Narayana Murty S.V.S.,Vikram Sarabhai Space Center |
Manwatkar S.K.,Liquid Propulsion Systems Center |
George M.,Liquid Propulsion Systems Center |
Ramesh Narayanan P.,Liquid Propulsion Systems Center
Materials Performance and Characterization | Year: 2016
During the routine testing of a cryogenic engine, failure of a copper alloy (Cu-CrTi-Zr) liner was noticed which led to the test abort. On close inspection of the liner, a circumferential crack with a length of 78 mm was observed on the divergent side of the thrust chamber. Roughening of the inner wall of the thrust chamber was noticed at the cracked location and extended circumference. Thinning of the copper liner wall was observed at the location of the crack indicating plastic yielding of the material at the location of failure. Fracture surface observations by scanning electron microscopy revealed features of material flow and softening at many locations indicative of exposure of fracture surface to high temperature after failure. Further, striation marks were noticed on the fracture surface indicative of fatigue. Very fine recrystallized grains were noticed in optical microscopy at the location of the crack. This is attributed to dynamic recrystallization occurring during deformation at high temperatures. Strain markings and slip bands were noticed in the interior of grains near the fracture edge. Based on extensive microstructural analysis of the failed hardware, it is concluded that the throat of thrust chamber failed due to "thermal ratcheting. © 2016 by ASTM International, 100 Barr Harbor Drive.
Shine S.R.,Indian Institute of Space Science and Technology |
Kumar S.S.,Liquid Propulsion Systems Center |
Suresh B.N.,Indian Space Research Organisation
Energy Conversion and Management | Year: 2013
The flow field associated with cylindrical coolant jets inclined in tangential and azimuthal direction employed inside a circular pipe has been studied. Numerical results are compared with in-house experimental data for a row of circumferential film cooling holes with two distinct geometric configurations. Results provide insight into the film cooling performance and the heat transfer characteristics associated with this type of film-cooling jets. Secondary flow recirculation zones are found near the jet exit in the regimes close to the wall and the center. Its occurrence and length is found to be controlled by the geometric configuration of the coolant hole. This secondary flow structure and the jet impingement on the wall are found responsible for developing a maximum local Nusselt number downstream of coolant injection. Reverse heat transfer regimes are noted for conjugate walls with higher thermal conductivity. The spreading of the coolant around the circumference is mainly due to the asymmetric vorticity levels present at the jet exit plane. Higher tangential orientation of the coolant jet with the mainstream has resulted in lower injectant concentration near the test section wall and lower effectiveness throughout the test section. The results indicate that through the use of optimal coolant injector configurations, reduction in coolant requirement can be achieved. © 2013 Elsevier Ltd. All rights reserved.
Babu S.,Indian Institute of Technology Madras |
Janaki Ram G.D.,Indian Institute of Technology Madras |
Venkitakrishnan P.V.,Liquid Propulsion Systems Center |
Reddy G.M.,Indian Defence Research And Development Laboratory |
Rao K.P.,Indian Institute of Technology Madras
Journal of Materials Science and Technology | Year: 2012
Friction stir lap welds were produced in 3 mm thick Alclad sheets of Al alloy 2014-T4 using two different tools (with triangular and threaded taper cylindrical pins). The effects of tool geometry on weld microstructure, lap-shear performance and failure mode were investigated. The pin profile was found to significantly influence the hook geometry which in turn strongly influenced the joint strength and the failure mode. Welds produced in alloy 2014-T4 Alclad sheets by using triangular and threaded taper cylindrical tools exhibited an average lap-shear failure load of 16.5 and 19.5 kN, respectively, while the average failure load for standard riveted joints was only 3.4 kN. Welds produced in alloy 2014-T6 Alclad sheets and in alloy 2014-T4 bare sheets (i.e., no Alclad) were comparatively evaluated with those produced in alloy 2014-T4 Alclad sheets. While the welds made (with threaded taper cylindrical tool) in T6 and T4 conditions showed very similar lap-shear failure loads, the joint efficiency of the welds made in T6 condition (43%) was considerably lower (because of the higher base material strength) than those made in T4 condition (51%). The Alclad layers were found to present no special problems in friction stir lap welding. Welds made with triangular tool in alloy 2014-T4 Alclad and bare sheets showed very similar lap-shear failure loads. The present work provides some useful insights into the use of friction stir welding for joining Al alloys in lap configuration. © 2012 The Chinese Society for Metals.
Singh S.P.,Institute of Management Sciences |
Singh V.K.,Liquid Propulsion Systems Center
International Journal of Production Research | Year: 2010
Multi-objective facility layout problem (mFLP) generates a different layout by varying objectives weights. Since the selection of objective weights in mFLP is critical, stages of designing layout having multiple objectives, the objective weights therefore play an important role in the layout design of mFLP. In practice, it is selected randomly by the layout designer based on his/her past experience that restricts the layout designing process completely designer dependent and thus the layout varies from designer to designer. This paper aims to resolve the issues of selecting the objective weight for each objective. We propose four methods to determine objective weight which makes the design process of mFLP completely designer independent.
Shine S.R.,Indian Institute of Space Science and Technology |
Sunil Kumar S.,Liquid Propulsion Systems Center |
Suresh B.N.,Indian Space Research Organization
International Journal of Heat and Mass Transfer | Year: 2012
A one dimensional analytical model of liquid film cooling in rocket combustion chambers operating at subcritical conditions is developed. The approach followed involves the selection of a control volume for mass and energy balance. The coolant evaporation rate per area is obtained from this energy balance. The present model incorporates mass transfer via entrainment by adapting suitable correlations from literature pertaining to annular flow conditions. The model predicted favourably with the experimental data available in open literature and produced superior results compared to all existing models. Results are presented for a mixed gas-water system under different conditions. Results indicate that convection dominates the heat transfer at the gas-liquid interface. Effects of gas Reynolds number, coolant inlet temperature, combustion chamber pressure, mass flow ratio of the liquid coolant to the free stream and the free stream turbulence on the liquid film length are presented in detail. © 2012 Elsevier Ltd. All rights reserved.
Vinayaravi R.,Liquid Propulsion Systems Center |
Kumaresan D.,College of Engineering, Trivandrum |
Jayaraj K.,College of Engineering, Trivandrum |
Asraff A.K.,College of Engineering, Trivandrum |
Muthukumar R.,College of Engineering, Trivandrum
Journal of Sound and Vibration | Year: 2013
Impact damping is a method for improving damping of a dynamic system by means of energy dissipation due to repeated collisions of a free mass on the base structure. This paper deals with the theoretical and experimental investigations carried out to study and characterize damping with respect to the level of base excitation. The mathematical model consists of a two degree of freedom system (in which the main system is modelled as single degree of freedom system (sdof)) which undergoes momentum transfer between main mass and impact mass. The velocity response obtained from the mathematical model for the main mass and impact mass clearly indicates that the damping of the system depends on the number of effective impacts and not on the total number of impacts. Here the effect of impact damping is studied for low frequency and high amplitude excitation. Optimum parameters are determined for design of impact damper based on the mathematical model. Experiments are conducted on a cantilever beam for various excitation levels. The damping characteristics obtained from test data are compared with the predictions made from mathematical model. A good match is obtained between theoretical and experimental results. It is also observed that the energy gets re-distributed to higher modes due to the high shock that occurs during collision of the impact mass with main mass. © 2012 Elsevier Ltd. All rights reserved.
Krishna S.C.,Vikram Sarabhai Space Center |
Tharian K.T.,Liquid Propulsion Systems Center |
Pant B.,Vikram Sarabhai Space Center |
Kottada R.S.,Indian Institute of Technology Madras
Journal of Materials Engineering and Performance | Year: 2013
The Cu-3Ag-0.5Zr alloy was produced by vacuum induction melting and subsequently processed through hot forging and rolling. Detailed microstructural characterization of solution-treated (ST) specimen shows three types of phases: Cu matrix, zirconium-rich phase, Cu-Ag-Zr intermetallic phase. Transmission electron microscopy studies together with energy-dispersive x-ray spectroscopy analysis established the presence of Zr-rich large particles in the ST condition. Aging at 450 C for 4.5 h after solution treatment resulted in the formation of uniformly distributed fine spherical silver precipitates with an average diameter of 9.0 ± 2.0 nm. Consequently, room temperature yield strength (YS) and ultimate tensile strength (UTS) of the aged specimen increased by 110% and 15%, respectively, compared to those of 120 and 290 MPa of the ST specimen. At elevated temperature, the YS decreased to 146 and 100 MPa at 540 and 640 C, respectively, for the aged sample. On the contrary, the YS increased to 140 MPa at 540 C, thereafter a decrease was observed with a value of 105 MPa at 640 C for the ST sample. This decrease in YS at higher temperatures is attributed to coarsening of precipitates and dissolution of the precipitates, whereas an increase in YS is attributed to in-situ aging of the samples. © 2013 ASM International.
Tharakan T.J.,Liquid Propulsion Systems Center |
Rafeeque T.A.,Liquid Propulsion Systems Center
Aerospace Science and Technology | Year: 2016
Sharp edged injection orifices used in thrust chambers and thermal regulation system of liquid rocket engines have to maintain a steady flow to ensure optimum performance. These orifices are subjected to backpressure and elevated temperature during actual operation. The sharp edged orifices do not always run full due to the orifice geometry and/or flow conditions. In some cases, the flow may change its characteristics from attached to detached flow or vice versa. Length of the orifice in relation to its diameter and the backpressure have been observed to play an important role in the abrupt changes in the flow characteristics. In order to comprehensively characterize this phenomenon and to clearly identify the governing parameters, discharge characteristics were determined experimentally for sharp edged injection orifice of 0.6 and 1.4 mm diameters with length-to-diameter ratios in range between 1.4 and 11.5. Cavitation numbers were varied in the range of 0.06 to 20.9 while Reynolds numbers were varied in the range of 13 000 to 62 500. The backpressure for the injection orifice was varied upto 3.6 MPa. The effect of backpressure, Reynolds number, cavitation number, length-to-diameter ratio, and injection pressure drop-to-backpressure ratio on discharge characteristics was brought out. The experimental investigation gives the detailed flow characteristics of sharp edged orifices in the presence of backpressure. © 2015 Elsevier Masson SAS. All rights reserved.
Agarwal D.K.,Liquid Propulsion Systems Center |
Vaidyanathan A.,Indian Institute of Space Science and Technology |
Kumar S.S.,Liquid Propulsion Systems Center
Applied Thermal Engineering | Year: 2013
The present work investigates kerosene-alumina nanofluid for its stability, thermal conductivity and viscosity at low volume concentration of nanoparticles. The study intends to explore the possible application of using kerosene-alumina nanofluid in regenerative cooling channels of semi-cryogenic rocket engine. Nanofluid is prepared and characterized with varying particle loadings of 0.05%-0.5% by volume, in steps, for two different particle sizes of 13 nm and 50 nm. Oleic acid, as a surfactant, is used to stabilize the nanofluid and an optimum volume ratio of oleic acid to alumina particle is determined for enhanced stability of nanofluid. Dynamic Light Scattering (DLS) method is used to determine the average particle size in the nanofluid thus prepared with time. 22% enhancement in thermal conductivity and 10% in viscosity at room temperature are obtained for 13 nm particle size nanofluid at 0.5% volume concentration. Lower enhancement in thermal conductivity and viscosity are noticed for nanofluid prepared with bigger nanoparticles. The effect of temperature on thermo-physical properties is also determined and a non-linear increase in thermal conductivity with temperature is noticed. At elevated temperature, nanofluids show higher enhancement in their thermo-physical properties. A simple method for assessing the stability of nanofluid is attempted by measuring the thermal conductivity of nanofluid with time. © 2013 Elsevier Ltd. All rights reserved.
Aswathy S.,Liquid Propulsion Systems Center |
Gopikuttan A.,Kerala University
Annals of Library and Information Studies | Year: 2013
The study analyses the publication pattern of faculty members of three universities in Kerala viz., University of Kerala, Mahatma Gandhi University and University of Calicut. Authorship pattern, Degree of Collaboration, the appropriateness of Lotka's Inverse Square Law and year-wise and designation-wise distributions have been studied. The year-wise distribution of publications indicates that there is a growth in the number of publications. It is found that multi-authorship dominates among university teachers and there is no statistically significant difference between the experience and productivity. Designation-wise Degree of Collaboration shows that Professors are having a high Degree of Collaboration which indicates that increase in the age and experience results in more collaborative papers. The Lotka's inverse square law seems to be rejected for the present data set.