摘要 :
Ignition delay times from undiluted mixtures of natural gas (NG)/H_2/Air and NG/NH_3/Air were measured using a high-pressure shock tube at the University of Central Florida. The combustion temperatures were experimentally tested b...
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Ignition delay times from undiluted mixtures of natural gas (NG)/H_2/Air and NG/NH_3/Air were measured using a high-pressure shock tube at the University of Central Florida. The combustion temperatures were experimentally tested between 1000-1500 K near a constant pressure of 25 bar. As mentioned, mixtures were kept undiluted to replicate the same chemistry pathways seen in gas turbine combustion chambers. Recorded combustion pressures exceeded 200 bar due to the large energy release, hence why these were performed at the high-pressure shock tube facility. The data is compared to the predictions of the NUIGMech 1.1 mechanism for chemical kinetic model validation and refinement. An exceptional agreement was shown for stoichiometric conditions in all cases but strayed at lean and rich equivalence ratios, especially in the lower temperature regime of H_2 addition and all temperature ranges of the baseline NG mixture. Hydrogen addition also decreased ignition delay times by nearly 90%, while NH_3 fuel addition made no noticeable difference in ignition time. NG/NH_3 exhibited similar chemistry to pure NG under the same conditions, which is shown in a sensitivity analysis. The reaction CH_3 + O_2 = CH_3O + O is identified and suggested as a possible modification target to improve model performance. Increasing the robustness of chemical kinetic models via experimental validation will directly aid in designing next-generation combustion chambers for use in gas turbines, which in turn will greatly lower global emissions and reduce greenhouse effects.
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摘要 :
This study explores the combustion characterization of high-fuel percentage, air-diluted mixtures of H_2 mixed with natural gas (NG) as well as mixtures of H_2 and NH_3 at temperatures and pressures relevant to turbine operating c...
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This study explores the combustion characterization of high-fuel percentage, air-diluted mixtures of H_2 mixed with natural gas (NG) as well as mixtures of H_2 and NH_3 at temperatures and pressures relevant to turbine operating conditions (20-30 bar, 1000-1500 K). Lower temperatures (below 1070 K) exhibit preignition characteristics due to non-homogeneity. An attempt to mitigate these occurrences at high pressures is investigated using the constrained reaction volume (CRV) stage-filling technique. Due to the need to further refine the facility CRV stage-filling uncertainty, only higher temperature data will be interpreted at this time. The test conditions in this study closely replicate the temperatures, pressures, and mixtures that would be seen in hydrogen-powered gas turbines, making it the first to explore such conditions. The experimental IDTs were compared against the current state-of-the-art chemical kinetic models for mechanism validation. The current work will advance H_2-powered turbines and aims to determine the optimum molecular ratio of H_2 when mixed with natural gas.
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摘要 :
Catalytic metal foils were adhered to the end wall of a shock tube with stoichiometric methane mixtures, achieving pressures from 18.9 to 24 atm and temperatures between 1178 - 1642 K. Preliminary results show little effect on vol...
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Catalytic metal foils were adhered to the end wall of a shock tube with stoichiometric methane mixtures, achieving pressures from 18.9 to 24 atm and temperatures between 1178 - 1642 K. Preliminary results show little effect on volumetric ignition delay time. Emission spectroscopy, laser Schlieren, and pressure histories record before the main ignition event. Activation energies have been found, and the feasibility of this technique to study catalytic surface effects have been established.
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Methane oxidation experiments have been performed at 100 and 200 bar in argon and CO_2 bath gases. The insight gained from qualitative laser absorption spectroscopy measurements using a helium-neon IR laser at 3391 nm clarifies th...
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Methane oxidation experiments have been performed at 100 and 200 bar in argon and CO_2 bath gases. The insight gained from qualitative laser absorption spectroscopy measurements using a helium-neon IR laser at 3391 nm clarifies the interpretation of ignition due to the dual-peaks seen in emissions traces during combustion in mixtures heavily diluted in CO_2. Further, it calls into question interpretation of other work in the pressure regime. Models were used and compared to qualitative laser absorption data to elucidate ignition delay time in experiments with multiple interpretations.
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This study reports the autoignition delay times of hydrogen/ammonia mixtures at conditions similar to turbine engine operating conditions (23 bar, 1100-1250 K). H_2 was mixed with NH3 and shock-heated using synthetic air as the ox...
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This study reports the autoignition delay times of hydrogen/ammonia mixtures at conditions similar to turbine engine operating conditions (23 bar, 1100-1250 K). H_2 was mixed with NH3 and shock-heated using synthetic air as the oxidizer. The data is compared against the current state-of-the-art NH3 chemical kinetic mechanisms found in the literature for undiluted fuel validation and refinement. Experiments were performed in a high-pressure shock tube and have shown detonation pressures reaching 200 bar. Lower temperature points have also exhibited non-ideal behavior, which calls for extensive chemical analysis to accurately report the IDTs. This work will aid in the design of air-breathing turbine engines using hydrogen and ammonia as fuel and develop a well-built NH_3-based chemical kinetic mechanism.
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摘要 :
Stoichiometric oxy-methane mixtures at pressures of 18.9 to 24 bar and temperatures between 1178 -1642 K were studied in a shock tube. Emission spectroscopy, laser Schlieren, pressure histories, and fixed wavelength laser absorpti...
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Stoichiometric oxy-methane mixtures at pressures of 18.9 to 24 bar and temperatures between 1178 -1642 K were studied in a shock tube. Emission spectroscopy, laser Schlieren, pressure histories, and fixed wavelength laser absorption spectroscopy at 3.39 μm has been used to measure methane decomposition rates and find the absorption cross-section of methane at 3.39 μm at these conditions. Various catalytic end walls were employed to determine any surface effects caused by the catalytic material observable at a location remote from the end wall.
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摘要 :
This study explores the combustion characterization of high-fuel percentage, air-diluted mixtures of H_2 mixed with natural gas (NG) as well as mixtures of H_2 and NH_3 at temperatures and pressures relevant to turbine operating c...
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This study explores the combustion characterization of high-fuel percentage, air-diluted mixtures of H_2 mixed with natural gas (NG) as well as mixtures of H_2 and NH_3 at temperatures and pressures relevant to turbine operating conditions (20-30 bar, 1000-1500 K). Lower temperatures (below 1070 K) exhibit preignition characteristics due to non-homogeneity. An attempt to mitigate these occurrences at high pressures is investigated using the constrained reaction volume (CRV) stage-filling technique. Due to the need to further refine the facility CRV stage-filling uncertainty, only higher temperature data will be interpreted at this time. The test conditions in this study closely replicate the temperatures, pressures, and mixtures that would be seen in hydrogen-powered gas turbines, making it the first to explore such conditions. The experimental IDTs were compared against the current state-of-the-art chemical kinetic models for mechanism validation. The current work will advance H_2-powered turbines and aims to determine the optimum molecular ratio of H_2 when mixed with natural gas.
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