22 research outputs found
A study of universal elements in classes of bases of topological spaces
Get PDFsummary:The universality problem focuses on finding universal spaces in classes of topological spaces. Moreover, in ``Universal spaces and mappings'' by S. D. Iliadis (2005), an important method of constructing such universal elements in classes of spaces is introduced and explained in details. Simultaneously, in ``A topological dimension greater than or equal to the classical covering dimension'' by D. N. Georgiou, A. C. Megaritis and F. Sereti (2017), new topological dimension is introduced and studied, which is called quasi covering dimension and is denoted by . In this paper, we define the base dimension-like function of the type dim, denoted by {b} - {dim}, and study the property of universality for this function. Especially, based on the method of ``Universal spaces and mappings'' by S. D. Iliadis (2005), we prove that in classes of bases which are determined by {b} - {dim} there exist universal elements
Catalytic exhaust gas fuel reforming for diesel engines - effects of water addition of hydrogen production and fuel conversion efficiency
No full textPrevious work in our laboratory has shown that the exhaust gas assisted fuel reforming process has the potential to provide a solution to the diesel engine exhaust emission problems. When simulated reformer product gas rich in hydrogen is fed to the engine, a reduction of both NO, and smoke emissions can be achieved. In this paper, the optimisation of the reforming process by water addition in the reactor is presented. Using a prototype catalyst at 290degreesC reactor inlet temperature, up to 15% more hydrogen in the reformer product was obtained compared to operation without water. The process has been found to be mainly a combination of the fuel oxidation, steam reforming and water gas shift reactions. The reforming process efficiency has been shown to improve considerably with water addition up to a certain level after which the adverse effects of the exothermic water gas shift reaction become significant. (C) 2004 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved
Partially premixed charge compression ignition engine with on-board H-2 production by exhaust gas fuel reforming of diesel and biodiesel
No full textThe application of the exhaust gas fuel reforming process in diesel engines has been studied experimentally as a way to assist the premixed charge compression ignition operation by substituting part of the main fuel with hydrogen-rich gas. The technique involves the injection of hydrocarbon fuel into a catalytic reformer fitted into the exhaust gas recirculation (EGR) system, so that the produced gas mixture is fed back to the engine as reformed EGR (REGR). First, experiments with simulated REGR were conducted with diesel as well as biodiesel as the main engine fuel. Then, experiments with the product gas of a monolith reformer were carried out. In both cases, REGR resulted in a higher premixed combustion rate and reduction of the diffusion combustion phase. The potential of the technique in terms of achieving reduction of smoke and NO., emissions and improved fuel economy has been shown and discussed in the paper. (c) 2004 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved
Correction: The effect of COVID rehabilitation for ongoing symptoms Post HOSPitalisation with COVID-19 (PHOSP-R): protocol for a randomised parallel group controlled trial on behalf of the PHOSP consortium (Trials, (2023), 24, 1, (61), 10.1186/s13063-023-07093-7)
No full text\ua9 2023, The Author(s).Following publication of the original article [1], it was noticed that the author name Dimitrios Megaritis was incorrectly written as Dimitrios Magaritis. The author group has been updated above and the original article has been corrected
Exhaust gas assisted reforming of rapeseed methyl ester for reduced exhaust emissions of CI engines
No full textThe nitrogen oxides (NO,) emissions of compression ignition (CI) engines fueled with biodiesel are generally higher compared to conventional diesel fuelling. Previous research work in CI engines has shown that the partial replacement of hydrocarbon fuels by hydrogen combined with exhaust gas recirculation (EGR) can reduce NOx and smoke emissions without significant changes to the engine efficiency. In the present study, the production of hydrogen-rich gas by catalytic exhaust gas assisted fuel reforming of rapeseed methyl ester (RME) has been investigated experimentally as a way to provide the required hydrogen for the reduction of biodiesel emissions. For comparison, tests with ultra low sulphur diesel (ULSD) were also performed. The reforming experiments were carried out in a mini reactor supplied with exhaust gas from a single cylinder Cl engine. In all cases, the reactor inlet temperature was kept at 290degreesC which was chosen as a typical low exhaust gas temperature of diesel engines operating at part load. The engine operating condition (speed, load) was the same in all the tests and the reactor product gas was examined as a function of the reactor fuel flow rate and the composition of fuel and engine exhaust gas. Up to 17% hydrogen content of the reformer product was achieved and the results indicated that the main reactions in the reformer were the exothermic complete oxidation of part of the fuel and the endothermic steam reforming reaction. Reforming of RME produced more hydrogen with higher fuel conversion efficiency compared to ULSD reforming. (C) 2004 Elsevier Ltd All rights reserved
Diesel exhaust-gas reforming for H2 addition to an aftertreatment unit
Get PDFThis is the post-print version of the final paper published in Chemical Engineering Journal. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2008 Elsevier B.V.The work described in this paper has been undertaken as part of the design of an integrated system comprising a diesel engine, an exhaust-gas fuel reformer and a NOx aftertreatment unit. The exhaust-gas reformer is used to provide hydrogen-rich reformate to the NOx aftertreatment unit, containing a hydrocarbon-SCR catalyst, in order to improve its NOx reduction activity at low exhaust-gas temperatures. The reformer configuration and operating parameters have been examined in order to optimise the performance of the hydrocarbon-SCR catalyst, which is promoted by the presence of H2 but inhibited by CO. The length of the catalyst bed inside the reformer is a key factor in determining the extent to which the water-gas shift reaction can contribute to the reforming process, and therefore strongly influences the proportions of CO and H2 in the reformate. However, it is also necessary for the reactant ratios at the reformer inlet to be controlled in response to changes in the engine operating conditions. In practice, this means that the rate of fuel addition to the reformer needs to be optimised for different exhaust gas compositions and space velocities
Low temperature exhaust gas fuel reforming of diesel fuel
No full textThe application of exhaust gas assisted fuel reforming in diesel engines has been investigated. The process involves hydrogen generation by direct catalytic interaction of diesel fuel with engine exhaust gas. Using a laboratory reforming mini reactor incorporated in the exhaust system of a diesel engine, up to 16% hydrogen in the reactor product gas was achieved at a reactor inlet temperature of 290 degreesC. The results showed that such levels of hydrogen can be produced with appropriate control of the reaction parameters at temperatures typical of exhaust gas temperatures of diesel engines operating at part load without any requirement for external heat source or air and steam supply. The use of simulated reformed fuel was shown to be beneficial in terms of engine exhaust emissions and resulted in reduction of NOX and smoke emissions. (C) 2004 Elsevier Ltd. All rights reserved
A study concerning splitting and jointly continuous topologies on C(Y, Z)
No full textLet Y and Z be two xed topological spaces and C (Y,Z) the set of all continuous maps from Y into Z. We construct and study topologies on C(Y,Z) that we call Fn(Tn)-family-open topologies. Furthermore, we find necessary and sufficient conditions such that these topologies to be splitting and jointly continuous. Finally, we present questions concerning a further study on this area.Keywords: Function spaces, splitting topology, jointly continuous topolog
A class of topological spaces between the classes of regular and urysohn spaces
No full textAbstract
The notion of rU-space is given and investigated. A space X is said to be a rU-space if X is a Hausdorff space and for every x ∈ X and every open neighbourhood V of x there exists an open neighbourhood U of x such that U ⊆ Cl(V) and Bd(U) ⊆ V. The class of rU-spaces is properly placed between the classes of regular and Urysohn spaces.</jats:p
Application of exhaust gas fuel reforming in diesel and homogeneous charge compression ignition (HCCI) engines fuelled with biofuels
No full textThis paper documents the application of exhaust gas fuel reforming of two alternative fuels, biodiesel and bioethanol, in internal combustion engines. The exhaust gas fuel reforming process is a method of on-board production of hydrogen-rich gas by catalytic reaction of fuel and engine exhaust gas. The benefits of exhaust gas fuel reforming have been demonstrated by adding simulated reformed gas to a diesel engine fuelled by a mixture of 50% ultra low sulphur diesel (ULSD) and 50% rapeseed methyl ester (RME) as well as to a homogeneous charge compression ignition (HCCI) engine fuelled by bioethanol. In the case of the biodiesel fuelled engine, a reduction of NOx emissions was achieved without considerable smoke increase. In the case of the bioethanol fuelled HCCI engine, the engine tolerance to exhaust gas recirculation (EGR) was extended and hence the typically high pressure rise rates of HCCI engines, associated with intense combustion noise, were reduced. (C) 2007 Elsevier Ltd. All rights reserved
