A Parametric Approach for Conceptual Integration and Performance Studies of Liquid Hydrogen Short–Medium Range Aircraft

Abstract

The present paper deals with the investigation, at conceptual level, of the performance of short–medium-range aircraft with hydrogen propulsion. The attention is focused on the relationship between figures of merit related to transport capability, such as passenger capacity and flight range, and the parameters which drive the design of liquid hydrogen tanks and their integration with a given aircraft geometry. The reference aircraft chosen for such purpose is a box-wing short–medium-range airplane, the object of study within a previous European research project called PARSIFAL, capable of cutting the fuel consumption per passenger-kilometre up to 22%. By adopting a retrofitting approach, non-integral pressure vessels are sized to fit into the fuselage of the reference aircraft, under the assumption that the main aerodynamic, flight mechanic, and structural characteristics are not affected. A parametric model is introduced to generate a wide variety of fuselage-tank cross-section layouts, from a single tank with the maximum diameter compatible with a catwalk corridor to multiple tanks located in the cargo deck, and an assessment workflow is implemented to perform the structural sizing of the tanks and analyse their thermodynamic behaviour during the mission. This latter is simulated with a time-marching approach that couples the fuel request from engines with the thermodynamics of the hydrogen in the tanks, which is constantly subject to evaporation and, depending on the internal pressure, vented-out in gas form. Each model is presented in detail in the paper and results are provided through sensitivity analyses to both the technologic parameters of the tanks and the geometric parameters influencing their integration. The guidelines resulting from the analyses indicate that light materials, such as the aluminium alloy AA2219 for tanks’ structures and polystyrene foam for the insulation, should be selected. Preferred values are also indicted for the aspect ratios of the vessel components, i.e., central tube and endcaps, as well as suggestions for the integration layout to be adopted depending on the desired trade-off between passenger capacity, as for the case of multiple tanks in the cargo deck, and achievable flight ranges, as for the single tank in the section.

Preliminary Performance Analysis of Medium-Range Liquid Hydrogen-Powered Box-Wing Aircraft

“…In the present study, it is the possibility of having a larger availability of internal volume, without penalties in terms of overall aircraft size and aerodynamic performance, that may represent the key feature of the box-wing for the integration of LH 2 propulsion [45]. In fact, for LH 2 -powered aircraft, the problem of integrating the tanks in the fuselage is crucial, and having a flexible solution in terms of available volume may be decisive for the actual implementation of this technology.…”

“…In this section, a summary of the design methodology, proposed more in detail in Ref. [45], is given. The developed methodology follows the schematic workflow depicted in Figure 5, and it allows for LH 2 retrofitting of kerosene aircraft (baseline) for both conventional (i.e., tube-and-wing, TW) and any unconventional airframe, such as the box-wing in the present case.…”

“…In case these verifications are not satisfied, the tank thicknesses are updated until convergence is reached. The selected material is the aluminum alloy AA2219, which has yield stress equal to 400 MPa at 20 K; the selected foam material is polystyrene, whose properties are described in [45].…”

“…In Ref. [45], a conceptual retrofitting methodology for hydrogen-powered box-wing (BW) aircraft is presented: this preliminary study on box-wings lays the foundation for further investigations, which this paper aims at dealing with.…”

A Review of Novel and Non-Conventional Propulsion Integrations for Next-Generation Aircraft

“…In this context, specific attention is being devoted to research into non-conventional solutions for the integration of the propulsion system, involving two different interconnected technological threads. From a general point of view, new types of propulsion systems are under investigation, and technologies involving new fuels, such as hydrogen [11][12][13][14][15][16][17][18] or sustainable aviation fuels [19][20][21][22], or electric and hybrid-electric powertrains [23][24][25][26][27][28][29][30][31][32], are under development to provide breakthrough forward advancements in the field. In addition to these important innovations, and in a way that is generally complementary, non-conventional powertrain/airframe integrations are increasingly being investigated since, either as standalone or in combination with previous new power supply concepts, they can contribute to general improvements in aircraft performance, with significant implications for reducing environmental impact.…”