The desire to gather acoustic data of a propeller in simulated hover without environmental effects is met with the challenge of recirculating flow in a closed anechoic chamber. Flow recirculation in an anechoic chamber is not ideal because the effects of it being ingested by the rotor cause unsteady loadings on the propeller. This unsteady loading causes vortex noise from the turbulence introduced by the recirculation of the flow. The aim is to study the acoustic signature of a propeller separate from external factors and engine noise. Two different propellers with three different screen combinations were tested in a closed anechoic chamber. The results of these tests showed that the screens are able to reduce the vortex and broadband noise levels, with the reduction being more pronounced when the dual screen was installed.

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I strävan efter att minska textilindustrins omfattande miljöpåverkan utvecklas nya metoder för textilåtervinning. Idag återvinns bomullstyg av Renewcell på deras anläggning i Kristinehamn. Den återvunna produkten, Circulose®, är en dissolvingmassa som kan användas för att spinna nya viskosfibrer som man i sin tur kan använda för att göra nya kläder. Föreliggande arbete är en förstudie om möjligheten att optimera Renewcellls återvinningsprocess. Arbetet inkluderar en optimering av massaprocessen vilket resulterar i en mer effektiv process som minskar förbrukningen av processkemikalier. / To reduce the extensive environmental impact of the textile industry, new methods for textile recycling are being developed. Today, cotton-based fabric is recycled by Renewcell at their facility in Kristinehamn. The recycled product, Circulose®, is a dissolving pulp that can be used to spin new viscose fibers, which in turn can be used to make new clothes. The present work is a feasibility study on the possibility of optimizing Renewcell's recycling process. The work includes an optimization of the pulp process, which results in a more efficient process with a reduced consumption of process chemicals.

In aquaculture, biosecurity consists of policies, procedures and measures used to prevent or control the spread of fish disease. The focus of this research was the practice of biosecurity in the recirculation sector of finfish aquaculture in the United States and Canada. Specifically, this research: 1) identified and characterized finfish recirculation facilities in the United States and Canada; 2) assessed biosecurity utilization in these facilities; 3) examined the relationship between biosecurity utilization and fish culture variables; 4) examined the relationship between biosecurity utilization and socio-demographics of personnel operating these facilities; 5) described the attitudes, perceptions and beliefs about fish disease and biosecurity utilization of personnel, and 6) described the lived-experience of biosecurity practice of workers at these facilities. This research was comprised of two separate components using different methodologies. The first component was a self-administered, mail-back questionnaire sent to the managers of 152 finfish recirculation facilities in the United States and Canada in fall of 2001. The second component was a series of in-depth interviews conducted with 31 workers at 12 salmonid recirculation facilities in spring of 2002. Grounded theory methodology was used for the interview process and subsequent data analysis for the second component. An 86% response rate was achieved in the mail survey. Aquaculture activities using recirculation technologies were quite varied in purpose of operation, size of production, and life stages held. Four groups of fishes dominated the recirculation sector and constituted the primary production of over 45% of this sector of aquaculture. This sector was heavily reliant on ground water resources. Forty-one percent of finfish recirculation facilities did not have a secondary source of water supply. Biosecurity utilization is not homogenous within the recirculation sector. Frequency of biosecurity utilization was related to primary water source, type of fish grown, purpose of the operation and country of operation. Biosecurity was an important concern of facility operators, although among facility operators there were differences in perception of disease risk and benefits of biosecurity utilization. Analysis of results of this study resulted in formulation of the Practice of Biosecurity Theory (PBT). The theory describes a three-phase process in the practice of biosecurity: (1) orientation, when workers begin their initiation into the practice of biosecurity; (2) routine, when practice of biosecurity becomes a habitual behavior; and (3) thoughtful approach, where knowledge of fish health needs and biosecurity practices are integrated into a repertoire of biosecurity strategies that are situation- and site-specific. The practice of biosecurity was affected by three environmental conditions; personal biography, management's role, and peer pressure. This research gives educators, extension agents, researchers and government policy-makers a quantitative description of finfish recirculation aquaculture in the United States and Canada. It also provides baseline information on biosecurity utilization in recirculation aquaculture. This research provides insight into the human dimensions aspect of the practice of biosecurity and, therefore, may have application to other areas of agri-business. / Ph. D.

The objective of this paper is to evaluate the effectiveness of leachate recirculation and bioreactor landfills at enhancing biodegradation, and to optimize the operation of a bioreactor. Waste Management has been examining leachate recirculation landfills for several years. Samples of Municipal Solid Waste (MSW) from existing leachate recirculation (LR) landfills were collected and analyzed for several physical and biochemical properties. These parameters of interest were moisture content, pH, density, temperature, volatile solids, cellulose/lignin ratios, and biological methane potential (BMP). Leachate recirculation increased the dry density 55% faster and decreased the BMP 125% more rapidly. Moisture content was the biggest factor influencing overall degradation. Therefore, leachate reciculation effectively increases biodegradation of MSW in landfills. Waste Management built a pilot-scale bioreactor in Franklin, WI, which was sampled for one year. It contained a bioreactor side and a control side. The volatile solids, cellulose, and BMP degradation rates for the bioreactor were increased by 56%, 87%, and 271% versus the control, respectively. Moisture content was the biggest factor influencing overall degradation. The column study is designed to optimize three parameters under the control of an operator: moisture content, initial aeration period, and biosolids addition. The optimum moisture content is above 45%, but it is not safe to operate heavy equipment on refuse with greater than 45% moisture. Initial aeration did not speed up the overall degradation, but it did shorten the acidogenic phase. Finally, biosolids did not have a significant effect on degradation rates. The columns maintained an average temperature of 70oF. / Master of Science

Anaerobic digestion is one of the most promising management options for dairy manure treatment. Manure wastewater from dairy farms has been used for methane production for decades. However, performance failure due to inadequate mixing is routine. In general, the mixng of anaerobic digester is achived throguh mechnical stirring, liquid circulation, and gas circulation, among which the gas circulation proves to be the most effcient way. In this work, we studied the liquid flow pattern of two differetn type of gas-circualtion based anaerobic digesters, with the aim to understand the effects of hydrodynamic behavior of the digesting liquid on the anaerobic digestion performance, so a better mixing strategy can be provided. We used two 20-L gas circulation based anaerobic digesters with confined (gas-lift) and unconfined (bubble column) design. The anaerobic digestion performance and mixing behaviors were studied at different gas recirculation rate. It was found that the biogas production from the bubble column was constantly higher than that from gas-lift digester. However, the overall flow of the two digesters, which is indicated by residence time distribution (RTD), showed a similar pattern. Furhter investigation of local liquid flow behavior using Computational Fluid Dynamic (CFD) indicate that the bubble column accumulated higher portion of sludge in the bottom of the digester, which has a higher TS and VS, COD, and biomethane production potential than those from the gas-lift digester. This is the reason that the biogas production from the bubble column is higher than the gas-lift digester. Through this study, a thorough characterization of the flow behavior of the anaerobic digester were developed, and provided a deep insight of its influence on the anaerobic digestion performance. / Master of Science

<p dir="ltr"> Diesel engines are widely used in various off-road settings, ranging from railroad locomotives and marine vessels to agricultural, construction, logging, and mining equipment. Diesel engines are favored due to their reliability, durability, high thermal efficiency, and capacity to generate significant power. However, they also emit a range of harmful pollutants, such as oxides of nitrogen (NOx), particulate matter (PM), carbon monoxide (CO), and hydrocarbons (HC). Over the past three decades, original engine manufacturers have faced increasingly stringent emission regulations. In the United States, the proposed Tier 5 emission standards aim to achieve a significant reduction in NOx emissions, targeting a reduction of up to 90%, as well as a reduction in particulate matter emissions of up to 75%. To meet these stringent regulations, original engine manufacturers are investigating new technologies.</p><p dir="ltr"> Cooled exhaust gas recirculation (EGR) is a widely used method to lower NOx emissions. The EGR flow rates are contingent on positive engine delta pressure (exhaust manifold pressure - intake manifold pressure) to drive EGR. Eaton’s Generation 3 Exhaust Gas Recirculation Pump (EGRP) eliminates the need for positive engine delta pressure and enables the application of a high-efficiency turbocharger. A high-efficiency turbocharger reduces the pumping work and thus improves fuel efficiency.</p><p dir="ltr"> Transient tests were conducted on a 13.6 L S750 John Deere Engine with both the stock hardware and the EGRP and high-efficiency turbocharger hardware, to evaluate the benefits of the new technology. The transient tests included the Constant Speed Load Acceptance Test (CSLA), the Nonroad Transient Cycle (NRTC), and the Low Load Application Cycle (LLAC). There was no aftertreatment systems in the test cell setup, so engine-out brake specific oxides of nitrogen (BSNOx) and engine-out brake specific particulate matter (BSPM) were examined. To evaluate the technology, results from the stock hardware setup were compared to the results from the EGRP and high-efficiency turbocharger setup.</p><p dir="ltr"> During the CSLA, the time response to 90% load with the EGRP-equipped engine was <a href="" target="_blank">generally slower</a> than the stock engine, with deviations ranging from 0.1s to 1.6s. This result was attributed to the EGR pump not reducing speed fast enough, resulting in insufficient fresh air to produce torque. In the NRTC, engine torque was compared between both configurations. It was discovered that the EGRP-equipped engine did not reach the desired torque setpoints. There was more EGR flow than expected and not enough fresh air. This pattern was also revealed in the LLAC.</p><h4> To ensure accurate comparisons, measured engine speed and load data from the EGRP configuration were used to establish a Modified NRTC and Modified LLAC. For the Modified NRTC, the brake specific fuel consumption (BSFC) improved by 1.3%, and the engine-out brake specific particulate matter improved by 33.1% with the EGRP and high-efficiency turbocharger. However, the engine-out BSNOx increased by 12.9%. For the Modified LLAC, the BSFC and engine-out BSNOx improved by 2.5% and 11.1%, respectively, with the EGRP setup. However, this improvement came at the expense of engine-out BSPM, which increased by 34.2%. The improvement in BSFC for both cycles could be attributed to the increased open-cycle efficiency seen in steady state data with the EGRP and high-efficiency turbocharger.</h4><p></p>

Landfill leachate characteristics vary depending on the operation type of the landfill and the age of the landfill. At landfills operated as bioreactors, where leachate recirculation is practiced, leachate ammonia nitrogen concentrations may accumulate to extremely higher levels than during single pass leaching, thereby requiring treatment before final discharge to a receiving system (Onay, 1998). Usually several physical/chemical wastewater treatment technologies are used to treat the leachate. In most cases the COD and BOD are treated, and then nitrification is performed in a separate sophisticated ex situ system. The additional costs of these systems can be very high. The use of a readily available media for in situ nitrification should be considered a prime objective to avoid extra costs. The possibility of removing ammonia nitrogen from bioreactor landfill leachate using trickling filter biofilm technology was studied in four laboratory scale reactors filled with four different types of packing media. The different packing media were examined to see which media is the most efficient at supporting ammonia removal biofilms. The highest efficiency was achieved by a packing media consisting of pine wood chips. The effects of varied concentration loading, varied hydraulic loading, and nitrification inhibitors were studied. Varied ammonia concentration did not have a huge impact on the ammonia removal rates (77-87%) in the reactor with pine wood media. The ammonia removal rates showed a strong dependence on hydraulic loading rate with the lowest loading rate producing the highest removal rates. Landfill leachate from the Middle Peninsula Landfill in Glens, Virginia was determined not to contain nitrifying inhibitors. Using a wood media filter chip and a low hydraulic loading rate was determined to be the best method to remove ammonia nitrogen from landfill bioreator leachate. / Master of Science

Rocket pump inducers are studied with a Navier-Stokes solver, the Moore Elliptic Flow Program, MEFP. Two redesigns of the Rocketdyne ADP inducer are performed. The first redesign changes the hub-tip ratio from 0.3 to 0.4. The second redesign influences the leading edge tip region. This part of the blade is rounded off in a meridional view, resulting in an increased sweep angle over the outer 30 percent of the blade height. Inlet recirculation and cavitation performance are the main concern of this thesis. The literature review focuses on these two areas and on previously performed inducer calculations. The calculation grid of the original design was altered for the two redesigns using a C-program. Then the new designs were investigated at three different flow rates: 110%, 100%, and 89%. Computational results were available at the same flow rates for the original design. The comparison of the results showed that the performed design changes did not significantly influence the recirculation performance. In fact for the redesign with the rounded-off leading edge the backflow increased. The cavitation performance showed some interesting changes. For both redesigns the minimum pressure was raised significantly. The case of the rounded-off leading edge showed an increase in minimum pressure at the leading edge and a decrease of minimum pressure over the rest of the leading edge height, thus resulting in probably better cavitation performance. A theory was presented that gives a possible explanation for the occurrence of inlet recirculation. The calculation results for the design changes of the Rocketdyne inducer are consistent with the theory, but the theory does not correctly predict the different recirculation performance of an SEP inducer. / Master of Science