On the Design of Functionally Integrated Aero-engine Structures: Modeling and Evaluation Methods for Architecture and Complexity

The drive for airplanes with radically reduced fuel consumption and emissions motivates engine manufacturers to explore innovative engine designs. The novelty of such engines results in changed operating conditions, such as newly introduced constraints, increased loads or rearranged interfaces. To be competitive, component developers and manufacturers must understand and predict the consequences of such changes on their sub-systems. Presently, such assessments are based on detailed geometrical models (CAD or finite element) and consume significant amounts of time. The preparation of such models is resource intensive unless parametrization is employed. Even with parametrization, alternative geometrical layouts for designs are difficult to achieve. In contrast to geometrical model-based estimations, a component architecture representation and evaluation scheme can quickly identify the functional implications for a system-level change and likely consequences on the component. The schemes can, in turn, point to the type and location of needed evaluations with detailed geometry. This will benefit the development of new engine designs and facilitate improvements upon existing designs. The availability of architecture representation schemes for functionally integrated (all functions being satisfied by one monolithic structure) aero-engine structural components is limited. The research in this thesis focuses on supporting the design of aero-engine structural components by representing their architecture as well as by developing means for the quantitative evaluation and comparison of different component designs. The research has been conducted in collaboration with GKN Aerospace Sweden AB, and the components are aero-engine structures developed and manufactured at GKN. Architectural information is generated and described based on concepts from set theory, graph theory and enhanced function–means trees. In addition, the complexities of the components are evaluated using a new complexity metric. Specifically, the developed modeling and evaluation methods facilitate the following activities: \ub7\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0 identification and representation of function–means information for the component\ub7\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0 representation and evaluation of component architecture\ub7\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0 product complexity evaluation\ub7\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0 early selection of load path architecture\ub7\ua0\ua0\ua0\ua0\ua0\ua0\ua0\ua0 impact assessment for the component’s functioning in the systemBy means of the methods developed in this thesis, the design rationale for a component is made explicit, and the storing, communicating and retrieving of information about the component in the future is enabled. Through their application to real-life engine structures, the usability of the methods in identifying early load carrying configurations and selecting a manufacturing segmenting option is demonstrated. Together, the methods provide development engineers the ability to compare alternative architectures. Further research could focus on exploring the system (engine) effects of changes in component architecture and improvements to the complexity metric by incorporating manufacturing information

N+3 Small Commercial Efficient and Quiet Transportation for Year 2030-2035

This study develops a future scenario that enables convenient point-to-point commercial air travel via a large network of community airports and a new class of small airliners. A network demand and capacity study identifies current and future air travel demands and the capacity of this new network to satisfy these demands. A current technology small commercial airliner is defined to meet the needs of the new network, as a baseline for evaluating the improvement brought about by advanced technologies. Impact of this new mode of travel on the infrastructure and surrounding communities of the small airports in this new N+3 network are also evaluated. Year 2030-2035 small commercial airliner technologies are identified and a trade study conducted to evaluate and select those with the greatest potential for enhancing future air travel and the study metrics. The selected advanced air vehicle concept is assessed against the baseline aircraft, and an advanced, but conventional aircraft, and the study metrics. The key technologies of the selected advanced air vehicle are identified, their impact quantified, and risk assessments and roadmaps defined

Electronic/electric technology benefits study

The benefits and payoffs of advanced electronic/electric technologies were investigated for three types of aircraft. The technologies, evaluated in each of the three airplanes, included advanced flight controls, advanced secondary power, advanced avionic complements, new cockpit displays, and advanced air traffic control techniques. For the advanced flight controls, the near term considered relaxed static stability (RSS) with mechanical backup. The far term considered an advanced fly by wire system for a longitudinally unstable airplane. In the case of the secondary power systems, trades were made in two steps: in the near term, engine bleed was eliminated; in the far term bleed air, air plus hydraulics were eliminated. Using three commercial aircraft, in the 150, 350, and 700 passenger range, the technology value and pay-offs were quantified, with emphasis on the fiscal benefits. Weight reductions deriving from fuel saving and other system improvements were identified and the weight savings were cycled for their impact on TOGW (takeoff gross weight) and upon the performance of the airframes/engines. Maintenance, reliability, and logistic support were the other criteria

Inductive interconnecting solutions for airworthiness standards and power-quality requirements compliance for more-electric aircraft/engine power networks

Driven by efficiency benefits, performance optimization and reduced fuel-burn, the aviation industry has witnessed a technological shift towards the broader electrification of on-board systems, known as the More-Electric Aircraft (MEA) concept. Electrical systems are now responsible for functions that previously required mechanical, hydraulic or pneumatic power sources, with a subset of these functions being critical or essential to the continuity and safety of the flight.;This trend of incremental electrification has brought along benefits such as reductions in weight and volume, performance optimization and reduced life-cycle costs for the aircraft operator. It has however also increased the necessary engine power offtake and has made the electrical networks of modern MEA larger and more complex. In pursuit of new, more efficient electrical architectures, paralleled or interconnected generation is thought to be one platform towards improved performance and fuel savings.;However, the paralleling of multiple generation sources across the aircraft can breach current design and certification rules under fault conditions. This thesis proposes and evaluates candidate interconnecting solutions to minimize the propagation of transients across the interconnected network and demonstrates their effectiveness with reference to current airworthiness standards and MIL-STD-704F power quality requirements.;It demonstrates that inductive interconnections may achieve compliance with these requirements and quantifies the estimated mass penalty incurred on the electrical architecture, highlighting how architectural and operating strategies can influence design options at a systems level. By examining the impact of protection operation speed on the electrical network, it determines that fast fault protection is a key enabling technology towards implementing lightweight and compliant interconnected architectures.;Lastly, this thesis addresses potential implications arising from alternate standards interpretations within the framework of interconnected networks and demonstrates the impact of regulatory changes on the electrical architecture and interconnecting solutions.Driven by efficiency benefits, performance optimization and reduced fuel-burn, the aviation industry has witnessed a technological shift towards the broader electrification of on-board systems, known as the More-Electric Aircraft (MEA) concept. Electrical systems are now responsible for functions that previously required mechanical, hydraulic or pneumatic power sources, with a subset of these functions being critical or essential to the continuity and safety of the flight.;This trend of incremental electrification has brought along benefits such as reductions in weight and volume, performance optimization and reduced life-cycle costs for the aircraft operator. It has however also increased the necessary engine power offtake and has made the electrical networks of modern MEA larger and more complex. In pursuit of new, more efficient electrical architectures, paralleled or interconnected generation is thought to be one platform towards improved performance and fuel savings.;However, the paralleling of multiple generation sources across the aircraft can breach current design and certification rules under fault conditions. This thesis proposes and evaluates candidate interconnecting solutions to minimize the propagation of transients across the interconnected network and demonstrates their effectiveness with reference to current airworthiness standards and MIL-STD-704F power quality requirements.;It demonstrates that inductive interconnections may achieve compliance with these requirements and quantifies the estimated mass penalty incurred on the electrical architecture, highlighting how architectural and operating strategies can influence design options at a systems level. By examining the impact of protection operation speed on the electrical network, it determines that fast fault protection is a key enabling technology towards implementing lightweight and compliant interconnected architectures.;Lastly, this thesis addresses potential implications arising from alternate standards interpretations within the framework of interconnected networks and demonstrates the impact of regulatory changes on the electrical architecture and interconnecting solutions

Aeronautical engineering: A continuing bibliography with indexes (supplement 245)

This bibliography lists 537 reports, articles, and other documents introduced into the NASA scientific and technical information system in October, 1989. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

The Potential of Liquid Hydrogen for long range aircraft propulsion

The growth of aviation needed to cater for the needs of society might be undermined by restrictions resulting from the environmental implications of air traffic. Hydrogen could provide an excellent alternative to ensure a sustainable future for aviation. Several challenges remain to be addressed though before its adoption can become reality. The liquid hydrogen tanks are one of the areas where considerable research is needed. Further insight into unusual restrictions on aircraft classes that would be thought of as ideal candidates for hydrogen is also required. Hydrogen fueled very large long range transport aircraft for instance suffer from the 80 m airport box constraint which leads to a strong decrease in performance compared to other aircraft classes. In this work 3 main tools are developed to look into some of these issues. An aircraft conceptual design tool has been set up to allow a comparison between kerosene and hydrogen on a common and hence fair basis. An engine performance assessment routine is also developed to allow the coupling of the design of engine and aircraft as one integrated system. As the link between both subsystems is the liquid hydrogen tank, a detailed design method for the tanks has also been created. With these tools it has been shown that the gravimetric efficiency for large transport aircraft varies by only a few percent for a wide range of fuel masses and aircraft diameters with values in the order of 76to 80%. The performance of the long range transport aircraft itself however varies strongly from one class to another. For aircraft with a passenger load around 400 passengers, takeoff weight reductions around 25% can be obtained for similar operating empty weights and fuel weights of about 30% of the equivalent kerosene fuel weight. For 550 passenger aircraft however, the takeoff weight reduction reduces strongly due to the need for a triple deck fuselage and the resulting increase in fuselage mass. Whereas for the first category of aircraft, a 3 to 6 times higher fuel price per energy content can be afforded for similar direct operating costs, this cost advantage is reduced by about a third for the 550 passenger aircraft. A twin fuselage configuration alleviates the geometrical restrictions and restores the potential for an aircraft family but does not yield strong weight reductions. In a subsequent study, the implications of unconventional engine cycles as well as drag reduction resulting from natural laminar flow through surface cooling should be assessed using the developed set of tools as this will reveal the full potential of hydrogen as an aviation fuel

Crew interface definition study, phase 1

The timeline analysis of the Shuttle orbiter missions which was conducted in the Phase I Crew Interface Definition Study and the requirements for the man-in-the-loop simulation study are presented. Mission definitions and objectives are presented as they relate to various Shuttle Orbiter missions. The requirements for crew participation and the information required by the crew are discussed, and finally the rationale behind the display concept and calling procedures is given. The simulation objectives, the simulation mechanization, including a detailed presentation of the display and control concept, the simulator test plan and the results are discussed

The effects of atmospheric turbulence on fuel consumption in extended formation flight

Includes bibliographical references.Extended formation flight (streamwise separations of between 10 to 40 spans), has been recently proposed as a method for reducing the induced drag of commercial aircraft. However, induced drag savings are not necessarily directly indicative of fuel savings. In a realistic environment, atmospheric turbulence will continuously perturb the formation’s aircraft and their wakes. As a result, each aircraft in the formation will experience fluctuations in aerodynamic loads. For an aircraft to maintain accurately its position within a formation, it must continually adjust its throttle setting. This dynamic throttling may result in inefficient engine operation, thereby detracting from the reductions in induced drag. In this work, a high-fidelity transient engine model, representative of a typical commercial high-bypass turbofan engine, has been incorporated within a simple twin-aircraft formation flight simulator. The aerodynamic interactions between aircraft were modelled using a horseshoe vortex method, specially adapted for extended formations. The aircraft were constrained to longitudinal motion, with altitude fixed. This created a two degree of freedom formation model that is analogous to wind tunnel experimentation. A simple proportional gain controller was used to manipulate the throttle settings, in an attempt to maintain the trail aircraft’s position relative to the leader, in a turbulent atmosphere. It was found that a fuel saving of approximately 25 may be achieved at a practical lateral separation of 1 span, corresponding to a stream-wise separation of 20 ± 0.3 spans, in moderate turbulence levels

Aeronautical Engineering: A continuing bibliography with indexes (supplement 206)

This bibliography lists 422 reports, articles and other documents introduced into the NASA scientific and technical information system in October 1986

Aeronautical engineering: A continuing bibliography with indexes (supplement 289)

This bibliography lists 792 reports, articles, and other documents introduced into the NASA scientific and technical information system in Mar. 1993. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics