Browsing by Author "Giannouloudis, Alexandros"

Now showing 1 - 5 of 5
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    Cluster-based tracking method for the identification and characterisation of vortices
    (Association Aéronautique et Astronautique de France (3AF), 2025-03-26) Ibanez, Claudia; Migliorini, Matteo; Giannouloudis, Alexandros; Tejero, Fernando; Zachos, Pavlos K.
    An unsupervised, flow-agnostic and automatic cluster-based tracking algorithm for the segmentation of vortex-dominated flows has been successfully developed. It combines the Rortex method and density-based clustering algorithms. The Rortex method differs shear from rotation and overcomes the sensitivity to user-defined thresholds that characterises current practice of vortex identification methods. The algorithm is demonstrated with experimental Stereoscopic Particle Image Velocimetry data from two cases; a high-Reynolds (≈ 106) vortex generated by a half-delta wing, and distorted flow in a scaled-model of a civil aero-engine intake under cross-wind conditions. The approach is a successful method for the segmentation of complex vortical flows under a wide range of conditions.
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    Design, development and testing of a high-pressure hydrogen micromix combustion rig
    (Cranfield University, 2023-03) Giannouloudis, Alexandros; Nalianda, Devaiah
    The aviation industry has been improving aircraft performance and cutting back emissions for decades now. The increasing urgency of climate change has been pushing this effort to become more intense leading in recent years to the adoption of the target of full decarbonisation by 2050. Significant reductions in non-carbon containing emissions have been targeted by the industry as well. In that context, the use of liquid hydrogen (LH₂) as a combustible fuel for aircraft propulsion is a promising solution. Hydrogen guarantees carbon-free flights at mission level, yet, state-of-the-art aircraft combustor technologies are not suitable for low-NOₓ hydrogen combustion. Consequently, alternative combustion concepts and technologies are under research, and micromix technology is one of them. This thesis presents the design, development and deployment of a high-pressure combustion rig for hydrogen micromix burners, and describes the process from conception to testing of three different injector geometries. In doing so, it highlights the challenges of designing the components and systems to operate with hydrogen, whilst ensuring safety. Based on the experience gained through the deployment of the experimental setup, potential problems have been identified and solutions have been suggested to improve it. This aspect of the work contributes towards future research efforts of developing larger-scale combustion rigs for testing hydrogen. Within the context of the rig development, different design philosophies and manufacturing routes are explored for micromix burners. The limitations and safety considerations for the different approaches are detailed, and guidelines are offered on how the setup may be improved. The successful implementation of a fabrication strategy that combines additive manufacturing with traditional machining of features with sub-millimetre dimensions (0.3mm) is a significant contribution to developing micromix burners. It further opens an area of research into the limitations and potential effects of applying additive manufacturing to future micromix combustors. NOₓ emissions measurements of three injector configurations with different momentum flux ratios (MFRs) taken at elevated pressures, air-inlet temperatures and equivalence ratios are presented. The results denote the impact of these parameters on NOₓ emissions and the sensitivity of the emission to changes in MFR. Comparisons with LES results further highlight the need to accurately represent phenomena that affect the momentum flux ratio (MFR) in the simulations. Failure to do so provides a misleading correspondence of NOₓ levels with MFR. When compared to a state-of-the-art kerosene burner at similar pressure and inlet temperature conditions, hydrogen micromix yielded lower NOₓ by 50% for the ”worst” injector configuration.
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    Effect of a fan on the unsteady distortion of s-duct intakes
    (Association Aeronautique et Astronautique de France (3AF), 2024-04) Migliorini, Matteo; Zachos, Pavlos K.; MacManus, David G.; Giannouloudis, Alexandros
    A key requirement for the integration of the propulsion and air induction systems is the assessment of the response of the fan to incoming flow distortion. This is especially crucial for the development of novel aircraft configurations with highly embedded engines. The recent advances in non-intrusive laser-based flow diagnostics increased the experimental capability to measure unsteady flows in convoluted intakes with high resolution in time and space. In the pathway to full-scale intake-engine tests, this work introduces the capability to successfully acquire non-intrusive high resolution flow distortion measurements in close proximity to a high-speed rotating fan. This also quantifies the impact of the fan on the inherent flow distortion of S-duct intakes. The measurements demonstrate that although the effect of the fan on the flow distortion is limited, the rotating blades can cause a local increase of the maximum levels swirl intensity at the blade tip region. Further development work on the ducted fan simulator is needed to operate the fan in the representative range of transonic rotors.
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    Experimental investigation of unsteady fan-intake interactions using time-resolved stereoscopic particle image velocimetry
    (Elsevier, 2025-07) Migliorini, Matteo; Zachos, Pavlos K.; MacManus, David G.; Giannouloudis, Alexandros
    Understanding engine response to unsteady intake flow distortion is a crucial requirement to de-risk the development of novel aircraft configurations. This is more critical for configurations with highly embedded engines. Recent advances in non-intrusive, laser-based flow diagnostics demonstrated the ability to measure unsteady flows in convoluted intakes with high resolution in time and space. This work presents novel non-intrusive, unsteady flow measurements ahead of a fan rotor coupled to a convoluted diffusive intake. The fan rotor caused a local increase of the maximum levels of swirl intensity at the blade tip region, as well as flow re-distribution at the interface plane between the fan and the inlet duct compared to the baseline configuration with no fan in place. This contributed to the reduction of the overall swirl angle unsteadiness across the main flow distortion frequencies. This research presents a notable advance in unsteady fan-intake interaction characterisation. The work shows that high-resolution optical measurements offer notably better understanding of these complex aerodynamic interactions and have the potential to be part of larger scale, industrial testing programmes for future product development and certification.
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    On the development of an experimental rig for hydrogen micromix combustion testing
    (The Combustion Institute, 2021-04-15) Giannouloudis, Alexandros; Sun, Xiaoxiao; Corsar, Michael; Booden, Scott J.; Singh, Gaurav; Abbott, David; Nalianda, Devaiah; Sethi, Bobby
    This work describes the development of a combustion rig, aimed at testing hydrogen-fuelled micromix burners for aero gas-turbines at pressures up to 15barg, inlet-air temperatures up to 600K and equivalence ratios (Φ) from leanblow- out to 0.5. It discusses the test facility used, and the design procedure of the experimental apparatus: the requirements of it, the design choices and implementation of instrumentation. Emphasis is placed on the design and manufacture of the burner. Comparison between Additive Manufacturing (AM) and micro-machining techniques for the sub-millimetre injection points shows that further research is needed in this area, to achieve adequate geometric accuracy of the injection holes economically. This rig forms a unique facility for hydrogen micromix testing, offering simultaneous measurements of NOx emissions, Flame-Transfer–Function (FTF) and flame imaging.