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Item type:Publication, Access status: without files , Thermal management investigations for fuel cell systems on-board commercial aircraftThe integration of fuel cell systems as an independent energy source (Auxiliary Power Unit, APU) requires enhanced aircraft cooling architectures. New environmental control systems and systems with an increased cooling demand are investigated in various research projects. Cooling system architectures can be designed which benefit from similar requirements, e.g. by using the same cooling loops. Additionally, an increased cooling demand makes the investigation of alternative heat sinks necessary. For detailed system investigations simulation studies are used. A model library has been created in Dymola/Modelica containing the necessary component models to simulate cooling systems. The used modeling approaches and main model information are presented in this article. In order to understand the basic system behavior a Design of Experiment (DOE) is useful. If only two or three parameters are considered, simulation studies can be performed for each possible parameter combination. Analyzing more parameters with this method is limited by the computational expense. With Latin hypercube sampling methods or low-discrepancy sequences, sampling plans with reduced sample numbers can be created. Analyzing large simulation models and identifying the most influential parameters is a time consuming work. Sensitivity analyses are used to quantify the parameters influence on key performance indicators like mass and energy consumption. The applied sensitivity analyses are variance-based methods. By using sensitivity indices the influence of the input parameter variance on the output variance can be measured and it can be identified whether parameters are essential or unessential. A significant advantage of this variance-based method is the model-free approach.Publicationtype: Conference Paper224 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , From airframer requirements to detailed technical specification of electromechanical actuators aided by knowledge-based methods(Society of Automotive Engineers, 2013-09-17); ; ; ; 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. In addition, analyzing representative mission profiles and extracting relevant flight data aid in the identification of active design drivers and speeds up requirement definition for the technology under consideration. These concepts are illustrated with a case study of a short-range aircraft's aileron EMA. Methods and tools described herein are being developed within the framework of the European research project Actuation 2015 which aims at the standardization of EMA components for aerospace applications.Publicationtype: Conference Paper58 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Towards more-efficient aircraft hydraulic systems : conceptual design of a variable-speed fixed-displacement electric motor pumpThis 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. The evaluation shows that losses can be decreased by 66% and noise emissions by 30 dBA in comparison to an original aircraft electric motor pump in use today.Publicationtype: Conference Paper62 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Multi-objective design of optimized diagnosis functions for high lift actuation systemsThis paper presents a model-based approach for the multi-objective design of optimized diagnosis functions for high lift actuation systems. These systems are used to augment lift at low speed during takeoff and landing, and are safety critical. This demands requirements to the detection of failures and the isolation of root causes in order to provide a high availability at low risk. Dedicated functions cover the determination of features, the detection of symptoms and the isolation of root causes by means of inference and resolution. The aim of the design approach is to provide these functions in an optimal manner with respect to multiple objectives. In order to be clear and traceable the approach consists of separate consecutive steps. These are arranged by using systems engineering principles. With respect to requirements, models of different levels of detail are developed and used to design stepwise all required functions. This is done by evaluating cause-effect matrices, temporal information about the appearance of effects, and a configuration graph. This contains relationships between sensors and symptoms and provides cost criteria for a final assessment. There, solutions of Pareto optimal diagnosis functions with respect to the design objectives are identified. A radial visualization method is used to display all optimal solutions and assist in the identification of a single solution. This solution has to be detailed in further steps. In summary, a clear support of the design process for diagnosis functions by multi-objective and multi-step optimization with practical application is presented.Publicationtype: Conference Paper63