Showing papers by "Defence Research and Development Laboratory published in 2008"
TL;DR: In this paper, a full-scale scramjet combustor with kerosene fuel injected from struts placed in the combustor flowpath was designed and analyzed using computational-fluid-dynamics software.
Abstract: Computational-fluid-dynamics-based design and analysis is presented for a full-scale scramjet combustor with kerosene fuel injected from struts placed in the combustor flowpath. Three-dimensional Navier-Stokes equations are solved with a K-e turbulence model using commercial computational-fluid-dynamics software. Combustion is modeled based on infinitely fast chemical kinetics. Lagrangian dispersed-phase analysis is considered for fueldroplet evaporation and mixing in the supersonic stream. Parametric studies are carried out to investigate the effect of combustor-inlet Mach number and total pressure on the flow development process. A higher combustor-entry Mach number and distributed-fuel-injection system will ensure the existence of predominant supersonic flow in the combustor. Simulations are also carried out to investigate two different kinds of fuel injection struts in the scramjet combustor performance. A distributed-fuel -injection system, required to avoid thermal choking, increases the three-dimensionality of the flowfield.
50 citations
TL;DR: Partially melted zone (PMZ) cracking susceptibility in AA6061 alloy was studied in this article, where role of different grain refiners such as scandium, zirconium and Tibor in the above fillers was studied.
43 citations
TL;DR: In this article, the improvement of mechanical properties of AA 5456 Alloy welds through magnetic arc oscillation process was investigated and regression models were developed to evaluate the effect of welding current, welding speed, amplitude and frequency on mechanical properties.
34 citations
TL;DR: In this article, the influence of post weld heat treatment on fatigue crack growth behavior of electron beam welded AA2219 aluminium alloy was reported and three post welding heat treated joints were evaluated.
24 citations
TL;DR: In this paper, the effect of post weld heat treatment on fatigue behavior of electron beam welded AA2219 aluminium alloy was reported, and three post welding heat treated joints, the solution treated and aged joints are enduring higher number of cycles under the action of cyclic loads.
21 citations
TL;DR: In this paper, microcrystalline straight grade carbide inserts have been used for end milling of Nimonic 263 under different machining environments, viz. conventional wet, cryogenic cooling with Liquid Nitrogen (LN2) and high pressure (HP) cooling.
Abstract: Microcrystalline straight grade carbide inserts have been used for end milling of Nimonic 263 under different machining environments, viz. conventional wet, cryogenic cooling with Liquid Nitrogen (LN2) and High Pressure (HP) cooling. Tool life, tool failure mode, chip morphology and surface finish generated during machining have been recorded and studied. Tool life improvement of as high as 275% was observed under HP cooling for certain parameter combinations compared to conventional wet. Machining under LN2 cooling produced worst results among all the three environments. This is attributed to the increased thermal fluctuation during machining under LN2 cooling. Chipping of cutting edge was found to be the most dominant failure mode for all the cases. Increase in Material Removal Rate (MRR) can be observed by superimposing iso-MRR curves on iso-tool life curves.
11 citations
TL;DR: The software package described here deals with the assessment of damage inflicted by missiles carrying pre-fragmented, bomblet, incendiary, runway-denial penetration submunition (RDPS), smart munition, and terminallyguided submunition warhead.
Abstract: The software package described here deals with the assessment of damage inflicted by missiles carrying pre-fragmented, bomblet, incendiary, runway-denial penetration submunition (RDPS), smart munition, and terminallyguided submunition warhead. The targets to be neutralised could be static, semistatic or mobile, like runways,bridges, bunkers, armoured tanks, soft-skinned vehicles, and personnel. This is graphical user interface(GUI)-based software, where the user can specify the target dimensions, target types, the number of missiles, its aimpoint, the type of warhead and the mode of operation. The software gives the number of targets that have beenneutralised effectively, as the output. This GUI-based software has been developed using Microsoft Visual Basic,Version 6.0. Defence Science Journal, 2008, 58(6), pp.745 -751 , DOI:http://dx.doi.org/10.14429/dsj.58.1702
6 citations
TL;DR: In this article, the effect of transverse liquid injection (distilled water) on the acoustic field generated by confined supersonic flow past a cavity was investigated. And the dependence of suppression/amplification of the acoustic amplitudes on the injection condition and cavity depths was ascertained.
Abstract: This paper describes an experimental investigation of the effect of transverse liquid injection (distilled water) on the acoustic field generated by confined supersonic flow past a cavity. The effect of cavity depth in the absence/ presence of liquid injection on the acoustic field is studied. In the presence of liquid injection, the effects of injection pressure and injection location on the acoustic field are investigated. The dependence of suppression/amplification of the acoustic amplitudes (compared with the absence of injection) on the injection condition and cavity depths is ascertained. In general, liquid injection in the presence of cavity resulted in higher amplitudes. Even square cavities that did not exhibit oscillations in the absence of injection generated significant acoustic amplitudes in the presence of liquid injection at high injection pressures. Phase-locked schlieren imaging was performed to sequence the fluid-dynamic events. Schlieren images indicate the interaction of the shock wave generated by the flow past the liquid jet and the oblique shock generated at the cavity-leading edge. The schlieren images show that the amplitude increase observed for higher injection pressures for a range of cavity depths is accompanied by an unsteady normal shock ahead of the cavity-leading edge (which does not span the entire width of the test model, but is located locally in front of the liquid jet).
3 citations
TL;DR: In this paper, a numerical analysis of an integrated liquid ramjet engine considering coupling phenomenabetween various sub-systems viz., air intake, combustor and nozzle has been reported, and the results include cold flow studies, heat addition in thecombustor and full engine analysis with coupled simulation of supersonic air-intake and combustion chamber along with the nozzle.
Abstract: The numerical simulation of an integrated, liquid-fuelled ramjet engine comprising supersonicair intake, subsonic combustor and a convergent-divergent nozzle has been carried out and theresults are discussed in this paper. These results include cold flow studies, heat addition in thecombustor and full engine analysis with coupled simulation of supersonic air-intake andcombustion chamber along with the nozzle. Overall ramjet operation depends on the performanceof the air intake and the combustion chamber. The coupling phenomena are very dominant andperformance of air intake is affected vastly by the combustor operation and vice versa. In thispaper, a numerical analysis of integrated liquid ramjet engine considering coupling phenomenabetween various sub-systems viz., air intake, combustor and nozzle has been reported.
3 citations
TL;DR: In this paper, the complexity arises because of the mixing of fuel and airstreams, and the burning of the resultant mixture, within the confined space of the combustion chamber, in a subsonic side-dump combustor.
Abstract: The liquid fuel ramjet system employing a subsonic side-dump combustor is simulated inthe present study, and the predictions are compared with the available experimental data. Thecomplex combustion phenomenon in a ramjet combustor has been carried out using probabilitydensity function (PDF) approach. The complexity arises because of the mixing of fuel and airstreams, and the burning of the resultant mixture, within the confined space of the combustionchamber. The predicted numerical results have been validated with the results available in openliterature for a two-dimensional case and with in-house experimental data for a three-dimensionalcase. The methodology allows different designs to be evaluated quantitatively based on theperformance metrics such as combustion efficiency, flame stability, etc.Defence Science Journal, 2008, 58(1), pp.3-14, DOI:http://dx.doi.org/10.14429/dsj.58.1620
01 Jan 2008
TL;DR: Issues related to integrity check of quantum cryptography based on qbits are described, which show the vulnerability of key distribution process and in turn vulnerability of secret message.
Abstract: Communication of key to the receiver of cipher message is an important step in any cryptographic system. But the field of cryptanalysis is also progressing keeping pace with progress in cryptography and everyday newer and faster computers with more and more memory space are appearing. Increasing the vulnerability of key distribution process and in turn vulnerability of secret message. People are exploring totally different areas of technology in search of a secure key distribution system. "Quantum cryptography" is one such technology with promises for future. This paper describes issues related to integrity check of quantum cryptography based on qbits.
25 Sep 2008
TL;DR: This work is trying to reduce the cupping artifact induced by beam hardening as well as metal artifact as they exist in the CT scan of a human hip after the femur is replaced by a metal implant.
Abstract: X‐ray Computed Tomography (CT) is a relatively new technique developed in the late 1970’s, which enables the nondestructive visualization of the internal structure of objects. Beam hardening caused by the polychromatic spectrum is an important problem in X‐ray computed tomography (X‐CT). It leads to various artifacts in reconstruction images and reduces image quality. In the present work we are considering the Artifact Reduction in Total Hip Prosthesis CT Scan which is a problem of medical imaging. We are trying to reduce the cupping artifact induced by beam hardening as well as metal artifact as they exist in the CT scan of a human hip after the femur is replaced by a metal implant. The correction method for beam hardening used here is based on a previous work. Simulation study for the present problem includes a phantom consisting of mild steel, aluminium and perspex mimicking the photon attenuation properties of a hum hip cross section with metal implant.