Does anyone remember what was the last post about? …. pause of 5 secs (like Dora and the Explorer). Yes, you’re absolutely right! It was about how to design a hydrogen tank in an aircraft. To remind you a bit, there are 3 main challenges to address: geometrical, structural, and thermal. Now, we’re gonna start by geometrical design.
What is the best geometry for hydrogen tank?
First thing first, the primary goal of geometrical design are simply to decide the outer shape and size quantitatively the hydrogen storage. Do you want a ball-shaped tank? Or rectangular box-like shape? Basically, it can be anything, but of course it will affect the performances, both subsystem-level performance and aircraft-level performance. Imagine if you choose prism-shaped tank, it’s gonna be definitely aesthetic! Until you realize that the volume of hydrogen can be contained inside is very low, therefore shortened the mission range significantly. So, the first criteria is the shape which can afford maximum volume considering the shape of airframe where the tanks are attached to. The possibilities are the tank which is installed inside fuselage, placed above the fuselage, or hanged on the wing. For the one inside the fuselage, it is certainly better to choose cylindrical rather than the cube one.
Then, by proposed by some researchers [2][3], the tank must have characteristic of high volume-to-area ratio. This is intended to minimize the heat transfer, thus will as well minimize the thickness of insulation layer. The another selection is usually based of the manufacture complexity related. At the end, most agree that cylinder with elliptical-ends turns out as the best shape [4][5].
How large would be the hydrogen tank?
Once the outer shape has been decided, the things left are to size the length, diameter, and any other geometrical parameters. Surely, there are many ways to do this sizing. One of them is a method proposed by a group of researchers from universities in Germany [6]. Their method instructs hydrogen tank designer to decide the tank’s diameter and the volume requirement of hydrogen to fulfill the flight mission. Then, by some magical set of equations which I won’t write them here, we will obtain the cylindrical length, elliptical length, surface area of the entire tank, and cross section area. If you are interested to know deeper the procedure, I suggest you reading the paper referred below [6].
Just to get the better sense on how big the hydrogen tank would be, I’ll give you an example. DLR of Germany had made a research about how installation of hydrogen storage affects the aircraft [7]. The reference aircraft is Airbus A320neo with 165 passengers and range of 3100 nm. With the hydrogen tank installed in the rear of fuselage as shown by the image below, the tank length is around 8 meters. This will increase the original length of fuselage from ~37 meters to ~45 meters. In other words, the hydrogen tank occupies ~18 percent of the fuselage length.
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[2] E. J. Adler and J. R. Martins, “Hydrogen-powered aircraft: Fundamental concepts, key technologies, and environmental impacts,” Fuel, vol. 32, p. 7.
[3] B. Khandelwal, A. Karakurt, P. R. Sekaran, V. Sethi, and R. Singh, “Hydrogen powered aircraft: The future of air transport,” Progress in Aerospace Sciences, vol. 60, pp. 45–59, 2013.
[4] A. J. Colozza and L. Kohout, “Hydrogen storage for aircraft applications overview,” tech. rep., 2002.
[5] K. Franzén and F. Jangelind, “States and prospects of hydrogen storage technologies in aircraft applications,” 2021.
[6] C. Winnefeld, T. Kadyk, B. Bensmann, U. Krewer, and R. Hanke-Rauschenbach, “Modelling and designing cryogenic hydrogen tanks for future aircraft applications,” Energies, vol. 11, no. 1, p. 105, 2018.
[7] Silberhorn, D., Atanasov, G., Walther, J. N., & Zill, T. (2019, September). Assessment of hydrogen fuel tank integration at aircraft level. In Deutscher Luft-und Raumfahrtkongress.
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