Novel Characteristics of Subsonic Coflowing Jets With Varying Lip Thickness

Naren Shankar Radha Krishnan,Dilip Raja Narayana

doi:10.5028/jatm.v12.1122

Naren Shankar Radha Krishnan, Dilip Raja Narayana

Open Access

https://doi.org/10.5028/jatm.v12.1122

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Abstract

Effect of Mach number on coflowing jet at lip thickness of 0.2 Dp, 1.0 Dp and 1.5 Dp (where Dp is primary nozzle exit diameter, 10 mm) at Mach numbers 1.0, 0.8 and 0.6 were studied experimentally. It was found that an increase in Mach number does not have any profound effect on axial total and static pressure variation for 0.2 Dp. Decreasing the mean diameter is due to the geometrical constraints. In this study, the primary nozzle dimension and secondary duct is maintained constant for comparison. For the case of 0.2 Dp, static pressure is almost equal to atmospheric pressure for all Mach numbers. Whereas for other two lip thickness, increase in Mach number marginally influences axial total pressure and profoundly varies static pressure. It is noted that it varies considerably up to 11.1% in the axial direction and up to 17% in the radial direction for Mach number 1.0. For lower Mach numbers, such variation is not observed. Increase in Mach number increases static pressure variation in the coflowing jet flow field with lip thickness 1.0 Dp and 1.5 Dp.

Highlights

Mixing in coflowing jet (CFJ) suppresses noise and reduces infrared (IR) signature in commercial aircraft turbofan engines
Axial static pressure was assumed constant in previous studies which becomes inappropriate with finite lip thickness and varying Mach number
In order to evaluate the changes in features of decay, the increase in primary jet exit Mach number, for lip thickness (LT) 0.2, 1.0 and 1.5 diameter primary nozzle (Dp), centerline and pitot pressure variation is plotted against axial distance based on primary jet exit Mach numbers 0.6, 0.8, and 1.0

Summary

Introduction

Mixing in coflowing jet (CFJ) suppresses noise and reduces infrared (IR) signature in commercial aircraft turbofan engines. Modification of coflowing nozzle can alter mixing in CFJ (Zaman and Papamoschou 2000; Papamoschou 2000; Shupe 2007). Such modifications do not require additional power source and that are called as passive control in CFJ. Some of the factors that are associated with CFJ include: lip thickness (LT), wake dominance, angular jet and mixing enhancement. It is well proven that increase in lip thickness enhances mixing because of wake dominance (Buresti et al 1994)

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Conclusion