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Article
Publication date: 1 June 2004

V. Wheatley, H.S. Chiu, P.A. Jacobs, M.N. Macrossan, D.J. Mee and R.G. Morgan

This paper describes a free‐piston driven expansion tube and its instrumentation. The facility is used to generate rarefied flows at speeds of approximately 10 km/s…

Abstract

This paper describes a free‐piston driven expansion tube and its instrumentation. The facility is used to generate rarefied flows at speeds of approximately 10 km/s. Although the flow in the tube itself is in the continuum regime, rarefied flow conditions are achieved by allowing the test gas to further expand as a free jet into the facility's test section. The test flow is surveyed to provide bar‐gauge pressure measurements. Numerical simulation is then used to describe more fully the test flow properties. The flows produced are suitable for the aerodynamic testing of small models at superorbital speeds and should provide data that are suitable for the calibration of Direct Simulation Monte‐Carlo codes.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 14 no. 4
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 1 January 2006

A.N. Shuaib

The purpose of this paper is to develop a procedure for deciding on the limits of initial clearance to which tubesheet holes can be enlarged before replacement in heat…

Abstract

Purpose

The purpose of this paper is to develop a procedure for deciding on the limits of initial clearance to which tubesheet holes can be enlarged before replacement in heat exchanger maintenance.

Design/methodology/approach

An empirical model that relates the hardness of roller expanded tubes and ligaments to initial clearance is developed from experimental data to predict the extent of tolerable levels of over‐enlargement of tubesheet holes before the joint loses its structural integrity. The developed model serves as an additional criterion to decide whether to keep or discard a tubesheet having over‐enlarged holes during heat exchanger maintenance.

Findings

The current industrial criterion does not directly include the effect of material degradation for over‐enlarged holes. The empirical models indicate that both tubes and ligaments suffer strain hardenings. A new procedure is proposed to supplement the current industrial criterion.

Practical implications

The procedure will assist maintenance managers/engineers in deciding on the replacement of heat exchanger tubesheets. The combined criteria will have an impact on the cost of heat exchanger maintenance and plant downtime.

Originality/value

The procedure proposed in this paper adds to the industrial criterion another one that caters for the degradation in properties that the tube, tubesheet, and surrounding ligaments will be subjected to during roller expansion. In other words, it considers the strain hardening of the tube and tubesheet materials in setting the initial clearance between the tube and tubesheet that ensures adequate joint integrity.

Details

Journal of Quality in Maintenance Engineering, vol. 12 no. 1
Type: Research Article
ISSN: 1355-2511

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Article
Publication date: 1 October 2005

Takao Koshimizu, Hiromi Kubota, Yasuyuki Takata and Takehiro Ito

To clarify the physical working principle of refrigeration in basic pulse tube refrigerators (BPTRs).

Abstract

Purpose

To clarify the physical working principle of refrigeration in basic pulse tube refrigerators (BPTRs).

Design/methodology/approach

A numerical simulation was performed. Transient compressible NS equation was solved utilizing the TVD scheme coupled with energy equation.

Findings

The periodic flow and temperature field were obtained. The movement of the gas particles and heat transfer between the gas particles and wall were analyzed. These numerical results explained the mechanism of surface heat pumping (SHP) which is known as the working principle of refrigeration in BPTR.

Research limitations/implications

Pulse tube refrigerator (PTR) is classified into the third generation. BPTR is the first generation. It is needed to clarify the working principle of refrigeration in the second and third generation by analyzing heat and fluid flow in the tube.

Practical implications

A very useful source of information to understand the physical working principle of refrigeration in BPTR.

Originality/value

The mechanism of SHP was shown by analyzing the heat exchange between the gas particles and pulse tube wall.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 15 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

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Abstract

Details

London Transport: A Hybrid in History 1905–1948
Type: Book
ISBN: 978-1-78973-953-4

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Article
Publication date: 1 April 1963

In the jet propulsion plant installation in an aircraft wing each chordwise extending square tube 119 is attached to a splitter plate 114 by vertical dowel pins 115 and by…

Abstract

In the jet propulsion plant installation in an aircraft wing each chordwise extending square tube 119 is attached to a splitter plate 114 by vertical dowel pins 115 and by bolts 116 passing through the tube and through a strip 117 attached to the splitter plate 114. A further strip 118 connects each tube 119 to the adjacent ram‐jet compartment cover 233. Spanwise extending stiffeners 227 on the adjacent turbojet compartment cover 230 are attached by fastenings 229 to brackets 231 secured to the tube by bolts 116, fasten ings 229 allowing spanwise thermal expansion. A strip 228 attached to the cover 230 lies on a joggled part of cover 233, also to allow thermal expansion. The tube 119 has a reinforcing web 119a. The joints 273 between the covers 230, 233 and the forward wing portion allow spanwise thermal expansion of the covers. The cover 233 is a sandwich comprising spanwise corrugations, and the splitter plate 114 has vertical corrugations. The cooling air which flows rearwardly through tube 119 is tapped off to flow through these corrugations through ports 119b, 119c respectively in the tube.

Details

Aircraft Engineering and Aerospace Technology, vol. 35 no. 4
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 17 January 2019

Shantaram Dond, Hitesh Choudhary, Tanmay Kolge, Archana Sharma and G.K. Dey

An electromagnet that can produce strong pulsed magnetic fields at kHz frequencies is potentially very favourable to exert a Lorentz force on the metallic workpiece. One…

Abstract

Purpose

An electromagnet that can produce strong pulsed magnetic fields at kHz frequencies is potentially very favourable to exert a Lorentz force on the metallic workpiece. One of the applications of the pulsed magnetic field is the electromagnetic forming where the design of robust electromagnet is critical. The purpose of this paper is to design a robust electromagnet (coil) for high velocity electromagnetic tube forming operation.

Design/methodology/approach

First of all, an analytical model is developed to design the electromagnet and predict the aluminium tube velocity under the action of the estimated pulsed magnetic field. Next, the finite element-based numerical model is used to test the robustness of the designed coil and validate the analytical model. The coil is fabricated and implemented for free forming of aluminium tube. Experimental results of tube displacement are further compared with numerical and analytical model results.

Findings

The experimental tube displacement results are showing a good match with analytical and numerical results. The designed electromagnet has generated a peak magnetic field around 14 T at 20 µs rise time and deformed the aluminium tube with a peak velocity of 160 m/s. Robustness of the electromagnet under the action of forming stress is insured by numerical stress analysis and experiments.

Practical implications

Though the designed model in this work is for the 2.4 mm aluminium tube forming, it can also be used for different tube materials, tube dimensions and other electromagnetic forming applications with some modifications.

Originality/value

The research results provide powerful theoretical, numerical simulation and experimental support for the robust electromagnet design.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 38 no. 2
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 3 December 2020

Fei Wang and Xiaobing Zhang

This study aims to present a numerical study on the flow and heat transfer performance of a water-cooled tube with protrusions in different geometrical parameters.

Abstract

Purpose

This study aims to present a numerical study on the flow and heat transfer performance of a water-cooled tube with protrusions in different geometrical parameters.

Design/methodology/approach

A new type of enhanced heat exchanger tube is designed. Protrusions are formed on the inner surface of the tube by mechanical expansion, compression and other processing methods. A three-dimensional numerical symmetry model is established by ANSYS for studying the influence of protrusion distance, protrusion radius and protrusion arrangement on flow and heat transfer characteristics in turbulent flow.

Findings

The results show that the protrusions increase the heat transfer area and improve the heat transfer effect but also increase the flow resistance. Performance evaluation criteria (PEC) is applied to evaluate the flow and heat transfer characteristics of convex tubes. When adopting the aligned protrusions arrangement, the radius of 2 mm and distance of twice the protrusion radius is most heat transfer effect. The PEC of protrusion tubes with a staggered arrangement are higher than those in aligned arrangement, and the maximum value is 2.36 when Reynolds number is 12,000.

Originality/value

At present, most of the protrusion technology applications are based on the cold plate heat dissipation of electronic devices, and the flow path is rectangular. Convex tube heat exchanger is a high-efficiency heat exchanger, which uses convex tubes instead of smooth tubes in tubular heat exchangers to enhance heat transfer and widely used in petroleum, chemical, textile, oil refining and other industries.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 31 no. 5
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 1 May 1961

ON Friday, March 24, 1961, the Minister of Aviation, Mr Peter Thorneyeroft, officially opened a new high supersonic speed wind tunnel at the Royal Aircraft Establishment…

Abstract

ON Friday, March 24, 1961, the Minister of Aviation, Mr Peter Thorneyeroft, officially opened a new high supersonic speed wind tunnel at the Royal Aircraft Establishment, Bedford. This tunnel provides the final stage in the present plans for expansion of the wind tunnel facilities at Bedford, being capable of providing speeds from Mach 2.5 up to Mach 5 in a working section measuring 4x3 ft. Three other tunnels arc already in operation at Bedford—these being the 13x9 ft. working section low‐speed tunnel, the 3x3 ft. tunnel, which is transonic and supersonic to Mach 2, and the 8x8 ft. tunnel, which is subsonic and supersonic to Mach 2.8.

Details

Aircraft Engineering and Aerospace Technology, vol. 33 no. 5
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 21 March 2008

Shafiqur Rehman and S.A. Khan

This paper aims to present the results of an experimental investigation carried out to control the base pressure in a suddenly expanded axi‐symmetric passage.

Abstract

Purpose

This paper aims to present the results of an experimental investigation carried out to control the base pressure in a suddenly expanded axi‐symmetric passage.

Design/methodology/approach

Four micro‐jets of 1 mm orifice diameter located at 90° interval along a pitch circle diameter of 1.3 times the nozzle exit diameter in the base region was employed as active controls. The test Mach numbers were 1.25, 1.3, 1.48, 1.6, 1.8, 2.0, 2.5 and 3.0. The jets were expanded suddenly into an axi‐symmetric tube with cross‐sectional area 4.84 times that of nozzle exit area. The length‐to‐diameter ratio of the sudden expansion tube was varied from 10 to 1. Nozzles generating the above jet Mach numbers were operated with nozzle pressure ratio in the range 3‐11. As high as 40 per cent increase in base pressure was achieved. In addition to base pressure, the wall pressure in the duct was also measured.

Findings

It is found that the wall pressure is not adversely influenced by the micro jets.

Originality/value

The paper provides information on internal supersonic flow.

Details

Aircraft Engineering and Aerospace Technology, vol. 80 no. 2
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 October 2006

Yabo Guan, Farhang Pourboghrat and Woong‐Ryeol Yu

The purpose of this paper is to provide an axisymmetric model of tube hydroforming using a Fourier Series based finite element method.

Abstract

Purpose

The purpose of this paper is to provide an axisymmetric model of tube hydroforming using a Fourier Series based finite element method.

Design/methodology/approach

Fourier series interpolation function, which considerably reduces the size of the global stiffness matrix and the number of variables, is employed to approximate displacements. The material of the tube is assumed to be elastic‐plastic and to satisfy the plasticity model that takes into account the rate independent work hardening and normal anisotropy. Numerical solution obtained from an updated Lagrangian formulation of the general shell theory is employed. The axial displacement stroke (a.k.a. axial feed) during tube hydroforming is incorporated using Lagrange multipliers. Contact constraints and boundary friction condition are introduced into the formulation based on the penalty function, which imposes the constraints directly into the tangent stiffness matrix. A forming limit curve based on shear instability and experimental measurements are used as fracture criteria.

Findings

The results obtained from this new formulation are compared against the nonlinear finite element code ABAQUS and experimental measurements for isotropic and transversely anisotropic tube materials. The hoop and axial strains predicted with AXHD code compared excellently with those from ABAQUS FEM code using plane stress axisymmetric (SAX1) and four‐node shell (S4R) elements. However, in the case of aluminum, the numerically predicted maximum hoop strain underestimated the actual hoop strain measured from the tube bulging experiment.

Practical implications

The axisymmetric hydroforming program (AXHD) developed in this work is very efficient in simulating the free‐forming stage of the tube hydroforming process under simultaneous action of internal pressurization and displacement stroke.

Originality/value

Although Fourier Series based finite element method has been used in metal forming, the extended application presented in this paper is novel in the finite element analysis of tube hydroforming.

Details

Engineering Computations, vol. 23 no. 7
Type: Research Article
ISSN: 0264-4401

Keywords

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