Characteristics of Underexpanded Co-Flow Jets

Srinivasarao, T.; Lovaraju, P.; Rathakrishnan, E.

doi:10.4028/www.scientific.net/amm.575.507

Cited by 5 publications

(5 citation statements)

References 4 publications

(4 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Various authors (Kwan and Ko, 1977;Srinivasarao et al, 2014a;Matsumoto, 1973) studied incompressible flow coaxial jets. Kwan and Ko (1977) studied incompressible coaxial jets and observed that the PCL increases in the presence of an outer jet as observed in compressible jets (Papamoschou, 1997;Srinivasarao et al, 2017;Srinivasarao et al, 2014b;Lovaraju and Rathakrishnan, 2011;Perumal et al, 2020;Papamoschou, 1997). They also classified the regions of coaxial jets, namely, the initial merging zone (IMZ) (Region 1), intermediate zone (IZ) (Region 2) and fully merged zone (FMZ) (Region 3) as shown in Figure 1.…”

Section: Introductionmentioning

confidence: 87%

Effect of varying velocity ratio and separation distance on thin lip coaxial jet

Krishnan

Ganesan

et al. 2023

AEAT

View full text Add to dashboard Cite

Purpose In comparison to a nozzle with a larger/finite separation distance (Thanigaiarasu et al., 2019), a thin-lip nozzle (Srinivasarao et al., 2017) minimizes drag. Coaxial nozzles with thin lips are an appropriate tool for studying high subsonic jets because it does not create a dominant re-circulation zone. This study aims to analyze the characteristic of separation distances, between primary and secondary nozzles, within the range of 0.7–3.2 mm which can be considered a thin lip. Design/methodology/approach A separation distance of 0.7 (Papamoschou, 2004), 1.7 and 2.65 mm (Lovaraju and Rathakrishnan, 2011) is considered for the present study. The main nozzle exit Mach number is maintained at a subsonic condition of Mach 0.6, and the co-flowing nozzle exit Mach number is varied from 0% (secondary jet stopped/single jet) to 100% (Mach 0.6) in steps of 20% with respect to the main nozzle exit Mach number. A comparison was made between these velocity ratios for all three lip thicknesses in the present study. Design mesh and analysis were done by using Gambit 2.6.4 and Fluent 6.12. Velocity contours and turbulence contours were studied for qualitative analysis. Findings When lip thickness increases from 0.7 to 2.65 mm, the potential core length (PCL) of the primary jet decreases marginally. Additionally, the PCL of the primary jet elongates significantly as the velocity ratio increases. The primary shear layer is dominant at 20% co-flow (20 PCF), less dominant at 60% co-flow (60 PCF) and almost disappeared at 100% co-flow (100 PCF). Concurrently, the secondary shear layer almost disappeared in 20 PCF, dominant in 60 PCF and more dominant in 100 PCF. Different zones such as initial merging, intermediate and fully merged zones are quantitatively and qualitatively analyzed. Practical implications Co-flow nozzle is used in turbofan engine exhaust. The scaled-down model of a turbofan engine has been analyzed. Core length is directly proportional to the jet noise. The PCL signifies the jet noise reduction in a high-speed jet. For a low-velocity ratio, the potential core is reduced and hence can reduce the jet noise. At the same time, as the velocity ratio increases, the mass flow rate of the coaxial increases. The increase in the mass flow increases the thrust of the engine. The aircraft engine designer should analyze the requirement of the aircraft and choose the optimal velocity ratio coaxial nozzle for the engine exhaust (Papamoschou, 2004). Originality/value There have been many research studies carried out previously at various lip thickness such as 0.4 (Georgiadis, 2003), 0.7 (Papamoschou, 2004), 1.5 (Srinivasarao et al., 2014a), 1.7 (Sharma et al., 2008), 2 (Naren, Thanigaiarasu and Rathakrishnan, 2016), 2.65 (Lovaraju and Rathakrishnan, 2011), 3 (Inturiet al., 2022) and 3.2 mm (Perumal et al., 2020). However, there is no proper study to vary the lip thickness in this range from 0.7 to 3.2 mm to understand the flow behavior of a co-flowing jet.

show abstract

Section: Introductionmentioning

confidence: 87%

Effect of varying velocity ratio and separation distance on thin lip coaxial jet

Krishnan

Ganesan

et al. 2023

AEAT

View full text Add to dashboard Cite

show abstract

“…CFJ from orifices with an annular gap 0.15 and 0.45 D p at Mach numbers 0.2, 0.4, 0.6, 0.8 and 1.0 and the corresponding NPRs 1.02, 1.12, 1.28, 1.52 and 1.89, respectively, were studied experimentally. The annular gap 0.45 D p found efficient mixing compared with 0.15 D p. (Srinivasarao et al (2014). CFJ with 3 mm LT (thin lip) (BR0.9) and 15 mm (thick lip) (BR0.5) at Mach number 0.6 and under-expanded (NPR 7) sonic jet, respectively, were studied experimentally.…”

Section: Introductionmentioning

confidence: 99%

Lip thickness effect on high bypass co-flowing jet mixing

Krishnan

Ganesan

2022

AEAT

View full text Add to dashboard Cite

Purpose The purpose of this study is to analyse numerically and experimentally the effects of lip thickness (LT) and bypass ratio on co-flowing nozzle under subsonic and correctly expanded sonic jet decay at different Mach numbers. Design/methodology/approach Co-flowing jets from co-flowing nozzles of different LTs, 0.2, 1 and 1.5 Dp (where Dp is the primary nozzle exit diameter = 10 mm), with an annular gap of 10 mm at main jet exit Mach numbers 0.6 have been studied experimentally and the other cases have been performed numerically. The co-flowing jet with 2 mm LT was used for comparison. Findings Co-flowing jet axial pitot pressure decay, axial static pressure decay, axial velocity decay, radial velocity decay and streamline velocity contours were analyzed. The results illustrate that the mixing of the co-flowing jet with profound LT is prevalent to the co-flowing jet with 2 mm LT, at all Mach numbers of the current study. Also, the LT of the co-flowing jet has a strong impact on jet mixing. Co-flowing jets with 10 mm and 15 mm LT with a constant co-flow width of 10 mm experience a considerably advanced mixing than co-flowing jets with 2 mm LT and a co-flow width of 10 mm. Practical implications The application of bypassed co-flow jet is in turbofan engine operates efficiently in modern civil aircraft. Originality/value All subsonic jets are considered correctly expanded with negligible variation in axial static pressure. However, in the present study, static pressure along the centerline varies sinusoidally up to 9% and 12% above and below atmospheric pressure, respectively, for primary jet exit Mach number 1.0. The sinusoidal variation is less for primary jet exit Mach numbers 0.6 and 0.8 in static pressure decay.

show abstract

“…They concluded that the potential core length of the primary jet increases when the NPR increases for the coflow configuration compared to that without the coflow. Srinivasarao et al (2014), conducted experiments to study the effects of lip thickness to characterize underexpanded coflow jets of annular configuration (2014). The supersonic core length was found to be shorter as in the case of thick lip when compared with the jets from nozzles with a thin lip at different underexpanded cases of NPRs 3, 5 and 7.…”

Section: Introductionmentioning

confidence: 99%

Investigation of mixing characteristics of coflow rectangular nozzle of aspect ratio 2 and 3

Murugesan¹,

Moorthi²,

Ramachandran³

2021

AEAT

View full text Add to dashboard Cite

Purpose The purpose of this study is to understand experimentally the mixing characteristics of a two-stream exhaust system with a supersonic Mach 1.5 primary jet that exits the rectangular C-D nozzle surrounded by a sonic secondary jet from a convergent rectangular nozzle by varying the aspect ratio (AR = 2 and 3) similar to those that can be available for future high-speed commercial aircraft. Design/methodology/approach This paper focuses on the experimental results of effects of AR at various expansion levels of jets issued/delivered from a central rectangular convergent-divergent nozzle of AR 2 and 3 surrounded by a coflow from a convergent rectangular sonic nozzle. The lip thickness of the primary nozzle is 2.2 mm. various nozzle pressure ratios (NPRs) ranging from 2, 3, 3.69 and 4 were chosen for pressure measurements. Findings For all the NPRs, AR 3 had a shorter core than AR 2. Also, AR 3 was found to decay faster in the transition and fully developed zones. The lateral plots show that the AR has an influence on the jet spread. Originality/value The structure of waves existing in the potential core of the rectangular coflow jet along with the major and minor axis planes was visualized by the shadowgraph technique.

show abstract

Characteristics of Underexpanded Co-Flow Jets

Cited by 5 publications

References 4 publications

Effect of varying velocity ratio and separation distance on thin lip coaxial jet

Effect of varying velocity ratio and separation distance on thin lip coaxial jet

Lip thickness effect on high bypass co-flowing jet mixing

Investigation of mixing characteristics of coflow rectangular nozzle of aspect ratio 2 and 3

Contact Info

Product

Resources

About