COUPLED LAGRANGIAN MONTE-CARLO PDF-CFD COMPUTATION OF GAS-TURBINE COMBUSTOR FLOWFIELDS WITH FINITE RATE CHEMISTRY

A coupled Lagrangian Monte Carlo Probability Density Function (PDF) - Eulerian Computational Fluid Dynamics (CFD) technique is presented for calculating steady three-dimensional turbulent reacting flow in a gas turbine combustor. PDF transport methods model turbulence-combustion interactions more accurately than conventional turbulence models with an assumed shape PDF. The PDF transport equation was solved using a La grangian particle tracking Monte Carlo (MC) method. The PDF modeled wa s over composition only. This MC module has been coupled with CONCERT, which is a fully elliptic three-dimensional body-fitted CFD code base d on pressure correction techniques. In an earlier paper (Tolpadi et a l., 1995), this computational approach was described, but only fast ch emistry calculations were presented in a typical aircraft engine combu stor. In the present paper, reduced chemistry schemes were incorporate d into the MC module that enabled the modeling of finite rate effects in gas turbine flames and therefore the prediction of CO and NOx emiss ions. With the inclusion of these finite rate effects, the gas tempera tures obtained were also more realistic. Initially, a two scalar schem e was implemented that allowed validation against Raman data taken in a recirculating bluff body stabilized CO/H-2/N-2-air flame. Good agree ment of the temperature and major species were obtained. Next, finite rate computations were performed in a single annular aircraft engine c ombustor by incorporating a simple three scalar reduced chemistry sche me for Jet A fuel. This three scalar scheme was an extension of the tw o scalar scheme for CO/H-2/N-2 fuel. The solutions obtained using the present approach were compared with those obtained using the fast chem istry PDF transport approach (Tolpadi et al., 1995) as well as the pre sumed shape PDF method. The calculated exhaust gas temperature using t he finite rate model showed the best agreement with measurements made by a thermocouple rake. In addition, the CO and NOx emission indices w ere also computed and compared with corresponding data.