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Boeing 737-400 passenger air conditioner control system model for accurate fault simulation
Get PDFThe aircraft environmental control system (ECS) is a highly integrated and complex system. The passenger air conditioner (PACK) is the heart of the ECS and has been reported as a key driver of unscheduled maintenance by aircraft operators. This is principally due to the PACK’s ability to compensate for degraded components, and hence mask their real condition, so that when failure occurs it is a major event. The development of an accurate diagnostic solution would identify the degradation early and hence focus effective maintenance and reduce cost. This paper is a continuation of the authors’ work on the development of a systematically derived PACK simulation for accurate fault diagnostics, utilizing a model-based approach. In practice, the PACK simulation accuracy is dependent on a number of factors, which include the understanding of its control system. The paper addresses this by taking an in-depth look at the factors controlling the operation of the PACK to enable the gap between the theoretical understanding of the PACK and the engineering design of the system to be bridged, and accurate simulations under healthy and degraded scenarios obtained. This paper provides a comprehensive explanation of the PACK control system elements (principally valves) and verifies their operation based on experimental test data acquired from a B737-400 aircraft. A discussion of the control used in the simulation is then given, resulting in the correct temperature, pressure, and flow being delivered to the cabin. The overall simulation results are then presented to demonstrate the importance of using a systematically derived control logic. They are then further used to assess the impact of degradation in the main PACK valves (PVs)
Scaling-up urban agriculture for a healthy, sustainable and resilient food system: the postharvest benefits, challenges and key research gaps
Get PDFSustainably ensuring food security and safety for the urban population is a major challenge. In this perspective, we present the concept of rurbanisation (the ruralisation of urban areas through increased urban agriculture) as a holistic strategy to provide a resilient food system. In particular, we focus on the postharvest benefits of urban agriculture for environmentally sustainable food supply chains, enhanced nutritional content of fresh produce and access to fresh, local and seasonal food. However, upscaling current urban agricultural systems requires improvement in current technologies and local infrastructure as well as the transfer of knowledge and skills to new urban farmers. This perspective summarises the main challenges that urban agriculture is currently facing from a postharvest quality and safety point of view, and highlights the research gaps and opportunities for improvements in that area
ℒ1 adaptive path-following of airships in wind
No full textThis paper proposes an adaptive, three dimensional (3D) path-following controller for airships in the presence of wind disturbances, which explicitly considers that wind speed is time-varying. The main idea is to formulate airship path-following as control design for systems in the presence of parametric uncertainties and external disturbances. Assuming that there is no prior information on wind, the proposed solution is based on the ℒ1 adaptive controller. This approach makes clear statements for performance specifications of the controller and relaxes the common assumption that wind speed is constant. This makes the design more realistic and the analysis more rigorous, because in practice, the wind speed may be time varying. The results of the simulation indicate that the path following system has a good performance and is robust against wind disturbances.Unmanned System
Deep-learning for flow-field prediction of 3D non-axisymmetric aero-engine nacelles
Get PDFComputational fluid dynamics (CFD) methods have been widely used for the design and optimisation of complex non-linear systems. Within this context, the overall process can typically have a large computational overhead. For preliminary design studies, it is important to establish design capabilities that meet the usually conflicting requirements of rapid evaluations and accuracy. Of particular interest is the aerodynamic design of components or subsystems within the transonic range. This can pose notable challenges due to the non-linearity of this flow regime. There is a need to develop low order models for future civil aero-engine nacelle applications. The aerodynamics of compact nacelles can be sensitive to changes in geometry and operating conditions. For example, within the cruise segment different flow-field characteristics may be encountered such as shock-wave boundary layer interaction or shock induced separation. As such, an important step in the successful design of these new architectures is to develop methods for fast and accurate flow-field prediction. This work studies two different metamodelling approaches for flow-field prediction of 3D non-axisymmetric nacelles. Firstly, a reduced order model based on an artificial neural network (ANN) is considered. Secondly, a low order model that combines singular value decomposition and an artificial neural network (SVD+ANN) is investigated. Across a wide geometric design space, the ANN and SVD+ANN methods have an overall uncertainty in the isentropic Mach number prediction of about 0.02. However, the ANN approach has better capabilities to predict pre-shock Mach numbers and shock-wave locations.European Union funding: 1010075982023 AIAA Aviation and Aeronautics Forum and Exposition (AIAA AVIATION Forum
A scenario-specific nexus modelling toolkit to identify trade-offs in the promotion of sustainable irrigated agriculture in Ecuador, a Belt and Road country
Get PDFIncreased demand for food due to development and population growth has prompted irrigated agriculture expansion, posing enhanced global challenges to water, energy, and food security. To confront these challenges, an approach that considers the water-energy-food-environment nexus can address multidimensional trade-offs that complicate the efficient use of resources and the achievement of Sustainable Development Goals. In order to provide insights into solutions to these challenges for a specific case, this study develops a modelling toolkit that integrates biophysical and socioeconomic aspects of nexus components in the context of agro-export and irrigation expansion in Ecuador, a Belt and Road Country. The nexus toolkit is applied to agricultural-development scenarios defined in participatory workshops and incorporates a water resources model, a lifecycle environmental assessment, and a socioeconomic analysis. The modelling exercise is constructed around specific scenario-determined land use patterns in the Santa Elena peninsula of Ecuador. Agriculture in the peninsula is water-limited, relying on delivery infrastructure and transfers from a neighbouring catchment. Impacts on nexus components are analysed for ten crops under two potential land-use scenarios: a substantial increase in irrigated area due to investment in irrigation infrastructure; and a substantial shift in land use towards export crops. The two have distinct impact on water and energy use, global warming potential, freshwater eutrophication, terrestrial acidification, and fine particulate matter formation. The results provide insights into future water and energy resource challenges and environmental and socioeconomic trade-offs associated with likely changes in irrigation expansion. The results for scenarios show that, for example, banana production has the greatest environmental impacts (e.g. a 519% increase in global warming potential and 452% increase in fine particulate matter forma for scenario 2), primarily due to water and energy requirements, despite the crop being mainly produced organically. In addition, total net income and labour demand increase (net income increases by 43% and 217% under scenarios 1 and 2, respectively) due to a larger crop area and crop intensification. Scale effects on labour demand are mainly due to labour intensity of maize in Ecuador, which is disadvantaged in the crop export scenario (an unexpected result). However, expanding irrigated areas would also increase total water and energy demand for irrigation, global warming potential, and freshwater eutrophication. This type of information enables stakeholders and decision-makers to design policies that achieve equitable and sustainable agricultural production, water use, and economic growth.Natural Environment Research Council (NERC): NE/R015759/1Journal of Cleaner Productio
Coupled propulsive and aerodynamic analysis of an installed ultra-high bypass ratio powerplant at high-speed and high-lift conditions
Get PDFTo achieve the targets proposed in the Flightpath 2050 for the aviation industry, more efficient propulsive systems are required. One possible solution is to increase the bypass ratio of the engines to increase the propulsive efficiency and reduce the specific fuel consumption. However, larger fan diameters are expected for these configurations, which results in an increase in the aerodynamic coupling between the powerplant and the airframe. The aim of this work is to develop and demonstrate a thrust and lift matching methodology for installed powerplants using a coupled aero-propulsive model. As a proof of concept, the aerodynamic performance of an ultra-high bypass ratio powerplant integrated with the airframe was evaluated across different flight conditions. This includes high-lift operating conditions such as end of runway; and high-speed conditions such as mid cruise. To evaluate the aerodynamic performance of the propulsion integration a combined assessment of the airframe and powerplant aerodynamics is required using computational fluid dynamics (CFD). The integration of the powerplant with the airframe has the potential to change the engine requirements across the aircraft operational envelope. To account for this the aerodynamic analysis is coupled with a turbomachinery model to adjust the engine thermodynamic conditions at a given operating point.2023 AIAA Aviation and Aeronautics Forum and Exposition (AIAA AVIATION Forum
Formic acid in hydrogen: is it stable in a gas container?
Get PDFFormic acid is an intermediate of the steam methane reforming process for hydrogen production. According to International Standard ISO 14687, the amount fraction level of formic acid present in the hydrogen supplied to fuel cell electric vehicles must not exceed 200 nmol·mol−1. The development of formic acid standards in hydrogen is crucial to validate the analytical results and ensure measurement reliability for the fuel cell electric vehicles industry. NPL demonstrated that these standards can be gravimetrically prepared and validated at 4 to 100 µmol·mol−1, with a shelf-life of 1 year (stability uncertainty 7%, k = 1) and shelf life (>1 year). Potential applications include the calibration of analysers and for studying the impact of formic acid on future application with relevant traceability and accuracy.Processe
Mapping water levels across a region of the Cuvette Centrale peatland complex
Get PDFInundation dynamics are the primary control on greenhouse gas emissions from peatlands. Situated in the central Congo Basin, the Cuvette Centrale is the largest tropical peatland complex. However, our knowledge of the spatial and temporal variations in its water levels is limited. By addressing this gap, we can quantify the relationship between the Cuvette Centrale’s water levels and greenhouse gas emissions, and further provide a baseline from which deviations caused by climate or land-use change can be observed, and their impacts understood. We present here a novel approach that combines satellite-derived rainfall, evapotranspiration and L-band Synthetic Aperture Radar (SAR) data to estimate spatial and temporal changes in water level across a sub-region of the Cuvette Centrale. Our key outputs are a map showing the spatial distribution of rainfed and flood-prone locations and a daily, 100 m resolution map of peatland water levels. This map is validated using satellite altimetry data and in situ water table data from water loggers. We determine that 50% of peatlands within our study area are largely rainfed, and a further 22.5% are somewhat rainfed, receiving hydrological input mostly from rainfall (directly and via surface/sub-surface inputs in sloped areas). The remaining 27.5% of peatlands are mainly situated in riverine floodplain areas to the east of the Congo River and between the Ubangui and Congo rivers. The mean amplitude of the water level across our study area and over a 20-month period is 22.8 ± 10.1 cm to 1 standard deviation. Maximum temporal variations in water levels occur in the riverine floodplain areas and in the inter-fluvial region between the Ubangui and Congo rivers. Our results show that spatial and temporal changes in water levels can be successfully mapped over tropical peatlands using the pattern of net water input (rainfall minus evapotranspiration, not accounting for run-off) and L-band SAR data.Remote Sensin
A deep-learning-based approach for aircraft engine defect detection
Get PDFBorescope inspection is a labour-intensive process used to find defects in aircraft engines that contain areas not visible during a general visual inspection. The outcome of the process largely depends on the judgment of the maintenance professionals who perform it. This research develops a novel deep learning framework for automated borescope inspection. In the framework, a customised U-Net architecture is developed to detect the defects on high-pressure compressor blades. Since motion blur is introduced in some images while the blades are rotated during the inspection, a hybrid motion deblurring method for image sharpening and denoising is applied to remove the effect based on classic computer vision techniques in combination with a customised GAN model. The framework also addresses the data imbalance, small size of the defects and data availability issues in part by testing different loss functions and generating synthetic images using a customised generative adversarial net (GAN) model, respectively. The results obtained from the implementation of the deep learning framework achieve precisions and recalls of over 90%. The hybrid model for motion deblurring results in a 10× improvement in image quality. However, the framework only achieves modest success with particular loss functions for very small sizes of defects. The future study will focus on very small defects detection and extend the deep learning framework to general borescope inspection.Engineering and Physical Sciences Research Council (EPSRC): 113174Machine
Conceptual design of a next generation supersonic airliner for low noise and emissions
Get PDFThe development of an innovative, medium-range supersonic airliner to meet low drag, low emissions and LTO noise requirements is presented in this paper, including a multi-disciplinary design framework targeting firstly to meet at least the current noise regulations for subsonic aircraft during take-off and landing and secondly to reduce the emission levels. The aircraft is designed to fly 4000 nm at Mach 2.2, carrying 100 passengers. The work contributes to the EU SENECA ((LTO) noiSe and EmissioNs of supErsoniC Aircraft) project, which aims to design different SST (SuperSonic Transport) aircraft platforms to investigate the emissions, the noise and the global environmental impact of supersonic aviation. Results from SENECA can support ICAO in the process of creating future certification requirements as well as form legislation guidelines specifically for the future supersonic commercial aircraft. The technical work includes the assessment of different aircraft-engine configurations, in terms of engine number and positions, on typical flight missions. This enables the evaluation of the baseline layouts that represent the best compromise among payload-range capability, aerodynamic performance, weight and noise. A multi-disciplinary airframe-engine integrated design is carried out in order to pursue a comparative analysis focusing on take-off noise for the different aircraft-engine combination platforms. Lastly, the investigation of the potential use of variable noise reduction systems (VNRS), such as a FADEC controlled thrust reduction during take-off, called Programmed Lapse Rate (PLR) is carried out to study their impact in the mitigation of the resultant noise in the airport environment.AIAA SciTech Forum 202