CoA. PhD, EngD, MPhil & MSc by research theses

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Browsing CoA. PhD, EngD, MPhil & MSc by research theses by Course name "PhD in the School of Engineering"

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    ItemOpen Access
    Experimental investigation of lubricant film thickness in an automotive final drive unit.
    (Cranfield University, 2013-11) Fusco, Lucia; Sherwood, Glenn
    Society has been aware of the environmental impact of vehicles for some time now, with governments trying to control and reduce this impact by introducing emissions standards to control pollutants as well as CO₂ emissions. One way in which total emissions can be reduced is by increasing the efficiency of vehicles as a whole, resulting in greater fuel economy. Related to increased transmission efficiency, lubricant flow within a final drive unit (FDU) was researched, enabling a better understanding of the system through visualisation and laser induced fluorescence (LIF) measurements. A LIF measurement technique has been developed, along with a quantitative wedge calibration method, to measure lubricant thicknesses within a Jaguar Land Rover X150 FDU. The measurements and data recorded in this thesis are taken from an original clear-cased replica FDU, which proved to be suitable for visualisation and LIF measurements. The results show lubricant thickness trends are dependent on the fill volume and rotational speed of the gear. The measured peak lubricant thickness on the carrier- and cover-side of the crown wheel increased with fill volume. As the fill volume increased, the amount of lubricant entrained by the crown wheel increased, resulting in the increased lubricant thickness. As the equivalent vehicle road speed increased to approximately 8mph, the measured lubricant thickness increased to its maximum value of 1.75mm for a fill volume of 900ml. From 8mph onwards, the lubricant thickness was found to decrease again to less than 0.1mm at around 10mph. Up to 8mph, gravity appeared to be the overriding influence, pulling the lubricant from the crown wheel. At 8mph, these forces seemed to be in balance, resulting in the greatest measured lubricant thickness. Above 8mph, the force from the gear rotation ejected lubricant from the crown wheel. Gathered data and relationships provide new quantitative metrics for measurement and enhanced understanding of lubricant movement within the FDU. The methodology and equipment developed here for studying the FDU are suitable for wider use in any geared or lubricated system.
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    Performance and CFD analyses for a novel and existing thrust reverser designs.
    (2014-04) Mahmood, Tashfeen; Sethi, Vishal
    The landing phase of any flight is the most important one with respect to safety. For a high bypass ratio turbofan engine, aircraft deceleration can be achieved by the use of thrust reversers, lift spoilers and brakes. The use of thrust reversers naturally contributes to a reduction in engine life while the use of brakes has operational limitations with respect to aircraft “turn-around times”. With a drive towards improved engine efficiency and lower overall weight, research into novel thrust reverser concepts is imperative to identify designs which offer improved reverser effectiveness and lower weight as well as ease of installation and storage. The main contributions to knowledge of this PhD research are related to feasibility assessments of the following two thrust reverser concepts: A novel vane target type hybrid reverser (VTTHR) design concept has been conceived and evaluated (at a preliminary level) by the author. The design incorporates a target type thrust reverser with cascade vanes. This idea may be patentable. NASA has developed and tested a core mounted target type thrust reverser (CMTTTR) for which experimental data is available in the public domain. The second contribution to knowledge of this PhD research is extensive studies of this design. These studies comprise 2D and 3D CFD analyses to assess design feasibility and provide an understanding of performance and flow physics of this thrust reverser for both static and landing conditions (not available in public domain). In addition to these studies, comprehensive studies of the impact of thrust reverser deployment on overall engine and component performance (for both a mixed and a separate exhaust high bypass ratio turbofan engine) were performed. The preliminary feasibility studies of the VTTHR, which were performed using 2D CFD, suggest that this new design may offer benefits in terms of greater reverser efficiency, weight and ease of storage, relative to conventional designs. Additionally, it was deduced from a large number of CFD investigations that this may be the only feasible “core mounted” thrust reverser design concept for future high bypass ratio engines. There are of course several additional studies (aerodynamic and structural) that need to be performed to mature this technology but the preliminary studies performed provide a good foundation for these. The use of a VTTHR reverser concept relocates reverser hardware to the core cowl, offering potential reductions in reverser and nacelle weight while allowing the nacelle lines to be optimized. Also, installation of VTTHR would benefit aircraft cruise performance, as during cruise flight there will be no losses due to flow leakage and pressure drops that normally occur across the stowed reverser hardware for conventional cascade type thrust reversers, thus, an improvement in specific fuel consumption and therefore mission fuel burn is expected. The CMTTTR models developed were successfully validated using experimental data. However it was concluded that this design may not be feasible because of issues related to reverser effectiveness, mass flow compatibility and runway clearance.