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Accurate and high-speed transient surface-temperature measurements of combustion devices including internal combustion (IC) engines, gas turbines, etc., provide validation targets and boundary conditions for computational fluid dynamics models, and are broadly relevant to technology advancements such as performance improvement and emissions reduction. Development and demonstration of a multi-infrared-channel pyrometry-based optical instrument for high-speed surface-temperature measurement is described. The measurement principle is based on multi-spectral radiation thermometry (MRT) and uses surface thermal radiation at four discrete spectral regions and a corresponding emissivity model to obtain surface temperature via non-linear least squares (NLLS) optimization. Rules of thumb for specifying the spectral regions and considerations to avoid interference with common combustion products are developed; the impact of these along with linear and non-linear MRT analysis are assessed as a function of temperature and signal-to-noise ratio. A multi-start method to determine the MRT-solution global optimum is described and demonstrated. The resulting multi-channel transient pyrometry instrument is described along with practical considerations including optical-alignment drift, matching intra-channel transient response, and solution-confidence indicators. The instrument demonstrated excellent >97% accuracy and >99% 2-sigma precision over the 400–800 °C range, with ~20 µs (50 kHz, equivalent to 0.2 cad at 2000 RPM IC-engine operation) transient response in the bench validation. [ABSTRACT FROM AUTHOR]

In this study, syngas combustion was investigated behind reflected shock waves in CO2 bath gas to measure ignition delay times (IDT) and to probe the effects of CO2 dilution. New syngas data were taken between pressures of 34.58-45.50 atm and temperatures of 1113-1275 K. This study provides experimental data for syngas combustion in CO2 diluted environments: ignition studies in a shock tube (59 data points in 10 datasets). In total, these mixtures covered a range of temperatures T, pressures P, equivalence ratios φ, H2/CO ratio θ, and CO2 diluent concentrations. Multiple syngas combustion mechanisms exist in the literature for modeling IDTs and their performance can be assessed against data collected here. In total, twelve mechanisms were tested and presented in this work. All mechanisms need improvements at higher pressures for accurately predicting the measured IDTs. At lower pressures, some of the models agreed relatively well with the data. Some mechanisms predicted IDTs which were two orders of magnitudes different from the measurements. This suggests that there is behavior that has not been fully understood on the kinetic models and is inaccurate in predicting CO2 diluted environments for syngas combustion. To the best of our knowledge, current data are the first syngas IDTs measurements close to 50 atm under highly CO2 diluted (85% per vol.) conditions. [ABSTRACT FROM AUTHOR]

The direct-fired supercritical CO2 (sCO2) cycles promise high efficiency and reduced emissions while enabling complete carbon capture. However, there is a severe lack of fundamental combustion kinetics knowledge required for the development and operation of these cycles, which operate at high pressures and with high CO2 dilution. Experiments at these conditions are very challenging and costly. In this study, a shock tube was used to investigate the auto-ignition tendencies of several mixtures under high carbon dioxide dilution and high fuel loading. Individual mixtures of oxy-syngas and oxy-methane fuels were added to CO2 bath gas environments and ignition delay time data were recorded. Reflected shock pressures neared 100 atm, above the critical pressure of carbon dioxide into the supercritical regime. In total, five mixtures were investigated with a pressure range of 70-100 atm and a temperature range of 1050-1350 K. Measured ignition delay times of all mixtures were compared with two leading chemical kinetic mechanisms for their predictive accuracy. The mixtures included four oxy-syngas and one oxy-methane compositions. The literature mechanisms tended to show good agreement with the data for the methane mixture, while these models were not able to accurately capture all behavior for syngas mixtures tested in this study. For this reason, there is a need to further investigate the discrepancies. To the best of our knowledge, we report the first ignition data for the selected mixtures at these conditions. Current work also highlights the need for further work at high pressures to fully understand the chemical kinetic behavior of these mixtures to enable the sCO2 power cycle development. [ABSTRACT FROM AUTHOR]