Modeling gaseous non-reactive flow in a lean direct injection gas turbine combustor through an advanced mesh control strategy

Abstract

Fuel efficiency improvement and harmful emissions reduction are the main motivations for the development of gas turbine combustors. Numerical computational fluid dynamics (CFD) simulations of these devices are usually computationally expensive since they imply a multi-scale problem. In this work, gaseous non-reactive unsteady Reynolds-Averaged Navier–Stokes and large eddy simulations of a gaseous-fueled radial-swirled lean direct injection combustor have been carried out through CONVERGE™ CFD code by solving the complete inlet flow path through the swirl vanes and the combustor. The geometry considered is the gaseous configuration of the CORIA lean direct injection combustor, for which detailed measurements are available. The emphasis of the work is placed on the demonstration of the CONVERGE™ applicability to the multi-scale gas turbine engines field and the determination of an optimal mesh strategy through several grid control tools (i.e., local refinement, adaptive mesh refinement) allowing the exploitation of its automatic mesh generation against traditional fixed mesh approaches. For this purpose, the normalized mean square error has been adopted to quantify the accuracy of turbulent numerical statistics regarding the agreement with the experimental database. Furthermore, the focus of the work is to study the behavior when coupling several large eddy simulation sub-grid scale models (i.e., Smagorinsky, Dynamic Smagorinsky, and Dynamic Structure) with the adaptive mesh refinement algorithm through the evaluation of its specific performances and predictive capabilities in resolving the spatial-temporal scales and the intrinsically unsteady flow structures generated within the combustor. This investigation on the main non-reacting swirling flow characteristics inside the combustor provides a suitable background for further studies on combustion instability mechanisms.

Modal decomposition of the unsteady non-reactive flow field in a swirl-stabilized combustor operated by a Lean Premixed injection system

“…The meshing strategy here employed is selected from a previous work where the authors defined a methodology to derive a mesh as a compromise between spatial resolution and computational cost in order to work out this multi-scale problem [62]. In this regard, the three-dimensional domain is discretized in a structured grid of hexahedrons with a base cell size of 2 mm.…”

“…This could be partly attributed to the fact that the PIV resolution used for measurements is 1 mm [56], which is larger than the LES filter size in the near-injection zone, resulting in smaller measured RMS values due to averaging effect within the probe. For a complete model validation and LES quality assessment, please refer to a previous work by the authors [62].…”

A CFD Modelling Approach of Fuel Spray under Initial Non-Reactive Conditions in an Optical Engine

“…Other work focused on studying the flame lift-off length using CFD models [26,27], while others studied the fuel spray under reactive conditions [28]. But there are few studies of fuel spray under non-reactive but evaporative conditions [29].…”

Static mesh adaptation for reliable large eddy simulation of turbulent reacting flows

“…Following RANS, anisotropic mesh adaptation using an Hessian-based error indicator considering small scale energy has also been recently proposed with the idea of identifying the optimal spatial resolution by minimizing the solution sensitivity 31 . The main limitation of these applications is linked to the use of struc-tured mesh which can hardly manage complex geometries, leaving the method to be applicable only to turbulent channel flows or to flows on backward-facing steps and only recently to swirling flows 32 . The simulation of complex geometries indeed require unstructured grids.…”