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

The Impact of Multiple Runway Aiming Points on Runway Capacity - Technical Capacity of a Single Runway

Environmental aspects of air transport are constraining factors for the present and future air transportation system. On the local scale, especially aircraft noise impacts the potential of traffic growth negatively. In order to reduce noise impact of aircraft operations around airports there are several technological and operational approaches. A promising measure to reduce aircraft noise is the adaption of approach procedures. A variety of concepts exist that aim at the adaption of the final approach trajectory, including the concept of multiple runway aiming points in which landing trajectories are optimized with respect to individual aircraft states and environmental conditions. By shifting the individual approach path, the noise carpet generated by the aircraft is shifted as close as possible to the airport0s center. In this paper, an approach to assess the impact of multiple runway aiming points resulting from optimized aircraft landing trajectories on the technical capacity of a runway system is investigated. Therefore equations that allow for the calculation of separation times between the possible aircraft pairings as well as a simulation environment to determine technical hourly capacity of a single-runway system are introduced. For the presentation of the results, different scenarios to assess the impact of the concept of multiple runway aiming points on arrival capacity and on the capacity curve of a single-runway system are investigate

Cabin Design for Minimum Boarding Time

Single and twin aisle cabin layouts of various capacities are compared regarding their boarding and debaording time. Basis is a boarding simulation and detailed cabin layout

Enhanced Assessment of the Air Transportation System

A framework has been developed to conduct sustainability studies of ATS and its sub elements separately. The framework shows the combination of Life Cycle Assessment (LCA), Life Cycle Cost Assessment (LCC) and Social Life Cycle Assessment (SLCA). The final results of the inventory analysis will be aggregated in a single value, expressed as Socio-Eco-Efficiency Index (SEEindex). This paper does not present the inventory calculations itself, but contains a proposed description of synthesis of the inventory results using Multiple Criteria Decision Aid (MCDA) methods

Zur Reduktion von Kraftstoffverbrauch und Emissionen an Verkehrsflughäfen

Die Forschungsarbeit stellt die Potentiale verschiedener technologischer Ansätze zur Reduktion des Kraftstoffverbrauchs und der Emissionen im Start- und Landezyklus an Verkehrsflughäfen auf Lufttransportsystemebene gegenüber. Die, für eine prospektive, globale Betrachtung notwendigen Faktoren sowie etwaige Interdependenzen werden innerhalb des hierfür entwickelten Modells berücksichtigt. Zu diesen Faktoren gehören u.a. die Entwicklung des Luftverkehrsaufkommens und der Flottenzusammensetzung, Flughafenkapazitäten sowie Prozesszeiten im Start- und Landezyklus. Unter Betrachtung verschiedener Szenarien werden Reduktionspotential ausgewählter Technologien quantifiziert und erfolgsversprechende Technologiekombinationen abgeleitet

A Forecast Model to determine the Potential for Fuel savings through Electric Taxiing at Airports

This study investigates the potential benefit achieved in terms of fuel savings through Electric Taxiing. It focusses on the airport, namely on the taxi processes, i.e. the time the aircraft is moving from the runway to the parking position (taxi-in) and from the parking position to the departure runway (taxi-out). By making use of technologies that enable Electric Taxiing, the aircraft is moved by an electric motor which is installed in the hub of the nose wheel or alternatively in the main landing gear bogies. To forecast the potential for fuel savings, models for air traffic growth, aircraft ground fuel consumption and the development of taxi times at specific airports are applied. The introduction of new aircraft types is also simulated and taken into account. Results are presented for various scenarios, which differ by the assumptions on future market penetration of electric taxiing technology

Modelling and Simulation of Vehicle Movements using a SPPTW-Algorithm and the Application to Airport Surface Movements Analysis

For the optimization of aircraft ground movements a method is described herein based on means of modelling and simulation. The paths of the vehicles are described as a network. Based on graph theory, an algorithm is developed that attempts to find the least time consuming, conflict-free path. The algorithm presented is based on one designed for Automated Guided Vehicles, which was adapted for an Advanced Surface Movement Guidance and Control System at airports. It is derived from a Dijkstra algorithm which calculates the shortest possible path between two nodes in a given network. Due to the fact that the time dependency of the planned paths are taken into account, approaches like this are called Shortest Path Planning with Time Windows (SPPTW), meaning that the path is segmented into parts of fixed duration. In case of a conflict, the vehicle is delayed in a preceding path segment or rerouted. The calculation of the paths for the different vehicles is initiated by a request, including the nodes at the start and at the end as well as the time at entry. The results of the simulations are used to estimate the performance of an airport airside system, with particular focus on the taxiway system