Periodic Reporting for period 2 - TRINIDAT (Tilt Rotor INlet Innovative Design And Testing)
Reporting period: 2020-08-01 to 2022-04-30
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 ended on 30 April 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 relied on dedicated CFD studies. The final validation has been made with full size model tests in the DNW-LLF 6m x 6m wind tunnel, allowing reliable testing at full scale Mach and Reynolds conditions.
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 relied on dedicated CFD studies. The final validation has been made with full size model tests in the DNW-LLF 6m x 6m 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.
This objective has been fully achieved. There are in total 26 large scale time-accurate unsteady CFD simulations that have been performed: 16 load cases for the complete configuration (including one simulation with surface roughness), 5 simulations for a configuration with wind tunnel walls but without rotor, and 5 simulations for a free flow configuration without rotor. For all simulations, the complete set of performance metrics (12 parameters) has been calculated, representing flow separation, total pressure losses, and flow uniformity and flow angles at the AIP.
O2 Optimize the intake geometry for superior intake performance in all flight conditions, at least better than with the basic intake geometry.
This objective has been fully achieved. Three load cases have been considered as the design points, i.e. the high-speed cruise, efficient cruise and hover conditions. A very significant improvement has been achieved. The design optimization has resulted in about 70% and 45% reduction, respectively, of the distortion coefficient for the cruise conditions and hover condition, respectively. Post-optimization assessment of the off-design conditions have shown that the same order of reductions have been achieved for the other load cases.
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 been fully achieved, with the conclusion that the effect of roughness to the engine inlet flow distortion is not appreciable.
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.
The optimized intake duct has been designed, manufactured and instrumented. Additional to the original scope vortex generators that can be mounted on the wing have been manufactured.
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).
Two wind tunnel test entries have been successfully conducted in the DNW-LLF. The first test took place in September 2020 and featured measurements with the basic intake. In the second entry, which took place in July 2021, both the basic and the optimized intake are tested. For both intakes, the static pressure distribution in the duct and around the intake lips are measured. The total pressure distortion and flow angularity conditions at the AIP are quantified under various free-stream and mass flow conditions representative for flight.
O6 Assess possible criticalities for NGCTR nacelle and intake design in terms of certification and/or operation envelopes in icing conditions.
Icing simulations have been performed and an assessment of the icing criticalities for the NGCTR nacelle and intake has been conducted. This analysis has also been executed for the optimized NGCTR configuration and the results for the baseline configuration and the optimized configuration have been compared.
O7 Assess possible criticalities for NGCTR nacelle and intake design in terms of certification and/or operation envelopes in snow conditions.
Snow effects on the nacelle components have been simulated and critical areas have been identified. Therefore, the assessment of the snow criticalities for the NGCTR nacelle and intake has been conducted. This analysis has also been executed for the optimized NGCTR configuration and the results for the baseline configuration and the optimized configuration have been compared.
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.
This objective has been fully achieved. There are in total 26 large scale time-accurate unsteady CFD simulations that have been performed: 16 load cases for the complete configuration (including one simulation with surface roughness), 5 simulations for a configuration with wind tunnel walls but without rotor, and 5 simulations for a free flow configuration without rotor. For all simulations, the complete set of performance metrics (12 parameters) has been calculated, representing flow separation, total pressure losses, and flow uniformity and flow angles at the AIP.
O2 Optimize the intake geometry for superior intake performance in all flight conditions, at least better than with the basic intake geometry.
This objective has been fully achieved. Three load cases have been considered as the design points, i.e. the high-speed cruise, efficient cruise and hover conditions. A very significant improvement has been achieved. The design optimization has resulted in about 70% and 45% reduction, respectively, of the distortion coefficient for the cruise conditions and hover condition, respectively. Post-optimization assessment of the off-design conditions have shown that the same order of reductions have been achieved for the other load cases.
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 been fully achieved, with the conclusion that the effect of roughness to the engine inlet flow distortion is not appreciable.
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.
The optimized intake duct has been designed, manufactured and instrumented. Additional to the original scope vortex generators that can be mounted on the wing have been manufactured.
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).
Two wind tunnel test entries have been successfully conducted in the DNW-LLF. The first test took place in September 2020 and featured measurements with the basic intake. In the second entry, which took place in July 2021, both the basic and the optimized intake are tested. For both intakes, the static pressure distribution in the duct and around the intake lips are measured. The total pressure distortion and flow angularity conditions at the AIP are quantified under various free-stream and mass flow conditions representative for flight.
O6 Assess possible criticalities for NGCTR nacelle and intake design in terms of certification and/or operation envelopes in icing conditions.
Icing simulations have been performed and an assessment of the icing criticalities for the NGCTR nacelle and intake has been conducted. This analysis has also been executed for the optimized NGCTR configuration and the results for the baseline configuration and the optimized configuration have been compared.
O7 Assess possible criticalities for NGCTR nacelle and intake design in terms of certification and/or operation envelopes in snow conditions.
Snow effects on the nacelle components have been simulated and critical areas have been identified. Therefore, the assessment of the snow criticalities for the NGCTR nacelle and intake has been conducted. This analysis has also been executed for the optimized NGCTR configuration and the results for the baseline configuration and the optimized configuration have been compared.
The impact of the work carried out is threefold. First, full characterization for the baseline intake, which is essential for Technology Demonstrator activities. Second, together with guidelines and optimized geometry the civil tilt-rotorcraft capabilities can be improved. Third, verification of the impact of the proposed solution on icing and snowing conditions will be done for certification purposes.