Filtered Rayleigh scattering diagnostic for multi-parameter thermal-fluids measurements : LDRD final report.

Abstract

Simulation-based life-cycle-engineering and the ASCI program have resulted in models of unprecedented size and fidelity. The validation of these models requires high-resolution, multiparameter diagnostics. Within the thermal/fluids disciplines, the need for detailed, high-fidelity measurements exceeds the limits of current Engineering Sciences capabilities and severely tests the state of the art; therefore, a diagnostic development effort is warranted. The focus of this LDRD is the development and application of filtered Rayleigh scattering (FRS) for highresolution, nonintrusive measurement of gas-phase velocity and temperature. This multiparameter technique adds significant experimental capability to several Sandia programs including Fire Science and Technology (FS&T) and Aerosciences programs in the Engineering Sciences Center (9100) and Reacting Flow Research at the Combustion Research Facility (8300).With FRS, the flow is laser-illuminated and Rayleigh scattering from naturally occurring sources is detected through a molecular filter. The filtered transmission may be interpreted to yield point or planar measurements of three-component velocities and/or thermodynamic state. Different experimental configurations may be employed to obtain compromises between spatial resolution, time resolution, and the quantity of simultaneously measured flow variables. This capacity for multi-parameter, non-intrusive instrumentation represents an unprecedented advance beyond presently available techniques in the Engineering Sciences Center and in the larger scientific arena. Furthermore, measurements may be made using naturally occurring scattering centers, eliminating potentially intractable difficulties associated with particulate or chemical seeding in a hypersonic or reacting environment. Molecular-filter absorption of scattered light from solid boundaries also makes FRS advantageous for detailed boundary-layer measurements. 4These advantages make FRS an attractive alternative to developed techniques and offer a substantial payoff impacting multiple thermal/fluids disciplines. Moreover, a virtually identical experimental configuration may be utilized for both aerodynamic and thermal diagnostic applications simply by adjusting the laser and molecular filter. These measurements are ideally suited for use in production-scale facilities, where many other techniques are difficult to implement.In this report, we present the results of a three-year LDRD-funded effort to develop FRS combustion thermometry and Aerosciences velocity measurement systems. The working principles and details of our FRS opto-electronic system are presented in detail. For combustion thermometry we present 2-D, spatially correlated FRS results from nonsooting premixed and diffusion flames and from a sooting premixed flame. The FRS-measured temperatures are accurate to within ±50 K (3%) in a premixed CH 4 -air flame and within ±100 K for a vortexstrained diluted CH 4 -air diffusion flame where the FRS technique is severely tested by large variation ...