Axial flow development characteristics of circular and triangular supersonic jets in the presence of an annular coflow at large separation distance

2019 ◽  
Vol 234 (3) ◽  
pp. 804-817
Author(s):  
A Sureshkumar ◽  
BTN Sridhar
Keyword(s):  
Experimental Studies ◽  
Axial Flow ◽  
Separation Distance ◽  
Wave System ◽  
Operational Conditions ◽  
The Core ◽  
Core Length ◽  
Supersonic Core Length ◽  
Jet Shapes ◽  
Two Jets

Experimental studies were conducted to assess the effect of an annular coflow which surrounded a supersonic core jet in a coaxial jet system. Two different core jet shapes were employed which were circular and equilateral triangular. The core jets were maintained at two different total pressures, i.e. 360 and 550 kPa which corresponded to overexpansion conditions. The effect of coflow which surrounded core jet at a distance larger than the core jet diameter was such that the supersonic core length of the core jet was reduced in contrast to the elongation which was reported by earlier researchers for closer distances between the two jets. The Schlieren images of the coaxial jet system had shown that the region between the jet boundary of core jet and inner boundary of the annular coflow had a strong interaction with core jet which was characterised by a wave system and vortices. This region caused a reduction in supersonic core length and weakening of shock structure in the core jet. These findings have been corroborated by total pressure measurements along the core jet centreline. For the same operational conditions, the coflow caused reduction in supersonic core length more for triangular core jet when compared to that for circular core jet.

Experimental study of supersonic co-flowing jet

2018 ◽  
Vol 233 (4) ◽  
pp. 1237-1249 ◽  
Author(s):  
De Satyajit ◽  
Ethirajan Rathakrishnan
Keyword(s):  
Experimental Study ◽  
Pressure Ratio ◽  
Nozzle Pressure Ratio ◽  
The Core ◽  
Core Length ◽  
Nozzle Pressure ◽  
Supersonic Core Length ◽  
Presence And Absence ◽  
The Waves ◽  
Length Reduction

A detailed experimental study was carried out to investigate the behaviour of a Mach 2 primary jet in the presence of a Mach 1.6 annular co-flow. The lip thickness of the inner nozzle was 7.75 mm. The characteristics of jets were investigated at nozzle pressure ratios 3 to 8, in steps of 1. At nozzle pressure ratios 3 to 7, the centre jet is overexpanded; and at nozzle pressure ratio 8, it is marginally underexpanded. Both primary and secondary jets were operated at the nozzle pressure ratio. Centreline pressure distribution was measured to examine the supersonic core length of the centre jet in the presence and absence of the co-flow at all nozzle pressure ratios. It is found that the co-flow reduces the core length of the primary jet at all overexpanded states. A maximum core length reduction of about 61% is at nozzle pressure ratio 4, whereas the core increases by 5% at the marginally underexpanded state corresponding to nozzle pressure ratio 8. The co-flow jet merges with the primary jet at 4 D, at nozzle pressure ratio 3, and at 8 D for nozzle pressure ratios above 4. Shadowgraph images of the jet in the presence and absence of co-flow reveal that the waves in the core of the jet are strongly influenced by the co-flow.

scholarly journals Scaling law for supersonic core length in circular and elliptic free jets

2021 ◽  
Vol 33 (5) ◽  
pp. 051707
Author(s):  
Arun Kumar Perumal ◽  
Ethirajan Rathakrishnan
Keyword(s):  
Scaling Law ◽  
Free Jets ◽  
Core Length ◽  
Supersonic Core Length

Influence of nozzle exit geometrical parameters on supersonic jet decay

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Prasanta Kumar Mohanta ◽  
B. T. N. Sridhar ◽  
R. K. Mishra
Keyword(s):  
Aspect Ratio ◽  
Nozzle Exit ◽  
Ambient Air ◽  
Schlieren Image ◽  
Geometrical Parameters ◽  
Image Study ◽  
Aspect Ratios ◽  
Core Length ◽  
Supersonic Core Length ◽  
The Impact

Abstract Experiments and simulations were carried on C-D nozzles with four different exit geometry aspect ratios to investigate the impact of supersonic decay characteristics. Rectangular and elliptical exit geometries were considered for the study with various aspect ratios. Numerical simulations and Schlieren image study were studied and found the agreeable logical physics of decay and spread characteristics. The supersonic core decay was found to be of different length for different exit geometry aspect ratio, though the throat to exit area ratio was kept constant to maintain the same exit Mach number. The impact of nozzle exit aspect ratio geometry was responsible to enhance the mixing of primary flow with ambient air, without requiring a secondary method to increase the mixing characteristics. The higher aspect ratio resulted in better mixing when compared to lower aspect ratio exit geometry, which led to reduction in supersonic core length. The behavior of core length reduction gives the identical signature for both under-expanded and over-expanded cases. The results revealed that higher aspect ratio of the exit geometry produced smaller supersonic core length. The aspect ratio of cross section in divergent section of the nozzle was maintained constant from throat to exit to reduce flow losses.

Analysis of a Large-Scale Cooling System Fan Gearbox Loads

2017 ◽  
Author(s):  
Charles H. O. Lombard ◽  
Daniel N. J. Els ◽  
Jacques Muiyser ◽  
Albert Zapke
Keyword(s):  
Large Scale ◽  
Cooling System ◽  
Axial Flow ◽  
Output Shaft ◽  
Blade Loading ◽  
Operational Conditions ◽  
Power Stations ◽  
Reverse Loading ◽  
Air Cooled Condensers ◽  
Input Side

South Africa’s coal-fired power stations use super heated steam to drive generator turbines. In arid regions, air-cooled condensers (ACCs) are used to condense the process steam. These ACCs consists of an array of over 200 axial flow fans, each driven by a motor via a reduction gearbox. Distorted fan inlet air flow conditions cause transient blade loading, which results in variations in output shaft bending and torque. A measurement project was conducted where the input and output shaft of such a gearbox were instrumented with strain gauges and wireless bridge amplifiers. Gearbox shaft speed and vibration were also measured. Torsional and bending strains were measured for a variety of operational conditions, where correlations were seen between gearbox loading and wind conditions. The input side experienced no unexpected loads from the motor or changing wind conditions, whereas output shaft loading was influenced by the latter. Digital filters were applied to identify specific bending components, such as the influence of fan hub misalignment and dynamic blade loading. Reverse loading of the gearbox was measured during the fan stop period, and vibration analysis revealed torsional and gearbox vibrations. This investigation documented reliable full scale ACC gearbox loads.

scholarly journals O2 State in 18 O by using Core – Polarization effects

2008 ◽  
pp. 66-72
Keyword(s):  
Perturbation Theory ◽  
Experimental Studies ◽  
Form Factors ◽  
Wave Model ◽  
Collective Model ◽  
Core Polarization ◽  
Polarization Effects ◽  
The Core ◽  
The Subject ◽  
Space Wave

Coulomb form factors for E0 transition in 18O are discussed taking into account core-polarization effects. These effects are taken into account through the collective model of Tassie and also through a microscopic perturbation theory including excitations up to 2p1f shell. Space wave model functions defined for the orbits 1 and 2125O nucleus has been the subject of extensive theoretical and experimental studies, which received much attention in last decade [Alex Brown et.al.2005]. The 18O system contains two neutrons in addition to the16O core distributed in the sd – shell. d1 are obtained from the diagonalization of the interaction Hamilonian of Wildenthal. The calculations include the 0 2state with excitation energies3.6337MeV. The core – polarization effects which incorporate the ollective model of Tassei describe the data very well for this state.

Machine Learning Application to CO2 Foam Rheology

2021 ◽  
Author(s):  
Javad Iskandarov ◽  
George Fanourgakis ◽  
Waleed Alameri ◽  
George Froudakis ◽  
Georgios Karanikolos
Keyword(s):  
Machine Learning ◽  
Oil Recovery ◽  
Experimental Studies ◽  
Training Data ◽  
Computational Time ◽  
Gradient Boosting ◽  
Operational Conditions ◽  
Co2 Foam ◽  
Modelling Techniques ◽  
Foam Rheology

Abstract Conventional foam modelling techniques require tuning of too many parameters and long computational time in order to provide accurate predictions. Therefore, there is a need for alternative methodologies for the efficient and reliable prediction of the foams’ performance. Foams are susceptible to various operational conditions and reservoir parameters. This research aims to apply machine learning (ML) algorithms to experimental data in order to correlate important affecting parameters to foam rheology. In this way, optimum operational conditions for CO2 foam enhanced oil recovery (EOR) can be determined. In order to achieve that, five different ML algorithms were applied to experimental rheology data from various experimental studies. It was concluded that the Gradient Boosting (GB) algorithm could successfully fit the training data and give the most accurate predictions for unknown cases.

Effect of flat wall length on decay and shock structure of a supersonic square wall jet

2021 ◽  
pp. 095441002110580
Author(s):  
Venkata Satya Manikanta Tammabathula ◽  
Venkata Sai Krishna Ghanta ◽  
Tharaka Narendra Sridhar Bandla
Keyword(s):  
Supersonic Jet ◽  
Leading Edge ◽  
Shock Structure ◽  
Wall Jet ◽  
Pressure Measurements ◽  
Maximum Enhancement ◽  
Flat Wall ◽  
Decay Behaviour ◽  
Core Length ◽  
Supersonic Core Length

Experiments were conducted to find the effect of wall length on the decay behaviour and shock structure of a supersonic wall jet issuing from c-d nozzle of the square-shaped exit. A straight flat wall of width same as the side length of the square was attached to the lip of the nozzle such that the leading edge of the wall and the side of the square aligned properly which allowed the supersonic jet to graze past the flat wall. Experiments were conducted with five different wall lengths, that is, [Formula: see text] = 0.5, 1, 2, 4 and 8. Wall pressure measurements were made from leading edge to the trailing edge of the wall along its centreline. Schlieren flow visualization of the jet flow over the wall for the different wall lengths revealed the shock pattern and the effect of the wall length on the shock structure. The shock structure and jet deflection were significantly affected due to the presence of the wall. There was an upward jet deflection for [Formula: see text] up to [Formula: see text] whereas a downward jet deflection was observed for [Formula: see text]. Noticeable changes in the shock structure were observed for the wall lengths up to 2 D h. The wall length also significantly affected the jet decay characteristics and supersonic core length. Maximum enhancement in jet decay and maximum reduction in supersonic core length resulted when the wall length was [Formula: see text]. However, when the wall length was increased to [Formula: see text], there was a significant reduction in jet decay and a recovery of [Formula: see text]. Presence of wall always resulted a reduction in Lsc irrespective of wall length. The wall effect was to induce a more precipitous pressure drop closer to the nozzle exit, and a more gradual drop farther from it for [Formula: see text] > [Formula: see text].

Electron Density Studies of Molecular Crystals

1997 ◽  
Author(s):  
Philip Coppens
Keyword(s):  
Charge Density ◽  
Electron Scattering ◽  
Experimental Studies ◽  
Molecular Crystals ◽  
Chemical Environment ◽  
Light Atom ◽  
Core Electron ◽  
The Core ◽  
Core Electrons ◽  
Electron Donor And Acceptor

Small molecules consisting of light-, few-electron atoms were the first species beyond atoms to yield to quantum-mechanical methods. Similarly, crystals of small light-atom molecules have served as most useful test cases of charge density mapping. The small number of core electrons in first-row atoms enhances the relative contribution of valence electron scattering to the diffraction pattern. Early studies, done just after automated diffractometers became widely available, were concerned with molecular crystals such as uracil (Stewart and Jensen 1967), s-triazine (Coppens 1967), oxalic acid dihydrate (Coppens et al. 1969), decaborane (Dietrich and Scheringer 1978), fumaramic acid (Hirshfeld 1971), glycine (Almlof et al. 1973), and tetraphenylbutatriene (Berkovitch-Yellin and Leiserowitz 1976). While thermal motion is often pronounced in molecular crystals, advances in low-temperature data collection have done much to alleviate this disadvantage. In recent years, subliquid-nitrogen cooling techniques have been increasingly applied. Among the most interesting aspects of molecular crystals are the influence of intermolecular interactions on the electronic structure. Physically meaningful Coulombic parameters pertinent to a molecule in a condensed environment can be obtained from the diffraction analysis, and can be used in the modeling of macromolecules. The enhancement of the electrostatic moments relative to those of the isolated species has been noted in chapter 7. But, beyond these considerations, molecular crystals are important in their own right. For example, crystals of aromatic molecules substituted with π-electron donor and acceptor groups are among the most strongly nonlinear optical solids known, considerably exceeding the nonlinearity of inorganic crystals such as potassium titanyl phosphate (KTP); while mixed-valence organic components of low-dimensional solids can become superconducting at low temperatures. The relation between such properties of molecular crystals and their charge distribution provides a continuing impetus for further study. The suitability of light-atom crystals for charge density analysis can be understood in terms of the relative importance of core electron scattering. As the perturbation of the core electrons by the chemical environment is beyond the reach of practically all experimental studies, the frozen-core approximation is routinely used. It assumes the intensity of the core electron scattering to be invariable, while the valence scattering is affected by the chemical environment, as discussed in chapter 3.

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