9 research outputs found

    A fuel cell system sizing tool based on current production aircraft

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    Electrification of aircraft is on track to be a future key design principal due to the increasing pressure on the aviation industry to significantly reduce harmful emissions by 2050 and the increased use of electrical equipment. This has led to an increased focus on the research and development of alternative power sources for aircraft, including fuel cells. These alternative power sources could either be used to provide propulsive power or as an Auxiliary Power Unit (APU). Previous studies have considered isolated design cases where a fuel cell system was tailored for their specific application. To accommodate for the large variation between aircraft, this study covers the design of an empirical model, which will be used to size a fuel cell system for any given aircraft based on basic design parameters. The model was constructed utilising aircraft categorisation, fuel cell sizing and balance of plant sub-models. Fifteen aircraft categories were defined based on the primary function and propulsion method of the aircraft. For each category, propulsive power and electrical generation requirements were calculated. Based on the results from categorisation and the flight envelope of the aircraft, fuel cell and balance of plant systems are defined. The total system mass and volume are given as outputs, along with polarisation and power curves for the fuel cell. This study finds that the model can accurately predict the electrical generation capability and propulsive requirements across the defined aircraft categories. In addition, the model can appropriately define key, high-level fuel cell parameters based on current Polymer Electrolyte Membrane (PEM) technology. Total fuel cell system mass and volume are calculated and shown to be reasonable for small aircraft. For larger aircraft with a Maximum Take-Off Weight (MTOW) greater than 50,000kg, current PEM technology is not able to match the gravimetric power density of existing APUs

    Managing loads on aircraft generators to prevent overheat in-flight

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    On future UAVs it is envisaged that the power requirements of all on-board electrical systems will increase. In most flight (mission) situations the installed power generation will have adequate capacity to operate the aircraft. It is possible that during abnormal situations such as coolant blockage the generators on-board may be forced to operate under very high load conditions. The main failure mechanism for a generator is overheating and subsequent disintegration of windings, hence the research problem being addressed here is to manage the loads upon the generator to prevent overheats. The research presented here summarizes the modeling of the generator and formation of the load management system. Results are presented showing the system reallocating loads after a fault during flight, preventing overheat of the generators and successfully completing the mission

    Results of the analysis on the occurrence of <i>B</i>. <i>pseudomallei</i> on the experimental field site.

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    <p>The odds ratio refers to the ratio of the odds of <i>B</i>. <i>pseudomallei</i> occurring in soil samples taken a year or more into the experiment from the treatment quadrants to the odds of <i>B</i>. <i>pseudomallei</i> occurring in soil samples from the control quadrants.</p

    Heat maps for the mean <i>B</i>. <i>pseudomallei</i> occurrence per quadrant for the dry and wet season; mean soil moisture (“0” dry (<4% vsw), “1” moist (4–20% vsw), “2” wet (>20% vsw)), mean pH and mean electrical conductivity EC, i.e. soil salinity (μS/cm).

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    <p>Heat maps for the mean <i>B</i>. <i>pseudomallei</i> occurrence per quadrant for the dry and wet season; mean soil moisture (“0” dry (<4% vsw), “1” moist (4–20% vsw), “2” wet (>20% vsw)), mean pH and mean electrical conductivity EC, i.e. soil salinity (μS/cm).</p

    Microcosm experiment.

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    <p><i>B</i>. <i>pseudomallei</i> load after 4 weeks inoculated in sand, sandy clay loam or clay with treatments in triplicate consisting of eight different fertilizers (Tables <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0003635#pntd.0003635.t002" target="_blank">2</a> and <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0003635#pntd.0003635.t003" target="_blank">3</a>), a water-only treatment and a control with no change. The y-axes are in log scale (+0.001) and represent the normalized <i>B</i>. <i>pseudomallei</i> load with the ratio of TTS1 copy number over pt7 control plasmid numbers.</p

    Microcosm experiment treatments.

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    <p>Nine treatments used (plus control) which were each applied in triplicate to each soil type. Fertilizers were applied as per manufacturer’s instructions. All treatments were added with the same amount of water. Ingredients are listed based on package labelling. Numbers indicate % w/w.</p><p>* organic matter 61.5%, organic carbon 35.7%</p><p>** water added to increase VSW of soil by 20%</p><p>Microcosm experiment treatments.</p

    The experimental field site.

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    <p>The setup consisted of two plots with six quadrants each (1x1 metre) with type of treatments or control indicated. Soil of two holes per quadrant (different holes for each round) was tested for <i>B</i>. <i>pseudomallei</i> on a quarterly basis approximately. The arrow marks the direction of the water run-off in the wet season. The number indicates the <i>B</i>. <i>pseudomallei</i> occurrence with the subscript number referring to the baseline occurrence before start of treatment (total 2 holes tested per quadrant) followed by the number of <i>B</i>. <i>pseudomallei</i> positive holes during treatment (total 26 holes tested per quadrant for the duration of the experiment).</p

    Longitudinal occurrence of <i>B</i>. <i>pseudomallei</i> (red line) on the experimental field site.

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    <p>The vertical blue lines indicate the start and end of the wet seasons. The y axis depicts the <i>B</i>. <i>pseudomallei</i> occurrence at total four holes per duplicate quadrants. The first measure was taken before treatments were applied.</p