scholarly journals Numerical Study of Characteristics of Underexpanded Supersonic Jet

2020 ◽  
Author(s):  
Priyadharshini Murugesan ◽  
Arjun Biju Kumar ◽  
Akhil Teja Kambhampati ◽  
Shashank Pillai ◽  
Girish Chandar Chandrasekar ◽  
...  
Keyword(s):  
Mach Number ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Supersonic Jet ◽  
Working Fluid ◽  
Shock Cell ◽  
Specific Heats ◽  
Supersonic Core Length ◽  
The Mean ◽  
Jet Characteristics

Correlations for the supersonic jet characteristics, the mean shock cell length and the supersonic core length, have been obtained in terms of the jet parameters. The jet parameters considered in this study are the exit diameter of the nozzle (de), the design Mach number (Me), the nozzle pressure ratio (NPR) and the ratio of specific heats of the medium (γ). The parameters were varied as follows: exit diameters, from 0.5 to 25 mm; Mach number from 1 to 3; the NPR from 2.14 to 35. Initially, working fluid used is cold air and then effect of variation of γ is taken into consideration. The computational model has been validated and then used for all the numerical simulations. A quadratic fit for both characteristics has been obtained which is applicable to any supersonic jet. The correlations developed are valid within the respective ranges of the parameters stated above.

Numerical analysis of supersonic co-flow jet with varying lip thickness

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sathish Kumar K ◽  
Naren Shankar R ◽  
Anusindhiya K ◽  
Senthil Kumar B.R
Keyword(s):  
Mach Number ◽  
Total Pressure ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Supersonic Nozzle ◽  
Experimental Result ◽  
Content Type ◽  
Jet Mixing ◽  
Mixing Characteristics ◽  
Jet Axis

Purpose This study aims to present the numerical study on supersonic jet mixing characteristics of the co-flow jet by varying lip thickness (LT). The LT chosen for the study is 2 mm, 7.75 mm and 15 mm. Design/methodology/approach The primary nozzle is designed for delivering Mach 2.0 jet, whereas the secondary nozzle is designed for delivering Mach 1.6 jet. The Nozzle pressure ratio chosen for the study is 3 and 5. To study the mixing characteristics of the co-flow jet, total pressure and Mach number measurements were taken along and normal to the jet axis. To validate the numerical results, the numerical total pressure values were also compared with the experimental result and it is proven to have a good agreement. Findings The results exhibit that, the 2 mm lip is shear dominant. The 7.75 mm and 15 mm lip is wake dominant. The jet interaction along the jet axis was also studied using the contours of total pressure, Mach number, turbulent kinetic energy and density gradient. The radial Mach number contours at the various axial location of the jet was also studied. Practical implications The effect of varying LT in exhaust nozzle plays a vital role in supersonic turbofan aircraft. Originality/value Supersonic co-flowing jet mixing effectiveness by varying the LT between the primary supersonic nozzle and the secondary supersonic nozzle has not been analyzed in the past.

Numerical Simulation of Supersonic Jet Control by Tabs with Slanted Perforation

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
G. Ezhilmaran ◽  
Suresh Chandra Khandai ◽  
Yogesh Kumar Sinha ◽  
S. Thanigaiarasu
Keyword(s):  
Numerical Simulation ◽  
Mach Number ◽  
Near Field ◽  
Pressure Ratio ◽  
Supersonic Jet ◽  
Pressure Gradients ◽  
Nozzle Pressure Ratio ◽  
Nozzle Pressure ◽  
Jet Control ◽  
Different Diameters

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.

scholarly journals Assessment of Short Rectangular-Tab Actuation of Supersonic Jet Mixing

Actuators ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 72 ◽  
Author(s):  
Abhash Ranjan ◽  
Mrinal Kaushik ◽  
Dipankar Deb ◽  
Vlad Muresan ◽  
Mihaela Unguresan
Keyword(s):  
Coming Out ◽  
Nozzle Exit ◽  
Stokes Equations ◽  
Cell Structure ◽  
Pressure Ratio ◽  
Supersonic Jet ◽  
Three Dimensional ◽  
Shock Cell ◽  
Jet Mixing ◽  
Nozzle Pressure

This work explores the extent of jet mixing for a supersonic jet coming out of a Mach 1.8 convergent-divergent nozzle, controlled with two short rectangular vortex-generating actuators located diametrically opposite to each other with an emphasis on numerical methodology. The blockage ratio offered by the tabs is around 0.05. The numerical investigations were carried out by using a commercial computational fluid dynamics (CFD) package and all the simulations were performed by employing steady Reynolds-averaged Navier–Stokes equations and shear-stress transport k−ω turbulence model on a three-dimensional computational space for more accuracy. The numerical calculations are administered at nozzle pressure ratios (NPRs) of 4, 5, 6, 7 and 8, covering the overexpanded, the correctly expanded and the underexpanded conditions. The centerline pressure decay and the pressure profiles are plotted for both uncontrolled and the controlled jets. Numerical schlieren images are used to capture the barrel shock, the expansion fans and the Mach waves present in the flow field. Mach contours are also delineated at varying NPRs indicating the number of shock cells, their length and the variation of the shock cell structure and strength, to substantiate the prominent findings. The outcomes of this research are observed to be in sensible concurrence with the demonstrated exploratory findings. A reduction in the jet core length of 75% is attained with small vortex-generating actuators, compared to an uncontrolled jet, corresponding to nozzle pressure ratio 5. It was also seen that the controlled jet gets bifurcated downstream of the nozzle exit at a distance of about 5 D, where D is the nozzle exit diameter. Furthermore, it was fascinating to observe that the jet spread increases downstream of the nozzle exit for the controlled jet, as compared to the uncontrolled jet at any given NPR.

Boundary Layer Suction via a Slot in a Transonic Compressor: Numerical Parameter Study and First Experiments

2004 ◽  
Author(s):  
K. Hubrich ◽  
A. Bo¨lcs ◽  
P. Ott
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Mach Number ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Parameter Study ◽  
Flow Angle ◽  
Boundary Layer Suction ◽  
Transonic Compressor ◽  
Shock Mach Number

In the present paper a numerical and experimental study aiming at the enhancement of the working range of a transonic compressor via boundary layer suction (BLS) is presented. The main objective of the investigation is to study the influence of BLS on the interference between shock wave and boundary layer and to identify the possible benefit of BLS on the compressor working characteristics. An extensive numerical study has been carried out for the DATUM blade and for 2 different suction location configurations for one speed line and varying back-pressure levels, ranging from choked conditions to stall. It was found that the working range of the transonic compressor with a nominal inlet Mach number of 1.2 and a nominal pre-shock Mach number of 1.35 could be increased by sucking 2% of flow on the SS away, in such a way that the maximum pressure ratio and maximum diffusion could both be increased by 10%, when compared to the DATUM case. For smaller pressure ratios with respect to the design pressure ratio, the BLS is located in a supersonic flow region and thus creates additional losses due to a more divergent flow channel, which additionally accelerates the flow and results in a higher pre-shock Mach number creating higher losses. First measurements carried out in LTTs annular cascade, do show reasonable agreement with the computations in terms of inlet Mach number, flow angle, main shock location and stall limit. The most pronounced difference between measurements and computations is the occurrence of a terminal normal channel shock behind a bowed detached shock wave and a separation on the SS of the blade, which were both not predicted by the CFD.

Volcanic supersonic jets: an experimental study of the effect of particles on the shock cell structure and acoustic emissions.

2021 ◽  
Author(s):  
Stefano Panunzi ◽  
Jacopo Taddeucci ◽  
Valeria Cigala ◽  
Ulrich Kueppers ◽  
Danilo Mauro Palladino ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Shock Tube ◽  
Ambient Pressure ◽  
Pressure Ratio ◽  
Supersonic Jet ◽  
Acoustic Signals ◽  
Shock Cell ◽  
Ejection Rate ◽  
Particle Ejection ◽  
Over Time

<p>Explosive volcanic eruptions eject a mixture of gas and pyroclasts into the atmosphere at a range of velocities. Directly above the vent, in the gas-thrust region, a supersonic jet may be generated that strongly controls the eruptive dynamics. To improve our quantitative understanding of volcanic supersonic jets, the effect on particles within them, and their acoustic emission, we have performed small-scale explosive eruptions in the laboratory using a shock-tube. The shock-tube is composed of 3 parts, a bottom (5.6 m long, elevated pressure) and a top (48mm long, ambient pressure) plexiglass cylinder (5 mm inner diameter), separated by an electrovalve.</p><p>We have run experiments using ambient air as gas and sand, with diameter between 0.1 and 0.3 mm, as particles. The gas volume was fixed while the pressure ratio (the shock-tube reservoir to ambient pressure ratio) was varied from about 4 to 8.4 to obtain supersonic flows. During the experiments, the jet was recorded with a high-speed camera operating at 34660 fps, and the resulting noise acoustic emission with microphones (6 Hz-140 kHz; 1000 kfps) positioned at 90° from the jet axis.</p><p>Among the acoustic signals produced by a supersonic jet (jet noise) we have particularly focussed on the broad-band shock noise (BBSN) that is emitted by the interaction between shock cells and the turbulence in the jet. We estimated the jet velocity using an acoustic model based on the identification of the peak frequency of the BBSN. We also identified the BBSN frequency and its variation over time by applying the complex Morlet wavelet transformation. As expected, the BBSN frequency is inversely proportional to the gas velocity. Concerning the video recording, we analysed the shock cells behaviour and their temporal oscillation due to the presence of particles. Finally, the particle ejection rate was calculated in every video frame.</p><p>We found that the acoustic signal and shock cells are influenced by the presence of particles. In fact, fluctuations in particle concentration are well visible and decelerate the flowing gas. As a consequence, there is a temporary decrease of the stand-off-distance between the vent and the first shock-cell and concurrent rise of the BBSN frequency. We noticed, in some cases, that the shock-cells disappear during a short time interval. The BBSN frequency and the stand-off-distance behaviour over time follow the oscillation of the particle ejection rate confirming their sensitivity to particle load variation.</p><p>The future prospectives of this embryonal study could lead to new instruments for determining either the amount of pyroclasts inside the volcanic jets and their exit velocity on the basis of the recorded acoustic signals.</p>

scholarly journals Numerical Study of Multistage Transcritical Organic Rankine Cycle Axial Turbines

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
L. Sciacovelli ◽  
P. Cinnella
Keyword(s):  
Numerical Study ◽  
Pressure Ratio ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Working Fluid ◽  
Dense Gas ◽  
Working Fluids ◽  
Inlet Conditions ◽  
The Impact

Transonic flows through axial, multistage, transcritical organic rankine cycle (ORC) turbines are investigated by using a numerical solver including advanced multiparameter equations of state and a high-order discretization scheme. The working fluids in use are the refrigerants R134a and R245fa, classified as dense gases due to their complex molecules and relatively high molecular weight. Both inviscid and viscous numerical simulations are carried out to quantify the impact of dense gas effects and viscous effects on turbine performance. Both supercritical and subcritical inlet conditions are studied for the considered working fluids. In the former case, flow across the turbine is transcritical, since turbine output pressure is subcritical. Numerical results show that, due to dense gas effects characterizing the flow at supercritical inlet conditions, supercritical ORC turbines enable, for a given pressure ratio, a higher isentropic efficiency than subcritical turbines using the same working fluid. Moreover, for the selected operating conditions, R134a provides a better performance than R245fa.

Study of Decay Characteristics of Hexagonal and Square Supersonic Jet

2017 ◽  
Vol 34 (2) ◽  
Author(s):  
Prasanta Kumar Mohanta ◽  
B. T. N. Sridhar
Keyword(s):  
Pressure Ratio ◽  
Supersonic Jet ◽  
Ambient Air ◽  
Hydraulic Diameter ◽  
Schlieren Image ◽  
Image Study ◽  
Jet Mixing ◽  
Core Length ◽  
Supersonic Core Length ◽  
The Impact

AbstractExperiments were carried on nozzles with different exit geometry to study their impact on supersonic core length. Circular, hexagonal, and square exit geometries were considered for the study. Numerical simulations and schlieren image study were performed. The supersonic core decay was found to be of different length for different exit geometries, though the throat to exit area ratio was kept constant. The impact of nozzle exit geometry is to enhance the mixing of primary flow with ambient air, without requiring tab, wire or secondary method to increase the mixing characteristics. The non-circular mixing is faster comparative to circular geometry, which leads to reduction in supersonic core length. The results depict that shorter the hydraulic diameter, the jet mixing is faster. To avoid the losses in divergent section, the cross section of throat was maintained at same geometry as the exit geometry. Investigation shows that the supersonic core region is dependent on the hydraulic diameter and the diagonal. In addition, it has been observed that number of shock cells remain the same irrespective of exit geometry shape for the given nozzle pressure ratio.

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