Characteristics of a co-flowing jet with varying lip thickness and constant velocity ratio

Abstract

Purpose This study aims to analyze co-flowing jets (CFJs) with constant velocity ratio (VR) and varying primary nozzle lip thickness (LT) to find a critical LT in CFJs below which mixing enhances and beyond which mixing inhibits. Design/methodology/approach CFJs were characterized with a constant VR and varying LTs. A single free jet with a diameter equal to that of a primary nozzle of the CFJ was used for characteristic comparison. Numerical simulation is carried out and is validated with the experimental results. Findings The results show that within a critical limit, the mixing enhanced with an increase in LT. This was signified by a reduction in potential core length (PCL). Beyond this limit, mixing inhibited leading to the elongation of PCL. This limit was controlled by parameters such as LT and constant VR. A new region termed as influential wake zone is identified. Practical implications In this study, the VR is maintained constant and bypass ratio (BR) was varied from low value to very high values. Presently, subsonic commercial turbo fan operates under low to ultra-high BR. Hence the present study becomes vital to the current scenario. Originality/value To the best of the authors’ knowledge, this is the first effort to find the critical value of LT for a constant VR for compressible co-flow jets. The CFJs with constant VR and varying LT have not been studied in the past. The present study focuses on finding a critical LT below which mixing enhances and above which mixing inhibits.

Study of Flow Field Inside a Can Combustor for Micro Gas Turbine Engine Under Nonreacting Flow Conditions

“…The major challenge in the design of diffuser system for gas turbine engines is that the maximum static pressure recovery should be achieved in the shortest possible length with minimum pressure loss (Lefebvre and Ballal 2010). Shankar et al (2019) studied the characteristics of a coflowing jet with varying lip thickness, the study shows that the total pressure decay increases with increase in lip thickness of coflowing jet. Karuppannan et al (2018) study of the flow behavior in the annular diffuser has been analyzed by simulating realistic downstream combustor liner and transition duct geometry.…”