OCR Text |
Show calculate this incremental NO production, attributable to FBN, the amount x K of concurrently produced thermal NO (for the same fuel) is also required. Its value is determined indirectly, by firing a nitrogen-free base fuel (b) under identical conditions and using the assumption that the two types of NO formations have proceeded independently of each other. Accordingly, the FBN conversion efficiency is expressed by the following equation: C^>NOx(i) - %0x(b) ^ N O (FBN) FBN conversion efficiency Measured total NO emission for fuel (i) x Measured NO emission for nitrogen-free base fuel (b) Amount of NO obtainable from the full conversion of x FBN in fuel (i) The strict applicability of the expression is limited to areas where properties of the nitrogen bearing (i) and base fuel (b) are nearly identical. Corrections may be required, e.g., for differences in fuel hydrogen contents, since a lower hydrogen content - through the rise of combustor temperature - could be responsible for a higher thermal NO formation for that fuel, as brought out by the results of this study. An example for the potential utility of the term, 'Tj.., in the comparison of two machines is given in Figure 9. NO Results x In Figure 7, NO emissions are presented for different fuels as a function of turbine load. The results were corrected to ISO, 15 percent oxygen, dry conditions and are relative to the NO emissions measured for the base diesel fuel at 100 percent load. The picture clearly shows the increase of NO with decreasing fuel hydrogen and also illustrates that FBN in shale oil and EDS has not significantly contributed to the total NO emissions. The *|N where: ^N0 (i) x ^ N 0 (b) x ^ N O (FBN) 1.4.8 |