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VR Sanal Kumar

Bio: VR Sanal Kumar is an academic researcher from Indian Space Research Organisation. The author has contributed to research in topics: Choking & Nozzle. The author has an hindex of 8, co-authored 103 publications receiving 347 citations. Previous affiliations of VR Sanal Kumar include Kumaraguru College of Technology & Indian Institute of Science.
Topics: Choking, Nozzle, Thrust, Boundary layer, Propellant


Papers
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Journal ArticleDOI
TL;DR: In this paper, the authors predict the ignition transient of a solid-propellant rocket motors with a nonuniform port, with sudden expansion and/or steep divergence/convergence or protrusions.
Abstract: PREDICTION and control of pressure and pressure-rise rate during the ignition transient of solid-propellant rocket motors with a nonuniform port are of topical interest. In certain designs, an ignition pressure spike and a high rate of pressure rise may adversely affect the steadiness and stability of burning, thermoviscoelastic response of the grain and inhibitors, and the dynamic response of the hardware parts.1 An excessive pressurization rate can cause a failure even when the pressure is below the design limit.2,3 Although, a great deal of research has been done in the area of solid rocket motors (SRMs) for more than six decades, the accurate prediction of the ignition transient in ports of high-performance solid rocket, with sudden expansion and/or steep divergence/convergence or protrusions has not previously been accomplished.

38 citations

Journal ArticleDOI
TL;DR: In this article, it has been shown conclusively that under certain conditions of step location, step height, and port height, which govern the velocity of gases at the step by the partially ignited propellant surface or by the igniter gas Row, secondary ignition can occur far downstream of the step, This is very likely to be within the recirculating Row region.
Abstract: Detailed theoretical and experimental studies on flame spread over nonuniform ports of solid propellant rockets have been carried out. An idealized two-dimensional laboratory motor was used for the experimental study with the aid of cinematography. A detailed numerical simulation of the flame spread has also been carried out with the help of a two-dimensional Navier-Stokes solver. Experimental results showing the phenomenon of secondary ignition have been reported earlier and also reviewed here with the inclusion of additional results of a three-dimensional geometry closer to a dual-thrust motor. In this paper more tangible results including the numerical modeling of flame spread have been reported. It has been shown conclusively that under certain conditions of step location, step height, and port height, which govern the velocity of gases at the step by the partially ignited propellant surface or by the igniter gas Row, secondary ignition can occur far downstream of the step, This is very likely to be within the recirculating Row region. The secondary ignition gives rise to two additional flame fronts, one of which spreads backward st a relatively lower velocity, presumably as a result of low reverse velocities present in the separation zone. This phenomenon is Likely to play an important role in the starting transient of solid propellant rockets with nonuniform ports.

37 citations

Journal ArticleDOI
TL;DR: In this paper, a more realistic experimental method was reported for the characterization of propellants at multiaxial stress conditions using a grain-pressurization test called the tubular test.
Abstract: The accurate thermoviscoelastic characterization of a solid propellant is critical for optimum design of grains for high-performance solid motors for space applications. A more realistic experimental method is reported for the characterization of propellants at multiaxial stress conditions using a grain-pressurization test called the tubular test. An idealized cylindrical grain with hydroxyl-terminated-polybutadiene-based propellant is used. From the measured outer radial expansion of the tubular specimen, creep compliance and the relaxation modulus of the propellant are computed based on linear viscoelastic theory. The relaxation-modulus data obtained from the tubular test are shown to be higher than the traditional uniaxial and strip biaxial tests at the same strain level. Different isothermal tubular tests are carried out at various strain levels, and master curves are generated. The tubular test with internal pressurization is found to be an easier, more inexpensive, and realistic method for predicting the relaxation-modulus values of solid propellants and to have great potential for the thermoviscoelastic characterization of solid propellants.

32 citations

Journal ArticleDOI
TL;DR: In this paper, a closed-form analytical model is developed for estimating the 3D boundary-layer-displacement thickness of an internal flow system at the Sanal flow choking condition for adiabatic flows obeying the physics of compressible viscous fluids.
Abstract: A closed-form analytical model is developed for estimating the 3D boundary-layer-displacement thickness of an internal flow system at the Sanal flow choking condition for adiabatic flows obeying the physics of compressible viscous fluids. At this unique condition the boundary-layer blockage induced fluid-throat choking and the adiabatic wall-friction persuaded flow choking occur at a single sonic-fluid-throat location. The beauty and novelty of this model is that without missing the flow physics we could predict the exact boundary-layer blockage of both 2D and 3D cases at the sonic-fluid-throat from the known values of the inlet Mach number, the adiabatic index of the gas and the inlet port diameter of the internal flow system. We found that the 3D blockage factor is 47.33 % lower than the 2D blockage factor with air as the working fluid. We concluded that the exact prediction of the boundary-layer-displacement thickness at the sonic-fluid-throat provides a means to correctly pinpoint the causes of errors of the viscous flow solvers. The methodology presented herein with state-of-the-art will play pivotal roles in future physical and biological sciences for a credible verification, calibration and validation of various viscous flow solvers for high-fidelity 2D/3D numerical simulations of real-world flows. Furthermore, our closed-form analytical model will be useful for the solid and hybrid rocket designers for the grain-port-geometry optimization of new generation single-stage-to-orbit dual-thrust-motors with the highest promising propellant loading density within the given envelope without manifestation of the Sanal flow choking leading to possible shock waves causing catastrophic failures. (C) 2018 Author(s).

31 citations


Cited by
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Book
01 Dec 1988
TL;DR: In this paper, the basic processes in Atomization are discussed, and the drop size distributions of sprays are discussed.Preface 1.General Considerations 2.Basic Processes of Atomization 3.Drop Size Distributions of Sprays 4.Atomizers 5.Flow in Atomizers 6.AtOMizer Performance 7.External Spray Charcteristics 8.Drop Evaporation 9.Drop Sizing Methods Index
Abstract: Preface 1.General Considerations 2.Basic Processes in Atomization 3.Drop Size Distributions of Sprays 4.Atomizers 5.Flow in Atomizers 6.Atomizer Performance 7.External Spray Charcteristics 8.Drop Evaporation 9.Drop Sizing Methods Index

1,214 citations

Journal ArticleDOI
TL;DR: In this paper, a 3D model of fuel flow in terms of the fuel's real properties and cracking reaction is built and validated through experiments to study the thermal behavior in the cracking reaction zone of regeneratively cooled scramjet cooling channels at different aspect ratios.

68 citations

Journal ArticleDOI
TL;DR: In this paper, the authors predict the ignition transient of a solid-propellant rocket motors with a nonuniform port, with sudden expansion and/or steep divergence/convergence or protrusions.
Abstract: PREDICTION and control of pressure and pressure-rise rate during the ignition transient of solid-propellant rocket motors with a nonuniform port are of topical interest. In certain designs, an ignition pressure spike and a high rate of pressure rise may adversely affect the steadiness and stability of burning, thermoviscoelastic response of the grain and inhibitors, and the dynamic response of the hardware parts.1 An excessive pressurization rate can cause a failure even when the pressure is below the design limit.2,3 Although, a great deal of research has been done in the area of solid rocket motors (SRMs) for more than six decades, the accurate prediction of the ignition transient in ports of high-performance solid rocket, with sudden expansion and/or steep divergence/convergence or protrusions has not previously been accomplished.

38 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the effect of boundary layer blockage on the internal flow choking in a dual-thrust motor and found that the blockage is greater in magnitude for the choked case than for the unchoked case.
Abstract: Theoretical studies have been carried out to examine internal flow choking in the inert simulators of a dual-thrust motor. Using a two-dimensional k-omega turbulence model, detailed parametric studies have been carried out to examine aerodynamic choking and the existence of a fluid throat at the transition region during the startup transient of dual-thrust motors. This code solves standard k-omega turbulence equations with shear flow corrections using a coupled second-order-implicit unsteady formulation. In the numerical study, a fully implicit finite volume scheme of the compressible, Reynolds-averaged, Navier-Stokes equations is employed. It was observed that, at the subsonic inflow conditions, there is a possibility of the occurrence of internal flow choking in dual-thrust motors due to the formation of a fluid throat at the beginning of the transition region induced by area blockage caused by boundary-layer-displacement thickness. It has been observed that a 55% increase in the upstream port area of the dual-thrust motor contributes to a 25% reduction in blockage factor at the transition region, which could negate the internal How choking and supplement with an early choking of the dual-thrust motor nozzle. If the height of the upstream port relative to the motor length is too small, the developing boundary layers from either side of the port can interact, leading to a choked,flow. On the other hand, if the developing boundary layers are far enough apart, then choking does not occur. The blockage factor is greater in magnitude for the choked case than for the unchoked case. More tangible explanations are presented in this paper for the boundary-layer blockage and the internal flow choking in dual-thrust motors, which hitherto has been unexplored.

34 citations