摘要:

An investigation of a method to control pollutant emissions from a propane diffusion flame by modifying the air infusion rate into it is presented. The modification was achieved by installing a set of Venturis around the burning gas jet(venluri-cascacling). Propane jet diffusion flames at three burner-exit Reynolds numbers (Re=3600, 5100 and 6500) corresponding to burner-rim-attached, in transition, and fully-lifted configurations were examined with several sets of Venturis of different sizes and spacing arrangements. Temperature and concentrations of CO2, O2, CO and NO in the exhaust products were measured with and without Venturis (baseline case). The largest effect of the venturi-cascade was observed at Re=5100. The lowest emissions of NO and CO were achieved with a venturi throat diameter/burner-exit diameter ratio (D/d) equal to 32±3. The influence of the size of Venturis was stronger than that of their spacing distribution. The flame structure measurements at those conditions showed that in the near-burner region of the venturi-cascaded flame the average values of temperature and CO2concentration were lower by 5% and 7% respectively than those in the baseline flame. However, in the mid-flame and far-burner regions of the venturi-cascaded flame the average temperature was higher by 13% and 12%, and the average CO2concentration was higher by 16% and 13%, respectively. In the near-burner, mid-flame, and far-burner regions, the venturi-cascaded flame had 16%, 5% and 3% lower average NO concentrations compared to the corresponding baseline flame. Laser Induced Fluorescence (LIF) measurements in the near-burner region of the venturi-cascaded flame indicated a decrease of 18%, 24% and 12% in the average concentrations of OH, CH and CN radicals, respectively, from their baseline values. However, in the mid-flame region, a 40% increase in OH from its baseline value was observed. In this region, CH and CN radicals were not detectable. The flow fields of the baseline and venturi-cascaded flames were numerically simulated using a computational fluid dynamics software package, and the role of Venturis in enhancing the influx of air was confirmed.

ISSN:0010-2202    

DOI:10.1080/00102209908924191

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Large-eddy simulation (LES) of turbulent premixed reacting flows in a gas turbine combustor (General Electric's lean premixed dry low-NOx LM6000) has been carried out to evaluate the potential of LES for design studies of realistic hardware. A flamelet model for the premixed flame is combined with a dynamic model for the subgrid kinetic energy to simulate the propagation of the turbulent flame in this high swirl and high Reynolds number flow. Comparison of the computed results with experimental data indicate good agreement in spite of relatively coarse grid resolution employed in the LES. These results provide significant confidence that LES capability for design studies of practical interest is feasible in the near future.

ISSN:0010-2202    

DOI:10.1080/00102209908924192

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A study of detailed species, velocity and temperature data of a pulverized coal flame is important to understanding the mechanisms which sustain the flame and lead to the formation of various pollutants such as NOx. The data can be particularly useful when compared to comprehensive combustion models which encapsulate the sub-models and processes of combustion. This data set contains in-situ axial and radial temperature, velocity and species concentrations for three swirl ratios of a pulverized coal flame located in a cylindrical, down-fired, 0.2 MWtreactor. Species measurements include CO, CO2, NO and O2. Velocity measurements were obtained using Laser Doppler Anemometry (LDA) and are summarized here after the method and results were reported in detail in a companion paper. The data show the change in structure of the coal flame as swirl is increased. At zero swirl the flame was located along a centerline jet, but as swirl increased, a recirculation zone was created which carried the combustion products up along the centerline of the reactor. Effluent NO was found to cone-late with the recirculation of products into the devolitilization zone and with the evidence of reduced mixing of fuel and secondary air at the primary tube outlet. Species measurements agreed with LDA results where concentration of O2were highest in the region of the secondary air jet. The species and temperature measurements are self consistent suggesting the data is accurate and will be useful when compared to combustion models.

ISSN:0010-2202    

DOI:10.1080/00102209908924193

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A two-color Laser Doppler Anemometer (LDA) was used to obtain axial and tangential velocity information in a 0.2 MW pulverized coal flame. In addition to the reacting flow data, a study on the accuracy of using coal as a seed panicle to measure gas phase velocity using LDA was performed. Non reacting flow velocity measurements were also obtained near the fuel inlet and in the quarl region of a geometrically identical burner to identify the velocity profile at several burner settings and to assist in establishing modeling inlet conditions. Both the reacting and non reacting velocity data were obtained at three or more swirl settings and various axial positions allowing a study of the affect of swirl on inlet turbulence and flame structure. The velocity results were compared with effluent NOxmeasurements. At the flow rates and accelerations experienced in this study, the coal particles were shown to be useful as seed particles for LDA gas phase velocity measurements. The coal-flame velocity indicated a centerline flame at 0 swirl transitioning to a radially directed flame with a central recirculation zone at swirl settings of 0.5 and 1.5. The transition of the flame structure to a central recirculation zone was also seen at the fuel inlet plane in the non reacting flow studies and was found to correlate with a decrease in measured effluent NOx. Measured axial velocity profiles 5 mm below the fuel inlet showed negetive axial velocities (in the opposite direction of the average flow velocity) were produced along the primary tube as swirl was increased from 0 to 1.5 with the transition occuring between 0.5 and 0.75 swirl. Transition in the flow near the fuel inlet correlated well with a drop in effluent NOxand with transitions in the recirculation zones measured further downstream. The strong interaction with burner velocity profiles and NOxsuggest velocity profile, in addition to swirl number, is an important measured boundary condition for modeling. The velocity data shown here in combination with a companion paper showing temperature and species data should provide important information needed to develop better models of pulverized coal combustion.

ISSN:0010-2202    

DOI:10.1080/00102209908924194

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor