Single-ended Laser-based Diagnostics for Thermometry and Speciation in Detonation-driven Combustors PDF Download

Author: Wen Yu Peng
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Languages : en
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Book Description
Detonation-driven combustors have received considerable research interest over the past several decades due to their theoretical thermodynamic advantages over conventional deflagration-driven combustion devices used in propulsion and power generation systems. The rotating detonation engine (RDE) architecture, in particular, has been identified as a promising path for achieving these thermodynamic advantages in practice due to their simple hardware geometries, lack of moving parts, ability to be continuously fed with propellants, and high operating frequencies. Central to increasing the technological readiness of RDEs is the development of robust, time-resolved sensors for in situ measurements of temperature and combustion products within the detonation chamber to validate computational models and guide practical design efforts. The work presented in this dissertation details the development, validation, and demonstration of a novel laser-absorption spectroscopy (LAS) sensor platform capable of performing time-resolved and simultaneous measurements of temperature, H2O, CO2, and CO concentrations within the annular gap of RDE test articles at the Naval Postgraduate School (NPS) in Monterey, CA. Despite the highly confined geometries (with path lengths on the order of 1 cm) and intense thermodynamic conditions (temperatures and pressures ranging from 700-2000 K and 2-8 atm, respectively) in the RDE test apparatus, the sensor achieved high-precision measurements of the target quantities through the use of four lasers probing strong mid-infrared absorption transitions near 2482, 2551, 4182, and 4854 nm and the implementation of wavelength-modulation spectroscopy (WMS), a LAS sensing technique capable of correcting for or rejecting many of the signal distortion sources commonly encountered in the harsh RDE detonation environment. The reported measurement rate of 44 kilosamples per second was sufficient to resolve intra-detonation cycle dynamics within the RDE. Additionally, to minimize perturbations to the combustion environment and to limit the hardware modifications needed for optical access into the RDE detonation chamber, the single-ended LAS sensing strategy--where the laser light was delivered into and collected from the detonation chamber through a single optical port--was used.