Windage measurements in a rotor stator cavity with rotor mounted protrusions and bolts

This paper reports an experimental investigation of the windage associated with enclosed rotor-stator systems with superposed throughflow, as commonly found in gas turbine engines. The term windage is often used to describe the viscous heating that arises from the interaction of surfaces and fluids in rotating disc systems. Since the presence of circumferentially discreet geometric features strongly alters the magnitude of Windage measured, the physical mechanisms collectively referred to as windage in this paper are separately described as part of the discussion of results. Tests have been carried out to measure windage directly in the form of shaft torque and also rotor surface temperature. Non-dimensional flow parameters are used to expand the relevance of the data obtained, which encompasses the ranges 0.17 x 107 ≤ Reφ ≤ 1.68 x 107and 0.24 x 105 ≤ Cw ≤ 1.06 x 105 which corresponds to 0.058 ≤ λT ≤ 0.631. Data has been obtained for smooth disc geometry and also with rotor mounted protrusions of N = 3, 9 and 18; D = 10 mm, 13 mm and 16 mm diameter; H = 11 mm, high, hexagonal bolt shaped protrusions. Bi-hexagonal (twelve sided) bolts of D = 13 mm effective diameter, and height, H = 11mm, were also tested with conditions closely matched to the 13 mm hexagonal bolts. Finally, tests with 10 mm diameter, 6 mm deep, pockets were also carried out. Over the range of conditions and geometries tested, increasing the number of bolts increases the moment coefficient and windage heating. At low values of turbulent flow parameter, λT, which correspond to rotational speeds between 8000 and 10000 rev/min, increasing the diameter of the bolts shows a clear trend for both increased windage torque and average disc temperature rise. For these conditions, there also appears to be a clear reduction in windage and temperature rise with the bi-hexagonal shaped bolts compared to the equivalent diameter hexagonal bolt form. Variation in the moment coefficient with the number and diameter of bolts is attributed to variations in form drag between the different configurations. The introduction of the recesses onto the disc has very little effect on either windage heating or moment coefficient; this is attributed to the component of windage mechanism in operation and also the relatively small size in comparison to the protrusions studied here. This work contributes to the understanding of windage in gas turbines by introducing new low uncertainty data obtained at engine representative conditions and as such is of benefit to those involved with the design of internal air systems and disc fixture

Who Let the Dogs Out: Tracking the Philosophical Life Among the Wolves and Dogs of the Republic

Following the scent of wolves and dogs in Plato's Republic, this essay attempts to track a path that leads us to one of the central teachings of the text itself: that the philosophical life is situated precariously between the tyrannical tendencies of the wolf and the blind obedience of the well-trained dog

The Voice of Singularity and a Philosophy to Come

This article traces what Schürmann calls the “double comprehension of being” in Kant in which the sense of being as pure givenness is said to be recognized but denied by Kant as his thinking undertakes its Copernican turn. Schürmann insists that this can be heard in the ambiguous ways the German terms “Position” and “Setzung” are used in Kant. Schürmann shows that these two terms point at various moments in Kant either to the notion of being as a category that arises from the transcendental operations of the subject or to being understood as pure givenness external to the transcendental subject. Schürmann argues that this second sense of being threatens to undermine the entire transcendental project and so must be denied by Kant. Drawing on this reading, I attempt to show that Schürmann’s own deep skepticism about philosophical language and particularly his insistence that language always involves the violent suppression of singularity is undermined by his own suggestion that the singular comes somehow to language in the tension between Position and Setzung in Kant. By attending to the voice of singularity as it expresses itself in Kant’s texts, this essay seeks to open the possibility of a “philosophy to come” that remains attuned to the dynamic between natality and mortality that is always at play in articulation

The Duplicity of Beginning

This essay is an immanent critique of the story Reiner Schürmann tells concerning the origins of metaphysics as an epoch of hegemonic principles. In both Heidegger on Being and Acting and Broken Hegemonies, Schürmann identifies Aristotle as the father of a metaphysics that understands being in terms of human fabrication. The Duplicity of Beginning attempts to problematize this reading by suggesting that it too is a fabrication that succumbs to Schürmann’s own critique of hegemonic metaphysics. This opens the possibility of reading the poetics of Aristotle’s thinking as bound to the “ravaged site” between natality and mortality

The Rhetoric of the Geometrical Method: Spinoza's Double Strategy

Rather than adopting an uncritical conception of the geometrical method as optimal due to its inherent objectivity, this article delineates the rhetorical power of the geometrical method as it is deployed by Spinoza in the Ethics. Specifically, the article focuses on the first fourteen propositions of the Ethics in order to illustrate how they are strategically set forth in an attempt to draw someone well versed in Cartesian doctrine into an argument intent on undermining the basic premises of the Cartesian metaphysical position

On Touch and Life in the De Anima

Although Aristotle is often thought to give canonical voice to the priority of vision as the most noble of the human powers of perceiving, this article demonstrates that in Aristotle, touch has a priority vision lacks. By tracing the things Aristotle says about touch in the De Anima and specifically the manner in which he identifies touch as a kind of mean condition, this essay argues that a deeper understanding of the nature of touch connects us humans more deeply to animal life and the natural world we inhabit

The Liberal Arts Endeavor

As my inaugural editorial note for the Journal of General Education, this short essay outlines the arts of liberty as a cultivated activity at the heart of General education in the United States. The challenge of the general education endeavor is to teach the virtues of the arts of liberty at scale, recognizing that our communities are enriched when citizens have the ability to practice liberty well

The ontological reappropriation of phronēsis

Ontology has been traditionally guided by sophia, a form of knowledge directed toward that which is eternal, permanent, necessary. This tradition finds an important early expression in the philosophical ontology of Aristotle. Yet in the Nicomachean Ethics, Aristotle's intense concern to do justice to the world of finite contingency leads him to develop a mode of knowledge, phronêsis, that implicitly challenges the hegemony of sophia and the economy of values on which it depends. Following in the tradition of the early Heidegger's recognition of the ontological significance of Aristotle's Ethics and of Gadamer's appropriation of phronêsis for hermeneutics, this article argues that an ontology guided by phronêsis is preferable to one governed by sophia. Specifically, it suggests that by taking sophia as its paradigm, traditional philosophical ontology has historically been determined by a kind of knowledge that is incapable of critically considering the concrete historico-ethico-political conditions of its own deployment. This critique of sophia is accomplished by uncovering the economy of values that led Aristotle to privilege sophia over phronêsis. It is intended to open up the possibility of developing an ontology of finite contingency based on phronêsis. Such an ontology, because it is guided by and must remain responsible to the concrete individual with which it is engaged, would be ethical at its very core