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Studies on flame spread acceleration and detonation kernel in a dual-thrust rocket

Ajith, S and Ragupathi, S and Amrith, M and Anandmoorthi, . and Vishak, R and Nichith, C and Vigneshwaran, S and Sulthan, ARM and Oommen, C and Sanal Kumar, VR (2019) Studies on flame spread acceleration and detonation kernel in a dual-thrust rocket. In: AIAA Propulsion and Energy Forum and Exposition, 2019, 19-22 Aug.,2019, Indianapolis; United States.

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Official URL: https://dx.doi.org/10.2514/6.2019-4209


Theoretical and numerical studies have been carried out for establishing the novel concept of the boundary-layer induced Sanal-flow-choking in high velocity transient (HVT) solid propellant rocket motors with sudden expansion / divergent port. The Sanal-flow-choking for the diabatic flow is a unique condition of any real-fluid-flow problem at which both the thermal-choking (Rayleigh flow effect) and the wall-friction induced flow-choking (Fanno flow effect) occur in a single fluid-throat region. We proved conclusively that at the subsonic igniter jet flow condition any dual-thrust motor (DTM) with large upstream port-length-to-diameter (l/d) ratio predisposes to the deflagration-to-detonation-transition (DDT) creating pressure-overshoots leading to the catastrophic failure of the HVT DTM as a result of the Sanal-flow-choking phenomenon and generation of strong shock waves. The detonation kernel is more susceptible in HVT DTMs producing the dominant reacting species with low heat capacity ratio. We observed that the flame spread acceleration is relatively higher for the DTM cases with the high propellant loading density, within the given envelop with large l/d ratio, owing to the enhanced propellant surface heating due to the boundary-layer heat transfer effects. We concluded that the undesirable detonation in any dual-thrust combustor could be eliminated by maintaining the lower-critical-detonation-index (LCDI) always higher than the total-to-static pressure-ratio at the fluid-throat and/or at the transition region of the combustor. This could be achieved in the HVT DTMs, without reducing the propellant loading density, by breaking the boundary-layer-blockage and/or increasing the heat-capacity-ratio of the gases generating from the igniter and/or the upstream-port of the motor for prohibiting the Sanal-flow-choking condition. We concluded that the l/d ratio, the heat capacity ratio of the species, total-to-static pressure ratio at the fluid-throat and the rheology of the fluid linking together determines the boundary-layer induced internal flow choking and detonation in DTMs. The concept of a critical detonation kernel established herein throws light to the global scientific community on the fundamental mechanism of the DDT in dual-thrust rockets.

Item Type: Conference Paper
Publication: AIAA Propulsion and Energy Forum and Exposition, 2019
Publisher: American Institute of Aeronautics and Astronautics Inc
Additional Information: cited By 2; Conference of AIAA Propulsion and Energy Forum and Exposition, 2019 ; Conference Date: 19 August 2019 Through 22 August 2019; Conference Code:229919
Keywords: Boundary layers; Combustion; Combustors; Density of gases; Detonation; Flame research; Heat transfer; Propulsion; Rockets; Shock waves; Solid propellants; Specific heat; Temperature control, Catastrophic failures; Deflagration to detonation transition; Fundamental mechanisms; Propellant surfaces; Scientific community; Solid propellant rocket motor; Static-pressure ratio; Strong shock waves, Flow of fluids
Department/Centre: Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering)
Date Deposited: 01 Jul 2020 10:44
Last Modified: 01 Jul 2020 10:44
URI: http://eprints.iisc.ac.in/id/eprint/64732

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