An experimental study of underexpanded sonic, coaxial, swirl jets

2004 ◽  
Vol 218 (1) ◽  
pp. 93-103 ◽  
Author(s):  
K-H Lee ◽  
T Setoguchi ◽  
S Matsuo ◽  
H-D Kim
Keyword(s):  
Static Pressure ◽  
Near Field ◽  
Flow Structures ◽  
Experimental Investigations ◽  
Pressure Measurements ◽  
Annular Nozzle ◽  
Free Jets ◽  
Underexpanded Jets ◽  
Secondary Stream ◽  
The Impact

The present study addresses experimental investigations of the near-field flow structures of an underexpanded sonic, dual, coaxial, swirl jet. The swirl stream is discharged from the secondary annular nozzle and the primary inner nozzle provides the underexpanded free jets. The interactions between the secondary swirl and primary underexpanded jets are quantified by a fine pitot impact and static pressure measurements and are visualized using a shadowgraph optical method. The pressure ratios of the secondary swirl and primary underexpanded jets are varied below 7.0. Experiments are conducted to investigate the effects of the secondary swirl stream on the primary underexpanded jets, compared with the secondary stream of no swirl. The results show that the presence of an annular swirl stream causes the Mach disc to move further downstream, with an increased diameter, and remarkably reduces the fluctuations of the impact pressures in the underexpanded sonic dual coaxial jet, compared with the case of the secondary annular stream with no swirl.

scholarly journals Experimental Investigations of a Recently Developed Supersonic Compressor Stage (Rotor and Stage Performance)

1974 ◽  
Author(s):  
H. Simon ◽  
D. Bohn
Keyword(s):  
Static Pressure ◽  
Pressure Ratio ◽  
Pressure Rise ◽  
Strong Shock ◽  
Wall Pressure ◽  
Experimental Investigations ◽  
Pressure Measurements ◽  
Compressor Stage ◽  
Pressure Transducers ◽  
Rotor Type

The experimental investigations of a recently developed supersonic compressor stage working with a strong shock wave both in the rotor and stator are described. The shock in the inlet area of the rotor is stabilized by the geometry of the rotor blade channel, whereas the position of shocks in the stator is controlled by the back pressure. Due to this, the static pressure rise is distributed to the rotor and stator avoiding a higher loading of the stator. In the first part the performance of the rotor alone has been investigated. The conducted probe and static wall pressure measurements allowed a detailed analysis of the flow through the rotor. The determined performance characteristics of the rotor show the peculiarities of the rotor at different speeds and throttle positions. In addition to the static wall pressure measurements the nonsteady pressure distributions have been measured at the casing wall by piezoelectric pressure transducers. Since this rotor (type ②) has been designed with the same relative inlet Mach number and turning as the previously investigated supersonic rotor (type ①), a direct comparison of these rotors can be made. In the second part of these investigations the rotor of type ② has been combined with a tandem cascade as a stator, to investigate the supersonic compressor stage. With heavy throttling a static pressure ratio of 3,5 (p3/p1) has been achieved. The evaluation of the probe measurements allowed a better estimation of the overall performance of this supersonic compressor stage.

Reducing Compressor Shroud Leakage Flows by Raising the Stator Hub Line: Low Speed Tests

2019 ◽  
Author(s):  
Henner Schrapp ◽  
Arne Dodegge ◽  
Volker Gümmer ◽  
Neil W. Harvey ◽  
Jörn Städing ◽  
...  
Keyword(s):  
Static Pressure ◽  
Pressure Ratio ◽  
Cross Flow ◽  
Suction Side ◽  
Experimental Investigations ◽  
Performance Measurements ◽  
Low Speed ◽  
Static Pressure Difference ◽  
Gap Height ◽  
The Impact

Abstract The paper describes experimental investigations of an alternative shrouded stator concept in a 2.5 stage low speed compressor. The idea of this new concept is to raise the stator hub line by a small amount, thus decelerating the flow upstream of the shroud cavity due to the into wind step and raising the static pressure. Downstream of the cavity the out of wind step changes the streamline curvature thus lowering the static pressure locally. As a result, the static pressure difference across the shroud is lower and the shroud flow is reduced. Tests were done at three seal gap heights under stator 1, both with a “neutral” (in–line) hub and a six percent “bump shroud”, i.e. the hub is raised by six percent annulus height. Performance measurements show the impact of the “bump shroud” geometry on the overall behavior of the compressor, i.e. efficiency and pressure ratio and the variation of these quantities with varying seal gap height. While the efficiency and pressure ratio of the compressor inevitably reduce with increasing seal gap height, the sensitivity of both is reduced by using “bump shrouds”. At small seal gap heights the “bump shroud” design behaves similarly to the neutral one, while at the design seal gap height it is superior. Thus, both the efficiency and the pressure ratio are less sensitive against seal gap height variations if the compressor is equipped with a raised hub line — leading to a more robust product. A similar behavior is seen at near stall conditions. The analysis of five hole probe measurements reveals the reason for the improved efficiency. The stator 1 losses were significantly reduced by the introduction of the “bump shroud”. This is mostly due to the reduced amount of shroud flow and the subsequent reduction of hub cross–flow in the stator. A comparison of losses with and without the raised hub line show not only a reduction of the losses near the hub, but also adjacent to the suction side of the stator due to reduced migration of hub boundary layer fluid onto the vane.

scholarly journals CFD Modeling of Effluent Discharges: A Review of Past Numerical Studies

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 856 ◽  
Author(s):  
Abdolmajid Mohammadian ◽  
Hossein Kheirkhah Gildeh ◽  
Ioan Nistor
Keyword(s):  
Numerical Modeling ◽  
Near Field ◽  
Cfd Modeling ◽  
Experimental Investigations ◽  
Field Zone ◽  
Jet Mixing ◽  
The Past ◽  
Cfd Models ◽  
Effluent Discharge ◽  
The Impact

Effluent discharge mixing and dispersion have been studied for many decades. Studies began with experimental investigations of geometrical and concentration characteristics of the jets in the near-field zone. More robust experiments were performed using Laser-Induced Fluorescence (LIF) and Particle Image Velocimetry (PIV) systems starting in the 20th century, which led to more accurate measurement and analysis of jet behavior. The advancement of computing systems over the past two decades has led to the development of various numerical methods, which have been implemented in Computational Fluid Dynamics (CFD) codes to predict fluid motion and characteristics. Numerical modeling of mixing and dispersion is increasingly preferred over laboratory experiments of effluent discharges in both academia and industry. More computational resources and efficient numerical schemes have helped increase the popularity of using CFD models in jet and plume modeling. Numerous models have been developed over time, each with different capabilities to facilitate the investigation of all aspects of effluent discharges. Among these, Reynolds-averaged Navier-Stokes (RANS) and Large Eddy Simulations (LES) are at present the most popular CFD models employing effluent discharge modeling. This paper reviews state-of-the-art numerical modeling studies for different types and configurations of discharges, including positively and negatively buoyant discharges, which have mostly been completed over the past two decades. The numerical results of these studies are summarized and critically discussed in this review. Various aspects related to the impact of turbulence models, such as k-ε and Launder-Reece-Rodi (LRR) models, are reviewed herein. RANS and LES models are reviewed, and implications for the simulation of jet and plume mixing are discussed to develop a reference for future researchers performing numerical investigations on jet mixing and dispersion.

Predictions of Impacting Sonic and Supersonic Jets

1997 ◽  
Vol 119 (1) ◽  
pp. 83-89 ◽  
Author(s):  
P. S. Cumber ◽  
M. Fairweather ◽  
S. A. E. G. Falle ◽  
J. R. Giddings
Keyword(s):  
Near Field ◽  
Supersonic Jets ◽  
Wall Jet ◽  
Pressure Oscillations ◽  
Free Jets ◽  
Underexpanded Jets ◽  
Free Jet ◽  
Model Predictions ◽  
Periodic Pressure ◽  
Spatially Periodic

A mathematical model of sonic and supersonic jets, validated previously by the present authors for the prediction of moderately and highly underexpanded free jets, is used to simulate the near field structure of jets which impact a flat surface orthogonally, and its accuracy assessed by comparing model predictions with experimental data available in the literature. For impacting, moderately underexpanded jets, results derived from the model are found to be in close agreement with data on the location of both free jet shocks, and the stand-off shock formed adjacent to the impacted surface. In addition, the model provides reasonable estimates of density within the free jet and stagnation regions of such flows, with the existence, or otherwise, of bubbles being successfully predicted. Measurements of pressure occurring on the surface of the impacted plate, produced by the impingement of both sonic and supersonic jets, are also predicted with reasonable accuracy, although the decaying amplitude of spatially periodic pressure oscillations within the wall jet region of these flows is slightly over predicted in some cases.

scholarly journals Experimental investigations on diesel engine using alumina nanoparticle fuel additive

2021 ◽  
Vol 13 (2) ◽  
pp. 168781402098840
Author(s):  
Mohammed S Gad ◽  
Sayed M Abdel Razek ◽  
PV Manu ◽  
Simon Jayaraj
Keyword(s):  
Diesel Engine ◽  
Diesel Fuel ◽  
Alumina Nanoparticles ◽  
Experimental Investigations ◽  
Fuel Additive ◽  
Alumina Nanoparticle ◽  
Fuel Injectors ◽  
Performance And Emission ◽  
And Performance ◽  
The Impact

Experimental work was done to examine the impact of diesel fuel with alumina nanoparticles on combustion characteristics, emissions and performance of diesel engine. Alumina nanoparticles were mixed with crude diesel in various weight fractions of 20, 30, and 40 mg/L. The engine tests showed that nano alumina addition of 40 ppm to pure diesel led to thermal efficiency enhancement up to 5.5% related to the pure diesel fuel. The average specific fuel consumption decrease about neat diesel fuel was found to be 3.5%, 4.5%, and 5.5% at dosing levels of 20, 30, and 40 ppm, respectively at full load. Emissions of smoke, HC, CO, and NOX were found to get diminished by about 17%, 25%, 30%, and 33%, respectively with 40 ppm nano-additive about diesel operation. The smaller size of nanoparticles produce fuel stability enhancement and prevents the fuel atomization problems and the clogging in fuel injectors. The increase of alumina nanoparticle percentage in diesel fuel produced the increases in cylinder pressure, cylinder temperature, heat release rate but the decreases in ignition delay and combustion duration were shown. The concentration of 40 ppm alumina nanoparticle is recommended for achieving the optimum improvements in the engine’s combustion, performance and emission characteristics.

scholarly journals A FEM-Based 2D Model for Simulation and Qualitative Assessment of Shot-Peening Processes

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2784
Author(s):  
Georgios Maliaris ◽  
Christos Gakias ◽  
Michail Malikoutsakis ◽  
Georgios Savaidis
Keyword(s):  
Process Parameters ◽  
Material Properties ◽  
Shot Peening ◽  
Qualitative Assessment ◽  
Experimental Investigations ◽  
Elastoplastic Material ◽  
Size Distributions ◽  
User Friendly ◽  
The Impact ◽  
2D Model

Shot peening is one of the most favored surface treatment processes mostly applied on large-scale engineering components to enhance their fatigue performance. Due to the stochastic nature and the mutual interactions of process parameters and the partially contradictory effects caused on the component’s surface (increase in residual stress, work-hardening, and increase in roughness), there is demand for capable and user-friendly simulation models to support the responsible engineers in developing optimal shot-peening processes. The present paper contains a user-friendly Finite Element Method-based 2D model covering all major process parameters. Its novelty and scientific breakthrough lie in its capability to consider various size distributions and elastoplastic material properties of the shots. Therewith, the model is capable to provide insight into the influence of every individual process parameter and their interactions. Despite certain restrictions arising from its 2D nature, the model can be accurately applied for qualitative or comparative studies and processes’ assessments to select the most promising one(s) for the further experimental investigations. The model is applied to a high-strength steel grade used for automotive leaf springs considering real shot size distributions. The results reveal that the increase in shot velocity and the impact angle increase the extent of the residual stresses but also the surface roughness. The usage of elastoplastic material properties for the shots has been proved crucial to obtain physically reasonable results regarding the component’s behavior.

Assessment of Unsteady Flows in Turbines

1992 ◽  
Vol 114 (1) ◽  
pp. 79-90 ◽  
Author(s):  
O. P. Sharma ◽  
G. F. Pickett ◽  
R. H. Ni
Keyword(s):  
Unsteady Flow ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Experimental Investigations ◽  
Flow Parameters ◽  
Research Activities ◽  
Flow Features ◽  
Computational Fluid Dynamics Cfd ◽  
Turbine Design ◽  
The Impact

The impacts of unsteady flow research activities on flow simulation methods used in the turbine design process are assessed. Results from experimental investigations that identify the impact of periodic unsteadiness on the time-averaged flows in turbines and results from numerical simulations obtained by using three-dimensional unsteady Computational Fluid Dynamics (CFD) codes indicate that some of the unsteady flow features can be fairly accurately predicted. Flow parameters that can be modeled with existing steady CFD codes are distinguished from those that require unsteady codes.

Experimental Inverstigations On the Pressure Fluctuations in the Sealing Gap of Dry Gas Seals with Embedded Pressure Sensors

2021 ◽  
Author(s):  
Jingjing Luo ◽  
Dieter Brillert
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Static Pressure ◽  
Pressure Sensors ◽  
Operating Conditions ◽  
Test Facility ◽  
Experimental Investigations ◽  
Mechanical Seals ◽  
Process Gas ◽  
Sealing Gap

Abstract Dry gas lubricated non-contacting mechanical seals (DGS), most commonly found in centrifugal compressors, prevent the process gas flow into the atmosphere. Especially when high speed is combined with high pressure, DGS is the preferred choice over other sealing alternatives. In order to investigate the flow field in the sealing gap and to facilitate the numerical prediction of the seal performance, a dedicated test facility is developed to carry out the measurement of key parameters in the gas film. Gas in the sealing film varies according to the seal inlet pressure, and the thickness of gas film depends on this fluctuated pressure. In this paper, the test facility, measurement methods and the first results of static pressure measurements in the sealing gap of the DGS obtained in the described test facility are presented. An industry DGS with three-dimensional grooves on the surface of the rotating ring, where experimental investigations take place, is used. The static pressure in the gas film is measured, up to 20 bar and 8,100 rpm, by several high frequency ultraminiature pressure transducers embedded into the stationary ring. The experimental results are discussed and compared with the numerical model programmed in MATLAB, the characteristic and magnitude of which have a good agreement with the numerical simulations. It suggests the feasibility of measuring pressure profiles of the standard industry DGS under pressurized dynamic operating conditions without altering the key components of the seal and thereby affecting the seal performance.

Mistuning and Damping of a Radial Turbine Wheel. Part 1: Fundamental Analyses and Design of Intentional Mistuning Pattern

2021 ◽  
Author(s):  
Alex Nakos ◽  
Bernd Beirow ◽  
Arthur Zobel
Keyword(s):  
High Stress ◽  
Forced Response ◽  
Experimental Investigations ◽  
Detailed Knowledge ◽  
Turbine Wheel ◽  
Operation Conditions ◽  
Radial Turbine ◽  
Influence Coefficients ◽  
Modes Of Vibration ◽  
The Impact

Abstract The radial turbine impeller of an exhaust turbocharger is analyzed in view of both free vibration and forced response. Due to random blade mistuning resulting from unavoidable inaccuracies in manufacture or material inhomogeneities, localized modes of vibration may arise, which involve the risk of severely magnified blade displacements and inadmissibly high stress levels compared to the tuned counterpart. Contrary, the use of intentional mistuning (IM) has proved to be an efficient measure to mitigate the forced response. Independently, the presence of aerodynamic damping is significant with respect to limit the forced response since structural damping ratios of integrally bladed rotors typically take extremely low values. Hence, a detailed knowledge of respective damping ratios would be desirable while developing a robust rotor design. For this, far-reaching experimental investigations are carried out to determine the damping of a comparative wheel within a wide pressure range by simulating operation conditions in a pressure tank. Reduced order models are built up for designing suitable intentional mistuning patterns by using the subset of nominal system modes (SNM) approach introduced by Yang and Griffin [1], which conveniently allows for accounting both differing mistuning patterns and the impact of aeroelastic interaction by means of aerodynamic influence coefficients (AIC). Further, finite element analyses are carried out in order to identify appropriate measures how to implement intentional mistuning patterns, which are featuring only two different blade designs. In detail, the impact of specific geometric modifications on blade natural frequencies is investigated.

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