The fully developed turbulent flow in a straight duct of square cross section has been simulated using the large eddy simulation (LES) technique. A mixed spectral-finite difference method has been used in conjunction with the Smagorinsky eddy-viscosity model for the subgrid scales. The simulation was performed for a Reynolds number of 360 based on friction velocity (5810 based on bulk velocity) and duct width. The simulation correctly predicted the existence of secondary flows and their effects on the mean flow and turbulence statistics. The results are in good qualitative agreement with the experimental data available at much higher Reynolds numbers. It is observed that both the Reynolds normal and shear stresses equally contribute to the production of mean streamwise vorticity.

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This paper is the first of two parts that describes an advanced CFD-based analysis system, developed at Pratt & Whitney, which has been used to optimize the PW6000 combustor exit temperature distribution. It utilizes a CFD calculation through the entire combustor domain to predict temperature distribution at the combustor exit. In this part, all components of the analysis system are presented, including the CAD and grid generation approach used to represent the complex combustor geometry, the core CFD solver, the Lagrangian fuel spray model, and the combustion model. In addition, the predictive capability of the system is established by comparing calculated exit temperature profiles to full annular rig test data for three aircraft gas turbine engine combustors: PW4090, PW4098, and a low-emissions technology development combustor. Comparisons of combustor airflow distribution and pressure drop are also presented to verify the accuracy of the tool. The paper demonstrates that the CFD-based analysis system is capable of calculating exit temperature distribution for a range of combustor configurations, and thus can be utilized as a predictive design tool. Part II demonstrates this predictive capability by applying the analysis tool to optimize the PW6000 combustor exit temperature distribution for turbine durability and life.