Passive control of coaxial jet with supersonic primary jet and sonic secondary jet

Perumal, Arun Kumar; Singh, Himanshu; Rathakrishnan, E.

doi:10.1063/5.0012468

Cited by 19 publications

(8 citation statements)

References 51 publications

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“…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: 86%

“…The lip thickness (separation distance between primary nozzle and secondary nozzle) value plays an important role in the evolution of a coaxial jet. By using a surrounding jet along with an inner jet, the convective Mach number reduces, thereby suppressing noise can be achieved (Perumal et al , 2020), (Bennett and Shankar, 2020), (Papamoschou, 2004), (Papamoschou, 1997). In applications of coaxial jets, such as fuel-air mixing in a scramjet combustion chamber and dual mode ramjet combustion chamber, rapid mixing of the primary jet and secondary jet additionally outer jet with the ambient atmosphere is required for better combustion efficiency.…”

Section: Introductionmentioning

confidence: 99%

“…Usually, scaled-down model of turbofan engines that resembles actual engines operate with thin lip thickness. The range varies from 0.03 Dp (where Dp is the value of primary nozzle exit diameter Dp) used by Georgiadis (2003), to 0.28 Dp used by Perumal et al (2020) as shown in Table 1 (a few studies are listed here for the past 50 years).…”

Section: Introductionmentioning

confidence: 99%

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

Krishnan

Ganesan

et al. 2023

AEAT

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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.

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Section: Introductionmentioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

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

Krishnan

Ganesan

et al. 2023

AEAT

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“…In addition, they proposed that the tab geometry effect and streamwise vortices positioned up to the jet's centerline would increase mixing by around 80%. The ongoing discussion of retardation in core length was investigated by Arun kumar et al (2020), in which the primary tabs show better mixing enhancement than secondary tabs resembles like characteristics of noncircular jets.…”

Section: Introductionmentioning

confidence: 99%

Investigation of slanted perforation diameter in tabs for supersonic jet control

Ezhilmaran¹,

Sekar²,

K.³

et al. 2023

AEAT

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Purpose This study aims to investigate the effect of slanted perforation diameter in tabs for the control of Mach 1.4 underexpanded supersonic jet flow characteristics. Design/methodology/approach Numerical investigation was carried out for NPR 5 to analyze the effect of slanted perforation diameter in tabs to control the Mach 1.4 jet. Four sets of tabs with slanted circular perforation geometries (Φp = 1, 1.5, 2 and 2.5 mm) were considered in this study. The inclination angle of 20° (αP) with reference to the jet axis was maintained constant for all the four tabs considered. Findings Determined value indicates there is a 68%, 71%, 73% and 75% drop in supersonic core for the Φp = 1, 1.5, 2.0 and 2.5 mm, respectively. The results show that the tabs with 2.5 mm perforation diameter were found to be efficient in reducing the supersonic jet core in comparison with other tab cases. The reduction in supersonic core length is due to the extent of miniscule vortices exuviating from slanted small and large diameter perforation in the tabs. Practical implications The concept of slanted perforation can be applied in scramjet combustion, which finds its best application in hypersonic vehicles and in noise suppression in fighter aircraft. Originality/value Slanted perforation and circular shapes with different diameters have not been studied in the supersonic regime. Examining the effect of circular diameter in slanted perforation is an innovation in this research paper.

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“…At NPR4, PCL increases to 104.34%. Recently, Perumal et al (2020) conducted experiments on supersonic CFJ (Mach 2 primary nozzle) and found an increase in PCL by 43% to 57.5% for NPR2.5 to 6.0. In this case, the lip thickness was 3.2 mm and the bypass ratio was around 1.9 to 2.5 for various NPRs.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of critical lip thickness of subsonic co-flowing jet

Shankar

Ganesan

Raja

et al. 2021

AEAT

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Purpose The effect of increasing lip thickness (LT) and Mach number on subsonic co-flowing Jet (CFJ) decay at subsonic and correctly expanded sonic Mach numbers has been analysed experimentally and numerically in this study. This study aims to a critical LT below which mixing enhances and above which mixing inhibits. Design/methodology/approach LT is the distance, separating the primary nozzle and the secondary duct, present in the co-flowing nozzle. The CFJ with LT ranging from 2 mm to 150 mm at jet exit Mach numbers of 0.6, 0.8 and 1.0 were studied in detail. The CFJ with 2 mm LT is used for comparison. Centreline total pressure decay, centreline static pressure decay and near field flow behaviour were analysed. Findings The result shows that the mixing enhances until a critical limit and a further increase in the LT does not show any variation in the jet mixing. Beyond this critical limit, the secondary jet has a detrimental effect on the primary jet, which deteriorates the process of mixing. The CFJ within the critical limit experiences a significantly higher mixing. The effect of the increase in the Mach number has marginal variation in the total pressure and significant variation in static pressure along the jet axis. Practical implications In this study, the velocity ratio (VR) is maintained constant and the bypass ratio (BR) was varied from low value to very high values for subsonic and correctly expanded sonic. Presently, commercial aircraft engine operates under these Mach numbers and low to ultra-high BR. Hence, the present study becomes essential. Originality/value This is the first effort to find the critical value of LT for a constant VR for a Mach number range of 0.6 to 1.0, compressible CFJ. The CFJs with constant VR of unity and varying LT, in these Mach number range, have not been studied in the past.

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Passive control of coaxial jet with supersonic primary jet and sonic secondary jet

Cited by 19 publications

References 51 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

Investigation of slanted perforation diameter in tabs for supersonic jet control

Numerical investigation of critical lip thickness of subsonic co-flowing jet

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