摘要:

The kinetic modeling of thermal decomposition of C3O2and formation of soot-like solid particles behind shock waves is carried out. The transformation of C atoms up to the cluster C30in the gas phase and the formation, growth, transfer, and coagulation of carbon solid particles are modeled with the help of a detailed gas phase kinetic scheme combined with a discrete Galerkin method. Together with the calculation of concentration profiles of small carbon clusters, precursors of solid panicles, soot-like solid particles, and fullerene-like solid particles, the temperature dependencies on the induction period, the growth rate constant, the yield, and the mean size of carbon solid particles are obtained for a mixture of 0.33 % C3O2in argon for the following experimental conditions: A pressure of 5.0 MPa and a temperature range of 1200 to 2250 K. The comparison of these calculated values with the experimentally measured ones is performed and the possible pathways of transformation of C atoms from C3O2to soot-like solid particles are analyzed.

ISSN:0010-2202    

DOI:10.1080/00102200008947344

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This paper investigates the feasibility of using acoustic excitation and coaxial air to control NOx production from a jet flame and tries to scale the NOx emission index of the jet hydrogen flame in the laminar regime. Applying both coaxial air and excitations through coaxial nozzle at low frequencies are found to be effective in reducing the flame length and the NOx emissions. A simple scaling law for NOx emission index from hydrogen jet flames with no coaxial air in the laminar regime is developed. The scaling, based on the flame length, nozzle diameter and exit velocity, for the residence time in the laminar jet flames is derived. The normalized NOx emission index, EINOX normalized by the residence time, can be scaled as the 1/2 power of the global strain rate in the laminar regime that is identical with Chen and Driscoll's (1990) scaling in the turbulent regime. This scaling result implies that effects of the buoyancy vortices, which prevail in the laminar regime, on the NOX production in a laminar hydrogen jet flame take place only through the residence time. With low frequency excitation, close to the flame flickering frequency, the normalized EINOX data have a similar power dependence, about 0.6, on the global strain rate, (UF/dF). The effect of the coaxial air on EINOX comes through reduction of the flame length. The derived simple scaling is not suitable for the coaxial-air cases. Reduction of both EINOX and EICO using acoustic excitaion with a suitable combination of frequency and amplitude is possible for propane jet flame; however, no simple scaling law is yet obtained

ISSN:0010-2202    

DOI:10.1080/00102200008947345

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

An experimental approach based on the simultaneous measurement of laser-induced fluorescence along a line and the transmission is discussed which allows the quantitative measurement of combustion intermediates. The technique is applied to measure in-cylinder number densities of OH radicals using an optically accessible two-stroke engine. OH radicals are recorded for different cylinder pressures during the expansion stroke. From the data pressure dependent probability density functions (pdfs) are obtained. Precalculated combustion scenarios based on an opposed jet geometry and on a homogeneous reaction scheme are used to analyse correlations between the measured OH number densities and other scalars, e.g, the temperature and O-atoms which are important for the detennination of NOxemissions in post-processing steps of CFD calculations. By the use of experimentally obtained pdfs for the OH radical and the correlation analyses, an improved estimation of pdfs for the temperature and O-atoms is presented.

ISSN:0010-2202    

DOI:10.1080/00102200008947346

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor