Visual Investigation of an Ejector Motive Nozzle

2010 ◽  
Author(s):  
Christian Tischendorf ◽  
Christian Lucas ◽  
Juergen Koehler ◽  
Wilhelm Tegethoff
Keyword(s):  
Energetic Efficiency ◽  
Refrigeration Cycle ◽  
Shape Parameters ◽  
Flow Conditions ◽  
Compressibility Effect ◽  
Free Jet ◽  
Key Issues ◽  
Ejector Nozzle ◽  
Physical Effects ◽  
Nozzle Geometries

Previous investigations by other authors, e.g. Lorentzen [1], have shown that in a conventional refrigeration cycle significant throttling losses occurs. With the help of an ejector, these losses can be reduced. As a result, the energetic efficiency (COP) of the refrigerant system will be improved. Investigations show that CO2 ejector cycles are feasible and that some systems have already been commercialized successfully. The key issues in the optimization of the ejector used in a refrigeration cycle are the geometries of the different ejector parts. To optimize the geometry, a deeper understanding of the physical effects and the flow conditions within the ejector are essential. So far there are only a few investigations published on this issue, e.g. Elbel [2], investigated the flow in the mixing section of the ejector. This paper presents experimental results for different ejector nozzle geometries and operational condiditons. The motive nozzle was investigated separately from the other ejector parts. Investigated were multi-hole nozzles and the effect of the jet shape. Parameters were chosen according to the typical conditions in ejector refrigeration systems. Based on these conditions, the free jet exiting the motive nozzle was observed. To investigate the jet shape, an new experimental setup was designed. The motive jet was visually observed in a glass cylinder. The combination of both the contraction and compressibility effect on mass flow rate was also investigated.

Impact of Mechanical Chevrons on Supersonic Jet Flow and Noise

2009 ◽  
Author(s):  
K. Kailasanath ◽  
Junhui Liu ◽  
Ephraim Gutmark ◽  
David Munday ◽  
Steven Martens
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Near Field ◽  
Supersonic Jet ◽  
Initial Step ◽  
Nozzle Geometry ◽  
Jet Flows ◽  
Flow Conditions ◽  
Nozzle Geometries ◽  
The Impact

In this paper, we present observations on the impact of mechanical chevrons on modifying the flow field and noise emanated by supersonic jet flows. These observations are derived from both a monotonically integrated large-eddy simulation (MILES) approach to simulate the near fields of supersonic jet flows and laboratory experiments. The nozzle geometries used in this research are representative of practical engine nozzles. A finite-element flow solver using unstructured grids allows us to model the nozzle geometry accurately and the MILES approach directly computes the large-scale turbulent flow structures. The emphasis of the work is on “off-design” or non-ideally expanded flow conditions. LES for several total pressure ratios under non-ideally expanded flow conditions were simulated and compared to experimental data. The agreement between the predictions and the measurements on the flow field and near-field acoustics is good. After this initial step on validating the computational methodology, the impact of mechanical chevrons on modifying the flow field and hence the near-field acoustics is being investigated. This paper presents the results to date and further details will be presented at the meeting.

Turbine Engine Icing Spray Bar Design Issues

1995 ◽  
Vol 117 (3) ◽  
pp. 406-412 ◽  
Author(s):  
C. S. Bartlett
Keyword(s):  
Supercooled Liquid ◽  
Propulsion System ◽  
Test Facility ◽  
Turbine Engine ◽  
Turbofan Engines ◽  
Free Jet ◽  
Spray System ◽  
Key Issues ◽  
Development Center ◽  
High Thrust

Techniques have been developed at the Engine Test Facility (ETF) of the Arnold Engineering Development Center (AEDC) to simulate flight through atmospheric icing conditions of supercooled liquid water droplets. Ice formed on aircraft and propulsion system surfaces during flight through icing conditions can, even in small amounts, be extremely hazardous. The effects of ice are dependent on many variables and are still unpredictable. Often, experiments are conducted to determine the characteristics of the aircraft and its propulsion system in an icing environment. Facilities at the ETF provide the capability to conduct icing testing in either the direct-connect (connected pipe) or the free-jet mode. The requirements of a spray system for turbine engine icing testing are described, as are the techniques used at the AEDC ETF to simulate flight in icing conditions. Some of the key issues facing the designer of a spray system for use in an altitude facility are identified and discussed, and validation testing of the design of a new spray system for the AEDC ETF is detailed. This spray system enables testing of the newest generation of high-thrust turbofan engines in simulated icing conditions.

scholarly journals Effects of Compressibility on the Performance of a Wave-Energy Conversion Device with an Impulse Turbine Using a Numerical Simulation Technique

2003 ◽  
Vol 9 (6) ◽  
pp. 443-450 ◽  
Author(s):  
A. Thakker ◽  
T. S. Dhanasekaran ◽  
M. Takao ◽  
T. Setoguchi
Keyword(s):  
Numerical Technique ◽  
Time History ◽  
Wave Climate ◽  
Simulation Technique ◽  
Flow Conditions ◽  
Impulse Turbine ◽  
Compressibility Effect ◽  
Time Period ◽  
Air Chamber ◽  
The Mean

This article presents work carried out to predict the behavior of a 0.6 m impulse turbine with fixed guide vanes as compared with that of a 0.6 hub-to-tip ratio turbine under real sea conditions. In order to predict the true performance of the actual oscillating water column (OWC), the numerical technique was fine-tuned by incorporating the compressibility effect. Water surface elevation versus time history was used as the input data for this purpose. The effect of compressibility inside the air chamber and the turbine's performance under unsteady and irregular flow conditions were analyzed numerically. Considering the quasi-steady assumptions, the unidirectional steady-flow experimental data was used to simulate the turbines characteristics under irregular unsteady flow conditions. The results showed that the performance of this type of turbine is quite stable and that the efficiency of the air chamber and the mean conversion efficiency are reduced by around 8% and 5%, respectively, as a result of the compressibility inside the air chamber. The mean efficiencies of the OWC device and the impulse turbine were predicted for 1 month, based on the Irish wave climate, and it was found that the total time period of wave data used is one of the important factors in the simulation technique.

CFD simulation on the effect of primary nozzle geometries for a steam ejector in refrigeration cycle

2013 ◽  
Vol 63 ◽  
pp. 133-145 ◽  
Author(s):  
Natthawut Ruangtrakoon ◽  
Tongchana Thongtip ◽  
Satha Aphornratana ◽  
Thanarath Sriveerakul
Keyword(s):  
Cfd Simulation ◽  
Refrigeration Cycle ◽  
Steam Ejector ◽  
Nozzle Geometries

Investigations of Dust Separation in a Gasturbine Pre-Swirl Cooling Air System Using New, Enhanced Simulation Methods

2005 ◽  
Author(s):  
O. Schneider ◽  
H. J. Dohmen ◽  
F. K. Benra ◽  
K. Jarzombek
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Navier Stokes ◽  
Flow Conditions ◽  
System A ◽  
Air System ◽  
Physical Effects ◽  
Film Cooling Holes ◽  
Cooling Air ◽  
First Time

In the last years the leading manufacturers enhanced the performance of heavy-duty gas turbines rapidly. With the increasing amount of cooling air passing the internal air system, a rising amount of air borne particles are transported to the film cooling holes at the turbine blade surface. Due to the size, these holes are critical for blockage. Experience with gas turbines during operation showed a complex interaction of cooling air under different flow conditions and its particle load. In this paper the results of a new Lagrange-Tracking simulation algorithm based on 3D-Navier-Stokes flow solution are shown for the first time. Compared to previously shown simulations the algorithm is enhanced by models, taking additional, relevant physical effects into account. The new simulation results are compared to experimental results and former simulations.

Compressibility and Rarefaction Effects on Pressure Drop in Rough Microchannels

2006 ◽  
Author(s):  
Giulio Croce ◽  
Paola D’Agaro ◽  
Alessandro Filippo
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Pressure Drop ◽  
Slip Flow ◽  
Major Effect ◽  
Flow Conditions ◽  
Fully Developed Flow ◽  
Compressibility Effect ◽  
Wide Range ◽  
Poiseuille Number

A numerical analysis of the flow field in rough microchannel is carried out with a finite volume compressible solver, including generalized Maxwell slip flow boundary conditions suitable for arbitrary geometries. Roughness geometry is modeled as a series of triangular shaped obstructions. Relative roughness from 0% to 2.65% were considered. Since for truly compressible flow we have no fully developed flow condition, the simulation is performed over the whole length of the channel. A wide range of Mach number is considered, from nearly incompressible to chocked flow conditions. Flow conditions with Reynolds number up to around 200 were computed. The outlet Knudsen number corresponding to the chosen range of Mach and Reynolds number ranges from very low value to 0.0249. Performance charts are presented in terms of both average and local Poiseuille number as a function of local Kn, Ma and Re. In particular, it appears that roughness strongly decreases the reduction in pressure loss due to rarefaction. Thus, roughness effect is stronger at high Kn. Furthermore, compressibility effect has a major effect on pressure drop, as soon as local Mach number exceed 0.3.

Subsonic Elector Nozzle Limiting Flow Conditions

2003 ◽  
Vol 125 (3) ◽  
pp. 851-854 ◽  
Author(s):  
L. J. De Chant
Keyword(s):  
Design Space ◽  
Reverse Flow ◽  
Control Volume ◽  
Flow Conditions ◽  
Efficient Tool ◽  
One Dimensional ◽  
Choked Flow ◽  
Ejector Nozzle ◽  
Classical Control ◽  
Good Agreement

This paper describes an analytical method used to provide information concerning limiting flows for subsonic ejector nozzles. Three potential limiting flows have been identified and modeled using reduced control volume based analysis: (1) incipient reverse flow into the secondary inlet, (2) choked flow in the secondary inlet, and (3) choked flow in the exit mixing stream. Comparison of the methods developed here with the classical control volume portion of an ejector nozzle code have been performed and show good agreement. As such, it is concluded, that within the scope of one-dimensional control-volume based computations, that the methods developed here provide an efficient tool to help delimit the design space acceptable for ejector operation.

Identification of Pulsation Mechanism in a Transonic Three-Stream Airblast Injector

2016 ◽  
Vol 138 (11) ◽  
Author(s):  
Wayne Strasser ◽  
Francine Battaglia
Keyword(s):  
Boundary Conditions ◽  
Industrial Applications ◽  
Driving Mechanism ◽  
Flow Conditions ◽  
Primary Droplet ◽  
Droplet Sizes ◽  
Computational Fluid Dynamics Cfd ◽  
Proportional Relationship ◽  
Nozzle Geometries ◽  
A Minor

Acoustics and ligament formation within a self-generating and self-sustaining pulsating three-stream injector are analyzed and discussed due to the importance of breakup and atomization of jets for agricultural, chemical, and energy-production industries. An extensive parametric study was carried out to evaluate the effects of simulation numerics and boundary conditions using various comparative metrics. Numerical considerations and boundary conditions made quite significant differences in some parameters, which stress the importance of using documented and consistent numerical discretization recipes when comparing various flow conditions and geometries. Validation exercises confirmed that correct droplet sizes could be produced computationally, the Sauter mean diameter (SMD) of droplets/ligaments could be quantified, and the trajectory of a droplet intersecting a shock wave could be accurately tracked. Swirl had a minor impact by slightly moving the ligaments away from the nozzle outlet and changing the spray to a hollow cone shape. Often, metrics were synchronized for a given simulation, indicating that a common driving mechanism was responsible for all the global instabilities, namely, liquid bridging and fountain production with shockletlike structures. Interestingly, both computational fluid dynamics (CFD) and the experimental non-Newtonian primary droplet size results, when normalized by distance from the injector, showed an inversely proportional relationship with injector distance. Another important outcome was the ability to apply the models developed to other nozzle geometries, liquid properties, and flow conditions or to other industrial applications.

scholarly journals Needle-Free Jet Injectors’ Geometry Design and Drug Diffusion Process Analysis

2021 ◽  
Vol 2021 ◽  
pp. 1-6
Author(s):  
Yunfei Wang ◽  
Long Yue ◽  
Lechuan Hu ◽  
Jing Wang
Keyword(s):  
Diffusion Process ◽  
Process Analysis ◽  
Subcutaneous Tissue ◽  
Nozzle Geometry ◽  
Drug Diffusion ◽  
Free Jet ◽  
Cylindrical Nozzle ◽  
Geometry Design ◽  
Nozzle Geometries ◽  
Jet Injectors

In order to study the injection and diffusion process of the drug in the subcutaneous tissue of a needle-free jet injectors (NFJIs) in detail and understand the influence of different nozzle geometry on the diffusion process of the drug, in this paper, numerical simulations were performed to study the diffusion process of the drug in the subcutaneous tissue of NFJIs with cylindrical nozzle. On this basis, the differences of the drug diffusion process with different nozzle geometries were analyzed. The results show that the drug diffused in the shape of ellipsoid in the subcutaneous tissue. The penetration of the drug into the subcutaneous tissue is deeper under the condition of conical nozzle and conical cylindrical nozzle at the same time. However, it takes longer to spread to the interface between skin and subcutaneous tissue in reverse.

Turbine Engine Icing Spray Bar Design Issues

1994 ◽  
Author(s):  
C. Scott Bartlett
Keyword(s):  
Supercooled Liquid ◽  
Propulsion System ◽  
Test Facility ◽  
Turbine Engine ◽  
Turbofan Engines ◽  
Free Jet ◽  
Spray System ◽  
Key Issues ◽  
Development Center ◽  
High Thrust

Techniques have been developed at the Engine Test Facility (ETF) of the Arnold Engineering Development Center (AEOC) to simulate flight through atmospheric icing conditions of supercooled liquid water droplets. Ice formed on aircraft and propulsion system surfaces during flight through icing conditions can, even in small amounts, be extremely hazardous. The effects of ice are dependent on many variables and are still unpredictable. Often, experiments are conducted to determine the characteristics of the aircraft and its propulsion system in an icing environment. Facilities at the ETF provide the capability to conduct icing testing in either the direct-connect (connected pipe) or the free-jet mode. The requirements of a spray system for turbine engine icing testing are described, as are the techniques used at the AEDC ETF to simulate flight in icing conditions. Some of the key issues facing the designer of a spray system for use in an altitude facility are identified and discussed, and validation testing of the design of a new spray system for the AEDC ETF is detailed. This spray system enables testing of the newest generation of high-thrust turbofan engines in simulated icing conditions.

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