Thesis (PH. D.)--University of Michigan, 1912. / Also issued in print.

Thesis (PH. D.)--University of Michigan, 1912. / eContent provider-neutral record in process. Description based on print version record.

Hannover, Universiẗat, Diss., 1998.

Th.--Sci.--Bordeaux 1, 1978. N°: 567.

No description available.

The improvement of the indicated thermal efficiency of an argon power cycle (replacing nitrogen with argon in the combustion reaction) is investigated in a CFR engine at high compression ratios in homogeneous charge compression ignition (HCCI) mode. The study combines the two effects that can increase the thermodynamic efficiency as predicted by the ideal Otto cycle: high specific heat ratio (provided by argon), and high compression ratios. However, since argon has relatively low heat capacity (at constant volume), it results in high in-cylinder temperatures, which in turn, leads to the occurrence of knock. Knock limits the feasible range of compression ratios and further increasing the compression ratio can cause serious damage to the engine due to the high pressure rise rate caused by advancing the combustion phasing. The technique proposed in this study in order to avoid intense knock of an argon cycle at high compression ratios is to cool the intake charge to subzero temperatures which leads to lower in-cylinder temperatures and hence, less possibility of having knock. The main variable in this study was the intake temperature which was investigated at 40.0 °C and -6.0 °C which corresponded to low and high compression ratios, respectively. Emission analysis shows that the low in-cylinder temperature of the cooled case led to less complete combustion, and so, lower combustion efficiency. Since nitrogen is replaced with argon, NOx was only formed in negligible amounts due to some nitrogen traces in the used gasses cylinders. Furthermore, the cooled charge required more work to be done in the gas exchange process due to the decrease in the intake pressure caused by cooling the intake which deteriorated the gas exchange efficiency. The heat losses factor was found to be the main parameter that dictated the improvement of the thermodynamic efficiency and it was found that the indicated thermal efficiency was deteriorated for the cooled case as a result of all the aforementioned factors. Although the values of the thermodynamic efficiency at high compression ratios did not meet the expectations based on the ideal Otto cycle due to the assumptions of the ideal cycle, the obtained values, in general, are relatively high.

To understand the behavior and performance of a new 100 kW pilot scale pressurized oxy-coal reactor, radiation measurements of the flame have been made using a Fourier Transform Infrared (FTIR) spectrometer. From these radiation measurements, gas temperatures were obtained using integrated spectral infrared (ISIR) emission from the CO2 and water vapor of the combustion product gases. Radiative emission from the product gases in the reactor were collected through a quartz window 1.524 m downstream of the burner. An optical probe focused culminated emission from the combustion chamber into a silica fiber which transported the radiative signal to the spectrometer. The method produced both wall and gas temperatures as well as total integrated intensity. Values for wall temperature ranged from 1150 to 1450K and gas temperatures ranged from 1150 to 1680K. The wall and gas temperature measurement trends were consistent with expected trends with periods of increasing and decreasing fuel flow rates. Temperatures could not be verified by independent measurements, but the absolute uncertainty of the gas temperature was estimated to be +100 and -50 K in the worst case, with the largest source of uncertainty being due to window fouling. These temperature and integrated intensity values were compared to measurements taken using thermocouple and radiometers at the same axial location on the reactor.

Carbon Capture and Storage (CCS) is a legitimate technology option that should be part of a balanced portfolio of mitigation technologies available Post-Kyoto Protocol framework after Paris 2015 and beyond the 2020s or the cost achieving 2 degrees Celsius stabilisation scenario will significantly increase. Oxy-fuel combustion as a CCS technology option increases fuel flexibility. Additionally, oxy-biomass as a bio-energy with CCS (BECCS) technology can achieve negative carbon dioxide (CO2) emissions in sustainable biomass systems. Also, oxygen (O2) production in an air separation unit (ASU) gives potential for extra operational flexibility and energy storage. In this work, new designs of 20 litre spherical (R-20) and 30 litre non-spherical (R-30) ignition chambers have been built at the University of Edinburgh to carry-out dust ignition experiments with different ignition energies for evaluating pulverised fuel ignitability as a function of primary recycle (PR) O2 content for oxy-fuel PF milling safety. A set of coals and biomasses being used (at the time of submitting this work) in the utility pulverised fuel boilers in the UK have been employed. Coal and biomass dusts were ignited in air and oxy-fuel mixtures up to 30 % v/v O2 balance mixture CO2 where peak pressures (Pmax) from ignition were recorded. Pressure ratios (Pmax/Pinitial) were determined the key parameter for positive ignition identification with a value above 2.5 to be considered positive. Particle size effects in coal and biomass ignition were evaluated. Results on biomass were more variable than with coals, requiring a stronger ignition source (5,000 J) mainly due to larger particle sizes. Finer biomass particles behaved similarly to air ignition in 25 % v/v O2 in CO2. Larger particles of biomass did not ignite at all for most cases even reaching 30 % v/v O2 in CO2. A reference coal used, El Cerrejon, behaved as expected with 30 % v/v O2 balance CO2 matching air case; particles between 75-53 microns had lower ignitability than finer below 53 microns but were critical in devolatilisation. Most fuels did not ignite in 21 % v/v in CO2 below 200 g/m3 concentrations. The use of adequate ignition energy strength is needed for the PF mill safety case, with 5,000 J energy required for the biomasses tested. An indication of potential ignition chamber volume and geometry effect has also been observed when comparing results from R-20 and R-30 ignition chambers. Important implications include that oxy-biomass PR with 21 % v/v O2 content would give improved pulverised fuel (PF) milling safety when compared to air firing but reduced ignitability and a 25 % v/v O2 balance CO2 atmosphere would approach to oxy-biomass ignition behaviour in air in mills.

Peptide hormones are responsible for cellular functions critical to the survival of an organism. Approximately 50% of all known peptide hormones are post-translationally modified at their C-terminus. Peptidylglycine alpha-amidating monooxygenase (PAM) is a bi-functional enzyme which catalyzes the activation of peptide pro-hormones. PAM also functionalizes long chain N-acylglycines suggesting a potential role in signaling as their respective fatty acid amides. As chain length increases for N-acylglycines so does the catalytic efficiency. This effect was probed further by primary kinetic isotope effects and molecular dynamics to better resolve the mechanism for improved catalytic function. The 1°KIE showed a linear decrease with increasing chain length. Neither the minimal kinetic mechanism nor the maximal rate for substrate oxidation was observed to be altered by substrate hydrophobicity. It was concluded that KIE suppression was a function of 'Pre-organization' - more efficient degenerate wave function overlap between C-H donor and Cu(II)-superoxo acceptor with increased chain length. Substrate activation is believed to be facilitated by a Cu(II)-superoxo complex formed at CuM. Benzaldehyde imino-oxy acetic acid undergoes non-enzymatic O-dealkylation to the corresponding oxime and glyoxylate products. This phenomena was further studied using QM/MM methodology using different Cu/O species to determine which best facilitated the dealkylation event. It was determined that radical recombination between a Cu(II)-oxyl and a substrate radical to form an unstable copper-alkoxide intermediate was best suited to carry out this reaction. Structure-function analysis was used to rationalize the electronic features which made a variety of diverse imino-oxy acetic acid analogues such unexpectedly good PAM substrates (104-5 M-1s-1). To observe the effect oxygen insertion and placement had on substrates between N-benzoylglycine and benzaldehyde imino-oxy acetic acid structures, PAM activity was correlated with NBO/MEP calculations on selected PHM-docked structures. This work concluded that the imino-oxy acetic acid was a favored substrate for PAM because its oxime electronically is very similar to the amide present in glycine-extended analogues.

Today, and for the foreseeable future, coal and other fossil fuels will provide a major portion of the energy services demanded by both developed and developing countries around the word. In order to reduce the emissions of carbon dioxide associated with combustion of coal for electricity generation, a wide range of carbon capture technologies are being developed. This thesis models the oxyfuel carbon capture process for pulverized coal and presents performance and cost estimates of this system in comparison to other low-carbon fossil fuel generators. Detailed process models for oxygen production, flue gas treatment, and carbon dioxide purification have been developed along with the calculation strategies necessary to employ these components in alternative oxyfuel system configurations for different types of coal-fired power plants. These new oxyfuel process models have been implemented in the widely-used Integrated Environmental Control Model (IECM) to facilitate systematic comparisons with other low-carbon options employing fossil fuels. Assumptions about uncertainties in the performance characteristics of gas separation processes and flue gas duct sealing technology, as well as plant utilization and financing parameters, were found to produce a wide range of cost estimates for oxyfuel systems. In case studies of a new 500 MW power plant burning sub-bituminous Powder River Basin coal, the estimated levelized cost of electricity (LCOE) 95% confidence interval (CI) was 86 to 150 [$/MWh] for an oxyfuel system producing a high-purity [99.5 mol% CO2] carbon dioxide product while capturing 90% of the flue gas carbon dioxide. For a CoCapture oxyfuel system capturing 100% of the flue gas CO2 together with all other flue gas constituents, the estimated LCOE 95% CI was 90 to 153 [$/MWh] (all costs in constant 2012 US Dollars). Using the IECM, an oxyfuel system for CO2 capture also was compared under uncertainty to an existing amine-based post-combustion capture system for a new 500 MW power plant, with both systems capturing 90% of the CO2 and producing a high-purity stream for pipeline transport to a geological sequestration site. The resulting distribution for the cost of CO2 avoided showed the oxyfuel-based system had a 95% CI of 44 to 126 [$/tonne CO2] while the amine-based system cost 95% CI ranged from 50 to 133 [$/tonne CO2]. The oxyfuel cost distribution had a longer tail toward more expensive configurations but over 70% of the distribution showed the oxyfuel-based system to be ~10[$/tonne CO2] lower in cost compared to the amine-based capture system. An evaluation of several low-carbon generation options fueled by coal and natural gas further considered both direct and indirect greenhouse gas emissions. This analysis showed oxyfuel to be economically competitive with all capture system considered, and also indicated oxyfuel to be the preferred carbon capture technology for minimizing overall carbon intensity. Combined, these results suggest that oxyfuel is a promising carbon capture technology, and the only one which offers the unique ability to capture all the combustion gases to become a truly zero emission coal plant. Realization of the latter option, however, is contingent on the development of new regulatory policies for underground injection of mixed flue gas streams that is outside the scope of this thesis.