Monte Carlo Probability Density Function Method for Gas Turbine Combustor Flowfield Predictions

A coupled Lagrangian Monte Carlo (MC) probability density function (PDF) Eulerian 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 was over composition only. The PDF transport equation was solved using a Lagrangian particle-tracking MC method. This MC module has been coupled with CONCERT, which is a fully elliptic three-dimensional body-fitted CFD code based on pressure correction techniques. CONCERT calculates the mean velocity and mixing frequency field that are required by the composition PDF in the MC module, whereas the MC module computes the PDF from which the mean density field is extracted and supplied to CONCERT. This modeling approach was initially validated against Raman data taken in a recirculating bluff body stabilized flame. The computed mixture fraction and its variance (as obtained from the calculated PDF) compared very well against the corresponding measurements made along several radial lines at different axial downstream positions and along the axis. A typical single annular aircraft engine combustor was also analyzed. In this preliminary study, the flowfield, fuel, and temperature distribution were obtained based on the assumption of fast chemistry. The solutions obtained using the present approach were compared with those obtained using a presumed-shape PDF method. The comparison of the calculated exhaust gas temperatures using these two approaches with measurements made by a thermocouple rake appeared to indicate better agreement with the PDF transport technique. (Author)