Periodic Reporting for period 1 - ENODISE (Enabling optimized disruptive airframe-propulsion integration concepts)
Período documentado: 2020-06-01 hasta 2021-11-30
In parallel with the ever-increasing growth of civil air transport, the world has seen an unexpectedly fast development of a new paradigm: Urban Air Mobility (UAM) and the associated Vertical Take-Off and Landing (VTOL) PAVs and Air Taxis. Following the successful deployment of drones for defence and professional applications, several fast-emerging companies have now successfully validated quite disruptive flying concepts. A common denominator of these innovative concepts is the formidable complexity of the aerodynamic and acoustic interactions, affecting both aerodynamic performance and noise emissions, compared with conventional tube-and-wing aircraft.
ENODISE focuses on future, disruptive civil air transport concepts and is designed to develop the knowledge, data, tools and methods that are necessary to understand, model and optimize engine-airframe aerodynamic and acoustic installation effects, with a strong focus on innovative architectures bringing a tighter integration of the propulsive system with the wing, fuselage or control surfaces.
Simplified geometrical configurations will be investigated with the aim to unravel the intricate aeroacoustics mechanisms involved in future aircraft architectures, and eventually enable their reliable simulation and optimization while mitigating the adverse effects.
The project’s objectives are the following:
- the development of a novel research approach, based on extensive parametric test campaigns complemented with numerical simulations, permitting to understand and quantify the favorable and adverse aerodynamic and aeroacoustic installation effects in novel propulsion integration concepts;
- to perform numerical optimization studies in clean vs. installed conditions to generate this background knowledge, and to validate the results quantitatively through experimental verification;
- the inclusion of innovative flow and acoustic control technologies in the optimization loop in order to design better integrated aircraft with minimal detrimental or favorable installation effects;
- the constitution of extensive, well documented and cross-validated experimental and numerical databases that will be made publicly available for benchmarking purposes.
ENODISE focuses on future, disruptive civil air transport concepts and is designed to develop the knowledge, data, tools and methods that are necessary to understand, model and optimize engine-airframe aerodynamic and acoustic installation effects, with a strong focus on innovative architectures bringing a tighter integration of the propulsive system with the wing, fuselage or control surfaces.
Simplified geometrical configurations will be investigated with the aim to unravel the intricate aeroacoustics mechanisms involved in future aircraft architectures, and eventually enable their reliable simulation and optimization while mitigating the adverse effects.
The project’s objectives are the following:
- the development of a novel research approach, based on extensive parametric test campaigns complemented with numerical simulations, permitting to understand and quantify the favorable and adverse aerodynamic and aeroacoustic installation effects in novel propulsion integration concepts;
- to perform numerical optimization studies in clean vs. installed conditions to generate this background knowledge, and to validate the results quantitatively through experimental verification;
- the inclusion of innovative flow and acoustic control technologies in the optimization loop in order to design better integrated aircraft with minimal detrimental or favorable installation effects;
- the constitution of extensive, well documented and cross-validated experimental and numerical databases that will be made publicly available for benchmarking purposes.
The consortium has been working on consolidating the necessary tools for the start of the experimental activities and the numerical work in the following months.
These tools include techniques for the identification of the dominant sources of noise.
Methods have also been developed for the archival, documentation and mining of the experimental and numerical datasets that will be generated by the project.
ENODISE studies both acoustic and pollutant emissions in order to find the best trade-off. Since the latter are directly correlated to the aeropropulsive efficiency of the different propulsion-airframe integrated concepts, techniques have been developed to permit the quantification of their thrust and drag. In parallel, the aerodynamic performance has to be related to the pollutant emissions. This work has started, considering CO2 emissions in priority.
These tools include techniques for the identification of the dominant sources of noise.
Methods have also been developed for the archival, documentation and mining of the experimental and numerical datasets that will be generated by the project.
ENODISE studies both acoustic and pollutant emissions in order to find the best trade-off. Since the latter are directly correlated to the aeropropulsive efficiency of the different propulsion-airframe integrated concepts, techniques have been developed to permit the quantification of their thrust and drag. In parallel, the aerodynamic performance has to be related to the pollutant emissions. This work has started, considering CO2 emissions in priority.
High-performance optimization frameworks do already exist; however, the result of the optimization is rarely (if ever) confirmed through laboratory verification.
Since the outcome of a CFD-based optimization is only as good as the flow simulation itself, more extensive validations of the simulation capabilities are needed when considering the complex aerodynamic and acoustic interactions that prevail in integrated propulsion systems. ENODISE will dedicate a significant effort to this aspect by combining research on fast turnaround LES running on GPUs with low-order stochastic and semi-analytical methods. It should be stressed that, if successful, this project will see the first multi-disciplinary optimization involving high-fidelity scale-resolved simulations.
Regarding flow and acoustic control, the implementation of porous materials at the edges of lifting surfaces was shown to lead to noise reductions up to 6 dB in some cases. Serrations at the leading edge of a blade can also reduce turbulence impingement noise by about 10 dB in certain frequency ranges. Acoustic shielding effects could be strongly enhanced through advanced liners, e.g. based on metamaterials tailored to yield anomalous reflective properties. Those technologies appear therefore to be promising to mitigate the adverse noise effects of a tighter thruster-airframe integration and will be further studied in this project.
The aerodynamic noise radiated by the fixed parts of the airframe (landing gear and high-lift devices in particular) would typically radiate noise in proportion of the 5-6th power of the flight speed. Moreover, high lift coefficients enable very short take-off distances and large climb/descent angles at low speeds, both beneficial to minimize noise footprint around airports and in urban environments. And since the efficiency of electric motors does not depend much on their size, the overall conversion efficiency of a large number of electric motors driving many small propellers can be as good as that of a single motor driving a single large propeller. When the electric power is provided by a common turbine, a quite high effective by-pass ratio (defined as the ratio of mass flow rate of all combined airflows by the one that enters the turbine) can be achieved, being generally beneficial to noise reduction. The use of power inverters between the generators and the fan motors allows the speed ratio to change in-flight, giving the effect of a variable-ratio gearbox. And naturally, the noise emitted by electric machines is much less than that associated to the compressor, combustor and turbine components: the noise generated by the electric motor system alone can be 8-20 dB below the fan noise for a regional jet-sized aircraft, and 17-29 dB lower than that of a single-aisle commercial transport class aircraft.
Other noise reduction strategies are possible. The multiplicity of propulsors opens interesting perspectives for tonal noise control via an adequate clocking of the propellers. The propulsors can also be distributed over the airframe in such a way to enhance noise shielding effects, in some cases low-frequency noise reductions of the order of 20 dB can be achieved. From an operational point of view, placing the DEP system on a movable control surface can combine the advantages of VTOL and efficient high-speed translation flight. The last point is particularly relevant to UAM concepts. For such vehicles, defining a baseline is obviously a difficult task given the scarcity of available data, but the company Uber estimated that a fleet of hundreds of VTOL aircrafts would be tolerated as long as their noise can blend in the city background noise, estimated at 67 dB(A). The BlackFly VTOL aircraft is reported to radiate 72 dB(A) to the ground from an altitude of 150 feet . One of the objectives of ENODISE is to provide an assessment of the chances for a state-of-the-art UAM concepts to meet this target. The absence of competing sources (other than the electric motors) suggests that dramatic net gains could be achieved.
With its contribution to ultra-efficient, more silent, regional, short-haul or long-haul commercial, transport aircraft as well as to the achievement of the Flightpath 2050 objectives in terms of noise and pollutant emissions, ENODISE promises to have significant societal impacts.
Since the outcome of a CFD-based optimization is only as good as the flow simulation itself, more extensive validations of the simulation capabilities are needed when considering the complex aerodynamic and acoustic interactions that prevail in integrated propulsion systems. ENODISE will dedicate a significant effort to this aspect by combining research on fast turnaround LES running on GPUs with low-order stochastic and semi-analytical methods. It should be stressed that, if successful, this project will see the first multi-disciplinary optimization involving high-fidelity scale-resolved simulations.
Regarding flow and acoustic control, the implementation of porous materials at the edges of lifting surfaces was shown to lead to noise reductions up to 6 dB in some cases. Serrations at the leading edge of a blade can also reduce turbulence impingement noise by about 10 dB in certain frequency ranges. Acoustic shielding effects could be strongly enhanced through advanced liners, e.g. based on metamaterials tailored to yield anomalous reflective properties. Those technologies appear therefore to be promising to mitigate the adverse noise effects of a tighter thruster-airframe integration and will be further studied in this project.
The aerodynamic noise radiated by the fixed parts of the airframe (landing gear and high-lift devices in particular) would typically radiate noise in proportion of the 5-6th power of the flight speed. Moreover, high lift coefficients enable very short take-off distances and large climb/descent angles at low speeds, both beneficial to minimize noise footprint around airports and in urban environments. And since the efficiency of electric motors does not depend much on their size, the overall conversion efficiency of a large number of electric motors driving many small propellers can be as good as that of a single motor driving a single large propeller. When the electric power is provided by a common turbine, a quite high effective by-pass ratio (defined as the ratio of mass flow rate of all combined airflows by the one that enters the turbine) can be achieved, being generally beneficial to noise reduction. The use of power inverters between the generators and the fan motors allows the speed ratio to change in-flight, giving the effect of a variable-ratio gearbox. And naturally, the noise emitted by electric machines is much less than that associated to the compressor, combustor and turbine components: the noise generated by the electric motor system alone can be 8-20 dB below the fan noise for a regional jet-sized aircraft, and 17-29 dB lower than that of a single-aisle commercial transport class aircraft.
Other noise reduction strategies are possible. The multiplicity of propulsors opens interesting perspectives for tonal noise control via an adequate clocking of the propellers. The propulsors can also be distributed over the airframe in such a way to enhance noise shielding effects, in some cases low-frequency noise reductions of the order of 20 dB can be achieved. From an operational point of view, placing the DEP system on a movable control surface can combine the advantages of VTOL and efficient high-speed translation flight. The last point is particularly relevant to UAM concepts. For such vehicles, defining a baseline is obviously a difficult task given the scarcity of available data, but the company Uber estimated that a fleet of hundreds of VTOL aircrafts would be tolerated as long as their noise can blend in the city background noise, estimated at 67 dB(A). The BlackFly VTOL aircraft is reported to radiate 72 dB(A) to the ground from an altitude of 150 feet . One of the objectives of ENODISE is to provide an assessment of the chances for a state-of-the-art UAM concepts to meet this target. The absence of competing sources (other than the electric motors) suggests that dramatic net gains could be achieved.
With its contribution to ultra-efficient, more silent, regional, short-haul or long-haul commercial, transport aircraft as well as to the achievement of the Flightpath 2050 objectives in terms of noise and pollutant emissions, ENODISE promises to have significant societal impacts.