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Technical Paper

Towards More-Efficient Aircraft Hydraulic Systems: Conceptual Design of a Variable-Speed Fixed-Displacement Electric Motor Pump

This paper describes the conceptual design of a variable-speed fixed-displacement electric motor pump for aircraft hydraulic systems. In contrast to today's approaches, the pump controls the constant system pressure by adapting the motor speed rather than the pump displacement or both. This concept might increase the pump's part load efficiency significantly. The paper starts with introducing and analyzing the dynamic requirements of aircraft hydraulic pumps and evaluating different pump concepts. The concept of an internal gear pump driven by a permanent magnet synchronous motor is selected. For this concept an experimental prototype is developed. The electric motor pump is modeled and a pressure controller is designed. The prototype is set up and tested on an experimental test bench regarding dynamics, efficiencies and noise emissions. The overall concept is evaluated regarding secondary power demand, system heat load, wear, reliability, noise, and mass.
Technical Paper

From Airframer Requirements to Detailed Technical Specification of Electromechanical Actuators Aided by Knowledge-Based Methods

Recent trends towards lighter and more efficient commercial aircraft have motivated airframers to consider the use of electromechanical actuators EMA as the primary means of power for aircraft flight control systems. The transition from state-of-the-art hydraulic actuation to new electromechanical technologies poses a great challenge to both airframers and system suppliers for the correct and complete definition of new requirements. Transient effects such as electric motor overheating and inertial loads, previously not present or irrelevant for hydraulic actuators, now have to be taken into account. A knowledge-based environment containing design drivers for electromechanical components is combined with a validation method in order to aid the systems engineer to accomplish such task. This approach offers the potential to guarantee that all requirements are covered by a new technology, and that they are complete and consistent.
Technical Paper

Optimization of the Power Allocation for Flight Control Systems

Due to a shift of the major aviation concerns to focus on enhancements of the successful programs instead of pushing their successors, the need for new methodologies for aircraft system architecture design emerges. Challenging the existing requirements and reconsidering the functions and their allocation could help to dissolve the system specific development paradigm and lead to beneficial architecture concepts. To help understand the mechanisms and boundary conditions of developing fault-tolerant systems, the first part of the paper gives an overview of the successive process of architecture design. The significant architectural design decisions and the concurrent safety assessment process are discussed. One crucial step in the design space exploration of future aircraft system architectures is the allocation of the consumers to the available power sources. Within the paper a methodology for the optimization of the power allocation for flight control systems is proposed.
Technical Paper

Virtual Integration of an All-Electric Flight Control System Architecture and the Aircraft Electrical Power Distribution Network

The aviation industry is facing major challenges due to increased environmental requirements that are driven by economic constraints. For this reason, guidelines like "Flightpath 2050", the official guide of European aviation, call for significant reductions in pollutant emissions. The concept of the More Electric Aircraft offers promising perspectives to meet these demands. A key-enabler for this concept is the integration of new technologies on board of the next generation of civil transportation aircraft. Examples are electro-mechanical actuators for primary and secondary flight controls or the fuel cell technology as innovative electrical energy supply system. Due to the high complexity and interdisciplinarity, the development of such systems is an equally challenging and time-consuming process.
Technical Paper

Architecture and Parameter Optimization for Aircraft Electro-Hydraulic Power Generation and Distribution Systems

The All-Electric-Engine with only electrical power offtake is a main goal in aircraft system development. The use of electric-motor pumps instead of engine-driven pumps for powering the central hydraulic systems could be a part of this objective. Additionally, the concept would meet the incremental development strategy performed by the aerospace industry today and saves costs by using state-of-the-art hydraulic actuation technology. This paper describes a process for optimizing such systems regarding their architecture and design parameters. For this task a methodology for the hydraulic consumer allocation called OPAL is used and extended by an automatic power system sizing. Feasible allocations, called permutations, are determined on the basis of preliminary system safety assessments regarding multiple top failure events. In the next step an automated sizing of the permutations is performed based on simplified hydraulic load analyses.
Technical Paper

Towards Operationally Robust Fuel Cell Systems for Aeronautical Applications

Fuel cell technology will play a decisive role in the process of achieving the ambitious ecological goals of the aviation industry. However, apart from its obvious environmental advantages, the integration of fuel cell technology into commercial aircraft represents a challenging task in terms of operational and economical aspects. Since fuel cell systems are currently exposed to an intense competition with well-established power sources onboard an aircraft, engineers are in pursuit of highly efficient and particularly lightweight fuel cell systems. Supported by model-based design in conjunction with elaborate optimization techniques this pursuit has led to highly specialized systems. These systems tend to use their components to full capacity, which typically implies marginal system robustness. In consequence, preliminary design studies propose fuel cell systems that are sensitive to partial faults, or even to the slightest deviation, or degradation of their components' behavior.
Technical Paper

Function-Driven Design and Evaluation of Innovative Flight Controls and Power System Architectures

For the shift to more-electric aircraft systems, the system specific design paradigm has to be dissolved and the allocation of functions has to be reconsidered. Including more degrees of freedom within the architecture design process for aircraft systems could lead to beneficial architecture concepts. However, new methods for conceptual systems design are required, to cope with the significantly increasing number of potential architecture variations to be evaluated. Within this paper, the GENESYS methodology enabling the design and evaluation of numerous architecture variations will proposed. The methodology consists of several modules, each dedicated to a specific process step of conceptual aircraft system design. Initially, a method for the design-independent analysis of the aircraft level functions and the identification of requirements for the aircraft systems will be illustrated.
Journal Article

Virtual Integration and Testing of Multifunctional Fuel Cell Systems in Commercial Aircraft

This paper focuses on the virtual integration and test approach used for the evaluation of an automation system developed for the multifunctional operation of fuel cells in commercial aircraft. In order to accomplish the virtual integration a model of the overall automation system is linked with a dynamic model of the complete fuel cell system. For this purpose a modeling approach for complex physical systems is described in this paper. During virtual testing various simulation runs are executed based on automatically generated test cases, which cover a complete flight mission. For this reason a flight mission is modeled as a Statechart that includes next to time- based flight phases also potential events and malfunctions (e.g. engine flame-out, cargo fire). An algorithm is described, which can find all possible state combinations including parallel event sequences.