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This work presents an experimental study on the influence of the pilot flame characteristics on the flame morphology and exhaust emissions of a turbulent swirling flame. A reduced-scale burner, inspired by that fitted in the AE-T100 micro gas turbine, was employed as the experimental platform to evaluate methane (CH4) and an ammonia-methane fuel blend with an ammonia (NH3) volume fraction of 0.7. The power ratio (PR) between the pilot flame and the main flame and the fuel composition of the pilot flame was investigated. The pilot power ratio was varied from 0 to 20% for both fuel compositions tested. The NH3 volume fraction in the pilot flame ranged from pure CH4 to pure NH3 through various NH3–CH4 blends. Flame images and exhaust emissions, namely CO2, CO, NO, and N2O were recorded. It was found that increasing the pilot power ratio produces more stable flames and influences most of the exhaust emissions measured. The CO2 concentration in the exhaust gases was roughly constant for CH4-air or NH3–CH4–air flames. In addition, a CO2 concentration reduction of about 45% was achieved for XNH3 = 0.70 compared with pure CH4, while still producing stable flames as long as PR ≥ 5%. The pilot power ratio was found to have a higher relative impact on NO emissions for CH4 than for NH3–CH4, with measured exhaust NO percentage increments of about 276% and 11%, respectively. The N2O concentration was constant for all pilot power ratios for CH4 but it decreased when the pilot power ratio increased for NH3–CH4. The pilot fuel composition highly affected the NO and N2O emissions. Pure CH4 pilot flames and higher power ratios produced higher NO emissions. Conversely, the NO concentration was roughly constant for pure NH3 pilot flames, regardless of the pilot power ratio. Qualitative OH-PLIF images were recorded to further investigate these trends. Results showed that the pilot power ratio and the pilot fuel composition modified the flame morphology and the OH concentration, which both influence NO emissions.

This work presents an experimental study on the influence of the pilot flame characteristics on the flame morphology and exhaust emissions of a turbulent swirling flame. A reduced-scale burner, inspired by that fitted in the AE-T100 micro gas turbine, was employed as the experimental platform to evaluate methane (CH[sub.4] ) and an ammonia-methane fuel blend with an ammonia (NH[sub.3] ) volume fraction of 0.7. The power ratio (PR) between the pilot flame and the main flame and the fuel composition of the pilot flame was investigated. The pilot power ratio was varied from 0 to 20% for both fuel compositions tested. The NH[sub.3] volume fraction in the pilot flame ranged from pure CH[sub.4] to pure NH[sub.3] through various NH[sub.3] –CH[sub.4] blends. Flame images and exhaust emissions, namely CO[sub.2] , CO, NO, and N[sub.2] O were recorded. It was found that increasing the pilot power ratio produces more stable flames and influences most of the exhaust emissions measured. The CO[sub.2] concentration in the exhaust gases was roughly constant for CH[sub.4] -air or NH[sub.3] –CH[sub.4] –air flames. In addition, a CO[sub.2] concentration reduction of about 45% was achieved for X[sub.NH3] = 0.70 compared with pure CH[sub.4] , while still producing stable flames as long as PR ≥ 5%. The pilot power ratio was found to have a higher relative impact on NO emissions for CH[sub.4] than for NH[sub.3] –CH[sub.4] , with measured exhaust NO percentage increments of about 276% and 11%, respectively. The N[sub.2] O concentration was constant for all pilot power ratios for CH[sub.4] but it decreased when the pilot power ratio increased for NH[sub.3] –CH[sub.4] . The pilot fuel composition highly affected the NO and N[sub.2] O emissions. Pure CH[sub.4] pilot flames and higher power ratios produced higher NO emissions. Conversely, the NO concentration was roughly constant for pure NH[sub.3] pilot flames, regardless of the pilot power ratio. Qualitative OH-PLIF images were recorded to further investigate these trends. Results showed that the pilot power ratio and the pilot fuel composition modified the flame morphology and the OH concentration, which both influence NO emissions.

Intrinsically defect-free asymmetric hollow fiber polyimide membrane modules were studied in the presence and absence of saturated and aromatic components. Results suggest that an essentially defect-free, non-nodular morphology offers advantages in stability under demanding operating conditions. Earlier work showed serious losses in performance of membranes comprised of similar materials, when the selective layer had a pronounced fused nodular nature as opposed to the intrinsically defect-free skin layers reported on here. Under some conditions for the ternary system, the permselectivity of the membrane is scarcely affected, while under other conditions, permselectivity is negatively affected by as much as 25%. In most cases, for the ternary feeds, significant depression in fluxes was observed due to competition between the CO2, CH4 and heavier hydrocarbons but the effect was even more pronounced for the toluene. In addition to steady state tests in the presence and absence of n-heptane and toluene, modules were conditioned for five days with ternary mixture of CO2, CH4 and one or the other of these heavy hydrocarbons. Following this conditioning process, the modules were studied with a simple binary 10% CO2/90% CH 4 mixture. These conditioning studies provide insight into the fundamental effects induced in the membrane due to the long term exposure to the complex mixtures. Following exposure to the ternaries containing n-heptane, negligible CO2 permeance increase was seen, while significantly increased permeances were seen under some conditions following toluene exposure even at low pressures of the ternary toluene/CO2/CH4 conditioning gas mixture. Although a more protracted process occurs in the case of heptane/CO 2/CH4 at 35°C and 500 ppm, a serious loss in selectivity occurs in the actual ternary tests after exposure for five days. The problem caused by 300 ppm toluene at 35°C is more immediately apparent, but the ultimate selectivity loss is similar. In addition to the selectivity, in the presence of toluene the permeability is also depressed significantly, presumably due to a greater capability to toluene to compete for added free volume elements introduced in the conditioning process. The permeation enhancement due to toluene exposure is lost slowly when the module downstream is put under vacuum and the gas no longer in contact with the module for up to three weeks. (Abstract shortened by UMI.)