Journal ArticleDOI
Rotation effects on axisymmetric sudden-expansion flows
Ronald M. C. So,Saad Ahmed +1 more
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In this paper, the effect of rotation on mixing in the dump combustor of a ramjet propulsion system was simulated by a Plexiglas tube of 63.5 mm I.D. and 76.2 cm long.Abstract:
The dump combustor of a ramjet propulsion system was simulated by a Plexiglas tube of 63.5 mm I.D. and 76.2 cm long. A convergent nozzle with an exit diameter of 43.2 mm was fitted to the inlet of the tube. Therefore, this arrangement provided a sudden expansion and gave a step height of 10.15 mm. Tube rotation effects on mixing in the dump combustor were examined by rotating the Plexiglas tube about its own axis at a constant speed. The flow downstream of the sudden expansion was studied using a one-color, one-component, laser-Doppler anemometer. Two conditions were investigated in detail, one with the tube rotating at 840 rpm and another with the tube stationary. In addition, three other experiments with different tube rotational speeds were carried out to determine the dependence of reattachment length on rotation. The average inlet velocity was set at ~ 10.6 m/s for all experiments. The results show that the primary reattachment length decreased as rotation increased because of the destabilizing effect due to the large shear created by the rotating tube wall. A detailed comparison of the flow characteristics with and without rotation present is made, and the effects of rotation on the flow are analyzed.read more
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Journal ArticleDOI
Variable density effects on axisymmetric sudden-expansion flows
G.J. Yoo,Ronald M. C. So +1 more
TL;DR: In this paper, a low-Reynolds-number full Reynolds stress closure that can account for viscous effects near a wall and thus avoid the use of wall functions is used to close the time-averaged Navier-Stokes equations.
Journal ArticleDOI
Characteristics of dump combustor flows
Ronald M. C. So,Saad Ahmed +1 more
TL;DR: In this article, the effects of rotation and turbulene in combustors with different inlet geometries and flow conditions were investigated, and it was shown that inlet geometry only has as indirect effect on the combustor flow.
Journal ArticleDOI
Computational studies of turbulent premixed flame based dump combustor
Debi Prasad Mishra,T. Vishak +1 more
TL;DR: In this article, the effects of various flow parameters such as inlet Reynolds number, inlet turbulence intensity and expansion ratio on important flow quantities like axial velocity, turbulent kinetic energy and turbulent dissipation rate have been studied extensively.
Journal ArticleDOI
Engineering design models for ramjet efficiency and lean blowoff
TL;DR: Combustion efficiency and lean blowoff semi-empirical preliminary design models, validated originally for laboratory axisymmetric flameholders and conventional gas turbine combustors, are extended to dump combustor ramjet geometries as discussed by the authors.
Journal ArticleDOI
A hybrid k‐ε turbulence model of recirculating flow
TL;DR: A satisfactory agreement of model predictions with experimental data reveals that the hybrid k-e model can perform better simulation of recirculating turbulent flows.
References
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Journal ArticleDOI
Shear-Layer Flow Regimes and Wave Instabilities and Reattachment Lengths Downstream of an Abrupt Circular Channel Expansion
L. H. Back,E. J. Roschke +1 more
Journal ArticleDOI
Turbulent Heat Transfer in the Separated, Reattached, and Redevelopment Regions of a Circular Tube
K. M. Krall,E. M. Sparrow +1 more
Journal ArticleDOI
Local Heat Transfer Downstream of an Abrupt Expansion in a Circular Channel With Constant Wall Heat Flux
TL;DR: In this paper, the authors measured the local heat transfer coefficients to an air flow downstream of an axisymmetric abrupt expansion in a circular pipe with a constant wall heat flux.
Journal ArticleDOI
Turbulent Flow in Axially Rotating Pipes
TL;DR: In this article, a fully developed turbulent flow was introduced into a long smooth pipe rotating about its axis, and changes of the flow pattern, together with hydraulic loss within the pipe, were examined by measuring the velocity and pressure distributions across sections at various distance from the pipe entrance.
Journal ArticleDOI
Flow Characteristics of Axisymmetric Expansions
TL;DR: In this article, a combination of analytical and experimental means was used to determine the characteristics of flow for four abrupt expansions with half angles of 15, 30, 45, and 90 degrees.