Browsing by Author "Boulanger, Andrew James"

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    Experimental Investigation of Microparticle Sand Sticking Probability from 1000°C to 1100°C
    Boulanger, Andrew James (Virginia Tech, 2017-12-05)
    Increasing commercial and military aircraft operations in arid environments are increasing the likelihood of sand and dust ingestion. Turbine engines are particularly susceptible to the ingestion of sand and dust, which can erode cold-section components and deposit onto hot-section components. Ultimately, the erosion and deposits will shorten the operational lifespan of these engines and limit their availability thereby increasing maintenance costs and risking safety. Mitigating these risks has become more prevalent in recent years due to increasing combustion temperatures in effort to increase fuel efficiency. Increasing combustion temperatures directly increases deposit formation onto hot-section components. Monitoring deposit formation on existing turbine engine platforms and improving deposit resilience on new designs has been the industry focus for the last two decades. This study focused on statistically modeling the initial onset of microparticle deposits onto an analogous hot-section surface. Generally, as deposits accumulate onto a hot-section surface, the existing deposit formation is more likely to bond with incoming particulate at a faster rate than an exposed bare surface. Predicting the initial deposits onto a bare surface can determine the accelerated deposition rate depending on subsequent particulate impinging onto the surface. To emulate the initial deposits, a HASTELLOY® X test coupon was exposed to 20 μm to 40 μm samples of Arizona Road Test Dust (ARD) at varying loadings and aerosol densities. The Virginia Tech Aerothermal Rig was used for all test scenarios at flow-particle temperatures between 1000°C to 1100°C. Several statistical models were developed as a function of many independent variables, culminating with a final sticking probability (SP) model. Overall, the SP of individual ARD particulate is a primary function of flow-particle temperature and normal impact momentum. Tangential impact momentum of a particle will decrease the SP, while surface temperatures reaching isothermal conditions with the flow will increase SP. However, there are specific cases where lower surface temperatures and high particle temperatures result in a high SP. Particle size was a strong predictor of SP where particles between 10 μm to 19 μm were 5 to 10 times greater than the 19 μm to 40 μm range. Additional studies will be necessary to examine some additional parameters that become more prominent with smaller particle sizes. Ultimately, the intention of the models is to assist turbine engine designers to improve resilience to deposit formation on hot-section components.
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    Feasibility Study of a Natural Uranium Neutron Spallation Target using FLiBe as a Coolant
    Boulanger, Andrew James (Virginia Tech, 2011-05-10)
    The research conducted was a feasibility study using Lithium Fluoride-Beryllium Fluoride (LiF-BeF2) or FLiBe as a coolant with a natural uranium neutron spallation source applied to an accelerator driven sub-critical molten salt reactor. The study utilized two different software tools, MCNPX 2.6 and FLUENT 12.1. MCNPX was used to determine the neutronics and heat deposited in the spallation target structure while FLUENT was used to determine the feasibility of cooling the target structure with FLiBe. Several target structures were analyzed using a variety of plates and large cylinders of natural uranium with a proton beam incident on a Hastelloy-N window. The supporting structures were created from Hastelloy-N due to their anti-corrosive properties of molten salts such as FLiBe and their resistance to neutron damage. The final design chosen was a "Sandwich" design utilizing a section of thick plates followed by several smaller plates then finally a section of thick plates to stop any protons from irradiating the bottom of the target support structure or the containment vessel of the reactor. Utilizing a proton beam with 0.81 MW of proton beam power at 1.35 mA with proton kinetic energies of 600 MeV, the total heat generated in the spallation target was about 0.9 MW due to fissions in the natural uranium. Additionally, the neutrons produced from the final design of the spallation target were approximately 1.25x1018 neutrons per second which were mainly fast neutrons. The use of a natural uranium target proved to be very promising. However, cooling the target using FLiBe would require further optimization or investigation into alternate coolants. Specifically, the final design developed using FLiBe as a coolant was not practically feasible due to the hydraulic forces resulting from the high flow rates necessary to keep the natural uranium target structures cooled. The primary reason for the lack of a feasible solution was the FLiBe as a coolant; FLiBe is unable to pull enough heat generated in the target out of the target structure. Due to the high energy density of a natural uranium spallation target structure, a more effective method of cooling will be required to avoid high hydraulic forces, such as a liquid metal coolant like lead-bismuth eutectic.