The transients arising from the addition of heat to a gas flow

1952 ◽  
Vol 48 (3) ◽  
pp. 482-498 ◽  
Author(s):  
P. M. Stocker
Keyword(s):  
Gas Flow ◽  
Practical Interest ◽  
Theoretical Interest

Problems involving the addition of heat to a flowing gas have received considerable attention in recent years. The practical interest lies in the application to ram jets and similar engines, and the presence of entropy gradients makes the problem of theoretical interest.

scholarly journals Gas flow through a bore-piston ring contact

2020 ◽  
pp. 146808742097112
Author(s):  
Baptiste Hallouin ◽  
Didier Lasseux ◽  
Gerald Senger
Keyword(s):  
Gas Flow ◽  
Piston Ring ◽  
Practical Interest ◽  
Contact Length ◽  
Ideal Gas ◽  
Ideal Gas Law ◽  
Thermodynamic Conditions ◽  
Sinusoidal Shape ◽  
Flow Through ◽  
Ic Engines

This work reports on the derivation of simplified but accurate models to describe gas flow through a bore-piston ring contact in reciprocating machines like compressors or IC engines. On the basis of the aperture field of a contact deduced from real measurements carried out on an expanding ring in a bore, a scale analysis on the complete compressible flow model is performed, assuming ideal gas law. It is shown that the flow can be treated as stationary and three distinct flow regimes can be identified (namely incompressible, compressible creeping, and compressible inertial regimes). Three dimensionless parameters characterizing these regimes are identified. While for the two former regimes, classical analytical Poiseuille type of models are derived, an Oseen approximation is further employed for the latter, yielding a quasi-analytical solution. The models are successfully compared to direct numerical simulations (DNS) of the complete initial set of balance equations in their steady form performed on an aperture field of sinusoidal shape. These simplified models are of particular practical interest since they allow an accurate gas flow-rate estimate through a real contact using the aperture field as the geometrical input datum, together with the thermodynamic conditions (pressure and temperature). This represents an enormous advantage as DNS is still very challenging in practice due to the extremely small value of the contact aperture to contact length ratio.

scholarly journals Bounds for Owen's Multilinear Extension

2007 ◽  
Vol 44 (4) ◽  
pp. 852-864 ◽  
Author(s):  
Josep Freixas
Keyword(s):  
Game Theory ◽  
Simple Game ◽  
Practical Interest ◽  
Simple Games ◽  
Theoretical Interest ◽  
Complex Component ◽  
Multilinear Extension ◽  
Voting System ◽  
Minimal Winning Coalitions ◽  
Minimal Blocking

Owen's multilinear extension (MLE) of a game is a very important tool in game theory and particularly in the field of simple games. Among other applications it serves to efficiently compute several solution concepts. In this paper we provide bounds for the MLE. Apart from its self-contained theoretical interest, the bounds offer the means in voting system studies of approximating the probability that a proposal is approved in a particular simple game having a complex component arrangement. The practical interest of the bounds is that they can be useful for simple games having a tedious MLE to evaluate exactly, but whose minimal winning coalitions and minimal blocking coalitions can be determined by inspection. Such simple games are quite numerous.

Evaluation of Leakage Through Graphite-Based Compression Packing Rings

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Mehdi Kazeminia ◽  
Abdel-Hakim Bouzid
Keyword(s):  
Gas Flow ◽  
Effective Diffusion ◽  
Practical Interest ◽  
Fugitive Emissions ◽  
Diffusion Term ◽  
Sealing Performance ◽  
Challenging Tasks ◽  
Packing Rings ◽  
Different Gases ◽  
Reliable Correlation

The prediction of leakage is one of the most challenging tasks when designing bolted flanged connections and industrial valves. Failure of these pressure vessel components can cause shutdowns but also accidents, loss of revenue, and environmental damages. With the strict regulations on fugitive emissions and environmental protection laws new tightness-based standards and design methods are being adopted to improve the sealing performance of bolted joints and valves. In addition, there is a practical interest in using a reliable correlation that could predict leak rates of one fluid on the basis of tests carried out with another on compressed packings. The paper presents an innovative approach to accurately predict and correlate leak rates in porous braided packing rings. The approach is based on Darcy–Klinkenberg to which a modified effective diffusion term is added to the equation. Experimentally measured gas flow rates were performed on a set of graphite-based compression packing rings with a large range of leak rates under isothermal steady conditions. Leakage from three different gases namely helium, nitrogen, and argon were used to validate the developed correlation. In the presence of the statistical properties of porous packings, the leak rates for different gases can be predicted with reasonable accuracy.

scholarly journals Asymptotic analysis of the Boltzmann–BGK equation for oscillatory flows

2012 ◽  
Vol 708 ◽  
pp. 197-249 ◽  
Author(s):  
Jason Nassios ◽  
John E. Sader
Keyword(s):  
Asymptotic Analysis ◽  
Boundary Conditions ◽  
Steady Flow ◽  
Gas Flow ◽  
Solid Wall ◽  
Practical Interest ◽  
Mean Free Path ◽  
Stokes Number ◽  
Second Order ◽  
Bgk Equation

AbstractKinetic theory provides a rigorous foundation for calculating the dynamics of gas flow at arbitrary degrees of rarefaction, with solutions of the Boltzmann equation requiring numerical methods in many cases of practical interest. Importantly, the near-continuum regime can be examined analytically using asymptotic techniques. These asymptotic analyses often assume steady flow, for which analytical slip models have been derived. Recently, developments in nanoscale fabrication have stimulated research into the study of oscillatory non-equilibrium flows, drawing into question the applicability of the steady flow assumption. In this article, we present a formal asymptotic analysis of the unsteady linearized Boltzmann–BGK equation, generalizing existing theory to the oscillatory (time-varying) case. We consider the near-continuum limit where the mean free path and oscillation frequency are small. The complete set of hydrodynamic equations and associated boundary conditions are derived for arbitrary Stokes number and to second order in the Knudsen number. The first-order steady boundary conditions for the velocity and temperature are found to be unaffected by oscillatory flow. In contrast, the second-order boundary conditions are modified relative to the steady case, except for the velocity component tangential to the solid wall. Application of this general asymptotic theory is explored for the oscillatory thermal creep problem, for which unsteady effects manifest themselves at leading order.

The Medicalization of Love and Narrow and Broad Conceptions of Human Well-Being

2015 ◽  
Vol 24 (3) ◽  
pp. 337-346 ◽  
Author(s):  
SVEN NYHOLM
Keyword(s):  
Practical Interest ◽  
Well Being ◽  
Negative Consequences ◽  
Theoretical Interest ◽  
Human Flourishing ◽  
Category Mistake ◽  
Closing Argument ◽  
Human Value ◽  
Health And Well Being ◽  
As If

Abstract:Would a “medicalization” of love be a “good” or “bad” form of medicalization? In discussing this question, Earp, Sandberg, and Savulescu primarily focus on the potential positive and negative consequences of turning love into a medical issue. But it can also be asked whether there is something intrinsically regrettable about medicalizing love. It is argued here that the medicalization of love can be seen as an “evaluative category mistake”: it treats a core human value (love) as if it were mainly a means to other ends (viz. physical health and hedonic well-being). It is also argued that Earp et al’s closing argument (that a scientific perspective on love actually adds more value to love) can be seen as involving another evaluative category mistake: it treats an object of desire and practical interest (namely, love) as if it mainly were an object of scientific contemplation and theoretical interest. It is concluded that, to relate love to health and well-being in a more satisfying way, we should construe the latter two in broader ways, whereby love is itself a component or element of human flourishing.

Kinematic Analysis of Plate Cam Profiles Not Analytically Defined

1982 ◽  
Vol 104 (1) ◽  
pp. 34-38
Author(s):  
A. Di Benedetto ◽  
A. Vinciguerra
Keyword(s):  
Kinematic Analysis ◽  
Practical Interest ◽  
Mathematical Induction ◽  
Theoretical Interest ◽  
Numerical Example ◽  
Dynamic Services ◽  
Numerical Derivative

The kinematic analysis of the follower of a plate cam with a profile not analytically defined is a matter of practical and theoretical interest. Practical interest is stimulated by the possibility, on the whole, to consider the dynamic services of the mechanism. Theoretical interest is connected to the numerical derivative procedure that is required by the kinematic analysis. Consequently, in this paper a method of approximate calculus is proposed in order to determine velocity, acceleration and jerk values of translating followers by algorithms that are obtained by mathematical induction through Newton’s formulas for repeating integrations. A numerical example given at the conclusion shows the degree of reliability of the proposed method.

A Predictive Model for Gas Flow Through a Bore-Piston Ring Contact

2013 ◽  
Author(s):  
Baptiste Hallouin ◽  
Didier Lasseux
Keyword(s):  
Analytical Solution ◽  
Predictive Model ◽  
Flow Rate ◽  
Gas Flow ◽  
Piston Ring ◽  
Practical Interest ◽  
Ideal Gas ◽  
Flow Equation ◽  
Gas Flow Rate ◽  
Flow Through

We report on the derivation of a simplified but accurate model to describe gas flow through a bore-piston ring contact. This is achieved by making use of a scale analysis on the classical mass, momentum and energy equations assuming that the gas obeys ideal gas law. The main regime of interest for practical application in reciprocating machines, corresponding to the compressible flow with inertia is identified and is shown to be free of unsteady terms in the simplified flow equation. For this regime, a quasi analytical solution is further provided that allows the estimation of the axial gas flow rate through the contact. This predictive model is successfully compared to direct numerical simulations of the complete initial set of balance equations performed on a model aperture field of sinusoidal shape. This simplified quasi analytical solution is of particular practical interest since it allows an accurate gas flow rate estimate through a real contact using the aperture field as the only input datum which would not permit a tractable direct numerical simulation otherwise.

scholarly journals Bounds for Owen's Multilinear Extension

2007 ◽  
Vol 44 (04) ◽  
pp. 852-864 ◽  
Author(s):  
Josep Freixas
Keyword(s):  
Game Theory ◽  
Simple Game ◽  
Practical Interest ◽  
Simple Games ◽  
Theoretical Interest ◽  
Complex Component ◽  
Multilinear Extension ◽  
Voting System ◽  
Minimal Winning Coalitions ◽  
Minimal Blocking

Owen's multilinear extension (MLE) of a game is a very important tool in game theory and particularly in the field of simple games. Among other applications it serves to efficiently compute several solution concepts. In this paper we provide bounds for the MLE. Apart from its self-contained theoretical interest, the bounds offer the means in voting system studies of approximating the probability that a proposal is approved in a particular simple game having a complex component arrangement. The practical interest of the bounds is that they can be useful for simple games having a tedious MLE to evaluate exactly, but whose minimal winning coalitions and minimal blocking coalitions can be determined by inspection. Such simple games are quite numerous.

Prediction of Leak Rates in Porous Braided Packing Rings

2015 ◽  
Author(s):  
Mehdi Kazeminia ◽  
Abdel-Hakim Bouzid
Keyword(s):  
Gas Flow ◽  
Effective Diffusion ◽  
Practical Interest ◽  
Fugitive Emissions ◽  
Diffusion Term ◽  
Sealing Performance ◽  
Challenging Tasks ◽  
Packing Rings ◽  
Different Gases ◽  
Reliable Correlation

The prediction of leakage is one of the most challenging tasks when designing bolted flanged connections and valves. Failure of these pressure vessel components can cause shutdowns but also accidents, loss of revenue and environmental damages. With the strict regulations on fugitive emissions and environmental protection laws new tightness-based standards and design methods are being adopted to improve the sealing performance of bolted joints and valves. However, there is a practical interest in using a reliable correlation that could predict leak rates of one fluid on the basis of tests carried out with another on compressed packings. The paper presents an innovative approach to accurately predict and correlate leak rates in porous braided packing rings. The approach is based onDarcy-Klinkenberg to which a modified effective diffusion term is added to the equation. Experimental measured gas flow rates were performed on a setof graphite based compression packing rings with a large range of leak rates under isothermal steady conditions. Leakage from three different gases namely Helium, Nitrogen and Argon were used to validate the developed correlation. In the presence of the statistical properties of porous packings, the leak rates for different gases can be predicted with reasonable accuracy.

TEM evaluation of graded SixGe1-x heterolayers

1991 ◽  
Vol 49 ◽  
pp. 894-895
Author(s):  
N. David Theodore ◽  
Mamoru Tomozane ◽  
Ming Liaw
Keyword(s):  
Heterojunction Bipolar Transistors ◽  
Gas Flow ◽  
Field Effect Transistors ◽  
Chemical Vapor ◽  
Dark Field ◽  
Bipolar Transistors ◽  
Structural Quality ◽  
Weak Beam ◽  
Transmission Electron ◽  
And Behavior

There is extensive interest in SiGe for use in heterojunction bipolar transistors. SiGe/Si superlattices are also of interest because of their potential for use in infrared detectors and field-effect transistors. The processing required for these materials is quite compatible with existing silicon technology. However, before SiGe can be used extensively for devices, there is a need to understand and then control the origin and behavior of defects in the materials. The present study was aimed at investigating the structural quality of, and the behavior of defects in, graded SiGe layers grown by chemical vapor deposition (CVD).The structures investigated in this study consisted of Si1-xGex[x=0.16]/Si1-xGex[x= 0.14, 0.13, 0.12, 0.10, 0.09, 0.07, 0.05, 0.04, 0.005, 0]/epi-Si/substrate heterolayers grown by CVD. The Si1-xGex layers were isochronally grown [t = 0.4 minutes per layer], with gas-flow rates being adjusted to control composition. Cross-section TEM specimens were prepared in the 110 geometry. These were then analyzed using two-beam bright-field, dark-field and weak-beam images. A JEOL JEM 200CX transmission electron microscope was used, operating at 200 kV.

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