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Compound uncertainty quantification and aggregation (CUQA) for reliability assessment in industrial maintenance
Get PDFThe mounting increase in the technological complexity of modern engineering systems requires compound uncertainty quantification, from a quantitative and qualitative perspective. This paper presents a Compound Uncertainty Quantification and Aggregation (CUQA) framework to determine compound outputs along with a determination of the greatest uncertainty contribution via global sensitivity analysis. This was validated in two case studies: a bespoke heat exchanger test rig and a simulated turbofan engine. The results demonstrated the effective measurement of compound uncertainty and the individual impact on system reliability. Further work will derive methods to predict uncertainty in-service and the incorporation of the framework with more complex case studies.Machine
Deep-learning methods for non-linear transonic flow-field prediction
Get PDFIt is envisaged that the next generation of ultra-high bypass ratio engines will use compact aero-engine nacelles. The design and optimisation process of these new configurations have been typically driven by numerical simulations, which can have a large computational cost. Few studies have considered the nacelle design process with low order models. Typically these low order methods are based on regression functions to predict the nacelle drag characteristics. However, it is also useful to develop methods for flow-field prediction that can be used at the preliminary design stages. This paper investigates an approach for the rapid assessment of transonic flow-fields based on convolutional neural networks (CNN) for 2D axisymmetric aeroengine nacelles. The process is coupled with a Sobel filter for edge detection to enhance the accuracy in the prediction of the shock wave location. Relative to a baseline CNN built with guidelines from the open literature, the proposed method has a 75% reduction in the mean square error for Mach number prediction. Overall, the presented method enables the fast prediction of the flow characteristics around civil aero-engine nacelles.Rolls-Royce plc2023 AIAA Aviation and Aeronautics Forum and Exposition (AIAA AVIATION Forum
Physical simulation and numerical simulation of flash butt welding for innovative dual phase steel DP590: a comparative study
Get PDFIn this study, the microstructure and performance of newly designed dual-phase steel (DP590) after joining by flash butt welding (FBW) for vehicle wheel rims was analysed and compared by two simulations, i.e., physical simulation and numerical simulation, due to the high acceptance of these two methodologies. Physical simulation is regarded as a thermal–mechanical solution conducted by the Gleeble 3500 simulator and which can distribute the heat-affected zone (HAZ) of the obtained weld joint into four typical HAZs. These are coarse-grained HAZ, fine-grained HAZ, inter-critical HAZ and sub-critical HAZ. A combination of ferrite and tempered martensite leads to the softening behaviour at the sub-critical HAZ of DP590, which is verified to be the weakest area, and influences the final performance due to ~9% reduction of hardness and tensile strength. The numerical simulation, relying on finite element method (FEM) analysis, can distinguish the temperature distribution, which helps us to understand the relationship between the temperature distribution and real microstructure/performance. Based on this study, the combination of physical and numerical simulations can be used to optimise the flash butt welding parameters (flash and butt processes) from the points of temperature distribution (varied areas), microstructure and performance, which are guidelines for the investigation of flash butt welding for innovative materials.Material
Control layer security: a new security paradigm for cooperative autonomous systems
Get PDFAutonomous systems often cooperate to ensure safe navigation. Embedded within the centralised or distributed coordination mechanisms are a set of observations, unobservable states, and control variables. Security of data transfer between autonomous systems is crucial for safety, and both cryptography and physical layer security methods have been used to secure communication surfaces - each with its drawbacks and dependencies. Here, we show for the first time a new wireless Control Layer Security (CLS) mechanism. CLS exploits mutual physical states between cooperative autonomous systems to generate cipher keys. These mutual states are chosen to be observable to legitimate users and not sufficient to eavesdroppers, thereby enhancing the resulting secure capacity. The CLS cipher keys can encrypt data without key exchange or a common key pool, and offers very low information leakage. As such the security of digital data channels is now dependent on physical state estimation rather than wireless channel estimation. This protects the estimation process from wireless jamming and channel entropy dependency. We review for first time what kind of signal processing techniques are used for hidden state estimation and key generation, and the performance of CLS in different case studies.Engineering and Physical Sciences Research Council (EPSRC): EP/V026763/1IEEE Vehicular Technology Magazin
Influence of abiotic factors on kinetics of viable populations of biocontrol agents in the phyllosphere of lettuce and strawberry leaves
Get PDFThere is little information on the effect of temperature, relative humidity (RH) and vapour pressure deficit (VPD) on the viable populations of two commercial biocontrol strains, Bacillus subtilis QST 713 (recently classified as B. velezensis) and Gliocladium catenulatum J1446 (syn. Clonostachys rosea). The PMAxx-qPCR molecular assay was used to quantify the viable biocontrol agent (BCA) populations on fully extended lettuce and strawberry leaves under a range of temperature and RH combinations. Overall, there was a small decline in the population size of viable cells for the two biocontrol organisms on strawberry and lettuce leaves within 10 days of application. However, for most experimental runs, which contained general UK agronomy climates, such a decline was not statistically significant. Moreover, for a few runs, the viable populations increased significantly in optimal BCA growth temperatures with high RH. Only temperature (ambient) and dew point significantly affected the rate of temporal changes in the viable biocontrol population size. Thus, an increasing temperature led to decreased daily mortality. It should be noted that much of the variability in the estimated daily mortality rates remains unaccounted for, thus unless under extreme conditions, the biocontrol efficacy in practice is less likely to be affected by the survival of biocontrol microbes but more likely by other factors that influence the density of biocontrol cells in the phyllosphere, especially dilution due to rapid host leaf expansion, spray coverage and rain wash-off.Plant Patholog
A review of aircraft environmental control system simulation and diagnostics
Get PDFThe aircraft Environmental Control System (ECS) enables the aircraft to maintain a comfortable and safe environment for its passengers throughout its operating envelope. The Pressurised Air Conditioner (PACK) is the heart of the ECS, and is composed of multiple sub-systems: heat exchangers, valves, compressor, turbine, and a water separator. The PACK’s principle function is to enable conditioning of the hot, high pressure bleed air from the engine or APU, for temperature, pressure and humidity against the cabin requirements. The operation of the PACK is governed by a control system which has the ability to mask degradation in its component during operation until severe degradation or failure results. The required maintenance is then both costly and disruptive. The PACK has been reported as major driver of unscheduled maintenance by the operators. The aviation industry is currently proactively exploring innovative health management solutions that aid the maintenance of aircraft key systems based on predictive based maintenance approaches using online condition monitoring techniques. This paper presents a comprehensive review of the simulation and diagnostic methodologies applicable to fault diagnostics of the ECS PACK. The existing literature suggests that model-based and data-driven methods are effective for conducting fault detection and isolation of the PACK system. The conceived findings indicate that the model-based diagnostic approach have been extensively employed to conduct PACK diagnostics at component level only. Their successful implementation requires robust experimental verification and validation against the actual data under healthy and faulty conditions. Although a substantial amount of work has been reported on developing first principles based simulation models and diagnostic strategies for the ECS, the acquired findings suggest that there is a compelling need for a verified and validated ECS simulation model to enable accurate PACK system-level diagnostics based on single and multiple component level degradation scenarios. It has also been identified that the existing literature lacks the evaluation of humidity regulation and the effect of the control system on the PACK performance characteristics. Finally, a taxonomy of diagnostic techniques and simulation models is compiled based on the available literature.Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineerin
How wavelength affects hydrodynamic performance of two accelerating mirror-symmetric undulating hydrofoils
Get PDFFish schools are capable of simultaneous linear acceleration. To reveal the underlying hydrodynamic mechanism, we numerically investigate how Reynolds number Re ¼ 1000–2000, Strouhal number St ¼ 0:2–0:7, and wavelength k ¼ 0:5–2 affect the mean net thrust and net propulsive efficiency of two side-by-side hydrofoils undulating in anti-phase. In total, 550 cases are simulated using immersed boundary method. The thrust increases significantly with the wavelength and the Strouhal number, yet only slightly with the Reynolds number. We apply a symbolic regression algorithm to formulate this relationship. Furthermore, we find that mirror-symmetric schooling can achieve a net thrust more than ten times that of a single swimmer, especially at low Reynolds numbers. The highest efficiency is obtained at St ¼ 0:5 and k ¼ 1:2, where St is consistent with that observed in the linear-accelerating natural swimmers, e.g., Crevalle jack. Six distinct flow structures are identified. The highest thrust corresponds to an asymmetric flow pattern, whereas the highest efficiency occurs when the flow is symmetric with converging vortex streets.Physics of Fluid
Applying System-Theoretic Process Analysis (STPA)-based methodology supported by Systems Engineering models to a UK rail project
Get PDFSystems safety in railways focuses on providing the necessary assurance that the railway system is operationally safe and meets all relevant regulatory requirements. Safety risks associated with changes in the UK railway are controlled through the Common Safety Method for Risk Evaluation and Assessment (CSM-RA). As part of the CSM-RA framework, various safety analysis methods such as Failure Modes and Effects Criticality Analysis (FMECA), Fault Tree Analysis (FTA), Event Tree Analysis (ETA) and other traditional analysis methods conducted via expert brainstorming such as Hazard Identification (HAZID) workshops have been relied upon for many years in the UK rail industry; aiming to evaluate and mitigate all reasonably foreseeable hazards. This paper reports a comparison case study of the application of a novel System-Theoretic Process Analysis (STPA)-based methodology against the traditional approach for hazard analysis in UK rail projects. The proposed methodology uses Systems Engineering (SE) models in each of its steps. The application of the novel methodology demonstrates that it is suitable for hazard identification and analysis in complex rail systems. It shows that the approach goes beyond the capabilities of traditional methods, provides insights into the interaction among system components and captures hazards within the context of the whole. The SE models used in this study prove to be valuable not only for illustrating the System of Interest (SOI) visually, but also providing a high-level understanding of the system and a more detailed understanding of component interactions. They also improved the focus, in scope, effectiveness, and efficiency of the analysis.Safety Scienc
The development of an advanced air mobility flight testing and simulation infrastructure
Get PDFThe emerging field of Advanced Air Mobility (AAM) holds great promise for revolutionizing transportation by enabling the efficient, safe, and sustainable movement of people and goods in urban and regional environments. AAM encompasses a wide range of electric vertical take-off and landing (eVTOL) aircraft and infrastructure that support their operations. In this work, we first present a new airspace structure by considering different layers for standard-performing vehicles (SPVs) and high-performing vehicles (HPVs), new AAM services for accommodating such a structure, and a holistic contingency management concept for a safe and efficient traffic environment. We then identify the requirements and development process of a testing and simulation infrastructure for AAM demonstrations, which specifically aim to explore the decentralized architecture of the proposed concept and its use cases. To demonstrate the full capability of AAM, we develop an infrastructure that includes advanced U-space services, real and simulated platforms that are suitable for future AAM use cases such as air cargo delivery and air taxi operations, and a co-simulation environment that allows all of the AAM elements to interact with each other in harmony. The considered infrastructure is envisioned to be used in AAM integration-related efforts, especially those focusing on U-space service deployment over a complex traffic environment and those analyzing the interaction between the operator, the U-space service provider (USSP), and the air traffic controller (ATC).European Union funding: 101017702Aerospac
Collision analysis for multiple satellites released from a common dispenser
Get PDFThe number of small spacecraft launched to space has increased dramatically in the past few years, and with the emergence of mega-constellations it is projected to increase even more in the coming decades. Small satellites are usually launched together in rideshare launches and released from a common dispenser when reaching nominal orbit. Due to the lack of available measurement and control capabilities, the release phase is vulnerable to collision risk, as small uncertainties in the initial position can quickly grow causing a high probability of collision. In this paper a framework for analysing the safety of a genric dispenser is proposed and applied to the study of a cylindrical dispenser. Through numerical simulations and linear covariance propagation, the evolution of the spacecraft state is retrieved and used for computing a set of performance metrics, such as the total probability of collision and the number of conjunction events. This method is then applied to a parametric analysis of the dispenser, examining how the performance metrics vary with parameters such as the velocity of release or the time between releases. The results thus obtained will be relevant to the safe design of spacecraft dispensers.ESA GNC and ICATT Conference, 202