Effect of Motive Nozzle Exit Position in a R-744 Two-Phase Ejector

2022 ◽  
pp. 237-247
Author(s):  
Kapil Dev Choudhary ◽  
M. S. Dasgupta ◽  
Shyam Sunder Yadav
Keyword(s):  
Nozzle Exit ◽  
Two Phase

Investigation of Nozzle Flow and Cavitation Characteristics in a Diesel Injector

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
S. Som ◽  
S. K. Aggarwal ◽  
E. M. El-Hannouny ◽  
D. E. Longman
Keyword(s):  
Nozzle Exit ◽  
Critical Role ◽  
Injection Pressure ◽  
Nozzle Flow ◽  
Two Phase ◽  
Cavitation Inception ◽  
Diesel Fuels ◽  
Needle Position ◽  
Primary Breakup ◽  
Cavitation Behavior

Cavitation and turbulence inside a diesel injector play a critical role in primary spray breakup and development processes. The study of cavitation in realistic injectors is challenging, both theoretically and experimentally, since the associated two-phase flow field is turbulent and highly complex, characterized by large pressure gradients and small orifice geometries. We report herein a computational investigation of the internal nozzle flow and cavitation characteristics in a diesel injector. A mixture based model in FLUENT V6.2 software is employed for simulations. In addition, a new criterion for cavitation inception based on the total stress is implemented, and its effectiveness in predicting cavitation is evaluated. Results indicate that under realistic diesel engine conditions, cavitation patterns inside the orifice are influenced by the new cavitation criterion. Simulations are validated using the available two-phase nozzle flow data and the rate of injection measurements at various injection pressures (800–1600 bar) from the present study. The computational model is then used to characterize the effects of important injector parameters on the internal nozzle flow and cavitation behavior, as well as on flow properties at the nozzle exit. The parameters include injection pressure, needle lift position, and fuel type. The propensity of cavitation for different on-fleet diesel fuels is compared with that for n-dodecane, a diesel fuel surrogate. Results indicate that the cavitation characteristics of n-dodecane are significantly different from those of the other three fuels investigated. The effect of needle movement on cavitation is investigated by performing simulations at different needle lift positions. Cavitation patterns are seen to shift dramatically as the needle lift position is changed during an injection event. The region of significant cavitation shifts from top of the orifice to bottom of the orifice as the needle position is changed from fully open (0.275 mm) to nearly closed (0.1 mm), and this behavior can be attributed to the effect of needle position on flow patterns upstream of the orifice. The results demonstrate the capability of the cavitation model to predict cavitating nozzle flows in realistic diesel injectors and provide boundary conditions, in terms of vapor fraction, velocity, and turbulence parameters at the nozzle exit, which can be coupled with the primary breakup simulation.

scholarly journals An integrated modeling approach for design and optimization of ejector pumps carrying two-phase fluid

2017 ◽  
Author(s):  
◽  
Khalid Sarhan Almutairi
Keyword(s):  
Nozzle Exit ◽  
Two Phase Flow ◽  
Flow Behavior ◽  
Geometric Parameters ◽  
Maximum Efficiency ◽  
Phase Flow ◽  
Two Phase ◽  
Design And Optimization ◽  
Numerical Predictions ◽  
A New Technique

An ejector pump uses a primary flow as a motive fluid to entrain another fluid, and can work with both incompressible flow and compressible flow, in either as a singlephase or two-phase mixture. Determining the behavior of the two-phase flow inside the ejector with different geometric parameters was the objective of this research. Three approaches were used to predict the performance and the capture the flow behavior inside it. An analytical model used the geometric parameters to calculate the loss factors for the first time and work as a basis for the two-phase flow ejectors. A fluid transportation system was built to verify analytical and numerical predictions and to explore optimum. Using a fitting parameter to capture the flow behavior inside the ejector was crucial for the accuracy of the numerical model. The fitting parameter is a new technique that uses an arbitrary fluid to match the induced air measurements numerically with the ones founded experimentally. To apply the three approaches, nine ejectors were built with different geometric parameters. The nozzle exit diameters are tested at three levels while the length mixing tube are tested at three levels as well. The results reveal that the diffuser angle of 5[degrees], the smallest nozzle exit diameter, and the longest mixing tube result on maximum efficiency and highest induced air. More investigation of two-phase ejectors is important to fully understand flow behavior and to increase efficiency. There are many improvements needed to this work in future.

scholarly journals CFD simulations of the diesel jet primary atomization from a multihole injector

2017 ◽  
Author(s):  
Charalambos Chasos
Keyword(s):  
High Pressure ◽  
Nozzle Exit ◽  
Cone Angle ◽  
Injection Pressure ◽  
Liquid Jet ◽  
Spray Cone Angle ◽  
Two Phase ◽  
Spray Cone ◽  
Breakup Length ◽  
Jet Breakup

High pressure multi-hole diesel injectors are currently used in direct-injection common-rail diesel engines for the improvement of fuel injection and air/fuel mixing, and the overall engine performance. The resulting spray injection characteristics are dictated by the injector geometry and the injection conditions, as well as the ambient conditions into which the liquid is injected. The main objective of the present study was to design a high pressure multi-hole diesel injector and model the two-phase flow using the volume of fluid (VOF) method, in order to predict the initial liquid jet characteristics for various injection conditions. A computer aided design (CAD) software was employed for the design of the three-dimensional geometry of the assembly of the injector and the constant volume chamber into which the liquid jet emerges. A typical six-hole diesel injector geometry was modelled and the holes were symmetrically located around the periphery of the injector tip. The injector nozzle diameter and length were 0.2 mm and 1 mm, respectively, resulting in a ratio of nozzle orifice length over nozzle diameter L/D = 5. The commercial computational fluid dynamics (CFD) code STAR-CD was used for the generation of the computational mesh and for transient simulations with an Eulerian approach incorporating the VOF model for the two-phase flow and the Rayleigh model for the cavitation phenomenon. Three test cases for increasing injection pressure of diesel injection from the high pressure multi-hole diesel injector into high pressure and high temperature chamber conditions were investigated. From the injector simulations of the test cases, the nozzle exit velocity components were determined, along with the emerging liquid jet breakup length at the nozzle exit. Furthermore, the spray angle was estimated by the average radial displacement of the liquid jet and air mixture at the vicinity of the nozzle exit. The breakup length of the liquid jet and the spray cone angle which were determined from the simulations, were compared with the breakup length and cone angle estimated by empirical equations. From the simulations, it was found that cavitation takes place at the nozzle inlet for all the cases, and affects the fuel and air interaction at the upper area of the spray jet. Furthermore, the spray jet breakup length increases with elapsed time, and when the injection pressure increases both the breakup length and the spray cone angle increase.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.5040

scholarly journals The Evolution of Interfaces for Underwater Supersonic Gas Jets

Water ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 488
Author(s):  
Xiaoyuan Zhang ◽  
Shipeng Li ◽  
Dian Yu ◽  
Baoyu Yang ◽  
Ningfei Wang
Keyword(s):  
Nozzle Exit ◽  
High Speed ◽  
Wake Flow ◽  
Interface Instability ◽  
Photographic Recording ◽  
Two Phase ◽  
Dominant Mechanism ◽  
Gas Jets ◽  
The Relationship ◽  
Unstable Interaction

The evolution of interfaces for underwater gas jets is the main morphological manifestation of two-phase unstable interaction. The high-speed transient photographic recording and image post-processing methods are used to obtain the interfacial change in a submerged gaseous jet at different stages after its ejection from the Laval nozzle exit. The relationship between the pressure pulsation in the wake flow field and the interfacial change is further analyzed by combining the experimental results with computational results. A theoretical model is employed to address the competition dominant mechanism of interface instability. The results show that the jet interface of a supersonic gas jet gradually changes from one containing wave structures to a transition structure, and finally forms a steady-state conical jet. The fluctuation of the jet interface results in the pulsation of the back-pressure. The dominant mechanism of the interface changes with the development and distribution of the jet, from Kelvin-Helmholtz (K-H) instability beyond the nozzle exit changing to Rayleigh-Taylor (R-T) instability in the downstream.

Performance of Solid-Liquid Two Phase Jet Pump Vacuuming Up Beach Sand

2010 ◽  
Author(s):  
K. Itoh ◽  
S. Nishigaki ◽  
I. Honda ◽  
T. Yoshida ◽  
A. Boda ◽  
...  
Keyword(s):  
Cross Section ◽  
Nozzle Exit ◽  
Single Phase ◽  
Flow Rate Ratio ◽  
Pump Efficiency ◽  
Phase Flow ◽  
Cross Section Ratio ◽  
Jet Pump ◽  
Two Phase ◽  
Section Ratio

The performance of the water-sand two phase jet pump has been evaluated for developing environmental sand purification systems. Three types of throat diameter, D = 26, 31, 37 mm, are tested with constant nozzle-exit diameter 20 mm in order to vary the cross section ratio of nozzle exit to throat, R = 0.59, 0.42 and 0.29. The coarse and fine natural sands extracted at Hirase-higashi beach and artificial crushed sand, of which the fineness modulus are 2.71, 2.03 and 2.88 respectively, are mixed in the secondary water flow. The concentration of sand is less than 18% in the present experiment. It is confirmed that the dependences of two-phase efficiency curve and of two-phase flow rate ratio curve upon cross section ratio R agrees with those of single phase flow. On the other hand, the effect of particle size appears in the range of decrement of pump efficiency. That is, it is found that the deviation between two phase and single phase efficiency is 10% on average for coarse sand, whereas the deviation is almost zero for fine sand.

On the Mechanism of Flashing Injection of Initially Subcooled Fuels

1984 ◽  
Vol 106 (1) ◽  
pp. 105-109 ◽  
Author(s):  
R. D. Oza
Keyword(s):  
Nozzle Exit ◽  
Cone Angle ◽  
Constant Volume ◽  
Spray Cone Angle ◽  
Two Phase ◽  
Spray Cone ◽  
Injector Nozzle ◽  
Exit Pressure ◽  
Flash Boiling

The mechanisms responsible for flash-boiling injection were investigated. Using an electromagnetic injector developed for this study, propane, methanol and Indolene were heated and injected into a constant-volume vessel. Two regimes of flash-boiling injection were identified. In the first regime, flash-boiling occurs within the injector nozzle without an increase in spray-cone angle. In the second regime, the nozzle exit pressure is sufficiently low that the two-phase compressible mixture created by flash-boiling within the injector nozzle is underexpanded at the nozzle exit and expands externally to increase the spray-cone angle.

Effect of Shock Loading on the Microstructure of Uniloy 326

1974 ◽  
Vol 32 ◽  
pp. 504-505
Author(s):  
K. P. Staudhammer ◽  
L. E. Murr
Keyword(s):  
Grain Size ◽  
Shock Loading ◽  
Current Investigation ◽  
Two Phase ◽  
05 C ◽  
Shock Deformation ◽  
Heat Treated

The effect of shock loading on a variety of steels has been reviewed recently by Leslie. It is generally observed that significant changes in microstructure and microhardness are produced by explosive shock deformation. While the effect of shock loading on austenitic, ferritic, martensitic, and pearlitic structures has been investigated, there have been no systematic studies of the shock-loading of microduplex structures.In the current investigation, the shock-loading response of millrolled and heat-treated Uniloy 326 (thickness 60 mil) having a residual grain size of 1 to 2μ before shock loading was studied. Uniloy 326 is a two phase (microduplex) alloy consisting of 30% austenite (γ) in a ferrite (α) matrix; with the composition.3% Ti, 1% Mn, .6% Si,.05% C, 6% Ni, 26% Cr, balance Fe.

Exsolution and inversion in pigeonite from the Whin Sill, Northern England

1978 ◽  
Vol 36 (1) ◽  
pp. 474-475
Author(s):  
P.P.K. Smith
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Homogeneous Nucleation ◽  
Silicate Mineral ◽  
Antiphase Boundaries ◽  
Two Phase ◽  
Primitive Form ◽  
The Core ◽  
Nucleation Mechanisms ◽  
And Inversion

Grains of pigeonite, a calcium-poor silicate mineral of the pyroxene group, from the Whin Sill dolerite have been ion-thinned and examined by TEM. The pigeonite is strongly zoned chemically from the composition Wo8En64FS28 in the core to Wo13En34FS53 at the rim. Two phase transformations have occurred during the cooling of this pigeonite:- exsolution of augite, a more calcic pyroxene, and inversion of the pigeonite from the high- temperature C face-centred form to the low-temperature primitive form, with the formation of antiphase boundaries (APB's). Different sequences of these exsolution and inversion reactions, together with different nucleation mechanisms of the augite, have created three distinct microstructures depending on the position in the grain.In the core of the grains small platelets of augite about 0.02μm thick have farmed parallel to the (001) plane (Fig. 1). These are thought to have exsolved by homogeneous nucleation. Subsequently the inversion of the pigeonite has led to the creation of APB's.

Shock consolidation of Ni-Ti alloy powder

1986 ◽  
Vol 44 ◽  
pp. 430-431
Author(s):  
Naresh N. Thadhani ◽  
Thad Vreeland ◽  
Thomas J. Ahrens
Keyword(s):  
Alloy Powder ◽  
Amorphous Material ◽  
Ti Alloy ◽  
Two Phase ◽  
Near Surface ◽  
Optical Micrograph ◽  
Shock Compaction ◽  
Powder Particles ◽  
Ti Powder ◽  
Rapidly Solidified

A spherically-shaped, microcrystalline Ni-Ti alloy powder having fairly nonhomogeneous particle size distribution and chemical composition was consolidated with shock input energy of 316 kJ/kg. In the process of consolidation, shock energy is preferentially input at particle surfaces, resulting in melting of near-surface material and interparticle welding. The Ni-Ti powder particles were 2-60 μm in diameter (Fig. 1). About 30-40% of the powder particles were Ni-65wt% and balance were Ni-45wt%Ti (estimated by EMPA).Upon shock compaction, the two phase Ni-Ti powder particles were bonded together by the interparticle melt which rapidly solidified, usually to amorphous material. Fig. 2 is an optical micrograph (in plane of shock) of the consolidated Ni-Ti alloy powder, showing the particles with different etching contrast.

A Comparison of Tem and Apfim to the Interpretation of Modulated Microstructures

1985 ◽  
Vol 43 ◽  
pp. 70-71
Author(s):  
M.G. Burke ◽  
M.K. Miller
Keyword(s):  
Low Temperature ◽  
Microstructural Characterization ◽  
Superlattice Reflection ◽  
High Volume ◽  
Atom Probe ◽  
Dark Field ◽  
Miscibility Gap ◽  
Second Phase ◽  
Two Phase ◽  
Probe Field

Interpretation of fine-scale microstructures containing high volume fractions of second phase is complex. In particular, microstructures developed through decomposition within low temperature miscibility gaps may be extremely fine. This paper compares the morphological interpretations of such complex microstructures by the high-resolution techniques of TEM and atom probe field-ion microscopy (APFIM).The Fe-25 at% Be alloy selected for this study was aged within the low temperature miscibility gap to form a <100> aligned two-phase microstructure. This triaxially modulated microstructure is composed of an Fe-rich ferrite phase and a B2-ordered Be-enriched phase. The microstructural characterization through conventional bright-field TEM is inadequate because of the many contributions to image contrast. The ordering reaction which accompanies spinodal decomposition in this alloy permits simplification of the image by the use of the centered dark field technique to image just one phase. A CDF image formed with a B2 superlattice reflection is shown in fig. 1. In this CDF micrograph, the the B2-ordered Be-enriched phase appears as bright regions in the darkly-imaging ferrite. By examining the specimen in a [001] orientation, the <100> nature of the modulations is evident.

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