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Tilt Rotor INlet Innovative Design And Testing

Periodic Reporting for period 1 - TRINIDAT (Tilt Rotor INlet Innovative Design And Testing)

Reporting period: 2019-02-01 to 2020-07-31

The TRINIDAT project is part of Clean Sky2 Fast Rotor Craft (CS2 FRC) and addresses the Next Generation Civil Tilt Rotor (NGCTR) configuration. The TRINIDAT project started at 1 February 2019 and will last until 31 January 2022.
The NGCTR configuration is being developed by Leonardo Helicopters. The main benefit of the NGCTR configuration is that it offers reduced travel time on short and medium distances up to 500 nautical miles (approx. 1000 km). The engine intake has a rather complex shape due to the tilting rotor head concept of the NGCTR configuration. The intake duct changes from an elliptical cross-section to an annular cross-section of the Air Intake Plane (AIP) for the engine. The TRINIDAT project addresses the aerodynamic characterization of the intake geometry (as supplied by Leonardo Helicopters) and optimization of the intake duct geometry (within certain given geometric constraints) by using CFD (Computational Fluid Dynamics) based optimization tools. The objective of the optimization study is to improve the flow steadiness and uniformity at the Air Intake Plane of the engines such as to comply with the requirements put forward by the engine manufacturer. The initial characterization and optimization will rely on dedicated CFD studies. The final validation will be made with full size model tests in the DNW-LLF 6x6 wind tunnel, allowing reliable testing at full scale Mach and Reynolds conditions.
The main objectives of TRINIDAT can be broken down into seven sub-objectives:
O1 Assessment of flow quality of the basic intake geometry in terms of flow separation, total pressure losses, and flow uniformity and flow angles at the Air Intake Plane (AIP) for a range of flight operation conditions.
The activities have been carried out for two configurations of geometry:
a) The isolated internal intake duct configuration, for which three different candidate geometries have been considered. Based on the assessment of the flow quality, a final baseline geometry has been selected for optimization in the later stages.
b) The complete configuration encompassing the rotating 3-bladed rotor with scheduled pitch and flap motions, wing with possible non-zero flap settings, external nacelle, and the internal intake duct itself.
The objective of CFD simulations of the complete configuration can be distinguished into three groups: (i) to provide reference data for optimization at design conditions, (ii) to provide extended analysis at off-design conditions, and (iii) to provide data for icing analysis. Apart from the code-to-code comparison that still needs to be performed between WP1 and WP2: (i) the first group has been completed, and (ii) the second group is on-going, with 9 out of 12 load cases have been completed. The third group which also falls within WP6, 5 out 9 load cases have been completed.
O2 Optimize the intake geometry for superior intake performance in all flight conditions, at least better than with the basic intake geometry.
WP 2 focus is to develop a CFD optimization model of the S-shape intake duct part of NextGen aircraft for different flight conditions, pre-selected in WP1.
The objective of CFD optimization of the CFD model consisting of the interface and S-shape duct can be distinguished in the following groups:
(a) Define and develop an CFD optimization model
(b) Integrate the interface loads in the optimization model
(c) Perform run and post-processing for the 3 load cases identified in WP1
(d) Define Adjoint Solver Setup
(e) Perform optimization loop and post-processing while improving Distortion Coefficient
(f) Provide optimised geometry (step format) for design and validation
Items (a) and (b) are completed, while point (c) is ongoing (as further detailed). Activities related to items (d-f) will be conducted in the next reporting period.
O3 Provide guidelines for surface finishing of the intake ducts, based on a CFD sensitivity study on the effects of surface roughness on engine inlet flow distortion.
This objective has not started yet. The analysis will take advantage of computational results that will become available from the achievement of O1 with a much reduced computational effort for an isolated intake duct configuration.
O4 Design and manufacture a well instrumented air intake wind tunnel model in which different air intake components (baseline and optimized intake ducts, all equipped with pressure ports) can be easily exchanged, such as to allow an efficient testing at realistic full scale conditions of the basic and optimized geometries. For the wind tunnel model only the RH nacelle geometry will be considered.
This objective was achieved, except for the optimized intake duct which will be further designed and manufactured in the next reporting period. Additional to the original scope all movable surfaces could be realized with remote control actuation. On the wing a mounting provision for vortex generators, aimed for the 2nd entry test, has been foreseen.
O5 Perform a high quality wind tunnel test to obtain a detailed experimental data base on the aerodynamic performance of the basic and optimized intakes in terms of performance parameters under representative flow conditions, to support the Critical Design Review (CDR) phase of the NGCTR Technology Demonstrator (TD).
The wind tunnel tests will be performed in the next reporting period.
O6 Assess possible criticalities for NGCTR nacelle and intake design in terms of certification and/or operation envelopes in icing conditions.
A set of icing conditions has been selected after analysis of the NGCTR operating envelope and the applicable certification specifications. Preliminary icing simulations have been performed, but the activities related to the assessment of the icing criticalities for the NGCTR nacelle and intake are to be conducted in the first half of the next reporting period.
O7 Assess possible criticalities for NGCTR nacelle and intake design in terms of certification and/or operation envelopes in snow conditions.
A set of snow conditions has been selected after analysis of the NGCTR operating envelope and the applicable certification specifications. The activities related to the assessment of the snow criticalities for the NGCTR nacelle and intake are to be conducted in the second half of the next reporting period.
The TRINIDAT project is still expected to support the development of an efficient and all weather civil tilt rotor aircraft, offering superior door-to-door transport capability. Specifically, detailed analysis and optimization of air intake for such configuration is still relevant for improving performance and efficiency.