Launching less weight into the air also means less energy consumption. The flipside is that electronics generate heat.
The cockpit is prepared for a simulation with measurements. Fraunhofer IBP
Construction of the three-part fuselage in the Ground Thermal Test Bench. Fraunhofer IBP
That is why the Ground Thermal Test Bench was set up at the Fraunhofer Institute for Building Physics IBP in Holzkirchen. This unique test facility allows researchers to investigate the problem of heat distribution aboard aircraft – and how to channel away unwanted heat.
Picture the scene: brilliant blue skies and the sun beating down. Just the thing for a beach holiday, you might say, but not when you’re sitting in a plane waiting to take off. As temperatures inside the cabin continue to rise – despite the air conditioning system’s best efforts – passengers are left hoping for a speedy go-ahead from the control tower. But it’s not just delayed takeoffs in hot countries that are prompting the aerospace community to tackle the problem of unwanted heat aboard aircraft. More and more it’s about the trend toward the all-electric aircraft, which presents new challenges to manufacturers and researchers alike.
In modern airliners, electronics already govern a variety of functional and control units, from the engines to radio communication, while fly-by-wire, a technology that converts movements of flight controls into electronic signals and transmits them via wires, is the state of the art in flight control systems. Not only that, but there are plans to replace current compressed-air and hydraulic systems, given that these call for compressors, pipes branching out in all directions and a not insubstantial amount of hydraulic fluid. This all adds to a jet’s weight, increasing its fuel consumption.
To save weight in aircraft, it is important to fit planes with lighter electronics systems, since lower weight means reduced emissions of pollutants such as carbon dioxide (CO2) and nitrous oxides (NOx) as well as improved fuel consumption. Launching less weight into the air also means less energy consumption. The flipside is that electronics generate heat – you need only think of a running computer or a cell phone on charge. That is why the Ground Thermal Test Bench was set up at the Fraunhofer Institute for Building Physics IBP in Holzkirchen. This unique test facility allows researchers to investigate the problem of heat distribution aboard aircraft – and how to channel away unwanted heat.
“The facility was developed as part of the EU Clean Sky project and allows us to simulate the conditions on the interior and exterior of the aircraft just as they would be if the aircraft was actually in flight or on the ground,” explains the researcher in charge of the test facility, Markus Siede from the Aviation business area at Fraunhofer IBP. “This means we can examine, compare and optimize a whole range of avionics systems.” Researchers can make use of the Ground Thermal Test Bench to test new developments step by step – from simulation calculations on the computer to experiments in small spaces known as simulation boxes and, ultimately, testing under real conditions using actual sections of aircraft fuselage and with test subjects. Conducting testing in this way offers a number of advantages, as it cuts down on the number of actual test flights required while bringing down costs and protecting the environment.
Test bench design
The Ground Thermal Test Bench at Fraunhofer IBP’s flight test facility comprises a cutting-edge cooling system, heat exchangers, several simulation chambers, an aircraft fuselage divided into three sections – cockpit, cabin and rear – and an aircraft calorimeter (ACC). The ACC is used to simulate the most extreme conditions such as rapid decompression and thermal shock (a rapid change of temperature in a material that causes mechanical tension between the outer and inner parts of the material as heat to or from its surface is conveyed more quickly than to its interior). The aircraft fuselage, meanwhile, gives researchers the opportunity to study individual test configurations in detail.
The ACC comes into play once computer simulations and thermal models have been completed. At this point the task is to validate parameters such as airflow patterns, thermal comfort, energy efficiency, exhaust emissions and temperature changes under real conditions. The simulation chamber gives researchers the opportunity to test modular measurements in a small space based on extreme changes in temperature and pressure.
Fraunhofer researchers use the fuselage to simulate the environment in the cabin and how this relates to the climate on the exterior of the aircraft. Here, original avionics components can be substituted by faithfully reconstructed dummy parts that share the same thermal properties as the actual components. This affords extra flexibility, as the heat emissions and geometry of these “equipment simulators” can be manipulated at will. There are a whole range of important questions to consider in the process: What heat sources are there on the interior? How is the temperature influenced by the passengers and the on-board electronics? Where exactly does heat build up? Is there a possibility that equipment will overheat and how does this affect its operation? The motivation behind the testing is to find solutions that will enable researchers to channel heat away and direct where it goes. A basic solution of the sort applied in server rooms in office buildings, where simply adding ventilation holes can reduce the temperature, is clearly not an option in aircraft. The problem is that an aircraft is exposed to huge changes in pressure during flight, meaning that simply exchanging air with the outside is far from straightforward. Creating openings in the exterior of the aircraft would also lead to turbulence, increasing the aircraft’s air resistance – and its fuel consumption. One interesting idea could be to make use of the fuel tanks as heat/cooling reservoirs.
In principle, the facility also presents the opportunity to carry out experiments with test volunteers, as the three-part fuselage can be fitted with seats.
“Of course, to test extreme scenarios – for instance, how damage to the fuselage in flight would affect passengers – we will be using the DressMAN we developed ourselves in-house. These dummies could also be used to investigate worst-case scenarios that are far too dangerous for human test subjects,” explains Siede.Temperatures high and low
A second, significantly smaller air treatment unit ensures that temperature and humidity in the cabin can be controlled with precision. Here, the range of temperatures is between three and 70 degrees Celsius. This allows researchers to simulate factors such as the high exterior temperatures before takeoff in a desert country and to identify solutions that can direct the heat involved away from the cabin in an energy-efficient way.
Tool helps cities to plan electric bus routes, and calculate the benefits
09.01.2017 | International Institute for Applied Systems Analysis (IIASA)
Realistic training for extreme flight conditions
28.12.2016 | Technical University of Munich (TUM)
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
24.04.2017 | Physics and Astronomy
24.04.2017 | Materials Sciences
24.04.2017 | Life Sciences