摘要:

Laboratory experiments have been performed to evaluate the performance of a premixed low-swirl burner (LSB) in configurations that simulate commercial heating appliances. Laser diagnostics were used to investigate changes in flame stabilization mechanism, flowfield, and flame stability when the LSB flame was confined within quartz cylinders of various diameters and end constrictions. The LSB adapted well to enclosures without generating (lame oscillations and the stabilization mechanism remained unchanged. The feasibility of using the LSB as a low NOxcommercial burner has also been verified in a laboratory test station that simulates the operation of a water heater. It was determined that the LSB can generate NOxemissions < 10 ppm (at 3% O2) without significant effect on the thermal efficiency of the conventional system. Our study has demonstrated that the lean premixed LSB has commercial potential for use as a simple economical and versatile burner for many low emission gas appliances.

ISSN:0010-2202    

DOI:10.1080/00102209808952088

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

With an adequate correction, thermocouples can be used for the measurement of high gas temperatures within enclosing walls of different temperatures. Considering heat radiation between thermocouple and surroundings, Fischer developed a two-sensor method for the case with only one unique surrounding surface temperature, which is widely used for this kind of correction. The modified two-sensor method derived in this paper is applicable to the case with different surface temperatures of the surroundings, if inter-reflections between the surrounding surfaces may be neglected. Fischer's correction may thus be considered as a special case of this modified two-sensor method.

ISSN:0010-2202    

DOI:10.1080/00102209808952089

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Axisymmetric ignition and flame propagation across propanol pools is investigated numerically with finite-rate one-step chemical kinetics, variable properties, and an adaptive finite-difference gridding scheme without forced gas-phase flow.

ISSN:0010-2202    

DOI:10.1080/00102209808952090

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Characteristics of flame propagation along a nonpremixed vortex ring, which is generated by the ejection of propane by a single stroke motion of a speaker, are investigated experimentally. A Nd:YAG laser is used as the ignition source to prevent it from disturbing the flow fields. A schlieren technique is adopted for flow visualization, through which the dimension and translational velocity of the vortex ring are measured and the ignition location and timing are determined. Flame shapes and flame displacement speeds are measured from ICCD images and high speed photographs.

ISSN:0010-2202    

DOI:10.1080/00102209808952091

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

An engineering model that can be used to obtain predictions of axial distributions of temperature and species concentrations in dump combustors has been formulated and used to study controlled waste (benzene) incineration. The model incorporates mean convection and molecular diffusion in a quasi-one dimensional formulation and uses a stochastic model to approximate the effects of turbulent mixing on the scalar fields. The inputs to the model are extracted from experimental data and results of Large Eddy Simulations (LES). It is shown here that this approach allows the model to be developed without requiring any ad-hoc constants that have to be calibrated or tuned. Comparisons of waste consumption rates and pollutant formation in the dump combustor with experimental data show that the model can capture the experimentally observed trends correctly. Furthermore, the predicted destruction efficiency of benzene and the predicted levels of CO and NO emission show that this model also achieves fairly good quantitative agreement. The ability of this model to do scaleup design studies of large scale incinerator is also demonstrated.

ISSN:0010-2202    

DOI:10.1080/00102209808952092

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The reduction of nitric oxide (NO) in simulated conditions of the reburning zone has been studied in a fused silica jet-stirred reactor operating at atmospheric pressure, in the temperature range 1100-1500 K, in diluted conditions. A mixture of CH4and C2H6(10:1), a natural gas blend, was used as reburning fuel. The initial mole fractions of NO, hydrocarbon and H2O have been varied as well as the temperature, and the equivalence ratio. From the present study it was demonstrated that the NO reduction potential varies as the temperature, the initial mole fraction of reburning fuel, and that the initial mole fraction of NO has only a minor effect on the reduction of NO when the reduction of NO is high. In conditions where the reduction of NO is low, the efficiency of the process tends to moderately increase with the initial concentration of NO. Optimal conditions for the reburning of NO can be obtained for particular combinations of equivalence ratio and temperature. These results, which clarify the influence of these important parameters on the kinetics of NO reburning, are generally in agreement with previous investigations. A detailed chemical kinetic modeling of the present experiments was performed (786 reversible reactions and 113 species). An overall reasonable agreement between the present data and the modeling was obtained although improvements of the model are still needed. The main route to NO reduction involves ketenyl radical. The model indicates that the reaction path: HCCO + NO → HCNO + CO followed by HCNO + H → HCN + OH is responsible for the occurrence of a minima for TFN atϕ≃ 1-25. According to the present modeling, the reduction of NO by CH4/C2H6mix can be summarized as: HCCO + NO → HCNO → HCN → NCO → HNCO → NHi; NHi, + NO → N2; NH + NO → N2O; N2O + M,H → N2.

ISSN:0010-2202    

DOI:10.1080/00102209808952093

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The interaction of a single vortex ring of gaseous fuel with a nonpremixed flame was examined. A burning vortex ring was generated by issuing fuel from a round nozzle and then igniting it by means of a residual flame sustained at the nozzle tip. Flow visualization was conducted through a time resolved Mie scattering, Schlieren, and flame luminosity records. The favorable range of test conditions, in which flame extinction caused by excessive strain does not occur, was provided. The main effects of combustion on the vortex are the significant alterations in the ring celerity as well as its growth rate, and the retardation of its instability. The comparison between vertically upward and downward evolving vortex flames showed that buoyancy force plays a significant role in the structure and developing characteristics of burning vortex rings. The formation of a ‘reacted core’ was observed in a real flame, as predicted by the earlier vortex pair analysis of Karagozian_and Manda (1986).

ISSN:0010-2202    

DOI:10.1080/00102209808952094

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The special problems associated with the destruction of highly fluorinated one and two carbon organics under combustion conditions are discussed in terms of their fundamental chemical kinetic properties. It is shown that the fluorinated compounds are in general more thermally stable than chlorinated organics and hydrocarbon fuels. Nevertheless, the conditions that are achievable in an incinerator are capable of effecting destruction to high levels. Special characteristics of the decomposition of highly fluorinated compounds are identified with the high strength of the C—F and H—F bonds and the weak HO—F and O—F bonds. We present results on the computer simulations of the combustion of methane and ethane in the presence of fluorinated compounds and suggest that this may be a means of making predictions regarding incinerability of such compounds. Perfluorinated methane, CF4, is particularly stable and its destruction almost certainly guarantees destruction of other organic compounds in the same input stream. The problem of the formation of fluorinated combustion by-products is also discussed. The great stability and other properties of the fluorinated compounds make them particularly suitable as surrogates during hazardous waste incineration.

ISSN:0010-2202    

DOI:10.1080/00102209808952095

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor