Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - IPANEMA (Inlet PArticle Separator Numerical ExperiMental Assessment)

Teaser

IPANEMA aims at developing numerical and experimental techniques for the design of inertial particle separators (IPS) in turboprop engine intakes. IPS aim at removing dust, rain, hail, ... from the main air flow by deviating it abruptly before entering the engine, such that...

Summary

IPANEMA aims at developing numerical and experimental techniques for the design of inertial particle separators (IPS) in turboprop engine intakes. IPS aim at removing dust, rain, hail, ... from the main air flow by deviating it abruptly before entering the engine, such that ingested particles are expelled from the main flow to a small bypass duct. IPS have a lower impact on engine efficiency, and can moreover be deactivated during the flight. Therefore, IPS contribute to the efficiency of the aircraft.

The experimental and numerical assessment of the separation efficiency, in particular during design, is not well mastered. The main aim is to improve the tools for accounting for the variability in particle size: smaller particles are much more likely to follow the flow whereas larger move independently and are therefore more readily evacuated. To ensure the industrial applicability of the techniques, an actual IPS will be studied during the project.

On the experimental side, the difficulties concern the injection of particles in the rig and measuring separation performance in terms of particle size. One can mention also the combination of particle measurements with measuring aerodynamic performance due to the vulnerability of the probes. A last difficulty concerns the combined detailed measurement of particle tracks and flow field in a complex geometry.

On the numerical side, no methods exist that combine sufficient accuracy to an acceptable cost. Highly versatile methods based upon Lagrange particle tracking and LES, are too expensive, while Eulerian RANS based methods used in industry typically do not account for size variability or are not calibrated for flow configurations prevalent in IPS. The aim is to provide an industrial simulation approach which offers the best compromise between precision and cost, by extending and calibrating Euler methods using new and highly resolved experimental and numerical data obtained during the project.

Although IPS have been studied previously, research was mainly targeted at assessing performance of specific geometries, whereas no significant effort is dedicated to improving models. The experimental data is typically limited to global performance, while low-cost/precision simulation approaches are used. In order to alleviate the lack of high-quality and relevant reference data for model development and physical comprehension of flow conditions prevalent in IPS, IPANEMA will publish high-resolution experimental and numerical validation data on canonical geometries.

Work performed

The main activity concerned the preparation of a campaign on a full scale IPS configuration provided by the topic manager. This additional campaign was agreed upon during the negotiations in order to support the development of IPS. The timing, as imposed by the intake development programme, as well as the compromise between the test matrix and desired instrumentation on the one hand, and the limitations of both the facility and the project planning are currently still under discussion.

Simultaneously, some of the work concerning the development of new experimental and numerical techniques could be undertaken, with a delay with respect to the planning. The specification of the new canonical reference database cases is postponed until the impact of the full-scale campaign on the actual geometry can be fully estimated.

The first activity at Cenaero concerned the definition of an accurate and reliable simulation strategy for assessing the aerodynamic performance of the IPS, as initial computations indicated a high sensitivity to turbulence modeling approach, turbulence boundary conditions, the specification of the operation point via boundary conditions at in- and outlets and the specifics of the post-processing routines. Subsequently, the flow in the IPS was analyzed in several operating conditions to identify the relevant flow regimes for canonical test cases and in support of the test rig setup. In parallel, the implementation of the numerical models was prepared. Next to the Euler-Lagrange implementation in the LES code, the QMOM was chosen for the Euler code and first prototype implementations were performed. Finally, an inventory of reference results in literature aided in further refining the choices for the canonical cases.

VKI has focused on the definition of the experimental facilities and the development of new experimental techniques. The first activity concerns the overall design of the blow-down facility, for both the full-scale test section (as requested by the topic leader) and the canonical cases. Then the preliminary selection of the measurement techniques was achieved: different configurations have been investigated and ranked in terms of performance and expected uncertainty levels. Using these informations and simulations, the detailed design of the facility was undertaken. Currently, the facility design is 80% completed, including the in- and outlet ducts as well as the interfaces to the device, the seeding mechanism, the aerodynamic instrumentation, the separation efficiency measurements and the traversing mechanisms. In the next weeks the filtering section design will be finalized, bringing the design process to 100% completion. At the same time, the testing procedure, enabling to combine aerodynamic performance assessment with separation efficiency measurements was established. The testing procedure will be further tuned during the commissioning phase of the facility. A second main activity concerns the development of simultaneous measurements of flow field and particle tracks using PIV and PTV. Thereto an in-house code was developed and validated, first on the basis of synthetic images (generated upon a physical model of the multiphase flow field) and then on an experimental test case was investigated.

Final results

Currently both the experimental setup, as well as the experimental and numerical techniques are still in development.

The progress beyond the state of the art will be threefold.

A new experimental technique, combining PIV and PTV, will enable the simultaneous acquisition of detailed flow-fields and particle trajectories in complex geometry. The simultaneous measurement is expected to provide a much better insight in the flow-particles interaction.

Two new numerical models will be developed. The first consists of a particle tracking strategy in an unstructured high order discontinuous Galerkin (DG) code enabling high resolution Large Eddy Simulations and therefore the acquisition of detailed statistical data. The second consists of the calibration of a RANS Euler-Euler approach, based upon the quadrature method of moments (QMOM), with focus on turbophoresis and interaction with the walls prevalent in IPS.

The modeling will be supported by new combined experimental and numerical reference data on both canonical cases as well as the actual IPS. On all flow field (PIV), detailed boundary condition data and separation efficiency as a function of particle size will be measured. The public canonical data will furthermore include detailed turbulence and particle statistics generated by high resolution LES/Lagrange simulations and combined PTV/PIV measurements.

All of these techniques will allow a more reliable design of IPS, and more generally components that involve particle-air separation. This includes also to the process industry, where the exhaust gases need to be cleaned before discharge.