Development and application of laser-based sensors for harsh combustion environments.

摘要

The development of diagnostics based on laser-absorption spectroscopy for combustion applications has been an important and active field of research over the past two decades due to the advantages of this non-intrusive optical sensing technique compared to traditional sensing methods. These optical sensors have shown the ability to provide in situ, time-resolved, line-of-sight measurements of temperature and gas species concentrations. Two propulsion concepts, pulse detonation engines (PDE) and homogeneous-charge compression ignition (HCCI) engines, have received particular interest over the past decade. Sensors based on laser absorption spectroscopy prove useful to the development of these modern propulsion systems to facilitate design advancements, improve efficiency, and reduce pollutant emissions.; Two novel, laser-based sensors employing ultraviolet wavelengths are developed and applied to measure time-resolved temperature and OH concentration in a single-cycle pulse detonation tube. These results, along with pressure data, are employed to evaluate two computational simulations utilizing different chemistry and heat transfer models to predict pulse detonation engine (PDE) flowfields.; A fiber optic-based, wavelength-multiplexed, near-infrared tunable-diode-laser absorption sensor designed to measure temperature is developed and applied to characterize a valveless multi-cycle PDE. The sensor is utilized to measure water vapor temperature profiles for both successful detonations and engine failure modes such as flame-holding. Improvements in both optical engineering and spectroscopic design over previous sensors enable measurements at engine operation rates up to 40Hz. The results provide valuable data for characterizing system performance and investigating component failure thresholds as engine operation rates are increased.; A wavelength-multiplexed, fiber-optic-based, line-of-sight, near-infrared diode-laser absorption sensor is developed for crank-angle-resolved measurements of temperature and water concentration in an HCCI engine. An initial demonstration of its use on two optical HCCI engines at Sandia National Laboratories is reported. The measurements encompassed both motored- and fired-engine operation. Key solutions to select appropriate water linepairs and to suppress crank-angle-dependent noise in the transmitted laser signals are reported. Data obtained through this sensor can provide critical engine characteristics such as combustion efficiency, peak combustion temperature, and autoignition temperature.