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Combined effect of nozzle pressure ratio and screech prone supersonic mach number in a suddenly expanded flow

Bashir, Musavir and Khan, Sher Afghan and Rajendran, Parvathy (2015) Combined effect of nozzle pressure ratio and screech prone supersonic mach number in a suddenly expanded flow. In: International Conference on Mechanical Engineering And Advanced Material (ICME-AM) 2015, 3rd-4th Dec. 2015, Kota Kinabalu, Sabah.

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Abstract

This paper presents the results of an experimental study to evaluate the effectiveness of the micro jets to control the base pressure in a suddenly expanded flow at supersonic Mach numbers. Four micro jets of 1mm orifice diameter located at 90 intervals along a pitch circle diameter of 1.3 times the nozzle exit diameter in the base region were employed as active controls. The Mach numbers of the present study were 1.8 and 2.0. The jets were expanded suddenly into an axi-symmetric circular tube with cross-sectional area 2.56, 3.24, 4.84 and 6.25 times that of the nozzle exit area. The Length to Diameter ratio of the suddenly expanded duct was varied from 10 to 1 and experiment were conducted for Nozzle Pressure Ratio (NPR) from 3 to 11. Jets were over, under, and correctly expanded depending upon the NPR of the respective runs. When flow from the nozzle was over expanded or under expanded an oblique shock or expansion fan will be positioned at the nozzle lip, which in turn will result in increase or decrease of the base pressure. From the results it was observed that at NPRs 3 the control was not effective, however, at NPR 5, 7, 9, and 11 a significant change in the base pressure for all the area ratios was seen. From the results it was concluded that the level of expansion, Mach number, length-to-diameter ratio, and area ratio played an important role to fix the value of the base pressure and the control effectiveness by the micro jets.

Item Type: Conference or Workshop Item (Plenary Papers)
Additional Information: 7395/46658
Uncontrolled Keywords: Base pressure, Active Control, Abrupt Expansion, Nozzle Pressure ratio.
Subjects: T Technology > TL Motor vehicles. Aeronautics. Astronautics > TL500 Aeronautics
T Technology > TL Motor vehicles. Aeronautics. Astronautics > TL780 Rockets
Kulliyyahs/Centres/Divisions/Institutes: Kulliyyah of Engineering > Department of Mechanical Engineering
Depositing User: Prof. Dr. Sher Afghan Khan
Date Deposited: 29 Jan 2016 15:31
Last Modified: 24 May 2016 09:11
URI: http://irep.iium.edu.my/id/eprint/46658

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