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: Turbulence & Mach number. The organization has 404 authors who have published 420 publications receiving 4183 citations. The organization is also known as: DRDL.

Plume-Ducting System Design of Vertical Launcher Using Computational-Fluid-Dynamics Tools

Abstract: V ERTICALLY launched canisterized missiles are very convenient operationally. The design challenge of the verticallaunch system (VLS) is to contain the initial impact of the rocket jet plume and safely discharge the rocket exhaust gas quickly away from the launch installations during firings of the missiles. The schematic of a typical plume-ducting system of a vertical launcher is shown in Fig. 1. Compact VLS needs an innovative mechanical design that requires understanding of the flow structures of the exhaust plumes. Bertin and Korst [1] and Bertin et al. [2] have explained the complex flow features in the VLS. When the jet plume exhausts from the rocket motor it impinges on the bottomwall of the gas-gathering tank (GGT) and then exits through the uptake after circulating in the plenum chamber. Complex flow interactions may make the flow fluctuate, and these unsteady loads need to be considered for the structural design. The large adverse pressure gradient associatedwith a strong shock wave causes a significant fraction of the exhaust flow tomove upstream into the annular gap between the rocket and launchtubewall. Of concern to the designer of VLS is the possibility that, in the event of a restrained firing (hang fire condition), the reverse flow will impinge on the missile causing critical heat-transfer problems. The study of impinging jets in a confined environment in current literature is rather limited. Batson and Bertin [3] obtained wallpressure distribution inside the launcher tube by conducting static rocket tests with cold gas as well as double base solid rocket propellant. Lee et al. [4,5] presented numerical solutions of a missile launcher for supersonic jet impingement. The effect of the plume-exit area of the plenum on the jet structure is studied, and the pressure and temperature rise in the plenum are compared with test data. It is clear that the complex jet-impingement process in a confined environment needs further investigation, and computational fluid dynamics (CFD) can play an important role to understand this complex flow physics and help to arrive at an efficient design of plume-ducting systems.But before using the computational methodology in the design exercise it is essential to validate the numerical tools to find out their range of applications and error band. In the present work, three-dimensional (3-D) viscous simulations are carried out to study the underexpanded plume impingement in a confined environment. 3-D Navier–Stokes equations are solved along with k-e turbulence model using a commercial CFD solver [6]. The computational tool is first validated against experimental results of rocket-exhaust impingement in a confined environment and then used to design a compact plumeducting system for a vertical launcher.

Polycyclic alkanes based high density hydrocarbon fuels preparation and evaluation for LFRJ application

Abstract: Two polycyclic alkane based high density thermally stable hydrocarbon fuels DPCR-2 and DPCR-3 were prepared from processed special petroleum fraction DPCR-1 for LFRJ application. These fuels were subjected to detailed physico-chemical characterization and found to have improved density (0.844 to 0.846 g cm−3 @ 20 °C), low aromatic content ( 62 °C). These newly developed fuels exhibit better properties than aviation turbine fuel (ATF/Jet A-1). The theoretical as well as experimental ramjet performance such as characteristic velocity and chamber pressure for both the fuels are higher than ordinary Jet-A1 and comparable with similar high density T-6 fuel. These fuels show superior storage characteristics in an elastomeric fuel system such as acrylonitrile butadiene rubber used in missile applications. DPCR-2 and DPCR-3 developed for LFRJ application are found to be very promising in terms of performance, density, availability and cost effectiveness in comparison with Jet A-1 fuel which is presently being used in a number of air breathing propulsion systems.

Combustion Experiments of HTPB/RFNA Mixed Hybrid Propellants

Abstract: A series of combustion experiments have been conducted for investigating the regression rates of mixed hybrid propellants using Red Fuming Nitrous Acid (RFNA) as liquid oxidizer and Hydroxyl-Terminated Polybutadiene (HTPB) with the addition of Ammonium Perchlorate (AP) upto 20 percent as the solid fuel. HTPB is the state-of-theart binder used in solid propellant rocket motors and is considered to be a potential candidate fuel for hybrid rocket applications due to its higher regression rate characteristics, greater fuel value, higher carbon/hydrogen ratio and solid loading capability. One of the effective ways of increasing the regression rates in hybrids is the addition of solid oxidizer such as AP in the fuel in small percentages. This type of configuration is called "mixed hybrid" and regression rate enhancement upto 100% is obtained. A series of static tests are conducted to establish the ignition and combustion in the hybrid mode. It is seen that the hybrid propellant has burnt smoothly. The ignition pressure could also be controlled and kept to a reasonable value. Stable combustion within a variation of chamber pressure ±2% and combustion efficiency above 0.95 was achieved. The characteristics of the combustion products are calculated using the NASA CEA code. Regression rate correlations for the different combinations are obtained using the experimental data and ballistic code developed for predicting the performance of hybrid system.

Computational Fluid Dynamics Simulation of Combustion Instability in Solid Rocket Motor : Implementation of Pressure Coupled Response Function

Abstract: Combustion instability in solid propellant rocket motor is numerically simulated by implementing propellant response function with quasi steady homogeneous one dimensional formulation. The convolution integral of propellant response with pressure history is implemented through a user defined function in commercial computational fluid dynamics software. The methodology is validated against literature reported motor test and other simulation results. Computed amplitude of pressure fluctuations compare closely with the literarture data. The growth rate of pressure oscillations of a cylindrical grain solid rocket motor is determined for different response functions at the fundamental longitudinal frequency. It is observed that for response function more than a critical value, the motor exhibits exponential growth rate of pressure oscillations.

Numerical Investigation of Hydrogen-fuelled Scramjet Combustor with Cavity Flame Holder

Abstract: Reacting flow field of a cavity-based hydrogen-fuelled supersonic combustion ramjet (scramjet) combustor has been explored numerically. 3-D RANS equations are solved alongwith k-e turbulence model and infinitely fast rate kinetics for combustion. The flow field inside the flame holding cavity and its effect on the mixing and reaction are explored in detail by performing simulations of two different combustors (with and without cavities) for which elaborate surface pressure measurements are available for reacting and non-reacting flows. Simulations capture all the finer details of the flow field and good match between computed surface pressures experimental values for different equivalence ratios forms the basis of further analysis. The cavity of the combustor behaves as an open cavity for both non-reacting and reacting flow-even though the flow patterns inside the cavity are quite different for both the cases. Flame-holding cavities are seen to augment mixing and reaction in small sized combustors. Defence Science Journal, Vol. 64, No. 5, September 2014, pp.417-425, DOI:http://dx.doi.org/10.14429/dsj.64.5191