Finite-rate entrainment effects on nitrogen oxide (NOx) emissions in staged combustors
| Autor: | James Li, Edwin Goh, Jerry Seitzman, Nam Y. Kim, Tim Lieuwen |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
010304 chemical physics
Combined cycle General Chemical Engineering Mass flow Mixing (process engineering) General Physics and Astronomy Energy Engineering and Power Technology 02 engineering and technology General Chemistry Mechanics Parameter space 01 natural sciences law.invention chemistry.chemical_compound Fuel Technology 020401 chemical engineering chemistry law 0103 physical sciences Combustor Environmental science Nitrogen oxide 0204 chemical engineering Entrainment (chronobiology) NOx |
| Zdroj: | Combustion and Flame. 230:111434 |
| ISSN: | 0010-2180 |
| DOI: | 10.1016/j.combustflame.2021.111434 |
| Popis: | Axially staged combustors offer the potential for achieving low NO x emissions from gas turbines at the elevated temperatures required to achieve at least 65% combined cycle efficiencies. While there is evidence that premixing between the main burner products and secondary stream reduces NO x , it is important to characterize the specific requirements needed to achieve low emissions at gas turbine conditions. This study examines the sensitivity of NO x to finite-rate, large-scale entrainment of the main and secondary streams under the simplifying assumption of infinitely-fast small-scale mixing. Essentially, this allows us to isolate the effects of limited large-scale entrainment rates by using a homogeneous/uniform condition for the entrained and reacting gases. We use a reduced-order reactor network model to examine a generic staged-combustor whose inputs are physical time scales that embody the finite-rate entrainment characteristics. With simulations conducted over a large parameter space at typical operating conditions (25 atm, 650 K air), the results show that, even when small-scale mixing is infinitely fast and the reaction zone is uniform, entrainment significantly affects NO x emissions due to its influence on the equivalence ratio — and thus the temperature and time — at which the entrained mixture ignites. Fuel-air staging is shown to be vital to NO x reduction in most practical cases where entrainment times exceed roughly 1 ms and the secondary stream finishes entraining before the main burner products. A constrained NO x minimization indicates that using the leanest possible main burner and re-routing as much air as possible to the secondary stage is key to low NO x with finite-rate entrainment; for example, less than 10 ppm NO x can be achieved if the secondary stage contains 20% of the total mass flow. |
| Databáze: | OpenAIRE |
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