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Article
Publication date: 1 December 1950

J. Kestin

IN the preliminary calculation for the design of a gas turbine or turbocompressor it is necessary to assume a value of the reheat factor R. The contemporary development of…

Abstract

IN the preliminary calculation for the design of a gas turbine or turbocompressor it is necessary to assume a value of the reheat factor R. The contemporary development of gas turbines and rotary compressors has aroused renewed interest in this quantity, which was studied earlier in connexion with steam turbines (refs. 1, 2, 7, 8 and 9). The paper contains an analysis of this value for a gaseous working fluid under appropriate assumptions; it is first calculated for an infinite number of stages with constant and variable specific heats; secondly, exact and approximate formulae are derived for finite numbers of stages of expansion and compression respectively and a method of estimating the heat recovery in turbines for working fluids with variable specific heats is indicated. Similar problems were considered in ref. 10 and the subject matter of Part III was presented to the Aeronautical Research Council (ref. 6).

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Aircraft Engineering and Aerospace Technology, vol. 22 no. 12
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 June 1950

J.S. Glass and J. Kestin

WHEN evaluating engine efficiencies, mean effective pressures or the work done by the piston in internal combustion engines or compressors, it is generally assumed that…

Abstract

WHEN evaluating engine efficiencies, mean effective pressures or the work done by the piston in internal combustion engines or compressors, it is generally assumed that the state of the working fluid is uniform throughout its mass. From this it follows that the expression for work where P denotes pressure and V, volume, holds. Now, it is known that, strictly speaking, this expression applies only in the limiting case of zero piston velocity, when the motion of the piston, and the thermodynamic process in the cylinder are said to be quasi‐static. The question, therefore, poses itself as to how far such an assumption is justified, when applied to a modern high‐speed reciprocating engine, say, an aircraft or motorcar engine, when piston velocities of the order of 40 ft./sec. are encountered.

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Aircraft Engineering and Aerospace Technology, vol. 22 no. 6
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 June 1953

J. Kestin and S.K. Zaremba

The paper discusses the types of singular points occurring in the first‐order ordinary differential equation which describes compressible viscous flow in a channel or…

Abstract

The paper discusses the types of singular points occurring in the first‐order ordinary differential equation which describes compressible viscous flow in a channel or stream tube of varying cross‐sectional area. The treatment is one‐dimensional, viscosity being allowed for by assuming a tangential stress acting on the circumference. The resulting patterns of the integral curves arc examined. It is shown that for convergent‐divergent channels whose profile has no point of inflexion, the singular point is a saddle point, as is the case in frictionlcss flow. However, the sonic section or the section of highest or lowest Mach number do not coincide with the throat but arc situated downstream of it in the divergent portion. The slopes of the integral curves which pass through the sonic section arc evaluated. When the convergent‐divergent channel has a point of inflexion in its profile there may be two singular points, the first being a saddle point and the second cither a spiral point or a nodal point. It is shown that spiral points are more likely to occur than nodal points and that, when they occur, there is no radical change in the Mach number variation along the channel due to friction. On the other hand, the existence of a nodal point admits the possibility of a continuous transition from supersonic to subsonic How in which the Mach number at exit may vary within certain limits, the Mach number in the second sonic section remaining always equal to unity. In all types of flow there arc portions of the channel over which the influence of friction outweighs that of area change.

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Aircraft Engineering and Aerospace Technology, vol. 25 no. 6
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 October 1951

J. Kestin and J.S. Glass

EXPERIMENTS on the rapid discharge of gases from cylinders show marked deviations from the accepted quasi‐steady theory. Agreement between experiment and calculation is…

Abstract

EXPERIMENTS on the rapid discharge of gases from cylinders show marked deviations from the accepted quasi‐steady theory. Agreement between experiment and calculation is obtained at the cost of assuming very large coefficients of discharge. It is shown in the present paper, that the discrepancies are due to the fact that the mass discharge is larger than that implied by the quasi‐steady theory, mainly owing to the omission of the considerable velocity of approach. The application of the wave theory of gas mechanics to the case of rapid discharge is sketched and it is shown that the deviations from the quasi‐steady theory predicted by it are of the same order of magnitude, as found experimentally.

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Aircraft Engineering and Aerospace Technology, vol. 23 no. 10
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 August 1948

J. Kestin

THE calculation of gas turbine efficiencies on the basis of the real properties of the working medium is a laborious process. Such a calculation involves the determination…

Abstract

THE calculation of gas turbine efficiencies on the basis of the real properties of the working medium is a laborious process. Such a calculation involves the determination of the composition of the combustion gases for a series of air/fuel ratios, and the evaluation of a number of thermodynamic properties at various temperatures and pressures, such as the enthalpy (total heat), entropy, specific heats, etc. These properties are calculated from the tabulated properties for the component gases with the aid of the rules for mixtures.

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Aircraft Engineering and Aerospace Technology, vol. 20 no. 8
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 October 1951

DEAR SIR, It is doubtful whether great practical importance can be attached to the precise location of the sonic section in a de Laval nozzle with friction present, under

Abstract

DEAR SIR, It is doubtful whether great practical importance can be attached to the precise location of the sonic section in a de Laval nozzle with friction present, under the assumptions of the one‐dimensional theory of flow. The truth of the matter, however, is that the equations of this approximation do lead to the conclusion that the condition of M 1, where M is the Mach number, prevails in the throat of a convergent‐divergent nozzle only in the limiting case of no friction, contrary to Mr Spalding's assertion in the August issue of AIRCRAFT ENGINEERING. It can occur in a section for which dA/dx 0 only if that section is at the exit of a convergent nozzle.

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Aircraft Engineering and Aerospace Technology, vol. 23 no. 10
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 January 1993

G. DE SAXCE, Z.Q. FENG and G. TOUZOT

This paper is devoted to the analysis of metal forming with assumption of rigid‐plastic behaviour with strain hardening. As opposed to the classical rate problem…

Abstract

This paper is devoted to the analysis of metal forming with assumption of rigid‐plastic behaviour with strain hardening. As opposed to the classical rate problem formulation based on Markov's principle and the explicit scheme, a more satisfactory incremental approach is deduced from Moreau's catching up algorithm. This implicit scheme, although more complicated, gives better results concerning convergence and numerical stability. Using an internal variable representing the strain hardening, an incremental strain energy density is defined which leads to a principle of minimum of the total incremental strain energy. In the numerical approximation using finite elements, the non‐linear equilibrium equations are solved by classical Newton's method. An approximation of Coulomb's criterion is used in order to represent friction with a rigid foundation. The simple compression test is simulated and shows that the implicit scheme is faster than the explicit one.

Details

Engineering Computations, vol. 10 no. 1
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 October 1955

W. Gordon Watson

THE problem of the expansion of a compressible fluid with friction and heat flow is one of great complexity. In this treatment it has been simplified to a one‐dimensional…

Abstract

THE problem of the expansion of a compressible fluid with friction and heat flow is one of great complexity. In this treatment it has been simplified to a one‐dimensional problem and the resulting relationships are thermodynamic. An expansion of this type cannot be described as reversible due to the presence of friction, and from this aspect the analysis may be suspect. However, any practical process is irreversible and it is common practice to apply to such processes an analysis which is theoretically confined to changes which occur reversibly. Thus, although the degree of irreversibility may be greater than usual in this case, there are many precedents for allowing the use of reversible thermodynamics in the analysis of irreversible changes. The relations for the expansion are well known, but the writer believes the analysis and discussion on the choking conditions of a nozzle are more general than anything yet published.

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Aircraft Engineering and Aerospace Technology, vol. 27 no. 10
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 February 1947

J. Lukasiewicz and M Inz.

THE graphical methods of one‐dimensional gas dynamics are reviewed and developed to obtain a complete representation of adiabatic flow of perfect gases in ducts of…

Abstract

THE graphical methods of one‐dimensional gas dynamics are reviewed and developed to obtain a complete representation of adiabatic flow of perfect gases in ducts of constant cross‐section. The dimensionless charts, from which the variation of the state of the gas along the duct axis can be determined, are analysed and the methods of their construction given. The form of the charts depends only on the value of the ratio of specific heats.

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Aircraft Engineering and Aerospace Technology, vol. 19 no. 2
Type: Research Article
ISSN: 0002-2667

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Book part
Publication date: 23 September 2014

Community perception of climate change is a factor in increasing local awareness of climate disaster risk. This encourages more disaster risk reduction actions by the…

Abstract

Community perception of climate change is a factor in increasing local awareness of climate disaster risk. This encourages more disaster risk reduction actions by the communities themselves, and thus, provides a driver for sustainable community disaster risk management (DRM) initiatives. Using these hypotheses, this chapter assesses whether the communities’ climate change perceptions, awareness of climate hazardous risk, and subsequent actions on DRR enable local DRM capacity to reduce the increasing climate disaster risk. The study conducts household surveys with an original questionnaire in four communities in Cartago City, Costa Rica.

Details

Local Disaster Risk Management in a Changing Climate: Perspective from Central America
Type: Book
ISBN: 978-1-78350-935-5

Keywords

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