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Agrawal G.,Liquid Propulsion System Center | Joseph J.,Liquid Propulsion System Center | Agarwal D.,Liquid Propulsion System Center | Pisharady J.C.,Liquid Propulsion System Center | Sunil Kumar S.,Liquid Propulsion System Center
IOP Conference Series: Materials Science and Engineering | Year: 2017

Cryogenic tanks used for space applications are filled with sub-cooled cryogenic propellants, whose liquid-vapor interface remains undisturbed for long periods of time prior to launch. During this period, substantial amount of heat leaks into the tank from external sources such as solar and ambient convective fluxes, even though the tank is well insulated. This results in thermal stratification near the liquid vapour interface. A transient, two-phase, thermodynamic model of stratification in a cryogenic tank is developed, considering propellant boundary layer flow due to natural convection close to tank wall. Continuity, momentum, energy and mass transfer equations are solved using finite difference-based formulations of SINDA/FLUINT simulator. The analytical model is validated with test results reported in literature. Subsequently, studies are carried out to investigate the effect of liquid sub-cooling in propellant tank on stratified mass and liquid temperature profile. The study shows that sub-cooling of cryogenic tank leads to significant increase in stratified mass. © Published under licence by IOP Publishing Ltd.

Karthikeyan M.,Liquid Propulsion System Center | Naikan V.N.A.,Indian Institute of Technology Kharagpur | Narayan R.,Liquid Propulsion System Center | Sudhakar D.P.,Liquid Propulsion System Center
International Journal of Performability Engineering | Year: 2016

This paper highlights the optimization of Orbital Tungsten Inert Gas (OTIG) welding process parameters by Design of Experiment (DOE) using Taguchi method forwelding of stainless steel of 6mm diameter and 0.7 mm thickness for satellite propulsion feed system. This proposed methodology identifies the optimum parameters for welding and brings out the significance of the individual parameter, combination of any of the two parameters (interaction effect) using Taguchi method by linear model analysis of Signal to Noise (SN) ratio and means verses input parameters. Detailed experiments were carried out and optimum parameters are arrived. Further these are tested by different methods to evaluate the strength required for intended application. This ensures sound and reliable weld joint. The optimum levels of these parameters thus developed are being followed and no call for any rework is reported thereafter. By varying the input parameters (current, RPM, gap between electrode and the job), the weld penetration level or weld quality has been studied in several 6mm diameter tube specimens andthe significance were studied and discussed in the test results.The Factorial Factor design is followed for minimum of 27 (three parameters and three levels=3x3=27) samples for this experiment. By further fine tuning the experiment, the optimized values achieved are current 18.35 Amps, electrode rotation 10 rpm and gap between electrode and job 0.8 mm. The weld specimen quality was verified in accordance with the user's quality standards and found satisfactory. This approach is easy to develop and easy to use that assures the best combination of parameters required for Orbital TIG welding which yield strong and defect free weld joint for Satellite application. © Totem Publisher, Inc.

Gupta R.K.,Vikram Sarabhai Space Center | Kumar V.A.,Vikram Sarabhai Space Center | Gururaja U.V.,Mishra Dhatu Nigam Ltd | Subramani K.,Liquid Propulsion System Center | And 4 more authors.
Metal Science and Heat Treatment | Year: 2015

Rings from titanium alloy Ti6Al4V used for making pressure vessels for launch vehicles are studied after annealing and after solution treatment and aging. The mechanical characteristics of the rings after quenching and aging do not always have the specified values, especially in thicker sections. The studied rings are of two sizes and have a final wall thickness of 30.5 and 17.5 mm. The effect of the temperatures of solution treatment and aging, of the quenching rate, and of the section thickness on the mechanical properties is studied, and the process is updated to provide the required properties. © 2015, Springer Science+Business Media New York.

Manikanda Kumaran R.,Indian Institute of Technology Madras | Sundararajan T.,Indian Institute of Technology Madras | Raja Manohar D.,Indian Space Research Organization | Raja Manohar D.,Liquid Propulsion System Center | And 2 more authors.
AIAA Journal | Year: 2012

The performance of a two-stage ejector during high-altitude testing of large-area-ratio satellite thrusters is numerically investigated. Since the flow rateof the exhaust from the satellite thrusterisvery low, self-ejector action of the exhaust is quite weak; therefore, a two-stage external ejector is required to create the desired low vacuum in the test chamber. The present work attempts to investigate the effects of various operational and geometric parameters on the performance of the two-stage ejector. Predicted results show that the downstream ejector (E2) operation is more critical for maintaining the required vacuum. However, for optimal performance, it is possible to tune the parameters such that both ejectors deliver the same suction effect. Maximum performanceofeach ejector is obtained when the primary jet expanding from the nozzle smoothly seals the mixer throat against backflow. Employing a low molecular weight fluid and high stagnation temperature helps in reducing the quantity of fluid required for test facility evacuation. Useful correlations have been derived to quantify the suction performance of the two-stage ejector, and the predicted results compare well with in-house experimental data. Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc.

Rao G.S.,Vikram Sarabhai Space Center | Sharma V.M.J.,Vikram Sarabhai Space Center | Raman S.G.S.,Indian Institute of Technology Madras | Amruth M.,Liquid Propulsion System Center | And 3 more authors.
Materials Science and Engineering A | Year: 2016

Effects of temperature and strain rate on the tensile properties of Cu-Cr-Zr-Ti alloy in annealed condition were investigated by varying the initial strain rates from 10-4 s-1 to 10-1 s-1 at RT, 300 °C, 450 °C, 600 °C and 700 °C. The yield strength (YS) and ultimate tensile strength (UTS) of the alloy increased with an increase in strain rate at RT and 300 °C, whereas at 450 °C, the material exhibited the highest YS and UTS at the lowest strain rate of 10-4 s-1. At 600 °C, the YS and UTS of the alloy increased with an increase in strain rate and showed the highest YS compared to all the temperatures tested. The alloy showed serrated yielding at 300 °C and at an initial strain rate of 10-4 s-1 whereas at 450 °C, serrated yielding was observed at 10-3 s-1 and 10-4 s-1 strain rates. Microstructural observations showed the presence of creep cavities at 450 °C and strain rate of 10-4 s-1. The creep cavities were present at higher strain rates as the test temperature is increased. Fractography indicates that the fracture is predominantly dimple fracture at RT and 300 °C and intergranular cracks were observed at 600 °C and 700 °C. © 2016 Elsevier B.V.

Sreedhar U.,Indian Institute of Technology Madras | Krishnamurthy C.V.,Indian Institute of Technology Madras | Balasubramaniam K.,Indian Institute of Technology Madras | Raghupathy V.D.,Liquid Propulsion System Center | Ravisankar S.,Liquid Propulsion System Center
Journal of Materials Processing Technology | Year: 2012

Online weld-monitoring systems are being developed to reduce the cost and delays in detecting defects and rectifying welding parameters. It is known that variations (a) in arc positioning, (b) in heat input and (c) due to the presence of contaminants distinctly manifest as differences in the spatial and temporal surface temperature distributions. In this paper, it is demonstrated that (i) offset positioned thermal imaging of online TIG welding is a feasible non-destructive monitoring technique for detecting porosities in the AA2219 welding, (ii) spatio-temporal temperature distributions close to and in the vicinity of the weld pool can provide statistically distinct features in defect-free and defective weld regions, and (iii) thermal image-based assessment compares very favorably with post-weld radiography assessment for significant defect occurrence. Given the high frame rates and temperature resolution of currently available infrared cameras, it is believed that infrared thermography can be a practical weld-monitoring option capable of providing reliable assessment comparable to more elaborate off-line assessment. © 2012 Elsevier B.V. All rights reserved.

Nadig D.S.,Indian Institute of Science | Jacob S.,Indian Institute of Science | Karunanithi R.,Indian Institute of Science | Manjunatha R.,Indian Institute of Science | And 4 more authors.
Cryogenics | Year: 2010

The integral diaphragm pressure transducers machined out of precipitation hardened martensite stainless steel (APX4) are widely used for propellant pressure measurements in space applications. These transducers are expected to exhibit dimensional stability and linearity for their entire useful life. These vital factors are very critical for the reliable performance and dependability of the pressure transducers. However, these transducers invariably develop internal stresses during various stages of machining. These stresses have an adverse effect on the performance of the transducers causing deviation from linearity. In order to eliminate these possibilities, it was planned to cryotreat the machined transducers to improve both the long-term linearity and dimensional stability. To study these effects, an experimental cryotreatment unit was designed and developed based on the concept of indirect cooling using the concept of cold nitrogen gas forced closed loop convection currents. The system has the capability of cryotreating large number of samples for varied rates of cooling, soaking and warm-up. After obtaining the initial levels of residual stress and retained austenite using X-ray diffraction techniques, the pressure transducers were cryotreated at 98 K for 36 h. Immediately after cryotreatment, the transducers were tempered at 510 °C for 3 h in vacuum furnace. Results after cryo treatment clearly indicated significant reduction in residual stress levels and conversion of retained austenite to martensite. These changes have brought in improvements in long term zero drift and dimensional stability. The cryotreated pressure transducers have been incorporated for actual space applications. © 2010 Published by Elsevier Ltd.

Sainadh A.,Vikram Sarabhai Space Center | Jeenu R.,Vikram Sarabhai Space Center | Jayaprakash J.,Vikram Sarabhai Space Center | Ramakrishnan S.,Liquid Propulsion System Center
62nd International Astronautical Congress 2011, IAC 2011 | Year: 2011

Rocket motors designed for high-altitude use is frequently tested under off-design conditions, for example at sea level. In such cases, it is expected that the flow in the rocket nozzle will separate for a considerable portion during test resulting in higher thrust than that computed assuming no flow separation. The thrust coefficient increment for this separated flow region has generally been predicted using empirical equations. In the present paper, the validity of the empirical equation developed by Kalt and Badalis verified for three solid motors of different size static tested at sea level conditions. The analysis showed that the empirical equations developed by Kalt and Badalcan give satisfactory results to compute the thrust with flow separation. Copyright ©2011 by the International Astronautical Federation. All rights reserved.

Dileep Kumar N.,Liquid Propulsion System Center | Thomas Tharian K.,Liquid Propulsion System Center | Isaac A.,Liquid Propulsion System Center | Venkitakrishnan P.V.,Liquid Propulsion System Center
Materials Science Forum | Year: 2015

Brazing is extensively used in liquid rocket engines for realizing various subsystems. In the case of cryogenic engines, brazing operation is done to realize the gas generator. Gas Generator is one of the major systems of cryogenic engine. It generates and supplies hot gases required for running turbine of main turbo pump. This uses liquid oxygen and gaseous hydrogen as propellant combination. Combustion chamber of Gas Generator is of double walled construction with the cylindrical outer shell of transition class ICSS-0716-301 austenitic-martensitic stainless steel and inner shell of ICSS-1218 321, aTi stabilized austenitic stainless steel material brazed together with Fe-Ni-Mn type braze alloy at a temperature of 1180°C. This temperature can cause the grain growth and related issues to the base material. Thus the present work focuses on the effect of the brazing/thermal cycle on mechanical properties and microstructure of the base materials in post braze condition. The results obtained on metallurgical/mechanical behavior of the material showed the different grain growth patterns in inner and outer shell materials. This helped in understanding the effect of brazing condition on the changes in mechanical properties of base materials. © (2015) Trans Tech Publications, Switzerland.

Karunanithi R.,Indian Institute of Science | Jacob S.,Indian Institute of Science | Nadig D.S.,Indian Institute of Science | Prasad M.V.N.,Liquid Propulsion System Center | And 4 more authors.
Physics Procedia | Year: 2015

The measurement of the cryogen level in a cryostage of space crafts is crucial. At the same time the weight of the sensor should be small as it affects the payload fraction of the space craft. An attempt to develop a HTS based level sensor of 400 mm for Liquid Oxygen (LOX) measurement was made. In the initial phase of testing, loss of superconductivity of HTS wire in LOX inside a cryostat was noticed. Thus, a new four wall cryostat was designed to have a stable LOX level to provide thermal stability to the HTS based LOX sensor. The calibration of the developed sensor was carried out against capacitance level sensor which was pre calibrated using diode array to verify its linearity and performance for different current excitation levels. The calibrations were carried out without heater wires. The automatic data logging was accomplished using a program developed in LabVIEW 11.0. © 2015 The Authors.

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