Unsteady Numerical Simulation of the Flow in a Direct Transfer Pre-Swirl System

Abstract

Results of fully unsteady numerical simulations of the flow in a direct transfer pre-swirl system are presented and compared with previously published experimental data from an aero-engine representative rig. The conditions considered include those where strong unsteady effects were observed experimentally. Two different rig builds are considered, with the main difference being in the design of the pre-swirl nozzles. The agreement between calculation and experiment is very good in terms of nozzle and receiver hole discharge coefficients and in identifying significant unsteady effects at certain conditions. Predicted cooling air delivery temperatures are lower than those measured. This may be due to heat transfer and other effects in the rig which have not been modelled. Present unsteady results also show agreement, where appropriate, with earlier steady CFD and an elementary model. Both calculations and measurements show similar performance in terms of delivery temperature for the two different builds studied, despite significant difference in pre-swirl nozzle discharge coefficients for the two builds. The calculations indicate that this is associated with the nozzle velocity coefficient being considerably higher than the discharge coefficient in one case.

Evaluation of Computational Fluid Dynamics and Coupled Fluid-Solid Modeling for a Direct Transfer Preswirl System

“…It is considered that this will not affect the conclusions presented here. This unsteady model is similar to that of Ciampoli et al [27], with the addition of the inner cavity in some cases, as shown in the figure.…”

“…The present unsteady simulations predicted very similar temperature drops to Ciampoli's [27] unsteady calculations, but predicted higher swirl velocity. Hence, the predicted temperature in Fig.…”

“…The results of the present calculations are significantly different from those of Ciampoli et al [27]. Present simulations predict 8% higher P in /p p than Ciampoli et al's simulations, despite using a similar mesh and boundary conditions.…”

“…Published experimental results for engine-representative preswirl geometries from these programs include measurements of discharge coefficient by Dittmann et al [20], use of particle image velocimetry by Geis et al [21], heat transfer measurements on the rotor disk [22] and evaluation of overall system performance in terms of measured delivery cooling air temperature by Geis et al [23] and Bricaud et al [24]. Computational analyses for these ICAS-GT programs have also been published by Benim et al [25,26], Chew et al [8], Ciampoli et al [27] and Cagan et al [28].…”

“…The calculations used stationary and rotating reference frames and a sliding plane approach as described by Ciampoli et al [27]. No mesh dependency study was carried out for the unsteady calculations, but the mesh density was based on previous experience for similar flows.…”