A Framework and Approach for Leveraging Unsteady Response in Turbocompressor Flowfields

Turbomachinery is an essential technology in the transfer of mechanical work to or from a fluid stream. Forming a cornerstone component in nearly all electrical energy production and air transportation propulsion systems, turbomachinery also accounts for significant en- ergy transfer due to its omnipresence in fluid handling, including water pumping and pro- cess machinery. As system designers look towards optimized arrangements that enhance system flexibility to highly variable conditions, increase the density of energy transfer, and reduce the amount of lost work, the performance and operability demands on turbomachin- ery components continue to increase. For turbocompressors, a turbomachinery subtype that transfer work to a fluid, the flowfield can be classified into two flow regimes, demarcated by a stability boundary representing an operational limit. For aerodynamic loadings above this stability limit, the flowfield is highly complex, exhibiting a broad range of temporal and spatial features, limiting work transfer and increasing entropy production. The blade- level instabilities, referred to as rotating stall, are the result of deleterious flowfield features, sensitive to perturbation, which have grown with aerodynamic loading. Based on the thesis that critical destabilizing flow structures exhibit coherent response to periodic excitation and can be usefully organized via tuned periodic forcing, the work presented herein emphasizes the dynamical behavior of a representative compressor flow- field under periodic transients and the difficulty in extracting useful information on flow- field response in the post-stall regime. A new analysis approach is developed that enables better understanding of the rotating stall process, providing guidance for the use of data- driven tools and new approaches for control development. Emerging decomposition and operator-based analysis approaches are borrowed from dynamical system modeling to aid in deducing the coherent structures, their unforced behaviors, and critical forcing frequen- cies. In this work, linear stability analysis and resolvent analysis are used to identify the underlying flow structures contributing to the onset of instability. Through a demonstrated surrogate model for compressor stability, a conceptual framework and practical approach are developed, such that the unsteady response of turbomachinery flows can be leveraged to achieve wider operability and enhance the transfer of usable work

Requirement of argininosuccinate lyase for systemic nitric oxide production

Nitric oxide (NO) is crucial in diverse physiological and pathological processes. We show that a hypomorphic mouse model of argininosuccinate lyase (encoded by Asl) deficiency has a distinct phenotype of multiorgan dysfunction and NO deficiency. Loss of Asl in both humans and mice leads to reduced NO synthesis, owing to both decreased endogenous arginine synthesis and an impaired ability to use extracellular arginine for NO production. Administration of nitrite, which can be converted into NO in vivo, rescued the manifestations of NO deficiency in hypomorphic Asl mice, and a nitric oxide synthase (NOS)-independent NO donor restored NO-dependent vascular reactivity in humans with ASL deficiency. Mechanistic studies showed that ASL has a structural function in addition to its catalytic activity, by which it contributes to the formation of a multiprotein complex required for NO production. Our data demonstrate a previously unappreciated role for ASL in NOS function and NO homeostasis. Hence, ASL may serve as a target for manipulating NO production in experimental models, as well as for the treatment of NO-related diseases

The Philosophy of Character Vertigo: An Essay on Choice, Anxiety, Freedom, and the Self

Many of the questions posed in this thesis are about the role of the self, the soul, and the will in the context of different character archetypes. These subjects, mused upon in great length by ancient and contemporary philosophers, are quite common in discussions of ontology and metaphysics. Thus, many of these puzzling questions -- such as how the soul affects the self -- are completely unanswerable. I do not seek to answer any of these questions necessarily, though I do have my own opinions about them, and I acknowledge that they are present in the text following. My sole purpose is to sketch a new model for interpreting and applying these questions, perhaps shedding philosophical light on how we ought to understand our relationship with our self

An Investigation Into the Variation of Centrifugal Compressor Sensitivity to Inlet Swirl With Initial Form Parameter Selection

Fixed-geometry centrifugal compressors have inherent limitations in the off-design operating range and performance that can be delivered. Variable inlet swirl, typically introduced with variable inlet guide vanes, has been a frequent tool implemented across many industries to extend the stable operating range and off-design efficiency. However, a review of available data in the literature reveals a large disparity in the effectiveness of variable inlet swirl for useful map movement. An ideal configuration responds to preswirl with a significant reduction in the mass flow at instability along with increased efficiency. Unfortunately, some cases reveal no movement in the surge line, with increases in inlet swirl only serving to reduce the stage efficiency. This study investigates underlying causes for the variation in sensitivity to inlet swirl amongst various compressor designs, represented by form parameters. An analytical model is established and then verified using CFD and selected test data to explore fundamental causes for decreased sensitivity to inlet swirl. Analytical and computational results suggest a new understanding of the governing parameters for inlet swirl sensitivity, and thus provide insight into the scenarios when inlet swirl is an effective tool for manipulation of performance characteristics. Synthesizing the underlying trends, guidelines are developed for design selections and operational situations when inlet swirl can be effectively implemented as a means to extend the stable operating range and off-design efficiency.</jats:p