18,971 research outputs found
Energy efficient engine high-pressure turbine detailed design report
The energy efficient engine high-pressure turbine is a single stage system based on technology advancements in the areas of aerodynamics, structures and materials to achieve high performance, low operating economics and durability commensurate with commercial service requirements. Low loss performance features combined with a low through-flow velocity approach results in a predicted efficiency of 88.8 for a flight propulsion system. Turbine airfoil durability goals are achieved through the use of advanced high-strength and high-temperature capability single crystal materials and effective cooling management. Overall, this design reflects a considerable extension in turbine technology that is applicable to future, energy efficient gas-turbine engines
Predictability of extreme events in a branching diffusion model
We propose a framework for studying predictability of extreme events in
complex systems. Major conceptual elements -- hierarchical structure, spatial
dynamics, and external driving -- are combined in a classical branching
diffusion with immigration. New elements -- observation space and observed
events -- are introduced in order to formulate a prediction problem patterned
after the geophysical and environmental applications. The problem consists of
estimating the likelihood of occurrence of an extreme event given the
observations of smaller events while the complete internal dynamics of the
system is unknown. We look for premonitory patterns that emerge as an extreme
event approaches; those patterns are deviations from the long-term system's
averages. We have found a single control parameter that governs multiple
spatio-temporal premonitory patterns. For that purpose, we derive i) complete
analytic description of time- and space-dependent size distribution of
particles generated by a single immigrant; ii) the steady-state moments that
correspond to multiple immigrants; and iii) size- and space-based asymptotic
for the particle size distribution. Our results suggest a mechanism for
universal premonitory patterns and provide a natural framework for their
theoretical and empirical study
Modeling and Control of Reaction Calorimeter System
In dealing with calorimetry, safety aspects are very important. It is therefore very useful to be able to study a process before carrying out experiments on it. A computer model can then be very useful to save time and money. The purpose of this thesis was to construct a computer model of the Chemisens reaction calorimeter, in the modeling software Dymola. For the purpose of the modeling, a new Dymola library was developed, specific for the calorimeter. The task was also to investigate the control of the calorimeter. The existing cascade control was implemented in the computer model as well as PID and LQG control. The results from the modeling were surprisingly good and the controllers also worked wel
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