The development of new Additive Manufacturing techniques helps to overtake design constrains characterizing the standard processes. This new reality can opens the space to the redesign of more efficient aircraft engine components. The engine turbine labyrinth seal honeycomb land is currently obtained shaping and welding a sheet metal to create an hexagon pattern. The employing of the DMLM additive manufacturing could led to the development of new geometries, different from the standard honeycomb land, able to increase the labyrinth sealing performances. In this research, innovative stator patterns, able to reduce the seal leakage mass flow rate, have been investigated. The identification of innovative lining pattern cell shapes has been performed by using numerical CFD analyses. The selection of the innovative lining pattern cell shapes has been performed among all numerical solutions investigated. The most promising solutions have been then experimentally verified. Firstly, a dedicated work has been accomplished, to verify whether ANSYS CFX code was capable of predicting labyrinth seal performances adequately in terms of mass flow leakage. Then, a dedicated simplified model has been developed, in order to explore the performances of new designs with a reasonable computational cost. An extended CFD analysis, on the honeycomb stepped labyrinth seal, has been performed, in order to investigate the stator part geometrical parameters affecting the discharge coefficient. A one-at-a-time approach has been employed, to investigate: cell wall thickness, cell depth, cell diameter and fin tip thickness. Moreover, the effect of varying the fin tip and cell relative position has been evaluated. Numerical results, for both convergent and divergent flow conditions, have been obtained and analyzed in terms of leakage variations. The obtained results are in good agreement with the data available in the literature . The analysis has highlighted the cell diameter as the most influencing geometrical parameter, for honeycomb labyrinth seal stator part. In order to define innovative stator lining cell shapes, some assumptions for the honeycomb labyrinth seal rubbing and thermal behaviors have been employed. Nineteen solutions have been numerically investigated, by leveraging on the knowledge in simulations acquired from the previous activity. A numerical model, of a double fin straight honeycomb labyrinth seal, able to reproduce engine conditions, has been implemented. CFD results have shown how the rhomboidal geometry could give a sensible improvement in the sealing performances. Two of the rhomboidal shapes analyzed have been flow tested, on a static rig, that was reproducing the same labyrinth seal geometry numerically investigated. The test samples have been manufactured by using the DMLM technique at 1x scale. The measurements performed, for several running clearances and pressure ratios, are then compared with the standard honeycomb seal data and numerical pre-test predictions. The rhomboidal cells thermal response has been tested in a facility available at the Energy Department of the Politecnico di Torino. The test rig is able to reproduce the outer band static part of a low pressure turbine stage and the blade tip labyrinth seal. It is working at high temperature and has been dimensioned in order to reproduce, in engine similitude, the non-dimensional numbers ruling LPT turbines thermal phenomena. The test article has been designed by integrating the innovative cells into the complete stepped shroud design. The part has been manufactured by means of DMLM technique. The results of the heat transfer model, reproducing the low pressure turbine test rig thermal behavior, have been compared with experimental data. Finally, the rubbing behavior, of innovative solutions, has been verified performing a rubbing test and comparing measurements with standard solution data.

ENERGY-EFFICIENT INNOVATIVE SEAL FOR AIRCRAFT ENGINES / Taurino, Roberto. - (2017).

ENERGY-EFFICIENT INNOVATIVE SEAL FOR AIRCRAFT ENGINES

TAURINO, ROBERTO
2017

Abstract

The development of new Additive Manufacturing techniques helps to overtake design constrains characterizing the standard processes. This new reality can opens the space to the redesign of more efficient aircraft engine components. The engine turbine labyrinth seal honeycomb land is currently obtained shaping and welding a sheet metal to create an hexagon pattern. The employing of the DMLM additive manufacturing could led to the development of new geometries, different from the standard honeycomb land, able to increase the labyrinth sealing performances. In this research, innovative stator patterns, able to reduce the seal leakage mass flow rate, have been investigated. The identification of innovative lining pattern cell shapes has been performed by using numerical CFD analyses. The selection of the innovative lining pattern cell shapes has been performed among all numerical solutions investigated. The most promising solutions have been then experimentally verified. Firstly, a dedicated work has been accomplished, to verify whether ANSYS CFX code was capable of predicting labyrinth seal performances adequately in terms of mass flow leakage. Then, a dedicated simplified model has been developed, in order to explore the performances of new designs with a reasonable computational cost. An extended CFD analysis, on the honeycomb stepped labyrinth seal, has been performed, in order to investigate the stator part geometrical parameters affecting the discharge coefficient. A one-at-a-time approach has been employed, to investigate: cell wall thickness, cell depth, cell diameter and fin tip thickness. Moreover, the effect of varying the fin tip and cell relative position has been evaluated. Numerical results, for both convergent and divergent flow conditions, have been obtained and analyzed in terms of leakage variations. The obtained results are in good agreement with the data available in the literature . The analysis has highlighted the cell diameter as the most influencing geometrical parameter, for honeycomb labyrinth seal stator part. In order to define innovative stator lining cell shapes, some assumptions for the honeycomb labyrinth seal rubbing and thermal behaviors have been employed. Nineteen solutions have been numerically investigated, by leveraging on the knowledge in simulations acquired from the previous activity. A numerical model, of a double fin straight honeycomb labyrinth seal, able to reproduce engine conditions, has been implemented. CFD results have shown how the rhomboidal geometry could give a sensible improvement in the sealing performances. Two of the rhomboidal shapes analyzed have been flow tested, on a static rig, that was reproducing the same labyrinth seal geometry numerically investigated. The test samples have been manufactured by using the DMLM technique at 1x scale. The measurements performed, for several running clearances and pressure ratios, are then compared with the standard honeycomb seal data and numerical pre-test predictions. The rhomboidal cells thermal response has been tested in a facility available at the Energy Department of the Politecnico di Torino. The test rig is able to reproduce the outer band static part of a low pressure turbine stage and the blade tip labyrinth seal. It is working at high temperature and has been dimensioned in order to reproduce, in engine similitude, the non-dimensional numbers ruling LPT turbines thermal phenomena. The test article has been designed by integrating the innovative cells into the complete stepped shroud design. The part has been manufactured by means of DMLM technique. The results of the heat transfer model, reproducing the low pressure turbine test rig thermal behavior, have been compared with experimental data. Finally, the rubbing behavior, of innovative solutions, has been verified performing a rubbing test and comparing measurements with standard solution data.
2017
File in questo prodotto:
Non ci sono file associati a questo prodotto.
Pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11583/2681688
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo