100-kHz Interferometric Rayleigh Scattering for multi-parameter flow measurements.

Simultaneous multi-point multi-parameter flow measurement using Interferometric Rayleigh scattering (IRS) at 100-kHz repetition rate is demonstrated. Using a burst-mode laser and an un-intensified high-speed camera, interferograms are obtained that contain spatial, temporal and scattered light frequency information. The method of analysis of these interferograms to obtain simultaneous multi-point flow velocity and temperature measurements is described.

Quantitative fuel-to-air ratio determination for elevated-pressure methane/air flames using chemiluminescence emission.

The fuel/air ratio (FAR) in a methane-air Hencken flame at pressures of 1-5 bar is measured using the chemiluminescence-based method. Emission spectra are used to investigate the effects of pressure on the (308 nm), (430 nm), and 2* (500 nm) emissions and the effect on equivalence ratio determination from the ratios of these emission peaks. Both / and 2/ ratios are linear to FAR at atmospheric pressure.

Fiber-coupled LWIR hyperspectral sensor suite for non-contact component surface temperature measurements.

We report on the development of a robust fiber-coupled long-wavelength infrared (LWIR) hyperspectral sensor suite for accurate and reliable non-contact surface temperature measurements in propulsion systems with limited optical access. We first experimentally investigate various state-of-the-art LWIR optical fibers and identify the ideal fiber for efficient coupling and transmission of LWIR signals. The effects of the fiber material, structure, bending, and thermal heating on LWIR fiber transmission are characterized.

Multispecies absorption spectroscopy of detonation events at 100 kHz using a fiber-coupled, time-division-multiplexed quantum-cascade-laser system.

A mid-infrared fiber-coupled laser system constructed around three time-division-multiplexed quantum-cascade lasers capable of measuring the absorption spectra of CO, CO, and NO at 100 kHz over a wide range of operating pressures and temperatures is demonstrated. This system is first demonstrated in a laboratory burner and then used to measure temperature, pressure, and concentrations of CO, CO, and NO as a function of time in a detonated mixture of NO and CH. Both fuel-rich and fuel-lean detonation cases are outlined.

Application of time-division-multiplexed lasers for measurements of gas temperature and CH4 and H2O concentrations at 30 kHz in a high-pressure combustor.

Two time-division-multiplexed (TDM) sources based on fiber Bragg gratings were applied to monitor gas temperature, H(2)O mole fraction, and CH(4) mole fraction using line-of-sight absorption spectroscopy in a practical high-pressure gas turbine combustor test article. Collectively, the two sources cycle through 14 wavelengths in the 1329-1667 nm range every 33 μs. Although it is based on absorption spectroscopy, this sensing technology is fundamentally different from typical diode-laser-based absorption sensors and has many advantages.

Fourier-transform absorption spectroscopy in reciprocating engines.

We have adapted our in-cylinder Fourier-transform spectroscopy technique to measure absorption spectra in a reciprocating engine. Previously, we had used the technique for emission spectroscopy; the upgrade to absorption spectroscopy mode is important because it allows for more quantitative analysis of gas properties than is possible with emission spectroscopy. Here, we discuss fuel, H(2)O, and CO(2) spectra measured in an engine using a spark-plug-based probe for optical access and use the water portion of the spectra to determine in-cylinder gas temperature.