OCR Text |
Show We also tried to estimate the probability density distributions of the air ratio from the temperature fluctuations of the burned gases. In the preliminary measurements of the temperature distribution in this combustion chamber, temperature profiles in the radial direction were found to be almost flat near the center of the combustion chamber. In the direction of the burned gas flow, for the flame with air ratio of 1.4, only a 15°C decline in 100 mm was observed. Therefore, it can be assumed that the thermal state in this chamber is adiabatic. Figure 10 shows the relationship between air ratio and burned gas temperature for a perfect mixing flame measured by a thermocouple. By referring to the relationship between the measured temperature and the air ratio, the measured temperature fluctuations were converted into air ratio fluctuations, and the probability density distribution of the air ratio was obtained. The standard deviations in the air ratio distributions are shown in Figure 11. The standard deviations were obtained only for air ratios ranging from 1.3 to 1.6, because for an air ratio of less than 1.3, the temperature fluctuations could not be measured due to the high temperature of the burned gases. The standard deviations are close to those calculated from the fuel concentration fluctuations. Although this is a crude estimation, the result shows that temperature fluctuations associated with air ratio fluc- 7 1800 Perfect mix ing oU -; 1600 ~ ~ 1400 t! 1200 0.0 0.5 1.0 1.5 Time (sec) 1800 Partial mixing p -; 1600 ~ Co E 1400 t! 1200 0.0 0.5 1.0 1.5 Time (sec) Rg.9 Burned gas temperature fluctuations 1800 r--~----------, 1700 o ~ 1600 :J 1\i ~ Q) a. ~ 1500 ~ 1400 - Adiabatic flame temperature ....- Perfect mixing 1300.1""'--~---=-~~---::-::5~~---=--::!---:-:t 1" 1 .2 1 .3 1 .4 1 . Air ratio Fig.10 Relationship between air ratio and burned 2.0 2.0 gas temperature measured by the thermocouple. |