Characterization of the influence of aluminum particle size on the temperature of composite-propellant flames using CO absorption and AlO emission spectroscopy

Ultrafast Laser Absorption Spectroscopy in the Mid-Infrared for Measuring Temperature and Species in Combustion Gases

“…2), as well as the substantial uncertainty in the absorbing path length. Notably, the measured CO mole fractions agree well with other LAS measurements in the literature [34]. 95% confidence intervals for temperature and χ CO L are plotted along with the measured time histories in Fig.…”

“…At 0.3 bar, the accuracy was lower compared to the high-pressure cases which was due to low signal levels. [34]. The lower than expected measured temperatures were likely due to a combination of heat loss, insufficient time and space for the product gas to fully reach equilibrium, and the path-integrated nature of the measurements [23].…”

Optical measurements in multiphase combustion

“…As an example, AlO and MgO emission spectroscopy, as an indicator of aluminum or magnesium combustion, have been applied to measure gas-phase temperature and ignition dynamics [108,156,122]. In addition, other spectral features including OH in ultra-violet region, or CO 2 and CO in the infrared have also been used to characterize propellant combustion [142,122].…”

“…As an example, AlO and MgO emission spectroscopy, as an indicator of aluminum or magnesium combustion, have been applied to measure gas-phase temperature and ignition dynamics [108,156,122]. In addition, other spectral features including OH in ultra-violet region, or CO 2 and CO in the infrared have also been used to characterize propellant combustion [142,122]. In many of these applications, emission spectroscopy has been used to indicate the presence of significant reactions (AlO is a reactivity marker due to rapid consumption) as well as for temperature characterization [41].…”

“…These species are well-characterized in detailed line lists in the HITRAN [121], and HITEMP databases [120]. In solid propellants, Ruesch et al applied scanned wavelength-modulation-spectroscopy with first-harmonic-normalized second-harmonic detection (WMS-2f /1f ) to measure CO mole fraction and temperature for a range of aluminum sizes, as shown in Figure 2.6(a) [122]. The CO gas-phase temperature, in Figure 2.6(b), was found to be higher with smaller aluminum particle sizes, where the micrometer-scale aluminum particles burn in a diffusion-controlled combustion regime while nano-scale aluminum burns within or very close to the kinetically controlled combustion regime, as discussed by Bazyn et al [7].…”