Nozzle Pressure Ratio Effects on Aerodynamics and Acoustics of a Highly-Heated Rectangular Supersonic Jet

Abstract This paper presents the numerical simulation of Mach 1.5 supersonic jet with perforated tabs. The jet with straight perforation tab was compared with jets having slanted perforated tabs of different diameters. The perforation angles were kept as 0° and 10° with respect to the axis of the nozzle. The blockage areas of the tabs were 4.9 %, 4.9 % and 2.4 % for straight perforation, 10° slanted perforation ( {{{\Phi }}_{\ }} = 1.3 mm) and 10° slanted perforation ( {{{\Phi }}_{\ }} = 1.65 mm) respectively. The 3-D numerical simulations were carried out using the software. The mixing enhancements caused by these tabs were studied in the presence of adverse and favourable pressure gradients, corresponding to nozzle pressure ratio (NPR) of 3, 3.7 and 5. For Mach number 1.5 jet, NPR 3 corresponds to 18.92 % adverse pressure gradients and NPR 5 corresponds to 35.13 % favourable pressure gradients. The centerline Mach number of the jet with slanted perforations is found to decay at a faster rate than uncontrolled nozzle and jet with straight perforation tab. Mach number plots were obtained at both near-field and far field downstream locations. There is 25 % and 65 % reduction in jet core length were observed for the 0° and 10° perforated tabs respectively in comparison to uncontrolled jet.

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Experimental Assessment of Corrugated Rectangular Actuators on Supersonic Jet Mixing

Actuators ◽

10.3390/act9030088 ◽

2020 ◽

Vol 9 (3) ◽

pp. 88

Author(s):

Thillaikumar T. ◽

Tamal Jana ◽

Mrinal Kaushik

Keyword(s):

Pressure Ratio ◽

Supersonic Jet ◽

Vortex Generators ◽

Military Aircraft ◽

Nozzle Pressure Ratio ◽

Engine Exhaust ◽

Jet Mixing ◽

Noise Characteristics ◽

Nozzle Pressure ◽

The Waves

To improve the stealth capability of a military aircraft, the reduction in core length is essential to reduce the heat signature and the noise characteristics of the engine exhaust. The efficacy of rectangular vortex generators in achieving these objectives has been demonstrated by several researchers, owing to their simplicity. One way of producing the mixed-size vortices is by providing corrugations on the edge of the tab (actuator). Therefore, in the current study, two tabs of aspect ratio 1.5, mounted diametrically opposite to each other at the outlet of a Mach 1.73 circular nozzle, are examined at varying levels of expansions, ranging from overexpanded to underexpanded jet states. In addition, to generate the mixed-size vortices, three corrugation geometries, i.e., rectangular, triangular, and semicircular, are configured along the tab edges. Both quantitative and qualitative investigations are carried out by using the pitot probe to measure the stagnation pressures and by utilizing a shadowgraph technique to visualize the flow field. The corrugated tabs generated a significant mixing, and among them, the tabs with triangular corrugations are found to be most effective. A maximum reduction of about 99.7% in the supersonic core is obtained with triangular corrugated tabs at near-correct-expansion, corresponding to nozzle pressure ratio (NPR) 5. Interestingly, the semicircular corrugated tab significantly reduces the asymmetry near the nozzle exit plane. The shadowgraph images confirm the efficacy of different corrugated tabs in reducing the strength of the waves, prevalent in the supersonic core.

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Supersonic Jet Control by Tabs with Slanted Perforation

International Journal of Turbo and Jet Engines ◽

10.1515/tjj-2018-0034 ◽

2018 ◽

Vol 0 (0) ◽

Author(s):

G. Ezhilmaran ◽

Suresh Chandra Khandai ◽

S. Pavithrabalan ◽

K. Udhayakumar

Keyword(s):

Mach Number ◽

Pressure Ratio ◽

Supersonic Jet ◽

Pressure Gradients ◽

Nozzle Pressure Ratio ◽

Pressure Decay ◽

Core Length ◽

Nozzle Pressure ◽

Jet Control

Abstract Control of Mach 1.8 circular jet with slanted perforated tabs is studied experimentally. Two sets of perforated tabs were used for this study. The perforation angles were 0° and 30° with respect to axis of the nozzle. The blockage areas of the tabs were 5 %. The mixing enhancements caused by these tabs were studied in the presence of adverse and favorable pressure gradients, corresponding to nozzle pressure ratio (NPR) of 4, 5.74 and 8. For Mach number 1.8, jet NPR 4 corresponds to 30 % adverse pressure gradients and NPR 8 corresponds to 39.37 % favorable pressure gradients. The pressure decay characteristics and shadowgraph images of perforated tabs at different NPR were compared. There is 45 % and 65 % reduction in jet core length were observed for the 0° and 30° perforated tabs respectively in both pitot and shadowgraph experiments in comparison to uncontrolled jet.

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Investigation of efficacy of low length-to-diameter ratio and nozzle pressure ratio on base pressure in an abruptly expanded flow

MATEC Web of Conferences ◽

10.1051/matecconf/201817201004 ◽

2018 ◽

Vol 172 ◽

pp. 01004

Author(s):

Fharrukh Ahmed ◽

S. A. Khan

Keyword(s):

Pressure Ratio ◽

Flow Regulation ◽

Base Pressure ◽

Regulation Mechanism ◽

Nozzle Pressure Ratio ◽

Control Efficacy ◽

Remarkable Change ◽

Cross Sectional ◽

Circular Duct ◽

Nozzle Pressure

This study has been carried out to assess the efficacy of the flow regulations in the form of tiny jets to regulate the pressure in the base region of an abruptly expanded duct. Four tiny jets of 1mm diameter placed at 90° intervals at 6.5 mm distance from the main jet in the wake region of the base were employed as flow management mechanism. The experiments were conducted at the inertia level of M = 2.5 & 3.0. The jets from the nozzles were expanded abruptly into a circular duct with four cross-sectional areas of 2.56, 3.24, 4.84 and 6.25. The L/D ratio of the enlarged duct considered was from 10 to 1 and experiments were conducted for Nozzle Pressure Ratio (NPR) from 3 to 11. Since the jets Mach numbers are high and the highest NPR tested was 11 which imply that the flow remains over expanded, even though, with increase in the NPR, the level of over expansion will decrease. It is well known that for over expanded nozzles an oblique shock will be formed at the nozzle lip, which in turn will result in the increase of the base pressure once it passes through the shock wave. From the results it is observed that for the NPRs 3 and 5 there is no appreciable gain in the base pressure, and hence, control employed as tiny jets are not effective, however, at NPR 7, 9, and 11 there is remarkable change in the base pressure values. This clearly indicates that NPR plays a significant role to decide on the magnitude of the base pressure and the control efficacy of the flow regulation mechanism as the tiny jets. It is found that the present method of flow regulation mechanism can be used as effective regulator of the base flows in an abruptly expanded duct. The control does not alter the nature of the flow in the enlarge duct.

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Optimum structure of a laval nozzle for an abrasive air jet based on nozzle pressure ratio

Powder Technology ◽

10.1016/j.powtec.2020.01.086 ◽

2020 ◽

Vol 364 ◽

pp. 343-362 ◽

Cited By ~ 12

Author(s):

Yong Liu ◽

Juan Zhang ◽

Jianping Wei ◽

Xiaotian Liu

Keyword(s):

Laval Nozzle ◽

Pressure Ratio ◽

Optimum Structure ◽

Nozzle Pressure Ratio ◽

Air Jet ◽

Nozzle Pressure

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MECHANISMS OF GENERATION AND SOURCES OF NOISE IN SUPERSONIC JETS

Akustika ◽

10.36336/akustika201932144 ◽

2019 ◽

Vol 32 ◽

pp. 144-150

Author(s):

Vladislav Emelyanov ◽

Aleksey Tsvetkov ◽

Konstantin Volkov

Keyword(s):

Pressure Ratio ◽

Supersonic Jet ◽

Numerical Data ◽

Jet Flows ◽

Noise Generation ◽

Noise Sources ◽

Cavity Depth ◽

Flow Parameters ◽

Nozzle Pressure ◽

Physical Pattern

Interest in the development of models and methods focused on the mechanisms of noise generation in jet flows is due to strict noise requirements produced by various industrial devices, as well as the possibilities of using sound in engineering and technological processes. The tools of physical and computational modeling of gas dynamics and aero-acoustics problems are considered, and noise sources and mechanisms of noise generation in supersonic jet flows are discussed. The physical pattern of the flow in free supersonic under-expanded jets is discussed on the basis of experimental and numerical data, as well as the flow structure arising from the interaction of a supersonic under-expanded jet with a cylindrical cavity. The influence of the nozzle pressure ratio and cavity depth on the sound pressure level, amplitude and frequency characteristics of the flow parameters is studied.

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Tab Aspect Ratio Effect on Supersonic Jet Mixing

International Journal of Turbo and Jet Engines ◽

10.1515/tjj-2014-0032 ◽

2015 ◽

Vol 32 (3) ◽

Cited By ~ 2

Author(s):

Mrinal Kaushik ◽

E. Rathakrishnan

Keyword(s):

Aspect Ratio ◽

Pressure Ratio ◽

Supersonic Jet ◽

Small Scale ◽

Jet Mixing ◽

Core Length ◽

Nozzle Pressure ◽

The Waves ◽

Length Reduction ◽

Better Than

AbstractThe efficacy of introducing mixing promoting small-scale vortices by two rectangular tabs, of aspect ratio 1.0, 1.5 and 2.0, placed at diametrically opposite locations at the exit of a Mach 1.73 convergent–divergent circular nozzle has been experimentally investigated, for NPRs from 4 to 8, covering overexpanded, correctly expanded and underexpanded states of the jet. The area blockage due to the each tab was 2.5% of the nozzle exit area. Keeping the blockage constant, the aspect ratio (defined as the ratio of length to width of the tab) was varied. A maximum core length reduction of 84.6% was caused by the tabs of aspect ratio 1.0, at underexpanded conditions corresponding to NPR (nozzle pressure ratio) 6. At this NPR, tabs of aspect ratio 1.5 and 2.0 caused core length reduction of 76.9% and 61.5%, respectively. The mixing promoting efficiency of aspect ratio 1.0 is found to be better than 1.5 and 2.0, at all NPRs of the present study, except NPR 5. The shadowgraph pictures of the uncontrolled and controlled jets clearly demonstrate the effectiveness of the tabs in weakening the waves in the jet core.

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Mixing Characteristics and Enhancement of Sonic Elliptic Jets from a Twin Elliptic Orifice

International Journal of Vehicle Structures and Systems ◽

10.4273/ijvss.12.2.23 ◽

2020 ◽

Vol 12 (2) ◽

Author(s):

S. Parameshwari ◽

Pradeep Kumar ◽

S. Thanigaiarasu ◽

E. Rathakrishnan

Keyword(s):

Boundary Layer ◽

Aspect Ratio ◽

System Design ◽

Pressure Ratio ◽

Jet Noise ◽

Nozzle Pressure Ratio ◽

Jet Mixing ◽

Nozzle Pressure ◽

Mixing Characteristics ◽

Ir Signature

The knowledge of jet mixing and its enhancement of elliptic jet are important in a propulsion system of aircraft, rocket, and missile’s system design for advancement of combustion via fuel-air mixture increment, lowering the jet noise and reduction of the plume infrared (IR) signature. The jet issuing from a twin elliptic orifice is non-uniform in shape that promotes the faster mixing and it influences by orifice exit conditions, so knowledge of absence of boundary layer and jet mixing characteristics is important. Hence, an experimental work helps to study the jet mixing for a twin elliptic orifice of aspect ratio two at nozzle pressure ratios of one, two, and three. The proximity between the orifices kept as one to 3mm in steps of one. The experimental readings were taken using pitot probe. The results revealed that jet mixing is faster and effective when the proximity between the orifices is closer to each other than the faraway distances at measured nozzle pressure ratios. Difference in orifice jet core exerted a noticeable influence at high proximity levels of nozzle pressure ratio of three and four for elliptic orifice.

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Control of Subsonic and Sonic Jets with Limiting Tabs

International Journal of Turbo and Jet Engines ◽

10.1515/tjj-2016-0037 ◽

2017 ◽

Vol 34 (1) ◽

Cited By ~ 3

Author(s):

T. Berrueta ◽

E. Rathakrishnan

Keyword(s):

Nozzle Exit ◽

Pressure Ratio ◽

Nozzle Pressure Ratio ◽

Jet Mixing ◽

Downstream Distance ◽

The Core ◽

Maximum Reduction ◽

Sonic Jet ◽

Nozzle Pressure ◽

Mach Numbers

AbstractAerodynamic mixing of subsonic and sonic jets with limiting tabs, with and without corrugations, has been studied experimentally. Limiting tab located at the nozzle exit and at a downstream distance of 0.5D has been considered in this study. Mixing caused by the tab at nozzle exit is found to be better that of tab at 0.5D, for both plain and corrugated geometries. Also, both tabs caused better mixing for underexpanded sonic jets than the correctly expanded sonic jet and subsonic jets. At nozzle pressure ratio 3 the plain tab at the nozzle exit reduced the core by about 56 % and the corrugated tab by about 51 %. But when the plain tab is placed at 0.5D the jet mixing is retarded. However, the corrugated tab at 0.5D enhances the mixing, though not up to the level of the same tab at 0D, at all Mach numbers except 0.6. The maximum reduction of core caused by shifted corrugated tab is 14 % for Mach 0.8 jet.

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Evaluation of Flip-Flop Jet Nozzles for Use as Practical Excitation Devices

Journal of Fluids Engineering ◽

10.1115/1.2910306 ◽

1994 ◽

Vol 116 (3) ◽

pp. 508-515 ◽

Cited By ~ 38

Author(s):

Ganesh Raman ◽

Edward J. Rice ◽

David M. Cornelius

Keyword(s):

Flow Visualization ◽

Pressure Ratio ◽

Tube Length ◽

Nozzle Pressure Ratio ◽

Velocity Perturbation ◽

Flip Flop ◽

Nozzle Pressure ◽

Jet Nozzle ◽

And Performance ◽

Made In

This paper describes the flowfield characteristics of the flip-flop jet nozzle and the potential for using this nozzle as a practical excitation device. It appears from the existing body of published information that there is a lack of data on the parameters affecting the operation of such nozzles and on the mechanism of operation of these nozzles. An attempt is made in the present work to study the important parameters affecting the operation and performance of a flip-flop jet nozzle. Measurements were carried out to systematically assess the effect of varying the nozzle pressure ratio (NPR) as well as the length and volume of the feedback tube on the frequency of oscillation of this device. Flow visualization was used to obtain a better understanding of the jet flowfield and of the processes occurring within the feedback tube. The frequency of oscillation of the flip-flop jet depended significantly on the feedback tube length and volume as well as on the nozzle pressure ratio. In contrast, the coherent velocity perturbation levels did not depend on the above-mentioned parameters. The data presented in this paper would be useful for modeling such flip-flop excitation devices that are potentially useful for controlling practical shear flows.

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