There is at present some uncertainty as to what the roles and requirements of the next generation of UAVs might be and the configurations that might be adopted. The incorporation of technological features on these designs is also a significant driving force in their configuration, efficiency, performance abilities and operational requirements. The objective of this project is thus to provide some insight into what the next generation of technologies might be and what their impact would be on the rest of the aircraft. This work involved the conceptual designs of two new relevant full-scale UAVs which were used to integrate a select number of these advanced technologies. The project was a CASE award which was linked to the Flaviir research programme for advanced UAV technologies. Thus, the technologies investigated during this study were selected with respect to the objectives of the Flaviir project. These were either relative to those already being developed as course of the Flaviir project or others from elsewhere. As course of this project, two technologies have been identified and evaluated which fit this criterion and show potential for use on future aircraft. Thus we have been able to make a contirubtion knowledge in two gaps in current aerospace technology. The first of these studies was to investigate the feasibility of using a low cost mechanical thrust vectoring system as used on the X-31, to replace conventional control surfaces. This is an alternative to the fluidic thrust vectoring devices being proposed by the Flaviir project for this task. The second study is to investigate the use of fuel reformer based fuel cell system to supply power to an all-electric power train which will be a means of primary propulsion. A number of different fuels were investigated for such a system with methanol showing the greatest promise and has been shown to have a number of distinct advantages over the traditional fuel for fuel cells (hydrogen). Each of these technologies was integrated onto the baseline conceptual design which was identified as that most suitable to each technology. A UCAV configuration was selected for the thrust vectoring system while a MALE configuration was selected for the fuel cell propulsion system. Each aircraft was a new design which was developed specifically for the needs of this project. Analysis of these baseline configurations with and without the technologies allowed an assessment to be made of the viability of these technologies. The benefits of the thrust vectoring system were evaluated at take-off, cruise and landing. It showed no benefit at take-off and landing which was due to its location on the very aft of the airframe. At cruise, its performance and efficiency was shown to be comparable to that of a conventional configuration utilizing elevons and expected to be comparable to the fluidic devices developed by the Flaviir project. This system does however offer a number of benefits over many other nozzle configurations of improved stealth due to significant exhaust nozzle shielding.The fuel reformer based fuel cell system was evaluated in both all-electric and hybrid configurations. In the ell-electric configuration, the conventional turboprop engine was completely replaced with an all-electric powertrain. This system was shown to have an inferior fuel consumption compared to a turboprop engine and thus the hybrid system was conceived. In this system, the fuel cell is only used at loiter with the turboprop engine being retained for all other flight phases. For the same quantity of fuel, a reduction in loiter time of 24% was experienced (compared to the baseline turboprop) but such a system does have benefits of reduced emissions and IR signature. With further refinement, it is possible that the performance and efficiency of such a system could be further improved. In this project, two potential technologies were identified and thoroughly analysed. We are therefore able to say that the project objectives have been met and the project has proven worthwhile to the advancement of aerospace technology. Although these systems did not provide the desired results at this stage, they have shown the potential for improvement with further development.

No description available.

Abstract After the ban against private-owned gas service stations was lifted in 1987, some domestic trading firms took advantage of the special feature of gasoline products as well as Taiwan¡¦s unique oil price structure to import low-quality oil products for blending into gasoline-equivalent products, which would then be sold to independent service station owners mushrooming in accordance with the oil market deregulation. According to the statistics of import/export at Taiwan customs and the comparison between supply and demand of relative industries, it is agreed that an annual total of approximate 400,000 kiloliters of various imported oil products would be blended into gasoline or diesels for sale. Moreover, as Taiwan government has been continuously providing a 14% oil price subsidy against a sluggish fishing industry caused by depleting fishing resources, the fishing fuels in glut, at an estimate of 410, 000 kiloliters a year, would be illegally sold as diesel in domestic gas service stations for higher profits. These practices have not only directly affected tax revenues of local governments, but also infringed upon the legal rights of petroleum refineries, putting the orderliness of petroleum production and sale in jeopardy. In addition, as such illicit practices are usually carried out near makeshift storage tanks with ineligible filling facilities, they have posed great threats to public safety and environment. As it is difficult to detect and thereby root out the underground transactions of such inferior gasoline and diesels, the police that was authorized insufficiently on legal aspects would carry out inspections at key roads and intersections only passively, which has posed but limited intimidation over illegal transactions of unqualified gasoline products. Realizing the facts, this survey takes the historical data on relative factors and market survey figures as basis for calculation and analysis, which is used then to assume the normal demand of gasoline and diesel markets and to establish a conclusive alarming model for flow direction. Besides, it obtains affecting variables such as market segmentation, channel characteristics, customer behaviors, price gap and business environments through interviews and questionnaires, to determine limits on the alarming model and the alarming value. Comparing with the actual consumption of gasoline and diesels, we can then judge if there remains any abnormality concerning the sales volume of gasoline and diesels. If any abnormal sign shown, we can check the alarming model item by item for timely management and control, so as to supervise and check the underground transactions of inferior gasoline and diesels. We also hope that the survey report on ¡§the Alarming Model over the Flow of Inferior Gasoline and Diesels and Its Application¡¨ could provide practical references for the detection and elimination of inferior gasoline and diesels so that the illicit and unsafe practice could be inhibited once and for all.

published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

The scarcity of fossil fuel and its environmental impact have shifted the world focus on green innovations At a time when the use of fossil fuel means increasing energy scarcity and an environmental crisis in the world in which we live, we need green innovations now more than ever. Growing attention has been drawn to the use of biofuels, such as bioethanol and biodiesel, which have gradually come to make up part of the total energy supply. Uncertainties about the environmental and ecological aspects of the production and consumption of biofuel still exist despite its rapid development. A life cycle analysis (LCA) evaluates the two principal functional parameters 1) energy efficiency and 2) Greenhouse Gas (GHG) balance of different feedstocks for biodiesel production from the cradle to the grave. By accounting a life cycle analysis stage by stage, we can ascertain the change in GHG emissions and energy demand that result from the various uses of feedstocks for the production of biodiesel. In this thesis, various life cycle analysis models are reviewed and evaluated with emphasis on specific biofuels. Different LCA models depend on different LCA calculation under different situations, including GREET, LEM, SimaPro, etc. The software SimaPro was used to compare the life cycle GHG emissions and energy demand from conventional petroleum fuels and several hydro-processed renewable green diesels. A consistent methodology was used for selected fuel pathways to facilitate relatively equitable comparisons. The building of life cycle flow tree in SimaPro combined the input and output with an emphasis on the following stages 1) raw material farming and acquisition, 2)liquid fuel production, 3)transport, 4)refueling, 5)liquid fuel conversion to biodiesel and 6) end uses. Consistent impact assessment methods were chosen for simulation, equitable comparisons and comprehensive analysis of selected fuel pathways for the calculation of Global Warming Potential (GWP) and Cumulative Energy Demand (CED). However, the results of the entire lifetime estimates vary dramatically in production chains, which make it difficult to take a holistic view about energy intake and yields, economic costs and values, environmental impacts and their benefits. Apart from the diversity in system boundaries and life cycle inventories, a variance in terminologies and the limitations of interdisciplinary communication are the main factors that affect the quality of the results. / published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

Respirometric experiments were performed to evaluate the role of nitrogen in aerobic diesel biodegradation. Specific objectives included 1) evaluating the effects of water potential induced by various nitrogen amendments on diesel biodegradation rates in arid region soils, 2) comparing concurrent effects of C:N ratios and soil water potential on diesel degradation rates, and 3), measuring gross rates of nitrogen cycling processes in diesel-contaminated soil to determine duration of fertilizer bioavailability. In all studies, increasing nitrogen fertilization resulted in a decrease in total water potential and correlated with an increase in lag phase and overall reduction in microbial respiration. Highest respiration and estimated diesel degradation was observed in the 250 mg N/kg soil treatments regardless of diesel concentration, nitrogen source, or soil used, suggesting an inhibitory osmotic effect from higher rates of nitrogen application. The depression of water potential resulting in a 50% reduction in respiration was much greater than that observed in humid region soil, suggesting higher salt tolerance by microbial populations of arid region soils. Due to the dependence on contaminant concentrations, use of C:N ratios was problematic in optimizing nitrogen augmentation, leading to over-fertilization in highly contaminated soils. Optimal C:N levels among those tested were 17:1, 34:1, and 68:1 for 5,000, 10,000 and 20,000 mg/kg diesel treatments respectively. Determining nitrogen augmentation on the basis of soil pore water nitrogen (mg N/kg soil H₂0) is independent of hydrocarbon concentration but takes into account soil moisture content. In the soil studied, optimal nitrogen fertilization was observed at an average soil pore water nitrogen level of 1950 mg N/kg H₂0 at all levels of diesel contamination. Based on the nitrogen transformation rates estimated, the duration of fertilizer contribution to the inorganic nitrogen pool at 5,000 mg/kg diesel was estimated at 0.9, 1.9, and 3.2 years in the 250, 500, and 1000 mg/kg nitrogen treatments respectively. The estimation was conservative as ammonium fixation, gross nitrogen immobilization, and nitrification were assumed as losses of fertilizer with only gross mineralization of native organic nitrogen contributing to the most active portion of the nitrogen pool.

The goal of this research was to design, build and test a small burner and heat exchanger system that could be used as a source of heat for thermoelectric modules (TEMs) for the purpose of generating portable electric power for soldiers in the field. The project was conducted as a subcontract to Marlow Industries Inc. which was under contract from the U.S. Army. The scale of the burner thermal output was to be in the approximate range of 2 kW of heat production and it was to be able to operate on a liquid fuel, specifically JP8. The first burner investigated was a custom burner designed and built at UT. It was tested with various fuel and air delivery systems. Different methods to start it, with the goal of developing an electrical starting system, were also investigated. It was capable of operating at outputs over 1 kW, but was difficult to start reliably and fuel vaporization characteristics were sensitive to operating conditions. Two commercial burners were also studied, each with somewhat different designs. One of those burners, manufactured by MSR, was chosen to be further tested in conjunction with a heat exchanger and thermoelectric modules. The performance of the thermoelectric modules used in this study was determined to be very dependent on an attached resistive load, with a peak power output occurring at approximately 3 ohms. Power output was also determined to increase linearly with increasing temperature difference between the hot and cold sides of the module. Power output followed similar trends as open circuit voltage. The temperatures of the heat exchanger across its width were very uniform, but the accuracy in centering the heat exchanger over the burner could significantly affect temperatures. The time to reach steady state temperatures was relatively insensitive to the length of the heat exchanger. The presence of attached thermoelectric modules reduced the temperature of the heat exchangers and exhaust gas slightly. Reducing the heat exchanger length resulted in higher metal temperatures. Without cooling the cold side of the thermoelectric modules, performance increased while the system was heating up, but then dropped after reaching a peak. Cold side cooling improved thermoelectric performance by increasing its temperature difference. Active cooling with a blower and heat sink provided even better performance than passive cooling using just a heat sink at the expense of a larger parasitic load. The TEMs on the 5 inch long heat exchanger could generate 6.32 W with passive cooling, but active cooling would produce no net power. The 11 inch long heat exchanger could generate 12.8 W with passive cooling, and 16 W net could be generated with active cooling. A heat exchanger efficiency calculation showed that the 16, 11 and 5 inch long heat exchangers were about 94.4%, 93.4%, and 90.7% efficient respectively. This efficiency was defined as the ratio of the heat transferred to the heat exchanger to the heat released in the flame. / text

Recent optimistic revisions to projections for recoverable natural gas resources in the United States have generated renewed interest in the possibility of greater utilization of natural gas as a transportation fuel. Against a backdrop of significant policy challenges for the United States, including air quality concerns in urban areas, slow economic growth and high unemployment, and a rising unease with regard to an increasing dependence on foreign oil; natural gas offers the nation’s transportation sector an opportunity to reduce mobile emissions, lower fuel costs, create jobs and reduce dependence on imported oil. While the current focus for expanded use of natural gas in the transportation sector emphasizes heavy duty and fleet vehicles, there may also be potential for increased use for passenger vehicles. Inconvenience, with regard to refueling, and high incremental vehicle costs, however, are seen as major obstacles to greater adaptation. This analysis examines the benefits and drawbacks of natural gas vehicles from the passenger vehicle perspective and includes data from a cross-country road trip. The report includes a review of market trends and possible development scenarios and concludes with recommendations to minimize the potential challenges of greater adaptation of natural gas vehicles in the passenger vehicle market. / text

No description available.

South Africa produces alternative fuels from a number of different sources. The properties of a fuel are known to affect the nature of combustion in compression-ignition engines significantly, and have occasionally resulted in engine failures. Combustion analyses have been conducted on a wide range of fuels and combustion has been thoroughly quantified. However, the role played by the different combustion variables in failures was not known. The result was that it was not possible to predict the implications of variations in the nature of combustion. There was thus a need to investigate the relative role of combustion variables in the failure of engines. The mechanisms of combustion and engine failure were studied. All the variables required to determine combustion and engine durability were measured simultaneously. This research required the development of a complete engine research facility as well as specialized transducers. Fast response surface thermocouples were designed and constructed in order to monitor transient surface temperatures. Heat transfer rates were then calculated with the aid of Fourier analysis. Dynamic stresses were monitored by strain-gauges applied to the engine. A special high speed data acquisition system was developed. An existing heat release model was modified and used to calculate combustion rates. A comprehensive finite element model was developed to calculate piston temperatures and stresses. The role of each combustion variable in stress and durability was investigated by statistical analysis. The results successfully identified the causes of combustion related engine failures. The primary cause of engine failure was found to be thermal loading. The principal cause of any variation in thermal loading and thus engine durability was maximum cylinder pressure. The life of the engine was proved to be determined almost entirely by peak cylinder pressure. The role of the rate of pressure rise was proved to be insignificant. All the implications of variations in the nature of combustion can now be determined accurately. It will thus be possible to optimise engine modifications and fuel properties before validation by durability testing. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1989.