OCR Text |
Show (1) However, the chemical kinetics model used assumed a homogeneous mixture, which limits the information gained to identifying dominant chemical reactions and overall temperature effects. To scale the plasma process up to practical applications and to optimize its performance, more detailed information is required. Opposed Jets Experiment The plasma injection process is diffusional in nature, involving the mixing of the radical gas stream with the combustion flue gas. At the interface of these two streams, the NOx reduction reactions occur. Because the interface is turbulent and the reactions are at non-equilibrium, the study of the fundamentals of the plasma injection process for NOx reduction is difficult. To study the fundamentals of plasma injection at conditions relevant to the turbulent mixing process, an experiment using opposing laminar jets of plasma gas and NOx-laden gas has been designed. The laminar opposed jets reaction system serves as a model for simulating the laminar eddy reactions in turbulent mixing layers. In addition, this system can be used to quickly investigate alternative process gas combinations at a wider range of operating conditions. The main apparatus of the opposed jets experiment currently underway is shown in crosssection in Figure 6. The inductively coupled plasma gun used by Zhou provides the lower jet of ammonia radicals and carrier gas, while a hot tube arrangement provides for the temperature control of the NOx-laden gases for the upper jet. Where the two jets meet, a stagnation plane is fonned. Temperature and NOx concentration data is taken in the vicinity of this plane and, coupled with a numerical analysis of the opposed jets system, insight into the NOx reduction mechanism can be gained. Laminar opposed jet systems have been used extensively in the past to investigate fundamental processes in turbulent diffusion flames (e.g., Potter, et.al. (1959), Hahn, et.a!. (1981), Miller, et.al. (1992». As such, the fluid mechanics, heat transfer, and mass diffusion in these systems is well known. The numerical analysis of the current system will capitalize on this work while paying attention to differences between the past and proposed systems. For example, analysis of the current system will not involve the high temperature gradients associated with the diffusion flame experiments. In solving the opposed jet system, the fluid mechanics will have a known solution and the temperature and species profiles will be simulated. Reactions will likely be simulated with CHEMK, a chemical kinetics solver (Whitten and Hogo, 1980). 7 |