Literatura académica sobre el tema "Hydrogen injection"

The purpose of this investigation was to determine whether hydrogen injected into a diesel internal combustion engine has the potential to reduce overall fuel consumption. The most economical means of performing the required tasks was used whenever possible in an attempt to mimic a small off-grid application. The genset was a small 4kW compression ignition diesel. The electrolyzer was an off-the-shelf model designed for automotive applications. It combines hydrogen and oxygen output and is currently found from many manufacturers over the internet. It was found that the H2/02 mixture actually did help conserve fuel by about 18% in a low load case but generally, savings were under 5%. At a higher proportion of generator rated load, fuel consumption was shown to increase with H2/02 injection by up to 5%, thus the H2/02 output must be optimized to achieve any savings. Reasons for this phenomenon are discussed and recommendations for further research are included.

The objective of this research was to investigate analytically and experimentally the use of free radicals for ignition and flameholding in supersonic flows. An analytical investigation of the effects of adding small quantities of radicals to a stoichiometric mixture of hydrogen and air was performed using a finite-rate chemical kinetics code. The results of these calculations indicate that small additions of hydrogen atoms, oxygen atoms, nitrogen atoms, or hydroxyl radicals are effective in promoting ignition. These analytical results were qualitatively verified in a Mach 2 flow experiment using hydrogen atoms generated by a plasma torch. The supersonic combustion tests were conducted in a direct-connect mode at atmospheric pressure with either ambient temperature air or burner-heated vitiated air with total temperatures from 1200 to 4000 R. Both semi-freejet and ducted configurations were used. The experimental results indicate that hydrogen atoms from a low-power plasma torch provide an effective ignition and flameholding source for hydrogen-fueled Mach 2 flows at total temperatures as low as 1065 R, the lowest temperature tested. A reduction in the minimum total temperature required for ignition of several hydrocarbon fuels was also demonstrated. A piloted fuel injector configuration designed to take maximum advantage of the hydrogen atoms from the plasma torch was conceived and fabricated. The injector design consisted of five small upstream pilot fuel injectors, a rearward-facing step and three primary fuel injectors downstream of the step. The hydrogen atoms from the plasma torch were injected in the recirculation region downstream of the step. Three other ignition sources were also tested as comparisons: an argon plasma, a pyrophoric mixture of silane and hydrogen, and a surface discharge device. Hydrogen-fueled supersonic combustion tests were conducted at conditions similar to those described earlier. Hydrogen atoms generated by the plasma torch proved to be the most effective ignition source, causing ignition for a torch input power of 780 W, the lowest power tested. The combination of the hydrogen atoms and the piloted fuel injector was shown to be a very effective igniter and flameholder for scramjet operation over a simulated flight envelope (Mach 3 to Mach 6, low to moderate altitudes).<br>Ph. D.<br>incomplete_metadata

Iron is an essential micronutrient for the growth of planktonic species. It is an integral element of numerous enzymes and proteins with important functions in photosynthesis and respiratory electron transport. In contrast to iron, hydrogen peroxide (H202) is ubiquitous in seawater. Phytoplankton are known to generate reactive oxygen species (ROS) such as superoxide and H202 . This production, in conjunction with membrane bound reductases, may affect an organism's ability to access nutrients such as iron. The work presented in this thesis describes the development and optimisation of sensitive flow injection-chemiluminescence techniques to assess redox processes at the cellular level and their application to investigate marine processes. Two flow injection methods, one based on direct sample injection and another involving the preconcentration of iron, were used to determine iron (II) and dissolved iron and assess potential interference from a number of metals and H202. The results demonstrated the increased oxidation of Fe(II) in the presence of H202 (half life reduced from 10.4 to 3.5 min at 50 nM H202) and confirmed the ability of the pre-concentration method to remove this matrix interference. The accuracy and precision of the pre-concentration method were confirmed through analysis of samples collected on two international intercomparison studies. The results demonstrated that the method was precise (- 8 %RSD) and provided a suitably low limit of detection (17 pM) for the determination of dissolved iron. Dust deposition is an important source of iron to remote open ocean regions. The solubility of iron and aluminium in North Atlantic waters was assessed through an on-deck dissolution experiment. Calculated solubilities of iron released from six differing dust samples were low and varied from 0.001 to 0.04 %, whereas the release of aluminium ranged from 0.06-9.0 %. Solubility was inversely correlated with particle concentration, where higher solubility was observed for lower particle concentrations. A versatile and adaptable FI system was developed, with a low detection limit (0.4 - 1.3 nM), excellent precision (1.1-1.8 %RSD) and the capability of sensitive real-time determination of H202 over a wide dynamic range. The results from laboratory based assays using a novel in-line filter approach demonstrated H202 production by the diatom species Thalassiaira ueiss weissflogii with observed concentrations in the range 30- 100 nM. In addition, through field studies carried out in two different oceanic regions (English Channel and Ross Sea), a previously unreported correlation between phytoplankton biomass and surface H20 1 concentrations was observed. The FI-CL instrumentation for the determination of Fe(II) was successfully adapted and optimised for the continuous in-line measurements of Fe(II) generated by diatoms. This technique provided a low detection limit (11 pM) and excellent precision (6.3 ± 3.2 % RSD). In further laboratory based assays with T. ueissflogii, preliminary results indicated pM changes in Fe(II) generation following the reduction of organically bound Fe(Ill).

Experiments were conducted to investigate the feasibility of in situ upgrading of heavy oil by the use of an orgametallic catalyst and a hydrogen donor (tetralin). The experiments used a vertical injection cell into which a mixture of sand, water, and Jobo oil was thoroughly mixed and packed. Two types of runs were conducted: a run where the tetralin and catalyst were mixed within the mixture before packing into the cell, and the other was conducted by injecting a slug of the tetralin-catalyst solution before commencing with the steam injection. The Jobo oil used had an oil gravity of 12.4° API and a viscosity of 7800 cp at 30°C. The injection cell was placed in a vacuum jacket and set to a reservoir temperature of 50°C. Superheated steam at 273°C was then injected into the injection cell at a rate of 5.5 cc/min (cold water equivalent). The cell outlet pressure was maintained at 500 psig. Produced liquid samples were collected periodically through a series of separators. The produced oil was divided into two halves and several measurements and analyses were carried out on them. These included viscosity, density, elemental analysis and liquid composition. Experimental results indicated that tetralin alone was a worthy additive and increased recovery by 15% compared to that of pure steam. The premixed tetralincatalyst run showed improved recovery to that of pure steam by 20%. Experiments also showed that, when the tetralin-catalyst solution was injected rather than mixed, the results were equivalent to tetralin injection runs. Oil production acceleration was displayed by all the runs with tetralin and tetralin-catalyst but was more pronounced with the availability of catalyst.

This thesis describes the design, assembly and optimisation of a flow injection-chemiluminescence (FI-CL) procedure for the determination of hydrogen peroxide (H2O2) in seawater. An overview of the biogeochemical importance of H2O2 in seawater is presented in Chapter One. The use of both flow injection and chemiluminescence based methods are also reviewed. Chapter Two describes the type of analytical instrumentation used in both flow injection and chemiluminescence methods. Each component is described and its suitability to the FI-CL method discussed. Two detection systems; photomultiplier tube and photodiode, and two flow cell designs; coiled glass and lamina, were compared for their suitability to the method. A charge coupled device was used to obtain the CL spectra of the luminol CL reaction and automation of the FI manifold is also described. Chapters Three and Four describe the optimisation of the FI-CL method and its suitability to the determination of H2O2 in natural waters (river, estuarine and sea). Matrix efifects are investigated and a standard addition procedure described. The analytical figures of merit for H2O2 determination include a limit of detection of 10 nM and a linear range of 10-500 nM. The application of the fully optimised method to the in situ determination of H2O2 in the western Mediterranean is described in Chapter Five. Hydrogen peroxide depth profiles are presented from different geographical areas and diurnal variations in H2O2 concentration discussed. The final experimental chapter investigates the photochemical generation of H2O2 in both synthetic and natural water matrices. Ambient light incubations at sea and artificial light incubations in the laboratory were made.

Hydrogen, as an alternative to conventional aviation fuels, has the potential to increase the efficiency of a gas turbine as well as reduce emissions of greenhouse gases. In addition to significantly reducing the number of pollutants due to the absence of carbon, burning hydrogen at low equivalence ratios can significantly reduce emissions of oxides of nitrogen (NOx). Because hydrogen has a wide range of flammability limits, fuel lean combustion can take place at lower equivalence ratios than those with typical hydrocarbon fuels. <p> Numerous efforts have been made to develop gas turbine fuel injectors that premix methane/natural gas and air in fuel lean proportions prior to the reaction zone. Application of this technique to hydrogen combustion has been limited due to hydrogen's high flame rate and the concern of the reaction zone propagating into the premixing injector, commonly referred to as flashback. In this investigation, a lean-premixing hydrogen injector has been developed for application in small gas turbines. The performance of this injector was characterized and predictions about the injector's performance operating under combustor inlet conditions of a PT6-20 Turboprop have been made.<br>Master of Science

The effects on combustion derived by the blending of hydrogen with traditional fuels adopted for internal combustion engines have been studied. Results derived by emission tests of a gasoline-fed vehicle equipped with a system for the production of hydrogen on-board have been analysed. The energy balance for the engine was evaluated. It demonstrated the increase of fuel consumptions to perform electrolysis process on-board the vehicle. Afterwards, numerical simulations based on a detailed kinetic model have been performed to calculate pollutant emissions produced by methane and iso-octane (which represents gasoline) compared with a mixture composed of 10% mol/mol by hydrogen. Chemical species studied were residual hydrocarbons, nitrous oxides and carbon monoxide. Notable variations of pollutant has not been calculated for methane, wherease iso-octane showed a reduction of the aforementioned pollutants when hydrogen was introduced. In the end operating costs have been analysed. The use of stored hydrogen produced by methane steam reforming found a reduction by 7% of costs, compared to the production via electrolysis.