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Article

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Council, Reports and Technical Memoranda of the United…

Abstract

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Council, Reports and Technical Memoranda of the United States National Advisory Committee for Aeronautics and publications of other similar Research Bodies as issued.

Details

Aircraft Engineering and Aerospace Technology, vol. 30 no. 10
Type: Research Article
ISSN: 0002-2667

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Article

Gus Nasif, R.M. Barron, Ram Balachandar and Julio Villafuerte

Application of cold spray technology may exhibit significant benefits for the additive manufacturing process, particularly for producing intricate objects. To ascertain…

Abstract

Purpose

Application of cold spray technology may exhibit significant benefits for the additive manufacturing process, particularly for producing intricate objects. To ascertain the feasibility of such an application, this paper aims to present a numerical investigation of the effect of scaling down a convergent-divergent (de Laval) nozzle, which is typically used in the cold spray industry, on the compressible flow parameters and thermal characteristics.

Design/methodology/approach

The Navier–Stokes equations and energy equation governing compressible flow are numerically solved using a finite volume method with a coupled solver. The conjugate heat transfer technique is used to couple fluid and solid heat transfer domains and predict the local heat transfer coefficient between the solid and fluid. The use of various RANS turbulence models has also been investigated to quantify the effect of the turbulence model on the simulation.

Findings

The numerical results reveal that the flow and thermal characteristics are altered as the convergent-divergent nozzle is scaled down. The static pressure and temperature profiles at any section in the nozzle are shifted toward higher values, while the Mach number profile at any section in the nozzle is shifted toward a lower Mach number. The turbulent kinetic energy at the nozzle exit increases with the scaling down of the nozzle geometry. This study also provides convincing evidence that the adiabatic approach is still suitable even though the temperature of the nozzle wall is extremely high, as required for industrial application. Results indicate that it is feasible to use the available capabilities of the cold spray technology for additive manufacturing after scaling down the nozzle.

Originality/value

The idea of adopting cold spray technology for additive manufacturing is new and innovative. To develop this idea into a viable commercial product, a thorough understanding of the flow physics within a cold spray nozzle is required. The simulation results discussed in this paper demonstrate the effect that scaling down of a convergent-divergent nozzle has on the flow characteristics in the nozzle.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

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Article

Elham Mohammadi and Alireza Toloei

The purpose of this paper is to analyze the flowfield structure and performance of dual secondary injection system for thrust vectoring in a convergent‐divergent nozzle

Abstract

Purpose

The purpose of this paper is to analyze the flowfield structure and performance of dual secondary injection system for thrust vectoring in a convergent‐divergent nozzle and to compare it with a single secondary injection system.

Design/methodology/approach

Dual secondary injection for thrust vectoring in a convergent‐divergent nozzle is studied by solving three‐dimensional Reynolds‐averaged Navier‐Stokes equations by the means of Fluent. Realizable k‐ε turbulent model with enhanced wall‐treatment approach is used for viscous model. Density‐based solver and explicit scheme are employed in the computational model. In order to study the effect of injection location on the flowfield, distance between ports is considered as the key variable.

Findings

Results show that under some circumstances, dual secondary injection system is more effective than a single injection system with the same mass flow rate. The study shows that when the distance between two ports is 8.5 times of the injection port's diameter (or more) and in the same time the first injection port is at least 1 throat diameter far from the nozzle throat, this system will show a better performance. In addition, this system reduces the probability of bow shock impingement to the opposite wall and consequently, the side force production has less limitation.

Practical implications

Dual secondary injection for thrust vector control (SITVC) needs less secondary flow and therefore it makes less reduction in the primary thrust. It means that for a specific primary thrust, less mass fuel is needed which makes it more economic regarding the traditional SITVC systems.

Originality/value

The paper's value lies in using a three‐dimensional model to study the effect of two ports distance on SITVC performance and comparison among the performance of dual and single injections when there is an impingement.

Details

Aircraft Engineering and Aerospace Technology, vol. 83 no. 4
Type: Research Article
ISSN: 0002-2667

Keywords

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Article

An exposition of the need of supersonic aircraft to have a variable geometry intake and a fully variable convergent‐divergent nozzle for optimum performance. POWERPLANTS…

Abstract

An exposition of the need of supersonic aircraft to have a variable geometry intake and a fully variable convergent‐divergent nozzle for optimum performance. POWERPLANTS for supersonic aircraft bear only a superficial resemblance to the propulsive units of their subsonic counterparts. A typical subsonic turbojet powerplant consists of a high compression engine with a short fixed intake, and, possibly, a variable convergent nozzle. The supersonic aircraft on the other hand requires a powerplant with a sophisticated variable geometry intake having its own automatic control system and a fully variable convergent‐divergent nozzle in order to extract the full performance throughout the speed range from the slightly lower pressure ratio engine.

Details

Aircraft Engineering and Aerospace Technology, vol. 41 no. 2
Type: Research Article
ISSN: 0002-2667

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Article

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.

Details

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

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Article

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.

Details

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

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Article

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.

Details

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

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Article

Mubarak A.K. and Tide P.S.

The purpose of this paper is to design a double parabolic nozzle and to compare the performance with conventional nozzle designs.

Abstract

Purpose

The purpose of this paper is to design a double parabolic nozzle and to compare the performance with conventional nozzle designs.

Design/methodology/approach

The throat diameter and divergent length for Conical, Bell and Double Parabolic nozzles were kept same for the sake of comparison. The double parabolic nozzle has been designed in such a way that the maximum slope of the divergent curve is taken as one-third of the Prandtl Meyer (PM) angle. The studies were carried out at Nozzle Pressure Ratio (NPR) of 5 and also at design conditions (NPR = 3.7). Experimental measurements were carried out for all the three nozzle configurations and the performance parameters compared. Numerical simulations were also carried out in a two-dimensional computational domain incorporating density-based solver with RANS equations and SST k-ω turbulence model.

Findings

The numerical predictions were found to be in reasonable agreement with the measured experimental values. An enhancement in thrust was observed for double parabolic nozzle when compared with that of conical and bell nozzles.

Research limitations/implications

Even though the present numerical simulations were capable of predicting shock cell parameters reasonably well, shock oscillations were not captured.

Practical implications

The double parabolic nozzle design has enormous practical importance as a small increase in thrust can result in a significant gain in pay load.

Social implications

The thrust developed by the double parabolic nozzle is seen to be on the higher side than that of conventional nozzles with better fuel economy.

Originality/value

The overall performance of the double parabolic nozzle is better than conical and bell nozzles for the same throat diameter and length.

Details

Aircraft Engineering and Aerospace Technology, vol. 91 no. 1
Type: Research Article
ISSN: 1748-8842

Keywords

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Article

J.R. Palmer

AT the present time turbojet aircraft types which are capable of level flight Mach numbers well into the supersonic range are appearing in increasing numbers. Yet, while…

Abstract

AT the present time turbojet aircraft types which are capable of level flight Mach numbers well into the supersonic range are appearing in increasing numbers. Yet, while this represents in a sense a new phase in the evolution of piloted aircraft, from the point of view of the propulsion engineer it is rather the end of an era, in that hitherto the turbojet engines employed have been essentially subsonic engines suitably strengthened. Henceforth we may expect to see the use of engines specifically designed for the appropriate range of Mach number, and it is the purpose of this article to review some of the implications of this change of outlook in so far as they affect the prediction of engine performance.

Details

Aircraft Engineering and Aerospace Technology, vol. 28 no. 11
Type: Research Article
ISSN: 0002-2667

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Article

I. Carl Romer and AH B.S. Bulent Cambel.

In this paper the isothermal flow of perfect gases is discussed following the gas dynamic approach of applying the continuity, momentum and energy equations. Flow…

Abstract

In this paper the isothermal flow of perfect gases is discussed following the gas dynamic approach of applying the continuity, momentum and energy equations. Flow functions for isothermal, reversible, one‐dimen‐sional flow are derived and these are represented graphically. Isothermal flow in convergent‐divergent nozzles is analysed and the variation of the derived flow functions is depicted.

Details

Aircraft Engineering and Aerospace Technology, vol. 27 no. 12
Type: Research Article
ISSN: 0002-2667

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