A numerical study was carried out to improve the design of an autothermal reformer for the onboard production of hydrogen to be used in fuel-cell- powered auxiliary power units (APU) to provide heating and electricity in long haul trucks when they are at rest. The development of these auxiliary power units is based upon the use of power generated by solid oxide fuel cell (SOFC) system, instead of from a conventional gasoline engine. The present work was undertaken to improve the design of a prototype autothermal fuel reformer that had been developed by the Fuel Cell Research Centre (FCRC) at Queen’s University to convert liquid hydrocarbon truck fuel to a hydrogen rich product gas. In this development work and in the previous work iso-octane (C8H18) has been used as a surrogate fuel. Using this surrogate of gasoline, the reformer was simulated using various inlet steam/carbon (H2O/C), oxygen/carbon (O/C) molar ratios and gas-hourly-space-velocity (GHSV). In the reformer considered the reforming process is carried out in a compact tubular reactor with a centerline thermocouple tube using a 2% Pt-ZrCe based catalyst with a local porosity of 0.6. During the initial simulations, it was observed that near the start of the catalyst region there were large temperature gradients due to an exothermic partial oxidation reaction. In order to reduce the temperature gradients and facilitate heat transfer by conduction along the reformer, the central thermocouple tube was replaced with a central solid rod. The effects of variations in the thermal conductivity of central solid rod, of the reactor wall, of the catalyst bed, of the inert porous material near the inlet and the outlet of the catalyst bed, of the gas hourly space velocity, of the effectiveness factor of the chemical reaction mechanism on the performance of the reactor were studied. The results so obtained were analyzed to determine potential design improvements that would increase the hydrogen output. The results were compared with the previous numerical and experimental results obtained in the previous studies of the reformer and found to be in good agreement with the general trends of the temperature profiles as well as the outlet molar concentrations of product species. After the analysis and evaluation of all the results, it was found that by replacement of central thermocouple tube with central solid rod made of high conductivity material and by using material for inert porous region at the outlet that had a thermal conductivity equal to that of the catalyst bed led to more even temperature profiles within the catalyst region. It was also found that the hydrogen molar percentage output could be increased by approximately more than 25% and that the length of the reactor could be reduced by 20mm by incorporating these changes in the reformer design. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2009-03-09 12:14:27.627

Gas turbine engines provide thrust for aircraft engines and supply shaft power for various applications. They consist of three main components. That is, a compressor followed by a combustion chamber (burner) and a turbine. Both turbine and compressor components are either axial or centrifugal (radial) in design. The combustion chamber is stationary on the engine casing. The type of engine that is of interest here is the gas turbine auxiliary power unit (APU). A typical APU has a centrifugal compressor, burner and an axial turbine. APUs generate mechanical shaft power to drive equipments such as small generators and hydraulic pumps. In airplanes, they provide cabin pressurization and ventilation. They can also supply electrical power to certain airplane systems such as navigation. In comparison to thrust engines, APUs are usually much smaller in design. The purpose of this research was to investigate the possibility of combining the three components of an APU into a single centrifugal rotor. To do this, a set of equations were chosen that would describe the new turbomachinery cycle. They either were provided or derived using quasi-one-dimensional compressible flow equations. A MathCAD program developed for the analysis obtained best design points for various cases with the help of an optimizer called Model Center. These results were then compared to current machine specifications (gas turbine engine, gasoline and diesel generators). The result of interest was maximum specific power takeoff. The results showed high specific powers in the event there was no restriction to the material and did not exhaust at atmospheric pressure. This caused the rotor to become very large and have a disk thickness that was unrealistic. With the restrictions fully in place, they severely limited the performance of the rotor. Sample rotor shapes showed all of them to have unusual designs. They had a combination of unreasonable blade height variations and very large disk thicknesses. Indications from this study showed that the single radial rotor turbomachinery design might not be a good idea. Recommendations for continuation of research include secondary flow consideration, blade height constraints and extending the flow geometry to include the axial direction. / Master of Science

Heavy-duty trucks are in idle operation during long periods of time, providing the vehicles with electricity via the alternator at standstill. Idling trucks contribute to large amounts of emissions and high fuel consumption as a result of the low efficiency from fuel to electricity. Auxiliary power units, which operate independently of the main engine, are promising alternatives for supplying trucks with electricity. Fuel cell-based auxiliary power units could offer high efficiencies and low noise. The hydrogen required for the fuel cell could be generated in an onboard fuel reformer using the existing truck fuel. The work presented in this thesis concerns hydrogen generation from transportation fuels by autothermal reforming focusing on the application of fuel cell auxiliary power units. Diesel and dimethyl ether have been the fuels of main focus. The work includes reactor design aspects, preparation and testing of reforming catalysts including characterization studies and evaluation of operating conditions. The thesis is a summary of five scientific papers. Major issues for succeeding with diesel reforming are fuel injection, reactant mixing and achieving fuel cell quality reformate. The results obtained in this work contribute to the continued research and development of diesel reforming catalysts and processes. A diesel reformer, designed to generate hydrogen to feed a 5 kWe polymer electrolyte fuel cell has been evaluated for autothermal reforming of commercial diesel fuel. The operational results show the feasibility of the design to generate hydrogen-rich gases from complex diesel fuel mixtures and have, together with CFD calculations, been supportive in the development of a new improved reformer design. In addition to diesel, the reforming reactor design was shown to run satisfactorily with other hydrocarbon mixtures, such as gasoline and E85. Rh-based catalysts were used in the studies and exhibit high performance during diesel reforming without coke formation on the catalyst surface. An interesting finding is that the addition of Mn to Rh catalysts appears to improve activity during diesel reforming. Therefore, Mn could be considered to be used to decrease the noble metal loading, and thereby the cost, of diesel reforming catalysts. Dimethyl ether is a potential diesel fuel alternative and has lately been considered as hydrogen carrier for fuel cells in truck auxiliary power units. The studies related to dimethyl ether have been focused on the evaluation of Pd-based catalysts and the influence of operating parameters for autothermal reforming. PdZn-based catalysts were found to be very promising for DME reforming, generating product gases with high selectivity to hydrogen and carbon dioxide. The high product selectivity is correlated to PdZn interactions, leading to decreased activity of decomposition reactions. Auxiliary power systems fueled with DME could, therefore, make possible fuel processors with very low complexity compared to diesel-fueled systems. The work presented in this thesis has enhanced our understanding of diesel and DME reforming and will serve as basis for future studies. / QC 20100804

<p>Heavy-duty trucks are in idle operation during long periods of time, providing the vehicles with electricity via the alternator at standstill. Idling trucks contribute to large amounts of emissions and high fuel consumption as a result of the low efficiency from fuel to electricity. Truck manufacturers are working to develop equipment using auxiliary power units to supply the trucks with electricity, which operate independently of the main engine. Fuel cell-based auxiliary power units could offer high efficiencies and low noise and vibrations. The hydrogen required for the fuel cell can be generated in an onboard fuel reformer. This thesis is devoted to hydrogen generation from dimethyl ether, DME, by autothermal reforming focusing on the application of fuel cell auxiliary power units. In the search for alternative fuels, DME has lately been identified as a promising diesel substitute.</p><p>The first part of the thesis gives an introduction to the field of DME reforming with a literature survey of recent studies within the area. Included are also results from thermodynamic equilibrium calculations.</p><p>In the following parts of the thesis, experimental studies on autothermal reforming of DME are presented. A reformer constructed to generate hydrogen to feed a 5 kW_e polymer electrolyte fuel cell is evaluated with emphasis on trying to work close to a practically viable process, i.e. without external heating and using gas mixtures resembling real conditions. Additional experiments have been conducted to investigate the use of catalytic oxidation of dimethyl ether as a heat source during startup. The results of these studies are presented in Paper I.</p><p>In the second experimental study of this thesis, which is presented in Paper II, Pd-based monolithic catalysts are evaluated at small scale for use in autothermal reforming of DME. A screening of various catalyst materials has been performed followed by a study of the influence on the product composition of varying operating parameters such as oxygen-to-DME ratio, steam-to-DME ratio, and temperature.</p>

The current Auxiliary Power Unit (APU) contributes a lot to the greenhouse effect in terms of emissions, and in the form of noise and also is very heavy. The need for more electricity has increased in aircrafts and therefore major aircraft suppliers like Boeing and Airbus want to switch to more electric aircraft (MEA) which is lighter and has less environmental impacts. The purpose of this work is to investigate the possibilities of replacing today's traditional APU with fuel cells. In this work presents six different common fuel cell types which used commercially in various areas in the market. We have also analyzed and investigated the most suitable fuel cell types and have chosen to apply the SOFC-GT Hybrid Systems. We have investigated and compared both systems with pros and cons. We have used different methods in this work including the FOI3-method and Safran &amp; Honeywell for calculations of emissions for all systems. Finally, we have analyzed and investigated the emissions, noise and weight for both systems. / Nuvarande Auxiliary Power Unit (APU) bidrar mycket negativt till växthuseffekten i form av emissionsutsläpp och även i form av buller och är dessutom mycket tunga. Behovet av mer elektricitet ökar i flygplan och därför vill stora flygplanstillverkare såsom Boeing och Airbus övergå till more electric aircraft (MEA) vilket är lättare och har mindre miljöpåverkan. Syftet med detta arbete är att undersöka möjligheterna av att ersätta dagens traditionella APU mot bränsleceller. I detta arbete presenteras sex olika bränslecellstyper som finns på marknaden och används kommersiellt inom olika områden. Vi har analyserat och undersökt de lämpligaste bränslecellstyper för applicering och därefter har vi valt att implementera SOFC- GT Hybridsystemen. Vi har undersökt och jämfört båda systemens för- och nackdelar. Metodmässigt används bland annat FOI3-Metoden och Safran &amp; Honeywell för beräkningar av utsläpp av emissioner för samtliga system. Slutligen har vi analyserat och undersökt skillnader i utsläpp av emissioner, buller och vikt för båda systemen.

Heavy-duty trucks are in idle operation during long periods of time, providing the vehicles with electricity via the alternator at standstill. Idling trucks contribute to large amounts of emissions and high fuel consumption as a result of the low efficiency from fuel to electricity. Truck manufacturers are working to develop equipment using auxiliary power units to supply the trucks with electricity, which operate independently of the main engine. Fuel cell-based auxiliary power units could offer high efficiencies and low noise and vibrations. The hydrogen required for the fuel cell can be generated in an onboard fuel reformer. This thesis is devoted to hydrogen generation from dimethyl ether, DME, by autothermal reforming focusing on the application of fuel cell auxiliary power units. In the search for alternative fuels, DME has lately been identified as a promising diesel substitute. The first part of the thesis gives an introduction to the field of DME reforming with a literature survey of recent studies within the area. Included are also results from thermodynamic equilibrium calculations. In the following parts of the thesis, experimental studies on autothermal reforming of DME are presented. A reformer constructed to generate hydrogen to feed a 5 kWe polymer electrolyte fuel cell is evaluated with emphasis on trying to work close to a practically viable process, i.e. without external heating and using gas mixtures resembling real conditions. Additional experiments have been conducted to investigate the use of catalytic oxidation of dimethyl ether as a heat source during startup. The results of these studies are presented in Paper I. In the second experimental study of this thesis, which is presented in Paper II, Pd-based monolithic catalysts are evaluated at small scale for use in autothermal reforming of DME. A screening of various catalyst materials has been performed followed by a study of the influence on the product composition of varying operating parameters such as oxygen-to-DME ratio, steam-to-DME ratio, and temperature. / QC 20101115

Heavy-duty diesel truck engines are routinely idled at standstill to provide cab heating or air conditioning, and in addition to supply electricity to comfort units such as radio and TV. Idling is an inefficient and unfavorable process resulting in increased fuel consumption, increased emissions, shortened engine life, impaired driver rest and health, and elevated noise. Hydrogen-fueled, polymer-electrolyte fuel-cell auxiliary power unit (PEFC-APU) as a silent external power supply, working independently of the main engine, is proposed as viable solution for better fuel economy and abatement of idling emissions. In a diesel PEFC-APU, the hydrogen storage problem is circumvented as hydrogen can be generated onboard from diesel by using a catalytic reformer. In order to make catalytic diesel PEFC-APU systems viable for commercialization research is still needed. Two key areas are the development of reforming catalyst and reformer design, which both are the scope of this thesis. For diesel-reforming catalysts, low loadings of Rh and RhPt alloys have proven to exhibit excellent reforming and hydrogen selectivity properties. For the development of a stable reforming catalyst, more studies have to be conducted in order to find suitable promoters and support materials to optimize and sustain the long-term performance of the Rh catalyst. The next step will be full-scale tests carried out at realistic operating conditions in order to fully comprehend the overall reforming process and to validate promising Rh catalysts. This thesis can be divided into two parts; the first part addresses the development of catalysts in the form of washcoated cordierite monoliths for autothermal reforming (ATR) of diesel. A variety of catalyst compositions were developed containing Rh or RhPt as active metals, CeO2, La2O3, MgO, Y2O3 as promoters and Al2O3, CeO2-ZrO2, SiO2 and TiO2 as support materials. The catalysts were tested in a bench-scale reactor and characterized by using N2-BET, XRD, H2 chemisorption, H2-TPR, O2-TPO, XPS and TEM analyses. The second part addresses the development and testing of full-scale reformers at various realistic operating conditions using promising Rh catalysts. The thesis shows that a variety of Rh on alumina catalysts was successfully tested for ATR of diesel (Papers I-IV). Also, zone-coating, meaning adding two washcoats on specific parts of the monolith, was found to have beneficial effects on the ATR catalyst performance (Paper II). In addition, RhPt supported on CeO2-ZrO2 was found to be one of the most active and promising catalyst candidates for ATR of diesel. The superior performance may be attributed to higher reducibility of RhiOx species and greater dispersion of Rh and Pt on the support (Paper IV). Finally, two full-scale diesel reformers were successfully developed and proven capable of providing high fuel conversion and hydrogen production from commercial diesel over selected Rh catalysts (Papers II-III, V-VI). / QC 20110418

<p>The purpose of this research was to determine what components of a complex centrifugal  compression system inlet needed to be modelled to accurately predict the swirl and total pressure  distortions at the compressor face. Two computational models were developed. A full-fidelity case  where all the inlet geometry was modelled and a reduced model where a small portion of the inlet  was considered. Both the numerical cases were compared with experimental data from a research  compressor rig developed by Honeywell Aerospace. The test apparatus was designed with a  modular inlet system to develop swirl distortion patterns. The modular inlet system utilized  transposable baffles within the radial-to-axial section of the inlet and blockage plates of varying  sizes and geometries at the inlet to this section.  Discerning the dominant inlet component that dictates distortion behavior at the compressor  face would allow the reduced modelling of inlet components for compression systems and would  allow coupling with more tortuous systems. Furthermore, it would reduce the design iteration and  simulation time of the inlet systems. Several investigations utilizing a reduced model only  considering a radial-to-axial inlet are available in literature, but no comprehensive justification has  been presented as to the impact this has on the distortion behavior.   Experimental surveys of flow conditions just upstream of the inducer of the centrifugal  compressor were conducted at several operating conditions. The highest and lowest mass flow  rates of these operating points were simulated using ANSYS CFX 2020R1 for both the  computational models. Multiple inlet configurations were simulated to test the robustness of the  reduced model in comparison to the full fidelity. The numerical simulations highlighted  shortcomings of the instrumentation used to characterize the experimental flow field at the inducer,  particularly with respect to total pressure distortion. Furthermore, transient pressure data were  measured in experiment and indicated unsteady fluctuations in the inlet that would not be captured  by steady computational fluid dynamic simulations. These data matched locations of disagreement  with swirl distortion behavior at high mass flow rates. This suggested that transient vortex  movement occured at the aerodynamic interface plane in certain configurations.   The total pressure distortion metrics between the two models were remarkably comparable.  Furthermore, the simplified model accurately predicted the mixing losses associated with the  blockage plates at the inlet to the radial-to-axial inlet using a simple inlet extension. Swirl  18  distortion was dictated by the radial-to-axial inlet. The reduced model data trends were comparable  with experiment for both the baffle and blocker plate configurations. The swirl intensities for all  configurations were comparable between the two models. The reduced model swirl directivity  trends matched those of experiment. The most notable deviations between the full-fidelity model  and the reduced model were observed with swirl directivity numerics. </p>