Fundamentals Turbulent Combustion Studies
Current work on turbulent combustion fundamentals focuses on flame-front wrinkling pheneomena. The dynamics of turbulent flames are studied using a new Cinema Stereoscopic Particle Image Velocimitry (CS-PIV) system. This system uses multiple high-speed digital video cameras and high-rep-rate Nd:YAG lasers to capture the three components of velocity in three dimensions (spatial plane and time) and the position of the flame front. This allows for the three vorticity components to be estimated and movies of the dynamic vorticity field to the obtained. Eddies are tracked as they interact with a turbulent premixed flame front and the dynamics of the interaction is recorded. The ability of eddies to wrinkle, stretch, and accelerate the flame are measured along with any instabilities that may occur. The results are used for the development and validation of combustion models and to further the understanding of turbulent flame dynamics. Previous work has included studies of the scalar dissipation rate, flame stabilization, quenching, flame structure, and a variety of other topics.
Supersonic Combustion Studies
Current supersonic combustion work is focused on a transverse hydrogen fuel jet injected into supersonic flow upstream of a flame-holding cavity. This combination of classical fluid dynamic elements is similar to many scramjet combustor designs. The study will involve measuring blow-off limits and combustion efficiency for a range of test conditions. Furthermore, PIV and CH-PLIF (with ethylene doped into the hydrogen) will be used to study the reaction in detail. The goal is to gain a better understanding about why the fuel is not burning completely in certain areas. This can, in turn, lead to intelligent design solutions for scramjet combustors.
A model gas turbine combustor with a new GE TAPS injector is studied in this project. GEAE has a developed a new lean premixed, prevaporized gas turbine injector to meet NOx emissions requirements. The combustor can be operated with high flow rates and at elevated pressures and temperatures. Diagnostics such a PIV to measure velocity and PLIF to measure the reaction layers are being utilized to better understand the flame holding and mechanisms by which the pilot stabilizes the main flame. These measurements will also be used by GE to assess LES simulations used by GE in their design process.
Rocket Combustion and Mixing Experiments
A laboratory scale gaseous rocket engine is used to study the interaction between fluid dynamic mixing and combustion under conditions found in throttled down rocket engines. To this end, a single coaxial jet injector is studied by varying velocity, density and diameter ratios to obtain mixing relations for the growth of the primary and secondary cores along with the stoichometric contour. Laser diagnostic techniques utilized include Acetone and OH PLIF. Results are used is the derivation of mixing relations and the development and verification of combustion and mixing models. (Sponsor: NASA)
