Two-dimensional supersonic flows out of rocket nozzles are one of three flow types: over-, perfectly-, or under-expanded. In under-expanded flows, an expansion fan is centered at the top and bottom tip of the rocket nozzle. When the waves from the expansion wave cross through the centerline and intersect the free boundary, the waves are reflected as compression waves. For higher exit-to-ambient pressure ratios, the compression waves coalesce and eventually form a barrel shock. The purpose of this study was to use the Method of Characteristics (MOC), a mathematical procedure for solving hyperbolic partial differential equations, to simulate the formation of the barrel shock. A MOC code was developed in the Python programming language to accomplish task. Results of the MOC code compared favorably with CFD results.

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A gas-phase system to oxidize and remove the platinum and palladium from automotive catalytic converter units was studied. The effects of varying reaction temperature, time and reactant gas concentration upon yields were monitored using a colorimetric procedure based on the regent p-nitroso-N, N-dimethyl amiline. Chlorine plus carbon monoxide at 700°-900°C. displayed the most promise for commercial application.

Experiments were conducted to determine the suitability of a chromized steel for use in automotive exhaust applications. Due to government regulations leading to higher temperatures and a more corrosive environment within the automotive exhaust system, Cr-lean alloys such as Type 409 no longer suffice. The high cost of increasing alloying elements to reduce the corrosion susceptibility of exhaust components has led to exhaust manufactures moving toward a sacrificially protected aluminized stainless steel (Type 409Al). Yet, costs remain high due to the stainless steel substrate. Arcanum Alloys have designed a process in which an IF steel coil is chromized using a Cr-rich slurry, creating a thin but corrosion resistant layer. This chromized layer drastically increases the corrosion resistance, without affecting the formability of the interstitial-free (IF) steel substrate and remaining cost-effective. The localized corrosion resistance of the chromized IF steel (XHOM) was measured against current generation ferritic stainless steels in a simulated interior (exhaust gas condensate) and exterior (NaCl (aq)) automotive exhaust environment. Electrochemical polarization measurements along with atmospheric corrosion tests were conducted to characterize and compare the localized corrosion susceptibility of XHOM and benchmark ferritic stainless steels. The specific tests include the following: I. Potentiodynamic polarization curves in NaCl (aq), measuring the corrosion potential (Ecorr), critical current density (icrit) and breakdown potential (Eb). II. Double loop electrochemical potentiokinetic reactivation (DLEPR) testing measuring the ratio of the activation critical current density (ia) and the reactivation critical current density (ir). III. Salt-fog testing (ASTM B117) (external) and exhaust gas condensate exposure testing (internal), measuring the mass loss, pitting density, maximum pit depth and corrosion rate. Although Type 409 and Type 439 exhibited evidence of sensitization in the mill annealed condition, all materials exhibited a resistance to further sensitization during heat treatment, indicating sensitization will not occur during service. The electrochemical polarization curves in the NaCl (aq) resulted in XHOM yielding the highest breakdown potential, yet XHOM also exhibited the highest corrosion rate during the salt fog (ASTM B117) exposure. The latter is due to exposure of the XHOM cut edge where only the plan surface was exposed during the electrochemical polarization measurements. A galvanic couple exists between the chromized coating (cathode) and steel substrate (anode) leading to rapid corrosion of the substrate when exposed. When the cut edge of XHOM is masked, the corrosion rate drops drastically, performing comparably to the highly ferritic stainless steels. During the salt fog (ASTM B117) exposure, pitting of XHOM and Type 409 was caused by cut edge corrosion leading to corrosion product migrating down the panel surfaces and initiating under deposit pitting. A singular pit was observed on the XHOM surface, which led to delamination of the coating surrounding the pit, caused by the galvanic couple at the coating substrate/interface once the substrate was penetrated. The overall corrosion resistance ranking of the materials in the external environment incorporating corrosion rate and pit depth is as follows: Type 436 ≈ XHOM Masked Edges ≈ Type 439 > Type 409Al > Type 409 > XHOM Edges Exposed. Strain was also found to have an effect on the localized corrosion susceptibility of XHOM in NaCl (aq), unlike Type 409, which exhibited no change. The influence of the drain hole manufacturing method (punching and drilling) on the corrosion susceptibility of XHOM and Type 409 was also measured. The punching method caused a smearing effect of the chromized coating, which served to partially cover and protect the cut edge. The main corrosion mechanism that occurred within the external environment is cut edge corrosion, which led to under deposit pitting. Heat treatment of samples prior to testing in the internal exhaust environment led to an intermetallic phase change within the aluminized coating on Type 409Al, drastically reducing the corrosion resistance of the material. An as-received aluminized Type 409 (Type 409Al-A) sample was tested in exhaust condensate exposure conditions to measure the difference in corrosion rate. XHOM with the cut edges exposed exhibited a corrosion rate comparable to Type 409 and heat treated aluminized Type 409, which is promising as XHOM already has an advantage in cost and formability. The overall corrosion resistance ranking of the materials exposed in the internal exhaust environment incorporating corrosion rate and pit depth is as follows: Type 409Al-A > Type 436 > Type 439 > Type 409 ≈ XHOM Edges Exposed ≈Type 409Al-H (heat-treated). / Thesis / Master of Applied Science (MASc)

Fine particulate matter (PM2.5) constitutes a significant component of ambient air pollution that has been implicated in the pathogenesis of metabolic disorders, including insulin resistance and type 2 diabetes. Among PM2.5 constituents, diesel exhaust particles (DEP) are prevalent particulates that infiltrate the bloodstream to drive systemic pathologies. The purpose of this study was to characterize the metabolic response of adipose tissue to DEP. We aimed to provide a comprehensive understanding by exploring mitochondrial bioenergetics, characterizing the inflammatory marker profile, including adipokines, and conducting a detailed histological analysis of adipocytes to provide valuable insights to the evolving understanding of the intricate interplay between pollution and adipose tissue function. Following daily inhalation exposure to DEP in mice, we observed a selective increase in adipose tissue mass and altered mitochondrial respiration in the adipose tissue. Furthermore, we observed increased pro-inflammatory cytokines, changes in adipokine secretion, and alterations in adipose histology reflective of adipocyte hypertrophy. In conclusion, exposure to DEP disrupts adipose tissue function by altering adipocyte mitochondrial function and contributing to inflammation. These novel findings provide valuable insights that may facilitate the development of therapeutic interventions addressing metabolic disorders in the future.