OCR Text |
Show For the second pair of cycles, tested in June 1998. the oscillating combustion cycle was conducted at a very low frequency and a somewhat higher amplitude. This yielded a substantial fuel savings and a moderate reduction in N O x over the whole cycle, but exceeded 4 0 % during the heat up portion of the cycle (see Figure 13). -Steady (Baseline) Oscillating Combustion (6% reduction) Time into cycle, nr Time into cycle / / > / s y-^S '•'•'' Steady (Baseline) Oscillating Combustion NO* reduction (-11 - 42%) Avg NOx reduction (18%) N \ * N f c - " • .* • ^ ^ - ' ^ - ao 60 . 40 :o .0 -Steady (Baseline) - Oscillating Combustion NOx Re<Jucoon (0 - 47%) ..Avg. N O x Seduction (32%) Time into cycle, nr Time into cycle, hr (a) T9 cycle. June 1998 (b) T2 cycle, September 1998 Figure 13. F U E L U S A G E A N D N O x EMISSION C O M P A R I S ON (Axis numbers removed to protect proprietary data) For the third pair of cycles, tested in July 1998, the oscillating combustion cycle was conducted at a higher frequency and the same amplitude. This was expected to yield better fuel savings due to increased heat transfer resulting from the increased combustion turbulence from the higher frequency, but only yielded a small fuel savings. This cycle had a much lower product temperature; therefore baseline N O x emissions were much lower. Oscillating combustion seems to perform better when the heat up period is a substantial part of the cycle and when the baseline N O x is high. For the fourth pair of cycles, tested in June 1998, the oscillating combustion cycle was conducted at same and lower frequencies but at a much higher amplitude. The oscillation frequency was the same as the last test for the heat up period, but was reduced during the soak period to help reduce N O x then. This yielded the same fuel savings as the last test, which had the same cycle type, but a substantial reduction in N O x over the whole cycle, and reaching almost 5 0 % at the end of the heat up portion of the cycle (see Figure 13). In should be noted that the oscillating combustion cycle from this pair of cycles emitted almost the exact same amount of N O x as the steady flow cycle from the previous pair of cycles even thoueh 5 0 % more steel was annealed. (afrc98p doc) 10 |