Transportability of a laser-induced fluorescence calibration for NO at high pressure

Obtaining quantitative measurements of NO concentration via laser-induced fluorescence (LIF) at high pressure requires application of a suitable calibration. While it is best to calibrate as close to the measurement condition as possible, this is not always feasible. To assess the transportability of a calibration factor at high pressure, we have calculated ratios between linear LIF signals corresponding to a constant NO concentration at different measurement and calibration conditions for high-pressure ethane flames. We find that pressure broadening limits the utility of calibrating at a pressure different from that of the measurement, although a calibration performed at a higher pressure is applicable over a wider range of pressures than one performed at atmospheric pressure. If one calibrates at the same pressure, it is best to calibrate at a temperature within 500 K of the measurement temperature. In general, the calculations indicate that a judicious choice of a calibration condition will guarantee a measured NO concentration within a factor of two of the actual NO concentration.