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Author

T. Sundararajan

Other affiliations: Indian Institutes of Technology
Bio: T. Sundararajan is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Supersonic speed & Diffuser (thermodynamics). The author has an hindex of 4, co-authored 7 publications receiving 51 citations. Previous affiliations of T. Sundararajan include Indian Institutes of Technology.

Papers
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Journal ArticleDOI
TL;DR: In this article, the authors deal with the high-altitude simulation and testing of upper stage rocket motors with large nozzle area ratios, using second-throat exhaust diffusers (STED).
Abstract: This paper deals with the high-altitude simulation and testing of upper stage rocket motors with large-nozzle area ratios, using second-throat exhaust diffusers (STED). To evaluate the performance ...

32 citations

Journal ArticleDOI
TL;DR: In this article, the performance characteristics of a high altitude test facility for testing large area ratio rocket engines have been investigated, and the predicted results show that the desired vacuum level is attained when the primary jet flow attaches to the ejector duct walls smoothly, thereby arresting any back flow.
Abstract: In the present study, performance characteristics of a high altitude test facility for testing large area ratio rocket engines have been investigated. Steady-state numerical simulations have been performed initially to highlight the effects of operational parameters on a high altitude test facility operation. Later, the performance of the test facility during the startup phase of the rocket motor has been analyzed. The predicted results show that during the initial high altitude test facility evacuation, the desired vacuum level is attained when the primary jet flow attaches to the ejector duct walls smoothly, thereby arresting any back flow. However, at the fully started condition of the motor, the self-ejector action of the rocket plume plays a major role in maintaining the desired vacuum condition and, hence, the ejector flow rate can be reduced significantly. The injection of water as a fine spray cools the hot gas to a sufficiently low temperature (∼600 K) prior to its release into the atmosphere. T...

6 citations

Proceedings ArticleDOI
18 Aug 2008
TL;DR: In this paper, a numerical analysis has been conducted to analyze the performance of a second throat supersonic diffuser at various diffuser exit pressures by solving axi-symmetric Navier-Stokes equations using finite volume discretisation technique.
Abstract: This paper describes the influence of back pressure on the performance of a second throat ejector-diffuser system. Second throat ejector-diffuser (STED) is a subsystem in the high altitude test facility of large area ratio rocket motors. STED is employed to create the low pressure environment (of the order of a few thousand Pascals) corresponding to the high altitude flight situation, in a ground testing installation. During full flow condition (steady state operation) of the rocket motor, often the self pumping action of the rocket exhaust plume may itself be sufficient to maintain the low vacuum level required for the motor testing. However, during the initial startup and shut down phases of the rocket motor, an external ejector system is necessary for avoiding back flow of the motor exhaust into the vacuum test chamber. Therefore, in the present study, a numerical investigation has been conducted to analyze the performance of a second throat supersonic diffuser at various diffuser exit pressures. Simulations have been carried out for an adiabatic diffuser (without wall cooling) by varying the back pressure from 50,000 Pa to 150,000 Pa. Diffuser heat transfer analysis (with wall cooling) has been simulated only for a back pressure of 93,000 Pa. The flow pattern, shock location, shock structure, pressure gradients and temperature distributions in the diffuser system are investigated in detail. A decoupled ejector analysis has also been carried out to study the variation of suction pressure with mass flow rate of driving fluid (nitrogen) used in the ejector system. The analysis has been carried out by solving axi-symmetric Navier-Stokes equations using finite volume discretisation technique. The numerical findings agree well with the available in-house experimental data.

3 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the starting transient and plume blowback at diffuser breakdown of a straight cylindrical supersonic exhaust diffuser with no externally supplied secondary flow are numerically investigated.

36 citations

Journal ArticleDOI
TL;DR: In this paper, the design and operational parameters of rocket exhaust diffusers equipped to simulate high-altitude rocket performance on the ground were investigated and characterized using a comprehensive approach (theoretical, numerical, and experimental).
Abstract: The design and operational parameters of rocket exhaust diffusers equipped to simulate high-altitude rocket performance on the ground were investigated and characterized using a comprehensive approach (theoretical, numerical, and experimental). The physical model of concern includes a rocket motor, a vacuum chamber, and a diffuser, which have axisymmetric configurations. Further, the operational characteristics of a rocket exhaust diffuserwereanalyzed froma flowdevelopmentpointof view.Emphasiswasplacedondetailed flowstructure inthe diffuser, to observe the pressure oscillation in both the vacuum chamber and diffuser, which determines the minimum rocket-motor pressure required to start the diffuser. Numerical simulations were compared with experimental data on startup and in operational conditions to understand the effects of major design parameters, including the area ratio of diffuser to rocket-motor nozzle throat, the rocket-motor pressure, and the vacuumchamber size. Nomenclature Ad = inner cross-sectional area of diffuser Ade = exit cross-sectional area of diffuser Ae = exit cross-sectional area of rocket nozzle At = throat cross-sectional area of rocket nozzle

27 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of essential performance parameters on the starting transient of a straight cylindrical supersonic exhaust diffuser (SED) are numerically investigated in terms of SED length and pre-evacuation configuration.

24 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigate the secondary flow characteristics and the associated vacuum generation caused with an increase in the primary pressure ramping in zero-secondary flow ejectors, and they find that with the jet expansion reaching a critical level, the fluid supply from the reverse flow is suddenly entrained back into the main jet at the maximum jet expansion point.
Abstract: This paper aims to investigate the secondary flow characteristics and the associated vacuum generation caused with increase in the primary pressure ramping in zero-secondary flow ejectors. The sudden expansion of the primary jet into the diffuser during the ejector start-up results in flow separation from the shear layer formed between the primary and inducted flows and produces large recirculation bubbles in the top and bottom sides of the jet. These recirculation bubbles cause an induced flow from ambient air into the diffuser duct as well. The fluid supply from the reverse flow due to the shear layer separation and the induced flow from ambient air provide a counter momentum against fluid entrainment from a vacuum chamber. As a result of this, the initial vacuum generation process progresses in a slow rate. Thereafter, the primary jet expansion reaches a critical level and a rapid vacuum generation can be seen. It is found that with the jet expansion reaching a critical level, the fluid supply from the reverse flow is suddenly entrained back into the main jet at the maximum jet expansion point. This suddenly reduces the counter-momentum which has been prohibiting the entrainment of fluid from the vacuum chamber and results in rapid evacuation. This is followed by a stage in which the vacuum chamber pressure is increasing due to the attainment of a constant Mach number at the diffuser inlet and the jet pressure ramping. It is found that the secondary flow dynamics and the vacuum generation processes in rectangular and round ejectors show a close resemblance.

24 citations

Journal ArticleDOI
TL;DR: In this paper, the performance of a second-throat ejector diffuser system employed in high-altitude testing of large-area-ratio rocket motors is considered under various steady and transient operating conditions.
Abstract: The performance of a second-throat ejector―diffuser system employed in high-altitude testing of large-area-ratio rocket motors is considered under various steady and transient operating conditions. When the diffuser attains started condition, supersonic flow fills the entire inlet section and a series of oblique shock cells occurring in the diffuser duct seal the vacuum environment of the test chamber against backflow. The most sensitive parameter that influences the stagnation pressure needed for diffuser starting is the second-throat diameter. Between the throat and exit diameters of the nozzle, there exists a second-throat diameter value that corresponds to the lowest stagnation pressure for starting. When large radial/axial gaps exist between the nozzle exit and diffuser duct, significant reverse flow occurs for the unstarted cases, which spoils the vacuum in the test chamber. However, the starting stagnation- pressure value remains unaffected by the axial/radial gap. Numerical simulations establish that it is possible to arrive at an optimum diffuser geometry that facilitates early functioning of the high-altitude-test facility during motor ignition phase. The predicted axial variations of static pressure and temperature along the diffuser for the testing of a cryogenic upper-stage motor agree well with available experimental data.

24 citations