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Assessing Test Suite Quality for Scenario Classes in Automated Driving
Get PDFTesting is an integral part of ensuring safety for automated driving systems. Moving away from distance-based approaches, scenario-based development has become the industry's state of the art. Therein, concrete test cases are generated from scenario classes that should cover the operational design domain. The number of scenario classes is finite, but each scenario class describes an infinite number of concrete test cases. For a given scenario class, test suite quality depends on the number of test cases and the value of these test cases. In this talk, we explore how test suite quality can be assessed appropriately
Optimization of thermochemical energy storage reactors using machine learning
No full textThermochemical energy storage (TCES), where thermal energy is stored in a reversible chemical reaction in a porous powder bed, is a promising technology for large-scale and long-term thermal energy storage. It has been under long-standing investigation for prospective applications, such as the capture of excess heat from industrial processes or storing energy in concentrated solar power plants, to offset their unpredictable energy generation. This study investigates TCES in the SrBr2-system, which offers a high energy capacity and near-perfect reversibility.
However, the scaling up of these reactors is hindered by the limited heat transfer from the heat source, such as reactor walls, to the powder bed. To address this challenge, heat conducting structures, such as fins, are incorporated into the bed to enhance thermal contact and shorten transport paths. Moreover, structural changes through mechanical and physical alteration of the powder bed, as well as changes in the microstructure, lead to changing heat and mass transport properties of the porous medium during cycling. Additionally, deformation of the bed can lead to detachment from the heat conducting surfaces.
Even though physical modeling these effects can be done in principle, developing and parametrizing these models is challenging due to the substantial structural changes happening on multiple scales in the reacting bed. In this contribution, we attempt to overcome these challenges through hybrid modelling, i.e. the combination of physical and data-driven methods.
To this end, experimental work is carried out on the macroscale (cm) by thermochemical cycling reactive beds within reactors and measuring conversion and local temperatures inside reactors over time. In addition, imaging of the microstructure (µm) is done using µCT imaging of smaller samples, which can be used to compute effective transport parameters. Then, the available data is used to build a multi-scale model, combining data driven techniques and physical simulations.
In a second step, ML techniques are used to improve the heat transfer inside the reactor by designing optimized heat conducting structures. As direct simulations are prohibitively time consuming, we construct an ML-Based surrogate model, which is trained with a representative sample of physical simulations, and which can predict the performance of the reactor based on the structures’ geometry. This can be done either by training a neural network on simulated data or by using techniques, such as model order reduction, where the non-linearities are handled by a neural network. The surrogate model is then coupled with a topology optimization algorithm based on the level-set method, which is used to calculate optimal geometries for the heat conducting structures. Our contribution will center on the modeling techniques employed and the preliminary optimization results obtained
Manufacturing, Modelling and Testing of Acoustic Liners Extended with Flexible Walls
Get PDFThis study investigates a novel acoustic liner concept from an acoustical and manufacturing perspective. The proposed damping system combines a conventional Helmholtz resonator with additional structural resonances due to flexible walls. Promising flexible wall materials were characterised in terms of their mechanical properties by dynamic mechanical analysis and their resistance to environmental influences. Based on these results, flat liner samples with a flexible intermediate wall were designed, manufactured and experimentally tested. A process chain with a pre-tensioning device for preserving the stress state during the joining process was developed for technical production. Compared with a conventional liner, the new type of liner exhibits additional low-frequency and, in particular, broadband damping. Numerical simulations of the liner showed good agreement with the experimental results, highlighting the role of the flexible wall. In addition, broadband dissipation was observed for the same installation space compared with the reference. This type of liner was then converted into an engine-like curved structure to investigate the influence of higher acoustic modes. Therefore, the design, production, engine integration and acoustic characterisation of a new liner concept with flexible walls for low-frequency and broadband dissipation of engine noise were successfully demonstrated
Gas Flaring Efficiencies of Selective Oil and Gas Facilities in the Sultanate of Oman
Get PDFThis study presents the first thorough examination of flaring emissions in Oman using a novel
airborne platform. The measurements were performed during the METHANE-To-Go-Oman field
experiment funded by UNEP's International Methane Emissions Observatory (IMEO), which was
conducted from November to December 2023
Comparison of SpaceX's Starship with winged heavy-lift launcher options for Europe
Get PDFThe remarkable progress SpaceX made in the first four integrated flight tests of their Starship and Super Heavy launcher configuration indicates that a fully reusable space transport system might become a reality within a few years. Such a system could revolutionize the global launch market, especially if it is able to achieve its forecasted payload capacity of more than 100 t into LEO. Therefore, it is necessary to gain a deep understanding of the capabilities of this system and compare it to potential future European options for heavy and super-heavy space transport systems. This paper uses the publicly available data from Starship’s first four integrated flight tests for a thorough technical analysis of its current capabilities. The flight tests allow a calibration and update of our earlier-presented Starship models with real flight data. These updated models will be used to gain an understanding of its high-level system properties and to extrapolate the actual LEO capabilities of the early operational Starship versions. The second part of the paper will investigate a potential European option for launching similar payloads of 50 t and more into LEO, based on building blocks currently proposed or under investigation. This configuration employs a reusable winged first stage based on the SpaceLiner concept’s booster stage. The stage uses cryogenic liquid hydrogen and cryogenic liquid oxygen and is recovered with in-air capturing (IAC). For the second stage, an expendable cryogenic stage is optimized to maximize the payload capacity. Finally, the paper compares the technical characteristics of the presented winged launch vehicle to the Starship’s capabilities to highlight the key advantages of the two differing approaches and identify promising future development roadmaps for European launchers
Designing a Conceptual Model and Data Extraction Pipeline for Flight Test Cards
Get PDFThe goal of this bachelor's thesis is to design a conceptual model and a data extraction pipeline for flight test cards, which are protocols created as Word files and filled with results and remarks by the flight test engineer. The concept is necessary because, in the current DLR workflow, flight test cards are stored as PDF files, which is not an optimal solution for matching and comparing flight test card data. This creates the need for a database to ensure suitable accessibility and efficient retrieval of flight test card data. The solution is tailored to the needs of DLR, the German aerospace research and technology center, particularly for all institutes involved in flight test analysis. This is because DLR is actively developing and researching new technologies in the field of aeronautics, and understanding these flight tests requires data from flight test cards. To achieve this, various approaches for extracting data from flight test cards will be explored, including different OCR techniques and table detection methods. The most suitable approach was selected and implemented into a pipeline to automatically extract data from the flight test cards. For efficient storage and querying of the extracted data, a data model was designed to link the flight test card information with the recorded sensor data and the additional information of the flight test, enabling better analysis of the maneuvers performed at DLR. Therefore, the content of the flight test cards was analyzed, along with methods for storing this data, to develop a suitable database model that meets the specific requirements derived from the flight test card content. This addresses the need for flight test cards to fully understand the executed maneuvers. The results of this thesis demonstrate that it is possible to automatically extract data from flight test cards, offering a clear advantage over the current solution. However, as a conceptual model, it also highlights several areas for improvement before the system can be deployed in production. This thesis serves as a foundation for further development and enhancements, with the ultimate goal of integrating the system into DLR’s operational workflow for flight test cards
Influence of Lift-Induced Upwash on Propeller Blade Deformation: A Digital Image Correlation Study for Next-Generation Open Rotor Engines
No full textThe present study investigates the deformation of propeller blades in the presence of a wing, specifically analysing the lift-induced upwash effects through experimental measurements conducted in a wind tunnel. The objective is to quantify the impact of non-uniform inflow on blade bending, with a particular focus on the aerodynamic interactions between the rotor and the wing. Image Pattern Correlation Technique (IPCT) was employed to measure blade deformation, leveraging high-resolution optical methods
to capture structural response under varying flight conditions
Visual assistance system for manual composite scarf repair
No full textThe Visual assistance system for manual composite scarf repair is a assistance system. It features a automated creation of the scarf geometry icombined with a continuous deviation analysis. It can be used for complex scarfs with curved geometries and ist suitable for large repairs. It also inkluds support for additional processes
SpaceLiner 8 definition: relevant aerodynamic and aerothermodynamic issues
Get PDFThe SpaceLiner fully reusable launcher and ultra-high-speed
rocket-propelled passenger transport is in conceptual design
phase. The ongoing concept evolution is addressing system
aspects of the next configuration release 8. The challenge of the
passenger stage SLP8 design is to find an aerodynamic shape that
allows both long-range glide missions with good hypersonic L/D,
as in the case of current SpaceLiner 7, and ballistic jumps outside
the atmosphere over populated landmasses.
The paper describes the latest architecture variation of the
SpaceLiner 8 configuration still under definition. The focus is on
the aerodynamic shape evaluation with search for trimmable
designs in a very broad range of flight Mach-number and AoA.
Some of the trajectories reach up to 120 km altitude and are in the
transition regime from continuum to rarefied flow. Hence,
dedicated DSMC-calculations are performed for selected high
altitude points of the trajectory and obtained coefficients are to be
included into a refined AEDB and will subsequently be checked
on system impacts. The aerothermal issues are investigated along
different full mission profiles and suitable thermal protection
concepts are preliminarily sized and evaluated