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NDT Application from Conventional to Digital Radiography for the Aircraft Maintenance Industry

SORT Engineering GmbH-Adel A. Ghobbar
  • Technical Paper
  • 2019-01-1907
To be published on 2019-09-16 by SAE International in United States
Technological innovation can provide improved productivity, increased cost savings, and it can keep or make an organisation competitive. Digital radiography for non-destructive testing (NDT) is such a promising innovation. In organisations with large scale utilisation of non-destructive testing, a transition from film to digital radiography is easily justified. Nevertheless, this is not the case for every organisation. Next to the operational workflow, system flexibility, quality, and regulatory issues also play a role in the trade-off. Especially in the aircraft maintenance industry, where the non-destructive operation is related to a lot of different factors. Motivated by the developments of digital radiography, the NDT department of KLM Engineering & Maintenance (E&M) requested advice in reconsidering their conventional film radiography capabilities. The objective of this research was to assess the feasibility of digital radiography at KLM E&M. First, a thorough understanding of the technical and practical principles behind conventional radiographic testing was built up. Regulatory and process requirements were identified and several digital radiographic systems for industrial purposes were analysed. Based on the requirements, only computed radiography (CR)…

Optical investigation of mixture formation in a small bore DISI engine by laser induced exciplex fluorescence (LIEF)

Technische Univ. Braunschweig-Alexander Pauls, Peter Eilts
  • Technical Paper
  • 2019-24-0133
To be published on 2019-08-15 by SAE International in United States
Legislative and customer demands in terms of fuel consumption and emissions are an enormous challenge for the development of modern combustion engines. Downsizing in combination with turbocharging and direct injection is one way to increase efficiency and therefore meet the requirements. This results in a reduction of the displacement and thus the bore diameter. The application of direct injection with small cylinder dimensions increases the probability of the interaction of liquid fuel with the cylinder walls, which may result in disadvantages concerning especially particulate emissions. This leads to the question which bore diameter is feasible without drawbacks concerning emissions as a result of wall wetting. The emerging trends towards long-stroke engine design and hybridization make the use of small bore diameters in future gasoline engines a realistic scenario. In the previous project “GDI Boundary Bore” the feasibility of an SI engine with direct injection and small bore diameter was shown by the analyses of two different cylinder head concepts (3V and 4V). For the acquirement of deeper understanding of the mixture formation in such engines…

Experimental characterization of methane direct injection from an outward-opening poppet-valve injector

Istituto Motori CNR-Maurizio Lazzaro, Francesco Catapano, Paolo Sementa
  • Technical Paper
  • 2019-24-0135
To be published on 2019-08-15 by SAE International in United States
The in-cylinder direct injection of natural gas represents a further step towards cleaner and more efficient internal combustion engines (ICE). However, the injector design and its characterization, either experimentally or from numerical simulation, is challenging because of the complex fluid dynamics related to gas compressibility. In this work, the underexpanded flow of methane from an outward-opening poppet-valve injector has been experimentally characterized by Schlieren and Shadowgraph high-speed imaging. The jet evolution was also followed through Mie-scattering imaging using n-heptane droplets as a tracer. The investigation has been performed at ambient temperature and pressure and different nozzle pressure ratios (NPR) ranging from 10 to 17. The gaseous jet has been characterized in terms of its macroscale parameters.

High-speed imaging of a vaporizing GDI spray: a comparison between Schlieren, Shadowgraph, DBI and Scattering

Istituto Motori CNR-Maurizio Lazzaro
  • Technical Paper
  • 2019-24-0037
To be published on 2019-08-15 by SAE International in United States
The evolution of the liquid and vapor phases of an iso-octane GDI spray was investigated in a constant volume vessel, under inert environment, using high-speed imaging techniques. The tests were performed in nitrogen, at temperatures and density varying between the operating conditions representative of late injection, flash boiling conditions and early injection in a GDI engine. Large scale parameters of the spray (penetration length, spray angle, projected area) were obtained by processing schlieren, shadowgraph, DBI and scattering images. The segmentation of spray images, for both the liquid and vapor phase, was carried out through a novel image processing method. The method bases upon an "optimal" filtering of spray images by means of variational methods, an original thresholding procedure based on the iterative application of the Otsu's method, and the highlighting of the schlieren/shadowgraph textures of the vapor phase through the main curvatures of the image surface. The boundaries of the vapor phase were obtained from the schlieren and shadowgraph images of the spray. The processing method allows distinguishing unequivocally the contours of the vapor phase,…

Optical evaluation of directly injected methane using a newly developed highly repetitive laser diagnostics system

Universität Bayreuth-Mirko Geiger
  • Technical Paper
  • 2019-24-0134
To be published on 2019-08-15 by SAE International in United States
New certification procedures like WLTP and RDE, as well as more stringent emission regulations in general, demand for further improvements in engine research and development. In order to meet the challenges of reducing pollutants while maintaining high performance and high efficiency many different approaches are discussed. Beside various concepts for new combustion strategies and alternative fuels, gaining detailed knowledge about the ongoing processes inside engines and combustion chambers during the different operation modes is of major importance. With their influence on combustion and emission formation, fuel injection and mixture formation are playing an important role for further improvements in modern propulsion systems. With the help of optical measurement systems based on laser induced (exciplex) fluorescence (LIF/ LIEF), an advanced understanding of these mechanisms can be obtained. However, additional challenges arise when it comes to analyzing transient engine operation and cyclic fluctuations as well as rating their contribution to the formation of emissions. This study contains the evaluations of the injection and mixture formation inside a rapid compression machine (RCM) with directly injected methane. Equipped with…

Imaging and vibro-acoustic diagnostic techniques comparison for a GDI fuel injector

Istituto Motori CNR-Luigi Allocca, Daniela Siano, Alessandro Montanaro, Maria Antonietta Panza
  • Technical Paper
  • 2019-24-0058
To be published on 2019-08-15 by SAE International in United States
This work presents the results of an experimental investigation on a GDI injector, in order to analyze fuel injection process and atomization phenomenon, correlating imaging and vibro-acoustic diagnostic techniques. A single-hole, axially-disposed, 0.200 mm diameter GDI injector was used to spray commercial gasoline in a test chamber at room temperature and atmospheric backpressure. The explored injection pressures were ranged from 5.0 to 20.0 MPa. Cycle-resolved acquisitions of the spray evolution were acquired by a high-speed camera. Contemporarily, the vibro-acoustic response of the injector was evaluated. More in detail, noise data acquired by a microphone sensor were analyzed for characterizing the acoustic emission of the injection, while a spherical loudspeaker was used to excite the spray injection at a proper distance detecting possible fuel spray resonance phenomena. In order to monitor vibration throughout the injection event, the injector was also equipped with an accelerometer sensor, adhesively mounted on the holder. Tests in both dry and fuel injection conditions allowed to distinct the pure mechanical operation of the injector related to the needle opening and closing, and…

Morphological characterisation of gasoline soot-in-oil: development of semi-automated 2D-TEM and comparison with novel high-throughput 3D-TEM

Univ of Nottingham-Ephraim Haffner-Staton
University of Nottingham-Antonino La Rocca, Alasdair Cairns, Mike Fay
  • Technical Paper
  • 2019-24-0042
To be published on 2019-08-15 by SAE International in United States
Morphology of soot nanoparticles is characteristically complex and 3-dimensional, and plays a defining role in soot-related phenomena. Morphological characterisation of soot is essential to understand the extent of such effects, including harm to human health, and develop strategies to mitigate them. Use of 2D-TEM for characterisation is associated with numerous and significant sources of error and uncertainty related to a 2D-3D information gap. Volume reconstruction by 3D-TEM avoids many of these sources of error, and has been shown in simulation studies to be highly accurate. However, the technique has traditionally been too slow to permit study of enough individual structures to satisfactorily characterise a bulk soot-sample. Similarly, the prevalence of manual image processing in 2D-TEM studies of soot can limit characterisations to as few as 50 individual particles per sample. In this study a methodology has been developed to permit high-throughput tilt-series acquisition of soot nanoparticles for use in 3D-TEM volume reconstructions. This technique involves semi-automated 2D-TEM image processing via automated segmentation to screen large areas of TEM grids for suitable structures. Automated selections can…

Large Eddy Simulations and Tracer-LIF Diagnostics of wall film dynamics in an optically accessible GDI research engine

ETH Zurich-Nicolò Frapolli, Konstantinos Boulouchos
ETH Zurich/Combustion+FlowSolutions GmbH-Yuri M. Wright
  • Technical Paper
  • 2019-24-0131
To be published on 2019-08-15 by SAE International in United States
Large Eddy Simulations (LES) and tracer-based Laser Induced Fluorescence (LIF) measurements have been performed to study the dynamics of fuel wall-films on the piston top of an optically accessible, four-valve pent-roof GDI research engine for a total of eight operating conditions. Starting from a reference point, the systematic variations include changes in engine speed (600; 1,200 and 2,000 RPM) and load (WOT and 500 mbar intake pressure); concerning the fuel path the Start Of Injection (SOI=360°, 390° and 420° CA after gas exchange TDC) as well as the injection pressure (10, 20 and 35 MPa) have been varied. For each condition, 40 experimental images were acquired phase-locked at 10° CA intervals after SOI, providing valuable insights with respect to the wall film dynamics in terms of spatial extent, thickness and temperature. The simulation framework was developed as follows: first, the spray model was calibrated using spray morphology evolution data of the same injector, characterized in a constant volume spray chamber by means of high-speed shadow imaging. In a second step, the wall impingement and film…

Global Temperature Mapping and Crystallization Analysis of Supercooled Water Droplet Freezing Using Luminescent Imaging Technique

University of Notre Dame-Wesley Chad Patterson, Hirotaka Sakaue
Published 2019-06-10 by SAE International in United States
A prominent environmental phenomenon that greatly affects many industries including automotive, aeronautics, energy transmission, etc. is icing. One mechanism by which this occurs and plagues our machines and infrastructures that are exposed to the atmosphere is the icing of supercooled water droplets on a surface - either by impact against a surface or spontaneous nucleation and crystallization of a droplet at rest. The process by which nucleation propagates during the liquid-to-solid phase change and the thermodynamic implications in regards to latent heat generation and transfer are not fully understood on the single droplet scale. An attempt to better resolve these unknowns in both spatial and temporal domains has been made here. Previous efforts have implemented a unique temperature sensing technique utilizing luminescent dyes. A thermally sensitive luminescent paint coated onto the surface of interest allows direct mapping of the heat transfer from the supercooled liquid droplet undergoing freezing to the surface. This technique also provides insight into the nucleation propagation speed along the droplet-substrate interface. This, in conjunction with a high-speed color camera and an…
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Wind Tunnel Measurements of Simulated Glaciated Cloud Conditions to Evaluate Newly Developed 2D Imaging Probes

Artium Technologies Inc.-William D. Bachalo
CIRA, Italian Aerospace Research Centre-Biagio M. Esposito
Published 2019-06-10 by SAE International in United States
Instrumentation that has been used for characterization of mixed-phase and glaciated conditions in the past, like the OAP probes, are subject to errors caused by variations in diffraction on the images away from the object plane and by the discrete nature of their particle detection and sizing. Correction methods are necessary to consider their measurements adequate for high ice water content (IWC) environments judged to represent a significant safety hazard to propellers and turbofan engine operability and performance. For this reason, within the frame of EU FP7 HAIC project, instrumentation characterization and validation is considered a major element need for successful execution of flight tests campaigns. Clearly, instrumentation must be sufficiently reliable to assess the reproducibility of artificial clouds with high ice water content generated in icing tunnels. Instruments are required to measure these conditions with a sufficient level of accuracy for the purposes of the testing. Currently, there is an anticipated basic uncertainty of a factor of 2-5 when measuring clouds in-situ. This may be worse for thunderstorm core regions, because of the poorly…
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