Water fugacity and oxygen fugacity can be controlled concomitantly in solid‐media high‐pressure apparatus by using CO2‐H2O vapors and the double‐capsule technique with oxygen buffers. Calculations based on an ideal‐solution model yield values of the fugacities of O2, H2, and H2O in the samples.

The purpose of this study was to characterize experimental n-heptane combustion behavior in a direct-injection constant-volume combustion chamber (DI-CVCC), using chamber pressure to infer ignition delay and heat-release rate. Measurements generally displayed expected trends and indicated entirely premixed combustion with no mixingcontrolled phase. A significant finding was the observation of negative temperature coefficient (NTC) behavior. Comparing results with CHEMKIN-PRO simulations, it was found that a homogeneous combustion model was reasonably accurate for ignition delays longer than 5 ms. The combination of NTC behavior and homogeneous fuel-air mixtures suggests that this DI-CVCC can be useful for validation of chemical-kinetic mechanisms.

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Lean premixed (LPM) combustion is a common strategy in the turbine industry for power generation to reduce emissions of nitric oxides and other pollutants. LPM combustion tends to produce thermoacoustic instabilities under specific conditions. Previously we have shown that an appropriately designed ring-shaped porous insert located on the dump plane can mitigate thermoacoustic instabilities in LPM swirl-stabilized combustion for a range of operating conditions, and explained results based on time-resolved flowfield measurements. In this study, experiments are conducted at higher inlet air temperatures than used before, and the flame structure in the combustor without and with porous insert is investigated for the first time using time-resolved OH planar laser-induced fluorescence technique operated at 10 kHz. Large pressure oscillations in the fuel-air mixing tube demonstrate the existence of thermoacoustic instabilities without the porous insert. The pressure oscillations diminish with the porous insert, which is attributed to the changes in the flow field and flame structure.