microstructure and examining its strength, it was confirmed that porous ceramic reinforced by glass fiber could be produced. In addition, to examine the environmental suitability of the ceramic, the pH of immersion liquid was measured and acid resistance tests were carried out. The immersion solution of the ceramic was neutral or slightly alkaline, the mass loss of the ceramics in the acid resistance test was small and the reduction in bending strength after the tests was also very small. The ceramic is considered to be environmentally benign. The results suggest that the manufacture of porous glass fiber reinforced ceramic can be an effective means to recycle waste GFRP. It is expected that the ceramic could be used as a construction material because of its lightweight, high strength properties and environmental suitability.
To research the mechanism of automobile aerodynamic noise which transmits to the inside of a cabin, the flow structure and sound field have been investigated by making experimental measurements at the wind tunnel and performing Computational Fluid Dynamics (CFD) based on the Lattice Boltzmann Method (LBM). The noise transmitted at a window glass on the front side is focused in this study. Pressure fluctuations on the side window glass contain both hydrodynamic pressure fluctuations induced by the flow field and acoustic pressure fluctuations propagated from noise sources. It was found by examining the experimental transmission loss that on the side window glass it is close to the random incidence mass law in the high frequency range. To verify the outside sound field, the wave number - frequency spectrum method was applied to computational results in the region behind and outside a sideview mirror. Hydrodynamic and acoustic fluctuations were researched in the wave number - frequency region. This result suggests that the sound field behind the mirror is not a directional sound field but a diffuse sound field.