Browsing by Author "Sherwood, Glenn"

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    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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    Experimental investigation of the cooling characteristics of a monobloc cast iron brake disc with fingered hub
    (SAGE, 2019-05-02) Tirovic, Marko; Topouris, Stergios; Sherwood, Glenn
    The paper compares heat dissipation characteristics of two interchangeable ventilated brake discs, a standard solid hub and a newly developed fingered hub version, both single piece cast designs. The tests were conducted on a specially developed Thermal Flow Rig, which enables disc induction heating to 450°C and cooling for a range of rotational and air speeds, in parallel and angular cross flow. The Rig facilitated very accurate and repeatable experiments to be conducted for numerous combinations of operating conditions. From the recorded cooling curves, average heat transfer coefficients for convection and radiation were extracted and the results also presented in a generic form, using Nusselt numbers. The fingered design demonstrated superior convective heat dissipation, with the improvements varying depending on the rotational speed, air cross flow velocity and angle, as well as disc temperature. The gains were ranging from 3.5% to over 20%. The fingered design is 8.5% lighter and being a single piece cast disc, it remains inexpensive to mass produce.
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    Flow visualization and particle dispersion measurements inside an ambulance rear saloon while stationary and in motion
    (SAE International, 2022-04-07) Lawson, Nicholas J.; Blackburn, Kim; Sherwood, Glenn; Brighton, James; Atkinson, Helen V.
    The following paper presents flow field and particle dispersion data from a UK National Health Service (NHS) ambulance, under static and dynamic driving conditions and when using different ventilation modes. Data was recorded using laser sheet flow visualisation, particle image velocimetry and hot wire anemometry, from a common plane positioned about the patient centreline. Results indicated a significant influence of the ceiling fan ventilation system on gross flow field behaviour, with the ventilation fan on extract or intake mode. With either ventilation mode, flow velocities in the patient region were found to double from a quiescent condition, to around 50mm/s – 100mm/s. Particle dispersion data also showed dispersion decay rates over five times faster when using the ceiling fan extraction system. All these results were consistent when the vehicle was stationary or driving at a constant speed of 60mph. However, with the vehicle under dynamic driving conditions, such as acceleration or braking, the regular flow patterns were substantially disrupted, with bulk movement of the flow in the direction of the acceleration or braking action. Under these dynamic conditions, the magnitude of the net velocity change on the fluid exceeded any flow generated from the ceiling ventilation system.
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    A technical, environmental and economic assessment of future low-carbon heavy-duty powertrain technologies
    (Cranfield University, 2012-02) Plumb, Colin James; Sherwood, Glenn
    The development of low-carbon powertrains, to both reduce our reliance on fossil fuels and minimise greenhouse gas emissions, has become a key technological focus for automotive companies. This study investigates, assesses, and critiques future powertrain solutions to determine which technologies demonstrate the ability to both satisfy the environmental requirements while fulfilling the demands of commercial vehicle heavy-duty drive cycles. The implications of low-carbon technologies on the automotive industry are also reviewed. The technologies discussed are identified through; industry research, patent reviews, published low-carbon roadmaps, and academic literature. The internal combustion engine is expected to remain the primary heavy-duty powertrain technology until beyond 2030. Although increased electrification is anticipated, the demands of heavy-duty drive cycles prohibit the use of the current electric and hybrid electric powertrain technologies being developed for light-duty applications. Increasing engine efficiency will remain a key focus of truck and engine manufacturers as the reduction of fuel consumption and CO2 emissions becomes a legislative requirement. Waste heat recovery and parasitic loss reduction technologies are expected to be seen on the majority of new truck models. The use of alternative fuels in the existing diesel powertrain offers the fastest route to reducing both GHG and exhaust emissions. Biofuels which can be blended with mineral diesel and easily integrated with the current infrastructure are likely to dominate the alternative fuels market. It is anticipated that over the next 5 to 10 years the choice of automotive fuels will diversify as countries move to utilise local biomass resource and increase their own energy security. Existing technical competencies, strategic assets, and R&D expertise puts established manufacturers in a good position to maintain their market position and also gain competitive advantage in emerging markets as they aim to implement stricter emissions legislation.