Control of base pressure with micro‐jets : part I

Abstract

Purpose

This paper aims to present the results of an experimental investigation carried out to control the base pressure in a suddenly expanded axi‐symmetric passage.

Design/methodology/approach

Four micro‐jets of 1 mm orifice diameter located at 90° interval along a pitch circle diameter of 1.3 times the nozzle exit diameter in the base region was employed as active controls. The test Mach numbers were 1.25, 1.3, 1.48, 1.6, 1.8, 2.0, 2.5 and 3.0. The jets were expanded suddenly into an axi‐symmetric tube with cross‐sectional area 4.84 times that of nozzle exit area. The length‐to‐diameter ratio of the sudden expansion tube was varied from 10 to 1. Nozzles generating the above jet Mach numbers were operated with nozzle pressure ratio in the range 3‐11. As high as 40 per cent increase in base pressure was achieved. In addition to base pressure, the wall pressure in the duct was also measured.

Findings

It is found that the wall pressure is not adversely influenced by the micro jets.

Originality/value

The paper provides information on internal supersonic flow.

Citation

Rehman, S. and Khan, S.A. (2008), "Control of base pressure with micro‐jets : part I", Aircraft Engineering and Aerospace Technology, Vol. 80 No. 2, pp. 158-164. https://doi.org/10.1108/00022660810859373