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Show Measurement and Interpretation - 17 - of Flames Issued from a Generic Multi-Fuel Burner 6'300 eft. (') rn CD as 250 .J:l ~ ~ CI) E 200 Z 13> -E )( o 150 Z 1.5 2.0 2.5 3.0 3.5 4.0 Tertiary Air Injection Location (m) IFRF-~ 4.5 Fig. 4.5. NOx Emissions for Natural Gas Reburning with Variation in Tertiary Air Injection Location. 5. MATIlEMATICAL MODELING Detailed in-flame measurements were conducted for the baseline oil burner as defined in section 4.1 as well as similar conditions with natural gas and light fuel oil firing. The detailed in-flame measurements consisted of gas temperature, velocity, and species: CO, C02, NOx and 02' Due to the very high flame luminosity, the LDV system was unable to detect Doppler signals in the center of the flames. At the time of the measurements, the receiving optics was equipped with two 40 nm band pass filters which could not provide a sufficient reduction of the background light below the Doppler signal amplitude. It is expected that the future use of 1 J.1ffi interferometric filters will alleviate this problem. Calculations are currently being conducted using the commercial CFD code, FLUENT. Space allocations preclude a detailed description of the code. Shown in Figs. 5.1-5.4 are comparisons of model calculations and measured values. The predictions of temperature follow the flame structure well. The major discrepancy lies in the under-prediction of the temperature gradient at the flame front. The species concentrations shown good agreement between the measured and calculated values. The velocity components are well predicted with the strong peak in the axial velocity present due to the combustion air stream. |
