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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Rate of pressure rise during combustion of diesel fuels

Hurn, R. W., January 1947 (has links)
Thesis (M.S.)--University of Wisconsin--Madison, 1947. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Flow system modeling with applications to fuel cell systems

Shaffer, Christian Edward. January 2005 (has links)
Thesis (M.S.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains xii, 111 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 100-102).

Process parameters and conditions for batch production of eco-fuel briquettes

Pilusa, Tsietsi Jefrey 04 September 2012 (has links)
M.Tech. / In this work, eco-fuel briquettes made from a mixture of 32% spent coffee grounds, 23% coal fines, 11% saw dust, 18% mielie husks, 10% waste paper and 6% paper pulp contaminated water, respectively were investigated. Various processing stages such as briquetting, drying, combustion and flue gas emissions were investigated in order to evaluate the socio-economic viability of the batch production of eco-fuel briquettes from biomass waste material. Each stage was studied independently in order to develop basic models that contained material and energy balances. A screw press briquetting machine was designed and fabricated as part of this work to be tested against the legacy foundation Porta press, and the Bikernmayer hand brick press. The compaction of the biomass waste material into briquettes follows the principle of physical interlocking of the fine particles within the plant fibres, natural material binding due to released cellulose content, as well as reduction in porosity, due to a simultaneous dewatering and compaction action. The processing variables such as cycle times and pressure were studied. The Bikernmayer press is preferred as it produced briquettes of higher bulk densities and lower moisture content as compared to the other presses. The drying was investigated in a laboratory scale convective dryer to establish typical convection parameters. A drying system that utilizes produced briquettes as a heating medium is proposed, and here drying will be effected over a refractory brick fireplace by means of convection and radiation. A basic model was set up to include radiation with the convection to predict a drying time of 4.8 hours. The combustion of briquettes was investigated using a POCA ceramic stove linked to the testo Portable Emission Analyzer System. This enabled an air-to-fuel ratio of 1.44 and a burning rate of 2g per minute to be established. The energy transfer efficiency for boiling a pot of water was found to be 85%. The gas emissions were found to be within the acceptable limits, as set out by OSHA. A standard initial economic evaluation was performed based on a briquette selling price of R2.26 per kilogram for the ease of accommodating the local market. The financial model for both Porta press and screw press were not economically viable, as their running costs were greater than the gross project revenues. For the Bikernmayer conceptual model, with a total capital investment of R669, 981+ VAT (this includes one year operating cost) and a project life of five years, the gross Process parameters and conditions batch production of eco-fuel briquettes profit margin is 44%, the profitability index is 5.33 and the internal Rate of return 31.44%. The net present value and return period are R676, 896 and 0.408 years respectively. The customer profile as currently at hand is 17% of the selected area within 80 m radius from production site. The remaining 83% will be in need of energy as they become aware of the new product offering. The selling of the briquettes should be accompanied by an education process, to avoid the dangers of heating indoors. The principal driver for this project is socio economic development and it is being strengthened by Eskom’s inability to provide sufficient energy. A secondary driver is the global drive to reduce emissions and fossil fuel usage; this technology does exactly this whilst diverting waste from landfill. In the Polokwane declaration (2008), it is stated that South Africa will have no calorific waste to landfill by 2014. Hence legislation will also provide a major part of the drive.

Cesium hydrogen sulphate and cesium dihydrogen phosphate based solid composite electrolyte for fuel cell application.

Naidoo, Sivapregasen January 2004 (has links)
No abstract available.

Modelling catalyst layers in PEM fuel cells : effects of transport limitations and non-uniform platinum loading

Schwarz, David Hans. 10 April 2008 (has links)
No description available.

Investigation of a U-shaped fuel cell flow channel with particle image velocimetry (PIV)

Martin, Jonathan Jackie. 10 April 2008 (has links)
Flow through an experimental model of a U-shaped flow channel is used to investigate the hydrodynamic phenomena that occur within serpentine reactant transport channels of fuel cells. Achieving effective mixing within these channels is crucial for the proper operation of the fuel cell and proper understanding and characterization of the underlying fluid dynamics is required. Particle image velocimetry (PIV) is used to investigate the three-dimensional structure of the flow by analyzing the velocity and associated vorticity field over two perpendicular channel cross-sections. A range of Reynolds numbers, 109 I Re I 872, corresponding to flow rates encountered in a fuel cell operating at low to medium current densities is investigated. The effect of the flow rate is characterized in terms of the instantaneous and time-averaged representations of the velocity vectors, out-of-plane vorticity and the velocity streamlines. At the lowest Reynolds numbers, the flow is steady and is characterized by high vorticity regions associated with shear layers separating from the sharp convex comers of the U-bend and reattaching on downstream surfaces. The flow also exhibits the classical secondary Dean flow pattern with two symmetric circulation zones. Transition takes place in the range 381 I Re I 436 as the two recirculation zones, which originally develop in the U-bend region, merge into one separation region. This transition is accompanied by the generation of additional vortices in the secondary flow plane. The relationship between the flow in both planes and the transition is examined along with properties of the instability including RMS, Reynolds stress, and the oscillation frequency. The quantitative flow visualization results obtained presented here should be useful in guiding numerical models of fuel cells, and indicate that the commonly used assumption of steady laminar flow should be revisited, and alternative models developed.

Algorithm development for electrochemical impedance spectroscopy diagnostics in PEM fuel cells

Latham, Ruth Anne. 10 April 2008 (has links)
No description available.

Operation optimisation towards generation efficiency improvement in Saudi Arabia using LSS, simulation and mathematical programming

Althaqafi, Mohammad January 2017 (has links)
The efficiency of fossil power generation has improved in recent decades with the different types of fuel and advancing technologies playing a crucial role in this trend. The Kingdom of Saudi Arabia (KSA) is considered among the lowest countries in the world in terms of generation efficiency. As a consequence, recent studies have proposed upgrading the generation stock with highly efficient units, and increasing the share of natural gas over oil to improve the average efficiency. However, despite efforts being made in that direction in the past few years, they have not had a significant impact and there have been few studies in the literature aimed at tackling what the real issues are in the kingdom. This research explores the causes leading to the current level of energy efficiency in KSA using Lean Six Sigma (LSS) and a simulation model, subsequent to which a new framework is developed aimed at delivering sustained continuous improvement. Firstly, LSS is applied to identify the primary area of waste and secondly, the actual efficiency is measured using real data collected from KSA. Subsequently, the outcomes are analysed through utilising a simulation model that has been designed and tested to ensure accurate results are obtained. Following this, an improvement plan is proposed using mathematical models and mathematical programming, which was implemented using a simulation model. Finally, controlling the obtained improvement is included for sustaining its continuity. The main contribution of this thesis lies in the integration of LSS and a simulation model to identify the most influential factors in relation to the generation efficiency level in KSA in terms of their impact on fuel and emissions. Moreover, this research involves developing a new merit order using a mathematical model and mathematical programming for optimisation. The novelty can be seen in combining the quality and quantity of production to generate a single operation measure. The results show that the power plants' operation is a primary cause of the current level of efficiency, while the generation stock has the potential to deliver higher efficiency levels. Around 3.5 and 6% improvement in efficiency have been achieved over the two research stages. This figure has resulted in a fuel saving worth $1.8 billion, significant reduction in subsidies and 8.5 Mtonnes reduction in the total CO2 produced. Finally, this thesis provides a framework based on incentives for power providers that can ensure continuous improvement.

Life assessment of rubber articles in fuels

Selldén, Emmy January 2013 (has links)
The choice of rubber material for use in sealings and hoses in the fuel system is of great importance. If a wrong type of rubber is used, premature failure during service may occur. This impacts the environmental performance, the safety during driving, uptime and economy of the transport. In this diploma work, rubbers for use in sealing and hoses in the fuel system have been evaluated to assess which materials have the potential to be used under long-term use in contact with commercial fuels.   Three commercial fuel hoses, nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), ethylene-acrylic rubber (AEM) and fluorocarbon rubber (FKM) of varying types and compositions have been evaluated in diesel with 7% RME (rapeseed methyl ester), 100% biodiesel of RME and ethanol fuel. Tests were performed by immersing the materials in fuel and measure the compression set and changes in properties like volume, hardness, tensile strength and elongation at break.   The results showed that one NBR material, one AEM and all FKM are potential materials for long term use in diesel with 7% RME. All types of NBR and two types of FKM (terpolymers, peroxide cured) may be used in ethanol fuel. NBR and HNBR were the only rubbers evaluated in biodiesel. NBR and HNBR with an ACN content of ~30% might be used in 100% RME at lower temperatures for shorter periods. The aging resistance in air was good for HNBR, AEM and FKM but poor for NBR. Life assessment of rubber articles in fuels

A survey of current advances in fuel cell technology

White, Clifford Martin, 1924- January 1961 (has links)
No description available.

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