Numerical simulation of the internal flow of swirl atomizer under ambient pressure

2016 ◽  
Vol 230 (15) ◽  
pp. 2650-2659 ◽  
Author(s):  
Qing-fei Fu
Keyword(s):  
Flow Rate ◽  
Ambient Pressure ◽  
Internal Flow ◽  
Pressure Oscillation ◽  
Spray Angle ◽  
Volume Of Fluid Method ◽  
Volumetric Fraction ◽  
Swirl Injectors ◽  
Rate Oscillation ◽  
Swirl Atomizer

This paper presents the simulation study of internal flow of open-end swirl injectors under steady and oscillating ambient pressures. A two-dimensional swirl axisymmetric model based on the volume of fluid method was developed to study the effect of ambient pressure on the internal flow of open-end swirl injectors. The response of injector flow to the ambient pressure oscillation was investigated by superimposing periodical oscillation of ambient pressure at the spout outlet. The results show that the variation of ambient pressure affects the liquid phase volumetric fraction within the gas–liquid shear layer. The spray angle near the wall remains constant independent of the ambient pressure. The velocity distribution on different axial sections rarely varies with ambient pressure. When the ambient pressure oscillated, the ambient pressure oscillation would cause the flow rate oscillation at the spout. The phase delay between the flow rate oscillation at spout and the ambient pressure oscillation is proportional to the oscillation frequency.

Nonlinear Breakup Model for a Liquid Sheet Emanating From a Pressure-Swirl Atomizer

2007 ◽  
Vol 129 (4) ◽  
pp. 945-953 ◽  
Author(s):  
Ashraf A. Ibrahim ◽  
Milind A. Jog
Keyword(s):  
Flow Field ◽  
Ambient Pressure ◽  
Internal Flow ◽  
Liquid Sheet ◽  
Nonlinear Instability ◽  
Breakup Length ◽  
Sheet Breakup ◽  
Swirl Atomizer ◽  
Pressure Swirl ◽  
Pressure Swirl Atomizer

Predictions of breakup length of a liquid sheet emanating from a pressure-swirl (simplex) fuel atomizer have been carried out by computationally modeling the two-phase flow in the atomizer coupled with a nonlinear analysis of instability of the liquid sheet. The volume-of-fluid (VOF) method has been employed to study the flow field inside the pressure-swirl atomizer. A nonlinear instability model has been developed using a perturbation expansion technique with the initial amplitude of the disturbance as the perturbation parameter to determine the sheet instability and breakup. The results for sheet thickness and velocities from the internal flow solutions are used as input in the nonlinear instability model. Computational results for internal flow are validated by comparing film thickness at exit, spray angle, and discharge coefficient with available experimental data. The predictions of breakup length show a good agreement with semiempirical correlations and available experimental measurements. The effect of elevated ambient pressure on the atomizer internal flow field and sheet breakup is investigated. A decrease in air core diameter is obtained at higher ambient pressure due to increased liquid-air momentum transport. Shorter breakup lengths are obtained at elevated air pressure. The coupled internal flow simulation and sheet instability analysis provides a comprehensive approach to modeling sheet breakup from a pressure-swirl atomizer.

Study on the Design Methodology of Swirl Nozzle for Nuclear Reactor Pressurizer

2017 ◽  
Author(s):  
Xiong Cao ◽  
Zhiwei Ding
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Design Methodology ◽  
Nuclear Reactor ◽  
Internal Flow ◽  
Spray Angle ◽  
Spray Nozzle ◽  
Reactor Coolant ◽  
Atomization Performance ◽  
Coolant System

Pressurizer is one of the most important components in reactor coolant system of a nuclear power plant, which operates normally at pressure of 15.4 MPa and temperature of 345°C[1]. The main function of pressurizer is to regulate the pressure in the reactor coolant system by either cooling the steam or heating the saturated water in its upper zone. When the pressure in the reactor coolant system increases, it will distribute cold water to decrease its temperature and pressure through atomizing the reactor coolant with swirl spray nozzle in pressurizer. Swirl nozzle is the key part of pressurizer with swirl structure of full cone spray pattern, and the atomization performance include drop size, spray angle and distribution, also it is characterized by huge flow rate and low pressure drop, and its atomization performance decides the quality of pressure control of the reactor coolant system. To enhance the independent design level of both pressurizer and cooling system, it’s necessary to study the atomization performance of swirl nozzle for nuclear reactor pressurizer. Aimed at improving atomization performance of swirl spray nozzle, the structure design methodology of nuclear reactor pressurizer was studied systematically in three aspects including theory design, numerical simulation and test confirm in this thesis. Through designing the swirl nozzle structure according to similar design formula of spray nozzle in theory, especially studying the influence of different structures that mainly include internal swirl structure on internal flow field of swirl nozzles, the primary structure parameters of swirl nozzle were confirmed. Then, through numerical simulation of the internal flow field, flow rate and pressure drop, and swirl core structure of the swirl nozzle (by building physical model and mathematic model according to the spray nozzle structure), the atomization performance of the nozzle was analyzed. On this basis, the typical swirl nozzle was designed and tested, which included spray angle, flow rate as well as pressure drop tests, and spray drop tests, and the applicability of the computational fluid dynamics (CFD) method was verified when it was applied in swirl nozzle design. Finally, the design method of swirl nozzle with deep groove of swirl core for pressurizer was put forward. Through this studying of theoretical calculation, numerical simulating and test, the correlation between the structural parameters of swirl nozzle and atomization performance was achieved, meanwhile design, analysis and test methods of spray nozzle with low pressure drop and huge flow rate were established. It is helpful to realize the independent design of pressurizer’s swirl nozzle and even to put forward the design methodology of pressurizer’s swirl nozzle with our own characteristic.

scholarly journals Effect of Low Ambient Pressure on Spray Cone Angle of Pressure Swirl Atomizer

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Zhengyan Guo ◽  
Yi Jin ◽  
Kai Zhang ◽  
Kanghong Yao ◽  
Yunbiao Wang ◽  
...  
Keyword(s):  
High Speed ◽  
Ambient Pressure ◽  
Cone Angle ◽  
Spray Angle ◽  
High Speed Photography ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Swirl Atomizer ◽  
Pressure Swirl ◽  
Pressure Swirl Atomizer

Pressure swirl atomizers are widely used in gas turbine combustor; this paper is aimed at researching the effect of low ambient pressure (0.1 MPa to 0.01 MPa, lower than an atmosphere) on the spray cone angle of pressure swirl atomizer. The spray angle is captured by high-speed photography; then, an image post program is used to process the spray angle magnitude. A mathematical model of a single droplet’s movement and trajectory based on force analysis is proposed to validate the spray angle variation. The maximum variation of the spray cone angle, which is observed when fuel supply pressure drop through the atomizer is 1 MPa as the ambient pressure decreases from 0.1 MPa to 0.01 MPa, is found to be 23.9%. The experimental results show that the spray cone angle is expected to increase with the ambient pressure decrease; meanwhile, mathematical results agree well with this trend.

The Overview of Natural Circulation Characteristics of a Marine Reactor Under Ocean Condition

2009 ◽  
Author(s):  
Jia Zhong ◽  
Xingtuan Yang ◽  
Shengyao Jiang
Keyword(s):  
Flow Rate ◽  
Natural Circulation ◽  
Density Wave ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Actual Condition ◽  
Rolling Motion ◽  
Core Flow ◽  
Rate Oscillation ◽  
Ocean Conditions

Marine reactor would be influenced by ocean conditions such as rolling, inclination and heaving which made system coolant fluctuate and changed the ability of natural circulation of the system. The paper summarizes the study of effects of ocean conditions upon flow characteristics of natural circulation, including the researches of Japan, South Korea and China. The result shows that the ocean conditions have some effects upon natural circulation, and the structure of the loop would affect the experiment result. Generally, Inclination would reduce the ability of natural circulation, the larger the inclination angle, the more decrease the ability of natural circulation. Rolling would cause core flow rate oscillation and the amplitude of oscillation increases as rolling angle increase and rolling period decrease. Heat transfer in the core is enhanced by the rolling motion and the enhancement is thought to be caused by the internal flow due to rolling motion. The flow oscillation caused by rolling motion would overlap the density wave oscillation which made the system more instable. Heaving would also cause core flow rate oscillation and the amplitude of oscillation increases as heaving acceleration increase and heaving period increase. It is also found that the improved RETRAN procedure can be used to simulate the thermal-hydraulic characteristics of marine reactor under ocean conditions. The parameters of the current experiment have some differences with the actual condition of the marine reactor, so some further research should be done.

scholarly journals Effect of ambient pressure oscillation on the primary breakup of cylindrical liquid jet spray

2020 ◽  
Vol 12 ◽  
pp. 175682772093555
Author(s):  
Zhen Zhang ◽  
Dong-hyuk Shin
Keyword(s):  
Surface Tension ◽  
Mass Flow Rate ◽  
Flow Rate ◽  
Liquid Surface ◽  
Ambient Pressure ◽  
Pressure Oscillation ◽  
Liquid Jet ◽  
Liquid Surface Tension ◽  
Primary Breakup ◽  
Ambient Gas

The present simulation study investigates the effects of ambient pressure oscillation on cylindrical liquid jet sprays, using the volume of fluid method. The research is motivated by combustion instability in combustion engines, where strong harmonic pressure oscillation can damage internal structures. Oscillating pressure modulates not only the fuel mass flow rate but also the ambient gas density and liquid surface tension, and in liquid sprays, the ambient fluid density and surface tension can have substantial effects on spray breakup. In order to investigate the multiple property changes with ambient pressure oscillation, therefore, a new solver in OpenFOAM is developed. In the solver, liquid mass flow rate, ambient gas density, and liquid surface tension change simultaneously as a result of pressure oscillation. Simulations were conducted at a Reynolds number of 2000 and Weber number over 2000, conditions that are conducive to primary breakup in laminar flows. The simulations show that oscillations in ambient pressure significantly strengthen the surface instability of the liquid ligament, which depends on the surface tension–pressure coefficient, the mean pressure, and the amplitude of oscillation.

Pressure-Scaling of Pressure-Swirl Atomizer Cone Angles

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
D. R. Guildenbecher ◽  
R. R. Rachedi ◽  
P. E. Sojka
Keyword(s):  
Pressure Drop ◽  
Ambient Pressure ◽  
Cone Angle ◽  
Spray Angle ◽  
Subsequent Increase ◽  
A Value ◽  
Nozzle Pressure ◽  
Swirl Atomizer ◽  
Pressure Swirl ◽  
Pressure Swirl Atomizer

An experimental investigation was conducted to study the effects of increased ambient pressure (up to 6.89MPa) and increased nozzle pressure drop (up to 2.8MPa) on the cone angles for sprays produced by pressure-swirl atomizers having varying amounts of initial swirl. This study extends the classical results of DeCorso and Kemeny, (1957, “Effect of Ambient and Fuel Pressure on Nozzle Spray Angle,” ASME Transactions, 79(3), pp. 607–615). Shadow photography was used to measure cone angles at x∕D0=10, 20, 40, and 60. Our lower pressure results for atomizer swirl numbers of 0.50 and 0.25 are consistent with those of DeCorso and Kemeny, who observed a decrease in cone angle with an increase in nozzle pressure drop, ΔP, and ambient density, ρair, until a minimum cone angle was reached when ΔPρair1.6∼100MPa(kg∕m3)1.6 (equivalent to 200psi(lbm∕ft3)1.6). Results for atomizers having higher initial swirl do not match the DeCorso and Kemeny results as well, suggesting that their correlation be used with caution. Another key finding is that an increase in ΔPρair1.6 to a value of 600MPa(kg∕m3)1.6 leads to continued decrease in cone angle, but that a subsequent increase to 2000MPa(kg∕m3)1.6 has little effect on cone angle. Finally, there was little effect of nozzle pressure drop on cone angle, in contrast to findings of previous workers. These effects are hypothesized to be due to gas entrainment.

On the Influence of the Slot Orifice in Diesel Common Rail Nozzle

2018 ◽  
Vol 11 (1) ◽  
pp. 55-69 ◽  
Author(s):  
Giancarlo Chiatti ◽  
Ornella Chiavola ◽  
Fulvio Palmieri ◽  
Roberto Pompei
Keyword(s):  
Cross Section ◽  
Flow Rate ◽  
Experimental Analysis ◽  
Common Rail ◽  
Spray Angle ◽  
The Novel ◽  
Hydraulic Behavior ◽  
Reference Information ◽  
Light Duty ◽  
Set Up

Background:The paper deals with a diesel common rail nozzle in which a novel orifice layout is implemented.Objective:Its influence on the nozzle mechanical-hydraulic behavior and on the spray shape transient development is experimentally investigated.Methods:In the research, a solenoid injector for light duty diesel engines is equipped with the novel nozzle prototype and tested. The prototype layout is described, pointing out the features of the nozzle orifices, in which a Slot cross-section is adopted; the investigation is accomplished extending the hydraulic tests and the spray visualizations to a reference nozzle with standard holes. The influence of the hole layout on the mechanical-hydraulic behavior of the nozzle is assessed by experimental analysis based on the rate of injection measurement, in comparison with the reference nozzle. Once the hydraulic behavior of the novel nozzle has been characterized in terms of mass flow rate, the slot influence on the spray shape is assessed analyzing the macroscopic features such as the penetration distance and the spray angle, in non evaporative conditions. The study is carried out under transient injection conditions, for different injection pressures, up to 1400 bar.Results:The results on spray characteristics also provide reference information to set up spray models suited to take the Slot orifice into account.

scholarly journals Effect of Air Injection on the Internal Flow Characteristics in the Draft Tube of a Francis Turbine Model

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1182
Author(s):  
Seung-Jun Kim ◽  
Yong Cho ◽  
Jin-Hyuk Kim
Keyword(s):  
Flow Rate ◽  
Draft Tube ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Air Injection ◽  
Low Flow ◽  
Francis Turbine ◽  
Navier Stokes ◽  
Vortex Rope

Under low flow-rate conditions, a Francis turbine exhibits precession of a vortex rope with pressure fluctuations in the draft tube. These undesirable flow phenomena can lead to deterioration of the turbine performance as manifested by torque and power output fluctuations. In order to suppress the rope with precession and a swirl component in the tube, the use of anti-swirl fins was investigated in a previous study. However, vortex rope generation still occurred near the cone of the tube. In this study, unsteady-state Reynolds-averaged Navier–Stokes analyses were conducted with a scale-adaptive simulation shear stress transport turbulence model. This model was used to observe the effects of the injection in the draft tube on the unsteady internal flow and pressure phenomena considering both active and passive suppression methods. The air injection affected the generation and suppression of the vortex rope and swirl component depending on the flow rate of the air. In addition, an injection level of 0.5%Q led to a reduction in the maximum unsteady pressure characteristics.

A Numerical Approach for the Simulation of Internal Nozzle Flow in a Pressure Swirl Atomizer Using Different Turbulent Models and Towards an Effective Inlet Weber Number

2013 ◽  
Author(s):  
Ahmadreza Abbasi Baharanchi ◽  
Seckin Gokaltun ◽  
Shahla Eshraghi
Keyword(s):  
Weber Number ◽  
Computational Cost ◽  
Internal Flow ◽  
Numerical Approach ◽  
Reynolds Stress Model ◽  
Multiphase Model ◽  
Vof Model ◽  
Swirl Atomizer ◽  
Pressure Swirl ◽  
Pressure Swirl Atomizer

VOF Multiphase model is used to simulate the flow inside a pressure-swirl-atomizer. The capability of the Reynolds Stress Model and variants of the K-ε and K-ω models in modeling of turbulence has been investigated in the commercial computational fluid dynamics (CFD) software FLUENT 6.3. The Implicit scheme available in the volume-of-fluid (VOF) model is used to calculate the interface representation between phases. The atomization characteristics have been investigated as well as the influence of the inlet swirl strength of the internal flow. The numerical results have been successfully validated against experimental data available for the computed parameters. The performance of the RNG K-ε model was found to be satisfactory in reducing the computational cost and introducing an effective Weber number for the flow simulated in this study.

scholarly journals Analysis of metrological characteristics of elbow flowmeter under rotating state

2021 ◽  
Vol 12 ◽  
pp. 24
Author(s):  
Yu Wang ◽  
Ruiwei Li ◽  
Lin Luo ◽  
Lin Ruan
Keyword(s):  
Flow Rate ◽  
Measurement Accuracy ◽  
Discharge Coefficient ◽  
Water Flow Rate ◽  
Internal Flow ◽  
Metrological Characteristics ◽  
Centrifugal Acceleration ◽  
Flow Rate Measurement ◽  
Fitting Method ◽  
Cfd Method

The application of elbow flowmeter in rotary equipments is beneficial to reduce the pipeline complexity. However, the intervention of centrifugal acceleration will lead to the change of metrological characteristics of elbow flowmeter. Based on the analysis of the differential pressure formation mechanism of the environmental acceleration on the elbow flowmeter, the calculation formula of the flow rate measurement with the elbow flowmeter in the rotating state is derived, and the fitting method of the discharge coefficient is put forward. The CFD method was used to analyze the internal flow field of the elbow flowmeter under rotating state, summarize the pressure distribution characteristics of the pipe wall, and verify the feasibility of the discharge coefficient fitting strategy by simulation. The results show that for the elbow flowmeters with diameters of 10 mm and 15 mm and the radius to diameter ratio of 1.5, as long as the water flow rate is between 1.5 m/s and 5 m/s, the measurement accuracy can be guaranteed to be above 4%.

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