Defence Research and Development Laboratory

About: Defence Research and Development Laboratory is a facility organization based out in Hyderabad, India. It is known for research contribution in the topics: Mach number & Turbulence. The organization has 404 authors who have published 420 publications receiving 4183 citations. The organization is also known as: DRDL.

Propellant Grade Hydrazine in Mono/Bi-propellant Thrusters: Preparation and Performance Evaluation

Abstract: Propellant grade hydrazine was prepared with 64 per cent yield and 95.5 per cent purity. Purity of the propellant grade hydrazine was determined using wet chemical, gas chromatographic (GC) and eudiometric methods. It was observed that the compositions containing blends of hydrazine-methyl alcohol-ammonium nitrate and hydrazine-methyl alcohol-ammonium perchlorate were not found to be frozen even after cooling to -65 °C for 30 minutes. Mono and bi-propellant thrusters were designed and developed to demonstrate the performance of prepared propellant grade hydrazine as a promising rocket fuel. Five static tests with 22 N thruster and one static test with 1 N thruster were performed successfully in mono-propellant mode. The hurdles of chamber pressure oscillations were overcome by compact packing of the catalyst. The desired decomposition and chamber pressure were achieved. One static test was performed successfully with 60 N bi-propellant thruster. The desired chamber pressure and thrust were achieved. The combustion was smooth and C* achieved was higher than that of UH-25, N2O4 combination. The performance of prepared propellant grade hydrazine shows it as a promising rocket fuels.Defence Science Journal, Vol. 65, No. 1, January 2015, pp.31-38, DOI:http://dx.doi.org/10.14429/dsj.65.7986

Improvement of strain tolerance of functionally graded TBCs through laser surface micro-texturing

Abstract: Atmospheric plasma-sprayed thermal barrier coating made up of YSZ and LaMgAl11O19/YSZ was plasma-sprayed over nickel-based superalloy. The coated surfaces are textured using a picosecond pulsed laser for different groove geometries. The scanning parameters were optimised to minimise the occurrences of re-cast layer and horizontal cracks. The textured samples were subjected to thermal shock cycles to study their thermal stability. The width-to-depth ratio (W d) and the groove spacing between the adjacent texture were varied to analyse and correlate their geometrical influence in providing thermal stress–strain tolerance. The textured samples exhibit higher lifetime compared to the YSZ and LaMgAl11O19/YSZ as-sprayed surface. The induced thermal stress and minimal strain tolerance in the as-sprayed surfaces result in the traditional interface delamination failure where the failure occurs at the bond coat–ceramic layer interface. The textured grooves having higher W d restrain the propagation of crack across the coating thickness and provide improved strain tolerance. The horizontal cracks initiated at the edge propagates across the textured layer chipped the groove segments within the ceramic bulk layer. The LaMgAl11O19/YSZ-based textured sample having W d of 0.8 and 300 µm groove spacing exhibits higher lifetime of 219 thermal cycles. This implies the significance of groove density in improving the thermal shock resistance of TBCs.

Thermal Reactivity of Double‐Base Rocket Propellants

Abstract: Thermal decomposition studies on double-base propellants have been carried out in air and vacuum using differential scanning calorimetric, thermogravimetric and mass spectrometric techniques. Low temperature (90 degree C-170 degree C) decomposition seems to involve diffusion controlled process, the mechanism in air and vacuum being different. High temperature (170 degree -205 degree C) decomposition involves bond breakage.

A simple hybrid finite volume solver for compressible turbulence

Abstract: Summary A simple, explicit, hybrid finite volume method for simulating compressible turbulence is developed by combining a fourth-order central scheme and a shock-capturing simple low-dissipation advection upstream splitting method. The total flux on each of the cell faces is computed as a weighted average of central/nondissipative and upwind/dissipative fluxes. The weights are determined using an unphysical oscillation sensor in addition to a more traditional discontinuity sensor used in earlier studies. Shocks are well captured, but overshoots in density are predicted around contact discontinuities that are normal to the flow. The use of the latter sensor effectively prevents these overshoots from generating spurious oscillations that travel away from the contact lines. The efficacy of the proposed method for direct or large-eddy simulations of supersonic turbulence is established using several canonical test problems. Copyright © 2015 John Wiley & Sons, Ltd.