Periodic Reporting for period 1 - BinCola (Evaluation of the Benefits of innovative Concepts of laminar nacelle and HTP installed on a business jet configuration)
Période du rapport: 2018-11-01 au 2020-02-29
Business aviation will contribute to meet Europe’s strategic vision for a prosperous, modern, competitive and climate neutral economy by 2050. The Clean Sky project BinCola (Evaluation of the Benefits of innovative Concepts of laminar nacelle and horizontal tail plane (HTP) installed on a business jet configuration) prepared some vital ground, i.e. to exploit Natural Laminar Flow (NLF) for maximising future business jet efficiency. Scaled NLF wind tunnel tests at flight relevant conditions are essential to advance robust NLF design guidelines, and were performed to mature the computational and experimental tools and methods to design next generation business jets.
The European Transonic Windtunnel GmbH (ETW) operates at high Reynolds numbers and is one of only two wind tunnels in the world (the other is the National Transonic Facility at NASA, Langley) that is capable of authentically replicating the aerodynamics of a real aircraft during take-off, landing and operation at high altitude. ETW's unique pressurised and cryogenically operated testing facilities were a prerequisite for the very specific ambitions of the BinCola project.
The BinCola consortium consists of ETW (project coordinator), Deharde GmbH (responsible for manufacturing the wind tunnel models and associated coatings) and Laserline Gesellschaft für Entwicklung und Vertrieb von Diodenlasern GmbH (which developed the array of laser and optics that were used to heat up the surfaces of the scale models in the testing process). Dassault Aviation as topic manager, collaboratively investigated the use of extended laminarity on the nacelles (engine housings) and on the HTP of a business jet, to reduce drag and increase aerodynamic performance. The idea is to improve the efficiency of future aircraft by reducing fuel consumption and lowering CO2 and NOx emissions in line with Horizon 2020 objectives.
The European Transonic Windtunnel GmbH (ETW) operates at high Reynolds numbers and is one of only two wind tunnels in the world (the other is the National Transonic Facility at NASA, Langley) that is capable of authentically replicating the aerodynamics of a real aircraft during take-off, landing and operation at high altitude. ETW's unique pressurised and cryogenically operated testing facilities were a prerequisite for the very specific ambitions of the BinCola project.
The BinCola consortium consists of ETW (project coordinator), Deharde GmbH (responsible for manufacturing the wind tunnel models and associated coatings) and Laserline Gesellschaft für Entwicklung und Vertrieb von Diodenlasern GmbH (which developed the array of laser and optics that were used to heat up the surfaces of the scale models in the testing process). Dassault Aviation as topic manager, collaboratively investigated the use of extended laminarity on the nacelles (engine housings) and on the HTP of a business jet, to reduce drag and increase aerodynamic performance. The idea is to improve the efficiency of future aircraft by reducing fuel consumption and lowering CO2 and NOx emissions in line with Horizon 2020 objectives.
Within the Clean Sky project BinCola effective and efficient cryogenic pressurised NLF testing at flight-relevant conditions have been established, comprising of:
• Temperature Sensitive Paint (TSP),
• Precision TSP coating by milling and polishing,
• Infrared (IR) laser radiation and Carbon Nanotube (CNT) based heating to locate laminar / turbulent boundary layer transition.
New capabilities demonstrated and database collated for an innovative jet design featuring laminar nacelles and a laminar horizontal tail plane (HTP):
• Benefits from use of extended laminarity shown,
• Data vital to advance and validate numerical tools,
• CNT based TSP heating challenging but valuable for specific cases,
• IR based TSP heating suited for high-productivity testing, ca. 5 times faster and less costly compared with common temperature-step method.
Relevant wind tunnel tests were successfully performed during September 2019 at flight Mach numbers (aircraft flight speed relative to the speed of sound) and Reynolds numbers (the ratio of inertia force to viscous or friction force). The data obtained can be used to determine where the flow changes from laminar to turbulent, aka the transition zone at model scale. The tests, carried out at ETW, were effectively a validation exercise to advance computational work carried out by Dassault Aviation, which had performed computational fluid dynamics (CFD) simulations to predict where that transition zone would occur.
In order to effectively and efficiently localize the transition zone on an aircraft part (such as a nacelle) in the wind tunnel, the first task was to evaluate and determine which of the two types of TSP technologies, developed and applied by the German Aerospace Center DLR for cryogenic conditions (down to -163 °C), would be most appropriate for the testing process.
One option was to use a fixed infrared laser beam distributed via a lens to heat up the TSP-coated model parts. The TSP then shows where the surface heat flux is higher or lower, so that it is possible to distinguish where the flow stays laminar or becomes turbulent, revealing the transition zone. The other option is to embed a layer of carbon nanotubes below the same TSP. Then, by attaching two wires and feeding electricity through it, it heats up, creating a temperature difference between the surface of the model and the air flow around it. From that, it is also possible to observe where the laminar and turbulent boundary layer occur.
The BinCola project successfully verified and quantified the benefits that an innovative aircraft design may gather from making use of natural laminar flow (NLF) on engine nacelles and horizontal tail planes. Besides the main goal of the BinCola project, ETW enhanced the productivity of its NLF test methods by establishing infrared laser heated TSP. Compared with the classical method, which provokes a heat flux by step-changing of the flow temperature, the infrared laser method is about 5 times quicker and less costly.
Another relevant factor is the use of a business jet model in the project. On a business jet, laminar flow is easier to be exploited than on large commercial jets. Due to their smaller size and the associated lower flight Reynolds numbers, it is easier to maintain laminar flow over large portions of the aircraft surface in a ’natural’ manner, in other words by proper shaping of the aircraft surface. More laminarity means lighter engines, less energy consumption, and cleaner aircraft.
Regarding exploitation and dissemination, a press release was published on the ETW website www.etw.de. The performed Clean Sky project is going to be incorporated in the company profile listing ongoing and completed European research projects. As a major dissemination item, a video clip featuring the “Innovative Application of Temperature Sensitive Paint (TSP)” has been produced and published on the ETW website (https://www.etw.de/publications/learn-more-movie/bincola-measurements(s’ouvre dans une nouvelle fenêtre)).
A paper about the CNT methodology of the “Application of Temperature sensitive paint to investigate Laminar-to-Turbulent Transition on Nacelles”, developed within BinCola was presented on the AIAA SciTech Forum in Orlando, Florida by DLR. The “New Efficient Method for Transition Detection by TSP on a Full Span Model by use of Infra-Red Laser” was orally presented by ETW on the same conference. Furthermore oral presentations on the CEAS conference in Bordeaux in February 2020 have been given by representatives of Dassault and ETW.
A further relevant activity is a more comprehensive article published in the periodically released “ETW-News” available for download on the ETW-website.
• Temperature Sensitive Paint (TSP),
• Precision TSP coating by milling and polishing,
• Infrared (IR) laser radiation and Carbon Nanotube (CNT) based heating to locate laminar / turbulent boundary layer transition.
New capabilities demonstrated and database collated for an innovative jet design featuring laminar nacelles and a laminar horizontal tail plane (HTP):
• Benefits from use of extended laminarity shown,
• Data vital to advance and validate numerical tools,
• CNT based TSP heating challenging but valuable for specific cases,
• IR based TSP heating suited for high-productivity testing, ca. 5 times faster and less costly compared with common temperature-step method.
Relevant wind tunnel tests were successfully performed during September 2019 at flight Mach numbers (aircraft flight speed relative to the speed of sound) and Reynolds numbers (the ratio of inertia force to viscous or friction force). The data obtained can be used to determine where the flow changes from laminar to turbulent, aka the transition zone at model scale. The tests, carried out at ETW, were effectively a validation exercise to advance computational work carried out by Dassault Aviation, which had performed computational fluid dynamics (CFD) simulations to predict where that transition zone would occur.
In order to effectively and efficiently localize the transition zone on an aircraft part (such as a nacelle) in the wind tunnel, the first task was to evaluate and determine which of the two types of TSP technologies, developed and applied by the German Aerospace Center DLR for cryogenic conditions (down to -163 °C), would be most appropriate for the testing process.
One option was to use a fixed infrared laser beam distributed via a lens to heat up the TSP-coated model parts. The TSP then shows where the surface heat flux is higher or lower, so that it is possible to distinguish where the flow stays laminar or becomes turbulent, revealing the transition zone. The other option is to embed a layer of carbon nanotubes below the same TSP. Then, by attaching two wires and feeding electricity through it, it heats up, creating a temperature difference between the surface of the model and the air flow around it. From that, it is also possible to observe where the laminar and turbulent boundary layer occur.
The BinCola project successfully verified and quantified the benefits that an innovative aircraft design may gather from making use of natural laminar flow (NLF) on engine nacelles and horizontal tail planes. Besides the main goal of the BinCola project, ETW enhanced the productivity of its NLF test methods by establishing infrared laser heated TSP. Compared with the classical method, which provokes a heat flux by step-changing of the flow temperature, the infrared laser method is about 5 times quicker and less costly.
Another relevant factor is the use of a business jet model in the project. On a business jet, laminar flow is easier to be exploited than on large commercial jets. Due to their smaller size and the associated lower flight Reynolds numbers, it is easier to maintain laminar flow over large portions of the aircraft surface in a ’natural’ manner, in other words by proper shaping of the aircraft surface. More laminarity means lighter engines, less energy consumption, and cleaner aircraft.
Regarding exploitation and dissemination, a press release was published on the ETW website www.etw.de. The performed Clean Sky project is going to be incorporated in the company profile listing ongoing and completed European research projects. As a major dissemination item, a video clip featuring the “Innovative Application of Temperature Sensitive Paint (TSP)” has been produced and published on the ETW website (https://www.etw.de/publications/learn-more-movie/bincola-measurements(s’ouvre dans une nouvelle fenêtre)).
A paper about the CNT methodology of the “Application of Temperature sensitive paint to investigate Laminar-to-Turbulent Transition on Nacelles”, developed within BinCola was presented on the AIAA SciTech Forum in Orlando, Florida by DLR. The “New Efficient Method for Transition Detection by TSP on a Full Span Model by use of Infra-Red Laser” was orally presented by ETW on the same conference. Furthermore oral presentations on the CEAS conference in Bordeaux in February 2020 have been given by representatives of Dassault and ETW.
A further relevant activity is a more comprehensive article published in the periodically released “ETW-News” available for download on the ETW-website.
Beyond the specific mission of the BinCola project, ETW was enabled to contribute its unique features to advance aeronautics research into product innovation, to advance its own test methods and tools and to establish these in the aircraft design processes to the benefit of ETW’s industrial clients. It also allows ETW to team up with academia, other research establishments and SMEs to boost European aviation R&D.
Finally, the results and the methodology of collecting such data are extremely useful for the airframers. Together with other experimental and computational data, a unique database can be established to advance the exploitation of laminar flow control towards clean aviation.
Finally, the results and the methodology of collecting such data are extremely useful for the airframers. Together with other experimental and computational data, a unique database can be established to advance the exploitation of laminar flow control towards clean aviation.