A Methodology for Fully-Coupled CFD Engine Simulations, Applied to a Micro Gas Turbine Engine

Abstract

The development of new generations of aircraft engines with reduced environmental impact heavily relies on high-fidelity 3D numerical analysis of the main engine components, compressor, combustion chamber, turbine and their interactions, including the transient and off-design behavior of the full engine. Unlike component-by-component analysis, which requires separate assumptions for the pressure and temperature boundary conditions for each component, a fully coupled approach requires only knowledge of the compressor inlet and turbine outlet flow conditions. In addition, the engine rotation speed can also be varied during the simulation to converge to the correct balance of power between compressor and turbine. This integrated approach provides a detailed description of the flow field inside the full engine at the desired operating point with one single CFD simulation. The full engine simulation methodology can be developed at several levels: (1) RANS simulations with mixing-plane interfaces between components; (2) advanced RANS treatment with inputs from the nonlinear harmonic (NLH) methodology to allow for tangential non-uniformity, such as hot streaks entering the turbine nozzle from the combustor; (3) inclusion of the unsteady rotor-stator interactions, via NLH, in compressor and turbine stages; (4) coupling with LES simulations in the combustor. This paper presents results from levels (1) and (2) of this methodology applied to a micro-turbine gas engine including the HP compressor, combustor, HP and LP turbines and the exhaust hood. The geometry has been obtained from the redesign of the KJ66 micro gas turbine engine using preliminary design tools. The injection and burning of fuel inside the combustion chamber are modeled with a simplified flamelet model. The paper presents the approach and results of the full engine simulation; as well as the initial steps towards level (3).

Fully Coupled Whole-Annulus Investigation of Combustor–Turbine Interaction with Reacting Flow

“…Tables 1 and 2 present the operational and geometrical parameters of the redesign micro gas turbine employed in this study. The currently investigated turbine geometry differs from the original geometry designed by Schreckling [18], so it is denoted as a redesign variation in the same way other researchers have (for example, see Teixera et al [20]). In the validation stage, three operating points at a 40,000, 80,000, and 120,000 rpm shaft speed are chosen to compare the numerical prediction against the experimental data as well as against the numerical prediction using a different method (throughflow).…”

“…The unsteady simulation gave more details of transient flow behavior during its operation. Teixera et al [20] demonstrated a capability to perform an integrated fully coupled engine simulation on a redesign of KJ66. The component-to-component interactions were captured using mixing-plane interfaces and a nonlinear harmonic methodology.…”

A Large Design Space Multidisciplinary Optimization of a Mixed Flow Micro Gas Turbine Compressor Stage

“…Full engine optimizations are inherently computationally expensive and are mostly performed beyond academic research. One such optimization of a KJ66 MGT engine was completed by Teixeira et al (2018) with the aim of reducing fuel burn while maintaining thrust performance.…”

A Performance Simulation Methodology for a Whole Turboshaft Engine Based on Throughflow Modelling

“…There have been a few reports on threedimensional whole-engine calculations [8] in recent years. Teixeira and colleagues from Numeca [9,10] conducted steady-state and unsteady-state three-dimensional numerical simulations of the micro turbojet engine KJ66. The total number of grids is approximately 19.2 million, of which the computational domain includes one blade passage for every turbomachinery blade row, a 60 • sector for the combustion chamber, and a half exhaust hood.…”