Absolute ozone absorption cross section in the Huggins Chappuis minimum (350–470 nm) at 296 K

We report the ozone absolute absorption cross section between 350–470 nm, the minimum between the Huggins and Chappuis bands, where the ozone cross section is less than 10−22 cm2. Ozone spectra were acquired using an incoherent broadband cavity enhanced absorption spectrometer, with three channels centered at 365, 405, and 455 nm. The accuracy of the measured cross section is 4–30%, with the greatest uncertainty near the minimum absorption at 375–390 nm. Previous measurements vary by more than an order of magnitude in this spectral region. The measurements reported here provide much greater spectral coverage than the most recent measurements. The effect of O3 concentration and water vapor partial pressure were investigated, however there were no observable changes in the absorption spectrum most likely due to the low optical density of the complex.

Absolute ozone absorption cross section in the Huggins Chappuis minimum (350–470 nm) at 296 K

We report the ozone absolute absorption cross section between 350–470 nm, the minimum between the Huggins and Chappuis bands, where the ozone cross section is less than 10−22 cm2. Ozone spectra were acquired using an incoherent broadband cavity enhanced absorption spectrometer, with three channels centered at 365, 405, and 455 nm. The accuracy of the measured cross section is 2 %. Previous measurements vary by more than an order of magnitude in this spectral region. The measurements reported here provide much greater spectral coverage than the most recent measurements. We report a minimum absorption cross section of 3.4×10−24 cm2 at 381.8 nm, which is 22 % lower than the previously reported value. The effect of O3 concentration and water vapor partial pressure were investigated, however there were no observable changes in the absorption spectrum most likely due to the low optical density of the complex.

In Situ Optical Diagnostics for Measurements of Water Vapor Partial Pressure in a PEM Fuel Cell

A fiber optic coupled diode laser sensor has been constructed for in situ measurements of water vapor partial pressure in active proton-exchange membrane (PEM) fuel cell systems. The bipolar plate of a prototypical PEM fuel cell was modified to allow for transmission of a near infrared laser beam through the flow channels on either the fuel or oxidizer side of its membrane-electrode assembly. The laser wavelength was scanned over several water rotational and vibrational transitions and the light absorption was detected by measuring the transmitted laser power through the device. The intensity and line shape of the measured transition was used to extract path-averaged values for the water vapor partial pressure. Measurements were initially taken in a non-operating cell with known temperature and humidity input gas streams to calibrate and test the optical device. A technique for rapid determination of the water partial pressure was developed. The optical technique is applicable over a significant temperature and humidity operating range of a PEM fuel cell. The measurement technique was applied to an operating PEM fuel cell system to examine the effects of incoming gas humidity and load on the water vapor partial pressure variation in one of the flow channels.

Exposure Test Results of Lu2Si2O7 in Combustion Gas Flow at High Temperature and High Speed

In order to understand recession behavior and the amount of recession of Lu2Si2O7 in the combustion gas flow, sintered Lu2Si2O7 specimens were manufactured by hot pressing and exposed under various combustion gas flow conditions (T = 1300–1500 °C, P = 0.3 MPa, V = 150 m/s, PH2O = 27–69 kPa, t = 10h). After the exposure tests, etch pits, which are assumed to form due to volatilization of SiO2 in the grain boundary phase, were observed at the surface of specimen. The amount of Lu2SiO5 phase at the surface of specimen increased with the increase of gas temperature or water vapor partial pressure. A corresponding decrease in the amount of Lu2Si2O7 phase was observed. Furthermore, by using the average weight loss rate for exposure times of ten hours, the influence of gas temperature and water vapor partial pressure on weight loss rate was examined, and the amount of recession under gas turbine conditions was calculated.

Degradation of Silicon Carbide in Combustion Gas Flow at High-Temperature and Speed

Effects of various basic factors of combustion gas flow conditions on degradation behaviors of silicon carbide have been experimentally determined. The exposure tests were performed for widely varied experimental parameters of the gas temperatures (T = 900–1500°C), pressure (P = 0.3–0.8MPa), gas flow rate (V = 50–250m/s), water vapor partial pressure (PH2O = 32–82kPa) and oxygen partial pressure (PO2 = 24–44kPa). Degradation behaviors of silicon carbide were expressed as the weight loss of the substrate. The weight loss rate depends on the water vapor partial pressure remarkably. The effect of the oxygen partial pressure on the weight loss was smaller than that of the water vapor partial pressure, and the weight loss decreased with the increase of the oxygen partial pressure. Considering the effects of partial pressures of oxygen and water vapor, the gas temperature and the pressure didn’t have much effect on the weight loss. The weight loss depends on the gas flow rate, the increase rate of the weight loss for the gas flow rate becomes small with the gas flow rate. Consequently, the water vapor partial pressure, the oxygen partial pressure, the gas temperature, the pressure and the gas flow rate dependence of the weight loss rate is expressed as PH2O1.9 V0.6 P0.3 / PO20.6.