Component-led integrative optimisation methodology for avionic thermal management

The modern military aircraft can be defined as a System of Systems (SoS); several distinct systems operating simultaneously across boundary interfaces. As the on-board subsystems have become more complex and diverse, the development process has become more isolated. When considering thermal management of distributed heat loads, the aircraft has become a collection of individually optimised components and subsystems, rather than the implementation of a single system to perform a given task. Avionic thermal management is quickly becoming a limiting factor of aircraft performance, reliability and effectiveness. The challenge of avionic thermal management is growing with the increasing complexity and power density of avionic packages. The aircraft relies on a heat rejection growth capacity to accommodate the additional through-life avionic heat loads. Growth capacity is defined as an allowable thermal loading growth designed into the system by the underutilisation of spatial and cooling supply at aircraft introduction; however, this is a limited resource and aircraft subsystem cooling capability is reaching a critical point. The depleted growth capacity coupled with increased avionic power demands has led to component thermal failure. However, due to the poor resolution of existing data acquisition, experimental facilities or thermodynamic modeling, the exact inflight-operating conditions remain relatively unknown. The knowledge gap identified in this work is the lack of definitive methodology to generate high fidelity data of in-flight thermal conditions of fast-jet subsystems and provide evidence towards effective future thermal management technologies. It is shown that, through the development of a new methodology, the knowledge gap can be reduced and as an output of this approach the unknown system behaviour can be defined. A multidisciplinary approach to the replication, analysis and optimisation of a fast-jet TMS is detailed. The development of a new Ground Test Facility (GTF) allows previously unidentified system thermal behaviour to be evaluated at component, subsystem and system level. The development of new data to characterise current thermal performance of a fast jet TMS allows recommendations of several new technologies to be implemented through a component led integrative system optimisation. This approach is to consider the TMS as a single system to achieve a single goal of component thermal management. Three technologies are implemented to optimise avionic conditions through the minimisation of bleed air consumption, improve avionic reliability through increased avionic component isothermalisation and increase growth capacity through improved avionic heat exchanger fin utilisation. These component level technologies improved system level performance. A reduction in TMS bleed air consumption from 1225kg to 510kg was found to complete a typical flight profile. A peak predicted aircraft specific fuel consumption saving of 1.23% is seen at a cruise flight condition because of this approach to avionic thermal management

Sensitivity Analysis of a Neural Network based Avionic System by Simulated Fault and Noise Injection

The application of virtual sensor is widely discussed in literature as a cost effective solution compared to classical physical architectures. RAMS (Reliability, Availability, Maintainability and Safety) performance of the entire avionic system seem to be greatly improved using analytical redundancy. However, commercial applications are still uncommon. A complete analysis of the behavior of these models must be conducted before implementing them as an effective alternative for aircraft sensors. In this paper, a virtual sensor based on neural network called Smart-ADAHRS (Smart Air Data, Attitude and Heading Reference System) is analyzed through simulation. The model simulates realistic input signals of typical inertial and air data MEMS (Micro Electro-Mechanical Systems) sensors. A procedure to define the background noise model is applied and two different cases are shown. The first considers only the sensor noise whereas the latter uses the same procedure with the operative flight noise. Flight tests have been conducted to measure the disturbances on the inertial and air data sensors. Comparison of the Power Spectral Density function is carried out between operative and background noise. A model for GNSS (Global Navigation Satellite System) receiver, complete with constellation simulator and atmospheric delay evaluation, is also implemented. Eventually, a simple multi-sensor data fusion technique is modeled. Results show good robustness of the Smart-ADAHRS to the sensor faults and a marginal sensitivity to the temperature-related faults. Solution for this kind of degradation is indicated at the end of the paper. Influences of noise on input signals is also discussed

Aeronautical engineering: A continuing bibliography with indexes (supplement 267)

This bibliography lists 661 reports, articles, and other documents introduced into the NASA scientific and technical information system in June, 1991. Subject coverage includes design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; theoretical and applied aspects of aerodynamics and general fluid dynamics; electrical engineering; aircraft control; remote sensing; computer sciences; nuclear physics; and social sciences

Preparation of Loads and Aeroelastic Analyses of a High Altitude, Long Endurance, Solar Electric Aircraft

High altitude, long endurance aircraft can serve as platform for scientists to make observations of the earth over a long period of time. Staying airborne only by solar electric energy is, as of today, a challenge for the aircraft design and requires an extremely light weight structure at the edge of the physically possible. This paper focuses on the loads and aeroelastic aspects of such a configuration, discusses the selected strategies and presents the applied methods and tools, including the resulting models prepared for the HAPomega configuration currently under development at the DLR. Because of the structural flexibility and the slow speed of the aircraft, flight mechanical and flight control aspects interact with aeroelastics e.g. during a gust encounter, making a non-linear time domain simulation necessary. Both maneuver and gust loads are used for the structural sizing and result in a very light and slender airframe with very low eigenfrequencies

Aeronautical Engineering: A continuing bibliography (supplement 138)

This bibliography lists 366 reports, articles, and other documents introduced into the NASA scientific and technical information system in July 1981

Aeronautical engineering: A continuing bibliography with indexes, supplement 103, December 1978

This bibliography lists 457 reports, articles, and other documents introduced into the NASA scientific and technical information system in November 1978

Cost Analysis of eVTOL Configuration Design for an Air Ambulances System in Japan

Electric-vertical-takeoff-and-landing (eVTOL) aircraft, known as urban air mobility or flying cars, are being considered for widespread use as air taxis, emergency medical transportation, sightseeing vehicles, and rural transportation, owing to their reduced-size, low-cost, and low-noise characteristics. In this study, we conduct an interview at a Japanese hospital that currently uses a helicopter for medical emergencies to output the mission profile. Due to current battery-technology limitations, the new air ambulance, which will deliver a doctor to a patient, is conceived as having 2 passengers, including the pilot. Two eVTOL configurations are studied: a fixed-wing craft and a multi-rotor. The purpose of this study is to develop a cost model for a new air ambulance through a combination of 3 approaches: top-down, bottom-up, and parametric. The cost model is constructed to analyze the production cost of each configuration, broken down into the capital expense and direct operating cost. The result shows that the multi-rotor’s production cost is lower than the fixed-wing craft. The direct operating cost of a fixed-wing craft at high flight hours is higher than that of the multi-rotor. Scenario analysis shows a result that the capacity difference of a battery has a significant difference in the cost in the years 2020 and 2030 due to the high cost of battery replacement

Effect of Progressive Integration of On-Board Systems Design Discipline in an MDA Framework for Aircraft Design with Different Level of Systems Electrification

The on-board design discipline is sometimes ignored during the first aircraft design iterations. It might be understandable when a single on-board system architecture is considered, especially when a conventional architecture is selected. However, seeing the trend towards systems electrification, multiple architectures can be defined and each one should be evaluated during the first tradeoff studies. In this way, the systems design discipline should be integrated from the first design iterations. This paper deals with a progressive integration of the discipline to examine the partial or total effect of the systems design inside an MDA workflow. The study is carried out from a systems design perspective, analyzing the effect of electrification on aircraft design, with different MDA workflow arrangements. Starting from a non-iterative systems design, other disciplines such as aircraft performance, engine design, and aircraft synthesis are gradually added, increasing the sensibility of the aircraft design to the different systems architectures. The results show an error of 40% in on-board systems assessment when the discipline is not fully integrated. Finally, using the work-flow which allows for greater integration, interesting differences can be noted when comparing systems with different levels of electrification. A possible mass saving of 2.6% of aircraft MTOM can be reached by properly selecting the systems technologies used

Air Force Institute of Technology School of Engineering. Contributions to Air Force Research and Development, Calendar Year 1977

This report contains abstracts of Master of Science Theses, Doctoral dissertations, and selected faculty publications completed during the 1977 calendar year at the School of Engineering, Air Force Institute of Technology, at Wright-Patterson Air Force Base, Ohio

TRANSIENT THERMAL PERFORMANCE ENHANCEMENT OF PHASE CHANGE MATERIALS THROUGH NOVEL PIN ARRANGEMENTS UNDER VARIED GRAVITY CONDITIONS

This thesis presents a comprehensive examination of encapsulation techniques and performance enhancement strategies for Phase Change Materials (PCMs) in the thermal management of spacecraft avionics. This research contributes to optimizing PCM applications in spacecraft through historical analysis, transient thermal performance enhancement, and computational studies. The first chapter explains the significance of PCMs in passive thermal management since the beginning of space-age technology, it underlines the low thermal conductivity of PCMs and the necessity of incorporating materials with high thermal conductivity, such as metal foams, to improve heat transfer. It also discusses various advancements in PCM research for spacecraft thermal management applications like the shape-stabilized PCMs and also explains in details various encapsulations techniques for PCMs. This chapter also reflect upon the various efforts done by space agencies (NASA, ESA and ISRO) towards understanding the feasibility of phase change materials for spacecraft thermal management applications. It also examines the effect of various parameters such as direction of heat flow and orientation of PCM to obtain tailored heat transfer research which can be leveraged by phase change materials for effective thermal management of spacecraft avionics. The subsequent chapter examines the transient thermal performance of a particular PCM, RT82, using novel pin arrangements. Through the strategic placement of fins, thermal conductivity and heat transfer surface area are enhanced. This study investigates numerically the melting characteristics under microgravity, terrestrial gravity, and hypergravity. This study focuses on the improvement in thermal performance brought about by fin integration under differing gravitational conditions. The final chapter explores computational studies concentrating on the geometrical optimization of PCM encapsulation in Triplex Tube Heat Exchangers (TTHX) utilizing novel annular-fin configurations. This research examines the impact of fin shape, size, and positioning on the thermal characteristics of PCM. It identifies encapsulation geometries that facilitate vortex-like melting patterns, thereby accelerating PCM melting rates. In addition, it evaluates the heat transfer performance of these configurations under varying gravity conditions, elucidating the physics underlying the enhancement of melting performance. In conclusion, this thesis demonstrates that judicious encapsulation techniques and geometric optimisation significantly enhance the thermal management effectiveness of PCMs in spacecraft. This research paves the way for innovation in spacecraft thermal management systems employing PCMs by interweaving historical context with performance enhancement strategies and computational insights