摘要:

We have obtained quantitative LIF measurements of NO concentration in the postflame zone of a series of flat, laminar, premixed C2H6/O2/N2flames at pressures ranging from 3.05 to 14.6 atm. The temperatures of the flames were 1600-1850K, indicating that most of the NO produced in the flames is prompt NO. We have found that the equivalence ratio corresponding to the peak NO concentration at a given pressure shifts towards leaner conditions with increasing pressure. In addition, we have modeled the flames using two chemical kinetics models: the Glarborg-Miller-Kee mechanism as modified by Drake and Blint (GMK-DB), and the Miller-Bowman mechanism (MB). Both models accurately predict the pressure trends of NO formation, while the quantitalive agreement with measurements is, in general, good for the GM K-DB model and poor for the M B model. Explanations are provided both for the poor agreement found with the MB model and for the shift in peak NO concentration with pressure.

ISSN:0010-2202    

DOI:10.1080/00102209408935402

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We describe linear stability results for flames fueled by mixtures of air and particles. Nonsimilarity between the temperature and fuel concentration fields gives rise to an intrinsic pulsating instability for unconfined flames (a single mode). Acoustic interactions for confined propagating flames generate acoustic instabilities (an infinite number of modes) when the gas-phase velocity is different from that of the solid phase (i.e. there is slip). The confinement modes can not, in general, be classified as intrinsic, fundamental, first-harmonic, etc. For example, for propagation in a tube with flame initiation at the open end, a mode can start as the second harmonic but finish, when the flame is at the closed end, as the fundamental. Instabilities tend to be suppressed in spherical flames generated by point ignition in a confinement vessel. The triggering of acoustic instabilities in gas turbines by slip between fuel drops and air is discussed, and we show that the role of slip is quite different when the condensed phase is injected at a finite point rather than being dispersed throughout the gas phase.

ISSN:0010-2202    

DOI:10.1080/00102209408935403

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

This paper presents the results of a study designed to determine the effects of natural gas cofiring on particle ignition delay for variously sized pulverized coal and coke particles exposed to realistic combustor conditions. A fluidized bed feeder injects small numbers of particles (typically three to five) into a drop tube furnace at temperatures from 1300K to 1500K with heating rates up to 102K/sec. Individual particle ignition times are recorded using an optical sensor at the furnace entrance and a photomultiplter tube at the furnace exit. Ignition delay measurements were performed for various inlet gas velocities, particle volatilities and gas compositions (including variations in oxygen, methane, natural gas, nitrogen and carbon dioxide concentrations). Ignition measurements with particles of different volatile contents, ranging from 7.5% to 36.1%, show that addition of 1% methane by volume reduces the ignition delay of low volatile particles to a level similar to the ignition delays for high volatile coal of the same particle size. Experimental results are compared with ignition delays predicted by using a thermal model of particle behavior coupled with two ignition models—one model based on energy absorption and the other based oh devolatilization. The thermal model includes the effects of gas phase combustion, particle size and swelling, gas and particle velocity and temperature. The energy-ignition model requires an experimentally determined ignition energy for each tested coal. The devolalilization-ignition model predicts ignition delay using a single value for the minimum volatile concentration required for ignition for all tested coals. Both ignition models accurately predict the measured ignition delay for various volatile contents and sizes in cofiring experiments.

ISSN:0010-2202    

DOI:10.1080/00102209408935404

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

This paper presents and discusses measurements of local flame temperature, local gas species concentrations and incident wall heat fluxes obtained in a 250 MWe residual fuel-oil front fired utility boiler. The work is aimed at improving knowledge of the efficiency of the thermal processes involved in large industrial boilers and covers three different operating conditions, which include load and air-fuel ratio variations.

ISSN:0010-2202    

DOI:10.1080/00102209408935405

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor