High-Bandwidth Noninvasive Sensor Systems For Measuring Enthalpy and Mass Flux in Detonation-Powered Devices

The objective of the proposed Phase-II research effort is to build and deliver a hyperspectral sensor to perform velocity, temperature, pressure, and H2O concentration measurements at the end of a detonation tube and the exhaust of a detonation-powered turbine at a rate of 50 kHz. These measurements will help quantify the efficiencies of detonation-powered devices. High-speed measurements of temperature, H2O mole fraction, pressure, and velocity will allow determination of the enthalpy and mass-flux in-and-out of the detonation-powered devices. We have successfully demonstrated this approach during the Phase-I research effort. In the phase II effort, one-piece, all-silica fiber-collimators suitable for measurements in the detonation environment along multiple lines-of-sight will also be designed, delivered, and demonstrated in a suitable test rig in consultation with AFRL scientists. Despite using absorption spectroscopy for determining the temperature, pressure, and H2O concentration, the hyperspectral technology is fundamentally different from typical diode laser-based absorption sensors and has many advantages, specifically: monitoring many spectral features over a wide spectral range at very high speeds (~ 50 kHz) and thereby providing more accurate measurements of more parameters than a typical diode-laser strategy. The proposed hyperspectral sensor system offers flexible coverage of such a broad spectral range that it is automatically suitable for virtually all applications within 5 psia to 1000 psia for a temperature range of 270K to 3000K. BENEFIT: Development of compact sensor systems for measuring temperature, pressure, and velocity at a rate of 50 kHz will enable engine manufacturers to investigate the performance of PDEs and detonation-powered devices and will also provide valuable high-bandwidth data to the numerical modeler. This sensor system will also help studying the ignition and flame growth phenomena and monitor the combustion processes and relevant dynamic phenomena at realistic operating conditions for the first time. This capability is particularly critical for the design and modeling of advanced, detonation-powered or ultra-compact, low-emission, gas turbine engines and for development of real-time combustion-control strategies. This technology will yield significant payoffs in military and commercial aviation as well as land- and sea-based power generation, and has broad impacts for on-board sensing and control. Other high-speed gasdynamic research as in shock tubes and explosion studies are poised to benefit as well. Beyond gasdynamic measurements, the sensing approach has applicability in microscopy and in biological imaging. For example, the hyperspectral sources developed in this effort could supplant swept-sources currently used for 4-D optical coherence tomography, offering new imaging capabilities such as greater ranging depth. Also, with minor modifications, the sensor system might become important in pulsed magnetic fields research as well as homeland security applications such as imaging of hazardous gases.