Numerical Simulation on Flow Structure of a Steam-Jet Pump Influenced by Primary Nozzle Geometries

2011 ◽  
Vol 130-134 ◽  
pp. 1703-1707 ◽  
Author(s):  
Xiao Chun Dai ◽  
Jian Huo
Keyword(s):  
Fluid Dynamics ◽  
Flow Structure ◽  
Mixing Process ◽  
Nozzle Outlet ◽  
Jet Pump ◽  
Entrainment Ratio ◽  
Great Loss ◽  
Mixing Chamber ◽  
Throat Diameter ◽  
Nozzle Geometries

The aim of the paper is to reveal the flow structure and the mixing process of a steam-jet pump by using a computational fluid dynamics code FLUENT. Discusses the effect on a steam-jet pump’s entrainment ratio when the throat diameter of the primary nozzle as well as the outlet diameter of the primary nozzle is varied. Analyzes the position of shock wave which will bring the steam-jet pump’s performance a great loss. The performances of a steam-jet pump are studied by changing back pressures while the distance between primary nozzle outlet and mixing chamber inlet (DPM) is varied. The entrainment ratios of a steam-jet pump with different values of DPM and different back pressures are calculated.

Numerical Simulation of Performance of Steam Ejector Influenced by the Distance between Nozzle Outlet and Mixing Chamber Inlet

2011 ◽  
Vol 299-300 ◽  
pp. 970-973
Author(s):  
Xiao Chun Dai ◽  
Guo Jin Liao
Keyword(s):  
Numerical Simulation ◽  
Geometric Parameters ◽  
Experimental Results ◽  
Nozzle Outlet ◽  
Entrainment Ratio ◽  
Optimum Range ◽  
Steam Ejector ◽  
Mixing Chamber ◽  
Throat Diameter

The performance of a steam ejector was simulated using FLUENT. The performance of steam ejector was studied by changing the distance between primary nozzle outlet and mixing chamber inlet (DPM) while operating pressures and other geometric parameters were not varied. The entrainment ratios of the steam ejector with different values of DPM were calculated. The optimum range of DPM was given, which is changed from 1.8 to 2 times of the throat diameter of hybrid diffuser pipe. The errors of the CFD results to the experimental results of the entrainment ratio are not more than 15%.

scholarly journals Numerical investigation on the effect of second throat diameter on two-throat nozzle ejector

2021 ◽  
Vol 2047 (1) ◽  
pp. 012020
Author(s):  
F T Jia ◽  
D Z Yang ◽  
J Xie
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Simulation Model ◽  
Flow Velocity ◽  
Working Conditions ◽  
Static Pressure ◽  
Two Phase ◽  
Entrainment Ratio ◽  
Mixing Chamber ◽  
Throat Diameter

Abstract The employment of two-phase ejectors in the CO2 refrigeration systems is widely developed recently. Due to the lack reports on the two-throat nozzle ejectors, the performance of CO2 two-throat nozzle ejector varied with different second throat diameter (D t ) was numerically investigated under different primary pressures (P p ). The accuracy of established numerical simulation model was confirmed with the assistance of experimental data summarized in the literature. The simulated results show that the two-throat nozzle ejector performance corresponding to entrainment ratio (Er) is of better stability with relatively bigger D t under different working conditions. Next, the axial static pressure corresponding to bigger D t is lower than that of smaller one at pre-mixing chamber. And the secondary flow velocity of bigger D t is accelerated better as compared to that of smaller one.

Numerical Study on the Flow Structure of a Steam-Jet Vacuum Pump at Different Throat Length

2012 ◽  
Vol 542-543 ◽  
pp. 1053-1056
Author(s):  
Xiao Chun Dai
Keyword(s):  
Flow Structure ◽  
Software Package ◽  
Numerical Study ◽  
Simulation Software ◽  
Vacuum Pump ◽  
Back Pressure ◽  
Jet Pump ◽  
Flow Process ◽  
Entrainment Ratio ◽  
Flow Phenomena

The aim of the study is to reveal the complication of the flow process of a steam-jet by using the simulation software package (FLUENT). The paper is able to analyze the flow phenomena inside the steam-jet when its throat length was varied. It is found that the entrainment ratio remains unchanged when the throat length is varied. It is also found that the shocking position moved closer to the exit of the vacuum pump and the critical back pressure of the steam-jet pump increased with the elongation of the throat.

Computational fluid dynamics simulation of the supersonic steam ejector. Part 2. Optimal design of geometry and the effect of operating conditions on the ejector

2011 ◽  
Vol 226 (3) ◽  
pp. 715-723 ◽  
Author(s):  
L Cai ◽  
H T Zheng ◽  
Y J Li ◽  
Z M Li
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Optimal Design ◽  
Critical Pressure ◽  
Operating Conditions ◽  
Dynamics Simulation ◽  
Working Fluid ◽  
Entrainment Ratio ◽  
Steam Ejector ◽  
Mixing Chamber

The aim of this study is to investigate the use of computational fluid dynamics in predicting the performance and optimal design of the geometry of a steam ejector used in a steam turbine. In the current part, the real gas model was considered using IAPWS IF97 model, and the influences of working fluid pressure and backpressure were investigated. The results illustrate that working critical pressure and backflow critical pressure exist in the flow. Moreover, the entrainment ratio reaches its peak at the working critical pressure. The performance of the ejector was nearly the same when the outlet pressure was lower than the critical backpressure. Effects of ejector geometries were also investigated. The distance between the primary nozzle and the mixing chamber was at optimum, the length of the mixing chamber and the diameter of the throat had an optimal value according to the entrainment ratio. When the length of the diffuser or throat was decreased within a range, the entrainment ratio did not change significantly.

scholarly journals Numerical Investigation of the Effect of Air Leaking into the Working Fluid on the Performance of a Steam Ejector

2021 ◽  
Vol 11 (13) ◽  
pp. 6111
Author(s):  
He Li ◽  
Xiaodong Wang ◽  
Jiuxin Ning ◽  
Pengfei Zhang ◽  
Hailong Huang
Keyword(s):  
Flow Structure ◽  
Mass Fraction ◽  
Internal Flow ◽  
Working Fluid ◽  
Physical Parameters ◽  
Entrainment Ratio ◽  
Air Mass ◽  
Steam Ejector ◽  
Primary Fluid ◽  
Mass Fractions

This paper investigated the effect of air leaking into the working fluid on the performance of a steam ejector. A simulation of the mixing of air into the primary and secondary fluids was performed using CFD. The effects of air with a 0, 0.1, 0.3 and 0.5 mass fraction on the entrainment ratio and internal flow structure of the steam ejector were studied, and the coefficient distortion rates for the entrainment ratios under these air mass fractions were calculated. The results demonstrated that the air modified the physical parameters of the working fluid, which is the main reason for changes in the entrainment ratio and internal flow structure. The calculation of the coefficient distortion rate of the entrainment ratio illustrated that the air in the primary fluid has a more significant impact on the change in the entrainment ratio than that in the secondary fluid under the same air mass fraction. Therefore, the air mass fraction in the working fluid must be minimized to acquire a precise entrainment ratio. Furthermore, this paper provided a method of inspecting air leakage in the experimental steam ejector refrigeration system.

Numerical Simulation of Start-Up Jets in a Mixing Chamber

2010 ◽  
Author(s):  
Chenzhou Lian ◽  
Dmytro M. Voytovych ◽  
Guoping Xia ◽  
Charles L. Merkle
Keyword(s):  
Transient Flow ◽  
Three Dimensional ◽  
Cost Effective ◽  
Grid Refinement ◽  
Mixing Process ◽  
Quantitative Estimates ◽  
Start Up ◽  
Mixing Chamber ◽  
Parametric Analyses ◽  
Transient Mixing

Numerical simulations of a transient flow of helium injected into an established background flow of nitrogen were carried out to identify the dominant features of the transient mixing process between these two dissimilar gases. The geometry of interest is composed of two helium slots on either side of a central nitrogen channel feeding into a ‘two-dimensional’ mixing chamber. Simulations were accomplished on both two- and three-dimensional grids using an unsteady DES approach. Results are compared with experimental measurements of species distributions. Unsteady 2-D solutions give a reasonable qualitative picture of the transient mixing process in the middle of the chamber and enable cost-effective parametric analyses and grid refinement studies. The 2-D solutions also provide quantitative estimates of representative characteristic times to guide the 3-D calculations. The 3-D solutions give a reasonable approximation to span-wise events.

scholarly journals AN INVESTIGATION TURBULENCE MODEL OF STANDARD k- TO GET OPTIMUM PARAMETERS OF TURBULENCE CONSTANTS (cµ, c1, AND c2) OF COMPRESSIBLE FLUID DYNAMICS IN A CONFINED JET

2021 ◽  
Vol 56 (5) ◽  
pp. 294-317
Author(s):  
A. I. Siswantara ◽  
H. Pujowidodo ◽  
M. A. Budiyanto ◽  
G. G. Ramdlan Gunadi ◽  
C. D. Widiawaty
Keyword(s):  
Fluid Dynamics ◽  
Turbulence Model ◽  
Compressible Fluid ◽  
Turbulence Modeling ◽  
Reference Model ◽  
Fluid Pressure ◽  
Secondary Data ◽  
Entrainment Ratio ◽  
Air Jet ◽  
Compressible Fluid Dynamics

This research aims to find the optimal standard k-e turbulence model constants (cµ, c1e, and c2e) for better predicting compressible fluid dynamics in an air jet ejector. The turbulence field in a jet flow plays an important role in influencing the performance of the momentum transfer process at a shear layer in nozzle application for momentum source and mixing process. In this research, some activities have been done before analyzing and optimizing the turbulence model constants, including preliminary turbulence modeling study for compressible flow in the air-jet ejector, verification, and validation with primary experimental data as well as by other secondary data. The preliminary studies in turbulence modeling presented that the turbulence modeling of a 3mm air jet-ejector resulted in a similar trend of the relation between entrainment ratio and motive fluid pressure. The results showed that the sensitive parameters in the standard k-emodel dissipation and diffusion terms, cµ, c1e, and c2e, strongly affected the optimum value of turbulence kinetic energy (k) and dissipation rate (e), compared to the reference model. Better k and e could be obtained by changing the c2e into positively proportional, but the cµ and c1e must be changed with opposite proportionality. It was found that the optimum standard k-e model constants in the case of air-jet ejector with 3 mm nozzle diameter for cµ, c1e, and c2e are 0.05, 1.48, and 1.88, respectively, with the error values for k being -8.88% and e being -17.44%.

scholarly journals Effect of geometrical factors interactions on design optimization process of a natural gas ejector

2019 ◽  
Vol 11 (9) ◽  
pp. 168781401988036
Author(s):  
Amin Hassan Amin ◽  
Ibrahim Elbadawy ◽  
E Elgendy ◽  
M Fatouh
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Natural Gas ◽  
Optimum Design ◽  
Average Error ◽  
Minor Effect ◽  
Optimization Approach ◽  
Entrainment Ratio ◽  
Geometrical Factors ◽  
Discharge Pressure

Enhancing the ejector entrainment ratio plays an important role in the ejector performance. In this article, a surrogate-based optimization approach along with computational fluid dynamics technique has been employed to optimize the entrainment ratio of a single-phase ejector working with natural gas. Nine ejector geometrical factors have been varied to maximize the ejector entrainment ratio. Validation results of the presented computational fluid dynamics model were in a good agreement with the experimental data from the literature with an average error of 0.6% in the critical mode. Reported results showed that the optimum design achieves entrainment ratio of 19.45% at 12, 2, and 5.2 MPa motive pressure, induced pressure, and discharge pressure, respectively. Moreover, the primary nozzle convergent angle and throat length are insignificant factors. Furthermore, secondary nozzle inclination angle has a minor effect on the entrainment ratio of the optimum design.

CFD Study of Pitch Variations On Helically Coiled Pipe in Laminar Flow Region

2020 ◽  
Author(s):  
Anwer Faraj ◽  
Itimad D J Azzawi ◽  
Samir Ghazi Yahya ◽  
Amer Al-damook
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Laminar Flow ◽  
Friction Factor ◽  
Flow Structure ◽  
Flow Region ◽  
Alternative Solution ◽  
Experimental Investigations ◽  
Coil Diameter ◽  
Computational Fluid Dynamics Cfd

Abstract Experimental investigations of the flows inside helically coiled pipe are difficult and may also be expensive, particularly for small diameters. Computational fluid dynamics (CFD) packages, which can easily construct the geometry and change the dimensions with 100% of accuracy, provide an alternative solution for the experimental difficulties and uncertainties. Therefore, a computational fluid dynamics (CFD) study was conducted to analyse the flow structure and the effect of varying the coil pitch on the coil friction factor, through utilising different models' configurations. Two coils were tested, all of them sharing the same pipe and coil diameter: 0.005m and 0.04m respectively. Pitch variations began with 0.01 and 0.05 m for the first, second model respectively. In this study, the velocity was analysed, and the effects of this reduction on coil friction factor were also examined using laminar flow. The results were validated by Ito's equation for the laminar flow.

scholarly journals Numerical and Experimental Study on the Internal Flow of the Venturi Injector

Processes ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 64 ◽  
Author(s):  
Hao Li ◽  
Hong Li ◽  
Xiuqiao Huang ◽  
Qibiao Han ◽  
Ye Yuan ◽  
...  
Keyword(s):  
Energy Loss ◽  
Internal Flow ◽  
Hydraulic Performance ◽  
Mixing Process ◽  
Cavitation Model ◽  
Precise Control ◽  
Mixing Chamber ◽  
Numerical Simulation Methods ◽  
The Stability ◽  
Good Agreement

To study the appropriate numerical simulation methods for venturi injectors, including the investigation of the hydraulic performance, mixing process, and the flowing law of the two internal fluids, simulations and experiments were conducted in this study. In the simulations part, the cavitation model based on the standard k–ε turbulence and mixture models was added, after convergence of the calculations. The results revealed that the cavitation model has good agreement with the experiment. However, huge deviations occurred between the experimental results and the ones from the calculation when not considering the cavitation model after cavitation. Thus, it is inferred that the cavitation model can exactly predict the hydraulic performance of a venturi injector. In addition, the cavitation is a crucial factor affecting the hydraulic performance of a venturi injector. The cavitation can ensure the stability of the fertilizer absorption of the venturi injector and can realize the precise control of fertilization by the venturi injector, although it affects the flow stability and causes energy loss. Moreover, this study found that the mixing chamber and throat are the main areas of energy loss. Furthermore, we observed that the internal flow of the venturi injector results in the majority of mixing taking place at the diffusion and outlet sections.

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