Refueling of LH2 Aircraft—Assessment of Turnaround Procedures and Aircraft Design Implication

Green liquid hydrogen (LH2) could play an essential role as a zero-carbon aircraft fuel to reach long-term sustainable aviation. Excluding challenges such as electrolysis, transportation and use of renewable energy in setting up hydrogen (H2) fuel infrastructure, this paper investigates the interface between refueling systems and aircraft, and the impacts on fuel distribution at the airport. Furthermore, it provides an overview of key technology design decisions for LH2 refueling procedures and their effects on the turnaround times as well as on aircraft design. Based on a comparison to Jet A-1 refueling, new LH2 refueling procedures are described and evaluated. Process steps under consideration are connecting/disconnecting, purging, chill-down, and refueling. The actual refueling flow of LH2 is limited to a simplified Reynolds term of v · d = 2.35m2/s. A mass flow rate of 20 kg/s is reached with an inner hose diameter of 152.4mm. The previous and subsequent processes (without refueling) require 9 min with purging and 6 min without purging. For the assessment of impacts on LH2 aircraft operation, process changes on the level of ground support equipment are compared to current procedures with Jet A-1. The technical challenges at the airport for refueling trucks as well as pipeline systems and dispensers are presented. In addition to the technological solutions, explosion protection as applicable safety regulations are analyzed, and the overall refueling process is validated. The thermodynamic properties of LH2 as a real, compressible fluid are considered to derive implications for airport-side infrastructure. The advantages and disadvantages of a subcooled liquid are evaluated, and cost impacts are elaborated. Behind the airport storage tank, LH2 must be cooled to at least 19K to prevent two-phase phenomena and a mass flow reduction during distribution. Implications on LH2 aircraft design are investigated by understanding the thermodynamic properties, including calculation methods for the aircraft tank volume, and problems such as cavitation and two-phase flows. In conclusion, the work presented shows that LH2 refueling procedure is feasible, compliant with the applicable explosion protection standards and hence does not impact the turnaround procedure. A turnaround time comparison shows that refueling with LH2 in most cases takes less time than with Jet A-1. The turnaround at the airport can be performed by a fuel truck or a pipeline dispenser system without generating direct losses, i.e., venting to the atmosphere. © 2022 by the authors.Licensee MDPI, Basel, Switzerland

DLR Design Challenge 2022: Design of a next generation VTOL firefighting aircraft

Since 2017, the German Aerospace Center (DLR) has been organizing an annual student competition on conceptual aircraft design titled DLR Design Challenge. This education and training initiative is set to challenge the next generation of aircraft designers with topics tailored to current research questions in the field of aeronautics. This year’s challenge was about the development of an aerial firefighting system of systems including vehicle and fleet design with a strong emphasize on operationally-driven design aspects. This paper proposes a design for a next generation vertical take-off and landing firefighting aircraft with an expected entry into service in 2030, that is working intelligently and interconnected in a group of four. The design won the DLR Design Challenge 2022 and the underlying work covers the preliminary design including the structural concept, aerodynamic simulations, weight and balance calculations and the concept for water intake and deployment. The designed aircraft is characterized by a considerable high payload ratio that features vertical take-off and landing capabilities while showing efficient horizontal flight properties with a very competitive cost basis. The 24-hr operability during various weather conditions and challenging fire scenarios is ensured using a wide variety of sensors and a modern glass-cockpit combining pilot comfort with indispensable safety aspects. Due to its modular design, every aircraft can be comfortably converted to a passenger or freight version during firefighting off-season or for cargo and crew supply during the missions

DLR DESIGN CHALLENGE 2022: DESIGN OF A NEXT GENERATION VTOL FIREFIGHTING AIRCRAFT

Since 2017, the German Aerospace Center (DLR) has been organizing an annual student competition on conceptual aircraft design titled DLR Design Challenge. This education and training initiative is set to challenge the next generation of aircraft designers with topics tailored to current research questions in the field of aeronautics. This year’s challenge was about the development of an aerial firefighting system of systems including vehicle and fleet design with a strong emphasize on operationally-driven design aspects. This paper proposes a design for a next generation vertical take-off and landing firefighting aircraft with an expected entry into service in 2030, that is working intelligently and interconnected in a group of four. The design won the DLR Design Challenge 2022 and the underlying work covers the preliminary design including the structural concept, aerodynamic simulations, weight and balance calculations and the concept for water intake and deployment. The designed aircraft is characterized by a considerable high payload ratio that features vertical take-off and landing capabilities while showing efficient horizontal flight properties with a very competitive cost basis. The 24-hr operability during various weather conditions and challenging fire scenarios is ensured using a wide variety of sensors and a modern glass-cockpit combining pilot comfort with indispensable safety aspects. Due to its modular design, every aircraft can be comfortably converted to a passenger or freight version during firefighting off-season or for cargo and crew supply during the missions

Accelerating the path towards carbon-free aviation

This paper, created by a group of aviation and energy experts from renowned universities and research centres in Europe, who oversee the fields of energy carriers, energy storage and conversion, propulsion, aerodynamics, flight mechanics, controls, structures, materials, multidisciplinary design, and life‐cycle engineering, aims to give an overview and assessment of promising future technologies. The paper therefore identifies the potential as well as research demands of these technologies on the path to a sustainable and more environmentally friendly aviation

Special Issue “11th EASN International Conference on Innovation in Aviation & Space to the Satisfaction of the European Citizens”

This Special Issue contains selected papers from works presented at the 11th EASN International Conference on “Innovation in Aviation & Space to the Satisfaction of the European Citizens” (http://easnconference [...

Special issue “10th easn international conference on innovation in aviation & space to the satisfaction of the european citizens”

This Special Issue contains selected papers from works presented at the 10th EASN International Conference on Innovation in Aviation & Space to the Satisfaction of the European Citizens, which was held successfully from the 2nd until the 4th of September, 2020. Due to the COVID pandemic, it was the first time in the history of the EASN Conference series that the event took place in a virtual format. The event included 9 keynote lectures and more than 320 technical presentations distributed in close to 50 sessions. Important also to underline that 48 HORIZON2020 projects have disseminated their latest research results as well as the future trends on the respective technological field at this event. In total, the 10th EASN International Conference was attended by more than 350 participants from 37 countries worldwi

Special Issue “11th EASN International Conference on Innovation in Aviation & Space to the Satisfaction of the European Citizens”

This Special Issue contains selected papers from works presented at the 11th EASN International Conference on “Innovation in Aviation & Space to the Satisfaction of the European Citizens” (http://easnconference [...

UAS as flexible and innovative test platform for aircraft configuration and systems testing

Today new technologies are available, which can be decisive for the success of future aircraft design. However, the gap between conventional designs and new visions often comes with a high financial risk. This complicates the integration of innovations significantly. The “Flightpath 2050 Europe’s Vision for Aviation” asks for new aircraft concepts and configurations to meet future requirements such as emission (CO2, NOx), noise and fuel consumption reduction. Scaled UAS are one way for getting new configurations and technologies into flight test while reducing the risk of exploding costs. UAS are cost-efficient test platform systems for two main tasks of future aircraft tests: Testing new configurations and advancing new aircraft systems and technologies from upstream research to TRL5-6. UAS can represent a connection between innovative research and flight demonstration. This paper focuses on the UAS as an innovative test platform and a tool for feasibility demonstration as well as its impact on new technologies and the implementation of innovative concepts. An example of a UAS test platform is given in the paper based on a 33,3% scale model of the e-Genius. It is developed as flying wind tunnel in order to better understand the effects of configuration changes on flight performance