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Author

R. Manikanda Kumaran

Other affiliations: Purdue University
Bio: R. Manikanda Kumaran is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Injector & Stagnation temperature. The author has an hindex of 4, co-authored 5 publications receiving 180 citations. Previous affiliations of R. Manikanda Kumaran include Purdue University.

Papers
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Journal ArticleDOI
TL;DR: In this article, the effect of header shape (rectangular and triangular) on flow mal-distribution and the manufacturing tolerances along the channel length and between the channels was investigated, and the results clearly illustrate that flow separation and recirculation bubbles occurring in the inlet header are primary responsible for the flow mal distribution between channels.

119 citations

Journal ArticleDOI
TL;DR: In this article, a study of flow mal-distribution in U-type micro-channel configuration is presented, where numerical simulations indicate that flow deceleration and associated pressure recovery in the inlet header lead to flow separation and recirculation which cause oscillations in channel-wise mass flow distribution.

46 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

Journal ArticleDOI
TL;DR: In this article, a second throat ejector using nitrogen as the primary fluid is considered for the creation of a low vacuum in a high-altitude testing facility for large-area-ratio rocket motors.
Abstract: DOI: 10.2514/1.39219 In the present work, a second throat ejector using nitrogen as the primary fluid is considered for the creation of a low vacuum in a high-altitude testing facility for large-area-ratio rocket motors. Detailed numerical investigations have been carried out to evaluate the performance of the ejector for various operational conditions and geometric parametersduring thenonpumpingandpumpingmodesof operation.Inthenonpumpingmode,the lowestvacuum chamberpressureisattainedwhentheprimaryjetjustexpandsuptothemixerthroatandtheresultingsingleshock cellsealsthethroatagainstanybackflow.Thestudyillustrateshoweachgeometricandoperationalparameterofthe ejector can be optimized to meet the test requirements in a high-altitude testing facility byensuring that the primary jet completely expands without a strong impact on the duct wall. When the rocket motor is fully started, due to the self-pumping action, the required vacuum is almost maintained by the exhaust flow itself and the external nitrogen ejector plays only a supplementary role. Numerical predictions for both nonpumping and pumping modes of operation have been validated with experimental data obtained from a scaled-down model of a high-altitude testing facility.

23 citations

Journal ArticleDOI
TL;DR: In this paper, the performance of a two-stage external ejector during high-altitude testing of large-area-ratio satellite thrusters is numerically investigated, and the predicted results compare well with in-house experimental data.
Abstract: The performance of a two-stage ejector during high-altitude testing of large-area-ratio satellite thrusters is numerically investigated. Since theflowrate of the exhaust from the satellite thruster is very low, self-ejector action of the exhaust is quite weak; therefore, a two-stage external ejector is required to create the desired low vacuum in the test chamber. The present work attempts to investigate the effects of various operational and geometric parameters on the performance of the two-stage ejector. Predicted results show that the downstream ejector (E2) operation is more critical for maintaining the required vacuum. However, for optimal performance, it is possible to tune the parameters such that both ejectors deliver the same suction effect.Maximumperformance of each ejector is obtained when the primary jet expanding from the nozzle smoothly seals the mixer throat against backflow. Employing a low molecular weight fluid and high stagnation temperature helps in reducing the quantity of fluid required for test facility evacuation. Useful correlations have been derived to quantify the suction performance of the two-stage ejector, and the predicted results compare well with in-house experimental data.

4 citations


Cited by
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Journal ArticleDOI
01 Feb 2021-Energy
TL;DR: In this article, the advantages and shortcomings of thermal enhancement technologies in different structural micro heat sinks are presented, and the barriers and challenges for the developments of thermal management of electronic devices by micro heat sink are discussed, and future directions of the research topic are provided.

217 citations

Journal ArticleDOI
Guodong Xia1, J. Jiang1, J. Wang1, Yuling Zhai1, D.D. Ma1 
TL;DR: In this paper, the authors studied the fluid flow and heat transfer in micro-channel heat sinks with different inlet/outlet locations (I, C and Z-type), header shapes (triangular, trapezoidal and rectangular) and microchannel cross-section shapes (the conventional rectangular microchannel, the microchannel with offset fan-shaped reentrant cavities and the micro channel with triangular reentrants cavities) were numerically studied with computational domain including the entire microchannel heat sink.

163 citations

Journal ArticleDOI
TL;DR: In this article, the experimental studies on flow visualization, pressure drop and heat transfer characteristics of microchannels presented by different researchers are summarized, some different flow patterns observed in microchannel geometry such as bubble nucleation in thin film, periodic variation of flow pattern, flow circulation, bubble suppression and cross-channel flow are explained briefly.

126 citations

Journal ArticleDOI
TL;DR: In this article, the effect of header shape (rectangular and triangular) on flow mal-distribution and the manufacturing tolerances along the channel length and between the channels was investigated, and the results clearly illustrate that flow separation and recirculation bubbles occurring in the inlet header are primary responsible for the flow mal distribution between channels.

119 citations

Journal ArticleDOI
TL;DR: In this paper, a multi-layer manifold microchannel cooling system was designed to effectively lower the cell surface temperature and improve the uniformity of surface temperature distribution, and the results showed that the hybrid concentrating photovoltaic (CPV) cells have a satisfactory net output power due to their lower pumping power and the higher electrical output of CPV cells.

101 citations